Process for synthesizing nano barium ferrite powder by microwave induction and low-temp combustion

Method for preparing superfine tungsten powder

The invention discloses a method for preparing superfine tungsten powder, which comprises the following steps: A, mixing tungstate and magnesium powder according to a molar ratio of the tungstate to the magnesium powder of 1-6:3-25, then compacting the mixture and filling the mixture into a vertical annular cylinder or a disc container made of carbon felt, filling the mixture into a high-pressure container to carry out self-propagating high-temperature synthesis, and naturally cooling a synthesized product after the synthesis; and B, taking out the synthesized product to carry out material crushing, soaking the product in 1 to 10 mol/L hydrochloric acid solution for 1 to 5 hours to make MgO impurities in the product totally dissolved in hydrochloric acid, filtering the product and washing the product by deionized water repeatedly till no Cl is in the filtrate through the detection of AgNO3, and finally drying the product for 1 to 5 hours in an oven at the temperature of between 100 and ...

Method for preparing high thermal-conductivity aluminium nitride ceramics

Method for promoting Sialon ceramic agglutinating densification

The present invention relates to a method for accelerating sialon ceramic sintering compaction by applying a layer of sizing material on the surface of sialon sample. Said sizing material is made up by using Si3N4, AlN or Si, nd YAM2Y2O3.Al2O3), YAG(3Y2O3.5Al2O3), Al2O3, Y2O3, SiO2 or C powder and PVB (polyvinyl butyral), and one or several kinds of anhydrous acids (phosphoric acid, boric acid, silicic acid, acetic acid and oxalic acid) or their inorganic or organic derivatives at least containing one acid radical, adding anhydrous alcohol and mixing them. After having been sintered, the porosity of the sialon sample coated with said sizing material can be obviously reduced.

Leadless thick film conductor slurry composition for aluminium nitride substrate

A lead-free thick-film conductor slurry composition used inaluminum nitride substrate characterizes that the conductor slurry is composed of conducting power: 50-80 wt%, lead-free Ba borosilicate Ca class glass powder; 1-15 wt% and organic media. The Ba borosilicate Ca class glass powder contains: (wt%) SiO210-30, B2O3 15-50, CaO15-45 BaO10-30, Al2O3 1-5, K2O1-5, Na2O1-10 with 0.5 CuO or TiO2 addition. The organic media are composed of organic adhesive: 1-20% and organic solvent 80-90 wt% with the advantages of lead-free, low resistance on the thick-film conductor surface and strong adhesion with Al nitride ceramics substrate suitable for thick-film IC.

Process for preparation of transparent aluminium nitride ceramic

自蔓延高温合成制备β－氮化硅晶须的方法

... 一种自蔓延高温合成β-Si#-[3]N#-[4]晶须的制备方法，属于陶瓷粉末制备领域。本发明是由商业硅粉和α-Si#-[3]N#-[4]粉按9～5∶1～5的比例混合，加入晶须生长助剂，在3～10MPa的氮气中反应制备的。晶须生长助剂选用镧系稀土氧化物中的一种，如Y#-[2]O#-[3]、La#-[2]O#-[3]、Gd#-[2]O#-[3]中的一种，加入量为硅粉和α-Si#-[3]N#-[4]粉混合后总重量的0.5～10wt％(优先推荐加入量2～5wt％)。本发明的特点是：由本发明制备的β-Si#-[3]N#-[4]晶须，其长径比在7～10之间，而且晶体结构完整、表面光滑。在生产过程中，不需预先压块，直接将反应混合物装入内壁涂有氮化硼的多孔石墨坩埚中，通电点燃反应物，反应在2～10分钟之内完成，该反应无环境污染，耗能低，产率接近100％，适合于工业大规模生产。 ...

Process for synthesizing nano barium ferrite powder by microwave induction and low-temp combustion

A process for synthesizing nanometre BaFe12O19 powder includes such steps as proportionally mixing the inorganic salt (nitrate or carbonate) of Ba2+ or Fe3+, citric acid and chloride (potassium chloride, sodium chloride, or their combination in mol ratio of NaCl/KCl=1:0.5-1.5), microwave inducing, low-temp. combustion for 2-10 min, heat treating under 900 deg.c for 0.2-10 hr and water washing to obtain nanometre hexagonal crystal of BaFe12O19. Its advantages are simple process, low energy consumption, and regulatable magnetic performance of product.

Process for preparation of transparent aluminium nitride ceramic

A process for preparing transparent ceramic of aluminium nitride features that its powdered starting material (7-8 microns) is obtained by self-spreading, its sinter assistant is industrially pure calcium carbide (3 wt.%) or the industrially pure calcium carbide and rare-earth oxide-CaC2 (2-4 wt.%) + Re2O3 (1-3 wt.%), where Re is one of Y, Ce, Sm, Dy, Er, and Yb, and the process includes hot pressing, or not pressing or low-temp hot pressing, and high-temp thermal treatment. Obtained A1N ceramic has maxmal transmission rate greater than 60% for ultraviolet, visual and near infrared band and density up to 3.26 g/cu.cm.

