Analysis of Ni-coating's influence on wetting of Ag solder
Ni-coating's influence on the wetting progress in metal-ceramic bonding was analysed in this paper. Firstly Ag's contact angle was measured through high-temperature experiments, which turned out to be 100° and 25° on non-coated and Ni-coated ceramic substrates, respectively. Then a mathematical model was originally built up to catch the phase interface's motion on different substrates, considering fluid dynamics, melting and solidification, surface tension and liquid-solid heat transfer. Results indicated that Ni-coating affected the angle α directly and could reduce abnormity of joint structure through enhancing Ag solder's wettability on ceramic.
Preparation of coatings on alumina ceramic for wettability
Abstract To improve the wetting ability between ceramic and metal, titanium and copper coatings on alumina ceramics were prepared by infiltration of molten salt and electroless plating, respectively. A Ti/Cu bi-layer was also obtained by combining the two methods. The preparation process was optimized. The phase composition of the coatings was analyzed by X-ray diffraction (XRD). And the wettability of the titanium coating was investigated. The results showed that the copper droplet was easily spread on the surface of titanium coated alumina. The titanium coated alumina was well composited with high chromium white cast iron and the interface between ceramic and metal was well combined.
Numerical analysis and experimental observation of guidewire motion in a blood vessel model.
We have developed a computer-based system to simulate a guidewire in blood vessels for surgical planning, intra-operative assistance, and to facilitate the design of new guidewires. In this study, we compared simulation results with experimental results for validation of the simulation system. First, we inserted a commercial guidewire into a poly (vinyl alcohol) hydrogel blood vessel model using a two-axis automatic stage and measured the position of the guidewire tip and the contact force between the guidewire and the vessel. The experimental apparatus can be used not only for the validation of numerical analyses, but also as a simulation system. Second, similarly to the experiment, the motion of the guidewire in the blood vessel model was calculated when the proximal part of the guidewire model was pushed and twisted. The model of the guidewire is constructed with viscoelastic springs and segments, and the proximal part of the guidewire model is constrained by the fixed catheter model. Collisions between the guidewire and the vessel are calculated, and the contact forces are determined according to the stiffness of the vessel wall. The same tendency was seen in the trajectories and the contact force of both the experimental and simulated guidewire tips.