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Improving the flow field uniformity of catalytic converter can promote the catalytic conversion of NO to NO2. Firstly, the physical and mathematical models of improved catalytic converter are established, and its accuracy is verified by experiments. Then, the NO catalytic performance of standard and improved catalytic converters is compared, and the influences of structural parameters on its performance are investigated. The results showed that: (1) The gas uniformity, pressure drop and NO conversion rate of the improved catalytic converter are increased by 0.0643, 6.78% and 7.0% respectively. (2) As the cell density combination is 700 cpsi/600 cpsi, NO conversion rate reaches the highest, 73.7%, and the gas uniformity is 0.9821. (3) When the tapered height is 20 mm, NO conversion rate reaches the highest, 72.4%, the gas uniformity is 0.9744. (4) When the high cell density radius is 20 mm, NO conversion rate reaches the highest, 72.1%, the gas uniformity is 0.9783. (5) When the tapered end face radius is 20 mm, NO conversion rate reaches the highest, 72.0%, the gas uniformity is 0.9784. The results will provide a very important reference value for improving NO catalytic and reducing vehicle emission.

Practical application of SrCo0.8Fe0.2O3-–δ(SCF) perovskite oxide for oxygen separation is hindered by poor stability. Here, we developed new KxSr1–xCo0.8Fe0.2O3–δ membrane material by optimizing K+ doping in A-site of prototypical SCF. The partial substitution of Sr2+ with K+ can lead to the enhanced mechanical strength and intermediate-temperature oxygen permeation stability. It is found that the doping content of K+ should be lower than 20% because the excessive doping of K+ in A-site of SrCo0.8Fe0.2O3–δcan destroy their cubic perovskite structure. While x ≥ 0.2, some diffraction peaks different from cubic perovskite can be evidenced by X-ray diffraction and their oxygen permeation flux also decreases rapidly. Among the fabricated membranes, K0.1Sr0.9Co0.8Fe0.2O3–δexhibits the highest oxygen permeation flux (1.5 cm3 min−1 cm−2 at 950°C) under an air/He gradient. More important is that K0.1Sr0.9Co0.8Fe0.2O3–δ displays a stable oxygen permeation performance during over 120 h permeation operation at 750°C.

Myocarditis is a disease characterized by localized or diffuse inflammation of the myocardium without efficient treatment. This study explored the regulatory mechanism of microRNA-133 (miR-133) secreted from bone marrow mesenchymal stem cell-derived exosome (BMSC-Exo) on myocardial fibrosis and epithelial–mesenchymal transition (EMT) in viral myocarditis (VMC) rats through regulating mastermind-like 1 (MAML1). BMSCs in rats were isolated and cultured to identify their immune phenotype and osteogenic and adipogenic ability, and BMSC-Exo were extracted and identified. Exosomes were obtained through ultracentrifugation, which were identified by transmission electron microscope and western blot analysis. The rats were injected with Coxsackie B3 virus for preparation of VMC model, and cardiomyocytes were isolated, cultured and grouped in the same way as animal experiments (NCExo, Ad-miR-133aExo, Adas-miR-133aExo). In vivo and in vitro experiments were conducted to figure out the roles of exosomal miR-133a and MAML1 in inflammation, apoptosis, EMT, fibrosis, and cell viability. The targeting relationship between miR-133a and MAML1 was verified by dual luciferase reporter gene assay. BMSC-Exo raised miR-133a expression in VMC rats and effectively improved the VMC rat cardiac function and myocardial fibrosis, increased cardiomyocyte viability and inhibited the EMT process. Elevated miR-133a in exosomes strengthened the improvements. Silenced miR-133a effectively reversed the effects of BMSC-Exo on VMC rats. miR-133a targeted MAML1. Inhibition of MAML1 improved cardiac function and myocardial fibrosis in VMC rats and could reverse the effect of miR-133a-silenced exosomes on VMC rats. Our study suggests that elevated exosomal miR-133a suppresses myocardial fibrosis and EMT in rats with VMC via down-regulating MAML1, thereby inhibiting the progression of myocarditis. Supplementary Information The online version contains supplementary material available at 10.1186/s11671-021-03559-2.

Magnetic agglomeration of CoB nanoparticles in the hydrogen production from the hydrolysis of NaBH4 aqueous solution always degrades their catalytic activity. This work aims at the rational development of robust supported CoB catalyst that is active and stable towards NaBH4 hydrolysis. In this study, PANI nanotubes derived from PS nanofiber templates are firstly synthesized by the polymerization of aniline followed by the template removal. CoB nanoparticles are then decorated into PANI nanotubes via an impregnation and chemical reduction method. It can be found that CoB nanoparticles can be confined into the internal surface of PANI nanotubes which improves the dispersion and anchored stability of CoB nanoparticles. The as-prepared CoB/PANI composite catalyst exhibits a high catalytic performance and recycling stability. The hydrogen production rate as high as 2300 ml. min−1. g − 1 is achieved and the activation energy was calculated to be only 37.75 kJ/mol. Meanwhile, CoB/PANI catalyst displays excellent stability in NaBH4 hydrolysis during five cycles. The experimental results indicated that as-synthesized CoB/PANI composite catalysts are very efficient towards hydrogen production from NaBH4 hydrolysis.

