Nano-Structure of Amorphous and Cluster-Assembled Materials

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Nonequilibrium materials such as amorphous- and nanocrystallinc- and cluster-assembled-materials reveals superior magnetic, optical, mechanical, and corrosion-resistant properties in comparison with equilibrium crystalline materials. In this project, we studied thermal stability and magnetic relaxation phenomena in amorphous and nanocrystalline materials through the human exchange and collaboration between Institute for Materials Research, Tohoku University and Department of Physics, Assiut University (Egypt). The following are the outlines of our results.1) We measured X-ray diffraction, differential scanning calorimetry and transmission electron micrograph for binary As_xSe_<1.x> and Bi_xSe_<1.x> alloy films, and ternary Ge_<20>Se_<60>Sb_<20> and As_<46>Te_<46>In_8 alloy films prepared by rapid quenching. In the binary films, amorphous and crystalline phases coexist, while in the ternary films, an amorphous phase is predominant. The crystallization temperature is about 500K for these films. In the ternary films, which are importans specimens in this project, the crystalline phase appears and its grain size increases very rapidly above 500K.We are observing spectral chilnges in optical reflection and absorption accompanied by amorphous-crystal transformation.2) We prepared Fe/Au granular films by an ionized cluster beam method. Magnetic measurements indicate that Fe clusters reveal superparamagnetic characters. The magnetic relaxation time estimated from the Mossbauer spectra is consistent with the one extrapolatcd from the frequency- and temperature-dependence of magnetic susceptibility.3) We prepared a TiN compound and an Al/SiC composite by mechanical milling and plasma sintering. Thes are good candicates for nanocrystalline refractry materials, which show almost full density, and high mechanical-strength and -hardness.