Abstract: Improved refractories for resisting attack of molten titanium aluminum and similar metals are provided by the inclusion of sulfur. Metal, oxygen, and sulfur combinations, wherein sulfur is present at from 10 to 60 atomic percent, are particularly useful.Disclosed is a material having the atomic formula M.sub.a S.sub.b O.sub.c where O is oxygen, S is sulfur, and M is at least one metal selected from the scandium subgroup of the periodic table transition metals (scandium, yttrium and the rare earths) and aluminum. In an alternate material, M is comprised of at least two elements, the first selected as above and the second selected from the alkaline earth metal group. A preferred material is formed by mixing and firing CaS and Y.sub.2 O.sub.3 in proportions which results in (Ca+Y).sub.0.43 S.sub.0.14 O.sub.0.43.

Abstract: A ceramic composition suitable for use as a high-temperature structural material, particularly for use in apparatus exposed to oxidizing atmospheres at temperatures of 400 to 1600.degree. C., is found within the triangular area ABCA of the Si.sub.3 N.sub.4 --SiO.sub.2 --M.sub.2 O.sub.3 ternary diagram depicted in FIG. 1. M is selected from the group of Yb, Dy, Er, Sc, and alloys having Yb, Y, Er, or Dy as one component and Sc, Al, Cr, Ti, (Mg +Zr) or (Ni+Zr) as a second component, said alloy having an effective ionic radius less than 0.89 A.

Abstract: Ceramic material, and cryogenic refrigeration apparatus containing thermal energy absorbing elements made of the ceramic material, which is a dielectric insulator and has values of specific heat at selected temperatures below 15.degree. K. that are greater than or at least equal to the values of specific heat of pure lead at those same temperatures. Material consists essentially of a crystalline phase with a composition defined by the molar formula selected from: (1) AB.sub.2 O.sub.4 where A is Group 2b metal ions with or without other divalent metal ions and B is Cr ion with or without other trivalent metal ions, (2) AB.sub.2 O.sub.6 where A is Mn and/or Ni ion(s) with or without other divalent metal ions and B is Nb and/or Ta ion(s), and (3) A.sub.2 BCO.sub.6 where A is Pb ion with or without other divalent metal ions, B is Gd or Mn with or without other trivalent metal ions and C is Nb and/or Ta ion(s). Elements include regenerator packings, thermal dampers and dielectric insulation.

Abstract: A ceramic component suitable for preparing MHD generator electrodes having the compositional formula: Y.sub.x (Mg.sub.y Cr.sub.z).sub.w Al.sub.(1-w) O.sub.3 where x=0.9 to 1.05, y=0.02 to 0.2, z=0.8 to 1.05 and w=1.0 to 0.5. The component is resistant to the formation of hydration products in an MHD environment, has good electrical conductivity and exhibits a lower electrochemical corrosion rate than do comparable compositions of lanthanum chromite.

Abstract: A process for continuous or interrupted machine cutting of solid cast iron by milling, turning or boring with a shaped tool, wherein said shaped tool is a ceramic consisting essentially of Si.sub.3 N.sub.4 and 4-12% by weight Y.sub.2 O.sub.3, produced by hot pressing at a pressure and a temperature of 1700.degree.-1750.degree. C. to achieve substantially full density.

Abstract: The instant invention is directed to the production of glass-ceramic articles from thermally crystallizable glass compositions containing, by weight, about 40-85% SiO.sub.2 and 2.5-17% N as basic constituents and utilizing such modifiers as the alkali metals, the elements of Groups IIA and IIB of the Periodic Table, boron, and aluminum to obtain practical glass-forming compositions. In general, at N contents greater than about 3.5%, the predominant crystal phase developed in situ will customarily comprise "nitrogen mullite", silicon oxynitride (Si.sub.2 ON.sub.2), and/or .beta.'-Si.sub.3 N.sub.4 solid solution. The crystal phase which has been denominated in the literature as "nitrogen-mullite" has a lath-like morphology and, hence, is useful in reinforcing the crystalline body. Where the predominant crystal phase comprises a silicate, it is believed that nitrogen is present in some manner within the silicate crystal structure. The parent thermally crystallizable glasses appear to be self-nucleating, i.e.

Abstract: Barium titanate series semiconductive ceramics having a positive temperature coefficient of electric resistance are disclosed. The ceramics consist mainly of a barium titanate series compound and contain specifically limited small amounts of titanium dioxide, silicon oxide, aluminum oxide, at least one element selected from the group consisting of rare earth elements, yttrium, bismuth, antimony, niobium, tantalum and tungsten, at least one element selected from the group consisting of manganese, copper, iron and chromium, and zinc oxide. The ceramics are low in the variance of electric resistance values and have a low water absorption and hence are low in the change of electric properties due to the lapse of time.

