A high-temperature optical fiber thermometer made from single crystal sapphire has been developed for use from 600 to approximately 2000 °C. The device consists of a small blackbody cavity which is sputtered on the end of a thin (0.25–1.25-mm diameter, 0.05–0.30-m length) sapphire fiber, a connecting low-temperature glass fiber, and a conventional optical detector. The radiance from the cavity is used to measure its temperature. The present instrument is calibrated at a single temperature and uses the fundamental radiation laws to extrapolate to other temperatures. It is accurate and has a high sensitivity and rapid temporal response. There appear to be a number of applications of the device both in science and industry.

The oxidation of MoSi2 , Mo5Si3 , and Mo3normalSi has been studied at temperatures of 1300°–2000°K, and at oxygen partial pressures of 2–20 Torr. Below 1970°K, at oxygen pressures around 10 Torr, measurements of the rate of total oxygen consumption vs. time show an initial period of high linear rate, an intermediate region where the rate declines sharply with time, and a final plateau region of virtually zero oxidation rate. For each of the silicides, the total oxygen consumed prior to the attainment of the plateau decreases with temperature, and under given experimental conditions is largest for Mo3normalSi , less by a factor of about six for Mo5Si3 , and less by another factor of six for MoSi2 . The oxidized samples display a smooth glassy outer oxide layer that bridges across the tops of the cracks in the alloys and an inner oxidized zone, consisting of several irregular phases. Electron micro‐probe analysis and x‐ray photomicrographs of the oxidized specimens show that the outer protective oxide is pure SiO2 , within the limits of detectability, i.e., the outer oxide contains less than 0.1% Mo. The inner oxide layer contains SiO2 , molybdenum rich phases, including the terminal solid solution phase, and the original alloy phase. Evidence is presented that suggests that the oxide layers grow by inward diffusion of oxygen to the oxide/alloy interface where preferential oxidation of silicon occurs. The excellent oxidation resistance of the molybdenum silicides derives from the formation of this continuous layer of pure silica. Above 1970°K, at oxygen pressures above 10 Torr, an increased oxidation rate is observed due to formation of normalSiOfalse(normalgfalse) at the alloy/oxide interface, which causes rupture of the protective oxide. Below 1970°K, at oxygen pressures near 2 Torr, the rate of oxidation of MoSi2 is linear at all times since the oxygen partial pressure is insufficient to maintain a protective SiO2 layer on the alloy surface.

Wide bandwidth gas temperature measurements in the transition duct exit of a gas turbine show that large gas temperature fluctuations occur at any point in the duct exit. The temperature fluctuations increase with engine thrust level, exceeding 1000 deg F at takeoff. Probabilistic and spectral analyses of the data indicate that the gas temperature fluctuations are due to nonaxial displacements of partially mixed secondary air jet zones in the transition duct exit. The jet zones are driven by the combustion processes in the forward sections of the main burner. The combustion processes regeneratively and nonlinearly amplify the longitudinal resonant acoustic pressure modes of the diffuser duct and the main burner and generate periodic velocity fluctuations in the combustion products leaving the forward sections of the main burner. Surface temperature waves induced at the leading edge of the first-stage turbine nozzle guide vanes by the main burner exhaust gases are also obtained from the data. Surface temperature fluctuations exceeding 30 deg F occur at takeoff. The fluctuations are of sufficient amplitude to cause a significant increase in the rate of oxidation of the turbine components.

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