Silicon carbide (SiC) possesses extreme hardness, very good electrical, thermal and mechanical properties as well as excellent resistance to corrosion and thermal shock. As such, it is one of the primary candidate materials for use in systems for the production and conversion of energy at elevated temperatures. It is currently employed in or being considered for use in heat exchangers or waste heat recouperators in various prototype fossile fuel systems. Specific examples of its potential use include (1) indirectly fired turbine engines wherein the turbine section is separated and protected from the combustor by a SiC heat exchanger; (2) coal fired systems which heat air in a fluidized bed containing a SiC heat exchanger; (3) coal gasifiers wherein the outlet channels will be of SiC because of the particle erosion, high temperatures (1673K) and pressures on these systems; (4) critical parts for gas turbines, the Sterling engine and adiabatic diesel engines; (5) high temperature bearings and (6) first wall materials for fusion reactors.

The structural changes of graphite-like boron nitride caused by multiple shock-compressions were investigated. Wurtzite type, zinc blende type, new modification and amorphous of BN induced by multiple shock-compressions were obtained. Formation mechanism of high dense form boron nitride under shock compression was discussed.

When propellant cylinders are fired at low speeds against a steel plate, detonations are often observed. Since the process is not repeatable, and shock heating is not significant, it is natural to consider the possibility of detonation caused by hot spots. Several mechanisms are compared, and it is suggested that interfacial friction of closed cracks seems to be the most likely mechanism.

Electron spin resonance (ESR) has been used to characterize the paramagnetic defects present in both single crystal and powder rutile (TiO2) subjected to explosive shock loading and preserved for post-shock study. The Ti+3 defect concentration produced by the shock process is an order of magnitude larger than values reported for vacuumreduced rutile. The ESR lineshape is characteristic of a conducting material, and the estimated microwave resistivity in the shock-loaded powder is more than an order of magnitude lower than the minimum dc value measured in vacuum-reduced rutile. It appears that shock-wave loading leaves the rutile in a defect state not achieved in prior work.

After some years of relatively little activity, the field of solid-state lasers has again become an important research area. Laser operation has been demonstrated in new combinations of laser-active ions and host crystals to provide wavelength-tunable output and the promise of greatly improved efficiency. This paper will discuss several currently interesting classes of laser materials: divalent-transition-metal-doped, rutile- and perovskite-structured fluoride crystals such as Co:MgF2 and V:KMgF3 , Ti3+-doped materials including Ti:A12O3 and a variety of large-lattice-size garnet crystals doped with Cr3+ and/or Nd3+.

Dielectric insulator materials have played a critical role in the development of high peak power solid state lasers for use in inertial confinement fusion research: as laser gain media; as transparent substrates for lenses, mirrors, and polarizers; and as active optical materials in nonlinear harmonic generators and electro-optical devices. Materials have been developed which have exceptionally high resistance to damage in the presence of intense optical beams (> GW/cm2) and which possess other properties which optimize their functions in the laser systems. Fusion lasers built to date have been designed for “single shot” operation, and the dielectric insulator materials developed for use in them have had to function under only extremely low average power loading. As we look to the future, fusion laser systems will be required to operate repetitively (few Hz) and deliver high average power output (> MW) at an efficiency greater than 10 percent. Insulator materials for use in these systems must be selected and developed on the basis of their combined mechanical, thermal, and optical properties. In this presentation, I will summarize the important characteristics of currently used insulator materials, identify figures of merit for materials needed in future systems, and outline a methodology for identifying and evaluating new materials meeting the stringent performance requirements of future fusion laser systems.

Remarkable progress has been made in the lightguide technology over the past ten years. The realization of low loss optical fibers approaching intrinsic material limit and long life semiconductor lasers has stimulated rapid deployment of lightwave communication systems. Within the past five years the world wide fiber production capacity has grown from a few thousand to over one million kilometers per year. The impetus for this phenomenal growth can also be traced to recent advances in computer technology allowing low cost processing and storage of a great deal of complex information. This combination of information processing and transmission technologies is bringing a host of new services such as voice, data and visual communications, CATV, videotex and facsimile transmission, over the same network. One could therefore expect an accelerating growth in deployment of lightwave communication systems.

The potential for using structural ceramic materials in components of advanced heat engines including the gas turbine and adiabatic diesel has recently been demonstrated by results in DOE and DOD engine development programs. Status of these efforts, technical needs for candidate ceramic materials, and research opportunities in new DOE and NASA ceramic technology programs oriented to heat engines are reviewed.

Impurity centers in quartz play a significant role in the behavior of precision crystal resonators subjected to ionizing radiation. The substitutional Al center, charge compensated by Na, Li, H or a hole, is now known to be the primary contributing factor in most radiation-induced effects. Acoustic loss measurements, ESR measurements, optical studies and IR studies of these defects, over extended temperature ranges, have contributed substantially to our understanding of the impurity centers' role. Radiation-induced frequency and acoustic loss changes in quartz crystal resonators are now understood in terms of the evolving character of the defect center in a radiation field. This understanding has prompted material modification efforts such as high temperature electrolysis and doping technologies which permit, for instance, the fabrication of frequency control devices that are little affected by hostile environments.

In composite materials for electro-mechanical applications, the importance of the mode in which the constituent phases are interconnected (connectivity) was stressed. For the tensor properties of mechanical, piezoelectric, and dielectric behavior, controlling the manner in which fields and fluxes thread through the composite can make orders of magnitude change in the coupled properties.

Examples were drawn from piezoelectric ceramic:polymer composites for uniaxial and hydrostatic (hydrophone) pressure sensing where the 1:3 connected transversely reinforced composite can be shown to exhibit a figure of merit more than 103 that of the piezoceramic phase alone. In these systems, the importance of poisson ratio effects in the polymer phase were evident, and some new composite systems where the hydrostatic stiffness of the elastomer phases may be better exploited were considered.

In electro-thermal applications such as in pyroelectric composites, the requirements of small-size and low-thermal mass put rigorous limits upon the scale of the composite microstructure. Techniques which achieve the appropriate scaling were described and preliminary data showed strong enhancement of the secondary effects in these composites were presented.

The interactions and compounds formed between Ti and LiNbO3, occurring before the true Ti in-diffusion process for optical wa veguides production,have been studied by using different analysis techniques.The relationship between lattice modifications and H concentration profile in proton exchanged LiNbO3 waveguides are also reported.

Novel photo-induced optical phenomena observed for AgX-intercalated mica compounds are presented, where X=NO3 , Cl, Br, or I. All compounds are newly synthesized and exhibit photochromism switched by alternate illumination with 0.3∼0.4 µm and 0.7∼0.8 µm light. AgNO3 -mica furthermore yields peculiar oscillatory phenomena under continuous illumination with ∼0.8 µm light. A hypothetical mechanism for these photo-induced effects is discussed on the basis of the nonlinear excitation and relaxation processes of AgX molecules sandwitched between mica layers.