An Ultrasonic Sensor for Process Modeling and Proces Control of Ceramic Superconductors
This research demonstrates the feasibility of utilizing nondestructive ultrasonic sensors to monitor the effects of oxygen content, processing time and temperature on the resultant mechanical, structural, and electrical properties of high temperature ceramic superconductors. Ultrasonic velocity changes, as a function of processing time and temperature, have clearly been shown to indicate the transformation between orthorhombic and tetragonal phases in Y-Ba-Cu-O.
Fast Leaky Modes on Cylindrical Metal-Ceramic Interfaces
In our previous work [1,2,3,], we have studied in detail the radial-axial modes in an infinitely clad isotropic rod. We have shown that in metal matrix composites, where the fibers are stiffer than the matrix, many of these modes are leaky, transmitting energy into the surrounding medium. The existence of this leakage energy offers a potential means for monitoring and imaging the characteristics of the interface zone [2,3,4,]. Detailed numerical methods have been developed for analyzing radial-axial leaky modes in composite systems [1]. The present paper shows an example of these methods applied to determining the sensitivity of the maximum phase velocity to the matrix density changes for leaky modes.
Growth Ridges, Etched Hillocks, and Crystal Structure of Lithium Niobate
Growth feature of a LiNbO3 crystal obtained by the pulling method has been studied. The formation of growth ridges was interpreted as the intermittent growth of the form {102̄}, which was the most readily grown form from the melt. The point group of the high temperature, paraelectric phase was uniquely determined as 3̄2/m from the symmetry elements of the configuration of ridges. On (001̄) planes, the triangular etched hillocks were observed. Orientations of the hillocks on the antiparallel domains were related by 2-fold rotation axis parallel to [100] consistent with the phase transition of the type 3̄2/m→3m. The atomic arrangement in the form {102̄} was examined, and a three-dimensional framework of the corner-shared Nb-O octahedra, similar to the one in perovskite, was found.