THE EFFECT OF MATTALOPORHYRINS ON ASPHALT OXIDATION. II. THE EFFECT OF VANADYL CHELATES FOUND IN PETROLEUM

ABSTRACT

Four selected asphalts were blended with zero to five wt. percent of fractions rich in vamady cheltes prepared from two crude oils. The mixture was -coated in a teflon -support, and the whole was heated in an oven at. 113±2°C for 24 hours. The mixture then was analyzed for increases ketone, acid and anhydride functions.

in general, functions rich in vanady ponphyrims tended to promote asphalt oxidation, particularly as measured by increase in kentones. Corelation of vanadyl ponphyrim concentration with asphalt oxidation is observed to the direct only if asphalts are mixed with varying amounts of the same fraction derived from the same crude Possible reasons for this phenomenon are discussed in terms of oxidation susceptibility of aspha1ts, the importance of molecular associations, and the relative catalytic activities of metallaporphyrins and other metal chelates     

Nanophase catalytic oxides: I. Synthesis of doped cerium oxides as oxygen storage promoters

Doped CeO₂ materials were synthesized with the aim to improve the performance of CeO₂ as oxygen storage promoter in gas catalytic reactions. The coprecipitation method was used for the synthesis of fine oxalate precursors of high homogeneity and well defined composition. The chemical and morphological properties of both the coprecipitated oxalates and the calcined oxides were examined. The influence of doping of different metal cations into the CeO₂ structure on the oxygen storage capacity in particular was investigated. Some of the doped oxides Ce_0.9M_0.1 O_{2 − δ} (M = Ca, Nd, Pb, etc.) give an increased oxygen storage capacity, 20–40% higher than the undoped. Their redox activity also remarkably increased.     

Kinetics of the dissolution of uranium dioxide in nitric acid. I

The kinetics of the dissolution of uranium dioxide in nitric acid have been investigated over a range of acid concentration from 0·3 to 37·0 molal. A change in the reduction mechanism for nitric acid is indicated at about 16 molal concentration. A proposed mechanism for the initial rate period of dissolution is consistent with experimental results and with the known thermodynamics of the system.     

Control of Halogen Atom in Inorganic Metal-Halide Perovskites Enables Large Piezoelectricity for Electromechanical Energy Generation

Regulating the strain of inorganic perovskites has emerged as a critical approach to control their electronic and optical properties. Here, an alternative strategy to further control the piezoelectric properties by substituting the halogen atom (I/Br) in the CsPbX₃ perovskite (X = Cl, Br) structure is adopted. A series of piezoelectric materials with excellent piezoelectric coefficients (d₃₃) are unveiled. Iodine-incorporated CsPbBr₂I demonstrates the record intrinsic piezoelectric response (d₃₃ ≈47 pC N⁻¹) among all inorganic metal halide perovskites. This leads to an excellent electrical output power of ≈ 0.375 mW (24.8 µW cm⁻² N⁻¹) in the piezoelectric energy generator (PEG) which is higher than those of the pristine/mixed perovskite references with CsPbX₃ (X = I, Br, Cl). With its structural phase remaining unchanged, the strained CsPbBr₂I retains its superior piezoelectricity in both thin film and nanocrystal powder forms, further demonstrating its repeatability and versatility of applications. The origin of high piezoelectricity is found to be due to halogen-induced anisotropic lattice strain in the unit-cell along the c-axis, and octahedral distortion. This study reveals an avenue to design new piezoelectric materials by modifying their halide constituents and paves the way to design efficient PEGs for improved electromechanical energy conversion.     

High Temperature Tribological Characterisation of Laser Nitrided Nickel-Based Superalloy

The surface of a nickel-based superalloy used for air-borne gas turbine application was laser nitrided to improve the tribological properties. An optimal laser power and scanning speed was derived to avoid any possible variation in elemental composition of the treated surface. The metallurgical modification over the treated surfaces was studied along the cross-section through microstructural characterisation to understand the refining mechanism and possible nitriding. The coarse grains present over the base material surface reoriented to fine equiaxed grains under lower power and higher interaction time. The grains were refined with higher scanning power and lower interaction time. The higher thermal gradient and cooling rate combination attributed to the refining mechanism. Further increase in the laser power resulted in the formation of columnar grains at the treated depth. The presence of nitride species was observed over the treated surface, which improved the microhardness. All laser treated samples were subjected to wear analysis at ambient and high temperature. The treated pin surface exhibited a combination of adhesive and abrasive wear mechanism. A significant reduction in wear rate was observed for samples treated with high power and lower interaction time.