Active Stainless Steel/SnO2-CeO2 Anodes for Pollutants Oxidation Prepared by Thermal Decomposition

Stainless steel plates were successfully coated with SnO₂-CeO₂ films (SS/SnO₂-CeO₂) by brush coating with a solution of stannous chloride and cerium trichloride followed by thermal decomposition. It is proven that the properties of SnO₂ films can be evidently improved by Ce doping, and 600°C is the optimum temperature to prepare SS/SnO₂-CeO₂ anodes. The physicochemical and electrochemical properties as well as the electrocatalytic activity of the electrodes were investigated. It is found that the novel electrodes have compact microstructure, high overpotential for oxygen evolution (1.60 V vs SCE), excellent electrochemical stability, relatively low cost and excellent catalytic activity for oxidizing pollutants. An industrial dye wastewater, which is hard to be purified by using conventional chemical flocculation methods, was oxidated by employing the SS/SnO₂-CeO₂ anodes, and 83.00% of color and 48.62% of chemical oxygen demand (COD) removal was achieved under the cell voltage of 5 V within only 2 min, and the electricity consumption is only 1.83 kWh for oxidizing 1 m³ of dye wastewater.     

Investigation on MgB2 Wires Doped by ZrH2

ZrH₂-doped MgB₂ wires, with the component of Mg:ZrH₂:B= (1-x):x:2(x = 0, 5, 8, and 10%), were fabricated through thein situ powder-in-tube method by using low-carbon steel tube as the sheath material Samples were sintered at 750^{^}C for 1h in a flow of high-purity argon.The lattice parameters a and c of MgB₂exhibit a little decrease with the doping of ZrH₂.J_c(B)property of MgB₂wires are improved gradually with the increase of x, reaches the best whenx = 8%, but decreases significantlywhen x = 10%. The decrease of MgB₂grain size, the excellent grain connection, and the substitution of Zr⁴⁺for Mg²⁺which is caused by the doping of ZrH₂, are responsiblefor the enhancement of J_c(B)property forthe doped MgB₂wires. PACS: 74.70.Ad; 74.62.Dh; 74.62.Bf; 74.25.Sv     

Morphology effect on the performances of SnO2 nanorod arrays as anodes for Li-ion batteries

Ni foam suppported-SnO₂ nanorod arrays with controllable diameter were prepared via a template-free growth method, which was a convenient route for the large-scale growth of pure-phase metal oxide nanorod arrays on metal substrates. The relationship between electrochemical behavior and the shape of SnO₂ nanorod arrays has been investigated in detail. SnO₂ nanorod arrays with diameter of about 25 nm, as anode materials for Li-ion batteries revealed a capacity of 607 mAh g⁻¹ (at 0.2 C) up to 50 cycles. The superior performance of the SnO₂ nanorods can be mainly attributed to small size of nanorods which reduce volume expansion and lithium diffusion length.     

Experimental research on residual carbon of Y211 inclusions in a melt-textured Y123/Y211 composite

The inherent doping of residual carbon during the preparation of Y₂BaCuO₅ (Y211) inclusions would degrade the physical and mechanical performance of the Y₁Ba₂Cu₃O_7-x (Y123) superconducting matrix. Y211 precursor powders were prepared by the oxalate coprecipitation process in this study. Residual carbon contents of Y211 powders under different heat treatment processes were studied by the high-frequency combustion infrared absorption method. The residual carbon content of Y211 reached the current best level ～0.012% when calcined in O₂ flow at 950°C for 20?h. Y211 powders with the lowest carbon content were used to prepare a small batch of melt-textured Y123/Y211 composites. All samples were single-domain crystals without macro defects, which were usually caused by the emission of CO₂. Among them, one sample (Ø27?mm?×?14?mm) has a maximum levitation force of 71?N (77?K, 0.5?T), with critical current density J_c of 3.2?×?10⁸ A/m² (77?K, 0?T).     

