Advanced Materials Research Vol. 739

Abstract: Lead zirconium titanate Pb (Zr_0.52Ti_0.48)O₃ (PZT) thin films have been deposited on Pt/Ti/Si substrate by rf-magnetron sputtering. X rays diffraction revealed that at 600°C the PZT thin film had crystallized into ABO₃ perovskite phase. Degree of crystallization depended on annealing temperature. The perovskite grains were textured predominantly along the (110) direction. The grain size was about 140 nm and almost unchanged under different annealing temperature. With the annealing temperature increasing, the degree of crystallization was improved. La_0.5Sr_0.5CoO₃(LSCO) thin film was grown on Pt/Ti/Si as buffer layer. PZT with LSCO buffer layer was intensively (110) preferred orientation and the morphology of PZT thin film changed greatly.

Abstract: An atomistic simulation of the structural properties of the Rh7-xTxB3 series, where T is Fe, Cr, Mn, has been carried out using interatomic pair potentials based on the lattice inversion method. Calculated results show T atoms can stabilize Rh7-xTxB3 with Th7Fe3-type structure, and T atoms substitute for Rh with a strong preference for the 2b sites. The phase stability of the intermetallics Rh7-xTxB3 is tested by many means including random atom shift, global deformation and high temperature disturbance under the control of the pair potentials. Calculated unit-cell parameters for Rh7-xTxB3 agree with the experimental data very well. All the above results indicate that the potentials are valid for studying the structural properties of these kinds of complex structure of transition metal boride.

Abstract: The thermal conductivity (TC) of compression moulded polycarbonate (PC) and PC filled with 2.5-5% iron oxide (α-Fe₂O₃), cupric oxide (CuO) or magnesium oxide (MgO) nanoparticles, prepared by extrusion, was studied using a thermal conductivity analyser (TCA). The effect of type and content of nanoparticles on the thermal conductivity was investigated. The experimental TC values of the PC nanocomposites showed an increase with an increase in the level of nanoparticles concentration. The TC improvement in PC/CuO nanocomposite was greater than that of other nanocomposites. Several models were used for prediction of the TC in the nanocomposites. In all nanocomposites the TC values correlated well with the values predicted by the Ce Wen Nan model up to 5wt%.

Abstract: The surface modification process for coarse wool fiber which was oxidized by KMnO₄ first, and then MnO₂ covering on the fiber was reduced with Na₂SO₃ was studied. The method for surface modification of coarse wool fiber was determined from comparative analysis, the optimum oxidation process was as follows: concentration of KMnO₄ at 3g/L, time 15min, temperature 50°C, ratio of water and wool fiber was 50:1, and the optimum reduction process: Na₂SO₃ concentration at 20g/L, time 8min, temperature 55°C, ratio of water and wool fiber was 50:1. Compared with original wool fiber,the breaking strength and fineness of modified coarse wool fiber decreased, while the moisture regain increased from 15% to 18%.

Abstract: The high magnetic anisotropy may enhance the thermal stability of the magnetic tunnel junction of CoFeB/MgO/CoFeB, which is a promising candidate for the high performance magnetic random access memory (MRAM). However, the interface stabilized perpendicular magnetic anisotropy (PMA) is not completely understood at this moment. In this study, we fabricated separated top and bottom Ta-CoFeB-MgO thin films and found both structures showed strong PMA after a 300 °C post annealing. However, the top structure has thicker magnetic dead layer and much higher coercivity relative to the bottom structures. The asymmetry between the top and bottom Ta-CoFeB-MgO structures may be attributed to the crystalline structure and interface diffusion. X-ray photoelectron spectroscopy depth profile reveals that the boron diffuses mainly toward to the Ta side at CoFeB-Ta interface in both top and bottom structures. It is mainly Ta that appears at the CoFeB-MgO interface of top structure while it is TaO_x that appears at the CoFeB-MgO interface of bottom structure. A detailed discussion about the chemical states at the interface in Ta-CoFeB-MgO thin films will be given.

Abstract: The Mg₂NiH₄ hydrogen storage material was prepared by magnetic field assisted combustion synthesis (MACS). It is found that the high magnetic field promotes the formation of Mg₂NiH₄. The high pressure differential scanning calorimetry (HPDSC) test results indicate that the optimum hydriding and dehydriding onset temperatures are 434 K and 525 K, respectively. However, the peak temperatures associated with LT à HT are similar for all samples. The Vant Hoff results show that a high magnetic field has no obvious effect on the entropies and enthalpies of these compounds.

Abstract: GDL-4 is a new kind of tool steel, but the machinability was the key factor for the application of it. In order to improve the machinability of GDL-4 tool steel, the factors influencing the machinability, such as the thermal property, work hardening exponent, carbides were studied comparing with M2 in this paper. The results show that under the same cutting condition, the thermal property is the key factor which makes the machinability of GDL-4 worse, and Si is the key element affecting the thermal property.

Abstract: The SAMs was prepared on aluminum alloy by self-assembly membrane technology. The surface morphology of the SAMs was analyzed by scanning electron microscopy (SEM). The electrochemical properties of the SAMs and bare Al alloy samples were researched by Potentiodynamic polarisation and electrochemical impedance spectroscopy in a 3.5-wt.% NaCl solution. The results showed that corrosion current density of the sample with the SAMs was 3.033×10^-9 Acm^-2. The impedance of SAMs was three times than the bare Al alloy. The SAMs had better corrosion resistance than the sample of the bare aluminum alloy substrate.

Abstract: The anti-oxidation stability of waste oil biodiesel (WME) was evaluated on an oxidation simulator set up by the author. The results showed that oxidative stability of WME was worse than that of petrodiesel by exhibiting higher acid values and peroxide values, as well as greater viscosity increases after oxidation. Furthermore, a conjecture was taken about the configurational changes and the oxidation mechanisms of unsaturated fatty acid methyl ester molecules in the oxidation process, according to the principles of free radical reactions and the results of both infrared and ultraviolet spectroscopic analysis. An idea was put forward that, during oxidation, cis-trans isomerization might occur in unsaturated fatty acid methyl ester molecules and conjugated double-bond might produce due to transfer of double-bond.

Abstract: The heat seawater method was designed and the accelerated aging tests of the neoprene were carried in laboratory. The toughness and strength of the neoprene in aging time was investigated. The rule of toughness and strength and aging time was studied. The service life prediction functions of the neoprene were established and service life at 25°C was estimated based on the index of toughness and strength. It is concluded that toughness and strength of the neoprene decreases in exponential form with aging time, and the service life of the neoprene used in sea water at 25°C is 29.5 years.