Abstract: A porous molybdenum disilicide-based material prepared by preheating a preform consisting of size-controlled molybdenum (Mo) powder and content-controlled silicon (Si) powder and igniting the preform to initiate self-propagating high temperature synthesis, and a method for preparing the same, are disclosed. The method comprises the steps of a) mixing molybdenum (Mo) powder and silicon (Si) powder in the stoichiometric ratio of 1:2; b) molding the mixed powder into a preform; c) preheating the preform under inert atmosphere; and d) igniting the top end of the preheated perform. The porous molybdenum disilicide-based material can control its pore size by appropriately controlling the size of molybdenum (Mo) powder, the content of silicon (Si) powder and preheating condition. Therefore, since the pore size gradient of the porous material is possible to form, the porous material can be used for filters with improved dirt-holding capacity.

Abstract: A large amount of spinel type silicon nitride powders of a high-pressure phase is produced by mixing raw powders having a particle size of 10 &mgr;m or less of &agr;-, &bgr;- or amorphous silicon nitride, each of which is a low pressure phase, with non-nitrified metal powders at a ratio of 50 weight % or more, preferably copper powders with a particle size of 100 &mgr;m or less, forming a compact with porosity of 50% or less and 10% or more, preferably around 30%, by pressing mixture powders obtained, and subjecting the compact to shock wave compression treatment at a pressure of 20GPa or more, preferably around 60GPa.

Abstract: A process for the production of silicon nitride (Si3N4) is described. According to this process nitrogen and/or nitrogen compounds are reacted with silicon and/or silicon compounds in a reaction chamber by means of a subgroup element or a subgroup element oxide. The process can be carried out in a simple and rapid manner and has a high yield.

Abstract: The present invention relates to the provision of materials intended for use in an oxidative medium at high temperatures, including the manufacture of high-temperature electric heaters, parts, sensors and tools operating at temperatures of up to 1900° C. and higher. On the basis of suicides—solid solutions (Mo,W)5Si3 and (Mo,W)Si2 as well as Novotn{grave over (y)} phase (Mo,W) 5Si3C containing molybdenum and tungsten, a heat-resistant material is proposed, which makes it possible to produce parts fully made therefrom and a broad range of other heat-resistant materials for the provision of protective coatings and soldered joints: “REFSIC” composite materials, carbon, silicon carbide materials, refractory metals and their alloys.

Abstract: A method of forming a crystalline phase material includes, a) providing a stress inducing material within or operatively adjacent a crystalline material of a first crystalline phase; and b) annealing the crystalline material of the first crystalline phase under conditions effective to transform it to a second crystalline phase. The stress inducing material preferably induces compressive stress within the first crystalline phase during the anneal to the second crystalline phase to lower the required activation energy to produce a more dense second crystalline phase. Example compressive stress inducing layers include SiO2 and Si3N4, while example stress inducing materials for providing into layers are Ge, W and Co. Where the compressive stress inducing material is provided on the same side of a wafer over which the crystalline phase material is provided, it is provided to have a thermal coefficient of expansion which is less than the first phase crystalline material.

Abstract: A process for preparing silanes of the formula 1: RaSiHbCl4-a-b  (1) where R is methyl or ethyl, a is 0, 1, 2 or 3 and b is 0 or 1, from hydrogen chloride gas and reactants selected from among a) silicon metal, b) disilanes and oligosilanes whose radicals are selected from among H, R and Cl,  and mixtures thereof, wherein the hydrogen chloride gas is prepared from H2 and Cl2 in a concerted process.

Abstract: Disclosed are methods of purifying mixtures comprising nanofibers and/or nanotubes and residual catalyst particles that are covered by outer layers of the nanotube or nanofiber material. The mixtures are exposed to electromagnetic radiation, which induces localized heating in the residual catalyst particles. The localized heating creates breaches in the outer layers. Thereafter, the residual catalyst particles may be removed under relatively mild conditions that do not significantly affect the structural integrity of the nanotubes or nanofibers. The methods of the invention have been used to particular advantage in the purification of single wall carbon nanotubes (SWNTs) synthesized using metal catalysts. For these SWNTs, microwave radiation is preferably used to induce the localized heating, the outer layers are preferably removed at least in part by carrying out the localized heating under air, and the residual catalyst may be removed by exposure to relatively dilute aqueous acid.

