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10 factors influencing the preparation of ultrafine quartz powder by ball millin

From : clirik    Date : 2019-01-12 15:59

Ultra-fine quartz powder is a kind of high-quality neutral inorganic filler. It has strong acid resistance, stable physical and chemical properties, good light transmission, high dielectric, high humidity resistance, radiation resistance, excellent high temperature resistance and high Low purity, low expansion, low stress and other properties, widely used in plastics, rubber, paints, coatings, ceramics, inks and catalytic and gas filtration materials. Moreover, ultra-fine quartz powder is also a functional material, and it has a broad application prospect in combination with new functional materials. Therefore, the development of ultra-fine quartz powder has practical significance.
Preparation of ultra-fine quartz powder requires the use of a variety of mechanical equipment, including: ball mill, vibration mill, agitator mill, jet mill, high-speed impact mill, colloid mill, etc. and as a matching equipment for fine grading equipment. Among them, the high-energy ball milling method requires less equipment and simple process for preparing ultra-fine quartz powder, but there are many factors that affect the composition and performance of the final product. Among them, raw material properties, ball milling strength, ball milling environment, ball milling atmosphere, ball ratio, ball milling time and ball milling temperature are the main factors.
(1) The influence of the nature of the raw materials. The composition of the material system and the ratio of each component are the material basis for determining the composition of the final product. Different raw material compositions and group distribution ratios give different ball milling products even under the same ball milling conditions.
(2) The influence of ball milling strength. The high-speed high-frequency impact collision of the grinding medium on the high-energy planetary grinding is beneficial to the energy conversion and the transport and diffusion of molecules, atoms and ions. Ball milling strength has an important influence on the formation of mechanically alloyed amorphous. When the strength is low, the powder forms amorphous for a long time, and even cannot form amorphous; when the strength is high, the time for forming amorphous is greatly shortened, and the range of the amorphous component is expanded, and when the ball milling energy is high to a certain extent It is more desirable to form a stable compound rather than an amorphous one. For multi-component oxide systems with high hardness and strength, because the valence bond is firmer, the bond energy is higher, and the ball milling strength is low, it is impossible to cause lattice distortion, distortion, etc., which means no mechanical force. chemical reaction.
(3) The impact of the ball mill environment. For the grinding of inorganic non-metals, there are usually two methods of grinding by dry method and wet method. The dry method is simple, and the wet method can often obtain a smaller particle size of the milled product. However, the time for wet grinding to produce a phase change is much higher than that of the dry method. This is because the wet friction coefficient is small, the interface energy of the particles in water is smaller than the surface energy in the air, and thus it is difficult for the powder particles to accumulate enough. Energy to overcome the activation barrier required for phase transitions. When the dry grinding is to a certain extent, the occurrence of phase transition is almost inevitable. The internal structural changes of mechanically induced materials usually require that the particle (grain) size and free energy reach the limit, while in the wet grinding environment, the dissolution and "reconstruction" of the fractured surface, good lubrication and cooling environment are hindered. The particle size and free energy reach the limit, which hinders the occurrence of polycrystalline transformation.
(4) The influence of slurry concentration. In the process of wet ball milling, the slurry concentration is also an important process parameter, which is directly related to the particle size and ball milling efficiency of the powder. It can be seen from the experiment that the ball milling effect is getting better with the increase of the slurry concentration, but when the slurry concentration reaches a certain value, the influence of the ball milling time on the particle size of the powder becomes smaller.
(5) The influence of the size of the grinding media. In high-energy ball milling, small-sized carbide balls or zirconia balls, alumina balls, etc. are used because the small-sized balls are advantageous for increasing the friction area between the grinding medium and the material.
(6) The influence of the ratio of the material to the ball. In order to achieve higher ball milling energy, a much smaller ball ratio than conventional ball mills is typically employed. When the amount of charge and the size of the ball are constant, the mean free path of the ball motion depends on the amount of ball loaded. When the ball loading amount is too small, the material ball ratio is too large, and the chance of grinding the material is reduced. Conversely, when the ball ratio is too small, the average free path of the ball is reduced, and the mechanical force cannot be fully utilized, thereby reducing the mechanical reaction of the mechanical force. degree.
(7) The influence of ball milling time. The length of the milling time directly affects the composition and purity of the milled product. MA amorphization and crystal transformation of some metals or alloys are only carried out within a certain time range. When the grinding time is too short, the internal energy concentration of the material is too small to destroy the bond valence bond; the grinding time is too long. Other chemical changes may occur. For mechanical chemical synthesis of inorganic non-metallic materials, ball milling is usually required for a longer period of time.
(8) The effect of the ball milling rate. The effect of ball milling speed on product particle size is similar to the effect of ball milling time.
(9) The effect of grinding aids. Grinding aids are chemical substances that can significantly improve the pulverization efficiency and reduce energy consumption during powder preparation, mainly surfactants, dispersants, and the like. Adding a small amount of grinding aid during ball milling can improve the efficiency of ball milling.
(10) The effect of temperature. During the grinding process, the temperature of the powder will increase due to the friction and impact of the ball mill on the powder. The local temperature rise is beneficial to the solid phase reaction, but the increase of the overall temperature will aggravate the agglomeration between the materials and the grinding ball and the wall. Adhesion, when grinding certain organic substances, too high temperature will cause it to decompose. It is generally believed that the temperature rise of the powder during grinding should not exceed 350K.

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