A molecular dynamics simulation study was performed to investigate the formation and evolution mechanisms of nano-clusters during the rapid solidification of liquid CaToMg30 alloy. The cluster-type index method （CTIM...A molecular dynamics simulation study was performed to investigate the formation and evolution mechanisms of nano-clusters during the rapid solidification of liquid CaToMg30 alloy. The cluster-type index method （CTIM） was adopted to describe microstructure evolutions of nano-clusters during solidification. Results indicate that amorphous structure is mainly formed with three bond-types of 1551, 1541 and 1431 at the cooling rate of 5~1011 K/S, and glass transition temperature Tg is about 530 K; the icosahedron cluster of （12 0 12 0） plays a key role in formation of amorphous structure, and smaller Mg atoms are much more probable to be central atoms of icosahedron clusters; and nano-clusters are mainly formed by combining medium-size clusters. Interestingly, it was also found that formation and evolution processes of the nano-cluster display a three-stage feature which is analogous to crystallization process of amorphous alloy.展开更多
A larger-scale Mg70Zn30 alloy system including 100000 atoms has been simulated by using the molecular dynamics method to investigate the icosahedral medium-range order （IMRO） formed in the MgToZn30 metallic glass. I...A larger-scale Mg70Zn30 alloy system including 100000 atoms has been simulated by using the molecular dynamics method to investigate the icosahedral medium-range order （IMRO） formed in the MgToZn30 metallic glass. It is found that the simulated pair distribution function of Mg70Zn30 metallic glass is in good agreement with the experimental results. The glass transition temperature Tg is near 450 K under the cooling rate of 1×10^12 K/s. The icosahedral local structures play a critical role in the formation of metallic glass, and they are the dominant local configurations in the Mg70Zn30 metallic glass. The IMRO in the Mg70Zn30 metallic glass is characterized by certain types of extended icosahedral clusters combined by intercross-sharing atoms in the form of chains or dendrites. The size distributions of these IMRO clusters present a magic number sequence of 19, 23, 25, 27, 29, 31, 33, 35, 37, 39,..., and the magic clusters can be classified into three types according to their compactness. The IMRO clusters grow rapidly in a low-dimensional way with cooling, but this growth is limited near Tg.展开更多
Cu-30Ni-xRE(x=0–0.213 wt.%) alloy was prepared by adding rare earths(RE) in melted Cu-30Ni alloy using metal mould casting method.The effects of RE on corrosion resistance of the alloy in simulated seawater were inve...Cu-30Ni-xRE(x=0–0.213 wt.%) alloy was prepared by adding rare earths(RE) in melted Cu-30Ni alloy using metal mould casting method.The effects of RE on corrosion resistance of the alloy in simulated seawater were investigated using optical microscope,scanning electronic microscope with energy-dispersive spectrometer and electrochemical measurement system.The results showed that the corrosion resistance of Cu-30Ni alloy was greatly improved by adding proper amount of RE,whereas excess addition of RE worsened ...展开更多
Titanium and titanium alloys are currently being used for clinical biomedical applications due to their high strength, corrosion resistance and elastic modulus. The Ti-30Ta alloy has gotten extensive application as th...Titanium and titanium alloys are currently being used for clinical biomedical applications due to their high strength, corrosion resistance and elastic modulus. The Ti-30Ta alloy has gotten extensive application as the important biomedical materials. The substrate surface of the Ti-30Ta alloy was altered either by chemical or topographical surface modification. The biocompatibility of an implant is closely related to its surface properties. Thus surface modification is one of effective methods for improving the biocompatibility of implants. The development status of biomedical materials has been summarized firstly, the biomedical application. In this study Ti-30Ta alloy surface was investigate as-casting (Group 1) modified with alkaline and heat-treatments in NaOH with 1.5M at 60°C for 24 hrs (Group 2), alkaline and heat-treatments with SBF-coatings by immersion in NaOH and SBFX5 for 24hrs (Group 3), anodization process was performed in an electrolyte solution containing HF (48%) and H2SO4 (98%) with the addition of 5% dimethyl sulfoxide (DMSO) 35V for 40 min (Group 4) and ion beam etching with 1200 eV ions with a beam current of 200 mA for a 3 hrs etch (Group 5). SEM was used to investigate the topography, EDS the chemical composition, and surface energy was evaluate with water contact angle measurement. SEM results show different structure on the surface for each group. EDS spectra identified similarity on Group 1, 4 and 5. The results indicate for group 2 an amorphous sodium tantalate hydrogel layer on the substrate surface and for group 3 the apatite nucleation on substrate surface. The Group 4 shows unorganized and vertically nanotubes and Group 5 shows a little alteration in the topography on the substrate surfaces. Overall the contact angle shows Group 5 the most hydrophobic and Group 4 the most hydrophilic. The study indicates Group 3 and 4 with potential for biomedical application. The next step the authors need to spend more time to study group 3 and 4 in the biomedical sciences.展开更多
