Y.H. Qiang

Influence of annealing temperature on performance of dye-sensitized TiO2 nanorod solar cells

Single-crystal rutile TiO2 nanorod (NR) arrays have been synthesized on the fluorine-doped tin oxide substrates, followed by an annealing at 200–600xa0°C. It is found that DSSCs fabricated using TiO2 NR arrays which undergo annealing display an increased efficiency than those that do not undergo annealing. The optimal efficiency of 4.42% power conversion is achieved in the DSSC made with 500xa0°C annealed arrays, which show a 450% increase in the overall conversion efficiency. The improvement is ascribed to the increased light harvesting, the enhanced electric contact and the suppressed recombination of the injected electrons with redox species in the electrolyte.

Improved performance of perovskite solar cell by controlling CH3NH3PbI3−xClx film morphology with CH3NH3Cl-assisted method

Sequential deposition solution-based method has been widely used for the fabrication of perovskite solar cells (PSCs). However, there is still a challenge to achieve homogeneous and consecutive surface of the perovskite layers. In this work, CH3NH3PbI3−xClx layers were prepared by a modified two-step solution method. Specifically, the optimum amount of CH3NH3Cl pre-added into PbI2 precursor solution, the appropriate size of pinholes and voids appear in PbI2 films and leave room for the growth of CH3NH3PbI3−xClx crystal. Under this condition, the crystal grains size is diminished and the surface coverage ratio of CH3NH3PbI3−xClx film is enhanced, which prevent the combination of electron-hole pairs on the interface between perovskite layer and TiO2 substrate. By varying the CH3NH3Cl amounts, the PSC devices displayed the highest power conversion efficiency of 13xa0%, which was obviously higher than that of the one prepared via transitional routes (10.32xa0%). As a result, we developed a simple and repeatable route for controllable synthesis of perovskite absorption layers, which is demonstrated to be effective to improve the performance of PSCs.

Self-assembled synthesis of hollow Nb3O7F nanomaterials based on Kirkendall effect and its photocatalytic properties

Abstract Hollow niobium oxide fluoride was successfully synthesised by a facile hydrothermal approach in the hydrofluoric acid/hydrogen peroxide solution without any template. By selecting hydrogen peroxide as oxygen source which could ceaselessly release oxygen gas, niobium diboride could be oxidised and corroded to form niobium oxide fluoride nanomaterials in situ. The hollow structure may result from Kirkendall effect. Significantly, the method may provide a direct route to synthesise some novel oxide nanomaterials using non-oxide ceramic as raw materials. The photodegratation experiments show that niobium oxide fluoride catalysts have better photocatalytic properties than commercial P25 TiO2 catalysts, indicating that this kind of hierarchical nanomaterials could be a promising candidate as a photodegradation material.

CNT–G–TiO2 layer as a bridge linking TiO2 nanotube arrays and substrates for efficient dye-sensitized solar cells

This study incorporated a 3-D hybrid material comprising graphene and carbon nanotubes (CNTs) into a TiO2 composite paste to adhere TiO2 nanotube arrays (NTAs) as photoanodes. The effect of the proportion of CNTs to graphene on the dye-adsorption ability of bonding layers was investigated and the optimal proportion of 2:1 provided a greatest degree of dye absorption. The DSSC efficiencies firstly increased and then decreased with increasing amount of CNT–G hybrid. The optimized DSSC efficiency of 6.17% was achieved at a suitable concentration (0.1 wt%) of CNT–G, which is due to a balance between electron transport and light harvesting in the photoanode.

Study on the Microstructure and Properties of WC Steel Bonded Carbide by Composite Electroslag Remelting

The composite electroslag remelting technology was prepared with Cr12Mo1V1 steel as matrix, and the WC particles as hard phase steel bonded carbide. By means of metallographic analysis and scanning electron microscopy and other methods to study the microstructure and grinding crack morphology of the composites, and rockwell hardness and friction and wear experiment was carried out. The results show that WC particles had no obvious slant phenomenon, partly dissolved in the steel matrix, Fe3W3C multiple carbides precipitated after cooling. And the external hardness and abrasion resistance fo the roll were higher than the core, combined with good WC particles and steel matrix, and wear surface grinding marks was small, shallow furrowed, improved the roll wear resistance and service life.

