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The effect of electromagnetic stirring at a continuous casting strand on the distribution of inclusions along the thickness of gear steel blooms was investigated. Inclusions in the subsurface of continuous casting blooms were Al2O3·CaO·CaS·MgO, similar to those in the molten steel of continuous casting tundish. Inclusions at 1/4 thickness from the loose side and the center of the bloom were Al2O3·CaS·MgO. The spatial distribution in the number density and composition of inclusions along the thickness from the loose side to the fixed side of the bloom was non-uniform but symmetric. The electromagnetic stirring efficiently improved steel cleanliness by lowering the average number density and area fraction of inclusions in the whole section of the CC bloom from 58.14 #/mm2 and 176.82 ppm to 30.90 #/mm2 and 111.67 ppm, respectively, and by increasing the average size and the maximum size of inclusions from 2.73 and 20.84 μm to 2.99 and 76.02 μm, respectively. More large-size inclusions contained K and Na by the slag entrainment in the mold with electromagnetic stirring were detected than those without electromagnetic stirring. Seven mm of the bloom from the loose side was analyzed for inclusions with size > 1.0 μm every 1 mm depth. The average CaO content of inclusions with size > 1.0 μm within the 7 mm subsurface of the bloom increased from 5.67 wt pct without electromagnetic stirring to 16.12 wt pct with electromagnetic stirring and increased from 10.24 wt pct without electromagnetic stirring to 21.31 wt pct with electromagnetic stirring for > 3.0 μm inclusions, which confirmed that unreasonable current electromagnetic stirring operation parameters will lead to slag entrainment.

In order to improve the conductivity of titanium bipolar plate under the premise of ensuring its corrosion resistance for the proton exchange membrane fuel cell (PEMFC), the nitride coatings are deposited on the surface of titanium bipolar plate via a powder immersion reaction assisted coating (PIRAC) method. Both the scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) show that the dense titanium nitride coatings with the thickness around 1.5–2.5 μm are successfully prepared. Furthermore, the X-ray photoelectron spectroscopy (XPS) results confirm the presence of TiN, TiNxOy and TiO2 phases on the surface of nitride coatings, and the content of these phases is tunable by adjusting the prepared temperatures. Both the microstructure, the thickness and the composition of the nitride coatings could be associated with the corrosion resistance and the interfacial contact resistance of the nitrided samples. We find that the nitrided samples prepared at 1000 °C could be the ideal mixed coating materials with the proper combination of the corrosion resistance and the interfacial contact resistance, which also show the best long-term stability in simulated PEMFC cathode environment.

In order to inhibit the corrosion of carbon support and agglomeration of Pt nanoparticles in conventional Pt/XC-72 catalyst, the conventional Pt/C catalyst was modified by in-situ deposition of amorphous tungsten carbide (WC) at the catalyst/support interface. The results show that proper amount of WC can improve the performance and durability of catalyst, and excessive addition of W element will combine with oxygen and transform into WO3, thus covering Pt nanoparticles and reducing the active site of catalyst. When W content is controlled at 20 wt%, the half-wave potential (E1/2) of oxygen reduction reaction (ORR) polarization curve of Pt-WC (20 wt% W, PWC20) catalyst is positively shifted by 31 mV compared with that of conventional Pt/XC-72 catalyst, and the mass activity and specific activity of catalyst are increased by about 2.0 times at 0.85 V. After 10,000 cycles of accelerated durability test (ADT), the electrochemical active area (ECSA) of PWC20 catalyst decreased by 21.7% and the E1/2 was negatively shifted by 22 mV, while the ECSA of conventional Pt/XC-72 catalyst decreased by 49.49% and E1/2 shifted by 42 mV negatively. The peak current density of methanol oxidation reaction (MOR) is 1.41 times higher than that of conventional Pt/XC-72, and the forward scanning potential of methanol oxidation shifts 36 mV negatively. After 1000 cycles of ADT, the forward peak current density decreased by 15.23%, while the conventional Pt/XC-72 decreased by 26.62%. The results of CO stripping voltammetry and X-ray photoelectron spectroscopy (XPS) analysis show that the modification of catalyst/support interface by WC significantly improves the anti-CO toxicity ability of conventional Pt/C. The synergistic effect between WC and Pt enhances the metal-support interaction. The durability of catalyst toward ORR and MOR was improved by the modification of catalyst/support interface, and the performance and durability of proton exchange membrane fuel cell (PEMFC) cathode catalyst layer were also improved.

