Abstract: A heat resistant, low expansion phosphate compound and sintered bodies thereof, having a composition of RZr.sub.4 P.sub.6 O.sub.24 (R is one or more cations of IIa group in the periodic table, such as Ba, Sr and Ca): an average thermal expansion coefficient between room temperature and 1,400.degree. C. of -10.about.+10.times.10.sup.-7 /.degree.C.; and having a high temperature type crystalline structure having R3c symmetry at room temperature. The sintered body of the invention can be manufactured by mixing and shaping starting materials, firing the resulting shaped body at 1,400.degree. C..about.1,700.degree. C. to provide a sintered body with a composition of RZr.sub.4 P.sub.6 O.sub.24 and then, keeping the obtained sintered body at a high temperature of not lower than a temperature of phase transition between a high temperature type and a low temperature type crystalline structure, followed by quenching.

Abstract: Zirconium based granules are produced by the steps of forming an aqueous solution of a zirconium compound such as zirconium acetate, combining the aqueous solution with a phase stabilizer, and then heating the solution to evaporation thereby forming amorphous zirconium based granules.In an alternate embodiment, an alcohol solution of a zirconium compound such as zirconium propoxide in propanol is acidified and hydrolyzed with water. The partially or fully hydrolyzed zirconium complex is mixed with a phase stabilizer to form a homogeneous solution. The solution is then subjected to evaporation by heat to form amorphous zirconium based granules.Zirconia fibers are produced by making aqueous solutions of the amorphous zirconium based granules containing the phase stabilizer to the desired viscosity, fiberizing the solution, and finally converting the fibers under appropriate conditions.

Abstract: Zirconium oxide sinter for use in forming a thin film thereof by vapor deposition etc., having a purity not less than 99.0% by weight with unavoidable hafnium oxide and a density more than 4.9 g/cm.sup.3. Desirably the sinter further contains calcium oxide in an amount from 50 to 2000 ppm. The sinter can produce a uniform zirconium oxide thin film which can be used in optical applications with superior characteristics.

Abstract: A sinterable powder of zirconium dioxide and additives from the group of oxides consisting of titanium, tantalum, as well as optionally magnesium, aluminum, scandium, yttrium and rare earths, incorporated in the crystal lattice of the zirconium dioxide. The sinterable powder is obtained by coprecipitation of zirconium hydroxide and the hydroxides and/or hydrated oxides of the additives from an essentially aqueous solution, with drying and calcining. Hydrolysis-sensitive starting materials, such as, TiCl.sub.4, are used in the form of their reaction products with multivalent alcohols, such as, ethylene glycol.

Abstract: A refractory for casting a basic substance comprises 100 parts by weight of a refractory aggregate having as main ingredients 3 to 40% by weight of zircon and 97 to 60% by weight of magnesia and a suitable amount of a binding agent. Another refractory for casting a basic substance comprises 100 parts by weight of a refractory aggregate having as main ingredients 3 to 40% by weight of zircon and 97 to 60% by weight of magnesia, not more than 7 parts by weight of metallic fibers, and a suitable amount of a binding agent. The refractories for casting a basic substance are used for ladles, tundishes, vacuum degasing furnaces, mixers, and the like.

Abstract: Compositions having the general formula (Ca.sub.x Mg.sub.1-x)Zr.sub.4 (PO.sub.4).sub.6 where x is between 0.5 and 0.99 are produced by solid state and sol-gel processes. In a preferred embodiment, when x is between 0.5 and 0.8, the MgCZP materials have near-zero coefficients of thermal expansion. The MgCZPs of the present invention also show unusually low thermal conductivities, and are stable at high temperatures. Macrostructures formed from MgCZP are useful in a wide variety of high-temperature applications. In a preferred process, calcium, magnesium, and zirconium nitrate solutions have their pH adjusted to between 7 and 9 either before or after the addition of ammonium dihydrogen phosphate. After dehydration to a gel, and calcination at temperatures in excess of 850.degree. C. for approximately 16 hours, single phase crystalline MgCZP powders with particle sizes ranging from approximately 20 nm to 50 nm result. The MgCZP powders are then sintered at temperatures ranging from 1200.degree. C. to 1350.

