| Based on the model of shock melting's influence to interface temperature at 'metal sample/ transparent window', which was proposed by Hua Tan, Chengda Dai and T. J. Ahrens, and experimental measurements of shock temperature with bulk metal sample, which was proposed by Hua Tan and Chengda Dai, this thesis used instantaneous multi-channel pyrometer in LSD and 'bulk sample/single crystal LiF' setup to obtain iron's melting temperature at 127 GPa and 134 GPa, shock temperature at 186 GPa and 134 GPa.(1) The melting temperature is at the impedance-matching pressure 127GPa and 134GPa by shocked iron samples and window of single-crystal LiF. Melting temperature results in this thesis are between the shock melting and static experiment results, locate round the melting curve calculated by Anderson(2002). The melting temperature was fitted with Lindemenn's melting law and extrapolated to 330GPa(the pressure at interface of inner-core and outer-core). A value of 5709+ 506K was found. In the experiments of this thesis the shock temperature 3881?64K at 186GPa and 4591?94K at 204GPa was e measured. The results are consistent with calculated results of McQueen and Brown(1986), and agree with calculated shock temperature in this thesis, which considered heat electron's contribution to specific heat and Greneisen parameter of iron at high pressure.(2) According to 'model of three-layers thermal conduction', the temperature at interface of 'sample/window' will soon attenuate to temperature at ideal interface, if the gap between bulk sample and transparent window is thin enough. The iron samples and window material used in this thesis were fine polished . The width of gap in the interface is round 0.5 um. The signal detected in experiments attenuated to a stable value quickly, which is greed with result educed form 'model of three-layers thermal conduction'.(3) Calculation shows that the iron sample will melt when release to 127GPa and 134GPa from shock state in experiments of this thesis. Based on above model, the temperature of 'iron sample/ LiF window' in experiments was taken directly for melting temperature at interface, thus the difficulty in data processing due to absence of metal parameters at high pressure was avoided. The melting temperature obtained in this thesis is consistent with measurements of bulk iron meterite offered by Chengda Dai. The results proved again that 'model of three-layer thermal conduction' has good applicability in melting temperature measurements at high pressure by optical radiation detection menthod.(4) Specific capacity and Gruneisen parameter at high pressure was used in calculation of iron shock temperature and phase graph. The effect of thermal motion of electron has beengenerally neglected in previous work. But the experiment results show that thermal motion of electron will affect temperature greatly at the temperature and pressure range in this thesis. Several models which contain the distribution of electronic thermal motion have been used to calculate specific capacity and Griineisen parameter. It was found that electronic thermal motion and lattice libration are in same importance at high temperature. Effective Griineisen parameter include electronic Griineisen parameter and lattice Griineisen, which is higher than what used in previous works. Thermal conductivity of LiF crystal was calculated, the maximum of 19.2W/mK at 33GPa was found. The value will descend with temperature rising , and fall to 19.2W/mK at 150GPa. While thermal conductivity of iron is not a explicit function of temperature, only changed with specific volume according to research of Yan Bi.(5) Deflection caused by the gap between sample/window to interface temperature was calculated. The result shows that the width of 'high temperature layer' is about equal to width of initial gap. Precise surface observation of iron sample and LiF window shows that typical width of gap between 'iron sample/LiF window' is round 0.5um. It will cause 200-300K temperature higher to ideal interface temperature in theoreti... |
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