Reliable detection and quantification of myoglobin (Mb) in blood plasma is of significance for clinical diagnosis and management of acute myocardial infarction (AMI). Here, we describe a homemade platform combining efficient core-shell upconversion nanoparticles (UCNPs) and lateral flow assay (LFA) for ultrasensitive and specific fluorescence ratiometric evaluation of Mb in clinical blood samples. After a systematic optimization, this platform was able to reach a limit of detection as low as 0.21 ng/ml, a linear range of 0.5–400 ng/ml, a recovery rate of 90.6–110.5%, an inter-assay coefficient of variation (CV) of 3.0–6.2%, an intra-assay CV of 8.8–13.6%, and a detection time of 10 min. Furthermore, the acquired concentration results were unresponsive to the interference of high-bilirubin, high-lipids, and hemolysis, and a range of other biomarkers (CRP, PCT, and BSA), substantiating robust Mb-specific detection. Importantly, the platform showed a significant linear correlation (R2 = 0.9484) with clinically used Abbott Chemiluminescence detection system (CLDS) on evaluation of Mb concentration in 50 clinical human blood plasmas. The achievement of rapid, sensitive and reliable quantification of Mb in clinical plasma promises the prevalent use of the described platform for on-field diagnosis or rule-out of AMI in clinical practice.

In this paper, an order-structured cathode catalyst layer consisting of Pt-TiO 2 @PANI core-shell nanowire arrays that in situ grown on commercial gas diffusion layer (GDL) are prepared and applied to membrane electrode assembly (MEA) of proton exchange membrane fuel cell (PEMFC). In order to prepare the TiO 2 @PANI core-shell nanowire arrays with suitable porosity and prominent conductivity, the morphologies of the TiO 2 nanoarray and electrochemical polymerization process of aniline are schematically investigated. The MEA with order-structured cathode catalyst layer is assembled in the single cell to evaluate the electrochemical performance and durability of PEMFC. As a result, the PEMFC with order-structured cathode catalyst layer shows higher peak power density (773.54 mW cm −2 ) than conventional PEMFC (699.30 mW cm −2 ). Electrochemically active surface area (ECSA) and charge transfer impedance (R ct ) are measured before and after accelerated degradation test (ADT), and the corresponding experimental results indicate the novel cathode structure exhibits a better stability with respect to conventional cathode. The enhanced electrochemical performance and durability toward PEMFC can be ascribed to the order-structured cathode nanoarray structure with high specific surface area increases the utilization of catalyst and reduces the tortuosity of transport pathways, and the synergistic effect between TiO 2 @PANI support and Pt nanoparticles promotes the high efficiency of electrochemical reaction and improves the stability of catalyst. This research provides a facile and controllable method to prepare order-structured membrane electrode with lower Pt loading for PEMFC in the future.

Lithium-excess layered cathode materials Li[Li 0.2 Mn 0.54 − x Sm x Co 0.13 Ni 0.13 ]O 2 (x = 0, 0.01, 0.03, 0.05) with different quantities of Sm were synthesized by the coprecipitation-calcination method. The rare earth element samarium (Sm) was introduced into the structure of Li[Li 0.2 Mn 0.54 Co 0.13 Ni 0.13 ]O 2 as the replacement at Mn sites. The refinement unit cell parameters from the X-ray powder diffraction patterns illustrate the doping of Sm facilitates enlarging the lithium ions diffusion passageway space of the Li[Li 0 . 2 Mn 0.54 Co 0 . 13 Ni 0.13 ]O 2 structure. The Li[Li 0.2 Mn 0.51 Sm 0.03 Co 0.13 Ni 0.13 ]O 2 electrode presented the best electrochemistry properties. The initial discharge capacity is 287.5 mAh g − 1 and the initial coulombic efficiency increases from 81.31% to 85.34% with a constant current density of 12.5 mA g − 1 , which can be attributed to the suppression of the oxygen release from the structure at the initial charge-discharge process. The Li[Li 0·2 Mn 0.51 Sm 0.03 Co 0.13 Ni 0.13 ]O 2 electrode delivers 236.1 mAh g − 1 after 40 cycles and the capacity retention ratio is 82.12% while only 206.8 mAh g − 1 and 70.85% are obtained after 40 times of cycling for the pristine electrode. The Nyquist plots indicate that the electrical conductivity and interfacial electrochemical reaction activity increase as well.