A molecular dynamics (MD) simulation study has been performed for the rapid solidification of Cu70Ni30 adopting the quantum Sutton-Chen many-body potentials. By analyzing the bond-types and the relation of atomic aver...A molecular dynamics (MD) simulation study has been performed for the rapid solidification of Cu70Ni30 adopting the quantum Sutton-Chen many-body potentials. By analyzing the bond-types and the relation of atomic average energy versus temperature, it was demonstrated that as cooling rate being 2 × 1012 K/s, the Cu70Ni30 formed fcc crystal structures and freezing point was found. In addition, having analyzed the transformation of microstructures and the detail of crystal growth by using atomic trace and visual method, not only could the formation of binary disordered solid solution be showed, but also the solidification of liquid metals and the crystal growth processes could be further understood.展开更多
DEM数据源及分辨率会影响流域特征参数的提取,进而影响水文模拟结果。将ASTER 30 m DEM、SRTM 90 m DEM及基于ASTER 30 m DEM的40 m、50 m、60 m、70 m、80 m、90 m重采样DEM作为HEC-geo HMS模型输入,提取流域特征,采用HEC-HMS模型,以...DEM数据源及分辨率会影响流域特征参数的提取,进而影响水文模拟结果。将ASTER 30 m DEM、SRTM 90 m DEM及基于ASTER 30 m DEM的40 m、50 m、60 m、70 m、80 m、90 m重采样DEM作为HEC-geo HMS模型输入,提取流域特征,采用HEC-HMS模型,以西笤溪流域为研究区域,分析2011年6月和2011年8—9月的两场降雨径流过程中,DEM数据源和分辨率对水文模拟输出的影响。研究结果表明,两次径流模拟结果与实测数据拟合都较好,模型确定性系数都大于0.82,但是单峰的洪水模拟效果总体更好,基于SRTM 90 m的模型确定性系数比基于ASTER 30 m DEM、重采样90 m DEM的模型确定性系数都大。基于重采样DEM的模型确定性系数变化较大,而且与分辨率的变化呈非线性关系。在HEC-HMS的模拟中,基于ASTER 30 m DEM和基于SRTM 90 m DEM的模拟输出结果相对误差相差3%~5%,基于SRTM 90 m DEM和基于重采样90 m DEM的模拟输出结果相对误差相差2%~4%,基于重采样DEM的模拟输出结果相对误差相差最大达到了11%。展开更多
基金Project(50831003) supported by the National Natural Science Foundation of ChinaProject(20114BAB215026) supported by Jiangxi Provincial Natural Science Foundation,ChinaProject(ZD201002) supported by Fund for Basic Scientific Research of Gannan Medical University,China
文摘A molecular dynamics simulation study was performed to investigate the formation and evolution mechanisms of nano-clusters during the rapid solidification of liquid CaToMg30 alloy. The cluster-type index method （CTIM） was adopted to describe microstructure evolutions of nano-clusters during solidification. Results indicate that amorphous structure is mainly formed with three bond-types of 1551, 1541 and 1431 at the cooling rate of 5~1011 K/S, and glass transition temperature Tg is about 530 K; the icosahedron cluster of （12 0 12 0） plays a key role in formation of amorphous structure, and smaller Mg atoms are much more probable to be central atoms of icosahedron clusters; and nano-clusters are mainly formed by combining medium-size clusters. Interestingly, it was also found that formation and evolution processes of the nano-cluster display a three-stage feature which is analogous to crystallization process of amorphous alloy.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50831003)the Special Fund for Basic Scientific Research of Central Colleges, Chang’an Univeristy (Grant No. CHD2009JC169)
文摘A larger-scale Mg70Zn30 alloy system including 100000 atoms has been simulated by using the molecular dynamics method to investigate the icosahedral medium-range order （IMRO） formed in the MgToZn30 metallic glass. It is found that the simulated pair distribution function of Mg70Zn30 metallic glass is in good agreement with the experimental results. The glass transition temperature Tg is near 450 K under the cooling rate of 1×10^12 K/s. The icosahedral local structures play a critical role in the formation of metallic glass, and they are the dominant local configurations in the Mg70Zn30 metallic glass. The IMRO in the Mg70Zn30 metallic glass is characterized by certain types of extended icosahedral clusters combined by intercross-sharing atoms in the form of chains or dendrites. The size distributions of these IMRO clusters present a magic number sequence of 19, 23, 25, 27, 29, 31, 33, 35, 37, 39,..., and the magic clusters can be classified into three types according to their compactness. The IMRO clusters grow rapidly in a low-dimensional way with cooling, but this growth is limited near Tg.
