WO2020027887A1

WO2020027887A1 - Ceramics and ceramic composites

Info

Publication number: WO2020027887A1
Application number: PCT/US2019/028214
Authority: WO
Inventors: James C. Mcmillen
Original assignee: Arconic Inc.
Priority date: 2018-07-31
Filing date: 2019-04-19
Publication date: 2020-02-06

Abstract

Compositions for and methods of making ceramics and ceramic composites are provided. A mixture of starting materials is introduced into a reactor chamber. The starting materials comprise a precursor material and a ceramic support material. The precursor material comprises a boron source and a carbon source. The precursor material is carbothermically reacted with a nitrogen source in the reactor chamber in the presence of the ceramic support material to thereby form a ceramic material comprising a boron nitride and the ceramic support material. During the carbothermically reacting, the ceramic support material promotes permeation of the nitrogen source through the precursor material.

Description

CERAMICS AND CERAMIC COMPOSITES

FIELD

[0001] The present disclosure relates to compositions for and methods of making ceramics and ceramic composites. More specifically, the present disclosure relates to carbothermically producing ceramic material comprising boron nitride and ceramic support material.

BACKGROUND

[0002] Through carbothermic synthesis, it is possible to make various boride, nitride, and/or carbide ceramic powders. The ceramic powder can then be processed into final ceramic products for a wide variety of applications.

SUMMARY

[0003] An aspect of the present disclosure is directed to a method for making a composition. More specifically, a mixture of starting materials is introduced into a reactor chamber. The starting materials comprise a precursor material and a ceramic support material. The precursor material comprises a boron source and a carbon source. The precursor material is carbothermically reacted with a nitrogen source in the reactor chamber in the presence of the ceramic support material to thereby form a ceramic material comprising a boron nitride and the ceramic support material. During the carbothermically reacting, the ceramic support material promotes permeation of the nitrogen source through the precursor material.

[0004] An additional aspect of the present disclosure is directed to a mixture. More specifically, the mixture comprises a precursor material and a ceramic support material. The precursor material comprises a boron source and a carbon source. The mixture is suitable for carbothermically reacting the precursor material in the mixture with a nitrogen source to produce a ceramic material comprising a boron nitride and the ceramic support material. During the carbothermically reacting, the ceramic support material promotes permeation of the nitrogen source through the precursor material.

[0005] It is understood that the inventions disclosed and described in this specification are not limited to the aspects summarized in this Summary. The reader will appreciate the foregoing details, as well as others, upon considering the following detailed description of various non-limiting and non-exhaustive aspects according to this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The features and advantages of the examples, and the manner of attaining them, will become more apparent, and the examples will be better understood, by reference to the following description taken in conjunction with the accompanying drawings, wherein:

[0007] FIG. l is a flow chart illustrating a non-limiting embodiment of a method for making ceramics and/or ceramic compositions according to the present disclosure;

[0008] FIG. 2 is a SEM image of a ceramic material produced from a mixture of starting materials comprising 7% by weight boron nitride according to the present disclosure; and

[0009] FIG. 3 is a SEM image of a ceramic material produced from a mixture of starting materials comprising 7% by weight titanium boride according to the present disclosure.

[0010] Corresponding reference characters, if any, indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate certain embodiments, in one form, and such exemplifications are not to be construed as limiting the scope of the appended claims in any manner.

DETAILED DESCRIPTION

[0011] Various embodiments are described and illustrated herein to provide an overall understanding of the structure, function, and use of the disclosed articles, systems, and methods. The various embodiments described and illustrated herein are non-limiting and non-exhaustive. Thus, the invention is not limited by the description of the various non limiting and non-exhaustive embodiments disclosed herein. Rather, the invention is defined solely by the claims. The features and characteristics illustrated and/or described in connection with various embodiments may be combined with the features and characteristics of other embodiments. Such modifications and variations are intended to be included within the scope of this specification. As such, the claims may be amended to recite any features or characteristics expressly or inherently described in, or otherwise expressly or inherently supported by, this specification. Further, Applicant reserves the right to amend the claims to affirmatively disclaim features or characteristics that may be present in the prior art. The various embodiments disclosed and described in this specification can comprise, consist of, or consist essentially of the features and characteristics as variously described herein.

[0012] Any patent, publication, or other disclosure material identified herein is incorporated herein by reference in its entirety unless otherwise indicated, but only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material expressly set forth in this specification. As such, and to the extent necessary, the express disclosure as set forth in this specification supersedes any conflicting material incorporated by reference herein. Any material, or portion thereof, that is said to be incorporated by reference into this specification, but which conflicts with existing definitions, statements, or other disclosure material set forth herein, is only incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material. Applicant reserves the right to amend this specification to expressly recite any subject matter, or portion thereof, incorporated by reference herein.

[0013] Any references herein to“various embodiments,”“some embodiments,”“one embodiment,”“an embodiment,” or like phrases, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases“in various embodiments,”“in some embodiments,”“in one embodiment,”“in an embodiment,” or like phrases, in the

specification do not necessarily refer to the same embodiment. Furthermore, the particular described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Thus, the particular features, structures, or characteristics illustrated or described in connection with one embodiment may be combined, in whole or in part, with the features, structures, or characteristics of one or more other embodiments without limitation. Such modifications and variations are intended to be included within the scope of the present embodiments.

