Advanced Materials Research Vols. 123-125

Abstract: The preparation and characterization of cellulosic fibre-reinforced polypropylene composite foams is presented. The cellulose fibres were isolated from a barley straw obtained from local sources. They were compounded with the polymer in the melt state to obtain composites with nominal concentrations of 10 and 20% by weight. After compression-moulding the composite samples were foamed in a high-pressure batch-process employing CO2 as foaming agent. The effects of the fibre loading on the basics characteristics of the foams was investigated.

Abstract: Two-step for wood esterification with oxalic acid and cetyl alcohol is developed in this study. The esterified wood powder was investigated by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results show that ester groups substituted parts of the original alcoholic hydroxyl groups, and crystallization occurred during the modification. In addition, surface wettability, moisture adsorption and water absorption tests for wood specimen have showed that the modification improves the moisture and water resistance.

Abstract: In this study, untreated and alkali-treated vetiver fibers were characterized by thermogravimetric analysis, BET surface analysis, X-ray diffraction and FTIR (ATR) microspectroscopy,. It was revealed that the alkaline treatment influenced properties of vetiver fiber. By the treatment, some hemicellulose and lignin were removed, resulting in higher decomposition temperatures. In addition, the specific surface area were decreased, and crystalline structure was altered. However, no evidence of changes in surface functional groups was observed.

Abstract: In this study, the effect of wood fiber concentrations on the mechanical properties of composites, prepared by using MAPP as the coupling agent, was investigated. In the sample preparation, four levels of fiber loading and three compounding temperatures were used. Most major changes in composite performance occurred at fiber contents above 30 wt%.The results clearly showed that the fiber loading of 30 and 40 wt% at 190oC was provided adequate reinforcement to increase the tensile and flexural strength of the PP powder. The modulus also increased with increasing the fiber content, because poplar fibers are believed to be more rigid than polymer. However, the addition of wood fibers resulted in a decrease in elongation and impact properties of the composites.

Abstract: Components based on composites reinforced with vegetable fibers have awaked interest in various industrial fields. The thermal properties of fibers, matrix and composite define the temperature limits for application and processing of these materials. In this work, a thermal analyzer TGA was used to evaluate the degradation and thermal events of vegetable fibers (abaca, curaua, fique, sisal, cellulose and in natura fibers from sugarcane bagasse and straw), polypropylene (PP) and PP composites reinforced with 15 wt% fibers. Samples were studied by using 30 to 600°C at 5°C.min-1 flow rate under helium or air atmosphere. TG curves from fibers showed weight loss in multiple stages. Before the thermal degradation peak, the abaca composite was more thermally stable, followed by fique, curaua and sisal composites. Thermal stability of composites was inferior for neat PP; however, it had a significant increase for the fiber.

Abstract: Currently, several research groups and industries are studying applications for the residues from agribusiness, other than burning them. Thinking about a better use for the sugarcane bagasse, this study aims to obtain membranes of cellulose acetate composite with oxidized lignin, both isolated from sugarcane bagasse. Thus, we obtain a product with higher commercial value, from a natural fiber residue from agribusiness, which has applications in water and effluent treatment, and further contributes to the maintenance of the environment. Macromolecular components of bagasse (hemicellulose, cellulose and lignin) were separated by applying a steam explosion pre-treatment for the removal of the hemicellulose, a basic treatment with NaOH to separate the lignin and obtain crude cellulose pulp. This pulp was bleached and acetylated, and subsequently membranes of cellulose acetate were synthesized, incorporating oxidized lignin to these membranes in order to increase the metal retention capacity of these membranes. The acetylated material was analyzed by IR, confirming acetylation. Degree of substitution was determined by volumetry, yielding a value of 1.7, featuring a diacetate. The synthesized membranes were analyzed by SEM, showing a dense structure. Tests were conducted to evaluate metal retention, and the average capacity of removal was 15% Cu+2 in steady-state experiments. Retention capacity in membranes is 20 times higher than the retention using chromatographic columns separation.

