Abstract: A method may include applying a layer comprising a carbon source on a surface of a substrate including silicon; applying a layer comprising silicon on the layer comprising elemental carbon; and heat treating at least the layer comprising the carbon source to cause carbon from the layer comprising the carbon source to react with at least one of silicon from the substrate or silicon from the layer comprising silicon to form silicon carbide.

Abstract: A particulate composite ceramic material may include: particles of at least one first ultra-high-temperature ceramic “UHTC,” the outer surface of the particles being at least partially covered by a porous layer made of at least one second UHTC in amorphous form; and the particles defining a space therebetween; optionally, porous clusters of the at least one second ultra-high-temperature ceramic in amorphous form, distributed in said space; a dense matrix and at least one third UHTC in crystallized form at least partially filling the space; optionally, a dense coating made of at least the third UHTC in crystallized form, covering the outer surface of the matrix, the matrix and the coating representing 5% to 90% by mass with respect to the total mass of the material. A part may include such a particulate ceramic composite material.

Abstract: A method of manufacturing a composite sintered body includes a step (Step S11) of molding mixed powder in which Al2O3, SiC, and MgO are mixed, into a green body having a predetermined shape and a step (Step S12) of generating a composite sintered body by sintering the green body. Then, in Step S11, the ratio of SiC to the mixed powder is not lower than 4.0 weight percentage and not higher than 13.0 weight percentage. Further, the purity of Al2O3 in Step S11 is not lower than 99.9%. It is thereby possible to suppress the abnormal grain growth of Al2O3 and suitably manufacture a composite sintered body having high relative dielectric constant and withstand voltage, and low tan ?.

Abstract: The present invention relates to preceramic polymer grafted nanoparticles and as well as methods of making and using same. Advantages of such preceramic polymer grafted nanoparticles include, reduced out gassing, desired morphology control and desirable, distinct rheological properties that are not found in simple mixtures. As a result, Applicants' preceramic polymer grafted nanoparticles can be used to provide significantly improved, items including but not limited to hypersonic vehicles, jets, rockets, mirrors, signal apertures, furnaces, glow plugs, brakes, and armor.

Abstract: A seal assembly for a gas turbine engine having a seal formed of a carbon material; and a seal seat positioned for rotation relative to the seal, wherein the seal and the seal seat each have a sealing surface which together define a sliding seal, and further having a carbon film on the sealing surface of the seal seat.

Abstract: A barrier coating resin formulation comprising at least one polycarbosilane preceramic polymer, at least one organically modified silicon dioxide preceramic polymer, at least one filler, and at least one solvent. A barrier coating comprising a reaction product of the at least one polycarbosilane preceramic polymer and the at least one organically modified silicon dioxide preceramic polymer and the at least one filler is also disclosed, as are articles comprising the barrier coating, rocket motors comprising the barrier coating, and methods of forming the articles.

Abstract: A SiC epitaxial wafer in which a SiC epitaxial layer is formed on a 4H—SiC single crystal substrate having an off angle and a substrate carbon inclusion density of 0.1 to 6.0 inclusions/cm2, and wherein a density of large pit defects caused by substrate carbon inclusions and contained in the SiC epitaxial layer is 0.5 defects/cm2 or less.

Abstract: A method of producing a ceramic matrix composite including a protective ceramic coating thereon comprises applying a surface slurry onto an outer surface of an impregnated fiber preform. The surface slurry includes particulate ceramic solids dispersed in a flowable preceramic polymer comprising silicon, and the impregnated fiber preform comprises a framework of ceramic fibers loaded with particulate matter. The flowable preceramic polymer is cured, thereby forming on the outer surface a composite layer comprising a cured preceramic polymer with the particulate ceramic solids dispersed therein. The cured preceramic polymer is then pyrolyzed to form a porous ceramic layer comprising silicon carbide, and the impregnated fiber preform and the porous ceramic layer are infiltrated with a molten material comprising silicon. After infiltration, the molten material is cooled to form a ceramic matrix composite body with a protective ceramic coating thereon.

Abstract: Novel N-alkyl substituted perhydridocyclic silazanes, oligomeric N-alkyl perhydridosilazane compounds, and N-alkylaminodihydridohalosilanes, and a method for their synthesis are provided. The novel compounds may be used to form high silicon nitride content films by thermal or plasma induced decomposition.