Agglomeration of CoB catalysts is a severe problem in hydrogen generation from NaBH4 hydrolysis. Herein, highly dispersed carbon nanofiber immobilized CoB catalysts (CoB/CN) were synthesized by a combined prereduction and carbonization method, which is used in hydrogen generation from NaBH4 hydrolysis. Morphological evolution of carbon nanofibers, phase structure and elemental distribution of CoB/CN catalysts are explored by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Compared to Co/carbon nanofiber catalysts (Co/CN) without prereduction, CoB/CN catalysts can afford higher CoB dispersity and specific surface area because the migration rate of cobalt species during carbonization is effectively retarded by prereduction. Hence the agglomeration of magnetic CoB nanoparticles can be effectively inhibited. The hydrogen generation experiment shows that CoB/CN catalysts process higher catalytic activity and lower activation energy than Co/CN.

The objective of this article is to determine the influence mechanism of the cathode materials on the transition process of the arc modes in high-current drawn vacuum arcs under the external axial magnetic field (AMF). Six kinds of pure metal of Cu, W, Mo, Fe, Cr, and Al were selected as the cathode materials. A high-speed charge-coupled device (CCD) video camera was selected to record the arc appearance. The experimental results indicate that the cathode materials had a great effect on the arc modes in the high-current vacuum arcs with the application of AMF. Under the cathode of W and Mo, the arc modes turned to the constriction arc mode and the anode spot arc mode more easily than that under the cathode of Cu, Fe, Cr, and Al, with the increase of the arc current. For various cathode materials and same anode, the critical current density inputting to anode surface for the transform of vacuum arc modes was different. This should be caused by the differences in the constricted characteristics and the ion energy of the vacuum arcs, which took a significant effect on the transition process of the arc modes in the vacuum arcs under AMF. The higher ion energy would lead to a more active anode, which resulted in the positive ion and metal vapor from the anode. Moreover, the cathode materials played different roles in the various stages of the discharging process of the drawn vacuum arcs. The effect of cathode material on the transition process of the arc modes in the high-current vacuum arc mainly took in Stage II, which sustained from the end of the bridge arc column to the arc current peak and dominated the transition process of the arc modes.

Porous carbon supported Cu/Cu2O/CuO ternary catalysts were fabricated by pyrolysis, in which composition modulation of Cu/Cu2O/CuO was successfully realized by adjusting annealing atmosphere. The correlation between annealing atmosphere and composition of Cu/Cu2O/CuO ternary nanoparticles was deeply investigated. XRD and SEM measurement shows that the composition proportion of Cu/Cu2O/CuO can be effectively controlled by adjusting the annealing atmosphere. HR-TEM and EDS analysis showed that Cu/Cu2O/CuO ternary nanoparticles are highly dispersed into the carbon matrix and harvest more hetero-junction active sites. The effect of Cu/Cu2O/CuO composition on their catalytic activity was investigated in catalytic reduction from p-nitrophenol to p-aminophenol. The experimental result indicated that the catalytic activity of Cu/Cu2O/CuO ternary catalysts exhibits higher catalytic activity than Cu2O/CuO or CuO particles. This work provides a new strategy for synthesizing and modulating porous carbon-supported Cu/Cu2O/CuO ternary nanoparticles.

Ce0.8Sm0.2O1.9-Sm0.6Sr0.4FeO3−δ (SDC-SSF) dual-phase ceramic membranes with sandwich-structure were fabricated by chemical etching method. By this method, SSF perovskite particles was etched from both sides of SDC-SSF dual phase membrane, and a SDC/SDC-SSF/SDC three-layer membrane with sandwich structure could be obtained. Crystal phase, microstructure and elemental distribution of SDC-SSF sandwich-structured membranes were investigated. XRD and SEM-EDS results demonstrate that SDC fluorite particles can be well reserved to form porous supports after leaching out SSF perovskite particles and a SDC-SSF dense functional layer was firmly sandwiched between two SDC porous supports, in which common shrinkage mismatch between thin film and porous support can be readily avoided. Thickness of SDC-SSF dense layer can be precisely controlled by changing the etching time. Oxygen permeation tests reveal that our SDC-SSF membranes exhibit an obviously improved oxygen permeation flux. Especially while cobalt-based catalysts were introduced into SDC porous supports, its oxygen flux could be further increase up to 0.95 ml·min−1·cm−2.

CuCr contact materials are dominant in vacuum circuit breakers. It is interesting to find superior material than the CuCr. Mo has a higher melting point and boiling point, so that it becomes a potential candidate to replace Cr. The objective of this paper is to compare the distribution characteristics of cathode spots (CSs) on Cr and Mo cathodes in drawn vacuum arcs with an external axial magnetic field (AMF). The experiments were carried out in a demountable vacuum chamber. A pair of Helmholtz coils were set in the chamber to supply a uniform AMF. The arc current in the experiments was 10 kA (rms) at 44.5 Hz. The AMF flux density were 75, 133, and 187 mT, respectively. The experimental results showed that, under the three levels of AMF, the constriction of the CSs of Mo cathode was more serious than those of Cr cathode, which would lead to the more severe erosion of Mo cathode. Especially, before current zero, much cathode spot plasma particles jetted from the Mo cathode contact, while that of Cr cathode was much less. Therefore, Mo could not replace Cr for vacuum circuit breakers, indicating that the thermal parameters could not be used alone as a criterion for selecting contact materials.

