Liquid Two-step Restore Of New Technologies And Surface Modification Process, Preparation Of Ultrafine Copper Powder

Because of the special physical and chemical performances, the ultra-fine copper powder was widely used in many fields such as electrical field, conductive paint, catalyzer, lubricant additive and so on. There were many processes of preparation of the copper powder, while the reduction process of liquid phase has many excellences, such as the simple manipulation and equipment, low cost, tend to realize the industrialized production, so it became the main preparation methods of ultra-fine powder of the current laboratory and industrial. In this paper the spherical type of ultra-fine copper powders with the smaller particle size and distribution, electrical conductivity, density large, were prepared by liquid-phase chemical reduction process. Reducer A pre-reduction, two steps reducer B addition,surface modification and the performances of the ultra-fine copper powders were studied. The performance of the ultra-fine and the electrical copper powders were compared. The mechanism of preparation of the ultra-fine copper powders by two steps reduction process was showed, and the conclusions can be got as following:(1) Compared reducer A pre-reduction with the direct reduction method, the reducer A pre-reduction can improve the particle size, distribution and uniformity, and two steps reducer B addition can further improve the uniformity of size and be conducive to form spherical type powders.This is the key to preparation of spherical, uniform size ultra-fine powder. (2)In the reducer A pre-reduction process the temperature of the mixed, the concentration of reducer A and NaOH solution and the temperature of reaction system have great impact on the size of the powder prepared. In the two-step reducer B reduction process,the volume of reducer B, add the additive proportion of reducer B in the two steps and the reaction temperature have a greater impact on the size and density of ultra-fine powders prepared. The effect of the amount of dispersants on the size of the powders is little smaller, but it's bigger on the distribution of particle size and the shape of the powders.(3)①The better conditions of the reducer A re-reduction process is:The solution mixed temperature is 30℃; the concentration of reducer A is 2.0～2.5mol/L; the concentration of NaOH solution is 2.2～3.0mol/L; the reaction temperature of the system is 65～75℃.②The better two-step reducer B reductive preparation process condition is:The volume of the reducer B is 15～25ml; the additive proportion of reducer B in the two steps is:2:8～3:7;the reaction temperature:50～55℃; the amount of dispersants is 1.0～2.0g/L.(4) In this paper two processes were adopted for modifying the ultra-fine copper powders, which were the process of making silver or orgnic substance covered on the copper powders.The results showed that the ultra-fine powder modified by the two processes have the good anti-oxidation performance and according to their different advantages they can be used in different sides.(5) The study on the performance of ultra-fine copper powder indicates:The copper powders prepared by the process under the best conditions have good performances,such as good colour, similar spherical type, the size of about 1μm as well as the narrow size distribution, better conductivity and high density and the antioxidant capacity of room and high temperatures are good.(6)The study on the mechanism of the preparation process showed that:In the liquid phase two-step reduction method was equivalent to delay the growing time of Cu2O and separate the formation and growth period,it's better for the uniform size of the particles.In this process the spherical particle is the result of gathered and diffused pattern models. The growth of the copper crystal was controlled by the thermodynamics and dynamics.