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Spatially resolved oxidation of nanocrystalline silicon surfaces has been studied using Fourier Fourier-transformed infrared microscopy. At the same time, photoluminescence (PL) quenching has been recorded. Both characteristics are related to the increase of silicon oxide species on the sample surfaces. Illumination of surfaces by blue light increases oxidation rates and speeds PL quenching in the form of a stretched exponential function. A possible explanation of this behavior considering quantum dots and quantum wires present in the material is proposed.

It is critical to mitigate the problem of elemental interdiffusion between the traditional PtAl coatings and the alloy substrate under severe high-temperature service environments. In this work, gradient PtAl coatings containing Re-based diffusion barriers were prepared by sequentially electroplating Ni–Re, Ni, and Pt layers between traditional PtAl coatings and Ni-based single-crystal superalloys, followed by final vapor-phase deposition of infiltration. It is shown that the chemical composition of the lower part of the coating is similar to that of the single-crystal superalloy, and the presence of Re-based diffusion barriers leads to lower elemental diffusion fluxes between the coating and the substrate, thus mitigating the precipitation of TCP phases from the substrate during the high-temperature oxidation process. Gradient PtAl coatings containing Re-based diffusion barriers have excellent mechanical properties due to the precipitation of a small amount of TCP phase from the matrix, while generating an Al₂O₃ film with good oxidation resistance.

Mn(III) complexes of meso-tetra(o,o′-dichlorophenyl)porphyrin, tetra-tert-butyl-tetraazaporphine and 3,5-octanitrophthalocyanine are efficient catalysts of naphthalene oxidation by peracetic acid in acetonitrile solution. The pathways of the reaction and the nature of intermediates and final products depend on the catalyst structure. For meso-tetra(o,o′-dichlorophenyl)porphyrin MnCl and tetra-tert-butyl-tetraazaporphine MnCl the single primary oxidation product is 1-naphthol. For 3,5-octanitrophthalocyanine MnCl, two pathways of naphthalene oxidation yielding 1-naphthol (as the primary product) and 1,4-naphthoquinone are proposed. The pathway of 1,4-naphthoquinone formation in the 3,5-octanitrophthalocyanine MnCl-catalysed reaction seems to involve two intermediates, 1,4-endo-peroxy-1,4-dihydro- and 2,3-epoxy-1,4-endo-peroxy-1,2,3,4-tetrahydronaphthalene.

Octakis(alkoxymethyl) cobalt phthalocyanines with relatively short side chains were synthesized which exhibited no thermotropic liquid crystalline behaviour. The final products as well as the intermediates have been characterized by proton magnetic resonance, infrared and electron spectra and elemental analysis. Cyclic voltammograms were measured for octakis(alkoxymethyl) cobalt phthalocyanines in order to examine their electron transfer properties. The electron transfer properties of octakis (alkoxymethyl) cobalt phthalocyanines depend on the kind and number of substituents and are due to the interaction between the phthalocyanine ring, the central metal which is influenced by the conjugated π electron current of the porphyrazine ring.

The study of haemin-catalysed oxidation reactions was extended to substituted aromatic rings. Both electron-donating and electron-withdrawing substituents on aromatic rings act as para- and meta-directing agents in the presence of tetrakis(2,6-dichlorophenyl)porphyrin iron(III) chloride as catalyst and m-chloroperbenzoic acid as oxidant. A new kinetic method for measuring relative rates of epoxidation of alkenes and related compounds has been developed; while steric hindrance results in decreasing the rate of hydroxylation, electron-rich and electron-withdrawing substituents were found to increase the rate of hydroxylation. A linear relationship between the logarithm of the relative rate of hydroxylation and σ Hammet is obtained, although electron-donating and electron-withdrawing substituents fit separate lines. Addition of pyridine to haemin was shown to increase the yield of epoxidation but decrease the yield of aromatic hydroxylation.

