疏水性材料的等离子体表面改性工艺研究

通过等离子体连续处理仪对疏水性材料表面进行表面改性而提高了其润湿性。研究了不同反应条件对高分子材料表面改性的影响;通过测定样品表面的接触角等性能评价了其表面亲水性的变化。经过等离子体表面处理,聚四氟乙烯的接触角有了显著下降;聚乙烯电池隔膜的吸碱率为自身重量的3.5倍,爬高率初始3 min接近100 mm;硅橡胶的接触角由105°下降到30°;聚酯的接触角由98°到15°。通过对材料表面进行丙烯酸接枝,评价了时效性的影响;初步探讨了真空紫外辐射对表面改性的影响。结果表明:改性后疏水性材料表面的润湿性得到了明显改善,该技术与设备在工业应用方面非常具有推广价值。     

基于二硫键的三重刺激响应可控润湿性表面的构建

合成了一种双-[3-（三甲氧基硅）丙基]-二硫化物（TPDS）,并将其接枝到具有优异光热转化能力的聚多巴胺改性表面（PDA-Glass）,获得了二硫键功能化表面（2S-PDA-Glass）。利用X射线光电子能谱仪对该表面进行了表征,采用水接触角测定仪表征了2S-PDA-Glass在980 nm近红外光、365 nm紫外光及50℃温度刺激下可控润湿性。结果表明,接枝于表面上的二硫键在3种刺激源下均可发生断裂,被还原成亲水的巯基,导致表面水接触角由78°下降到55°左右;而表面巯基被三氯化铁氧化后又重新形成二硫键,表面水接触角可再次升至78°左右,实现了多重刺激响应的可控润湿性。使得材料可以在不同的环境中自由选择刺激源,应用范围更为广泛。     

温度响应性Fe@PNIPAM泡沫的制备及油水分离性能研究

以泡沫Fe为基底,通过简单的一步自由基聚合法,将温敏性聚N-异丙基丙烯酰胺(PNIPAM)修饰到泡沫铁基底表面,制备了表面润湿性可控的温度响应性油水分离材料.当体系温度低于临界溶解温度(LCST)时,材料表现出超亲水性,其水接触角为0°;当体系温度高于LCST时,材料表面呈疏水性,其水接触角可达135.2°.在外界温度...     

铝合金表面预处理及其镀镍工艺优化

本实验分别采用打磨、混合碱处理、水合肼处理和电晕处理四种方式对AA5052铝合金基体表面进行预处理,探讨了预处理方式对铝合金表面润湿性和表面形貌的影响,并在此基础上对铝合金表面镀镍工艺参数进行优化。通过接触角仪和扫描电子显微镜对镀层润湿性以及表面形貌进行表征,得到最佳化学镀镍条件:镀液温度为75℃,镀液pH值在6.2~6.4之间,化学镀时间40min。通过循环伏安法(CV)探索得到了最佳电化学镀镍条件:电镀时间为240s,电流密度为5mA/cm2,镀液温度为60℃。实验表明,该实验条件下可以得到理想的镍镀层,且该方法可以广泛应用于其他相关的材料研究领域。     

环氧树脂-固化剂混合液体与铜基材料的润湿性能研究

采用静滴法观察了液态纯固化剂和20%树脂-80%固化剂混合液体与铜基材料的润湿行为,测定了298～363K温度范围内的接触角,评价了两种液体与铜基材料的润湿性.结果表明,接触角随时间呈下降趋势,初始接触角随着试样中环氧树脂比例的增加而降低,温度对固化剂平衡接触角的影响较小.在同样的温度条件下,加入树脂后的液体的平衡接触角小于纯固化剂的平衡接触角.     