[0014] In this specification, unless otherwise indicated, all numerical parameters are to be understood as being prefaced and modified in all instances by the term“about,” in which the numerical parameters possess the inherent variability characteristic of the underlying measurement techniques used to determine the numerical value of the parameter. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter described herein should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0015] Also, any numerical range recited herein includes all sub-ranges subsumed within the recited range. For example, a range of“1 to 10” includes all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10. Any maximum numerical limitation recited in this specification is intended to include all lower numerical limitations subsumed therein, and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein. Accordingly, Applicant reserves the right to amend this specification, including the claims, to expressly recite any sub-range subsumed within the ranges expressly recited. All such ranges are inherently described in this specification.

[0016] The grammatical articles“a,”“an,” and“the,” as used herein, are intended to include “at least one” or“one or more,” unless otherwise indicated, even if“at least one” or“one or more” is expressly used in certain instances. Thus, the foregoing grammatical articles are used herein to refer to one or more than one (i.e., to“at least one”) of the particular identified elements. Further, the use of a singular noun includes the plural, and the use of a plural noun includes the singular, unless the context of the usage requires otherwise.

[0017] An aspect of the present disclosure relates to utilizing a ceramic support material (e.g., rigidifying compounds) in combination with a precursor material to enhance gas permeability to the precursor material while it undergoes a chemical transformation via a carbothermic reaction to form a ceramic material product. In various embodiments, the ceramic material product may be boron nitride. The ceramic support material also may provide structural support to the precursor material during the carbothermic reaction. Use of the ceramic support material according to the present disclosure may improve a yield of the ceramic material product (e.g., boron nitride) produced in the carbothermic reaction (e.g, with little, low, or no residual carbon and/or boron carbide produced) relative to a yield achieved when conducting an otherwise identical reaction without use of a ceramic support material. Upon completion of the carbothermic reaction, the ceramic support material and byproducts, if any, produced therefrom may be separated from the ceramic material product. However, in various embodiments, separation of the ceramic support material and/or byproducts, if any, produced therefrom from the ceramic material product may not be required.

[0018] Referring to FIG. 1, a flow chart illustrating a method for making ceramics and/or ceramic compositions is provided. As illustrated, starting materials comprising a precursor material and a ceramic support material can be mixed together to form a mixture of starting materials 102. In various embodiments, the starting materials may comprise, consist essentially of, or consist of the precursor material and the ceramic support material. The precursor material comprises a boron source and a carbon source. The boron source can comprise, for example, at least one of boric oxide and boric acid. The carbon source can comprise, for example, at least one of carbon black, graphite, coke, and carbon resin. In various examples, the precursor materials do not contain nitrogen.

[0019] The ceramic support material can be stable in a reducing atmosphere at a temperature suitable for carbothermic formation of a ceramic material product, such as, for example, boron nitride ( e.g ., 1400 to l600°C). A melting temperature of the ceramic support material can be greater than a temperature of a carbothermic reaction of the precursor material. For example, the melting temperature of the ceramic support material can be at least l500°C, such as, for example, at least l600°C, at least l700°C, at least 2000°C, at least 2500°C, at least 2900°C, or at least 3000°C. The ceramic support material can comprise, for example, at least one of boron nitride (BN), boron carbide (B₄C), titanium nitride (TiN), titanium diboride (T1B2), titanium carbide (TiC), silicon nitride (S13N4), silicon carbide (SiC), aluminum boride (AIB2), aluminum nitride (A1N), aluminum carbide (AI4C3), chromium nitride (CrN), chromium boride (CrB), chromium carbide (CnCri), zirconium nitride (ZrC), zirconium diboride (ZrBn), hafnium diboride (FliFk), hafnium nitride (HfN), hafnium carbide (HfC), niobium nitride (NbN), niobium dibroide (NbB2), niobium carbide (NbC), tantalum nitride (TaN), tantalum diboride (TaB2), and tantalum carbide (TaC). In various embodiments, the ceramic support material can comprise, consist essentially of, or consist of boron nitride. In various embodiments, the ceramic support material can be a non-oxide compound and/or a non-carbonate compound. For example, the ceramic support material may not contain any oxygen. In various examples, the ceramic support material can comprises naturally occurring oxide layers, such as, for example, less than 2% oxygen by weight, less than 1% oxygen by weight, or less than 0.1% oxygen by weight, based on the total weight of the ceramic support material. In various embodiments, the ceramic support material can comprise, consist essentially of, or consist of at least one of a boride, a carbide, and a nitride.

[0020] The ceramic support material can provide structural support to the precursor materials and/or the resulting ceramic material product throughout the chemical transformation of the precursor materials into the ceramic material product (e.g., boron nitride synthesis via a carbothermic reaction). Thus, the ceramic support material can provide a structural support function, whereby the precursor material in a reactor is less likely to deform when heated during the carbothermic reaction and the flow of gas through inter- and intra-granular pores in the mixture of starting materials is thereby enhanced or facilitated.

