IL285845A - Glass composition for coating and bonding of polycrystalline spinel (transparent ceramic) substrates - Google Patents

Description

GLASS COMPOSITION FOR COATING AND BONDING OF POLYCRYSTALLINE SPINEL (TRANSPARENT CERAMIC) SUBSTRATES TECHNICAL FIELD The present disclosure relates generally to an article of manufacture and a process of producing thereof, wherein the article includes a glass-coated spinel substrate.

BACKGROUND The cost of production of ceramic parts in current technologies, and specifically, in ceramics comprising spinel structures, is high due to an expansive processing and polishing procedure. In ceramic polishing, the expansive machining or polishing of the surfaces is unavoidable in most cases in which the end product is required to transmit light. The difficulties involved in polishing ceramics, and particularly spinel substrates, can result in up to 80% of the part cost being incurred during this stage.

Thus, there is a need in the art for a process for producing a light transmitting article including a spinel substrate, wherein the process is cost effective as well as reliable in terms of quality.

SUMMARY Aspects of the disclosure, according to some embodiments thereof, relate to a glass-coated spinel substrate. According to some embodiments there is provided a glass composition configured to be applied, in a form of a glass paste, to a spinel substrate.

According to some embodiments, the glass paste composition is configured to coat an unpolished surface of spinel substrate. According to some embodiments, the glass-paste coated spinel substrate is then dried and heat-treated using a specific heat treatment to convert the glass paste into a glassy film. According to some embodiments, the composition of the glass is such that the coated spinel substrates can turn the unpolished spinel substrate (which is not transparent) into a transparent article including the spinel substrate and the glass coating.

Advantageously, coating an unpolished spinel substrate using a glass coating having a composition configured to turn the spinel substrate transparent, or in other words, increase the light transmittance in relation to the unpolished spinel substrate, enables reduction in the cost of production of transparent spinel substrates. Accordingly, instead of a need to polish a spinel substrate, which is an expensive process, the glass coating as described herein may be coated onto an unpolished spinel substrate. Moreover, the glass coating can be polished if required, since glass polishing is not an expensive process.

Advantageously, the adherence of the glass composition as described herein onto a spinel substrate reduces the surface flaws of the spinel substrate, thereby increasing the overall strength of the spinel substrate. In contrast, the polishing of the spinel substrate without a coating may increase the flaws on a surface thereof.

According to some embodiments, there is provided a glass composition for coating a spinel substrate, wherein the thermal expansion coefficient of the glass composition is smaller than the thermal expansion coefficient of the spinel substrate.

Advantageously, a glass coating having a lower thermal expansion coefficient than the thermal expansion coefficient of the spinel substrate enables the glass coating to apply a compressive force onto the spinel substrate, thereby reducing gaps in an interface therebetween and/or increasing the overall strength of the glass-coated spinel substrate.

According to some embodiments, there is provided a glass composition for coating a spinel substrate wherein the index of refraction of the glass coating is about the same as the index of refraction of the spinel substrate. Advantageously, matching the index of refraction of the glass coating to the index of refraction of the spinel substrate enables an increase in transparency of the article including the glass-coated spinel substrate.

According to some embodiments, there is provided a process for coating a spinel substrate with a glass composition, wherein the glass composition used to coat the spinel substrate does not crystalize during coating process. Since the crystallization of the glass would produce crystals in the glass coating, which may have different index of refraction than the glass, the crystals may cause light to scatter and therefore reduce transmission.

Accordingly, crystals in the glass coating may also change the thermal expansion of the glass coating. Therefore, it is advantageous that the glass composition used to coat the spinel substrate does not crystalize during coating process.

According to some embodiments, there is provided a process bonding two or more glass-coated spinel substrates. Advantageously, the bonding of two or more spinel substrates using the glass composition enables production of large-scale windows and/or armor that is transparent to light, using a plurality of smaller-scale spinel substrates.

According to some embodiments there is provided an article including a glass coated spinel substrate, including a glass coating including in terms of mole percent of the total composition: (a) 20.0-28% PbO, (b) 0.1-7.0% MgO, (c) 0.1-7.0% ZnO, (d) 0.1­ 7.0% Al2O3, (e) 50.0-57.0% SiO2, and (f) 0.1-1.5% TiO2.

According to some embodiments, the spinel substrate is unpolished.

According to some embodiments, at least a portion of the substrates are unpolished.

According to some embodiments, the glass coating further includes an index of refraction of between about 1.718 and 1.73.

According to some embodiments, the article includes a plurality of coated spinel substrates which are bonded together by the glass coating.

According to some embodiments, the glass coating is configured to apply a compressing pressure onto the spinel substrate.

According to some embodiments, a thermal expansion coefficient of the glass coating is smaller than the thermal expansion coefficient of the spinel substrate, thereby applying a compressing pressure onto the spinel substrate.

According to some embodiments, the glass coating includes a thermal expansion coefficient of between about 5.8×10-6 and 7.02×10-6 C-1.

According to some embodiments, the glass coating includes a glass transition temperature of between about 550°C and 570°C.

According to some embodiments, the article is transparent to transmission of infrared light.

According to some embodiments, the article has a transmission of above 80% for wavelengths above 400nm.

According to some embodiments, the article has a transmission of above 85% for wavelengths above 700nm.

According to some embodiments, the interface between the glass coating and the spinel substrates is devoid of gaps.

According to some embodiments, the article includes 0.01-1.0 mole% of any one of BaO, La2O3, and Bi2O3, or any combination thereof.

According to some embodiments, the article includes up to 0.5 mole% alkali metal oxides.

According to some embodiments, the article includes 25.0-26.0% PbO.

According to some embodiments, the article includes 5.5-6.5% MgO.

According to some embodiments, the article includes 5.5-6.5% ZnO.

According to some embodiments, the article includes 5.5-6.5% Al2O3.

According to some embodiments, the article includes 54.5-55.5% SiO2.

According to some embodiments, the article includes 0.5-1.5% TiO2.

According to some embodiments, the article is resistant to corrosion at (atmospheric conditions) 1atm.

According to some embodiments, the article is used in a transparent missile head.

According to some embodiments, the article is used for transparent armor windows.

According to some embodiments there is provided a glass coating composition of a spinel substrate, the coating composition including, in terms of mole percent of the total composition: (i) 20.0-28% PbO, (ii) 0.1-7.0% MgO, (iii) 0.1-7.0% ZnO, (iv) 0.1-7.0% Al2O3, (v) 50.0-57.0% SiO2, and (vi) 0.1-1.5% TiO2.

According to some embodiments, the composition further includes 0.01-1.0% BaO, La2O3, and/or Bi2O3.

According to some embodiments, the composition further includes up to 0.5% alkali metal oxides.

According to some embodiments, the composition further includes 25.0-26.0% PbO.

According to some embodiments, the composition further includes 5.5-6.5% MgO.

According to some embodiments, the composition further includes 5.5-6.5% ZnO.

According to some embodiments, the composition further includes 5.5-6.5% Al2O3.

According to some embodiments, the composition further includes 54.5-55.5% SiO2.

According to some embodiments, the composition further includes 0.5-1.5% TiO2.

According to some embodiments, there is provided a process for producing a glass powder for producing the glass coating composition for coating of a spinel substrate as disclosed herein, the process including: preparing a mixture of: 2.0-3.0 wt% MgO, 4.0­ .0 wt% ZnO, 23-40 wt% SiO2, 0.1-1.5 wt% TiO2, 0.1-7 wt% Al(OH)3, and 40-90 wt% of any combination of PbO, Pb3O4, and lead bisilicate glass, melting the mixture to form a melt and incubating the melt at a temperature between about 1200°C to 1500°, pouring the molten composition into water to form a frit, and grinding the frit, thereby producing the glass powder.

According to some embodiments, the process further includes drying the frit in an oven at a temperature of between about 100°C to 200°C.

According to some embodiments, the lead bisilicate glass includes Hammond Lead glass B15.

According to some embodiments, the Hammond lead B15 glass includes 63wt.% PbO, 34wt.% SiO2, 2wt.% Al2O3 and 1wt.% TiO2.

According to some embodiments, the process further includes grinding the frit with deionized water.

According to some embodiments, the process further includes grinding the frit with isopropanol.

According to some embodiments, the process further includes screening the powder/slip through a 325 mesh screen.

According to some embodiments, the process further includes drying the screened powder in an oven at a temperature of between about 100°C to 200°C.

According to some embodiments, incubating the melt is at a temperature between about 1250°C to 1500°C.

According to some embodiments there is provided a paste composition for coating of a spinel substrate, including: 60-80% glass powder, the glass powder including the glass composition as disclosed herein, 10-30% medium, 2.0-8.0% terpineol, and 2.0-8.0% dibutylcarbitol.

According to some embodiments, the medium includes a solution of ethyl cellulose.

According to some embodiments, the medium includes 40-50% terpineol.

According to some embodiments, the medium includes 40-50% dibutylcarbitol.

According to some embodiments, the ratio of terpineol to dibutylcarbitol in the paste composition is 1:1.

According to some embodiments there is provided a process for coating a spinel substrate with a glass composition, the process including: applying a glass paste to a spinel substance, thereby forming a paste-coated spinel substrate, wherein the glass paste includes the glass composition as disclosed herein, heating, at a first heating ramp, the paste-coated spinel substrate to a first temperature of about 350°C, dwelling at the first temperature, heating, at a second heating ramp, the paste-coated spinel substrate to a second temperature of about 500°C, dwelling at the second temperature, heating, at a third heating ramp, the paste-coated spinel substrate to a third temperature of about 1100°C, dwelling at the third temperature, thereby forming a glass-coated spinel substrate, cooling the glass-coated spinel substrate to a fourth temperature of about 560°C, dwelling at fourth temperature, and cooling the glass coated spinel to about 25°C.

According to some embodiments, the first heating ramp includes a slope of about 2-5°C/min.

According to some embodiments, dwelling at the first temperature is for a period sufficient for evaporating one or more solvents within the glass paste, and/or sufficient for decomposing and/or pyrolyzing of most of the polymers within the glass paste.

According to some embodiments, the second heating ramp includes a slope of about 0.5-2°C/min.

According to some embodiments, dwelling at the second temperature is for a period sufficient for evaporating and/or decomposing of all organic materials within the glass paste.

According to some embodiments, the third heating ramp includes a slope of about 15-25°C/min.

According to some embodiments, dwelling at the third temperature is for a period sufficient for fully melting the paste-coating into a glassy transparent film, thereby forming a glass-coated spinel substrate.

According to some embodiments, cooling the glass-coated spinel substrate to 25°C includes a cooling ramp having a slope of about 15-25°C/min.

According to some embodiments, cooling the glass-coated spinel substrate to °C includes at least two cooling ramps separated by a dwelling stage at the fourth temperature.

According to some embodiments, a first cooling ramp includes a slope of about -25°C/min.

According to some embodiments, a second cooling ramp includes a slope of about -25°C/min.

According to some embodiments, the predetermined temperature is sufficient for annealing a coat of the paste-coated spinel substrate.

According to some embodiments, the process further includes dwelling, at the dwelling stage and/or at the fourth temperature, for between about 0.7 to 3.5 hours.

