189 results about "Pressureless sintering" patented technology

The invention relates to a hard alloy micro-texture tool based on discharge plasma pressureless sintering and a preparation method. Comprising the following steps: preparing a micro-texture male die pressing head; wC-Co mixed powder is obtained; the pressure head in the step (1) is adopted to apply 150-180 MPa pressure to the WC-Co mixed powder, the pressure is maintained for 60 min, and a biscuit is obtained after demolding; putting the biscuit into a graphite mold, assembling the mold, carrying out vacuum pressureless sintering on the biscuit, heating to 1300-1400 DEG C at the heating rate of 90-110 DEG C / min, carrying out heat preservation for 10 + / -2 minutes, and then cooling to room temperature along with a furnace to obtain a hard alloy block with a micro-texture on the surface; and the micro-texture surface of the hard alloy block is only polished to be bright. According to the method, thermal damage and fusion edge collapse are thoroughly avoided, and high-precision, namely high geometric fidelity, high efficiency, namely short sintering period and low-cost preparation of the microstructure is realized.

The invention provides a method for preparing a zirconium boride ceramic material through pressureless sintering, and belongs to the technical field of zirconium boride ceramics. The method comprises the steps of preparing zirconium boride composite powder, modifying silicon carbide nanowires and mixing and sintering. The method for modifying the silicon carbide nanowire comprises the steps of acid treatment and modification, the modification step comprises the following steps: adding aluminum isopropoxide into absolute ethyl alcohol, adding a nitric acid solution, stirring for 1.5-2.0 hours at the temperature of 60-63 DEG C, adding the acid-treated silicon carbide nanowire, carrying out ultrasonic dispersion and water bath evaporation, then drying, putting into a muffle furnace, and carrying out heat preservation for 2.0-2.2 hours at the temperature of 490-500 DEG C to obtain a modified silicon carbide nanowire; the ceramic material prepared by adopting the method disclosed by the invention is high in density, good in mechanical property and excellent in high-temperature oxidation resistance and stability in a complex environment.

The invention relates to a method for preparing MgAlON ceramic with high infrared transmittance by utilizing coarse powder pressureless sintering, and belongs to the field of ceramic preparation. A method for preparing MgAlON ceramic with high infrared transmittance by utilizing pressureless sintering of coarse powder comprises the steps that pure-phase MgAlON powder and a sintering aid are subjected to ball-milling mixing, drying and granulation to obtain mixed powder of MgAlON and the sintering aid, the mixed powder is formed and subjected to pressureless sintering in the nitrogen atmosphere to obtain the MgAlON ceramic, the atomic ratio of Mg to Al to O to N in the pure-phase MgAlON powder is 1: (10-20): (15-25): (2-4), and the atomic ratio of Mg to Al to O to N in the sintering aid is 1: (10-20): (15-25): (2-4). The D50 of the mixed powder of the MgAlON and the sintering aid is 1.1-2.0 [mu] m, and the particle size distribution range is 0.2-10 [mu] m. According to the method, the difficulty of a ball-milling process is small, the risk that impurities are introduced due to particle refinement can be effectively reduced, sintering equipment is easy to obtain, the heat preservation time in the pressureless sintering process is short, the obtained ceramic is high in infrared transmittance, good in energy-saving effect, high in efficiency, low in cost and suitable for preparation of large-size and complex-shape sample pieces, and industrialization is easy to achieve.

The invention relates to the technical field of preparation of silicon carbide ceramic special-shaped beams, in particular to a pressureless sintered silicon carbide ceramic special-shaped beam and a preparation method thereof.The pressureless sintered silicon carbide ceramic special-shaped beam comprises the following components and structures: material composition: a base material is silicon carbide powder, the particle size is in bimodal distribution, a main phase is 3-5 microns, and a nanophase is 0.5-1 micron; a composite sintering aid; through innovative design of material composition and structure, multi-scale synergistic reinforcement and surface gradient protection are realized, bimodal distributed silicon carbide powder is adopted as a matrix, and through the synergistic effect of a micron-sized particle skeleton and nano-particle filling pores, internal cracks caused by uneven shrinkage of a special-shaped section are remarkably reduced, so that the surface gradient protection performance is improved. And meanwhile, the composite sintering aid can inhibit abnormal growth of crystal grains, synergistically reduce the sintering temperature and reduce the deformation risk of the multi-cavity structure, the crack propagation resistance of the corner angle is greatly improved through the gradient reinforcement phase, and the problem that a hardened layer at the special-shaped corner angle is not uniform is solved through deep siliconizing reinforcement.

