Abstract: The stabilization of zirconia when used as a ceramic by various stabilizers has been known but a new and improved stabilized particulate zirconia has now been developed showing the important advantages.The particulate zirconia now developed is coated with a hydrous oxide of titanium and/or of aluminium and with at least one hydrous oxide of yttrium, calcium, magnesium, strontium or cerium.

Abstract: A novel basic refractory composition is disclosed. This composition has high resistance to calcium silicates such as cement clinkers and slag formed in steelmaking operations. It also has superior resistance to thermal shock and stresses such as load in high temperature. A refractory brick produced from this composition can be used in the firing zone of a rotary kiln and successfully withstands cement firing operations for a significantly longer period than conventional refractory bricks.The basic refractory composition consists of a synthetic calcium zirconate based clinker in combination with raw materials for magnesia; the molar ratio of CaO to ZrO.sub.2 in said clinker is in the range of 0.5-1.1, at least part of said clinker being in the form of particles having a size not smaller than 0.5 mm, ZrO.sub.2 being present in an amount of 4-49 wt % of said composition, the sum of CaO and MgO being 50-95 wt %, and the sum of ZrO.sub.2, CaO and MgO being at least 80 wt %.

Abstract: A basic refractory shape resulting from firing a batch consisting essentially of a magnesite and a zirconia; said batch containing for each 100 percent by weight thereof about 3 to 20 percent by weight of coarse zirconia having a particle size of 150-mesh Tyler, or greater, and 0 to 20 percent by weight of fine zirconia having a particle size of finer than 150-mesh Tyler and a slide gate assembly comprising at least one such shape.

Abstract: Magnesia partially-stabilized zirconia ceramic materials can be prepared from "unpurified" zirconia which contains at least about 0.05 weight percent silica. Despite the relatively high silica content, a thermal shock resistant material can be produced by a firing schedule which includes heating to a top temperature at a specified rate and cooling back to room temperature at specified rates and which incorporates a thermal aging step at 1000-1200.degree. C. Differences in microstructure and monoclinic zirconia content, with consequent differences in physical properties of the ceramic material, can be attained by variations in the firing and thermal-aging schedules.

Abstract: A high strength zirconia ceramic composition consisting essentially of a compound of ZrO.sub.2 containing less than 5.0 mol % Y.sub.2 O.sub.3 as a stabilizer and further containing 1-30 wt % aluminum and magnesium contents to the amount of the compound of ZrO.sub.2 in terms of Al.sub.2 O.sub.3 and MgO. In the case that the compound of ZrO.sub.2 further contains CeO.sub.2 as a stabilizer, the total amount of Y.sub.2 O.sub.3 and CeO.sub.2 is determined to be 1.0-15 mol % to the amount of the compound of ZrO.sub.2.

Abstract: The invention consists of zirconia base with high hydrothermal stability which:(a) consists essentially of at least 40 weight % of partially stabilized zirconia of the ZrO.sub.2 -Y.sub.2 O.sub.3 -CeO.sub.2 system wherein the proportion of ZrO.sub.2, Y.sub.2 O.sub.3, and CeO.sub.2 is within the range defined by the line connecting points F, G, L, M, N and K in a ternary diagram (ZrO.sub.2, YO.sub.1.5, CeO.sub.2), the vertices of said points being given by the following molar % of ZrO.sub.2, YO.sub.1.5, and CeO.sub.2, respectively:F (88, 10, 2),G (89, 10, 1),L (93.5, 4, 2.5),M (93, 2, 5),N (88, 1, 11), andK (86, 1,13),and 3 to 60 weight % of at least one of Al.sub.2 O.sub.3, MgO.Al.sub.2 O.sub.3, spinel and mullite, and(b) has a mean crystal grain size not exceeding 2 micrometers and a bending strength of at least 100 kgf/mm.sup.2, said ZrO.sub.2 containing a minimum of 50 volume % tetragonal crystal structure and a maximum of 5 volume % monoclinic crystal structure when tested in steam of 180.degree. C.

Abstract: High density fine ceramic sintered bodies are disclosed, which have a maximum pore diameter of not more than 10 .mu.m and a porosity of not more than 0.5%. A process for producing such high density fine ceramic sintered bodies comprises the steps of mixing a ceramic raw material powder with a sintering aid, grinding the resulting mixture granulating and shaping the mixture, and firing the shaped body. The granulated powder is once forcedly dried, and upon necessity is added with water and/or sieved to obtain a uniform granulated powder having a given amount of water.

