Applied Mechanics and Materials Vols. 268-270

Abstract: A numerical investigation was conducted to determine the mechanical behavior of C/SiC composites bolt under room temperature and elevated temperature. The influence of the contact friction coefficient on the stress and displacement was considered in the finite element analysis. The FEA results provided some valuable data for the engineering application of C/SiC composites bolt.

Abstract: Aiming at flexible oxidation in the MLCC production, the surface modification of the ultrafine nickel powders has been carried out to coat Ni powders with CaZrO3 by using chemical precipitation method. CaZrO3-coated composite ultrafine nickel powders have been synthesized in methanol-water solvent by both precipitation agents solution and zirconium-calcium solution dripped into the Ni-particle-dispersed methanol solution at the meantime. Composite nickel powders obtained under the optimum conditions were characterized, It was approved that those composite nickel powders still possessed good dispersion, the resistance to oxidation and shrinkage were improved greatly.

Abstract: The 91×91 complete energy matrix of 4f2 configuration ion Pr3+ in octahedral cubic crystal field has been constructed based upon the combination of Racah’s group-theoretical consideration with Slater’s wavefunctions. The energy levels of the neat hexachloride elpasolite crystals Cs2NaPrCl6 containing rare earth Pr3+ ion have been calculated. The results imply that the diagonalization to the complete energy matrix can be received as an effective method of performing a theoretical calculation to the rare earth compounds.

Abstract: Fe3+-doped TiO2/diatomite composite photocatalyst were prepared by sol-gel method with titanium isopropoxide used as precursor material. The samples were characterized by SEM, XRD, XPS, BET surface area analysis and UV-Vis techniques. The results showed that the optimum concentration of Fe3+ in the composite catalyst was 0.2wt% when the quantity of TiO2 loaded on the diatomite was 30.3wt%. Compared with the un-doped photocatalyst, the Fe3+-doped sample exhibited red shifts of absorption edge and significant enhancement of light absorption at 400～600 nm.

Abstract: Basalt fiber has good sea water resistance, heat resistance and sound insulation. This shows that, basalt fiber is ideal material for ship manufacturing. Because of the bad fiber permeability, using VARTM process to produce large basalt fiber marine components still has deficiency. Taking basalt fiber/vinyl resin composite shell as object, research was taken to find the method of improving resin flow velocity and suitable resin injection strategy system in VARTM process. The results show that air release additive contributes to the resin’s flow in preform body, and the tensile strength and flexural strength of components increase with the increase of air release additive’s quantum when the quantum less than 0.5%. The resin flow’s frontier of the components made by sequence injection strategy is always keeping the same and its velocity is uniform, which makes its quality is better than that made by embranchment injection strategy.

Abstract: Two novel luminescent molecules based on tetrahedral silicon core with the carbazole and benzimidazole groups, bis(6-(1H-benzo[d]imidazol-1-yl)-9-ethyl-9H-carbazol-3-yl)dimethylsilane (1) and bis(6-(1H-benzo[d]imidazol-1-yl)-9-ethyl-9H-carbazol-3-yl)diphenylsilane (2), were designed, synthesized and fully characterized by IR, 1H NMR, 13C NMR and elemental analysis. Thermal results show that these compounds have high thermal stability and glass-transition temperature (Tg). The results based on the photophysical properties and molecular calculations reveal that they are fluorescent with emission in the region of violet to blue and own large HOMO-LUMO band gaps, making them potentials as blue emitters, host materials or charge blocking materials in organic light-emitting diodes (OLEDs) display.

Abstract: After the devastating floods in the Europe and Czech Republic especially, in 1997, 2002 and 2007 years, the need of the anti-flood protection was very actual and delicate. One of the ways, how to solve this problem in the case of usual or lower water level, is the usage of anti-flood barriers. The paper is focused on the experimental verification of the actual behaviour, load-carrying capacity and failure mechanisms of the cantilevers made of FRP composite profiles PREFEN, which are in reality used as columns of anti-flood barriers. The investigated water-proof profile of H-cross-section is composed of epoxy resin and glass fibres.

Abstract: The tribological behavior of Si3N4-hBN composites sliding on Fe-B alloy without lubrication was investigated by using a pin-on-disc wear tester. The results showed that, the addition of hBN to Si3N4 could not effectively improve the tribological characteristics of Si3N4-hBN when it slid against Fe-B alloy. Without lubrication, the wear of Si3N4-hBN composites was resulted from cracking and fracture, while the hard phase Fe2B in Fe-B alloy spalled off during the friction test. So, high friction coefficients (>0.9) and high wear coefficients (>1×10-5mm3/Nm) were obtained.

Abstract: The Poly(L-lactic acid)(PLLA)/surface-grafting silica(g-SiO2) nanocomposites were prepared by melt blending. The isothermal crystallization behavior of PLLA/g-SiO2 nanocomposites with different content of g-SiO2 was investigated by optical depolarizer. In isothermal crystallization from melt, the induction periods and half times for overall PLLA crystallization (95°C Tc 120°C) were affected by the crystallization temperature and the content of g-SiO2 in nanocomposites. The results showed that g-SiO2 as a kind of heterogeneous nucleating agent can reduce induction periods and half times for overall PLLA crystallization. The thermal properties of PLLA/g-SiO2 samples were also investigated by differential scanning calorimetry (DSC), The results showed that the crystalline degree of PLLA was improved as the presence of g-SiO2.