The invention discloses Si-based MAX phase powder and a preparation method thereof, and belongs to the technical field of ceramic material preparation. The preparation method of the Si-based MAX phase powder comprises the following steps: mixing a transition metal source, polysiloxane, a solvent, a curing agent and a platinum catalyst to obtain a mixed solution; the curing agent is vinyl modified siloxane; heating and curing the mixed solution to obtain a solid precursor; and crushing the solid precursor into powder, and then carrying out pressureless sintering in a protective atmosphere, thereby obtaining the product. According to the method, subsequent ball milling and other procedures are omitted, and impurity introduction to the product is avoided. According to the invention, the operation difficulty is greatly reduced, the production efficiency is improved, the energy consumption is reduced, and large-scale and low-cost production is realized.

The invention provides a preparation method of a carbon fiber reinforced boron carbide composite material, and belongs to the technical field of boron carbide composites.The preparation method comprises the steps that S1, 88-92 parts by weight of boron carbide powder and 5-7 parts by weight of modified graphene nanosheets are mixed, subjected to wet ball milling treatment, filtered and dried, and primary powder is obtained; the modified graphene nanosheet is prepared by modifying a graphene nanosheet with a silane coupling agent; s2, uniformly mixing the primary powder obtained in the step S1 with 8-10 parts of porous carbon fibers to obtain final powder, and granulating and sieving the final powder by using a binder to obtain mixed granules; and S3, pouring the mixed granules obtained in the S2 into a mold, maintaining the pressure for 5-8 minutes under 280-300 MPa, releasing the pressure, stripping from the mold, keeping the temperature at 2100-2300 DEG C for 1.5-2 hours, carrying out vacuum pressureless sintering, and cooling to room temperature along with a furnace to obtain the carbon fiber reinforced boron carbide composite material. The toughness of the prepared composite material can be enhanced, and meanwhile, the thermal conductivity of the composite material is improved.

The application discloses a ZTA ceramic particle preform, preparation and application of realizing metallurgical interface combination between ZTA and high manganese steel matrix. The application adopts a ball milling process to prepare a slurry from high manganese steel powder, Zr-Fe powder, ZTA micro powder and ethanol, soaks ZTA particles in the slurry, takes out and dries and sinter, obtains ZTA particles with a single layer of coating, soaks the ZTA particles in high manganese steel powder slurry again, obtains ZTA particles with two layers of coating, obtains ZTA ceramic preform through pressureless sintering, realizes solidification of the double coating layers, and the ZTA ceramic porous preform can effectively promote high manganese steel melt infiltration and prevent the preform from collapsing under thermal shock during casting. Through the bridge effect of the FeZr-ZTA-high manganese steel powder double coating layers, a metallurgical combination interface is formed between the ZTA and the high manganese steel matrix, so that the prepared ZTA ceramic particle reinforced high manganese steel composite material has excellent three-body wear resistance.