Abstract: A process is described for the preparation of a ceramic green body by hydrolyzing at least one alkoxide selected from each of two specified groups to form a dispersion of their reaction product, concentrating the dispersion to a sediment without drying it, and admixing a binder and a plasticizer with the sediment to make a ceramic slip formulation. A release agent can optionally be admixed. The slip formulation is then cast as a ceramic green body. The proportions of alkoxides can be adjusted, as desired, to produce a ceramic green body which is dielectric and useful for microcapacitors or as a conductor.

Abstract: A dielectric ceramic composition for temperature compensating monolithic ceramic capacitors consists essentially of a solid solution composed of barium oxide, strontium oxide, silicon oxide and zirconium oxide, which, when calculated in terms of BaO, SrO, SiO.sub.2 and ZrO.sub.2 respectively and expressed by the formula:x(BaO.sub.1-.alpha. SrO.sub..alpha.)--ySiO.sub.2 --zZrO.sub.2(wherein x, y, z are the weight percentages of the respective components, x+y+z=100, and 0.ltoreq..alpha..ltoreq.0.9), have compositional proportions falling within the polygonal area defined by the points A, B, C and D in FIG. 1, the sets of x, y and z at said points A, B, C and D being as follows:______________________________________ x y z ______________________________________ A 50 49 1 B 50 20 30 C 15 20 65 D 15 84 1 ______________________________________The composition may contain, as an additive, aluminum oxide in an amount of not more than 20 parts by weight in terms of Al.sub.2 O.sub.

Abstract: A method is provided of preparing high-purity mixtures of zirconia and another metal oxide substantially free of sodium oxide impurity. Trioxydizirconium ion and a salt of another metal in an aqueous solution are added to a highly basic solution, resulting in the homogeneous precipitation of the combined hydroxides or hydrous oxides. The precipitate is recovered, washed with the water and then with an organic solvent, and then dried, most preferably employing an azeotropic distillation procedure. The resulting material is then calcined to provide a mixture of zirconia with the other metal oxide. In a preferred embodiment, the zirconia mixtures are in the form of fine powders which can be sintered to form a product having greater than 99% of its theoretical density.

Abstract: Disclosed herein is a method of manufacturing dense cordierite, which includes steps of molding a powder mainly consisting of cordierite crystals and having an average particle size of not more than 5 .mu.m, firing a resulting molding at a temperature of from 1,350.degree. to 1,430.degree. C., whereby the sintered body having a porosity of not more than 6% and a bulk specific gravity of not less than 2.4 is obtained.

Abstract: Whisker-toughened ZrO.sub.2 products containing 5-20 volume percent SiC whiskers of relatively low aspect ratio (<20) in a stabilized polycrystalline ZrO.sub.2 matrix are provided, exhibiting a room temperature fracture toughness (K.sub.IC) at least 1.25 times that of the ZrO.sub.2 matrix, with relatively low porosity and good strength.

Abstract: The invention relates to a sintered body of a ceramic composite material based on alumina, refractory hard phases and ZrO.sub.2, HfO.sub.2 and/or partially stabilized ZrO.sub.2 with a relative density of more than 98%. The sintered body according to the invention has chromium integrated in amounts corresponding to in all 1-20 weight % and ZrO.sub.2, HfO.sub.2 and/or partially stabilized ZrO.sub.2 present as 2-16 weight % with these latter phases present to more than 70% in the tetragonal crystal modification. Furthermore, the refractory hard constituents are present as particles with a grain size of less than 10 .mu.m and/or as whiskers or fibers with a diameter of less than 5 .mu.m and a length/diameter ratio of >10.

Abstract: Crystalline solid solutions and diphasic mixtures having a composition of Ca.sub.1-x M.sub.x Zr.sub.4 P.sub.6 O.sub.24, where M is Ba and/or Sr and X is between about 0.25 and 0.75, have been produced which display both low anisotropy and near zero bulk thermal expansion behavior.

Abstract: A high mechanical strength of zirconia refractory body can be provided by a process for producing the refractory body made of at least partially stabilized zirconia and having a predetermined shape comprising:mixing fine particles of zirconia belonging to a monoclinic system, fine particles of stabilizer composed of at least one substance selected from a group consisting essentially of MgO, CaO and Y.sub.2 O.sub.3 and a binder;granulating the resulting mixture to form granulated particles;shaping the granulated mixture into a predetermined form; andfiring the shaped mass thus formed in such a condition as to cause sintering of the zirconia particles and stabilization of zirconia simultaneously.

