No abstract available

[en] A pseudo-curved neutron monochromator with a continuously variable curvature was constructed with four flat pieces of oriented pyrolytic graphite (OPG). Curvatures which yield maximum diffracted intensities were determined for neutrons of wavelengths 1 A and 2.4 A. The increase of the intensity relatively to that of a flat monochromator is by a factor of 2 and 1.5, for 1 A and 2.4 A, respectively. The neutron flux at three positions along the neutron path was determined by gold foils activation and compared with the flux from flat monochromators of OPG and copper

[en] The neutron transmission measurements through oriented pyrolytic graphite (P.G. crystal) were carried out in the wavelength band from 0.15 nm to 6.5 nm at different orientations of the (002) plane of the crystal w.r.t. the neutron beam direction. It was found that the P.G. crystal may be tuned for optimum scattering of second-order neutrons in the wavelength ranging between 0.112 nm and 0.425 nm, by adjusting the filter in an appropriate orientation. The reflectivity of (002), (004) and (006) planes of P.G. were measured and the following results are obtained: the reflectivity of (002) plane was found to be 99% by (transmission method). The ratio of the integrated intensity of the reflected neutrons from (004) and (006) is 3.14+-0.25 and is found to be in agreement with the calculated ratio. The measurements were performed using the fixed scattering angle spectrometer installed in front of the ET-RR-1 reactor horizontal channel

[en] A microsection with the cut surface being normal to the coating is made from the finished coated ceramic fuel particle. The density is determined by means of X-radiation of 3 to 7 keV using absorption measurement. For calibration of this absorption measurement glass pyrocarbon is applied (microradiography or direct absorption measurement). (RW)

[en] Experiments show that conditions exist whereby graphite can be baked out sufficiently so that further gas evolution is not of significance. POCO, GIS, and Pyrocarb all have almost the same activation energies for release and all exhibit the property of being easier to clean up after an initial high temperature bake-out. Data presented indicate that the release rate follows a logarithmic rate law

No abstract available

No abstract available

[en] Pyrolytic carbon coatings are employed in the production of coatings to retain fission products for small nuclear fuel particles. The invention provides a process for coating items with pyrolytic carbon. The process consists in heating the items to be coated to a temperature of between 800⁰C and 2200⁰C approximately in a sealed containment and allowing a gas mixture to flow through the containment at a given rate that allow the gas mixture to be heated to a temperature close to that of the items by entraining a gaseous decomposition and the pyrolytic carbon deposit. The mixture contains an inert gas fraction and a hydrocarbon fraction, the latter comprising between 25 and 65% by volume of acetylene, the balance being propylene

[en] Highlights: • A facile route for the deposition of pyrocarbon (PyC) interphase is established. • PyC interphase was deposited via pyrolysis of PAN polymer. • PyC coating thickness was optimized to 0.5 μm to get better mechanical property. • C/SiBOC composite with PyC interphase showed better oxidation resistance property.

[en] The study of interaction of atomic hydrogen with quasi-monocrystalline pyrolytic graphite (QMPG) by means of temperature programmed thermal desorption (TPD), scanning tunnel microscopy (STM) and atomic force microscopy (AFM) revealed pronounced effects of atomic hydrogen sorption on the surface morphology. The initially flat graphite surface with well-ordered atomic structure was changed after sorption of hydrogen atoms into a rough one with ''bumps'' up to 5 nm in height and 100 nm in diameter. After thermal release of hydrogen the surface became again atomically flat with etch-pits 1-2 layers in depth. It is suggested that the sorbed atomic hydrogen is stored between graphene layers as H₂ molecules. (orig.)