低压环境下闪蒸喷雾冷却不同润湿性表面的实验研究北大核心CSCD

对低压环境下闪蒸喷雾冷却不同润湿性表面的实验现象和换热特性开展研究,结果显示:喷雾至亲水表面和光滑铜表面的汽化过程分为四个阶段,即液膜形成阶段、液膜剧烈汽化阶段、固定液膜接触线的汽化阶段和液膜界面收缩阶段。进而研究了表面润湿性、环境压力、工质温度对两种表面温度变化的影响。结果表明,表面温度随时间都呈下降的趋势;亲水表面润湿性较好,喷雾阶段表面温度下降较快;环境压力越低,液体汽化越剧烈,表面的最终平衡温度也越低,但在喷雾阶段存在最佳环境压力使冷却效果最好,本文实验条件下,最佳环境压力为1.9 kPa;工质初始温度对表面最终温度影响很小。     

真空低温环境导热填料界面接触热阻实验研究

真空低温环境下,接触热阻对热传递有十分重要的影响。根据接触热阻产生机理和实验测试原理,建了一套真空低温环境下固体界面接触热阻测试的实验装置。实验对比研究了不同温度和不同预紧力条件下,固体界面裸接与在界面之间添加真空硅脂、铟膜、石墨烯、石墨片导热填料时的接触热阻。实验结果表明,接触界面的接触热阻都随温度升高和预紧力增大而减小。在接触界面添加真空硅脂或铟膜后接触热阻随预紧力变化非常,裸接或添加石墨烯的接触热阻随预紧力变化较大,但是当预紧力大于2.5 N·m时其接触热阻基本不变。温度越低时添加导热填料减小接触热阻的效果越明显。总之在两界面之间添加铟膜时效果最佳,此时接触热阻随预紧力和温度的变化都较小,此种情况下接触热阻最小可以达到3.5×10~(-6)K·m~2/W。     

大气压等离子体射流改性船体钢表面亲水性研究

在室温下,采用大气压等离子体射流对船体钢进行表面改性,通过水接触角测量、扫描电镜、X射线光电子能谱等分析测试方法研究了等离子体射流处理前后船体钢表面润湿性、表面形貌及化学特性的变化。研究结果表明,船体钢经大气压空气等离子体射流处理后在其表面引入了大量含氧基团,处理2s表面的水接触角就可以降到30°以下;处理后材料表面的亲水性受处理时间及放电电流的影响且在空气中放置时会出现老化效应,处理时间越长,老化效应越弱。     

低压环境下闪蒸喷雾冷却不同润湿性表面的实验研究

对低压环境下闪蒸喷雾冷却不同润湿性表面的实验现象和换热特性开展研究,结果显示:喷雾至亲水表面和光滑铜表面的汽化过程分为四个阶段,即液膜形成阶段、液膜剧烈汽化阶段、固定液膜接触线的汽化阶段和液膜界面收缩阶段。进而研究了表面润湿性、环境压力、工质温度对两种表面温度变化的影响。结果表明,表面温度随时间都呈下降的趋势;亲水表面润湿性较好,喷雾阶段表面温度下降较快;环境压力越低,液体汽化越剧烈,表面的最终平衡温度也越低,但在喷雾阶段存在最佳环境压力使冷却效果最好,本文实验条件下,最佳环境压力为1.9 kPa;工质初始温度对表面最终温度影响很小。     

Cu-Mo-C在TiO上的润湿性研究

研究了Cu在一氧化钛上的润湿及Mo、C的加入对其润湿性的影响。结果表明Cu在一氧化钛上的润湿属非反应型润湿,但存在相间溶解。纯Cu在一氧化钛上的润湿性较差,在真空条件下1083～1450℃接触角为120～68°。Cu中加入Mo、C,在润湿过程中Mo、C在TiO/Cu界面富集,并形成Mo、C与Ti(C、O)的固溶体混合物,可显著改善润湿。加入Mo、C2％以上,其接触角降至20°以下     

Wettability of carbon surfaces by pure molten alkali chlorides and their penetration into a porous graphite substrate