The significant roles of Nb and Mo on enhancing high temperature urea corrosion (HTUC) resistance of ferritic stainless steels applied in selective catalytic reduction (SCR) system of commercial vehicle were investigated. By slightly increasing of Nb or Mo, the reactivation rate (Ra) of ferritic stainless steels was significantly reduced, indicating an improvement in HTUC resistance. High temperature nitriding induced by the decomposition of urea resulted in precipitation of chromium nitride particles, which caused chromium depletion in the matrix and resultant deterioration of corrosion resistance. Moreover, the high temperature oxidation accompanied by thermal fatigue further accelerates the formation and exfoliation of oxide layer, showing detrimental consequences on service life of materials for commercial vehicle.

The cast duplex stainless steels were investigated in order to understand the plastic deformation behaviors and fracture mechanisms after thermal aging at 400°C for up to 10,000 h. Tensile strength has an obvious improvement, but the yield strength has a slightly increase after long-term thermal aging. Microcracks initiate in the ferrite and extend to phase boundaries, leading to the fracture of ferrite before the tensile failure of specimen. Nanoindentation tests indicate that hardness in ferrite continuously increases with aging time, but not strongly affected by deformation degree. Electron backscattered diffraction observations reveales that high-stress concentration on the phase boundaries causes the phase boundary separating. The dislocations pile-up at spinodal decomposition precipitates in ferrite phases and along G-phase boundaries, leading to the reduction of mechanical property of the ferrite.

Orbital ordering below 30 K was previously observed in the ferromagnetic ${\text{YTiO}}_{3}$ compound both by polarized neutron diffraction (PND) and x-ray magnetic diffraction (XMD). In this paper we report a procedure for the joint refinement of a unique spin-density model based on both PND and XMD data. The distribution of the unpaired $3d$ electron of titanium is clearly seen on the magnetization density reconstructed by the maximum entropy method from the PND data collection at 5 K. The ${\text{Ti}}^{3+}$ $3d$ orbital populations obtained by joint model refinement are discussed in terms of the orbital ordering scheme. Small but significant magnetic moments on apical oxygen ${\text{O}}_{1}$ and yttrium atoms are found. The agreement between experimental and theoretical spin densities obtained using density functional theory is discussed.

A novel and sensitive colorimetric sensor for determination of methyl parathion (MP) was developed based on a lanthanum (La 3+ ) functionalized gold nanoparticles (Au NPs-La) probe. In this assay, a new type of crosslinking molecule-La 3+ , possessing strong coordination effect on oxygen-containing functional groups, was first applied in the Au NPs-based colorimetric assay. On account of the oxygen-containing thiophosphate, MP could combine with La 3+ and induce the aggregation of Au NPs-La probes through coordination–bonding interactions, resulting in a variation of the solution color from red to blue. Further, the color change was in situ monitored with ultraviolet visible (UV–vis) spectrophotometer for the quantitative detection of MP. In contrast with the commonly designed Au NPs-based colorimetric assays, a novel Au NPs-La probe, which equipped with the same type of binding sites with Au NPs and analyte molecules, was explored and used for optical detection of MP. Under optimized conditions, the colorimetric assay exhibited a linear correlation to the concentration of MP in the range from 0.5 nM to 0.5 μM with a detection limit of 0.1 nM (S/N = 3). The developed sensor is simple, without using complicated instruments, and has enormous potential applications in rapid and on-site monitoring for MP in real samples.

The effect of hydrophilic treatment within the anode diffusion layer for direct methanol fuel cell (DMFC) has been investigated. By nitrated treatment, the surface structure and wettability of diffusion layer can be tuned. The anode micro-porous surface of carbon paper with hydrophilic adhesive after nitrated treatment presents more multi-hole structures with about 30 μm large pores and about 5 μm small pores, which were significantly larger than commercial carbon cloth and carbon paper without nitrated treatment. FTIR and EDS show that the surface of micro-porous layer has more oxygenic groups and the contact angles test also indicates that it becomes more hydrophilic after nitrated treatment. It is indicated that the anode charge transfer resistance and internal resistance dramatically decrease after nitrated treatment on the EIS test. The performance of assembled cell is also evaluated of which the power density of cell using novel diffusion layer (260 mW/cm 2 ) is significantly higher than cell using commercial diffusion layer. The results indicate that this novel multi-porous and hydrophilic anode diffusion layer is suitable to DMFC.

