A novel one-step electrochemical method to obtain crystalline titanium dioxide films at low temperature

A crystalline titanium dioxide (TiO₂) thin film on various metal substrates such as hot-dip-galvanized (HDG), electrochemically galvanized (EG) and cold rolled steel (CRS) has been successfully prepared for the first time by simple one-step electrodeposition method from alkaline aqueous solution containing potassium titanium oxalate and hydroxylamine. The as-grown titanium dioxide films are composed of a mixture of anatase, rutile and brookite structures and have a good crystalline state. The present investigation reveals that the electrochemical deposition of crystalline titanium dioxide on different metal substrates from single electrochemical bath is possible and very promising as a preparation method for industrial applications.     

High probability of single molecule junction formation with Ag electrodes

We use a scanning tunneling microscope-based break-junction technique to compare the probability of the formation of a single-molecule junction for a series of amine-terminated oligophenyl and alkane species using either Ag or Au as electrodes. For all molecules, we find that there is a significantly higher probability of junction formation when using Ag electrodes than with Au electrodes. We also find that longer molecules have a higher probability than shorter molecules to form a junction for both Ag and Au electrodes. For all molecules, the measured molecular junction length that is formed with the Ag electrodes was longer than that formed with Au electrodes. Furthermore, we can make a single atomic oxygen junction and can measure its conductance using Ag electrodes. These observations are attributed to a narrower gap of the Ag electrodes compared to that of the Au electrodes after the metal contact ruptures. Since there is a high probability of a molecular junction forming when using Ag electrodes, we can therefore perform a statistical analysis within the context of the material properties that are suitable for future molecular electronics.     

A thermodynamic study of nonstoichiometric cerium dioxide

Thermogravimetric measurements were performed on nonstoichiometric CeO_2?x in the temperature range 750–1500°C and from oxygen pressures of 10^?2 to 10^?26 atm. From this data the deviation from stoichiometry x = x(T, P_o2) was determined. The thermodynamic quantities Δ$\text{H}$_o2 and Δ$\text{S}$_o2 were calculated in the region 0.001? x ? 0.3 and found to be independent of temperature.In the composition region 0.001< x < 0.006, the variation of Δ$\text{S}$_o2 with x is consistent with a defect model involving randomly distributed doubly ionized oxygen vacancies. The experimental dependence of x and σ (electrical conductivity) is shown to be consistent with this model as Δ$\text{H}$_o2 (≈ -10 eV) exhibits a slight dependence on x. It is postulated that the variation in Δ$\text{H}$_o2 may result from lattice parameter increases with x, while the defects remain essentially randomly distributed.In the composition region 0.006 < x < 0.1, x ∝ with 1 < n < 5, and in the region 0.1 < x < 0.3, x ∝ with n increasing rapidly with x to n? 30. This behavior is believed to result from increasing defect interaction with increasing departures from stoichiometry. It is interesting to note that the ordered phase observed by Bevan and Kordis between CeO_1·72 and CeO_1·70 was not observed in this study at temperatures between 1300° and 1500°C.     

Electrocatalytic reduction of alkyl iodides in tetrahydrofuran at silver electrodes

Recent interest in the electrocatalytic activity of silver towards the reduction of alkyl iodides has led us to investigate whether the effect is observed in tetrahydrofuran (THF) at room temperature. Using platinum electrodes in THF for the reduction of alkyl halides at 298 K has been hampered by the solvent window, which ‘obscures’ the voltammetric signals of interest. In order to overcome these problems, voltammetry has been performed at low temperature and was shown to extend the voltammetric window, leading to accurate electrochemical analyses and even novel changes in mechanism(s) of the reactive species following electron‐transfer (ET). Herein, it is shown that for a primary and tertiary alkyl iodide in THF, electroreduction at silver leads to a significant shift in the reduction potential to more positive values compared to platinum. In addition, following reduction, a characteristic series of oxidation peaks are observed and are shown to be due to the specific activity of iodide ions towards silver following reductive cleavage of the parent alkyl iodide. This characteristic feature is not observed with other halide ions: bromide and chloride. Preparative electrolyses at controlled‐potential have suggested that the reduction of the above alkyl iodides is a one‐electron concerted process. The ‘free’ iodide ions act as a monitor of reaction progression, and the carbon‐centred radical either dimerises and/or abstracts a hydrogen atom from the electrolyte/solvent; 1‐iodoadamantane giving percentage yields of 58% adamantane and 39% 1,1'‐biadamantane, the primary alkyl iodide, prepared in‐house, giving 67% R‐H and 25% R‐R. Copyright © 2007 John Wiley & Sons, Ltd.     

