Abstract: A ceramic insulated wire has a conductor core of copper or copper alloy, a stainless steel layer around the conductor core and a chromium oxide film (2A) around the stainless steel layer. The chromium oxide film (2A) is surrounded by an outer ceramic insulator formed by a vapor deposition method. Cladding the conductor core with stainless steel is done by inserting the core lengthwise into a stainless steel pipe, plastically working the resulting composite body to provide a desired size, and oxidizing the stainless steel which contains sufficient chromium for the formation of the chromium oxide film to have a thickness within the range of 10 nm to 1000 nm. The outer ceramic insulator formed by vapor deposition is made of Al.sub.2 O.sub.3, SiO.sub.2, AlN and Si.sub.3 N.sub.4 which provide an excellent heat resistance while the chromium oxide film substantially increases the bonding strength.

Abstract: A heat and oxidation resistant electrically conductive composite conductor has a core (1) made of copper or a copper alloy, an electrically conductive ceramics layer (2) around the core (1), and a nickel layer (3) on the exterior of the electrically conductive ceramics layer (2). Such a conductor is produced by coating the outer surface of the core copper alloy binder and covering the coated core with a nickel tape under an atmosphere of an inert gas or a reducing gas, welding the seam of the tape, clading the so formed conductor by a cladding die, and drawing the clad conductor. The composite conductor has a high conductivity which is not reduced even when the conductor is exposed to a high temperature operating condition.

Abstract: An insulated electrical conductor wire has a conductor core containing Ni or Ni alloy at least in its outer surface, an oxide layer of Ni or Ni alloy formed by oxidation treatment of the outer surface of the conductor, and an insulating inorganic compound outer layer formed on the oxide layer of Ni or Ni alloy. The insulating inorganic outer layer is intimately bonded to the oxide layer and provides an improved heat resistance and insulability.

Abstract: A preferred composite which is useful at temperatures in excess of about 0.degree. C. comprising a ceramic matrix and 40-60% on volume basis of coated and uncoated fibers embedded in the matrix generally parallel to each other and in a controlled arrangement; the matrix is selected from the group consisting essentially of silicon nitride, silicon carbide and zirconium titanate; the fibers are silicon carbides fibers 5-20 microns thick; the coating on the coated fibers is boron nitride 0.1-0.3 microns thick; cross-section of the composite contains about one half, on volume basis, of uncoated fibers in one band extending from one side edge of the cross-section to the opposite side edge; the composite having unexpectedly improved strength and/or toughness compared to a composite composed of only coated or only uncoated fibers.

Abstract: A shaped ceramic-ceramic composite article comprising a ceramic monolith, preferably in the shape of a hollow tube, having a ceramic fiber matrix thereover, coated with carbonaceous material and overcoated with silicon carbide.

Abstract: Fiber reinforced glass or glass-ceramic matrix composite articles are described which comprise spaced apart face sheets connected by ribs which extend between the face sheets. The fibers in the ribs are interwoven with the fibers in the face sheets, thereby producing a structure having high shear strength.

Abstract: An insulated wire is suitable for use as a distribution wire, a wire for winding a coil or the like, which is used in a high-vacuum environment or in a high-temperature environment such as a high vacuum apparatus or a high temperature service apparatus. The insulated wire has a base material (1) forming a substrate, a chromium oxide CrO.sub.3-x containing intermediate layer (2) on the substrate, and an oxide insulating layer (3) on the intermediate layer. The base material (1) is an electrical conductor. The chromium oxide containing layer (2) is so formed that the ratio of oxygen to chromium O/Cr is not less than 0.5 but less than 1.5 to avoid the formation of chromic oxide Cr.sub.2 O.sub.3 which reduces the adhesive bonding strength. The oxide insulating layer (3) is formed by applying a precursor solution of a metallic oxide onto the chromium oxide containing layer (2) by a sol-gel method or an organic acid salt pyrolytic method.

