Analytical modeling of intumescent coating thermal protection system in a JP-5 fuel fire environment

The thermochemical response of Coating 313 when exposed to a fuel fire environment was studied to provide a tool for predicting the reaction time. The existing Aerotherm Charring Material Thermal Response and Ablation (CMA) computer program was modified to treat swelling materials. The modified code is now designated Aerotherm Transient Response of Intumescing Materials (TRIM) code. In addition, thermophysical property data for Coating 313 were analyzed and reduced for use in the TRIM code. An input data sensitivity study was performed, and performance tests of Coating 313/steel substrate models were carried out. The end product is a reliable computational model, the TRIM code, which was thoroughly validated for Coating 313. The tasks reported include: generation of input data, development of swell model and implementation in TRIM code, sensitivity study, acquisition of experimental data, comparisons of predictions with data, and predictions with intermediate insulation

CO oxidation on gold in acidic environments: particle size and substrate effects

The electrooxidation of carbon monoxide on titania- and carbon-supported gold nanoparticles of mean diameters <6.5 nm was studied in 0.5 M HClO4. The samples were prepared by physical vapor deposition, and the activity of the supported particles compared with the reaction at bulk, polycrystalline gold. Carbon-supported gold exhibited activity for CO oxidation only at potentials similar to that observed for bulk gold. Decreasing the particle size below ~2.5 nm resulted in a sharp decay in catalytic activity. Titania-supported gold exhibited catalytic activity at overpotentials significantly below those of bulk gold, and the activity was strongly particle-size-dependent. A maximum in activity was observed at ~3.0 nm, and a sharp reduction in activity is observed below ~2.5 nm. The results highlight two important effects. Titania is responsible for a strong substrate-induced activity for CO electrooxidation on gold particles. In addition to the induced activity at low overpotentials, this titania-supported gold is also shown to exhibit activity at high potentials where normally the oxidation of the gold poisons the reaction. The second observation is that the oxidation is inhibited on particles below 2.5 nm in size, irrespective of the support