Kinetic Oxidation Studies of Pentoxifylline by N-Chlorosuccinimide in Acidic Medium Using Iridium(III) Chloride as Inhibitor

In present study, the kinetics and mechanism of oxidation of pentoxifylline (PTX) by N-chlorosuccinimide (NCS) in acidic conditions at 40 ± 0.1 ºC is reported. The reaction depicts first-order kinetics in regard to [NCS], [PTX] and [HClO4]. The reaction rate goes on decreasing as the concentration of iridium(III) chloride is increased. This shows that iridium(III) chloride plays the role of an inhibitor in the reaction under investigation. Nil impact of [Hg(OAc)2], [NHS] and dielectric constant (D) of the medium on the rate of oxidation of pentoxifylline have been observed. This reaction has been investigated from 308-323 K and the monitored rate of reaction suggests a direct relationship between temperature and the rate of reaction. From the graph between log k and 1/T, value of activation energy (Ea) was numerated and more activation parameters like enthalpy of activation (ΔH#), entropy of activation (ΔS#) and free energy of activation (ΔG#) were calculated with the help of activation energy (Ea). On account of experimentally determined the kinetic orders and activation parameters, a most plausible reaction path has been suggested for the oxidation of pentoxifylline in presence of Ir(III) as an inhibitor.

Kesan Logam Pengisi Terhadap Struktur Terkimpal Al 6061 Yang Teroksida Pada 600°C

Samples of STK 6061 ER 4043 and STK 6061 ER 5356 were welded respectively using ER 4043 (Al-5%Si) and ER 5356 (Al-5%Mg) filler metal and were oxidized in air environment at 600oC for 40 hours. The focus of the analysis is on the welded metal where the base metal and the filler metal melt together to produce different chemical compositions. The analysis includes kinetic oxidation, material defect testing, surface morphology characterization using SEM-EDX, cross sectioning, elemental mapping and the oxide phases formed on the alloy surface. The results show that welded metal containing Mg tends to accelerate and accelerate the oxidation process, whereas welded metal containing Si may increase the resistance to oxidation.

Atmospheric CO2 levels from 2.7 billion years ago inferred from micrometeorite oxidation

Earth’s atmospheric composition during the Archean eon of 4 to 2.5 billion years ago has few constraints. However, the geochemistry of recently discovered iron-rich micrometeorites from 2.7 billion–year–old limestones could serve as a proxy for ancient gas concentrations. When micrometeorites entered the atmosphere, they melted and preserved a record of atmospheric interaction. We model the motion, evaporation, and kinetic oxidation by CO2 of micrometeorites entering a CO2-rich atmosphere. We consider a CO2-rich rather than an O2-rich atmosphere, as considered previously, because this better represents likely atmospheric conditions in the anoxic Archean. Our model reproduces the observed oxidation state of micrometeorites at 2.7 Ga for an estimated atmospheric CO2 concentration of >70% by volume. Even if the early atmosphere was thinner than today, the elevated CO2 level indicated by our model result would help resolve how the Late Archean Earth remained warm when the young Sun was ~20% fainter.

The Kinetics Of Ti-1Al-1Mn Alloy Thermal Oxidation And Charcteristic Of Oxide Layer

The main goal of the study was to carry out the treatment of cyclic oxidation of Ti alloy (Ti-1Al-1Mn) in air atmosphere. Based on measurements of mass gain of titanium alloy samples (Ti-1Al-1Mn) the kinetic oxidation curves during cyclic annealing were determined. The oxidized surface of the titanium alloy was carefully observed with optical microscopy equipment and the geometrical development, shape and surface morphology were defined. The phase composition of the obtained oxide layers on the Ti-alloy with qualitative analysis of the X-ray were defined. Since titanium alloys are among the most widely used metallic materials in dental prosthetics the corrosion measurements in a solution simulating the environment of the oral cavity were carried out. The results confirmed that the used titanium alloy easily covered with oxides layers, which to some extent inhibit the processes of electrochemical corrosion in artificial saliva solution.