Abstract: Some variations provide a preceramic resin precursor formulation comprising: first molecules comprising at least one Si—C bond and/or at least one Si—N bond, wherein the first molecules include at least one silyl hydride group (Si—H) available for hydrosilylation; and second molecules with at least one unsaturated carbon-carbon bond attached to a UV-active functional group. The first molecules and second molecules may be reacted, via hydrosilylation with a homogeneous or heterogeneous metal-containing catalyst, to produce third molecules comprising a hydrosilylation-modified polysilazane that contains the UV-active functional group. Many possible starting formulations are described, and methods are disclosed for carrying out the chemical reactions to generate the hydrosilylation-modified polysilazanes. The hydrosilylation-modified polysilazanes may then be 3D-printed and thermally treating to fabricate a ceramic material.

Abstract: Provided are an aluminum-silicon-carbide composite having high thermal conductivity, low thermal expansion, and low specific gravity and a method for producing the composite. Provided is an aluminum-silicon-carbide composite formed by impregnating a porous silicon carbide molded body with an aluminum alloy. The ratio of silicon carbide in the composite is 60 vol % or more, and the composite contains 60-75 mass % of silicon carbide having a particle diameter of 80 ?m or more and 800 ?m or less, 20-30 mass % of silicon carbide having a particle diameter of 8 ?m or more and less than 80 ?m, and 5-10 mass % of silicon carbide having a particle diameter of less than 8 ?m.

Abstract: A process for manufacturing a composite part includes introducing an adhesion promoter into the pores of a fibrous preform formed by threads covered with a coating having —OH groups on its surface, the adhesion promoter including an electron-withdrawing group G1 that is reactive according to a reaction of substitution or of nucleophilic addition with the —OH groups, and a reactive group G2; grafting the adhesion promoter to the surface of the coating by a reaction of substitution or nucleophilic addition of the —OH groups on the group G1; introducing a ceramic precursor resin into the pores of the fibrous preform; polymerizing the resin introduced and bonding the grafted adhesion promoter to the resin by chemical reaction between these two compounds at the level of the group G2, and forming a ceramic matrix phase in the pores of the fibrous preform by pyrolysis of the polymerized resin.

Abstract: A preceramic resin formulation comprising a polycarbosilane preceramic polymer, an organically modified silicon dioxide preceramic polymer, and, optionally, at least one filler. The preceramic resin formulation is formulated to exhibit a viscosity of from about 1,000 cP at about 25° C. to about 5,000 cP at a temperature of about 25° C. The at least one filler comprises first particles having an average mean diameter of less than about 1.0 ?m and second particles having an average mean diameter of from about 1.5 ?m to about 5 ?m. Impregnated fibers comprising the preceramic resin formulation are also disclosed, as is a composite material comprising a reaction product of the polycarbosilane preceramic polymer, organically modified silicon dioxide preceramic polymer, and the at least one filler. Methods of forming a ceramic matrix composite are also disclosed.

Abstract: In the latent heat storage body (100) according to the present invention, the surface of a core particle (10) composed of a latent heat storage material of a metal or an alloy is coated with an oxidized film of a compositional element of the core particle (10). Hence, the step of separately fabricating the core particle and the oxidized film (20) corresponding to a shell accommodating the core particle and accommodating the core particle inside the shell becomes unnecessary. Further since the core particle exhibits no expansion when transforming from a solid phase to a liquid phase, the component of the melted latent heat storage material stays inside the space covered with the oxidized film and the oxidized film is never damaged. Further, the oxidized film (20) can be made chemically stable.

Abstract: A method of manufacturing a silicon carbide (SiC) sintered body and a SiC sintered body obtained by the method are provided. The method includes: preparing a composite powder by subjecting a SiC raw material and a sintering aid raw material to mechanical alloying; and sintering the composite powder, wherein the sintering aid is at least one selected from the group consisting of an Al—C-based material, an Al—B—C-based material, and a B—C-based material. Accordingly, a SiC sintered body that can be sintered at low temperature, can be densified, and has high strength and high electrical conductivity can be prepared.

Abstract: Organosilicon chemistry, polymer derived ceramic materials, and methods. Such materials and methods for making polysilocarb (SiOC) and Silicon Carbide (SiC) materials having 3-nines, 4-nines, 6-nines and greater purity. Processes and articles utilizing such high purity SiOC and SiC.

