Effect of Doping Concentration on Grain Boundary Conductivity of Samaria Doped Ceria Composites

This work aims to study the effect of Sm3+ doping concentration on the grain boundary ionic conductivity of ceria. The materials were prepared by a modified co-precipitation method, where molecular water associated with the precursor has been utilized to facilitate the hydroxylation process. The synthesized hydroxide / hydrated oxide materials were calcined and the green body (pellet) has been sintered at high temperature in order to achieve highly dense (~ 96 %) pellet. The structural analyses were done using XRD and Raman spectroscopy, which confirm the single phase cubic structure of samaria doped ceria (SDC) nanoparticles and the surface morphology of sintered samples was studied using FESEM. The ionic conductivity was measured by AC impedance spectroscopy of the sintered pellets in the temperature range of 400-700 °C, which shows superior grain boundary conductivity. The grain boundary ionic conductivity of around 0.111 S/cm has been obtained for 15SDC composition at 600 °C.

Adsorption of vanadium with amorphous hydrated chromium oxide

Vanadium is recognized as a potentially dangerous pollutant following closely on lead, mercury and arsenic. Vanadium removal from wastewater prior to discharge is essential. In this work, an amorphous hydrated chromium oxide was prepared and its vanadium adsorption ability studied. As-prepared, the hydrated oxide showed high efficiency in vanadium adsorption – e.g., from 300 to 0.75 mg-V·L−1. The effects of pH, adsorbent dosage, temperature, adsorption time and the presence of other ions on the vanadium removal rate were investigated, and optimal parameters determined. Dynamic adsorption results showed that pseudo-second-order kinetics could be used to interpret the kinetic curve and that the process was that of chemisorption. The Langmuir isotherm was found to fit the adsorption behavior well.

Surface structure of Amur region high grade native gold

The purpose of the research is to study the surface structure of high grade gold. The subject of research is gold ore fields in the Amur region. The object of the study is samples of native high grade gold grains from these fields. The study uses the methods of thermodynamics and X-ray electron microscopy. The study results in revealing a multilayer structure of the surface of high grade minerals of the Amur region native gold with the following levels: a boundary layer with zero oxidation degree Au0 in the form of yellow metallic gold; an oxide layer with the oxidation degree Au+1 in the form of purple Au2O; an oxide layer with the oxidation degree Au+3 in the form of a yellow-brown Au2O3; a hydrated oxide layer with the oxidation degree Au+3 in the form of a red-yellow-brown Au(OH)3. The methods of electron microscopy have allowed to identify external surface structures – dense oxide layers of the form of Au2O3 and loose hydrated layers of the form of Au(OH)3, whereas the inner layers of metallic and monovalent gold are not visible. Important thermodynamic characteristics of the presented levels are the values of standard oxidation-reduction potentials (E°), which determine their physicochemical properties: for metallic gold E° = +1.68 V; for the oxide layer with the oxidation degree Au+1 in the form of Au2O – E° = +0.32 V; for the oxide layer with the oxidation degree Au+3 in the form of Au2O3 – E° = +1.36 V; for the hydrated oxide layer with the oxidation degree Au+3 in the form of Au(OH)3 – E° = +0.7 V. The results of the conducted studies indicate that the surface structure has several layers that lower the oxidation-reduction potential, which explains the generation and formation of migratory forms of gold in humid hypergene conditions of natural environment.

Selective Crystallization of Aluminophosphate Molecular Sieve with AEL Structure

The influence of temperature and ageing of initial aluminophosphate gels on their chemical and phase composition was studied. The hydrated oxide (boehmite) was used as the source of aluminum to prepare gels containing ammonium phosphate, undissolved pseudoboehmite and amorphous aluminophosphate in different proportions. The gel with predominant amorphous aluminophosphate was shown to provide selective crystallization of high phase purity AlPO4-11 with the crystallinity degree close to 100 %. The developed method for preparation of these disperse molecular aluminophosphate sieves AlPO4-11 is a step to crystallization of silicoaluminophosphates SAPO-11 that are promising Russian catalysts for industrial processes of hydroisomerization of n-paraffins used for manufacturing of Arctic diesel fuel, III group oils and isomerization of butenes.

Refining of degasifying and removing of non-metallic impurities during aluminium alloy production

In melting aluminum and aluminum alloy, molten aluminum reacts readily with oxygen, cacbon monoxide and cacbon dioxide; it also reacts with adsorbed water, water present in hydrated oxide films on metal charges, water vapor in the atmosphere of the furnace to form oxides and hydrogen. As a result, a higher level of hydrogen is retained in the metal. In solid aluminum, hydrogen in excess of the solution limit can precipitate as H2 at grain boundaries. Thus, refining and degasifying can be improved mechanical properties of material.