Abstract: An article comprising a non-conductive substrate having a sub-micron thickness of a sulfur-doped oxidizable metal coating thereon. Optionally, the sulfur-doped oxidizable metal-coated substrate may be further coated with (i) a promoter metal which is galvanically effective to promote the corrosion of the oxidizable metal, discontinuously coated on the oxidizable metal coating, and/or (ii) a salt, to accelerate the galvanic corrosion reaction by which the oxidizable metal coating is oxidized. When utilized in a form comprising fine diameter substrate elements such as glass or ceramic filaments, the resulting product may usefully be employed as an evanescent chaff. In the presence of atmospheric moisture, such evanescent chaff undergoes oxidation of the oxidizable metal coating so that the radar signature of the chaff transiently decays.

Abstract: An optical fiber preform includes a core made from a fluoride glass which is doped with a rare earth, and a cladding surrounding the core. The cladding is made from one of an oxide glass and a fluoroxide glass. The core has a characteristic of amplification at 1.3 .mu.m-band. The cladding does not have absorption at 1.3 .mu.m-band. The preform is useful as a material for a fiber optical amplifier in optical communication systems.

Abstract: An insulated wire has a conductor, a first insulating metal oxide layer which is formed around the conductor, and a second insulating metal oxide layer, containing ceramic particles mixed by addition and formed around the first insulating metal oxide layer. The so formed insulating metal oxide layers are produced by changing a precursor of a metal oxide into the ceramic state. This change is caused by a method such as a sol-gel method or a thermal decomposition method. The mixed ceramic particles are more preferably in the form of fine platelets. This insulated wire has an excellent flexibility, emits no gas, can maintain its insulation even at a high temperature, and has a high breakdown voltage.

Abstract: This composite material with a fibrous reinforcement has refractory fibres (2) embedded in a nonmetallic matrix (4) and an interphase material (6) interposed between the fibres and the matrix, the interphase material being boron carbonitride with a lamellar or amorphous structure containing in atomic %, 0 to 98% nitrogen, 1 to 99% carbon and 1 to 99% boron. The composition of the interphase material can be homogeneous or vary gradually from the fibre-material interface (8) to the material-matrix interface (10).

Abstract: A tin oxide fiber expressed by the general formulaSn.sub.(1-y) Z.sub.y O.sub.2 (I)wherein Z is a metal element of the Group V of the periodic table, and y is 0 to 0.3, having a diameter which is greater than 1 .mu.m or having a length which is greater than 3 mm and having an aspect ratio which is greater than 10.This fiber is process for producing a tin oxide fiber comprising spinning an alcohol solution of a tin compound soluble in alcohol, or spinning an alcohol solution of said tin compound and a compound of a metal of the Group V of the periodic table that is soluble in alcohol, followed by heating.

Abstract: A protective coating for a reinforcement phase exposed to molten silicon or silicon alloy infiltrant comprises, an inner layer material resistant to reaction with the molten infiltrant, an interlayer of a reactive material that reacts with the infiltrant to form compounds having a melting temperature greater than the infiltrant, and an outer layer material resistant to reaction with the molten infiltrant. Materials resistant to reaction with molten silicon are a metal carbide from the group consisting of carbides of titanium, hafnium, zirconium, and tantalum; a metal nitride from the group consisting of nitrides of boron, silicon, aluminum, titanium, zirconium, hafnium, niobium, and tantalum; a metal boride from the group consisting of borides of titanium, zirconium, hafnium, silicon, and aluminum, or combinations thereof.

Abstract: A laminate comprising (a) a carrier having a heat conductivity of at least 10 W/mK and a thickness of 10 to 100 .mu.m, and (b) a dielectric adhesive layer which is applied to at least one surface of said substrate and which contains a heat-conductive filler and has a thickness of 5 to 500 .mu.m and a heat conductivity of 1 W/mK. The flexible laminate, or a dielectric and self-supporting adhesive film which contains a heat-conductive filler and has a heat conductivity of at least 1 W/mK, is suitable for removing heat from leadframes which have electrically insulated contact surfaces for electrical and electronic components and which are encapsulated with a synthetic resin moulding material, typically dual-in-line plastic packages, by bonding the rear sides of the contact surfaces to the leads.

