Porous TiO2 nanowire microsphere constructed by spray drying and its electrochemical lithium storage properties

Porous TiO₂ nanowire microspheres with greatly decreasing agglomeration were successfully prepared by spray drying of hydrothermal reaction suspension, followed by calcination at 350°C. The as‐obtained nanowire microspheres with TiO₂‐B structure reach an initial discharge capacity 210 mAh g^?1 with an irreversible capacity 25 mAh g^?1 at a current density of 20 mA g^?1. For the 450°C‐calcined one with anatase TiO₂ crystal structure, the initial discharge capacity is 245 mAh g^?1 but with a much higher irreversible capacity of 80 mAh g^?1. The hierarchical porous structure in the 350°C‐calcined TiO₂ nanowire microspheres collapsed at 450°C, annihilating the main benefit of nanostructuring. Microsc. Res. Tech. 77:170–175, 2014. © 2013 Wiley Periodicals, Inc.     

One-step preparation and characterization of zinc tungstate–carbon nanoparticles with application to lithium-ion batteries

Zinc tungstate–carbon nanoparticles were synthesized by a one-step hydrothermal process followed by heat treatment. X-ray diffraction results indicated that the addition of glucose prevented grain growth of zinc tungstate during the hydrothermal process and subsequent heat treatment. Transmission electron microscopy images showed that the zinc tungstate nanoparticles were coated by carbon with a thickness of 1 nm following heat treatment at 550°C and a diameter of 10 nm with a homogeneous morphology. Electrochemical measurements showed that the zinc tungstate–carbon nanoparticles reached an initial discharge capacity of 990 mAh g^?1 at a current density of 50 mA. g^?1. The specific capacity of the zinc tungstate-carbon nanoparticles was maintained at approximately 400 mAh g^?1 after 50 cycles, exhibiting better stability than pure zinc tungstate due to the carbon coating providing high conductivity with the zinc tungstate nanoparticle.     

Adsorption properties of aqueous methylene blue on mesocellular foam silica: Equilibrium,kinetic, isotherm,and thermodynamic characterization

Abstract

Mesocellular foam silica was prepared by a hydrothermal synthesis protocol. The surface and pore structure of mesocellular foam silica were characterized by low temperature nitrogen adsorption isotherms, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared (FT-IR) spectroscopy. The methylene blue was adsorbed by the synthetic mesocellular foam silica; the optimized adsorption conditions were evaluated and the maximum adsorption capacity of methylene blue by mesocellular foam silica was determined to be 215.5?mg g^?1. The kinetics of the adsorption of methylene blue by mesocellular foam silica were in accordance with a quasi-second-order kinetic equation. The results were analyzed by Langmuir and Freundlich adsorption isotherm models. The adsorption of methylene blue on mesocellular foam silica was shown to follow the Freundlich adsorption isotherm model. The Gibbs free energy change during adsorption showed that this process was spontaneous. The enthalpy change in the process was –28.868?J·mol^?1 K^?1, indicating that the adsorption is exothermic. The negative value of entropy –49.296?J·mol^?1 K^-1 shows that the system disorder decreases due to adsorption.     

Friction and Wear Behaviors of Ag/MoS2/G Composite in Different Atmospheres and at Different Temperatures

Silver-based composite with 15?vol% MoS₂ and with 5?vol% graphite was prepared by powder metallurgy method. The impacts of the counterface materials, atmosphere, and temperature on the tribological behavior of the composite were investigated. It was found that when sliding against brass less effective lubricating film formed, causing a higher friction and wear comparing with ASTM-1045 steel. With the increasing proportion of oxygen in the O₂/N₂ atmosphere, the wear rate and friction coefficient ascended slightly. At 200?°C, the combination lubrication of graphite, MoS₂, and Ag contributed to a low friction coefficient (0.07) and wear rate (6.56?×?10^?6?mm³/Nm). At 400?°C, graphite lost its lubricating role, while silver became excessively soft. Large amount of MoS₂ was oxidized into MoO_3, and the residual MoS₂ formed some island-like lubricating films. Severe adhesive wear occurred on the contact surface, which led to a high friction coefficient (0.25) and a great increase of the wear rate (23.2?×?10^?6?mm³/Nm). At 600?°C, a relatively low friction coefficient (0.1) was obtained because of the formation of high-temperature solid lubricants, (Ag₂Mo₄O₁₃ and Ag₂Mo₂O₇) and liquid Ag₂Mo₂O₇. However, the wear rate at 600?°C was the highest (32.6?×?10^?6?mm³/Nm) due to the thick transfer layer.     

