Principle of Detailed Balance and the Second Law of Thermodynamics in Chemical Kinetics

The principle of detailed balance is shown to be a sufficient condition for the second law of thermodynamics in thermally equilibrated elementary chemical reactions. For an elementary reaction, the principle of detailed balance relates the forward and the reverse rate constants through the reaction equilibrium constant. It is shown that, in addition to the long known thermodynamic inconsistency at chemical equilibrium state, departure from this principle introduces an extra source/sink of entropy in the entropy balance for an elementary chemical reaction. The departure results in the wrong final chemical equilibrium state and, depending on the choice of the reverse rate constants, may lead to negative entropy productions during kinetic transients.

RUTHENIUM DOPED ZnO SEMICONDUCTOR: SYNTHESIS, CHARACTERIZATION AND PHOTODEGRADATION OF AZO DYE

Ruthenium doped zinc oxide was synthesized by a simple sol–gel method via ultrasonication. The samples were characterized by X-ray diffraction, high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscope (HR-TEM), energy dispersive spectroscopy (EDS) and UV-visible spectroscopy techniques and tested for the feasibility as a heterogeneous photocatalyst. The photocatalytic activity of Ru doped ZnO was tested using an azo dye, congo red (CR) in an aqueous solution, as a model compound. For comparison, the photocatalytic activity of pure ZnO was also performed. The parameters studied include the effect of initial CR concentration, photocatalyst weight and charge transfer phenomenon. The observed reaction mechanism was rationalized based on the elementary chemical reaction occurring in the irradiated heterogeneous reaction mixture. Total mineralization of CR was observed for both pure and Ru doped ZnO system. However, the photocatalytic activity of Ru doped ZnO was found to be higher than that of a pure ZnO .

Phenomenological and Elementary Reaction Analysis of Poly-crystalline Silicon CVD Process

Thickness uniformities of poly-crystalline silicon thin films, deposited by a commercial LPCVD reactor, were investigated through a phenomenological and elementary reaction analysis. To understand the deposition rate and its profile in radius direction of ø 6”h silicon wafer, concentration distributions of film precursors were examined by solving basic diffusion equations of film precursors in the CVD system. The experimental thickness distribution can be simulated very well with the solution by optimizing η, the sticking probabilities of the precursors. While most of the silicon deposition was made by source precursor (mono-silane, SiH4), two kinds of intermediate species with sticking probabilities of 5X10-2 and 7X10-4 were found to contribute the deposition. Subsequently, elementary chemical reaction analysis of poly-crystalline silicon CVD process was performed using ChemKinTM and two chemical species, SiH2 and Si2H6, were identified as the possible candidates for the intermediate species.