Catalyst coated membrane (CCM) is the core component of proton exchange membrane (PEM) water electrolysis and the main place for electrochemical reaction and mass transfer. Its properties directly affect the performance of PEM water electrolysis. Aiming at decreasing the polarization loss and the ohmic loss, a novel CCM embedded with Cs 1.5 HPA in the skeleton of the Nafion ® ionomer and the Nafion ® membrane was prepared and possessed functionality of improved protonic conductivity. Meanwhile, the Cs 1.5 HPA-Nafion ionomer content in the catalyst layers was further optimized. The SEM, EDS and pore volume distribution measurement showed that the Cs 1.5 HPA embedded in the CCM without agglomeration and the micropore and mesopore were well distributed in the catalyst layer. Furthermore, CCMs were tested in a PEM water electrolyser at 80 °C, beneficial effects on both the Tafel slope and the iR loss were obtained due to the improved protonic conductivity as well as the appropriate pore structure and increased specific pore volume. The performance of the electrolyser cell was obviously improved with the novel CCM. The highest cell performance of 1.59 V at 2 A cm −2 was achieved at 80 °C. At 35 °C and 300 mA cm −2 , the cell showed good durability within the test period of up to 570 h.

A sandwich-type electrochemical immunosensor for the detection of avian leukosis virus subgroup J (ALV-J) based on a novel multiple-promoted silver enhancement strategy is described. Owing to the admirable features of carbon nanotubes-iron oxides magnetic composites (CIMC), catalytic performance of gold nanoparticles (Au NPs) and adsorptive and reductive properties of humic acids (HAs), the Au NPs and HAs labeled, antibody functionalized, and bovine serum albumin (BSA) blocked CIMC (CIMC-Au-HAs/Ab 2 -BSA) were assembled and applied as a triple signal amplified method in ALV-J detection. Furthermore, β-cyclodextrin functional graphene sheets (CD-GS) were used as matrixes for immobilization of antibodies due to the huge surface area and superior electrical conductivity. The primary procedures are as follows: firstly, CD-GS were used as the immunosensor platform for immobilizing antibodies. Subsequently, after the sandwich-type assembly, CIMC-Au-HAs/Ab 2 -BSA was fabricated onto the immunosensor surface to adsorb and catalytic reduction of Ag + to Ag. Then the deposited Ag was detected by differential pulse voltammetry (DPV) in KCl solution. To embody the function of CIMC, adsorptive and reductive properties of HAs, and catalytic performance of Au NPs, response signals of various labels were compared in detail. The immunosensor displayed good analytical performance for the detection of ALV-J ranging from 10 2.05 to 10 4.50 TCID 50 /mL with a detection limit of 110 TCID 50 /mL (S/N = 3). Thus, the newly designed immunosensor showed a promising potential in clinical applications.

A novel and feasible method of enhancing the low temperature (−40 °C) impact toughness of coarse grained heat affected zone (CGHAZ) is put forward. By slightly increasing the holding time at peak temperature, the completeness of austenite-bainite transformation was enhanced and the toughness of CGHAZ was improved significantly. The product bainite was refined with increased holding time and more crystallographic variants from different Bain groups, namely, more Bain group boundaries were formed, which proved to be effective in preventing crack propagation. Moreover, when the inter-spacing of these boundaries is controlled below the critical Griffith crack length by self-accommodation during transformation, micro-cracks can be arrested by these high angle boundaries, thereby suppressing brittle fracture initiation and increasing fracture properties.

Proton exchange membrane liquid water electrolyser operated blow 80 °C suffers from insufficient catalyst activity and durability due to the slow oxygen evolution kinetics and poor stability. Aiming at enhancing oxygen electrode kinetics and stability, composite materials consisting of antimony doped tin oxide and Cs-substituted phosphotungstate were synthesized as the support of iridium oxide and possessed functionality of mixed electronic and protonic conductivity. At 80 °C under dry ambient atmosphere, the materials showed an overall conductivity of 0.33 S cm −1 . The supported IrO 2 catalysts were characterized in sulfuric acid electrolyte, showing significant enhancement of the oxygen evolution reaction (OER) activity. Electrolyser tests of the catalysts were conducted at 80 °C with a Nafion membrane. At an IrO 2 loading of 0.75 mg cm −2 and a Pt loading of 0.2 mg cm −2 , the cell performance of a current density of 2 A cm −2 at 1.66 V was achieved. The cell showed good durability at 35 °C under a current density of 300 mA cm −2 in a period of 464 h.

The LiMn 2 O 4 nanofiber cathode was synthesized by electrospinning. It forms porous “network-like” morphology with 150 nm in diameter and ~20 µm in length. For comparison, LiMn 2 O 4 nanoparticle cathode was synthesized by the sol–gel thermolysis process. The nanofiber cathode processes superior cycling stability and rate capacity. The AC impedance results show that the nanofiber cathode has much lower degradation, probably due to the suppressed Mn 3+ disproportionation process.

