渗透探伤中金属价电子对渗透作用的影响

从分子间作用力观点,阐述了金属渗透探伤过程中渗透液分子极性对金属固体润湿接触角和毛细管现象的影响.     

Au-30%Si合金熔体与石墨的润湿性及铺展动力学

采用改良座滴法在真空条件下研究Au-30%Si(摩尔分数)合金与石墨在1373~1473 K温度范围内的润湿性及铺展动力学。结果表明:随着温度升高,该体系润湿性得到改善,T=1373 K时,体系终态接触角高达100°,呈不润湿;当T≥1393 K时,随着温度的升高,接触角的变化速率明显加快,接触角减小至16°,呈现良好的润湿性。界面反应产物SiC的形成使得固/液界面能不断降低,为润湿铺展提供驱动力。通过建立新的反应润湿动力学模型,从能量角度阐述润湿铺展机制,预测体系固/液界面能随反应时间的延长呈指数关系降低。在反应控制阶段,理论计算与实验结果一致。     

不同润湿性液体在粗糙表面的润湿滞后现象

润湿滞后是表征液体脱离固体表面难易程度的核心参数。为了研究不同润湿性状态下的润湿滞后现象,在定量描述固体表面粗糙度的基础上,首次在3种不同粗糙度固体表面上对强亲水到疏水范围内的液体进行系统的Wenzel接触角及润湿滞后实验,在通过Wenzel理论及静摩擦力理论验证座滴法与体积法实验结果准确性的前提下,进一步研究不同润湿性状态下杨氏接触角、粗糙度与润湿滞后之间的定性关系。结果表明:固体样品1(固体表面粗糙度,r=1.15)的润湿滞后效应在不同润湿状态下保持一常数,而固体样品2(r=1.64)及固体样品3(r=2.29)的润湿滞后效应在θ_e=90°附近达到最大,随着亲水和疏水程度的增加,润湿滞后效应均不断减小;粗糙度与润湿滞后的关系也并不单调,在亲水状态下,润湿滞后效应随着粗糙度的增加而减小,而在中性润湿状态下未发现明显规律。     

界面反应对铝熔体与Si3N4多孔陶瓷界面的润湿作用

应用界面润湿理论从热力学角度计算了铝熔体和Si3N4陶瓷存在界面反应时的润湿角;通过测量不同浸渗时间下浸渗厚度,结合浸渗动力学模型,获得实际浸渗过程中铝合金熔体与Si3N4多孔预制体之间润湿角,并将该试验结果与上述理论计算结果相比较.研究表明:Al/Si3N4界面反应过程对熔体与预制体的润湿起到重要作用;应用界面润湿理论计算得到T=1223 K(950℃)时,Al/Si3N4界面实际接触角θ值为60.2°,界面反应对界面接触角的贡献达到47.6°,计算结果与浸渗动力学试验吻合.     

基于MATLAB分析不同形貌对金属表面润湿性能的影响

目的 研究不同形貌的微结构表面对金属表面润湿性能的影响。方法 首先在金属材料表面建立一级与二级微结构模型,然后整理得出不同微结构模型评定参数的公式,最后利用Matlab对不同形貌表面相关公式进行模拟计算,绘制得到不同形貌表面润湿特性三维曲线。结果 一级微结构中,球形微结构模型表面表观接触角θ皆为定值,即完全润湿θc=74.443°,不完全润湿θw=131.720°。其余微结构模型利用Matlab模拟计算,均可以得到光滑的三维曲线,其中在铜基表面设计制备三维方柱阵列微结构,可获得超疏水特性。二级微结构中,比较完全润湿状态,不完全润湿状态粗糙因子f远小于Υ。在不完全润湿状态中,粗糙因子f趋近于0,与完全润湿状态模拟的表观接触角结果相比,不完全润湿状态下,采用三维阵列微结构研究金属表面微结构对表观接触角的影响最为合适。结论 模拟条件相同的情况下,改变金属表面微观形貌会引起润湿性能的改变。金属表面润湿性能与表面微细结构以及微结构参数均存在映射关系,但是表面微结构的维度并非越高越好,一级微结构同样也可以得到所需疏水性能。在外在影响因素相同的条件下,若要研究分析金属表面微结构参数的改变对表观接触角的影响,采用三维阵列微结构最为合适。     

氧化锆粉末的表面改性研究

采用表面改性剂C对ZrO2粉末表面进行改性处理,制备出了有机/无机包覆的陶瓷粉末。研究了表面改性对粉末粒度和粒度分布的影响,利用SEM观察了表面改性前后粉末的团聚和微观形貌,测试了不同改性剂含量粉末的沉降时间和润湿接触角。研究结果表明:(1)超声波分散时间越长,粉末的中位径粒度越小;(2)改性粉末在二甲苯溶液中的粒度减小,团聚度降低;(3)粉末在二甲苯溶液中的沉降时间快慢为:to<>θ0.5%C>θ3%C≈θ5%C,改性粉末在非极性溶液中的分散性、稳定性和润湿性得到明显提高。     

