Papers by Keyword: Wetting

Abstract: The Mo-Ni (Co)-Si metallizing coatings on the SiC ceramic substrate were prepared by vacuum cladding process. The wetting and spreading of molten Al on coated SiC ceramic substrates at 900 oC were investigated by the sessile drop technique, and the interfacial behavior of the Al/coated SiC wetting couples was analyzed. The experimental results showed that the final contact angle of Al/M20NiSi coated SiC was close to 0o. With the increase of Mo content in the Mo-Ni-Si coating, the shape of the sessile drop became very irregular due to the strong interactions between the Al drop and the coating, so it was unable to precisely characterize the contact angles of Al/Mo30NiSi and Al/Mo40NiSi systems. The final contact angle of Al/Mo10CoSi coated SiC system was also close to 0o, however, the final contact angle of Al/Mo20CoSi coated SiC system climbed to ~42o with the Mo content increasing from 10 at.% to 20 at.%. The significant increase of contact angle may be caused by the accumulation of Mo near the triple line which can impede the spreading of Al drop.

Abstract: The wetting and spreading of molten Cu, Ag and Ag-28Cu (wt.%) on the WC-Co cemented carbide were investigated by the sessile drop technique at different temperatures, and the interfacial behaviors of the metal/WC-Co couples were analyzed by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The experimental results showed that the testing temperature and the composition of drop can play a key role in the wetting and spreading, and the good wettability with contact angle of less than 40^o can be obtained. Moreover, the strongest interactions can be produced between the molten Cu and the WC-Co substrate at the higher temperature of 1100 ^oC due to the strong interdiffusion and solid solution between Cu and Co, resulting in the lowest equilibrium contact angle of ~0^o. In addition, smooth and clean interfaces, without formation of visible interfacial reaction layer, were observed in all the three wetting systems. This work may also provide guidance to brazing of the cemented carbide.

Abstract: The aim of research consisted in the study of wettability of Sn-based solders on ceramic Al₂O₃ material by heating with electron beam without flux application. The Sn-based solders alloyed with active elements as Ti, La, Ce and Ga were applied for soldering. The active elements contained in solder volume oxidise during soldering in air. This problem can be eliminated by application of electron beam in vacuum. Soldering consisted of 15 minutes heating to desired temperature then dwelling on this temperature for 5 minutes and a slow cooling down in vacuum. The desired soldering temperature was 950 °C. The best wettability on Al₂O₃ substrate was achieved with SnAg3,5Ti4(Ce,Ga) solder, with wetting angle of 62°. The interactions between the solder and substrate were identified in the joint interface, ensuring the creation of a stable bond.

Abstract: The wetting behavior and the interaction at the liquid-solid interface are significant in preparation of metallic glass composite. In this paper, the wetting behavior and the interfacial interaction between Ti_32.8Zr_30.2Ni_5.3Cu₉Be_22.7 (denoted as ZT3) bulk metallic glass (BMG) alloy melt and Ti6Al4V (denoted as TC4) substrate at different temperatures were investigated using sessile drop method. The results show that ZT3 alloy melt wetted the substrate well. With the increase of temperature, the droplet spread out rapidly and then came to equilibrium gradually. The equilibrium contact angle under 1273 K stabilized at about 15°. Dendrite phase generated at the interface during the wetting progress. The composition of the interface product transformed from Ti_69.8Zr_24.2Al_2.2V₁Cu_2.8 to Ti_73.6Zr_15.3Al₅V_2.7Cu_2.6Ni_0.8 with the temperature rising from 973 K to 1273 K. Meanwhile, the dissolution of the TC4 substrate increased with increasing the temperature.

