Papers by Keyword: Surface Energy

Abstract: In this present work, TiN films with various thicknesses (from 0.3 μm to 2 μm) were deposited by DC reactive magnetron sputtering on Ti6Al4V substrates. The evolution of texture and microstructure were studied by X-ray diffraction and Scanning Electron Microscopy, respectively. The XRD characterization indicates that the preferred texture of TiN films is changed from (111) to (100) with increasing the film thickness. The microstructure characterization shows that their microstructure transform from continuous into columnar with increasing the TiN film thickness. It is considered these results are arised from the change of overall energy including surface energy and strain energy with the film thickness. The hardness of TiN film increases with increasing the film thickness.

Abstract: The low-index (001), (111) and (110) surfaces of austenitic NiTi were investigated by the use of first principles calculations. The calculated results showed that the non-polar NiTi (110) surface was the most stable under most of the Ti chemical potential. The polar Ni terminated NiTi (001) surface was the most stable under Ni-rich conditions. The Ni-terminated surfaces were more stable than their corresponding Ti-terminated surfaces in the entire range of Ti chemical potential. The surface interlayer relaxations of the Ni-terminated surfaces were much larger than those of the corresponding Ti-terminated surfaces. The Ti atoms in the surface layer of the non-polar NiTi (110) surface were more outward than Ni atoms.

Abstract: The paper presents the theoretical calculations of the structure and morphology of ZrO₂ nanocrystals. The equilibrium morphology shapes of tetragonal and cubic nanocrystals were determined. It was shown that the equilibrium morphology was determined by an appropriate set of faces of tetragonal and cubic phases of zirconium oxide.

Abstract: The mechanical properties of fibre reinforced polymer composites strongly depend on the interfacial bonding between fibre and matrix. The main objective of this paper is to compare the interfacial bonding between kenaf fibre reinforced POM with that of PET fibre reinforced POM in a hybrid composite. Continuous twisted kenaf, and PET yarn were used for the investigation. Each fibre yarn was half embedded in POM by compression moulding. The yarns were extracted from the matrix by single fibre pull out test method. The result of the investigation revealed that the interfacial shear strength of approximately 31.4 MPa between kenaf and POM is higher compared to 24.3 MPa obtained between PET fibre and POM. This may be due to higher surface energy of kenaf fibre with respect to POM in the composite The FESEM micrograph further demonstrates good interfacial adhesion between kenaf and POM in the composite.

Abstract: In this study there was found that ionizing beta radiation increased the strength of bonded joints and improved the adhesion properties of polypropylene (PP). Generally, for the formation of quality bonded joint it is important to wet the adhesive bonding surface well. Wettability is characterized by the contact angle of wetting. The liquid has to have a lower surface tension than the solid in order to be able to wet the solid substance. The measurement results indicated that ionizing beta radiation was a very effective tool for the improvement of adhesive properties and increased the strength of bonded joints of polypropylene. Bonded surfaces with ionizing beta radiation doses of 0, 33, 66 and 99 kGy were irradiated. The best results were achieved by irradiation at dose of 66 kGy by which the highest surface energy and the highest strength of bonded joints of PP were achieved. The strength of bonded joints after irradiation was increased up to 450 % compared to untreated material. A similar trend was observed even for surface energy.

Abstract: Classical EPD has typically been conducted in organic solvent media. Many suitable solvents are volatile and highly flammable and this limits the industrial application of the technique on the basis of safety alone. Aqueous EPD may be seen as a safer method, but issues relating to electrolysis and surface energy phenomena become prominent and can create interferences and variability unless the substrate type and its preparation are compatible with the aqueous EPD chemistry and its deposition method. As EPD layers become thinner, factors such as substrate surface structure and wettability become more critical. Industrial processes utilising some principles of EPD for applying paint from water-based preparations are well established in the metal finishing sector. Consequently there is a significant body of practical experience available from this sector that can be of use in translating classical EPD from a solvent to an aqueous technique while avoiding interferences inherent in the use of water as the deposition medium. In this paper, substrate selection is discussed in relation to the electrolyte content of the system where phenomena such as dissolution and micro-arcing can occur. The initial wetting of the substrate must be considered prior to applying voltage. Surface preparation techniques and the methods of introducing the substrate into the EPD dispersion all can have an impact on the final result. Note: This paper is based on the authors’ personal and practical experience of industrial electrophoretic painting over more than 40 years. Only metal substrates are discussed because these have been almost exclusive in this sector during that time. Non-metal substrates such as conductive plastics, graphite and carbon fibre have also been coated with electrophoretic paints but this is not yet at any significant scale and so no general principles have been established

Abstract: Based on their properties, PPS fibers are a promising material for reinforcing elastomeric components that are subjected to high mechanical and thermal loads. The use of this material is at present hindered because of the low adhesion between the fiber and matrix. Atmospheric pressure plasma treatments based on the dielectric barrier discharge were performed on PPS fibers using air as reactive gas for different treatment durations in order to improve the adhesion. The effects of these treatments have been characterized by determining the surface energy, and the residual tensile strength as well as by analyzing the surface chemistry. Required conditions for an improved wetting behavior and a significant increase in the polar component of the surface energy could then be identified.

Abstract: Effect of the magnetic prehistory on the temperature dependence of the heat capacity of the superconducting Pb, La, Sn. has been studied. As soon as the external magnetic field riches the value H_ext = H_C the superconductivity is completely destroyed. The trapped flux was produced in the ring specimen after the magnetic field was turned off at T < T_C. We observed a difference of the value of the heat capacity between zero field cooled (ZFC) and field cooled (FC) states in zero magnetic field for the ring specimen. It is found that the FC heat capacity is smaller than the heat capacity both in the normal and in superconducting states.

Abstract: The absolute surface energies of three major low index surfaces of cubic silicon carbide (3C-SiC) are determined by first-principles density functional theory calculations. Calculations show that among clean 3C-SiC surfaces the Si-terminated 3C-SiC(001)-(3x2) surface has the lowest energy. The second and third lowest energy surfaces are the Si-terminated 3C-SiC(111)-(√3x√3) surface and the nonreconstructed 3C-SiC(110) surface. Hydrogen passivation greatly reduces both the absolute surface energies of the low index 3C-SiC surfaces and the surface energy anisotropy. In particular, the surface energies of fully passivated 3C-SiC(110) and (111) surfaces become indistinguishable at hydrogen-rich deposition conditions.

Abstract: In Pb-free Al-Sn welding of electrolytic parts, single-crystal Sn whiskers easily form and can cause problems such as short circuits. Here we report that the growth of Sn whiskers in the weld zone of Al electrolytic condenser leads was suppressed in a vacuum environment. We examined the effect of the environment and weld metal microstructure in order to understand how to control and prevent whisker growth. In vacuum, the weld zone did not form whiskers after more than 100 h, whereas in air, whiskers grew within several hours. This suggests that whiskers require oxygen to form. The growth can be explained by the energy balance between the potential energy of the weld metal and the surface energy of the whisker. Our results will contribute to developing techniques for suppressing the formation of Sn whiskers during the percussion welding of Al electrolytic capacitor leads.