Structural Studies on High Temperature Inorganic Materials

本研究的目的是借助各种实验方法来阐明高温材料的原子结构，特别是非晶态，包括玻璃态和熔融态。此外，还尝试开发用于这些研究的仪器。两个实验室共同研制的核磁共振高温探针的测试是其中的重要课题之一。这里描述了最后三个主题及其现状。含钠硅酸钠熔体中Na^+离子周围的局部结构^<23>在硅酸钠和硅酸铝中观察到高达1700‰的Na核磁共振谱。得到了^<23>Na化学位移的组分依赖性。从与晶体的化学位移比较，Na离子附近最近的阶数为7 - 2。含铁硅酸盐玻璃的红外/可见吸收光谱研究目的是观察比普通d-d跃迁多的吸收。初步试验表明，当Fe_3O_4含量高达10摩尔%时，在可见光范围内有明显的吸收。尖晶石（MgAl_2O_4）的有序-无序动力学已知在高温下，有序尖晶石上四面体位置的Mg和八面体位置的Al倾向于混合。在以前的工作中，只研究了淬火样品。在本工作中，进行了高温下的直接测量。观察到混合在700℃左右开始。在1400℃以上，在四面体Al的位置有一个尖峰，表明化学交换非常迅速。另一方面，对经过不同时间间隔加热然后淬火的天然尖晶石进行室温MAS-NMR，可以评估四面体位置Al的量作为时间间隔的函数。值得注意的是，除了上述主题外，还启动了含有高温高压淬火的水的^<17>O NMR。由于研究时间有限，我们对CNRS （Orleans）的访问只是对我们项目的一个开始和启发，未来的前景更为重要。为此，法国项目组团赴日反访是非常可取的。少

It was aimed at the present study to clarify the atomistic structures of high temperature materials, especially amorphous states including glassy and molten states, with the aids of various experimental methods. The development of apparatus for those studies was also subsidiarily tried. Test of the high temperature probe for NMR which have been developed in the both laboratories was one of the important issues. Here are described the final three themes and their present situations.1. The local structure around Na^+ ion in sodium bearing silicate melt^<23>Na NMR spectra in sodium silicate and aluminosilicate were observed up to 1700ﾟC. The composition dependence of ^<23>Na chemical shift was obtained. From the comparison of chemical shifts with that of crystals, number of the nearest order around Na ion was seven.2. IR/Visible absorption spectroscopy of iron bearing silicate glassesIt was aimed to observe extra absorption than ordinary d-d transition. A couple of preliminary test shows … More that at Fe_3O_4 content of as high as 10 mole%, absorption was observed at the visible range.3. Order-disorder dynamics of Spinel(MgAl_2O_4)It is known that Mg(at tetrahedral site at the ordered spinel) and Al(at octahedral site) tend to mix at high temperature. In previous works, only the quenched samples have been studied. In the present work, the direct measurement at high temperatures was carried out. The mixing was observed to start at around 700ﾟC. A sharp peak at the position of tetrahedral Al was found above 1400ﾟC implying very rapid chemical exchange.On the other hand, room temperature MAS-NMR of natural spinels which have been heated for various time intervals and then quenched, made it possible to evaluate the amount of Al at tetrahedral site as a function of the intervals.It may be worthy of note that in addition to the themes above mentioned, ^<17>O NMR of water containing high temperature-high pressure quenched albeit glass was initiated.In view of limited research periods, our visit to CNRS (Orleans) was just a initiation and inspiration of our project and future prospects are more important. Counter visit of French group to Japan by French project is highly desirable for that purpose. Less