机车高温水冷却方案的探讨

根据机车散热的特点,分析了目前机车用扁铜管翅片散热器存在的问题,介绍了热管换热器和板翅式换热器,提出了较为可行的解决方案。。     

Thermodynamic properties of titanium dioxide,niobium dioxide and their solid solutions at high temperature

By means of thermogravimetric measurements, it has been possible to obtain information on the nature of the intrinsic and extrinsic defects of TiO₂, NbO₂ and solid solutions Nb_yTi_1?yO_2±x Pure TiO₂ is an oxygen-deficient oxide The main defects are oxygen vacancies, doubly ionized V^.._o or singly ionized V^._o, and interstitial titanium Ti³_i NbO₂ is a metal-deficient oxide The main defects are neutral niobium vacancies. The solid solutions Nb_yTi_1?yO_2±x may be divided into two groups If y > 0 04, the behavior is analogous to that of NbO₂; with the same defects, but the width of the homogeneity range decreases with the titanium content and Nb_{0 04}Ti_{0 96}O₂ is a stoichiometnc oxide If y < 004, the oxides are both metal deficient and oxygen deficient according to the oxygen partial pressure. We have particularly studied the solution Ti_{0 995}Nb_{0 005}O₂ In the oxygen-deficient domain, the main defects are assumed to be neutral or singly ionized oxygen vacancies In the metal-deficient domain, the main defects are metal vacancies V⁴_Ti From these results we have deduced the nature of intrinsic defects in TiO₂ to be Schottky defects: 2V^.._O + V⁴_T1.     

Dimensional reduction of the two Higgs doublet model at high temperature

Dimensional reduction and effective field theory methods are applied to the Two Higgs Doublet Model at finite temperature. A sequence of two effective three-dimensional field theories which are valid on successively longer distance scales is constructed. The resulting Lagrangian can be used to study different aspects of the phase transition in this model as well as the sphaleron rate immediately after the phase transition. Received: 14 March 1999 / Published online: 22 October 1999     

A thermodynamic and electrical conductivity study of nonstoichiometric cerium dioxide

Thermodynamic and dc electrical conductivity measurements were performed on nonstoichiometric CeO_2−x to characterize the electrical behavior and defect structure in the vicinity of the n to p transition. Using the mass action approach, activation energies of 2.57, 1.15 and 0.63 eV were obtained for the electron, hole and ionic partial conductivities respectively (600–1000°C, 1<P_o2<10⁻⁴ atm). Thermodynamic measurements of 99.99%CeO_2-x by electrochemical coulometric titration yielded expressions for point defect concentrations per cm³ and nonstoichiometry in the impurity dominated region at 800°C as follows:

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. Thermodynamic constant composition measurements revealed a decrease in the partial molar enthalpy (from - 10 eV) with decreasing stoichiometry for x<10^−2.8. This decrease is attributed to defect reaction involving both holes and electrons.     

Sonochemical reduction of carbon dioxide

Sonolysis of carbon dioxide dissolved in water was performed from a standpoint of reducing this material in atmosphere. During one hour of sonication, the amount of CO2 decreased to about half at 5 degrees C under CO2-Ar atmosphere. The decreasing rate for CO2 followed the order Ar > He > H2 > N2 and it was down with increasing temperature in the range of 5-45 degrees C. The most favorable concentration for reducing CO2 was 0.03 (mole fraction of CO2 in gas phase). This concentration in gas phase means an equal mixture of CO2 and Ar in water, because CO2 is more soluble than Ar. Since carbon dioxide dissolved in water would be partly ionized, the roles of ions on the sonolysis were also examined. Gaseous reaction products were CO, H2 and a small amount of O2. Carbon monoxide and hydrogen might be obtained from CO2 and H2O by sonolysis, respectively. Both gases are fuel and react each other to C1 compounds such as methanol, and so on. Therefore, irradiation of ultrasonic waves should be an important technique for reducing CO2.     

