| Hydrogen,due to its simple atomic structure,is one of the classical systems for the study of condensed matter.Metallic hydrogen is deemed to be a high-density energetic material and high-temperature superconductor.The research on metallic hydrogen has been listed as one of the major scientific issues in the field of compression science.In the previous studies on hydrogen,the experimental and theoretical results showed that the metallization pressure for hydrogen was as high as several megabars.The metallization pressure is so high,that it has become a research focus to explore technical ways to reduce hydrogen metallization pressure.One of the studies most worth mentioning is the idea of chemical precompression of the group IVa atoms.Now,it have been discovered that in group IVa hydrides?CH4,SiH4?hydrogen atoms have already undergone the chemical precompression exerted by heavy elements.Once the group IVa hydrides further impelled by external pressure,it may easily enter their metallic phases.Therefore,it is possible to obtain alloys of metallic hydrogen under relatively low pressure.The metallization of the group IVa hydrides is an important subject in the field of hydrogen-rich celestial magnetic field,superconducting materials and new energy research.The conductivity measurement result is the most direct evidence to determine if the sample is metallized.By means of dynamic pressure technology,researchers have obtained pressure dependence of resistivity for hydrogen fluid,found the experimental evidence of hydrogen metallization,but little is known for the group IVa hydrides system under high pressure.Therefore,it is necessary to carry out dynamic loading and conductivity measurement for the group IVa hydrides.Based on the above consideration,this thesis conducted an experimental study on the resistivity of hydrogen,methane and silane under shock compression.In this thesis,the experimental measurement technique for the resistivity of the dense fluids under shock wave loading was established;the pressure dependence of the resistivity of the pure hydrogen and two hydrogen-rich fluids?CH4 and SiH4?with the shock state were studied.Based on the obtained data at different temperature-pressure conditions,the conductive characteristic of different systems was explored.With this experimental technique,the characteristics of fluid silane resistivity under44138 GPa were obtained.It was found that fluid silane changed from insulator to semiconductor in this pressure range,and the minimum value of resistivity was found to be about 3×10-3?·cm.The resistivity data of fluid methane under 89145GPa were also obtained,as well as those of hydrogen resistivity under 12.493GPa.In this work,under the presence of chemical precompression of C and Si elements,the variation rules of the resistivity of these hydrogen-rich systems with pressure and temperature were studied.The influence of the group IVa atoms mixed into hydrogen-rich fluids on the resistivity of the systems was revealed.The following conclusions are summarized in this work:?1?In the same pressure range,the resistivity of methane is obviously higher than that of silane and hydrogen,it shows that the methane molecule maybe more stable,or the decomposition product remains low conductivity;?2?The effects of silicon and carbon elements in the hydrogen-rich fluid did not significantly reduce the resistivity,it is inferred that the effect of chemical precompression by the group IVa atoms under shock compression is not obvious,on the contrary,the methane system has a tendency to increase the metallization pressure;?3?According to semiconductor theory,the characteristics of electronic mobility gap varying with density were explained for hydrogen?methane and silane,and the metallization conditions of methane and silane were deduced..This work provides a reference for the study of metallic hydrogen,hydrogen-rich celestial magnetic field,superconducting materials and new energy. |
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