Role of Brassica juncea (L.) Czern. (var. Vaibhav) in the phytoextraction of Ni from soil amended with fly ash: selection of extractant for metal bioavailability

A pot experiment was carried out to study the potential of the plant of Brassica juncea for the phytoextraction of metal from fly ash amended soil and to study correlation between different pool of metals (total, DTPA, CaCl(2) and NH(4)NO(3)) and metal accumulated in the plant in order to assess better extractant for plant available metals. The results of total metal analysis in the soil revealed the presence of Cr, which was found below detection limit (BDL) in the plants. The fly ash (FA) amendments and soil samples were extracted with different extractants and the level of metal vary from one extractant to another. The regression analysis between total and extractable metals showed better regression for all the tested metals except Mn (R(2)=0.001) in DTPA extraction. Correlation coefficient between metal accumulation by the plant tissues and different pool of metals showed better correlation with DTPA in case of Fe, Zn and Ni, whereas, Cu was significantly correlated with NH(4)NO(3) and other metals (Pb, Mn) with CaCl(2). The soil analysis results revealed that the mobility and plant availability of metals (Fe, Mn, Zn, Ni) within the profiles of amended soils was influenced by the change in pH, however, Pb and Cu was not affected. The metal accumulation in total plant tissues was found in the order of Fe>Ni>Zn>Mn>Cu>Pb and its translocation was found more in upper part. The plants grown on soil amended with 25%FA have shown significant increase in plant biomass, shoot and plant height, whereas, no significant effect was observed in root length. The cluster analysis showed 10%FA behave differently on the basis of physico-chemical properties and metal behavior. Thus, it may be concluded that B. juncea can be used for phytoextraction of metals, especially Ni in fly ash amendment soil.     

Joint between MoSi2 and 316L stainless steel surfaces and its interfacial mechanical properties

In this study, we proposed a new method using the spark plasma sintering technique to join ceramics to alloys. MoSi₂ and 316L stainless steel were chosen as sample materials and can be welded well with graded interlayers. We found that dense uniformed joints were achieved because of the comparable coefficient of thermal expansion of the interlayers. Furthermore, such a compatibility between the graded interlayers prevented MoSi₂ with low toughness from the occurrence of microcracks resulted from the residual stresses formed during cooling of the joint.     

Effects of ZnNb2O6 addition on BaTiO3 ceramics for energy storage

BaTiO₃ ceramics were prepared using solid state reaction with addition of ZnNb₂O₆, to investigate the effects of ZnNb₂O₆ addition on structure and properties. The results show that the ZnNb₂O₆ addition lowers sintering temperature, decreases grain size, while introduces second phase (Ba₂Ti₅O₁₂) for x ≥ 7.26 wt%. The dielectric breakdown strength is enhanced with the increasing doping level of ZnNb₂O₆ and reaches a maximum value at x = 7.26 wt%, exhibiting a maximum energy storage capability.     

Sol-gel derived TiO2 coating on plasma nitrided 316L stainless steel

Titania film is coated on plasma nitrided 316L stainless steel by sol-gel method. Crystallization of titania as well as N loss and formation of Fe₂O₃ occurs during the annealing heat treatment. The titania film has short cracks within the grooves of plasma etched grain boundaries. With the increase of annealing temperature and duration, surface hardness of the samples is increased, but the toughness is decreased due to oxidization of the surface layer. The coating sample heat treated at 350 °C for 10 min and 450 °C for 10 min has better corrosion resistance than the nitrided stainless steel tested by the potentiodynamic polarization in 0.9% NaCl solution. Water contact angle of the titania film on the rough nitrided steel substrate decreases with UV irradiation treatment, reaching 17° after 3 h treatment.     

Characteristics of stacked CuInS2 and CuGaS2 layers as determined by the growth sequence

CuInS₂ and CuGaS₂ thin films have been prepared sequentially from elemental evaporation sources onto conventional soda lime glass substrates heated at 350 °C during the deposition process. The gradient in the structure and composition of the stacked layers has been investigated for the two possible growth sequences. Structural depth profiling and crystallographic phase analysis were performed by grazing incidence X-ray diffraction. The atomic distribution in the films depth was analyzed by X-ray photoelectron spectroscopy combined with sputter etching. Formation of the quaternary compound CuIn_1 − xGa_xS₂, with a high Ga content x > 0.80, has been detected with different distribution depending on the growth sequence.     

Intramolecular Electron Transfers in Donor/Acceptor Linked Molecules Based on Endohedral Lanthanide Metallofullerenes

Chemical syntheses and intramolecular electron transferring behaviors in the electron donor/acceptor conjugates based on endohedral metallofullerenes, La₂@C₈₀ and La@C₈₂, are overviewed. A study on the photo-induced excited states of a La₂@C₈₀ derivative connected with an electron donor revealed the formation of a distinct radical ion pair state. A La@C₈₂ derivative linked with an electron donor demonstrated an unprecedented ion/anion pair state, and La₂@C₈₀ tethered with an acceptor showed a fullerene donor system, in which the fullerene acts as an electron donor. Using endohedral lanthanide metallofullerenes for intramolecular electron transferring systems opens a new door for developing novel molecular materials.     

