Effect of silver doping on the phase transformation and grain growth of sol-gel titania powder

Pure and Ag doped TiO₂ powders were prepared by the sol-gel process. The effect of Ag doping on TiO₂ anatase to rutile phase transformation was investigated by means of XRD, TEM, SEM, DSC-TG, and surface morphological characterization. It is found that the Ag doping promotes the phase transformation but has a depression effect on the anatase grain growth. The mechanism is proposed. With a suitable amount (ca. 2–6 mol%), the Ag dopant reduces anatasegrain size and increases the specific surface area of TiO₂ powder, which exhibits a great potential in improving the TiO₂ photocatalytic activity.     

掺杂镧、铈和锆对TiO2热稳定性的影响

本文研究了由Ti(SO₄)₂水解制得的纳米TiO₂粉体的热稳定性以及掺杂La、Ce和Zr后其热稳定性影响的变化规律。发现锐钛矿相晶体的生成对样品的比表面积有较大的影响，而通过掺杂可对此产生抑制作用，从而提高TiO₂的热稳定性。文中就不同掺杂离子的影响机理进行了讨论。     

Effect of polyethylenimine on the dispersion and electrophoretic deposition of nano-sized titania aqueous suspensions

The dispersion and electrophoretic deposition (EPD) behavior of an aqueous suspension of nano-sized titania particles stabilized with a dispersant of polyethylenimine (PEI) were systematically investigated. The adsorption behavior of PEI on the titania surfaces indicated a high affinity adsorption of PEI at a high pH value while a low affinity adsorption was observed at a low pH value, which is consistent with the viscosity behavior of the suspension. The influences of the suspension pH, the added amount of PEI and the salt addition on the electrophoretic deposition behavior of the suspensions were studied.     

Electrolytic deposition of oxide films in the presence of hydrogen peroxide

Cathodic electrosynthesis of TiO₂, Nb₂O₅, PZT, composite RuO₂–TiO₂ and Al₂O₃–TiO₂ films and powders was performed. In the proposed approach, TiO₂, Nb₂O₅, PZT film formation on platinized silicon or/and Pt substrates was achieved via peroxoprecursors. Obtained deposits were characterized by XRD, SEM, Auger and SIMS methods. The crystallization behaviour of the deposits has been studied. Possible cathodic reactions which underlie the deposition process and the role of hydrogen peroxide are discussed. ©     

Effect of alternating electric current frequency on the viscosity of coal tar

The results of a study on the effect of alternating electric current on the relative viscosity of coal tar from Shubarkol coal are reported. The optimum conditions of treatment were established. It was found that the entropy of activation is the main characteristic responsible for structure rearrangements in the organic matter of tar. The tar samples were analyzed by chromatography-mass spectrometry before and after treatment with alternating electric current, and an increase in the amount of phenols was detected.     

Transient mass transfer rate of Cu ion caused by copper electrodeposition with alternating electrolytic current

Copper electrolysis is carried out in a stagnant 0.05 M CuSO₄ aqueous electrolyte under alternating current (AC) condition. Transient mass transfer rate of Cu²⁺ ion caused by copper electrodeposition with AC is studied theoretically and experimentally with the holographic interferometer. The effect of buoyancy convection developing along the vertical plane electrodes on the transient concentration boundary layer (CBL) structure accompanying with AC is focused on. Two different electrode configurations, the horizontal cathode over anode and the vertical electrode settings, are employed for this purpose. The CBL thickness tends to increase over long duration time in the former configuration, while it converges to a steady-state value in the latter. Both calculated and measured concentration profiles in the vertical electrode configuration exhibit the characteristic transient behaviors composed of the pulsating CBL (PCBL) in the vicinity of the cathode surface and the stationary CBL (SCBL) outside the PCBL. The appearance of the SCBL is ascribed to mass transfer by advection, and the overall CBL thickness depends on the hydrodynamic conditions such as the magnitude of buoyancy convection.     

