Advanced Materials Research Vols. 415-417

Abstract: A new fixturing method, based on the principles of strong magnetic field and friction-clamping, is presented. The method can completely constrain the bottom of the NOMEX honeycomb with the friction force between iron powder and honeycomb walls, honeycomb and clamping plane produced from the gravity of the iron powder injected into the honeycomb and the magnetic force produced by the additional strong magnetic field. To analyze the reliability of the method, firstly, the milling force and its distribution are predicted with FEM and experiment method under the condition of different cutting parameters. Then, the fixturing strength and the milling force are analyzed comparatively in the low-reliability and -stability zone during the milling process. It is proved by experiments and analysis that the fixturing method has the advantages of low cost, being easy to use, and no pollution.

Abstract: The elevated-temperature performance of LiCo_0.02Cr_0.02Mn_1.96O₄ cathode material, by SiO₂-Al₂O₃ surface modification, has been studied. The cathode material was been deal with SiO₂-Al₂O₃, and then heated on certain temperature to get rid of organic material. The material structures that been modified (unmodified) were characterized by XRD, SEM and SpectraPlus. X-ray diffraction shows that all the samples have perfect spinel structure. The cycle stability of charge & discharge has been improved at 55°C. The results of the charge/discharge curves shows that the modified cathode materials have better performance than those unmodified, according to the inhibition of decline of reversible capacity of spinel LiCo_0.02Cr_0.02Mn_1.96O₄.Therefore, cycle performance has improved so obviously that 87.92% of the initial capacity were preserved respectively after 100 cycles. As cathode material of Lithium-ion battery, the modified spinel material is one of the most competitive substitutes for LiCoO₂.

Abstract: A material is radially anisotropic piezoelectric when its generalized Hooke’s law at each material point referred to a spherical coordinate system is the same everywhere. In a recent paper by Ting, the remarkable nature at the center of a sphere has been shown when a spherically uniform linear anisotropic elastic material is subjected to a uniform traction at the surface of the sphere. This paper extends elastic material for piezoelectric material, and shows that the singular problems also prevail in piezoelectric material. When a sphere of piezoelectric material is subjected to a uniform traction and electric potential at the surface of the sphere, for a certain range of material parameter, the stress, the electric field and the electric potential at the center of the sphere are infinite. When the sphere is subjected to a uniform tension, a cavitation occurs at the center of the sphere. If the applied traction is a uniform pressure, a black hole occurs at the center of the sphere. The singular problems depend only on one non-dimensional material parameter and the direction of the applied traction, while is independent of the magnitude of the traction.

Abstract: In this paper, the growth mechanism of MgO in the as-cast ZnO coated Mg₂B₂O₅ whisker reinforced AZ31B composite. The elements distribution of interfacial vicinity are analyzed by electron probe microanalysis (EPMA) and microstructures of MgO and MgZn₂ are observed by transmission electron microscope (TEM). The crystallographic orientation relationship between the Mg₂B₂O₅ and MgO in the ZnO coated Mg₂B₂O₅ whisker reinforced AZ31B composite is investigated to be [010]_Mg2B2O5 // [011]_MgO and (102)_Mg2B2O5//(111 )_MgO. The formation of intermetallic phase MgZn₂ is discussed.

Abstract: In the present study magneto-polymer composite coatings are fabricated using nano Zn ferrite, Mn ferrite, Ni ferrite, Zn-Mn ferrite and Zn-Ni ferrite by spraying method. The complex permeabilities, Complex permittivities and microwave absorbing properties within the low frequency of these composites were characterized and investigated. The results showed that the magnetism of the mixed spinel ferrites ( Mn ferrite, Zn-Ni ferrite, Zn-Mn ferrite) are strong but the dielectric properties are weaker, while the magnetism of the normal spinel ferrites (Zn ferrite) is the weakest but provide with a big storage capability of electric energy. The absorbing characteristics of the spinel ferrites are better at 300 kHz-1.5GHz, with minimum absorption of 12.5 dB and the maximum absorption at 480MHz, 1050 MHz and 1400 MHz. The microwave absorbing property of the mixed spinel ferrite Zn-Mn ferrite is best having the RL value being -42.5 dB at 1400GHz.

Abstract: The nano-particle modified epoxy resin adhesive was prepared by adding different types of nanoparticles to the epoxy resin adhesives.The influence of the kinds and amount of nanoparticles on the mechanical properties of epoxy resin adhesive was investigated.The investigation results indicated that the addition of three kinds of nanoparticles including nano-silica,nano-titanium dioxide,nano zinc oxide to epoxy resin adhesive has a significant influence on the mechanical properties of nano-composites.And tensile strength and breaking elongation of nano-composites reached the maximum when the amount of nanoparticle reached 4wt%.In addition,the toughening mechanisms of nano-particles modified epoxy resin adhesives was analysed.

Abstract: In order to improve performance of 4-UPS-RPS high-speed spatial parallel robot, the elastic dynamics optimization design was executed. The influence law of the mass of moving platform and the diameter of driving limbs on the dynamic performance, which includes kinematics output response and maximum dynamic stress of driving limbs, were discussed. On these grounds, the mass of moving platform and the diameter of driving limbs were optimized. The simulation results show obvious improvement of the dynamics performance for 4-UPS-RPS parallel robot, therefore the theoretical basis are provided.

Abstract: The antioxidant capacities and anti-aging properties of whey hydrolysates fermented by Lactobacillus plantarum TUST200209 and its purified whey peptides were studied, which were dose-dependent and category-dependent. The treatment groups were orally administered high dose (1.5g/kg/day) and low dose (0.5/kg/day) of whey hydrosyates and its purified peptides, and high dose (1.5g/kg/day) of 0.9% saline (vehicle group and aged model group) and mixture of whey and Lactobacillus plantarum TUST200209 in senescence accelerated Kunming mice for six weeks, respectively. Whey hydrolysates and its purified peptides could increase levels of superoxide dismutase, glutathione peroxidase, and decrease contents of malondialdehyde in serum, quadriceps femoris and mitochondria, and for the high dose of whey peptides, most of the increase was significant (P＜0.05) compared with vehicle group. It demonstrated that the whey hydrolysates could significantly retard aging of the mice induced by free radical, especially for its purified peptides.

Abstract: In the present study, Mg₂Si nanoparticles of high purity were successfully synthesized through low-temperature reaction by using MgH₂ and Si powders as rawmaterials. The size of Mg₂Si particles is about 50nm. The bulk nanocomposites xSiO₂/Mg₂Si_0.8Sn_0.2(x = 0, 0.1, 1 and 2wt. %) were followed by field-Activated and pressure-assisted synthesis (FAPAS). The effects of SiO₂ addition on the microstructure and thermoelectric properties of Mg₂Si_0.8Sn_0.2 were studied. The field emission scanning electron microscopy shows that the nanometer-sized SiO₂ particles disperse homogeneously in Mg₂Si_0.8Sn_0.2 matrix. Among all of the samples, 1wt. % SiO₂/Mg₂Si_0.8Sn_0.2 exhibits the best figure of merit (ZT = 0.25 at 573 K), which is 24% higher than that of the sample without SiO₂, indicating that the thermoelectric properties of Mg₂Si_0.8Sn_0.2 can be enhanced effectively by the dispersion of nanometer-sized SiO₂.