New method for coating microspheres with zirconium carbide and zirconium carbide--carbon graded coats

A new method for the chemical vapor deposition of ZrC and C--ZrC alloys has been developed. This process has been applied to the fabrication of coated particle nuclear fuels of the type used in the large High-Temperature Gas-Cooled Reactor. A powder feeder is used to supply ZrCl$sub 4$ to the fluidized bed coating furnace where it undergoes reaction with a hydrocarbon to form ZrC. Quantitative metering of the ZrCl$sub 4$ makes it possible to control the deposition of the ZrC and the codeposition of the C--ZrC alloys on the fuel particles. Examples of both types of coats made using the described technique are discussed and illustrated. (auth

Modification of the sulfur dioxide-iodine thermochemical hydrogen cycle with lanthanum sulfites and sulfates

Variable composition, insoluble dilanthanum oxide-sulfite-sulfate-hydrates were prepared by reaction of lanthanum dioxymonosulfate with aqueous sulfur dioxide. These compositions reacted with iodine to yield sulfate in the solid phase, and hydrogen iodide and water in the gas phase. The highest yield of hydrogen iodide measured was 32% at 660 K for a few seconds reaction time of iodine with a reactant containing oxide-sulfite-sulfate with the approximate stoichiometry numbers, 0.9, 1.1, 1.0. Higher yields of hydrogen iodide were obtained by a second iodine oxidation after separation of the first solid product. These reactions are adaptable to a water splitting thermochemical cycle in which hydrogen is made by catalytic decomposition of hydrogen iodide at 700 K, and oxygen results from decomposition of the solid product at 1300 K

100 MHz fiber optic single transient gamma ray detection system

A fiber optic system has been developed to measure single transient gamma rays. The gamma ray signature is converted to light by the Cerenkov process in a 20 cm length of radiation resistant optical fiber. The signal is transmitted over 1 km of optical fiber and detected by state-of-the-art, 175 MHz analog receivers. The receivers are based on silicon PIN detectors with transimpedance hybrid amplifiers and two stages of power amplification. The dc coupled receivers have less than 2% distortion up to 5 volts with less than 10 mV rms noise and a responsivity of 37,500 V/watt at 800 nm. A calibration system measures relative fiber to fiber transit time delays and ''system'' sensitivity. System bandwidth measurements utilized an electron linear accelerator (Linac) with a 50 ps electron pulse as the Cerenkov light source. The system will be described with supporting calibrationa and characterization data of parts of the system and the whole system

rf plasma synthesis of ultrafine, ultrapure silicon carbide powder

Ultrafine, ultrapure silicon carbide powder has been produced by reaction of silane and methane in a high temperature rf plasma. Preliminary studies include the effect of gas composition and of powder (plasma temperature) on the stoichiometry of the powder. The carbon-to-silicon ratio of the powder was varied from 1.0 to 1.9 by changing the process conditions. The powder has a BET surface area of 101 m/sup 2//g, which is equivalent to a particle diameter of 18.5 nm. A particle size in the range of 10 to 20 nm was measured by transmission electron microscopy. X-ray diffraction results indicate a domain size of 7.5 nm and a crystal structure of beta (cubic) silicon carbide. Spectrographic analysis shows that metallic impurities are lower than high quality grade commercial powder. Because of the high surface area, the powder must be stored and processed in an inert atmosphere to prevent severe contamination with oxygen

Release rates of liposomal contents are controlled by kosmotropes and chaotropes

Contents release from redox-responsive liposomes is anion-specific. Liposomal contents release is initiated by the contact of apposed liposome bilayers having in their outer leaflet 1,2-dioleoyl-sn-glycero-3- phosphoethanolamine (DOPE), whose presence is due to the redox-stimulated removal of a quinone propionic acid protecting group (Q) from Q-DOPE lipids. Contents release occurs upon the phase transition of DOPE from its lamellar liquid-crystalline phase (Lα) to its hexagonal-II inverted micelle (HII) phase. Contents release is slower in the presence of weakly hydrated chaotropic anions versus highly hydrated kosmotropic anions and is attributed to ion accumulation near the zwitterionic DOPE headgroups, in turn altering the headgroup hydration, as indicated by the Lα → HII phase transition temperature, TH, for DOPE. The results are significant, not only for mechanistic aspects of liposome contents release in DOPE-based systems but also for drug delivery applications wherein exist at drug targeting sites variations in the type and concentration of ions and neutral species. © 2013 American Chemical Society