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11.
Two-dimensional simulations of the spinodal decomposition of self-stressed, binary thin films using a Cahn-Hilliard model are presented. Two different sets of mechanical boundary conditions are considered, and compositional strains for a cubic-anisotropic system under plane strain are treated. A composition-dependent interaction energy is assumed at the free surface. Numerical solution of the coupled Cahn-Hilliard and elastic equilibrium equations are obtained using an efficient nonlinear multigrid method. Results of simulations show that, for large enough compositional strain, surface-directed decomposition occurs at the traction-free surface, even when there is negligible surface interaction energy initially attracting one of the components. This decomposition is controlled by elasticity, and results in a local alignment of phases perpendicular to the free surface, in contrast to the parallel alignment produced by surface energy in stress-free systems. 相似文献
12.
Al-Si3N4材料浸渗工艺研究 总被引:1,自引:0,他引:1
用β-Si3N4纳米颗粒浆料浸渍多孔聚合物材料,通过加热烧蚀掉聚合物,制备出三维空间连续网络结构预制块体,再通过无压浸渗将已熔炼好的铝液浸渗到预制体中,成功制备出陶瓷与金属相互贯穿的Si3N4/Al金属基复合材料。利用座滴定法测试了Al在Si3N4基片上的润湿角,探讨了其浸渗机理,分析了润湿角、浸渗力、浸渗温度和浸渗时间对Si3N4/Al金属基复合材料浸渗行为的影响。 相似文献
13.
润湿平衡法是一种定性、定量评价器件可焊性的试验方法。文章针对OSP样品进行润湿天平试验时,浸锡角度的选择及其对试验的影响,作了探讨。文章旨在通过分析其中的机理,深入理解润湿天平曲线物理意义,以及为更好地运用IPC/J-STD-003B 2007可焊性测试标准提供参考借鉴。 相似文献
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M. A. Martinez F. Velasco J. Abenojar A. Chiminelli R. Breto 《The Journal of Adhesion》2015,91(12):937-949
The applications (and repair) of glass fiber reinforced epoxy composites are increasing in different industries (wind turbines, boats, chassis of buses, etc.) due to specific strength and low cost. Their major disadvantage is the difficulty to shape complex components. This problem can be solved manufacturing different parts, being adhesively bonded afterwards. This work studies the effect of atmospheric pressure plasma torch compared to grit-blasting to improve adhesion. After surface treating different parts, the changes of wettability and surface energy were measured. Treated samples were bonded with polyurethane and epoxy adhesives, and the quality of the bond was evaluated using pull-off adhesion tests and fracture strength test under cleavage loads. Obtained results allow to select the most adequate treatment in terms of mechanical requirements. 相似文献
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D. Hellborg B. Bergenståhl C. Trägårdh 《Chemical Engineering and Processing: Process Intensification》2010
Mixing of powders into liquids is a common unit operation. Mixing can be divided into several steps: imbibation of the powder into the liquid being the first. Under some circumstances, for instance, if the powder has poor wetting properties, imbibation can be the rate-determining step. In this study imbibation in a commercial mixer was studied and a method to measure powder imbibation in a model that simulates the commercial mixer was developed. The imbibation mechanism in the commercial mixer is based on a wave drawing the powder down into the liquid, and surface flow transporting it towards the wave. A wave imbibation model was constructed based on the same mechanisms, in which physical parameters such as wave height, surface velocity and surface residence time could be varied. An experimental procedure was used to determine the maximum imbibation rate. Measurements were found to have good reproducibility, with a standard error of means of 4.7% for spray-dried sodium caseinate. The maximum imbibation rates were found to be of the same magnitude in the commercial mixer and the wave imbibation model: 0.04 kg/s m in the commercial mixer and 0.06–0.16 kg/s m in the wave imbibation model for spray-dried sodium caseinate powder. 相似文献
18.
In this work, we propose a simple but effective method to fabricate BaO–B2O3–SiO2 glass/ceramic composites with different microstructures that depend on the high-temperature wetting affinity. The experimental results showed that the wetting affinity between oxide ceramic and the BaO–B2O3–SiO2 glass matrix could strongly affect the driving force of densification and crystallization and finally the microstructure of the glass/ceramic composites. It was found that suitable amounts of alumina powders could obviously increase the driving force for sintering of glass by increasing the capillary pressure. In this case, the contact angle between alumina and glass matrix is about 24° at high temperature and a densified and homogeneous microstructure of glass/alumina composite was obtained. On the contrary, rutile powders additive was found to result in higher phase separation and crystallization during the sintering of glass/rutile composites. In this case, the contact angle between rutile and glass matrix is about 124° at high temperature, and the sintered body has a lower dielectric loss than the sample with alumina additive. Therefore, the microstructure and dielectric property of glass/ceramic composites could be controlled by adjusting the ceramic composition and wetting affinity between ceramic additive and glass matrix in our study. 相似文献
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采用传统座滴法研究了低熔点合金(Bi-Sn)和高熵合金(AlCoFeNiCr和CuCoFeNiCr)之间的润湿行为及界面特征。借助扫描电子显微镜(SEM)和能谱分析(EDS)分析了Bi-Sn/AlCoFeNiCr和Bi-Sn/CuCoFeNiCr界面微观结构。结果表明:AlCoFeNiCr和CuCoFeNiCr高熵合金都是结构单一的固溶体,但Bi-Sn熔体在CuCoFeNiCr高熵合金基体上的润湿性明显地优于Bi-Sn熔体在AlCoFeNiCr高熵合金基体上的润湿性;Bi-Sn/CuCoFeNiCr界面发生剧烈的化学反应,有大量的界面反应物生成,Bi-Sn熔体中的原子Sn主要是沿着CuCoFeNiCr高熵合金中的富铜相扩散,而Bi-Sn/AlCoFeNiCr界面平直,且随着润湿温度的升高,Bi-Sn熔体中的原子向AlCoFeNiCr高熵合金基体的扩散程度加强并伴随化学反应,出现类似"皮下潜流"现象;由于CuCoFeNiCr高熵合金中富铜相的存在,为Bi-Sn在CuCoFeNiCr高熵合金基体上的铺展提供了"润湿通道"。 相似文献