CuSn预合金粉芯复合银钎料的润湿铺展机理

研究了添加质量分数为30%～70%CuSn预合金粉复合银钎料在T2紫铜基体上的润湿铺展过程,并讨论了CuSn预合金粉复合银钎料在紫铜基体上的润湿铺展机理.结果表明,在与紫铜基体的润湿铺展过程中,初始接触角由30%CuSn的119°降低到70%CuSn的94°.最终接触角由30%CuSn的15°下降到70%CuSn的7°.当粉芯中CuSn合金粉含量为60%时,钎料在铜板上的润湿面积达到530.04 mm²,相比于未添加CuSn合金粉时提高了约66%.由于低熔点CuSn预合金粉的前驱润湿作用使复合银钎料表面张力降低,初始接触角和最终接触角随着CuSn预合金粉含量的增加而减小. CuSn预合金粉在钎焊过程中先于BAg30CuZnSn钎料外皮熔化,形成熔融的铜锡液态合金薄层,降低了固液界面张力.随后,熔化的BAg30CuZnSn箔带在先期熔化的铜锡液态薄层上铺展,并与其发生溶质原子的扩散反应,最终形成液态复合钎料.低熔点CuSn预合金粉的加入,使复合银钎料在铜上的润湿性能显著改善.添加40%CuSn预合金粉复合银钎料与铜基体的反应润湿界面均匀致密,其中白色富Ag相互连接,...     

十二烷基硫酸钠水溶液液滴在微凹槽阵列PDMS表面上的电润湿行为实验研究

目的 研究十二烷基硫酸钠(Sodium dodecyl sulfate, SDS)水溶液液滴在微凹槽阵列聚二甲基硅氧烷(Polydimethylsiloxane, PDMS)表面的电润湿行为特征。方法 采用注入析出法，测量含KCl的SDS水溶液液滴在微凹槽阵列非浸润表面的接触角滞后。通过施加直流电压，研究SDS浓度和表面粗糙度对含KCl的SDS水溶液液滴的电润湿行为的影响。结果 微凹槽阵列非浸润表面表现出较强的润湿各向异性，与平行于微凹槽方向上的表观接触角(110°≤θ_e≤141°)、前进角(116°≤θ_a≤144°)和后退角(99°≤θ_r≤137°)相比，垂直于微凹槽方向上的表观接触角(142°≤θ_e≤165°)、前进角(159°≤θ_a≤177°)和后退角(118°≤θ_r≤140°)普遍更大。当表面固定时，水溶液液滴电润湿的启动电压和饱和电压，以及发生润湿状态转变所需的电压均随着SDS浓度的增加而减小。当水溶液中SDS的浓度固定时，沿垂直于凹槽方向的启动...     

Fe78B13Si9熔体与铁的润湿行为

采用座滴法研究了真空条件下1 180~1 220℃之间Fe78B13Si9熔体在纯铁上的润湿行为,结合DeGennes液滴润湿动力学模型分析了Fe78B13Si9熔体在纯铁上的润湿动力学。结果表明:Fe78B13Si9熔体与铁间有良好的润湿性,平衡接触角在10°~40°之间;Fe78B13Si9熔体与铁的润湿为反应性润湿,润湿过程中由于熔体与基体之间的溶解和相互扩散,熔体体积首先增大,然后随着熔体等温凝固的进行又逐渐减小;由于熔滴体积在润湿过程中不断变化,以及测量接触角与实际接触角的差异,De Gennes液滴润湿动力学模型不能描述Fe78B13Si9熔体在铁基体上的铺展规律。     

控制气氛下的AgCuTi/TiAl润湿铺展动力学

采用热台原位加热法系统研究了不同保护气体流量对润湿铺展过程、润湿铺展最大半径、润湿铺展动力学以及界面组织结构的影响.保护气体为氩气,保护气体流量分别为5,10,15 mL/s;加热曲线设定最高温度为1273 K,保温时间120 s;采用扫描电镜、能谱分析、光学显微镜等分析了界面组织结构.结果表明,保护气体流量为15 mL/s时,润湿铺展等效半径最大,原始半径0.9 mm的钎料铺展半径达到约1.4 mm.各种保护条件下,AgCuTi/TiAl体系的润湿铺展动力学过程相似,铺展半径与时间之间呈n次幂关系,即rn~kt;润湿铺展中钎料熔敷/TiAl的界面结构为:残余钎料的富银相/AlCuTi三元相层(AlCu₂Ti, AlCuTi, Ti₃Al)/TiAl母材,保护条件对其影响不大.     

