Preparation of Nanostructured Si<Subscript>x</Subscript>N<Subscript>1−x</Subscript> Thin Films by DC Reactive Magnetron Sputtering for Tribology Applications

In this work, nanostructured silicon nitride (Si_xN_1?x) thin films were prepared by reactive magnetron sputtering using an Ar/N₂ gas mixture of 1:1. The structures and fractional compositions of the prepared samples were determined by x-ray diffraction (XRD) and electron-dispersion x-ray diffraction (EDS) patterns as functions of inter-electrode distance. They showed that the prepared films were polycrystalline and the partial amount of silicon (x) is in the range 0.825–0.865 as the inter-electrode distance was in the range 2.5–7.5 cm. The particle sizes of the prepared nanostructures were determined by field-effect scanning electron microscopy (FE-SEM) to be about 38 nm. The measured Vickers microhardness of the prepared films showed relatively high values (570-750 kg.f/mm²) and decreased with decreasing film thickness, which is inversely proportional to the inter-electrode distance. These results encourage using these nanostructures for coating of wearable tools in industrial tribology applications.     

Preparation and characterization of high-surface-area titanium dioxide by sol-gel process

One of the important ways to improve photocatalytic efficiency is to prepare catalyst with enhanced surface area. In this work, titanium dioxide (TiO₂) nanoparticles having enhanced surface area were synthesized under the interference of SiO₂. The mixed oxide, SiO₂-TiO₂ (10% mol% Si), was prepared by a sol-gel procedure using titanium tetra-n-butoxide as Ti-precursor. The commercial SiO₂ nanoparticles were added into the TiO₂ sols after hydrolysis. After condensation and calcination heat treatment, the SiO₂-TiO₂ nanoparticles were obtained. To achieve the purpose of obtaining the high-surface-area TiO₂, the SiO₂ was removed subsequently by aqueous NaOH solution. The TiO₂ products were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), electron spectroscopy for chemical analysis (ESCA), and by N₂ adsorption-desorption isotherm. A fine mesoporous structure was formed for as-prepared TiO₂ after calcination at 400^°C and the average pore diameter was about 7 nm. The porous TiO₂ products possess mixing phases of anatase and rutile. Phase transformation from anatase to rutile occurred when the samples were calcined. The phase transition temperature is sensitive to the silicon content. The particle size of ～43 nm remained constant upon calcinations from 500 to 700^°C. The specific surface area was increased up to 66% compared to regular TiO₂ samples that were prepared by the similar sol-gel procedure. The porous TiO₂ nanostructures exhibited enhanced photocatalytic performance to decompose methylene blue under UV irradiation.     

Facile preparation of electrodes based on WO3 nanostructures modified with C and S used as anode materials for Li-ion batteries

An appropriate morphological and structure matrix configuration where lithium ions could insert and de-insert is essential for lithium-ion batteries (LiB). Tungsten oxides (WO₃) are especially attractive materials for this aim. In this research, the effects of the morphology and composition of WO₃ nanostructures on the charge/discharge behavior for Li-ion batteries are methodically examined. On the one hand, nanostructured WO₃ thin film was effectively synthesized by an electrochemical procedure. Then, an annealing treatment at 600°C in air environment for 4 h was carried out. In the second electrode synthesized, a carbon layer was uniformly deposited on WO₃ nanostructures to obtain a WO₃/C electrode. Finally, WO₃/WS₂ electrodes were prepared by means of in situ sulfurization of WO₃ one-step solid-state synthesis using tungsten trioxide (WO₃) and thiourea as precursor material. By using X-ray photoelectron spectroscopy, X-ray diffraction analysis, transmission electron microscopy, Raman spectra, and field-emission scanning electron microscopy, the three electrodes have been morphologically characterized. Electrochemical properties were analyzed by cyclic voltammogram, galvanostatic charge/discharge cycling, and electrochemical impedance spectroscopy. Among all the synthesized samples, WO₃/C nanostructures reveal the best performance as they exhibit the greatest discharge capacity and cycle performance (820 mA h g⁻¹).     