基金Project Financially supported by Major State Basic Research Development Program of China (2007CB616903)
文摘Cu-30Ni-xRE(x=0–0.213 wt.%) alloy was prepared by adding rare earths(RE) in melted Cu-30Ni alloy using metal mould casting method.The effects of RE on corrosion resistance of the alloy in simulated seawater were investigated using optical microscope,scanning electronic microscope with energy-dispersive spectrometer and electrochemical measurement system.The results showed that the corrosion resistance of Cu-30Ni alloy was greatly improved by adding proper amount of RE,whereas excess addition of RE worsened ...
基金supported by the National Key Research and Development Program of China (2021YFA1301504)the National Natural Science Foundation of China (91953101)the Chinese Academy of Sciences Strategic Priority Research Program (XDB37040202)
基金Brazilian agencies CNPq via grant Doctored sandwich (201271/2010-9) Fapesp project number 2010/ 10174-8 and 2010/07231-0
文摘Titanium and titanium alloys are currently being used for clinical biomedical applications due to their high strength, corrosion resistance and elastic modulus. The Ti-30Ta alloy has gotten extensive application as the important biomedical materials. The substrate surface of the Ti-30Ta alloy was altered either by chemical or topographical surface modification. The biocompatibility of an implant is closely related to its surface properties. Thus surface modification is one of effective methods for improving the biocompatibility of implants. The development status of biomedical materials has been summarized firstly, the biomedical application. In this study Ti-30Ta alloy surface was investigate as-casting (Group 1) modified with alkaline and heat-treatments in NaOH with 1.5M at 60°C for 24 hrs (Group 2), alkaline and heat-treatments with SBF-coatings by immersion in NaOH and SBFX5 for 24hrs (Group 3), anodization process was performed in an electrolyte solution containing HF (48%) and H2SO4 (98%) with the addition of 5% dimethyl sulfoxide (DMSO) 35V for 40 min (Group 4) and ion beam etching with 1200 eV ions with a beam current of 200 mA for a 3 hrs etch (Group 5). SEM was used to investigate the topography, EDS the chemical composition, and surface energy was evaluate with water contact angle measurement. SEM results show different structure on the surface for each group. EDS spectra identified similarity on Group 1, 4 and 5. The results indicate for group 2 an amorphous sodium tantalate hydrogel layer on the substrate surface and for group 3 the apatite nucleation on substrate surface. The Group 4 shows unorganized and vertically nanotubes and Group 5 shows a little alteration in the topography on the substrate surfaces. Overall the contact angle shows Group 5 the most hydrophobic and Group 4 the most hydrophilic. The study indicates Group 3 and 4 with potential for biomedical application. The next step the authors need to spend more time to study group 3 and 4 in the biomedical sciences.
基金supported by the National Natural Science Foundation of China(Grant No.50271026).
文摘A molecular dynamics (MD) simulation study has been performed for the rapid solidification of Cu70Ni30 adopting the quantum Sutton-Chen many-body potentials. By analyzing the bond-types and the relation of atomic average energy versus temperature, it was demonstrated that as cooling rate being 2 × 1012 K/s, the Cu70Ni30 formed fcc crystal structures and freezing point was found. In addition, having analyzed the transformation of microstructures and the detail of crystal growth by using atomic trace and visual method, not only could the formation of binary disordered solid solution be showed, but also the solidification of liquid metals and the crystal growth processes could be further understood.
文摘DEM数据源及分辨率会影响流域特征参数的提取,进而影响水文模拟结果。将ASTER 30 m DEM、SRTM 90 m DEM及基于ASTER 30 m DEM的40 m、50 m、60 m、70 m、80 m、90 m重采样DEM作为HEC-geo HMS模型输入,提取流域特征,采用HEC-HMS模型,以西笤溪流域为研究区域,分析2011年6月和2011年8—9月的两场降雨径流过程中,DEM数据源和分辨率对水文模拟输出的影响。研究结果表明,两次径流模拟结果与实测数据拟合都较好,模型确定性系数都大于0.82,但是单峰的洪水模拟效果总体更好,基于SRTM 90 m的模型确定性系数比基于ASTER 30 m DEM、重采样90 m DEM的模型确定性系数都大。基于重采样DEM的模型确定性系数变化较大,而且与分辨率的变化呈非线性关系。在HEC-HMS的模拟中,基于ASTER 30 m DEM和基于SRTM 90 m DEM的模拟输出结果相对误差相差3%~5%,基于SRTM 90 m DEM和基于重采样90 m DEM的模拟输出结果相对误差相差2%~4%,基于重采样DEM的模拟输出结果相对误差相差最大达到了11%。
