Process parameters for diamond synthesis assisted by DC plasma using a water-ethylene glycol solution

Influence of the liquid composition, concentration of the potassium acetate, substrate-liquid distance and liquid layer thickness on the diamond formation were surveyed under a constant current for deposition during 1 h. Optimum deposition conditions were found to be 0.1 mol % potassium acetate, 8 mm substrate-liquid distance and 10–20 mm liquid layer thickness. Diamond forming liquid composition was then examined under a constant substrate temperature. It ranged from 60 to 99.9 mol % ethylene glycol; end compositions showed a poor yield. A constant substrate temperature was maintained under a constant current for temperatures lower than 900 °C. However, an important current reduction was required during the deposition to keep the substrate temperature higher than 1000 °C.     

Deposition of nano-crystalline graphite films by cathodic plasma electrolysis

Atmospheric pressure plasma deposition of nano-crystalline graphite films on titanium substrates from a predominantly ethanolic liquid phase was carried out under varying applied voltage. A thorough study of the plasma electrolytic deposition mechanisms has been performed. The investigation of the composition, structural properties, and the morphology of these graphite coatings have been performed by visible and ultraviolet Raman spectroscopy, X-ray Photoelectron Spectroscopy, Scanning Electron Microscopy and X-ray elemental microanalysis. The experimental evidence of the reduction of the work function and the enhancement of the plasma intensity with the presence of the carbon film has been reported. These properties make such nano-crystalline graphite coatings very attractive for the production of inexpensive cold cathodes for electronics and plasma devices.     

Synthesis of carbon films containing diamond particles by electrolysis of methanol

Carbon films containing diamond particles were deposited onto a Si (100) substrate by electrolysis of methanol under a direct current potential of 1200 V, with a current density of about 52 mA/cm², at atmospheric pressure and in the temperature range of 50-55 °C. The surface morphology, microstructure and crystalline structure of the deposited films were characterized by scanning electron microscopy (SEM), Fourier transformation infrared (FTIR) spectroscopy, Raman spectroscopy and transmission electron microscopy (TEM) respectively. The SEM images show that the films are formed by particle clusters and a surrounding glassy phase. The Raman spectra of the films indicate that the particle clusters are composed of diamond and that the glassy phase is composed of amorphous carbon. The FTIR measurements suggest the existence of hydrogen which is mainly bonded to the sp³ carbon in the films. The transmission electron diffraction patterns further indicate that the particles in the films consist of single-crystalline diamond. Both TEM and Raman measurements have confirmed unambiguously the formation of diamond crystals in the deposit, although the particles are not uniformly distributed on the entire surface.     

Degradation of dye solution by an activated carbon fiber electrode electrolysis system

Degradation of 29 dyes by means of an activated carbon fiber (ACF) electrode electrolysis system was performed successfully. Almost all dye solutions tested were decolorized effectively in this ACF electrolysis process. Internal relationships between treatment mechanisms and chemical composition of the dye have been discussed in this paper. Generally, it is shown that higher solubility leads to greater degradation in the process. Dyes with many -SO3-, COO-, -SO2NH2, -OH, hydrophilic groups, and azo linkages are susceptible to reduction. However, dyes with many -C=O, -NH-and aromatic groups, and hydrophobic groups, tend to be adsorbed. For dyes with -SO3-, COOH and -OH groups, if their molecules linearly spread in solution and have a significant tendency to form colloids by hydrogenous bonding, they also tend to be adsorbed and flocculated. Typical dynamic electrolysis of dye Acid Red B, Vat Blue BO and Disperse Red E-4B shows how the two major mechanisms, degradation and adsorption, act differently during treatment. Reduction occurs evenly during treatment. During the dominant adsorption process, after certain amount of iron is generated, colloid precipitation occurs and TOC and color are rapidly removed.     

Structural study of single-walled carbon nanotube films doped by a solution method

Herein, we have studied a structure of SWNT films doped by organic molecules. In this study, we reacted organic molecules with SWNT films by a vapor phase and a liquid phase, respectively. The structure of doped SWNT films was investigated using synchrotron X-ray powder diffraction measurements, and we found the clear difference between the vapor phase reaction (v-doped) and the liquid phase reaction (I-doped). In v-doped SWNT films, organic molecules are predominantly encapsulated inside SWNTs, although molecules adsorbed on the surface of SWNT bundles in l-doped SWNT films.     