Abstract: A sintered body of zirconia material for an oxygen concentration sensor exhibiting an electromotive force in accordance with the difference in the concentration of oxygen between a gas tested and a reference gas, consisting essentially of partially stabilized sintered zirconia and at least one additive selected from the group of yttrium oxide, calcium oxide and ytterbium oxide which zirconia has a cubic phase and a monoclinic phase existing in mingling relation. The ratio of the X-ray diffraction intensity of the surface (111) of the monoclinic phase to the X-ray diffraction intensity of the surface (111) of the cubic phase or the ratio I(111)/I(111) is in the range between 0.05 and 0.40, and the value of the X-ray diffraction intensity ratio caused by heating the sintered zirconia material to, and holding the same at, the temperature range between 200.degree. and 300.degree. C. minus the former ratio of the X-ray diffraction intensity is in the range between -0.05 and +0.10.

Abstract: A high strength silicon nitride sintered material having a modulus of rupture of about 100 kg/mm.sup.2 or more, which is prepared by sintering a mixture of about 88.7 to 98% by weight of silicon nitride (Si.sub.3 N.sub.4) and the balance a sintering aid comprising Al.sub.2 O.sub.3, Y.sub.2 O.sub.

Abstract: A transparent or translucent article of manufacture such as a discharge tube for a metal vapor arc lamp is formed from a high density ceramic composition having a perovskite structure and having the formula:ABO.sub.3wherein A can be lanthanum, cerium, praseodymium or neodymium and B has a smaller ionic radius and can be aluminium, scandium, lutecium or the like.

Abstract: A process and products produced thereby, e.g., alumina tools, in which ceramic powder particles are subjected to high transmissive energy milling under dry conditions and with given ratios of impacting media to powder, the milling being conducted for a period beyond the threshold point of the powder constituents, whereby dense, composite powder particles are obtained having an interdispersion of initial constituent particles, a large internal interfacial surface within individual product powder particles, etc.

Abstract: A fired ceramic having dense and low thermal expansion characteristics comprises 0.3 to 8 wt. % of at least one of rare earth oxides and has a thermal expansion coefficient of less than 0.3% and a porosity of less than 10%.The fired ceramic having dense and low thermal expansion characteristics comprises a main component of cordierite, lithium aluminosilicates or aluminum titanate.The rare earth oxide is preferably Y.sub.2 O.sub.3 and can be CeO.sub.2 or La.sub.2 O.sub.3.

Abstract: A method for increasing the porosity and crushability characteristics thereof embodies the firing of a ceramic compact comprising a reactant fugitive filler material and a ceramic material in a controlled atmosphere.

Abstract: A method for simultaneously forming an integral barrier layer on selected external surfaces of a fired ceramic article and for increasing the porosity content and crushability characterstics thereof embodies the firing of a ceramic compact comprising a reactant fugitive filler material and a ceramic material in a controlled atmosphere.

Abstract: There is disclosed a process for producing a metastable precursor powder having about 20 to 60 percent of the silicon thereof in the nitride form. This process includes a controlled nitriding step using silicon, alumina, and either aluminum or aluminum nitride as starting materials. There is also disclosed a process for producing sialon from this precursor powder. This process includes the steps of doping the precursor powder, cold pressing or slip casting the doped powder, and then carrying out a controlled sintering step under a nitrogen atmosphere.

Abstract: A polycrystalline alumina has at least 50% unit surface area provided by crystals of at least 60 .mu.m, and preferably 100 .mu.m size. This improves the in-line transmission value and hence lamp efficiency in a tube for a high pressure metal vapor lamp having an envelope of alumina.

Abstract: A colloidal dispersion is disclosed in which colloidal particles of an inorganic substance, and a compound of a Group IIA, or of a Group IIIA, or of a lanthanide (rare earth) element are dispersed throughout a liquid. The colloidal dispersion can be dried to form gels and the gels calcined to form porous ceramic materials.

Abstract: A ceramic component suitable for preparing MHD generator electrodes consists of HfO.sub.2 and sufficient Tb.sub.4 O.sub.7 to stabilize at least 60 volume percent of the HfO.sub.2 into the cubic structure. The ceramic component may also contain a small amount of PrO.sub.2, Yb.sub.2 O.sub.3 or a mixture of both to improve stability and electronic conductivity of the electrode. The component is highly resistant to corrosion by molten potassium seed and molten coal slag in the MHD fluid and exhibits both ionic and electronic conductivity.

