Applied Mechanics and Materials Vol. 487

Abstract: The internal friction of Ti-35.4Nb-0.05C (wt.%) was investigated using a dynamic mechanical analysis (DMA) Q800 from TA Instruments. It has been shown that a relaxational peak is observed in the water-quenched Ti-35.4-Nb-0.05C alloy on tanδ-temperature curve. The activation energy and pre-exponential factor of the peak are H_q=1.82±0.1 eV and τ_0q=1.7×10^-19±1 s, respectively. The activation energy value is a little larger than that of the water-quenched Ti-35.4-Nb alloy. The peak height is decreased compared with the water-quenched Ti-35.4-Nb alloy.

Abstract: This study derived the five parameters in Johnson-Cook equation of CP titanium Gr2. Quasi-static and dynamic compression tests were designed to measure mechanical properties at strain rates of 10^-3s^-1 and 6000s^-1. In order to secure the validity of tested data, a novel fixture was proposed to reduce the displacement measurement error in MTS testing system and the signal processing procedure of compressive split Hopkinson pressure bar for the present study was demonstrated. With the tested data and calculated adiabatic heating temperature rise, parameters A, B, n, m, C have been derived based on mathematical deduction and solve. It was found that the constructed constitutive model fit the tested data well and was able to restore the yield strength value at high strain rate.

Abstract: Molybdenum disilicide (MoSi₂) matrix composites with various contents of carbon nanotubes (CNTs) were fabricated by sintering in vacuum at 1550°C for 1 h. The oxidation behaviors of CNTs/MoSi₂ composites at 1300°C for 200 h in air were studied. Results showed that MoSi₂ matrix composites with no more than 8 % CNTs in volume had good oxidation resistance at 1300 °C, although addition of CNTs reduced the high temperature oxidation resistance of MoSi₂. An approximate linear relationship was found between the weight gain of CNTs/MoSi₂ composites and the content of CNTs. The oxidation resistance of CNTs/MoSi₂ composites at high temperature decreased with the increasing of CNTs contents. Since the gaseous products were formed during the oxidation process and escaped from the oxide film, the protective film became loose which offered channels for the oxygen soaking into the composites. Thus the oxidation resistance of CNTs/MoSi₂ composites was decreased.

Abstract: In order to improve the mechanical properties of the glass fiber reinforced nylon 6 composites (GFRPP6/MCES) with microcapsules, different ratios of nanoreinforcing materials are added into this self-healing composite material which is used in gears, and how the nanoreinforcing material affects the mechanical properties of the self-healing composite is studied by testing its tensile property, bending property, impact strength and hardness. The results show that the appropriate amount of nanoreinforcing material can improve the mechanical properties of the self-healing composite. Whats more, when its content comes to 4wt%, the mechanical properties reached the maximum value and the improvement effect is the most obvious.

Abstract: ZnS_0.59Se_0.41 alloy nanowires were prepared on gold-coated Si substrates by the thermalevaporation of a mixture of ZnSe and ZnS powders. Field-effect transistors (FETs) constructed fromthe ZnS_0.59Se_0.41 NWs verified their p-type nature with a hole concentration of 3.1×10¹⁸ cm^-3.Inaddition,the photoresponse indicates their potential for photoelectric applications.

Abstract: Barium Strontium Titanate (BST) a common topic in the microelectronic field for many devices which is mainly on dynamic random access memories (DRAM). There are many methods of preparing Ba_xSr_1-xTiO_3; barium strontium titanate. In this work, sol-gel method was used as it has some advantages like better homogeneity, lower cost, lower processing temperature and easier fabrication. Ba_xSr_1-xTiO₃ solution was deposited on the silicon substrate of 4 different thicknesses with different ratio of the concentration of Barium (Ba). The thickness of the thin film has a linear increase as the Ba content increases.

Abstract: The current advancement of LED has prompt thermal challenges from the packaging point of view. The reliability of the LED is significantly influenced by each of its packaging component. This paper presents the investigation of heat slug size effect on the junction temperature and stress of single chip LED through simulation method. Ansys version 11 was utilized and the analysis was done with copper diamond rectangular heat slug under natural convection condition at ambient temperature of 25 °C.The simulation results indicated that junction temperature and the stress of the single chip LED is influenced by the size of heat slug.

Abstract: The Lambda 950 spectrometers are designed to investigate and examine surface coating on test specimen by using the light source. The objective of this research is to investigate the factors that affect the surface roughness and reflectance after different parameter of Reactive Ion Etching (RIE) process. There are four parameters to control the RIE process which is temperature, vacuum, RF (Radio Frequency) power and gas flow. The parameters in this research are using a Full Factorial Experimentation technique, the Design of Experiment (DOE). The AFM (Atomic Force Microscope) and Lambda 950 spectrometer are used to analyse the surface roughness and light reflectance of the specimen. The result showed all four parameters of RIE were give effect on surface roughness and surface reflectance. The parameter of gas flow is the most influence factor for surface roughness and surface reflectance compared to other parameters in this work.

Abstract: Potentiodynamic and potentiostatic polarization experiments showed that the nanocrystallized bulk 304 stainless steel (nano304SS) exhibited a superior pitting resistance in 0.5 mol/L HCl solution, in comparison to the bulk 304 austenitic stainless steel (304SS). X-ray photoelectron spectroscopy characterization indicated that a passive film was formed on the nano304SS which was richer in Cr and denser than that on the 304SS