Abstract: A silicon based conductive material based on a semiconductor silicon and having an electric resistivity of 10−3(&OHgr;·m) or less at ambient temperature which has been unattainable heretofore, while facilitating production and handling. An electric resistivity of 10−6 (&OHgr;·m) or less, which is common for conductors can be realized by adding relatively large quantities of various kinds of elements to silicon. The conductive material can be provided in a semiconductor silicon substrate in a desired pattern by ion beam implantation and patterning. It can be employed not only in the form of a substrate, a rod or a wire, but also in the form of fine particles dispersed in a resin or glass to be employed in various applications requiring conduction, including a conductive sheet material.

Abstract: Provided is an SiGe crystal having an improved performance index and excellent machinability as a material constituting a thermoelectric element, neither degradation in characteristics nor cracking occurring during use. Crystal grains forming the crystal are 5×10−5 mm3 or more in size.

Abstract: Noval silico-titanates and the methods of making and using the said titanates are disclosed. Nb-doped silico-titanates are particularly useful for selectively removing cesuim from radioactive wastes.

Abstract: A proportion of Cu3Si in a contact mass is determined by treating the mass with an inorganic ammonium salt, which selectively dissolves all forms of copper including free copper in deference to Cu3Si, which is not dissolved. An initial copper content of the contact mass is determined, the contact mass is treated with an inorganic ammonium salt composition to extract copper in a molecular form other than Cu3Si and extracted copper is subtracted from the initial copper content.

Abstract: A method of preparing a substantially homogenous, alkali-metal silicon clathrate composition containing the silicon clathrate MxSi136 (3≦x≦24). The silicon clathrate is prepared by rapidly heating an alkali-metal silicide under a high vacuum to a decomposition temperature of at least 365° C. The produced silicon clathrates are in a substantially homogenous MxSi136 phase with only small amounts of a metallic silicon clathrate phase, MySi46. A method of reducing the alkali-metal content of a silicon clathrate MxSi136 (x>0) is also provided.

Abstract: A luminescent substance contains silicon and nitrogen as major components and has an amorphous structure. The silicon content of the luminescent substance is greater than the stoichiometric silicon content of Si3N4, and the luminous intensity of the luminescent substance has a maximum at approximately 2.2 eV. The luminescent substance has a high luminous efficiency and a short luminous decay lifetime. A light-emitting device includes this luminescent substance and a substrate. The luminescent substance can be readily formed on the substrate by a chemical vapor deposition process.

Abstract: A method of making a compound selected from metal and silicon carbides and nitrides includes the steps of providing a solution of a coal-derived material in a solvent, the coal-derived material having a composition, free of solvent, of 70 to 91 percent by mass of carbon, 2 to 6 percent by mass of hydrogen and 3 to 20 percent by mass of oxygen, and a source of an oxide of silicon or the metal, causing the coal-derived material in solution and the source of the oxide to interact, removing the solvent to form a precursor and heat treating the precursor to produce the compound.

Abstract: A method and an apparatus is provided for removing wafer processing by-products from gas fluid exhaust systems utilizing an energy source placed within an exhaust channel either alone or in combination with a cleaning gas. The placement of the energy source in an exhaust channel enables emitted energy to react with wafer processing by-products to convert the by-product residues to more removable forms. Additionally provided is a cleaning gas source internal to the exhaust channel to further react with and convert exiting by-product residues to gaseous fluids.