Low temp. sintering of aluminum nitride ceramics

The low-temp. sintering method of AlN ceramic is characterized by that (1): the initial AlN powder material adopted by said invention is the powder material obtained by general carbontherma reductionmethod or high-temp. self-extending method; (2) the selected additive material is technical-grade CaC2 and monovalent metal oxide and rare earth oxide; (3).sintering temp. is less than 1600 deg.C. The AlN ceramic prepared by said invented method has good performance price ratio, heat conductivity is 130-230 W.m(-1).K(-1), dielectric loss is 1 X 10 to the power 16 ohm.cm.

Low-temp. sintering method for preparing aluminium nitride ceramics

QICK PREPARATION METHOD FOR THE REACTION SINTERING MATERIAL OF HIGHLY COMPACT SILICON NITRIDE

Method for preparing superfine tungsten powder

The invention discloses a method for preparing superfine tungsten powder, which comprises the following steps: A, mixing tungstate and magnesium powder according to a molar ratio of the tungstate to the magnesium powder of 1-6:3-25, then compacting the mixture and filling the mixture into a vertical annular cylinder or a disc container made of carbon felt, filling the mixture into a high-pressure container to carry out self-propagating high-temperature synthesis, and naturally cooling a synthesized product after the synthesis; and B, taking out the synthesized product to carry out material crushing, soaking the product in 1 to 10 mol/L hydrochloric acid solution for 1 to 5 hours to make MgO impurities in the product totally dissolved in hydrochloric acid, filtering the product and washing the product by deionized water repeatedly till no Cl<-> is in the filtrate through the detection of AgNO3, and finally drying the product for 1 to 5 hours in an oven at the temperature of between 100and ...

Leadless thick film conductor slurry composition for aluminium nitride substrate

Method for promoting sialon ceramic agglutinating densification

Preparation method of tungsten carbide powder

The invention discloses a preparation method of tungsten carbide powder. The method comprises the following steps: A. mixing tungstate, magnesium powder and carbon powder at a mol ratio of 1-6:3-25:1-8, compacting and packing in a vertical annular cylinder or disc container which is made from carbon fiber felt, packing into a high pressure vessel for combustion synthesis in argon atmosphere, and naturally cooling; and B. taking out a combustion synthetic product for crushing, dipping in 1-10mol/L hydrochloric acid solution for 1-5h to fully dissolve a synthesis byproduct MgO impurity in the hydrochloric acid, filtering, washing with deionized water, repeating filtering and washing for a plurality of times till no Cl<-> is detected in filtrate with AgNO3, and drying the washed material in a drying oven at the temperature of 100-110 DEG C for 1-5h to obtain the final product tungsten carbide powder. The preparation method has the advantages of low raw material cost and simple process equipment ...

用于轴承球的赛隆陶瓷材料及其制备方法

... 一种用于轴承球的赛隆(sialon)陶瓷及其制备方法，采用本发明的配方及特定的烧结工艺，得到的材料由25～45wt％的α-sialon相、β相Si#-[3]N#-[4]、B相(Y#-[2]SiAlO#-[5]N)，H相(Y#-[5](SiO#-[4])#-[3]N)，少量YAG相(3Y#-[2]O#-[3]・5Al#-[2]O#-[3])及玻璃相组成。采用三阶段保温烧结法，且在第二、第三阶段为防止高温分解，炉内氮气压力分别保持在0.15～0.22和1.0～5.0MPa范围。制备的轴承球压碎负荷不低于同尺寸轴承钢球的45％，维氏硬度大于16.5GPa。球抛光切面上气孔率(按体积比)为＜0.2％。 ...

Self-spread high-temp synthesis process for preparing beta-silicon nitride whisker

A process for preparing beta-Si3N4 whisker by high-temp self-spread synthesis includes mixing Si powder with alpha-Si3N4 powder in a ratio of (5-9):(1-5), adding whisker growing aid, loading in porous graphite crucible with inner surface coated with boron nitride, igniting the raw materials, and reaction in nitrogen atmosphere under 3-10 MPa for 2-10 min. Its advantages are 7-10 of length/diameter ratio, complete structure and smooth surface of crystal, no environmental pollution, and high yield (near 100%).

Process for producing aluminum nitride powders by self diffusion process at high temperature

A process for preparing high-temp synthetic aluminium nitride powder features that Al and aluminium nitride powder are mixed in the ratio of 1-10:1-2, solid diluent (2-10 wt.%) that is ammonium salt (NH4F and NH4Cl) and AlF3 is added, and high-pressure nitrogen (5-15 MPa) is introduced to mix with liquid mixture. The reaction takes place in vertical cylindrical or disk container made of porous aluminium foil. Adding diluent can lower reaction and reduce oxygen content and impurities in reaction system.

