Advanced Materials Research Vol. 748

Abstract: The detonation of fine aluminum-oxygen mixtures was numerical simulated using a hybrid combustion model. The emphasis was laid on the influence of the decomposition of Al₂O₃ on the detonation structure. Results showed that including the decomposition of Al₂O₃ will limit the gas temperature behind the detonation wave below a certain value. On the other hand, a double-wave structure will appear in the pressure profiles in cases with rich-dust condition if the decomposition of Al₂O₃ is not included.

Abstract: This review provides some recent progress of the research in machinability assessment of magnesium alloys. Surface integrity and cutting temperature as the main machinability terms are widely discussed in this paper. Machining parameters, such as cutting speed, feed, depth of cut, play important roles in developing good surface finish and high quality surface integrity. Achieving good surface finish (low surface roughness) is a main objective in machining, especially for biomedical applications. Cutting temperature during machining has to be taken into considerations. High temperature during cutting leads to low surface finish and higher tool wear rate, leading to low tool life and poorer surface finish.

Abstract: PLA toughened by kenaf green composite were produced involving chemi-mechanical method. The effect of chemical treatment on the surface morphology and flexural properties of PLA/kenaf green composite was investigated. The effect of kenaf fiber loading which is varying for 2%, 4% and 6% on the flexural properties was also investigated. The sample was test for flexural properties according to ASTM D790 and the surface morphology was observed using scanning electron microscope (SEM). The results show that PLA composite toughened with 6% of kenaf gave higher value for MOE which is 944.46 MPa compared to 2% and 4% kenaf loading. This is due to a stiffer material was introduced into PLA matrix. The MOR value for neat PLA is 38.78Mpa. However, the value for MOR was decreased by increasing fiber loading which are 33.43, 28.93 and 29.69 Mpa for 2%, 4% and 6% respectively.

Abstract: The failure behavior of polyether polyurethane films irradiated by UV depends on its molecular structures evolvement. The molecular structure evolvement of the polyether polyurethane films under UV irradiation were studied by in-situ FTIR spectra in this paper. It has been found that some oxygen contained groups such as hydroxyl group and carbonyl group increase; on the contrary, ether bond and CH₂ decrease with the UV irradiation time. The aromatic ring maintains changeless. However, -NH group has not be determined due to the interference of the-OH and O-C=O. Results from FTIR and SEM have shown that UV photodegradative processes participated by oxidization occur mostly in ether segments and is accompanied by crosslinkage. Using the absorbance band of aromatic ring as the base the service life of polyether polyurethane can be determined by the change rate of C-O-C and-CH₂ during UV irradiation. After UV irradiation, the polyether polyurethane film has higher color difference value and lower UV light transparence.

Abstract: In this paper we present results of structural analysis of SnO₂ films deposited by spray pyrolysis and designed for application in conductometric gas sensors. The aim of this analysis was summarizing the results obtained in this field, highlighting a correlation between material structure and its gas sensing properties, and formulating some general regularities typical for metal oxides.

Abstract: Powder metallurgy techniques have emerged as a promising way for the fabrication of nanotube reinforced metal matrix composites. The present study reports on the investigation of the optimum consolidation conditions that give the best mechanical properties, for different carbon nanotubes weight percentages and extrusion ratios, while minimizing any chemical interfacial reactions between the matrix and the reinforcements. The conditions investigated were hot compaction followed by hot extrusion, cold compaction followed by hot extrusion, and hot compaction followed by cold extrusion. The tensile behaviors for samples of the three processing conditions were evaluated and compared. An increase in the yield strength of the carbon nanotubes CNT composites under most conditions were observed. The highest strength values for composites were obtained using the hot compaction/cold extrusion route at extrusion ratio 4:1, on the expense of the ductility. Better strength values were obtained for the hot compaction/hot extrusion route at higher extrusion ratio of 5:1 with restoring good ductility.

Abstract: nfluence of Ar gas pressure on the SHS reaction products from WO₃/B₂O₃/Al system has been investigated. The pressure of Ar gas has a significant effect on the phase separation and microstructures of SHS products. Increase in Ar gas pressure has a effect on the phase compositions of SHS products and results in the increase of the amount of W₂B. Furthermore, the crystalize sizes of W₂B increase with the increase of Ar gas pressure from 0.3 to 0.5 MPa, respectively.

Abstract: The Fe-Al₂O₃ composite has been prepared by high-frequency induction heated combustion synthesis (HFIHCS) from Fe₂O₃ and Al powders. The standard Gibbs energy minimization method was used to calculate the equilibrium compositions of the reacting species. The composition and microstructure of HFIHCS products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX).

Abstract: The solid content of kaolin pigment suspension used in paper coatings must be as high as possible in order to minimize the drying cost. X-ray photoelectron spectroscopy (XPS) analysis on elemental compositions showed that, the kaolin combined less dispersants possessed worse dispersion capacity. Therefore, the effect of pre-adsorption of organic or inorganic negatively charged polymers sodium polyacrylate (PAA) and sodium hexametaphosphate (HMP) on the dispersing performance of concentrated kaolin suspensions was investigated, moreover, the effect of pre-adsorbing with or without grinding processing was evaluated. It was found that the viscosity of PAA pre-adsorbed kaolin decreased considerably, probably due to the stronger electrostatic repulsion. And grinding treatment had a dramatical influence on the dispersing behavior of kaolin with PAA pre-adsorbed on, resulting in low relative viscosity at high solid content.