Abstract: A composite comprising a ceramic matrix having immersed ceramic reinforcing fibers is strengthened and toughened by providing a multi-layer ceramic coating surrounding each fiber. The multiple layers in the fiber coating are not bonded to one another. As a result, the multiple layers separate from one another in the presence of an advancing crack in the ceramic matrix, thereby permitting the fibers to pull out of the matrix and avoid premature fiber breakage. The choice of materials for the fiber coating is not limited by any requirement to establish a particular type of chemical bond between the coating and the fiber. Instead, the invention relies only upon the mechanical tendency of the unbonded multiple layers in the fiber coating to separate to promote fiber pull-out from the matrix in the wake of an advancing crack.

Abstract: The subject invention relates to a coated reinforcement material comprising a Si-containing reinforcement having a coating of the general formula:Al.sub.x O.sub.y N.sub.zwhereinx is up to about 60 atomic % of the coating;y is from about 20 atomic % to about 55 atomic % of the coating; andz is from about 5 atomic % to about 45 atomic % of the coating, with the proviso that x+y+z=100.The invention further relates to a high strength, high temperature performance composite comprising a Si-containing reinforcement material having a coating comprising aluminum, oxygen and nitrogen, said coated reinforcement material in combination with a matrix material.

Abstract: An arc hardfacing rod including a tubular member, a filler material, an insulating coating and a plurality of discrete metal carbide particles set within the insulating coating such that a surface of a portion of the metal carbide particles is uncovered. The filler carbide particles include tungsten carbide particles, titanium carbide particles, tantalum carbide particles, niobium carbide particles, zirconium carbide particles, vanadium carbide particles, hafnium carbide particles, molybdenum carbide particles, chromium carbide particles, silicon carbide particles and boron carbide particles, cemented composites and mixtures thereof. Adhered to the exterior surface of the tubular member is an insulating coating including a coating flux and a coating bonding agent. A plurality of discrete metal carbide particles are set within the insulating coating such that a surface of a portion of the metal carbide particles is uncovered.

Abstract: A fiber coating which allows ceramic or metal fibers to be wetted by molten metals is disclosed. The coating inhibits degradation of the physical properties caused by chemical reaction between the fiber and the coating itself or between the fiber and the metal matrix. The fiber coating preferably includes at least a wetting layer, and in some applications, a wetting layer and a barrier layer between the fiber and the wetting layer. The wetting layer promotes fiber wetting by the metal matrix. The barrier layer inhibits fiber degradation. The fiber coating permits the fibers to be infiltrated with the metal matrix resulting in composites having unique properties not obtainable in pure materials.

Abstract: Refractory filaments in the form of a multifilament tow or fabrics woven therefrom are coated with protective oxide coatings to provide reinforcing materials that are useful in creating refractory composites. The refractory filaments are contacted with a liquid medium which contains a metal oxide or metal oxide precursor so that a substantially continuous coating of metal oxide or metal oxide precursor forms on the surface of each of the filaments. The filaments are then treated to substantially remove residual components of the liquid medium other than the metal oxide or metal oxide precursor. The coated filaments are stabilized, the above steps optionally are repeated to increase the coating thickness, and the coated filaments are heated to convert the metal oxide or metal oxide precursor into substantially continuous, uniform metal oxide coatings on the filaments.

Abstract: A ceramic fiber/ceramic matrix composite has ceramic fibers and a porous coating on the fibers. A ceramic matrix contacts the porous coating, the fiber and coating being immersed in the ceramic matrix. The porous coating is selected from the group including Si.sub.3 N.sub.4, SiC, ZrO.sub.2, Al.sub.2 O.sub.3, SnO.sub.2 and Ta.sub.2 O.sub.5. The pores are generally empty so as to render the coating frangible to promote fiber de-bonding and pull-out in the wake of an advancing crack in the matrix. In order to keep the pores empty, a non-porous sealing layer is formed over the porous coating which closes the pores without filling them. The ceramic matrix remains generally outside of the pores, whereby said pores remain empty after the fiber and coating are immersed in the ceramic matrix.

