75 results about "Gas pressure sintering" patented technology

The invention provides high-heat-conductivity silicon nitride ceramic and a preparation method thereof, which are used for solving the technical problem that the existing heat conductivity is low. Thepreparation method comprises the following steps: performing deoxygenation treatment on silicon nitride powder, naturally cooling the silicon nitride powder, and grinding and sieving the obtained silicon nitride powder; mixing the powder and a sintering aid under the action of a mixed medium, and drying and sieving after mixing to obtain powder; performing pressing formation to obtain a silicon nitride ceramic green body; and performing gas pressure sintering to obtain the silicon nitride ceramic material. Compared with the prior art, the high-heat-conductivity silicon nitride ceramic and thepreparation method thereof have the following advantages: the silicon nitride powder is subjected to deoxygenation treatment, the oxygen content of the original powder is low, the degree of reducingthe lattice oxygen content in the sintering process is higher, and phonon scattering is avoided, so that the heat conductivity of the silicon nitride ceramic is improved; and the prepared silicon nitride ceramic has high heat conductivity, high thermal shock resistance and high-temperature resistance, is safe to use and is a silicon nitride ceramic substrate material with excellent mechanical, thermal and electric comprehensive performance.

The invention discloses a microwave vacuum air pressure sintering furnace, which comprises a furnace body, wherein the furnace body is connected with a vacuum pumping device and a pressurizing device, a heat insulation box body used for material sintering and heat loss reduction is arranged in the furnace body, the furnace body is provided with a micro wave generator used for feeding microwaves into an inner cavity of the furnace body, the microwave generator comprises a microwave source used for giving out the microwaves and a wave guide used for feeding the microwaves generated by the microwave source into the furnace body, the number of the microwave generator is one, a waveguide feed opening is formed in a direction towards the center of the heat insulation box body arranged in the furnace body, or the number of the microwave generators is several, the engaging directions of the microwave sources and the waveguide are in mutually vertical arrangement in the two adjacent microwave generators, in addition, the feeding-in direction of the waveguide engaged with the corresponding microwave sources deviates from the center of the heat insulation box, and the deviation distance of the feeding-in direction from the center of the heat insulation box is the odd number times of the wavelength of the microwaves. The uniform and fast sintering of high-density components adopting complicated structures can be realized.

The invention relates to a method for preparing silicon nitride ceramic with high strength, high toughness and high thermal conductivity. The preparation method comprises the following steps: uniformly mixing 94-88% by mass of silicon powder and 6-12% by mass of a sintering aid, grinding, drying, adding a binder, granulating, and carrying out compression molding to obtain a ceramic biscuit, wherein the sintering aid comprises a rare earth oxide and an alkaline earth metal oxide; after the ceramic biscuit is subjected to glue discharging, nitriding at a temperature of 1380-1450 DEG C to obtaina silicon nitride ceramic billet body; and sintering the silicon nitride ceramic billet body at a temperature of 1850-1950 DEG C under air pressure to obtain the silicon nitride ceramic material.

A sintered ceramic material for high speed machining of heat resistant alloys is provided comprising SiAlON grains and 0.2-20 v / o intergranular phase. At least 80 v / o of said SiAlON phase is beta SiAlON having a z-value greater than 1.0, but less than 1.5. The ceramic material has a Vickers Hardness HV1 of more than 1530 and it is produced by gas pressure sintering.

The invention discloses a preparation method of a high-thermal-conductivity silicon nitride substrate, which belongs to the technical field of ceramic material preparation. Silicon nitride powder is adopted as a raw material, rare earth oxide and alkaline earth metal oxide are added to serve as a mixed sintering aid, the adding amount is 6 wt%-10 wt%, a high-molecular compound is added, ball milling and mixing are conducted in an organic solvent, and slurry is formed. Tape casting is carried out to form a green body, presintering of the green body in nitrogen at 1400-1600 DEG C for 1-5 hours is conducted, and heat preservation in an air pressure sintering furnace at 1800-2000 DEG C for 2-10 hours is carried out under the nitrogen pressure of 0.5-3 MPa. The silicon nitride powder used in the invention is high-purity alpha-phase silicon nitride, has very high specific surface area and high sintering activity, and can effectively reduce the densification temperature. The added high-molecular carbon-containing compound is a multi-component compound and is degreased and pre-sintered in an inert atmosphere, so that the thermal conductivity of the product can be improved. The thermal conductivity of the prepared silicon nitride ceramic substrate is not lower than 90 W / m.K, and the bending strength is not lower than 800 MPa.