According to some embodiments, dwelling at the dwelling temperature of about 560°C is for a period sufficient for annealing at least a portion of a glass surrounding the coated spinel substrates.

According to some embodiments there is provided a process for bonding two or more glass-coated spinel substrates, the process including: placing two or more glass- coated spinel substrates in contact, heating, at a first heating ramp, the glass-coated spinel substrates to a first dwelling temperature of about 1100°C, dwelling at the first temperature, cooling, at a first cooling ramp, the glass-coated spinel substrates to a second dwelling temperature of about 560°C, dwelling at the second temperature, and cooling, at a second heating ramp, the glass-coated spinel substrates to about 25°C.

According to some embodiments, the process further includes dwelling, at about 25°C, for at least about 2 hours.

According to some embodiments, the first heating ramp includes a slope of about 12-26°C/min.

According to some embodiments, the first cooling ramp includes a slope of about 12-26°C/min.

According to some embodiments, the second cooling ramp includes a slope of about 12-26°C/min.

According to some embodiments, dwelling at the dwelling temperature of about 560°C is for a period sufficient for annealing at least a portion of a glass surrounding the coated spinel substrates.

Certain embodiments of the present disclosure may include some, all, or none of the above advantages. One or more other technical advantages may be readily apparent to those skilled in the art from the figures, descriptions, and claims included herein.

Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In case of conflict, the patent specification, including definitions, governs. As used herein, the indefinite articles "a" and "an" mean "at least one" or "one or more" unless the context clearly dictates otherwise.

BRIEF DESCRIPTION OF THE FIGURES Some embodiments of the disclosure are described herein with reference to the accompanying figures. The description, together with the figures, makes it apparent to a person having ordinary skill in the art how some embodiments may be practiced. The figures are for the purpose of illustrative description and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the disclosure. For the sake of clarity, some objects depicted in the figures are not drawn to scale. Moreover, two different objects in the same figure may be drawn to different scales. In particular, the scale of some objects may be greatly exaggerated as compared to other objects in the same figure.

In block diagrams and flowcharts, optional elements/components and optional stages may be included within dashed boxes.

In the figures: FIG. 1 shows a flowchart of functional steps in a process for producing a glass powder having the composition for the glass coating, in accordance with some embodiments of the present invention; FIG. 2 shows a flowchart of functional steps in a process for coating a spinel substrate with a glass composition, in accordance with some embodiments of the present invention; FIG. 3 shows a flowchart of functional steps in a process for bonding two or more glass- coated spinel substrates, in accordance with some embodiments of the present invention; FIG. 4 shows a graph depicting a comparison of light transmittance of an exemplary polished spinel substrate (JH-052-33A) and a glass-coated semipolished (JH-052-31A) spinel substrate in the ultraviolet (UV)-visible (VIS) range, in accordance with some embodiments of the present invention; FIG. 5 shows a graph depicting a comparison of light transmittance of an exemplary polished spinel substrate (JH-052-33A) and a glass-coated semipolished spinel substrate (JH-052-31A) in the infrared (IR) range, in accordance with some embodiments of the present invention; FIG. 6 shows a graph depicting a comparison of light transmittance of two glass bonded spinel substrates (JH-052-36) and two polished spinel substrates taped together at the periphery with cellotape (JH-052-33B), in accordance with some embodiments of the present invention; FIG. 7 shows a graph depicting a comparison of FTIR of two glass bonded spinel substrates (JH-052-36) and two polished spinel substrates taped together at the periphery with cellotape (JH-052-33B), in accordance with some embodiments of the present invention; FIG. 8 shows a graph depicting a comparison of light transmittance of a polished spinel substrate (JH-052-33A), two polished spinel substrates taped together at the periphery with cellotape (JH-052-33B) and two glass bonded spinel substrates (JH-052-36), in accordance with some embodiments of the present invention; FIG. 9 shows a graph depicting a comparison of light transmittance of sequential (JH- 052-17) and co-firing (JH-051-73) of glass coated unpolished spinel substrates, in accordance with some embodiments of the present invention; FIG. 10 shows a graph depicting a comparison of FTIR of sequential and co-firing of glass coated spinel substrates, in accordance with some embodiments of the present invention; FIG. 11A and FIG. 11B show images of sequential-fired and co-fired glass coated spinel substrates, respectively, in accordance with some embodiments of the present invention; FIG. 12A and FIG. 12B show images of bonded glass coated spinel substrates, in accordance with some embodiments of the present invention; FIG. 13 shows a graph depicting a comparison of light transmittance of glass-bonded and uncoated spinel substrates, in accordance with some embodiments of the present invention; and FIG. 14 shows a graph depicting a comparison of FTIR of glass-bonded and uncoated spinel substrates, in accordance with some embodiments of the present invention.

DETAILED DESCRIPTION The principles, uses and implementations of the teachings herein may be better understood with reference to the accompanying description and figures. Upon perusal of the description and figures present herein, one skilled in the art will be able to implement the teachings herein without undue effort or experimentation. In the figures, same reference numerals refer to same parts throughout.

In the following description, various aspects of the invention will be described.

For the purpose of explanation, specific details are set forth in order to provide a thorough understanding of the invention. However, it will also be apparent to one skilled in the art that the invention may be practiced without specific details being presented herein.

Furthermore, well-known features may be omitted or simplified in order not to obscure the invention.

The term "substrate" as used herein may refer to a material which provides a material on which processing is conducted. A "substrate" may be a base, and/ may include one more surfaces of a material, for a coating to be placed onto.

The term "spinel" or "spinel substrate" as used herein may be interchangeable and may refer to a substrate, wherein at least a portion of the substrate is composed of a mineral belonging to the spinel group. According to some embodiments, the spinel includes a general formulation of AB2X4. The spinel or spinel substrate may include a magnesium-aluminate spinel (MgAl₂O₄).

The term "polishing" or "polished" as used herein may refer to a process of smoothing a surface of a substrate. The polished substrate may include a smoothed surface (that had been polished), which may be a product of an applied abrasive substance in repetition to the surface of the substrate, thereby reducing the roughness of the surface.

The term "coating" "glass coating" or "coat of glass" as used herein may be interchangeable and refer to a glass used to cover at least a portion of a surface of a substrate. The coating may adhere to the surface of the substrate.

The term "light transmittance" as used herein may refer to the light that is able to pass through a material, such as, for example, the substrate, the glass coating, and any combination thereof.

The term "transparent to transmission of light" as used herein may refer to a transmission of light having of at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

The term "thermal expansion coefficient" as used herein may refer to the measure of the size of an object changes with a change in temperature. The thermal expansion coefficient measures the fractional change in size per degree change in temperature at a constant pressure, such that a lower coefficient corresponds to a lower change in size with a change in temperature.

The term "index of refraction" or "refractive index" as used herein may be interchangeable and refer to a unit-less value corresponding with how fast light travels through the material. The refractive index determines how much the path of light is bent, or refracted, when entering a material.

The term "resistant to corrosion" as used herein may refer to a property of the material in which it is resistant to deterioration caused by any one or more of general corrosion, pitting corrosion, stress corrosion, uniform corrosion, stress corrosion, service corrosion, and the like.

The term "lead bisilicate glass" may refer to a glass including PbO. According to some embodiments, "lead bisilicate glass" as used herein may also include SiO2. Lead bisilicate glass may include lead alumina bisilicates, which may contain about 1-3% Al2O3. The term " lead bisilicate glass" may refer to a glass composition including of PbO and SiO2, wherein the molar ratio of SiO2 to PbO is about 2. The term "lead bisilicate glass" may refer to a glass composition including 1% to 4% wt.% Al2O3 and/or TiO2.

The term "paste" as used herein may refer to a suspension of granular glassy material and/or glass powder in a fluid.

The term "powder" as used herein may refer to a solid substance including particles that may flow freely in relation to each other. A powder may be dry or may be combined with a liquid to produce a paste or a slip.

The term "frit" as used herein may refer to a ceramic composition what has been granulated. The process of creating a frit may include any one or more of melting and quenching the composition. Frit may be produced in water or other liquids.

The term "slip" as used herein may refer to a ceramic slurry, which may include a mixture of solids (such as, for example, a powder or frit) suspended in a liquid.

The term "heating ramp" as used herein may refer to at least a portion of a heat treatment in which the temperature increases as a function of time at a specific rate (or slope). The temperature may increase in a heating ramp until reaching a specific temperature of the heating ramp.

The term "cooling ramp" as used herein may refer to at least a portion of a heat treatment in which the temperature decreases as a function of time at a specific rate (or slope). The temperature may decrease in a cooling ramp until reaching a specific end temperature of the cooling ramp.

The term "slope" as used herein may refer to the slope of a heating ramp or a cooling ramp, and may indicate the rate of heating and/or cooling of the heating ramp and/or the cooling ramp, respectively, as described hereinabove.

The term "dwelling" or "dwelling stage" as used herein may be interchangeable and refer to at least a portion of a heat treatment or a stage in a heat treatment in which the temperature (or dwelling temperature) is maintained the same or essentially the same, thereby allowing the material undergoing the heat treatment to reach and/or remain at the dwelling temperature.

The term "firing" or "co-firing" as used herein may refer to heating a slip, paste, or powder. According to some embodiments, "firing" or "co-firing" may include applying a heat treatment process and/or may be interchangeable with a heat treatment process.

According to some embodiments, the term "firing" or "co-firing" may be interchangeable with one or more heating ramps. According to some embodiments, the term "firing" or "co-firing" may be interchangeable with one or more dwelling stages.

Article of a Glass Coated Spinel According to some embodiments, there is provided an article including a glass coated spinel substrate. According to some embodiments, the glass coated spinel substrate may include a glass coating and one or more spinel substrates.

According to some embodiments, the spinel substrate may include a magnesium­ aluminate spinel (MgAl₂O₄). According to some embodiments, the spinel substrate may include substitutional elements. According to some embodiments, the spinel substrate may be polycrystalline. According to some embodiments, the spinel substrate may include one or more unpolished surfaces. According to some embodiments, the spinel substrate may include one or more polished surfaces.

According to some embodiments, and as described in greater detail elsewhere herein, the glass coating is configured such that the light transmission of the article including an unpolished and/or semipolished spinel substrate and a glass coating is larger than an article having an unpolished and/or semipolished spinel substrate without a glass coating. An unpolished surface of the spinel substrate coated by glass enables a reduction of polishing steps in the preparation of the article, while increasing the light transmittance thereof. Moreover, according to some embodiments, the unpolished surface of the spinel substrate may increase the adhesion of the glass coating to the spinel substrate. According to some embodiments, and as described in greater detail elsewhere herein, the physical and/or chemical properties of the glass coating are such that allow adhesion to the spinel substrate while preventing gaps (or blistering mechanisms) from forming during the glass coating process.

According to some embodiments, the term "semipolished" as used herein may refer to a substrate which has one surface that is polished. According to some embodiments, the term "semipolished as used herein may refer to a substrate which has one surface that is polished and an opposing surface that is unpolished. According to some embodiments, when coating a semipolished substrate using a glass coating, the glass coating is applied at least to the unpolished surface.

According to some embodiments, the article may include a plurality of coated spinel substrates which may be bonded together by the glass coating. According to some embodiments, at least a portion of the spinel substrates may be polycrystalline. According to some embodiments, all of the plurality of spinel substrates may be polycrystalline.

