Continuous fiber ceramic composites (CFCCs) are being considered as high temperature structural materials for gas turbine applications due to their high temperature capability, toughness, and durability. Polymer impregnation and pyrolysis (PIP) derived CFCCs are one class of these materials that can be fabricated using widely available polymer composite processing methods. This paper will discuss the general PIP fabrication process and thermo-mechanical properties of these materials, and show examples of complex prototype gas turbine components that have been fabricated and evaluated.Copyright © 1999 by ASME

Continuous fiber ceramic matrix composites (CFCCs) are currently being developed for a variety of high-temperature applications, including use in advanced heat engines. For such composites, knowledge of porosity distribution and presence of defects is important for optimizing mechanical and thermal behavior of the components. The assessment of porosity and its distribution is also necessary during composite processing to ensure component uniformity. To determine the thermal properties of CFCC materials, and particularly for detecting defects and nonuniformities, the authors have developed an infrared thermal imaging method to provide a single-shot full-field measurement of thermal diffusivity distributions in large components. This method requires that the back surface of a specimen receives a thermal pulse of short duration and that the temperature of the front surface is monitored as a function of time. The system has been used to measure thermal diffusivities of several CFCC materials with known porosity or density values, including SYLRAMIC{trademark} SiC/SiNC composite samples from Dow Corning and SiC/SiC and enhanced SiC/SiC samples from DuPont Lanxide Composites, to determine the relationship of thermal diffusivity to component porosity or density.

A unique fuel cell coupled with a low power nuclear reactor presents an attractive approach for SDI burst power requirements. The high power, long duration bursts, quoted in the open literature, (100 MWe, 200 sec) appear achievable within a single shuttle launch limitation with appropriate development of the concept. The system performance advantages result from a significant breakthrough in fuel cell design. The monolithic design employs the same thin ceramic components used in other oxide fuel cells in a strong, lighweight honeycomb structure of small cells, and thus can achieve very high power per unit mass or volume. The light weight and low volume as well as the efficiency and reliability of electrical systems, are advantageous in space applications.

The conductivity of porous cermets at 1000°C was determined as a function of Ni content between 15 and 50 volume percent (v/o) of total solids for two different zirconia particle sizes (23 and 47 m2/g). Below Ni contents of 30 v/o, ionic conduction through the zirconia phase dominated. At 30 v/o Ni, a greater than three order of magnitude increase in the conductivity was observed, corresponding to a change in mechanism to electronic conduction through the Ni phase. The conductivity of cermets made with a Ni content greater than 30 v/o Ni was found to decrease with increasing temperature between 700° and 1000°C. While the conductivity of the cermets with the larger particle size zirconia was higher by more than a factor of four, all the samples studied had the same activation energy, . The increase in conductivity with zirconia particle size is attributed to improved Ni particle‐to‐particle contact, resulting from the Ni phase being able to cover more completely the surface of the zirconia matrix where it resides.

Abstractat 1000 °C has been measured as a function of the Ni content (15‐50 vol.%) using cermets with two different ZrO2 particle sizes.

A new fuel cell design, called the ''monolithic fuel cell,'' is being developed at Argonne National Laboratory. The monolithic design employs the same thin ceramic components used in other oxide fuel cells in a strong, lightweight honeycomb structure of small cells, and thus can achieve very high power per unit mass or volume. The light weight and low volume, as well as the efficiency and reliability of electrical systems, are advantageous is space and terrestial systems.

A new fuel cell design, called the ''monolithic fuel cell,'' is being developed at Argonne. The monolithic design employs the same thin ceramic components used in other oxide fuel cells in a strong, lightweight honeycomb structure of small cells, and thus can achieve very high power per unit mass or volume. The light weight and low volume, as well as the efficiency and reliability of electrical systems, are advantageous in space and terrestrial systems.