Amorphization of Serpentine at High Pressure and High Temperature

Kawai-type multianvil ultrahigh-pressure technology

Since the large-volume press with a double-stage multianvil system was created by the late Professor Naoto Kawai, this apparatus (Kawai-type multianvil apparatus or KMA) has been developed for higher-pressure generation, in situ X-ray and neutron observations, deformation experiments, measurements of physical properties, synthesis of high-pressure phases, etc., utilizing its large sample volume and capacity in stable and homogeneous high temperature generation compared to those of competitive diamond anvil cells. These advancements in KMA technology have been made primarily by Japanese scientists and engineers, which yielded a wealth of new experimental data on phase transitions, melting relations, and physical characteristics of minerals and rocks, leading to significant constraints on the structures, chemical compositions, and dynamics of the deep Earth. KMA technology has also been used for synthesis of novel functional materials such as nano-polycrystalline diamond and transparent nano-ceramics, opening a new research field of ultrahigh-pressure materials science.

A nanocrystalline-amorphous mixed layer obtained by ultrasonic shot peening on pure titanium at room temperature

A nanocrystalline-amorphous (NC-A) mixed layer was obtained by ultrasonic shot peening (USP) on pure titanium at room temperature and observed by X-ray diffraction pattern (XRD), scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM). The results showed that the amorphization percentage in the NC-A mixed layer increased continuously with the increase of the peening duration, shot diameter and sonotrode amplitude or the decrease of the peening distance. The maximum amorphization percentage achieved in this study was 44.09%. Moreover, with the amorphization percentage in the NC-A mixed layer increasing, the surface hardness increased constantly. Base on the experimental results, the amorphization mechanism during USP treatment was also analyzed.

In situ observation of the formation of 10 A phase from talc + H(2)O at mantle pressures and temperatures

Development of an x-ray-transparent capsule that is suitable for water-saturated experiments has allowed the high-pressure and high-temperature synthesis of 10 angstrom phase from talc + H(2)O to be observed in situ in a multianvil apparatus with synchrotron radiation. The reaction talc + H(2)O = 10 angstrom phase was observed within 20 minutes at 6 gigapascals and 500 degrees C. The higher pressure vapor-absent reaction talc = 10 angstrom phase + enstatite + coesite was also observed. The 10 angstrom phase is therefore a good candidate for transporting water into Earth's mantle at subduction zones. The in situ technique may allow the hydration of other high-pressure mantle phases to be observed under dynamic conditions.