阅读说明：本技术 一种高纯度、低成本二硅化钼的制备方法 (Preparation method of high-purity and low-cost molybdenum disilicide ) 是由 张洪涛 于 2020-07-31 设计创作，主要内容包括：一种高纯度、低成本二硅化钼的制备方法,将原料三氧化钼、二氧化硅和高纯石墨粉,加入工业干粉成型剂,在混料器中混料,按照1公斤每份放入油压机压制,获得压制块料；将压制块料用500公斤真空无压烧结炉真空烧结,送电抽真空至3Pa,350℃烧结1小时-2小时,1620℃保温,炉内真空度为20Pa-25Pa之间继续升温；1850℃保温10小时-15小时,降温,温度降低1250℃,真空度抽到3Pa-4Pa,保温5小时,硅和钼充分化合,停电降温,得到二硅化钼。以氧化钼为原料,原料成本低廉,且整个工艺合理可控,可以制备出单相高纯度二硅化钼,适合工业化生产。(A preparation method of high-purity low-cost molybdenum disilicide comprises the steps of adding industrial dry powder forming agent into raw materials of molybdenum trioxide, silicon dioxide and high-purity graphite powder, mixing the raw materials in a mixer, and putting 1 kg of the mixture into an oil press for pressing to obtain a pressed block material; vacuum sintering the pressed block material in a 500 kg vacuum pressureless sintering furnace, transmitting power, vacuumizing to 3Pa, sintering at 350 ℃ for 1-2 hours, preserving heat at 1620 ℃, and continuously heating up when the vacuum degree in the furnace is 20-25 Pa; 1850 deg.C maintaining for 10-15 hr, cooling to 1250 deg.C, pumping to 3-4 Pa in vacuum degree, maintaining for 5 hr, fully combining silicon and molybdenum, and stopping power to cool to obtain molybdenum disilicide. The molybdenum oxide is used as a raw material, the cost of the raw material is low, the whole process is reasonable and controllable, single-phase high-purity molybdenum disilicide can be prepared, and the method is suitable for industrial production.)

1. A preparation method of high-purity low-cost molybdenum disilicide is characterized by comprising the following steps:

the method comprises the following specific steps:

(1) mixing raw materials of molybdenum trioxide, silicon dioxide and high-purity graphite powder according to a molar ratio of 1:2:7, adding an industrial dry powder forming agent accounting for 1% of the total mass of the molybdenum trioxide, the silicon dioxide and the high-purity graphite powder, mixing in a 250-liter V-shaped mixer, wherein the particle size of the molybdenum trioxide is 325 meshes, the particle size of the silicon dioxide is 400 meshes, the particle size of the high-purity graphite is 325 meshes, and mixing for more than 6 hours to obtain a mixed material;

(2) putting the mixed material obtained in the step (1) into a 500-ton oil press for pressing according to 1 kg per part, wherein the pressing pressure is 30MPa, one mixed material is pressed each time, the tight combination is ensured not to be loose,the pressing density is more than or equal to 3.2g/cm³Obtaining pressed lump materials;

(3) vacuum sintering the pressed lump material by using a 500 kg vacuum pressureless sintering furnace, and continuously vacuumizing the whole vacuum sintering process, wherein the charging amount is 200 kg each time;

first heating

Turning on a power supply, transmitting power, evacuating, simultaneously transmitting power to a furnace body, raising the temperature by 30Kw/h, setting the temperature of the vacuum pressureless sintering furnace to 350 ℃, keeping the temperature for 1-2 hours when the vacuum degree is stabilized between 3-8 Pa, and continuously transmitting power and raising the temperature;

second heating

Setting the temperature of a vacuum pressureless sintering furnace to 1620 ℃, continuously transmitting power and increasing the temperature by 50Kw/h, starting to change the vacuum degree in the furnace to between 3 and 200Pa at 1400 ℃, continuously preserving the temperature at 1620 ℃, and continuously transmitting power and increasing the temperature when the vacuum degree in the furnace is stabilized to between 20 and 25 Pa;

