Advanced Materials Research Vols. 287-290

Abstract: Energy deficiency and heat generation are key problems for electronics of mobile devices such as smart phone, portable multi-media player, and MP3 player. Generally, they adopt lithium-ion battery which has the degradation of voltage quality and inefficient energy consumption under high temperature caused by heat dissipation from the electronics. The elevated operating temperature makes the battery’s lifetime shorter. To overcome the problems, heat sink with fins are usually attached to the electronic devices for reducing the temperature by efficient heat transfer. The fins are slender beams which can be vibrated easily by transverse force. Therefore, it is possible to increase heat transfer rate by vibrating the fins. Prior research work reported that the transverse vibration results in higher heat dissipation. However, they have focused on not the single isolated fins but the crowded fins. In this paper, the experimental investigation for vibration-assisted isolated fins is presented. The vibration is engaged by a shaker that gives external harmonic excitation force with the wide span of frequency. Also the frequency response of the fin is investigated under a room and elevated temperature of the fin. The heating power and temperature of the fin are measured for the cases with and without vibration. Thermal resistance from the heater to fin is key performance index to evaluate the heat dissipation capability. The effective vibration conditions to enhance the heat transfer are discussed. The result showed that the vibration-assisted fin dissipates more heat from the source than the non vibration-assisted one. Therefore, it can be expected that the vibration-assisted fin can be applied to improve the performance of the mobile electronics and even make longer the battery’s lifetime.

Abstract: The Cu films were deposited on P type Si (111) substrates by ionized cluster beam (ICB) technique. The interface reaction and atomic diffusion of Cu/Si (111) system were studied at different annealing temperatures by X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS). Some significant results were obtained: For the Cu/Si (111) samples prepared by ionized cluster beams at V_a=3 kV, the interdiffusion of Cu and Si atoms occurred in the as deposited samples. The RBS spectra features were changed with a very small extent with increasing the annealing temperature. There are no copper-silicide phases observed by XRD before and after being annealed at different temperatures. The reason may be that there is a thermally stable interface between Cu films and Si substrates formed.

Abstract: Keeping deposition temperature and oxygen pressure constant at 300°C and 4.0×10^-2Pa, respectively, deposition of ZnO thin films with c-axis oriented (002) hexagonal wurtzite crystal structure was achieved by pulsed filtered cathodic vacuum arc deposition (PFCVAD) system at various negative substrate bias on Si(100). The surface morphology was characterized using AFM, and crystallographic structure was studied by means of X-ray diffraction. Based on the biaxial strain model, Strain properties of the ZnO films were investigated by calculation from XRD data. The calculated results revealed that the as-deposited ZnO films exhibited only tensile stress and the tensile stress increased with the elevation of the negative substrate bias. Occurrence of the tensile stress is suggested to be the result of relatively high deposition temperature and the improved deposition rate by elevating the negative substrate bias. It provides a potential method to control the intrinsic stress in the ZnO films by modulation of deposition temperature and the negative substrate bias of PFCVAD system.

Abstract: Lead strontium zirconate titanate (Pb_0.92Sr_0.08)(Zr_0.65Ti_0.35)O₃ (PSZT) thin films were grown on Pt (111)/Ti/SiO₂/Si(100) substrates using a simple sol-gel method. X-ray diffraction studies confirmed that all the PSZT films undergone various thermal process show highly preferred (001)-orientation. On the surface image of the thin film, many clusters are found, which are composed by grains in size of 0.5-0.8 mm. Between the clusters, the nano-size grain is about 50-80 nm. The root mean square (RMS) roughness of the film surfaces is 5.1 nm. PSZT thin film exhibit excellent ferroelectric behavior, demonstrated by reproducible hystersis loops with high remnant polarization (P_r =49 μC cm^-2) and relative low coercive field (E_c=53.5 kV cm^-1). The pyroelectric coefficients (p) were measured, at 26 °C, the p=215 mC m^-2 K^-1 for PSZT films. The dielectric properties as well as phase transition behavior were characterized and a ferroelectric to paraelectric transition were found in the vicinity of 196 °C.