The invention relates to a method for improving low-temperature aging resistance of zirconia ceramic by utilizing defect engineering, which comprises the following steps: S1, preparation of zirconia slurry: taking zirconia powder with 3 mol% of yttrium oxide as a stabilizer as a raw material, and weighing the zirconia powder and deionized water according to a mass ratio of (1.5-2.5): 1; citric acid or acetic acid or nitric acid is dropwise added into deionized water, and the pH is adjusted to be 2.5-4; adding zirconium oxide powder into the adjusted aqueous solution step by step, and stirring to obtain zirconium oxide slurry; s2, introduction of powder intragranular defects: pouring the zirconium oxide slurry obtained in the step S1 into a sand mill, carrying out sanding treatment for 8-12 hours by adopting zirconium oxide microbeads as a medium, and introducing blade dislocation and lattice distortion crystal defects into zirconium oxide powder crystals; s3, after the powder containing the intragranular defects obtained in the step S2 is formed, pressureless sintering is conducted at the temperature of 1350-1425 DEG C in the air atmosphere, and the compact 3Y-TZP zirconia ceramic containing the intragranular defects is obtained. The phase transformation of the zirconia ceramic from a tetragonal phase to a monoclinic phase can be effectively inhibited, and the low-temperature aging resistance of the zirconia ceramic is improved.

The invention provides a MoAlB-SiC composite material as well as a preparation method and application thereof, and belongs to the technical field of ceramic matrix composite materials. The preparation method of the composite material comprises the following steps: mixing Mo powder, Al powder and B powder according to a molar ratio of 1: (1-2): 1, carrying out wet ball milling, drying, and carrying out vacuum pressureless sintering to obtain MoAlB powder; and S2, adding SiC particles with the mass percentage of 5%-20% into the MoAlB powder obtained in the step S1, carrying out wet ball milling, drying, and carrying out electric field assisted direct current heating rapid hot pressed sintering to obtain the MoAlB-SiC composite material. The MoAlB-SiC composite material obtained through the preparation method is high in density, secondary phases are reduced, the mechanical performance and the high-temperature oxidation resistance of the MoAlB material are enhanced by adding SiC, and the preparation method has great significance for preparing the high-strength MoAlB-based ceramic composite material.

Provided are an oxide sintered body mainly containing a molybdenum oxide, a sputtering target containing the sintered body, and an oxide thin film formed by the sintered body. In the present invention, by adding a specific (pseudo) metal oxide in a prescribed range to a molybdenum oxide and a niobium oxide which are difficult to sinter, the sinterability can be improved and high-density characteristics can be ensured even if pressureless sintering is performed.

The present invention discloses an in-situ pressureless sintering method for preparing a TiB2 / MgAl2O4 composite ceramic material, relating to the technical field of special ceramics. The method comprises the following steps: S1, ball-milling TiO2, B4C, MgO, Al2O3, and LiF, drying, and sieving to obtain a powder; S2, adding a binder to the powder for granulation; S3, press-molding the granulated powder; and S4, calcining the molded material at 1600-1700°C for 50-90 minutes, followed by holding at 500-600°C for 1-2 hours. The TiB2 / MgAl2O4 composite ceramic material is prepared using a one-step in-situ method. The composite ceramic material has a uniform microstructure, a strong reaction driving force, a simplified process, and a compact flow. It also exhibits excellent dielectric properties and can be used to manufacture absorbing materials, reducing electromagnetic wave reflection and improving stealth performance. Furthermore, the one-step in-situ reaction process produces abundant heterogeneous interfaces on a microscale, effectively improving the material's polarization loss performance.

The application relates to a dual-phase mosaic middle-entropy oxide anti-ablation ceramic and a preparation method thereof, and belongs to the technical field of ceramic materials. The method comprises the following steps: firstly, high-temperature heat treatment is adopted to prepare dual-phase middle-entropy oxide ceramic powders ((Hf, Zr, Ti)O2 and (Hf, Zr)TiO4) with different proportions; and then, a composite-phase mosaic structure ceramic is prepared by means of pressureless sintering. The method not only provides a theoretical basis for optimal anti-cyclic ablation performance component design of Hf-Zr-Ti-based multicomponent ultrahigh-temperature ceramic, but also lays a material foundation for the application of the prepared ceramic powder in substrate modification and coating preparation in the future. In addition, the pressureless sintering preparation of the dual-phase mosaic middle-entropy oxide anti-ablation ceramic block can realize low-cost and large-scale production. The process can not only realize low-cost and large-scale production, but also obtain uniformly distributed dual-phase middle-entropy oxides, fully exert the mutual synergistic effect among multicomponent oxides, and simultaneously improve the resistance to cyclic thermal shock and the anti-ablation performance of the ceramic block.