A CTAB-assisted hydrothermal synthesis of VO2(B) nanostructures for lithium-ion battery application

Nanostructured VO₂(B) was synthesized via a combined hydrothermal method using V₂O₅ as a source material and oxalic acid powder as a reductant. Especially, cetyltrimethylammonium bromide (CTAB) was used as template and then three different morphologies of the VO₂(B): nanobelts, nanoflowers and nanoflakes were obtained through the change of the experimental conditions. The morphology and crystalline structure of the prepared products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Furthermore, the electrochemical charge–discharge cycling properties of the VO₂(B) nanostructures in lithium-ion battery were investigated. The results indicated that the belt-like, flower-like and flake-like VO₂(B) nanostructures have the initial specific discharge capacity of 205.2, 254.0 and 56.0 mA h g⁻¹, and that the morphology of VO₂(B) nanostructures can deeply affect the service performance of batteries. According to the experiments, this CTAB-assisted hydrothermal method provides an insight into the preparation and application of nanostructured VO₂(B) as cathode material in lithium-ion battery.     

Nanocarbon production by arc discharge in water

Carbon nanostructures (onions, nanotubes and encapsulates) were generated by arc discharge in water between pure and catalyst-doped graphite electrodes. These structures were of fine quality and crystalline morphology, similar to those formed in He arc plasma. Emission spectroscopy was performed to assess the plasma components (H, O, C and C₂) and temperature values. C₂ radicals were determined quantitatively, between 10¹⁵ and 10¹⁶ cm⁻² depending on graphite anode composition.The temperature was between 4000 and 6500 K.     

V<Subscript>2</Subscript><Emphasis Type="Italic">O</Emphasis><Subscript>5</Subscript>/SiO<Subscript>2</Subscript> as a Heterogeneous Catalyst in the Synthesis of bis(indolyl)methanes Under Solvent Free Condition

The heterogeneous catalyst of V₂ O ₅/SiO₂ was prepared and characterized with Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy. XRD of the silicon dioxide used reveals the amorphous nature while the spectrum of the prepared catalyst shows sharp intense peaks at about (20.2, 26.1, 31.0 and 47.3^°) and less intense sharp peaks at about (51.1, 55.2, 57.1 and 60.4^°) indicating formation of a crystalline phase with orthorhombic geometry. The FTIR spectra of the catalyst showed characteristic vibration stretching bands of V ?O at their specified position. An efficient and facile approach for the synthesis of bis(indolyl)methanes through a catalytic one pot reaction. Indole and aromatic aldehydes were stirred in the presence of a catalytic amount of the prepared and characterized heterogeneous catalyst V₂ O ₅/SiO₂ at 50^°C under solvent free condition. This procedure has advantages in competition with the previously reported methods, in terms of high yield, green catalyst, mild reaction condition, simple procedure, lack of toxicity, low cost, and simplicity of workup.     

Preparation of carboxy sulfonic acid-containing copolymer scale inhibitors and their scale inhibition effect on CaCO3

Free radical polymerization was selected to obtain a promising copolymer scale inhibitor IA-AM-SAS with good water solubility and temperature and salt resistance, which is suitable for the treatment of surface pipeline water in oil fields, using itaconic acid (IA), acrylamide (AM), and sodium acrylsulfonate (SAS) as the monomers. The structure of the synthesized copolymer was verified by Fourier transform infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy. Thermogravimetric results showed that the copolymer does not undergo significant thermal degradation at temperatures below 356°C, indicating that the copolymer has good thermal stability. The molecular weights of the polymers at different monomer ratios were measured using gel permeation chromatography and the relationship between the molecular weights and scale inhibition performance was discussed. The results showed that the scale inhibition effect was best when the monomer molar ratio n(IA): n(AM): n(SAS) was 0.5:2:1.5 and the number of average molecular weight of the prepared copolymer was 7712 g/mol, and the inhibition efficiency of CaCO₃ was 84.02% when IA-AM-SAS was at a concentration of 30 mg L⁻¹, and the inhibition rate was measured by the standard of static scale inhibition test in the oilfield measured. The range of conditions (PH, Ca²⁺ concentration, water temperature, and time) of the static scale inhibition test was then expanded using a one-way controlled variable experiment to explore the performance of IA-AM-SAS scale inhibitors under different water quality conditions. The scale inhibition mechanism was explored by scanning electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. Briefly, the combination of multiple functional groups enables IA-AM-SAS to be applied in complex and challenging environments.     

