Method for preparing high-purity mullite monocrystal through kyanite concentrate at low temperature

Abstract

The invention relates to a method for preparing a high-purity mullite monocrystal, in particular to the method for preparing the high-purity mullite monocrystal by utilizing a kyanite concentrate as a raw material at low temperature. The invention aims to provide the method for producing the mullite monocrystal with the advantages of energy conservation and consumption reduction, high yield, high purity, low temperature and environmental friendliness. The method is characterized by comprising the following steps of: (1) mixing kyanite concentrates of the same particle size with industrial Al2O3 in a ball grinder, wherein mass fractions of Al2O3 and SiO2 in a mixed sample accord with a mullite chemical structure; and (2) putting catalyst AlF3 outside the mixed sample, and carrying out heat treatment in two steps in a sealed high temperature resistant container: step 1, finishing nucleation of the mullite from the room temperature to a temperature of 900 DEG C; and step 2, at the temperature of 900-1100 DEG C, finishing crystallization of the mullite; and taking out after naturally furnace cooling to the room temperature to obtain the high-purity mullite monocrystal. Compared with the existing method, the method provided by the invention has the advantages of low synthesis temperature, high yield and purity, energy conservation and environmental friendliness, and is suitable for industrial production.

Description

technical field [0001] The invention relates to a method for preparing high-purity mullite single crystal at low temperature from kyanite concentrate, which belongs to the technical field of new materials. Background technique [0002] Mullite (Mullite, 3Al 2 o 3 2SiO2 2 ) is a chain silicate mineral with less natural mullite, and no deposits of industrial value have been found so far. Mullite has low thermal conductivity and is a poor conductor of oxygen ions, and has excellent thermal stability and high temperature chemical stability, high refractoriness, good thermal shock resistance, chemical corrosion resistance, creep resistance, high softening temperature under load, and electrical resistance. Strong insulation, is an ideal heat insulation material. [0003] Mullite single crystal has no internal or surface defects. In addition to the excellent properties of polycrystalline mullite, its mechanical properties are better than polycrystalline mullite. Mullite single...

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Problems solved by technology

[0007] There are a large number of documents and patents on the synthesis method of mullite single crystal, but high temperature calcination and low purity of single crystal are common problems

Long-term high temperature will consume a lot of energy, which also means that a large amount of pollutants will inevitably be produced. When the temperature is higher than 1300 ° C, the production requirements for equipment will be greatly increased, and the basic investment will inevitably be increased.

When mullite single crystal is applied to thermal barrier materials, the economic benefits are high, and low-purity crystals will seriously affect the performance of metal-based thermal barrier materials

For example: in CN102206865A, the synthetic single crystal is attached to the surface of kyanite, and the particle size of the powder kyanite raw material is already very small, so it is difficult to separate the crystal on the surface of kyanite as a reinforcing and toughening agent for composite materials The problem to be solved: When kyanite is decomposed at high temperature, there is irreversible volume expansion. Mullite crystals containing kyanite impurities are used as strengthening and toughening agents for materials, not only can not achieve the effect of strengthening and toughening, but will cause material Performance drop

In the synthesis of CN102351522A and many traditional mullite crystals, because the temperature is higher than 1200 ° C, mullite begins to sinter, the growth of the crystal is limited, and the prepared product is in a block or sintered state, and it is impossible to obtain dispersed high-purity Mullite single crystal

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