Abstract: Methods and systems for catalyzing the low temperature formation of silicon nitride. The methods and systems utilize catalytically reactive silica particles that are suspended by moving air within a reaction chamber and which are maintained at a temperature sufficient to cause the suspended silica particles to become catalytically reactive in the presence of carbon and nitrogen gas. Typically, the reaction chamber is maintained at a temperature in a range from about 150° C. to about 500° C. Moisture is generally provided by the organic matter, although additional moisture may be introduced into the reaction chamber in order to maintain reactivity of the silica particles. The silicon nitride is preferably deposited onto the surface of a metallic substrate, which might be located either within or externally to the reaction chamber. Depending on the ratio of oxygen to nitrogen provided within the reaction chamber, silicon nitride or a mixture of silicon nitride and silicon oxynitride will be produced.

Abstract: A novel material Si.sub.X C.sub.y N.sub.z, having a crystal structure similar to that of a.Si.sub.3 N.sub.4 with carbon atoms substituting most of the Si sites, is synthesized in crystalline form onto crystalline Si substrates by microwave plasma enhanced decomposition of carbon, silicon and nitrogen containing gasses.

Abstract: A process for nitriding materials containing silicon to form a silicon nitride material predominantly in the alpha phase is disclosed which includes nitriding the silicon-containing material by (a) heating the silicon-containing material in an atmosphere containing at least hydrogen in the temperature range of about 0.degree. C. to about 800.degree. C. and (b) thereafter, nitriding the silicon-containing material by subjecting the silicon-containing material to a nitriding atmosphere containing at least nitrogen gas in the temperature range of from about 1000.degree. C. to about 1450.degree. C. to effect nitriding.

Abstract: A method of producing silicon nitride ceramics and silicon nitride ceramic composites. A mixture comprising a polysilazane and an additive effective to increase coupling between the mixture and electromagnetic energy is converted to a preceramic intermediate. The preceramic intermediate is treated with electromagnetic energy and thereby converted to a silicon nitride ceramic and/or a silicon nitride ceramic composite.

Abstract: Silicon sulfide is manufactured from the fine powder of silicon having a particle size in the range of 60 to 100.mu., covered thoroughly with sulfur at lower temperature less than 700.degree. C. in vacuum. In order to produce the silicon sulfide, silicon should be ground in a non-oxidizing atmosphere to prevent the formation of a silicon oxide layer that remains in the product and degrades the purity of the product. The silicon powder is dispersed sufficiently in the molten sulfur. At this time, the quantity of added sulfur needs more than 1.1 times in comparison with the stoichiometric quantity of silicon sulfide. All surfaces of silicon powder should be covered with sulfur to avoid sintering between silicon particles in the whole process of the reaction.

Abstract: Silicon nitride powder is continuously prepared by feeding metallic silicon powder into a fluidized bed comprising silicon nitride powder and nitrogen or ammonia gas and discharging a nitrided product from the fluidized bed. The metallic silicon powder is pretreated at a temperature of 1,000.degree.-1,400.degree. C. under a vacuum of 0.001-100 Torr before it is subject to nitriding reaction.

Abstract: Silicon nitride nanowhiskers predominantly having diameters substantially less than about 200 nm are disclosed. The nanowhiskers of Si.sub.3 N.sub.4 are produced by reacting gaseous SiO and N.sub.2 at elevated temperature and pressure in a reaction zone in the presence of a plurality of disperse carbon nanotubes having a diameter of from 3.5 to 70 nm.

Abstract: The invention relates to a process for the preparation, by nitriding, of a refractory powder containing more than 40% of silicon nitride from spent contact masses issuing from chlorosilane synthesis. The process involves mixing with the copper-free spent mass, silicon or a silicon-rich alloy and optionally a refractory compound to adjust the non-oxidised silicon content to a predetermined value >30%, heating the mixture in a nitrogen atmosphere to trigger the exothermic nitriding reaction, then reducing the product obtained to powder. The refractory powder thus obtained can be mixed with an organic binder to produce taphole blocking masses for blast furnaces or electric furnaces for pyrometallurgy.

