Abstract: An alumina silica sintered ceramic that is produced by the normal sintering method and which has bending strength of at least 300 MPa at room temperature and at least 400 MPa at an elevated temperature, for example, 1,300.degree. C. is disclosed.This sintered ceramic is produced by a process comprising the following steps: providing a chiefly amorphous starting powder that consists of 62-73 wt % Al.sub.2 O.sub.3 and correspondingly 38-27 wt % SiO.sub.2 ; calcining this starting powder to make a calcined product that is chiefly composed of a crystalline phase and which contains oxides of an alkali metal and an alkaline earth metal in a total amount of no more than 1,500 ppm; pressing the ground particles of the calcined product into a compact; and sintering the compact at 1,500.degree.-1,750.degree. C. and at atmospheric pressure.

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: An .alpha.-SIALON powder composed essentially of .alpha.-SIALON having the formula M.sub.x (Si,Al).sub.12 (O,N).sub.16 wherein M is at least one element selected from the group consisting of Li, Mg, Ca, Mn, Y and lanthanide metals and O<x.ltoreq.2.

Abstract: Silicon nitride-alumina composite ceramics composed of silicon nitride crystals, .alpha.-alumina crystals and .beta.'-sialon crystals, wherein the silicon nitride crystals and the .beta.'-sialon surrounded the .alpha.-alumina crystals so as to prevent the connection of the .alpha.-alumina crystals. And a method for producing the silicon nitride-alumina composite ceramics which has the steps of preparing a mixture powder composed of 20 to 70 wt % of alumina powder and silicon nitride powder as a remainder, the average particle diameter of the alumina powder being two or more times as large as that of the silicon nitride powder, and firing the mixture powder in an atmosphere of inactive gas.

Abstract: A silicon nitride sintered body having an improved oxidation resistance or wear resistance has in its surface a coating of silicon carbide. Particularly, the coating of silicon carbide is formed by CVD process.

Abstract: Organophilic clays which are effective fluid loss control additives for oil base well-working fluids are prepared from a swelling smectite clay and one or more phosphatides. Preferred phosphatides are phosphoglycerides obtained from vegetable oils, most preferably commercial lecithin such as soybean lecithin. The organophilic clays may also contain quaternary ammonium compounds.

Abstract: The present invention relates to a novel additive for hydraulic cements, mortars and concretes, particularly for improving the mechanical strengths and the workability and for reducing sweating and segregation, which is characterized in that it is a protein hydrolysate having a pH less than or equal to 6, comprising substances selected from the group constituted by proteins, polypeptides, aminoacids and mixtures thereof, and obtained by treating 100 volumes of an aqueous composition containing at least one protein substance selected from the group constituted by proteins, polypeptides and mixtures thereof, with at least one bacterial strain producing lactic acid having a population greater than or equal to 10.sup.2 germs/cm.sup.3, in the presence of 0.5 to 30 parts by weight of a source of carbon belonging to the family of carbohydrates, for at least 2 hours, at a temperature of between 0.degree. and 65.degree. C. and at a pH less than or equal to 6.

Abstract: A process and product for achieving uniform, stabilized working and setting times for phosphate-bonded magnesia cements, wherein a solid phosphate is mixed with an aqueous ammonium phosphate solution and magnesium oxide to form a cement. The solid phosphate may be provided dry or in a slurry, and may be first mixed with the ammonium phosphate solution or the magnesium oxide. Introduction of the solid phosphate into the cement stabilizes the setting time of the cement, which otherwise may vary from a few minutes to several hours, depending upon the characteristics of the ammonium phosphate solution. The ammonium phosphate solution may be supplied as a 10-34-0 composition that is readily available commercially. In one embodiment of the invention, the solid phosphate is provided as an ammonium phosphate mixture of an 18-46-0 composition, having an ammonium phosphate content above the solubility limit of ammonium phosphate in water.

Abstract: A novel cured extruded article of a metal fiber-reinforced hydraulic material is provided, wherein protrusion of the metal fibers at the extruded surfaces thereof is substantially prevented. The cured extruded article is produced by extruding a blend mixture comprising an inorganic hydraulic material, water, a reinforcing amount of metal fibers having a specified sectional area and a specified length, and a protrusion-preventing amount of non-metal fibers having a specified length into an article, and then curing the resulting article. The extruded article can be glazed by applying a glazing agent onto a desired surface thereof, heating it to a high temperature up to 1000.degree. C., and then hydrating it.

Abstract: A process for making aerated concrete by pretreating aggregates prior to incorporation into a cement slurry is disclosed. The pretreatment involves addition of reactive agents, such as aluminum powder and cellulose derivatives, in an aqueous dispersion to common cement additives such as sand, fibers, etc., and drying. Upon use in a cement slurry to form concrete, the reactive agents generate gases on the aggregates which form macrovoids uniformly distributed throughout the concrete.

Abstract: A dielectric ceramic composition consisting essentially of a BaO-TiO.sub.2 -WO.sub.3 ternary system wherein molar percentages of BaO, TiO.sub.2 and WO.sub.3 are within the range enclosed by a line joining the points of A(21.5, 78.5, 0), B(40.0, 30.0, 30.0), C(37.0, 30.0, 33.0), D(20.0, 75.0, 5.0), E(21.5, 75.0, 3.5) and A of a composition diagram shown in the attached FIGURE, the range excluding molar percentages of BaO, TiO.sub.2 and WO.sub.3 laying on a line joining said points A, E and D. In the dielectric ceramic composition, up to 10 mole % of TiO.sub.2 may be replaced by tetravalent metal oxide and, further, MnO is contained in amounts of 3 mole % or less with respect to 100 mole % of the sum of BaO, TiO.sub.2 and WO.sub.3. Since the dielectric ceramic composition has a beneficial combination of dielectric properties, particularly a high Q, properly small dielectric constant and sufficiently small temperature coefficient of resonant frequency, .tau..sub.f, and .tau..sub.

