High temperature oxidation properties of Al-Cu-Si alloys for latent heat energy storage

The effect of Cu content on the high temperature oxidation properties of the phase change material(PCM)Al-Cu-Si alloys was studied.The oxidation kinetics curves at 600◦C were achieved for Al-Cu-Si alloys with 35-55%Cu,which all follow the cubic law.With an increase in the Cu content from 35 to 55%,the weight gain decreases from 5.75 to 3×10^(−4) g/cm^(2) after 96 h isothermal oxidation.The oxidation rate also decreases with Cu content,the maximum and minimum rates are 1.52 and 0.32×10^(−5) g/cm^(2)•h,a nearly 4 times difference.Oxidation does not change the phase composition of Al-Cu-Si alloys,but coarsens the microstructure.The latent heat and the starting temperature of phase change after 96 h oxidation at 600◦C have variations of less than 10%and 6◦C,respectively,indicating that the Al-Cu-Si alloys have good thermal stability after high temperature oxidation.

Oxidation Properties of Silver Alloy Powders and Microstructures of Oxidized Powders for Making Electrical Contact Composites

The oxidation properties of silver alloy powders and microstructures of oxidized powders have been investigated by thermo gravity analysis(TGA), scanning electron microscopy(SEM) and wave dispersive X ray spectroscopy(WDEX). Ag Sn RE alloy powders have been oxidized completely at 610 ℃ within 60 min, with an external pure silver scale forming around each oxidized particle. It is useful to produce electrical contact composites. The excellent oxidation properties of Ag Sn RE alloy powders are attributed to the ideal microstructure of the oxidized powders.

Enhanced oxidation and overheating resistance of the extruded Mg–Zn–Al–Mn magnesium alloy by Calcium addition

The effects of Ca addition on the microstructure and oxidation properties of a new Mg alloy were studied.The oxidation behavior of the alloys was analyzed by thermal analysis and material characterization of the alloys exposed in flame environment;and both electrical and induction furnaces.Moreover,the surface layers were characterized using field emission scanning electron microscopy,and X-ray diffraction technique.It was found that increasing the Ca addition reduces the grain size and increases the fraction of the secondary phases,and enhances the mechanical properties.Moreover,increasing the Ca contents resulted in the formation of a dense CaO/MgO layer on the surface prohibited the oxygen diffusion and assisted in protection of the substrate against further oxidation.Therefore,ignition temperature was increased from 680℃ to 890℃ after addition of the Ca element.The mechanical properties and ignition behavior of the current materials was compared with the literature which it showed an excellent combination of the properties in the developed alloys.

THE SELECTIVE OXIDATION OF ALCOHOLS-STUDIES ON THE SYNTHESIS AND PROPERTIES OF HEXAHYDROPYRIDINE CHROMIUM TRIOXIDE HYDROCHLORIDE

A new Cr(Vl)complex,hexahydropyridine chromium trioxide hydrochloride is developed.Its behavior and seiectivity on alcohols are investugated

Tribological Properties of Few-layer Graphene Oxide Sheets as Oil-Based Lubricant Additives

The performance of a lubricant largely depends on the additives it involves. However, currently used additives cause severe pollution if they are burned and exhausted. Therefore, it is necessary to develop a new generation of green additives. Graphene oxide（GO） consists of only C, H and O and thus is considered to be environmentally friendly. So the tribological properties of the few-layer GO sheet as an additive in hydrocarbon base oil are investigated systematically. It is found that, with the addition of GO sheets, both the coefficient of friction（COF） and wear are decreased and the working temperature range of the lubricant is expanded in the positive direction. Moreover, GO sheets has better performance under higher sliding speed and the optimized concentration of GO sheets is determined to be 0.5wt%. After rubbing, GO is detected on the wear scars through Raman spectroscopy. And it is believed that, during the rubbing, GO sheets adhere to the sliding surfaces, behaving like protective films and preventing the sliding surfaces from contacting with each other directly. This paper proves that the GO sheet is an effective lubricant additive, illuminates the lubrication mechanism, and provides some critical parameters for the practical application of GO sheets in lubrication.

