Research of Copper Foam Prepared by Forming-Knitting and Infiltration

Using forming-knitting technology and organic materials, copper foam with high porosity (>80%) and open-pore structure was successfully prepared. According to the method of immersion, the technical characteristics of metal paste performance and influence factors of sinter process were discussed. The pore morphology and compressibility of copper foam were detected simultaneously, and the structural property of copper foam prepared by the process of once-infiltrating was compared with the one of copper foam prepared by the process of twice-infiltrating. The results show that pH value of metal paste has a large influence on rheological properties of slurry. By twice-infiltrating process, the microstructure of copper foam was altered. In case of the porosity dropping indistinctly, the compression stress of copper foam platform was raised from 0.5 MPa to 1 Mpa which was of great significance to improve the energy absorption capacity of the material.

Enhanced Pool Boiling Heat Transfer on Copper Foam Welded Surfaces

Enhanced pool boiling heat transfer of the porous structure is critical to the thermal management technology.In this paper,pool boiling heat transfer experiments are performed on copper foam welded surfaces in de-ionized water to investigate the effects of basic parameters of copper foam on heat transfer enhancement.Boiling phenomenon is observed to facilitate the understanding of enhancement mechanism.The results show that copper foam welded surfaces can significantly enhance the pool boiling heat transfer performance,reduce the boiling incipience temperature by 7-9℃,and reach two times heat transfer coefficient compared with smooth plain surfaces due to numerous nucleation sites,extended surface areas,and enhanced turbulent effect.Pore density and thickness of foam have two side effects on heat transfer.

Synthesis and characterization of copper foams through a powder metallurgy route using a compressible and lubricant space-holder material

In the present work,a compressible and lubricating space-holder material commonly known as "acrawax" was used to process Cu foams with various pore sizes and various porosities.The foams were processed without using binders to avoid contamination of their metal matrices.The lubricant space-holder material was found to facilitate more uniform flow and distribution of metal powder around the surface of the space holder.In addition,the use of acrawax as a space-holder material yielded considerably dense cell walls,which are an essential prerequisite for better material properties.The foams processed with a smaller-sized space holder were found to exhibit better electrical and mechanical properties than those processed with a coarser-sized space holder.The isotropic pore shape,uniform pore distribution throughout the metal matrix,and uniform cell wall thickness were found to enhance the properties pertaining to fine-pore foam samples.The processed foams exhibit properties similar to those of the foams processed through the lost-carbonate sintering process.

Experimental study and correlation development for the two-phase frictional pressure drop of flow boiling in copper foam fin microchannels

Flow boiling in microchannels with porous walls has received extensive attention in recent years. Compared with the emphasis on heat transfer, there is a lack of research on the effect of the porous wall structures on the pressure drop characteristics. In this study, systematic experiments are performed to measure the pressure drop of water-vapor two-phase flow in five microchannels with copper foam fins, which consist of nine or six channels and fins of copper foam. The porosities of the foam fins range from0.78 to 0.82 and ratios of fin width to channel width range from 0.5 to 2. The channels are approximately 0.5 or 1 mm in width and 1 mm in height. Both adiabatic and flow boiling experiments are conducted with water at mass fluxes ranging from 66 to 407 kg/(m^(2)s). In the adiabatic experiments, the average quality in channels is between 0.017 and 0.846. In the flow boiling experiments, the outlet quality of channels is between 0.040 and 0.863. Slug flow, churn flow, annular flow, and wispy-annular flow are observed in adiabatic experiments. A two-phase frictional pressure drop correlation based on the Lockhart-Martinelli model is developed for copper foam fin microchannels by introducing the effects of the mass flux, porosity, ratio of fin width to channel width, and heating condition step by step. The mean absolute percentage errors of the new correlation are 7.53% for 325data points under adiabatic conditions and 5.51% for 268 data points under flow boiling conditions, respectively. This work provides insight into the correlations of frictional pressure drop in microchannels with porous walls.

Flow boiling heat transfer in copper foam fin microchannels with different fin widths using R134a

Heat sinks of copper foam fin microchannels are developed to deal with cooling challenges.The heat sinks consist of fins made of copper foam and channels.The channels are 0.5 mm in width and 1 mm in height,and the fins are 0.5 and 2.0 mm in width.Flow boiling experiments are conducted using R134a at subcooled and saturated inlet conditions.The heat flux is between 22 and 172 W/cm^(2),and the mass flux ranges from 264 to 1213 kg/(m^(2)s).The influence of the quality,the heat flux,and the mass flow rate on the heat transfer coefficient is obtained.It is found that wider fin raises the heat transfer coefficient.A correlation is developed based on heat transfer mechanisms,and it predicts the experimental result with a 12%mean absolute error.Compared with a solid fin microchannels heat sink,the heat transfer coefficient of the copper foam fin microchannels is higher(up to 60%)when the heat flux is lower than 100 W/cm^(2).The copper foam fin microchannels may enhance the heat transfer coefficient and reduce the pressure drop at the same time.

