Ion‐beam synthesis of 3C‐SiC surface layers on silicon

The attempt to grow 3C‐SiC thin films on silicon substrates has become an area of significant scientific interest, largely as a consequence of the impressive electrical properties that this polytype displays. In this paper, we have utilized low‐energy (20 keV) high‐fluence carbon implantation and a subsequent annealing step to form layers of 3C‐SiC directly on a silicon surface, and have investigated the effect of implantation fluence on the resultant materials properties. The quality of the Si/SiC interface is shown to be highly fluence‐dependent, with the formation of voids decreasing significantly with increased fluence. The conversion of carbon into 3C‐SiC is found to be most efficient at near‐stoichiometric concentrations, while at higher implantation fluences clusters of excess carbon are discovered to form within the silicon and to diffuse to the surface of the grown 3C‐SiC layer upon annealing. Copyright © 2011 John Wiley & Sons, Ltd.     

The aid of calorimetry for kinetic and thermal study

Journal of Thermal Analysis and Calorimetry - Phosphoric acid, a non-renewable chemical, is used in different industries. Production of this chemical from natural phosphate can be done by two...     

Thermal risk assessment for the epoxidation of linseed oil by classical Prisleschajew epoxidation and by direct epoxidation by H2O2 on alumina

Journal of Thermal Analysis and Calorimetry - Substitution of fossil feedstock by vegetable oils is growing due to environmental constraints and oil depletion. Among the different valorization...     

Stability of hydrogen peroxide during perhydrolysis of carboxylic acids on acidic heterogeneous catalysts

This paper describes a study of the stability of hydrogen peroxide in the presence of different aluminosilicate materials, in connection with an investigation of carboxylic acid perhydrolysis. During the reaction, aluminosilicate materials such as H-β zeolites, mesoporous material H-MCM-41 and alumina initiate the decomposition of hydrogen peroxide. The reason of the spontaneous decomposition of H₂O₂ is related to the partial dealumination of these zeolites. However, in the case of experiments carried out with H-ZSM-5 zeolite catalysts, a slight catalytic effect on the perhydrolysis and no spontaneous decomposition of hydrogen peroxide were noticed. The use of cation exchange resins as catalysts is more kinetically beneficial than H-ZSM-5 zeolite catalysts.     

Activity-Based Models to Predict Kinetics of Levulinic Acid Esterification

The solvent is of prime importance in biomass conversion as it influences dissolution, reaction kinetics, catalyst activity and thermodynamic equilibrium of the reaction system. So far, activity-based models were developed to predict kinetics and equilibria, but the influence of the catalyst on kinetics has not been succesfully predicted by thermodynamic models. In this work, the thermodynamic model ePC-SAFT advanced was used to predict the activities of the reactants and of the catalyst at various conditions (temperature, reactant concentrations, γ-valerolactone GVL cosolvent addition, catalyst concentration) for the homogeneously acid-catalyzed esterification of levulinic acid (LA) with ethanol. Different kinetic models were applied, and it was found that the catalyst influence on kinetics could be predicted correctly by simultaneously solving the dissociation equilibrium of H₂SO₄ catalyst along the reaction coordinate and by relating reaction kinetics to proton activity. ePC-SAFT advanced model parameters were only fitted to reaction-independent phase equilibrium data. The key reaction properties were determined by applying ePC-SAFT advanced to one experimental kinetic curve for a set of temperatures, yielding the reaction enthalpy at standard state , activation energy and the intrinsic reaction rate constant k=0.011 s⁻¹ at 323 K, which is independent of catalyst concentration. The new procedure allowed an a-priori identification of the effects of catalyst, solvent and reactant concentration on LA esterification.