Deposition and microstructure of Ti-containing diamond-like carbon nanocomposite films

Ti-containing diamond-like carbon (DLC) films were deposited by plasma decomposition of CH₄/Ar gas mixtures with an introduction of tetrakis(dimethylamino)titanium (TDMAT, Ti[(CH₃)₂N]₄), which was used as a precursor of titanium. The films deposited were found to be nanocomposite coatings consisting of TiN nanocrystalline clusters and amorphous hydrocarbon (a-C:H), indicating that the nanocrystalline clusters were embedded in the DLC matrix. The crystallinity of TiN clusters, as well as the Ti atomic concentrations in the films, increased with an increase of substrate temperature. The substrate temperature applied to form a crystalline phase in the DLC matrix induced a graphitization of amorphous hydrocarbon matrix. The increase of volume fraction of TiN nanocrystalline clusters in the DLC matrix enhanced the mechanical properties of nanostructured coatings, although the graphite-like structural transition of DLC matrix happened due to the applied heating.     

聚合物表面类金刚石薄膜的制备与应用

聚合物固有的柔软、易老化、不耐磨等特点,使它们的进一步应用受到限制.在聚合物表面制备1层DLC薄膜,将两种材料的优异性能结合起来,将极大地拓宽聚合物应用领域、提高聚合物应用价值.综述了近年来在聚合物表面制备类金刚石薄膜的研究进展,重点将介绍聚合物上DLC薄膜的制备方法、相关核心问题的解决及聚合物上制备DLC薄膜的应用前景.     

Synthesis of carbon nanofibres from a liquid solution containing both catalyst and polyethylene glycol

Carbon nanofibres (CNFs) exhibiting bamboo-like, hollow fibril morphology were prepared from a mixture of polyethylene glycol (PEG) and iron-based compounds such as Fe(2)(SO(4))(3)·nH(2)O, Fe(NO(3))·9H(2)O or FeO(OH) by a thermal process. These materials were well mixed in distilled water prior to thermal treatment in an air/nitrogen atmosphere. With increasing temperature, the mixture underwent solvent removal, dehydrogenation, thermal decomposition, carbonization and catalytic graphitization to form CNFs. Results show that CNFs can be formed with different PEG/catalyst ratios (100/1-1000/1 by weight) at 750?°C. The catalyst effect is discussed for the formation of bamboo-like CNFs. The diameter of the CNFs was about 30-50?nm while the length was a few micrometres.     

Deposition of amorphous hydrogenated carbon films on Si and PMMA by pulsed direct-current plasma CVD

A pulse-modulated direct-current methane plasma is used to deposit amorphous hydrogenated carbon (a-C:H) films on Si and polymethyl methacrylate (PMMA) substrates. The structure and mechanical properties of the films are examined by applying a negative pulse bias voltage of 0.5 to 3 kV to the substrate at a pulse bias period of 100 to 200 μs. The deposition rate on both Si and PMMA increases with increasing the net input power, independent of the pulse period. The Raman spectra demonstrate that the films on Si are diamond-like carbon (DLC), while those on PMMA are polymer-like or soft amorphous carbon because of higher crystallinity of the sp² phase and lower nanoscale hardness. The residual compressive stress of the films on PMMA is constantly low ranging from 0 to 2 GPa due exclusively to high flexibility of PMMA, which causes the easy relief of the stress and thus the density decrease in the films.     

Titanium dioxide thin films prepared by electrolysis from aqueous solution of titanium-lactic acid complex for dye-sensitized solar cells

Titanium oxide (TiO_x) thin films were prepared on transparent conducting substrate (fluorine-doped tin oxide) by cathodic electrolysis of a solution containing a titanium bis(ammonium lactato)dihydroxide and an ammonium nitrate at 323 K. Post-deposition treatment: calcination at 723 K or hot-water treatment at > 363 K promoted the growth of an anatase type crystalline phase in the TiO₂ thin film, as evidenced by X-ray diffraction and X-ray photoelectron spectroscopy. The calcined films were used as electrodes of a dye-sensitized solar cells and the cells' energy conversion efficiency was comparable to that obtained with commercially available TiO₂ nanoparticle electrodes.     

Deposition of nanostructured photocatalytic zinc ferrite films using solution precursor plasma spraying

Deposition of pure spinel phase, photocatalytic zinc ferrite films on SS-304 substrates by solution precursor plasma spraying (SPPS) has been demonstrated for the first time. Deposition parameters such as precursor solution pH, concentration, film thickness, plasma power and gun-substrate distance were found to control physico-chemical properties of the film, with respect to their crystallinity, phase purity, and morphology. Alkaline precursor conditions (7 < pH ≤ 10) were found to favor oxide film formation. The nanostructured films produced under optimized conditions, with 500 mM solution at pH ～ 8.0, yielded pure cubic phase ZnFe₂O₄ film. Very high/low precursor concentrations yielded mixed phase, less adherent, and highly inhomogeneous thin films. Desired spinel phase was achieved in as-deposited condition under appropriately controlled spray conditions and exhibited a band gap of ～1.9 eV. The highly porous nature of the films favored its photocatalytic performance as indicated by methylene blue de-coloration under solar radiation. These immobilized films display good potential for visible light photocatalytic applications.     