CoB/ZIF-8 supported catalysts were successfully prepared using Co/Zn-ZIF-8 as the precursor by single-step reduction, which was applied in hydrogen release from the hydrolysis of NaBH4. Reducible Co ions of Co/Zn-ZIF-8 can be partially in-situ transformed into CoB by direct reduction, whereas ZIF-8 framework structure can be well preserved due to the resistance of Zn to reducing ambiences. Accordingly, CoB active components can be highly loaded onto ZIF-8 support to produce CoB/ZIF-8 catalysts. The texture evolution of Co/Zn-ZIF-8 during reduction was investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscope and nitrogen adsorption–desorption isotherms. Compared with the reduction of Co-ZIF-67, the framework structure of Co/Zn-ZIF-8 can be effectively preserved although Co ions of Co/Zn-ZIF-8 were partially reduced into cobalt-based alloy. In the hydrogen release from hydrolysis of NaBH4, CoB/ZIF-8 supported catalyst exhibits excellent catalytic activity. The effect of NaOH concentration, NaBH4 concentration and reaction temperature on hydrolysis reaction of NaBH4 was deeply studied based on this catalyst. Compared with other published catalysts, this catalyst exhibits relatively low activation energy of about 57.72 kJ mol−1.

Lithium-thionyl chloride batteries possess the highest specific energies of all of those commercially available batteries. These batteries also have high operating voltages, with stable outputs, wide operating temperature ranges, long storage lives, and are of low cost. The main limitation of lithium-thionyl chloride batteries is the low discharge capacity at high discharge rates, which limits their commercial uses. In this study, a porous cathode carbon support was prepared by introducing ammonia bicarbonate as a pore-forming agent. The porous cathode carbon support that formed was systematically characterized by BET, SEM, and XRD. The porous carbon support was then assembled into an ER18505M battery system to characterize the electrochemical performance of the battery. The effect of pore structure on the electrochemical performance was determined and revealed the preparation of a high capacity lithium-thionyl chloride battery with a high discharge rate.

The objective of this paper is to propose a novel contact structure for 126 kV vacuum interrupters, and determine its arc characteristics. The contact consists of an inner arcing contact and an outer main contact. A 3/4 coil-type contact with contact diameter of 100 mm was used as the arcing contact. A butt type contact with diameter of 140 mm was used as the main contact. For this contact, nominal rated current flows through both the main contact and arcing contact. When breaking the fault current, the main contact first opens and current transfers to arcing contact. Then the arcing contact opens and vacuum arc burns and distinguishes between the arcing contact. Drawn arc experiments of the novel contact were carried out in an L-C discharging circuit. Experiment current was up to 30 kA rms. From the experimental results, the proposed contact can control vacuum arc effectively, and the erosion on outer main contact was slight. With the increasing of vertical distance between inner arcing contact and outer main contact, the arc expanded to outer main contact later. And in partial erosion case, the erosion on outer main contact was more severe than in normal case.

CuCo2O4 spinel nanoparticles were successfully preparedvia a sol–gel method, which were firstly employed in catalytic reduction of p-nitrophenol to produce p-aminophenol. CuCo2O4 morphologies can be controlled in this paper. It can be found that the sintering temperature has an important impact on their phase structure and microstructure. Especially the treatment temperature above 700 °C can induce a rapid growth for CuCo2O4 nanoparticles. The catalytic test proved that CuCo2O4 nanoparticles exhibit excellent catalytic activity towards the reduction of p-nitrophenol. Comparative experiments indicated that CuO and CuCoOx nanoparticlesalso exhibit certain catalytic activity in the p-nitrophenol reduction but no any catalytic activity can be observed for Co3O4. Meanwhile, it can be found that the catalytic activity of CuCo2O4 is slightly higher than CuFe2O4 under the same synthesis condition.

ZnO, CeO2, TiO2, ZnO-CeO2 (ZC), CeO2-TiO2, ZnO-TiO2 (ZT) and ZnO-CeO2-TiO2 (ZCT) powders were fabricated using a combustion synthesis (CS) method for applying to photo-degradation and decoloration of Methyl blue with them as catalysts. Ascorbic acid (C6H8O6) and nitrate were used as fuel and raw materials, respectively. The powder was obtained when the processing parameters were optimized. C6H8O6 as fuel was used for the preparation of ZnO, CeO2, TiO2, ZC, CT, ZT and ZCT powders. The produced particles were characterized using scanning electron microscopy (SEM) for the particle morphology, UV for absorbent properties, IR for purity of sample, and XRD for phase, particle size and crystallinity of the samples. In addition, these particles showed good photocatalytic and decolorizing activity, which provided an opportunity for these materials to be used for the degradation and decoloration of Methyl blue.

SiO2/TiO2 hybrid nanofibers were prepared by electrospinning and applied for photocatalytic degradation of methylene blue (MB). The phase structure, specific surface area, and surface morphologies of the SiO2/TiO2 hybrid nanofibers were characterized through thermogravimetry (TG), X-ray diffraction (XRD) analysis, Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy (SEM), etc. XRD measurements indicated that doping of silica into TiO2 nanofibers can delay the phase transition from anatase to rutile and decrease the grain size. SEM and BET characterization proved that silica doping can remarkably enhance the porosity of the SiO2/TiO2 hybrid nanofibers. The MB adsorption capacity and photocatalytic activity of the SiO2/TiO2 hybrid nanofibers were distinguished experimentally. It was found that, although increased silica doping content could enhance the MB adsorption capacity, the intrinsic photocatalytic activity gradually dropped. The SiO2 (10 %)/TiO2 composite nanofibers exhibited the highest MB degradation rate, being superior to SiO2 (20 %)/TiO2 or pure TiO2.