A novel multi-walled carbon nanotubes–CeO2–Au nanocomposite (MWCNTs–CeO2–Au) was synthesized by a facile two-step precipitation method and used for solid-phase extraction of methyl parathion (MP). The MWCNTs–CeO2–Au nanocomposite combined the individual properties of MWCNTs (high conductivity and exceptional adsorption affinity) and nanoparticles (high surface area and special catalytic activity), and realized the efficient enrichment and electrochemical stripping voltammetric detection of MP. An ultra-low detection limit of 3.02 × 10−11 M for MP was obtained at MWCNTs–CeO2–Au nanocomposite modified electrode, suggesting the high sensitivity of the nanocomposite based electrochemical sensor. Moreover, the proposed electrochemical sensor was successfully employed for the determination of MP in water and soil samples.

In this paper, direct methanol fuel cell's (DMFC's) electrochemical process was successfully investigated in situ using Electrochemical Impedance Spectroscopy (EIS) method. Under three-electrode system, anode and cathode's polarization overpotential, charge transferring resistance and active surface were independently measured in order to reveal the degradation factors after 50 h stability testing. The results showed that Ru's dispersing, membrane's swelling and water flooding were main reasons resulting in performance decline. And SEM images confirmed these conclusions. Moreover, cathode's degradation was less serious than anode and it could be recovered. Traditional equivalent circuit model of self-breathing DMFC was modified according to a fact that the dielectric relaxation phenomenon of porous electrode occurred at cathode rather than anode.

Proton exchange membrane water electrolysers operating at typically 80 °C or at further elevated temperatures suffer from insufficient catalyst activity and durability. In this work, antimony doped tin oxide nanoparticles were synthesized and further doped with an inorganic proton conducting phase based on tin pyrophosphates as the catalyst support. The materials showed an overall conductivity of 0.57 S cm−1 at 130 °C under the water vapor atmosphere with a contribution of the proton conduction. Using this composite support, iridium oxide nanoparticle catalysts were prepared and characterized in sulfuric and phosphoric acid electrolytes, showing much enhanced catalytic activity. Electrolyzer tests were conducted at both 80 °C with an Aquivion™ membrane and at 130 °C with a phosphoric acid doped Aquivion™ membrane. Significant improvement in the anodic kinetics was achieved on the composite supported catalysts at 130 °C although the electrolyzer cells showed higher ohmic resistance primarily from the membrane and catalyst layer. A durability test of electrolyzer cells was carried out at 130 °C under a current density of 400 mA cm−2 in a period of up to 760 h, showing rather good stability of the system.

An anode catalyst layer (ACL) with novel microstructure for direct methanol fuel cells (DMFCs) based on the catalyst coated membrane (CCM) technique is prepared by heating-spray method in this paper. The morphology and pore distribution of the novel ACL are characterized by scanning electron microscopy (SEM) and specific surface area (BET) analysis, respectively. A continuous flocculent structure with abundant micropores and a clear hierarchical distribution of pore diameter are obtained in the ACL. The DMFC performance is investigated by polarization curves measurements. In compared with traditional ACL, the novel structure ACL has larger active surfaces and exhibits higher performance with 39% increase in maximum power density during the single cell test at 80 °C. The possible reason for the increased performance has been analyzed and ascribed to the novel structure for the ordered mass transfer and the reduced internal resistance.

A nanoporous manganese oxide (MnO 2 ) film was fabricated via a polystyrene templated electrodeposition in the solution containing MnSO 4 . The nanoporous MnO 2 film obtained has been characterized by field emission scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge methods. The specific capacitance of 1018 F g −1 was observed at a low current density of 500 mA g −1 . When the current density increased to 30.0 A g −1 , the specific capacitance of 277 F g −1 remained. The high capacitance retention at high rates makes the prepared MnO 2 a promising candidate for supercapacitor applications.

Porous Li4Ti5O12 has been synthesized via a simple template method using phenol–formaldehyde resin as template. SEM, TEM, XRD, nitrogen adsorption, galvanostatic charge–discharge, and ac impedance tests are used to characterize the appearance, structure, and electrochemical performance of the samples. The micrometer-scale crystal particles exhibit rough surface, large specific surface area, porous structure, and superior electrochemical performance. The initial discharge specific capacity is 167 mAh g−1 under 0.2 C discharge rate, when the rate increases to 2.0 C, the capacity still retains to 112 mAh g−1, exhibiting excellent rate capability.

