Applied Mechanics and Materials Vol. 606

Abstract: ZnO nanosheetlike structures were synthesized on zinc (Zn) foil substrates by electrochemical deposition method in ZnCl₂ aqueous solutions at a temperature of 90 °C. In addition, the synthetic parameters in this work allow additional structural direction for ZnO nanoscaled structures. The morphology growth from smooth plane structures to nanosheet like structures could be accomplished by modifying the current densities of electrodeposition. In the photoluminescence (PL) spectra of the as-synthesized ZnO samples, typically there are few oxygen vacancies or interstitial Zn centers would be produced when the electrochemical deposition was performed out with a low current density. The UV peak is usually considered as the characteristic emission of ZnO nanosheetlike structures and attributed to the band edge emission or the exciton transition. All XRD diffraction peaks of ZnO nanosheetlike structures are shown in a good agreement with hexagonal structure. The average particle size was calculated using the Debye-Scherrer formula. ZnO nanosheetlike structures processed for various current densities have different size.

Abstract: Lubricant oils play essential role in manufacturing processes for reducing friction and wear between contact parts at different speeds. Palm fatty acid distillate (PFAD) is a new source from vegetable oil and has potential as an alternative source of mineral lubricant oils. This study was performed at various speeds (800, 1200, and 1600 rpm) and at a constant load (392N), temperature (75°C), and time (1 h) using a four-ball tribotester. To evaluate the PFAD results, similar experiments were done using hydraulic oil, and the results were compared mutually. The results showed that the anti-friction, anti-wear, viscosity, and flash temperature parameter (FTP) of PFAD were higher than those of hydraulic mineral oil.

Abstract: In_xSe_1-x (x = 0.4, 0.5, 0.6) thin films are deposited at room temperature on glass substrates with thickness ~500nm by thermal evaporation technique. The X-Ray diffraction analysis showed that both the as-deposited films In₂Se₃ and InSe (x= 0.4 and 0.5) are amorphous in nature while the as-deposited film In₃Se₂ is polycrystalline and the values of energy gap are E_g=1.44eV for In₂Se₃, E_g=1.16eV for InSe and E_g=0.78eV for In₃Se₂. The same technique used with insert Argon gas at pressure 0.1 mbar where In_xSe_1-x (x = 0.4, 0.5, 0.6) thin films are deposited at room temperature on glass substrates with thickness ~100nm. The X-Ray diffraction analysis showed that the as-deposited films In₂Se₃ are amorphous in nature while the as-deposited film InSe and In₃Se₂ are Nanocrystalline with grain size 33nm and 55nm respectively and the values of energy gap are E_g=1.55eV for InSe and E_g=1.28eV for In₃Se₂. The energy gap of InSe thin films increase with Argon gas assist and phases changes from amorphous and polycrystalline to nanostructure material by thermal vacuum deposition technique.

Abstract: This paper describes the thermoluminescence properties of RE⁺³(RE=Nd, Sm) doped optical fiber SiO₂ prepared by CorActive company in Canada. The samples were exposed to 6 MV X-ray irradiation at dose ranging from 0.5 to 4 Gy at hospital Sultan Ismail, Johor Bahru, Malaysia using the LINAC accelerator. After exposure and a certain delay of 12 h to get uniform control of thermal fading, the optical fiber TL yield was readout using a TL reader. The optical fiber demonstrated a linear TL response versus of the absorbed dose. The linearity increases with the increasing dose while in the case of Sm-doped optical fiber; the response is comparatively smaller than Nd-doped optical fiber. Also, the glow curve of RE⁺³ ions doped optical fiber is compared with the undoped fibers. The results exhibit that the glow curve peaks are shifted to higher temperature due to rare-earth doping. As the results indicate the TL response strongly depends on the doping type of materials. All these TL characteristics are proposing this commercial optical fiber very decisive TL material.