Calcium-doped Ba0.33Sr0.33Ca0.33Co0.8Fe0.2O3−δ perovskite material was successfully synthesized via a modified sol–gel method. The phase structure, surface morphology and oxygen permeation properties of Ba0.33Sr0.33Ca0.33Co0.8Fe0.2O3−δ were investigated in detail based on XRD, SEM and oxygen permeation test. The experimental results show that the synergistic effect of Ba2+/Sr2+/Ca2+ can obviously improve calcium doping content in A-site lattice and maintain pure cubic perovskite phase. The Arrehenius plot showed that the order-disorder transition for Ba0.33Sr0.33Ca0.33Co0.8Fe0.2O3−δ occurs around 700 °C which is lower than other similar materials doped with two metal ions. Oxygen permeation test indicates that maximum oxygen flux through Ba0.33Sr0.33Ca0.33Co0.8Fe0.2O3−δ membrane reaches up to 1.5 ml min−1 cm−2 at 950 °C which display a promising oxygen permeability.

In this study, ammonia-based molecular beam epitaxy (NH3-MBE) was used to grow catalyst-assisted GaN nanowires on (11¯02) r-plane sapphire substrates. Dislocation free [112¯0] oriented nanowires are formed with pentagon shape cross-section, instead of the usual triangular shape facet configuration. Specifically, the cross-section is the result of the additional two nonpolar {101¯0} side facets, which appear due to a decrease in relative growth rate of the {101¯0} facets to the {101¯1} and {101¯1} facets under the growth regime in NH3-MBE. Compared to GaN nanowires grown by Ni-catalyzed metal–organic chemical vapor deposition, the NH3-MBE grown GaN nanowires show more than an order of magnitude increase in band-edge to yellow luminescence intensity ratio, as measured by cathodoluminescence, indicating improved microstructural and optical properties.

In this paper, friction stir processing (FSP) with B4C particles (B4Cp) is used to improve the surface modification of 6061 aluminum alloy. Optical microscopy, scanning election microscopy, and energy-dispersive X-ray analysis have been performed to investigate the microstructure and the distribution of B4Cp. Wear resistance and microhardness were evaluated in detail. It is observed that the increasing number of FSP passes causes a more uniform distribution of B4Cp. The homogeneous distribution of B4Cp was observed in the weld zone, which significantly improved the wear resistance and microhardness of the surface composite layer as compared to those of the as-received Al alloy.

Helical nanofibers are prepared through in situ growth on the surface of a tetrapod-shaped ZnO whisker (T-ZnO), by employing a precursor decomposition method then adding substrate. After heat treatment at 900 °C under argon, this new composite material, named helical nanofiber-T-ZnO, undergoes a significant change in morphology and structure. The T-ZnO transforms from a solid tetrapod ZnO to a micro-scaled tetrapod hollow carbon film by reduction of the organic fiber at 900 °C. Besides, helical carbon nanofibers, generated from the carbonization of helical nanofibers, maintain the helical morphology. Interestingly, HCNFs with the T-hollow exhibit remarkable improvement in electromagnetic wave loss compared with the pure helical nanofibers. The enhanced loss ability may arise from the efficient dielectric friction, interface effect in the complex nanostructures and the micro-scaled tetrapod-hollow structure.

Composite nanofiber sheets containing multiwalled carbon nanotubes and cobalt chloride dispersed in PAN (polyacrylonitrile) were produced by an electrospinning technique. The synthesized PAN/CoCl 2 /CNTs composite nanofiber was used as the catalyst for hydrogen production from the hydrolysis of sodium borohydride. FT-IR characterization showed that the pretreated CNTs possess different organic functional groups which help improve the compatibility between CNTs and PAN organic polymer. SEM (scanning electron microscopy), TEM (transmission electron microscopy) and EDX (energy-dispersive X-ray technique) were used to characterize the composite nanofiber and it was found that CNTs can be coaxially dispersed into the PAN nanofiber. During the hydrolysis of NaBH 4 , this PAN/CoCl 2 /CNTs composite nanofiber exhibited higher catalytic activity compared to the composite without CNTs doping. Kinetic analysis of NaBH 4 hydrolysis shows that the reaction of NaBH 4 hydrolysis based on this catalyst can be ascribed to the first-order reaction and the activation energy of the catalyst was approximately 52.857 kJ/mol. Meanwhile, the composite nanofiber catalyst shows excellent stability and reusability in the recycling experiment.

Complex axial and radial type III-nitride InGaN/GaN nanowire LEDs are realized using a recently developed top–down fabrication approach which enables high quality GaN-based nanowires with independently controlled height, pitch, and diameter. In this paper, we report on the fabrication, structural characterization, and luminescence of these two different structures and discuss their relative merits, weaknesses, and prospects in the context of the field. Axial (left) and radial (right) nanowire LEDs fabricated by a two-step top–down method.

Focused ion beam (FIB) milling and lift-out was used to prepare atom probe tomography (APT) specimens from GaN-InGaN multi-quantum well (MQW) nanowire arrays. Modifications to the conventional FIB lift-out technique enable the site-specific analysis of different regions of a single nanowire heterostructure. Three dimensional (3-D) reconstructions of quantum wells generated by analysis along different directions with respect to the heterointerface demonstrate both the capabilities and limitations of atom probe tomographic analysis. The methods described herein can be applied to the site-specific analysis of other complex 3-D heterostructures. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A s elf-cleaning and transparent TiO 2 nano-structured film coating was fabricated onto a glass substrate by electrospinning. It was found that the addition of diethanolamine (DEA) to the TiO 2 precursor solution remarkably changes the microscopic morphology of the resulting TiO 2 coating. In that, as the DEA's amount was increased, the resulting coating changed from opaque fibers to transparent nanoparticles under the same electrospinning conditions which was confirmed by Scanning Electron Microscopy (SEM). Meanwhile, the experimental results showed that the DEA/TiO 2 coating containing nanoparticles display better optical transmittance, e.g., a maximum transmittance of over 90% was achieved around 600 nm when the glass was coated with the nanoparticles at an electrospinning feed rate of 0.18 ml/h. The photocatalytic properties of the particle-like TiO 2 coating was studied using Congo red decay and silver ion reduction experiments. Together these experiments proved that this novel TiO 2 film/coating comprising electrospun nanoparticles possesses excellent photocatalytic activities. Lastly, water contact angle measurements proved that the coating is superhydrophilic.

