Papers by Keyword: EPMA

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Authors: Zhao Bing Cai, Xue Jia Pang, Xiu Fang Cui, Xin Wen, Zhe Liu, Mei Ling Dong, Yang Li, Guo Jin
Abstract: In order to improve the surface properties of Ti-6Al-4V, high-entropy alloy coatings were prepared by in-situ laser cladding on the surface of Ti-6Al-4V substrate. The microstructure, micro-hardness, corrosion resistance and wear resistance were investigated. The results showed that the high-entropy alloy coating was composed of BCC high-entropy alloy phase, α-Ti phase and (Ni, Co)Ti2 phase. The micro-hardness of the high-entropy alloy coatings is much higher than that of Ti-6Al-4V substrate. The coating also has a better corrosion resistance than Ti-6Al-4V substrate, even superior to 304SS in 3.5wt.% NaCl solution at room temperature. Compared with Ti-6Al-4V substrate, the high-entropy alloy coating has a greater wear resistance with the wear mass loss decreased 28.2% and 23.1%, respectively. Wear patterns of Ti-6Al-4V substrate and high-entropy alloy coatings are the coexistence of adhesive wear and abrasive wear, but the wear degree of high-entropy alloy coatings is lower.
Authors: S. Yoneda, E. Ohta, Yoshikazu Shinohara, T. Kimura, Isao A. Nishida, H.T. Kaibe
Authors: Kentaro Kinoshita, Tatsuya Makino, Takatoshi Yoda, Kazufumi Dobashi, Satoru Kishida
Abstract: Both a low and a high resistance states which were written by the voltage application in a local region of NiO/Pt films by using conducting atomic force microscopy (C-AFM) were observed by using scanning electron microscope (SEM) and electron probe micro analysis (EPMA). The writing regions are distinguishable as dark areas in a secondary electron image and thus can be specified without using complicated sample fabrication process to narrow down the writing regions such as the photolithography technique. In addition, the writing regions were analyzed by using energy dispersive X-ray spectroscopy (EDS) mapping. No difference between the inside and outside of the writing regions is observed for all the mapped elements including C and Rh. Here, C and Rh are the most probable candidates for contamination which affect the secondary electron image. Therefore, our results suggested that the observed change in the contrast of the secondary electron image is related to the intrinsic change in the electronic state of the NiO film and a secondary electron yield is correlated to the physical properties of the film.
Authors: Qing Kun He, Chang Ying Shi
Abstract: s: Electron microprobe technology is widely used to component analysis of metals, minerals and geology. Elements of sedimentary rock including B, Ga, Ba, Sr, Co, V, Cr, Mn, Fe, Ni were analyzed by EPMA respectively. It was discussed that marine faces and continental facies, oxidation environment and reducing environment, the depth of water and salinity influence on sedimentary rock, respectively. Then the influence of marine faces, continental faces, oxidation environment, reducing environment and the depth of water and salinity on sedimentary rock was discussed respectively. The results show that EPMA is a useful instrument to analyze the components of sedimentary rock.
Authors: Ma Qian, David H. StJohn, Sally K. Maloney, Malcolm J. Couper
Authors: Toshiyasu Nishimura
Abstract: The iron rust phase has been analyzed by using EPMA, TEM and EIS after simulating marine corrosion tests. The ultrafine grained (UFG) weathering steel containing Si and Al showed higher corrosion resistance than carbon steel in the test. Si and Al were identified as Si 2+ and Al 3+ in the complex oxide of inner rust by EPMA and TEM. It was demonstrated by EIS that the resistance at the low frequency region corresponded to that of corrosion reaction of rusted steels (Rt). The Rt value of this steel increased after the continuous formation of inner rust, which implied that Si and Al took part in the conversion of complex oxides into fine structure that prevented the penetration of Cl ions.
Authors: B.T. Min, S.W. Hong, J.H. Kim, I.K. Park, H.D. Kim
Abstract: For the study of a steam explosion phenomenon in a nuclear reactor, prototypic corium, a mixture of UO2 and ZrO2 was melted in a cold crucible by applying an induction heating technique. The molten corium was then poured into cold water. It was fragmented into very small particles, so called debris, which enables a very rapid heat transfer to the water. Some cases led to steam explosions by thermal expansion of the water. After the tests, all the debris particles were dried and classified by their size. From the analysis by using EPMA, it was shown that the particles generated by a steam explosion had fine and irregular forms. It is known that real corium (including UO2) hardly leads to a steam explosion, different from pure ZrO2 or metal. A reason for this was previously suggested in that the corium generated hydrogen gas during melt-water interaction, and it enclosed the melt drops to prevent a direct contact of the corium and water. In order to confirm this fact, the debris particles were analyzed with ICP-AES for their typical element contents, EPMA for the homogeneity of the solid solution, XRD for the chemical compounds, and TGA and hydrogen reduction analysis for the percentage of the debris oxidation and reduction. These analyses showed that hydrogen was not directly related to steam explosion. Meanwhile, the material characteristics of the corium compositions are newly suggested to be the most probable reason for the occurrence of a steam explosion so far.
Authors: Magdalene Edet Ikpi, Jun Hua Dong, Wei Ke
Abstract: The corrosion behaviour of AM60 magnesium alloy containing 1.88 wt.% Cd in 0.1 M NaCl solution was investigated by weight loss and hydrogen evolution measurements. The microstructure was evaluated using EPMA. Cd was observed to have an even distribution, hence, no new phase was formed. The corrosion resistance was enhanced by the addition of Cd. The rate of corrosion reduced by a factor of 1.5 times that of AM60 alloy. The microstructure played a crucial role as the presence of defects in the alloys initiated and accelerated corrosion.
Authors: Xiao Jiang Liu, Guang Ming Cao, Yong Quan He, Tao Jia, Zhen Yu Liu
Abstract: Red scale is the main surface defect of hot-rolled silicon steel plate due to the formation of fayalite. Studies have been done on high temperature oxidation of Fe-Si alloy, but effect of temperature on structure of outer Fe oxide layer is not fully discussed. Thermogravimetric analyzer (TGA) was used to simulate isothermal 60-min oxidation process of Fe-2.2Si alloy under air condition at 700°C-1200°C. Cross-sectional scale morphology and elemental distribution of the oxide layer were investigated by electron probe microanalysis (EPMA). It is found that in order to observe internal oxide precipitates clearly it is helpful that the sample is etched with nitric acid solution in alcohol firstly and then etched with hydrochloric acid solution in alcohol. At 700°C-1150°C outer Fe oxide layer is mostly composed of Fe2O3 and at 1200°C it consists of FeO + Fe3O4 + Fe2O3 + mixture of FeO/Fe2SiO4.
Authors: Qu Bo He, Dong Zhe Wang, An Zhong Zhao, Rui Tang, Hai Ding Liu, Deng Hua Chen, Yan Mo
Abstract: In order to improve the purity of bearing steel, the VIM+ESR+VAR triple smelting process was used to smelt 9Cr18Mo stainless bearing steel. The content of harmful elements, non-metallic inclusions and microstructure of the steel were studied. The results show that, the content of harmful elements of the steel is very low. A fairly small number of non-metallic inclusions are uniformly distributed and fine. The purity of the steel reaches a higher level. After thermal processing and heat treatment, the microstructure of the steel is the same as 9Cr18Mo bearing steel smelted by normal process, but the primary carbides in the steel is more uniform distribution and finer.
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