thirdly heating up

Setting the temperature of the vacuum pressureless sintering furnace at 1850 ℃, giving the power to 110Kw/h at most, continuously heating, continuously preserving the heat at 1850 ℃, changing the vacuum degree between 20 and 300Pa, preserving the heat, reacting for 10 to 15 hours, reducing the power of the vacuum pressureless sintering furnace when the vacuum degree in the furnace is reduced to 3 to 5Pa, and cooling;

cooling alloying reaction

And reducing the power of the vacuum pressureless sintering furnace to 20Kw/h, reducing the temperature to 1250 ℃, keeping the vacuum degree at 1250 ℃ at 3-4 Pa for 5 hours, and cutting off the power to reduce the temperature to obtain the molybdenum disilicide.

2. The method of claim 1 for the production of high purity, low cost molybdenum disilicide, wherein: the purity of the molybdenum trioxide is 99.5 percent, the purity of the silicon dioxide is 99.8 percent, and the purity of the high-purity graphite is 99.99 percent.

3. The method of claim 1 for the production of high purity, low cost molybdenum disilicide, wherein: when the V-shaped mixer mixes materials, the feeding amount is 100 kilograms at each time.

4. The method of claim 1 for the production of high purity, low cost molybdenum disilicide, wherein: the industrial dry powder forming agent is carboxymethyl cellulose.

Technical Field

The invention relates to a preparation method of molybdenum disilicide, in particular to a preparation method of high-purity and low-cost molybdenum disilicide.

Background

Molybdenum disilicide is a refractory metal silicide, and the radiuses of two atoms of Mo and Si are not greatly different, so that the two atoms of Mo and Si are combined to form MoSi in the atomic number ratio of 1:2₂Characterized by coexistence of metal members and covalent bonds, therefore, MoSi₂The ceramic has the dual properties of metal and ceramic, has high melting point, low density and excellent high-temperature oxidation resistance, and is widely applied to the fields of high-temperature parts, spray pipes, high-temperature filters, spark plugs and the like of aviation and automobile gas turbines.

Currently, molybdenum disilicide powder is obtained by mixing molybdenum powder and silicon powder and carrying out alloying reaction at the temperature of about 1300 ℃, and the molybdenum powder has high cost, so that the production of the molybdenum disilicide powder is limited. CN 105645416B discloses a low-cost production method of molybdenum disilicide, which is obtained by directly and uniformly mixing molybdenum sulfide and silicon powder serving as raw materials and roasting at the temperature of 1000-1600 ℃, wherein the molybdenum disilicide used in the method is a main component of native molybdenum ore in China, and the production cost is low. However, the purity of molybdenum disilicide is generally not high, so that a large amount of impurities are introduced in the raw material stage, the purity of the product is influenced, and the product cannot reach the high-purity standard.

Disclosure of Invention

The invention aims to solve the technical problem of providing a preparation method of high-purity and low-cost molybdenum disilicide, which takes molybdenum oxide as a raw material, has low raw material cost, reasonable and controllable whole process and can prepare single-phase high-purity molybdenum disilicide.

The technical scheme of the invention is as follows:

a preparation method of high-purity low-cost molybdenum disilicide comprises the following specific steps:

(1) mixing raw materials of molybdenum trioxide, silicon dioxide and high-purity graphite powder according to a molar ratio of 1:2:7, adding an industrial dry powder forming agent accounting for 1% of the total mass of the molybdenum trioxide, the silicon dioxide and the high-purity graphite powder, mixing in a 250-liter V-shaped mixer, wherein the particle size of the molybdenum trioxide is 325 meshes, the particle size of the silicon dioxide is 400 meshes, the particle size of the high-purity graphite is 325 meshes, and mixing for more than 6 hours to obtain a mixed material;

