石墨烯纳米片对AgCuTi钎料熔点与润湿性的影响

采用球磨法在AgCuTi钎料中添加不同质量分数的石墨烯纳米片(GNSs)制备出复合钎料,利用差示扫描量热仪(DSC),SEM以及XRD等方法研究了微量的石墨烯纳米片对AgCuTi钎料微观形貌、熔点以及在蓝宝石表面润湿性的影响. 结果表明,球磨法对GNSs-AgCuTi复合钎料的物相没有影响,石墨烯均匀地分散在AgCuTi颗粒周围;复合钎料熔点随着石墨烯含量的增加而降低,当石墨烯含量为0.5%,熔点降低了3.2 ℃;微量的石墨烯,改善钎料在蓝宝石表面的润湿性,0.3%GNSs-AgCuTi复合钎料的润湿角减小了4.4°,铺展面积增加了10 mm2,而过多的石墨烯也使得复合钎料的润湿性变差;石墨烯与元素Ti反应生成TiC,复合钎料与蓝宝石界面反应产物为Ti₃Cu₃O相.     

基于气泡动力学分段调控浸润性强化核态沸腾

基于多孔或微结构表面润湿性改性的核态沸腾强化传热,已得到广泛研究。利用CFD-VOF数值模拟方法,针对单晶硅微柱表面单气泡的生长及脱离过程,进行表面浸润性分段调控,实现气泡沸腾换热的全程强化。分别调控初始接触角为48°、60°、90°和110°后,同一时刻 （t = 0.152 ms） 变接触角为20°,对比研究分段调控浸润性对气泡动力学过程与表面换热性能的影响。结果表明：疏水性可提高气泡生长速率,增强微柱表面对气泡的黏附力,促进气泡在微结构缝隙内的横向铺展;t = 0.150 ms时接触角为110° 表面上气泡与底面接触面积增加1.3倍,微层蒸发功率增加1.2倍。需要指出的是,毛细效应随颗粒粒径变化趋势受到多孔介质复杂孔隙结构特征的影响。在当前粒径范围内,认为其具有正相关关系,但在更大范围内的对应关系,还需要在未来进一步深入揭示。     

Effect of surface curvature and wettability on nucleation of methane hydrate

Natural gas hydrate nucleation is a complex physical and chemical process that is not well understood presently. In this article, an improved thermodynamic model is proposed to analyze the effects of surface curvature and wettability on methane hydrate nucleation for the first time. The results indicate that methane hydrate nucleation is more difficult on hydrophilic curvature surfaces under the same conditions, with a larger critical nucleation radius and required energy barrier than on hydrophobic surfaces. Furthermore, a convex surface is more favorable for forming methane hydrate under the same conditions than a concave surface. The model's results are critical in elucidating the microscopic mechanism of methane hydrate nucleation and providing a theoretical foundation for developing technologies for strengthening and inhibiting hydrate formation.     

纳米结构表面液体沸腾传热的分子动力学模拟

为了从纳米尺度了解表面结构和润湿性对池沸腾液体与固体壁面的传热性能,本文采用分子动力学方法研究了超亲水至超疏水不同润湿性的液体氩在光滑表面和含凹、凸半球纳米结构表面的沸腾传热过程,分析了三种表面上液氩在受热过程的形态、温度、热流密度等相关参数的变化情况。结果表明,液氩层沸腾过程大致可分为液氩层吸附于固体表面和液氩层从壁面脱离两个加热阶段,当液氩层吸附于固体表面时,温度升高、热流密度及气态氩原子产生速度均大于液氩层脱离壁面时的情况,在这两个阶段亲水表面上氩原子温度变化有明显的拐点,而疏水表面在两个阶段加热过程相差不大。亲水表面上的微结构能吸附更多液氩原子,促进了气泡产生及加速温度、热流密度的变化,而在疏水及超疏水微结构表面,微纳结构与液氩间的气膜层促进了气泡产生,计算结果为池沸腾传热及微结构选择提供了理论依据。     