The invention discloses a method for rapidly preparing a high-performance Si3N4 ceramic ball at low cost. The method comprises the following steps: (1) with Si powder as a raw material, TiO2 powder as a nitridation catalyst and an additive for improving the performance of the ceramic ball, and Al2O3-Re2O3 as an assistant, wherein Re is any one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, mixing and drying Si, TiO2, Al2O3 and Re2O3 at the mass fraction ratio of (56%-99.44%) to (0.22%-17.44%) to (0.17%-13.3%) to (0.17%-13.3%) to obtain Si-TiO2-Al2O3-Re2O3 mixed powder; (2) pelleting the Si-TiO2-Al2O3-Re2O3 powder through a spray drying technology, putting into a mold, and molding the ceramic ball to obtain a ceramic ball blank through a cold isostatic pressing technology; and (3) processing the Si-TiO2-Al2O3-Re2O3 ceramic ball blank by virtue of a two-step heat preservation method and carrying out gas-pressure sintering to prepare the high-performance Si3N4 ceramic ball. The method is low in cost and high in efficiency; and the performance of the Si3N4 ceramic ball can be improved.

The present invention relates to a method for sintering of a silicon nitride based material using gas pressure sintering technique. It has been found that using a sintering atmosphere containing nitrogen and 0.1-10 vol-% carbon monoxide a cutting tool material is obtained with improved properties, particularly increased edge toughness, when machining heat resistant alloys.

The invention discloses aluminum-gallium co-doping zinc oxide nano-powder and a preparation method for a high intensity high conductivity sputtering coating target material thereof. The preparation method comprises the following steps: 1, dissolving high pure metal so as to form transparent aluminum nitrate, zinc nitrate and gallium nitrate solutions; 2, dosing: putting the three kinds of solutions in containers respectively according to the proportion; 3, performing chemical precipitation: mixing the transparent solutions as per proportion and specified procedures through adopting the homogeneous precipitation method so as to prepare aluminum-gallium co-doping zinc oxide nano-powder; 4, cleaning: washing the mixed precipitate via deionized water, and fully stirring till no other irons exist in the mixture; 5, calcining: putting the nano-powder into a high temperature furnace for calcination to obtain the aluminum-gallium co-doping zinc oxide nano-powder; 6, prilling: adding adhesive into the aluminum-gallium co-doping zinc oxide nano-powder and drying to obtain aluminum-gallium co-doping zinc oxide nano-powder to be formed; 7, forming: pressing the aluminum-gallium co-doping zinc oxide nano-powder to be formed into the initial blank; 8, sintering: putting the initial blank into the high temperature furnace for free pressure sintering or gas pressure sintering.

The invention relates to a method for preparing silicon nitride ceramic with high thermal conductivity, which comprises the following steps: uniformly mixing alpha-Si3N4 powder with a sintering aid, and carrying out compression molding to obtain a green body; and carrying out gas pressure sintering on the green body at the temperature of 1780-1950 DEG C in an inert atmosphere, and then cooling thesintered product to room temperature to obtain the silicon nitride ceramic; wherein the sintering aid is composed of silicide and alkaline earth metal oxide, the ratio of the alpha-Si3N4 powder to the sintering aid being (90mol%) : (10mol%) - (99mol%) : (1mol%).