The wettability of graphite and glassy carbon surfaces by pure molten alkali chlorides (NaCl, KCl, RbCl, CsCl) was measured by the sessile drop method. The contact angle was found to decrease with increase of the cation radius of the chloride. Using our measured and available literature data, a new, semi-empirical model is established to estimate the adhesion energy between the 20 alkali halide molten salts and graphite (or glassy carbon). The adhesion energy is found to increase with square of the radius of the cation, and the inverse of the radius of the anion of the salt. The minimum possible value for the surface energy of graphite (and glassy carbon) was found as 150 ± 30 mJ/m². The critical contact angle of spontaneous penetration (infiltration) of the molten chlorides into a porous graphite substrate was found experimentally below 90°, in the interval between 31° and 58°. This is explained by the inner structure of the porous graphite.     

镀铜石墨与铝熔体的润湿性

为了改善石墨与铝的润湿性,通过化学镀使石墨颗粒表面形成完整致密的铜镀层,然后将8%(质量分数)的镀铜石墨粉通过熔体搅拌法加入到铝合金基体中制得金属基复合材料.采用改进的座滴法分别测定了铝熔体与石墨、镀铜石墨的接触角.同时,利用扫描电镜(SEM)对石墨颗粒增强铝基复合材料的微观形貌进行了检测.结果显示,铝熔体与镀铜石墨的接触角为27°,其界面具有良好的润湿性,镀铜石墨粉在铝合金基体中分布均匀.     

Solidification contact angles of molten droplets deposited on solid surfaces

Droplet impact and equilibrium contact angle have been extensively studied. However, solidification contact angle, which is the final contact angle formed by molten droplets impacting on cold surfaces, has never been a study focus. The formation of this type of contact angle was investigated by experimentally studying the deposition of micro-size droplets (∼39 μm in diameter) of molten wax ink on cold solid surfaces. Scanning Electron Microscope (SEM) was used to visualize dots formed by droplets impacted under various impact conditions, and parameters varied included droplet initial temperature, substrate temperature, flight distance of droplet, and type of substrate surface. It was found that the solidification contact angle was not single-valued for given droplet and substrate materials and substrate temperature, but was strongly dependent on the impact history of droplet. The angle decreased with increasing substrate and droplet temperatures. Smaller angles were formed on the surface with high wettability, and this wetting effect increased with increasing substrate temperature. Applying oil lubricant to solid surfaces could change solidification contact angle by affecting the local fluid dynamics near the contact line of spreading droplets. Assuming final shape as hemispheres did not give correct data of contact angles, since the final shape of deposited droplets significantly differs from a hemispherical shape.     

Mn对熔融Zn-Mn合金与X80钢润湿行为的影响

研究了锌液中0.1%~0.5%(质量分数)Mn对X80钢表面润湿行为的影响。采用改良座滴法获得了450℃时Zn-Mn合金的接触角,通过SEM/EDS观察分析样品表面及界面的组织结构,研究了Zn-χMn(χ=0.1~0.5)合金与X80钢基板的润湿行为和界面反应。结果表明：锰元素对锌合金与钢基体间的润湿性反应起到正吸附作用。在450℃时,当熔体中的锰含量为0.1~0.5时,Zn-χMn合金与钢基间的润湿接触角从85°减小到62°。锌合金熔体/X80钢属于反应性润湿体系,生成的界面产物由FeZn₁₀(δ)、FeZn₁₃(ζ)和Fe₃Zn₁₀(Γ)/Fe₅Zn₂₁(Γ₁)相组成,润湿行为受锌合金界面反应影响。在铺展三相线前沿存在前驱膜,前驱膜的出现能够促进润湿。     

Effect of nanoparticles on sessile droplet contact angle

This paper investigates the change in contact angle of droplets of fluid containing dispersed nanoparticles (nanofluid) functionalized with thioglycolic acid molecules as a function of the concentration and size of nanoparticles, and the quality and composition of the substrate material. Bismuth telluride nanoparticles with an average size ranging from 2.5 to 10.4?nm and functionalized with thioglycolic acid groups were grown by a microemulsion method and dispersed in water. Experimental measurements of the contact angle of nanofluid droplets cast on smooth glass and silicon substrates show that the contact angle depends strongly on nanoparticle concentration. Moreover, smaller size nanoparticles lead to larger changes in contact angle at the same mass concentration. These findings contribute to understanding the role of functionalized nanoparticles in surface wettability.     