The fidelity of a Tersoff-based empirical potential model for the Ge–Si–O ternary atomic system is studied in detail, with the ultimate aim of validating the potential for later use in large-scale simulations of Ge selective epitaxial growth. Several comparisons are presented between the predictions of atomistic simulations based on the empirical potential studied here and prior experimental measurements and electronic structure calculations. The points of comparison include the structure and thermodynamics of bulk amorphous silica (a-SiO2), the a-SiO2 free surface, the c-Si/a-SiO2 interface, the c-Ge/a-SiO2 interface, and the desorption, wetting, and diffusion behavior of Ge atoms on a-SiO2 surfaces. A single fitting parameter, which describes the strength of the Ge–O interaction, is used to establish good agreement between the empirical potential predictions and experimental measurements across all points of comparison. We conclude that a Tersoff-based empirical potential, while it neglects explicit Coulombic interactions and is highly simplified, is a reasonable basis for probing certain features of the Ge/SiO2/Si material system.

A novel method called “HCl-chemical etching method” was developed to fabricate self-supported oxygen permeation membranes. Based on this method, Ce 0.85 Sm 0.15 O 1.925 –Ce 0.85 Sm 0.15 O 1.925 /Sm 0.6 Sr 0.4 Al 0.3 Fe 0.7 O 3− δ (SDC–SDC/SSAF) dual-phase self-supported oxygen permeation membranes were successfully prepared. SEM and XRD characterization showed that this dual-phase self-supported membrane is composed of SDC porous support and thin dense SDC/SSAF oxygen permeation layer. In the experiment, the porosity of porous support and thickness of dense layer can be precisely adjusted through this chemical etching technique. Oxygen permeation measurement demonstrated that oxygen permeation flux of SDC–SDC/SSAF dual-phase self-supported membrane reaches 0.43 ml min −1 cm −2 which is much higher than that of untreated samples at the same total membrane thickness. This technique provides a new idea for fabricating self-supported oxygen permeation membrane modules.

Continuous and defect-free Ni-MOF-74 membranes were prepared on α-alumina support via a layer-by-layer seeding technique followed by secondary growth crystallization. The seeded supports were examined by SEM–EDX and AFM which evidenced that a uniform and compacted seeding layer can be formed on porous substrate surface through four alternated immersion cycles. Then Ni-MOF-74 seeding layer can grow into continuous Ni-MOF-74 membranes under optimal synthesis solution conditions. The as-synthesized Ni-MOF-74 membranes were characterized by XRD, SEM, BET and TGA. The continuous and crack-free membranes can be synthesized based on comparatively more concentrated solution and yet excessively concentrated solution is disadvantageous to obtain the uniform and defect-free membranes. Gas permeation properties of the membranes were investigated for small gases such as H 2 , N 2 , CH 4 and CO 2 . Compared with other gases, Ni-MOF-74 membrane exhibits the stronger adsorption affinity to CO 2 and thus the permeation of CO 2 through Ni-MOF-74 membrane is dominated by surface diffusion. The high H 2 /CO 2 ideal selectivity can be obtained for Ni-MOF-74 membranes.

CoB catalysts supported on carbon nanotubes with open tips (o-CNTs) were successfully prepared and used in hydrogen production from NaBH4 hydrolysis. The properties and morphologies of o-CNTs supports and CoB/o-CNTs catalysts were characterized by FT-IR, XRD, SEM–EDX and TEM, which showed that o-CNTs possess different organic functional groups and many open tips and CoB can be effectively loaded. Compared with CoB catalysts supported on carbon nanotubes with closed tips (c-CNTs), CoB/o-CNTs exhibit significantly higher hydrogen production rate of up to 3041 ml min−1 g−1 under the same conditions. In the experiment, the effect of CoB loading, catalyst supports, and operation temperature on hydrogen production rate was investigated in detail, which demonstrated that o-CNTs possess higher CoB loading than c-CNTs. It was shown that the apparent activation energy of CoB/o-CNTs is 37.63 kJ mol−1, which is obviously lower than 44.43 kJ mol−1 of CoB/c-CNTs.

A TiO2 nanofiber from polyvinylpyrrolidone (PVP)/TiO2 was prepared with the electrospinning technique to decompose ethylene through photocatalytic oxidation. The photocatalytic activity of TiO2 nanofiber was improved by simply increasing the alkoxide concentration ranging from 50 to 75%. The experimental results revealed that both initial percent decomposition and overall percent decomposition are noticeably improved with the increase of alkoxide compositions. SEM characterization showed that the microstructure and specific surface area of the nanofibers can be effectively optimized with the alkoxide concentration increasing. Meanwhile, a comparison in photocatalytic reactivity between TiO2 nanofiber and commercial photocatalyst P25 was also done. It was found out that the TiO2 nanofiber has a slight edge over P25 powder in terms of decomposition efficiency.