The invention discloses a preparation method of a large-size silicon nitride crucible. According to the method, (1) silicon nitride powder, a dispersing agent, sintering aids, a binding agent and a solvent are well mixed, such that a slurry is obtained; (2) the slurry is added into a mold cavity of a gypsum mold under stirring; the mold is placed in an environment with constant temperature and constant humidity, such that the mold can absorb and discharge water; and a molded cured blank is obtained; (3) a mold core and side molds of the mold are removed, and the molded cured blank is placed in a curing furnace, such that the product is cured and dried, and a green body is obtained; (4) the green body is placed in a gas pressure sintering furnace, and is subjected to segmented sintering; when sintering is finished, the temperature is reduced, the pressure is released and the product is fetched from the furnace, such that the silicon nitride crucible is obtained. According to the invention, silicon dioxide and magnesium silicon nitride are adopted as sintering aids, such that the prepared silicon nitride crucible has low oxygen impurity and metal impurity contents, large bulk density, high high-temperature strength, and large size. The crucible can be widely applied in various non-ferrous metal smelting and silicon crystal ingot casting. The preparation method is simple to operate, and is easy to popularize.

The invention discloses a beta-SiAlON ceramic with a complex shape, and a preparation method thereof. The main crystal phase of the beta-SiAlON ceramic is beta-Si6-xAlxOxN8-x, wherein x is more than 0and not more than 4.2. The preparation method comprises the following steps: S1, EPTA, UDPA, PUA and n-octanol are mixed, and undergo ultrasonic treatment, ceramic powder is added, and the obtained mixture undergoes ball-milling; S2, the obtained ball-milled ceramic slurry is taken out and is placed in a 3D printer platform; S3, the 3D printer platform is rotated to make the ceramic slurry go through a scraper and form a flat slurry film, a needed complex shape ceramic model undergoes computer slicing treatment, and is output, and the flat slurry film is photocured to form a ceramic body; andS4, the ceramic body undergoes vacuum degreasing and air degreasing, and finally undergoes gas pressure sintering to obtain the beta-SiAlON ceramic with the complex shape. The preparation method hasthe advantages of simplicity in preparation, controllable process, convenience in adjustment of the material system, mass production, and suitableness for preparing ceramic matrix composite materialssuch as nitride ceramics.

The invention provides a silicon nitride ceramic ball and a preparation method thereof, and belongs to the technical field of ceramic materials. According to the invention, a vacuum injection-coagulation forming method is adopted, so that the forming of large-size and oversized silicon nitride ceramic balls with high sphericity degree and uniform density can be realized. Microwave drying is adopted, the drying speed is high, and deformation of a green body is small. According to the invention, the cold isostatic pressing treatment is carried out on the degummed ceramic balls, so that the compactness of the sintered ceramic balls is improved. A two-step air pressure sintering process is adopted, so that internal air holes of the ceramic ball can be removed, and the density can be further improved. According to the invention, the surfaces and the core parts of the large-size and oversized silicon nitride ceramic balls prepared by adopting the method of combining injection coagulation forming with cold isostatic pressing forming and two-step air pressure sintering have no obvious difference in properties such as relative density, Vickers hardness and fracture toughness. Homogenization of density and mechanical properties of large-size and oversized silicon nitride ceramic balls can be realized.

The invention discloses a TiC-Ni3Al composite material and a preparation method thereof, belongs to a metal-ceramic composite material and a preparation method thereof, and aims at solving the problem that the TiC-Ni3Al composite material with high compactness and high strength cannot be obtained by an existing preparation method. The TiC-Ni3Al composite material disclosed by the invention comprises a ceramic-phase TiC and binding-phase Ni3Al intermetallic compound, and is prepared by die forming, degreasing and gas-pressure sintering of TiC-Ni3Al composite powder; the TiC-Ni3Al composite powder is synthesized by high-energy ball milling induced self-propagating combustion reaction of Ti powder, Ni powder, Al powder, graphite powder and B powder as raw materials in the presence of argon; the preparation method of the TiC-Ni3Al composite material sequentially comprises the following steps: high-energy ball milling, die forming, degreasing, and gas-pressure sintering. The TiC-Ni3Al composite material is simple in process, high in efficiency and low in cost; the hardness of the prepared TiC-Ni3Al composite material is 86.0-91.5HRA; the bending strength is 1320-2165MPa; the breaking tenacity KIC is 8.66MPa.m1 / 2 to 17.48MPa.m1 / 2; and the TiC-Ni3Al composite material is suitable for being used as a cutting tool, a heat extrusion die and a high-temperature part of an aircraft engine.

