The shell-model molecular dynamics method was applied to simulate the melting temper- atures of SrF2 and BaF2 at elevated temperatures and high pressures. The same method was used to calculate the equations of state f...The shell-model molecular dynamics method was applied to simulate the melting temper- atures of SrF2 and BaF2 at elevated temperatures and high pressures. The same method was used to calculate the equations of state for SrF2 and BaF2 over the pressure range of 0.1 MPa-3 GPa and 0.1 MPa-7 GPa. Compared with previous results for equations of state, the maximum errors are 0.3% and 2.2%, respectively. Considering the pre-melting in the fluorite-type crystals, we made the necessary corrections for the simulated melting temper- atures of SrF2 and BaF2. Consequently, the melting temperatures of SrF2 and BaF2 were obtained for high pressures. The melting temperatures of SrF2 and BaF2 that were obtained by the simulation are in good agreement with available experimental data.展开更多
Dense polycrystalline cubic boron nitride(PcBN)composites were fabricated by high-pressure and high-temperature(HPHT)sintering using polysilazane(PSN)and Al as sintering additive.After high-energy ball milling,the cBN...Dense polycrystalline cubic boron nitride(PcBN)composites were fabricated by high-pressure and high-temperature(HPHT)sintering using polysilazane(PSN)and Al as sintering additive.After high-energy ball milling,the cBN fine particles were uniformly coated with PSN by ultrasonic treatment.After thermocuring and pyrolysis,the cBN–SiCN particles were mixed with Al The PcBN composites were prepared after sintering a1450°C for 10 min with a pressure of 5 GPa.The refining effect of high-energy ball milling on the c BN particles was studied by scanning electron microscopy(SEM)and laser particle size analyzer.The oxidation of the cBN particles after milling was investigated by nitrogen–oxygen analyzer.The phase composition and microstructure of the sintered PcBN composites were investigated by X-ray diffractometer(XRD)and SEM.The main phases of the sintered PcBN composites are c BN,AlN,SiC and Si3N4The conversion of cBN to hBN was inhibited by the formation of AlN.The mechanical properties of the sintered PcBN composites were improved by the appearance of SiC and Si3N4.The density and mechanical properties of the PcBN composites both increased with the content of the cBN particles increasing.The sintered sample with 60 wt%cBN,30 wt%PSN and 10 wt%Al showed the best results density of 99.7%,Vickers’hardness of(25.2±0.8)GPa and flexural strength of(602±15)MPa.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.10676025） and Research Center of Laser Fusion, China Academy of Engineering Physics.
文摘The shell-model molecular dynamics method was applied to simulate the melting temper- atures of SrF2 and BaF2 at elevated temperatures and high pressures. The same method was used to calculate the equations of state for SrF2 and BaF2 over the pressure range of 0.1 MPa-3 GPa and 0.1 MPa-7 GPa. Compared with previous results for equations of state, the maximum errors are 0.3% and 2.2%, respectively. Considering the pre-melting in the fluorite-type crystals, we made the necessary corrections for the simulated melting temper- atures of SrF2 and BaF2. Consequently, the melting temperatures of SrF2 and BaF2 were obtained for high pressures. The melting temperatures of SrF2 and BaF2 that were obtained by the simulation are in good agreement with available experimental data.
基金financially supported by the National Natural Science Foundation of China(No.51402264)the Natural Science Foundation of Henan Province(No.162300410242)the Excellent Young Faculty Research Foundation of Zhengzhou University(Nos.1421320049 and 1421320044)。
文摘Dense polycrystalline cubic boron nitride(PcBN)composites were fabricated by high-pressure and high-temperature(HPHT)sintering using polysilazane(PSN)and Al as sintering additive.After high-energy ball milling,the cBN fine particles were uniformly coated with PSN by ultrasonic treatment.After thermocuring and pyrolysis,the cBN–SiCN particles were mixed with Al The PcBN composites were prepared after sintering a1450°C for 10 min with a pressure of 5 GPa.The refining effect of high-energy ball milling on the c BN particles was studied by scanning electron microscopy(SEM)and laser particle size analyzer.The oxidation of the cBN particles after milling was investigated by nitrogen–oxygen analyzer.The phase composition and microstructure of the sintered PcBN composites were investigated by X-ray diffractometer(XRD)and SEM.The main phases of the sintered PcBN composites are c BN,AlN,SiC and Si3N4The conversion of cBN to hBN was inhibited by the formation of AlN.The mechanical properties of the sintered PcBN composites were improved by the appearance of SiC and Si3N4.The density and mechanical properties of the PcBN composites both increased with the content of the cBN particles increasing.The sintered sample with 60 wt%cBN,30 wt%PSN and 10 wt%Al showed the best results density of 99.7%,Vickers’hardness of(25.2±0.8)GPa and flexural strength of(602±15)MPa.