[0021] In various embodiments, the mixture of starting materials for the carbothermic reaction can comprise, based on the total weight of the starting materials, at least 1% by weight of the ceramic support material, such as, for example, at least 5% by weight ceramic support material, at least 10% by weight ceramic support material, at least 15% by weight ceramic support material, or at least 20% by weight ceramic support material. In various embodiments, the mixture of starting materials can comprise, based on the total weight of the starting materials, less than 20% by weight of the ceramic support material, such as, for example, less than 15% by weight ceramic support material, less than 10% by weight ceramic support material, or less than 5% by weight ceramic support material. In various

embodiments, the mixture of starting materials can comprise, based on the total weight of the starting materials, 1% to 20% by weight ceramic support material, such as, for example, 5% to 20% by weight ceramic support material, 5% to 15% by weight ceramic support material, 5% to 10% by weight ceramic support material, or 10% to 20% by weight ceramic support material. In certain embodiments, the mixture of starting materials includes ceramic support material, with the balance consisting of the precursor materials and impurities.

[0022] The mixture of starting materials may be solid and, in various embodiments, includes porosity for the efficient flow of gaseous reagents or byproducts. As used herein, a “porosity” refers to open space/volume that is not taken up by the solid mixture of starting materials in a reactor chamber. Porosity within the starting materials provides a possible passage for gas to enter the starting material mixture and contact precursor material within the mixture. In certain embodiments, the starting materials have a configuration that includes macro-porosity in at least a portion of the mixture of starting materials. As used herein, “macro-porosity” refers to the presence of voids that will permit gas to permeate through solid components. In various examples, the porosity of the starting materials can be in a range of 15% to 60%, such as, for example, 20% to 60%, 25% to 55%, 30% to 55%, 35% to 50%, 40% to 60%, 50% to 60%, or 40% to 50%.

[0023] In some embodiments, the starting materials comprise a plurality of granules. In some embodiments, the starting materials can be configured to include inter-granule porosity, which is measured between granules of a single starting material component ( e.g ., ceramic support material or precursor material).

[0024] In some embodiments, the inter-granule porosity area fraction in a particular starting material component prior to conducting the carbothermic reaction, measured in a cross- sectional area taken across the reactor chamber, can be at least 0.1, such as, for example, at least 0.2, at least 0.3, at least 0.4, at least 0.5, at least 0.6, or at least 0.7. In some

embodiments, the inter-granule porosity area fraction in a particular starting material component prior to conducting the carbothermic reaction, measured in a cross-sectional area taken across the reactor chamber, can be less than 0.8, such as, for example, less than 0.7, less than 0.6, less than 0.5, less than 0.4, less than 0.3, or less than 0.2. In some embodiments, the inter-granule porosity area fraction in a particular starting material component prior to conducting the carbothermic reaction, measured in a cross-sectional area taken across the reactor chamber, can be in a range of 0.1 to 0.8, such as, for example, 0.2 to 0.7, or 0.3 to 0.6.

[0025] In various embodiments, the mixture of starting materials can be configured to include intra-granule porosity, which is measured within a single granule of a starting material component. In certain embodiments, there is inter-granule porosity (>0 area fraction) but no intra-granular porosity (0 area fraction) in a particular starting material prior to conducting the carbothermic reaction.

[0026] In some embodiments, the intra-granule porosity area fraction in a particular starting material, measured in a cross-sectional area taken across the reactor chamber, can be at least 0.01, such as, for example, at least 0.05, at least 0.1, at least 0.2, at least 0.3, at least 0.4, or at least 0.5. In some embodiments, the intra-granule porosity area fraction in a particular starting material, measured in a cross-sectional area taken across the reactor chamber, can be less than 0.6, such as, for example, less than 0.5, less than 0.4 less than 0.3, less than 0.2, less than 0.1, or less than 0.5. In some embodiments, the intra-granule porosity area fraction in a particular starting material, measured in a cross-sectional area taken across the reactor chamber, can be in a range of 0.01 to 0.6, such as, for example, 0.1 to 0.5, 0.2 to 0.5, or 0.3 to 0.4.

[0027] Referring again to FIG. 1, in various embodiments, the mixture of starting materials can be dehydrated and, in various embodiments, dried 104. In certain embodiments, dehydrating/drying 104 can include granulating the mixture of starting materials. The mixture of starting materials can be introduced into a reactor chamber 106. The reactor chamber can be a carbothermic reactor chamber. The reactor chamber can be a continuous reactor chamber and the process shown in FIG. 1 can be a continuous process conducted over a time period, with additional starting materials introduced into the reactor chamber during the time period. In other embodiments, the reactor chamber can be a batch reactor chamber and the process shown in FIG. 1 can be a batch process. In various embodiments, the reactor can be a semi-continuous batch reactor chamber and the process shown in FIG. 1 can be a semi-continuous process. [0028] In certain embodiments, the starting materials can be heated in the reactor chamber 108 prior to carbothermically reacting the precursor material 110. The starting materials can be heated to a reaction temperature at which the precursor material melts but which is lower than the melting temperature of the ceramic support material. For example, the reaction temperature can be at least 500°C, such as, for example, at least 700°C, at least l000°C, or at least l400°C. In certain embodiments the reaction temperature can be less than l600°C. In various embodiments, the reaction temperature can be in a range of 500°C to 2000°C, such as, for example, 700°C to l600°C, l000°C to l600°C, or l400°C to l600°C. The heating can cause at least a portion of the precursor materials to melt and thereby become molten. For example, the heating can melt at least 50% by volume of the starting materials based on the total volume of the starting materials, such as, for example, at least 60% by volume of the starting materials, at least 70% by volume of the starting materials, at least 80% by volume of the starting materials, at least 90% by volume of the starting materials, or at least 99% by volume of the starting materials based on the total volume of the starting materials.