Abstract: A silicon nitride base sintered body having high strength and high density is formed by a normal sintering, namely by sintering without pressure. The sintered body is produced of silicon nitride and the metal oxides yttrium oxide and cerium oxide.A silicon nitride base sintered body having yet a higher strength and higher density can be produced by heating yttrium oxide and cerium oxide together for forming Y.sub.2 O.sub.3.2CeO.sub.2 before sintering.

Abstract: Polycrystalline ceramic bodies of Si.sub.3 N.sub.4 when prepared with a nucleating agent to obtain an intergranular phase which is substantially crystalline, exhibit improved mechanical strength at elevated temperatures over bodies having a glass-containing intergranular phase.

Abstract: Articles made from Si.sub.3 N.sub.4 ceramic alloy powders are protected during heating by loosely packing them in Si.sub.3 N.sub.4 before heating. Compacts made from Si.sub.3 N.sub.4 ceramic alloys are protected from both oxidation and from volatilization by the encompassing powder even though the furnace atmosphere is air.

Abstract: Mixed oxide compounds La.sub.2 O.sub.3.11Al.sub.2 O.sub.3, NdAlO.sub.3 and nonstoichiometric MgAl.sub.2 O.sub.3 are suitable for making cores and molds for casting advanced superalloy materials such as NiTaC-13.

Abstract: Disclosed are new polycrystalline ceramic bodies formed from melts containing as essential components P.sub.2 O.sub.5, Ta.sub.2 O.sub.3 and Al.sub.2 O.sub.3 and sometimes containing small amounts of SiO.sub.2. Also disclosed are such bodies in the form of planar dopant hosts for doping silicon or germanium with phosphorus. Methods of making both products are disclosed as well as how to use the dopant hosts in a doping process.

Abstract: An article of manufacture comprising a substantially transparent high density polycrystalline yttria-based body consisting essentially of yttria and from 0.1 to 5 wt. % MgO or from 0.1 to 5 wt. % MgAl.sub.2 O.sub.4.Transparent yttria-based bodies according to this invention are particularly useful as envelopes for high pressure sodium vapor lamps.

Abstract: An article of manufacture is provided comprising a substantially transparent high density polycrystalline yttria-base body consisting essentially of yttria and from about 0.01 to 5 wt. % alumina.A method for preparing the transparent yttria doped with alumina is also provided comprising admixing alumina or a precursor thereof with yttria or a precursor thereof, drying the admixed powders, calcining the admixed powders and pressing the calcined powders into a desired shape and thereafter sintering the shaped powder for about 1/4 to six hours at a temperature above the eutectic temperature at a sufficiently low oxygen atmosphere to prevent oxidative contaminants.

Abstract: Metal nitride sintered moldings are produced by mixing metal nitride powders with an organosilicon compound or an organosilicon high molecular weight compound as a binder, molding the mixture into a desired shape and heating the formed molding under a non-oxidizing atmosphere to sinter the metal nitride powders.

Abstract: A method of decreasing the electrical resistivity of a rare-earth chromite material by substituting bivalent metal ions for some of the chromium or rare-earth ions therein. The method includes applying a solution containing the bivalent metal ions to the rare-earth chromite under vacuum conditions, drying the solution on the chromite, and diffusing the bivalent metal ion into the rare-earth chromite by firing the chromite in a controlled atmosphere.

Abstract: This invention is directed to a burnt ceramics composition of matter for an endosseous implant to be inserted in the bone tissue of a living body. The composition of matter consists of 95-50% of Al.sub.2 O.sub.3 and 5-50% of more than one compound selected from the group consisting of ZrO.sub.2, La.sub.2 O.sub.3 and Y.sub.2 O.sub.3.

Abstract: Disclosed is a silicon nitride-based sintered material having high heat resistance and containing crystal compounds prepared from the silicon nitride and at least one oxide of a rare earth element.

Abstract: A composition consisting of 5 to 95 mol% of bismuth oxide (Bi.sub.2 O.sub.3) and 95 to 5 mol% of copper oxide (Cu.sub.2 O), or a composition consisting of 50 to 95 mol% of copper oxide (Cu.sub.2 O) and 50 to 5 mol% of manganese dioxide (MnO.sub.2), or a composition consisting of 5 to 95 mol% of bismuth oxide (Bi.sub.2 O.sub.3) and 95 to 5 mol% of manganese dioxide (MnO.sub.2), is thermally diffused in the grain boundaries of semiconductor ceramics composed mainly of strontium titanate (SrTiO.sub.3) to form highly insulating layers in the grain boundaries to thereby provide semiconductive ceramics wherein the rate of change of dielectric constant with temperature as well as the dielectric loss (tan .delta.) are smaller than in the conventional barium titanate type semiconductor products. Further, the insulation resistance is higher than in the conventional product.