Abstract: A fine powder of stabilized zirconia a process for its preparation and application of the powder in ceramic compositions to obtain good mechanical, thermomechanical and electrical properties.A zirconia hydrate sol having a pH between 0.5 and 5 and containing elementary acicular crystals having dimensions of from about 10 to 500 .ANG. which are agglomerated into submicron aggregates of from abuot 100 to 5000 .ANG. in diameter is mixed with a solution of a stabilizing agent, preferably yttrium; the suspension is dried; the dried suspension is calcined at a temperature of from about 700.degree. C. to 1,300.degree. C. for preferably from about 30 minutes to 24 hours; and if needed, the powder obtained is milled.

Abstract: A refractory composition which is suitable for forming a sliding gate to be used at the bottom of a ladle or tundish is provided. The refractory composition comprises 10 to 30 parts by weight of an alumina-magnesia spinel material containing 40 to 70% by weight of Al.sub.2 O.sub.3, 25 to 60% by weight of MgO and 10% or less of impurities, and 70 to 90 parts by weight of a magnesia material containing at least 90% by weight of MgO, wherein the composition contains 10 to 25% by weight of Al.sub.2 O.sub.3 and 75 to 90% by weight of MgO. 1 to 10 parts by weight of Al.sub.2 O.sub.3 material may be further added together with the alumina-magnesia spinel material and the magnesia material, to form the refractory composition.

Abstract: A ceramic consisting essentially of from 1 to 15 percent of glass and 99 to 85 percent of a mixture of particulate Al.sub.2 O.sub.3 and particulate ZrO.sub.2 is disclosed. ZrO.sub.2 is present in a sufficient amount, usually from 1/4 to 6 percent based on the weight of the ZrO.sub.2 and Al.sub.2 O.sub.3, to strengthen the ceramic significantly, by comparison with an otherwise identical ceramic where the particulate ZrO.sub.2 is replaced either by the glass or by particulate Al.sub.2 O.sub.3. The glass constitutes a vitreous phase bonding the particulates into a dense, gas impervious structure, and can be a calcium magnesium silicate glass containing from 45 to 80 percent of SiO.sub.2, from 8 to 55 percent of CaO and MgO, and not more than 15 percent of Al.sub.2 O.sub.3.

Abstract: The invention is based on the discovery that in a solid electrolyte galvanic sensor, e.g. an yttria-stablized zirconia body, it is not necessary, as has hitherto been believed, to eliminate all impurities to achieve the important performance characteristics of rapid response time, reduced susceptibility to aging, and improved reliability. It has now been found that these improvements can be obtained by reducing only the concentration of iron oxide (and any other variable valence oxides that sometimes occur) in the sample, and that it is unnecessary to lower the concentration of oxides of fixed valence elements, such as silicon, aluminum, magnesium, and the alkali and alkaline earth metals, many of which tend to occur frequently as impurities in ceramic materials. This inventive selective elimination of only the variable valence oxides saves substantial cost in manufacture without loss of the performance advantages mentioned above. Indeed, better mechanical properties are often obtained.

Abstract: Ceramic sintered mass having a mean grain size of no more than 3 microns of high toughness even at high temperatures is obtainable, the mass comprising 30-99.5% by weight of a component A as defined below and the balance being a component B as defined below:Component A: zirconia having a tetragonal and/or cubic system content of no less than 90% by weight, with the proviso that the tetragonal/cubic system ratio by weight is no less than 0.25, said zirconia including a stabilizer of Y.sub.2 O.sub.3, CaO, MgO, etc.Component B: one or more of borides, carbides and nitrides of Al, Si and an element in the groups 4a, 5a and 6a of the periodic table, and Al.sub.2 O.sub.3.The balance may incorporate a further component C, such as SiO.sub.2, Fe.sub.2 O.sub.3 and TiO.sub.2 and the like of no more than 3% by weight in the sintered mass.

Abstract: Zirconia powder is formed by dry grinding, and a slurry of the zirconia powder with a nonaqueous solvent is shaped and fired.