Wettability reversal of reservoir rock surface through surfactant stabilized microemulsion

In the process of the tertiary recovery of oil and gas resources, it is necessary to use external fluids to displace the crude oil in the reservoir. Whether the crude oil on the surface of the rock can be effectively displaced and the wettability of the rock can be changed to avoid re-adsorption by the crude oil is directly related to the level of oil recovery. Therefore, it is critical to study the cleaning and wettability reversal of reservoir rock surface. Because microemulsions have outstanding performance in changing the wettability of rocks and solubilizing crude oil, this paper uses cetyl trimethyl ammonium bromide (CTAB) as a surfactant and n-butanol as a co-surfactant to prepare microemulsions. The performance of microemulsions with different microstructures on the cleaning and wettability changes of crude oil on the rock surface were studied. The results show that the water-in-oil (W/O) microemulsion has good cleaning efficiency, and the oil removal rate on the sandstone core surface can reach 79.65%. In terms of changing the wettability of the rock surface, W/O, bi-continuous phase (B.C.) and oil-in-water (O/W) microemulsions can change the core surface from lipophilic to hydrophilic. And the effects of the B.C. and O/W microemulsions are more obvious. The microemulsion system that was prepared based on cationic surfactants has a good application prospect in changing the wettability of the reservoir and cleaning the adsorbed crude oil.     

Effects of Bi and rare earth metal on the microstructure and properties of Zn-based high-temperature solder

A novel Zn-based high-temperature solder was developed to join copper/steel at moderate temperature. The effects of Bi and rare earth metal on the microstructures, wettability of solders as well as the mechanical properties of solder joints were investigated. The results indicated that with the addition of Bi into Zn-Cu-Sn (ZCS) alloy, significant improvement in wettability is realized. When the content of Bi element is 1.5 wt. % in the solder, the spreading area researched over 200 mm². Further more, with the addition of RE, refined primary ε-CuZn₅ phases were formed and the shear strength of the solder joint was largely improved.     

In对Sn9Zn钎料润湿性能的影响

为了提高Sn9Zn共晶钎料的钎焊性能,通过合金化的方法添加了少量元素In,制备了Sn9Zn-xIn钎料。从钎料合金的熔化特性、润湿特性、界面显微结构和母材粗糙度这四个方面评价了不同In含量对Sn9Zn钎料润湿性能的影响。试验结果表明:少量元素In的添加可以降低钎料的熔点;随着In含量的增加,钎料的润湿力增大,润湿时间缩短,润湿性有明显提高;In含量增加,润湿界面层中Cu5Zn8化合物层厚度增加;对母材表面进行毛化处理,通过改变母材表面的微观几何结构,增大钎料与母材的相对接触面积,从而改善钎料的润湿性能。     

低银Sn-0. 45Ag-0. 68Cu-X 无铅钎料性能的对比研究

目的制备一种新型低银亚共晶Sn-0.45Ag-0.68Cu-X(SAC-X)无铅钎料,并对其综合性能进行探究。方法参照国家标准,对其漫流性、润湿性及力学性能进行了测试,并与Sn-37Pb,Sn-0.7Cu,Sn-3.5Ag-0.6Cu钎料进行了对比。结果 4种钎料漫流性和润湿性大小依次为:Sn-37Pb,Sn-3.5Ag-0.6Cu,SAC-X,Sn-0.7Cu,其中SAC-X钎料铺展率达78.5%,润湿时间为1.3 s,最大润湿力为3.18 m N;SAC-X钎料抗拉强度(40 MPa)与高银Sn-3.5Ag-0.6Cu钎料(44 MPa)相差不大,但延伸率是高银Sn-3.5Ag-0.6Cu的1.89倍。结论低银SAC-X钎料综合性能优良,与Sn-3.5Ag-0.6Cu钎料相差不大。