A ZnO decorated 3D copper foam as a lithiophilic host to construct composite lithium metal anodes for Li-O_(2) batteries

Lithium metal batteries(LMBs) with a high theoretical capacity are seen as a type of the most potential energy storage system.Unfortunately,the growth of lithium dendrite,the irreversible side reactions,and the infinite volume alteration still curb the practical utilization of lithium metal anodes,resulting in low Coulombic efficiency(CE) and safety problems,etc.Herein,we synthesize a lithiophilic 3D copper foam host with uniformly distributed nano-flower-like ZnO particles(CuF/ZnO) and obtain the composite lithium metal anode containing the Li_(2)O,LiZn alloy,and pure Li by the infusion of molten Li(CuF/Li_(2)O-LiZn@Li).Benefitting from the advantages of the 3D structure of copper foam and the lithiophilicity of ZnO sites,the composite lithium metal anode can restrain the volume alternation and regulate the uniform deposition of lithium.The symmetrical cells of the composite lithium metal anode have a 1600 h long cycle life with a low polarization voltage of 15 mV,and the Coulombic efficiency can maintain about 97.8% at 1.0 mA·cm^(-2),1.0mAh·cm^(-2).

Control of the morphology of electrodeposited three-dimensional copper foam by tuning the pressure

Three-dimensional （3D） copper foams have been formed by electrodeposition at different nitrogen pressures and examined by scanning electron microscopy. The results indicate that an increase in system pressure leads to a decrease of the pore size of the copper foam due to the suppressed coalescence of hydrogen bubbles, while the thickness of the copper foam increases with decreasing pressure. Also, the walls around the pores on the copper foam consist of copper dendrites, and the copper dendrites are made up of copper grains with sizes less than 1 l.tm. The average sizes of the copper grains decrease with increasing system pressure. It has been demonstrated that copper foams with controllable 3D structure formed by electrodeposition at different pressures are comparable to those obtained by electrodeposition at normal pressure in the presence of specific additives.

Thermostability,mechanical and tribological behaviors of polyimide matrix composites interpenetrated with foamed copper

Polyimide matrix composites interpenetrated with foamed copper were prepared via pressure impregnation and vacuum immersion to focus on their thermostability, mechanical and tribological behaviors as sliding electrical contact materials. The results show that the interpenetrating phase composites（IPC） are very heat-resistant and exhibit higher hardness as well as bending strength, when compared with homologous polyimide matrix composites without foamed copper. Sliding electrical contact property of the materials is also remarkably improved, from the point of contact voltage drops. Moreover, it is believed that fatigue wear is the main mechanism involved, along with slight abrasive wear and oxidation wear. The better abrasive resistance of the IPC under different testing conditions was detected, which was mainly attributed to the successful hybrid of foamed copper and polyimide.

Stearic Acid/Copper Foam as Composite Phase Change Materials for Thermal Energy Storage

The application of stearic acid in the latent thermal energy storage(LTES) systems is hindered due to its lower heat transfer rate. Stearic acid(SA) was blended with copper foam(CF) of pore numbers per inch(PPI) of 5, 20, and 40 to prepare composite phase change materials via a molten impregnation method. The thermal physical properties including latent heat, phase change temperature, and thermal energy storage density of composites were characterized. The thermogravimetric analysis indicated that the loadages of SA of SA/CF(5 PPI), SA/CF(20 PPI), and SA/CF(40 PPI) were 74.69%, 71.03%, and 63.54%, respectively;The latent heat of SA/CF(5 PPI), SA/CF(20 PPI), and SA/CF(40 PPI) were determined to 139.9 J·g^-1, 132.7 J·g^-1, and 117.8 J·g^-1, respectively. Meanwhile, the infrared thermal images of SA and SA/CF composites were provided to demonstrate the thermal energy storage and dissipation capability intuitively by the temperature response and surface temperature distribution. The infrared thermal images indicated the addition of CF also reduced the fluidity of liquid SA, and the SA/CF(40 PPI) had better internal heat transfer uniformity and thermal diffusion performance than SA/CF(5 PPI) and SA/CF(20 PPI). All these thermal properties suggested SA/CF(40 PPI) has the potential application in the latent thermal energy storage.

Electroless copper plating on microcellular polyurethane foam

In order to obtain substrates with good conductive foam for high porosity foam metal materials used in the metal electrodes,the technique of electroless copper plating on the microcellular polyurethane foam with pore size of 0.3 mm was investigated.The main factors affecting the deposition rate such as the solution composition,temperature,pH value and adding ultrasonic were explored.The results show that the optimum process conditions are CuSO4 16 g/L,HCHO 5 mL/L,NaKC4H4O6 30 g/L,Na2EDTA 20 g/L,K4Fe(CN)6 25 mg/L,pH value of 12.5-13.0 and temperature of 40-50℃.Under these technical conditions, the process has excellent bath stability.Adding ultrasonic on the process can elevate the deposition rate of copper by 20%-30%.The foam metal material with a porosity of 92.2%and a three-dimensional network structure,was fabricated by electro-deposition after the electroless copper plating.