Effect of deposition regimes on the properties of sol-gel films

The effect of technological factors of deposition of a film-forming solution in the Bi₂O₃-Fe₂O₃-TiO₂ system on the physical and physicochemical properties of the resulting three-component oxide film are described.Translated from Steklo i Keramika, No. 9, pp. 10–12, September, 1995.     

Effect of ion bombardment and hydrogen pressure during deposition on the optical properties of hydrogenated amorphous carbon thin films

Carbon-based thin films are ideal materials for several state-of-the-art applications, such as protective materials and as active films for organic electronics, medical, optoelectronic devices. In this work, we study in detail the effect of the ion-bombardment and the hydrogen partial pressure during deposition on the optical properties of hydrogenated amorphous carbon (a-C:H) thin films grown onto c-Si substrates by rf magnetron sputtering. The optical properties of the a-C:H films were investigated by phase modulated Spectroscopic Ellipsometry in a wide spectral region from the NIR to the Vis-far UV (0.7-6.5 eV). A dispersion model based on two Tauc-Lorentz oscillators, has been applied for the analysis of the measured < ε(ω)> of the a-C:H films to describe the π-π* and σ-σ* interband electronic transitions, that can describe accurately the optical properties of all amorphous carbons. The applied V_b influences the bombardment of the growing thin films with Ar ions affecting the content of sp² and sp³ hybridized carbon bonds in the films. As it was found, the increase of the applied negative voltage reduces the optical transparency of the a-C:H films. Also, the H incorporation has been found to change only the energy position of the σ-σ* transitions. Finally, from the study of the refractive index n(ω = 0 eV) it has been found that the increase of the ion bombardment during the films deposition is correlated to an increase in the films density.     

Fabrication of carbon nanotube thin films on flexible substrates by spray deposition and transfer printing

We present two different processes for the deposition of high quality CNT films on flexible substrates. The first is a simple and low cost transfer printing process that transfers CNT films deposited on glass to a flexible substrate in few steps. The second is the utilization of a low cost spray process for the direct deposition of CNT films on flexible substrates. Both processes are reliable, reproducible and result in highly uniform CNT films which are comparable to the state-of-the-art CNT films fabricated on glass substrates. CNT films with 19 nm thickness and with an optical transmission up to 86% at a sheet resistance of 250 Ω/sq have been fabricated on flexible substrates.     

Dielectrophoretic modeling of the dynamic carbon nanotube network formation in viscous media under alternating current electric fields

The dynamic formation of carbon nanotube (CNT) networks in liquids under the application of an alternating current electric field is investigated using the effective dipole modeling approach. Three mechanisms are investigated by a set of three independent nonlinear differential equations derived from dielectrophoretic theory, viz. CNT rotation, CNT-to-CNT Coulombic interactions, and CNT migration towards an electrode. The models consider the effect of the electric field magnitude and frequency, the CNT’s concentration and aspect ratio, and the viscosity of the surrounding medium. A layer at the CNT/liquid interface is included and the effect of such a layer’s permittivity, electrical conductivity and thickness is investigated. Modeling predictions allow the reconstruction of the dynamic sequence of events leading to an aligned CNT network, which strongly depends on the CNT’s aspect ratio and concentration. Experimental trends regarding the effect of frequency can only be captured by considering an interface layer in the model.     

Effect of substrate temperature on the selective deposition of diamond films

Selective diamond films on roughened Si(100) substrates with patternings have been achieved by microwave plasma chemical vapor deposition (MP-CVD). The films have been characterized by scanning electron microscopy (SEM) and Raman spectra. The influence of substrate temperature on the selective deposition of diamond films has been discussed in detail: the diamond nucleation density on the SiO₂ mask increased with substrate temperature while the effect of the selective deposition of diamond films deteriorated; the optimized deposition temperature conditions have been concluded.     