Abstract: A SiC single crystal having high crystallinity and a large diameter is provided. A SiC single crystal comprising a seed crystal with a c-plane and a non-c-plane, and a c-plane growth portion and an enlarged diameter portion that have grown from the c-plane and the non-c-plane of the seed crystal as origins in the direction of the c-plane and the direction of the non-c-plane, wherein a continuous region free of threading dislocations is present in a peripheral portion of a plane that is parallel to the c-plane of the seed crystal, and contains the seed crystal and the enlarged diameter portion, wherein the area of the continuous region occupies 50% or more of the total area of the plane.

Abstract: Disclosed is a process for producing a RBSiC member that has a large size and a complicated shape and possesses ceramic properties. The process is Selective Laser Sintering process which includes providing a raw material containing silicon carbide particles and a binder, forming a thin layer of the raw material, and sintering the thin layer by irradiating a desired area in the thin layer with laser to form a sintered thin layer, repeating the step of forming the sintered thin layer to obtain a green body, impregnating the green body with a carbon source and curing the green body impregnated with the carbon source to give a cured body, carbonizing an organic compound component in the cured body to give a fired body, and infiltrating the fired body with silicon and subjecting the fired body to reaction sintering to give a RBSiC member, wherein the fired body contains 8% to 30% by weight of carbon.

Abstract: The invention proposed a novel hot pressing flowing sintering method to fabricate textured ceramics. The perfectly 2-dimensional textured Si3N4 ceramics (Lotgering orientation factor fL 0.9975) were fabricated by this method. During the initial sintering stage, the specimen flowed along the plane which is perpendicular to the hot pressing direction under pressure, through the controlling of the graphite die movement. The rod-like ?-Si3N4 nuclei was easily to texture during the flowing process, due to the small size of the ?-Si3N4 nuclei and the high porosity of the flowing specimen. After aligned, the ?-Si3N4 grains grew along the materials flowing direction with little constraint. textured Si3N4 ceramics fabricated by this invention also showed high aspect ratio. Compared to the conventional hot-forging technique which contained the sintering and forging processes, hot pressing flowing sintering proposed is simpler and lower cost to fabricate textured Si3N4.

Abstract: The invention provides a susceptor capable of obtaining high-quality SiC semiconductor crystals by keeping the Si concentration and C concentration around a wafer constant and by preventing the generation of particles. A susceptor of graphite covered with silicon carbide is characterized in that at least one section of a part on which a wafer is placed is tantalum carbide or a graphite material covered with tantalum carbide. The part on which the wafer is placed may be a detachable member. A material around the part on which the wafer is placed may be a detachable graphite material covered with silicon carbide.

Abstract: A silicon carbide based material exhibiting high strength, good thermal shock resistance, high resistance to abrasion and being chemically stable to harsh environmental conditions is described. The carbide Ball Hill ceramic comprises a ?-SiAlON bonding phase in which sintering is facilitated by at least one rare earth oxide sintering agents incorporated within the Vibrating Sieve batch admixture as starting materials. The residual rare earth sintering aid being chosen so as to impart good mechanical and refractory properties.

Abstract: A method of forming a ceramic body including forming a mixture made of at least a first powder material (PM1) including carbon having a first average particle size (PS1), a second powder material (PM2) including carbon and different than the first powder material, the second powder material having a second average particle size (PS2) less than the first average particle size (PS1), and an aluminum content (AC2) greater than the aluminum content (AC1) of the first powder material, and further including forming a green body from the mixture, and sintering the green body and forming a ceramic body having a first type of grain having an average grain size of not greater than about 8 times the first average particle size (PS1).

Abstract: A bearing system having a bearing pair made up of at least one bearing and at least one running partner, wherein a coating which is made up of a layer of which the main constituent is amorphous SiO2 is applied to at least one running surface of the bearing pair.

Abstract: Sintered product exhibiting a relative density of greater than 97% and composed of: more than 92% by weight of silicon carbide, between 0.5% and 8% by weight of an amorphous secondary phase comprising the elements O, Si and one or two elements chosen from Al and Y, less than 2% of other elements, present in said product in the form of an additional phase or of unavoidable impurities, in which the silicon carbide is present in the form of crystalline grains and in which said secondary phase is amorphous and located essentially at the boundaries of the silicon carbide grains.