The application provides a low-temperature sintering silicon nitride ceramic powder, a silicon nitride ceramic and a preparation method thereof, and uses beta silicon nitride powder as raw material and low-melting-point glass powder as a sintering aid. The beta silicon nitride powder with a content of 75-90wt% and a particle size range of 0.5-1um is selected, and the low-melting-point glass powder with a content of 10-25wt% is added. The mixed powder is ball milled, dried and pressed into a sheet, and then cold isostatic pressing is carried out, and pressureless sintering is carried out at 1400-1600 DEG C under a nitrogen atmosphere to obtain a silicon nitride ceramic material. The beta silicon nitride powder provided by the application can directly sinter the beta silicon nitride ceramic at low temperature. The preparation method of the silicon nitride ceramic provided by the application reduces the sintering temperature of the silicon nitride, improves the preparation efficiency of the silicon nitride ceramic, and is mainly applied to refractory fire-resistant materials.

DEPCT6720 / 08 / 2567 Zirconia powder containing 2% by mol or more and 8% by mol or Less than that of the stabilizing element and 50 ppm or less of titanium (Ti) and containing Activation energies of 225 kJ / mol or more, and 300 kJ / mol or less, are provided. There is at least one zirconia powder that can produce sintered objects with high transparency. By using pressureless sintering, a method suitable for industrial production, the following can be employed: Zirconia powder production: methods for manufacturing calcined objects using zirconia powder and techniques. For the production of sintered objects using zirconia powder, the powder is desirablely manufactured by: The method involves the following steps: adjusting the pH of the raw material solution containing the source. Zirconium and its stabilized sources are at 3.5% or higher and 5.5% or lower. Heating the raw material solution to produce zirconia sol solution; mixing the zirconia solution. And alkaline solutions for co-sludge production and heat treatment of the co-sludge;

The invention relates to the technical field of modification of silicon carbide ceramic materials, in particular to a method for preparing a carbon nanotube toughened silicon carbide ceramic composite material. The method comprises the steps of dispersion of the carbon nanotubes, mixing and dispersion of the carbon nanotubes, silicon carbide raw powder and a sintering aid, preparation of mixed powder, compression molding, pyrolysis and glue removal, pressureless sintering and the like. According to the invention, the carbon nanotube with short length-diameter ratio (30-54) and high defect degree (ID / IG = 0.98) is selected as a modified material; the structure with short length-diameter ratio can effectively improve the dispersibility of the carbon nanotube in a matrix; due to the characteristic of high defect degree, interface bonding with a silicon carbide matrix is promoted through reactive sintering in the ultrahigh-temperature sintering process, so that the comprehensive performance of the composite material is remarkably improved. The bending strength and the fracture toughness of the prepared carbon nanotube toughened silicon carbide ceramic material can reach 529.05 Mpa and 4.74 MPa.m < 1 / 2 > respectively, and the method is simple in process, low in production cost, high in production efficiency and suitable for industrial preparation of the high-performance silicon carbide ceramic material.

The invention discloses a preparation process optimization method and device for a diamond reinforced metal matrix composite material, and relates to the technical field of composite material preparation. The method comprises the following steps: carrying out double-coating surface metallization modification treatment on diamond particles to form a composite coating; mixing the to-be-mixed powder and the to-be-mixed matrix powder according to a preset proportion to obtain composite matrix powder, and uniformly mixing the composite coating and the composite matrix powder to form a mixed raw material; real-time recording of pressureless sintering is carried out, a preparation record log is generated, feedback optimization is carried out on sintering process parameters, and sintering optimization process parameters are generated; and alloying treatment parameters are reconfigured to adjust sintering process parameters of subsequent batches of mixed raw materials, and preparation of the diamond reinforced metal matrix composite is achieved. The technical problem of unstable material performance caused by insufficient bonding strength of diamond and a metal matrix in the prior art is solved, and the technical effect of improving the performance of the diamond reinforced metal matrix composite material is achieved.

