Preparation of Al2O3 nanowires on 7YSZ thermal barrier coatings against CMAS corrosion

The commonly-employed material for thermal barrier coatings(TBCs)is 7 wt.%Y2O3 ZrO2(7YSZ),generally deposited by electron beam-physical vapor deposition(EB-PVD).Due to the increasing demand for higher operating temperature in aero-derivative gas turbines,a lot of effort has been made to prevent the premature failure of columnar 7YSZ TBCs,which is induced by the microstructure degradation,sintering and spallation after the deposition of infiltrated siliceous mineral(consisting of calcium magnesium aluminum silicate(CaO MgO Al2O3 SiO2,i.e.,CMAS)).A new method called Al-modification for columnar 7YSZ TBCs against CMAS corrosion was present.The Al film was magnetron-sputtered on the surface of the columnar 7YSZ TBCs,followed by performing vacuum heat treatment of the Al-deposited TBCs.During the heat treatment,the molten Al reacted with ZrO2 to formα-Al2O3 overlay that effectively hindered CMAS infiltration.Moreover,the Al film could evaporate and re-nucleate,leading to the generation of Al2O3 nanowires,which further restrained the moving of molten CMAS.

Oxygen vacancies enable the visible light photoactivity of chromium-implanted TiO2 nanowires

Although computational studies have demonstrated that metal ion doping can effectively narrow the bandgap of TiO_(2),the visible-light photoactivity of metal-doped TiO_(2) photoanodes is still far from satisfactory.Herein,we report an effective strategy to activate the visible-light photoactivity of chromiumimplanted TiO_(2) via the incorporation of oxygen vacancies.The chromium-doped TiO_(2) activated by oxygen vacancies(Cr-TiO_(2)-vac)exhibited an incident photon-to-electron conversion efficiency(IPCE)of~6.8%at450 nm,which is one of the best values reported for metal-doped TiO_(2).Moreover,Cr-TiO_(2)-vac showed no obvious photocurrent decay after 100 h under visible-light illumination.

Fast, green microwave-assisted synthesis of single crystalline Sb_2Se_3 nanowires towards promising lithium storage

In this work, a fast(0.5 h), green microwave-assisted synthesis of single crystalline Sb_2Se_3 nanowires was developed. For the first time we demonstrated a facile solvent-mediated process, whereby intriguing nanostructures including antimony selenide(Sb_2Se_3) nanowires and selenium(Se) microrods can be achieved by merely varying the volume ratio of ethylene glycol(EG) and H_2O free from expensive chemical and additional surfactant. The achieved uniform Sb_2Se_3 nanowire is single crystalline along [001]growth direction with a diameter of 100 nm and a length up to tens of micrometers. When evaluated as an anode of lithium-ion battery, Sb_2Se_3 nanowire can deliver a high reversible capacity of 650.2 m Ah g^(-1) at 100 mA g^(-1) and a capacity retention of 63.8% after long-term 1000 cycles at 1000 mA g^(-1), as well as superior rate capability(389.5 m Ah g^(-1) at 2000 mA g^(-1)). This easy solvent-mediated microwave synthesis approach exhibits its great universe and importance towards the fabrication of high-performance metal chalcogenide electrode materials for future low-cost, large-scale energy storage systems.

A new catalyst for urea oxidation: NiCo2S4 nanowires modified 3D carbon sponge

Urea oxidation is a significant reaction for utilizing urea-rich wastewater or human urine as sustainable power sources which can ease the water eutrophication while generate electricity. A direct urea-hydrogen peroxide fuel cell is a new kind of fuel cell employing urea as fuel and hydrogen peroxide as oxidant which possesses a larger cell voltage. Herein, this work tries to promote the kinetics process of urea oxidation by preparing low-cost and high-efficient NiCo2S4 nanowires modified carbon sponge electrode. The carbon sponge used in this work with a similar three-dimensional multi-channel structure to Ni foam, is prepared by carbonizing recycled polyurethane sponge which is also a process of recycling waste. The performance of the prepared catalyst in an alkaline solution is investigated in a three-electrode system.With the introduction of Co element to the catalyst, a reduced initial urea oxidation potential and a high performance are obtained. Furthermore, a direct urea-hydrogen peroxide fuel cell is assembled using the NiCo2S4 nanowires modified carbon sponge anode. Results indicate that the prepared catalyst provides a chance to solve the current problems that hinder the development of urea electrooxidation(high initial urea oxidation potential, low performance, and high electrode costs).