Abstract: In a method of forming polycrystalline SiC grain material, low-density, gas-permeable and vapor-permeable bulk carbon is positioned at a first location inside of a graphite crucible and a mixture of elemental silicon and elemental carbon is positioned at a second location inside of the graphite crucible. Thereafter, the mixture and the bulk carbon are heated to a first temperature below the melting point of the elemental Si to remove adsorbed gas, moisture and/or volatiles from the mixture and the bulk carbon. Next, the mixture and the bulk carbon are heated to a second temperature that causes the elemental Si and the elemental C to react forming as-synthesized SiC inside of the crucible. The as-synthesized SiC and the bulk carbon are then heated in a way to cause the as-synthesized SiC to sublime and produce vapors that migrate into, condense on and react with the bulk carbon forming polycrystalline SiC material.

Abstract: A method for making a gas turbine engine matrix composite structure. The method includes providing at least one metal core element, fabricating a matrix composite component about the metal core element, and removing at least part of the metal core element from the matrix composite component by introduction of a halogen gas.

Abstract: A pipe choke for use in drilling and mining operations comprising a body including a first end and a second end configured to couple to a pipe, an opening extending through the body from the first end to the second end, and wherein the body includes a first phase comprising recrystallized silicon carbide and a second phase comprising silicon.

Abstract: The invention relates to a refractory ceramic batch and to a refractory ceramic brick produced therefrom.

Abstract: A ceramics composite member includes a structure in which a first ceramic member and a second ceramic member are integrated with a joint portion. The joint portion has a texture in which a silicon phase having an average diameter of 0.05 ?m or more and 10 ?m or less is continuously provided in a network form in interstices of silicon carbide particles having an average particle diameter of 0.1 ?m or more and 0.1 mm or less.

Abstract: A silicon carbide powder for the production of a silicon carbide single crystal has an average particle diameter of 100 ?m or more and 700 ?m or less and a specific surface area of 0.05 m2/g or more and 0.30 m2/g or less. A method for producing a silicon carbide powder for the production of the silicon carbide single crystal including sintering a silicon carbide powder having an average particle diameter of 20 ?m or less under pressure of 70 MPa or less at a temperature of 1900° C. or more and 2400° C. or less and in a non-oxidizing atmosphere, thereby obtaining a sintered body having a density of 1.29 g/cm3 or more; adjusting particle size by means of pulverization of the sintered body; and removing impurities by means of an acid treatment.

Abstract: A ceramic sintered body includes tungsten carbide, zirconia, and alumina. The content of the tungsten carbide is 20 to 50 vol %, and the content of the zirconia is 5 to 25 vol %. The crystal phase of the zirconia is a tetragonal crystal or a mixture of tetragonal and monoclinic crystals. The ceramic sintered body does not substantially include Ti compounds. The average particle diameter of the tungsten carbide, the average particle diameter of the zirconia, and the average particle diameter of the alumina are all 1 ?m or less.

Abstract: Ceramic nanocomposites and methods for manufacturing the ceramic nanocomposites are disclosed. One method includes introducing to a fired green ceramic body having a ceramic matrix submicron particles having coefficient of thermal expansion lower than the coefficient of thermal expansion of the ceramic matrix and at least one type of location-controlling dopant at an amount that is sufficient to cover the majority of the ceramic matrix grain boundaries. One ceramic nanocomposite includes a ceramic matrix with submicron particles dispersed in the ceramic matrix, the submicron particles having a coefficient of thermal expansion lower than the coefficient of thermal expansion of the ceramic matrix and at least one dopant that covers the majority of the ceramic matrix grain boundaries, at a concentration that does not exceed the bulk solubility limit of the dopant in the ceramic matrix at the ceramic nanocomposite sintering temperature.

Abstract: A composition having nanoparticles of silicon carbide and a carbonaceous matrix or silicon matrix. The composition is not in the form of a powder. A composition having silicon and an organic compound having a char yield of at least 60% by weight or a thermoset made from the organic compound. A method of combining silicon and the organic compound and heating to form silicon carbide or silicon nitride nanoparticles.

Abstract: A composite article including a body made of recrystallized silicon carbide and an infiltrant, wherein the body comprises a static impact resistance of at least about 1800 MPa.