Abstract: A process for producing a high density ceramic of perovskite represented by the formula:ABO.sub.

Abstract: Thin inorganic sintered structures having strength and flexibility sufficient to permit bending without breakage in at least one direction to a radius of curvature of less than 20 centimeters, methods for making them, and products incorporating them, are described. Preferred sintered ceramic structures according to the invention can comprise zirconias, titanias, aluminas, silicas, rare earth metal oxides, alkaline oxides, alkaline earth metal oxides and first, second, and third transition series metal oxides and combinations thereof and therebetween. Sintered metal structures can also be provided.

Abstract: A molten steel pouring nozzle having, along the axis thereof, a bore through which molten steel flows. At least part of an inner portion of the molten steel pouring nozzle, which inner portion forms the bore, is formed of a refractory consisting essentially of:zirconia clinker comprising calcium zirconate: from 40 to 89 wt. %,where, a content of calcium oxide in the zirconia clinker being within a range of from 8 to 35 weight parts relative to 100 weight parts of the zirconia clinker;graphite: from 10 to 35 wt. %; andcalcium silicate: from 1 to 25 wt. %,where, a content of calcium oxide in the calcium silicate being within a range of from 40 to 54 weight parts relative to 100 weight parts of the calcium silicate.

Abstract: The present invention relates to a novel thermal spray material in any one of the forms of a particle mixture material, a granule material, and an electric fused material of 2CaO.SiO.sub.2 and CaO.ZrO.sub.2. As 2CaO.SiO.sub.2, .gamma.-2CaO.SiO.sub.2 is used. The ratio of .gamma.-2CaO.SiO.sub.2 to CaO.ZrO.sub.2 is specified by weight %. This invention relates also to a thermal sprayed member formed by thermal spraying this thermal spray material on a thermal resistant substrate.

Abstract: The invention relates to a refractory thixotropic self-hardening vibration compound on the basis of zirconium silicate having the following chemical composition (in % by mass);______________________________________ 20 to 30% SiO.sub.2 20 to 45% Al.sub.2 O.sub.3 0.7 to 1.4% TiO.sub.2 0.2 to 0.8% P.sub.2 O.sub.5 0 to 1.5% K.sub.2 O + Na.sub.2 O + LiO.sub.2 0 to 1.0% Fe.sub.2 O.sub.3 0 to 0.05% CaO residue ZrO.sub.

Abstract: The invention concerns a material for the covering of casting shrouds.It is comprised of a calcareous composition capable of liberating calcium oxide at a temperature at least equal to 1400.degree. C., its calcium content, expressed in calcium oxide, is between ca. 10% and ca. 60% and preferably between ca. 20% and ca. 50%, the said calcareous composition is bound by a binder chosen in the group comprised of those utilizing carbon/carbon bonds by sintering.Application to the metallurgy of ferro-alloys.

Abstract: Disclosed is colored, partially stabilized zirconia ceramics containing a colorant component and a stabilizer, wherein the zirconia ceramics contains 0.05 to 15% by weight of zirconium carbide based on the entire ceramics, the content of free carbon is lower than 0.1% by weight, and the crystal phase of the zirconia is composed of tetragonal crystals.This colored, partially stabilized zirconia ceramics is prepared by a process comprising molding a composition comprising 0.1 to 10 parts by weight of a colorant component and 90 to 99.9 parts by weight of zirconia and a stabilizer into a molded body having a predetermined shape, sintering the molded body, and sintering the obtained sintered body in a carbon atmosphere to form ceramics containing 0.05 to 15% by weight of zirconium carbide, in which the crystal phase of zirconia is composed of tetragonal crystals.

Abstract: Zirconium based granules are produced by the steps of forming an aqueous solution of a zirconium compound such as zirconium acetate, combining the aqueous solution with a phase stabilizer, and then heating the solution to evaporation thereby forming amorphous zirconium based granules.In an alternate embodiment, an alcohol solution of a zirconium compound such as zirconium propoxide in propanol is acidified and hydrolyzed with water. The partially or fully hydrolyzed zirconium complex is mixed with a phase stabilizer to form a homogeneous solution. The solution is then subjected to evaporation by heat to form amorphous zirconium based granules.Zirconia fibers are produced by making aqueous solutions of the amorphous zirconium based granules containing the phase stabilizer to the desired viscosity, fiberizing the solution, and finally converting the fibers under appropriate conditions.