A novel polyacrylonitrile (PAN)/phosphotungstic acid (PWA) doped PVDF composite membrane was successfully prepared by blending electrospinning. Impedance spectroscopy and scanning electron microscopy characterization showed that the electrospun composite membranes possess comparatively higher proton conductivity and well-defined microstructure. In particular, the addition of hydrophilic PAN can effectively improve the water uptake performance of composite membrane and simultaneously no obvious membrane swelling was found. The experimental results showed that excellent composite membranes can be obtained by 30% PAN doping, and more than 30% PAN doping will increase the diameter of composite nanofiber membrane and accelerate the loss of PWA. The production of high-quality composite membranes with optimized PAN and PWA compositions can be achieved, which are promising candidates for proton exchange electrolyte membranes.

We have investigated the correlated surface electronic and optical properties of [0001]-oriented epitaxial InN nanowires grown directly on silicon. By dramatically improving the epitaxial growth process, we have achieved, for the first time, intrinsic InN both within the bulk and at nonpolar InN surfaces. The near-surface Fermi-level was measured to be ∼0.55 eV above the valence band maximum for undoped InN nanowires, suggesting the absence of surface electron accumulation and Fermi-level pinning. This result is in direct contrast to the problematic degenerate two-dimensional electron gas universally observed on grown surfaces of n-type degenerate InN. We have further demonstrated that the surface charge properties of InN nanowires, including the formation of two-dimensional electron gas and the optical emission characteristics can be precisely tuned through controlled n-type doping. At relatively high doping levels in this study, the near-surface Fermi-level was found to be pinned at ∼0.95-1.3 eV above the valence band maximum. Through these trends, well captured by the effective mass and ab initio materials modeling, we have unambiguously identified the definitive role of surface doping in tuning the surface charge properties of InN.

GaN nanowires oriented along the nonpolar a-axis were analyzed using pulsed laser atom probe tomography (APT). Stoichiometric mass spectra were achieved by optimizing the temperature, applied dc voltage, and laser pulse energy. Local variations in the measured stoichiometry were observed and correlated with facet polarity using scanning electron microscopy. Fewer N atoms were detected from nonpolar and Ga-polar surfaces due to uncorrelated evaporation of N(2) ions following N adatom diffusion. The observed differences in Ga and N ion evaporation behaviors are considered in detail to understand the influence of intrinsic materials characteristics on the reliability of atom probe tomography analysis. We find that while reliable analysis of III-N alloys is possible, the standard APT procedure of empirically adjusting analysis conditions to obtain stoichiometric detection of Ga and N is not necessarily the best approach for this materials system.

Hydrogen production from NaBH4 hydrolysis is very important for environment-friendly fuel cells. Here Y-zeolite/CoCl2 doped PVDF (Polyvinylidene fluoride) composite nanofibers were prepared by co-electrospinning method and successfully applied into hydrogen production from NaBH4 hydrolysis. The effect of Y-zeolite doping on properties of composite nanofibers was investigated in detail. SEM, EDX (Energy-dispersive X-ray spectroscopy) and FT-IR characterization showed that nanosized crystalline Y-zeolite can be doped into the bulk of composite nanofiber and high-quality composite nanofiber with fine morphologies can be obtained. The doping of Y-zeolite can improve the wetting ability of PVDF-based nanofiber and thus help to the diffusion rate of reactants. This Y-zeolite/CoCl2 doped electrospun nanofiber as catalyst were applied into hydrogen production from NaBH4 hydrolysis and exhibits higher catalytic activity compared with that without Y-zeolite doping due to its improved surface hydrophilicity. Meanwhile, this composite nanofiber catalyst shows relatively good stability in hydrogen production without obvious loss of Y-zeolite.

Porous TiO 2 -based nanofiber was fabricated via a combined electrospinning and alkali-dissolution method. TiO 2 /SiO 2 composite nanofiber was firstly prepared by electrospinning and sintering, and then silica was leached out with alkaline solution from the bulk of TiO 2 /SiO 2 composite nanofiber to produce porous microstructure. The thermal decomposition and phase structure of the composite nanofiber precursor was investigated with TG/DSC and XRD, and optimal sintering temperature was obtained. SEM-EDX and FT-IR characterization show that most silica can be dissolved out from the composite nanofiber and thus porous nanofiber with excellent microstructure can be spontaneously formed. The effect of composite nanofiber composition on porous microstructure was studied, and it is found that the composite nanofiber with 20wt% silica can produce better porous microstructure compared to those with 10wt% and 30wt% silica. Meanwhile, porous TiO 2 nanofiber with 20wt% silica shows higher degradation efficiency to Congo Red.

Nucleation and eventual coalescence of Ge islands, grown out of 5 to 7 nm diameter openings in chemical SiO 2 template and epitaxially registered to the underlying Si substrate, have been shown to generate a low density of threading dislocations (≪10 6 cm − 2 ). This result compares favorably to a threading dislocation density exceeding 10 8 cm − 2 in Ge films grown directly on Si. However, the coalesced Ge film contains a relatively high density of stacking faults (5 × 10 7 cm − 2 ), and subsequent growth of GaAs leads to an adverse root-mean-square roughness of 36 nm and a reduced photoluminescence intensity at 20% compared to GaAs grown on Ge or GaAs substrates. Herein, we find that annealing the Ge islands at 1073 K for 30 min before their coalescence into a contiguous film completely removes the stacking faults. However, the anneal step undesirably desorbs any SiO 2 not covered by existing Ge islands. Further Ge growth results in a threading dislocation density of 5 × 10 7 cm − 2 , but without any stacking faults. Threading dislocations are believed to result from the later Ge growth on the newly exposed Si where the SiO 2 has desorbed from areas uncovered by Ge islands. The morphology and photoluminescence intensity of GaAs grown on the annealed Ge is comparable to films grown on GaAs or Ge substrates. Despite this improvement, the GaAs films grown on the annealed Ge/Si exhibit a threading dislocation density of 2 × 10 7 cm − 2 and a minority carrier lifetime of 67 ps compared to 4 to 5 ns for GaAs on Ge or GaAs substrates. A second oxidation step after the high temperature anneal of the Ge islands is proposed to reconstitute the SiO 2 template and subsequently improve the quality of Ge film.

