Effect Of Exciting Light On Crystallization Of Amorphous Sulfur And Stability Of Olivine Under Rapid Compression

The study of crystallization behavior of amorphous materials is of great significance to understand the amorphous material structure,crystallization mechanism as well as improve physical and chemical properties of materials.In this work,we researched the exciting light-induced crystallization behavior of bulk amorphous sulfur which prepared by the rapid pressure coagulation method..The structure stability of minerals under the high-temperature high-pressure is a basic subject in the filed of geoscience.In this paper,the structure stability of olivine minerals under rapid compression was studied by means of a self-made rapid compression apparatus.This dissertation is divided into three parts.The first part is about exciting light-induced crystallization behavior of amorphous sulfur.The second part is about the structural stability of olivine under rapid compression.The last part is about the first-principles calculations of the mechanical properties in In-Y intermetallic compounds.The summery is as follows:?1?Exciting light-induced crystallization behavior of bulk amorphous sulfur.Exciting light-induced the structure evolution and thermodynamic properties of the amorphous sulfur were detected at room temperature and ambient pressure by synchrotron X-ray diffraction and Raman spectroscopy techniques.It is found that with the increase of the intensity of the incident X-ray,crystallization peaks appeared in the diffraction spectrum of the amorphous sulfur sample in the exposure region,indicating that the light can cause the crystallization of the amorphous sulfur.The Raman analysis showed that with increasing laser power and exposure time,the decrease of the content of polymer chain in the amorphous sulfur indicated that the laser can cause the transition from polymer chain to S₈ ring.?2?The structural stability of olivine under rapid compression.In this paper,the effect of rapid compression on the stability of olivine structure was studied.In the first group,olivine samples were rapidly compressed to 3 GPa at 293 K,373 K,473 K,573 K,673 K and 773 K respectively.In the second group,the olivine samples were heated at 873 K,973K,1073 K and 1173 K for 2 hours before being rapidly compressed to 3 GPa at room temperature.The structure of the recovered samples were analyzed by synchrotron radiation X-ray diffraction,Raman spectroscopy,infrared absorption spectrum and scanning electron microscopy.The results showed that the structure of olivine was stable and there was no phase change and dehydration caused by temperature and rapid compression.The microstructure analysis of recovered olivine found that the gas pore diameter between grains decreased and the grains were refined.Due to the residual stress and grain refinement in the recovered samples,the Raman vibrational peaks of olivine(822 cm^-1and 854 cm^-1at room temperature)showed broadening and displacement.?3?First-principles calculations for the mechanical properties of In-Y intermetallic compounds.The mechanical stabilities,elastic and thermodynamic properties of In-Y intermetallic compounds?In-Y ICs?have been investigated by using a first-principles density functional theory?DFT?within ultrasoft pseudopotential plane-wave method.The lattice constants of In-Y ICs were calculated by the GGA-PBE method.It suggests that In-Y ICs are mechanically stable by analyzing the calculated elastic constants.Moreover,the elastic properties including shear modulus,Young's modulus,bulk modulus,ratio B/G and elastic anisotropy are derived from the elastic data C_ij.Compared with InY and In₃Y,InY₂ has the largest bulk modulus and the strongest anti-deformation ability in this work.In addition,according to the calculated ratio G/B and the Poisson's ratio values,it was found that these In-Y ICs are ductile materials,and the ductile of In-Y ICs rank as follows:In₃Y>InY>InY₂.Finally,Debye temperature and thermal conductivity have been predicted through different empirical formulas.These results have an important reference value for the design and application of In-Y ICs in the future.