Wollastonite (CaSiOThreeIt is a kind of white calcium containing metasilicate crystalline mineral, and naturally produced wollastonite is usually flaky. Needle like, radial or fibrous aggregates. It has a series of excellent properties such as high whiteness, brightness, high aspect ratio, low water absorption and oil absorption.
Follow the development of powder skills, composition skills and appearance modification skills.,Wollastonite powderSpray dryerThe application fields are constantly expanding and deepening.,It is mainly used in plastics, rubber, polymers, coatings and dyes. Ceramics, metallurgy, building materials Environmental protection and Asbestos Substitutes. China's wollastonite plays an important role in the world market.,It has occupied 2/3 of the foundry powder store in Europe.,However, the preparation technology of wollastonite acicular ultra-fine powder with high aspect ratio is lagging behind that of developed countries.
Preparation technology of wollastonite powder
Natural wollastonite products can be divided into five types according to their particle size: bulk, general, fine, ultra-fine and needle-like powder. The preparation methods of powders can be divided into physical preparation and chemical preparation according to the principle. Mechanical preparation is the main method in physical preparation.,In chemical preparationlab spray dryerDry sintering and melting are the main methods.
Mechanical failure can be divided into two ways: dry and wet.,Maintenance of fiber aspect ratio by wet microwave damage The fineness and slack of single fiber are better.;Dry energy consumption is high, but the problem of powder gathering is not wet.,Therefore, it is also a useful way.
ØChemical precipitation method
The preparation of wollastonite by chemical precipitation means the use of soluble salts containing silicon and calcium.,Dissolve it in water,After chemical reaction,Method of generating calcium silicateSmall spray dryerCalcium carbonate can be dried into powder.
Advantages: Simple process, easy to operate, a wide range of materials, low energy consumption, no need for expensive equipment.
Defects: the granularity of product composition is difficult to manipulate.
Sol-Gel method(sol gel)The method is to use inorganic salts or metal alkoxides as precursors. Sol is formed by dissolving the precursor in a solvent and forming a homogeneous solution. The solution reacts with the solvent to form a sol by hydrolysis or alcoholysis.;Sol aging, transpiration and drying Then change to gel. Nanoparticles are dispersed in the network structure of the gel.,Heat treatment of gel,Nanoparticles can be obtained.
Advantages: The equipment required is simple, less energy consumption, is a useful way to prepare high-quality inorganic ultra-fine powder.
Defect: heat treatment must be carried out, otherwise simple production stiff meeting and superfine particle growth.
Hydrothermal method is used in closed containers.,A solution consisting of water or other solvents for coal dissolving under certain temperature and pressure. Hydrothermal composition is an important way to prepare special structures and functional data.
Strength: highly active powder can be obtained, and hydrothermal is under low temperature, isobaric and liquid reaction conditions.,It is beneficial to the regular orientation of crystals and to control the size of products simply.
Defect: the price of the precursor is expensive.,It is not conducive to industrial production.
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