Abstract: The need for high current, high field, low loss, stable superconductors has led to the development of multifilamentary Nb.sub.3 Sn as the most promising candidate for use in superconducting machines. However, the brittle nature of Nb.sub.3 Sn and the high reaction temperature (.about.700.degree. C.) required to form it preclude the use of standard organic insulation systems. A recently developed class of high temperature dielectric materials which are characterized by unusually large specific heats and thermal conductivities at cryogenic temperatures offers the opportunity of providing increased enthalpy stabilization in a superconducting winding, as well as the required dielectric strength. The inorganic insulation system consists of a composite glass and ceramic powder vitrified at a temperature which coincides with the superconducting formation temperature of 600.degree.-800.degree. C.

Abstract: A composite material containing carbon is protected against oxidation by forming, on the composite material, an inner layer, an intermediate layer containing boron or a boron compound, and an outer layer of silicon carbide. The inner layer formed on the composite material before the intermediate layer is formed, is made of a refractory carbide that does not contain boron and that is at least 60 microns thick, said inner layer insulating the intermediate layer from the carbon contained in the composite material.

Abstract: The invention provides fibers formed of a blend of metal oxide, such as titanium or zirconium oxide, with etheric phosphazene. The invention optionally contains salt for antistatic fibers. The composition of the invention is formed by preparing solutions of etheric phosphazene and inorganic alkoxides, such as titanium isopropoxide. The solutions are then formed into fibers and cured at room temperature or with moderate heating. Fibers produced can be extensible, tough, hard, flexible, or brittle. They are multicomponent blends of the titaninum or zirconium oxide and phosphazene. The composite may be doped with low lattice energy salts to form conductive fibers.

Abstract: A pelletizer feed roller comprises a metal core having a ceramic layer with a rough outer surface bonded to the core. The outer surface of the ceramic layer is sealed with a penetrating sealer containing organic solvent and phenolic resin to prevent moisture contamination of the ceramic layer without adversely affecting the coefficient of friction of the feed roller.

Abstract: Finely divided silicon carbide materials, particularly powders, whiskers and short fibers, are provided with a titanium nitride surface coating by the process of (i) placing a low carbon diffusivity layer atop the silicon carbon, (ii) placing a titanium metal coating atop the low carbon diffusivity layer, and (iii) nitriding the titanium metal.

Abstract: A method of toughening a fiber/matrix ceramic composite consisting of non-oxide based ceramic fibers immersed in a ceramic matrix. The method includes, prior to immersing the fibers in the matrix, applying a metallo-organic solution of a noble metal to the fibers to form a coating of the solution on the fibers, evaporating the solvent from the solution and oxidizing the residual organic compounds whereby the coating becomes a pure noble metal and immersing the coated fibers in the matrix. The applying, evaporating, oxidizing and immersing steps are characterized by a limited raising of the temperature of the fibers. The coating is ductile so as to blunt advancing cracks in the matrix.

Abstract: The subject invention relates to a coated reinforcement material comprising a SiC reinforcement having a coating of at least three layers, wherein the layers are alternately A-material layers of the general formula:Al.sub.x O.sub.y N.sub.zwherein x is up to about 60 atomic % of the coating;y is from about 20 atomic % to about 55 atomic % of the coating; andz is from about 5 atomic % to about 45 atomic % of the coating, with the proviso that x+y+z=100, and B-material layers comprising a metal alloy, such that the first and last layers of the coating are A-material layers. The invention further relates to a high strength, high temperature performance composite containing the above-specified coated reinforcement.

