Abstract: A dense polycrystalline silicon nitride body is produced by hot-pressing a particulate mixture of silicon nitride and a magnesium silicide additive.

Abstract: A dense polycrystalline silicon nitride body is produced by hot-pressing a particulate mixture of silicon nitride and a beryllium additive.

Abstract: Type Ib or mixed type Ib-Ia natural diamond crystal is annealed at an annealing temperature ranging from about 1500.degree. C to about 2200.degree. C under a pressure which prevents significant graphitization of the diamond during the annealing to convert at least 20% of the total amount of type Ib nitrogen present in the crystal to type Ia nitrogen.

Abstract: A dense polycrystalline silicon nitride body is produced by hot-pressing a particulate mixture of silicon nitride and a beryllium additive.

Abstract: A gas mixture of silane and ammonia is heated at temperatures between about 600.degree. C and 1000.degree. C producing an amorphous powdery reaction product which, when heated at a calcination temperature of at least 1100.degree. C yields ultrafine Si.sub.3 N.sub.4 powder of high purity.

Abstract: A particulate dispersion of silicon nitride and beryllium additive is formed into a green body and sintered at a temperature ranging from about 1900.degree. to about 2200.degree. C in a sintering atmosphere of nitrogen at superatmospheric pressure producing a sintered body with a density ranging from about 80 to about 100%.

Abstract: A particulate dispersion of silicon nitride, magnesium additive and beryllium additive is formed into a green body and sintered at a temperature ranging from about 1800.degree. C to about 2200.degree. C in a sintering atmosphere of nitrogen at superatmospheric pressure producing a sintered body with a density ranging from about 80 to about 100%.

Abstract: A particulate dispersion of silicon nitride, magnesium additive and beryllium additive is formed into a green body and sintered at a temperature ranging from about 1800.degree. C to about 2200.degree. C in a sintering atmosphere of nitrogen at superatmospheric pressure producing a sintered body with a density ranging from about 80% to about 100%.

Abstract: A mass of cubic boron nitride(CBN) crystals, aluminum or aluminum alloy and a silicon carbide ceramic substrate are disposed in a container which is placed within a pressure-transmitting powder medium. Pressure ranging from about 20,000 psi to about 200,000 psi is applied to the powder medium resulting in substantially isostatic pressure being applied to the container and its contents. To the resulting shaped substantially-isostatic system of powder-enveloped container, heat and pressure are applied simultaneously whereby the aluminum or aluminum alloy is liquefied and infiltrated through the interstices between the CBN crystals and diffused into the contacting face of the silicon carbide substrate sufficiently to produce, upon cooling, an adherently bonded integral composite.

Abstract: A dense silicon carbide having improved properties is disclosed which is prepared by the addition of a carbonaceous additive to a boron doped silicon carbide and hot pressing the mixture at a sufficient temperature and pressure whereby a dense substantially nonporous ceramic is formed.

Abstract: A particulate mixture of .beta.-silicon carbide, boron carbide and a carbonaceous additive is formed into a green body and sintered producing a sintered body with a density of at least about 85% containing boron carbide in an amount ranging from about 10% to about 30% by weight of the total amount of silicon carbide and boron carbide present.

Abstract: Sensitive, fast-response apparatus is described for the detection of the presence of (a) aerobic or facultatively anaerobic bacteria, (b) certain body cell breakdown products in body fluids or (c) unusual contamination of the ambient by aerobic bacteria. The method employed, which enables dynamic, continuous observation of catalase-H.sub.2 O.sub.2 reaction, is based upon measuring the incremental increase of oxygen partial pressure within a hydrogen peroxide solution. The inherent catalase content in such bacteria and in most animal cells promotes the rapid decomposition of hydrogen peroxide resulting in the liberation of oxygen. This measurement of oxygen partial pressure is made directly from the hydrogen peroxide solution by means of an oxygen permeable membrane polarographic cell equipped with a cathode configuration providing improved sensitivity. The presence of small numbers of bacteria or other catalase-containing cells may be quantitatively determined by conducting the catalase-H.sub.2 O.sub.

Abstract: Abrasive particles are prepared by milling diamond particles, metal compound and milling balls to smear a coating of the compound on the diamond particles and firing the compound-coated diamond particles producing a rough granular adherent covering of metal and/or metal carbide surface coating chemically bonded to the diamond surface by metal carbide.

Abstract: A method for decrystallizing cellulose in natural cellulosic material which comprises admixing phosphoric acid with the cellulosic material to form a gel therewith, admixing tetrahydrofuran with the gel to extract the phosphoric acid forming a solution therewith and a precipitate of amorphous cellulose and recovering tetrahydrofuran and phosphoric acid from the solution for reuse in the process.

Abstract: A method of preparing a magnetic member composed of a non-magnetic substrate carrying a magnetic film of a transition metal-rare earth alloy comprising decomposing a rare earth metal compound below 1,000.degree. C to form a layer of rare earth metal on a substrate, decomposing a transition metal compound below 1,000.degree. C to form a layer of transition metal on the deposited rare earth metal, heating the metals to form an alloy thereof which has its preferred axis of magnetization substantially aligned and in a direction perpendicular to the plane of the substrate and magnetizing the film.

Abstract: A polycrystalline silicon body is produced by forming a particulate mixture of silicon powder having an average particle size less than 3 microns and boron in an amount ranging from 0.1% to 5% by weight of the silicon powder, shaping the particulate mixture into a green body and sintering the body to a density of at least 60% of the theoretical density of silicon.

Abstract: A polycrystalline silicon body is produced by shaping silicon powder having an average particle size less than 0.2 micron into a green body and sintering the body to a density of at least 60% of the theoretical density of silicon.

Abstract: A silicon carbide sintered body characterized by its microstructural stability at high temperatures is produced by forming a mixture of .beta.-silicon carbide powder, .alpha.-silicon carbide seeding powder, boron additive and a carbonaceous additive into a green body and sintering it to produce a sintered body with a density of at least 80% wherein at least 70% by weight of the silicon carbide is .alpha.-silicon carbide.

Abstract: A silicon carbide body with a density of at least 85% is machined to required specification and then fired at a temperature ranging from 1400.degree. C to 2100.degree. C in a firing atmosphere ranging in pressure from 10.sup..sup.-3 torr to 25 torr to increase its fracture strength by at least 10%.

Abstract: A dense polycrystalline silicon carbide body is produced by hot pressing a particulate mixture of silicon carbide and beryllium carbide.