Structural and optical properties of thermally reduced graphene oxide for energy devices

Natural intercalation of the graphite oxide, obtained as a product of Hummer＇s method, via ultra-sonication of water dispersed graphite oxide has been carried out to obtain graphene oxide（GO） and thermally reduced graphene oxide（RGO）.Here we report the effect of metallic nitrate on the oxidation properties of graphite and then formation of metallic oxide（MO） composites with GO and RGO for the first time. We observed a change in the efficiency of the oxidation process as we replaced the conventionally used sodium nitrate with that of nickel nitrate Ni（NO_3）_2, cadmium nitrate Cd（NO_3）_2,and zinc nitrate Zn（NO_3）_2. The structural properties were investigated by x-ray diffraction and observed the successful formation of composite of MO–GO and MO–RGO（M = Zn, Cd, Ni）. We sought to study the effect on the oxidation process through optical characterization via UV-Vis spectroscopy and Fourier Transform Infrared（FTIR） spectroscopy.Moreover, Thermo Gravimetric Analysis（TGA） was carried out to confirm 〉 90% weight loss in each process thus proving the reliability of the oxidation cycles. We have found that the nature of the oxidation process of graphite powder and its optical and electrochemical characteristics can be tuned by replacing the sodium nitrate（NaNO_3） by other metallic nitrates as Cd（NO_3）_2, Ni（NO_3）_2, and Zn（NO_3）_2. On the basis of obtained results, the synthesized GO and RGO may be expected as a promising material in antibacterial activity and in electrodes fabrication for energy devices such as solar cell, fuel cell,and super capacitors.

Preparation of new sunscreen materials Ce_(1-x)Zn_xO_(2-x) via solid-state reaction at room temperature and study on their properties

Superfine cerium-zinc oxides Ce1-xZnxO2-x with x = 0, 0.1, 0.3, 0.5, and 1.0 were obtained by grinding Ce（SO4）2·4H2O, ZnSO4·7H2O and NH4HCO3 under the condition of surfactant PEG-400 being present at room temperature, washing the mixture with water to remove soluble inorganic salts, drying at 80°C, and calcining.The precursor and its calcined samples were characterized using thermogravimetry and differential thermal analyses（TG/DTA）, UV-vis absorption spectroscopy, X-ray powder diffraction（XRD）, and scanning electron microscopy（SEM）.The results showed that superfine Ce1-xZnxO2-x behaved as an excellent UV-shielding material.The ZnO-doped CeO2 can facilitate the formation of crystalline state CeO2.The catalytic ability of products used in air oxidation of castor oil was investigated.The results showed that the catalytic abilities of products decreased with increasing zinc amount.

Influence of Deposition Pressure on Properties of ZnO：Al Films Fabricated by RF Magnetron Sputtering

Transparent conductive aluminum doped zinc oxide（ZnO：Al,AZO） films were prepared on glass substrates by rf（radio frequency） magnetron sputtering from ZnO： 3wt% Al_2O_3 ceramic target. The effect of argon gas pressure（PAr） was investigated with small variations to understand the influence on the electrical, optical and structural properties of the films. Structural examinations using X-ray diffraction（XRD） and scanning electron microscopy（SEM） showed that the ZnO：Al thin films were（002） oriented. The resistivity values were measured by four-point probe with the lowest resistivity of 5.76×10^（-4） Ω？cm（sheet resistance=9.6 Ω/sq. for a thickness=600 nm） obtained at the PAr of 0.3 Pa. The transmittance was achieved from ultravioletvisible（UV-VIS） spectrophotometer, 84% higher than that in the visible region for all AZO thin films. The properties of deposited thin films showed a significant dependence on the PAr.

Characterization of structural and electrical properties of ZnO tetrapods

ZnO tetrapods were synthesized by a typical thermal vapor-solid deposition method in a horizontal tube furnace.Structural characterization was carried out by transmission electron microscopy （TEM） and select-area electron diffraction （SAED）,which shows the presence of zinc blende nucleus in the center of tetrapods while the four branches taking hexagonal wurtzite structure.The electrical transport property of ZnO tetrapods was investigated through an in-situ nanoprobe system.The three branches of a tetrapod serve as source,drain,and ＂gate＂,respectively;while the fourth branch pointing upward works as the force trigger by vertically applying external force downward.The conductivity of each branch of ZnO-tetrapods increases 3-4 times under pressure.In such situation,the electrical current through the branches of ZnO tetrapods can be tuned by external force,and therefore a simple force sensor based on ZnO tetrapods has been demonstrated for the first time.