Abstract: Brittle fibers such as ceramic or carbon fibers are protected by a shroud of thermoplastic material surrounding the core. Such enshrouded yarns facilitate formation of fiber preforms used in the preparation of composite materials.

Abstract: A layer (16) forming interphase in a material having a lamellar structure is situated between the fibers of the texture and the matrix, and at least one layer (14) forming control interphase is situated between the surface of the fibers (10) and the lamellar interphase (16) in such a way as to define, for those cracks which have spread through the matrix (18) and the lamellar interphase (16), a preferential propagation zone away from direct contact with the actual fibers (10).

Abstract: Fiber-reinforced ceramic matrix composites incorporating a glass-ceramic matrix of lithium aluminosilicate composition in which is disposed a fiber reinforcement phase including at least one layer of unidirectionally oriented fibers (e.g. SiC), the matrix further comprising a whisker reinforcement phase selected from the group of SiC, alumina, HfC and Si.sub.3 N.sub.4, the whiskers imparting substantially improved transverse modulus of rupture strength and interlaminar shear strength to the composite.

Abstract: A discontinuous carbon fiber reinforced glass matrix composite includes a glass matrix, a plurality of carbon reinforcing fibers dispersed in the matrix, and a plurality of boron nitride reinforcing particles dispersed in the matrix. The composite may be fabricated by mixing glass powder and boron nitride reinforcing particles in a carrier liquid to create a slurry and adding a binder to the slurry. A continuous multifilament carbon fiber yarn is impregnated with the slurry and dried to remove the carrier liquid. The impregnated carbon fiber yarn is cut to a suitable length and is molded in a suitable molding means to form a carbon fiber reinforced glass matrix composite article.

Abstract: A far infrared ray emitting, odor-absorbing material is disclosed. The material comprises cellulose acetate fiber having adhered thereto an ultrafine powder of alumina hydrate or silica hydrate which is chemically produced in an aqueous dispersion of the cellulose acetate fiber. The material possesses a high far infrared ray emitting, odor-absorbing capability as well as many characteristics inherently possessed by cellulose acetate fibers, and can expand the utility of cellulose acetate in such fields as sanitary, health-care, and medical fields.

Abstract: Ceramic parts may be bonded by forming bonding layers of silicon dioxide, silicon, metal or metal oxide on the parts, placing the bonding layers adjacent one another and heating in an oxidizing ambient atmosphere to form an oxide bond therebetween. Pressure may be applied between the ceramic parts to aid in bonding. A reliable bonded ceramic structure is thereby provided.

Abstract: An insulated electrical wire is suitable for use as a distribution wire, a wire for winding coils, and for other electrical purposes. The wire can be used in a high-vacuum environment or in a high-temperature environment. This insulated electrical wire has a conductor core made of a base material (1), an anodic oxide layer (2), and an oxide insulating layer (3). The base material (1) forms a conductor core and has a surface cover of either an aluminum layer or an aluminum alloy layer at least on its outer surface. The anodic oxide layer (2) is formed on the surface layer. The oxide insulating layer (3) is formed on the anodic oxide layer by a sol-gel method or an organic acid salt pyrolytic method. This insulated electrical wire has a good heat resistance and a good insulating strength as well as excellent flexibility, and does not provide any gas adsorption source.

Abstract: Curable polyphenylene ether-polyepoxide compositions containing 1-methylimidazole as the primary curing catalyst have improved latency properties and are useful in the preparation of laminates and bonding sheets for printed circuit boards.

Abstract: An article comprising a non-conductive substrate which is coated with a sub-micron thickness of an oxidizable metal and overcoated with a microporous layer of an inorganic electrically insulative material. Optionally, the oxidizable metal-coated substrate may be sulfurized and/or further coated with (i) a promoter metal which is galvanically effective to promote the corrosion of the oxidizable metal, discontinuously coated on the oxidizable metal coating, and/or (ii) a salt, to accelerate the galvanic corrosion reaction by which the oxidizable metal coating is oxidized, prior to overcoating with the microporous insulative layer. Also disclosed is a related method of forming such articles, comprising chemical vapor depositing the oxidizable metal coating on the substrate and contacting the metallized substrate with a sol gel dispersion of the inorganic electrically insulative material which then is dried under suitable conditions to form the microporous layer on the substrate.

