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In recent years, the development and research of new materials have been actively carried out all over the world.
At present, the research of ultrafine powder mainly includes four aspects: preparation, microstructure, macroscopic properties and application, among which the preparation technology of ultrafine powder is the key.
There are many preparation methods of ultrafine powder, including solid phase method, liquid phase method and mineral machinery.
In this paper, some main preparation methods and progress of ultrafine powders are introduced.
Solid phase method is a kind of traditional pulverization industry, because of its advantages of low cost, large yield, simple preparation process, and the recent invention of high-energy ball milling, air pulverization and grading method, it is still used in some places where the purity and particle size of powders are not required to be high.
This method is mainly used to prepare ultrafine powders of brittle materials.
1.Mechanical crushing
Mechanical crushing is under the action of crushing force, solid material block or particle deformation and then break, produce finer particles.
The basic crushing methods of materials are crushing, shearing, impact crushing and grinding.
The crushing limit depends on the material type, the way of mechanical stress application, the crushing method, the crushing process condition, the crushing environment and other factors.
Typical crushing equipment are: Raymond Mill, ball mill, mixing mill, air mill and colloidal mill ，pulverizer mill,grinding mill machine ,micro powder grinding mill.
Most Mechanical crushing is for mining. There are many types of Stone Crushing Equipments such as: gypsum grinding mill limestone grinding mill machine,bentonite powder Raymond Mill,ultra fine grinding mill.Right now, Raymond Mill is the cheapest and the most popular ultra fine grinding mill.
According to accumulation and experimental analyses of on-site test data for more than thirty years, HD, a Chinese Raymond Mill manufacturer, has researched and developed the fifth-generation pendulous hanging Raymond Mill – DBMX Raymond Mill. All non-combustible and non-explosive brittle mineral products whose Moh's hardness are below Grade 7 and water content below 6% could be ground by this Raymond Mill.
HD-DBMD Multistage Raymond Mill is a world leading tool for powder grinding. HD-DBMD Raymond Mill absorbs world first-class industrial powder milling technology and organizes the technical experts and related engineers for elaborate design, test and improvement.
Performance Advantages Of Raymond Mill
The main transmission device adopts sealed gear box and pulley, so the transmission is stable and reliable.
Imported high-quality steel is used for important parts. High-performance wear-resistant materials are used for the grinding parts.
A Raymond Mill covers a small area, and can complete powder preparation efficiently and the fineness of the finished product is uniform and the screening rate can be as high as 99%;
The advantages of mechanical comminution are large yield, low cost and simple process, and the mechanical and chemical effects are produced in the comminution process to increase the activity of powder.
The disadvantage is that the purity, fineness and morphology of the product are not as good as the ultrafine powder prepared by chemical method.
The method is suitable for industrial production in large quantities, such as deep processing of mineral products.
2.Ultrasonic pulverization
Ultrasonic vibration is used to break the solid material, usually by dispersing the crushed material in a liquid (usually water) medium, and then the ultrasonic generator is placed in the liquid medium.
Then the ultrasonic generator (principle, efficacy, performance of the crushed material applicable to it, etc.) is placed in the liquid medium.
The ultrasonic generator produces a strong high-frequency ultrasonic vibration, which can be transferred to the solid particles in the liquid. When the energy accumulated in the solid particles is enough to overcome the binding energy of the solid structure, the solid particles are crushed.
Ultrasonic pulverization can only pulverize loose solid particles.
It is mainly used for dispersing agglomerated ultrafine solid particles in liquid to make emulsion with good dispersibility.
Therefore, it is called ultrasonic dispersion system.
3.Thermal decomposition method
This method is a method to generate new solid materials by thermal decomposition of solid materials.
S is for the solid phase;
G is for the gas phase.
To prepare powder by thermal decomposition, equation (1) or (2) must be used.
The preparation of ultrafine powder by solid phase thermal decomposition method is simple in equipment and can be heated with general resistance. The process is also easy to control. However, it is generally limited to the preparation of oxides.
4.High temperature solid phase reaction method
Firstly, according to the composition of the powder to be made, the composition and dosage of the reaction material are designed. The commonly used reactants are oxides, carbonates and hydroxides.
The reactant is fully and uniformly mixed, then compacted into a blank body, and then synthesized by calcining at an appropriate high temperature. The clinker block is then ground to the required size by a pulverizing machine. This method is often used to prepare electronic ceramic raw materials with complex composition.
In the process of reaction, it is necessary to pay attention to two problems: first, the selection of materials as the starting material often has a great impact on the process conditions of the synthesis of products;
Second, the order in which reactants participate in the reaction also has a great influence on the final products.
The advantage of this method is that it is suitable for mass production and the cost is not high.
The disadvantage is that the particle size can not be too fine