Characterization of Al rich oxide layers on austenitic stainless steels by fluorescence spectroscopy

Abstract

An Al rich oxide passivation technique has been developed to improve the corrosion resistance of the stainless steel to ozone added ultra-pure water. Fluorescence spectroscopy was applied to the study on the selective oxidation of aluminum containing austenitic stainless steel in low oxygen atmosphere at 1,353K. It was found that in the thermal oxidation under low oxygen pressure, the minor alloying constitution of Al resulted in the formation of thin oxide layers. The frequency shifts of fluorescence spectra show that the compressive stresses exist in the oxide layers as a result of the difference of the thermal expansion coefficients between substrate steels and α-Al₂O₃, and depends on the thickness of the oxide layers. It is confirmed that pure α-Al₂O₃ protective layers grown on the stainless steels, which remain stable and attached to the stainless steels in ozone added ultra-pure water. These act as a diffusion barrier and protect the stainless steels from the metal dissolution.     

Effect of precursor structure on Cu(InGa)Se2 formation by reactive annealing

Precursor structures of Mo/CuGa/In, Mo/In/CuGa, Mo/In/CuGa/In and Mo/CuGaIn were prepared on thin sodium-free glass by the sputtering of CuGa and In targets. In-situ phase evolution of precursors with temperature was investigated by a high-temperature X-ray diffraction system, which verified the existence and transformation of several intermetallics: Cu₂In, Cu₁₁In₉, Cu₃Ga, Cu₇In₃, Cu₉Ga₄ and Cu₁₆In₉ as well as elemental In. MoSe₂ layers produced during selenization were detected by scanning electron microscope and X-ray diffraction, with their thicknesses varying by precursor structure. Adhesion strength of Cu(InGa)Se₂ to each Mo layer was assessed by applying CdS chemical bath deposition process to each sample.     

Fabrication and investigation of influence of CaCO3 as foaming agent on Al-SiCp foam

Closed cell aluminum foams have been used in various disciplines of engineering. Aluminum foams provide high strength with the advantage of low weight. In the current research, CaCO₃ is used as a foaming agent for producing closed-cell aluminum foams. For the fabrication of homogenous foam, optimization of process parameters was done. The effect of SiC as a thickening agent on structural property of foams viz. density and porosity have been inspected. Foams with density 0.40–0.86 g/cm³ were produced. The produced foams were studied under axial compression tests for evaluating mechanical properties. It can be inferred from the results that by adding 3 wt.% CaCO₃, the uniform viscosity of melt was achieved and a homogeneous foam structure is achieved with optimum porosity. Also, 5 wt.% addition of CaCO₃ in melt and stirring speed at 1400 rpm tend to increase porosity and decrease cell wall thickness. The optimum values for thickening agent SiC, foaming agent CaCO₃ at stirring speed 1400 rpm were found out to be 15 wt.%, 3 wt.%. The effect of relative density, the addition of thickening and foaming agent is studied.     

Characterization of Hafnium-Zirconium-Oxide-Nitride films grown by ion beam assisted deposition

Hafnium-Zirconium-Oxide-Nitride (Hf_1−xZr_xO_1−yN_y) films are prepared by ion beam assisted deposition on p-Si and quartz substrates with a composite target of sintered high-purity HfO₂ and ZrO₂. The thermal stability and microstructure characteristics for Hf_1−xZr_xO_1−yN_y films have been investigated. EDS results confirmed that nitrogen was successfully incorporated into the Hf_1−xZr_xO₂ films. XRD and Raman analyses showed that the Hf_1−xZr_xO_1−yN_y films remain amorphous after 1100 °C under vacuum ambient, and monoclinic HfO₂ and ZrO₂ crystals separate from Hf_1−xZr_xO_1−yN_y films with a increase of the annealing temperature up to 1300 °C. Meanwhile, the Hf_1−xZr_xO_1−yN_y films can also effectively suppress oxygen diffusion during high temperature annealing. AFM measurements demonstrated that surface roughness of the Hf_1−xZr_xO_1−yN_y films increase slightly. Then the optical properties of the samples were observed in the ultraviolet-visible range at room temperature. The variation in E_g from 5.64 to 6.09 eV as a function of annealing temperature has also been discussed briefly.     