Si对SiC－Al系统浸润行为的影响

用液滴技术（Ｔｈｅ　Ｓｅｓｓｉｌｅ　Ｄｒｏｐ　Ｔｅｃｈｎｉｑｕｅ）、ＳＥＭ、ＥＤＳ等研究了Ｓｉ对ＳｉＣ－Ａｌ系统浸润行为的影响，结果表明，在较低温度下，Ｓｉ在熔融Ａｌ合金中的含量不明显影响Ａｌ对ＳｉＣ的浸润行为，然而，在高温下ＳｉＣ和Ａｌ的接触角θ值随时间而减小的速率随Ｓｉ含量的增加而增大；ＳｉＣ－Ａｌ系统从非浸润到浸润的转变温度随Ｓｉ含量的增加而降低；Ｓｉ的添加引起Ａｌ合金在ＳｉＣ表面扩展和向ＳｉＣ基体渗透，而且扩展和渗透的程度随Ｓｉ含量增加而增大。说明在Ａｌ合金中添加Ｓｉ可促进对ＳｉＣ的浸润。本研究还证实了基体参加反应可增强金属Ａｌ对ＳｉＣ陶瓷的浸润能力。     

Wetting and spreading of molten aluminium against AlN surfaces

Wetting and spreading of molten aluminium against AlN substrates were investigated between 1100 and 1290°C. The contact angles decreased linearly with time under isothermal conditions between 1100 and 1200°C. The isothermal rate of spreading of molten aluminium against AlN substrates was constant between 1220 and 1290°C and the rate increased exponentially with increasing temperature. Crystals of Al4C3 nucleated and grew on the substrate surface beneath the liquid. However, the formation of Al4C3 may not be solely responsible for the changes in contact angle and spreading. It is postulated that carbon contamination from the substrate and/or experimental equipment coupled with the low oxygen partial pressure of the chamber in the presence of graphite, were primarily responsible for the observed contact angle and spreading phenomena. The activation energy for the spreading process was 448 kJ mol-1, suggesting the presence of some chemical reaction at the interface. Carbon-rich aluminium may be initiating a continuous surface reaction with the AlN substrates by reducing the native oxide layer on the substrate surface.     

Modified technique of using conventional slider boat for liquid phase epitaxy of silicon for solar cell application

Epitaxial layers of silicon are grown on single crystal Si- substrate from a solution of silicon in indium using conventional graphite slider boat technique. The important problems of natural convection due to lower density of silicon compared to indium,poor wetting of substrate due to high angle of contact of indium solution on silicon substrate resulting in poor nucleation, melt removal from the growth substrate and saturation wafer associated with LPE in this technique are practically eliminated using sandwich method with simple modifications of the boat and the method of growth. Some experimental studies on the effect of different surface preparations of growth substrate are also reported. Growth results are shown and discussed. Further, improvization of slider boat to facilitate better study of growth parameters is suggested in the line of modification already carried out.     

Wetting of porous graphite by Cu–Ti alloys at 1373 K

The isotherm wetting of porous graphite substrates by the molten Cu–Ti alloys with 1, 3, 4 and 5 at.% Ti was investigated at 1373 K in a flowing Ar atmosphere using a modified sessile drop method. The wettability increases with increasing Ti content in the alloy and the equilibrium contact angle reaches 6° for the Cu–5 at.% Ti alloy. The improvement of the wettability is due to the formation of a substoichiometric TiC_x reaction layer at the interface. Increasing the Ti content makes the resultant TiC_x phase more substoichiometric and thus significantly promotes the wettability.