Materials Science and Nanotechnology I

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Authors: Abolfazl Zolfaghari, Davood Shahriari, Fatemeh Masoumi
Abstract: Ultrasonic testing of welds is a nondestructive evaluation method in which high-frequency sound waves are introduced into materials for the detection of imperfections or flaws in the material. These sound waves travel through the material and are reflected at interfaces such as surface boundaries, grain boundaries, cracks, and pores. The reflected acoustic energy is converted to electrical signals that are recorded and analyzed to determine the presence and location of flaws or discontinuities. The objective of this study is to present an expert system according to static patterns in pulse-echo inspection. It determines numbers, locations and types of weld defects based on DIN EN 1713. This paper gives a brief outline of how the expert system algorithm operates to identify a number of defect scenarios. Since the proposed algorithm is verified by experiments, it allows the user to automatically address and interpret any defects.
141
Authors: Rui Jin Yu, Jin Young Park, Hyun Kyoung Yang, Byung Kee Moon, Byung Chun Choi, Jung Hyun Jeong
Abstract: A new deep red-emitting Mn2+-activated SrLaGa3S6O phosphor was first prepared by a solid-state reaction method. Their luminescence properties were investigated by photoluminescence excitation and emission spectra. The emission spectrum shows a broad band with an emission maximum at 668 nm under the host excitation of 340 nm. The full width at half maximum (FWHM) of the emission peak is about 83 nm. The CIE chromaticity coordinates (x = 0.673 and y = 0.312) shows that the phosphor emission is in the deep red region and were very near to the NTSC standard values for red. Since the excitation band of the phosphor lies in the near UV excitable region, giving a deep red emission, it can be used for applications in near UV phosphor converted white LED lighting and display devices.
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Authors: Zhan Ming Li, You Li Zhu, Xiao Kun Du, Kai Liang Liu
Abstract: In this study, 30CrMnSiNi2A steel specimens were treated by shot peening technique. In order to evaluate the effects of shot peening process on the surface characteristics, the surface topography and roughness of the treated and untreated specimens were observed and analyzed using scanning electronic microscope (SEM) and surface profile tester. Surface microstructure and residual stress were observed and analyzed using transmission electron microscope (TEM) and X-ray stress apparatus respectively. Results show that the surface roughness of milling specimens could be reduced from Ra 4.45 μm to 2.39 μm using shot peening process. Severe plastic deformation and grain refinement were also induced by the process, and the average grain size of nano-structured regime was about 46 nm. Moreover, a 300 μm compressive residual stress layer with the -766.5 MPa compressive residual stresses was induced. At the same time, the anti-fatigue mechanism of shot peening was discussed.
149
Authors: Fateeha Nisar Siddiqui, Nada Saleh, Ayesha Rahat, Asif Israr, Atiq Ur Rehman
Abstract: Carbon Fiber Reinforced Composites are presently used in satellites structure for better performance during extreme thermal cycling space environment. These materials display unexpected failure because the satellite periodically goes into and out of the earth shadow region on orbit, leading to a change in its surface temperature. As the coefficient of thermal expansion of carbon fibers is an order of magnitude lower than that of the polymer matrix, repeated thermal stresses are generated in the composites under the alternative temperature field, resulting in damage to the materials and a decrease in mechanical properties. The main objective of this study is to develop an analytical model to predict the damage produce in the composites subjected to extreme thermal loading. These thermal loading also causes the material to release strain energy. The results are presented in terms of strain produced during thermal cycling and also in the process of delamination.
153
Authors: Gang Cheng Jiao, Zheng Tang Liu, Feng Shi, Lian Dong Zhang, Wei Cheng, Shu Fei Wang, Yu Jian Zhou, Zhuang Miao
Abstract: The GaAsP crystal material grown on GaAs substrate has been extensive applications in the area of photoelectronic device. There because GaAsP have advantageous photoelectronic performance and adjustable band gap. We report growth of GaAs1-xPx grown on GaAs substrate by solid source molecular beam epitaxy (SSMBE). On the basis of the optimized Ⅴ/Ⅲ flux ratio, appropriate growth rate, and the substrate temperature for sample growth, different composition GaAs1-xPx layers had been grown on GaAs top. Lattice-mismatched became the big challenges to high-quality epitaxial growth of the GaAs1-x Px materials on GaAs substrate. The crystalline quality, surface morphology were performed by applying high resolution X-ray diffractometry (HRXRD) and high resolution optical microscopy. The etched region and internal defect were also investigated.