Abstract: This work describes the electrical switching behavior of three telluride based amorphous chalcogenide thin film samples, Al-Te, Ge-Se-Te and Ge-Te-Si. These amorphous thin films are made using bulk glassy ingots, prepared by conventional melt quenching technique, using flash evaporation technique; while Al-Te sample has been coated in coplanar electrode geometry, Ge-Se-Te and Ge-Te-Si samples have been deposited with sandwich electrodes. It is observed that all the three samples studied, exhibit memory switching behavior in thin film form, with Ge-Te-Si sample exhibiting a faster switching characteristic. The difference seen in the switching voltages of the three samples studied has been understood on the basis of difference in device geometry and thickness. Scanning electron microscopic image of switched region of a representative Ge15Te81Si4 sample shows a structural change and formation of crystallites in the electrode region, which is responsible for making a conducting channel between the two electrodes during switching.

Abstract: The purpose of this study is to prescribe the influence of Si in WC-Ni Hard Metal. For the manufacture of WC-Ni Hard Metal according to Si content, the researcher manufactured WC-Ni mixed powder which 0wt.%~1.5wt.% of Si was added to after selecting Ni which a fixed amount of B was added to, and then manufactured sintered body by implementing vacuum-sintering to the mixed powder. This study implemented the analysis with HRA, TRS, XRD, SEM, and EPMA to observe densification, alloying reaction, and mechanical properties of the sintered body. In WC-Ni Hard Metal, shrinkage showed a tendency to increase as Si content increased. It is considered that the densification was promoted during liquid phase sintering, because a melting point of binder metal got lower as Si content increased. The hardness of WC-Ni Hard Metal was kept uniformly up to 0.6wt.%Si, and then it showed the tendency to increase from the level of 0.9wt.%Si. It is considered that the hardness of B and Si added to Ni binder metal formed BNi3 phase and Ni3Si phase which had high hardness, and these compound phases restrained the growth of WC particle. It is considered that transverse rupture strength of WC-Ni Hard Metal according to the increase of Si content was increased by the decrease of mean free path of WC particle caused by the improvement of fluidity according to the restrained growth of WC particle by of BNi3 phase and Ni3Si phase, and caused by the improved fluidity according to the decreased melting point of Ni binder metal.

Abstract: In this study, we attempt to investigate the effect of silica size on the thermal, mechanical and biodegradable properties of polylactide/amino-silica (PLA/SiO2) composite material, by preparing the PLA/ SiO2 hybrids containing different size of silica particle through twin-screw extruder. First of all, we prepared amino-functionalized silica particles through performing the conventional base-catalyzed sol-gel reaction of methyltrimethoxysilane (MTMS) and 3-aminopropyltrimethoxysilane (APTMS). The average diameter of silica particle employed in hybrids was 150 nm (S-silica) and 1μm (B-silica), respectively. Systematically comparative studies on the thermal properties and mechanical strength of hybrids containing two different sizes of SiO2 particles materials were carried out on a basis of studies of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). It should be noted that the mechanical strength of hybrids containing smaller size of silica particles was found to reveal significant improvement in storage modulus as compared to its corresponding counterpart based on the DMA investigation. Moreover, the thermal stability of hybrids containing smaller size of silica particles was found to reveal slight improvement in glass transition temperature as compared to its corresponding counterpart based on the DSC investigation. Eventually, the as-prepared hybrids were found to exhibit almost similar degradation behavior to that of neat PLA.

Abstract: The microstructure and properties of 7003 aluminum alloy before and after aging under various solid solution treatment parameters have been studied by electronic tensile machine, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS). It’s showed that the strength decreased while the ductility increased with raising the solid solution temperature before aging; the strength decreased and then increased while the ductility increased and then decreased with increasing the solid solution time. The strength of 7003 aluminum alloy after aging were evidently higher than those before aging, and the samples solutioned at 743 K for 70 min were of the best mechanical properties with YS=286 MPa, UTS=345 MPa, E=15.5%, which are higher than those of the original alloy by 2.1%, 1.5% and 29.1% respectively. Hence 743 K/70 min is one of the best solid solution regimes.