Abstract: A silicon carbide ceramic is provided which has a small amount of resistivity change due to changes in temperature and which is capable of generating heat by current application. The silicon carbide ceramic contains silicon carbide crystals having 0.1 to 25 mass % of 4H—SiC silicon carbide crystals and 50 to 99.9 mass % of 6H—SiC silicon carbide crystals, preferably having a nitrogen content of 0.01 mass % or less, more preferably containing two or more kinds of silicon carbide particles containing silicon carbide crystals and silicon for binding the silicon carbide particles to each other and having a silicon content of from 10 to 40 mass %.

Abstract: This disclosure concerns a method of making silicon carbide involving adding agricultural husk material to a container, creating a vacuum or an inert atmosphere inside the container, applying conventional heating or microwave heating, heating rapidly, and reacting the material and forming silicon carbide (SiC).

Abstract: The method comprises: using chemical vapor infiltration to form a first continuous interphase on the fibers of a fiber structure made of refractory fibers, the interphase having a thickness of no more than 100 nanometers; impregnating the fiber structure with a consolidation composition comprising a carbon or ceramic precursor resin; forming a fiber preform that is consolidated by shaping the impregnated fiber structure and using pyrolysis to transform the resin into a discontinuous solid residue of carbon or ceramic; using chemical vapor infiltration to form a second continuous interphase layer; and densifying the preform with a refractory matrix. This preserves the capacity of the fiber structure to deform so as to enable a fiber preform to be obtained that is of complex shape, while nevertheless guaranteeing the presence of a continuous interphase between the fibers and the matrix.

Abstract: There is provided a method for the fabrication of porous SiC ceramic. The method comprises oxidizing particles of SiC ceramic thereby forming amorphous silica on the surface of the particles. The oxidized SiC particles are then mixed with an additive. Alternatively, layer(s) of the additive is (are) deposited on their surface by sol-gel technique. The oxidized SiC particles mixed or coated with the additive are then mixed with at least one pore-former. Alternatively, the oxidized SiC particles mixed or coated with the additive are coated with layer(s) of a polymer or pore-former by in-situ polymerization. In embodiments where the oxidized SiC particles are mixed with an additive and a pore-former or polymer, a further additive may be used. In each of these embodiments, the resulting product is then compacted into a green body which is heated and sintered to yield the porous SiC ceramic material. There is also provided a porous SiC ceramic fabricated by the method according to the invention.

Abstract: A precursor formulation of a silicon carbide material that includes a ceramic material and a boron-11 compound. The ceramic material may include silicon and carbon and, optionally, oxygen, nitrogen, titanium, zirconium, aluminum, or mixtures thereof. The boron-11 compound may be a boron-11 isotope of boron oxide, boron hydride, boron hydroxide, boron carbide, boron nitride, boron trichloride, boron trifluoride, boron metal, or mixtures thereof. A material for use in a nuclear reactor component is also disclosed, as are such components, as well as a method of producing the material.

Abstract: The invention relates to a method for producing a polysilane-polycarbosilane copolymer solution. Said method comprises the preparation of a polysilane, obtained by the disproportionation of a methylchlorodisilane or a mixture of methylchlorodisilanes of formula Si2MenC16-n with a Lewis base as the catalyst, a subsequent thermal cross-linking of the polysilane to form an infusible polysilane-polycarbosilane copolymer that is soluble in inert solvents, in addition to the production of said solution by the dissolution of the polysilane-polycarbosilane copolymer in an inert solvent. The invention also relates to a method for producing oxygen-depleted ceramic fibers and other molded bodies with a composition similar to that of SiC. Said method comprises the spinning of the solution to obtain green fibers according to the dry spinning method and the pyrolysis of the dried green fibers in an inert gas atmosphere or a reductive atmosphere.

Abstract: Substrates suitable for mirrors used at wavelengths in the EUV wavelength range have substrates (1) including a base body (2) made of a precipitation-hardened alloy, of an intermetallic phase of an alloy system, of a particulate composite or of an alloy having a composition which, in the phase diagram of the corresponding alloy system, lies in a region which is bounded by phase stability lines. Preferably, the base body (2) is made of a precipitation-hardened copper or aluminum alloy. A highly reflective layer (6) is preferably provided on a polishing layer (3) of the substrate (1) of the EUV mirror (5).