The invention relates to a batch sintering method of a high-performance silicon nitride ceramic substrate. The method comprises the following steps: (1) stacking silicon nitride ceramic substrate biscuits in a boron nitride crucible, and laying a layer of boron nitride powder between adjacent silicon nitride ceramic substrate biscuits; (2) performing vacuum pumping step by step, and then performing debonding at 500-900 DEG C in a nitrogen atmosphere or a reducing atmosphere; and (3) carrying out air pressure sintering at the temperature of 1800-2000 DEG C in a nitrogen atmosphere to realize batch preparation of the high-performance silicon nitride ceramic substrate.

The invention belongs to the field of non-oxide-based ceramics and discloses a silicon nitride-based continuous function gradient ceramic ball as well as a preparation method and application thereof.The method comprises the following steps of mixing Si3N4, Al2O3 and Re2O3 respectively in mass fraction, and drying to obtain mixed powder; enabling the mixed powder to be subjected to isostatic coolpressing to obtain a ceramic ball green body, carrying out low-temperature pressureless sintering to obtain a ceramic ball blank; enabling the blank to be dipped in a TiO2 alcohol solution by using avacuum leak through method so as to enable a surface layer to contain TiO2, and then carrying out air pressure sintering to obtain a Si3N4-based continuous function gradient ceramic ball. According tothe ceramic ball prepared by utilizing the method, the relative density is greater than 96%, the surface layer hardness is 16-22GPa, the breaking tenacity is 4-7MPa / m<1 / 2>, the TiN particle sizes are100-500 nm, the dipping depth is 1-6mm, the core hardness is 15-20GPa, and the breaking tenacity is 5-8MPa / m<1 / 2>.

A method for manufacturing composite materials from a parent substance containing silicon nitride and metal silicide, having fixed electrical properties. The molded articles are made, virtually with their final contours, prior to a sintering operation. The parent substance containing Si3N4 and a metal silicide is subjected to a gas pressure sintering in a nitrogenous atmosphere. The metal silicide is of the form Me5Si3, where Me is a metal. As a function of a sintering temperature, a lower limit of partial nitrogen pressures is selected so that Si3N4 is stable at the lower limit and an upper limit of the partial nitrogen pressures is selected so that Me5Si3 is stable at the upper limit. The resulting composite material is a silicon-containing composite material made of Si3N4 and the metal silicide. The metal silicide is selected from the group of Nb5Si3, V5Si3, Ta5Si3 and W5Si3.

The invention relates to ultrafine high-purity AlON powder and a preparation method thereof, and belongs to the field of preparation of transparent ceramic powder. The method is realized by the following steps: firstly preparing mixed powder of Al2O3 and carbon powder; and placing the mixed powder into a BN crucible, and preparing the ultrafine high-purity AlON powder by adopting gas pressure sintering. The method provided by the invention adopts the traditional aluminum oxide and carbon powder as raw materials, and prepares the AlON powder under relatively-low-temperature conditions; the preparation process is simple and controllable, and the operability is strong; and the AlON powder prepared by the method has higher purity and a smaller particle size.

The invention discloses a preparation method of eutectic, reinforced and toughened silicon nitride ceramic, belonging to the technical field of ceramic preparation. According to the method, an alpha phase-beta phase eutectic structure is formed in a silicon nitride material, so the silicon nitride reinforced and toughened ceramic is obtained; and the ceramic has relative density of larger than 99%, fracture toughness of larger than 10 MPa.m<1 / 2>, Vickers hardness of larger than 18 Gpa and bending strength of larger than 600 MPa. The method comprises the following steps: 1) mixing a silicon nitride raw material, a sintering aid and the like in proportion, and performing spark plasma sintering (SPS) on the uniformly-mixed powder to obtain a primary sintered body with relative density of greater than 99% and an alpha phase content of greater than 90%; and then carrying out air-pressure sintering to generate the alpha / beta eutectic structure. The prepared silicon nitride ceramic has the same characteristics (high strength, good compactness, high temperature resistance and wear resistance) as traditional silicon nitride ceramic, is obviously improved in fracture toughness and plasticity, and can be widely applied to the field of special materials.

