Kinetics Of Gas Evolution Research Articles

Structural and photoelectrochemical studies of In 2O 3 modified TiO 2 in regard to hydrogen production through photoelectrolysis

A new photoelectrode system for photoelectrolysis of water based on TiO 2 has been synthesized. This comprises of a system with In 2O 3 islands overlaid on TiO 2 base. The TiO 2 is synthesized through anodic oxidation of “Ti” sheets under glow discharge conditions. The In 2O 3 islands are formed by first depositing “In” thin film on TiO 2 by electrodeposition followed by oxidation. The In 2O 3-TiO 2 photoelectrodes have been characterized through X-Ray Diffractometry, scanning electron microscopy and photoelectrochemical techniques. It has been found that as compared to TiO 2 where the typical photocurrent under illumination was 6 mA cm −2, the In 2O 3 overlaid TiO 2 exhibits a much higher photocurrent of 13 mA cm −2. The hydrogen gas evolution under photoelectrolysis employing TiO 2 photoanode was found to be 3 × 10 2 μ l h −1 over a cm 2 of electrode, on the other hand the In 2O 3 modified TiO 2 exhibited a higher hydrogen gas evolution rate of 8 × 10 2 μl h −1 over a cm 2 of electrode. Evidence and arguments have been put forward to show that the presence of In 2O 3 over TiO 2 makes the system possess the advantages of a colloidal photochemical system, and the better performance of the new photoelectrode is thought to be due to improved spectral response and catalytic activity of In 2O 3 in regard to the gas evolution kinetics.

The flowing‐afterglow technique, and approach to the study of polymer thermal degradation

AbstractWe describe here a relatively new analytical method1–3 for following the thermal reaction history of polymers by quantitatively detecting the evolution of gases and some volatiles by flowing‐afterglow spectroscopy. The thermal and oxidative stability of common plastics in many industrial and defense applications is of wide interest. We have studied the evolution of moisture and carbon dioxide from Li2CO3/Orlon‐filled diallyl phthalate (DAP) composites and have briefly examined the thermal stability of Estane 5703, a polyester‐based thermoplastic polyurethane. The results of these preliminary studies have shown the utility of FLAG spectroscopy as a means toward our understanding polymer stability and lifetimes in specified environments. FLAG data, combined with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) data, have extended our knowledge of Li2CO3/Orlon/DAP and Estane aging processes. The DAP composites evolve H2O and CO2 at near ambient temperatures, and we have described the kinetics of gas evolution and have attempted to describe the mechanism of thermal degradation. In the 25–120°C temperature range Estane 5703 evolves CO2 as a decomposition product and some adsorbed moisture.

An apparatus for kinetic‐mechanistic studies of polymer burning and regression rates: Poly(methyl methacrylate)

AbstractAn apparatus for determination of regression (weight‐loss) rates before, at, and after ignition as a function of oxidant gas flow rates has been constructed and successfully operated with poly(methyl methacrylate). In addition, flame temperatures, gas evolution kinetics and composition can be ascertained. The apparatus allows a proper evaluation of diffusion processes and chemically controlled processes. The regression rate for PMMA is directly proportional to the air flow rate. At low air flow rates the process is diffusion controlled and the energy of activation is identical with the heat of vaporization of the monomer. There is a liquid monomer layer and on top of it a stagnant vapor layer having the equilibrium vapor pressure of the monomer. At higher flow rates the energy of activation increases steeply. The layers become thin and defective and eventually thermal depolymerization becomes rate determining. This depolymerization has an energy of activation between 30 to 40 kcal mol−1. Experiments have also been carried out in closed quartz tubes. Explosion limits, ignition lags and energies of activation have been determined. The latter were evaluated by the method of Semenoff.

874. Method for investigating the kinetics of gas evolution in the vacuum treatment of liquid metals: V T Burtsev et el, Ind Lab, 31, 1965, 93–96, (in Russian)

874. Method for investigating the kinetics of gas evolution in the vacuum treatment of liquid metals: V T Burtsev et el, Ind Lab, 31, 1965, 93–96, (in Russian)

727. Kinetics of gas evolution in vacuum are smelting: L. N. Belyanchikov, R. N. Grigorash and A. V. Panov, Izv. Vyssh. Ucheb. Zaved. Chern. Metallurg. (9), 1961, 79–86.

727. Kinetics of gas evolution in vacuum are smelting: L. N. Belyanchikov, R. N. Grigorash and A. V. Panov, Izv. Vyssh. Ucheb. Zaved. Chern. Metallurg. (9), 1961, 79–86.

The light ageing of polymethylmethacrylate—I. The kinetics of gas evolution as affected by light of varying wavelength. The Quantum yield of photodegradation

1. (1) It is shown that photolysis of polymethylmethacrylate takes place on irradiation with ultraviolet light of wavelength less than 3500 Å. 2. (2) The quantum yield of the photodegradation process calculated on the basis of the volatile products evolved is 0·23 × 10 −3. 3. (3) The low quantum yield and the cessation of gas evolution after shutting off the light source leads to the assumption of a non-chain nature for the photolysis of polymethylmethacrylate irradiated in vacuum.

A recording sorption kinetics apparatus

AbstractAutomatic recordings of the rates of sorption and desorption of gases are obtained by measurement of the volume of the ambient gas under conditions of constant pressure and temperature. The apparatus, which approaches microgram sensitivity, is applicable in the field of diffusion of vapors in polymeric solids (and in obtaining the permeability coefficient). It is especially suited for rapid detection of rate changes and provides operational conveniences for extended measurements. Although exhibiting an over‐sensitivity at low pressures, the apparatus does not share the load‐sensitivity limitations of quartz spiral techniques. As a detector of the kinetics of gas evolution or consumption, the apparatus shows promise of application in other fields of research as well.

Pyrolysis of Dissolved Nitrocellulose

THE course of the thermal breakdown of the nitrocellulose molecule is not well understood. Previous studies of the chemical kinetics of the reaction have been carried out on the solid, and so have been hampered by the need to pyrolyse at low temperatures to reduce self-heating; and it is not certain how far the kinetics of gas evolution are complicated by reactions of the primary products, which probably include nitrogen peroxide. Further, the value of 46.7 kcal./mole recently found for the activation energy of the primary step by Wilfong, Penner and Daniells1 is difficult to understand in the light of Phillips's demonstration2 that the typical value for organic nitrates is 36–40 kcal.