Method of obtaining gallium from aluminate solution by electrolysis

Abstract

Gallium is an increasingly important material in the fields of semiconductors and energy transfer. A prime source of gallium is the aluminate solution that remains after the purification of bauxite. The authors have sought a way of reclaiming gallium economically by electrolysis of a laboratory aluminate solution without having to use a cathode of mercury – an environmental pollutant. Cathodes of copper, indium, 70In–30Ga, Wood's alloy, and mercury (for comparison) were used with a wide range of anodes. The study accounted for the effects of electrode material, temperature, current density, and initial gallium concentration on the yield, energy consumption, and utilization of both current and electrode. The best results were obtained with indium or In–Ga cathodes and with platinum, Pt–Ti, or stainless steel anodes, at 75°C and a current density of ~100 Am^?2. Electrolysis was more efficient the higher the gallium concentration, demonstrating that commercial–scale electrolysis of aluminate solution is unlikely to be economically viable without prior concentration of gallium.

MST/305     

Deposition of CNx thin films by plasma-activated chemical vapour deposition using various precursors as carbon source

CNx-thin films have been deposited by plasma-activated chemical vapour deposition with capacitively or inductively coupled r.f. plasma. Acetylene, methane, carbon monoxide and tetracyanoethylene have been used as carbon precursor. A strong dependence of the layer properties on the precursor was found. In some films the nitrogen to carbon ratio was close to that of C3N4. The highest nitrogen content was observed in films made from carbon monoxide as precursor in an inductively coupled argon/nitrogen plasma. The nitrogen was mainly incorporated with covalent nitrogen–carbon single bonds. X-ray diffraction measurements showed no reflections indicating crystallinity. In small grains (length ∼10 μm) found on the layer surface the stoichiometry corresponded nearly to that of C3N4, the oxygen content is very low. Further characterizations by TEM are intended. This revised version was published online in November 2006 with corrections to the Cover Date.     

Deposition of diamond-like carbon films by using liquid phase electrodeposition technique and its electron emission properties

We have deposited diamond-like carbon (DLC) films by electrodeposition technique in methanol liquid. XPS showed the films mainly contain carbon. IR spectrum indicated that as-deposited films are hydrogenated carbon films, with the hydrogen mainly bonded to sp³ carbon. Raman measurement suggested that the films consisted of sp³ and sp² carbon. The field emission (FE) property of DLC coated on Si has been measured. The field emission of DLC films started at an applied voltage of 160 V, compared with silicon tip arrays at 600 V, and an emission current of DLC films up to 55 A at 360 V was achieved.     

Deposition of cathode carbon films in the plasma of a low-current gas discharge at atmospheric pressure

Plasma-chemical deposition of carbon films is carried out under the conditions of an atmospheric-pressure dc discharge from a mixture of hydrocarbons (methane and butane–propane) with helium on substrates (Ni and Cu) that serve as the cathode in the process of discharge. The formation of predominantly disordered films from graphite crystallites is observed at small deposition times. An array of carbon nanotubes coated with structured carbon is formed, as the duration of deposition increases; layers of graphitized scales are formed along the film’s edges.     

Deposition of tungsten-alumina composite films by oxide evaporation

Tungsten-alumina composite films were deposited by the co-evaporation of tungsten trioxide and aluminum from separate sources, followed by the condensation and reaction of the vapours on heated substrates of molybdenum, titanium and alumina. Growth rates between 0.2 and 0.5 μm min^-1 were obtained at substrate temperatures of about 1000 °C. The deposits were shown to have good oxidation resistance, high microhardness and remarkably increased electrical resistance compared with the pure metal films.     

Deposition of superconductive thin films by laser PVD

Thin films of the superconductive YBa₂ Cu₃O_7–k have been deposited on SrTiO₃ substrates by means of a pulse laser ablation technique, with variable substrate temperature, number of pulses and repetition rate of the laser beam. High substrate temperatures and low rates of repetition resulted in good quality superconducting films.     

膜电解法制备纯氯化镍溶液的研究

介绍了以金属镍板为原料采用膜电解法制备纯氯化镍溶液的工艺.研究了电流密度、温度、极距、膜支撑方式等对电解制备氯化镍溶液过程的影响,并进行了长时间连续运行扩大试验.在电流密度为400A/m2,极距为18mm,膜靠向阴极的条件下电解,电流效率大于96%,平均槽电压小于2.3V,电溶1t镍的能耗小于2170kW.h,得到的纯氯化镍溶液pH约为5,Ni2 浓度大于80g/L;膜对镍的截留率大于99.5%.