The utility model discloses a pressureless sintering die, which belongs to the technical field of pressureless sintering, and adopts the technical scheme that the pressureless sintering die comprises a body, two sides of the body are respectively provided with a rotating piece, each rotating piece comprises a rotating disc, a cross rod is arranged on each rotating disc, a U-shaped groove is formed in the surface of the body close to the rotating piece, and the U-shaped grooves are communicated with the rotating pieces. A strip-shaped hole is formed in the U-shaped groove, and the body is connected with a handle through the strip-shaped hole. According to the scheme, the occupied area of the mold in a sintering furnace can be reduced, the number of sintered products is increased, materials in the mold can be evenly heated, and the sintering efficiency is improved.

The invention provides a chromium diboride target material and a preparation method thereof, and the preparation method comprises the following steps: performing wet ball milling on chromium diboride powder by using a binder to obtain ball-milled powder; performing cold isostatic pressing on the ball-milled powder to obtain a target material green body; and the target material green body is subjected to vacuum sintering, and the chromium diboride target material is obtained. According to the preparation method provided by the invention, the binder is added into the chromium diboride powder for wet ball milling, the strength among particles is enhanced, then a green body with relatively high density is prepared through cold isostatic pressing, then vacuum pressureless sintering is adopted, further densification of the target material is completed, and finally the chromium diboride target material with high density is prepared. And the density especially reaches 98.0% or above.

The invention belongs to the field of boron carbide production equipment, and particularly relates to a pressureless sintered boron carbide powder conveying device with visual inspection, which comprises a base, a vacuum suction machine main body is arranged on one side of the upper end surface of the base, a hose is communicated with a feeding hole of the vacuum suction machine main body, one end of the hose is communicated and fixedly connected with a suction pipe, and the other end of the hose is communicated with a feeding hole of the vacuum suction machine main body. A lifting plate is fixedly connected to one side of the material suction pipe, a first guide rail plate is fixedly connected to one side of the upper end face of the base, one end of the lifting plate is slidably connected to the first guide rail plate, and a material suction auxiliary assembly is further arranged on the base. According to the boron carbide powder suction device, the material suction auxiliary assembly is utilized, in the whole material suction conveying process, boron carbide powder in the container is gathered through the enclosure structure, all the boron carbide powder in the container can gradually move into the suction range of the material suction pipe, and all the boron carbide powder in the container can be sucked only by descending the material suction pipe at a constant speed; therefore, the process that an operator holds the material suction pipe by hand to suck the boron carbide powder in the container is omitted.

The invention relates to the field of ultrahigh-temperature ceramic materials, and discloses rare earth element doped quinary high-entropy boride powder and a preparation method thereof. The preparation method of the rare earth element doped quinary high-entropy boride powder comprises the following steps: 1) taking metal oxide powder, boron carbide powder and graphite powder as raw materials, and performing wet mixing to prepare mixed powder, 2) briquetting the mixed powder to prepare a green body, putting the green body into a high-temperature carbon tube furnace into which protective gas is introduced, heating, and carrying out pressureless sintering to obtain clinker; and 3) grinding the clinker to obtain the rare earth element doped high-entropy boride powder. The rare earth element doped quinary high-entropy boride powder prepared by the method has the advantages of high purity, no impurity phase, uniform metal element distribution and high rare earth element content, the preparation process is simple, the cost is low, the reaction temperature is lower, and large-scale production is facilitated.