Effects of Scale Composition on Oxidation Kinetics of Fe-based Superalloy

By oxidation weight gain method, four groups of Fe-based superalloys with different content of chromium, aluminium and silicon were tested at 1 200 ℃ for 500 hours. According to the oxidation weight gains, the oxidation kinetic curves were plotted, and the equations were regressed by least square method and non-linear curve fitting. The effects of different scale compositions on the morphology and oxidation kinetic law were studied further by analysis of X-ray diffraction （XRD） and scanning electron microscope （SEM）. It is found that the compounded scale is composed of Cr2O3, Al2O3, SiO2 and FeCr2O4, with compact structure and fine grains, possessing complete oxidation resistance at 1 200 ℃, and the oxidation kinetic curve follows the power function of y=axb （a0, 0b1）. When the compounded scale lacks Al2O3 or SiO2, it becomes weak in oxidation resistance, but the oxidation kinetic curve still follows the power function with bigger parameter b. When Cr2O3 is absent, the kinetic curve shows two parts： the slow adding of oxidation weight gains at the beginning and the ascending line in the end. Such scale loses oxidation resistance completely.

Studies on the Absorption of NO_2 by Polyethylene Glycol and the Oxidizing Properties of the Resulting Absorbent Product

PEG (Polyethylene glycol average molecular weight 300) is used as absorbent of NO2. The absorption efficiency is found to reach up to 97%. The absorbing product, PEG NO2, can be used to cleave benzyl ethers mildly and selectively to benzaldehyde and corresponding fatty alcohols, showing that PEG is a valuable oxidizing agent of benzyl ethers. As a carrier of NO2.PEG can be recovered and utilized repeatedly after the oxidation.

Synthesis and optical properties of turquoise-and green-colored brownmilleritetype Ba_2In_(2-x-y)Mn_xAl_yO_(5+x) codoped with manganese and aluminum

Brownmillerite-type oxides Ba_2In_（2-x-y）Mn_xAl_yO_（5＋x）（0 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5） were prepared at 1300°C through solid-state reaction. X-ray diffraction（XRD） analysis showed that the structure symmetry evolved from orthorhombic to cubic with increasing Mn and Al contents. When y was greater than 0.3, peaks associated with small amounts of BaAl_2O_4 and Ba_2InAlO_5 impurities were observed in the XRD patterns. When substituted with a small amount of Mn（x ≤ 0.3）, the Ba_2In_（2-x-y）Mn_xAl_yO_（5＋x） samples exhibited an intense turquoise color. The color changed to green and dark-green with increasing Mn concentration. UV–vis absorbance spectra revealed that the color changed only slightly upon Al doping. The valence state of Mn ions in Ba_2In_（2-x-y）Mn_xAl_yO_（5＋x） was confirmed to be ＋5 on the basis of X-ray photoelectron spectroscopic analysis. According to this analysis, the intense turquoise color of the Ba_2In_（2-x-y）Mn_xAl_yO_（5＋x） samples is rooted in the existence of Mn^（5＋）; thus, the introduction of Al does not affect the optical properties of the compounds.

Structural,Morphological and Electrical Properties of In-Doped Zinc Oxide Nanostructure Thin Films Grown on p-Type Gallium Nitride by Simultaneous Radio-Frequency Direct-Current Magnetron Co-Sputtering

Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and dc magnetron co-sputtering technique. The effect of In-doping on structural, morphological and electrical properties is studied. The different dopant concentrations are accomplished by varying the direct current power of the In target while keeping the fixed radio frequency power of the ZnO target through the co-sputtering deposition technique by using argon as the sputtering gas at ambient temperature. The structural analysis confirms that all the grown thin films preferentially orientate along the c-axis with the wurtzite hexagonal crystal structure without having any kind of In oxide phases. The presenting Zn, 0 and In elements＇ chemical compositions are identified with EDX mapping analysis of the deposited thin films and the calculated M ratio has been found to decrease with the increasing In power. The surface topographies of the grown thin films are examined with the atomic force microscope technique. The obtained results reveal that the grown film roughness increases with the In power. The Hall measurements ascertain that all the grown films have n-type conductivity and also the other electrical parameters such as resistivity,mobility and carrier concentration are analyzed.

