Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
  • C03C10/0009—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing silica as main constituent
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/078—Glass compositions containing silica with 40% to 90% silica, by weight containing an oxide of a divalent metal, e.g. an oxide of zinc
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C4/00—Compositions for glass with special properties
  • C03C4/005—Compositions for glass with special properties for opaline glass

Definitions

• the field of the invention is that of vitreous materials in the silico-soda-lime system. More specifically, the invention relates to a vitrocrystalline silico-soda-lime material which has good mechanical strength, in particular good resistance to the propagation of claws, and which allows improved quenching.
• the material according to the invention has these properties coupled with a pleasant aesthetic appearance.
• Glass in its broadest definition, is an amorphous material, free from crystalline and isotropic order.
• a phenomenon of crystallization called devitrification
• glass composition has been optimized for decades in order to limit this parasitic phenomenon. Indeed, when a crystallization occurs accidentally or uncontrollably, it causes the formation of relatively coarse crystals of very different sizes and distributed heterogeneously in the vitreous matrix, often in the form of needles on the surface. The presence of such crystals leads to an optical defect (decrease in transparency) and / or mechanical (decrease in resistance to mechanical stresses) of the resulting glass.
• a silico-soda-lime glass which is not conducive to heat, shows a strong expansion at the place where it is heated.
• the expanded glass exerts a thrust on the surrounding parts which causes a rupture of the glass object, it is the "thermal break".
• a known way to improve the mechanical strength of a glass, and in particular its resistance to the propagation of claws, is the application of a surface layer deposited on the glass.
• This technique aims to benefit from the specific mechanical strength of said layer vis-à-vis an external mechanical stress. Nevertheless, the thickness of the protective layer is limited and any macroscopic claw exposes an unprotected glass to the external environment or leads to the creation of a crack initiation in a weakened zone of the glass.
• the deposition of such a layer only improves the resistance to the propagation of glass claws and does not alter its coefficient of thermal expansion.
• glasses having an amorphous glassy phase and a crystalline phase are well known in the art. These glasses result from the controlled uniform devitrification of a glass.
• the transformation into semi-crystalline ceramic, also called vitrocrystalline or commonly glass-ceramic material is obtained from a glass by a controlled heat treatment which makes it possible to produce a high density of small crystals dispersed homogeneously in the volume of the material. Unlike uncontrolled devitrification, this homogeneous crystal distribution improves the mechanical properties of the product.
• Some ceramics have high resistance to claw and rupture and no expansion at high temperatures, making them virtually invulnerable to thermal shocks.
• the glass-ceramic is, for example, used for the manufacture of cooking plates or chimney walls.
• glass-ceramics based on the partial crystallization of a glass.
• Known compositions are based, for example, on Li 2 O-SiO 2 (silicates) or Li 2 O-Al 2 O 3 -SiO 2 systems (aluminosilicates). They also often have one or more nucleating agents such as TiO 2 , ZrO 2 or P 2 O 5 .
• vitrocrystalline materials Although many known vitrocrystalline materials have properties of mechanical and thermal resistance far superior to amorphous soda-lime-calcium glass, they are still much more expensive to produce and therefore non-transposable to current applications for reasons economic. Due to its ease of production and the low cost of raw materials, silica-soda-lime glass still holds a prominent place in the glass industry and in particular for the construction, automotive and automotive markets. the decoration.
• opaline glasses comprising a vitreous phase and a crystalline phase are also well known in the art and are obtained by introducing an opacifier, conventionally fluorides, into a silicate, an aluminosilicate or a borosilicate, by a intentional or controlled crystallization of crystals (in the case of the addition of fluorides, the crystals are typically CaF 2 or NaF).
• the opal glasses very present in the everyday life, are opaque and diffuse the light. They are therefore mainly used in decoration applications and in the manufacture of consumer products such as table services or lighting fixtures.
• Classic opal glasses, marketed under the brand name Arcopal® are milky white and are fluorosilicates.
• the object of the invention is in particular to overcome the drawbacks of the prior art by solving the technical problem, ie to obtain a soda-lime-silica material, that is to say belonging to the Na 2 O-CaO-SiO system. 2 , with increased mechanical properties, in particular good resistance to the propagation of claws, and which also allows improved quenching.