Effects of copper content on microstructure and mechanical properties of open-cell steel foams

The effects of copper content on the microstructural and mechanical properties of steel foams are investigated. Spherical urea granules, used as a water-leachable space holder, were coated with a mixture of iron, ultrafine carbon, and different amounts of copper powders. After the mixture was compacted and the space holder was removed by leaching, a sintering process was performed under an atmosphere of thermally dissociated ammonia. Microstructural evaluations of the cell walls were carried out using optical microscopy and scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy. In addition, compression tests were conducted to investigate the mechanical properties of the manufactured steel foams. The results showed that the total porosity decreases from 77.2% to 71.9% with increasing copper content in the steel foams. In the foams' microstructure, copper islands are mostly distributed in pearlite and intergranular carbide phases are formed in the grain boundaries. When the copper content was increased from 0 to 4 wt%, the elastic modulus, plateau stress, fracture stress, and fracture strain of manufactured steel foams improved 4.5, 6, 6.4, and 2.5 times, respectively.

调控聚氨酯发泡材料中的热分布控制高温体积收缩和泡孔结构

为解决在烤漆等高温环境下,车内发泡材料因体积收缩(空隙)而导致的阻隔、缓震作用失效及行驶风噪等问题,以高导热铜粉为改性填料、软质和硬质聚氨酯发泡材料为基体,制备并研究了不同的聚氨酯/铜粉复合材料。结果发现:铜粉含量不仅能有效控制发泡材料在高温下体积收缩现象,且泡孔尺寸和发泡密度也能得到提高;当铜粉含量达到4 wt.%时,软质和硬质聚氨酯发泡材料的体积收缩率分别降低为6.56%和1.77%,发泡密度分别达到0.106 g/cm^(3)和0.171 g/cm^(3),发泡材料的吸水率降低50%左右。因此,添加铜粉后的聚氨酯发泡材料具有防潮和低体积收缩特性。

泡沫铜对密闭管道内合成气爆炸特性影响的实验研究

为研究泡沫铜孔隙密度和H2体积分数对合成气爆炸特性的影响,在封闭的管道中安装了孔隙密度为15、25和40 ppi的泡沫铜,实验分析了当量比为1的合成气-空气在不同H_(2)体积分数时的火焰结构、尖端速度和超压等参数变化规律。实验结果表明:火焰在泡沫铜上游的行为是受“郁金香”火焰形成过程的影响,泡沫铜对其没有影响。但是孔隙密度和H2体积分数的改变不仅会影响“郁金香”火焰的形成时间,还会影响变形“郁金香”火焰的形成。泡沫铜将火焰分割促使其从层流向湍流转化,对爆炸火焰传播起到加速作用。泡沫铜会引起管道内超压和火焰尖端速度的极大提升,且孔隙密度越小,H_(2)体积分数越大,火焰穿过泡沫铜后的最大火焰尖端速度越大,压力上升幅度越大,超压峰值越高。

泡沫铜导离气泡强化流动沸腾换热实验研究

流动沸腾作为一种高效的换热方法,被广泛应用于高热流设备的冷却。在流动沸腾换热过程中可通过设置多孔疏水结构促进沸腾气泡脱离,为强化沸腾换热提供新思路。在截面为6 mm×4 mm的矩形通道顶部添加浸润角为140°的多孔泡沫铜;并在液相入口温度70、75和80℃,流速为6.94、10.42和13.89 cm/s的不同工况下,观测通道内沸腾两相流流型变化以及泡沫铜的吸气过程对流动沸腾换热性能的影响;基于气泡受力分析获得泡沫铜吸气强化流动沸腾的换热机理。结果显示,在本实验工况范围内添加脱气泡沫铜后,壁面过热度下降可达20.7%;泡沫铜的吸气率为0.81时,热通量可提高至152%;增大入口流速,泡沫铜强化效果显著增大,而入口温度对泡沫铜的吸气效果影响不明显。