The aim of this study is to demonstrate the effects of Ananas comosus L. leaves on diabetic-dyslipidemic rats. Hypoglycemic and hypolipidemic activities of the ethanolic extract of Ananas comosus L. leaves (EEACL) were evaluated in normal and alloxan-induced diabetic rats by oral glucose tolerance test and an olive oil load test. Anti-diabetic, anti-hyperlipidemic and anti-oxidative activities of EEACL were also investigated in diabetic-dyslipidemic rats induced by alloxan and a high-fat/high-cholesterol diet. EEACL at the dose of 0.40 g/kg significantly inhibited the increase in blood glucose in diabetic rats in oral glucose tolerance test, but did not cause any hypoglycerimic activity in normal rats. It also significantly inhibited the increase in postprandial triglycerides (TG) levels in both normal and diabetic rats in olive oil load test. After 15 days of treatment of diabetic dyslipidemic rats, EEACL significantly decreased blood glucose (-51.0%, P<0.01), TG (-50.1%, P<0.01), TC (-23.3%, P<0.01), LDL-c (-47.9%, P<0.01) and glycated albumin (-25.4%, P<0.01) levels, significantly increased serum high-density lipoprotein cholesterol levels (66.2%, P<0.01) and prevented lower body weight of diabetes (11.8%, P<0.05), significantly lowered lipid peroxidation productions of blood (-27.8%, P<0.01), brain (-31.6%, P<0.05), liver (-44.5%, P<0.01) and kidneys (-72.2%, P<0.05) compared with those in untreated diabetic dyslipidemic rats. These data suggest that EEACL has anti-diabetic, anti-dyslipidemic and anti-oxidative activities, which may be developed into a new plant medicine for treatment of diabetes and its complications.

The isothermal oxidation behavior of directionally solidified Ni-base superalloy DZ951 at 900, 1000 and 1100°C were investigated. Oxidized alloy was characterized by SEM, EDAX, XRD. A subparabolic time dependence (n = 0.18 at 900°C and n = 0.08 at 1000°C) of the oxide growth rate was determined at relatively low temperature, while alloy nearly followed parabolic law at 1100°C (n = 0.42). The severe composition segregation, which resulted from the solidification process, led to the formation of different scale on the dendritic and interdendritic regions at 900°C, however, this difference disappeared after oxidation at 1000 and 1100°C for long time. Furthermore, faceted and needle-shaped AlN precipitates developed in the alloy subsurface region after oxidation at 1100°C for 200h, while no internal corrosion products were found in 900 and 1000°C tests.

The influence of alloying elements on oxidation behavior of TiAl has been investigated using an ion-implantation technique and the mechanisms were discussed. The influence can be classified into several groups according to their effects. The implantation of β-forming elements, halogens, Cu and Zn results in a significant improvement of the oxidation behavior through formation of Al₂O₃ layer in the initial stage of oxidation. The improvement by Zn is attributed to the formation of complex oxide of Zn and selective oxidation of Al beneath the layer. The implantation of Al, Si or P is also effective. On the other hand, implantation of Ag, Se and other several elements enhance the oxidation. The deterioration by Ag or Se is explained in terms of Al depletion in the implanted layer.

By controlling the sputtering power, rotational speed of the substrate and sputtering time, Ni–Cr thin films with appropriate composition were fabricated by double-target magnetron co-sputtering techniques. The homogeneity and oxidation of Ni–Cr thin film has been studied by Auger electron spectroscopy (AES). The structures of Ni–Cr thin films were determined by an X-ray diffractometer (XRD). The oxidation and the resistance stability of the Ni–Cr thin film after rapid thermal process (RTP) have been studied. The relations between TCR and RTP techniques of Ni–Cr thin films were discussed.

The oxidation process of calcium hexaboride (CaB₆) ceramic sintered body with 28wt% nickel as a sintering aid was investigated systematically in this paper. DTA-TG was used to analyze the oxidation behavior at various temperatures. The morphologies of the oxidation surfaces and the interface between the oxide layer and the bulk material were given by EPMA and BSE, respectively. Element distribution on cross-sections was measured by an energy spectrum analyzer. It is found that CaB₆-28wt%Ni shows an excellent oxidation resistance below 1173K owing to the protection provided by calcium borate on the surface. Catastrophic fast oxidation begins at 1273K. The grain boundaries act as the diffusion channels for O₂ penetration. The existence of Ni doesn't affect the oxidation behavior of the matrix CaB₆. The mechanism of oxidation was also discussed in this paper.

