Kuochih Chou's research while affiliated with Shanghai University and other places

The Modified Quasichemical Model in the Pair Approximation (MQMPA) can effectively capture the thermodynamic features of a binary solution with Short-Range Ordering (SRO). If the model is used to treat a ternary solution, a geometric interpolation method must be employed to extend the bond energy expression from binary to ternary formalism. The aim of the present work is to implement such extension by means of a generic geometric interpolation approach. The generic method is unbiased and can be transformed into the widely used Kohler, Toop and Muggianu approaches with special interpolation parameters. The interpolation parameters can be calculated by the integration method as well as be optimized by ternary experimental data. The generic bond energy formalism (GBEF) has thus been derived to provide the MQMPA great flexibility to describe ternary solutions with complex configurations. Moreover, the GBEF is more concise than the formula derived by a combinatorial Kohler-Toop method. The concise GBEF is in the respect more conveniently programmed. Eventually, the Cu-Li-Sn liquid where both SRO and clustering among atoms occur is employed to validate the effectiveness and reliability of the GBEF within the MQMPA.

Model prediction is an effective method to obtain the physicochemical properties data of molten slags, which is difficult to test experimentally due to their high melting points. Empirical models are prevalent at present; however, it needs large amount of experimental data to fit the empirical parameters with narrow application scope. In this paper, the Kriging interpolation method modified with oxide property weights, is firstly introduced into the viscosity prediction of multicomponent slags. The prediction results of CaO–Al2O3–SiO2, CaO–Al2O3–CaF2, CaO–Al2O3–SiO2–MgO and CaO–Al2O3–SiO2–MgO–CaF2 systems showed that the predicted errors by the Modified Kriging Interpolation (MKI) method are smaller than those by various empirical models. It is anticipated that the MKI method can be extended to predicting the continuous physicochemical properties of multicomponent slags.

Pt/nitrogen-doped reduced graphene oxide (N-GO) catalysts were prepared by one-step microwave-assisted ethylene glycol reduction using N-methyl-2-pyrrolidone (NMP) as the nitrogen source. Nitrogen doping in GO and the deposition of highly dispersed platinum nanoparticles were completed at the same time. The effect of adding NMP on the microstructure and the electrocatalytic performance of Pt/N-GO catalysts were studied. The results show that Pt/N-GO catalysts have better particle size distribution and electrocatalytic performance than undoped catalysts. When the ratio of GO to NMP reaches 1:200, the peak current density of the catalyst is about 3 times that of the non-nitrogen-doped Pt/GO and Pt/C(JM) catalysts, indicating that the electrocatalytic performance of this catalyst is the best. Therefore, the development of a one-step synthesis of Pt/N-GO catalysts has a broad application prospects in direct ethanol fuel cells (DEFCs).

The prediction of glass forming ability (GFA) of alloys is of vital importance for the development of novel amorphous alloys. In this paper, the GFA of Cu-Zr-based alloys was calculated by an integrated thermodynamic parameter (PHSS), which involves the influences of mixing enthalpy (ΔHChem), mismatch entropy (Sσ) and configurational entropy (ΔSc). Our General Solution Model (GSM) was used for the prediction of ΔHChem, which showed better consistency with experimental data than Gallego or Takeuchi model. Besides, the correlations of PHSS with Critical Diameter (Dc) was found and fitted well with experimental data. Moreover, the glass forming ranges of two types of Cu-Zr-based alloys were predicted according to PHSS, which was verified by experiment and agreed well with the experimental data available in reference and our experimental results. Therefore, the prediction of PHSS combined with GSM model is expected to provide guidelines for the design of Cu-Zr-based amorphous alloys.

Double Line (DL) model is an efficient method for predicting the physicochemical properties of systems with limited solubility area, and linear interpolation is always taken for the boundary-property interpolation. In this paper, two nonlinear interpolation methods are introduced to optimize the interpolated results on the calculation boundary, which are used for the viscosity prediction of CaO-Al2O3-SiO2 system by DL model. The predicted results by two nonlinear interpolation methods show better agreements with the experimental data than those by linear interpolation. Besides, whatever the interpolation method is, the predicted mean deviations by DL model are always much smaller than those by empirical models (Ray model and Urbain model). It is anticipated that the introduction of nonlinear interpolation methods will improve the calculation accuracy of ternary melts by DL model.