Abstract: Two composition areas of partially stabilized ZrO.sub.2 /HfO.sub.2 alloys have been discovered which exhibit pseudo-plasticity through the presence of transformation bands and with the substantial absence of microcracking. The first area consists essentially, in mole percent, of 0.5-8% of at least one toughening agent in the indicated proportion selected from the group consisting of 0-8% YNbO.sub.4, 0-8% YTaO.sub.4, 0-8% RENbO.sub.4, 0-8% RETaO.sub.4, 0-8% YVO.sub.4, 0-8% REVO.sub.4, 0-8% MgWO.sub.4, 0-8% MgMoO.sub.4, 0-8% CaWO.sub.4, 0-8& CaMoO.sub.4, and 0-8% SnO.sub.2, and 0.5-10% of at least one stabilizer oxide in the indicates proportion selected from the group consisting of 0-3.5% Y.sub.2 O.sub.3, 0-3.5% Sc.sub.2 O.sub.3, 0-3.5% RE.sub.2 O.sub.3, 0-10% CeO.sub.2, 0-10% TiO.sub.2, 0-10% SnO.sub.2, 0-10% CaO, and 0-10% MgO, with the remainder ZrO.sub.2 /HfO.sub.2 alloy. The second area consists essentially, in mole percent, of 8-16% CeO.sub.2 and 0.25-5% Nb.sub.2 O.sub.5 and/or Ta.sub.2 O.sub.

Abstract: A ceramic material suitable for packaging of large scale integrated circuits is produced by the process of forming a mixture of a powdered glass ceramic material which is a glassy precursor to cordierite ceramic material, formed by the steps which are as follows:a. Mix tetragonal phase material selected from the group consisitng of zirconia or hafnia powder containing a stabilizing oxide compound selected from the group consisting of MgO, CaO and Y.sub.2 O.sub.3 and a glass frit powder or frit of a glassy precursor of cordierite glass ceramic to yield a suspension of solids. Preferably, a binder is included.b. Disperse the suspended solids to yield a dispersion of the zirconia or hafnia with the stabilizing oxide compound and the glassy precursor.c. Densify the dispersion of zirconia or hafnia with the stabilizing oxide compound and the glassy precursor by a sintering heat treatment at a temperature of about 840.degree. C.

Abstract: The ceramic sinter is composed of a metal oxide such as ZrO.sub.2 and 10-90 vol. % of metal fluoride which is selected from the group having not less than 2.5 electronegativity difference between fluoride and the metal element.The ceramic sinter has a thermal expansion coefficient of 15-20.times.10.sup.-6 /.degree.C. and is suitable for bonding with general use metals such as stainless steel to form a composite body of the ceramic sinter and the metal without causing a substantial thermal stress at the juncture thereof.

Abstract: A sinterable powder of zirconium dioxide and additives from the group of oxides consisting of titanium, tantalum, as well as optionally magnesium, aluminum, scandium, yttrium and rare earths, incorporated in the crystal lattice of the zirconium dioxide. The sinterable powder is obtained by coprecipitation of zirconium hydroxide and the hydroxides and/or hydrated oxides of the additives from an essentially aqueous solution, with drying and calcining. Hydrolysis-sensitive starting materials, such as, TiCl.sub.4, are used in the form of their reaction products with multivalent alcohols, such as, ethylene glycol.

Abstract: The present invention pertains to novel solid solutions involving V.sub.2 O.sub.3, ZrO.sub.2 and TiO.sub.2 and the method for their preparation. The compositions involving V.sub.2 O.sub.3, ZrO.sub.2 and TiO.sub.2 fall within the shaded area of a polygon in a ternary composition diagram of V.sub.2 O.sub.3, ZrO.sub.2 and TiO.sub.2 as shown in the drawing herein e.g., FIG. 1. These materials may be used as an oxidation catalyst or in the manufacture of high temperature refractories.

