Pyrolytic carbon coating

T. E. Hudson and J. W. Martin. Pyrolytic carbon coating of media improves gravel packing and fracturing capabilities. Patent EP 301626, 1989. 

Pyrolytic Carbon Coating Artificial Heart Valves Pyrolytic Carbon Coatings Spinal Surgery Bloactive Glass-Ceramic HA... 

The Retention of Iodine by Pyrolytic Carbon-Coated Nuclear Fuel Particles... 

The retention of fission product iodine and xenon by unirradiated and irradiated pyrolytic-carbon-coated (Th,U)C2 fuel particles has been studied in annealing experiments and has been compared with similar studies of the release (or retention) of barium and strontium. The objective was to study the effects of irradiation on the retention of the two types of fission products and to determine the mechanism of release which could account for the observed behaviors. In both unirradiated and irradiated particles, iodine and xenon were found to be retained highly by the impervious isotropic pyrolytic coating which was unaffected by the irradiation. In contrast, the fuel kernel which controls the release of the metallic species is damaged severely by the irradiation, resulting in a marked decrease in its ability to retain the metals. 

The fuel particles used in these studies were typical pyrolytic carbon-coated thorium-uranium dicarbide, (Th,U)C2, microspheres. The kernels, — 200/i in diameter, were prepared from Th02, U02, and C and converted to the carbide at temperatures below 2200°C., followed by a spheroidization above the melting point, 2450°-2500°C. The bare kernels were coated with a 30-50fi layer of low density (— 1.0 gram/cm.3) buffer pyrolytic carbon, followed by a 40-70/a layer of high density... 

Numerous studies by other workers (I, 10) have shown that the releases of iodine and the noble-gas fission products from pyrolytic carbon-coated fuel particles are controlled by diffusion of these nuclides through grain boundaries, cracks, and defects in the isotropic pyrolytic carbon coating. When coatings are intact, however, the release of these fission product nuclides is low. However, the pyrolytic carbon coating constitutes only a delaying barrier to the metallic nuclides barium and strontium through which they diffuse with diffusion coefficients of the order of 10 9 cm.2/sec. (at — 1400°C.). The steady-state release of these metallic nuclides is controlled instead by diffusion out of the fuel kernel,... 

Postactivation annealing fission product release measurements have shown that the excellent retention of iodine and noble fission gases by pyrolytic carbon-coated fuel particles is unaffected by irradiation up to 24% FIMA. These data are interpreted as indicating that the pyrolytic carbon coatings remain undamaged by these high levels of irradiation. 

Using uniform and straight nanochannels of an anodic aluminum oxide (AAO) film as a template, CNTs can be prepared by pyrolytic carbon deposition on the AAO film [109-116]. Briefly, the AAO film was subjected to carbon deposition from the pyrolytic decomposition of propylene at 800°C, which resulted in a uniform pyrolytic carbon coating on the inner wall of the template nanochannels. Then, the AAO template was removed with HF washing, and only carbon was left as an insoluble fraction. The formation process of carbon tubes using this chemical vapor deposition (CVD) technique is illustrated in Figure 3.8. 

Chloride media present a particular problem in electrothermal atomisation. Manning and Slavin [3] have described the determination of lead in magnesium and sodium chlorides at the 0.1/ugg-1 level, and their paper contains many points of relevance to other analyses. Pyrolytic carbon-coated... 

Preliminary results show it should be possible to operate the MHR with a coolant outlet temperature of up to 1 000°C using nuclear-grade graphite fuel blocks, carbon-carbon composite materials for control rods and other internal reactor components, and existing coated-particle fuel technology with silicon carbide (SiC) and pyrolytic carbon coatings. 

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