Advanced Materials Research Vol. 576

Abstract: Stainless steels suffer from classical sensitization when encounter at certain temperature which results in precipitation of chromium carbide along grain boundary with simultaneous depletion of chromium from near grain boundaries. This study focused on corrosion potential test at different sensitization condition. The degree of chromium carbide precipitation was measured based on thickness of grain boundary. With increasing holding time, the thickness of the chromium depletion zone also increases due to diffusion of chromium into solid solution. Corrosion potential test showed that the heated sample at 700°C for 60 minutes resulted in highest corrosion current density and shifted its corrosion potential to more active potential. The potential tend to increase with increasing the degree of chromium carbide precipitation.

Abstract: Fe-Mn alloys are prospective degradable materials for coronary stents. Several methods and strategies are investigated to produce excellence properties for this application, such as addition of alloying elements. The study is focused on the corrosion behavior of novel Fe-Mn alloys, i.e. Fe-25Mn-1C and Fe-35Mn-1C fabricated by powder metallurgy process. Addition of carbon is intended to obtain the phase that has ability to easily degradable without compromising its mechanical properties. The results show that austenite phase formed from this process and corrosion rate increased in proportion with the manganese addition from 32.2 mpy (Fe-25Mn-1C) to 43.7 mpy (Fe-35Mn-1C) using polarization methods. The presence of porosity, which cannot be extinguished by sintering, makes the degradation favorable. The results of this study indicate that these alloys have prospective properties to be applied as degradable biomaterials.

Abstract: This study shows the effect of using 3-aminopropyltriethoxysilane (APS) and maleic anhydride-grafted polypropylene (MAPP) as coupling agent on composite of RPP/MCC fiber. The compositions of MCC were varied from 0, 2, 4, 8 and 12 wt%. The compounded samples were prepared into test specimens by using injection moulding. The RPP/MCC composites with and without the coupling agent were characterized through mechanical testing of flexural and impact test. The incorporation of the modified MCC was found to increase the modulus and flexural strength. The flexural test indicates that the addition of 4 wt% MCC-APS and 8 wt% MCC-MAPP significantly increased the flexural strength of the RPP composite compared to the unmodified MCC. The impact test shows higher impact strength at 4 wt% of RPP/MCC-APS and 2 wt% of RPP/MCC-MAPP, respectively.

Abstract: Thermoplastic natural rubber (TPNR) nanocomposites were prepared by melt blending method with the optimum mixing parameters (140oC, 100 rpm, 12 min) using internal mixer (Haake 600 P). The aim of this work is to study the effects of organo-montmorillonite (OMMT) on the physical and mechanical properties of TPNR with and without coupling agent (maleic anhydride grafted polyethylene, MA-PE). Significant improvement in tensile strength and modulus of TPNR nanocomposites were obtained with the presence of MA-PE.

Abstract: Maghemite nanoparticle suspensions were synthesized using a co-precipitation method and characterized by a variety of techniques including XRD, TEM, magnetic measurement, DLS, and zeta potential. The stability of the suspension was monitored by measuring the particle size distribution using DLS over a period of two months. The diffraction pattern from XRD measurement confirmed that the particles were maghemite with an average crystallite size of 9.4 nm. TEM observations and analyses showed that the geometry of maghemite nanoparticles were nearly spherical with a mean physical diameter of 9.9 nm. The maghemite nanoparticles showed superparamagnetic behavior with saturation magnetization value of 32.20 emu/g. The mean hydrodynamic diameter of the suspension remained unchanged after two months which indicated no formation of aggregation. The hydrodynamic diameters recorded were 45.1 nm and 48.4 nm, respectively. Additionally, lack of sedimentation indicated that the suspension was stable. The suspension’s zeta potential values were 41.5 mV and 40.4 mV for as synthesized and after two month of storage respectively.

Abstract: Mesoporous γ-alumina with relatively high surface area of ca. 590 m2/g and pore size of ca. 2.0 nm to ca. 9.7 nm were successfully processed using facile and cost-effective method in the presence of renewable, low-cost templates. Controlled addition of water during the processing of the materials was found to control the rapid hydrolysis rate of alumina precursors resulting in mesoporous formation. In addition, these materials porosity was made up from framework porosity as well as textural porosity given rise from the aggregations of γ-alumina nanoparticulates. Regardless of the materials specific surface area value, the competitive adsorption amount of energy gas in 68 % humidity environment increased as relative crystallinity of the materials increased.

Abstract: In the current work, ZnO nanoflowers have been synthesized via sol-gel technique using a mixture of zinc-nitratetetrahydrate, ammonia and polyethylene glycol (PEG). Variation in PEG concentration and ammonia evaporation delay time was performed and the resulting nanoflowers have been investigated using x-ray diffraction (XRD) and scanning electronmicroscope (SEM). To explore the potential of the resulting ZnO nanorods, a prototype of dye sensitized solar cell (DSSC) has been fabricated. For this purpose, the nanorods were grown directly on conducting ITO substrates by nanoseeding technique. With a variation in nano seeding time for 2, 4 and 6 days, followed by hydrothermal process at 80oC for 20 hours, ZnO nanorods with average diameter of 82, 332 and 1385 nm have been synthesized. The performance test showed the resulting open circuit voltage (Voc) was increased from 398 to 486 mV when the diameter of ZnO nanorods increased from 82 to 332 nm. However, the Voc decreased slightly to 456 mV when the nanorods further increased to 1385nm. The phenomenon is related to the interaction between the semiconductor oxide and the Ruthenium complex organic dye.

Abstract: Thermal stability of nickel molybdenum electrodeposits was investigated. This investigation is important to show that electrodeposits can be used at elevated temperature and to understand electrodeposit behaviour as a function of temperature. Crack-free electrodeposits with up to 17 at% molybdenum were produced by the square pulse electro-deposition technique from a solution containing nickel sulphamate. The experiment was performed using vacuum furnace. Microstructure of deposits was investigated using microscope SEM, while the phase of deposits was studied using x-ray diffraction. Chemical composition of deposits was observed using energy dispersive x-ray analyzer and hardness of deposits was measured using micro hardness tester. The result shows that nickel molybdenum electrodeposits stable up to 400 oC. For 550 oC, grain growth was observed to start but the hardness of electrodeposits has no significant changed. Hardness analysis shows that hardness of electrodeposits does follow Hall Petch relationship.

Abstract: In this study, PMMA/TiO2 nanocomposite thin films were prepared by using sonication spin coating technique. The PMMA and TiO2 solution were mixed together and sonicated for 1h to confirm the homogeneity of the sample. The thin films obtained were then measured using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FTIR). FESEM micrograph reveals that the uniformity increases with the increase of TiO2 weight percentage.

Abstract: The purpose of this research work is to evaluate the effects of reinforcing high impact polystyrene (HIPS’s) with multiwall carbon nanotubes (MWCNTs) on the mechanical performance and the water absorption resistance. The significant changes in HIPS/MWCNTs nanocomposite on the mechanical performance and water absorption resistance were investigated with different weight percentage of MWCNTs in the range of 0.10 wt% to 10 wt%.