Abstract: The wetting and spreading behaviors of pure nickel and nickel based alloys on sintered ZrB₂-SiC ceramics and their interfacial microstructures were investigated in this presentation. The nickel-based alloys were mainly the commercial nickel-molybdenum-chromium products. The wetting and spreading properties were observed by a real-time thermal optical measurement system under flowing argon-5%hydrogen atmosphere. As temperature increased, the pure nickel cylinder sample on ZrB₂-SiC substrate had few changes before 1228°C except for the thermal expansion in size. After that, liquid phase formed and spread gradually on the ceramic substrate. The contact angle was about 15^o after holding 15min at 1600°C. Therefore, pure nickel could contact sintered ZrB₂-SiC ceramics well. Meanwhile, the introduction of molybdenum and/or chromium in the pure nickel was beneficial for the wetting of nickel on sintered ZrB₂-SiC ceramics. The contact angles of Ni-28Mo and Ni-16Mo-23Cr alloys on sintered ZrB₂-SiC ceramics after 1600°C/15min were 13^o and 2^o, respectively. In addition, the temperatures of the liquid drop formed rose obviously in contrast to the pure nickel. The SEM images indicated that the interfacial microstructures of Ni-based alloys on sintered ZrB₂-SiC ceramic substrates were uniform and the dissolved boundaries showed that they had a good bonding. However, some cracks were found in the Ni/ZrB₂-SiC system for their high thermal mismatch. On the other hand, the Ni-Mo (-Cr)/ZrB₂-SiC interface had few defections and evident elemental diffusion between the ceramic substrates and the alloys were found at the interface.

Abstract: We consider a heavy, incompressible, homogenous, isothermal magnetic fluid between two coaxial cylinders in case of wetting. There is a current-carrying straight wire on the axis of these cylinders. The magnetic fluid is immersed in a non-magnetic liquid with the same density (the case of hydroimponderability). We apply the Langevin law to describe a magnetic fluid magnetization. Using the general analytical solution for any axially symmetric shape of the magnetic fluid free surface in any axisymmetric magnetic field, we investigate the break-up and the rebuilding of the magnetic fluid bridge in case of wetting.

Abstract: The Ga penetration process along grain boundaries of Al-based alloys while they are in contact with Ga containing aqueous solution was studied. It was shown that exposure in the solution at room temperature leads to the liquid Ga penetration process, which started with 3 minutes delay. The penetration rate for Al-4.7 % Zn (13 μm/s) is two times less than penetration rate in pure Al. As for Al-Cu alloys it was shown that penetration process occurs only for the alloys with 1.6 % Cu and less, but for larger value of Cu concentration Ga did not penetrate in Al. Comparison of the effect with pure Ga spreading over the alloys surface showed that the absence of penetration connected with absence of wetting.

Abstract: Grain boundary liquid grooving process takes place during the contact of solid phase with the melt. The liquid bismuth network formation along grain boundaries (GBs) and triple junctions (TJs) was investigated in copper polycrystalline samples. The in situ experimental observation technique of Bi penetration through the Cu plate was used. The temperature dependencies of GB and TJ effective penetration depths were determined. The effect of the GB and TJ diffusion on the liquid channels growth mechanism was discussed.

Abstract: During the last years the carmakers interest is focused on polymer manufacturers to develop breakthrough solutions addressing the key drivers of reducing weight and cost. The use of polypropylene (PP) and other thermoplastic olefins is growing because of their low cost and good properties. Unfortunately, some of the same properties that make these plastics attractive to designers, also make them difficult to bond with adhesives or varnish. Non-polar character of PP results in poor surface properties and low wettability. Several methods of surface pretreatments have been used to improve its wettability, but all involves cost extending additional processing. Based on lessons from nature, one of the ways how to increase wettability is surface structuring. Injection mold insert designing and manufacturing process inspired by hydrophilic structure of the moss is presented. Due to cost reducing demands were used conventional processing methods.

Abstract: Moisture is one of the most deteriorating factors of buildings. The moisture content depends on hygroscopic equilibrium between buildings materials and environment, which is determined by the drying and wetting rate of masonry. So, the moisture content is not only determined by the water that is absorbed by the material, but also by the amount of water that is evaporated under favourable conditions, which is described by the drying process.This work presents the results of an experimental evaluation of the drying kinetics of solid red brick, considering the bulk moisture transfer. The drying kinetics was assessed considering different environment conditions (air temperature and humidity). The experimental results showed that the drying flux is extremely dependent of temperature and relative humidity in the first stage of the drying process. The values obtained were between 0.025 kg/m²h (T=15oC and RH=80%) and 0.135 kg/m²h (T=30oC and RH=50%), for the worst and better drying ambient conditions.Different first-order kinetics models, available in the literature, were adjusted to describe the drying process and estimate the equilibrium moisture content of the samples. The results point that Midilli et al. model allows the best fit and that the drying time constant is strongly affected by the drying air conditions. It was also estimated the apparent molecular diffusion coefficient for solid red brick samples and its variation with temperature.