Well-dispersed SnO2 nanocrystals on N-doped carbon nanowires as efficient electrocatalysts for carbon dioxide reduction

The conversion of carbon dioxide into valuable organic compounds is a highly promising approach to address the energy issues and environmental problems(e.g., global warming). Herein, we presents a facile and efficient method to prepare highly dense and well-dispersed SnO2 nanocrystals on 1 D N-doped carbon nanowires as advanced catalysts for the efficient electroreduction of CO2 to formate. The ultrasmall SnO2 coated on the N-doped carbon nanowires(SnO2@N-CNW) has been synthesized via the simple hydrothermal treatment coupled with a pyrolysis process. The unique structure enables to expose the active tin oxide and also provides the facile pathways for rapid transfer of electron and electrolyte along with the highly porous carbon foam composed with interconnected carbon nanowires. Therefore, SnO2@NCNW electrocatalyst exhibits good durability and high selectivity for formate formation with a Faradaic efficiency of ca. 90%. This work demonstrates a simple method to rationally design high-dense tin oxide nanocrystals on the conductive carbon support as advanced catalysts for CO2 electroreduction.

Realizing super-long Cu_2O nanowires arrays for high-efficient water splitting applications with a convenient approach

Nanowire(NW) structures is an alternative candidate for constructing the next generation photoelectrochemical water splitting system, due to the outstanding optical and electrical properties. NW photoelectrodes comparing to traditional semiconductor photoelectrodes shows the comparatively shorter transfer distance of photo-induced carriers and the increase amount of the surface reaction sites, which is beneficial for lowering the recombination probability of charge carriers and improving their photoelectrochemical(PEC) performances. Here, we demonstrate for the first time that super-long Cu_2O NWs, more than 4.5 μm,with highly efficient water splitting performance, were synthesized using a cost-effective anodic alumina oxide(AAO) template method. In comparison with the photocathode with planar Cu_2O films, the photocathode with Cu_2O NWs demonstrates a significant enhancement in photocurrent, from –1.00 to –2.75 mA/cm^2 at –0.8 V versus Ag/AgCl. After optimization of the photoelectrochemical electrode through depositing Pt NPs with atomic layer deposition(ALD) technology on the Cu_2O NWs, the plateau of photocurrent has been enlarged to –7 mA/cm^2 with the external quantum yield up to 34% at 410 nm. This study suggests that the photoelectrode based on Cu_2O NWs is a hopeful system for establishing high-efficiency water splitting system under visible light.

Synthesis and Photocatalytic Activity of One-dimensional ZnO-Zn2SnO4 Mixed Oxide Nanowires

Mixed oxide photocatalysts, ZnO-Zn2SnO4 （ZnO-ZTO） nanowires with different sizes were prepared by a simple thermal evaporation method. The ZnO-ZTO nanowires were characterized with a scanning electron microscope, X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive spectrom- eter, and X-ray photoelectron spectra. The photocatalytic activity of the ZnO-ZTO mixed nanowires were studied by observing the photodegradation behaviors of methyl orange aqueous solution. The results suggest that the ZnO-ZTO mixed oxide nanowires have a higher photocatalytic activity than pure ZnO and Zn2SnO4 nanowires. The photocatalyst concentration in the solution distinctly affects the degradation rate, and our results show that higher photodegradation efficiency can be achieved with a smaller amount of ZnO-ZTO nanowire catalyst, as compared to the pure ZnO and ZTO nanowires. Moreover, the photocatalytic activity can also be enhanced by reducing the average diameter of the nanowires. The activity of pure ZnO and ZTO nanowires are also enhanced by physically mixing them. These results can be explained by the synergism between the two semiconductors.