Abstract: A ceramic honeycomb structure containing SiO.sub.2, Al.sub.2 O.sub.3 and MgO primarily in the form of cordierite, mullite and corundum having a compositional gradient in the direction of the channels of the honeycomb and having extensive microcracking provides high resistance to thermal shock, and is useful as a substrate for catalysts.

Abstract: A filter for removing particulate matter from high temperature flowing fluids, and in particular gases, that is reinforced with ceramic fibers. The filter has a ceramic base fiber material in the form of a fabric, felt, paper of the like, with the refractory fibers thereof coated with a thin layer of a protective and bonding refractory applied by chemical vapor deposition techniques. This coating causes each fiber to be physically joined to adjoining fibers so as to prevent movement of the fibers during use and to increase the strength and toughness of the composite filter. Further, the coating can be selected to minimize any reactions between the constituents of the fluids and the fibers. A description is given of the formation of a composite filter using a felt preform of commercial silicon carbide fibers together with the coating of these fibers with pure silicon carbide. Filter efficiency approaching 100% has been demonstrated with these filters.

Abstract: A coated material obtained by applying a coat containing a metallic powder and/or a coloring pigment to a substrate and further applying a topcoat clear coating thereon, wherein said topcoat clear coating is a heat-hardening coat which contains a composition comprising a hydroxyl group-containing resin, a hydrolyzable silyl group-containing polymer and a hardening catalyst as the main component. This coated material is excellent in, for example, appearance, acid resistance, staining resistance, adhesiveness and hardness.

Abstract: A tape-formed or sheet-formed insulating material for use in windings and coils of electrical machines includes an insulating layer in the form of a homogeneous film of an organic polymer or in the form of a felt of a paper of fibres of an organic polymer and a protective layer coated on at least one side of the insulating layer which protects the insulating layer against degradation caused by corona. The protective layer comprises an organic polymer containing at least 10 percent by volume of a powdered filler in the form of chromium oxide, iron oxide or a mixture of chromium oxide and iron oxide. The filler preferably has an intrinsic resistivity of 10.sup.4 -10.sup.8 ohm m. The thickness of the protective layer and the total thickness of the protective layer, respectively, are preferably smaller than the thickness of the insulating layer and the resistivity of the protective layer is preferably in excess of 10.sup.10 ohm m.

Abstract: Single crystal whiskers of carbides, nitrides and carbonitrides of Ti, Zr, Hf, V, Nb, Ta, and W coated with one or more layers of different carbides, nitrides, or carbonitrides of Ti, Zr, Hf, Nb, Ta, or W or oxides of Al, Zr, or Hf. A process for the whisker production is also disclosed.

Abstract: A closable thermoplastic container for holding or conveying liquid hydrocarbon fuels and organic solvents, characterized in that at least those parts of said container which will come in contact with the liquid hydrocarbon fuels and organic solvents, is based on copolymers of CO or SO.sub.2, which polymers have been prepared by polymerization of CO or SO.sub.2 with at least one olefinically unsaturated compound A, and which polymers are made up of units --CO--(A')-- respectively --SO.sub.2 --(A')-- and in such a manner that the adjacent --CO-- respectively --SO.sub.2 -- units are separated by a single unit A', wherein the, or each, A' represents a monomer unit originating a compound A.

Abstract: Non-porous metal oxide-coated carbonaceous fibers capable of withstanding chemical degradation at temperatures above 1600.degree. C. and that are particularly useful in the construction of ceramic or metal composites without carbon-carbide hypereutectic formation or micro-cracking in metal and ceramic matrix composites, respectively, but with good interfacial bonding, thereby allowing the same to be favorably employed in space reentry vehicles, heat shields, high-performance aircraft, internal combustion engines, and the like.

