| Silica is a kind of mineral that exists widely in nature. It has many kinds of polymorphs and each polymorph can transform another under different temperatures and different pressures. Therefore, we can study the silica near the Earth's surface to infer how the rocks near the Earth's surface form. Coesite is a polymorph of silica existed in high pressure. Coesite is the product of ultrahigh-pressure metamorphism. It is an important symbol mineral to identify the effect of ultrahigh-pressure metamorphism. Generally, whether rock has coesite is a direct symbol of distinguishing whether the effect of ultrahigh-pressure metamorphism has been on the rock. During 50 years, the study of coesite in the earth′s surface has been regarded as a"window"for knowing the earth. In labs, a lot of work on the synthesis of coesite by a high static pressure and high temperature,including the effect of the initial state of materials on the synthesis of coesite has been carried out.Some scientists had advanced the hypothesis of plate subduction-exhumation. Because there has been no suitable and direct method with which to test and verify this formation mechanism of coesite up to now, although the hypothesis of plate subduction-exhumation has been queried, it is still the only one explanation of coesite formation in the earth's crust. However, it must be pointed out that there are many differences between the pressure induced by dynamic collisions and high static pressure. In the latter case, the pressure is hydrostatic or quasi-hydrostatic; so it is mainly a normal stress with a more homogeneous, and continuous role of time. In the former case, the pressure has both a normal and shear stress; it has obvious localization of and inhomogeneity in the pressure and the temperature, and a discontinuity in the role of time. For the hypothesis of subduction-exhumation of plate, only the high static pressure condition subducting into the upper-mantle has been considered while the collisions between the plates before and during the subducting process have been not. The role of mechanical ball milling (MBM) has been studied in our group. During the process of high-energy MBM, high local pressure and temperature can be generated by the impact of the steel ball, i.e. 3.0-6.0GPa and 600-900K,respectively. Also both a normal and shear stress can be produced by the high-speed collision of the steel ball with three-dimensional vibration. Comparing the collision between the plates in the earth and MBM, although the differences in space and speed of the collisions between the plates in the earth and MBM in laboratory are very great, and also all the specific ways of collision are not the same, it is found that there is a common localization features of pressure (including normal and shear stress) and temperature for the two kinds of collision phenomena. So through their similarity, these two seemingly very different in space and unrelated collision phenomena can be related to each other. MBM can be used to study a modeling synthesis for the coesite in the earth's crust according to the former common features, and can also be used to study the age-old collision dynamics of plates according to the latter differences through high frequency collision of balls in laboratory. Up to date, the effects of local dynamic pressure and shear stress on the synthesis of coesite (stishovite and diamond )have not yet been studied. So the research which is the transition ofα-Quartz—Coesite (α-Quartz—Stishovite) and Graphite—Diamond by a laboratory method combining high-energy mechanical ball milling and high static pressure is an important subject.As a kind of typical extreme condition, high-pressure method has been developed fast during the recent years on the aspects of big chamber and high pressure. The properties of high-pressure method are shortening the distance between the atoms effectively, changing the states of electrons and affecting phases changing courses. In the condition of high pressure and high temperature, the materials are given high energy on samples. So the high pressure method is effective to synthesize new materials. High pressure and high temperature method can mimic the state in the Earth. That can enlighten and help us comprehending much geologic phenomena.In this paper, we were selectedα-quartz and the mixture ofα-quartz, silicon as original materials. The original materials were treated with high-energy mechanical ball milling . We found thatα-quartz was completely amorphous by high-energy mechanical ball milling 40 hours. But mix quality percent 50% silicon intoα-quartz,α-quartz has been achieved completely amorphous only by high-energy mechanical ball milling 20 hours. This shows that the material of silicon is in favor of the amorphous of original material.The various samples were treated with high temperature and high pressure, which were made by high-energy mechanical ball milling. We researched the structure transition of the samples in different conditions of high pressure and high temperature. The sample ofα-quartz which was made by high-energy mechanical ball milling 5 hours was treated with 3.0GPa, 873K and 3.8GPa, 873 K .We found that synthesizedα-quartz crystal in these conditions of high temperature and high pressure. It synthesizedα-quartz crystal and FeSiO3 crystal in 3.0GPa, 1273K. But in 3.8GPa, 1273 K ,we not only synthesized coesite crystal but also FeSiO3 crystal. The sample ofα-quartz which was made by high-energy mechanical ball milling 1hour and 2 hours was treated with 3.8GPa, 1273K, we also found that synthesizedα-quartz crystal. The mixture ofα-quartz and silicon (quality ratio:α-quartz: silicon= 1:1) which was made by high-energy mechanical ball milling 15 hours. We found that synthesized coesite crystal and silicon crystal with 3.8GPa, 873K and 3.8GPa, 1273K. Compared with singleα-quartz ,two mixed that reduced the temperature condition on the synthesis of coesite. By high-energy mechanical ball milling 20 hours, We found that the product is only silicon crystal with 3.0GPa, 873K, 3.8GPa, 873K and 3.8 GPa, 1273K . The product is silicon crystal andα-quartz crystal with3.0GPa, 1273K, no coesite crystal exists.The experimental results show that mixing quality percent 50% silicon intoα-quartz is in favor of reducing the temperature of synthesis coesite,reducing the amorphous time ofα-quartz and picking up the refinement process for crystal . Find the ball milling threshold time on the mixture ofα-quartz and silicon synthesized coesite crystal, tmil < 20h.
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