Abstract: Application of whey soy proteins to wastewater processing and beverages were investigated under different conditions.Decoloration and deflavoring eficiency were determined using activated carbon under different temperature,and desalination with ion exchange resins and trypsin inhibitor activity(TIA)was investigated when tested in Sucrose addition and Citric acid addition.The experimental results of whey soy proteins wastewater pretreatment showed that the best conditions of decoloration de-flavoring were:10% of activated carbon,50°C of temperature,adsorption time for 40 min,and the best condition of desalination was 4.28mL/min of flux using ion exchanging resin.

Abstract: Microstructures of electron beam welded joints for TA15 titanium alloy with different hydrogen contents were observed and analyzed by SEM and TEM. And the influence of hydrogen on microstructure of the joints was investigated. The results show that the microstructure of the weld metal is lamellar α+β phase after hydrogen charging. In the range of hydrogen contents discussed in this study (from 0 to 0.101 wt%), With the increase of hydrogen content, there is little change in the appearance of the microstructure of the weld metal. The presence of hydrogen can promote the growth of twins in electron beam welded joints. With the increase of hydrogen content, the number of twins is increased. When hydrogen content reaches to a certainty level, hydrides are found in TA15 electron beam welded joints.

Abstract: ZnO thin films are grown on sapphire substrate by employing a Nd:YAG (1064nm) laser ablation in 1.3 Pa oxygen ambient. X-ray diffraction (XRD) and atomic force microscopy (AFM) observation show that as-grown thin film possess (0002) textured feature and form columnar inclined grains with a small size. The as-grown films show a little oxygen vacancies and Zn interstitial by the analysis of X-ray photoelectron spectroscopy (XPS) and Raman. The annealing treatment in oxygen ambient causes obvious improvement on the structure, surface morphology, compositions and optical properties by the analysis of XRD, AFM, XPS, Raman and photoluminescence (PL) spectra. It can be concluded that the increase of UV emission is oriented to the improvement of structure and decrease of intrinsic defects. The blue emission (430 nm) is attributed to the electronic transition from shallow donor level of Zn interstitial to top level of valence band.

Abstract: In this paper, the keyhole of YAG laser welding 5A90 Al-Li alloy was observed and measured through the high speed camera. The characteristics of the keyhole and the effects of welding parameters were studied. The characteristics of the absorption of laser energy and the susceptivity for heat input in welding 5A90 were given. The results show that in this welding condition, the keyhole of laser welding 5A90 is nearly a taper and the highest temperature area is in the bottom. There are clear effects of heat input on the characteristics, especially the surface radius of keyhole and plasma/vapor in keyhole. Another phenomena is observed that sometime plasma/vapor could disappear in 0.3ms welding time, and this feature will be more remarkable as decrease of heat input. It shows that the absorption of energy is unsteady. It is known that when this instability reaches a certain value, an unsteady weld will be formed.

Abstract: CdS, ZnO and ZnO/CdS core-shell nanorod films were prepared by chemical bath deposition. The samples were characterised by UV-Vis spectroscopy and scanning electron microscopy. The results show that the norder ZnO nanorods have been etched in the alkaline solution, at the same time, CdS was deposited on the ZnO surface. Effect of the concentration of OH^- on the optical prosperties of CdS films were investigated by the optical transmission spectra. The results show that the transmission decrease with the increasing of the concentration of OH^- due to increasing of the film thicknees, which can be ascribed to the increasing of S²⁺ concentration. The mechanisms of the forming of ZnO/CdS core-shell nanorods film in the alkaline solution were further analyzed.

Abstract: This paper investigates a new method, the Levenberg-Marquardt method, to calculate the phase equilibria of the Al-Cu-Mg ternary alloys. The Levenberg-Marquardt method is the best algorithm to obtain the least-square solution of non-linear equations. Its application to ternary Al-Cu-Mg system is executed in detail in this paper. The calculated phase equilibria agrees well with the experimental results. Furthermore, the Levenberg-Marquardt method is not sensitive to the initial values.