β-NiAl as a promising oxidation resistant coating material due to it high melting point and good oxidation resistant, however it reveals poor cyclic oxidation performance. In this paper, reactive element Dy doped β-NiAl coatings were prepared by electron beam physical vapor deposition (EB-PVD). Dy doping led to the grain refinement microstructure and Dy segregated mainly at grain boundaries. Cyclic oxidation behaviors of the coatings at 1100°C were investigated. The 0.05at.% Dy and 0.1at.% Dy doped coatings exhibited lower oxidation rate and better cyclic oxidation performance, as compared to the undoped coating. The effects of Dy addition on the morphologies and growth mechanism of the oxide scale were discussed.

NiAl has attracted increasing attentions because of its promising potential as protective coating materials for high temperature oxidation resistance. In this paper, Dysprosium (Dy) doped NiAl alloys were produced by arc melting. Cyclic oxidation of the alloys was carried out at 1200°C. The effects of Dy as a reactive element on the microstructure and failure of alumina scales on NiAl were investigated. For the melted alloy, Dy was mainly precipitated along the grain boundary and some within the grains in the form of DyNi₂Al₃ phase. Compared to Al₂O₃ scale formed on the undoped NiAl alloy, the microstructure of the scale was greatly changed and the ridge-like Al₂O₃ scale became less distinct on Dy-doped NiAl. The equi-axed alumina scale grew on NiAl, whereas the columnar alumina developed on Dy doped NiAl. The Dy dopant prevented the oxide scale from rumpling and the formation of cavities beneath the oxide scale. Due to this, the oxide scale adhesion was significantly improved. For Dy-doped NiAl, the scale failure mostly occurred surrounding the oxide protrusions where were rich in Dy.

A Mo(Si,Al)₂ coating is developed to protect Nb_ss/Nb₅Si₃ in situ composite by plasma spraying. The binary layers of this coating consist of an inner interdiffusion layer surrounded by Mo(Si,Al)₂ layer with C40 crystal structure. After oxidation at 1250°C for 100h, Mo(Si,Al)₂ coating exhibited an excellent protection against oxidation and good adherence to substrate. The oxidation curve followed parabolic law and even after oxidation at high temperature for 100h, the weight gain per unit area of Mo(Si,Al)₂ coating is 8.24mg/cm². No evident spalling of coating to substrate was observed but a continuous and compact layer of Al₂O₃ was formed on coating surface to prevent oxidation below coating and substrate.

Tin dioxide (SnO₂) thin films are obtained from resistive evaporation of metallic Sn followed by thermal oxidation at different temperatures in the range 200–500${}^{\circ }$C. Results show that, besides the thickness of the evaporated Sn thin film, the oxidation process of Sn into SnO₂ is highly dependent on the annealing time and temperature, presenting tin monoxide (SnO), as an intermediate compound, result of partial oxidation of the metallic Sn at intermediary time and temperature. The optical and electrical properties of the Sn thin films are altered by the oxidation degree of Sn into SnO${}_x$. These important characteristics are evaluated through UV-Vis, SEM, EDS, XRD and Impedance Spectroscopy. Increase in the optical bandgap energy as well as in the surface charge density, verified by electrical impedance, are observed on samples with higher annealing temperature and time, which indicate sequential oxidation process in these films.

GaSe nanoflakes on silicon substrates covered by SiO₂ films are prepared by mechanical exfoliation from the bulk Bridgman-grown GaSe crystals using a scotch tape. The thickness of SiO₂ films on Si substrates providing the highest optical contrast for observation of GaSe flakes is estimated by taking into account the spectral sensitivity of a commercial CMOS camera and broadband visible light illumination. According to our estimations, the optimal SiO₂ thickness is $\sim$126 nm for the visualization of GaSe flakes of 1–3 layers and $\sim$100 nm for the flakes of 40–70 layers. The obtained nanoflakes are investigated by optical and atomic force microscopy and Raman spectroscopy. The observed spectral positions of the Raman peaks are in agreement with the positions of the peaks known for bulk and nanolayered GaSe samples. It is found that the 50 nm thick flakes are stable but are covered by oxide structures with lateral size about 100 nm and height $\sim$5 nm after $\sim$9 months exposure to ambient atmosphere.