A NEW PROBE FOR IDENTIFYING PROPERTIES OF SUPPORTED METAL AND METAL OXIDE CATALYSTS

A novel molecular probe for identifying properties of supported transition metals and metal oxides catalysts was established.The catalytic mechanism of transition metals was proposed.

Configuration interaction studies on the spectroscopic properties of PbO including spin-orbit coupling

Lead oxide（Pb O）, which plays the key roles in a range of research fields, has received a great deal of attention. Owing to the large density of electronic states and heavy atom Pb including in Pb O, the excited states of the molecule have not been well studied. In this work, high level multireference configuration interaction calculations on the low-lying states of Pb O have been carried out by utilizing the relativistic effective core potential. The effects of the core-valence correlation correction, the Davidson modification, and the spin–orbital coupling on the electronic structure of the Pb O molecule are estimated. The potential energy curves of 18 Λ-S states correlated to the lowest dissociation limit（Pb（~3P_g） ＋ O（~3P_g）） are reported. The calculated spectroscopic parameters of the electronic states below 30000 cm^（-1）, for instance, X^1Σ~＋, 1~3Σ~＋,and 1~3Σ^-, and their spin–orbit coupling interaction, are compared with the experimental results, and good agreements are derived. The dipole moments of the 18 Λ-S states are computed with the configuration interaction method, and the calculated dipole moments of X^1Σ~＋and 1~3Σ~＋are consistent with the previous experimental results. The transition dipole moments from 1~1Π, 2~1Π, and 2~Σ to X^1Σ~＋and other singlet excited states are estimated. The radiative lifetime of several low-lying vibrational levels of 1~1Π, 2~1Π, and 2~1Σ~＋ states are evaluated.

Macroscopic Studies on the Properties of the Anodic Oxide Films on Titanium

The effect of fluoride ions on the formation and dissolution behaviour of anodic oxide films on Ti has been investigated in acidic fluoride media (pH=1) using impedance and galvanostatic techniques. A5 the fluoride ion concentration and temperature increase the rate of oxide film formation decreases while the dissolution process increases. oxide film formed at high tem-perature and formation voltage was found to contain more defect sites in the film than that formed at a lower one. Activation energies are calculated during the oxide film formation and dissolution and found to be 20.76 and 28.72 kJ/mol, respectively. Formation rate and reciprocal capacitance data are reported as a function of polarizing current density. Values are recorded for the electrolytic parameters A and B. Potentiostatic curves are derived from the galvanostatic results.

Apparent activation energy of mineral in open pit mine based upon the evolution of active functional groups

This study aimed to investigate the mechanism of mineral spontaneous combustion in an open pit. On the study of coal and mineral mixture in open pit mines, as well as through the specifc surface area and Search Engine Marketing (SEM) experiments, the specifc surface area and aperture characteristics of distribution of open pit coal sample and pit mineral mixture samples were analyzed. Thermal analysis experiments were used to divide the oxidation process was divided into three stages, and the thermal behavior characteristics of experimental samples were characterized. On the basis of the stage division, we explored the transfer law of the key active functional groups of the experimental samples. The apparent activation energy calculation of the key active groups, performed by combining the Achar diferential method with the Coats–Redfern integral method, microstructural and oxidation kinetic properties were revealed. The resulted showed that the mixed sample had high ash, the fxed carbon content was reduced, the specifc surface area was far lower than the raw coal, the large aperture distribution was slightly higher than the medium hole, the micropore was exceptionally low, the gas adsorption capacity was weaker than the raw coal, the pit coal sample had the exceedingly more active functional groups, easy to react with oxygen, more likely to occur naturally, and its harm was relatively large. The mixed sample contained the highest C–O–C functional group absorbance. The functional groups were mainly infuenced by the self-OH content, alkyl side chain, and fatty hydrocarbon in the sample. The main functional groups of the four-like mixture had the highest apparent activation energy, and the two reactions were higher in the low-temperature oxidation phase.