Method for preparing superfine boron carbide powder

The invention discloses a method for preparing boron carbide powder, which comprises the following steps: A, mixing borate, magnesium powder and carbon powder according to a mol ratio of 1-10:6-70:1-10, compacting the mixture and putting the mixture into an upright annular cylinder or a discoid container made from carbon felts, putting the upright annular cylinder or the discoid container into a high-pressure vessel to perform combustion synthesis in an argon gas atmosphere, and cooling the mixture naturally after the combustion synthesis; and B, taking out the product subjected to the combustion synthesis, crushing the product, soaking the product in 1 to 10 mol/L hydrochloric acid solution for 1 to 5 hours, so that a synthesis byproduct MgO impurity is completely dissolved in the hydrochloric acid solution, performing suction filtration on the mixture, adding deionized water to wash the mixture, repeating the suction filtration and the washing for a plurality of times until no Cl is detected ...

Preparation method for the reaction sintering material of highly compact silicon nitride

Preparation method of tungsten carbide powder

The invention discloses a preparation method of tungsten carbide powder. The method comprises the following steps: A. mixing tungstate, magnesium powder and carbon powder at a mol ratio of 1-6:3-25:1-8, compacting and packing in a vertical annular cylinder or disc container which is made from carbon fiber felt, packing into a high pressure vessel for combustion synthesis in argon atmosphere, and naturally cooling; and B. taking out a combustion synthetic product for crushing, dipping in 1-10mol/L hydrochloric acid solution for 1-5h to fully dissolve a synthesis byproduct MgO impurity in the hydrochloric acid, filtering, washing with deionized water, repeating filtering and washing for a plurality of times till no Cl<-> is detected in filtrate with AgNO3, and drying the washed material in a drying oven at the temperature of 100-110 DEG C for 1-5h to obtain the final product tungsten carbide powder. The preparation method has the advantages of low raw material cost and simple process equipment ...

Method for preparing superfine boron carbide powder

The invention discloses a method for preparing boron carbide powder, which comprises the following steps: A, mixing borate, magnesium powder and carbon powder according to a mol ratio of 1-10:6-70:1-10, compacting the mixture and putting the mixture into an upright annular cylinder or a discoid container made from carbon felts, putting the upright annular cylinder or the discoid container into a high-pressure vessel to perform combustion synthesis in an argon gas atmosphere, and cooling the mixture naturally after the combustion synthesis; and B, taking out the product subjected to the combustion synthesis, crushing the product, soaking the product in 1 to 10 mol/L hydrochloric acid solution for 1 to 5 hours, so that a synthesis byproduct MgO impurity is completely dissolved in the hydrochloric acid solution, performing suction filtration on the mixture, adding deionized water to wash the mixture, repeating the suction filtration and the washing for a plurality of times until no Cl<->is ...

Process for preparation of self-spread high-temp. synthesizing ferro-silicon nitride powder

A preparation method of self-spreading high-temp. synthetic silicon-iron nitride powder belongs to the field of non-oxide superfine powder preparation, and is characterized by that the metal silicon-iron powder and silicon-iron powder and silicon-iron nitride powder are mixed according to the ratio of 1-10:1-6, or silicon-iron powder, metal silicon powder and silicon-iron nitride powder are mixedaccording to the ratio of 1-10:1-6:1-6, then 1-10 Wt% of solid additive ammonium salt (NH4Cl or NH4F or their mixture) is added, and then the 3-15 MPa nitrogen gas is introduced. Said invention has no need of prebriquetting, and its reaction is implemented in vertical ring-shaped cylinder and disk-shaped container made of carbon felt, and its additive not only can slow down reaction speed, but also can reduce impurity content of whole reaction system, and can make the combustion product form loose structure.

Sialon ceramic material for bearing ball and its preparation

Through specific formulation and sintering process, the present invention obtains a kind of material comprising Alpha-sialon phase and Beta-phase Si3N4, B phase Y2SiAlO3N, N phase Y5(SiO4)3N, small amount of YAG phase 3Y2PO3.5Al2O3, and glass phase. The present invention adopts a three-stage temperature-maintaining sintering process and in its second and third stages, nitrogen pressure inside thefurnace is maintained under 0.15-0.22 MPa and 1.0-5.0 MPa respectively to prevent high-temperature decomposition. Bearing ball produced with the said ceramic material has a crushing load not lower than 45% that of a steel bearing ball in the same size, a Vickers hardness greater than 16.5 GPa and a porosity in polished surface smaller than 0.25 (by volume ratio).