159
Authors: Jun Fu, Yu Qin, You Yun Yu, Meng Jun Ye, Lian Xin Li
Abstract: As an important cushion layer, CA mortar ballastless track is crucial to the durability, safety of high-speed railway and the high-speed railway is influenced by the external environment. The regulation of temperature field evolvement of ballastless track is analyzed in this paper through a two-dimensional, transient finite element model built by ANSYS. The results show that the temperature of structure section caused by solar radiation and circumstances temperature is decreasing along depth in sunlight, and the internal temperature of structure is higher than the surface temperature at night. The integral temperature field of structure reaches the maximum at 1:00 p.m. and the vertical difference of the temperature inside the structure is also the largest, causing the most obvious temperature stress, which provides theoretical data for systematic research on ballastless track of high-speed railway.
163
Authors: Di Chu, Xu Dong Yue, Shu Xu, Jin Liu
Abstract: The influence of Nickel and Chromium alloy element on the primary austenite dendrite in D-type graphite was studied in this paper. The results show, as the addition amount of Nickel is equal to 0.64 percent, the development of the primary austenite dendrite is short and strong. As the addition amount of Chromium is equal to 0.64%, the primary austenite dendrite is no direction. The influence of us joins the Chromium alloy element on the change of organization. The adding amount of Nickel and Chromium is 0.6, 0.8 and 1.0 percent. The hardness of D type graphite increase with the amount added.
168
Authors: Mazhyn Skakov, Sherzod Kurbanbekov, Michail Scheffler
Abstract: In the present work the results of electrolytic-plasma treatment influence on the mechanical properties and structural-phase condition of steel’s 12Cr18Ni10Ti surface layers. In the work, the mechanical characteristics of steel’s surface layers are investigated, cemented in electrolytic plasma with the composition 10 % Nа2CO3 and 10 % С3Н8О3. The operational parameters for the processing are determined. The optimal content of components in saturating mixtures plasma by cementation defined. According to the study it is found that, after electrolyte plasma processing, high hardness increased in 2-2.5 times more than in the original condition. The hardened layer with thickness 30-65 µm is formed. It is shown that after the electrolyte-plasma processing of steel 12Cr18Ni10Ti, microstructure contains particles carbides and has fine-grained martensitic structure. The advantages this method are: small energy consumption high speeds annealing opportunity of local surface processing details complex configuration, operating in the conditions intensive loads, easy implementation process.
173
Authors: Mazhyn Skakov, Laila Zhurerova, Michael Scheffler
Abstract: The present work is devoted research of influence of various modes of electrolytic-plasma cementation on feature of change a structurally-phase conditions and hardening of a constructional steel 30CrMnSi. It is chosen scientifically proved low-power and resources-economy a processing kind which leads to formation stable ferrite-perlites structures, provides higher mechanical properties. Cementation process carried out with selection of different modes of electrolytic-plasma processing in the electrolyte containing water solution of 10 % of sodium carbonate and 10 % of glycerin. As the basic methods of research in work we used metallographic the analysis with microscope application «NEOPHOT-21», X-ray analysis on diffractometer Х’PertPRO in monochromatic CrKα - radiation, tests for microhardness for device PMT-3. It is established that a microstructure of samples steel 30CrMnSi at different modes of processing consist from α - phases, particle carbides. Microhardness of the initial sample makes approximately 3000 МPа, and after processing its microhardness makes 6100 МPа that speaks about of a processing mode. The developed technology of electrolytic-plasma cementation of constructional steels in the conditions of the arc category in electrolyte is the optimal as provides reliable quality and demanded properties of details, working in variable loadings and often exposed to wear, forms the strengthened, modified surface coating.
178
Authors: Xiao Feng He, Shuai Wang, Tie Jun Ge, Xue Quan Zhang, Chun Yu Zhang
Abstract: The melting and crystallization behaviors of Polypropylene/Syndiotactic1,2-polybutadiene (PP/s-PB) blends and neat PP were studied by using DSC, the results showed that the presence of s-PB in PP would have a strong impact on the crystallization capacity of PP. The presence of s-PB in PP could increase the crystallization temperature(Tc) of PP, and the s-PB could obviously lower supercooling temperature(Tm-Tc) of PP, but the s-PB in PP have a Slightly influence on the melting temperature(Tm) of PP. The proposed reason for those are that the crosslinking s-PB in high temperature is a nucleator for PP’s crystallization and increases PP’s crystalline rate. However, the s-PB lowers PP’s crystallinity. At the same time, the presence of PP in blends lowers s-PB’s crystallinity, but the PP in blends have a Slightly influence on the melting temperature(Tm) and crystallization temperature(Tc) of s-PB.
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