Advanced Materials Research Vols. 97-101

Abstract: Plasma spraying has been carried out under different spraying parameters, the particle in-flight behaviors have been measured to analyze the influence of argon flow rate, hydrogen flow rate and electrical current on the particle temperature and velocity. The particle velocity increased remarkably with the increase of the argon flow rate. The particle temperature was mainly influenced by the hydrogen flow rate, and increasing electrical current resulted in the increase of the particle temperature and velocity to some extent.

Abstract: Fracture of dental all-ceramic restoration is often observed in clinic. And the fracture mechanisms and processes of three-unit all-ceramic fixed partial dentures (FPDs) are still not clear. In this paper, the fracture mechanism and process of a three unit zirconia ceramic FPDs framework under simulated mechanical loading are calculated by using a self-developed numerical modeling code, the RFPA2D code. Acoustic emission showed that the fracture mechanism was tensile failure and the crack started at the lower boundary of the framework. The result revealed that the framework fracture pattern obtained by using the numerical simulation agreed with that observed in a previous laboratory test. The fracture process could be followed both in step-by-step and step-in-step. The RFPA2D code is suitable for the use as a complement to other tests and clinical observations in studying stress distribution, fracture mechanism and fracture process in ceramic FPDs framework.

Abstract: This study described a different nano-titania(TiO2)/polymer composite where TiO2 were uniformly deposited on the porous poly(styrene-divinyl benzene-co-maletic anhydride)　[poly(st-DVB-co-MAH)] microspheres. The morphology of the composite microspheres was analyzed by scanning electron microscope and X-ray diffraction. Both the diameter of the pore and the MAH functional groups played a crucial role in controlling the structure of TiO2 shell. The rutile nanoparticles were incorporated evenly onto the surface of the porous microspheres when microspheres with pore diameter of about 146.8 nm and with surface 30 wt% functional groups (MAH) were used as substrate.

Abstract: Magnetorheological (MR) elastomers are smart materials whose physical properties can undergo instantaneous and reversible change when subjected to different intensities of the magnetic field. This makes the MR elastomers have wide applications in the fields of vibration control. This work presents the vibration suppression of flexible beams with MR elastomers. An experiment system has been set up to investigate the vibration performances of a sandwich beam filled with MR elastomers. The vibration response of the beam subjected to different magnetic field intensity and excitation frequencies are demonstrated and evaluated. The results obtained indicate that vibration attenuation is achieved at different operating conditions by applying a magnetic field to the beam.

Abstract: Activated carbon (AC)/polyaniline (PANI) composite electrode materials were synthesized in this article. The effect of preparation such as BET surface area and porous size of AC on the electrochemical performances of AC/PANI composite material was investigated. The electrochemical performances of the composite were tested with cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectrometry in 6mol/L KOH solution using Hg/HgO as reference electrode. Composite surface morphology was examined by scanning electron microscope (SEM). The result shows that when the ratio of AC to aniline increases, the conversion of aniline and the capacitance value of composite also increase in keeping the ratio of AC to aniline constant. When AC: aniline : (NH4)2S2O8 =7:1:1, the conversion of aniline up to more than 95% and the capacitance value of electrode materials increased from 239F/g(pure AC) to 409F/g, which is 71.1% higher than pure AC. Pore structure of AC also has great effect on electrochemical performances of electrode material. With the increase of proportion of mesoporous, the electrochemical properties of composite are greatly increased.

Abstract: In this paper, the synthesis of four-layered functionally graded materials (FGMs) samples of (TiC)pNi/TiAl with titanium substrate by field-activated and pressure-assisted synthesis process (FAPAS) was investigated. It was shown that the TiC particles formed by in-situ combustion synthesis process were fine and distributed uniformly. Moreover, the imposition of the electric field and the combustion reaction of TiAl is the key for the successful synthesis of the FGMs during the process. The microstructure, phase composition of the interfaces and mechanical properties of the graded material were characterized. Moreover, the sample has an excellent thermal shock resistance ability and gradient distribution of micro-hardness across the substrate layers and the surface layer.

Abstract: Ionic polymer-metal composites (IPMCs) show great potential in a large variety of engineering fields as actuator materials. They mainly consist of electrodes and ionic polymer as the substrate material. Many metal materials can be used as the electrode material of IPMCs. In this paper palladium was adopted to get a compromise between the cost and the stability, and Pd-Nafion IPMC was fabricated by chemical plating as test sample. Preliminary experiments were accomplished with satisfactory result using a suit of self-made measurement setup. The results showed that palladium was a good electrode material. Although some previous work has investigated on the elastic modulus of IPMCs by tensile test, a simple method based on the cantilever beam theory to estimate the modulus is still proposed here, which does not need a tensile testing machine. By the method we got that the elastic modulus of the sample is 362.35MPa.

Abstract: The heat-shocking resistance of SiC(w)/ZrO2-MoSi2 ceramic composites prepared by hot-pressing sintering was studied by indentation-quench method together with the calculation of the crack propagation rate of ceramic nanocomposites. The results showed that the crack propagation rate of MoSi2 matrix ceramics samples decreased remarkably with the addition of ZrO2 and SiC nanoparticles. The crack propagation rate of SiC(w)/ZrO2-MoSi2 ceramic composites was obviously lower than that of ZrO2-MoSi2 ceramic composites, which revealed that the synergism between SiC(w) and ZrO2 was more advantageous to enhance the heat-shocking resistance of MoSi2 ceramic. Moreover, the ability of ZrO2 particles to hinder the heat-shocking crack propagation was better than that of SiC whiskers. The synergism between SiC(w) and ZrO2 changed the crack propagation path and shape in MoSi2 ceramics. The mechanisms of ZrO2 to improve the heat-shocking resistance of the MoSi2 ceramic were mainly phase transfer toughening, while that of SiC whiskers to improve the heat-shocking resistance of the MoSi2 ceramic were mainly crack deflection and bridge union.

Abstract: NiTiSMA/FC composites have been prepared by depositing ferroelectric ceramics films on NiTi shape memory alloy substrate with the sol-gel method. Heterojunction structure of the composites has been characterized by using X-ray diffraction and scanning electron microscope. The differences of the damping capacities between NiTiSMA/FC composites and NiTiSMA substrates have been tested by the Dynamic Mechanical Analyzer. The results show pure perovskite structure could be obtained in the FC films part of NiTiSMA/FC composites sintered at 650oC. The transitional TiO2 layer produced in-situ by the oxidation of the surface of the NiTiSMA substrate improves the combined function between the ceramic film and NiTiSMA substrate. When the temperature is lower than 20oC, the tanδ of NiTiSMA/FC composites is stabilized at 3.5%, the vibration frequencies (within 0.33-10Hz) have a small effect on damping capacities. Within the temperature of 20-40oC, there is a tanδ peak up to 5.0%.The damping capacities of NiTiSMA/FC composites are better than the pure NiTiSMA materials.

Abstract: Mg2Si/AM60 composites were fabricated by in-situ synthesis and the effects of different stirring technological parameters on the microstructures of semi-solid magnesium matrix composites were investigated in this paper. The results indicated that there were Chinese script type Mg2Si particles in the microstructures by addition crystal Si to the magnesium alloys. The mechanical stirring was used to fabricate the semi-solid composites and the results showed that the higher the stirring temperature and speed are, the finer and more homogeneous the spherical grains would be. If the temperature is too high, the grains will be melted. With the increasing of stirring time, the grains become fine, well-distributed and round at first, then grow up.