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Laser-induced breakdown spectroscopy using a microchip laser and a miniature spectrometer has been applied to the determination of carbon in steel. The goal was to investigate the capability of an apparatus, made up of commercial components, that could form the basis of a handheld device. The typical precision obtained in the range of C/Fe weight ratios of 0.001 to 0.01 was 4.3%, and the limit of detection was a C/Fe ratio of 400 ppm. This is higher than values reported for conventional systems and is primarily determined by systematic variations in the spectra and not by signal intensity levels. These systematic variations are ascribed to two causes: the use of an ungated detector and the spatial variability of the emission plume.

A model of the NASA Lewis SiC-chemical vapor deposition (CVD) process is described and the results presented. A key feature of the model is the direct coupling of gas phase chemical kinetics with diffusion. A deposition chemistry model using reactive sticking coefficients for each gas phase species provides the diffusion boundary conditions. Chemical characteristics of the SiC CVD process are discussed and a comparison between predicted and experimentally observed deposition rates is made. SiC deposition rates predicted by the model agree reasonably well with the observed rates. Qualitative agreement for deposition rate dependence on velocity is obtained, although lack of agreement on details of the behavior indicate that improvements in the fluid dynamic model are needed.

A nitrogen dioxide point sensor, based on a novel nondispersive gas filter spectroscopic scheme, is described. The detection scheme relies on the fact that the absorption spectrum of nitrogen dioxide in the 400-550 nm region consists of a complicated line structure superimposed on an average broadband absorption. A compensating filter is used to remove the effect of the broadband absorption, making the sensor insensitive both to small particles in the optical path and to potentially interfering gases with broadband absorption features in the relevant wavelength region. Measurements are obtained using a remote optical absorption cell that is linked via multimode fibre optics to the source and detection optics. The incorporation of blue light emitting diodes which spectrally match the nitrogen dioxide absorption allows the employment of electronic (instead of mechanical) switching between optical paths. A sensitivity of better than 1.0 ppm m column density (1 s integration time) has been observed; improvements in electronics and thermal stabilization should increase this sensitivity.

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