[0029] The precursor material can be carbothermically reacted with a nitrogen source in the reactor chamber in the presence of the ceramic support material 110. Carbothermically reacting the precursor material with the nitrogen source can comprise flowing the nitrogen source through the mixture of the starting materials. The ceramic support material physically supports the mixture of starting materials and promotes permeation of nitrogen source through the mixture of starting materials, which includes the precursor material. For example, the permeation of the starting materials can occur when at least 50% by volume of the precursor material is molten, such as, for example, at least 60% of the volume of the precursor material is molten, at least 70% of the volume of the precursor material is molten, at least 80% of the volume of the precursor material is molten, at least 90% of the volume of the precursor material is molten, or at least 99% of the volume of the precursor material is molten.

[0030] The nitrogen source can be gaseous. In various embodiments, the nitrogen source comprises at least one of nitrogen gas and ammonia. In some embodiments, the nitrogen source is configured as at least one of a purge gas and a sweep gas. The ceramic support material can enable the nitrogen source to enter the mixture of starting materials and exit the mixture of starting materials, thereby allowing the nitrogen source to contact precursor material within the mixture of starting materials. The permeation of the nitrogen source through the precursor material can ensure that sufficient nitrogen is present for the formation of a ceramic material product

[0031] With reference to FIG. 1, the mixture of starting materials can be pre-heated 108 and/or heated during carbothermically reacting 110 in order to facilitate the carbothermic reaction of the precursor material and the nitrogen source to produce a ceramic material product. For example, a carbothermic reaction to form boron nitride is shown in Scheme I.

Scheme I

B2O3 + 3C + N2 = 2BN + 3CO

The reaction shown in Scheme I has a Gibbs Free Energy indicating that the reaction may initiate at a temperature greater than l000°C. For example, the reaction of Scheme I may initiate at l048°C. Thus, the pre-heating 108 and/or heating 110 can be sufficient to initiate and sustain the carbothermic reaction for a time period. In various embodiments, the ceramic support material can carbothermically react with the nitrogen source.

[0032] In some embodiments, the nitrogen source can be admixed with another gas. For example, the nitrogen source may be mixed with a carrier gas that can be a non-reactive gas and/or a gas that is not a precursor to the carbothermic reaction to form a ceramic material product. In certain embodiments, the carrier gas can comprise at least one of argon and helium The carrier gas and the nitrogen source can be passed through the mixture of the starting materials during 110 at a partial pressure suitable to promote a carbothermic reaction between the precursor material and the nitrogen source. In various embodiments, the partial pressure of the nitrogen source can be in a range of 10% to 100% of the total pressure in the carbothermic reactor, such as, for example, 20% to 100%, 40% to 100%, 40% to 80%, 50% to 70%, or 60% to 90%. In various embodiments, the partial pressure of the nitrogen source can be suitable to promote nitridation of the boron source and/or limit nitridation of the ceramic support material, if desired.

[0033] In some embodiments, the flow rate and/or partial pressure of a gaseous nitrogen source introduced into the reactor chamber can be varied during the duration of the carbothermic reaction. For example, in certain embodiments of the process of FIG. 1 a flow of 100% nitrogen gas may be initiated as the nitrogen source through the reactor chamber, and then as the reaction progresses the nitrogen gas may be admixed to variable partial pressures with a carrier gas while not greatly exceeding the stoichiometric requirements of the nitrogen source. Optionally, the nitrogen gas/carrier gas mixture may be tapered to 100% carrier gas flowing through the reactor chamber as the reaction approaches full conversion of reagents/precursors to reaction product/ceramic product.

[0034] The carbothermic reaction can form a ceramic material product comprising a boron nitride and all or a portion of the ceramic support material 112. The boron nitride can be formed from a reaction between the precursor materials and the nitrogen source. The ceramic material product can be utilized in various powder metallurgical processes without the need to remove ceramic support material form the ceramic material product. In various embodiments, the ceramic material product is agglomerated 112.

[0035] In certain embodiments of the process of the present disclosure, the carbothermic reaction can form a secondary ceramic material product comprising a nitride derived from all of a portion of the ceramic support material in the starting materials. For example, boron carbide ceramic support material can be converted to boron nitride; titanium diboride ceramic support material can be converted to titanium nitride; titanium carbide ceramic support material can be converted to titanium nitride; silicone carbide ceramic support material can be converted to silicon nitride; aluminum boride ceramic support material can be converted to aluminum nitride; aluminum carbide ceramic support material can be converted to aluminum nitride; chromium boride ceramic support material can be converted to chromium boride; chromium carbide ceramic support material can be converted to chromium nitride; zirconium carbide ceramic support material can be converted to zirconium nitride; zirconium diboride ceramic support material can be converted to zirconium nitride; hafnium diboride ceramic support material can be converted to hafnium nitride; hafnium carbide ceramic support material can be converted to hafnium nitride; niobium diboride ceramic support material can be converted to niobium nitride; niobium carbide ceramic support material can be converted to niobium nitride; tantalum diboride ceramic support material can be converted to tantalum nitride; and tantalum carbide ceramic support material can be converted to tantalum nitride.