According to some embodiments, at least a portion of the spinel substrates may be unpolished. According to some embodiments, at least a portion of the spinel substrates of the plurality of coated spinel substrates may have varying polishing grades (or in other words, levels of polish).

According to some embodiments, the glass coating may cover at least a portion of one or more surfaces of the spinel substrate and/or at least a portion of the plurality of coated spinel substrates. According to some embodiments, the glass coating may substantially envelope the spinel substrate and/or at least a portion of the plurality of coated spinel substrates.

According to some embodiments, the glass coating may include any one or more of PbO, MgO, ZnO, Al2O3, SiO2, and TiO2, and any combination thereof. According to some embodiments, the glass coating may include any one or more of BaO, La2O3, and Bi2O3, or any combination thereof. According to some embodiments, the glass coating may include one or more alkali metal oxides.

According to some embodiments, the glass coating may include PbO in an amount of about 17.0-40.0% (mole percent). According to some embodiments, the glass coating may include PbO in an amount of about 20.0-30.0% (mole percent). According to some embodiments, the glass coating may include PbO in an amount of about 20.0-28.0% (mole percent). According to some embodiments, the glass coating may include PbO in an amount of about 25.0-26.0% (mole percent). According to some embodiments, the glass coating may include PbO in an amount of about 17%, 19%, 21%, 25%, 27%, 31%, %, 37%, or 40% (mole percent), including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the glass coating may include BaO, La2O3, Bi2O3, and/or any combination thereof, in an amount of about 0.01-1.3% (mole percent).

According to some embodiments, the glass coating may include BaO, La2O3, Bi2O3, and/or any combination thereof, in an amount of about 0.01-1.0% (mole percent).

According to some embodiments, the glass coating may include BaO, La2O3, Bi2O3, and/or any combination thereof, in an amount of about 0.01%, 0.04%, 0.09%, 0.13%, 0.20%, 0.28%, 0.35%, 0.55%, 0.60%, 0.70%, 0.85%, 0.95%, or 1.3% (mole percent), including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the glass coating may include MgO in an amount of about 0.05-10% (mole percent). According to some embodiments, the glass coating may include MgO in an amount of about 0.1-7.0% (mole percent). According to some embodiments, the glass coating may include MgO in an amount of about 5.5-6.5% (mole percent). According to some embodiments, the glass coating may include MgO in an amount of about 0.05%, 0.12%, 1.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.3%, 6.5%, 6.7%, 7%, 7.3%, 8%, 9%, or 10% (mole percent), including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the glass coating may include ZnO in an amount of about 0.05-10% (mole percent). According to some embodiments, the glass coating may include ZnO in an amount of about 0.1-7.0% (mole percent). According to some embodiments, the glass coating may include ZnO in an amount of about 5.5-6.5% (mole percent). According to some embodiments, the glass coating may include ZnO in an amount of about 0.05%, 0.12%, 1.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.3%, 6.5%, 6.7%, 7%, 7.3%, 8%, 9%, or 10% (mole percent), including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the glass coating may include Al2O3 in an amount of about 0.05-10% (mole percent). According to some embodiments, the glass coating may include Al2O3 in an amount of about 0.1-7.0% (mole percent). According to some embodiments, the glass coating may include Al2O3 in an amount of about 5.5-6.5% (mole percent). According to some embodiments, the glass coating may include Al2O3 in an amount of about 0.05%, 0.12%, 1.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.3%, 6.5%, 6.7%, 7%, 7.3%, 8%, 9%, or 10% (mole percent), including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the glass coating may include SiO2 in an amount of about 45-65% (mole percent). According to some embodiments, the glass coating may include SiO2 in an amount of about 50.0-57.0% (mole percent). According to some embodiments, the glass coating may include SiO2 in an amount of about 54.5­ 55.5% (mole percent). According to some embodiments, the glass coating may include SiO2 in an amount of about 45%, 47%, 50%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, or 65% (mole percent), including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the glass coating may include TiO2 in an amount of about 0.07-2% (mole percent). According to some embodiments, the glass coating may include TiO2 in an amount of about 0.1-1.5% (mole percent). According to some embodiments, the glass coating may include TiO2 in an amount of about 0.5-1.5% (mole percent). According to some embodiments, the glass coating may include TiO2 in an amount of about 0.07%, 0.1%, 0.12%, 0.15%, 0.25%, 0.35%, 0.4%, 0.5%, 0.55%, 0.65%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.35%, 1.5%, 1.65%, 1.85%, or 2% (mole percent), including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the glass coating may include between about 0% and 0.7% (mole percent) alkali metal oxides. According to some embodiments, the glass coating may include up to 0.7% (mole percent) alkali metal oxides. According to some embodiments, the glass coating may include up to 0.55% (mole percent) alkali metal oxides. According to some embodiments, the glass coating may include up to 0.5% (mole percent) alkali metal oxides. According to some embodiments, the glass coating may include up to 0.47%, up to 0.49%, up to 0.5%, up to 0.51%, up to 0.53%, up to 0.55%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the article of manufacture including glass coating and one or more spinel substrates may include one or more interfaces between the glass coating and one or more surfaces of the spinel substrates. According to some embodiments, the glass coating may be configured and/or composed of materials such that the one or more interfaces are devoid of gaps. According to some embodiments, the glass coating may be configured and/or composed of materials such that the one or more interfaces are devoid of blisters. According to some embodiments, the interface may be devoid of gaps due to the chemical properties of the glass coating. According to some embodiments, the interface may be devoid of gaps due to physical properties of the glass coating. For example, according to some embodiments, the glass coating may be configured to apply a compressing pressure onto the one or more spinel substrates.

According to some embodiments, the glass coating may have a smaller thermal expansion coefficient than a thermal expansion coefficient of the one or more spinel substrates. Advantageously, having a spinel substrate coated with a glass coating having a smaller thermal expansion coefficient than the spinel substrate therefore generates a compressing pressure, from the glass coating, onto the spinel substrate.

The thermal expansion coefficient of spinel is usually about 7.6×10-6 C-1.

Accordingly, in some embodiments, the glass coating includes a thermal expansion coefficient value below about 7.6×10-6 C-1. According to some embodiments, the glass coating includes a thermal expansion coefficient value sufficient to apply a compression force onto the spinel substrate that it is coated onto.

According to some embodiments, the glass coating includes a thermal expansion coefficient of between about 5.0×10-6 and 7.59×10-6 C-1. According to some embodiments, the glass coating includes a thermal expansion coefficient of between about .6×10-6 and 7.20×10-6 C-1. According to some embodiments, the glass coating includes a thermal expansion coefficient of between about 5.8×10-6 and 7.20×10-6 C-1. According to some embodiments, the glass coating includes a thermal expansion coefficient of about .0×10-6 C-1, 5.5×10-6 C-1, 5.8×10-6 C-1, 6.0×10-6 C-1, 6.6×10-6 C-1, 6.9×10-6 C-1, 7.0×10- 6, 7.1×10-6 C-1, or 7.2×10-6 C-1, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the glass coating may have a glass transition temperature of between about 540°C and 580°C. According to some embodiments, the glass coating may have a glass transition temperature of between about 545°C and 565°C.

According to some embodiments, the glass coating may have a glass transition temperature of between about 550°C and 570°C. According to some embodiments, the glass coating may have a glass transition temperature of about 540°C, 545°C, 547°C, 550°C, 553°C, 555°C, 557°C, 560°C, 563°C, 565°C, 567°C, or 570°C, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the glass coating may have a dilatometric softening temperature of between about 600°C and 620°C. According to some embodiments, the glass coating may have a dilatometric softening temperature of between about 600°C and 615°C. According to some embodiments, the glass coating may have a dilatometric softening temperature of between about 600°C and 610°C. According to some embodiments, the glass coating may have a dilatometric softening temperature of about 600°C, 601°C, 602°C, 603°C, 604°C, 605°C, 606°C, 607°C, 610°C, 615°C, or 620°C, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the article including the glass coating and the one or more spinel substrates may be transparent to transmission of light. According to some embodiments, the article including the glass coating and the one or more spinel substrates may be transparent to transmission of infrared light. According to some embodiments, the article including the glass coating and the one or more spinel substrates may be transparent to bands of light having wavelengths at least between 400nm and 4450nm. According to some embodiments, the article including the glass coating and the one or more spinel substrates may be transparent to bands of light having wavelengths at least between 400nm and 750nm. According to some embodiments, the article including the glass coating and the one or more spinel substrates may be transparent to bands of light having wavelengths at least between 750 and 4450nm. According to some embodiments, the article including the glass coating and the one or more spinel substrates may be transparent to bands of light having wavelengths of 400nm, 500nm, 650nm, 750nm, 900nm, 1000nm, 1500nm, 4444nm, 4450nm, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

The term "transparent to transmission of light" as used herein may refer to a transmission of light having of at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention. According to some embodiments, the article may have a transmission of above 80% for wavelengths above 400nm. According to some embodiments, the article may have a transmission of above 85% for wavelengths above 700nm. According to some embodiments, the article may have a transmission of above 85% for wavelengths above 1000nm. According to some embodiments, the article may have a transmission of above 90% for wavelengths above 700nm.

According to some embodiments, the index of refraction of the glass coating may be essentially similar to the index of refraction of the one or more spinel substrates, such that the index of refraction of the glass coating matches the index of refraction of the one or more spinel substrates. Advantageously, matching the index of refraction of the glass coating with the index of refraction of the spinel substrate enables the interface between the glass coating and the spinel substrates to be essentially invisible.

According to some embodiments, the index of refraction at least a portion of the one or more spinel substrates may be about between 1.712 and 1.736. According to some embodiments, the index of refraction at least a portion of the one or more spinel substrates may be about 1.71. Thus, according to some embodiments, the glass coating may have an index of refraction of between about 1.715 and 1.75. According to some embodiments, the glass coating may have an index of refraction of between about 1.718 and 1.73.

According to some embodiments, the glass coating may have an index of refraction of between about 1.715, 1.718, 1.721, 1.726, 1.73, 1.737, 1.74, or 1.75, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the article and/or glass coating may be resistant to corrosion. According to some embodiments, the article and/or glass coating may be resistant to corrosion at about 1atm, (i.e., atmospheric conditions). According to some embodiments, the glass coating may be configured to reduce and/or prevent general corrosion and/or erosion corrosion to the article.

Advantageously, the article may therefore be used in windows and/or armor type products, in which the transparency of a strong material is vital. Accordingly, in some embodiments, the article may be used in a transparent missile head. According to some embodiments, the article may be used for transparent armor windows.

Process For Producing a Glass Powder According to some embodiments, the glass coating may be produced by forming a glass powder. According to some embodiments, there is provided a process for producing a glass powder having the composition for the glass coating. According to some embodiments, there is provided a process for producing a glass powder which may be used in a process for producing the glass coating.

Reference is made to FIG. 1, which shows a flowchart of functional steps in a process for producing a glass powder having the composition for the glass coating, in accordance with some embodiments of the present invention.

According to some embodiments, at step 102, the process for producing a glass powder may include preparing a mixture of: MgO; ZnO; SiO2; TiO2; Al(OH)3; and any combination of PbO, Pb3O4 and lead bisilicate glass. According to some embodiments, the mixture may include any one or more of MgO, ZnO, SiO2, TiO2, Al(OH)3, PbO, Al2O3, Pb3O4, or any combination thereof. According to some embodiments, the mixture may include any one or more of BaO, La2O3, and Bi2O3, or any combination thereof.