Abstract: The invention provides a sintered ceria/zirconia ceramic and a method of making it. The product comprises a substantially homogeneous mixture of 76-92 mole % zirconia, 8-20 mole % ceria and 0.1-1.2 mole % lanthana and/or praseodymia. The method involves heating an artifact comprising said mixture to a temperature in the range 1200.degree.-1700.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 resultant, 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: Crystalline zirconium oxide powder with a BET surface of less than 30 m.sup.2 /g, preferably 10 to 20 m.sup.2 /g, a primary particle size of 0.1 to 0.5 .mu.m, a monoclinic crystal structure and, optionally, a content of Y.sub.2 O.sub.3 of 1 to 10% by weight and/or of 1 to 10 % by wt. MgO.It is produced by adding an aqueous zirconium salt solution optionally containing yttrium ions and/or magnesium ions under agitation into a vessel which contains an aqueous base solution such as e.g. sodium hydroxide solution with a content of NaOH which corresponds to an excess of at least 0.5 mole/1 NaOH. The mixture obtained in this manner is then treated hydrothermally at a temperature of 200.degree. to 400.degree. C., the product obtained is separated by filtration, washed chloride-free with water and dried at 100.degree. to 200.degree. C.The zirconium oxide power can be used to produce sintered ceramics.

Abstract: A semiconductor process chamber with electrolytic ceramic cell having one major surface in the chamber. A second major surface of the cell is outside the process chamber. When activated by heat and an electric current between the two major surfaces, the cell selectively removes oxygen from the processing chamber.

Abstract: This invention is directed to the production of ceramic alloys consisting essentially of partially stabilized ZrO.sub.2 and/or ZrO.sub.2 -HfO.sub.2 solid solution and/or HfO.sub.2 exhibiting high toughness through the inclusion of about 0.5-8 mole %, as expressed on the oxide basis, of YNbO.sub.4 and/or YTaO.sub.4 and/or MNbO.sub.4 and/or MTaO.sub.4, wherein M represents Mg.sup.+2, Ca.sup.+2, Sc.sup.+3 and/or a rare earth metal ion selected from the group of La.sup.+3, Ce.sup.+4, Ce.sup.+3, Pr.sup.+3, Nd.sup.+3, Sm.sup.+3, Eu.sup.+3, Gd.sup.+3, Tb.sup.+3, Dy.sup.+3, Ho.sup.+3, Er.sup.+3, Tm.sup.+3, Yb.sup.+3, and Lu.sup.+3 substituted for Y, and the use of at least 5 volume percent of such ceramic alloys to toughen hard refractory ceramics.

Abstract: A method of preparing colloidal zirconium oxide sols having substantially uniformly spherical particles in the size range of from about 0.01 to about 2.0 microns is described. The process comprises the steps of(A) preparing a liquid mixture comprising at least one zirconium salt and a compatible liquid vehicle;(B) contacting said liquid mixture with an anion exchange resin for a period of time sufficient to form a zirconium hydrate sol having a pH of at least about 5.0; and(C) recovering the zirconium hydrate sol from the resin. Colloidal size zirconium oxide powders can be prepared from the colloidal zirconium oxide sols by drying and calcining the sols at an elevated temperature. The zirconium oxide powders obtained in accordance with the present invention can be stabilized by the incorporation of certain stabilizers such as yttrium oxide, lanthanum oxide, cerium oxide, calcium oxide and magnesium oxide.

Abstract: A ceramic comprising a matrix of Al.sub.2 O.sub.3, ZrO.sub.2 (partially or fully stabilized) or mixtures of Al.sub.2 O.sub.3 and ZrO.sub.2 with strontium aluminate plate-shaped grains distributed throughout the matrix results in a ceramic with high toughness, high strength and good hardness. SrO/Al.sub.2 O.sub.3 molar ratios between 0.02 and 0.20 result in in-situ formation of plate-shaped grains approximately 0.5 .mu.m in thickness and 5.0 .mu.m in breadth in tetragonal zirconia polycrystalline ceramic matrices. The in-situ formation of strontium aluminates allows high volume loading of platelets to occur and high toughness is achieved without the loss of strength. High alumina compositions have the added benefit of higher strength, lower thermal expansion, higher modulus and higher thermal conductivity than zirconia ceramics with comparable toughness.