Abstract: In this study, cocoa (Theobroma cacao) pod husk (CPH) fiber reinforced themoplastic polyurethane (TPU) was prepared by melt blending method using Haake Polydrive R600 internal mixer. The composites were prepared with different fiber loading: 20%, 30% and 40% (by weight), with the optimum processing parameters: 190°C, 11 min, and 40 rpm for temperature, time and speed, respectively. Five samples were cut from the composite sheet. Mean value was taken for each composite according to ASTM standards. Increase of fibre loading showed increase in tensile strength and modulus and decreasing trend of strain.

Abstract: Natural clinoptilolite (Cli) and chabazite (Cha) were used as the carrier for two types of antibacterial agents: cetylpyridinium chloride (CPC) and silver cations (Ag). CPC-zeolites, Ag-zeolites and CPC-Ag-zeolites were characterized by Energy Dispersive X-ray (EDX) analyzer and Fourier Transform Infrared (FTIR) spectroscopy and proved the attachment of CPC molecules on Ag-zeolite in CPC-Ag-zeolite samples. The determination of Minimum Inhibition Concentration (MIC) against P. aeruginosa and B. subtilis in saline solution and distilled water was performed to observe the effect of chloride ions on the antibacterial activity of the studied samples. From the MIC values, a new modified zeolite with CPC and Ag (CPC-Ag-zeolites) showed better antibacterial activity compared to that of CPC-zeolites and Ag-zeolites and performed well in both saline solution and distilled water.

Abstract: The effect of melt temperature on the interfacial thermal resistance and solidification behaviour of A356/10% SiC_p during squeeze casting is studied. The melt pouring temperatures are considered in the investigation within the range of 750 - 900°C respectively. The squeeze pressure is kept constant at 100 MPa. It was observed that the solidification time increased with the melt temperature from 40 seconds at 750°C to 51 seconds at 900°C. The results also showed that the cooling rate decreased with melt temperatures. The solidification time calculated from the theoretical expression was found to be in good agreement with that obtained from the experimental cooling curves. The interfacial thermal resistance value increases from 0.000043 to 0.000203 m² K/W when the melt temperature is increased from 750 to 900°C.

Abstract: The maleic anhydride-grafted ethylene-octene copolymer (POE-g-MAH) and 2, 3-epoxy propoxy propyltrimethoxysilicane (KH-560) modified nano-silica particles/ POE nanocomposites were fabricated by solution coprecipitation. Tribological behaviors of these nanocomposites were investigated using a pin-on-disk friction and wear tester under dry friction condition, and worn surfaces were studied by scan electron microscope (SEM) and color 3D laser scanning microscope, respectively. The results indicated that the addition of the low inclusion (more than 10 wt%) of nano-silica particles could improve the reducing-friction and anti-wear abilities of the POE matrix composites, and modified nano-silica as the filler are superior to nano-silica in terms of the ability of decreasing friction coefficient and wear rate of the POE polymer materials. In both cases, appropriate treatments could effectively improve the mechanical and tribological properties of the POE matrix composites due to the enhanced nanosilicas-matrix interfacial bonding.

Abstract: Guided Bone Regeneration (GBR) membrane is used as a barrier to prevent soft tissue ingrowth and to encourage bone regeneration through cellular exclusion. This study aims to assess antibacterial properties of recently developed three-layered poly(lactic-co-glycolic acid) (PLGA) /lauric acid (LA) composite membrane towards Staphylococcus aureus. One of the outmost layers of three-layered membrane was incorporated with 1-3 wt% of LA. The composite membrane was developed using thermally induced phase separation/solvent leaching technique. SEM results shows formation of PLGA matrix with smaller pores by the addition of 1 wt% LA compared with pure PLGA membrane. Samples of 1.7 cm diameter disk containing 1, 2 and 3 wt% of lauric acid were tested and pure membrane without lauric acid was used as a control. Results showed that the zones of inhibition were 2.3 cm and 2.5 cm for the 2 wt% and 3 wt% LA-containing membranes, respectively. However, 1 wt% LA-containing membrane observed to have no inhibition at all, indicating that increasing concentration of LA has significant inhibition against Staphylococcus aureus. The 3 wt% LA composition will be used in the mechanically optimized membranes for degradation studies in future works.