Experimental ionization cross-sections of phosphorus and calcium by electron spectroscopic imaging

The absolute partial electron scattering cross-section for the phosphorus L_2,3-shell ionization was measured by electron spectroscopic imaging using poliovirus as a primary standard. The equivalent calcium cross-section was obtained in relation to phosphorus using the stoichiometric ratio for these two elements in hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂. At 80kcV, the partial cross-section of phosphorus was 2.26 times 10^?20 and 2.68 × 10^?20cm²/atom for poliovirus and hydroxyapatite, respectively, at 150eV loss for a 15-cV energy window and an acceptance angle of 15 mrad. Under the same conditions the calcium cross-section was 0.49 × 10^?20 cm²/atom at 360 eV loss. The experimental values are slightly higher than the theoretical cross-sections calculated either by hydrogenic or Hartree—Slater approaches.     

Devolatilization kinetics of olive leaves with application as a precursor for activated carbon production

The objectives of the study were to investigate the devolatilization kinetics of olive leaves and their utilization as precursors for activated carbon. The devolatilization process was performed using thermogravimetric analysis under nitrogen at heating rates of 10, 15, and 20°C min^?1 with kinetic evaluation by the Coats-Redfern and Horowitz-Metzger methods. Potassium hydroxide activated olive leaves were employed as precursors for the production of activated carbon at 700°C for 60?min. Brunauer–Emmett–Teller and infrared spectroscopy were used for the characterization of texture and chemical properties of activated carbon. The adsorption capacity of fabricated active carbon with 1422?m² g^?1 surface area for methyl orange was characterized and data fitted well with a Langmuir model (R²?=?0.9977). The monolayer adsorption capacity of the activated carbon on methyl orange was 714.86?mg?g^?1 and the kinetics followed a pseudo-second-order model.     

Resonance Rayleigh Scattering of K2Zn3[Fe(CN)6]2 Nanoparticles and its Application for the Determination of Vitamin C

Abstract

In Britton-Robinson buffer medium, (pH 4.43), potassium ferricyanide (K₃[Fe(CN)₆]) could react with vitamin C (VC) to produce potassium ferrocyanide (K₄[Fe(CN)₆]), which further reacted with Zn²⁺ to form potassium zinc hexacyanoferate K₂Zn₃[Fe(CN)₆]₂ nanoparticles. The shapes and diameters of the K₂Zn₃[Fe(CN)₆]₂ nanoparticles have been observed with transmission electron microscopy, which showed the shapes of these nanoparticles was cubic and their average sizes were about 50 nm in the presence of 2.0 × 10^?5 mol L^?1 VC. The characteristics of resonance Rayleigh scattering (RRS) spectra of this reaction have been studied. The optimum reaction condition for the determination of VC has been investigated. It was found that the RRS intensity of the system at the RRS peak of 363.4 nm was proportional to the VC concentration in the range of 4.0?80.0 µmol L^?1, and the detection limit (3σ) for VC was 0.075 µmol L^?1. A novel and simple RRS method for the determination of VC based on the formation of K₂Zn₃[Fe(CN)₆]₂ nanoparticles has been established.     

Electron and light microscopy studies on the domain structures of Zn3B7O13Cl, Zn3B7O13Br and Zn3B7O13I ferroic boracites

The domain structures of Zn₃B₇O₁₃Cl, Zn₃B₇O₁₃Br and Zn₃B₇O₁₃I boracite single crystals were studied by means of polarized light in conjunction with electron microscopy. Single crystals of the three compositions were grown by chemical transport reactions in closed quartz ampoules, at a temperature of 900 °C and were examined by polarizing optical microscopy (PLM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For both PLM and SEM, the same as‐grown samples were used without having to resort to metallization of the crystal faces. For TEM the single crystals were crushed and mounted on holey carbon films. Comparative electron microscope images were useful for revealing the domain structure of these ferroelectric/ferroelastic materials previously observed between the crossed polars of an optical microscope. X‐ray diffraction analysis of the pulverized crystals was performed for this triad of halogen boracites containing zinc as a common metal.     

