Recent Advances in Materials Science and Engineering
Applied Geology of Oil and Gas
Local Mechanical Properties XIII
International Conference on Material Science and Engineering III
Radiation-Thermal Effects and Processes in Inorganic Materials
Material and Manufacturing Technology IX
Smart Materials Technologies III
Advanced Materials – XV
Advanced Materials and Engineering Materials VII
Rehabilitation and Reconstruction of Buildings
Key Engineering Materials VIII
Advances in Fracture and Damage Mechanics XVII
Material and Manufacturing Technology IX
摘要: A new numerical method for homogenization of elastic properties of dispersedly-reinforced composites was presented. The method takes into account special model of adhesive contact. Homogenization of properties was performed by averaging the solutions of boundary value problems on representative volume cell (RVC) using the finite element method (FEM). A new approach of calculation of components of effective tensor of elastic moduli was proposed. A heterogeneous finite element model with elements of two types was built: three-dimensional tetrahedron elements for every phases and spring element with zero-length for adhesion layer with zero-thickness. The results of homogenization of elastic properties of dispersedly-reinforced composites with variable stiffness of the adhesive layer between phases were obtained and analyzed. The homogenization results were compared with the available experimental data.
摘要: This research studied the fabrication of graphene-reinforced aluminum composite via powder metallurgy and uniaxial pressing. The process started from mixing graphene with aluminum powder with various content of graphene (0.5, 1, 1.5, 2 and 4 wt.%) in acetone medium, followed by dispersion process at high frequency using an ultrasonic bath. The mixed composite powders were then formed into pellet and sintered at 600°C. The results showed that when graphene content in graphene reinforced aluminum composite is low (0.5wt.%, 1wt.% and 1.5wt.%), the hardness was enhanced. It was suspected that graphene could get into aluminum matrix and impede the grain growth of aluminum and dislocation movement. However, when excessive graphene content was added, graphene nanoplatelets tended to agglomerate, decreasing the hardness of composite. Similarly, the improvement of electrical and thermal conductivities was achieved with a low content of graphene. The well dispersion of graphene in aluminum matrix could facilitate the electron transport and to induce the pore reduction throughout the matrix.
摘要: This study is to investigate the phase stability, cold deformation, elastic strain recovery and mechanical properties of a new Ti-17Nb-6Ta-3Zr, at. %, alloy for biomedical applications. The alloy was produced by arc melting. A heavy cold-working up to 90 % was applied to the alloy to investigate the stability of the predominant β-bcc structure. Characterization of the deformed structures was performed by X-ray diffraction (XRD), hardness measurements and optical microscopy. Quasi-static compression testing was conducted to determine the yield stress for stress induced martensitic (SIM) transformation and the Young modulus. XRD analysis of the cold-worked structures revealed that α-martensite was induced after less than 5 % deformation. An outstanding combination of strength-elasticity properties with the yield strength of 600 MPa and a Young modulus of 37 GPa was achieved during the compression tests.
摘要: Osteoporosis is a chronic, metabolic and systemic skeletal disease characterized by low bone mineral density (BMD) and micro-architectural deterioration, resulting in increased bone fragility and fracture risk. Changes in the mineral structure occur due to aging or because of progressive pathologic processes such as osteoporosis, as well as in both aging and effects of bone diseases.
摘要: — tailoring material properties to specific application requirements is one of the major challenges in materials engineering. Grain size is a key factor affecting physical and mechanical properties of polycrystals materials. Grain size reduction in the metals and alloys can be achieved using Equal channel angular pressing (ECAP) method. In this work, Nanostructure thin walled copper tube specimens with 1 mm wall thickness and 23mm diameter have been produced successfully with ECAP method using flexible polyurethane rubber pad to prevent the tube walls from collapsing. Furthermore, this paper details the development of a numerical simulation to analyse the fabrication of thin walled tube through ECAP process. A copper tube was pushed through a channel with a series of 90° bends. During each successive bend, the magnitude of plastic strains accumulate in the copper tube. A three dimensional numerical simulation was used to model the process and determine the extent of plastic deformation that takes place during each bend process. The numerical simulation was developed using the finite element (FE) code, ABAQUS V6.13, and analysed using the explicit solver.