The application belongs to the technical field of ceramic matrix composite, and discloses a hypersonic aircraft hot end component and a preparation method and application thereof, and the method comprises the following steps: (1) printing a green body of the hypersonic aircraft hot end component to be prepared by taking ceramic-metal silicon-binder composite powder as raw materials; wherein the raw materials of the ceramic-metal silicon-binder composite powder comprise ceramic powder, metal silicon and organic binder; (2) after the green body is solidified, pressureless sintering is first carried out under the condition of nitrogen, then carbon precursor is infiltrated and reaction sintering is carried out, and then the hypersonic aircraft hot end component is obtained. By means of nitriding, uniformly distributed silicon nitride bonding phases and pyrolytic carbon are generated in the body, reaction sintering silicon infiltration converts the pyrolytic carbon into silicon carbide, the obtained material contains in-situ nitrided silicon nitride and secondary silicon carbide (beta-SiC) generated by reaction sintering silicon infiltration as bonding phases, and has more excellent mechanical properties.

The invention belongs to the technical field of ceramic tube preparation, and particularly relates to a pressureless sintered silicon carbide grinding medium and a preparation method thereof. The invention relates to a preparation method of a pressureless sintered silicon carbide grinding medium, which comprises the following specific steps: proportioning: preparing basic materials of the silicon carbide grinding medium according to the weight ratio: 98-99 wt% of submicron silicon carbide and 1-2 wt% of boron carbide; ball-milling and mixing; performing spray granulation; intensely stirring, mixing and granulating; drying the biscuit; dewaxing the biscuit; and sintering at high temperature to finish preparation. The preparation method is simple in technological process, use of large forming equipment such as a dry press and a cold isostatic press is avoided, the production input cost is greatly reduced, and the prepared pressureless sintered silicon carbide grinding medium is good in sphere sphericity degree, high in density, high in strength, high in toughness, ultrahigh in wear resistance, long in service life, resistant to high temperature and good in chemical stability.

The invention discloses a diamond string bead, a preparation method of the diamond string bead and a preparation method of a diamond wire saw. The preparation method of the diamond string bead comprises the following steps: adding cylindrical powder mixed with an organic binder into a die cavity of a main die; adding a plurality of diamonds into a die cavity of the main die according to a first rule, wherein the plurality of diamonds are positioned in the cylindrical powder; the lower pressing head is moved upwards, the upper pressing head is moved downwards, pressure is applied to the column powder and the diamonds in the die cavity from the upper side and the lower side, and a metal column containing multiple diamonds is formed through cold pressing; taking out and carrying out pressureless sintering on the metal cylinder; the carcass powder is added into a cold pressing die cavity; feeding the sintered metal cylinders into a cold pressing die cavity, arranging the metal cylinders in the cold pressing die cavity according to a second rule, and inserting the metal cylinders into the matrix powder; carrying out cold pressing treatment on the carcass powder and the metal cylinder to obtain a bead string working layer; and hot-pressing and sintering the bead working layer to obtain the diamond bead.

Provided is a zirconia sintered body with which both transparency and fracture toughness value can be achieved at high levels and which can be easily manufactured even by pressureless sintering. In this sintered body, the percentage content of Y2O3 in the whole composition is 1.7-2.9 mol%, the area average particle diameter of zirconia crystal particles is 0.6-1.1 μm, the area ratio of a first region composed of zirconia crystal particles having a particle diameter of 0.1 or more and less than 0.8 μm is 10-80%, the area ratio of a second region composed of zirconia crystal particles having a particle diameter of 0.8-3.2 μm is 20-90%, the average Y2O3 concentration C2 of zirconia crystal particles forming the second region is 2.0-3.2 mol%, the average Y2O3 concentration C1 of zirconia crystal particles forming the first region is 1.7-2.3 mol%, and when the difference in Y2O3 concentration is defined as ΔC≡C2-C1, the ΔC / C2 value is 0.1-0.5, the fracture toughness value of the sintered body measured by the IF method is 10.5 MPa·m0.5 or more, and the total light transmittance of the sintered body is 40% or more.

