Materials Science Forum Vol. 750

Abstract: PCL is one of the popular biomaterials used in tissue engineering scaffolds, but it is seldom shaped by photo-polymerization. Layered manufacturing techniques, also known as Rapid Prototyping (RP) processes, provide a great opportunity to fabricate 3D scaffolds without problems such as limited control of pore-size and restricted geometric shapes in traditional methods. In our previous researches, the Biomedical Dynamic Masking Rapid Prototyping System was developed to photo-cure biodegradable materials through visible light. In this research, the Dynamic Masking RP System was modified to photo-polymerize cross-linkable PCL to form tissue engineering scaffolds. The cross-linkable PCL was synthesized by reacting PCL and acryloyl chloride, and dissolved in acetone mixing with photo-initiator. The tensile test and degradation test were performed on the cured PCL samples. Fabrication of single-layer pattern was first tested to understand the system’s capability and showed the errors were within 7%. Two types of scaffold design concepts were adopted—one took square, hexagon, or triangle as a basic element to create 2D grid patterns, and the interconnected pore were produced by offsetting the 2D pattern in alternating layers; the other took a double-sided trapezoid as a unit and arrayed it into tube shape with interconnected pore network. Various PCL porous tube scaffolds have been successfully fabricated in this study. In the future, they can be utilized to cell growth or mass cell duplication applications.

Abstract: Analysis model of finite element method with a random distribution for thermoelectric composites was built. Thermoelectric properties including electrical resistivity, Seebeck coefficient and thermal conductivity of M/TiO_2–x (M = Cu, Ni, 304 stainless steel (304SS)) thermoelectric composites were investigated by the proposed model. Cu/TiO_2–x composite showed a large decrease in electrical resistivity while 304SS/TiO_2–x composite thermal conductivity was slightly increased. Calculated dimensionless figure-of-merit, ZT of Ni/TiO_2–x composite was higher than those of TiO_2–x and the other composites in a wide range of metal volume fractions because Ni has large absolute values of Seebeck coefficient, power factor and dimensionless figure-of-merit compared to the other two metals. It was found that power factor and dimensionless figure-of-merit of thermoelectric composites depended on the balance among electrical resistivity, thermal conductivity and Seebeck coefficient. The results revealed that it is important for M/TiO_2–x composites to choose suitable addition metal with high power factor and dimensionless figure-of-merit.

Abstract: The reaction behavior of CuAlO₂ during the annealing at high temperatures was investigated. The relationship between thermoelectric properties including electrical resistivity, excess oxygen doping and decomposition of CuAlO₂ was discussed. The evolution of CuAlO₂ compact during the annealing mainly included excess oxygen doping, decomposition of CuAlO₂ into CuAl₂O₄ and CuO and complete decomposition of CuAlO₂ as following pattern : CuAlO₂ → CuAlO_2+x → CuAlO₂+CuO+ CuAl₂O₄ → CuAl₂O₄+CuO. Electrical resistivity of the compacts was decreased with excess oxygen doping, but increased when CuO and CuAl₂O₄ were formed. Thermoelectric performance of the compacts was improved due to the excess oxygen doping.

Abstract: The influence of intermittent air introduction on the formation of Zn films during mechanical coating process was investigated. A series of contrast experiments were carried out. The XRD and EDS results showed that Zn particles were slightly oxidized. The SEM images indicated that disk-like zinc oxide (ZnO) nanocrystals were formed. The formation of disk-like ZnO made the morphology of Zn films more uneven and irregular. On the other hand, it increased the adhesion strength of Zn films to Al₂O3 balls and hence the exfoliation of Zn films was not found.

Abstract: A technique to detect delamination in composite materials by noncontact, rapid and high sensitive microwave reflectometry with a focusing mirror sensor was proposed. The focusing mirror sensor, which has high sensitivity and resolution, is expected to detect delamination sensitively. In this paper, the ability of microwave inspection to detect delamination in glass fiber reinforced plastic (GFRP) and carbon fiber reinforced plastic (CFRP) was verified. As the results, the existences of 100 μm thick delamination in 3 mm thick GFRP laminate and 2 mm thick CFRP laminate were detected.

Abstract: The microstructures and fatigue properties of the TNTZ added with Y or Y₂O₃ have been investigated. The results indicate that TNTZ added with Y or Y₂O₃ are all found to be composed of β phase and the small amount of Y₂O₃. The grain size of TNTZ added with Y or Y₂O₃ is smaller than that of TNTZ. The Young’s modulus of TNTZ added with Y or Y₂O₃ are maintained at a low level, and Young’s modulus of TNTZ added with Y is smaller than that of TNTZ added with Y₂O₃. The mechanical properties are both improved by adding Y or Y₂O₃, while the tensile strength of TNTZ added with Y₂O₃ is slightly higher than that added with Y. The high cycle fatigue limit of the alloys added with Y or Y₂O₃ are similar, while the low cycle fatigue strength of TNTZ added with Y is higher than that added with Y₂O₃. The improvement in fatigue properties ascribes to the microstructure refinement and the pining effect of Y₂O₃ particles. On the other hand, Y elements form Y₂O₃ with the Oxygen elements in the matrix, thus lead to the weakening of the Oxygen solution effect.

Abstract: A new method is proposed for mapping of phase distribution in electron holography. A stage-scanning system was used for moving the specimen to obtain a series of holograms with different specimen positions in a fixed electron-optics configuration. By applying a digital aperture which selects an area on holograms with different specimen positions, an interferogram of the specimen can be obtained directly without a complex reconstruction method such as the one using Fourier transformation. Experimental results for a Co particle demonstrated the practicability of this method.

Abstract: A modified two-dimensional (2-D) cellular automaton (CA) model was constructed to simulate dynamic recrystallization (DRX) process of GCr15 steel. Particle stimulated nucleation (PSN) was incorporated into the CA model to determine the influence of dispersed particles on the nucleation of DRX. In addition, the model included the effects of particles on increasing the dislocation density and pinning the grain boundaries for accurate determination of micro-structural evolution during DRX. The model was applied to simulate the DRX process of GCr15 bearing steel. DRX grain size and volume fraction were simulated using the CA model. The simulated results indicated that the simulated stable grain size of particle-containing model is closer to measured value than particle-free model. It was observed that DRX kinetics depends on both thermo-mechanical parameters and initial grain sizes. The calculated results were compared with the experimental findings in GCr15 bearing steel, the predictions show very good agreement with the experimental results.

Abstract: This paper is mainly a study the diffusion bonding of Mg-AZ31/Al-6061 by using the direct bonding method. After bonding process, multilayer field with Mg-Zn and Al-Zn have been confirmed by EPMA determination. Through the microstructure observed by SEM, bonding boundaries of Mg-AZ31/Al-6061 had good diffusion formation. The identification of the component on near interface was measured by XRD method. By using of these results, the mechanism of the magnesium alloy and aluminum alloys was discussed.

Abstract: This paper studies mainly the diffusion bonding of 3Y-TZP/SUS304 by using the chemical bonding method. In the bonding interface of 3Y-TZP and SUS304, the Ti-Cu powder/sheet was used as bonding materials. In bonding process, multi-alloy with Fe-Ti and Fe-Cu have been confirmed by Electron Probe Micro-Analyzer (EPMA) determination. Through the microstructure observed by AFM and SEM, bonding boundaries of 3Y-TZP/SUS304 by Ti-Cu powder/sheet had good formation. The distribution of the residual stress on near interface was measured by XRD method. By using of these results, the mechanism of the ceramic and stainless steel was discussed.