Template-Free Synthesis of Hierarchical m-ZrO2 Nanorods and its Formation Mechanism

Hierarchical ZrO2 nanorods have recently received considerable attention due to their special physical and chemical properties. However, traditional preparation methods are involved in expensive equipment, complicated process and high production cost. Here we report a simple hydrothermal approach to prepare hierarchical ZrO2 nanorod. The results show that as-synthesized products are composed of many nanorods with 80~150 nm in diameter and 15~20 μm in length. After annealing, the final product was involved into hierarchical monoclinic ZrO2 (m-ZrO2) nanorods, namely, the big nanorod was made up of many small nanorods with 20~30 nm in diameter and 300~500 nm in length. The possible formation mechanism was proposed based on a series of chemical reactions and the natural properties of zirconium.

Carbon Nanotubes Supported Pt Catalysts for Ethanol Oxidation in Alkaline Solutions

An efficient method for functionalizing carbon nanotubes (CNTs) is reported, which combined HF corrosion with sulfuric acid and nitric acid for further oxidation. The X-ray diffraction and transmission electron microscopy are employed to investigate the physic-properties of the prepared catalysts. Cyclic voltammetry and chronoamperometry methods are used to study the performance of the prepared catalysts. CNTs further treated with H2SO4 and HNO3 mixed solutions with the volume ratio of 1 to 3, heating at 100 oC for 2 h, used as catalysts supports exhibit significantly improved performance towards ethanol oxidation in alkaline solutions in comparison with other decorated CNTs. The reason could be attributed to the oxygen-contain functional groups on CNTs surface can efficiently improve the interaction between CNTs and metallic particles in catalysts.

Study on the Weldability of ZG30Cr06A Needling Material

ZG30Cr06A as a newly developed material is made into needling of mining machinery’s hydraulic support. Its tensile strength is up to 800MPa. In the paper, the weldability of ZG30Cr06A was thoroughly studied. The sensitivity to cold crack of ZG30Cr06A was tested by means of maximum hardness of HAZ and Y-slit type cracking test. And the variation of microstructure and properties of weld joints under different welding energy conditions was studied. The results show that ZG30Cr06A steel has a certain cold crack and hot crack tendency and a little reheat crack sensitivity in welding. Embrittlement and softening often appear in the HAZ. When the workspaces of 30mm were welded at room temperature, the maximum hardness of HAZ was up to 389HV. And the joints have a tendency to quenched hardening and bigger sensitive to cold crack. The welded joints would not produce cold crack when the preheat temperature is up to 120°C in welding. Because there is more influence of welding energy input on the microstructure and properties of joint, so in order to avoid the appearance of embrittlement and softening in HAZ and ensure weld quality, the welding energy input of ZG30Cr06A steel whose thickness is 30mm should be controlled less than 40 kJ/cm during the welding.

Effect of Working Current on Microstructure and Properties of Cylinder Hardened by Plasma Beam at Junction of the Hardening Traces

To improve wear resistance and service life of boron cast iron cylinder, plasma beam hardening on surface is adopted.Scanning electron microscope,X-ray diffractometer and micro-hardness tester is used to analyze the effect of working current on the structure and properties of plasma beam hardening layer at the junction of the hardening traces. The results show that the microstructure of hardening layer at the junction is hidden acicular martensite, retained austenite and flake graphite. With the increase of working current, the content of retained austenite decreases, the hardness and depth of the hardening layer increases. The highest hardness is not achieved at the surface of hardening layer but at the second-surface layer which has a certain distance to the surface. The uneven distribution of hardness in hardening layer leads to large gradient at the both sides of the highest hardness and the gradient decreases with the increase of working current.

Growth and Photovoltaic Performance of Single-Crystal TiO2 Nanorod Array Directly on Transparent Conducting Substrates

In this study, single-crystal TiO2 nanorod (NR) arrays were used as the photoanodes of dye sensitized solar cells (DSSC). The post-annealing treatment was carried out in air, O2, N2 and vacuum atomsphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been used to characterize the structure, morphology and crystallity of these samples. Although the nanorod arrays which undergo annealing remained the single-crystal structure without any change in the morphology, considerable improvement in the nanorod solar cell performance was obtained. The high efficicency of 4.42 % was achieved in the cells containing nanorods which were annealed in air at 500 °C for 30 min. In comparison, the cell fabricated using TiO2 samples without post- annealing treatment exhibited a low efficiency of just 2.1 %. Such a large improvement (280 %) was mainly attributed to the faster electron transport and the lower charge recombination rate after annealing due to an increase of the depletion width. Otherwise, the cell performance improvement may result from an enhancement in the adhension and electrical contact at the TiO2/FTO interface. The in-depth study shows that the solar cell efficiency was strongly dependent on the annealing ambience, too.