Abstract: Sinterable, morphologically and chemically homogeneous stabilized zirconia fine powders, e.g., yttrium-stabilized zirconia powders, are prepared by heat treating aerosol droplets which comprise a mixed precursor solution of at least one inorganic zirconium salt and at least one inorganic salt of a zirconia-stabilizing element, said heat treating including (a) heating the aerosol droplets to a temperature of from 400.degree. to 500.degree. C. for a period of time of from 4 seconds to 2 hours, and thereafter (b) calcining such droplets at a temperature of from 650.degree. to 1,250.degree. C.

Abstract: A molten steel pouring nozzle having along the axis thereof a bore through which molten steel flows. At least part of an inner portion of the molten steel pouring nozzle, which inner portion forms said bore, is formed with a refractory consisting essentially of:zirconia clinker comprising cubic zirconia andcalcium zirconate: from 40 to 85 wt. %,where, the content of calcium oxide in said zirconia clinker being within the range of from 3 to 35 weight parts relative to 100 weight parts of said zirconia clinker;graphite: from 10 to 30 wt. %;andat least one element selected from the group consisting of:silica: from 1 to 15 wt. %,andmagnesia: from 1 to 15 wt. %.

Abstract: Zirconia has been used in the manufacture of ceramics for many years. The desirability of stabilizing the crystal form has been recognized and one or more stabilising agents have been used. The present invention produced a stabilized zirconia carrying a coating of at least one hydrous oxide of yttrium, calcium, magnesium, strontium, barium, or cerium. Preferably also a hydrous oxide of zirconium is also present either a s a separate inner layer or mixed with the other hydrous oxide.

Abstract: A ceramic implant comprising a sintered body of zirconia and a coating layer of a porous sintered body of a mixture comprising .alpha.-tricalcium phosphate and zirconia, or hydroxyapatite and zirconia formed on the surface of the sintered body of zirconia.

Abstract: Disclosed are zirconia ceramics superior in mechanical strength, hardness and toughness and a method for producing them. The zirconia ceramics contain ca. 7-12 mol % of cerium oxide and ca. 2-7 mol % of magnesium oxide and have an average crystal grain size of crystal grains thereof of 1 .mu.m or less, at least ca. 80 mol % of the crystal grains being tetragonal grains and the balance being monoclinic grains, and have a bending strength of at least 100 kg/mm.sup.2, a fracture toughness of at least 10 MNm.sup.-1.5 and a Vickers hardness of at least 1000 kg/mm.sup.2. The method comprises calcining a hydrate obtained by coprecipitation method from water-soluble salts of cerium and magnesium and a basic salt of zirconium or a hydrate obtained by adding water-soluble salts of cerium and magnesium to a zirconium hydrate and neutralizing the mixture of hydrates, further grinding the calcined hydrate to obtain zirconia powders of 1 .mu.

Abstract: The present invention is in a sintered molding of partially stabilized zirconium oxide having a microstructure of 40 to 70 volume percent cubic phase, 30 to 70 volume percent tetragonal phase, and up to 10 volume percent monoclinic phase wherein the tetragonal phase is present in the form of precipitates less than 200 nm. A mixture of magnesia and yttria is used to stabilize the zirconia. Optionally, the sintered molding may further contain up to 20 wt. % spinel.

Abstract: Heat-resisting phosphate based compound sintered bodies are disclosed, which each contain not less than 10% by weight of a crystalline phase of RZr.sub.4 (PO.sub.4).sub.6 in which R is an element in Group IIa of the Periodic Table. A weight-reduced percentage of the sintered body when being thermally treated at 1,400.degree. C. for 100 hours is not more than 10%. A process for producing such phosphate based compound sintered bodies is also disclosed.

Abstract: A ceramic munitions projectile, particularly useful for practice or target munitions is provided. The projectile has a tensile strength greater than about 250 MPa, a critical stress intensity factor greater than about 6 MPam.sup.1/2, and a Weibull modulus greater than about 10. Preferably the projectile is frangible.

Abstract: This invention is primarily directed to the production of transformation toughened ZrO.sub.2 -containing ceramic alloys wherein the toughening agent is selected from the group consisting of a rare earth metal vanadate and a magnesium and/or calcium tungstate/molybdate, and SnO.sub.2 can be utilized as a toughening agent and/or a stabilizing agent for ZrO.sub.2.