In various examples, the ceramic support material and the parameters of the carbothermic reaction may be selected to adjust the output of a secondary ceramic material product formed during the reaction, if any.

[0036] The ceramic material product produced in the reactor chamber in the carbothermic reaction can be recycled back into the process. For example, the ceramic material product can be recycled back into step 102 in FIG. 1. The ceramic material product also can be subjected to downstream processing 114. For example, with reference to FIG. 1, the ceramic material can be deagglomerated 114. In various embodiments, the ceramic material product comprises a plate-like particle shape at step 112. In various embodiments, the ceramic material product can be recycled back into the process, such as into to step 102, after downstream processing at step 114.

[0037] At least a portion of the ceramic material product produced in the process shown in FIG. 1 can be processed in a molten metal refractory process to produce an article 116. In some embodiments, articles produced by the processing of ceramic material product made according to the present disclosure have commercial end uses in industrial applications, consumer applications ( e.g ., consumer electronics and/or appliances), or other areas. For example, the resulting articles can be utilized in the aerospace field, automotive field, transportation field, and/or building and construction field, and can be produced in a variety of forms including, for example: fasteners, sheet, plate, castings, forgings, extrusions, and post-processed additive manufacturing forms (e.g., structural applications and components like beams, frames, rails, brackets, bulkheads, spars, and ribs, among others).

Prophetic Examples

[0038] The amount of ceramic support material can be varied, which can affect the ceramic material product. As shown in Table 1, various 300 gram (g) mixtures of starting materials can be prepared with varying weight percentages of ceramic support material ranging from 2.5% by weight ceramic support material to 20% by weight ceramic support material (based on the total weight of the starting materials). In Table 1 each of the examples includes starting materials including a precursor material comprising boric acid as a boron source and carbon black or graphite as a carbon source, and boron nitride as a ceramic support material. Table 1 lists the concentration of the ceramic support material (CSM) in the starting materials based on the total weight of the starting materials, the components within the starting materials used, the amount of each component, the density of the each component, the volume of each component, the volume percentage of each component based on the total volume of the starting materials, the total amount of boron nitride in the ceramic material product after the carbothermic reaction, the boron nitride that is newly produced from the carbothermic reaction (e.g, total out minus total in), and the volume percentage of the newly produced boron nitride based on the total volume of the ceramic material product.

[0039] Table 1 : Ceramic support material (CSM) level and affect on boron nitride yield

[0040] The present inventors believe that utilizing boron nitride as a ceramic support material can promote permeation the nitrogen source through the starting materials, including the precursor material, during a carbothermic reaction and thereby facilitate the formation of boron nitride from the boric acid and carbon comprising the precursor materials. The mixture of starting materials comprising 2.5% by weight boron nitride as the ceramic support material can result in a ceramic material product comprising 92% by volume newly formed boron nitride ( e.g ., boron nitride that was not present in the starting materials); the mixture of starting materials comprising 5% by weight boron nitride as the ceramic support material can result in a ceramic material product comprising 85% by volume newly formed boron nitride; the mixture of starting materials comprising 7% by weight boron nitride as the ceramic support material can result in a ceramic material product comprising 79% by volume newly formed boron nitride; the mixture of starting materials comprising 10% by weight boron nitride as the ceramic support material can result in a ceramic material product comprising 74% by volume newly formed boron nitride; and the mixture of starting materials comprising 20% by weight boron nitride as the ceramic support material can result in a ceramic material product comprising 54% by volume newly formed boron nitride. If the ceramic support material comprises a portion of the ceramic material product of the carbothermic reactions shown in Table 1 (e.g., ceramic material product is recycled as ceramic support material) in a continuous carbothermic reactor process, the composition of the ceramic material product may not change since the ceramic material product is substantially similar to the ceramic support material.

[0041] In various embodiments of processes according to the present disclosure, the precursor material can be converted to a primary ceramic material product in the carbothermic reaction, and all or a portion of the ceramic support material may be converted to a secondary ceramic material product in the carbothermic reaction. In addition, all or a portion of the original ceramic support material may remain in the reactor chamber on completion of the carbothermic reaction. Table 2 lists the ceramic materials that may be present in the reactor chamber on completion of the carbothermic reaction when using various ceramic support materials along with precursor materials comprising boric acid and carbon and nitrogen gas as the nitrogen source. In each of examples listed in Table 2, the result is a mixed ceramic product comprising boron nitride, all or a portion of the original ceramic support material, and reaction products, if any, produced from ceramic support material reacting with the nitrogen source.

[0042] Table 2: Ceramic support material and resulting product chemistry

[0043] The composition of the mixed ceramic material product can depend on kinetics and/or thermodynamics of the potential carbothermic reaction of the ceramic support material with the nitrogen source. Thus, the mixed product composition can be altered by changing the composition of a mixture of ceramic support material.

[0044] In a continuous or semi-continuous process starting with a ceramic support material that differs from the desired ceramic material product of the carbothermic reaction ( e.g ., boron nitride), the composition of the ceramic material product can change as the continuous process or semi-continuous progresses if the ceramic material product is recycled into the process. For example, a semi-continuous process proceeding through 7 reaction cycles and initially commencing (process cycle 1) with a mixture of starting materials including 7% by weight titanium diboride based on the total weight of the starting materials is shown in Table 3. The values listed in Table 3 assume that (i) the kinetics of nitridation of titanium diboride proceed in each of process cycles 1-7 via reaction Scheme II and (ii) a single cycle in the semi-continuous process achieves a 50% conversion.