Membrane electrode assembly (MEA) after hot-pressing could not achieve its best performance before activated properly because the passages for protons, electrons, reactants and products in the MEA are not constituted completely. In this research, effective multi-step activation for MEA was proposed and the mechanism was discussed. The process includes three steps: methanol activation at room temperature, forced activation at intermediate temperature and proton activation at intermediate temperature. The performance of the MEA was correspondingly improved and reached respectively 54 mW cm−2, 61 mW cm−2, 78 mW cm−2, after each step of the activation. Apparently the performance was greatly enhanced by multi-step activation. The activation process of MEA is not only a process of the humidification of the proton exchange membrane but also a complex process for the establishment of the channels for electrons, ions, gases and liquids. Furthermore the conduction of electrons, ions and the transportation of the reactants and products are enhanced while the micro-structure of the MEA is kept stable.

A novel Pt–IrO 2 electrocatalyst was prepared using the dip-coating/calcinations method on titanium substrates. Titanium electrodes coated with oxides were investigated for oxygen evolution. Experimental results showed that Ti/Pt–IrO 2 electrode containing 30 mol% Pt in the coating exhibited significantly higher electrocatalytic activity for oxygen evolution compared to Ti/IrO 2 prepared by the same method, which is also supported by the electrochemical impedance data. Stability tests demonstrated Pt–IrO 2 electrocatalyst had a service cycle of 10,000 times in 0.1 M H 2 SO 4 solution. And the anode surface had hardly discovered cracks and had compact structures, which contributed to stable nature of the electrode together with good conductivity and specific interaction between Pt and IrO 2 formed during the calcination. Furthermore, the enhanced catalytic activity for O 2 evolution at Ti/Pt–IrO 2 electrode is preliminarily discussed using the Mott–Schottky analysis.

Highly oriented ZnO nanorod arrays were successfully prepared on the indium tin oxide (ITO) substrate using a galvanostatic electrodeposition method. The ITO substrate was pretreated with ZnO nanoparticles via simple low-temperature solution route. The crystallinity, micro- structure of surface, and optical properties of the obtained ZnO were characterized by X-ray diffraction, scanning electron microscope, and transmittance spectrum. The results indicate that the average diameter of ZnO nanorod arrays is about 30 nm, and the narrow size distribution ranges from 20 to 50 nm. The nanorod arrays are growing along [001] direction with an orientation perpendicular to the substrate. When the wavelength of incident is over 380 nm, the ZnO nanorod arrays show a high optical transmission of above 95%. Furthermore, the possible growth mechanism of the nanorod arrays was discussed.

Polymethylacrylic acid (PMA)/Polystyrene (PS) composite particles with different morphologies were prepared using reactive Y-shape surfactant AOA by controlling the content of surfactant and weight ratio of styrene/kerosene. High weight percentage of surfactant and weight ratio of styrene/kerosene lead to the structure of one large PS particle in which many PMA micro-gels were embedded, while low weight percentage of surfactant and weight ratio of styrene/kerosene led to composite particles with core/shell morphology. The formation mechanism of the particles with different morphologies was discussed in this article.

Graphite material was used as the electrode for an all-vanadium redox flow battery, and the electrode was modified by transition metallic ions to enhance its electrochemical behavior. An porous graphite composite electrode has high specific surface area and high current density. The electrode modified by transition metallic ions has improved catalysis behavior that can catalyze the V(II)-V(V) redox reaction showed by cyclic voltammograms. This article studied the impedance of the modified electrode by electrochemical impedance spectroscopy (EIS), and approved that the electrode modified by Co2+ and Mn2+ has a lower charge transfer resistance than the non-modified electrode. The effect of average particle size distribution is at lower frequencies that the slope of Warburg impedance is reduced by large particle size distribution. The voltage efficiency of the Co2+ modified electrode test cell is 81.5%, which is higher than that of the non-modified electrode.