Abstract: A silicophosphate laser glass having a composition comprising, in % by mole,45 to 70% P.sub.2 O.sub.5 ;5 to 20% SiO.sub.2 ;60 to 95% P.sub.2 O.sub.5 +SiO.sub.2 +Al.sub.2 O.sub.5 ;10%<Al.sub.2 O.sub.3 .ltoreq.20%;20%<(Al.sub.2 O.sub.3 +SiO.sub.2).ltoreq.30%;4 to 30% Li.sub.2 O+Na.sub.2 O+K.sub.2 O;0.01 to 12% Nd.sub.2 O.sub.3 ;0 to 5% La.sub.2 O.sub.3 +Y.sub.2 O.sub.3 +B.sub.2 O.sub.5 ;0 to 10% R'O; and0 to 1% Nb.sub.2 O.sub.5 +CeO.sub.2,wherein R' is Mg, Ca, Sr, Ba, Zn or Pb. The silicophosphate laser glass can construct an excellent laser glass as an amplifying medium.

Abstract: The present invention relates to a method for utilizing slag from metal production, particularly the silicate slag with a high iron oxide content resulting from copper or nickel proceses, in the production of heat-resistant, fire-resistant and/or alkali-resistant fibre material. According to the invention, the temperature dependence of the slag viscosity is changed by means of alloying the slag so that the relative proportion of the acidic components contained in the slag is increased.

Abstract: When a portion of the Pb of a Pb(Zn.sub.1/3 Nb.sub.2/3)O.sub.3 -based ceramic composition within the region bounded by lines connecting a, b, c and d points in the ternary composition diagram of the accompanying FIG. 1 is substituted by a small amount of Ba and/or Sr, a high dielectric constant type ceramic composition which has a small temperature coefficient of dielectric constant and which is effective as a material for multilayer ceramic capacitors is obtained.

Abstract: The invention relates to a method for utilizing slag from ferroalloy production in manufacturing heat-resistant, fire-resistant and/or alkali-resistant fiber materials, when the original slag is based on aluminum oxide and silicon oxide. According to the invention, aluminum oxide and/or silicon oxide is added into the molten slag in order to change the slag viscosity and to adjust the defibration temperature of the slag.

Abstract: A process for producing an aluminum nitride ceramic body having a composition defined and encompassed by polygon ABCFGH of FIG. 2, a porosity of less than about 10% by volume, and a thermal conductivity greater than 0.70 W/cm.K at 25.degree. C. which comprises forming a mixture comprised of aluminum nitride powder containing oxygen, gadolinium oxide, and free carbon, shaping said mixture into a compact, said mixture and compact having a composition wherein the equivalent % of gadolinium and aluminum ranges from point A to point F of FIG. 2, said mixture and said compact having an equivalent % composition of Gd, Al, O and N outside the composition defined and encompassed by polygon ABCFGH of FIG. 2, heating said compact to a temperature at which its pores remain open reacting said free carbon with oxygen contained in said aluminum nitride producing a deoxidized compact, said deoxidized compact having a composition wherein the equivalent % of Al, Gd, O and N is defined and encompassed by polygon ABCFGH of FIG.

Abstract: A process for producing a .beta.-sialon.silicon carbide complex includes mixing silicon nitride and silicon carbide with an aluminum alkoxide solution or a soluble aluminum salt solution and using the resulting homogeneous mixture as a starting material in forming a sintered body. The aluminum alkoxide solution or aluminum salt solution penetrates into the surface of each particle of the silicon nitride and silicon carbide, whereby the whole surface of each nitride and carbide particle is covered with aluminum alkoxide solution or aluminum salt solution, and homogeneous mixing is achieved. Therefore, defects such as pores, clusters of large grains, or unsintered parts are eliminated and the strength of the final sintered bodies is improved.

Abstract: An optical glass, n.sub.d .gtoreq.1.60 and v.sub.d .gtoreq.58, having a high chemical stability as well as resistance to phase separation and crystallization, comprises in percent by weight:______________________________________ SiO.sub.2 21.5-27.0; B.sub.2 O.sub.3 23.5-30.0 SrO 16.0-24.0; La.sub.2 O.sub.3 10.0-20; Al.sub.2 O.sub.3 1.5-5.0; BaO 5.0-14.0; ZrO.sub.2 0-4.0; Li.sub.2 O 0.5-5.0; Na.sub.2 O 0.8-2.5; K.sub.2 O 0-2.0.

Abstract: The invention relates to polycrystalline sintered articles comprising at least 50% by weight of crystalline silicon nitride phase of which at least 90% by weight is in the .beta.-form, and at least one secondary crystalline intergranular silicate phase, and having a density of at least 99% of the theoretically possible density, a modulus of elasticity at room temperature of less than 300 kN/mm.sup.2, a short-term bending strength at room temperatue, measured according to the 4-point method, of at least 600 N/mm.sup.2 which, up to 1200.degree. C., decreases by less than 50%, and a long-term bending strength, measured according to the 4-point method, which is characterized by a numerical value of more than 40 at 1200.degree. C. for the crack growth resistance parameter n.

Abstract: Stable slip casting composition having a total solids content of from 50 to 80 percent by weight on a base of finely divided, AlN-containing powders. It contains as liquid dispersion medium, water mixed with a water-soluble, aliphatic, polyvalent alcohol and admixtures for adjusting the viscosity required for slip casting. The liquid dispersion medium can contain, for instance, from 1 to 20 percent by weight of an alcohol such as glycerin calculated on the total weight of water and alcohol.