Abstract: The invention concerns a process for preparing titanates and zirconates respectively of formulas MTiO.sub.3 and MZrO.sub.3 where M is Ba.sup.2+, Sr.sup.2+, Ca.sup.2+, Pb.sup.2+ and Mg.sup.2+ to the exclusion of MgZro.sub.3, consisting of reacting an ester of formula M[H-(CH.sub.2).sub.n CO.sub.2 ].sub.2 where n=1-4 with the formula M'[O(CH.sub.2).sub.n CH.sub.2).sub.n CH.sub.3 ].sub.4 where M' is Ti or Zr bringing the reaction mixture to boil until the solvent is removed to yield a viscous translucent resin. The resin is cooled and further treated to obtain the desired product.

Abstract: A ZrO.sub.2 powder of very fine particle size adapted especially for the making of high density ceramics is produced by chlorinating a zirconium source material, such as zircon sand, to produce crude ZrCl.sub.4 solids; the solids are dissolved to form a ZrOCl.sub.2 solution from which ZrOCl.sub.2 crystals are precipitated; the crystals are dried and milled to a desired particle size; and the crystal particles are subjected to direct oxidation under controlled conditions to produce a very fine ZrO.sub.2 powder especially adapted to the making of high density ceramics.

Abstract: Solid, transparent, non-vitreous, microspheres (zirconia-silica) are formed by extractive gelation (extracting carboxylic acid away from zirconyl carboxylate) of a sol in liquid medium such as hot peanut oil. Zirconyl carboxylate precursor sol is prepared and added in droplet form to the liquid extractant (peanut oil) at an elevated temperature at which a carboxylic acid is liberated from the zirconyl carboxylate. The droplets remain in the extractant for sufficient time to form stable gel spheroids which are separated from the extractant and fired to convert them to durable spheroids useful as lens elements in retroreflective sheeting.

Abstract: The present invention provides a mixed conducting body, wherein it consists f 98 to 25 mol % of cubic or tetragonal zirconium dioxide, 1.5 to 25 mol % of an oxide stabilizing the zirconium dioxide phase and 0.5 to 50 mol % of at least one oxide of a metal of Group Va and VIa of the Periodic System of Elements and/or titanium dioxide, as well as the usual impurities.This body is outstandingly useful as electrode material for oxygen exchange reactions.

Abstract: An antireflection film made from a reliquified sol-gel hydrolyzation, condensation polymeric reaction product of a silicon, alkoxides and/or metal alkoxides, or mixtures thereof. The film is particularly useful for coating plastics.

Abstract: Zirconium based granules are produced by the steps of forming an aqueous solution of a zirconium compound such as zirconium acetate, combining the aqueous solution with a phase stabilizer, and then heating the solution to evaporation at a temperature below about 180.degree. C. preferably below thereby forming amorphous zirconium based granules.In an alternate embodiment, an alcohol solution of a zirconium compound such as zirconium propoxide in propanol is acidified and hydrolyzed with water. The partially or fully hydrolyzed zirconium complex is mixed with a phase stabilizer to form a homogeneous solution. The solution is then subjected to evaporation at a temperature below about 180.degree. C. or below to form amorphous zirconium based granules.Zirconia fibers are produced by making aqueous solution of the amorphous zirconium based granules containing the phase stabilizer to the desired viscosity, fiberizing the solution, and finally converting the fibers under appropriate conditions.

Abstract: A novel solid solution has a composition of R.sub.y Zr.sub.4 Si.sub.x P.sub.6-x O.sub.24 (R is at least one forming bivalent or trivalent element 0.ltoreq.x.ltoreq.2, 2/3.ltoreq.y.ltoreq.2). Furthermore, a heat-resistant sintered body and heat-resistant phosphate based compound sintered body comprises the above solid solution and has excellent heat resistance and high temperature stability. And also, a method of producing such sintered bodies is disclosed.

Abstract: In processes of forming a refractory mass on a surface, a mixture of refractory particles and oxidizable particles which react exothermically with oxygen to generate sufficient heat to soften or melt at least the surfaces of the refractory particles are sprayed against that surface to bring about formation of said refractory mass. To promote the reliable and consistent formation of a durable refractory mass, the granulometry of the particles which are sprayed in the mixture is such that the 80% and 20% grain sizes of the refractory particles (that is, the screen mesh sizes G.sub.80 and G.sub.20 through which respectively 80% and 20% by weight of the particles will pass) have a mean greater than the mean of the 80% and 20% grain sizes of the oxidizable particles and the size range spread factor f(G) of the refractory particles is at least 1.