Silicon nitride materials with high strength, fracture toughness values, and Weibull moduli simultaneously, due to unique large grain reinforcing microstructures and well engineered grain boundary compositions. The invention demonstrates that, surprisingly and contrary to prior art, a silicon nitride material can be made which simultaneously has high strength above about 850-900 MPa, a Weibull above about 15 and high fracture toughness (above about 8 and 9 MPa·m1 / 2), and has reinforcing grains longer than 5 μm, typically longer than 10 μm in the microstructure without compromising its properties and reliability. The product of this invention can be processed using a variety of densification methods, including gas-pressure sintering, hot pressing, hot isostatic pressing, but is not limited to these, and does not require multiple heat treatments for all of these features to be achieved.

The invention relates to a preparation method of a high-thermal-conductivity net-size silicon nitride ceramic substrate, which comprises the following steps of (1) mixing at least one of silicon nitride powder and silicon powder as original powder, a sintering aid, a dispersing agent, a defoaming agent, a binder and a plasticizer in a protective atmosphere, and performing vacuum degassing to obtain mixed slurry, (2) carrying out tape casting and drying in a nitrogen atmosphere to obtain a first biscuit, (3) carrying out shaping pretreatment on the obtained first biscuit to obtain a second biscuit, (4) debonding the obtained second biscuit in a nitrogen atmosphere with micro-positive pressure at 500-900 DEG C to obtain a third biscuit, and (5) placing the obtained third biscuit in a nitrogen atmosphere, and carrying out air pressure sintering at 1800-2000 DEG C to obtain the high-thermal-conductivity net-size silicon nitride ceramic substrate.

The invention discloses a preparation method of Al2O3-Si3N4 gradient material with a beta-Sialon transition layer. The preparation method includes: using beta-Sialon powder, Al2O3 powder, Si3N4 powder and Y2O3 powder as raw materials to prepare each single layer of mixed powder, grinding each single layer of mixed powder in an agate mortar, stacking the power layer by layer in a mould using powder laminating to form 10-20 layers of original gradient stacks, forming by pressing at a pressure of 15-25MPa, and preserving heat in a pressure sintering furnace for 3-5 hours at a nitrogen pressure of 4-6MPa and a temperature of 1600-1800 DEG C to obtain the Al2O3-Si3N4 gradient material with the beta-Sialon transition layer, wherein purity of the Z=3 beta-Sialon powder is above 97%, the purity of the Al2O3 powder, the Si3N4 powder and the Y2O3 powder is above chemical purity, and the granularity of the Al2O3 powder, the Si3N4 powder and the Y2O3 powder is 800nm-1000nm. The gradient material prepared by the method is even in gradient distribution, and no stress concentration occurs among layers. In addition, the preparation method is simple and practicable in process, and industrial production is facilitated.

The invention belongs to the field of ceramic preparation, and particularly relates to a method for preparing high-strength and high-thermal-conductivity silicon nitride ceramic through two-step sintering. The method comprises the following steps: mixing silicon nitride powder and a sintering aid with an organic solvent according to a certain ratio, granulating, pressing, degreasing, pretreating for 1-5 hours under the conditions of low temperature, normal pressure and nitrogen introduction, and sintering at a high temperature under the nitrogen pressure of 0.9-10 MPa. In the first-step pretreatment, the content of the magnesium oxide sintering aid is adjusted according to the oxygen content of the silicon nitride powder, the oxygen content of a green body is reduced before sintering by utilizing the low-temperature reaction characteristic of magnesium oxide and silicon dioxide on the surface of the silicon nitride powder, and then the second-step air pressure sintering is performed. Compared with the sintered body which is not pretreated, the silicon nitride ceramic subjected to two-step sintering has higher density, the total oxygen content and the second phase content are obviously reduced, and the silicon nitride ceramic of which the thermal conductivity is greater than 90W / m.K and the bending strength is greater than 750MPa can be prepared.