• Another object of the invention is to provide a soda-lime-silica material having, in addition to the desired mechanical strength and the fact that it allows an improved quenching, the desired aesthetic character depending on the application to which it is applied. intended.
• the invention proposes in this context to provide a silico-soda-lime material which is transparent or alternatively, having an attractive milky opaque appearance and comparable to that of opal glasses but without the addition of opacifier.
• an object of the invention is to provide a solution to the disadvantages of the prior art that is simple, economical and with a low environmental impact. 4. Presentation of the invention
• the invention relates to a vitrocrystalline material having as main components SiO 2 , Na 2 O and CaO.
• the vitrocrystalline material comprises crystalline particles consisting essentially of SiO 2 and dispersed homogeneously in the volume of an amorphous matrix.
• the material according to the invention makes it possible to solve the disadvantages of the materials of the prior art and to solve the technical problem raised.
• the inventors have indeed demonstrated that it was possible, unlike the teaching of the state of the art, to obtain a vitrocrystalline silico-sodo-calcium material. It is indeed supported in the scientific literature, and in particular in the article by Strnad et al. published in Physics and Chemistry of Glasses (Vol.14 No.2 April 1973), that it is impossible to produce a homogeneous crystallization in the volume of a glass belonging to this system and that only heterogeneous, uncontrolled crystallization can be obtained in this case.
• the state of the art also proposes no glass-ceramic in the soda-lime-silica system comprising an amorphous phase and a crystalline phase dispersed homogeneously in the volume of said amorphous phase.
• the transparency required in the common applications of silico-soda-lime glass has always led the skilled person to consider only amorphous materials and has always pushed to optimize the composition of the glass as well as its manufacturing process to avoid or at least limit the parasitic phenomenon of devitrification.
• vitrocrystalline silico-sodic-calcium material makes it possible to achieve higher CET values than corresponding amorphous glass.
• the vitrocrystalline silico-soda-lime material according to the invention thus has an increased mechanical strength, in particular a good resistance to the propagation of claws, and it also allows improved quenching.
• the vitrocrystalline material of the invention is, moreover, economically and aesthetically acceptable for common applications in the building, automobile, decoration or flacon industry.
• the crystalline particles dispersed homogeneously in the volume of an amorphous matrix have a size of between 5 nm and 500 ⁇ m.
• the crystalline particles in order to obtain a material that is transparent, have a size of between 5 nm and 500 nm.
• the crystalline particles in order to obtain a material having an opaque milky appearance, comparable to that of opal glasses, have a size of between 500 nm and 500 ⁇ m.
• the invention also relates to a sheet made of vitrocrystalline material as described above and an article comprising at least one such sheet.
• the present invention will be described in more detail and in a non-restrictive manner.
• the attached figure shows a photograph obtained by electron microscopy of a material according to the invention.
• the material according to the invention is a vitrocrystalline material.
• vitrocrystalline is meant a material which has both a glassy phase and a crystalline phase and which results from the controlled devitrification of a glass.
• the material according to the invention is a soda-lime-silica material, that is to say which belongs to the Na 2 O-CaO-SiO 2 system.
• the material of the invention therefore has SiO 2 main components, Na 2 O and CaO.
• the material of the invention comprises, as a percentage by total weight, 60 to 85% of SiO 2 , 1 to 25% of Na 2 O and 1 to 25% of CaO.
• the material of the invention may comprise other components in minor amounts such as K 2 O, MgO, Al 2 O 3 , BaO, various dyes or residues from redox modifying additives (NaNO 3 , Na 2 SO 4 , coke ).
• these components if present in the material of the invention, will not exceed a total of 15% by weight of the material.
• the material is free of the fluorine element.
• a material therefore has a low environmental impact, particularly compared to opal lenses whose opacifier is conventionally based on fluorides.
• the term "free" means in the present invention that the material has the fluorine element only in the trace state.
• the material comprises the fluorine element only in content of less than 500 ppm by weight.