Abstract: Disclosed are new polycrystalline ceramic bodies formed from melts containing as essential components P.sub.2 O.sub.5, Ta.sub.2 O.sub.3 and Al.sub.2 O.sub.3 and sometimes containing small amounts of SiO.sub.2. Also disclosed are such bodies in the form of planar dopant hosts for doping silicon or germanium with phosphorus. Methods of making both products are disclosed as well as how to use the dopant hosts in a doping process.

Abstract: A method for producing a dense and impervious stabilized hafnium oxide ceramic having zero percent water absorption is disclosed. The hafnium oxide is stabilized in the sense that a solid solution with Y.sub.2 O.sub.3 is formed. The solid solution has a cubic crystal structure which, because of its similarity to the structure of the mineral fluorite, is sometimes called a "fluorite phase"; unlike hafnium oxide alone, which undergoes a destructive phase transformation from tetragonal to monoclinic during cooling, the cubic structure of the solid solution remains stable during cooling of a ceramic article.

Abstract: A method of producing a ceramic product which comprises the step of forming a powder mixture consisting essentially of a first component consisting of compounds containing the elements silicon, aluminum, oxygen and nitrogen in proportion such that the ratio of the total number of silicon and aluminum atoms to the total number of oxygen and nitrogen atoms lies in the range 0.735 to 0.77 and such that said compounds react together during the subsequent sintering process to produce a single phase ceramic material obeying the general formula:Si.sub.6-z Al.sub.z O.sub.z N.sub.8-zwhere z is between 0.38 and 1.5, and between 0.1 and 10% by weight of a second component in the form of an oxide of at least one of the further elements yttrium, scandium, cerium, lanthanum and the metals of the lanthanide series. The mixture is then sintered in a protective environment at a temperature between 1600.degree. C and 2000.degree.

Abstract: Thermistors (NTC) containing a mixture of terbium oxide and a material selected from the group consisting of samarium and ytterbium oxide are useful in high temperature environments.

Abstract: A composite body consisting of two or more formed parts of densely sintered aluminum oxide and a metal such as an envelope for a mercury vapor discharge lamp with a metal halide filling. The parts are connected together with material which comprises at least two of the oxides SiO.sub.2, Al.sub.2 O.sub.3 and B.sub.2 O.sub.3 and at least one of the trivalent oxides La.sub.2 O.sub.3 and Y.sub.2 O.sub.3. This material is applied at a relatively low temperature and is resistant to the gas filling up to approximately 1350.degree. C.

Abstract: The present invention concerns insulating ceramic substances, passive with respect to corrosive molten metals such as aluminium or steel, having a controlled porosity, withstanding without cracking repeated thermal shocks. Such ceramics are obtained by sintering without charge at a low temperature after addition of a fluoride.

Abstract: Aluminum titanate composition being stable at high temperature comprises 1.5 to 20 wt. % of Sn component as SnO.sub.2 and/or 0.5 to 10 wt. % of rare earth element component as rare earth oxide.

Abstract: An article of manufacture is provided comprising a substantially transparent high density polycrystalline yttriabase body consisting essentially of yttria and from about 6 to 14 mole percent lanthana.A method for preparing the transparent yttria doped with lanthana is also provided comprising admixing or co-precipitating lanthana or a precursor thereof with yttria or a precursor thereof, washing, drying and screening the mixture, calcining the admixed or co-precipitated powders, pressing the calcined powders into a desired shape and thereafter sintering the shaped powder for from about 1/6 to 6 hours at a temperature above the H-phase transition and for from about 1/2 to 6 hours at a temperature below the H to C phase transition, said sintering being effected at a sufficiently low oxygen atmosphere to prevent oxidative contaminants.

Abstract: In a method for fabricating highly dense, polycrystalline silicon nitride bodies, a mixture of silicon nitride powder and an oxide, hydride or nitride of an element of the lanthanide series in powder form is hot pressed at a temperature ranging from 1600.degree. to 1750.degree. C for a period of 30 to 60 minutes. The method is particularly useful for fabricating structural components, such as stators, blades, airfoils and buckets in high performance gas turbine engines.

