Papers by Keyword: Diffusivity

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Authors: Jing Zhong, Kai Wang, Li Jun Zhang
Abstract: A coupling interface between phase-field model with finite interface dissipation and the CALPHAD (CALculation of PHAse Diagram) thermodynamic and atomic mobility databases is developed. It robotizes the procedures that provides the composition and temperature dependent properties in multicomponent and multi-phase systems. Based on the developed coupling interface, different CALPHAD properties can be directly coupling in the phase-field simulation.
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Authors: Li Jun Zhang, Dan Dan Liu, Wei Bin Zhang, Shao Qing Wang, Ying Tang, Na Ta, Ming Wei, Yong Du
Abstract: A new atomic mobility database for Fcc_A1, L12, Bcc_A2, Bcc_B2, and liquid phases in the Al-Cu-Fe-Mg-Mn-Ni-Si-Zn system has been established via a hybrid approach of experiment, first-principles calculations and DICTRA (DIffusion Controlled TRAnsformation) software, focusing on the atomic mobility parameters in ternary systems. Various diffusivities can be computed as a function of temperature and composition. The reliability of this diffusivity database is further validated by comparing the calculated and measured diffusion properties in a series of ternary and quaternary diffusion couples, including concentration profiles, diffusion paths, interdiffusion fluxes, and so on. The effect of the diffusivity database on microstructure evolution during solidification is demonstrated by the phase field simulation of primary (Al) grains in Al356.1 alloy. The simulation results indicate that such accurate diffusivity database is highly needed for the quantitative simulation of microstructural evolution during solidification.
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Authors: Abhishek A. Sharma, Sanjay S. Mane
Abstract: The thermal diffusion behavior of ion-implanted Arsenic (As) in SiGe alloy has been investigated and modeled. This paper introduces a neural network based model consisting of physics-based and process-based parameters for evaluating the effective diffusivity of Arsenic through SiGe accurately. The parameters that served as the input to the neural network included Ge content, diffusion temperature and anneal time. The model was validated for the germanium content of up to 45% with the reported data and the existing simulation models in Silvaco. The model incorporates all the effects associated with the change in the process parameters which affect the diffusivity of As in relaxed-SiGe. The model was found to be extremely accurate in predicting the exact dependencies of As diffusivity on physics-based and process parameters. The proposed empirical process model may find suitable application in prediction of thermal diffusion behavior of As in SiGe process-flow with emphasis on reduced computational time.
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Authors: Guo Tao Zhang, Zhi Yuan Rui, Rui Cheng Feng, Chang Feng Yan
Abstract: The motion of interstitial atoms (one of the point defects) in material is random under certain temperature. However, the diffusion of interstitial atoms has priority along some certain directions to the others, so it is necessary to reveal the phenomenon (the phenomenon also can be called anisotropic). In order to illustrate the anisotropic and reveal the magnitude of probability of the micro crack formation along crystal axes, some formulae derived from former literatures have been adopted, and the values of diffusion probability and diffusivity of interstitial atoms-Ti or Al along 〈110〉and〈100〉have been calculated. The conclusion that the diffusion of interstitial atoms along different crystal axis has different diffusivity is verified by the comparison of the results of calculations.
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Authors: Mihai Ovidiu Cojocaru, Mihaela Raluca Condruz, Florică Tudose
Abstract: In this paper was followed the processing flow of aluminum-alumina compositions (10÷20% alumina) in powder state, aiming to obtain aluminum matrix composites reinforced with alumina particles, starting from selecting and mixing the grading fraction of both components reaching up to sintering; it was analyzed the way in which reflects the variation of grading fraction ratio (expressed through average particle diameter in the analyzed fractions limits) on the level of technological interest features: apparent density, tapped density, flowability, presability and on densification after sintering (in various environments). By transmission electron microscopy was observed that aluminum particles showed on the surface a nanoscale oxide film, so the sintering occurs between congeneric areas – by solid phase sintering mechanisms [1, 2, 3]. The analysis of thermophysical properties revealed a decrease of thermal diffusivity at an increase of alumina, simultaneous with the decrease of the densification level.
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Authors: Abhijeet Moon, R. Balasubramaniam
Abstract: Hydrogen diffusivity was estimated in three different eutectoid rail steels (C-Mn, Cu-Mo and Ni-Cu-Cr) at ambient temperatures using the technique of sub-surface microhardness profiling after cathodic hydrogen charging in 0.5mol/l sulphuric acid at a current density of 0.1A/cm2 for 24 hours. The increase in the concentration of hydrogen at a certain depth below the surface was related to the microhardness increase at this location as compared to the bulk value. The procedure used to obtain the diffusion coefficient of hydrogen from the microhardness profiles is discussed. The hydrogen diffusivity values in all of the rail steels were found to be similar (of the order of 10-13m2/sec). The estimated hydrogen diffusivity in the rail steel was lower than in pure iron (10-8m2/sec). Possible reasons for the difference are discussed.
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Authors: Jimoh K. Adewole, Ibnelwaleed A. Hussein, Usamah A. Al-Mubaiyedh
Abstract: A mathematical model for predicting the permeability of natural gas in polymer nanocomposites was developed and tested using experimental data. The model takes into account the effects of pressure, temperature, crystallinity and nanoparticle loading. Three model parameters (, and) were obtained. The parameter is a measure of the activation energy, described the effect of nanocomposite loading, and can be used to describe the effect of gas concentration on the. Polymer nanocomposites were prepared using high density polyethylene as polymer matrix and Cloisite 15A as nanoclay. The proposed model was used to predict the permeability of the nanocomposites to pure CH4 and mixed CH4/CO2 gases (containing 80 mol% CH4) at pressures up to about 106 bar and temperatures between 30 to 70°C. Predicted results show that the developed model provides an excellent description of natural gas permeation in pure HDPE and its nanocomposites.
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Authors: H. Nakashima, Taizoh Sadoh, H. Kitagawa, K. Hashimoto
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Authors: A.V. Mironov, A.V. Pokoev, D.I. Stepanov, I.S. Trofimov
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Authors: Semih Senkader, A. Giannattasio, Robert J. Falster, Peter R. Wilshaw
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