Abstract: An improved process for producing polycrystalline, translucent sintered aluminum oxide tubes for use as high pressure gas discharge lamps is provided, in which an aluminum oxide powder mixture is dispersed and foamed prior to plasticizing. Into the dried powder plasticizing components based on PVA or low viscosity, weakly swelling methylcellulose adhesives in the form of a paste are mixed and the powder mixture subsequently cold formed to tubular form by extrusion. The application of these measures results not only in an especially low surface roughness with an average value of 0.2 micron, but also in a mechanical strength of at least 320 N/mm.sup.2 and an in-line light transmission of more than 64%.

Abstract: Substantially spherical mono-sized particles of zirconia can be prepared by the forced hydrolysis of an aqueous solution of zirconyl chloride. A zirconyl chloride solution having a molarity up to about 0.4 is heated for at least 72 hours at a temperature of at least 95.degree. C. to generate suspended particles of hydrated zirconium oxide, which are recovered and calcined to provide the mono-sized zirconia powders. In preferred embodiments, mono-sized powders of a mixture of zirconia with one or more of its stabilizing metal oxides is prepared by precipitating the metal in the form of its hydroxide onto pre-formed zirconium-containing particles.

Abstract: Preparation of a ceramic green body by hydrolyzing two groups of alkoxides to form a dispersion of their reaction product, concentrating the dispersion to a sediment without drying it, and admixing a binder solution, plasticizer and release agent with the sediment to make a ceramic slip formulation. The slip formulation is then cast as a ceramic green body. The proportions of alkoxides can be adjusted to produce a ceramic green body which is dielectric and useful for microcapacitors.

Abstract: A body of monolithic or composite partially stabilized zirconia is subjected to intense surface heating which raises the temperature of the exposed surface to 1100.degree. C.-1600.degree. C. without heating the interior of the body above 600.degree. C.-800.degree. C., and then the body is cooled. The heat treated body shows increased wear resistance and surface hardness as compared with an untreated body.

Abstract: A silicon nitride sintered body essentially consisting of compounds of Sr, Mg, Ce, Zr and Al in amounts of from 0.1 to 18% by weight when calculated as SrO, from 0.2 to 25% by weight when calculated as MgO, from 0.1 to 20% by weight when calculated as CeO.sub.2, from 0.1 to 15% by weight when calculated as ZrO.sub.2 and from 1 to 20% by weight when calculated as Al.sub.2 O.sub.3, respectively, and the balance being silicon nitride. A method of manufacturing the silicon nitride sintered body is also disclosed. The silicon nitride sintered body has a low thermal conductivity while high mechanical strength and high fracture toughness being maintained.

Abstract: Magnesium oxide ceramic bodies may be strengthened by inclusion of zirconium oxide particles, and may be further sintered to a density approaching theoretical density by conventional sintering techniques by inclusion of sintering aids, such as manganese oxide and iron oxide.

Abstract: A high strength metal working tool such as cutting tools and dies made of a zirconia-base sintered material comprising 50 to 98 weight percent of zirconia (ZrO.sub.2) containing 1.5 to 5 mol percent of yttira (Y.sub.2 O.sub.3) and 50 to 2 weight percent of alumina (Al.sub.2 O.sub.3) and/or spinel (MgAl.sub.2 O.sub.4) and having a three point bending strength of not less than 1700 MPa.

Abstract: This invention is directed to the preparation of ZrO.sub.2 bodies partially stabilized through the inclusion of 0.5-10% Y.sub.2 O.sub.3 with 1-10% of a secondary stabilizer selected from the group of MgO, CaO, CuO, ZnO, and CeO.sub.2. The method comprises sintering a shaped batch at 1600.degree.-1800.degree. C., quickly cooling the sintered shape to 1000.degree.-1475.degree. C., holding said shape within that temperature range to cause precipitation of tetragonal ZrO.sub.2 as islands within cubic ZrO.sub.2 grains, and then cooling to room temperature. The final product exhibits a microstructure consisting essentially of about 50-70% cubic ZrO.sub.2, greater than 20% and up to 50% tetragonal ZrO.sub.2, and less than 10% monoclinic ZrO.sub.2.

Abstract: Disclosed is a process for the production of a zirconia type black decorative article which comprises sintering an unsintered molded body comprising a matrix composed mainly of zirconia and at least one stabilizer contained in the matrix, said stabilizer being selected from Y.sub.2 O.sub.3, MgO, CeO.sub.2 and CaO, at a temperature of 1400.degree. to 1600.degree. C. in a non-oxidizing atmosphere so that the molded body becomes black, and subjecting the sintered body to the mirror polishing treatment. The decorative article prepared according to this process has a black and glossy mirror surface and also has high flexural strength and high toughness.

