Nano-Structure of Amorphous and Cluster-Assembled Materials

非平衡材料，如非晶态、纳米晶态和团簇组装材料，与平衡晶态材料相比，具有优异的磁学、光学、机械和耐蚀性能。在这个项目中，我们通过东北大学材料研究所和埃及Assiut大学物理系之间的人类交流与合作，研究了非晶态和纳米晶材料的热稳定性和磁弛豫现象。1)测量了As_xSe_&lt；1.x&gt；和BixSe_&lt；1.x&gt；1.x&gt；三元Ge_&lt；20&gt；Se_&lt；60&gt；Sb_&lt；20&gt；和As_&lt；46&gt；Te_&lt；46&gt；In_8合金薄膜的X射线衍射、差示扫描量热法和透射电子显微镜。在二元薄膜中，非晶相和晶相并存，而在三元薄膜中，非晶相占主导地位。薄膜的晶化温度约为500K。在本项目的重要样品--三元薄膜中，在500K以上出现了晶相，其颗粒尺寸迅速增大。我们观察到光学反射和吸收的光谱寒冻伴随着非晶晶化转变。2)我们用电离团束方法制备了Fe/Au颗粒膜。磁性测量表明，Fe团簇具有超顺磁性。由穆斯堡尔谱估算的磁弛豫时间与磁化率随频率和温度的变化关系推算出的磁弛豫时间基本一致。3)采用机械球磨和等离子烧结的方法制备了TiN化合物和Al/SiC复合材料。它们是用于纳米耐火材料的良好的烛酸盐，表现出几乎全密度，高机械强度和硬度。

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.