Contemporary Approaches in Material Science and Materials Processing Technologies

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Authors: David Manas, Martin Ovsik, Miroslav Manas, Michal Stanek, Pavel Stoklasek, Martin Bednarik, Ales Mizera
Abstract: The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Micromechanical changes in the surface layer of glass-filled PA-6 modified by beta radiation were measured by instrumented test of microhardness. The specimens were prepared by injection technology and subjected to radiation doses of 0, 66, 99, 132 kGy. Measurements of microhardness showed considerable changes of behavior of surface layer in middle as well as high radiation doses with higher values of indentation hardness and stiffness.
Authors: Ladapak Chumprasert, Narit Funsueb, Apichart Limpichaipanit, Athipong Ngamjarurojana
Abstract: In this research, Barium titanate (BT) additive in lanthanum modified lead zirconate titanate (PLZT) was used to stabilize the PLZT ceramics. Oxide powders were synthesized by mixed oxide synthetic route via a rapid vibro-milling technique. It was prepared with the chemical formula of 0.95 Pb0.91La0.09 (Zr0.65Ti0.35)0.9775O3 -0.05 BaTiO3 to investigate the dielectric properties of PLZT ceramics. The modified PLZT ceramics were fabricated at variation of sintering temperatures of 1200-1275°C for 4 hours. By employing X-ray diffraction (XRD), it was found a pure perovskite with rhombohedral structure. The relaxor behavior was observed from the dielectric measurements. The suitable sintering temperature of 0.95 PLZT - 0.05 BT was 1275°C (εr=10463, tanδ=0.0125 and Tm=70°C).
Authors: Tian Tian Shao, Xiao Long Cai, Jie Fang Wang, Li Sheng Zhong, Na Na Zhao, Yun Hua Xu
Abstract: Micro-nanostructure tantalum carbide (TaC) ceramic was prepared on grey cast iron matrix by the combined process of casting and heat treatment. The theoretical foundation of the nanoindentation technique was introduced in detail, and hardness/modular–displacement curve was received from continuous stiffness measurement (CSM). The results show that, elastic modulus (E) and hardness (H) variation with impression depth depend on size effect and matrix effect. There is no impression pile up effecting on hardness value. It was iron (Fe) existing in micro-nanostructure TaC ceramic during heat treatment , which is the main reason of improving creep property of the TaC ceramic. Study on micro-nanostructure TaC ceramic with high hardness, high elastic modulus and good creep property is meaningful to the application in the area of engineering.
Authors: Guang Fen Zhou, Jie Ren
Abstract: The initial growth mechanisms of atomic layer deposition of Hafnium dioxide thin films using Cp2Hf (CH3)2 precursor have been investigated. The calculations show that CH4 elimination reaction is energetically more favorable than CpH elimination reaction. As a result, the two ―CH3 ligands of Cp2Hf (CH3)2 may be dissociated prior to the two ―Cp rings. According to the activation barrier analysis, one CpH elimination may occurs sequentially following the first CH4 elimination reaction. During the pulse of Cp2Hf (CH3)2 precursor, the byproduct CH4 and a small amount of CpH are released.
Authors: Cai Yun Jia, Rui Ding, Jun Cheng Liu, An Fa Liu, Dong Xiao Teng
Abstract: High alumina foam ceramics products with low density, high specific surface area, low thermal conductivity, corrosion resistance and other excellent physical and chemical properties are suitable for chemical, metallurgy and other related fields [1-4]. Alumina foam ceramics that compression strength increased by 200%, was prepared by Rizwan Ahmad through impregnation process using foamed rubber [5]. However foamed rubber was expensive and could be decomposed creating poisonous gases at high temperature. Zhou l z [6] prepared mullite porous ceramics with high strength by gel-casting method. Gel-casting is an effective method for preparation of ceramics products with large size and complicated shape. Fiber reinforced dense ceramics composite materials with excellent performance have been studied widely [7-10], it is also an important issue to adequately investigate the reinforcement of porous ceramics with fiber.
Authors: Mei Li Wang, Jian Zhong Li, Zu Yuan Yu, Xue Li
Abstract: Ceramic materials are widely used in industries because of their excellent properties such as high hardness, strength, resistance to heat and corrosion. The high strength of sintered ceramics posts the difficulty to be processed into the desired shapes and dimensions. Direct processing of ceramic green body is easy to cause edge damage due to the lower strength, leading to low surface accuracy. When the green body of ceramics is pre-sintered, the mechanical strength of green body is enhanced and the machining accuracy is improved. In this paper, micro holes are drilled in ceramics sheets pre-sintered at different temperatures. The influence of processing parameters is analyzed. It was found that the tool has the longest life when the pre-sintering temperature of ceramic green body was 800°C. The quality of the inlet and outlet of micro holes was improved significantly when the coolant was used in machining.
Authors: Xue Li, Jian Zhong Li, Zu Yuan Yu, Mei Li Wang, Shuang Hu Xu
Abstract: As the requirements of MEMS continuously increase, the micro ceramic structures are widely used due to their favorable material properties such as high strength, hardness and resistance to high temperature, wear and erosion. However, the sintered ceramic compact is hard to be machined as its high strength. On the other hand, the low strength of green ceramic body makes it difficult to guarantee the machining accuracy. In this paper, ceramic compacts are pre-sintered below the sintering temperature. Pre-sintered ceramic compacts have suitable strength and are easy to be machined. Simple ceramic micro structures are easily generated with micro tools fabricated on line by wire electrical discharge grinding method (WEDG). Extensive experiments are carried out to investigate the influence of the strength of pre-sintered ceramic compact on the tool wear. It was found that the best machining results are achieved under the conditions of using the tool with a semi-circle cross section, the tool rotation speed of 1500 rpm and the pre-sintered ceramic compact formed under the pressure of 150MPa within the range of experimental conditions in this study.
Authors: Daniel Véras Ribeiro, S.C. Figueiredo, Alexandre T. Machado, F.R. Valenzuela Diaz, C.A.C. Souza
Abstract: Rotary-vacuum-filter mud (RVFM) is waste generated during the manufacturing process of titanium dioxide. In this work, RVFM and ceramic bricks containing different ratios of this waste are investigated. The mud samples were characterized using thermal analysis (TG/DTG). The aim of the present work was to determine the effect of adding RVFM on the ceramic properties of clay, such as apparent porosity, water absorption, linear shrinkage and flexural strength, used to produce blocks and tiles. Samples were dried out at 110°C and fired at 800°C, 950°C and 1100°C. The addition of RVFM tends to increase the apparent porosity and water absorption and to decrease the flexural strength of the ceramic specimens. Based on the results, ceramic specimens with 20% RVFM content burned at 800°C can not be used as bricks, and ceramic specimens with 20% RVFM content fired at 800°C and 950°C can not be used as tiles, according to Brazilian standards.
Authors: Igor Dobovšek
Abstract: We present an analysis of residual and interface stresses, caused by a change in external temperature field, due to mismatch in thermal and elastic characteristics in a dissimilar system of a thin film and a flexible substrate. A representative volume element of the system is defined as a heterogeneous two-phase layered element bonded at an interface in a sense of coherent bi-layer, where each phase possesses distinct elastic and thermal characteristics. We use a spatial averaging technique with particular form of strain field that satisfies compatibility equations in the bulk and at the interface. Derived special rule of mixtures yields rigorous estimates for residual stress distribution through thickness of the representative volume element. Corresponding distributions of stress fields are calculated for distinct magnitudes of compositional parameter representing the volumetric fraction of the film.

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