Microscopic polar clusters can play an important role in the phase transition of ferroelectric perovskite oxides such as $\mathrm{BaTi}{\mathrm{O}}_{3}$, which have shown coexistence of both displacive and order-disorder dynamics, although their topological and dynamical characteristics are yet to be clarified. Here, we report sharp increases in the widths and intensities of Bragg peaks from a $\mathrm{BaTi}{\mathrm{O}}_{3}$ single crystal, which are measured in situ during heating and cooling within a few degrees of its phase transition temperature ${T}_{C}$, using the neutron time-of-flight Laue technique. Most significantly sharper and stronger increases in peak widths and peak intensities were found to occur during cooling compared to that during heating through ${T}_{C}$. A closer examination of the Bragg peaks revealed their elongated shapes in both the paraelectric and ferroelectric phases, the analysis of which indicated the presence of microdomains that have correlated $\ensuremath{\langle}111\ensuremath{\rangle}$-type polarization vectors within the {110}-type crystallographic planes. No significant increase in the average size of the microdomains $(\ensuremath{\sim}10\phantom{\rule{0.16em}{0ex}}\mathrm{nm})$ near ${T}_{C}$ could be observed from diffraction measurements, which is also consistent with small changes in the relaxation times for motion of Ti ions measured with quasielastic neutron scattering. The current observations do not indicate that the paraelectric-ferroelectric phase transition in $\mathrm{BaTi}{\mathrm{O}}_{3}$ is primarily caused by an increase in the size of the microscopic polar clusters or critical slowing down of Ti ionic motion. The sharp and strong increases in peak widths and peak intensities during cooling through ${T}_{C}$ are explained as a result of microstrains that are developed at microdomain interfaces during paraelectric-ferroelectric phase transition.

Highly oriented ZnO nanorod arrays with controlled diameter and length, narrow size distribution and high orientation consistency have been successfully prepared on ITO substrates at different growth temperatures by using a simple hydrothermal method. XRD results indicate that the nanorods are high-quality single crystals growing along [001] direction with a high consistent orientation perpendicular to the substrate. SEM images show that the nanorods have average diameters of about 30–70 nm by changing growth temperature. The thin films consisting of ZnO nanorods with controlled orientation onto ITO substrates allow a more efficient transport and collection of photogenerated electrons through a designed path. For a sandwich-type cell, the relatively high overall solar energy conversion efficiency reaches about 2.4% when the growth temperature is at 95 °C.

A general spin symmetry argument is proposed for spin currents in semiconductors. In particular, due to the symmetry with respect to spin polarization of the helicity eigenstates of the Luttinger Hamiltonian for a hole-doped semiconductor, the spin polarized flux from a single helicity eigenstate induced by an external electric field, is canceled exactly when all such contributions from eigenstates that are degenerate in energy are summed. Thus, the net spin current predicted by Murakami et al. (Science 301 (2003) 1348), cannot be produced by such a Hamiltonian. Possible symmetry breaking mechanisms which may generate a spin current are discussed.

Taking Mo-Si compounds as model systems, we show that the coefficients of thermal expansion (CTEs) of complex structures can be calculated precisely from first principles by incorporating the Debye model for acoustic response. Specifically, we obtain a nearly isotropic CTE in MoSi2 but a highly anisotropic CTE in Mo5Si3. The CTE anisotropy in Mo5Si3 is due to an elastically more rigid basal plane and a higher anharmonicity along the c axis. As the structure of 5-3 compounds is modified from D8m to D8l by boron substitutions (Mo5SiB2), we predict a significant decrease in the CTE anisotropy, which is confirmed by experiments.

Using the adiabatic approximation, we derive the equations of motion for local spin moments which are valid for itinerant as well as tight-binding spins. Material parameters in the equations of motion can be obtained using standard density functional methods, because they depend only on the energy and Berry phase of the constrained ground state of frozen spin configurations. For the calculation of spin waves in a collinear magnet, it is sufficient to know the quadratic forms of total energy and spin component along the symmetry axis as functions of the spin deviations from the ground state configuration. {copyright} {ital 1999} {ital The American Physical Society}

Bloch waves may be reflected and transmitted by planar interfaces. In this paper, we show how the reflection and transmission amplitudes for Bloch waves can be calculated within the layer Korringa-Kohn-Rostoker formalism. The calculated transmission probability is used to calculate the spin-dependent tunneling conductance for magnetic tunnel junctions formed from ZnSe semiconducting layers sandwiched between two ferromagnetic Fe layers. {copyright} {ital 1999} {ital The American Physical Society}

A random-phase approximation theory for spin waves in a ferromagnetic Kondo lattice model is presented. In the strong-coupling limit, this theory agrees with the existing theoretical results, in which the magnetic coupling is taken to be infinite a priori. It is shown explicitly that, in the strong-coupling limit, the spin-wave spectrum of the system is identical to that of a short-range Heisenberg model for the case of a single conduction band with short-range hopping integrals. In the intermediate coupling regime, on the other hand, more complicated effects, such as softening or disappearance of spin waves, are likely to be observed.