The invention discloses a gas-pressure-sintering ultra-fine grain WC / Co / diamond-C2Cr3 hard alloy. The hard alloy is prepared from the following components by granularity and weight percentage: 0.8-micron (90.70, 89.40 and 87.44) percent of WC powder, 0.8-micron (7.90, 7.78 and 9.72) percent of Co powder, 0.25-micron (1.23, 2.55 and 2.58) percent of diamond powder and (0.17, 0.27 and 0.26) percent of chromium carbide. The preparation method comprises the following steps: (1) mixing WC powder and Co powder at a rotating speed of 100 revolutions / minute for 16 hours by using anhydrous ethanol as a dispersive medium, respectively adding the diamond powder and the chromium carbide to mix for 8 hours, and taking out and baking; and (2) putting the dried raw materials in an air pressure sintering furnace, heating to 900 DEG C at a speed of 30-50 DEG C / min, and sintering at a pressure of 9Mpa. The method is low in sintering temperature and low in energy consumption and can be used for sintering complicated samples, and the hard alloy has excellent mechanical performance and is suitable for volume production.

The invention belongs to the technical field of manufacturing of turbine rotor of a pressurizer, in particular to a material for preparing a turbine rotor of the pressurizer and a method for preparing the turbine rotor by the material. The material for preparing the turbine rotor of the pressurizer comprises the components in parts by weight as follows: 85-90 parts of silicon nitride powder, 1-8 parts of boron nitride nanotube powder, 2-4 parts of aluminite powder, 2-4 parts of silicon powder and 3-5 parts of zirconium oxide powder. The method for preparing the turbine rotor by the material comprises the steps of: (1) preparing a raw material; (2) preparing a paste material; (3) injection moulding; (4) setting and drying; and (5) gas pressure sintering of mould constraint. The turbine rotor of the pressurizer prepared by the material is light in weight, good in toughness, high in strength, low in specific gravity and good in proportionality, and small in lag proportionality, small in deformation, small in accumulated carbon and long in service life under supernormal work conditions such as high temperature, high pressure and high speed. Meanwhile, the method for preparing the turbine rotor by the material is simple in steps, convenient to operate and is beneficial for industrialized production in a large scale.

The invention discloses a boron nitride-based composite ceramic die material and a preparation method thereof. The material is prepared from, by mass, 50.0-58.0% of boron nitride, 21.3-24% of tungsten carbide, 11.0-13.8% of zirconia, 1.0-1.8% of yttrium oxide, 3.2-3.8% of samaria, 1.8-2.2% of bismuth oxide, 1.6-2.0% of copper oxide and 2.1-2.4% of molybdena, wherein boron nitride is formed by mixing boron nitride nano-powder with the particle size of 5-15 nm and boron nitride micro-powder with the particle size of 15-25 [mu]m according to a mass ratio of 1:0.12-0.15. The preparation method comprises the following steps: weighing all raw material powders in proportion, carrying out ball milling mixing, drying the above obtained mixture, grinding and sieving the dried mixture, carrying out granulation molding, and carrying out gas pressure sintering to obtain the material. The material has the advantages of excellent fracture toughness, excellent hardness, excellent bending strength, excellent antifriction and anti-wear performances, strong ageing resistance and strong defect resistance, and can be widely applied to die materials.

The invention discloses a method for preparing a bulk ceramic material from iron-silicon nitride powder. The method comprises the following steps: firstly, placing a raw material in a ball mill and carrying out ball milling by virtue of a wet balling method, uniformly mixing and drying the ball-milled and uniformly mixed material to obtain mixed power; secondly, placing the mixed power in a hydraulic press and carrying out pre-press molding and placing the mixed power in a cold isostatic press for carrying out cold isostatic pressing to obtain a green body; and thirdly, placing the green body in a gas pressure sintering furnace for carrying out gas pressure sintering and cooling in the furnace to obtain the bulk ceramic material. According to the method, by virtue of the technological processes of uniformly mixing the raw material by virtue of the wet balling method to obtain the mixed powder and carrying out pre-press molding and cold isostatic pressing on the mixed powder to obtain the green body in combination with the gas pressure sintering, the bulk ceramic material with low porosity and large bulk density is prepared and the bulk ceramic material has the advantages of excellent high-temperature resistance and mechanical properties and can be used as a structural part ceramic to prepare kiln furniture or other refractory materials for high-temperature kilns.