Independent trafficking of flavocytochrome b558 and myeloperoxidase to phagosomes during phagocytosis visualised by energy‐filtering and energy‐dispersive spectroscopy‐scanning transmission electron microscopy

When polymorphonuclear leukocytes (PMNs) phagocytose opsonised zymosan particles (OPZ), free radicals and reactive oxygen species (ROS) are formed in the phagosomes. ROS production is mediated by NADPH oxidase (Nox), which transfers electrons in converting oxygen to superoxide (O₂^?). Nox‐generated O₂^? is rapidly converted to other ROS. Free radical‐forming secretory vesicles containing the Nox redox center flavocytochrome b558, a membrane protein, and azurophil granules with packaged myeloperoxidase (MPO) have been described. Presuming the probable fusion of these vesicular and granular organelles with phagosomes, the translation process of the enzymes was investigated using energy‐filtering and energy‐dispersive spectroscopy‐scanning transmission electron microscopy. In this work, the primary method for imaging cerium (Ce) ions demonstrated the localisation of H₂O₂ generated by phagocytosing PMNs. The MPO activity of the same PMNs was continuously monitored using 0.1% 3,3′‐diaminobenzidine‐tetrahydrochloride (DAB) and 0.01% H₂O₂. A detailed view of these vesicular and granular structures was created by overlaying each electron micrograph with pseudocolors: blue for Ce and green for nitrogen (N).     

Determination of propyl gallate in edible oil by high-performance liquid chromatography with chemiluminescence detection

A novel and convenient method based on high-performance liquid chromatography coupled with chemiluminescence (HPLC) for the determination of propyl gallate in edible oil is reported. The detection was based on the inhibition of chemiluminescence between luminol and hydrogen peroxide in alkaline solution. The analysis was performed using a C₁₈ column with isocratic 60:40 methanol/water. Under the optimum conditions, the concentration of propyl gallate was linear from 9?×?10^?6?mol?L^?1 to 1?×?10^?4?mol?L^?1 with a detection limit of 2?×?10^?7?mol?L^?1. The method is simple, sensitive, and inexpensive and was used for the determination of propyl gallate in edible oil.     

Determination of uranium in Egyptian graniteic ore by gamma,alpha, and mass spectrometry

Three methods were employed for the determination of uranium in granitic ore rock samples. Gamma spectrometry is a non-destructive technique while alpha spectrometry and inductively coupled plasma–mass spectrometry (ICP-MS) are destructive methods needing application of radiochemical separation before uranium measurement. In gamma spectrometry, the activity concentration of uranium is measured via its daughter (^234mPa) in the decay series, while in alpha spectrometry and inductively coupled plasma mass spectrometry (ICP-MS), the activity concentration of uranium is measured directly. The activity concentrations of uranium in the samples by gamma spectrometry were between 36.7?±?0.5 and 239?±?2.3?Bq g^?1. The activity concentrations of uranium by alpha spectrometry and ICP-MS were from 28.7?±?1 to 145?±?1?Bq g^?1 and 34.3?±?1.4 to 155.9?±?1.6?Bq g^?1, respectively. The ICP-MS and alpha spectrometry methods provided reliable results. The uranium concentrations obtained by gamma spectrometry were, however, systematically too high.     

Determination of magnetic field using a Fabry–Perot cavity containing novel nanoparticles

Mn_0.75Zn_0.25Fe₂O₄ nanoparticles were used to characterize magnetic fields using an all-fiber Fabry–Perot interferometer. The 20-nm nanoparticles were fabricated with citrate and displayed a coercive field of approximately 10?mT. The nanoparticles were dispersed in oleic acid to prepare a magnetic fluid to fill a Fabry–Perot structure fabricated by arc splicing with conventional single-mode and hollow core photonic crystal fibers. This device provided sensitivity and resolution of 0.11?dB/mT and 0.09?mT, respectively. Thermal analysis indicated that the magnetic measurements are weakly depending on temperature (0.7?pm/°C and 7?×?10^?3?dB/°C). This device offers low-cost fabrication, simple implementation and may be used in several industrial applications.     