According to some embodiments, the mixture may include one or more alkali metal oxides. According to some embodiments, the mixture may include between about 0% and 0.7% (mole percent) alkali metal oxides.

According to some embodiments, at step 104, the process may include melting the mixture to form a melt. According to some embodiments, at step 106, the process may include incubating the melt at a temperature between about 1200°C to 1500°C, thereby obtaining a molten composition. According to some embodiments, the process may include incubating the melt for a period of 0.5 to 2.5 hours. According to some embodiments, at step 108, the process may include pouring the molten composition into water to form a frit. According to some embodiments, at step 110, the process may include grinding the frit, thereby producing the glass powder.

According to some embodiments, preparing the mixture may include combining any one or more of the MgO, ZnO, SiO2, TiO2, Al(OH)3, PbO, Al2O3, Pb3O4, BaO, La2O3, Bi2O3, the one or more alkali metal oxides, or any combination thereof.

According to some embodiments, the preparing the mixture may include adding MgO in an amount of about 2.0-3.0 wt% (weight percent). According to some embodiments, the preparing the mixture may include adding MgO in an amount of about 2.2-2.7 wt%. According to some embodiments, the preparing the mixture may include adding MgO in an amount of about 2.0 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, or 3.0 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the preparing the mixture may include adding ZnO in an amount of about 3.5-5.5 wt% (weight percent). According to some embodiments, the preparing the mixture may include adding ZnO in an amount of about 4.0-5.0 wt%. According to some embodiments, the preparing the mixture may include adding ZnO in an amount of about 4.3-4.8 wt%. According to some embodiments, the preparing the mixture may include adding ZnO in an amount of about 3.5 wt%, 3.7 wt%, 4.0 wt%, 4.1 wt%, 4.3 wt%, 4.4 wt%, 4.5 wt%, 4.6 wt%, 4.7 wt%, 4.8 wt%, 4.9 wt%, 5.1 wt%, 5.3 wt%, 5.5 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the preparing the mixture may include adding SiO2 in an amount of about 20-40 wt% (weight percent). According to some embodiments, the preparing the mixture may include adding SiO2 in an amount of about 23-37 wt%. According to some embodiments, the preparing the mixture may include adding SiO2 in an amount of about 28-35 wt%. According to some embodiments, the preparing the mixture may include adding SiO2 in an amount of about 20 wt%, 23 wt%, wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 33 wt%, 35 wt%, 37 wt%, or 40 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the preparing the mixture may include adding TiO2 in an amount of about 0.1-1.5 wt% (weight percent). According to some embodiments, the preparing the mixture may include adding TiO2 in an amount of about 0.4-1.0 wt%. According to some embodiments, the preparing the mixture may include adding TiO2 in an amount of about 0.7-0.9 wt%. According to some embodiments, the preparing the mixture may include adding TiO2 in an amount of about 0.1 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.3 wt%, or 1.5 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the preparing the mixture may include adding Al(OH)3 in an amount of about 0.1-7 wt% (weight percent). According to some embodiments, the preparing the mixture may include adding Al(OH)3 in an amount of about 3-7 wt%. According to some embodiments, the preparing the mixture may include adding Al(OH)3 in an amount of about 4.5-6.7 wt%. According to some embodiments, the preparing the mixture may include adding Al(OH)3 in an amount of about 0.1 wt%, 0.7 wt%, 1.2 wt%, 2 wt%, 3 wt%, 3.5 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.3 wt%, 6.4 wt%, 6.5 wt%, 6.7 wt%, or 7 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the preparing the mixture may include adding PbO, Pb3O4, lead bisilicate glass, or any combination thereof. According to some embodiments, the lead bisilicate glass may include Hammond lead glass B15. According to some embodiments, the lead bisilicate glass and/or the Hammond lead glass B15 may be a source of any one or more of the PbO, SiO2, Al2O3 and TiO2 for the mixture.

According to some embodiments, the preparing the mixture may include adding PbO, Pb3O4, lead bisilicate glass, or any combination thereof, in an amount of about 40­ 90 wt% (weight percent). According to some embodiments, the preparing the mixture may include adding PbO, Pb3O4, lead bisilicate glass, or any combination thereof, in an amount of about 45-86 wt%. According to some embodiments, the preparing the mixture may include adding PbO, Pb3O4, lead bisilicate glass, or any combination thereof, in an amount of about 40 wt%, 45 wt%, 50 wt%, 55 wt%, 57 wt%, 60 wt%, 63 wt%, 67 wt%, 70 wt%, 72 wt%, 75 wt%, 77 wt%, 80 wt%, 81 wt%, 83 wt%, 85 wt%, 86 wt%, 87 wt%, or 90 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the preparing the mixture may include adding PbO in an amount of about 0.01-90 wt% (weight percent). According to some embodiments, the preparing the mixture may include adding PbO in an amount of about 0.01-5 wt%. According to some embodiments, the preparing the mixture may include adding PbO in an amount of about 0.01-35 wt%. According to some embodiments, the preparing the mixture may include adding PbO in an amount of about 0.01 wt%, 0.5 wt%,5 wt%, 15 wt%, 25 wt%, 35 wt%, 45 wt%, 55 wt%, 65 wt%, 75 wt%, 85 wt%, or 90 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the preparing the mixture may include adding Pb3O4 in an amount of about 0.01-90 wt% (weight percent). According to some embodiments, the preparing the mixture may include adding Pb3O4 in an amount of about 0.01-35 wt%. According to some embodiments, the preparing the mixture may include adding Pb3O4 in an amount of about 0.01-15 wt%. According to some embodiments, the preparing the mixture may include adding Pb3O4 in an amount of about 0.01 wt%, 0.5 wt%, 5 wt%, 15 wt%, 25 wt%, 35 wt%, 45 wt%, 55 wt%, 65 wt%, 75 wt%, 85 wt%, or 90 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the preparing the mixture may include adding lead bisilicate glass in an amount of about 0.01-90 wt% (weight percent). According to some embodiments, the preparing the mixture may include adding lead bisilicate glass in an amount of about 5-60 wt%. According to some embodiments, the preparing the mixture may include adding lead bisilicate glass in an amount of about 20-90 wt%.

According to some embodiments, the preparing the mixture may include adding lead bisilicate glass in an amount of about 0.01 wt%, 5 wt%, 15 wt%, 25 wt%, 35 wt%, 45 wt%, 55 wt%, 65 wt%, 75 wt%, 85 wt%, or 90 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the lead bisilicate glass may include about 50­ 75 wt% PbO. According to some embodiments, the lead bisilicate glass may include about 50-70 wt% PbO. According to some embodiments, the lead bisilicate glass may include about 50-65 wt% PbO. According to some embodiments, the lead bisilicate glass may include about 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, or 75 wt%, PbO, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the lead bisilicate glass may include about 25­ 40 wt% SiO2. According to some embodiments, the lead bisilicate glass may include about 30-37 wt% SiO2. According to some embodiments, the lead bisilicate glass may include about 25 wt%, 30 wt%, 33 wt%, 35 wt%, 37 wt%, or 40 wt% SiO2, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the lead bisilicate glass may include about 0.5­ 3.5 wt% Al2O3. According to some embodiments, the lead bisilicate glass may include about 1-3 wt% Al2O3. According to some embodiments, the lead bisilicate glass may include about 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, or 3.5 wt% Al2O3, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the lead bisilicate glass may include about 0.2­ 3.0 wt% TiO2. According to some embodiments, the lead bisilicate glass may include about 0.5-3.0 wt% TiO2. According to some embodiments, the lead bisilicate glass may include about 0.2 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, or 3.0 wt%, TiO2, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the process may include mixing the mixture.

According to some embodiments, the process may include placing the mixture in a crucible for heating thereof. According to some embodiments, the crucible may include a platinum crucible. According to some embodiments, the process may include heating the mixture. According to some embodiments, the process may include heating the mixture using a furnace, such as, for example, a box furnace.

According to some embodiments, at step 104, the process may include melting the mixture to form a melt. According to some embodiments, melting the mixture may include heating the mixture and/or the furnace to at least about 1200°C. According to some embodiments, the process may include heating the mixture and/or the furnace to at least about 1300°C. According to some embodiments, the process may include heating the mixture and/or the furnace to at least about 1350°C. According to some embodiments, the process may include heating the mixture and/or the furnace to at least about 1500°C.

According to some embodiments, the process may include heating the mixture and/or the furnace to at least about 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, or 1550°C, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, at step 106, the process may include incubating the melt at a temperature between about 1250°C to 1500°C, thereby obtaining a molten composition. According to some embodiments, the process may include incubating the melt at a temperature of at least about 1200°C. According to some embodiments, the process may include incubating the melt at a temperature of at least 1350°C. According to some embodiments, the process may include incubating the melt at a temperature of at least about 1500°C. According to some embodiments, the process may include incubating the melt at a temperature of at least about 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, or 1550°C, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the process may include incubating the melt for a period of about 0.5 to 3 hours. According to some embodiments, the process may include incubating the melt for a period of about 1 to 2.5 hours. According to some embodiments, the process may include incubating the melt for a period of about 0.5 to 2.5 hours. According to some embodiments, the process may include incubating the melt for a period of at least about 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 2.25, or 2.5 hours, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the process may include mixing the melt during the heating of the furnace and/or the mixture. According to some embodiments, the process may include mixing the melt during the incubating of the melt. According to some embodiments, mixing the melt may include swirling the melt within the crucible.

According to some embodiments, at step 108, the process may include pouring the molten composition into water to form a frit. According to some embodiments, the water may include tap water. According to some embodiments, the process may include pouring the molten composition into water, wherein the water is at a temperature of between about 20°C to 30°C, for example, such as, at room temperature (about 25°C).

According to some embodiments, the process may include pouring the molten composition into water, wherein the water is at a temperature of between about 10°C to 40°C.

According to some embodiments, the process may include collecting the frit.

According to some embodiments, the process may include drying the frit. According to some embodiments, the process may include drying the frit using an oven. According to some embodiments, the process may include drying the frit in an oven at a temperature of between about 100°C to 200°C. According to some embodiments, the process may include drying the frit in an oven at a temperature of at least about 100°C, 150°C, or 200°C, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, at step 110, the process may include grinding the frit, thereby producing a glass powder. According to some embodiments, griding the frit may include ball milling the frit. According to some embodiments, the process may include grinding the frit with deionized water. According to some embodiments, the process may include grinding the frit with deionized water, wherein the weight/mass ratio between the frit and the deionized water is about 1:1. According to some embodiments, the process may include grinding the frit with deionized water, wherein the weight/mass ratio between the frit and the deionized water is between 2:1 and 1:2.

According to some embodiments, the process may include grinding the frit with isopropanol. According to some embodiments, the process may include grinding the frit with isopropanol, wherein the mass ratio between the frit and the isopropanol is about 1:0.7854. According to some embodiments, the process may include grinding the frit with isopropanol, wherein the ratio between the frit and the isopropanol is between about 2:1 to 1:2.