The invention discloses a silicon nitride crucible which is prepared from one or more of the following raw materials of powder, a barium-containing compound, SiO2, aluminum oxide, mullite, a dispersant, high-purity deionized water, an organic matter monomer, a cross-linking agent, an initiator, a catalyst, a polymerization inhibitor and an adhesive. The invention discloses a method of preparing the silicon nitride crucible with sintering after reaction. The method comprises the following steps of 1) preparing an Si-based green body with a gel casting method or a slip casting method; 2) performing nitridation at 1000-1500 DEG C; 3) performing high-temperature gas pressure sintering; and 4) performing post-treatment. The invention also discloses a method for preparing the silicon nitride crucible with high-temperature gas pressure sintering. The method comprises the following steps of 1) preparing an Si3N4-based green body with the gel casting method or the slip casting method; and 2) performing high-temperature gas pressure sintering. The prepared silicon nitride crucible has the advantages of high-temperature resistance, low oxygen content, long service life and capability of repeated use for a long time and has a wide market prospect.

An aluminum nitride (AlN), alumina, magnesia, beryllia or other dielectric matrix with a ZrC dispersed phase is provided. Mixed powders of aluminum nitride or other dielectric phases and ZrC, with or without Y2O3, CaO, Li2O, La2O3, and other rare earth metal oxides or mixtures thereof are formed by dry pressing (or isostatic pressing, injection molding or other similar methods known to those familiar with the art). Consolidation at high temperatures (and or pressures) to a virtually dense material with densities of over 95%, preferably higher than 97% of theoretical density can be attained by hot pressing, hip-ing, gas-pressure sintering or pressureless sintering (including microwave sintering). A controlled inert atmosphere is required to prevent the oxidation or other reaction of the carbide phase. Ar or similar atmosphere is preferred to avoid reactions with ZrC. Materials produced according to the invention can have real dielectric constants in at least the 8-40 range, with the loss tangents ranging from 0.01-0.3 at 2 GHz. The materials described have lossy properties over a wide frequency range (0.5 to over 20 GHz), and at temperatures from 2 K to above room temperature.

The invention relates to a high-temperature air pressure sintering furnace. The high-temperature air pressure sintering furnace comprises a furnace chamber, a furnace body, a furnace cover, a heating body, a furnace cover hydraulic lifting and horizontal moving system and a furnace floor lifting and horizontal moving system. The furnace chamber is of a double-layer structure. The sidewalls of the furnace body are provided with heating body mounting holes. The heating body is a U-shaped heating body, and the two ends of the heating body are cold ends. The outer sides, corresponding to the positions where the cold ends of the heating body stretch out, of the furnace body are further provided with cold end wiring chambers. The cold ends of the heating body are arranged in the cold end wiring chambers. The portions between the cold ends of the heating body and the corresponding heating body mounting holes are sealed through high-pressure sealing elements. Each cold end wiring chamber is of a double-layer structure. Inner cavities of the double-layer structures are filled with circulating cooling water. By the adoption of the high-temperature air pressure sintering furnace, the phenomena that fusion of cable clamps, arcing, short circuit, oxidation and breakage of the cold ends of the heating body happen at the wiring positions of the cold ends of the heating body due to a too high temperature of the cold ends of the heating body in a high-temperature high-air-pressure environment can be avoided; moreover, the high-temperature air pressure sintering furnace has the advantages that the furnace chamber is light in weight, the heat preservation effect is good, operation is simple, and maintenance is convenient.

The invention relates to a preparation process of an IGBT ceramic substrate, which comprises the steps of preparing a large IGBT ceramic green body by adopting a dry pressing combined isostatic pressing, grouting or gel casting forming process; preparing a bulk ceramic sintered body through sintering supplemented by air pressure sintering or hot pressing sintering, cutting the bulk ceramic sintered body into rod-like sizes required by IGBTs, and placing the rod-like sizes on a diamond wire cutting machine for cutting so as to be able to prepare IGBT ceramic substrates in batches. The ceramic prepared according to the method is high in density, and the density can reach 95% or above. Meanwhile, the preparation efficiency of the IGBT ceramic substrate can be greatly improved, the thickness of the substrate can be adjusted according to different requirements, the operation is easier and more feasible compared with a tape casting method, the thickness uniformity and the surface evenness ofthe ceramic substrate can be accurately controlled at the same time, and the quality of the substrate is improved.