Recovery Of Copper In Used Copper Clad Laminates And Its Use In Enhanced Heat Transfer

After entering the 21 st century,China has achieved rapid development in information technology and industrial technology.The speed of research and development,use,and disposal of electronic products has been greatly accelerated,with the consequent increase in electronic waste electronic products.If we do not deal with it properly,they will be extremely harmful to the environment where we live.Therefore,it is very important to properly recycle and reuse valuable resources in electronic waste.Copper clad laminates are very important substrates for scrap circuit boards and contain most of the metal copper.As a non-ferrous metal closely related to human production and life,copper is widely used in various fields.Since the exploitation of copper resources was reduced in our country,it is of great theoretical significance and practical value to effectively recycle this part of metal copper for environmental pollution and sustainable development.This article focuses on the reuse of metallic copper purified from scrap copper clad plates as the research object.Leaching copper ions through the microbial method,and then recovering high-purity copper sulfate by using the crystallization method.Followingly,hydrothermal method was used to prepare nano-coppers with different morphologies,and nanocomposites were prepared with dimethicone to investigate their enhanced heat transfer properties.In addition,nano-copper oxide was further synthesized to investigate the effect of copper oxide nanowires on the enhanced heat transfer performance of nanofluids.At the same time,the models and mechanisms of thermal conductivity and viscosity were analyzed in depth.The main contents and results are as follows:(1)High purity copper sulfate was recovered by microbiological crystallization method,and spherical and linear copper nanoparticles were prepared by hydrothermal method.(2)Dimethicone was used as the matrix to fill spherical and linear nano-copper,and nano-copper/dimethicone nanocomposites with different volume fractions were prepared.The effects of different morphology of nano-copper and filling volume fraction on the thermal conductivity of composites were explored,and a theoretical model was established to explain the principle of thermal conductivity enhancement.The study found that the thermal conductivity of dimethicone is as low as 0.15 W/mK.Due to the high thermal conductivity of the fillers,the thermal conductivity of the composites increases with the addition of copper nanowires(CuNWs)and copper particles(CuNPs).The thermal conductivity of composites depends on the size and shape of the copper nanoparticles.The thermal conductivity of CuNPs and CuNWs dimethicone composites was 0.25 W/mK and 0.41 W/mK,respectively.At a filling volume fraction of 10%,which indicates that CuNWs have higher thermal conductivity than CuNPs under certain conditions.The thermal conductivity of CuNPs and CuNWs increased by 66.7% and 173.3%,respectively,compared to the dimethicone matrix.(3)CuO nanospheres and CuO nanowires were synthesized by hydrothermal method and thermal oxidation method.The morphologies and crystal structures of the samples were analyzed by characterization.Meanwhile,nanofluids were prepared with dimethicone as the base fluid.The influence of CuO nanowires on the thermal conductivity of nanofluids was investigated and verified.The effect of filling volume fraction and the shape of particles to the thermal conductivity and viscosity were studied while the thermal conductivity,viscosity model and mechanism were analyzed in detail.The experimental data show that the thermal conductivity of nanofluids increases with the increase of the volume fraction of CuO nanowires or CuO nanospheres,which almost exhibits a linear relationship.When nanofluids were added with 0.75 vol.% CuO nanowires,the thermal conductivity increased by 60.78%,much higher than that of spherical CuO.The nanofluid presents a typical Newtonian behavior,and the measured viscosity of the CuO nanowires nanofluid only increased by 6.41% at 0.75 vol.%.