Scheme II

TiB₂ + 2N₂ = 2BN + TiN

[0045] After each of process cycles 1-6 listed in Table 3 a portion of the mixed ceramic material product is recycled into the next cycle of the semi-continuous process to provide 7% by weight of ceramic support material to the carbothermic reaction. Table 3 lists the composition of the solid products after each of the process cycles 1-7 in a semi-continuous process utilizing recycling of ceramic support material in this way.

[0046] Table 3: Ceramic material product composition over multiple cycles when utilizing a ceramic support material comprising titanium diboride

[0047] A semi-continuous process starting with a mixture of starting materials having 7% by weight aluminum carbide based on the total weight of the starting materials is shown in Table 4. A total of 6 process cycles are shown in Table 4. After each of process cycles 1-5 listed in Table 4 a portion of the mixed ceramic material product is recycled into the next cycle of the semi-continuous process to provide 7% by weight of ceramic support material to the carbothermic reaction. Table 4 lists the composition of the solid products produced in each of the process cycles 1-6 in a semi-continuous process utilizing recycling of ceramic support material in this way.

[0048] Table 4: Ceramic material product composition over multiple cycles when utilizing a ceramic support material comprising aluminum carbide.

[0049] It is believed this trend occurs with any nitrogen reactive ceramic support material. However, as shown in Tables 3 and 4, the compositions of the ceramic material product change based on the chemistry of the ceramic support material. Therefore, in various embodiments of a continuous process or a semi-continuous, the amount of the carbon source introduced in to the reactor chamber may need to be reduced to account for carbon derived from a carbide reaction of the ceramic support material with the nitrogen source.

[0050] A semi-continuous process commencing with a mixture of starting materials initially including 7% by weight silicon carbide (based on the total weight of the starting materials) as the ceramic support material is shown in Table 5. The data in Table 5 assumes minimal, if any, reaction between silicon carbide and the nitrogen source. A total of 7 process cycles are shown in Table 5. After each of process cycles 1-6 listed in Table 5 a portion of the mixed ceramic material product is recycled into the next cycle of the semi-continuous process to provide 7% by weight of ceramic support material to the carbothermic reaction. Table 5 lists the composition of the solid products produced in each of the process cycles 1-7 in a semi- continuous process utilizing recycling of ceramic support material in this way.

[0051] Table 5: Ceramic material product composition over multiple cycles when utilizing a ceramic support material comprising silicon carbide.

[0052] The median particle size of the ceramic support material can affect the carbothermic reaction efficiency. In various embodiments, the ceramic support material has a median particle size of less than 1 millimeter (mm) such as, for example, less than 900 micrometer (pm), less than 500 pm, less than 100 pm, less than 50 pm, less than 20 pm, less than 15 pm, less than 10 pm, or less than 1 pm.

[0053] As used herein,“median particle size” refers to the diameter at which 50% of the volume of the particles have a smaller diameter than the given value (e.g., Dso), and is determined in accordance with ASTM standard B822.

[0054] Table 6 illustrates the ceramic material product that can result from different particle sizes of boron nitride ceramic support material at 7% by weight based on the total weight of the starting material. The starting material can also comprise 73.4% by weight boric acid and 19.6% by weight carbon. [0055] Table 6: Ceramic support material at 7% by weight with varying particle size

Examples

[0056] FIGs. 2-3 are SEM images of ceramic material product. FIG. 2 illustrates a ceramic material product produced from starting materials comprising 7% by weight boron nitride according to the present disclosure. FIG. 3 illustrates a mixed ceramic material product produced from a mixture of starting materials comprising 7% by weight titanium diboride according to the present disclosure. In FIG. 3, the mixed ceramic material comprises titanium diboride, titanium nitride, and boron nitride. FIGs. 2-3 show an improved plate-like structure over a commercially available boron nitride powder as shown in FIG. 5C of ET.S. Patent Publication 2018/0029886. The content of ET.S. Patent Publication 2018/0029886 is incorporated herein by reference in its entirety, but only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material expressly set forth in this specification.

[0057] Various aspects of the invention according to the present disclosure include, but are not limited to, the aspects listed in the following numbered clauses.

1. A method, comprising:

introducing into a reactor chamber a mixture of starting materials comprising a precursor material comprising a boron source and a carbon source, and

a ceramic support material; and

carbothermically reacting the precursor material with a nitrogen source in the reactor chamber in the presence of the ceramic support material to thereby form a ceramic material comprising a boron nitride and the ceramic support material;

wherein during the carbothermically reacting, the ceramic support material promotes permeation of the nitrogen source through the precursor material. The method of clause 1, wherein a melting temperature of the ceramic support material is greater than a temperature at which the precursor material is

