Preparation and application of molybdenum silicate

Molybdenum Disilicide, MoSi2 is a kind of silicon Molybdenum compound, also known as Molybdenum Disilicide, Molybdenum silicide has high melting point, low density, good thermal conductivity and good electrical conductivity and excellent high temperature oxidation resistance, high elastic modulus, low thermal expansion coefficient, high strength, good resistance to chemical corrosion and thermal shock resistance, are widely used in high temperature heating element component materials and high temperature oxidation resistance coating materials, is also the most development potential of high temperature structural materials and wear-resistant materials.
With the rapid development of powder metallurgy and material technology. Molybdenum silicide preparation also made significant progress, in the traditional arc smelting, casting and powder compacting push technology, on the basis of the late 1980 s self-propagating high temperature synthesis (SHS), mechanical alloying (MA), such as hot pressing (HP) technology has achieved rapid development, they overcame the molybdenum silicide high melting point, difficult synthesis, traditional craft and material easy oxidation of faults in the synthetic process. In recent years, new technology of spark plasma sintering and new development of SHS and MA have appeared. However, these methods all use molybdenum powder and silicon powder as raw materials. Because of the high price of molybdenum powder, the raw material cost is high.
China is a country rich in molybdenum deposits. By the end of 2008, according to the National Bulletin of Mineral Resources reserves, China has 411 proved molybdenum deposits, and the reserves of molybdenum deposits have reached 12.3223 million tons, ranking first in the world. And China molybdenum ore to the primary molybdenum sulfide ore – based. If molybdenum disilicide can be prepared by replacing molybdenum powder with molybdenum sulphide at a lower price, the raw material cost of preparing molybdenum disilicide will be greatly reduced, thus reducing the production cost of molybdenum disilicide. Moreover, the direct use of China’s molybdenum sulfide resources can eliminate the long process from molybdenum sulfide to molybdenum sulfide, which can reduce resource consumption and environmental pollution.
A method of preparing molybdenum disilicide at low cost using MoS2 powder and Si powder as raw material is provided to solve the problem that the cost of preparing molybdenum disilicide as raw material is too high. To achieve the above purpose, the technical scheme provided by the invention is as follows: a method for preparing molybdenum silicide at a low cost, in which MoS2 powder and Si powder are used as raw materials, mixed and roasted uniformly in the furnace, and the molybdenum silicide product is obtained after cooling. The technical scheme provided by the invention, compared with the existing known technology, has the following beneficial effects :(1) using MoS2 powder as raw material, the invention can effectively utilize China’s abundant MoS2 resources and reduce the production cost of preparing molybdenum silicide; (2) The preparation process of the invention eliminates the production process from MoS2 to Mo, shorens the process, saves resources and reduces the production cost; (3) Through the control of the proportion of raw materials, the selection of roasting process and other reasonable selection of process parameters, the prepared molybdenum silicide has high purity and less impurities.
Molybdenum silicide has a high melting point of 2030℃ and operating temperature of 1625℃. Molybdenum silicide can at temperatures higher than 800 ℃, the oxidation reaction, generated on the surface of a layer of silicon oxide with self-healing ability of dense, continuous glass thin layer, the isolation of oxygen and molybdenum silicide further contact, to prevent its further oxidation, due to the high temperature of glass coating of liquidity, it will also be able to fill the thermal stress of crack and emptiness of air bubbles, so it has excellent high temperature oxidation resistance, studies have shown that the high temperature oxidation resistance can reach 1700 ℃. Molybdenum silicide coatings there are still some disadvantages of the existing, mainly in the low temperature range, molybdenum silicide accelerated oxidation happens, the product oxide at high temperature has the instability MoO3 whisker, result in a silicon oxide layer fracture and osteoporosis, siliconizing molybdenum oxide layer crack and pulverization, and nanometer molybdenum silicide can solve the disadvantages.
CN201711283387.6 solves the technical problem of easy fracture and porosity of existing molybdenum silicide coatings, and provides a kind of nano-molybdenum silicide high-temperature resistant coating. The present invention adopts the following technical scheme: a nano-molybdenum silicide high-temperature resistant coating is prepared from the following raw materials with the following quality ratio: molybdenum silicide 50 ~ 70 parts, resin emulsion 100 parts, functional filler 20 ~ 40 parts, adhesive 3 ~ 6 parts, thickener 3 ~ 6 parts, solvent 20 ~ 40 parts; The resin emulsion is one or a combination of waterborne acrylic resin emulsion or silicone resin emulsion, and the solvent is deionized water or softening water. The preparation method of the nanometer molybdenum silicide high temperature resistant coating comprises the following steps:
(1) Add molybdenum silicate powder to ball mill for 10-15 times grinding and freeze drying to prepare molybdenum silicate nanoparticles; Grind the functional filler ball 5-10 times;
(2) Stir fully and evenly nanometer molybdenum silicide, functional filler, resin emulsion and deionized water treated by ball grinding, and then let stand for more than half an hour to defoamer and deaerate; Add thickener, stir at low speed, sift and thicken to form paint finished product. The nanometer molybdenum silicide high-temperature resistant coating of the present invention solves the problem of accelerated oxidation of molybdenum silicide within the range of low temperature, effectively prevents the fracture and porosity of silicon oxide layer, and makes the oxidation protective layer of molybdenum silicide coating not easy to produce crack and powder.

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