Effect of Trace O Element on High-temperature Wettability Between Ni_3Al Melt and Y_2O_3 Ceramic

Effect of trace O element on the high-temperature wettability between Ni_3Al scrap melt and Y_2O_3 ceramic at 1873 K is investigated. With the increase in O content in Ni_3Al scrap melt from 6 to 21 ppm, the equilibrium contact angle decreases from 93.3° to 88.9°. The initial surface tension and adhesive work of molten Ni_3Al scrap drop from 3153.5 to 807.4 mN m~(-1) and from 2974.6 to 882.2 mN m~(-1), respectively. The average spreading rate increases from 0.03° s~(-1) to 0.17° s~(-1). The whole wetting processes are divided into four periods. The main driving force for spreading in period(1) is the adsorption and diffusion of active atoms around the interface. Trace O content in Ni_3Al scrap has a significant impact on interfacial reactions which mostly take place in the second stage, and can accelerate the spreading process on Y_2O_3 substrate. The reaction products during wetting process are Y_3Al_5O_(12), YAlO_3 and Al_2O_3.     

Al-Mg合金对2D石墨纤维网的润湿性及铺展速率分析

本文使用静滴法研究了不同Mg含量(3.2, 4.5, 6.5, 8.5, 10, 13, 17 wt.% Mg)的Al-Mg合金在M40石墨纤维网上的润湿行为,重点讨论了Mg元素含量对润湿性及铺展速率的影响。 随着Al-Mg合金中的Mg含量从3.2 wt.%增加至17 wt.%,初始润湿角从115o降低到88.5o,而最终润湿角则由 96.7o降低到71o。由于M40石墨纤维的表面组织性质与普通石墨有较大的区别,因此与高密度碳平板相比,Al-Mg合金在石墨纤维网上的初始润湿角更小。而润湿角随Mg含量的增加而减小主要是源于Mg含量的增加可以显著降低Al-Mg合金的表面张力。基于Dezellus方程,进一步计算了Al-Mg合金在石墨纤维网上的铺展速率,计算结果与实验结果基本吻合。基于Miedema模型计算得到的铺展速率系数k也与实验结果基本吻合,此结果证明了Miedema模型在铺展速率计算方面应用的合理性。计算与实验结果均表明Mg元素含量的增加虽然可以显著降低润湿角,但对铺展速率影响不大。     

高黏附性超疏水表面的制备及耐腐蚀性

利用电化学沉积技术在碳钢基底上制备了Co-Ni过渡层,再通过双辉等离子表面合金化技术(DGPSA)在过渡层上沉积了Cr涂层,经全氟辛基三氯硅烷(PFTEOS)溶液修饰后,制备出了具有高黏附性的超疏水表面。利用扫描电镜(SEM)、EDS、X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)、接触角测量仪、电化学测试等方法表征了涂层的形貌、物相组成、润湿性能、粘附性以及耐腐蚀性能,探究了DGPSA技术不同沉积时间对Cr涂层表面形貌和润湿性能的影响。结果表明,在沉积温度为750 ℃,沉积时间30 min 时,制备出了具有微纳米乳突状结构的高黏附性超疏水表面,水滴接触角达到159°,水滴在样品倾斜180°也不发生滚落。电化学测试结果证明制备的超疏水表面具有出色的耐腐蚀性能,对碳钢基底起到了良好的腐蚀防护作用。     

Enhanced wetting of dual-phase metallic solids by liquid metals: A new effect of interfacial reaction

The wetting of Cu–Fe two-phase composites by molten Sn is studied by the sessile drop technique under high vacuum at 400 °C. In this system Sn reacts with both solid components, forming intermetallic compounds. It is found that the curve of contact angle vs. the surface fraction of components passes through a minimum, behaviour that cannot be interpreted by existing models describing wetting of heterogeneous surfaces and/or reactive wetting. It is shown that the observed enhanced wetting can be explained by the dissolution contrast of Cu and Fe phases, leading to interfacial microroughness, thus providing an additional driving force for wetting. In order to take into account this new effect of interfacial reactions on wettability, an equation similar to Wenzel’s equation is established. It is shown that this equation can explain the change in wettability of composites when Sn is replaced by SnPb eutectic presenting a lower reactivity than pure Sn, as well as the effect on wettability observed when the scale of composite microstructure is changed with the surface fraction of components remaining constant.     