MnOx/CeO2 catalysts for the low-temperature selective catalytic reduction of NO with NH3

CeO₂–nanorod support was synthesized by hydrothermal method and different manganese oxides (MnO, MnO_2, and Mn₂O₃) were impregnated over support by the wet-impregnation forming MnO/CeO₂-NR, MnO₂/CeO₂-NRm and Mn₂O₃/CeO₂-NR. The physico-chemical properties of the as-prepared catalysts were analyzed using x-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscope–energy-dispersive x-ray spectroscopy (SEM–EDX), hydrogen-temperature-programmed reduction (H₂-TPR), and Raman spectroscopy. These catalysts were further analyzed for NO reduction using NH₃ as a reducing gas in the temperature range of 50 to 450°C. The results confirmed that MnO₂/CeO₂-NR gave the maximum NO conversion (65%) and N₂ selectivity (89%) among all catalysts. Further, MnO₂/CeO₂-NR catalyst was studied for the effect of MnO₂ loading and more than 90% NO conversion and N₂ selectivity were obtained in the temperature range of 250 to 300°C.     

Novel simple solvent-less preparation,characterization and degradation of the cationic dye over holmium oxide ceramic nanostructures

Pure holmium oxide ceramic nanostructures were prepared via a new simple approach. Nanostructures were synthesized by heat treatment in air at 600 °C for 5 h, utilizing [Ho L(NO₃)₂]NO₃ (L=bis-(2-hydroxy-1-naphthaldehyde)-butanediamine Schiff base ligand), as precursor, which was prepared via a solvent-free solid–solid reaction from different molar ratios of holmium nitrate and Schiff base ligand. The as-prepared nanostructures were characterized by field emission scanning electron microscopy (FESEM), thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), energy dispersive X-ray microanalysis (EDX), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. It was found that the calcination temperature and molar ratio of holmium nitrate and Schiff base ligand have significant and key effect on the morphology and particle size of the holmium oxide. To investigate the catalytic properties of as-obtained holmium oxide nanostructures, the photocatalytic degradation of rhodamine B as cationic dye under ultraviolet light irradiation was performed.     

Design and Properties of New Lead-Free Solder Joints Using Sn-3.5Ag-Cu Solder

This article aims to reduce the melting temperature of lead-free solder alloy and promote its mechanical properties. Eutectic tin-silver lead-free solder has a high melting temperature 221 ^°C used for electronic component soldering. This melting temperature, higher than that of lead–tin conventional eutectic solder, is about 183 ^°C. The effect of the melt spinning process and copper additions into eutectic Sn-Ag solder enhances the crystallite size to about 47.92 nm which leads to a decrease in the melting point to about 214.70 ^°C, where the reflow process for low heat-resistant components on print circuit boards needs lower melting point solder. The results showed the presence of intermetallic compound Ag₃Sn formed in nano-scale at the Sn-3.5Ag alloy due to short time solidification. The presence of new intermetallic compound, IMC from Ag_0.8Sn_0.2 and Ag phase improves the mechanical properties, and then enhances the micro-creep resistance especially at Sn-3.5Ag-0.7Cu. The higher Young’s modulus of Sn-3.5Ag-0.5Cu alloy 55.356 GPa could be attributed to uniform distribution of eutectic phases. Disappearance of tin whiskers in most of the lead-free melt-spun alloys indicates reduction of the internal stresses. The stress exponent (n) values for all prepared alloys were from 4.6 to 5.9, this indicates to climb deformation mechanism. We recommend that the Sn_95.7-Ag_3.5-Cu_0.7 alloy has suitable mechanical properties, low internal friction 0.069, low pasty range 21.7 ^°C and low melting point 214.70 ^°C suitable for step soldering applications.     

