Research on the production of leafing aluminum powder

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In the production of leafing aluminum powder process, the revolving speed of ball mill should be confirmed firstly. When the revolving speed is low, the grinding medium will rise to a low height along with the ball mill cylinder, which means that it will fall along the cylinder wall or the ball mill will rotate in its main line; when the revolving speed is too high, the grinding balls will absorb closely to the cylinder wall and both of them will move circularly under the effect of centrifugal force. However, the optimum efficiency of ball-milling cannot be achieved under these two kinds of conditions. After the revolving speed is confirmed, the ratio of medium that have different diameters can have important effect on the flakiness formation and grinding of aluminum powder. When the grinding ball rises to a certain height along with the cylinder wall, it will detach from the cylinder wall and fall in parabola. By this time, the grinding ball will reach its most effective travel in the ball mill and has biggest impact force. The large aluminum powder will be grinded into flakelet ones by repeatedly squeezing the grinding balls that have bigger diameters and those small diameter ones and eventually form the finished products. In addition, grinding aid will also has certain effect on the flakiness formation of aluminum powder, which can speed up the velocity and process of the flakiness formation of aluminum metal powder.

aluminum nanopowder

Rotational speed, also known as the critical speed of rotation, is started when the ball mill begins its centrifugal movement. According to the formula, the critical speed of rotation will become lower when the swing diameter of the grinding ball in the ball mill is larger. As the grinding ball in the outmost layer of cylinder wall has large swing diameters, its products will have low centrifugal critical speed; while as the grinding ball in the innermost layer of cylinder wall has small swing diameters, its products will have high critical speed. It is obviously that by using the critical speed of inner layer as the revolving speed of ball mill, the grinding balls in the ball mill cavity will all move centrifugally and will not have grinding effect at this time; when the critical speed of outer layer is used as the revolving speed of ball mill, the grinding balls in its inner layer will all in centrifugal state. It seems that both of the above two standards are unreliable. According to the practical experiment conditions as well as the basic production principle and experiences, the best ball milling effect can be achieved by grinding the powders at the ball mill revolving speed of 130r/min in the first 10 hours and 120r/min in the later 4 hours.

The technological process

Put 300 mesh spherical aluminum powders, 200# paint solvent, grinding aid and 5# steel ball into the roller and close it; put the roller on the rotary mill, grinding it at the revolving speed of 130r/min in the first 10 hours and continuously grinding it at the revolving speed of 120r/min in the later 4 hours. After the grinding process is finished, filter the steel ball and use vacuum filtration machine for the pumping filtration of aluminum powder liquid. As aluminum is a kind of very active metal and is extremely easy to oxide as well as due to the limited experiment conditions, this experiment generally uses natural drying at shade place that has normal temperature and ventilation condition. Afterwards, screen the leafing aluminum powders timely and send the standard products for further check and analysis. By testing the grinded aluminum powder via SEM electron microscope, we can see that this kind of aluminum powder will have 0125-0129 loose specific weight as well as have good floatability and bright color.

In conclusion, the leafing aluminum nanopowder can be grinded and produced by filtering, drying and screening the aluminum powder before grinding it about 14 hours under the ball material ratio of 40:1, stearic acid added, auxiliary material ratio of 1:25 and grinding medium material ratio of 2:1. It is visible that wet milling roller machine process is workable in producing leafing aluminum powder. It is noteworthy that wet milling roller machine process applied in the experiment can only produce small amount of products that are enough for experiment research and is still needed to be improved so as to form batch production.