According to some embodiments, the process may include grinding the frit for a period of between about 10 and 25 hours. According to some embodiments, the process may include grinding the frit for a period of between about 13 and 21 hours. According to some embodiments, the process may include grinding the frit for a period of at least , 13, 15, 18, or 21 hours, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the process may include grinding the frit to a powder or slip. According to some embodiments, the size of at least a portion of the particles within the powder or slip may be below about 50 µm. According to some embodiments, the size of at least a portion of the particles within the powder or slip may be below about 45 µm. According to some embodiments, the size of at least a portion of the particles within the powder or slip may be below about 44 µm.

According to some embodiments, the process may include screening the powder or slip through a mesh screen. According to some embodiments, the mesh screen may be a standard mesh 325 screen. According to some embodiments, the mesh screen may be a standard mesh 270 screen. According to some embodiments, the mesh screen may be a standard mesh 400 screen.

It is to be understood that the screening includes but is not limited to a powder and/or a slip.

According to some embodiments, the process may include drying the screened powder or slip, thereby forming the glass powder. According to some embodiments, the process may include drying the screened powder or slip using an oven. According to some embodiments, the process may include drying the screened powder or slip in an oven, wherein the oven and/or the powder or slip are at a temperature of between about 100°C to 200°C. According to some embodiments, the process may include drying the screened powder or slip in an oven, wherein the oven and/or the powder or slip are at a temperature of between about 130°C to 180°C. According to some embodiments, the process may include drying the screened powder or slip in an oven, wherein the oven and/or the powder or slip are at a temperature of between about 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, or 200°C, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

Paste Composition for Coating a Spinel Substrate According to some embodiments, there is provided a paste composition for coating of a spinel substrate. According to some embodiments, the paste composition may include the glass powder as described hereinabove. According to some embodiments, the paste composition may include the glass powder having the composition for the glass coating as described hereinabove. According to some embodiments, the paste composition may include the glass powder as formed using the process for producing a glass powder having the composition for the glass coating, as described in greater detail elsewhere herein.

According to some embodiments, the paste composition may include the glass powder in an amount of between about 60 wt% to 80 wt% (weight percent). According to some embodiments, the paste composition may include the glass powder in an amount of between about 65 wt% to 75 wt%. According to some embodiments, the paste composition may include the glass powder in an amount of about 60 wt%, 65 wt%, 70 wt%, 75 wt%, or 80 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, weight percent (or wt%) as used herein may refer to the percent of weight of the glass powder out of the total weight of the paste.

According to some embodiments, the paste composition may include a medium.

According to some embodiments, the paste composition may include the medium in an amount of between about 10 wt% to 30 wt% (weight percent). According to some embodiments, the paste composition may include the medium in an amount of between about 15 wt% to 25 wt%. According to some embodiments, the paste composition may include the medium in an amount of about 10 wt%, 15 wt%, 20 wt%, 10 wt%, 10 wt%, wt%, 10 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, weight percent (or wt%) as used herein may refer to the percent of weight of the medium out of the total weight of the paste.

According to some embodiments, the medium may include a solution of ethyl cellulose. According to some embodiments, the medium may include a solution of one or more polymers, such as methyl cellulose and hydroxyethyl cellulose. According to some embodiments, the viscosity of the medium may be controlled by adding different grades of the one or more polymers. According to some embodiments, the viscosity of the medium may be controlled by adding different grades of ethyl cellulose. According to some embodiments, the viscosity of the medium may be controlled by the grade of ethyl cellulose, for example, by using a grade 100 of DOW chemicals. According to some embodiments, using the grades of DOW chemicals, the polymers and/or ethyl cellulose having a grades value of lower than 100 may result in a lower viscosity of the medium.

According to some embodiments, using the grades of DOW chemicals, the polymers and/or ethyl cellulose having a grade value larger than 100 may result in a higher viscosity of the medium.

According to some embodiments, the medium may include ethyl cellulose in an amount of between about 1.0 wt% to 20 wt% (weight percent). According to some embodiments, the medium may include ethyl cellulose in an amount of between about .0 wt% to 15 wt%. According to some embodiments, the medium may include ethyl cellulose in an amount of about 1.0 wt%, 2.0 wt%, 5.0 wt%, 7.0 wt%, 10 wt%, 12 wt%, wt%, 17 wt%, or 20 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, weight percent (or wt%) as used herein may refer to the percent of weight of the ethyl cellulose out of the total weight of the medium.

According to some embodiments, the medium may include terpineol. According to some embodiments, the medium may include terpineol in an amount of between about wt% to 55 wt% (weight percent). According to some embodiments, the medium may include terpineol in an amount of between about 40 wt% to 50 wt%. According to some embodiments, the medium may include terpineol in an amount of about 30 wt%, 35 wt%, 40 wt%, 43 wt%, 45 wt%, 47 wt%, 50 wt%, or 55 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, weight percent (or wt%) as used herein may refer to the percent of weight of the terpineol out of the total weight of the medium.

According to some embodiments, the medium may include dibutylcarbitol.

According to some embodiments, the medium may include dibutylcarbitol in an amount of between about 30 wt% to 55 wt% (weight percent). According to some embodiments, the medium may include dibutylcarbitol in an amount of between about 40 wt% to 50 wt%. According to some embodiments, the medium may include dibutylcarbitol in an amount of about 30 wt%, 35 wt%, 40 wt%, 43 wt%, 45 wt%, 47 wt%, 50 wt%, or 55 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, weight percent (or wt%) as used herein may refer to the percent of weight of the dibutylcarbitol out of the total weight of the medium.

According to some embodiments, the ratio between the weight percent of terpineol to dibutylcarbitol in the medium may be about 1:1. According to some embodiments, the ratio between the weight percent of terpineol to dibutylcarbitol in the medium may be about 3:4, 2:3, 1:2, 1:1, 2:1, 3:2, or 4:3, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the ratio between the weight percent of terpineol to ethyl cellulose in the medium may be between about 1:4 to 1:5. According to some embodiments, the ratio between the weight percent of terpineol to ethyl cellulose in the medium may be about 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the ratio between the weight percent of dibutylcarbitol to ethyl cellulose in the medium may be between about 1:4 to 1:5.

According to some embodiments, the ratio between the weight percent of dibutylcarbitol to ethyl cellulose in the medium may be about 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the paste composition may include terpineol.

According to some embodiments, the paste composition may include terpineol in an amount of between about 1.0 wt% to 10.0 wt% (weight percent). According to some embodiments, the paste composition may include terpineol in an amount of between about 2.0 wt% to 8.0 wt%. According to some embodiments, the paste composition may include terpineol in an amount of between about 3.5 wt% to 6.5 wt%. According to some embodiments, the paste composition may include terpineol in an amount of about 1.0 wt%, 2.0 wt%, 3.0 wt%, 3.5 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, 5.5 wt%, 6.0 wt%, 7.0 wt%, 8.0 wt%, or 10.0 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, weight percent (or wt%) as used herein may refer to the percent of weight of the terpineol out of the total weight of the paste composition.

According to some embodiments, the paste composition may include dibutylcarbitol. According to some embodiments, the paste composition may include dibutylcarbitol in an amount of between about 1.0 wt% to 10.0 wt% (weight percent).

According to some embodiments, the paste composition may include dibutylcarbitol in an amount of between about 2.0 wt% to 8.0 wt%. According to some embodiments, the paste composition may include dibutylcarbitol in an amount of between about 3.5 wt% to 6.5 wt%. According to some embodiments, the paste composition may include dibutylcarbitol in an amount of about 1.0 wt%, 2.0 wt%, 3.0 wt%, 3.5 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, 5.5 wt%, 6.0 wt%, 7.0 wt%, 8.0 wt%, or 10.0 wt%, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, weight percent (also referred to herein as wt%) as used herein may refer to the percent of weight of the dibutylcarbitol out of the total weight of the paste composition.

According to some embodiments, the ratio between the weight percent of terpineol to dibutylcarbitol in the paste composition may be about 1:1. According to some embodiments, the ratio between the weight percent of terpineol to dibutylcarbitol in the paste composition may be about 3:4, 2:3, 1:2, 1:1, 2:1, 3:2, or 4:3, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, there is provided a process for preparing the paste composition. According to some embodiments, the process may include mixing any two or more of the glass powder, the medium, the terpineol, and the dibutylcarbitol, or any combination thereof. According to some embodiments, the process may include grinding any two or more of the glass powder, the medium, the terpineol, and the dibutylcarbitol, or any combination thereof, thereby forming the paste composition.

According to some embodiments, the grinding may include using a pestle and mortar.

According to some embodiments, the griding may include a using a Muller, such as, a glass Muller. According to some embodiments, the grinding may include using a three- roll mill.

Process for Coating a Spinel Substrate According to some embodiments, there is provided a process for coating a spinel substrate with a glass composition. According to some embodiments, the process for coating a spinel substrate with a glass composition is configured to produce an article including a glass-coated spinel substrate, such as the article described in greater detail elsewhere herein.

Advantageously, producing a glass-coated spinel substrate, in which the spinel substrate may be unpolished, may eliminate the expensive polishing process that is commonly required to convert unpolished spinel to transparent spinel.

According to some embodiments, the process for coating a spinel substrate with a glass composition may include at least 3 ramp segments, wherein each ramp segment includes heating and/or cooling. According to some embodiments, the process for coating a spinel substrate with a glass composition may include at least 4 ramp segments, wherein each ramp segment includes heating and/or cooling. According to some embodiments, the process for coating a spinel substrate with a glass composition may include at least 5 ramp segments, wherein each ramp segment includes heating and/or cooling.

According to some embodiments, the process for coating a spinel substrate with a glass composition may include at least 3 dwell segments, wherein each dwell segment includes maintaining the temperature essentially constant. According to some embodiments, the process for coating a spinel substrate with a glass composition may include at least 4 dwell segments, wherein each dwell segment includes maintaining the temperature essentially constant. According to some embodiments, the process for coating a spinel substrate with a glass composition may include at least 5 dwell segments, wherein each dwell segment includes maintaining the temperature essentially constant.

According to some embodiments, the process may include firing the glass-coated spinel substrate. According to some embodiments, the process may include firing two or more glass-coated surfaces of the glass-coated spinel substrate. According to some embodiments, the process may include firing the two or more glass-coated surfaces sequentially, or in other words, firing the two or more surfaces at individual heat treatments. According to some embodiments, the process may include firing the two or more surfaces at at least partially overlapping heat treatments. According to some embodiments, the process may include co-firing the two or more glass-coated surfaces, or in other words, firing the two or more surfaces at the same time or during the same heat treatment process.

Reference is made to FIG. 2, which shows a flowchart of functional steps in a process for coating a spinel substrate with a glass composition, in accordance with some embodiments of the present invention.

According to some embodiments, at step 202, the process may include applying a glass paste to a spinel substance, thereby forming a paste-coated spinel substrate.

According to some embodiments, at step 204, the process may include heating, at a first heating ramp, the paste-coated spinel substrate to a first temperature of about 350°C.