Single-electron transistor based on a single cluster molecule at room temperature

A single-electron molecular transistor is implemented at room temperature on the basis of a stable Langmuir monomolecular film consisting of a mixture of stearic acid and carborane clusters. Control of the tunneling current with the aid of an independent voltage source is recorded at room temperature. The results are compared with the “orthodox” theory of single-charge electronics. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 7, 510–514 (10 October 1996)     

类桑拿法制备的周期性结构Mo金属催化电极及其在电解水制氢中的应用

采用类桑拿法制备了聚苯乙烯微球模板, 结合双层Mo金属结构, 获得了具有周期性结构的Mo金属催化电极. 通控制氧气对聚苯乙烯球的刻蚀时间, 可有效调制Mo金属催化电极的横、纵向尺寸, 从而获得不同的衬底比表面积. 通过原子力显微镜表面形貌测试、电化学线性扫描、塔菲尔测试以及阻抗谱分析表明: 增大刻蚀时间可有效提高Mo金属催化电极的表面粗糙度和比表面积, 进而降低电荷传输电阻和塔菲尔斜率, 促进催化电极/电解液界面处析氢反应的进行. 采用类桑拿法和双层Mo金属结构制备周期性结构的方法简单, 可大面积化, 同时低温磁控溅射法制备的Mo金属催化电极成本低廉, 温度兼容多种太阳电池器件, 具有形成高效一体化光水解制氢器件的潜力.     

A novel calculation strategy for optimized prediction of the reduction of electrochemical window at anode

The reduction of the electrochemical window(EW) of electrolytes plays a significant role in assessing their compatibility with the anode in lithium-ion batteries. However, the accurate calculation of the reduction of EW is still challenging due to missing the solvation effects, condensation effects, kinetic factors, and the passivation on anodes. The theoretical prediction of the intrinsic and apparent EW is confirmed by a comprehensive experimental analysis of ethylene carbonatedimethyl carbona...     

Chemisorption of CO2 at oxide electrodes in the presence of oxygen and water

Interaction of O₂ with the surface of SnO₂ - MeO_x (Me=V, Nb, Ta) solid solutions is investigated experimentally and the parameters for different chemisorbed species are evaluated. The chemisorption process is modeled by making use of quantum chemical processes. The geometry and thermodynamic parameters of chemisorbed carbon dioxide are calculated. Cluster approximation is shown to describe well the interaction of tin dioxide semiconductors with carbon dioxide. Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11–18 Sept, 1994.     

Investigation of thermodynamic properties of cerium dioxide by statistical moment method

The thermodynamic properties of the cerium dioxide (CeO₂) are studied using the statistical moment method, including the anharmonicity effects of thermal lattice vibrations. The free energy, linear thermal expansion coefficient, bulk modulus, specific heats at the constant volume and those at the constant pressure, C_V and C_P, are derived in closed analytic forms in terms of the power moments of the atomic displacements. The temperature dependence of the thermodynamic quantities of cerium dioxide is calculated using three different interatomic potentials. The influence of dipole polarization effects on the thermodynamic properties and thermodynamic stability of cerium dioxide have been studied in detail.     

The structure of the water molecule in liquid water

The slow neutron scattering measurements of Walford, Clarke and Dore for liquid heavy water at 21°C for incident neutron wavelengths of 0·694 Å and 0·347 Å [7] have been reinterpreted using a sophisticated correction for recoil and detector effects [10] for the molecular contribution to the scattering cross-section. For momentum transfer greater than 6 Å^-1 the liquid structure contribution is negligible and a very good agreement between theory and experiment is obtained. It is concluded that the intramolecular oxygen nucleus-deuteron distance is 0·98₃±0·00₈ Å, and that the deuteron-deuteron distance is 1·55±0·02 Å. This molecular structure is nearer to that of the molecule in the vapour than that in ice I for the conventional interpretation for ice I. It is concluded that there is an environmental effect on the molecular internuclear distances at most of order 0·01 Å for the molecule in the orthobaric liquid near the triple point.