摘要: This research studied the preparation of titanium dioxide (TiO2) composite films with the incorporation of tin oxide and reduced graphene oxide (SnO2-RGO) for uses as photoanodes in dye-sensitized solar cells (DSSCs). The experimental procedure started with the synthesis of graphene oxide by Hummer's method, followed by the preparation of SnO2-RGO composite materials by hydrothermal process. The resultant SnO2-RGO was sequentially mixed with TiO2 to prepare the composite films by doctor-blade method. The results indicated that the addition of graphene oxide into SnO2 could reduce the band gap, avoid the agglomeration, and improve the dispersion of tin oxide particles (SnO2). According to the efficiency tests of the obtained photoanodes, a small amount of RGO could significantly affect the DSSC’s performance. Without RGO, TiO2-SnO2 photoanodes exhibited very poor performance. This could be due to low dye-adsorption capability and low electron transfer ability. The addition of excess amount of RGO in photoanode could, however, lead to negative effects such as charge trapping and lower solar cell efficiency.
摘要: The Dy3+-doped glasses of the M2O3:CaO:SiO2:B2O3 (M2O3 = Y2O3 and La2O3) materials have been successfully fabricated with the 0.5 % mol of the Dy2O3 concentration, and thoroughly investigated based on the physical, optical, photo- and radioluminescence properties. The developed glass materials were prepared from the compositions of 25M2O3:10CaO:10SiO2:(55-x)B2O3:0.5Dy2O3 by the conventional melt-quenching technique at 1,400°C. The clear sample of the doped La2O3 glass demonstrated higher density and the molar volume than those of the doped Y2O3 glass. From the spectrophotometry, the absorption peaks of the Dy3+ ions were clearly observed in both glasses. The photoluminescence (PL) spectra of the developed glasses indicated two-colors with two strongest peaks at 577 nm (4F9/2®6H13/2) and 482 nm (4F9/2®6H15/2). In addition, the emission spectra from the radioluminescence (RL) were identical to those from the PL measurements. From the results of the PL and RL measurements, the Y2O3 glass had higher emission in the intensity than the La2O3 glass. The X-ray absorption near edge spectroscopy (XANES) with the synchrotron radiation was carried out in fluorescent-yield mode to determine the average oxidation number of the Dy ions dispersed in the glass matrices. The DyL3-edge XANES spectra of both developed glasses were nearly identical with the sharp white line at 7795.5 eV and the edge energy of 7793 eV. Compared to the XANES spectrum of the pure Dy2O3 standard, both glasses showed the difference smaller than 0.5 eV, and therefore confirmed the oxidation number of the Dy ions of 3+.
摘要: In this new world, polymer nanocomposites have developed to be one of the latest evolutionary steps in the polymer technology, besides showing a great deal to become the most versatile industrial advanced materials. In comparison with conventional composites, nanocomposites demonstrate significantly higher levels of mechanical performance with less content of particles. Thus, this study was carried out to investigate the effect of nano& micron size of clay particles to mechanical properties of epoxy adhesive. Three types of mechanical test were performed; tensile, impact and shear test. The result shows that the tensile strength was increase by using micron clay while shear and impact strength was increase by using nanoclay. The dispersion of clay in the epoxy adhesive is very important because it will affect the mechanical properties of epoxy adhesive itself. The function of clay to enhance the properties of epoxy adhesive is more effective when the clay is well dispersed. FESEM shows that the nanoclay was well dispersed in the epoxy adhesive while micron sized clay was partially intercalated.
摘要: As industry enters into high-tech society, the use of fossil energies is increasing. The demand of solar photovoltaic cell is increasing and according to this increase, the amount of waste photovoltaic cell will increase, too. However, compared to the increase of photovoltaic facility and technology, research about recycling method of waste photovoltaic cell is slow. Therefore, this study continued research to collect cooper and tin which are valuable metals from cooper ribbon electrode recovered from waste photovoltaic electrode. To effectively separate the coating layer when handling bulk of cooper ribbon electrode, heat treating furnace of hydrodynamic vibrating is developed and tin and cooper which are valuable metals are collected by using Hydro-metallurgical process used with nitric acid. The purity of cooper’s basic materials after heat treatment of hydrodynamic vibrating was 98.88wt.% and the purity of tin and cooper collected from the coating layer was measured as 98.07wt.% and 98.44wt.% each.