Electrochemical determination of hydrogen peroxide using a novel prussian blue–polythiophene–graphene oxide membrane-modified glassy carbon electrode

A polythiophene–graphene oxide compound membrane and Prussian blue were deposited sequentially on the surface of a glassy carbon electrode by cyclic voltammetry. Due to its excellent electrocatalysis and its analogy with peroxidase enzymes, Prussian blue has been widely used in amperometric biosensors. The polythiophene–graphene oxide compound membrane exhibited good electroconductibility and a large specific surface area. The fabricated Prussian blue/polythiophene/graphene oxide/glassy carbon electrode was characterized by transmission electron microscopy, scanning electron microscopy, and cyclic voltammetry. Under the optimal experimental conditions, the detection of hydrogen peroxide was studied by its amperometric current–time curve. Due to the presence of polythiophene–graphene oxide compound membrane and Prussian blue, the hydrogen peroxide sensor shows a linear calibration range of 1.0?×?10^?6–1.0?×?10^?4?mol?L^?1, detection limits of 3.2?×?10^?7?mol?L^?1 at a signal-to-noise ratio of 3, and recoveries from 95.0 to 105.0%. The results show that the modified glassy carbon electrode has potential practical application for the determination of hydrogen peroxide based on its sensitivity and long-term stability.     

XPS study of CMP mechanisms of NiP coating for hard disk drive substrates

Chemical mechanical polishing (CMP) mechanisms of NiP coating plated on Al-Mg alloy substrates have been investigated with an X-ray photoelectron spectroscope (XPS). The XPS results indicate that after cleaning, the disk surface contains a thin layer of Ni(OH)₂ and P₂O₃, followed by a thin NiO and P₂O₃ layer. It is also deduced that during polishing, the disk surface has an oxidization layer with Ni²⁺ and P³⁺ species. The experimental investigations reveal that the CMP mechanisms involve a simultaneous process of surface chemical passivation and nano-particle wear.     

Tribochemical synthesis of zinc ferrite

A comparative tribochemical study of zinc ferrite synthesis from -FeOOH + 2ZnCO₃·3Zn(OH)₂ and -FeOOH + 2ZnCO₃·3Zn(OH)₂ was carried out. It was found that the end product of tribochemical activation is thermally unstable, partially inverse, zinc ferrite, (Zn_0.74Fe_0.26)_tetra[Fe_1.74Zn_0.26]_octaO₄. The synthesis kinetics is rate-limited by the tribochemical dehydration of the two polymorphous forms of Fe(III) oxyhydroxides and is considerably higher for the -FeOOH + 2ZnCU₃ · 3Zn(OH)₂ system.     

Effect of the Synergetic Action on Tribological Characteristics of Ni-Based Composites Containing Multiple-Lubricants

Ni-based self-lubricating composites with multiple-lubricants addition were prepared by a powder metallurgy technique, and the effect of multiple-lubricants on tribological properties was investigated from room temperature to 700?°C. The synergetic effects of graphite, MoS₂, and metallic silver lubricants on the tribological characteristics of composites were analyzed. XRD analysis showed that new Cr _x S _y and Mo₂C phase were formed in the composites containing graphite, MoS₂ and metallic Ag lubricants during the sintering process. The average friction coefficients (0.69?C0.22) and wear rates (11.90?C0.09?×?10^?5?mm³?N^?1?m^?1) were obtained when rubbing against Inconel 718 alloy from room temperature to 700?°C due to synergetic lubricating action of multiple-lubricants. A smooth lubricating was gradually generated on the worn surface, and the improving of tribological properties was attributed to the formation of lubricious glaze film on the worn surface and their partially transferred to the counterface. The graphite played the main role of lubrication at room temperature, while molybdate phase and graphite were responsible for low friction coefficients and wear rates at mid/high temperatures. The synergetic lubricating effect of molybdate (produced in the rubbing process at high temperatures) iron oxide (transfer from disk material to the pin) and remaining graphite multiple-lubricants play an important lubricating role during friction tests at a wide temperature range.     

Effects of Fluid Film Pressure on Hydrodynamic Lubrication

The effect of pressure upon hydrodynamic lubrication is reflected by the variation of the density and viscosity of the lubricant.

Proceeding from the function that relates density to pressure in the case of liquids, the author obtains the generalized differential equation of a variable π upon which pressure distribution, as well as other characteristics, depends. This equation is integrated in the case of two-dimensional motion; as an application, the problem of plane surfaces and constant viscosity is discussed and it is shown that parameter K ? 6Vμ₁l/βh₂ ²(h¹/h₂? 1) has an important influence.