According to some embodiments, at step 206, the process may include dwelling at the first temperature. According to some embodiments, at step 208, the process may include heating, at a second heating ramp, the paste-coated spinel substrate to a second temperature of about 500°C. According to some embodiments, at step 210, the process may include dwelling at the second temperature. According to some embodiments, at step 212, the process may include heating, at a third heating ramp, the paste-coated spinel substrate to a third temperature of about 1100°C. According to some embodiments, at step 214, the process may include dwelling at the third temperature. According to some embodiments, at step 216, the process may include cooling the glass-coated spinel substrate to a fourth temperature of about 560°C. According to some embodiments, at step 218, the process may include dwelling at the fourth temperature. According to some embodiments, at step 220, the process may include cooling the glass-coated spinel substrate to about 25°C.

According to some embodiments, at step 202, the process may include applying a glass paste to a spinel substance, thereby forming a paste-coated spinel substrate.

According to some embodiments, the glass paste includes the glass composition as described in greater detail elsewhere herein. According to some embodiments, applying the glass paste to the spinel substrate may include layering the glass paste (or the paste composition as described in greater detail elsewhere herein) to one or more spinel substrates. According to some embodiments, the one or more spinel substrates may be unpolished.

According to some embodiments, at step 204, the process may include heating, at a first heating ramp, the paste-coated spinel substrate to a first temperature. According to some embodiments, the first temperature may be about 350°C. According to some embodiments, the first temperature may be between about 300°C to 400°C.

According to some embodiments, the first heating ramp may include a slope of about 2-5°C/min. According to some embodiments, the first heating ramp may include a slope of about 1-8°C/min. According to some embodiments, the first heating ramp may include a slope of about 1°C/min, 3°C/min¸ or 5°C/min, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, at step 206, the process may include dwelling at the first temperature. According to some embodiments, the process may include dwelling at a temperature that is no more than 25°C higher or lower than the first temperature. According to some embodiments, the process may include dwelling at a temperature that is no more than 50°C higher or lower than the first temperature.

According to some embodiments, the process may include dwelling at the first temperature for between 1 to 3 hours. According to some embodiments, the process may include dwelling at the first temperature for between 1.5 to 2.5 hours. According to some embodiments, the process may include dwelling at the first temperature for between 1, 1.5, 2, 2.5, or 3 hours, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the dwelling at the first temperature may be at a temperature and/or a duration sufficient for evaporating one or more solvents within the glass paste. According to some embodiments, the dwelling at the first temperature may be at a temperature and/or a duration sufficient for decomposing and/or pyrolyzing of most of polymers within the glass paste.

According to some embodiments, at step 208, the process may include heating, at a second heating ramp, the paste-coated spinel substrate to a second temperature.

According to some embodiments, the second temperature may be about of about 500°C.

According to some embodiments, the second temperature may be between about 400°C to 600°C.

According to some embodiments, the second heating ramp may include a slope of about 0.5-2°C/min. According to some embodiments, the second heating ramp may include a slope of about 0.2-3°C/min. According to some embodiments, the second heating ramp may include a slope of about 0.2°C/min, 0.5°C/min, 0.7°C/min, 1°C/min, 2°C/min, or 3°C/min, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, at step 210, the process may include dwelling at the second temperature. According to some embodiments, the process may include dwelling at a temperature that is no more than 25°C higher or lower than the second temperature. According to some embodiments, the process may include dwelling at a temperature that is no more than 50°C higher or lower than the second temperature.

According to some embodiments, the process may include dwelling at the second temperature for between 0.1 to 0.5 hours. According to some embodiments, the process may include dwelling at the second temperature for between 0.1 to 1 hours. According to some embodiments, the process may include dwelling at the second temperature for between 0.1, 0.2, 0.3, 0.5, or 1 hours, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the dwelling at the second temperature may be at a temperature and/or a duration sufficient for evaporating and/or decomposing all, or most, of organic materials within the glass paste.

According to some embodiments, at step 212, the process may include heating, at a third heating ramp, the paste-coated spinel substrate to a third temperature. According to some embodiments, the third temperature may be about 1100°C. According to some embodiments, the process may include heating, at a third heating ramp, the paste-coated spinel substrate to a third temperature. According to some embodiments, the third temperature may be about 1100°C, thereby forming a glass-coated spinel substrate.

According to some embodiments, the third temperature may be between about 950°C to 1250°C. According to some embodiments, the third temperature may be between about 1000°C to 1200°C.

According to some embodiments, the third heating ramp may include a slope of about 15-25°C/min. According to some embodiments, the third heating ramp may include a slope of about 17-23°C/min. According to some embodiments, the third heating ramp may include a slope of about 15°C/min, 17°C/min, 20°C/min, 21°C/min, 23°C/min, or °C/min, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, at step 214, the process may include dwelling at the third temperature. According to some embodiments, the process may include dwelling at the third temperature, thereby forming a glass-coated spinel substrate.

According to some embodiments, the process may include dwelling at a temperature that is no more than 25°C higher or lower than the third temperature. According to some embodiments, the process may include dwelling at a temperature that is no more than 50°C higher or lower than the third temperature.

According to some embodiments, the process may include dwelling at the third temperature for between 0.2 to 1 hours. According to some embodiments, the process may include dwelling at the third temperature for between 0.3 to 0.7 hours. According to some embodiments, the process may include dwelling at the third temperature for between 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 1 hours, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the dwelling at the third temperature may be at a temperature and/or a duration sufficient for fully melting the paste-coating into a glassy transparent film, or in other words, a glass-coating on the spinel substrate.

According to some embodiments, at step 216, the process may include cooling the glass-coated spinel substrate to a fourth temperature of about 560°C. According to some embodiments, cooling the glass-coated spinel substrate may include at least two cooling ramps and at least one dwelling stage therebetween.

According to some embodiments, the dwelling stage may include dwelling at the fourth temperature. According to some embodiments, at step 218, the process may include dwelling at the fourth temperature. According to some embodiments, the dwelling at the fourth temperature may be sufficient for annealing the coat of glass of the glass- coated spinel substrate.

According to some embodiments, the fourth temperature is about 560°C.

According to some embodiments, the fourth temperature is between about 540°C to 580°C. According to some embodiments, the fourth temperature is about 540°C, 550°C, 560°C, 570°C, or 580°C, including any value and range therebetween. Each possibility represents a separate embodiment of the invention. According to some embodiments, the process may include cooling the glass-coated spinel substrate to about 25°C. According to some embodiments, the process may include cooling the glass-coated spinel substrate to between about 15°C to 35°C.

According to some embodiments, at least one of the cooling ramps may have a slope of about 15-25°C/min. According to some embodiments, at least one of the cooling ramps may have a slope of about 10-30°C/min. According to some embodiments, at least one of the cooling ramps may have a slope of about 10°C/min, 15°C/min, 20°C/min, 25°C/min, or 30°C/min, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, process may include dwelling at the fourth temperature between two cooling ramps. According to some embodiments, the predetermined temperature is sufficient for annealing a coat of the glass-coated spinel substrate.

According to some embodiments, the process may include dwelling, at the dwelling stage and/or at the fourth temperature, for a period of between about 0.7-3.5 hours. According to some embodiments, the process may include dwelling, at the dwelling stage and/or at the fourth temperature, for a period of between about 1 to 3 hours.

According to some embodiments, the process may include dwelling, at the dwelling stage and/or at the fourth temperature, for a period of about 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.4, 1.6, 2, 2.5, 2.9, 3, or 3.5 hours, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

Process for Bonding Two or More Spinel Substrates According to some embodiments there is provided a process for bonding two or more glass-coated spinel substrates. According to some embodiments, the two or more glass-coated spinel substrates may be one or more products of the method for coating a spinel substrate with a glass composition, as described in greater detail hereinabove.

Advantageously, bonding of two or more spinel substrates may enable fabrication of large windows using a plurality of (smaller) spinel substrates.

Reference is made to FIG. 3, which shows a flowchart of functional steps in a process for bonding two or more glass-coated spinel substrates, in accordance with some embodiments of the present invention.

According to some embodiments, at step 302, the process may include placing two or more glass-coated spinel substrates in contact. According to some embodiments, at step 304, the process may include heating, at a first heating ramp, the glass-coated spinel substrates to a first dwelling temperature of about 1100°C. According to some embodiments, at step 306, the process may include dwelling at the first temperature.

According to some embodiments, at step 308, the process may include cooling, at a first cooling ramp, the glass-coated spinel substrates to a second dwelling temperature of about 560°C. According to some embodiments, at step 310, the process may include dwelling at the second temperature. According to some embodiments, at step 312, the process may include cooling, at a second heating ramp, the glass-coated spinel substrates to about °C.

According to some embodiments, at step 302, the process may include placing two or more glass-coated spinel substrates in contact. According to some embodiments, placing two or more glass-coated spinel substrates in contact may include positioning two or more glass-coated spinel substrates such that at least a portion of two or more surfaces of the two or more glass-coated spinel substrates are abutting.

According to some embodiments, at step 304, the process may include heating, at a first heating ramp, the glass-coated spinel substrates to a first dwelling temperature.

According to some embodiments, the first dwelling temperature may be about 1100°C.

According to some embodiments, the first dwelling temperature may be between about 1000°C to 1200°C. According to some embodiments, the predetermined temperature is about 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the first heating ramp may include a slope of about 12-26°C/min. According to some embodiments, the first heating ramp may have a slope of about 10-30°C/min. According to some embodiments, the first heating ramp may have a slope of about 10°C/min, 12°C/min, 15°C/min, 20°C/min, 25°C/min, or 30°C/min, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, at step 306, the process may include dwelling at the first dwelling temperature.

According to some embodiments, the process may include dwelling at the first dwelling temperature for between 0.2 to 1 hours. According to some embodiments, the process may include dwelling at the first dwelling temperature for between 0.3 to 0.7 hours. According to some embodiments, the process may include dwelling at the first dwelling temperature for between 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 1 hours, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, at step 308, the process may include cooling, at a first cooling ramp, the glass-coated spinel substrates to a second dwelling temperature.

According to some embodiments, the second dwelling temperature may be about 560°C.

According to some embodiments, the second dwelling temperature may be between about 540°C to 580°C. According to some embodiments, the second dwelling temperature may be about 540°C, 550°C, 560°C, 570°C, or 580°C, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the first cooling ramp includes a slope of about 12-26°C/min. According to some embodiments, the first cooling ramp may have a slope of about 10-30°C/min. According to some embodiments, the first cooling ramp may have a slope of about 10°C/min, 12°C/min, 15°C/min, 20°C/min, 25°C/min, or 30°C/min, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, at step 310, the process may include dwelling at the second swelling temperature. According to some embodiments, the process may include dwelling at the first dwelling temperature for between 0.6 to 1.5 hours. According to some embodiments, the process may include dwelling at the first dwelling temperature for between 0.8 to 1.2 hours. According to some embodiments, the process may include dwelling at the first dwelling temperature for between 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, or 1.5 hours, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the second dwelling temperature and/or period may be sufficient for annealing at least a portion of a glass surrounding the coated spinel substrates.

According to some embodiments, at step 312, the process may include cooling, at a second heating ramp, the glass-coated spinel substrates to about 25°C. According to some embodiments, the process may include cooling, at a second heating ramp, the glass- coated spinel substrates to about 15°C to 35°C. According to some embodiments, the process may include cooling, at a second heating ramp, the glass-coated spinel substrates to about 15°C, 20°C, 25°C, 30°C, or 35°C, including any value and range therebetween.