• the glass is free of the lithium element. Since lithium oxide is more expensive than oxides such as Na 2 O and CaO, such a soda-lime type glass is therefore of undeniable economic interest, in particular compared with the glass-ceramic materials known from the state of the art. which include, most often, lithium oxide. Exempt of the lithium element means that the glass of the invention comprises this element only in trace. Preferably, the glass comprises the lithium element only in content of less than 500 ppm by weight.
• the glass may comprise lithium in amounts of up to about 3% by weight, expressed in the form of the oxide.
• the presence of lithium in these quantities makes it possible to reduce the viscosity of the glass in the molten state and thus to promote crystallization.
• the glass of the invention is free of the lead element. Exempt from the lead element means that the glass of the invention comprises this element only in the trace state.
• the glass of the invention is free of the boron element. Free from the boron element means that the glass of the invention comprises this element only in the trace state.
• the material according to the invention comprises crystalline particles dispersed homogeneously in the volume of an amorphous matrix.
• the material may comprise crystalline particles in the form of an assembly of several particles or in isolated form.
• the crystalline particles have a size which is not smaller than 5 nm and which is not greater than 500 ⁇ .
• size we mean the largest dimension of the particles.
• the crystalline particles have a size which is not less than 5 nm and which is not greater than 500 nm.
• the vitrocrystalline material according to this embodiment is transparent, in addition to having increased mechanical strength.
• the crystalline particles have a size which is not less than 500 nm and which is not greater than 500 ⁇ .
• the vitrocrystalline material according to this embodiment has, in addition to increased mechanical strength, a pleasing milky opaque appearance, comparable to that of opal glasses.
• the crystalline particles according to the invention consist essentially of SiO 2 .
• Impurities such as components from the material composition and found essentially in the amorphous matrix, may be present in a minor amount. If such impurities are present in the crystalline particles, they are preferably in an amount of less than 5% by weight in total. More preferably, they are in an amount of less than 2% by weight in total.
• the crystalline particles are in the form of a single polymorph of this component.
• the crystalline particles are in the form of several polymorphs of SiO 2 .
• the material according to the invention may also comprise particles according to each of these last two embodiments.
• Examples of polymorph of SiO 2 are quartz (a or ⁇ ), cristobalite ( ⁇ or ⁇ ) or tridymite ( ⁇ or ⁇ ).
• the crystalline particles of SiO 2 are essentially in the form of cristobalite.
• the material of the invention comprises crystalline particles consisting essentially of SiO 2 and dispersed homogeneously in the volume of an amorphous matrix. Considering the composition by total weight of the material, this amorphous matrix is therefore depleted of SiO 2 because of the presence of crystalline particles.
• the vitrocrystalline material according to the invention has an increased mechanical strength, in particular a good resistance to the propagation of claws, in comparison with a corresponding amorphous glass.
• the mechanical strength of a material is often expressed in terms of hardness and toughness.
• Hardness characterizes the ability of a material to be scratched or scratched (expressed in MPa or GPa).
• Toughness is the ability of the material to resist the propagation of an existing crack.
• Fragility B or "brittleness" can complement these parameters and corresponds to the ratio between hardness (H) and toughness (Kc), H / Kc (expressed in ⁇ ° ' 5 ).
• H hardness
• Kc toughness
• H / Kc Expressed in ⁇ ° ' 5
• the vitrocrystalline material according to the invention has a brittleness less than 6.5 ⁇ "05.
• this value is of the order of 7 ⁇ " 05 for an amorphous silico-soda-lime glass, without treatment. particular.
• vitrocrystalline material has a higher CET than a corresponding amorphous glass.
• the heating or partial cooling of a material can, if it has a low thermal conductivity, lead to stresses that can cause thermal breakages as is the case for sand-soda-lime glass.
• the importance of this phenomenon of expansion or contraction of a material respectively during heating or partial cooling is conventionally defined by the coefficient of linear thermal expansion.
