Advanced Materials Research Vols. 79-82

Abstract: The complex {1,1’-[ o-phenylenebis (nitrilomethylidyne) ] di-2-naphtholato} copper(II) was optimized by the DFT method at B3LYP/LANL2DZ level, and the frontier molecular orbitals, natural bond orbitals, nonlinear optical properties and Mülliken charge population of the optimized complex were exploited and analyzed. The calculated results show that the complex has stable structure and it keeps some potential applications in optic materials field.

Abstract: For the analysis of various extruder models are used not only testing, but also diverse simulation techniques. Of them, the three-dimensional technique is widely used recently. In this study, the breaker plate in a polymer resin extruder was analyzed. The breaker plate changes the rotational motion of the polymer resin extruded from the screw barrel into a straight line motion before it passes through the die. Also, the size and number of circular holes in a breaker plate directly affect polymer resin extrusion molding. In this study, a 3-D modeling was used to conduct the structural improvement of breaker plates, and the thermal/flow analysis program CFdesign was used to conduct a dynamic property analysis in a bid to achieve the production stability of extruders.

Abstract: High-density AlN ceramics were fabricated without sintering additives at high pressure (5.0 GPa) and temperature (1300-1700 °C). The sintered bodies were characterized by XRD and micro-Raman spectroscopy (MRS). The values of residual stresses due to the distortion of the AlN lattice were assessed using the Micro-Raman Spectroscopy (MRS). Residual compression stress of the AlN ceramics sintered at 5.0 GPa and 1700 °C for 125 min is -2.0 GPa. The residual compression stress increased according to the extension of the sintering time.

Abstract: NiO/γ-Al2O3 adsorbent was prepared by wet impregnated method. XRD, SEM-EDS, nitrogen adsorption techniques were used to characterize the adsorbents and GC-FPD was utilized to analyze the composition of gasoline before and after reaction. X-ray diffraction patterns indicate that noncrystal NiO particles are supported on the surface of γ-Al2O3. The results show that NiO/γ-Al2O3 adsorbent could be used to remove sulfur compounds and is effective on removing benzothiophene (BT). The maximum desulfurization efficiency appears when NiO content reaches 16%, and the total sulfur adsorption capacity is 1.84mg/g, however for 16%Ni/γ-Al2O3 the value reaches 3.495mg/g.

Abstract: One of the major limitations for wider use of pultruded fiber reinforced polymeric (PFRP) composites in the civil engineering sector has been their behavior under elevated temperature and ultimately fire. This limitation arises not only due to the reduction in mechanical properties at high temperatures, including increased propensity to creep, but also due to limitations on the continuous working temperature causing permanent damage to the material as a result of thermal and oxidative degradation. Significant gains in property retention at high temperatures with crystalline polymers have been derived from the incorporation of fibrous reinforcement, but the development of new polymer matrices is the key for further elevation of the useful temperature range. This paper presents summary results of a research project focused on characterizing the viscoelastic behavior of commercially-produced, off-the-shelf unidirectional PFRP materials subjected to elevated temperature environments.

Abstract: LaPO4 was added to Al2O3 ceramic matrix to improve the machinability of the composites. Different from the traditional way of making Al2O3/LaPO4 composite, coating method is introduced. In the present work, LaPO4-coated α-Al2O3 powders were synthesized through the heterogeneous precipitation method and sintered into Al2O3/LaPO4 composites by pressureless sintering at 1600°C for 2h. The phase components and microstructure of Al2O3/LaPO4 composites are presented according to variations of lanthanum phosphate (LaPO4) content (10 wt.%, 20 wt.%, 30 wt.%, 40 wt.%). From the TEM image, it can be seen that the coated powders have a clear core-shell structure and the thickness of the coating varies from 5 to 15 nm approximately. X-ray diffraction analysis showed that only Al2O3 and LaPO4 phases exist in the Al2O3/LaPO4 composites which indicated that there is good chemical compatibility between Al2O3 and LaPO4 phase. Microstructure development of Al2O3/LaPO4 composites has been explored by SEM, the coating structure became less recognized after sintering, layered and fiber shaped LaPO4 was obviously observed in the Al2O3/LaPO4 composites with the increase of LaPO4 addition. The LaPO4 inhibited grain growth of Al2O3 by distributing at the Al2O3 grain boundaries. The weak interface of Al2O3/LaPO4 and layered soft LaPO4 phase can be responsible for the machinability of the composites.

Abstract: Nanometer LaPO4 powders were synthesized by liquid-liquid direct precipitation method. La(NO3)3•6H2O and (NH4)3PO4•3H2O were used as raw materials. The calcining temperature was 900°C, 1000°C, 1100°C, respectively. DTA result shows that the LaPO4 precursor is LaPO4•4H2O. The calicined powders were characterized by X-ray powder diffraction (XRD) and Scanning Electron Microscope (SEM), and exhibited a pure LaPO4 phase with a monazite structure about 50-100 nm in diameter size. With the calcining temperature increasing, the crystallization of the LaPO4 became better and the grain shape changed from elongated grain shape to spherical grain shape.

Abstract: Eu doped LaPO4 nanocrystals were successfully synthesized by molten salt method calcined at 700°C. The structure, morphology and photoluminescence of as-synthesized product were characterized. The results reveal that all the doped samples are well crystalline at 700°C and assigned to the monoclinic monazite-type structure of the LaPO4 phase. It has been shown that the obtained nanocrystals to be long rod-like with diameters of 5-10 nm and length of 100-150 nm. The luminescence intensities strongly improved due to the high crystallinity because of the molten salt as the medium in thermal treatment posscess.

Abstract: Effects of silicon concentrations in Ni-Cr-based alloys on the formation of oxide scales were examined in reduced atmosphere. The morphology and oxide scale were compared based on the Si content. The formation and growth kinetics of the oxide scale are rather sensitive to the alloy microstructures and their corresponding Si contents. Oxide ridges formed on the eutectic structure preferentially, while a thinner and homogeneous oxide scale grew from the austenite matrix. The thicknesses of the oxide ridges and the oxide layer on the austenite matrix are dependent of their corresponding Si contents. The ridge-like feature indicates that the austenite/carbide phase boundaries offer fast diffusion paths for metal atom outward diffusion. The formation of SiO2 sub-layer at the oxide scale/metal interface can act as an effective diffusion barrier for atom outward diffusion.

Abstract: To characterize the thermomechanical response, especially the superelastic behavior of NiTi shape memory alloys (SMAs), the DSC and tensile cycle test of NiTi of different annealing temperature have been presented. There’s no remarkable phase transformation peak, however, the stable tensile cycle curve and maximum dissipated energy have been observed at annealing temperature of 673K.