Each possibility represents a separate embodiment of the invention.

According to some embodiments, the second cooling ramp includes a slope of about 12-26°C/min. According to some embodiments, the second cooling ramp may have a slope of about 10-30°C/min. According to some embodiments, the second cooling ramp may have a slope of about 10°C/min, 12°C/min, 15°C/min, 20°C/min, 25°C/min, or °C/min, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the process may include dwelling, at about °C. According to some embodiments, the process may include dwelling for at least about 1.5 hours. According to some embodiments, the process may include dwelling for at least about 2 hours. According to some embodiments, the process may include dwelling for at least about 1.5, 2, or 2.5 hours, including any value and range therebetween. Each possibility represents a separate embodiment of the invention.

In the description and claims of the application, the words "include" and "have", and forms thereof, are not limited to members in a list with which the words may be associated.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In case of conflict, the patent specification, including definitions, governs. As used herein, the indefinite articles "a" and "an" mean "at least one" or "one or more" unless the context clearly dictates otherwise.

It is appreciated that certain features of the disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the disclosure. No feature described in the context of an embodiment is to be considered an essential feature of that embodiment, unless explicitly specified as such.

Although stages of methods according to some embodiments may be described in a specific sequence, methods of the disclosure may include some or all of the described stages carried out in a different order. A method of the disclosure may include a few of the stages described or all of the stages described. No particular stage in a disclosed method is to be considered an essential stage of that method, unless explicitly specified as such.

Although the disclosure is described in conjunction with specific embodiments thereof, it is evident that numerous alternatives, modifications and variations that are apparent to those skilled in the art may exist. Accordingly, the disclosure embraces all such alternatives, modifications and variations that fall within the scope of the appended claims. It is to be understood that the disclosure is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth herein. Other embodiments may be practiced, and an embodiment may be carried out in various ways.

The phraseology and terminology employed herein are for descriptive purpose and should not be regarded as limiting. Citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the disclosure. Section headings are used herein to ease understanding of the specification and should not be construed as necessarily limiting.

EXAMPLES Example 1.

In exemplary procedures, a glass composition for coating a spinel substrate was produced.

The composition of batch 1 in grams and in weight percent is presented in Table 1 below.

Table 1: Glass composition for batch 1 Ingredient weight(grams) Weight percent(wt.%) MgO 9.069 2.25 ZnO 18,309 4.54 SiO2 8.526 2.11 TiO2 -- -- Al(OH)3 24.663 6.11 PbO 2.0 0.5 Hammond lead glass 340.827 84.49 B15 In this example, the use of Hammond lead glass B15 as a source of PbO, SiO2, Al2O3 and TiO2 is presented. The Hammond lead glass B15 in this example, in weight percent, included: 34% SiO2; 63% PbO; 2% Al2O3; and 1% TiO2.

Example 2.

In exemplary procedures, a glass composition for coating a spinel substrate was produced.

The composition of batch 2 in mole percent and in weight percent is presented in Table 2 below.

Table 2: Glass composition for batch 2 Ingredient Mole percent Weight percent(wt.%) PbO 25.83 54.89 MgO 5.98 2.30 ZnO 5.98 4.63 Al2O3 5.98 5.81 SiO2 55.08 31.51 TiO2 1.13 0.86 Example 3.

In exemplary procedures, a glass composition for coating a spinel substrate was produced.

The glass transition temperature (Tg), dilatometric softening temperature (Td), coefficient of thermal expansion (CTE), and index of refraction (Nd) of the glass compositions is presented in Table 3 below.

Table 3: Properties for glass compositions of batches 1, 2, 3, and 4 Glass Code Tg (C°) Td(C°) Nd CTE100-300C (10-6) Batch 1 568 605 7.02 1.727 Batch 2 553 602 6.1 1.727 Batch 3 565 606 5.89 1.719 Batch 4 564 610 6.0 1.728 Example 4.

Reference is made to FIG. 4, which shows a graph depicting a comparison of light transmittance of an exemplary polished spinel substrate (JH-052-33A) and a glass-coated semipolished (JH-052-31A) spinel substrate in the ultraviolet (UV)-visible (VIS) range, in accordance with some embodiments of the present invention, and to FIG. 5, which shows a graph depicting a comparison of light transmittance of an exemplary polished spinel substrate (JH-052-33A) and a glass-coated semipolished spinel substrate (JH-052- 31A) in the infrared (IR) range, in accordance with some embodiments of the present invention.

In an exemplary procedure, a semi polished spinel substrate was coated using a glass paste including the glass composition as described hereinabove. According to some embodiments, a semipolished spinel substrate may include a substrate which has one large surface polished and the opposite large surface unpolished, wherein the glass coating is applied to the unpolished face. Accordingly, the semi-polished spinel substrate included at least one polished surface and at least one unpolished surface. The unpolished surface was ground, coated using the glass paste, and fired. The glass coating was applied only to the at least one unpolished surface of the spinel substrate.

The light transmittance of the first article, including the glass-coated semi polished spinel substrate, labeled as JH-052-31A in the graph of FIG. 4, shows a light transmittance of above 70% for wavelengths over 375nm, a light transmittance of above 80% for wavelengths over 419nm, a light transmittance of above 85% for wavelengths over 563nm.

A second spinel substrate included a polished spinel substrate without a glass coating and was labeled as JH-052-33A in the graph of FIG. 4. Accordingly, no glass coating was used in the polished spinel substrate labeled JH-052-33A.

The light transmittance of the second article, including the polished spinel substrate labeled as JH-052-33A, in the graph of FIG. 4, shows that polished spinel with no glass coating has transmittance above 200nm. Accordingly, it shows that glass coated spinel does not transmit below 300nm, which may be due to the absorption of Pb+2.

In the comparison as depicted by FIG. 4 and FIG. 5, the light transmittance of the second article is higher than the light transmittance of the first article, up to a wavelength of 391nm, and above 391nm, the light transmittance of the first article is higher than the light transmittance of the second article.

Example 5.

Reference is made to FIG. 6, which shows a graph depicting a comparison of light transmittance of two glass bonded spinel substrates(JH-052-36) and two polished spinel substrates taped together at the periphery with cellotape (JH-052-33B), in accordance with some embodiments of the present invention, FIG. 7, which shows a graph depicting a comparison of FTIR of two glass bonded spinel substrates (JH-052-36) and two polished spinel substrates taped together at the periphery with cellotape (JH-052-33B), in accordance with some embodiments of the present invention, and to FIG. 8, which shows a graph depicting a comparison of light transmittance of a polished spinel substrate (JH- 052-33A), two polished spinel substrates taped together at the periphery with cellotape (JH-052-33B) and two glass bonded spinel substrates (JH-052-36), in accordance with some embodiments of the present invention.

In an exemplary procedure, three articles including spinel substrates were compared.

The first article included one polished spinel substrate having a width of about 0.8cm (referred to herein as JH-052-33A). The first article JH-052-33A was made from one polished spinel substrate.

The second article included two polished spinel substrates taped together at the circumference and having a total width of about 1.6cm (referend to herein as JH-052- 33B). The second article JH-052-33B was made from two polished spinel substrates which were taped at the circumference, and has a total thickness about 1.6 cm. The article JH-052-33B has 4 reflections (two from each substrate).

The third article included two spinel substrates bonded by glass. The third article (referred to herein as JH-052-36) is made by bonding two semipolished spinel substrates by one layer of glass coating. First, one semipolished spinel substrate was coated by glass paste and heat treated to obtain glass coated semipolished spinel, like article JH-052-31A, then another semipolished spinel substrate was placed on the glass coated substrate where the unpolished surface of the second substrate was in contact with the glass coated surface and the two substrates were subjected to bonding heat treatment.

The third article JH-052-36 included two glass-coated spinel substrates, wherein the spinel substrates were coated using the glass paste as described hereinabove and bonded by firing thereof. The article JH-052-36 included a bonded spinel made from two semipolished. spinel substrates which were coated (only unpolished surface of one substrate was coated) and then bonded together to form a 1.6 cm thick spinel. The article JH-052-36 has two substrates, thereby the article JH-052-36 behaves as a monolithic substrate (and has only 2 reflections). Since the bonded surfaces of the article are not seen by the light, the article JH-052-36 has reflection losses from top and bottom faces only.

As depicted in FIG. 6, FIG. 7, and FIG 8, the transmittance of the article JH-052- 36 is greater than the transmittance of the article JH-052-33B at wavelengths above 388nm. Article JH-052-36 also reaches a light transmittance of above 80% for wavelengths above 533nm, and a light transmittance of above 85% for wavelengths above 832nm.

Example 6.

Reference is made to FIG. 9, which shows a graph depicting a comparison of light transmittance of sequential (JH-052-17) and co-firing (JH-051-73) of glass coated unpolished spinel substrates, in accordance with some embodiments of the present invention, and to FIG. 10, which shows a graph depicting a comparison of FTIR of sequential and co-firing of glass coated spinel substrates, in accordance with some embodiments of the present invention.

Reference is made to FIG. 11A and FIG. 11B show images of sequential-fired and co-fired glass coated spinel substrates, respectively, in accordance with some embodiments of the present invention.

In an exemplary procedure, a first article (referred to herein as article JH-052-17 and as depicted in FIG. 11A) was formed by coating two surfaces a spinel substrate and firing each of the sides sequentially. The first article, JH-052-17 glass coating was applied to one surface of the substrate and fired, and then the glass coating was applied to a second surface and fired, or in other words, the sides were fired by sequential firing. In the first article, JH-052-17, one surface underwent two firings, and the second surface underwent only one firing.

In an exemplary procedure, a second article (referred to herein as article JH-051- 73 and as depicted in FIG. 11B) was formed by coating two surfaces a spinel substrate and co-firing the sides, or in other words, firing both sides at the same time. Accordingly, glass paste was applied to one surface, the paste was dried, then the glass paste was applied to second surface and dried, after which the substrate was fired to produce glass coating. In the second article, JH-051-73, both surfaces underwent only one firing.

As depicted in FIG. 9 and FIG 10, the light transmittance through the article JH- 051-73 is greater than the transmittance of the article JH-052-17 at wavelengths above about 320nm. This may be due to the absorption of the glass transmission being zero below 300nm. Accordingly, the transmission of the cofired substrate is larger than that of the substrate coated by sequential firing.

Thus, it is shown that co-firing the sides of the spinel substrate during the coating process may increase the light transmittance of the produced article.

Example 7.

Reference is made to FIG. 12A and FIG. 12B show images of bonded glass coated spinel substrates, in accordance with some embodiments of the present invention.

In an exemplary procedure, four spinel substrates were coated using the glass composition as described hereinabove, and were then bonded to form a single unit, as depicted in FIG. 12A.

In an exemplary procedure, three spinel substrates were coated using the glass composition as described hereinabove, and were then bonded to form a single unit, as depicted in FIG. 12B. As depicted in FIG. 12A and FIG. 12B, the spinel substrates were places such that surfaces (or portions of the surfaces) of the substrates were abutting each other.

Example 8.

Reference is made to FIG. 13, which shows a graph depicting a comparison of light transmittance of glass-bonded and uncoated spinel substrates, in accordance with some embodiments of the present invention, and to FIG. 14, which shows a graph depicting a comparison of FTIR of glass- bonded and uncoated spinel substrates, in accordance with some embodiments of the present invention.

