Design And Fabrication Of Superhydrophilic Copper Based Micro/Nanostructure Surface And Boiling Heat Transfer Performance Study

With the development of microminiaturization,integration and high power of electronic devices,the reliability and safety of microelectronic devices caused by high heat flux are facing severe challenges.At present,the heat dissipation problems of microelectronic devices are mainly manifested in the excessive local heat flux density and the easy accumulation of heat in the local area,which results in the excessive local temperature and uneven temperature distribution.Therefore,there is an urgent need for high heat flux heat dissipation technology in small-scale space.How to use existing or newly developed micro-nanofabrication technology to design and develop high-efficiency boiling heat transfer interface materials has become the focus of current research.As a liquid-gas phase transition process,boiling heat transfer can achieve efficient heat transfer,so it is widely used in thermal management,heat dissipation of electronic devices and other industrial field.Copper Micro/nanostructures for enhancing boiling heat transfer performance has advantages of high specific surface area,excellent thermal conductivity,good wettability and extremely high potential nucleation site density.Taking this as a starting point,the copper microcavities/nanocones structure with high thermal conductivity and the flower-like copper-nickel micro-nano composite structure were constructed in situ on the surface of the copper specimen to enhance boiling heat transfer performance.The mechanism of high efficiency boiling heat transfer was also analyzed.This study is of great significance for understanding the structure-property relationship between micro-nanostructure and boiling heat transfer performance.At the same time,it provides a new idea for developing high performance boiling surface and realizing high efficiency utilization of energy.Micropore/nanocone composite structures were prepared on the surface of copper specimen by one-step electrochemical deposition.The micro-nano porous copper film consists of copper nanocones and microcavities composed of copper nanocones;this irregular and open microcavities are interconnected,forming a unique micro-nano porous structure.Compared with flat copper surfaces,the advantages of this structure for boiling heat transfer performance are as following:artificial microcavities can provide far more nucleation sites and reduce the onset of nucleation boiling;the introduction of this tapered structure helps to accelerate the growth and transport of bubbles,while the nanotips helps bubbles to quickly detach from heated surface and increase the renewal frequency of bubble.The increase of surface wettability is beneficial to liquid rewetting,preventing surface sintering and the forming of vapor film.Because of these unique effects,it has excellent boiling heat transfer performance:the onset of nucleate boiling is 8 K,the critical heat flux density and heat transfer coefficient are 272 W cm^-2 and 105kW m^-2 K^-1,respectively.Compared with the smooth surface,the starting point of nucleate boiling decreased by 32%,while the critical heat flux and heat transfer coefficient increased by 64%and 147%,respectively.Nickel nanocones were electrochemically deposited on copper nanocones to prepare copper-nickel flower-like structures for enhancing boiling heat transfer performance.We found that compared with the single copper nanocone,this flower-like structure can further increase the critical heat flux by increasing the specific surface area and capillary capacity,and the maximum critical heat flux is284 W cm^-2.The onset of nucleate boiling is further reduced to 7 K due to the increase of nucleation sites,and the maximum heat transfer coefficient is 147 kW m^-2K^-1 due to the increase of the number of energy exchange centers.Compared with the flat surface,onset of nucleate boiling decreases by 68%,the critical heat flux increases by 71%,and the corresponding maximum heat transfer coefficient increases by 250%.Compared with the single porous copper nanocone structure,its boiling heat transfer performance also increased slightly:the onset of nucleate boiling decreased by 14%,the critical heat flux increased by 5%,and the corresponding maximum heat transfer coefficient increased by 35%.