Comparative analysis of crystal field effects and optical spectroscopy of six-coordinated Mn ion in the Y2Ti2O7 and Y2Sn2O7 pyrochlores

The electronic energy levels of the six-coordinated Mn⁴⁺ ion in the pyrochlores Y₂B₂O₇ (B = Sn⁴⁺, Ti⁴⁺) have been computed using the exchange charge model of crystal field theory. The calculated Mn⁴⁺ energy levels and their trigonal splitting are in good agreement with the experimental spectra. The calculated crystal field parameters show that the higher crystal field strength in Y₂Sn₂O₇ arises from an increased orbital overlap effect between the Mn⁴⁺ ion and the nearest oxygen ions, which are located at the 48f crystallographic position of the pyrochlore lattice. This increased overlap in Y₂Sn₂O₇ occurs despite the fact that the Mn⁴⁺-O²⁻ bond distance in Y₂Sn₂O₇ is longer than in Y₂Ti₂O₇ and is attributed to a lack of hybridization (covalent bonding) between the filled 2p orbital of oxygen ion occupying the 48f site of the pyrochlore lattice and the filled Sn⁴⁺ 4d¹⁰ orbital. The low temperature emission spectrum of Mn⁴⁺ activated Y₂Sn₂O₇ is analyzed in terms of a weak zero phonon line (R-line) with accompanying vibrational side bands.     

Speciation of Cr(III) and Cr(VI) in environmental samples determined by selective separation and preconcentration on silica gel chemically modified with niobium(V) oxide

In this study a new method for chromium speciation in water using solid phase extraction coupled to a flow injection system and flame atomic absorption spectrometry was developed. The adsorption behavior of Cr(III) and Cr(VI) on Nb2O5-SiO2 allowed the selective separation of Cr(III) from Cr(VI) in the pH range of 6-9. Thus, a method for Cr(III) preconcentration and extraction using Nb2O5-SiO2 was developed. Total chromium was determined after the reduction of Cr(VI) to Cr(III) using sodium sulfite in acidic medium. The operational variables of the preconcentration and reduction procedures were optimized through full factorial and Doehlert designs. The limit of detection for Cr(III) was 0.34microgL(-1) and the precision was below 4.6%. Results for recovery tests using different environmental samples were between 90 and 105%. Certified reference materials (NIST 1640 and NIST 1643e) were analyzed in order to check the accuracy of the proposed method, and the results were in agreement with the certified values.     

SiO2/TiO2 multilayer films grown on cotton fibers surface at low temperature by a novel two-step process

A novel two-step process was developed to synthesize and deposit SiO₂/TiO₂ multilayer films onto the cotton fibers. In the first step, SiO₂ particles on cotton fiber surface were synthesized via tetraethoxysilane hydrolysis in the presence of cotton fibers, in order to protect the fibers against photo-catalytic decomposition by TiO₂ nanoparticles. In the second step, the growth of TiO₂ nanoparticles into the modified cotton fiber surface was carried out via a sol-gel method at the temperature as low as 100 °C. The as-obtained SiO₂/TiO₂ multilayer films coated on cotton fibers were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy and X-ray diffraction, respectively.     

Palladium infiltration in high surface area microporous silica nanoparticles

Metallic Pd clusters were embedded into a host matrix of microporous SiO₂ nanoparticles via a solution reduction of Pd(NO₃)₂ by hydrazine hydrate. The infiltration of 33 wt.% Pd leads to a 13% porosity loss of SiO₂ nanoparticles, which demonstrated an initial surface area of 748 m²/g. The presence of Pd in the pores was demonstrated by EDS spectroscopy and by X-ray diffraction. The metallic guest species presumably reside in the accessible micropores with an estimated size about 1.3 nm. Hydrogen uptake was measured for Pd-infiltrated SiO₂ nanoparticles. A possible mechanism for the formation of composite nanoparticles is proposed based on electrostatic interaction between Pd²⁺ and SiO₂ nanoparticles.     

Novel method for doping nano TiO2 photocatalysts by chemical vapour deposition

Highly active photocatalytic Fe-doped nano TiO₂ was successfully synthesised by chemical vapour deposition (CVD) method using FeCl₃ as Fe source. CVD was carried out by evaporating FeCl₃ at 350°C in nitrogen flow during 30–90?min. The amount of Fe incorporated into TiO₂ framework is adjusted by the amount of FeCl₃ used and the evaporation time. The obtained sample was characterised by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), energy dispersive X-ray spectroscopy (EDS), UV-Vis, Fourier transform-infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activities of the samples were tested in photocatalytic decomposition of 2-propanol in liquid phase using visible light instead of UV light irradiation. Non-doped TiO₂ and high Fe loading TiO₂ samples showed very low photocatalytic activity, whereas the low Fe loading TiO₂ sample exhibited high photocatalytic activity under visible light. The high photocatalytic activity of this sample was rationalised by the existence of defects (Ti–OH groups) as the active sites.