In an exemplary procedure, six articles, JH 052-100A, JH 052-100B1, JH 052- 100C, JH 052-100D1, JH 052-100E, and JH 052-100F1, were produced using polished spinel substrates that each had two polished surfaces.

The first article, article JH-052-100A, included a polished spinel substrate having dimensions of 3.2 by 3.2 by 0.8 cm3. Article JH-052-100A did not include a glass coating.

The second article, article JH-052-100B1, included a glass-coated spinel substrate, having one layer of glass on one polished surface thereof. The remining surface of the article JH-052-100B1 was not coated. Article JH-052-100B1 has dimensions of 3.2 by 3.2 by 0.8 cm3.

The third article, article JH-052-100C, included two polished spinel substrates which were taped together at the circumference. Article JH-052-100C did not include a glass coating.

The fourth article, article JH-052-100D1, included a "sandwich" of two spinel substrates bonded by one layer of glass coating therebetween.

The fifth article, article JH-052-100E, included four polished spinel substrates that were taped together at the circumference. Article JH-052-100E did not include a glass coating.

The sixth article, article JH-052-100F1, included four spinel substrates that were bonded by three glass layers. The three glass layers were produced by first coating three of the spinel substrates, then placing the spinel substrates such that each one of the three glass layers is positioned between two of the spinel substrates.

As depicted in FIG. 13 and FIG 14, the comparison of JH-052-100A (polished spinel), which was polished and had no glass coating, with JH-052-100B1 (polish spinel coated on one surface by glass), which was polished and had a glass coating, shows that glass coating has similar transmittance to polished spinel above 370nm. The glass coating slightly reduced the transmittance in the VIS (the visible light range of wavelengths).

In comparison, article JH-052-31A, a glass-coated semipolished spinel substrate, had better transmittance than article JH-052-100A (polished spinel) in the VIS (the visible light range of wavelengths).

The light transmittance through the third article, article JH-052-100C, which included two spinel substrates without any glass coating layers, was lower than the light transmittance through the fourth article, article JH-052-100D1, which included two spinel substrates with a layer of glass therebetween, for wavelengths above about 480nm.

Moreover, the difference between the transmittance of article JH-052-100C and article JH-052-100D1 for wavelengths above about 480nm was about 10%.

The transmittance of the glass bonded sandwich JH-052-100D1 was better (in the VIS) than the two taped polish spinel substrates JH-052-100C.

The light transmittance through the fifth article, article JH-052-100E, which included four spinel substrates without any glass coating layers, was lower than the light transmittance through the sixth article, article JH-052-100F1, which included four spinel substrates with layers of glass therebetween, for wavelengths above about 470nm.

Moreover, the difference between the transmittance of JH-052-100E and JH-052-100F1 for wavelengths above about 470nm was about 40%.

As depicted in FIG. 13 and FIG 14, the light transmittance through coupled spinel substrates which did not include a glass coating was lower than the light transmittance through coupled spinel substrates with glass coating layers connecting the spinel substrates. 28545/3

Claims (50)

CLAIMS CLAIMED IS:

1. An article comprising a glass coated spinel substrate, comprising: a glass coating comprising in terms of mole percent of the total composition: a. 20.0-28% PbO; b. 0.1-7.0% MgO; c. 0.1-7.0% ZnO; d. 0.1-7.0% Al O ; 2 3 e. 50.0-57.0% SiO ; and 2 f. 0.1-1.5% TiO . 2

2. The article of claim 1, wherein the spinel substrate is unpolished.

3. The article of any one of claims 1-2, wherein the glass coating further comprises an index of refraction of between 1.718 and 1.73.

4. The article of any one of claims 1-3, further comprising a plurality of coated spinel substrates which are bonded together by the glass coating.

5. The article of claim 4, wherein at least a portion of the substrates are unpolished.

6. The article of any one of claims 1-5, wherein the glass coating is configured to apply a compressing pressure onto the spinel substrate.

7. The article of any one of claims 1-6, wherein a thermal expansion coefficient of the glass coating is smaller than the thermal expansion coefficient of the spinel substrate, thereby applying a compressing pressure onto the spinel substrate.

8. The article of any one of claims 1-7, wherein the glass coating comprises a thermal -6 -6 -1 expansion coefficient of between 5.8×10 and 7.02×10 C . - 48 - 28545/3

9. The article of any one of claims 1-8, wherein the glass coating comprises a glass transition temperature of between 550°C and 570°C.

10. The article of any one of claims 1-9, wherein the article is transparent to transmission of infrared light.

11. The article of any one of claims 1-10, further comprising a transmission of above 80% for wavelengths above 400nm.

12. The article of any one of claims 1-11, further comprising a transmission of above 85% for wavelengths above 700nm.

13. The article of any one of claims 1-12, wherein the interface between the glass coating and the spinel substrates is devoid of gaps.

14. The article of any one of claims 1-13, further comprising 0.01-1.0 mole% of any one of BaO, La O , and Bi O , or any combination thereof. 2 3 2 3

15. The article of any one of claims 1-14, further comprising up to 0.5 mole% alkali metal oxides.

16. The article of any one of claims 1-15, further comprising 25.0-26.0 mole% PbO.

17. The article of any one of claims 1-16, further comprising 5.5-6.5 mole % MgO.

18. The article of any one of claims 1-17, further comprising 5.5-6.5 mole % ZnO.

19. The article of any one of claims 1-18, further comprising 5.5-6.5 mole % Al O . 2 3

20. The article of any one of claims 1-19, further comprising 54.5-55.5 mole % SiO . 2

21. The article of any one of claims 1-20, further comprising 0.5-1.5 mole % TiO . 2

22. The article of any one of claims 1-21, wherein the article is resistant to corrosion at (atmospheric conditions) 1atm.

23. A glass coating composition of a spinel substrate, the coating composition comprising, in terms of mole percent of the total composition: (i) 20.0-28% PbO; (ii) 0.1-7.0% MgO; - 49 - 28545/3 (iii) 0.1-7.0% ZnO; (iv) 0.1-7.0% Al O ; 2 3 (v) 50.0-57.0% SiO ; and 2 (vi) 0.1-1.5% TiO . 2

24. The composition of claim 23, further comprising 0.01-1.0% BaO, La O , and/or 2 3 Bi O . 2 3

25. The composition of any one of claims 23-24, further comprising up to 0.5% alkali metal oxides.

26. The composition of any one of claims 23-25, further comprising 25.0-26.0% PbO.

27. The composition of any one of claims 23-26, further comprising 5.5-6.5% MgO.

28. The composition of any one of claims 23-27, further comprising 5.5-6.5% ZnO.

29. The composition of any one of claims 23-28, further comprising 5.5-6.5% Al O . 2 3

30. The composition of any one of claims 23-29, further comprising 54.5-55.5% SiO . 2

31. The composition of any one of claims 23-30, further comprising 0.5-1.5% TiO . 2

32. A process for producing a glass powder for producing the glass coating composition for coating of a spinel substrate of any one of claims 23-31, the process comprising: preparing a mixture of: 2.0-3.0 wt% MgO, 4.0-5.0 wt% ZnO; 23-40 wt% SiO ; 2 0.1-1.5 wt% TiO ; 2 0.1-7 wt% Al(OH) ; and 3 40-90 wt% of any combination of PbO, Pb O and lead bisilicate 3 4 glass; - 50 - 28545/3 melting the mixture to form a melt and incubating the melt at a temperature between 1200°C to 1500°; pouring the molten composition into water to form a frit; and grinding the frit, thereby producing the glass powder.

33. The process of claim 32, further comprising drying the frit in an oven at a temperature of between 100°C to 200°C.

34. The process of any one of claims 32-33, wherein the lead bisilicate glass comprises Hammond Lead glass B15 comprising 63wt.% PbO, 34wt.% SiO , 2 2wt.% Al O and 1wt.% TiO . 2 3 2

35. The process of claims 32-34, further comprising screening the powder and drying the screened powder in an oven at a temperature of between 100°C to 200°C.

36. The process of any one of claims 32-35, wherein incubating the melt is at a temperature between 1250°C to 1500°C.

37. A paste composition for coating of a spinel substrate, comprising: 60-80% glass powder comprising a composition of any one of claims 23- 31; 10-30% medium; 2.0-8.0% terpineol; and 2.0-8.0% dibutylcarbitol.

38. A process for coating a spinel substrate with a glass composition, the process comprising: applying a glass paste to a spinel substance, thereby forming a paste- coated spinel substrate, wherein the glass paste comprises the glass composition of any one of claims 23-31; heating, at a first heating ramp, the paste-coated spinel substrate to a first temperature of 350°C; dwelling at the first temperature; - 51 - 28545/3 heating, at a second heating ramp, the paste-coated spinel substrate to a second temperature of 500°C; dwelling at the second temperature; heating, at a third heating ramp, the paste-coated spinel substrate to a third temperature of 1100°C; dwelling at the third temperature, thereby forming a glass-coated spinel substrate; cooling the glass-coated spinel substrate to a fourth temperature of 560°C; dwelling at fourth temperature; and cooling the glass coated spinel to 25°C.

39. The process of claim 38, wherein the first heating ramp comprises a slope of 2- 5°C/min.

40. The process of any one of claims 38-39, wherein dwelling at the first temperature is for a period sufficient for evaporating one or more solvents within the glass paste, and/or sufficient for decomposing and/or pyrolyzing of most of the polymers within the glass paste.

41. The process of any one of claims 38-40, wherein the second heating ramp comprises a slope of 0.5-2°C/min.

42. The process of any one of claims 38-41, wherein dwelling at the second temperature is for a period sufficient for evaporating and/or decomposing of all organic materials within the glass paste.

43. The process of any one of claims 38-42, wherein the third heating ramp comprises a slope of 15-25°C/min.

44. The process of any one of claims 38-43, wherein dwelling at the third temperature is for a period sufficient for fully melting the paste-coating into a glassy transparent film, thereby forming a glass-coated spinel substrate. - 52 - 28545/3

45. The process of any one of claims 38-44, wherein cooling the glass-coated spinel substrate to 25°C comprises a cooling ramp having a slope of 15-25°C/min.

46. The process of any one of claims 38-45, further comprising dwelling, at the dwelling stage and/or at the fourth temperature, for between 0.7 to 3.5 hours.

47. The process of any one of claims 38-46, wherein dwelling at the dwelling temperature of 560°C is for a period sufficient for annealing at least a portion of a glass surrounding the coated spinel substrates.

48. A process for bonding two or more glass-coated spinel substrates, the process comprising: placing two or more glass-coated spinel substrates in contact; heating, at a first heating ramp, the glass-coated spinel substrates to a first dwelling temperature of 1100°C; dwelling at the first temperature; cooling, at a first cooling ramp, the glass-coated spinel substrates to a second dwelling temperature of 560°C; dwelling at the second temperature; and cooling, at a second heating ramp, the glass-coated spinel substrates to 25°C.

49. The process according to claim 48, wherein the first heating ramp comprises a slope of 12-26°C/min.

50. The process of any one of claims 48-49, wherein dwelling at the dwelling temperature of 560°C is for a period sufficient for annealing at least a portion of a glass surrounding the coated spinel substrates.