盐水微滴/泡沫铜复合体系中甲烷水合物生成动力学研究

提高海水水合储气速率和储气密度对水合物技术规模化应用至关重要。将一定浓度的NaCl溶液与疏水性气相纳米二氧化硅高速搅拌分散成微米级盐水微滴。8.0 MPa、274.15 K条件下,利用不同硅含量的盐水微滴进行水合储甲烷实验,研究甲烷水合物生成动力学特性。结果表明,硅含量2.5%(质量分数)的盐水微滴分散性和储气性能最佳,储气量达141.01 cm^(3)·cm^(-3),储气速率达7.37 cm^(3)·cm^(-3)·min^(-1)。进一步将该硅含量盐水微滴填充至开孔泡沫铜中,构建盐水微滴/泡沫铜复合水合储气体系。研究发现,泡沫铜三维巢状金属骨架能显著加速水合反应热的转移,提高微滴水合储气性能。5.0~8.0 MPa下,相较于盐水微滴单一体系,复合体系水合储气量提高4.72%~21.70%,最大储气速率提高38.25%~110.58%。

具有光电双驱动的柔性硫化铜/密胺泡绵的制备及性能研究

通过化学沉积法在密胺泡绵骨架上生成硫化铜,制备出具有光热、电热性能的硫化铜/密胺泡绵复合材料。研究表明,在低电压(1~4V)的驱动下,硫化铜/密胺泡绵复合材料表面饱和温度可达30~145℃,并且在功率为0.2~1.4W/cm^(2)的激光下材料表面可以实现30~160℃的温度变化。硫化铜/密胺泡绵优异的光热和电热转换性能使其可用于除冰和海水淡化,并将在全天候便携式的可穿戴加热器方面具有巨大的应用前景。

表面负载还原氧化石墨烯对泡沫铜热扩散系数的影响

为研究及提升泡沫铜的热扩散性能,利用不同溶剂制备氧化石墨烯混合溶液,通过机械沉积(GO-无水乙醇-丙酮混合溶液沉积)、电沉积(GO-CuS4O混合溶液电沉积、KH550改性GO电沉积)两种不同的沉积方法将氧化石墨烯(GO)附着到经过预处理的泡沫铜表面,后通过高温还原法去除氧化石墨烯表面多余的含氧基团,将其还原为还原氧化石墨烯(rGO),研究材料热扩散性能及泡沫铜表面rGO的存在状态。研究结果表明,通过GO-无水乙醇-丙酮混合溶液沉积的泡沫铜表面沉积层最为均匀完整,经高温还原后性能提升也最为明显,其低温热扩散系数由纯泡沫铜的29.06 mm^(2)/s提高为56.81 mm^(2)/s,提升了95.5%。与热扩散系数为50.26 mm^(2)/s的T2铜片相比,其热扩散系数亦提高13.09%。GO在泡沫铜表面的沉积方式对沉积效果影响显著,GO经过高温还原为rGO后均可以有效提升泡沫铜的热扩散性能。

铜尾矿/聚磷酸铵阻燃聚氨酯的制备及研究

以聚磷酸铵(APP)/铜尾矿(CTS)为阻燃体系,采用一步全水发泡法制备硬质聚氨酯泡沫/聚磷酸铵/铜尾矿(RPUF/APP/CTS)复合材料。阻燃测试表明,RPUF-30APP的极限氧指数(LOI)达到24.0%,垂直燃烧测试达到V-0级别,其阻燃性明显提高。锥形量热测试表明,RPUF-30APP的热释放速率峰值(PHRR)由纯样的300.5 kW/m^(2)降低至139.4 kW/m^(2),下降幅度高达53.6%;总热释放(THR)由纯样的40.0 MJ/m^(2)下降至28.1 MJ/m^(2),降低幅度高达29.8%,表明APP/CTS体系明显降低复合材料燃烧过程中的热释放,其火灾安全性提高。炭渣分析表明,CTS/APP/RPUF复合材料燃烧过程中形成了致密的炭层,提高了复合材料的阻燃性能。该研究为CTS提供了一个新的应用领域,并为提高聚合物的防火安全性铺平了道路。

石墨烯增强铜基复合材料的制备及性能研究

以三维泡沫铜为基体,采用化学气相沉积得到石墨烯铜复合体,同时解决了石墨烯在铜基体中分散性和界面结合问题,再用铜粉填充泡沫铜孔隙,然后真空热压制备石墨烯增强铜基复合材料。探究了石墨烯对铜基体复合材料导电性及拉伸性能的增强效果。研究发现,石墨烯对铜基体性能有明显增强作用,在50 sccm甲烷通量下15 min时沉积的石墨烯性能增强效果最佳。热压制备的石墨烯增强铜基复合材料的导电性能达到86.2%IACS,抗拉强度提高到338 MPa,屈服强度也达到214 MPa。

部分填充金属泡沫对蓄冰球凝固性能的影响

为了提高蓄冰球的储能效率,解决相变材料(PCM)导热率低引起的换热效果差的问题,向相变材料中添加高导热的金属泡沫以加速固液相变过程。采用数值模拟的方式,对金属泡沫填充后蓄冰球综合性能进行分析。结果显示:金属泡沫全填充节省了超过81%的凝固时间;外向内填充方式下,综合性能最佳的填充半径比为9/13。