Photovoltage enhancement of dye sensitised solar cells by using ZnO modified TiO2 electrode

Abstract

A ZnO modified TiO₂ (ZnO/TiO₂) film was prepared by immersing TiO₂ electrodes in Zn(Ac)₂ aqueous solution. The open circuit voltage of a dye sensitised solar cell (DSSC) with the ZnO/TiO2 film electrode has a dramatic enhancement, compared to the DSSC with the TiO₂ film electrode. However, the short circuit current density of the DSSC with the ZnO/TiO₂ film electrode is lower than that with TiO₂ electrode. The film electrodes were characterised by SEM, EDX and UV-vis, and the photoelectric performance of DSSCs were measured. The photovoltage enhancement is attributed to the formation of a flat-band potential energy barrier by ZnO at TiO₂/electrolyte interface. The decline of the photocurrent with ZnO/TiO₂ film electrode is due to poor dye absorption on larger particles of ZnO.     

New BST–silica suspension coating material for dielectric thin films fabricated at low temperatures

Abstract

A new Ba_0·7Sr_0·3TiO₃ (BST)–silica suspension has been developed as a coating material for dielectric thin films. Using a spin on glass (SOG) wet process, a thin layer consisting of nanoparticles of BST and silica was formed on an Al/SiO₂/Si wafer. The BST–silica suspension was made by mixing a BST nanoparticle dispersion with methyl siloxane oligomer. A silicon wafer was coated with the BST–silica suspension using a spin coater and heat treated. The sample was then coated with methyl siloxane oligomer and heat treated again, and finally, a top electrode was applied. The Al/SiO₂/BST–SiO₂/Al/SiO₂/Si stack thus prepared is a metal insulator metal (MIM) capacitor. The electrical properties of the MIM capacitor were evaluated and its capacitance, dissipation factor and voltage coefficient of capacitance were determined to be 1054 pF mm^?2, <0·1 and <100 ppm V^?1 respectively.     

纳米TiO2/SO42-的合成及光催化降解性能研究

研究了以工业级钛酸异丙酯为前驱体,正丙醇为溶剂,浓硫酸作催化剂和抑制剂,乙酰丙酮为稳定剂,采用溶胶-凝胶法制备纳米TiO2/SO42-。利用XRD、SEM、FT-IR、UV-vis、N2吸附-脱附测定BET表面积对所制备的材料进行了表征。结果表明:纳米TiO2/SO42-催化剂在可见光区的吸收较强,所制备的催化剂与未经改性的TiO2相比,吸收边从350 nm红移到430 nm左右,其红移效果显著。在紫外灯照射下进行了光催化降解亚甲基蓝溶液的催化剂性能研究,探讨了pH值、反应温度、亚甲基蓝初始质量浓度以及催化剂用量对降解率的影响。结果表明:光催化降解亚甲基蓝在中性条件下的降解率较高,碱性环境下达到最佳;最佳反应温度为35~55℃;初始浓度越大降解率越小;处理30 mL亚甲基蓝溶液所需催化剂为30 mg。     

Analysis of technology improvement opportunities for a 1.5 MW wind turbine using a hybrid stochastic approach in life cycle assessment

This paper presents an analysis of potential technological advancements for a 1.5 MW wind turbine using a hybrid stochastic method to improve uncertainty estimates of embodied energy and embodied carbon. The analysis is specifically aimed at these two quantities due to the fact that LCA based design decision making is of utmost importance at the concept design stage. In the presented case studies, better results for the baseline turbine were observed compared to turbines with the proposed technological advancements. Embodied carbon and embodied energy results for the baseline turbine show that there is about 85% probability that the turbine manufacturers may have lost the chance to reduce carbon emissions, and 50% probability that they may have lost the chance to reduce the primary energy consumed during its manufacture. The paper also highlights that the adopted methodology can be used to support design decision making and hence is more feasible for LCA studies.     

敏化纳米晶TiO2太阳电池

介绍了敏化纳米晶TiO2 太阳电池的结构、工作原理和技术指标。阐述了敏化纳米晶太阳电池相比于硅太阳电池的低成本及优于光电化学电池的关键技术 ,讨论了其总的光电转换效率高的原因及影响因素。并对敏化纳米晶太阳电池的有机染料和无机材料光敏化剂的选择 ,总的光电能转换效率、开路电压和短路电流目前研究达到的水平进行了综述 ,在此基础上提出了将其商业化的一些值得深入研究和需要解决的问题     

Joining of γ-TiAl to low alloy steel by electron beam welding

Abstract

The weldability of cast γ-TiAl with a low alloy steel by electron beam welding was investigated in this study. It was found that when a higher heat input was employed, solid state cracking appeared in the welds due to a high thermal stress, as well as formation of a brittle TiC phase and a small fraction of Ti₃Al intermetallic. Crack free welding could be achieved if welding parameters were properly controlled such that thermal stress was released and formation of TiC and Ti₃Al was minimised.     

