$B!!!! (JThe microgravity condition is expected to be useful in the study of material processing because the physical and chemical processes become simple. Optical observation methods provide much information on the processes and preferable for the investigation of these phenomena in real-time. In this dissertation, the methodology of optical observation techniques for fluid/crystal phenomena during material processing in microgravity conditions is described first. Next, these observation techniques are applied to the investigation of the growth processes of materials, which will lead to new technologies in space utilization and aerospace engineering.
$B!!!! (JIn chapter 1, the background and objective of this study are described.
$B!!!! (JIn chapter 2, the improvement of optical observation techniques suitable for the observation of material processing in microgravity conditions is discussed. A two-beam interferometer with double-mirror reflection optics was developed for the observation of the transport phenomena in liquids together with the solid-liquid interface process in vibrational conditions. An incoherent moire $B!- (J interferometric technique, which eliminates wavefront deformation by the interference of two interferograms taken at different times, made it possible to visualize the temperature profile in a liquid. Next, a finite bandwidth interferometric microscope was developed to measure the thickness of small crystals. By controlling the coherent length of the light source for an microscope, clear interferometric fringes without speckles were obtained.
$B!!!! (JThe development of a dynamic light scattering technique for short-time microgravity experiments is also presented. A photon counter with a large memory capacity made it possible to use the dynamic light scattering technique with a high time resolution. The application of this technique is addressed.
$B!!!! (JIn chapter 3, an interferometric study of the solid-liquid interface during the unidirectional solidification processes of a transparent organic material is described. A two-beam interferometer developed for a rocket experiment worked well and the temperature distribution in the liquid was obtained in microgravity condition. The transfer of latent heat released at the interface raised the temperature of the liquid ahead of the interface to form a temperature-reversed layer. A model for the growth process controlled by interface kinetics taking into account supercooling in the liquid was also constructed. Comparison with the experimental results showed qualitative agreement.
$B!!!! (JIn chapter 4, direct observation of zeolite crystal growth is described. A finite bandwidth interferometric microscope was used for three-dimensional observation of small crystals growing in a pressurized hot solution cell. The growth rates and the apparent activation energies for three crystal faces were measured to show their significant dependence on the growth conditions, such as the synthesis temperature and concentration. Based on these results, the growth mechanism is discussed.
$B!!!! (JIn chapter 5, this study is summarized. The availability of the observation methods developed for microgravity experiments and their applications are discussed.