Papers by Keyword: Quantum Chemistry

Abstract: A fundamental study on finishing aided by an ultraviolet ray (generally mashining:referred to as U-RAM^R) was conducted to evaluate its applicability to the polishing of aluminum alloy. Qualitative analysis with X-ray photoelectron spectroscopy (XPS) was used to estimate the chemical reaction induced on Al surfaces that were immersed in some solutions. Inductively coupled plasma spectroscopy (ICPS) was employed to quantitatively analyze the amount of oxidized/dissolved Al, Mg and Fe. The following conclusions were obtained by investigation of the aluminum alloy polishing process. Aluminum does not dissolve in TiO₂-solution, whereas a small amount of Al dissolves into cathilon dye solution. Although only a small amount of Al dissolves in TiO₂-cathilon dye solution in the absence of UV irradiation, the amount of Al dissolved increases slightly under UV irradiation with the formation of oxide, nitrogen oxide and nitride on the Al surface. In addition, a small amount of an aluminum chloride dissolves into TiO₂-cathilon dye solution. An Al alloy (A5052) surface was made flat by polishing with TiO₂-cathilon dye slurry under UV irradiation.

Abstract: The experimental data on efficiencies of a series of 7 ureides and 5 acetylides as inhibitors (IN) of corrosion of mild steel in Postgate B media compared to quantum chemical data; the following descriptors found to be essential to describe the inhibitive properties under given conditions: energies of the boundary molecular orbitals (HOMO and LUMO) and dipole moment. The inhibitive properties of the chosen ureides under given conditions are based on electron donating rather than accepting properties of their molecules. PM/3 method was found to be preferable compared to other quantum chemical methods used (i.e., MNDO, AM/1), and even non-empiric ab initio methods because it is found to be more helpful in explaining the mechanism of inhibitive action of organic species.

Abstract: The interaction between bentonitic clays and exchangeable cations Na+, К+, Ca++, and Mg++ is studied theoretically. It is stated that the insertion of exchangeable cations into the interlaminar space leads to reducing of the interlayer distance as compared with that calculated for the undoped clay. At that, the clay particles having Mg++ on their surface demonstrate more stable structure upon the increase of moistening. The calculation results for Mg++ compare well with the experiment performed.

Abstract: Based on the theory of coordinate inhibition three nitrogen-containing active structures of different aromatic in coal were established. Using quantum chemistry calculation method, the effect of hydrogen bonding on the formation of complexes that formed by three nitrogen-containing active structures of different aromatic and inhibitor were calculated in B3LYP/6-311G* levels. The results show that hydrogen bond can make H₂O participation in forming complexes which formed by three nitrogen-containing active structures of different aromatic and metal ions. Hydrogen bonds play a molecular recognition and guiding role in the process of H₂O involved in the formation of complexes. After H₂O participating ligand through hydrogen bonds, the complexes formed Ca-O-H-O four-membered ring structure in the geometrical structures. It Shows that its stability are improved and not easy to contacts with O or reacting. It making coal spontaneous combustion can be well inhibition. After H₂O participating ligand, aromatic change had little effect in stability of the complexes. It shows that different ranks of coal can get better inhibition effect after H₂O participating ligand.

Abstract: Our main purposes were to establish ultraviolet-ray aided machining (here after reffered to as U-RAM) and clarify the chemical and mechanical polishing mechanism. The inner/outer surfaces of small cup-type nickel tube is strongly required to polish, simultaneously. The present study deals with the new development of simultaneous polishing technology and the verify of polishing phenomena that uses a photocatalyst and a cathilon (a luminous dye: Cathilon Brilliant Flavine; hereafter referred to as cathilon) excited by an ultraviolet ray (hereafter referred to as UV). Measurements and observations clarified that TiO₂ of 0.18-μm grain size polished chemically/mechanically the outer surface using cathilon, and cathilon chemically polished the inner surface of small cup-type nickel tube, simultaneously. Further measurements indicated that the chemical erosion roughened the inner surface, when cathilon increased from 2.5, 5 to 20wt%. An increase of TiO₂ to 20wt% at 20wt% of cathilon did not result the flatter surface. Aluminum oxide does not provide the polishing ability due to the poor photocatalyst effect compared with TiO₂.