The application relates to the technical field of ceramic wave-transparent materials, in particular to a Si3N4 ceramic wave-transparent material and a preparation method thereof. The Si3N4 ceramic wave-transparent material is prepared by mixing alpha Si3N4 powder, a composite sintering aid, a DMAA gel system component and water to prepare Si3N4 slurry, carrying out gel solidification on the Si3N4 slurry to obtain a wet blank, and then carrying out segmented drying, degreasing and pressureless sintering to obtain the Si3N4 ceramic wave-transparent material. The Si3N4 ceramic wave-transparent material prepared by the application has high compactness, low dielectric constant (epsilon=2.8-3.5), low dielectric loss (tan delta <=5*10 ‑3 -6), excellent wave-transparent performance and high-temperature mechanical performance, and is suitable for large-scale preparation of high-temperature wave-transparent scenes such as aerospace and radar antenna covers.

This invention discloses a method for preparing and applying a top metal layer on a power semiconductor chip, relating to the field of power semiconductor interconnect technology. The method includes: coating a metal sintering material onto the top of a power semiconductor chip or wafer, followed by sintering; when the sintering is pressure sintering, baking the metal-coated power semiconductor chip or wafer at a first temperature; after baking, covering the surface of the baked metal sintering material with an insulating material, and then performing pressure sintering at a second temperature; when the sintering is pressureless sintering, performing pressureless sintering of the metal-coated power semiconductor chip or wafer at a third temperature; the first temperature is lower than the second and third temperatures; the thickness of the metal sintering material coating is 1~1000μm; the wafer is an uncut power semiconductor chip precursor. The technical solution provided by this invention is simple and low-cost.

According to the cerium oxide target material and the preparation method thereof provided by the invention, cerium oxide powder with the particle size of 10-500 m is placed in a mold and transferred into a pressureless sintering environment for pressureless sintering treatment, and the cerium oxide target material is obtained; wherein the pressureless sintering treatment adopts multi-stage stepped heating, and comprises the following steps: a low-temperature heating stage: heating from room temperature to 300-400 DEG C, and keeping the temperature for 2-4 hours; in the medium-temperature heating stage, the temperature is increased to 700-800 DEG C from 300-400 DEG C, and heat preservation is conducted for 2-4 hours; and in the high-temperature heating stage, the temperature is increased to 1100-1500 DEG C from 700-800 DEG C, and heat preservation is conducted for 2-7 hours. Cerium oxide powder with the particle size of 10-500 m is placed in a mold for pressureless sintering treatment, the pressureless sintering treatment adopts a multi-stage stepped heating mode, the cerium oxide target material with the high density of 80%-95% can be prepared, the target material is not prone to cracking, and the good large-scale application prospect is achieved.

The present invention relates to a method for rapidly pressureless sintering to prepare high-transparency AlON ceramics by adding nano-Y2O3, belonging to the field of preparation of transparent ceramic materials. A method for rapidly pressureless sintering to prepare high-transparency AlON ceramics by adding nano-Y2O3. The nano-Y2O3 powder with a high specific surface area is added as a sintering aid to the pure-phase AlON powder, and the raw materials are mixed by ball milling. The mixed powder is prepared into AlON transparent ceramics with high transparency in a wide wavelength band by pressureless sintering. Among them, the nano-Y2O3 powder with a high specific surface area is obtained by calcining yttrium acetate powder after nodular graphite in air. This method only uses a general ball milling method to achieve uniform mixing of raw materials. The sintering uses pressureless sintering technology, with easy availability of equipment and easy implementation of technology. The heat preservation time in the sintering process is short, with good energy-saving effect, high efficiency, low preparation cost, and easy industrialization.

This invention discloses a copper-based powder metallurgy friction plate for wind turbine torque limiters and its preparation method. The friction plate blank is first subjected to pressureless sintering to obtain a pre-sintered blank, and then the pre-sintered blank is re-pressed to obtain a re-pressed friction plate blank. The re-pressed friction plate blank is then assembled with a copper-plated steel backing to obtain a composite blank, which is then subjected to pressure limiting sintering to obtain the final product. The preparation method of this invention, through the synergy of pressureless pre-sintering, re-pressing, and pressure limiting sintering, obtains a copper-based powder metallurgy friction plate for wind turbine torque limiters with small deformation, high density, and excellent mechanical and tribological properties.