The aligned growth of III-nitride nanowires, along with results providing insights into the nanowire properties obtained using electrical, optical and structural characterization techniques, are discussed. A new "top-down" approach for fabricating ordered arrays of high quality GaN-based nanorods with controllable height, pitch and diameter is also presented, along with results from preliminary LEDs grown on these nanorod arrays. Additionally, a novel application of aligned nanowire arrays as strain-relief templates for the growth of high quality GaN is demonstrated.

The deformation, fracture mechanisms, and the fracture strength of individual GaN nanowires were measured in real time using a transmission electron microscope-scanning probe microscope (TEM-SPM) platform. Surface mediated plasticity, such as dislocation nucleation from a free surface and plastic deformation between the SPM probe (the punch) and the nanowire contact surface were observed in situ. Although local plasticity was observed frequently, global plasticity was not observed, indicating the overall brittle nature of this material. Dislocation nucleation and propagation is a precursor before the fracture event, but the fracture surface shows brittle characteristic. The fracture surface is not straight but kinked at (10-10) or (10-11) planes. Dislocations are generated at a stress near the fracture strength of the nanowire, which ranges from 0.21 to 1.76 GPa. The results assess the mechanical properties of GaN nanowires and may provide important insight into the design of GaN nanowire devices for electronic and optoelectronic applications.

The effects of sintering temperature on the properties of Ce(0.85)Sm(0.15)O(3-delta)-Sm(0.6)Sr(0.4)FeO(3-delta) (SDC-SSF) dual-phase membranes were investigated. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), alternating current impedance and oxygen permeation techniques were employed to study the phase structure, element transport, microstructure, grain size and oxygen permeation through dual-phase membranes sintered at different temperatures. Sintering temperature has complex effects on dual-phase membranes compared with single-phase perovskite membranes. XRD and EDX analysis results reveal that the surfaces of dual-phase membranes were mainly coated by fluorite oxide with a thickness of about 45 mu m when the membrane was sintered at 1500 degrees C. Fluorite grains were gradually transferred from the inner layer to the outer layer with the increase of sintering temperature, which leads to a decrease in electronic conductivity of the membrane surface. The grain size increased with the rising of sintering temperature, which has negatively effect on oxygen permeation when the sintering temperature is higher than 1425 degrees C. (C) 2010 Elsevier B.V. All rights reserved.

Based on the fractal nature of pore size in sandstone and grindingbody within a certain range and the Andreasen equation in theory, using the optimization theory of traditional tem- porary plugging agent for reference, we established a new temporary plugging method for reservoir protection. This new method emphasizes on the formulation and optimization of solid filling particles and softening particles. It is good in easy operation and strong applicability. Indoor experiments with the natural core from Hailaer area were conducted using this new method. Compared with traditional methods, the filtration reduced significantly and the permeability recovery was improved greatly, which verified the rationality of this new method.

Cerium-doped perovskite materials, BaCe0.15CoxFe0.85-xO3-, were synthesized by a sol-gel method. Phase structure and microstructure of BaCe0.15CoxFe0.85-xO3-were investigated using XRD and SEM. The critical doping value of x=0.15 for cerium ions can be obtained for BaCe0.15CoxFe0.85-xO3-. This paper further investigated the effect of cobalt ions on the phase structure of BaCe0.15CoxFe0.85-xO3-. As the cobalt doping content is more than 0.6, BaCe0.15CoxFe0.85-xO3- deviates from cubic perovskite phase completely. Oxygen permeation test revealed that the oxygen permeability of BaCe0.15CoxFe0.85-xO3- series increases with the increase of cobalt doping. Among BaCe0.15CoxFe0.85-xO3-materials, BaCe0.15Co0.4Fe0.45O3-exhibits cubic perovskite structure and excellent oxygen permeation performance.

Mixed ionic-electronic conducting perovskite oxides, BaCe0.1CoxFe0.9-xO3-delta, were synthesized with a combined citric acid and EDTA complexing method. The structure and oxygen permeability of BaCe0.1CoxFe0.9-xO3-delta series was investigated by X-ray diffraction (XRD), scanning electron microscope.(SEM) and oxygen permeation operation. XRD characterization showed that pure cubic perovskite structure can be obtained only if the content of cobalt and cerium in B-site of Ba-Ce-Co-Fe-O series is no more than 40% and 15%, respectively. Lattice parameters of BaCe0.1CoxFe0.9-xO3-delta gradually increase with cobalt and cerium content, iodine titration experiment revealed that the doping of cerium ions with big radius can keep B-site cobalt and iron ions in low valence state. Oxygen permeation operation showed that oxygen permeation flux of all BaCe0.1CoxFe0.9-xO3-delta membranes gradually increases with testing time in the initial stage, and the time to reach steady state becomes longer with the increase of cobalt content. After reaching permeation steady state, BaCe0.1Co0.4Fe0.5O3-delta exhibits highest oxygen flux amongst BaCe0.1CoxFe0.9-xO3-delta series. (C) 2010 Elsevier Ltd. All rights reserved.