• This coefficient of thermal expansion or TEC corresponds to the elongation per unit length for a variation of 1 ° C (expressed in ° C)
• the vitrocristallin material according to the invention has a CTE, as measured for a temperature change from 25 to 300 ° C, which is higher than 100.10 "7 / ° CA comparison, the TEC, for the same temperature range of an amorphous silico-soda-lime glass, without any particular treatment, is of the order of 90.degree.-107.degree.
• the material of the invention allows for improved quenching.
• material which allows an improved quenching is meant a material which requires, in order to obtain a compression stress on the surface equivalent to that of a corresponding amorphous glass, a quenching at a lower temperature and / or for a shorter time. Therefore, this advantage allows an energy gain which results in an additional positive effect of the invention from an environmental and economic point of view.
• the term "material which allows improved quenching” also means a material which exhibits, with an equivalent heat treatment, a compressive stress on the surface greater than that of a corresponding amorphous glass.
• the term "material which allows improved quenching” also refers to a material which allows the quenching of "thin" sheets made of this material.
• the vitrocrystalline silico-soda-lime material according to the invention can be obtained by any process capable of generating crystalline particles of SiO 2 in the volume of an amorphous matrix.
• the material according to the invention can be obtained by two ways: (i) a controlled heat treatment of the material in the molten state (ceramization), or (ii) a controlled annealing of a material of the same overall composition but previously solidified in the amorphous state.
• a heat treatment called ceramization is performed.
• the ceramization generally comprises, in a known manner, the following steps, which may be repeated several times: a) raising the temperature to the temperature T (ceramification plateau) which is situated beyond the nucleation interval;
• the material according to the invention can be used to manufacture articles of different shapes and sizes. It can, for example, be used to make vials, globes for lighting and decorative objects.
• the vitrocrystalline material of the invention can be used to make a sheet of said material.
• it can, for example, be used for a worktop in a kitchen or a laboratory, for tables and shelves or as a coating ground (pavement, footbridge).
• the material can also be used to manufacture solar panels or automotive glazings.
• An example of an article according to the invention comprising more than one sheet of said vitrocrystalline material is a wall wall which is "laminated" to improve the security aspect, that is to say which comprises two sheets assembled by one or several plastic interlayer films.
• a composition Cl comprises, as a percentage by total weight, 80.3% of SiO 2 , 10.3% of Na 2 O and 9.4% of CaO.
• composition Cl This composition was melted at a temperature of 1550 ° C. and then poured into a mold of 4 cm ⁇ 4 cm over a centimeter in height.
• the amorphous glass obtained by gradually cooling the composition C1 was then heat-treated by heating (annealing) at a temperature of 1000 ° C. for 1 h, followed again by progressive cooling at room temperature.
• the material M1 was obtained for the composition Cl.
• the coefficient of linear thermal expansion (CET), hardness and brittleness were evaluated for material Ml.
• the hardness (H) and brittleness (B) were determined by Vickers indentation (load: 0.5 kg, application time: 25 sec.) While the CET was obtained using a dilatometer for a temperature range of 25 to 300 ° C (ISO 7991: 1987). These techniques will not be further exposed because well known to those skilled in the field of vitreous and vitrocrystalline materials.
• the material M1 according to the invention has a good mechanical strength, in particular a good resistance to the propagation of claws relative to a corresponding amorphous silico-soda-lime glass. They also show a coefficient of thermal expansion much higher than that of an amorphous silico-soda-lime glass.
• material M1 was also analyzed by scanning electron microscopy and by X-ray diffraction.
• the figure shows a photograph obtained by scanning electron microscopy of material M1.
• this material comprises particles which are dispersed homogeneously in the volume of a matrix.
• the particles are crystalline and the matrix is amorphous.
• This material is therefore a vitrocrystalline material.
• the crystalline particles are crystals of SiO 2 in the form of cristobalite and have a size that varies from about 0.5 ⁇ to about 5 ⁇ .
• the material Ml has a milky and opaque white appearance and therefore has an aesthetic appearance comparable to that of fluorine opal glasses.

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• Chemical Kinetics & Catalysis (AREA)
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• Geochemistry & Mineralogy (AREA)
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• Dispersion Chemistry (AREA)
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• Silicates, Zeolites, And Molecular Sieves (AREA)

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• 2009
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