Magnesium and its alloys are significant superior metallic materials for structural components in automobile and aerospace industries due to their excellent physicomechanical properties. The Mg–rare earth (RE) systems have attracted great interests because RE additions can improve both the deformability and the strength of Mg alloys through solid solution strengthening and precipitation hardening mechanisms. This paper focuses on the interface stability, together with thermodynamics and kinetics of nucleation and growth of the key phases and matrix phases in Mg–RE alloys. In this paper, the theory and recent advances on Mg–RE alloys, especially for the interface stability, thermodynamics and kinetics of nucleation and growth of the key phases and matrix phases, together with their relationships with micro-structures, and macroscopic properties, are reviewed. By combining the thermodynamics/kinetics integrated simulations with various advanced experimental techniques, “reverse” design of Mg–RE alloys starting from the target service performance is put forward as a kind of scientific paradigm with rational design.

The hot deformation behavior of spray-formed 1.28C–6.4W–5Mo–4.2Cr–3.1V–8.5Co high speed steel is investigated in the 950–1100°C temperature range at a strain rates of 0.1 to 50 sec–1 and a true strain of 1.0. The activation energy for hot deformation is obtained. The relation between the flow stress and Zener–Hollomon parameter is successfully analyzed via the hyperbolic sine function under the whole range of deformation conditions. By a microstructural analysis for the breakdown of carbide networks in the temperature range and different strain rates, the size and distributing character of carbide grains are given. The appropriate ranges of deformation temperature and strain rate are provided to obtain fine spheroidal carbide particles and their uniform distribution.

Grain refinements were an effective method to improve the mechanical properties of aluminium alloy, and heterogeneous nucleation was widely applied in industry to achieve a grain-refined. In this study, grain refinement behavior of 55%Al-Zn-1.6%Si alloy by Al-Ti-B was investigated. In order to obtain the microstructure in situ, high-temperature liquid quenching by stainless steel pipe was used to capture the sample snapshots. Then, the effect of Al-5Ti-0.2B on the alloy was analyzed by microstructure, solid fraction and grain size. Our results show that the grain size of 55Al-Zn-Si alloy decreased after the Al-5Ti-0.2B addition to some extent, and in order to understand the effect of refinement, it was necessary to analyze the mechanisms of Ti in 55Al-Zn-Si alloy. Meanwhile, during the process of solidification, the solid fraction of 55Al-Zn-Si alloy was further increased with the temperature decreasing, and the result was consistent with our calculation of phase diagram. Finally the reactions were identified using calculation of phase diagram.

Rare earth (RE) elements have been added into Mg-based hydrogen storage alloys to form Mg-based RE-Mg hydrogen storage alloys due to their active properties. These alloys have attracted extensive attention owning to their good hydrogen storage performance. However, because of the lack of the guidance by phase diagrams in the RE-Mg system, the material design is aimlessly and would fall into a " cooking" exploration. For the study of hydriding and dehydriding kinetics, the current experimental measurement mainly repeated on determining the relationship between reaction fraction and time at isothermal condition. Few research focused on the effect of temperature, pressure, particle size… on the reaction rate, much less the particle size distribution, heating rate and other factors. This work investigates the Mg-Ni-RE (La, Nd, Ce, Y)-H quarternary system based on the thermodynamic and kinetic calculations. The calculation based on thermodynamic database reveals the thermodynamic stability of hydrogen storage alloys and hydrides. The Pressure-Composition-Temperature (PCT) curves are predicted through CALPHAD method. The thermodynamic calculation and experimental results of in situ X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM) indicate the thermodynamic mechanism of hydriding and dehydriding. Meanwhile, the isothermal and non-isothermal hydriding/dehydriding kinetics are investigated and the reacted fraction is expressed as a function of temperature, pressure, particle size, particle morphology etc. This method not only simplifies the calculation, but also makes the physical quantities easy to discuss theoretically. A new concept " characteristic time" is introduced, which will act an important role in the research of hydrogen storage materials. © 2016, The Editorial Board of Materials China. All right reserved.