激光织构化不同材料表面对润湿性能的影响

采用激光微织构加工技术分别在SAF2507双相不锈钢和碳纤维增强聚醚醚酮(CF/PEEK)表面制备不同形状、面积占有率的微织构凹坑，通过润湿性试验分析时间、液滴体积、微织构形状与面积占有率、液滴种类对润湿性的影响。结果表明：液滴润湿材料表面过程中，固液接触角先随时间迅速减小，后保持在一个较为稳定的值；使用体积较大的液滴测量接触角时，液滴铺展的速度减缓，接触角的测量值变小；CF/PEEK表面的接触角随微织构面积占有率的增大而减小，SAF2507表面的接触角随微织构面积占有率的增大而增大；微织构面积占有率相同的表面，方柱形微织构表面的接触角小于圆柱形微织构表面，润湿效果更好；天然海水在光滑和织构表面的接触角均小于蒸馏水。     

水洗钎剂下SnAgCu系钎料对不同基板的润湿特性

选用商用水洗钎剂，采用润湿平衡法，研究了低银SnAgCu系钎料合金在表面贴装元器件及紫铜板上的润湿特性。研究结果表明，在Ag的质量分数为2．5％时，SnAg2．5Cu0．7钎料合金具有最大的润湿力和铺展面积及最小的润湿角。其润湿力高于现行商用SnAg3．8Cu0．7钎料合金，完全可满足表面组装元器件对其润湿性能的要求。     

Wetting behavior of eutectic Al–Si droplets on zinc coated steel substrates

Transient spreading behavior, joint properties and metallurgical compositions are investigated for different hot-dip and electro-galvanized zinc coatings. The main focus is set on the effect of coating thicknesses and droplet size. While most of the droplets are observed on surfaces at room temperature, the case of pre-heated substrates is also accounted for. Both the coating thickness and the droplet size have little effect on the resulting wetting angle compared to the effect of preheating or the absence of a coating. The transient spreading behavior significantly differs for different coating types. The coating thickness affects heat transfer into the substrate during the initial stage of wetting. The metallurgical composition shows that the coating is removed over a broad interfacial area, while it accumulates at the toe of the deposited braze metal most likely due to fluid dynamic effects.     

Spreading of Cu–Si alloys on oxidized SiC in vacuum: experimental results and modelling

The wetting behaviour of a Cu–40 at.% Si alloy, non-reactive with SiC, on oxidized (0001) faces of α-SiC single crystals is studied at temperatures close to the melting point of copper by the “dispensed drop” technique under high vacuum. The experiments focused on wetting kinetics to determine the mechanisms controlling the rate of spreading under conditions allowing for “in situ” deoxidation of silicon carbide. It is shown that spreading occurs in three stages: (i) an initial stage consisting of a rapid spreading of the alloy on the oxidized SiC up to a contact angle which is close to that on vitreous silica, (ii) a second stage with a zero spreading rate during which the alloy goes through the oxide layer by dissolution near the triple line allowing an intimate contact between the alloy and the SiC surface to be established, and (iii) a final stage during which the alloy spreads with a constant rate up to a contact angle equal to that of clean SiC. These results are interpreted on the basis of a dissolution–diffusion–evaporation process occurring in the vicinity of the solid–liquid–vapour triple line.     

Microscopic Approach of Adhesion and Wetting of Liquid Metal on Solid Ionocovalent Oxide Surface

The adhesion and wetting of non-reactive liquid metals with solid ionocovalent oxides are studied on thebasis of the experimental work of adhesion W data obtained with the sessile drop method.An analysis of theexperimental W values of different liquid metals on various solid oxides is first performed to evidence the de-pendence of the work of adhesion of a metal/oxide system on the electron density of the metal and on thethermodynamic stability of the oxide.An electronic model is then proposed to describe the microscopic mech-anism of metal-oxide interactions.Based on the model,the contact angle and the work of adhesion of differentliquid metals on various solid oxides can be interpreted and estimated,and their correlations to the variousphysical quantities of the oxides can be easily deduced.The basic consideration of the model is that the adhe-sion between a metal and an oxide is assured by the electron transfer from the metal into the oxide valenceband which is not completely filled of electrons at high temperatures,and is enhanced when this electron trans-fer at the metal/oxide interface is intensified.The influence of interface defects on the wetting and adhesion issuggested and discussed.     

Zn挥发对Ag-Cu-Zn钎料在TiC-Ni金属陶瓷表面润湿性的影响

采用Ag-Cu-Zn钎料对TiC-Ni金属陶瓷进行润湿.结果表明,真空条件下,以22.5℃/min的速率加热至810℃,保温10 min,Ag-Cu-Zn/TiC-Ni金属陶瓷三相线附近界面生成了连续的(Cu,Ni)组织.钎料在TiC-Ni金属陶瓷表面润湿过程先后经历孕育阶段、铺展阶段、钉扎阶段、回撤阶段和平衡阶段,最...