Optimized CeO_(2) Nanowires with Rich Surface Oxygen Vacancies Enable Fast Li-Ion Conduction in Composite Polymer Electrolytes

Low-cost and flexible solid polymer electrolytes are promising in all-solid-state Li-metal batteries with high energy density and safety.However,both the low room-temperature ionic conductivities and the small Li^(+)transference number of these electrolytes significantly increase the internal resistance and overpotential of the battery.Here,we introduce Gd-doped CeO_(2) nanowires with large surface area and rich surface oxygen vacancies to the polymer electrolyte to increase the interaction between Gd-doped CeO_(2) nanowires and polymer electrolytes,which promotes the Li-salt dissociation and increases the concentration of mobile Li ions in the composite polymer electrolytes.The optimized composite polymer electrolyte has a high Li-ion conductivity of 5×10^(-4)4 S cm^(-1) at 30℃ and a large Li+transference number of 0.47.Moreover,the composite polymer electrolytes have excellent compatibility with the metallic lithium anode and high-voltage LiNi_(0.8)Mn _(0.1)Co_(0.1)O_(2)(NMC)cathode,providing the stable cycling of all-solid-state batteries at high current densities.

Electrostatic Field Enhanced Photocatalytic CO_(2) Conversion on BiVO_(4) Nanowires

The recombination loss of photo-carriers in photocatalytic systems fatally determines the energy conversion efficiency of photocatalysts.In this work,an electrostatic field was used to inhibit the recombination of photo-carriers in photocatalysts by separating photo-holes and photo-electrons in space.As a model structure,(010)facet-exposed BiVO_(4)nanowires were grown on PDMS-insulated piezo-substrate of piezoelectric transducer(PZT).The PZT substrate will generate an electrostatic field under a certain stress,and the photocatalytic behavior of BiVO_(4) nanowires is influenced by the electrostatic field.Our results showed that the photocatalytic performance of the BiVO_(4) nanowires in CO_(2)reduction in the negative electrostatic field is enhanced to 5.5-fold of that without electrostatic field.Moreover,the concentration of methane in the products was raised from 29% to 64%.The enhanced CO_(2) reduction efficiency is mainly attributed to the inhibited recombination loss of photo-carriers in the BiVO_(4) nanowires.The increased energy of photo-carriers and the enhanced surface absorption to polar molecules,which are CO in this case,were also play important roles in improving the photocatalytic activity of the photocatalyst and product selectivity.This work proposed an effective strategy to improve photo-carriers separation/transfer dynamics in the photocatalytic systems,which will also be a favorable reference for photovoltaic and photodetecting devices.

Epitaxial Growth and Thermoelectric Measurement of Bi2Te3/Sb Superlattice Nanowires

Superlattice nanowires are expected to show further enhanced thermoelectric performance compared with conventional nanowires or superlattice thin films. We report the epitaxial growth of high density Bi2Te3/Sb superlattice nanowire arrays with a very small bilayer thickness by pulse electrodeposition. Transmission electron microscopy, selected area electron diffraction and high resolution transmission electron microscopy were used to characterize the superlattice nanowires, and Harman technique was employed to measure the figure of merit （ZT） of the superlattice nanowire array in high vacuum condition. The superlattice nanowire arrays exhibit a ZT of 0.15 at 330 K, and a temperature difference of about 6.6 K can be realized across the nanowire arrays.

Facile Preparation of Mn_2O_3 Nanowires by Thermal Decomposition of MnCO_3

Mn2O3 nanowires with diameters of about 130 nm and lengths up to tens of micrometers were synthesized by the thermal decomposition of MnCO3 precursors. It was identified that the growth of the cubic Mn2O nanowires was preferential along the [001] direction. The intermediate stage containing melting state and the particles of manganese oxide played an important role for the formation of Mn2O3 with one-dimensional structure. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize the morphology and crystal structure of the precursors and final products. Thermogravimetry analysis was also carried out to find the mechanism for the formation of Mn2O3 nanowires. The growth of the nanowires was proposed to be dominated by the conventional melt-growth mechanism.

Synthesis and characterization of β-Ga_2O_3@GaN nanowires

In this work, we prepared the β-Ga_2O_3@GaN nanowires(NWs) by oxidizing GaN NWs. High-quality hexagonal wurtzite GaN NWs were achieved and the conversion from GaN to β-Ga_2O_3 was confirmed by x-ray diffraction, Raman spectroscopy and transmission electron microscopy. The effect of the oxidation temperature and time on the oxidation degree of GaN NWs was investigated systematically. The oxidation rate of GaN NWs was estimated at different temperatures.