Abstract: A process for the production of silicon-containing ceramic whiskers is disclosed which includes the steps of:(a) forming a solid body of a mixture including an organosilicon polymer having a number average molecular weight of 500-50,000 and having a skeleton consisting of silicon atoms or silicon atoms and carbon atoms, and carbon; and(b) pyrolyzing the solid body in a noble gas atmosphere or a nitrogen gas atmosphere to form silicon carbide or silicon nitride whiskers.

Abstract: A process for preparing silicon carbide fiber by the carbothermal reduction of silica fiber. In the first step of the process, a specified silica fiber is contacted with a source of elemental carbon to produce a reactant mass; the silica fiber is comprised of at least about 99.5 weight percent of silica, has a density of at least about 2.15 grams per cubic centimeter, has a diameter of from about 1 to about 100 microns and an aspect ratio of at least about 30. From about 3.2 to about 5.0 moles of carbon are present in the carbon source for each mole of the silica. The reactant mass is heated at a temperature of from about 1,400 degrees centigrade to about 2,300 degrees centigrade for at least about 0.5 hours.

Abstract: The invention relates to material silicon nitride powder used for production of silicon nitride ceramics products. Provided herein is a material powder which can offer a compact having a homogeneous packing structure of the powder with good reproducibility and also to provide a method for producing the same. Accordingly to the method, a silicon nitride powder is heat treated in two-stage processing, one stage in an inert gas or reducing atmosphere at 100.degree. C.-1000.degree. C. for 5-600 min., and another stage in an oxidizing atmosphere at 300.degree. C.-1200.degree. C. for 5-600 min. As a result of this treatment, a silicon nitride powder is obtained in which its powder particles are crystalline in their interior and are coated with an amorphous layer having a 1-10 nm surface thickness and composed mainly of Si, N, O, and H, an atomic number ratio of oxygen to nitrogen (O/N) of the surface layer being within a range of 0.1-2.0.

Abstract: The present invention relates to a new process for the manufacture of fine powder of silicon nitride, to this powder and to the sinters obtained from the latter. The process comprises the reaction, in a nitrogen countercurrent and in continuous fashion, of silica, carbon and a seed crystal, in the presence of a volatile compound of a metal chosen from the group consisting of Be, Mg, Ca, Sr, Ge, Sn, Ti, Hf, Na and Ba, in a reaction zone possessing a temperature gradient, comprising a hot zone in which the said metal compound passes into the gaseous state and a cold zone in which the said metal compound in the gaseous state condenses, the said metal compound in the gaseous state being carried from the hot zone to the cold zone by the nitrogen countercurrent.

Abstract: A silicon nitride powder which provides a water-based slurry with a low viscosity and a high powder concentration. The silicon nitride powder has a specific surface area of 6 to 25 m.sup.2 /g, a number of coarse particles of coarse primary particles, agglomerated particles and/or fused particles, and having a size of 3 to 50 .mu.m, of not more than 1000 per 1 cm.sup.3 of the powder, a number of foreign metallic particles, having a size of more than 20 .mu.m, of not more than 3 per 1 cm.sup.3 of the powder, and a number of foreign metallic particles, having a size of 10 to 20 .mu.m, of not more than 15 per 1 cm.sup.3 of the powder.

Abstract: A crystalline silicon nitride powder having a high specific surface area and an enhanced sintering property is produced with a high producibility and a large scale, by calcining a silane material comprising at least one nitrogen-containing silane compound in a nitrogen-containing inert gas mixed with 0.1 to 5%, based on the total volume of the mixed gas, of molecular oxygen, preferably at 600.degree. to 1200.degree. C.; baking the resultant amorphous silicon nitride powder in a nitrogen-containing inert gas preferably at 1400.degree. to 1700.degree. C.; and milling the resultant crystalline silicon nitride powder in a mixed gas atmosphere comprising 5 to 40% by volume of molecular oxygen and the balance consisting of an inert gas preferably at 0.degree. to 100.degree. C.