Abstract: Improved Si.sub.3 N.sub.4 /ZrO.sub.2 composite ceramics are described, having low thermal conductivity and which are substantially free of surface spalling and material degradation. Such composites are produced by incorporating an additive, e.g. MgO, CaO or Y.sub.2 O.sub.3, preferably Y.sub.2 O.sub.3, in suitable molar proporations based on ZrO.sub.2, and sintering the mixture with Si.sub.3 N.sub.4. In a preferred embodiment a powder mixture of 70% Si.sub.3 N.sub.4 and 30% ZrO.sub.2, by volume, and containing 6.6 mole percent Y.sub.2 O.sub.3 based on ZrO.sub.2, is formed and is sintered to produce a composite ceramic. The Y.sub.2 O.sub.3 is preferably pre-reacted with the ZrO.sub.2 to form a solid solution. A sintering aid, preferably Al.sub.2 O.sub.3, e.g. in an amount of about 2 to about 4%, by weight of the total mixture, can be added to permit production of the Si.sub.3 N.sub.4 /ZrO.sub.2 composite by pressureless sintering.

Abstract: A process for producing a ceramic body suitable for surgical implantation that has high strength and toughness and good compatibility with bone material. A porous material is provided by semi-sintering a ceramic compact. The pores in the surface of the porous material are filled with a first powder of either tricalcium phosphate or apatite or both, or with a material of the fine powder and a powder of a material substantially the same as the material of the ceramic compact. The porous material is then fired at the sintering temperature of the ceramic compact. Following sintering, the surface of the porous material is coated with a fine apatite powder or a finally pulverized mixture of apatite and a calcium phosphate base frit. The resulting assembly is then fired at a temperature up to about 1,350.degree. C.

Abstract: A high toughness sintered body is described, consisting essentially of from 40 to 99.5% by weight of Component A, and 0.5 to 60% by weight of Component B, wherein the mean grain size of the sintered body is 3 microns or less, and Components A and B are as follows:Component A: ZrO.sub.2 containing a stabilizer, such as Y.sub.2 O.sub.3, CaO, and MgO, in which the fraction of the tetragonal and cubic ZrO.sub.2 constitutes at least 90% by weight, and the ratio of the tetragonal ZrO.sub.2 to the cubic ZrO.sub.2 is at least 1/3; andComponent B: at least one of Al.sub.2 O.sub.3 and TiN, with impurities being 3% by weight or less of SiO.sub.2, 0.5% by weight or less of Fe.sub.2 O.sub.3, and 0.5% by weight or less of TiO.sub.2, provided that the total amount is 3% by weight or less.

Abstract: A method for manufacture of a high toughness sintered body, characterized by sintering a shaped body of a mixed powder consisting essentially of from 40 to 70% by weight of a first component of powdered ZrO.sub.2 containing at least one stabilizer selected from the group consisting of Y.sub.2 O.sub.3, CaO, and MgO and having an average particle diameter of not more than 1.mu. and from 30 to 60% by weight of a second component of powdered .alpha.-Al.sub.2 O.sub.3 having an average particle diameter of not more than 1 .mu.m, which mixed powder may also contain not more than 3% by weight of SiO.sub.2, not more than 0.5% by weight of Fe.sub.2 O.sub.3, or not more than 0.5% by weight of TiO.sub.2 in a combined proportion of not more than 3% by weight at a temperature in the range of from 1400.degree. C. to 1600.degree. C. under normal pressure thereby producing a sintered body wherein at least 90% by weight of ZrO.sub.

Abstract: A liquid transfer ball formed from sintered zirconium oxide particles which exhibits utility as the ball element of a ball pen writing instrument to transfer ink from an ink reservoir to a writing surface such as paper. The ball exhibits a porosity of less than 8% by volume and is immune to corrosive action of inks.

Abstract: The invention is characterized by two main methods of producing stabilized or partially stabilized zirconia powders with controlled particle size by use of complexing agents and hydrothermal treatment. A further embodiment of the invention is characterized by a combination of the first two methods to produce powders containing more than one major particle size. The invention also allows use of low cost readily available starting material, controlled doping level and incorporation of dual constituents such as MgO, CaO; Y.sub.2 O.sub.3, MgO; or Y.sub.2 O.sub.3, CaO in the structure for production of stabilized zirconia. Triply stabilized zirconia containing Y.sub.2 O.sub.3, MgO and CaO may also be produced. A final embodiment of the invention allows the production of dually and triply stabilized zirconia by hydrothermal treatment without the use of complexing agents.