Porous NiCo_2O_4 nanowires supported on carbon cloth for flexible asymmetric supercapacitor with high energy density

Recently, binary metal oxides have been considerably researched for energy storage since it can provide higher electrical conductivity and electrochemical activity than single components. Besides, rational arrays structure design can effectively enhance the utilization of active material. In this article, we synthesis a porous NiCo_2O_4 nanowires arrays, which were intimate contact with flexible carbon cloth（CC）by a facile hydrothermal reaction and calcination treatment. The rational array structures of NiCo_2O_4 facilitate the diffusion of electrolyte and effectively increase the utilization of active material. The asobtained NiCo_2O_4@CC electrode exhibits a high capacitance of 1183 mF cm^（-2） and an outstanding capacitance retention of 90.4% after 3000 cycles. Furthermore, a flexible asymmetric supercapacitor（ASC）using NiCo_2O_4@CC as positive electrode and activated carbon cloth（ACC） as negative electrode was fabricated, which delivers a large capacitance of 750 mF cm^（-2）（12.5 F cm^（-3））, a high energy density of 0.24 mWh cm^（-2）（3.91 mWh cm^（-3））, as well as excellent cycle stability under different bending states.These remarkable results suggest that as-assembled NiCo_2O_4@CC//ACC ASC is a promising candidate in flexible energy storage applications.

Coexistence of antiferromagnetic and ferromagnetic in Mn-doped anatase TiO_2 nanowires

A series of Mn-doped TiO2 nanowires(NWs) were prepared by hydrothermal method at the mole fraction of Mn changing from 0 to 12.0%.X-ray powder diffraction(XRD) analysis shows that all the samples have pure anatase structure.SEM and TEM studies show that the diameter and the length of the Mn-doped TiO2 NWs are larger than those of the undoped TiO2 NWs.Energy dispersive X-ray spectroscopy(EDX) reveals that the samples are composed of Ti,Mn and O.According to magnetization measurements,all samples show ferromagnetic behavior,but only the undoped TiO2 NWs are completely ferromagnetic with a saturated magnetization about 1.0 mA·m2/kg.Mn-doped TiO2 samples exhibit antiferromagnetic and ferromagnetic(AF-FM) behaviors simultaneously.Photoluminescence(PL) spectra demonstrate the existence of MnO2 sublattice.These observations indicate that an AF-WF crossover is induced by the coexistence of TiO2 sublattice and MnO2 sublattice.

Comparable Studies of Adsorption and Magnetic Properties of Ferrite MnFe_2O_4 Nanoparticles,Porous Bulks and Nanowires

The spinel ferrites MnFe2O4 nanowires were synthesized by hydrothermal route,porous MnFe2O4 and nanoparticles morphologies were synthesized by sol-gel method with egg white.The structures,morphologies,magnetic properties and adsorption properties of these obtained ferrites with different morphologies were studied contrastively.Results show that the obtained samples exhibit ferromagnetic properties.This realizes convenient magnetic separation from solution when they are used in the treatment of organic dyes wastewater.However,the contrastive studies show that the saturation magnetizations（Ms） of MnFe2O4 with different morphologies are different and the Ms follows the order：Ms（porous）〈Ms（nanoparticles）〈Ms（nanowires）.In addition,the adsorptions of methylene blue（MB） onto these ferrites depend on ferrites＇ morphologies seriously.The adsorption rate of MB on the porous MnFe2O4 is much higher than those onto the other two samples because the porous structure can provide high efficient mass transport through the pores.