Abstract: A silicon nitride powder containing .beta.-phase and .alpha.-phase at a ratio by weight (.beta./.alpha.) of from 0.018 to 0.032, and composed of crystallites 0.2 .mu.m or less in diameter.

Abstract: A silicon nitride powder with which a highly reliable silicon nitride with high strength and small strength and dimensional variances is obtainable is disclosed. By setting the amount of their surface acidic groups per B.E.T. surface area to not less than 0.2 .mu.eq/m.sup.2, their dispersibility in a mixing solvent is drastically improved. By using them, moldings with high density and homogeneity can be obtained, thereby enabling in turn a highly reliable sintered product of silicon nitride with high strength and small strength and dimensional variances to be easily manufactured. Besides, in the silicon nitride powder, the proportion of the silicon [Si*] belonging to SiO.sub.2, of the surface silicon [Si], which is determined by the X-ray photoelectron spectroscopy (XPS), should be not less than 0.07 in its atomic ratio [Si*/Si] and that to silicon of the surface carbon [C] which is determined by XPS in the same way should be not more than 0.20 in its atomic ratio [C/Si].

Abstract: This invention relates a high density green bodies, particularly high density silicon nitride spherical green bodies having substantially no radial density gradients.

Abstract: Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

Abstract: The present invention relates to a silicon-containing material which exhibits sufficient hydrophilicity and sufficient electropositivity to bind DNA from a suspension containing DNA and permit elution of the DNA from the material. Generally, the hydrophilic and electropositive characteristics are expressed at the surface of the silicon-containing material. Preferred silicon-containing materials of the present invention include boron silicate, aluminum silicate, phosphosilicate, silica carbonyl, silica sulfonyl and silica phosphonyl. The silicon-containing materials of the present invention are particularly useful in processes for purification of DNA from other cellular components. In these processes, a suspension of cellular components is placed in contact with the silicon-containing material, the silicon-containing material is washed to remove all cellular components other than DNA which are bound to the material, and the bound DNA is eluted from the material.

Abstract: Disclosed is a powder of silicon nitride particles having a specific surface area of from 5 to 20 m.sup.2 /g. When an aqueous solution of a polyvinyl alcohol having a mean degree of polymerization of X and a degree of saponification of Y (mol %) is adsorbed to the powder, the amount of saturated adsorption at 20.degree. C. is not higher than the amount of adsorption to be represented by:Amount of Adsorption (mg/m.sup.2)=0.000112X+0.523Y/100-0.207 (1)Also disclosed is a low-viscosity silicon nitride-containing aqueous slurry containing said powder.

Abstract: The invention relates to material silicon nitride powder used for production of silicon nitride ceramics products. Provided herein is a material powder which can offer a compact having a homogeneous packing structure of the powder with good reproducibility and also to provide a method for producing the same. According to the method, a silicon nitride powder is heat treated in two-stage processing, one stage in an inert gas or reducing atmosphere at 100.degree. C.-1000.degree. C. for 5-600 min., and another stage in an oxidizing atmosphere at 300.degree. C.-1200.degree. C. for 5-600 min. As a result of this treatment, a silicon nitride powder is obtained in which its powder particles are crystalline in their interior and are coated with an amorphous layer having a 1-10 nm surface thickness and composed mainly of Si, N, O, and H, an atomic number ratio of oxygen to nitrogen (O/N) of the surface layer being within a range of 0.1-2.0.

Abstract: Silicon nitride powder is prepared by nitriding metallic silicon powder in a nitriding gas atmosphere at a temperature of 1,000.degree. C.-1,500.degree. C. Midway the nitriding step, the nitrided product is heat treated in an inert non-oxidizing gas atmosphere or vacuum at a temperature higher than the nitriding temperature, but lower than 1,600.degree. C. The product is nitrided again, obtaining high .alpha.-content silicon nitride powder.