Abstract: The present invention provides a fine-grained ceramic formed body of 0.5 to mole % rare earth oxide and 0.5 to 7 mole % MgO-containing ZrO.sub.2, wherein the cubic granules thereof are coated with Mg-Al spinel particles.The present invention also provides a process for the production of such formed bodies, wherein a ZrO.sub.2 powder alloyed with rare earth oxide, which contains small amounts of Al.sub.2 O.sub.3, is pressed and sintered in the presence of MgO at a temperature of from 1400.degree. to 1600.degree. C. and optionally subsequently tempered at a temperature of from 1200.degree. to 1350.degree. C.

Abstract: Novel partially stabilized zirconia ceramic compositions exhibiting improved toughness comprising: a major component consisting of ZrO.sub.2, a minor stabilizing component Y.sub.2 O.sub.3 and an effective amount of a toughening agent (e.g., Ta.sub.2 O.sub.5). The toughness of the tetragonal zirconia polycrystal (e.g., 96% ZrO.sub.2, 3 mole % Y.sub.2 O.sub.3) can be increased nearly three-fold by replacing 1% of the ZrO.sub.2 with Ta.sub.2 O.sub.5. Empirical equations based on ratios of fundamental lattice parameters (e.g. c/a) quantitatively relating to the stability/instability of tetragonal zirconia oxide are disclosed and used in a novel method for improving the toughness of the ceramic compositions.

Abstract: Magnesia partially stabilized zirconia materials, having a cubic phase zirconia content in the range 70 to 25 percent (by volume) and a metal oxide additive which forms an insoluble zirconate, and a microstructure in the form of grains of stabilized cubic phase zirconia containing precipitates of tetragonal phase zirconia, are produced for use at low (less than 400.degree. C.) intermediate (between 400.degree. C. and 700.degree. C.), high (700.degree. C. to 1000.degree. C.) or very high (greater than 1000.degree. C.) temperatures. The higher the temperature of use of the ceramic material, the more the tetragonal precipitates need to be transformed into monoclinic phase zirconia. The extent to which the tetragonal precipitates are transformed is controlled by the way in which a fired, pressed mixture of the ceramic components is cooled from about 1400.degree. C. to about 1000.degree. C. An "ageing" of the ceramic material may be effected by an isothermal hold, preferably at 1350.degree. C. and then at 1100.

Abstract: A composite ceramic material having improved properties is disclosed as well as several methods for preparing the same. The composite powder is substantially comprised of zirconia and spinel phases, produced by precipitation and calcination of the precipitate of the oxide forming precursor salts. A preferred method for introducing the zirconium is as a soluble and/or decomposable salt during precipitation of the spinel forming hydroxyl or halo hydroxyl spinel forming salts. The zirconium salt decomposes to zirconia during calcining and/or sintering of the powder resulting from the precipitation. A preferred composite is that obtained from magnesium and aluminum salts, resulting in a MgAl.sub.2 O.sub.4 spinel and intimately admixed ZrO.sub.2 which contains a stabilizing agent.

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 base on the 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: Calcined powder of coagulated spherical particles having a secondary coagulated particle size of 0.2 .mu.m to 3 .mu.m, composed of primary particles of less than 500 .ANG. in the crystalline size, and obtained by calcining ultrafine zirconia particles with or without other metal compounds is disclosed. As the ultrafine zirconia particles, coagulated spherical zirconia particles composed of ultrafine monoclinic primary particles of less than 100 .ANG. in the crystalline size, coagulated with each other into a substantially spherical shape with the size of the coagulated particles being in a range from 0.2 .mu.m to 3 .mu.m is preferably used.

Abstract: A ceramic munitions projectile, particularly useful for practice or target munitions is provided. The projectile is preferably made of zirconia which is densified by a pressureless sintering method. The projectile has sufficient toughness to withstand acceleration and torque created during projectile firing and trajectory.