Abstract: A multilayer laminate comprises a first perforated film of propylene homopolymer or copolymer, and a second film bonded to the first film and including a bonding layer of ethylene vinyl acetate copolymer and an outer heat sealable layer.

Abstract: A metal-coated substrate, e.g., of glass, ceramic, or a hydroxy-functionalized material, wherein the improvement comprises a polysilicate, titania, or alumina interlayer between the substrate and the metal coating. The interlayer may have a porous microstructure, e.g., a polysilicate interlayer with an average pore size on the order of 50-150 Angstroms.Such articles, e.g., in the form of metal-coated fibers, may suitably be employed as reinforcing media in material composites having utility in structural applications, such as EMI shielding elements.Also disclosed is a corresponding method for forming a metal coating on a substrate by the provision of an interlayer of the above type. The interlayer may suitably be formed by applying to the substrate a sol gel dispersion of the polysilicate, titania, or alumina material, followed by drying of the applied dispersion.

Abstract: An electrical conductor is provided with an electrical insulation (11) surrounding the conductor (10) and a surrounding protective layer (12) which protects the insulation against degradation caused by corona. The protective layer consists of an organic polymer containing at least 10 percent by volume of a powdered filler in the form of chromium oxide, iron oxide, or a mixture of chromium oxide and iron oxide. The filler preferably has an intrinsic resistivity of 10.sup.4 -10.sup.8 ohm m. The thickness of the protective layer is preferably smaller than the thickness of the underlying insulation (11) and its resistivity preferably exceeds 10.sup.10 ohm m. The conductor is used, among other things, in windings and coils for electrical machines.

Abstract: A preservative element, for timber or masonry in the form of a shaped element containing an organic boron compound, especially a boro-organic ester. Preferably the element also contains inorganic boron salts or acids, with or without the addition of other inorganic compounds having fungicidal and/or insecticidal properties.

Abstract: Reinforcing Si.sub.3 N.sub.4 ceramics with preoxidized SiC whiskers improves flexural strength and WEIBULL modulus over that of comparable bulk Si.sub.3 N.sub.4 ceramics or Si.sub.3 N.sub.4 ceramics reinforced with neat SiC whiskers. Hot isostatic pressing further improves the physical properties of said ceramics.

Abstract: A composite ceramic-ceramic material is disclosed having a fibrous reinforcing ceramic and a ceramic matrix made of a geopolymeric compound containing:(a) a poly(sialate) geopolymer M.sub.n (--Si--O--Al--O--).sub.n and/or poly(sialate-siloxo) M.sub.n (--Si--O--Al--O--Si--O--).sub.n, M representing at least one alkaline cation, and n the degree of polymerization;(b) ultrafine silicious and/or aluminous and/or silico-aluminous constituents, of size smaller than 5 microns, preferably lower than 2 microns,the said geopolymeric compound being obtained by polycondensation at a temperature between 20.degree. C. and 120.degree. C. of an alkaline alumino-silicate reaction mixture, the composition of the principal constituents of the said geopolymeric compound expressed in terms of mole ratios of the oxides being between or equal to following values:M.sub.2 O/SiO.sub.2 --0.10 TO 0.95,SiO.sub.2 /Al.sub.2 O.sub.3 --2.50 TO 6.00,M.sub.2 O/Al.sub.2 O.sub.3 --0.25 TO 5.70,M.sub.2 O representing either Na.sub.2 O and/or K.

Abstract: Ceramic bodies having a balanced overall stress pattern in which are present individual stress zones of compressive and tensile stresses and the techniques for forming said bodies are disclosed. The bodies are formed by having slightly different compositional patterns from one zone to another whereby during cooling there is a differential volumetric expansion or contraction in one zone as compared to an adjacent zone. The volumetric expansion or contraction is caused by a material which undergoes a phase transformation during the cooling from the sintering temperatures utilized to sinter the ceramic body, whereby such phase transformation is accompanied by a volumetric change.