Abstract: A ceramic material based on Sialon, in particular on .beta.'-Sialon is obtained by reducing an aluminosilicate precursor by means of a gas phase comprising a mixture of hydrogen and nitrogen doped with a gaseous carbon compound. The gaseous carbon compound is a gas containing carbon in combined form, e.g. an alkane, and its concentration by volume in the gas is less than 3%. The method is particularly suitable for forming Sialon-based coatings on substrates that are solid or fibrous. For composite materials constituted by a fiber preform densified by means of a matrix, the method can be used to form an interphase coating on the fibers of the preform prior to densifying the preform, or the method can be used to form a matrix that is based on Sialon.

Abstract: A silicon-nitride beta-phase material including a non-densified structure of beta silicon nitride crystals having appreciable strength without any significant amount of liquid forming agents is made by comminuting a slurry including a mixture of silicon powder and water to form non-oxidized surfaces on the silicon powder and to allow chemical reaction between the silicon and the water, reducing the water content of the reacted slurry to a degree sufficient to form a resultant dry mass, nitriding the dry mass by exposure to a nitriding gas including at least nitrogen to form a mass of alpha-phase silicon nitride, and converting the resultant silicon nitride mass at a conversion temperature of from about 1450.degree. C. to about 2100.degree. C. to convert the silicon nitride from an alpha-phase material to a non-densified beta phase silicon nitride material.

Abstract: Described herein is a method and apparatus for continuously growing single crystal whiskers of silicon carbide, silicon nitride, boron carbide and boron nitride by the VLS process under controlled reaction conditions. A growth substrate such as a plate of solid graphite is coated with a suitable VLS catalyst and is conveyed through a tubular furnace, into which is separately introduced two feed gases. The first feed gas contains a cationic suboxide precursor such as silicon monoxide or boron monoxide. The second feed gas contains an anionic precursor compound such as methane or ammonia. The precursor compounds react upon exposure to the catalyst by the VLS process to produce crystalline whiskers. The associated apparatus includes a conveyor assembly that continuously circulates multiple substrate growth plates through the furnace and past a harvesting device which brushes the whiskers from the plates and removes them by vacuum collection. Whiskers of uniform size, shape, and purity are produced.

Abstract: A silicon nitride sintered body comprising 3.5% by weight or less of aluminum, 3.5% by weight or less of oxygen and the balance of silicon nitride; and a silicon nitride sintered body comprising 90% by weight or more of silicon nitride, 3.5% by weight or less of aluminum, 3.5% by weight or less of oxygen and from 0.01 to 10% by weight of at least one metallic element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fin, Fe, Co, Ni, Nd, and Ho. These sintered bodies have a density of 3.15 g/cm.sup.3 or more and a thermal conductivity of 40 W/mK or more.

Abstract: Whisker-free particulates of silicon nitride (Si.sub.3 N.sub.4), e.g., spheres, beads, or a variety of other shaped articles exhibiting a regular and controlled particle size, are produced by incorporating a primary reaction mixture of silica and carbon into a porous, carbon-based matrix material, next carbonitriding the composite thus formed, and characteristically eliminating excess carbon from the carbonitrided composite.

Abstract: Carbothermally reduce a metal oxide to its corresponding metal nitride or metal carbide powder in a vertical gravity flow reactor by adding precursor pellets containing the metal oxide, a thermally decomposed binder material and carbon or a source of carbon directly to a heated reaction zone within the reactor. The pellets form a pellet bed, the top of which must be maintained within the heated reaction zone. The binder material is a blend of wheat and corn starches, optionally in conjunction with another binder such as melamine. The binder material thermally decomposes to a carbonaceous residue which functions both as an additional source of carbon and as a binder for the precursor pellets. The reactor may be modified by adding an internal vent line to remove volatile materials from the heated reaction zone before they have an opportunity to condense on internal reactor surfaces.

Abstract: A method of converting non-densified alpha-phase silicon nitride to beta-phase silicon nitride which includes heating a walled container enclosing a non-densified alpha-phase silicon nitride mass to an elevated temperature for a sufficient length of time so that the non-densified alpha-phase silicon nitride mass converts to a beta-phase silicon nitride mass. The walled container is formed of a silicon nitride-containing material which is stable at temperatures of at least 1700.degree. C. and is compatible with silicon nitride. Additionally, the walled container has an opening therein to allow placement of the non-densified alpha-phase silicon nitride mass therein.

