【作者】 张世来；

【导师】 刘福生；

【作者基本信息】 西南交通大学 ， 凝聚态物理， 2010， 硕士

【摘要】 金属冲击熔化线测量一直是动高压研究领域中一个重要的研究课题,在此方面的实验和理论研究工作已经持续了几十年。但在实验条件的控制和理论分析方面还存在一些问题未解决,所以人们对此类实验结果的一致性还未形成共识。目前在动高压领域,测量金属熔化线的方法主要包括冲击熔化和卸载熔化两种方法。其中卸载熔化温度测量主要是借助于金属／窗口界面温度,再获得熔化温度。该研究工作在两个方向取得进展：一是从实验方法上改善金属与窗口之间的接触状况以获得无异常辐射尖峰的真实界面辐射信号；二是从理论方法上建立热传导模型对发生在界面处的物理过程给出正确描述。本文通过改进样品制备技术,可重复地获得了无异常尖峰的界面辐射信号,在冲击-卸载熔化压力附近研究了铁／蓝宝石界面辐射特性和界面温度历史,并研究了卸载熔化效应与界面温度历史的关系。论文在以下几个方面取得具有一定创新性结果：(1)基本解决了理想接触界面制备问题。本文对金属样品进行了精细的抛光处理,并采用多点同时压靶的方式,先后在多个压力点获得了无尖峰界面辐射信号,基本实现理想接触界面制备过程的可重复性。(2)直接观测到由金属熔化相变引起的金属／界面温度变化特征。当金属样品冲击-卸载以后,如果其内部无熔化相变时,界面辐射及界面温度稳定;而当金属样品内部有熔化相变发生时,界面辐射及界面温度呈现不稳定特征：发射率随时间增加同时界面温度缓慢降低。此现象在以往的研究中少见报道。(3)建立了熔化相变-热传导耦合模型,解释了实验观测结果。本文结合熔化相变动力学模型与热传导方程对实验现象给出一种理论解释。理论计算所给出的温度变化趋势与实验观测结果一致,据此估计出高温高压下铁熔化相变的成核速率和核长大速率。更多还原

【Abstract】 The measurement of melting-curve of metals at high pressures is an important topic in field of dynamic high-pressure science, which has been researched for several decades. But some problems are still required to be solved. At present, there are two paths to reach the melt states for metals, which include shock induced melting and unload-induced melting. In the later method, the melting temperature is deduced from the measured temperature of metal/window interface. The challenge is how to get the inierface temperature without the effects of air gap. The achievement were made at two aspects:The first was to improve the contact condition betweem the metal and window, the other was to develop the theoretical model based on heat conduct.By improving the technique of sample preparation, in this work the radiation of interface without "peak" feature of air gap is obtained with good repetition. At pressures of shock-release melting, the radiation characteristics and the temperature history of iron/sapphire interface are investigated, and the relationship between the dynamics of release melting and the time dependence of surface temperature is found. In the following aspects this work reaches new results:(1) The nearly ideal contacted interface has been prepared. The radiation without "peak" feature was obtained by refined surface polishing and reasonable target assembling at different pressure points. The repeatability of ideally contacted interface preparation was nearly achieved.(2) The characteristics of the interface temperature variation was directly observed. After the metal sample being shocked and released, if there was melting phase transition in the metal, the radiation and temperature of the metal/sapphire interface was unsteady,but if there wasn’t melting phase transition in the metal, the radiation and temperature of the metal/sapphire interface was steady.This unsteady experimental signal is a new phenomenon.(3) Explained the experimental result by establish melting phase transition kinetics-heat conduct equation. This paper explained the unsteady history of radiation and temperature at the metal/sapphire interface by transformation kinetics combined with heat conduction equation. When the result of theoretical calculation was consistent with the result of experiment, the nucleation rate and nuclear growth rate under high temperature and high pressure can be confirmed.更多还原