Abstract: A ceramic compact having a high transverse rupture strength is provided by a low cost sintering method. This ceramic compact comprises 55 to 96% by volume of a first component, 4 to 45% by volume of a second component and at most 3% by volume of unavoidable impurities:First Component: ZrO.sub.2 consisting of at least 80% by weight of at least one of tetragonal system and cubic system and the balance of mono-clinic system, in which at least one member selected from the group consisting of oxides of Group IIIa (Including Sc, Y, La) elements of the Periodic Table, CaO, MgO, and mixtures thereof are dissolved to form a solid solution.Second Component: at least one member selected from the group consisting of carbonitrides, oxycarbides, oxynitrides and carboxynitrides of group IVa (Including Ti, Zr, Hf), Va (Including V, Nb, Ta) and VIa (Including Cr, Mo, W) elements of the Periodic Table, and mixtures or solid solutions thereof.

Abstract: Ceramic shaped articles are disclosed which are formed of dense, non-metallic, mechanically resistant materials and contain eutectic constituents consisting of zirconium oxide, hafnium oxide and at least one other high-melting oxide and mixtures thereof. The composition exhibits excellent hardness, wear properties and bending strength. A method for preparing the articles is also disclosed wherein the appropriate mixture in a hypoeutectic, eutectic, or hypereutectic ratio is heated to its melting point, poured into a preheated mold and cooled.

Abstract: A thermal spray powder comprising particles with a central core of a material selected from the group consisting of zirconium oxide, magnesium oxide, hafnium oxide, cerium oxide, yttrium oxide and combinations thereof. The core then has discrete aluminum particles and silicon dioxide homogeneously disposed in a binder deposited thereon to form the thermal spray powder which may be thermal sprayed to produce an abradable and erosion resistant coating.

Abstract: A zirconia type sintered body consisting essentially of 50 to 98% by weight of zirconia (ZrO.sub.2) containing 1.5 to 5 mole % of yttria (Y.sub.2 O.sub.3) and 50 to 2% by weight of alumina (Al.sub.2 O.sub.3), spinal (MgAl.sub.2 O.sub.4) or mullite (3Al.sub.2 O.sub.3.2SiO.sub.2), and having a three-point bending strength of at least 1700 MPa is provided. This sintered body is prepared by a process wherein a powdery composition consisting essentially of 50 to 98% by weight of (a1) a powder of zirconia containing 1.5 to 5 mole % of yttria or (a2) a mixture comprising 1.5 to 5 mole % of a yttria powder and 95 to 98.5 mole % of a zirconia powder and 2 to 50% by weight of (b) a powder of an alumina type oxide selected from alumina, an alumina-magnesia type oxide, an alumina-silica type oxide, a mixture of alumina and magnesia and a mixture of alumina and silica is subjected to a hot isotactic pressing treatment under a pressure of at lesast 50 MPa at temperature of 1300.degree. C. to 1700.degree. C.

Abstract: Zirconia powder is formed by dry grinding, and slurry of the zirconia powder with nonaqueous solvent is shaped and fired.

Abstract: Stabilized sintered zirconia bodies are made by employing zirconia powders made from rapidly quenched co-fusions of zirconia with a stabilizing metal oxide. Finer crystallinity and higher strength is achieved in the fired body.

Abstract: A method for determining an amount of non-stabilized zirconia in a ceramic specimen involves subjecting the ceramic specimen to an environment having a controlled temperature and humidity and measuring mechanical and/or chemical properties of the specimen to determine if any deterioration of the specimen has occurred.

Abstract: Highly densified silicon nitride sintered bodies having excellent mechanical strength and oxidation resistance consist essentially of Si.sub.3 N.sub.4 and contain Y, Mg and Zr, in which a content of Si.sub.3 N.sub.4 is 95-70% by weight, a content of yttrium is 15-2% by weight calculated as Y.sub.2 O.sub.3, a content of magnesium is 15-0.5% by weight calculated as MgO and a content of zirconium is 13-0.5% by weight calculated as ZrO.sub.2 and are produced by forming a mixed raw powder consisting of 95-70% by weight of silicon nitride raw powder, yttrium compound of 15-2% by weight calculated as Y.sub.2 O.sub.3, magnesium compound of 15-0.5% by weight calculated as MgO and zirconium compound of 13-0.5% by weight calculated as ZrO.sub.2 into a shaped body, said yttrium compound, magnesium compound and zirconium compound being sintering aids, and firing the shaped body at a temperature of 1,650.degree.-1,800.degree. C. under ambient pressure in a nitrogen or an inert gas atmosphere.

