A new method to calculate mutual-diffusion coefficients of the binary alloy has been proposed in this report.At first self-diffusion coefficient of the constituent element was calculated using molecular dynamics method,thermodynamic factor of the alloy was got with the NRTL (non-random-two-liquid) equation,then mutual-diffusion coefficient was obtained with Darken formula.Using this method the mutual-diffusion coefficient of Pb-Mg alloy with different Pb content was calculated.The calculated values were compared with the available experimental ones and the reason of the maximal mutual-diffusion coefficient appearing at 33.3 at.%Pb was discussed.Partial pair correlation function and partial coordination number were calculated to analyze the effect of the melt structure on mutual-diffusion coefficient.
LIU YuanYuan,JIA GuoBin & YANG Bin National Engineering Laboratory of Vacuum Metallurgy,Kunming University of Science and Technology,Kunming 650093,China
Molecular dynamics simulation was used to simulate the thermodynamic properties of three binary alloys,Pb-Ag (1:1),Pb-Ag (4:1),and Pb-Ag (9:1).The energy functions,such as excess free energy,cohesive energy,and formation energy,were calculated.The calculated values agree well with the experimental ones.The atomic interactions were analyzed in macroscopic and microcosmic views and both are consistent well.
JIA Guobin,LIU Yuanyuan,YANG Bin,and LIU Dachun National Engineering Laboratory of Vacuum Metallurgy,Kunming University of Science and Technology,Kunming 650093,China
Indium tin oxide(ITO)nanopowders were prepared by a modified chemical co-precipitation process.The influence of different SnO2 contents on the decomposition behavior of ITO precursors,and on the phase and morphology of ITO precursors and ITO nanopowders were studied by X-ray diffractometry,transmission electron microscopy and differential thermal and thermogravimetry analysis methods.The TG-DSC curves show that the decomposition process of precursor precipitation is completed when the temperature is close to 600 ℃and the end temperature of decompositionis somewhat lower when the doping amount of SnO2 is increased.The XRD patterns indicate that the solubility limit of Sn4+ relates directly to the calcining temperature. When being calcined at 700℃,a single phase ITO powder with 15%SnO2(mass fraction)can be obtained.But,when the calcining temperature is higher than 800℃,the phase of SnO2 will appear in ITO nanopowders which contain more than 10%SnO2.The particle size of the ITO nanopowders is 15-25 nm.The ITO nanoparticles without Sn have a spherical shape,but their morphology moves towards an irregular shape when being doped with Sn4+.