For circular cylindrical surfaces, the density depends on an integral expression the solution of which is obtained by means of conventional graphical and numerical computations.

By admitting finally that the viscosity also varies with pressure, a general method is given for solving the two-dimensional problem.     

Effect of rotary instrument associated with different irrigation techniques on removing calcium hydroxide dressing

Calcium hydroxide [Ca(OH)₂] residues in root canals may compromise sealing of filling and endodontic treatment success. The aim of this study was to compare the efficacy of using rotary instrument associated with EndoActivator, EndoVac, passive ultrasonic irrigation (PUI), and conventional needle irrigation (CNI), in Ca(OH)₂ removal from root canal, by means of scanning electron microscopy (SEM) images. Sixty‐six human canines were prepared with the Protaper system up to F5 and filled with Ca(OH)₂. After 7 days, Ca(OH)₂ was removed with rotary instrument F5 associated with the irrigation techniques used in each group (n = 15): GI (CNI), GII (EndoVac), GIII (EndoActivator) and GIV (PUI). In all groups 15 mL of 2.5% NaOCl and 3 mL of 17% EDTA were used for Ca(OH)₂ removal. The Ca(OH)₂ residues was evaluated by SEM in the middle and apical third using a system of scores. The results were analyzed by the Kruskal‐Wallis and Dunn tests (α = 0.05). None of the techniques completely removed the Ca(OH)₂ from root canals. There was no difference between EndoActivator, EndoVac and PUI (P > 0.05), but the three techniques removed more Ca(OH)₂ than the CNI (P < 0,05), in the middle and apical thirds of the root canal. It was concluded that the rotary instrument combined with EndoActivator, EndoVac, and PUI was shown to be more efficient than the rotary instrument combined with the CNI in removing Ca(OH)₂ from the root canal. Microsc. Res. Tech. 77:642–646, 2014. © 2014 Wiley Periodicals, Inc.     

Modification of Mo-Si alloy microstructure by small additions of Zr

Molybdenum and its alloys are potential materials for high-temperature applications. However, molybdenum is susceptible to embrittlement because of oxygen segregation at the grain boundaries. In order to alleviate the embrittlement small amounts of zirconium were alloyed to a solid solution of Mo-1.5Si alloy. Two Mo-based alloys, namely Mo-1.5Si and Mo-1.5Si-1Zr, were investigated by the complementary high-resolution methods transmission electron microscopy and atom probe tomography. The Mo-1.5Si alloy shows a polycrystalline structure with two silicon-rich intermetallic phases Mo₅Si₃ and Mo₃Si located at the grain boundaries and within the grains. In addition, small clusters with up to 10 at% Si were found within the molybdenum solid solution. Addition of a small amount of zirconium to Mo-1.5Si leads to the formation of two intermetallic phases Mo₂Zr and MoZr₂, which are located at the grain boundaries as well as within the interior of the grain. Transmission electron microscopy shows that small spherical Mo-Zr-rich precipitates (<10 nm) decorate the grain boundaries. The stoichiometry of the small precipitates was identified as Mo₂Zr by atom probe tomography. No Si-enriched small precipitates were detected in the Mo-1.5Si-1Zr alloy. It is concluded that the presence of zirconium hinders their formation.     

Initial steps in the surface chemistry of vapor phase lubrication by organophosphorus compounds

The surface chemistry of trimethylphosphite (CH₃O)₃P has been studied on Cu(111) and Ni(111) surfaces in order to model the initial steps in the reactions of vapor phase lubrication by organophosphorus compounds. The initial reactions involve scission of the P–O bonds to deposit methoxy groups (CH₃O_(ad)) on the surfaces. On the Cu(111) surface the formation of CH₃O_(ad) species occurs only after oxidation of the surface. The CH₃O_(ad) groups on Cu(111) decompose by β‐hydride elimination to produce formaldehyde (O=CH₂) and adsorbed hydrogen. CH₃O_(ad) groups are formed from (CH₃O)₃P on the clean Ni(111) surface and decompose by complete dehydrogenation to CO and adsorbed hydrogen atoms. This chemistry is very similar to that observed for CH₃OH on these surfaces. These results suggest that alkoxides are important intermediates in the decomposition of vapor phase lubricants on metal surfaces. This revised version was published online in July 2006 with corrections to the Cover Date.