Abstract: The present invention relates to materials and more particularly to particulate materials suitable for use as thermal spraying powders.There is disclosed a process for the preparation of a particulate material suitable for use as a thermal spraying powder which includes treating a mixture comprising an inorganic substance as a major component (as defined in the Specification) and a sol to gel the sol thereby to form an intermediate material comprising inorganic substance and gel and heating the intermediate material.One example of thermal spraying is plasma spraying.

Abstract: Disclosed is a nasicon compound and a method of making it. The nasicon compound is rhombohedral at room temperature and has the general formulaM.sub.1+x+O.02y+0.04z M'.sub.2-0.02(y+z) M".sub.0.02y M"'.sub.0.02z M"".sub.x M""'.sub.3-x O.sub.12where M is selected from lithium, sodium, calcium, and silver, M' is selected from zirconium, titanium or hafnium, M" is selected from yttrium, scandium or lanthanum, M"' is selected from magnesium, calcium, strontium or barium, M"" is selected from silicon and germanium, M""' is selected from phosphorous and arsenic, x is about 1.6 to about 2.2, y is about 0 to about 15, and z is about 0 to about 15. The preferred compound isNa.sub.1+x Zr.sub.2 Si.sub.x P.sub.3-x O.sub.12.A sodium sulfur battery using the nasicon compound is also disclosed.

Abstract: A ceramic body of zirconium dioxide containing, if desired, aluminum oxide, and partially stabilized with yttrium oxide and/or one or more rare earth oxides (e.g., cerium dioxide) and/or magnesium oxide and/or calcium oxide is partially stabilized with 0.5 to 5 mole-% of yttrium oxide and/or 5 to 12 mole-% of magnesium oxide and/or calcium oxide and/or cerium dioxide or one or more rare earth oxides, is 30 to 100% in the tetragonal lattice modification and has in the surface region a content of yttrium oxide, cerium dioxide, magnesium oxide, calcium oxide or rare earth oxide that is 1 to 20 mole-% higher than the average content, such that the body is coated with a thin, PSZ-like layer in a more highly stabilized tetragonal or with a layer that is predominantly in the cubic lattice form.

Abstract: This invention provides a process for producing a fine grain metastable tetragonal zirconia which has an average particle size less than about 1000 angstroms in diameter.The process involves multistage thermolysis of precursor solids comprising a homogeneous mixture of .beta.-ketonate compounds of zirconium and a stabilizer metal such as yttrium.

Abstract: A ceramic body of zirconium dioxide containing, if desired, aluminum oxide, nd partially stabilized with yttrium oxide and/or one or more rare earth oxides (e.g., cerium dioxide) and/or magnesium oxide and/or calcium oxide is partially stabilized with 0.5 to 5 mole-% of yttrium oxide and/or 5 to 12 mole-% of magnesium oxide and/or calcium oxide and/or cerium dioxide or one or more rare earth oxides, is 30 to 100% in the tetragonal lattice modification and has in the surface region a content of yttrium oxide, cerium dioxide, magnesium oxide, calcium oxide or rare earth oxide that is 1 to 20 mole-% higher than the average content, such that the body is coated with a thin, PSZ-like layer in a more highly stabilized tetragonal or with a layer that is predominantly in the cubic lattice form.

Abstract: The invention is a ceramic composition containing a new class of dispersant for hindering crack propagation by means of one or more energy-dissipative mechanisms. The composition is composed of a ceramic matrix with dispersed particles of a transformation-prone rare-earth niobate, tantalate or mixtures of these with each other and/or with a rare-earth vanadate. The dispersants, having a generic composition tRMO.sub.4, where R is a rare-earth element, B is Nb or Ta and O is oxygen, are mixed in powder form with a powder of the matrix ceramic and sintered to produce a ceramic form or body. The crack-hindering mechanisms operates to provide improved performance over a wide range of temperature and operating conditions.