Anodic Oxidation on Structural Evolution and Tensile Properties of Polyacrylonitrile Based Carbon Fibers with Different Surface Morphology

Polyacrylonitrile （PAN） based carbon fibers with different surface morphology were electrochemically treated in 3 wt% NH4HCO3 aqueous solution with current density up to 3.47 A/m 2 at room temperature, and surface structures, surface morphology and residual mechanical properties were characterized. The crystallite size （La） of carbon fibers would be interrupted due to excessive electrochemical etching, while the crystallite spacing （d（002）） increased as increasing current density. The disordered structures on the surface of carbon fiber with rough surface increased at the initial oxidation stage and then removed by further electrochemical etching, which resulting in continuous increase of the extent of graphitization on the fiber surface. However, the electrochemical etching was beneficial to getting ordered morphology on the surface for carbon fiber with smooth surface, especially when the current density was lower than 1.77 A/m 2 . The tensile strength and tensile modulus could be improved by 17.27% and 5.75%, respectively, and was dependent of surface morphology. The decreasing density of carbon fibers probably resulted from the volume expansion of carbon fibers caused by the abundant oxygen functional groups intercalated between the adjacent graphite layers.

Effects of MgO and TiO_2 on the viscous behaviors and phase compositions of titanium-bearing slag

The effects of MgO and TiO_2 on the viscosity, activation energy for viscous flow, and break-point temperature of titanium-bearing slag were studied. The correlation between viscosity and slag structure was analyzed by Fourier transform infrared（FTIR） spectroscopy. Subsequently, main phases in the slag and their content changes were investigated by X-ray diffraction and Factsage 6.4 software package. The results show that the viscosity decreases when the MgO content increases from 10.00wt% to 14.00wt%. Moreover, the break-point temperature increases, and the activation energy for viscous flow initially increases and subsequently decreases. In addition, with increasing TiO_2 content from 5.00wt% to 9.00wt%, the viscosity decreases, and the break-point temperature and activation energy for viscous flow initially decrease and subsequently increase. FTIR analyses reveal that the polymerization degree of complex viscous units in titanium-bearing slag decreases with increasing MgO and TiO_2 contents. The mechanism of viscosity variation was elucidated. The basic phase in experimental slags is melilite. Besides, as the MgO content increases, the amount of magnesia–alumina spinel in the slag increases. Similarly, the sum of pyroxene and perovskite phases in the slag increases with increasing TiO_2 content.

Rietveld refinement,microstructure,mechanical properties and oxidation characteristics of Fe-28Mn-xAl-1C(x=10 and 12 wt.%)low-density steels

The quantitative relationship between microstructure and properties of austenitic Fe-28Mn-xAl-1C（x=10 and 12 wt.%）low-density steels was evaluated using Rietveld method to refine X-ray diffraction（XRD）patterns.The results showed that a typical three-phase austenitic steel was obtained in the forged Mn28Al10（i.e.Fe-28Mn-10Al-1C）steel,which included about 92.85 wt.% γ-Fe（Mn,Al,C）（austenite）,5.28 wt.%（Fe,Mn）_3AlC_（0.5）（κ-carbide）,and 1.87 wt.% α-Fe（Al,Mn）（ferrite）.For the forged Mn28Al12（i.e.Fe-28Mn-12Al-1C）steel,nevertheless,only about 76.64 wt.% austenite,9.63 wt.%κ-carbide,9.14 wt.%ferrite and 4.59 wt.% Fe_3Al（DO_3）could be obtained.Nanometerκ-carbide and DO_3 were mainly distributed in austenite grains and at the interface between austenite and ferrite,respectively.The forged Mn28Al10 steel had a better combination of strength,ductility and specific strength as compared with the forged Mn28Al12 steel.The ductility of the forged Mn28Al12 steel was far lower than that of the forged Mn28Al10 steel.The oxidation kinetics of Mn28Al10 steel oxidized at 1323 Kfor 5-25 h had two-stage linear rate laws,and the oxidation rate of the second stage was faster than that of the first stage.Although the oxidation kinetics of Mn28Al12 steel under this condition also had two-stage linear rate laws,the oxidation rate of the second stage was slower than that of the first stage.When the oxidation temperature increased to 1373K,the oxidation kinetics of the two steels at 5-25 hhad only onestage linear rate law,and the oxidation rates of the two steels were far faster than those at 1323K for5-25 h.The oxidation resistance of Mn28Al12 steel was much better than that of Mn28Al10 steel.Ferrite layer formed between the austenite matrix and the oxidation layer of the two Fe-Mn-Al-C steels oxidized at high temperature.