Abstract: A SiC ceramic material includes a bundle of SiC continuous fibers in a porous SiC ceramic matrix, has thermal insulation properties, a high level of strength and a high degree of toughness. A SiC ceramic structure is made of the SiC ceramic material. It is produced by preparing a pressure-sintered compact using a slurry prepared by mixing SiC powder and carbon powder in a liquid and by gasifying and releasing the carbon powder. The SiC ceramic structure can be produced by heating a reaction preparation containing a bundle of SiC continuous fibers and Si powder to a temperature equal to or higher than the melting point of silicon causing a reaction of the carbon component and Si powder and thereby obtaining a reaction-sintered compact, and by gasifying and releasing the carbon component from the reaction-sintered compact. The SiC ceramic can be produced by a chemical vapor deposition method.

Abstract: Provided is a silicon carbide ceramic having a small amount of resistivity change due to temperature change and being capable of generating heat by current application; and containing silicon carbide crystals having 0.1 to 25 mass % of 4H—SiC silicon carbide crystals and 50 to 99.9 mass % of 6H—SiC silicon carbide crystals, preferably having a nitrogen content of 0.01 mass % or less, more preferably containing two or more kinds of silicon carbide particles containing silicon carbide crystals and silicon for binding these silicon carbide particles to each other and having a silicon content of from 10 to 40 mass %.

Abstract: A ceramics sliding member for use in ultrapure water or pure water of the present invention is made of a non-continuous-pore SiC sintered body. The non-continuous-pore SiC sintered body includes ?-SiC at a ratio of 20% by weight or more thereto and has an average crystal structure whose aspect ratio is 2 or greater.

Abstract: A composition having nanoparticles of silicon carbide and a carbonaceous matrix or silicon matrix. The composition is not in the form of a powder. A composition having silicon and an organic compound having a char yield of at least 60% by weight or a thermoset made from the organic compound. A method of combining silicon and the organic compound and heating to form silicon carbide or silicon nitride nanoparticles.

Abstract: To obtain a ceramic fiber-reinforced composite material, by melt-infiltrating a composite material substrate obtained by forming ceramic fibers into a composite with a matrix formed of an inorganic substance, with an alloy having a composition that is constituted by a disilicate of at least one or more transition metal among transition metals that belong to Group 3A, Group 4A or Group 5A of the Periodic Table and silicon as the remainder, and having the silicon content ratio of 66.7 at % or more.

Abstract: A pipe choke for use in drilling and mining operations comprising a body including a first end and a second end configured to couple to a pipe, an opening extending through the body from the first end to the second end, and wherein the body includes a first phase comprising recrystallized silicon carbide and a second phase comprising silicon.

Abstract: There is provided a silicon carbide-based porous body which can avoid excessive temperature elevation when it is used as a filter and the captured particulate matter (PM) is burnt for removal and which is low in strength reduction caused by heat cycle. The silicon carbide-based porous body comprises a plurality of silicon carbide (SiC) particles as an aggregate and a plurality of binding phases which bind the silicon carbide particles to each other, wherein of the binding phases, the phase having the largest volume is either of a Si phase and a phase (a metal silicide phase) made of at least one member selected from the group consisting of a Ti silicide, a Zr silicide, a Mo silicide and a W silicide, all having a linear thermal expansion coefficient at 40 to 800° C., higher than that of Si by at least 3×10?6 (° C.

Abstract: A silicon carbide based porous material, which contains a metal silicide in an amount of 1 to 30% by mass and having a porosity of 38 to 80%, is provided.

Abstract: The present invention pertains to a process for producing unmeltable polysilane-polycarbosilane copolymers which are soluble in inert solvents, comprising the steps providing the product of a disproportionation of a methylchlorodisilane or a mixture of several methylchlorodisilanes of the composition Si2MenCl6-n, wherein n=1?4, wherein the disproportionation was carried out with a Lewis base as a catalyst, wherein this product is a chlorine-containing, crude polysilane/oligosilane containing hydrocarbon groups, and thermally postcrosslinking the crude polysilane/oligosilane to a polysilane-polycarbosilane copolymer, characterized in that the chlorine content of the polysilane-polycarbosilane copolymer is lowered by reacting the crude polysilane/oligosilane with a substitution agent, by which chlorine bound therein is replaced with a chlorine-free substituent. Green fibers and low-oxygen/oxygen-free ceramic fibers with a very low chlorine content can be produced using this process.