Abstract: Mixed oxide compounds La.sub.2 O.sub.3 . 11Al.sub.2 O.sub.3, NdAlO.sub.3 and nonstoichiometric MgAl.sub.2 O.sub.3 are suitable for making cores and molds for casting advanced superalloy materials such as NiTaC-13.

Abstract: Dense, ceramic compositions fabricated within the Si.sub.3 N.sub.4 -Si.sub.2 N.sub.2 O-Y.sub.2 Si.sub.2 O.sub.7 compatibility triangle in the Si.sub.3 N.sub.4 -SiO.sub.2 -Y.sub.2 O.sub.3 system are extremely stable in oxidizing environments and particularly suited for use as a high temperature structural material. In addition, the hot-pressed, densified articles fabricated from compositions within the compatibility triangle exhibit improved strength and creep resistance at elevated temperatures relative to commercial Si.sub.3 N.sub.4.

Abstract: A dielectric ceramic composition for high frequencies consisting essentially of 83 to 99.8 wt% of a basic composition composed of 22 to 43 wt% of titanium dioxide, 38 to 58 wt% of zirconium dioxide and 9 to 26 wt% of stannic oxide, and 0.2 to 17 wt% of one or two addditives selected from the group consisting of lanthanum oxide, cobaltic oxide and zinc oxide. The dielectric ceramic composition has high permittivity and high Q and is suitable for use as dielectric resonators in microwave bandpass filters, or as antennas employed at microwave frequencies, or as substrates for microwave circuits.

Abstract: An article of manufacture is provided comprising a substantially transparent high density polycrystalline yttria-base body consisting essentially of yttria and from about 0.01 to 5 wt. % alumina.A method for preparing the transparent yttria doped with alumina is also provided comprising admixing alumina or a precursor thereof with yttria or a precursor thereof, drying the admixed powders, calcining the admixed powders and pressing the calcined powders into a desired shape and thereafter sintering the shaped powder for about 1/4 to 6 hours at a temperature above the eutectic temperature at a sufficiently low oxygen atmosphere to prevent oxidative contaminants.

Abstract: A ceramic suitable for use in the casting of advanced superalloy materials has a structure including a predetermined porosity content and a material microstructure characterized by a high density of microcracks.

Abstract: A method for manufacturing heat-resistant reinforced composite materials having a fibrous structure which comprises mixing 99.8 to 90 percent by weight of a first component selected from the group consisting of the nitrides or carbides of aluminum, silicon and boron and mixtures thereof and 0.2 to 10 percent by weight of a second component selected from the group consisting of the rare earth oxides and mixtures thereof, molding the mixture into a desired shape, and sintering the molded mass to create a fibrous structure therein, said first component being 0.2 to 3.0 microns in average particle size, and said second component being 0.1 to 2.0 microns in average particle size.

Abstract: A ceramic article suitable for use in the casting of advanced superalloy materials has a structure of a predetermined porosity content and consists of either 3Y.sub.2 O.sub.3 .multidot. 5Al.sub.2 O.sub.3, Y.sub.2 O.sub.3 .multidot. Al.sub.2 O.sub.3 or 2Y.sub.2 O.sub.3 .multidot. Al.sub.2 O.sub.3 or two-phase mixtures of these single-phase materials.

Abstract: A semiconductor ceramic composition having positive temperature characteristics which comprises titanates of barium, lead and calcium which have 1 - 40 mole % of lead titanate and 1 - 22 mole % of calcium titanate and 38 - 98 mole % of barium titanate and 0.03 - 0.6 mole % of a semiconductor-forming component based on said titanates.

Abstract: Adhesive plaster compositions are provided by treating particles of Y.sub.2 O.sub.3, Eu.sub.2 O.sub.3, Gd.sub.2 O.sub.3 or Nd.sub.2 O.sub.3 with dilute acid solutions. The resulting compositions have been found to spontaneously harden into rigid reticulated masses resembling plaster of Paris. Upon heating, the hardened material is decomposed into the oxide, yet retains the reticulated rigid structure.

Abstract: The crushability of a ceramic article suitable for use in the casting and directional solidification of advanced superalloy materials is enhanced by utilizing a two-phase mixture of material and inducing microcracks in the material. The crushability is further enhanced by forming the article to include a predetermined porosity content.

Abstract: A non-linear resistor comprises a sintered body of a ceramic composition which comprises 99.94 to 80.0 mole % of zinc oxide as ZnO, 0.02 to 10.0 mole % of the specific rare earth oxide selected from the group consisting of oxides of cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium as R.sub.2 O.sub.3, and 0.04 to 10 mole % of manganese oxide as MnO.