Effects of crystallization and dopant concentration on the emission behavior of TiO2:Eu nanophosphors

Uniform, spherical-shaped TiO₂:Eu nanoparticles with different doping concentrations have been synthesized through controlled hydrolysis of titanium tetrabutoxide under appropriate pH and temperature in the presence of EuCl₃·6H₂O. Through air annealing at 500°C for 2 h, the amorphous, as-grown nanoparticles could be converted to a pure anatase phase. The morphology, structural, and optical properties of the annealed nanostructures were studied using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy [EDS], and UV-Visible diffuse reflectance spectroscopy techniques. Optoelectronic behaviors of the nanostructures were studied using micro-Raman and photoluminescence [PL] spectroscopies at room temperature. EDS results confirmed a systematic increase of Eu content in the as-prepared samples with the increase of nominal europium content in the reaction solution. With the increasing dopant concentration, crystallinity and crystallite size of the titania particles decreased gradually. Incorporation of europium in the titania particles induced a structural deformation and a blueshift of their absorption edge. While the room-temperature PL emission of the as-grown samples is dominated by the ⁵D₀ - ⁷F _j transition of Eu⁺³ ions, the emission intensity reduced drastically after thermal annealing due to outwards segregation of dopant ions.     

Synthesis of flake-like bismuth tungstate (Bi2WO6) for photocatalytic degradation of coomassie brilliant blue (CBB)

Bismuth tungstate (Bi₂WO₆) flake-like nanostructures with zigzag periphery and 30–40 nm thickness in high yield were produced by facile and efficient modified hydrothermal technique. The as-synthesized nanostructures were characterized by X-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Bi₂WO₆ nanostructures were investigated as visible light photocatalyst to degrade model dye coomassie brilliant blue (CBB). The role of hydrogen peroxide (H₂O₂) used as initiator was also studied by varying concentrations during photocatalysis. It was observed that photocatalytic activity significantly enhanced for lower initiator concentrations. The growth mechanism for nanostructures was also discussed briefly.     

Controllable synthesis of micronano-structured LiMnPO4/C cathode with hierarchical spindle for lithium ion batteries

LiMnPO₄/C with hierarchical spindle structures was synthesized by a facile solvothermal method at 180?℃ for 10?h. The morphology and structure of the prepared materials were controlled through the adjustment of hexamethylenetetramine (HMT). The synthesized materials were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Quantachrome instrument(Quabrasorb SI-3MP) and Fourier transform infrared spectroscopy (FTIR), and so on. The prepared LiMnPO₄/C exhibits good electrochemical performance, for instance, there are 153.2, 126.3, 110.2?mA?h?g^?1 at 0.05?C, 1?C, 2?C respectively. The promising properties of the materials results from unique hierarchical nanostructures and the uniform thin carbon coating of particle surface, which improve the ionic and electronic transfer of LiMnPO₄.     