Mechanical and chemical properties of Ni3Si and Ni3(Si,Ti) alloys multiphased by chromium addition

Abstract

The alloying behaviour and microstructure of Ni–Si–Cr ternary and Ni–Si–Ti–Cr quaternary alloys were first characterised by optical microscopy, X-ray diffraction, and scanning electron microscopy with electron probe analysis. The microstructures of the Ni–Si–Cr ternary alloys consisted of large dispersed Ni₅Si₂ phase and finely precipitated Ni₃Si phase in nickel solid solution, while the Ni–Si–Ti–Cr quaternary alloys consisted of finely precipitated Ni₃(Si,Ti) phase and nickel solid solution. Then, the high temperature mechanical properties, bend strength, and oxidation and corrosion properties of the alloys were investigated. The Ni–Si–Cr ternary alloys showed significant strengthening over a wide range of temperatures, and also large compressive plastic deformation at high temperatures. The strength and fracture toughness at ambient temperatures were correlated with the volume fraction of Ni₅Si₂ phase. The Ni–Si–Ti–Cr quaternary alloys did not show increased yield strength, but exhibited improved tensile ductility and plasticity over a wide range of temperatures. Both Ni–Si–Cr ternary and Ni–Si–Ti–Cr quaternary alloys showed substantially improved oxidation resistance in air at 1173 K, compared with Ni₃Si and Ni₃(Si,Ti) alloys. Also, the Ni–Si–Cr ternary and Ni–Si–Ti–Cr quaternary alloys showed corrosion resistance comparable to that of the Ni₃Si and Ni₃(Si,Ti) alloys.     

Water purification using solar energy: effect of sulphur on photocatalytic properties of TiO2

Abstract

The present work considers the effect of sulphur on several properties of titanium dioxide (TiO₂) including electronic structure, defect disorder and photocatalytic properties. While the reports on the mechanism of sulphur incorporation into the TiO₂ lattice are conflicting, there is a consensus that sulphur leads to reduction of band gap and enhanced photocatalytic performance. The latter effect suggests that light absorption, which is determined by an electronic structure, plays the key role in the conversion of the light energy into the chemical energy that is required for photocatalytic decomposition of organic contaminants in water. Analysis of the reported data suggests that different processing procedures result in different doping mechanisms. It is argued that most of the experimental data reported so far are not well defined and, therefore, are not compatible. Consequently, the progress in the science of photocatalysis requires collection of empirical data that are well defined.     

Construction and validation of master sintering curve for TiO2 for pressureless sintering

Abstract

One of the ultimate objectives for sintering research is to predict densification results under different thermal profiles for a given processing method. This paper studies the construction and validation of the master sintering curve (MSC) for rutile TiO₂ for pressureless sintering. The MSC was constructed using dilatometry data at two heating rates and was then validated using isothermal holds at three different temperatures. The scanning electron microscopy (SEM) observation shows that the partially sintered samples have the same density under different heating procedures, which demonstrates that the assumptions of the model are reliable. The concept of the MSC could be used to predict the sintering shrinkage and final density and calculate the activation energy. A value of 105 kJ mol^-1 for TiO₂ was obtained. The MSC could be applied to predict the sintering profile to prepare ceramics with required density and a minimum of grain growth.     

Space charge limited conduction and determination of density of localised states in semiconductor cobalt doped TiO2

Abstract

The space charge limited conduction (SCLC) mechanism in Co doped TiO₂ has been investigated at different temperatures. At lower electric fields, ohmic behaviour is observed while at higher electric fields nonohmic behaviour is observed. The results obtained confirm the presence of SCLC in Co doped TiO₂. The electronic parameters such as the position of the Fermi level above the valence band edge E _F, the density of states in valence band N _V and effective mass of holes m _h were found as 12·32 meV, 1·26 × 10¹⁵ m^?3 and 1·33 × 10^?7 m_e, respectively. The distribution of localised states in the forbidden band gap of the Co doped TiO₂ was characterised by current–voltage measurements and the density of localised states near the Fermi level N(E_F) was found to be 2·11 × 10¹⁷ eV^?1 m^?3.