carbothermically reacted in the reactor chamber in the presence of the ceramic support material. The method of any of clauses 1 to 2, wherein the ceramic support material comprises at least one of boron nitride, boron carbide, titanium nitride, titanium diboride, titanium carbide, silicone nitride, silicon carbide, aluminum boride, aluminum nitride, aluminum carbide, chromium nitride, chromium boride, chromium carbide, zirconium nitride, zirconium diboride, hafnium diboride, hafnium nitride, hafnium carbide, niobium nitride, niobium dibroide, niobium carbide, tantalum nitride, tantalum diboride, and tantalum carbide. The method of any of clauses 1 to 2, wherein the ceramic support material consists of boron nitride. The method of any of clauses 1 to 4, wherein the starting materials comprise at least 1 percent by weight of the ceramic support material based on the total weight of the starting materials. The method of any of clauses 1 to 5, wherein the starting materials comprise 1 percent to 20 percent by weight of the ceramic support material based on the total weight of the starting materials. The method of any of clauses 1 to 6, wherein a mixture of the starting materials in the reactor chamber comprises a porosity area fraction in a range of 0.05 to 0.5. The method of any lf clauses 1 to 7, wherein the ceramic material has a plate-like particle shape. The method of any of clauses 1 to 8, wherein the nitrogen source comprises at least one of nitrogen gas and ammonia. The method of any of clauses 1 to 9, wherein the carbon source comprises at least one of carbon black, graphite, coke, and carbon resin. The method of any of clauses 1 to 10, wherein the boron source comprises at least one of boric oxide and boric acid. The method of any clauses 1 to 11, further comprising heating the starting materials in the reactor chamber prior to carbothermically reacting the precursor material with the nitrogen source in the reactor chamber in the presence of the ceramic support material. The method of clause 12, wherein the heating comprises heating the starting materials at which the precursor material melts but that is lower than a melting temperature of the ceramic support material. The method of clause 1, wherein carbothermically reacting the precursor material with the nitrogen source in the reactor chamber in the presence of the ceramic support material comprises flowing the nitrogen source through the mixture of the starting materials. The method of any one of clauses 1 to 14, further comprising flowing a carrier gas through the mixture of the starting materials. The method of clause 15, wherein the carrier gas comprises at least one of argon and helium. The method of any of clauses 1 to 16, wherein carbothermically reacting the precursor material with the nitrogen source in the reactor chamber in the presence of the ceramic support material comprises flowing a carrier gas and the nitrogen source through the mixture of the starting materials at a partial pressure suitable to promote a carbothermic reaction between the precursor material and the nitrogen source. The method of any of clauses 1 to 17, further comprising dehydrating the starting materials prior to carbothermically reacting the precursor material with the nitrogen source in the reactor chamber in the presence of the ceramic support material. The method of clause 18, further comprising granulating the starting materials after dehydrating the starting materials. The method of any of clauses 1 to 19, wherein the reactor chamber is a continuous reactor chamber and carbothermically reacting the precursor material with the nitrogen source in the reactor chamber in the presence of the ceramic support material is a continuous process over a time period. The method of clause 20, further comprising recycling the ceramic material into the reactor chamber. The method of any of clauses 1 to 19, wherein the reactor chamber is a batch reactor chamber and carbothermically reacting the precursor material with a nitrogen source in the reactor chamber in the presence of the ceramic support material is a batch process. The method of any of clauses 1 to 22, further comprising processing the at least a portion of the ceramic material in a molten metal refractory process to produce an article. A mixture comprising:

a precursor material comprising a boron source and a carbon source; and a ceramic support material that promotes permeation of a nitrogen source through the precursor material;

wherein the mixture is suitable for carbothermically reacting the precursor material in the mixture with a nitrogen source to produce a ceramic material comprising a boron nitride and the ceramic support material. The mixture of clause 24, wherein the ceramic support material has a melting temperature greater than a temperature required to facilitate a carbothermic reaction of the precursor material. The mixture of any of clauses 24 to 25, wherein the ceramic support material comprises at least one of boron nitride, boron carbide, titanium nitride, titanium diboride, titanium carbide, silicone nitride, silicon carbide, aluminum boride, aluminum nitride, aluminum carbide, chromium nitride, chromium boride, chromium carbide, zirconium nitride, zirconium diboride, hafnium diboride, hafnium nitride, hafnium carbide, niobium nitride, niobium dibroide, niobium carbide, tantalum nitride, tantalum diboride, and tantalum carbide.

27. The mixture of any of clauses 24 to 25, wherein the ceramic support material consists of boron nitride.

28. The mixture of any of clauses 24 to 27, wherein the mixture comprises at least 1

percent by weight of the ceramic support material based on the total weight of the mixture.

29. The mixture of any of clauses 24 to 27, wherein the mixture comprises 1 percent to 20 percent by weight of the ceramic support material based on the total weight of the mixture.

30. The mixture of any of clauses 24 to 29, wherein the mixture has a porosity area

fraction in a range of 0.05 to 0.5.

31. The mixture of any of clauses 24 to 30, wherein the carbon source comprises at least one of carbon black, graphite, coke, and carbon resin.

32. The mixture of any of clauses 24 to 31, wherein the boron source comprises at least one of boric oxide and boric acid.

[0058] One skilled in the art will recognize that the herein described components, devices, operations/actions, and objects, and the discussion accompanying them, are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific examples/embodiments set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components, devices, operations/actions, and objects should not be taken as limiting. While the present disclosure provides descriptions of various specific aspects for the purpose of illustrating various aspects of the present disclosure and/or its potential applications, it is understood that variations and modifications will occur to those skilled in the art. Accordingly, the invention or inventions described herein should be understood to be at least as broad as they are claimed and not as more narrowly defined by particular illustrative aspects provided herein.

