Experimental Study On Ultrafine And High Pure Copper Powder Prepared By High-pressure Hydrothermal Reduction

The ultrafine copper powder could be used to instead of MLCC precious metal electrode base on its superfine powder of small size effect,quantum size effect,surface effect and macroscopic quantum tunneling effect.And it also can be widely used in in the manufacture of conductive coatings,advanced lubricant additives,catalysts and nano copper materials.The fabricate of ultrafine copper powder is mainly focus on vapor deposition,electrolysis and mechanical technology,liquid phase reduction technology and so on.Nevertheless,these methods are both difficult to overcome in the aspects of product purity,particle size,production cost,reducing efficiency and environmental protection.Thus,this article introduce the high pressure hydrothermal reduction technology for the fabrication of the ultrafine copper powder.In a high-pressure reactor,microcrystalline cellulose is used as reducing agent,the fabrication of the ultrafine copper powder by hydrothermal reduction.The technique hold the advantages of no pollution to the environment,the product of high purity,uniform particle size distribution and good dispersion properties compare with others.The reaction mechanism of copper oxide cellulose hydrothermal reduction was studied.For the reaction temperature and reaction time,reducing agent dosage,catalyst dosage,liquid-solid ratio and stirring speed on the copper product purity,phase composition,microstructure and particle size distribution effect,the techniques such as X-ray diffraction(XRD),scanning electron microscopy(SEM)and laser particle size distribution measurement instrument were used.And the dynamic analysis of high pressure water and heat on the copper oxide reduction process was also studied.(1)The microcrystalline cellulose can be decomposed into lower carboxylic acids,aldehydes and ketones product in alkaline solution,and further hydrolysis and release of H· form of heat medium water reduction,reduction in the water heat medium by CuO-Cu2O-Cu process step by step.(2)The best quality of ultrafine copper powder could be fabricated in the ratio of microcrystalline cellulose and CuO and NaOH is 6:5:5,the reaction temperature is220 ?,the reaction time is 2h,The ratio of liquid to solid 4:1,speed of 300r/min,can be prepared for high purity pure copper powder more than 99%.(3)The kinetics of hydrothermal reduction process showed that the apparent activation energy of CuO reaction was E=65.996kJ/mol,and the reaction process was controlled by chemical reaction.(4)The micro morphology of the material and the product showed that the particle size of CuO was 4.28×10-6m,which was polygonal crystal structure.The formation of spherical Cu particles on the surface of CuO crystal gradually with the hydrothermal reduction process.(5)With the increasing of reduction temperature,the particle size decreases,theparticle size tends to be uniform,and the distribution becomes narrow.When the reaction temperature is 215~230?,the average particle size of Cu particles is 2.3~2.4×10-7m.