Preparation of functionally graded glass by the ultracentrifuge method combined with sol-gel method and the physical properties.

由于胶体粒子的分子量较大，在相对较低的重力场下，胶体粒子很容易在液体（溶胶）中发生沉降，但要诱导原子的沉降需要100万g数量级的非常高的加速度场。我们可以用溶胶-凝胶法在比熔融法更低的温度下制造玻璃。本研究的目的是利用超离心法结合溶胶-凝胶法制备分子尺度的梯度玻璃，并对其物理性质进行研究。2000年，我们研制出了一种能在40-80℃下，在轴向与超离心方向一致的大型试样圆柱形胶囊中产生高达30000 G加速度场的超离心机。首次制备了SiO_2-TiO_2体系的梯度玻璃。2001年，研究了制备梯度大块玻璃的适宜条件，重点研究了离心前胶体的生长时间。通过多次试验，获得了具有分子级梯度结构的透明SiO_2-TiO_2玻璃。通过XRD和EPMA方法证实了分子尺度上的梯度结构。我们沿加速场观察了许多点的红外吸收光谱，并在分子尺度上证实了梯度结构。2002年，我们尝试在ZrO_2-SiO_2、Al_2O_3-SiO_2、B_2O_3-SiO_2、V_2O_3-SiO_2等体系中制备分子级梯度玻璃，并成功制备了ZrO_2-SiO_2、Al_2O_3-SiO_2体系。通过多次溶胶-凝胶工艺试验，减少了梯度玻璃的裂纹数量。证实了用超离心和溶胶-凝胶相结合的方法可以制备分子级配或复合体膜玻璃。我们将继续进行这项研究，以制备用于工业的功能分级材料。

It is expected that sedimentation of colloid particles can easily occur in liquid (sol) under a comparatively low gravity field due to the large molecular weigh, although a very high acceleration field of the order of 1 million g was necessary to induce the sedimentation of atoms. We can manufacture glass by sol-gel method at lower temperatures than the melting method. The purpose of this study is to prepare the graded glass in molecular-scale by the ultracentrifuge method combined with sol-gel method, and to access the physical propertiesIn 2000, we produced an ultracentrifuge which can generate acceleration field up to 30,000 G at 40-80 ℃ in large specimen cylindrical capsules whose axis is coincide with the ultrcentrifuge direction. The graded glass in SiO_2-TiO_2 system was for the first time prepared. In 2001, the proper condition to prepare the graded bulk glass was examined especially focusing on The growth time of colloids before the centrifugation. A transparent SiO_2-TiO_2 glass with molecular-scale graded structure was obtained through many trials. The graded structure in molecular scale is confirmed by XRD and EPMA methods. We observed the infra-red absorption spectra at many points along acceleration field, and confirmed the graded structure in molecular-scale. In 2002, we tried to prepare the molecular-scale graded glass in ZrO_2-SiO_2, Al_2O_3-SiO_2, B_2O_3-SiO_2, V_2O_3-SiO_2 systems, etc., and succeeded in ZrO_2-SiO_2, Al_2O_3-SiO_2 systems. The number of crack of the graded glass was reduced by many trial of sol-gel process. It was confirmed that the graded or composite bulk or film glass in molecular-scale could be fabricated by the ultracentrifuge method combined with sol-gel method. We are going to proceed this research to prepare the functional graded materials for industry.