Tungsten hexacarbonyl and hydrogen peroxide as precursors for the growth of tungsten oxide thin films on titania nanoparticles

W(CO)₆ and H₂O₂ were used in an atomic layer deposition (ALD)‐like process to grow thin WO_x films onto TiO₂ powders in a fluidized bed reactor. Carbonyl precursors are not widely used in this application, so that deviations from an ideal ALD process, previously not examined with W(CO)₆, were identified. The resulting WO_x films were a result of both ALD‐like and chemical vapor deposition‐based growth modes. A chemical reaction mechanism incorporating a combination of these two growth modes was inferred. As the move to expand the range of ALD precursors meets with the desire to scale up these processes, the simultaneous appearance of both these growth modes is likely to become more and more common, and so understanding the interaction of these two types of surface reactions is key to progress in the field. The films were observed to inhibit the anatase‐to‐rutile phase transformation in the TiO₂ powders upon high temperature annealing, while crystallization of the amorphous WO₃ was also not observed. Changes in the local bonding within the WO₃ were observed and associated with changes in the structural nature of the film and its interface to the substrate. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1278–1286, 2014     

The effect of titania content on the physical properties of polyimide/titania nanohybrid films

In this study, a series of PI/TiO₂ nanohybrid materials were prepared from polyamic acid of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride/3,3′-diaminodiphenyl sulfone, and titania precursor by the sol-gel method. The titania content in the hybrid system was varied from 0 to 5 wt %. The physical and mechanical properties of the hybrids such as refractive index, optical transmission, and tensile strength were investigated. It was determined that incorporation of titania precursor into the PI matrix improved the refractive indices and tensile modulus of the hybrid films. It was observed that the optical transmittance and tensile strength of the nanohybrids were slightly decreased with the increasing titania content. It was determined that the hybrid films might have enhanced the UV shielding properties compare to the PI films. Furhermore, the hybrid materials showed better thermal stability than the PI. SEM studies demonstrated that titania particles (1 and 3 wt %) were distributed homogeneously through the PI matrix. The effect of the titania content in the PI on DC conductivity and dielectric constant were also analyzed. For the PI film containing 5 wt % titania, activation energy value increased to 1.0 eV from the value of 0.65 eV. DC conductivity value of the films depending on titania content varied between 3.0 × 10⁻¹¹ and 1.4 × 10⁻¹⁰ S/cm at room temperature. Relative dielectric constants of the films were calculated from capacitance measurements depending on frequency (40–100 kHz) at different temperatures (303–360 K). The values increased with the increasing titania content. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of rare earth doping on sol-gel derived PZT thin films

We have studied the effect of rare earth dopants (Nd, Gd and Ce) on the phase formation behavior and electrical properties of sol-gel derived Pb_1.05(Zr_0.53Ti_0.47)O₃ thin films. In all these films the perovskite phase is obtained up to 5 at% doping and beyond that pyrochlore phase was found to coexist with the perovskite phase. Ce and Gd doping(1-2 at%) exhibited improved ferroelectric and dielectric properties as compared to the undoped PZT films. Nd doping (2 at%) was found to be effective to increase the retained switchable polarization of undoped PZT from 63% to 84%. The transition temperature of undoped PZT film was found to be reduced with Nd doping. The Nd doped films also exhibited typical relaxor behavior and a diffuse phase transition, characteristic of the relaxor material. Introduction of Nd into the PZT lattice probably introduces disorder in the B site of ABO₃ lattice which causes the observed relaxor behavior     

Effect of doping with nickel and copper on catalytic behaviour of wide-pore zeolites with different pore structures

The catalytic properties of wide-pore zeolites, namely Ni- and Cu-doped faujastie H-Y and H-mordenite (H-M) are compared on the example of conversion of n-hexane. After thermal pretreatment of ion-exchanged zeolites, reduction with hydrogen (P ≤ 40 bar) leads to a large number of metallic clusters and crystallites as well as ionic species in the zeolites. Notwithstanding this variety, the different types of catalysts can be divided into three classes: classical bifunctional catalysts (for example NiHM, NiHY) with ion exchange degrees > 30%, monofunctional catalysts, such as CuHM and CuHY with high copper contents (ion exchange degree > 40%) and metal-doped (Ni and Cu) zeolites which, depending on the conditions of pretreatment, act as bifunctional and/or monofunctional compounds and, therefore, show very unstable reaction behaviour. In addition to the extent of reduction, the cation distribution affects the activity and deactivation behaviour and, to a lesser extent, the product selectivity. The reaction mechanism of bifunctional catalysis is similar to that observed in platinum-doped catalysts, while the mechanism of monofunctional catalysis resembles the process on undoped zeolites.     