Electrochemical preparation and properties of nanostructured Co3O4 as supercapacitor material

Nanostructured Co₃O₄ was prepared via a simple two-step process: cathodic electrodeposition of cobalt hydroxide from additive free nitrate bath and then heat treatment at 400 °C for 3 h. The prepared oxide product was characterized by powder X-ray diffraction, infrared spectroscopy, surface area measurement, scanning electron microscopy, and transmission electron microscopy. Morphological characterization showed that the oxide product was composed of porous nanoplates, and BET measurement displayed that the oxide plates have the average pore diameter and the surface area of 4.75 nm and 208.5 m² g⁻¹, respectively. The supercapacitive performance of the nanoplates was evaluated using cyclic voltammetry and charge–discharge tests. A specific capacitance as high as 393.6 F g⁻¹ at the constant current density of 1 A g⁻¹ and an excellent capacity retention (96.5% after 500 charge–discharge cycles) was obtained. These results indicate that Co₃O₄ nanoplates can be recognized as high-performance electrode materials.     

A new simple route for the preparation of nanosized copper selenides under different conditions

In this paper copper selenide nanostructures were synthesized via a simple hydrothermal method based on the reaction between copper salt and SeCl₄ in water. The reduction reaction of SeCl₄ to Se and then Se²⁻ was carried out by three types of reductants: N₂H₄.H₂O, KBH₄, and metallic Zn. Different compositions of copper selenides were obtained by changing the molar ratio of the precursors. At the temperature of 120 °C for a 12 h period of time, when the molar ratio of Cu/Se is 1:1 or 2:1, the product is pure and found to be CuSe and Cu_1.8Se, respectively. A mixture of the different phases of copper selenides is obtained by making use of 1:2, 3:2 and 3:1 M ratios between Cu and Se. With an increasing reaction temperature up to 210 °C, the mixture of Cu₃Se₂ and CuSe is prepared from 1:1 M ratio of precursors. The effects of copper salt, surfactant, amount of hydrazine, reaction time and temperature on the morphology and particle size of products are also investigated. The synthesis can be performed conveniently and safely. The products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) analysis. Photoluminescence (PL) is used to study the optical property of copper selenides.     

Influence of Zn-substitution on structural,morphological, electrical,and gas sensing properties of ZnxAl2O4 (x = 0.1 to 0.5) synthesized by a sol-gel auto-combustion method

The nanosphere decorated needle-like morphology of zinc-substituted aluminate having general formula Zn_xAl₂O₄ (x = 0.1, 0.2, 0.3, 0.4, and 0.5) (ZAN) samples were synthesized by a sol-gel auto-combustion method. The phase formation and stability temperature were confirmed by TG-DTA analysis. XRD study confirmed the formation of a cubic spinel structure of ZAN samples. The effect of Zn-substitution on structural and morphological properties of aluminate were investigated using X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), Field emission scanning electron microscopy (FESEM), and Energy dispersive X-ray analysis (EDAX). The D.C. electrical resistivity study of ZAN samples revealed that resistance decreased with increasing temperature confirmed semiconducting nature. Nanosphere existing on micro-needles of zinc-substituted aluminate gas sensor revealed sensing to several analyte gases such as H₂S, Cl₂, CH₃OH, SO₂, and NO₂ working at room temperature to 300 ^°C. The Zn_0·4Al₂O₄ compositional gas sensor produced the highest response at operating temperature 200 ^°C to 100 ppm H₂S. The results revealed that the prepared nanosphere decorated needles of the ZAN sensor was sensitive and selective to H₂S gas.     

Mesoporous copper–cerium–oxygen hybrid nanostructures for low temperature catalytic oxidation of carbon monoxide

Mesoporous copper–cerium–oxygen hybrid nanostructures were prepared by one-pot cetyltrimethylammonium bromide surfactant-assisted method, and were characterized by thermogravimetry, X-ray diffraction, transmission electron microscopy, nitrogen adsorption–desorption, X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. Low temperature carbon monoxide oxidation was used as probe reaction to investigate the application of the prepared mesoporous copper–cerium–oxygen hybrid nanostructures in catalysis. The product calcined at 400 °C, with disordered wormlike mesoporous structure, high specific surface area (SSA) of 117.4 m²/g and small catalyst particle size of 8.3 nm, shows high catalytic activity with the 100 % CO conversion at 110 °C, indicating its potential application in catalysis. Catalytic activity results from the samples calcinied at different temperature suggested that high SSA, small catalyst particle size, finely dispersed CuO species and synergistic effect between CuO and CeO₂ were responsible for the high catalytic activity of the catalysts.     