Abstract: The inhibition effect of excellent environmental-friendly corrosion inhibitors-Vitamins B of hot dipping Zn coated steel in diluted HCl was investigated using quantum chemistry analysis and weight loss test. Calculation result shows Vitamins B have a number of active centers. The value of Mulliken charge, distribution of HOMO and LUMO implies its good ability of electron exchange with metal surface. The test results indicate IE% increased with the inhibitor concentration, and the highest IE reached 97%.

Abstract: Coal spontaneous combustion needs to have enough oxygen and heat, on the one hand, water salts inhibitor can isolate from coal exposure to air; on the other hand, water salts inhibitor interact with active groups in coal to form complex, increase the stability of coal and boost the heat of spontaneous combustion of coal. This paper has made use of quantum chemical calculation’s software Gaussian 03 to calculate the complex what coal’s active groups and Ca2+ inhibitor interacted to form, and research the mechanism for inhibitor suppressed the spontaneous combustion of coal.

Abstract: Hydroquinone derivatives are studied as inhibitors of microbiological corrosion and hydrogen absorption by mild steel in water salt media that supports development of sulfate reducing bacteria (SRB). The chosen composition of the media is close to sea water containing biogenic H2S. Н2S content, bacterial titer in corrosive media, its pH, Redox potential Eh, and φ of steel together with the quantity of hydrogen absorbed by surface steel sub-layers, were measured. Protective action against corrosion achieved by the best compounds studied, reached the values of 65…84%, while against hydrogen absorption by steel samples − 60…72%. The presence of the studied derivatives of hydroquinone at concentration C= 5 mMoldm–3 resulted in the decrease of SRB cell count at the rate of 48…84%, the suppression rate being at the values of 29…57%.

Abstract: The main purposes of this study were to lessen the deformities in the machined surface, to make the crystal grains on the machined surface appear, and to apply this machining at the micrometer level instead of at the nanometer level. The present study targets the development of a polishing technique that uses a photocatalyst and a luminous dye (Cathilon Brilliant Flavine; hereafter referred to as cathilon) excited by an ultraviolet ray. Nickel (hereafter referred to as Ni) was polished chemically and mechanically at the sub-micrometer level under an ultraviolet-ray irradiation. Measurements clarified that TiO₂ of 0.1 μm grain size mechanically polished the Ni, and cathilon chemically polished Ni. A flat surface was attained on the Ni by chemical and mechanical polishing using both the TiO₂ and cathilon, when they were irradiated by an ultraviolet ray. Further measurements indicated that the corrosion of Ni surface became large under an ultraviolet-ray excitation. The eroded trace was large when cathilon is rich. Though much TiO₂ tends to roughen Ni surface, the flat surface was obtained in the case of much TiO₂ and much cathilon due to both equivalent influences.

Abstract: Imidazoline derivative inhibitors are successfully used in oil-gas field for CO2 and H2S corrosion. The inhibition performance and inhibition mechanism of imidazoline with thioureido to prevent corrosion of steel in saltwater saturated with CO2 were studied by polarization curves and electrochemical impedance spectroscopy (EIS), in the meantime, quantum chemical analysis was used to analysis the results. The results of electrochemical measurements indicated that the inhibitor belonged to mixed-type inhibitor which mainly inhibited anodic process and worked as “negative catalysis”. The inhibition efficiencies increased then decreased with the increase in inhibitor concentration. The electrochemical results have also been supplemented by quantum chemical analysis. It was found that the chemical adsorption of the imidazoline with thioureido molecule on Q235 steel depended on the imidazoline ring and thioureido, thus the inhibitor had good corrosion inhibition.