Synthesis of carbon nanotube/epoxy composite films with a high nanotube loading by a mixed-curing-agent assisted layer-by-layer method and their electrical conductivity

A mixed-curing-agent assisted layer-by-layer method is reported to synthesize carbon nanotube (CNT)/epoxy composite films with a high CNT loading from ∼15 to ∼36 wt.%. The mixed-curing-agent consists of two types of agents, one of which is responsible for the partial initial curing at room temperature to avoid agglomeration of the CNTs, and the other for complete curing of epoxy resin at high temperature to synthesize epoxy composite films with good CNT dispersion. The electrical conductivity of the composites shows a value up to ∼12 S/m, which is much higher than that for CNT/epoxy composites with a low CNT loading prepared using conventional methods.     

Effect of N doping on properties of diamond-like carbon thin films produced by RF capacitively coupled chemical vapor deposition from different precursors

In this paper, we report results concerning properties of diamond-like carbon (DLC) thin films obtained in different experimental conditions: various RF power values and different precursors (methane, acetone and toluene or in combination with nitrogen). The deposition rate of DLC thin films obtained from precursors with low ionizing energy and high number of carbon atoms in molecule as acetone and toluene was higher (142 nm/min for acetone and 607 nm/min for toluene as compared with 79 nm/min for methane at 400 W input power). The highest value of hardness was obtained from methane (18 GPa). In the case of acetone and toluene precursors, the hardness increased with input power to the highest values of 16.8 and 14.8 GPa. By utilizing nitrogen as doping element, the resistivity of DLC thin films obtained from methane and acetone decreased from values higher than 10⁷ Ω cm to lower values of 12.5×10³ Ω cm for 3.79% nitrogen atomic concentration in the case of films obtained from methane and 40×10³ Ω cm for 4.26% nitrogen atomic concentration in the case of films obtained from acetone.     

交、直流交替氧化对3005铝合金电解着色的影响

采用交、直流交替氧化的方法,改变3005铝合金在硫酸介质中阳极氧化膜的结构与组成,探讨其对膜层电解着色性能的影响。结果表明,交、直流氧化的顺序及相关电解着色参数对电解着色膜性能产生明显的影响。最佳氧化及着色工艺条件为:直流氧化电流密度1～2A/dm2,交流氧化电压15～20V,着色电压5～7V,着色温度20～30℃,着色时间2～7min。由此可获得浅茶色、桃红色、朱红色、紫黑色等一系列具有高装饰性的铝阳极氧化着色膜。     

Effect of plasma polymer deposition methods on copper corrosion protection

The behavior of plasma polymer coating for Cu corrosion protection was investigated in dc cathodic polymerization, with and without anode magnetron enhancement, af magnetron glow discharge polymerization, and rf glow discharge polymerization. The combination of visual and scanning electron microscopy observations established general trends in an accelerated wet/dry cycle corrosion testing environment containing 0.1N chloride ions. Dc anodic magnetron cathodic polymerization of TMS offered the best Cu corrosion protection due to an enhanced deposition uniformity and adhesion of the deposited plasma polymer to the Cu substrate. No corrosion was observed after 25 wet/dry cycle accelerated corrosion tests when uncoated Cu suffered a severely generalized attack in one cycle. Superior corrosion protection was also performed by an af plasma polymerized coating of C₄F₁₀ + H₂ (1 : 1) at a low-energy input density and of methane at high-energy input and high deposition thickness carried out in the range of this study. The application of plasma polymers which showed high water vapor permeation resistance and surface dynamic stability ǵreatly reduced the pitting densities. © 1996 John Wiley & Sons, Inc.