First-principles local-density-functional calculations have been used to investigate the defect properties of FeAl: (1) the ordering behavior and equilibrium point defects; (2) the binding interactions among vacancies; and (3) the mechanism underlying the hydrogen-induced embrittlement effect. The point defect structure is dominated by substitutional antisite defects on both sublattices and thermal vacancies on the Fe sublattice. It is predicted that the binding between vacancies is strongly attractive when vacancies are aligned along the [100] direction, and becomes weakly repulsive when vacancies are [110]a or [111]a apart (where a is the lattice constant). The binding interaction between vacancies is found to manifest the oscillations in the vacancy-induced charge density on neighboring lattice sites. Energetically, vacancies (and/or vacancy clusters) provide favorable lattice sites for hydrogen segregation. The hydrogen-induced embrittlement is explained in terms of a charge transfer mechanism and the localization behavior of induced charge at the hydrogen site.

The optical properties of metallis {alpha}- and {gamma}-Ce were investigated by spectroscopic ellipsometry in the energy range 1.5--5.4 eV. The samples were thin films deposited {ital in} {ital situ} at room temperature and at 25 K for {gamma}- and {alpha}-Ce, respectively. The measured conductivities decrease in magnitude as the thickness increases, which can be explained with a microscopic surface roughness model. The optical conductivity increases upon entering the {alpha} phase because of the increased number of electrons per unit volume due to the volume collapse. The energy band structures and the optical conductivities were calculated using the linearized-augmented-plane-wave (LAPW) method within density-functional theory, treating both the 4{ital f} and 5{ital p} electrons as bandlike. The application of the partial sum rule to angular-momentum-decomposed optical conductivities shows that the 4{ital f} electron contributions in the measured energy range is small.

A comparative description of the crystallographic structural details and the magnetic properties of Ni-Mn-Ga magnetic shape memory alloys are necessary to understand the physical origins of their magnetoelastic properties. The crystallographic structural details of an off-stoichiometric Ni${}_{2}$Mn${}_{1.14}$Ga${}_{0.86}$ alloy have been obtained from the refinement of high-resolution single-crystal neutron diffraction data, following a (3 $+$ 1)-dimensional [(3 $+$ 1)-D] superspace formalism. In particular, the structure adopts a $P$2/$m$($\ensuremath{\alpha}$0$\ensuremath{\gamma}$)00 superspace group symmetry with the following fundamental lattice parameters: $a$ $=$ 4.255(4) $\AA{}$, $b$ $=$ 5.613(4) $\AA{}$, $c$ $=$ 4.216(3) $\AA{}$, a commensurate periodicity of 5M, and a modulation wave vector of $\stackrel{P\vec}{\mathbf{q}}=2/5\stackrel{P\vec}{\mathbf{c}}$. The magnetic properties of the crystal are characterized from magnetic susceptibility measurements, as well as from neutron diffraction intensities. The overall magnetic moment per unit cell is 2.7 $\ensuremath{\mu}$${}_{\mathrm{B}}$ per Ni${}_{2}$Mn${}_{1.14}$Ga${}_{0.86}$ formula unit and the magnetic moments are aligned along the $b$ axis. The modulations of the atomic site displacements, site occupancies, and magnetic moments are elucidated from a (3 $+$ 1)-D refinement of the neutron diffraction intensities. In addition to atomic displacements corresponding to shear waves along $\ensuremath{\langle}110\ensuremath{\rangle}$, distortions of the Ni-centric tetrahedra are also evident. Physical interpretations for the different structural distortions and their relationship to magnetic properties are discussed.

Using constrained local spin density functional theory it is possible to directly calculate the adiabatic magnon dispersion curve. Small amplitude magnons with wavelengths between 2 and 32 atomic layers were constructed and the energy change with respect to amplitude within the frozen potential approximation was calculated. The resulting dispersion curves give the spin wave stiffness for [111] face-centered-cubic Co and Ni in fair agreement with experiment. In Fe the stiffness was calculated along [100] and [110] directions. The two values of stiffness were found to be nearly equal to each other and roughly half the measured value. It was found that the calculated Fe stiffness did not change upon addition of gradient corrections to the local density approximation, indicating that the source of discrepancy is not likely a failure of the local density approximation. It is argued that the adiabatic approximation is more likely the source of discrepancy since the magnetic interactions in Fe are longer ranged ...