The influence of ablation products on the ablation resistance of C/C-SiC composites and the growth mechanism of SiO_2 nanowires

Ablation under oxyacetylene torch with heat flux of 4186.8（10%kW/m2 for 20 s was performed to evaluate the ablation resistance of C/C-SiC composites fabricated by chemical vapor infiltration（CVI） combined with liquid silicon infiltration（LSI） process.The results indicated that C/C-SiC composites present a better ablation resistance than C/C composites without doped SiC.The doped SiC and the ablation products SiO2 derived from it play key roles in ablation process.Bulk quantities of SiO2 nanowires with diameter of 80 nm-150 nm and length of tens microns were observed on the surface of specimens after ablation.The growth mechanism of the SiO_2 nanowires was interpreted with a developed vapor-liquid-solid（VLS） driven by the temperature gradient.

Thermal Stability of Fe_2O_3 Nanowires

The thermal stability of α-Fe203 and γ-Fe2O3 nanowires was studied by post annealing the samples at different temperatures. Before and after annealing, the samples were characterized by X-ray diffraction and scanning electron microscopy. The α-Fe2O3 nanowires are stable at the temperatures up to 600℃, and the crystalline structure becomes more perfect after annealing. This behavior supplies a way to improve the quality of the α-Fe2O3 nanowires. The γ-Fe2O3 nanowires become unstable when annealed at 350℃. Raman spectra of both nanowires have been measured, which also indicate that the γ-Fe203 nanowires are transformed into α-Fe2O3 under the strong laser beam.

Fabrication and Characterization of Fe-Doped In2O3 Dilute Magnetic Semiconducting Nanowires

Fe-doped In2O3 dilute magnetic semiconducting nanowires are fabricated on A u-deposited Si substrates by the chemical vapor deposition technique. It is confirmed by energy dispersive x-ray spectroscopy （EDS）, x-ray photoelectron spectroscopy （XPS） and Raman spectroscopy that Fe has been successfully doped into lattices of In2O3 nanowires. The EDS measurements reveal a large amount of oxygen vacancies existing in the Fe-doped In2O3 nanowires. The Fe dopant exists as a mixture of Fe2＋ and Fe3＋, as revealed by the XPS. The origin of room-temperature ferromagnetism in Fe-doped In2O3 nanowires is explained by the bound magnetic polaron model.

High Purity and Large-scale Preparation of β-Ga_2O_3 Nanowires and Nanosheets by CVD and Their Raman and Photoluminescence Characteristics

Ga2O3 nano-structures, nanowires and nanosheets are produced on Au pre-coated(111) silicon substrates with chemical vapor deposition(CVD) technique. By evaporating pure Ga powder in the H2O atmosphere under ambient pressure the large-scale preparation of β-Ga2O3 with monoclinic crystalline structure is achieved. The crystalline structures and morphologies of produced Ga2O3 nano-structures are characterized by means of scanning electron microscope(SEM), X-ray diffraction(XRD), selected area electron diffraction(SAED) and transmission electron microscope(TEM). Raman spectrum reveals the typical vibration modes of Ga2O3. The vibration mode shifts corresponding to Ga2O3 nano-structures are not found. Two distinguish photoluminescence(PL) emissions are found at about 399 nm and 469 nm owing to the VO-VGa excitation and VO-VGa-O excitation, respectively. The growth mechanisms of Ga2O3 nanowires and nanosheets are discussed with vapor-liquid-solid(VLS) and vapor-solid(VS) mechanisms.

Wet-Chemical Synthesis and Optical Property of ZnSe Nanowires by Ag₂Se-Catalyzed Growth Mechanism

High-quality II-VI semiconductor ZnSe nanowires were facilely prepared in the oleic acid and oleylamine mixed solution at low temperatures of 130°C-200°C through an Ag2Se-catalyzed growth mechanism. Oleylamine served as an effective reducing agent and a surfactant in the synthesis. Many of the resultant nanowires were terminated by an Ag2Se catalyst particle at one of their ends, confirming that the nanowire growth followed a catalytic mechanism. The crystal structure of Ag2Se catalyst was examined, which exhibited a metastable tetragonal phase, not the common orthorhombic phase. Meanwhile, the optical properties of as-synthesized ZnSe nanowire solid powder were evaluated by the UV-Visible diffuse reflectance and photoluminescence spectroscopy and a significant blue shift was observed compared to the bulk ZnSe with a band gap of 2.7 eV. This work would provide an alternative and effective catalytic route for the preparation of one-dimensional (1D) nanostructures of ZnSe and other metal selenides.