Structural characterization and electrochemical properties of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> anode materials synthesized by a hydrothermal method

Cobalt oxide [Co₃O₄] anode materials were synthesized by a simple hydrothermal process, and the reaction conditions were optimized to provide good electrochemical properties. The effect of various synthetic reaction and heat treatment conditions on the structure and electrochemical properties of Co₃O₄ powder was also studied. Physical characterizations of Co₃O₄ are investigated by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller [BET] method. The BET surface area decreased with values at 131.8 m²/g, 76.1 m²/g, and 55.2 m²/g with the increasing calcination temperature at 200°C, 300°C, and 400°C, respectively. The Co₃O₄ particle calcinated at 200°C for 3 h has a higher surface area and uniform particle size distribution which may result in better sites to accommodate Li⁺ and electrical contact and to give a good electrochemical property. The cell composed of Super P as a carbon conductor shows better electrochemical properties than that composed of acetylene black. Among the samples prepared under different reaction conditions, Co₃O₄ prepared at 200°C for 10 h showed a better cycling performance than the other samples. It gave an initial discharge capacity of 1,330 mAh/g, decreased to 779 mAh/g after 10 cycles, and then showed a steady discharge capacity of 606 mAh/g after 60 cycles.     

Removal of Boron from Molten Si and Si-Cu Using Ammonia Containing Gas

All the reported thermodynamics analysis implied that ammonia is a promising reagent for removing boron from silicon, but efforts to employ it in silicon refining have failed in practice. As such, there are few reports detailing this process. In this study, this process was analyzed experimentally. Various concentrations of ammonia were introduced to remove boron from silicon in the temperature range of 1200–1550 ^°C with a total pressure of 1 atm. Boron containing nitrides precipitates were detected in the furnace tube. The effect of ammonia content in the feeding gas was explored. It implied that higher ammonia partial pressures promote the boron removal. The experimental results have suggested that ammonia could remove boron from silicon in the form of volatiles, such as BH_x (x = 1, 2, 3) and B₃ H ₆ N ₃, in practice. The reaction-rate constant was limited to 10^?6– 10^?7 m/s in pure ammonia at 1450 ^°C. Moreover, a higher ammonia flow rate resulted in lower boron removal ratio. It was indicated that the rate determining steps of boron removal and silicon loss in this process were the chemical reaction at the surface of the melt and the transport of ammonia from gas phase to the surface, respectively. The relationship of the boron-removal rate with temperature followed a “V”-shaped curve, which implied the limit of thermodynamic factors at high temperature and the limit of kinetic factors at temperatures lower than 1300 ^°C. Based on the analysis results, temperature-programed reaction was designed to promote the boron-removal efficiency doubled. Cu was used to decrease the liquidus temperature of Si based alloy in the process. As a result, more than 80% boron in Si-Cu alloy could be removed.     

Effect of Cu and Zr Co-doped SiO<Subscript>2</Subscript> Nanoparticles on the Stability of Phases (Quartz-Tridymite-Cristobalite) and Degradation of Methyl Orange at High Temperature

SiO₂ nanoparticles doped by 10 mol% Zr and 10 mol% Cu were prepared via the sol-gel method in a controled process. The effects of doping and calcination temperature on the structural and photo-catalytic properties of SiO₂ nanopowders were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis absorption spectroscopy. The phases of cristobalite, quartz and tridymite were found at a calcinations temperature range of 800 to 1000 ^°C and only cristobalite phase was formed at a temperature of 1200 ^°C. The degradation of methyl orange was examined under visible light radiation indicating that the effect of doped elements (Zr, Cu) on SiO₂ reduces the band gap effectively.