(2) putting the mixed material obtained in the step (1) into a 500-ton oil press for pressing according to 1 kg per part, wherein the pressing pressure is 30MPa, the mixed material is pressed one block each time, the tight bonding is ensured not to be loose, and the pressing density is more than or equal to 3.2g/cm³Obtaining pressed lump materials;

(3) vacuum sintering the pressed lump material by using a 500 kg vacuum pressureless sintering furnace, and continuously vacuumizing the whole vacuum sintering process, wherein the charging amount is 200 kg each time;

first heating

Turning on a power supply, transmitting power, evacuating, simultaneously transmitting power, increasing temperature power by 30Kw/h, setting the temperature of the vacuum pressureless sintering furnace to 350 ℃, keeping the vacuum degree to 3Pa, keeping the temperature to 350 ℃, keeping the temperature for 1-2 hours, and keeping the vacuum degree to 3-8 Pa according to the vacuum degree, so as to ensure that moisture of the material is discharged, and avoid incomplete carbon reduction reaction and residual impurities caused by violent material reduction and material block body cracking under a high-temperature state;

second heating

Continuously supplying power and heating, setting the temperature of a vacuum pressureless sintering furnace to 1620 ℃, continuously supplying power and heating power to 50Kw/h, starting to perform carbon reduction reaction at 1400 ℃, reducing the vacuum degree in the furnace by 3-200 Pa, and continuously preserving heat at 1620 ℃, so that part of the furnace is slowly reduced to prevent subsequent high-temperature concentrated massive gas release reaction, the gas is not smoothly exhausted by a vacuum system, the silicon and molybdenum are combined to have a splash phenomenon, the heat preservation time is determined according to the vacuum degree, and the temperature is continuously raised when the vacuum degree in the furnace is 20-25 Pa;

thirdly heating up

The optimal temperature of the carbon reduction reaction is 1850 ℃, the temperature of the vacuum pressureless sintering furnace is set to be 1850 ℃, the power is given to 110Kw/h at most, the temperature is continuously raised, the heat preservation reaction time is 10-15 hours, the vacuum degree is 20-300Pa, and the vacuum degree is reduced to 3-5Pa, which indicates that the carbon has fully reduced the oxygen of the molybdenum trioxide and the silicon dioxide, the power of the vacuum pressureless sintering furnace is reduced, and the temperature is reduced;

cooling alloying reaction

And reducing the power of the vacuum pressureless sintering furnace to 20Kw/h, reducing the temperature to 1250 ℃, ensuring the full combination reaction of silicon and molybdenum, avoiding the volatilization of silicon elements, ensuring the alloying degree of molybdenum disilicide, pumping the vacuum degree to 3Pa-4Pa, preserving the heat for 5 hours, fully combining the silicon and the molybdenum, and cutting off the power to reduce the temperature to obtain the molybdenum disilicide.

Furthermore, the purity of the molybdenum trioxide is 99.5%, the purity of the silicon dioxide is 99.8%, and the purity of the high-purity graphite is 99.99%.

Furthermore, when the V-shaped mixer mixes materials, the feeding amount is 100 kg each time.

Furthermore, the industrial dry powder forming agent is carboxymethyl cellulose, and is evaporated by high-temperature firing without residual impurities.

The invention has the beneficial effects that:

the method takes molybdenum trioxide and silicon dioxide as raw materials, the raw materials are easy to obtain, the cost is low, high-purity graphite powder is taken as a reducing agent, the molybdenum trioxide and the silicon dioxide are reduced through three-stage heating and heat preservation, the reduction degree of the raw materials is good, pure-phase molybdenum disilicide is obtained through cooling and sintering, the product purity is high, the whole process is reasonable and controllable, the alloying degree of the produced molybdenum disilicide can reach 100 percent, and the method is suitable for industrial production.

Drawings

FIG. 1 is an X-ray diffraction pattern of molybdenum disilicide of the present invention;

FIG. 2 is a particle size distribution report for molybdenum disilicide of the present invention;

FIG. 3 is a pictorial representation of a molybdenum disilicide in accordance with the present invention.

Detailed Description