In the present study, a theoretical model is presented to assess the failure temperature for ultra-high temperature ceramics (UHTCs). Unlike traditional thermal shock theory, the parameters, such as thermal expansion coefficient and Young's modulus, are considered a function of temperature in the present model. The oxide film of UHTCs is also believed to grow under high temperature. Considering two kinds of conditions, the critical elevated temperature for delamination is calculated using Griffith's theory. By establishing the relation between temperature and the mechanical properties of UHTCs, it is found that the failure behavior of UHTCs is strongly affected by the oxide film thickness, initial temperature and the heating rate.

The effects of electrical parameters including applied voltages, duty cycles, and frequencies, on the structures of titania film by micro arc oxidation (MAO) technology were studied. Micro arc oxidation was conducted for Ti with pulsed dc power supply. The voltage was controlled at various constant applied voltages (200, 230, 270 V) with various pulse frequencies (dc, 20, 30, 40, 50 kHz) for 3 minutes, and the pulse current was measured with time. There seems to be a minimum absolute duty period (26 μs) in order to allow oxide thickness to grow, because with a duty period lower than 26 μs, the oxide may stop growing. In other words, with less than 26 μs, it is hard for Ti ions to diffuse through the oxide film to grow to a certain thickness.

The effects of oxidation on the weight change (D_W) and modulus change (D_E) of an uncoated C/SiBC were investigated in 600–1000°C. The results show that larger D_W does not mean larger damage. D_E is more sensitive to the oxidation process than D_W. At lower temperatures, a small D_W can result in a large D_E. The results result from the different oxidation rates of carbon fibers and pyrocarbon interphase.

In this study, the ReaxFF reactive force field is applied to simulate the melting and annealing behaviors of aluminum (Al) nanoparticles (ANP) by molecular dynamics (MD) simulations. Potential energy, specific heat and FCC lattice number are used to study the thermal behavior of the entire phase transition process. First, the melting and solidification process of 3nm cubic Al and Al₂O₃ models under constant-pressure/temperature ensemble (NPT) system was simulated without boundary, and the steady-state simulation was discussed at specific temperature points. The non-boundary simulation proved the effectiveness of the Reaxff reactive force field for ANP phase transition simulations. It is confirmed that the physical properties of Al and Al₂O₃ could be effectively reflected in the MD simulations. ANP with low oxidation degree cannot be completely ignored in engineering applications. The existence of oxide layer hinders the annealing behavior. Therefore, this study also carried out an additional simulation process of 6 nm ANP and its oxide particles in canonical ensemble (NVT). Those obtained results show that a small amount of oxide layer can greatly change the thermal properties of ANP. If the surface of ANP is isolated, then its melting point could be increased by at least 30K.

The oxidation of the single crystal stepped Pt₃Ti(510) surface at oxygen pressures below 10^-5 mbar and at a temperature of 770 K was studied by means of X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS) and low energy electron diffraction (LEED). Scanning tunneling microscopy (STM) was used to follow the evolution of the surface morphology on the atomic scale. The clean surface studied in ultrahigh vacuum conditions was found by LEIS to be composed of platinum only in the outermost surface plane. LEED and STM indicate that the clean Pt₃Ti(510) surface consists of (100) terraces separated by double atomic steps. The exposure of the clean surface to oxygen at pressures in the range of 10^-7–10^-5 mbar leads to the growth of a titanium oxide layer (with a composition close to TiO) which covers completely the substrate surface. The TiO film has long range order and exhibits complex LEED patterns. The STM measurements indicate that the ordered array of steps is kept in the early stages of the oxide film growth, whereas a change of the step morphology and step orientation is observed during the oxidation process.