Claims

CLAIMS What is claimed is:

1. A method, comprising:

a ceramic support material; and

wherein during the carbothermically reacting, the ceramic support material promotes permeation of the nitrogen source through the precursor material.

2. The method of claim 1, wherein a melting temperature of the ceramic support material is greater than a temperature at which the precursor material is carbothermically reacted in the reactor chamber in the presence of the ceramic support material.

3. The method of claim 1, wherein the ceramic support material comprises at least one of boron nitride, boron carbide, titanium nitride, titanium diboride, titanium carbide, silicone nitride, silicon carbide, aluminum boride, aluminum nitride, aluminum carbide, chromium nitride, chromium boride, chromium carbide, zirconium nitride, zirconium diboride, hafnium diboride, hafnium nitride, hafnium carbide, niobium nitride, niobium dibroide, niobium carbide, tantalum nitride, tantalum diboride, and tantalum carbide.

4. The method of claim 1, wherein the ceramic support material consists of boron

nitride.

5. The method of claim 1, wherein the starting materials comprise at least 1 percent by weight of the ceramic support material based on the total weight of the starting materials.

6. The method of claim 1, wherein the starting materials comprise 1 percent to 20 percent by weight of the ceramic support material based on the total weight of the starting materials.

7. The method of claim 1, wherein a mixture of the starting materials in the reactor chamber comprises a porosity area fraction in a range of 0.05 to 0.5.

8. The method of claims 1, wherein the ceramic material has a plate-like particle shape.

9. The method of claim 1, wherein the nitrogen source comprises at least one of nitrogen gas and ammonia.

10. The method of claim 1, wherein the carbon source comprises at least one of carbon black, graphite, coke, and carbon resin.

11. The method of claim 1, wherein the boron source comprises at least one of boric oxide and boric acid.

12. The method of claim 1, further comprising heating the starting materials in the reactor chamber prior to carbothermically reacting the precursor material with the nitrogen source in the reactor chamber in the presence of the ceramic support material.

13. The method of claim 12, wherein the heating comprises heating the starting materials at which the precursor material melts but that is lower than a melting temperature of the ceramic support material.

14. The method of claim 1, wherein carbothermically reacting the precursor material with the nitrogen source in the reactor chamber in the presence of the ceramic support material comprises flowing the nitrogen source through the mixture of the starting materials.

15. The method of claim 1, further comprising flowing a carrier gas through the mixture of the starting materials.

16. The method of claim 15, wherein the carrier gas comprises at least one of argon and helium.

17. The method of claim 1, wherein carbothermically reacting the precursor material with the nitrogen source in the reactor chamber in the presence of the ceramic support material comprises flowing a carrier gas and the nitrogen source through the mixture of the starting materials at a partial pressure suitable to promote a carbothermic reaction between the precursor material and the nitrogen source.

18. The method of claim 1, further comprising dehydrating the starting materials prior to carbothermically reacting the precursor material with the nitrogen source in the reactor chamber in the presence of the ceramic support material.

19. The method of claim 18, further comprising granulating the starting materials after dehydrating the starting materials.

20. The method of claim 20, wherein the reactor chamber is a continuous reactor chamber and carbothermically reacting the precursor material with the nitrogen source in the reactor chamber in the presence of the ceramic support material is a continuous process over a time period.

21. The method of claim 1, further comprising recycling the ceramic material into the reactor chamber.

22. The method of claim 1, wherein the reactor chamber is a batch reactor chamber and carbothermically reacting the precursor material with a nitrogen source in the reactor chamber in the presence of the ceramic support material is a batch process.

23. The method of claim 1, further comprising processing the at least a portion of the ceramic material in a molten metal refractory process to produce an article.

24. A mixture comprising: a precursor material comprising a boron source and a carbon source; and a ceramic support material that promotes permeation of a nitrogen source through the precursor material;

wherein the mixture is suitable for carbothermically reacting the precursor material in the mixture with a nitrogen source to produce a ceramic material comprising a boron nitride and the ceramic support material.

25. The mixture of claim 24, wherein the ceramic support material has a melting

temperature greater than a temperature required to facilitate a carbothermic reaction of the precursor material.

26. The mixture of claim 24, wherein the ceramic support material comprises at least one of boron nitride, boron carbide, titanium nitride, titanium diboride, titanium carbide, silicone nitride, silicon carbide, aluminum boride, aluminum nitride, aluminum carbide, chromium nitride, chromium boride, chromium carbide, zirconium nitride, zirconium diboride, hafnium diboride, hafnium nitride, hafnium carbide, niobium nitride, niobium dibroide, niobium carbide, tantalum nitride, tantalum diboride, and tantalum carbide.

27. The mixture of claim 24, wherein the ceramic support material consists of boron nitride.

28. The mixture of claim 24, wherein the mixture comprises at least 1 percent by weight of the ceramic support material based on the total weight of the mixture.

29. The mixture of claim 24, wherein the mixture comprises 1 percent to 20 percent by weight of the ceramic support material based on the total weight of the mixture.

30. The mixture of claim 24, wherein the mixture has a porosity area fraction in a range of 0.05 to 0.5.

31. The mixture of claim 24, wherein the carbon source comprises at least one of carbon black, graphite, coke, and carbon resin.

32. The mixture of claim 24, wherein the boron source comprises at least one of boric oxide and boric acid.