We have demonstrated the scalability of a process previously dubbed as Ge “touchdown” on Si to substantially reduce threading dislocations below 10 7 /cm 2 in a Ge film grown on a 2 inch-diameter chemically oxidized Si substrate. This study also elucidates the overall mechanism of the touchdown process. The 1.4 nm thick chemical oxide is first formed by immersing Si substrates in a solution of H 2 O 2 and H 2 SO 4 . Subsequent exposure to Ge flux creates 3 to 7 nm-diameter voids in the oxide at a density greater than 10 11 /cm 2 . Comparison of data taken from many previous studies and ours shows an exponential dependence between oxide thickness and inverse temperature of void formation. Additionally, exposure to a Ge or Si atom flux decreases the temperature at which voids begin to form in the oxide. These results strongly suggest that Ge actively participates in the reaction with SiO 2 in the void formation process. Once voids are created in the oxide under a Ge flux, Ge islands selectively nucleate within the void openings on the newly exposed Si. Island nucleation and growth then compete with the void growth reaction. At substrate temperatures between 823 and 1053 K, nanometer size Ge islands that nucleate within the voids continue to grow and coalesce into a continuous film over the remaining oxide. Coalescence of the Ge islands is believed to result in the creation of stacking faults in the Ge film at a density of 5 × 10 7 /cm 2 . Additionally, coalescence results in films of 3 µm thickness having a root-mean-square roughness of 8 to 10 nm. We have found that polishing the films with dilute H 2 O 2 results in roughness values below 0.5 nm. However, stacking faults originating at the Ge–SiO 2 interface and terminating at the Ge surface are polished at a slightly reduced rate, and show up as 1 to 2 nm raised lines on the polished Ge surface. These lines are then transferred into the subsequent growth morphology of GaAs deposited by metal-organic chemical vapor deposition. Room temperature photoluminescence shows that films of GaAs grown on Ge-on-oxidized Si have an intensity that is 20 to 25% compared to the intensity from GaAs grown on commercial Ge or GaAs substrates. Cathodoluminescence shows that nonradiative defects occur in the GaAs that spatially correspond to the stacking faults terminating at the Ge surface. The exact nature of these nonradiative defects in the GaAs is unknown, however, GaAs grown on annealed samples of Ge-on-oxidized Si, whereby annealing removes the stacking faults, have photoluminescence intensity that is comparable to GaAs grown on a GaAs substrate.

We describe efforts to epitaxially integrate GaAs with Si, using thin, relaxed Ge layers. The Ge films are deposited by molecular beam epitaxy using a self-assembled, selective-area growth technique, where atomic Ge etches an SiO 2 mask layer and then grows from pores extending to the Si substrate. The resulting Ge film coalesces over the SiO 2 mask and is planarized, using H 2 O 2 -based chemical–mechanical polishing. We subsequently deposit a GaAs/AlAs heterostructure on the polished Ge on Si substrate by metal-organic vapor phase epitaxy. While the initial Ge films were completely relaxed and dislocation-free, they contain a high density of stacking faults that propagate through the GaAs/AlAs heterostructure. These stacking faults create phase domains that appear as non-radiative recombination centers in cathodoluminescence images. Further development of two-step Ge epitaxy with an anneal near the Ge melting point eliminates stacking faults in the Ge, but decomposes the SiO 2 mask allowing threading dislocations to form and propagate through the GaAs/AlAs heterostructure. We discuss our strategy to prevent the loss of the SiO 2 mask and thus reduce threading dislocations.

A novel system has been developed for the imaging of carrier transport within semiconductor nanostructures by operating a near field scanning optical microscopy (NSOM) within a scanning electron microscope. Luminescence associated with carrier recombination is collected with high spatial resolution to monitor the motion and recombination of charge generated by use of an electron beam as an independent point source. Light is collected in the near field from a scanning fiber using tuning fork feedback in an open architecture combined AFM/NSOM system allowing independent motion of sample and tip. From a single image, it is possible to obtain a direct measure of minority carrier diffusion length. This technique has been used in the near-field collection mode to image the diffusion of holes in n-type GaN–AlGaN core-shell nanowires, grown via Ni-catalyzed MOCVD. Measurements were made on tapered nanowires ranging in diameter from 500 to 800 nm, with lengths up to ∼30 μm. The average 1-dimensional carrier diffusion length was measured to be 1.2±0.2 μm in the low injection limit. In addition, it is possible to map the luminescence that is waveguided to the end of the structure, imaging waveguide modes.

A new dual-phase composite membrane made of Sm(0.15)Ce(0.85)O(1.925) and Sm(0.6)Sr(0.4)Fe(0.7)Al(0.3)O(3-delta) was reported. The membrane shows good oxygen permeation flux and high stability for syngas production. 1100 h operation under syngas generation in the composite membrane reactor was reported to verify the stability of the materials under both strongly oxidative and reducing environments. XRD and SEM results showed that there is no difference between the spent and as-prepared membranes. (C) 2008 Elsevier B.V. All rights reserved.

Asymmetric dual-phase composite membranes for oxygen separation were conveniently fabricated by an acid leaching technique. A thin dense layer of Ce0.85Sm0.15O1.925/Sm0.6Sr0.4FeO3−i was left by controlling the degree of acid leaching, and a porous substrate of Ce0.85Sm0.15O1.925 with a fluorite structure was formed after dissolution of Sm0.6Sr0.4FeO3−i with a perovskite structure in HCl. Thus, a thin dense layer and a porous substrate can be fabricated in a single step in which traditional shrinkage mismatch and chemical reaction between thin dense layers and porous substrates can be avoided. The thickness of the dense layer can be controlled by varying the acid leaching time. Hence, dual-phase composite membranes with high oxygen flux can be obtained.