Abstract: Si.sub.3 N.sub.4 -based sintered compositions containing MgO and optionally other sintering additives, which after sintering, has a flexural strength level at room temperatures of .gtoreq.800 MPa, measured by the four-point bending method, and a Weibull modulus of >15, is produced by mixing MgO, any additional sintering additives and Si.sub.3 N.sub.4 powder to form a mixture, calcining the mixture in an oxygen-free atmosphere to obtain a pre-synthesis mixture, and adding the pre-synthesis mixture to uncalcined Si.sub.3 N.sub.4 powder which is then sintered.

Abstract: High-packing silicon nitride powder is prepared by reacting metallic silicon powder having a mean particle size of 1 to 10 .mu.m and a purity of at least 99% directly with nitrogen for forming silicon nitride powder, milling the silicon nitride powder in a dry attritor until the tap density exceeds 0.9 g/cm.sup.3 and the content of particles having an aspect ratio of up to 3 exceeds 95% by weight, and further milling the silicon nitride powder in a wet attritor for finely dividing coarse particles having a particle size of at least 2 .mu.m. The silicon nitride powder has a tap density of at least 0.9 g/cm.sup.3 and a mean particle size of 0.4 to 0.6 .mu.m and contains at least 95% by weight of particles having an aspect ratio of up to 3 and up to 5% by weight of coarse particles having a particle size of at least 2 .mu.m. The powder is moldable into a high density compact, from which a sintered part having improved dimensional precision and strength is obtained.

Abstract: A process for nitriding materials containing silicon to form a silicon nitride material predominantly in the alpha phase is disclosed which includes nitriding the silicon-containing material by (a) heating the silicon-containing material in an atmosphere containing at least hydrogen in the temperature range of about 0.degree. C. to about 1420.degree. C. and (b) thereafter, nitriding the silicon-containing material by heating the material in a nitriding atmosphere containing at least nitrogen gas in the temperature range of from about 1000.degree. C. to about 1450.degree. C.

Abstract: The present invention relates to a process for the production of low-needle silicon nitride of high .alpha.-content, wherein an amorphous nitrogen-containing silane compound is mixed with a crystalline or amorphous compound comprising the elements silicon, phosphorus and nitrogen to form a mixture which is heat-treated at temperatures above 1000.degree. C. to form the low-needle silicon nitride. The present invention also relates to the silicon-, nitrogen- and phosphorus-containing compound which is used as the starting material in the process for the production of the low-needle silicon nitride, and the process for the production of the silicon-, nitrogen-and phosphorus-containing compound.

Abstract: Low residual stress, stoichiometric or near stoichiometric, silicon nitride and silicon carbide films with thicknesses of one micron or greater are produced by reacting porous silicon with a nitrogen or carbon containing gas, such as ammonia or methane, at an appropriate temperature and pressure. The gas diffuses into the pores and reacts with the silicon skeletal structure. Because the initial structure is porous and the pore spaces provide strain relief during the addition reaction and subsequent volume expansion, the resultant film has relatively low residual stress. Either porous or solid films can be produced. This process provides a means to chemically stabilize porous silicon layers and their morphologies.

Abstract: Process for direct nitriding of metals of relatively low melting point with the aid of a nitrogen-containing gas, in which a powder of at least one of the metals is mixed with a refractory powder, the mixture is heated under an atmosphere of nitrogen-containing gas at atmospheric pressure until the start of a rapid and exothermic nitriding reaction, and this reaction, which proceeds at a temperature generally higher than that of the melting point of the metals without apparent melting being observed, is allowed to proceed until all of the metals have been consumed, in order to obtain a highly porous solid mass which is easy to grind and is based on metal nitrides or metal oxynitrides.