Surfactant-free dielectrophoretic deposition of multi-walled carbon nanotubes with tunable deposition density

The effects of AC field strength and AC frequency on the density of dielectrophoretically deposited multi-walled carbon nanotubes (MWCNTs) were investigated and explained in terms of existing theory. We show that while both parameters can be used to control deposition density, the experimentally observed frequency trend can not be explained by the theoretical Clausius-Mossotti factors. We demonstrate the ability to make surfactant-free dispersions of long, difficult to disperse MWCNTs and use them with dielectrophoresis to make clean, single and few connections between electrodes.     

Nitrogen-doped diamond films selected-area deposition by the plasma-enhanced chemical vapor deposition process

The nitrogen-doped diamond films have been successfully synthesized by using urea as the nitrogen source. Selected-area deposition of diamond nuclei was formed by using a SiO₂ layer as the masking material. Diamond pads, around 9 μm in diameter, were obtained when the N-doped diamond films were deposited on these patterned diamond nuclei using the chemical vapor deposition process. An emission current density as high as 200 μA/cm², with a turn-on field of around 8 V/μm, was obtained. However, the diamond emitters broke down easily, which is ascribed to the localized melting of the substrate materials surrounding the diamond pads.     

Electrophoretic deposition of doped ceria: Effect of solvents on deposition microstructure

Electrophoretic deposition of doped ceria has been carried out in non-aqueous solvent to prepare coatings on different substrates and free standing films. It has been found that uneven deposition occurred in ethanol, while in butanol deposition yield is low having very little variation with deposition time. On the other hand, good deposit obtained in acetyl acetone medium, but had a porous structure. The best result however was obtained in mixed solvent. Effect of adding charge modifying additives in the ceria suspension on the deposit microstructure has been studied. Mechanism of charging in the non-aqueous medium to modify the surface properties of the suspended particles has been discussed.     

Comparison between wet deposition and plasma deposition of silane coatings on aluminium

Silane coatings are applied to metal surfaces for various purposes, e.g., to form a protective layer against corrosion or to act as a primer for subsequent coating. In this work bis-1,2-(triethoxysilyl) ethane (BTSE) was used as a precursor to deposit coatings on Al 99.99% substrates with three different techniques: dipcoating (water based solution), vacuum plasma and atmospheric plasma. Infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS) and field emission gun-scanning electron microscope (FE-SEM) were used to characterise the structure, composition and surface morphology of the silane coatings. The aim of this investigation is to compare the surface and bulk characteristics of the films prepared with the three different methods, in order to get information on how the BTSE molecule is modified by the deposition technique.     

Electrospray evaporation and deposition

Electrospray transport, evaporation and deposition on a heated substrate is investigated theoretically by Lagrangian tracking of single droplets. The droplet mass and heat transfer are calculated under forced convection and compared to limited cases of electrospray transport only or droplet evaporation only. Segregation of primary and satellite electrospray droplets is observed also, in agreement with data in the literature. The arriving droplet diameter and spatial distribution at the substrate show that evaporation barely affects droplet transport. In contrast, droplet size and salt concentration can be affected significantly by evaporation. It is shown also how process parameters such as substrate temperature, initial droplet diameter and vapor transport may affect the film quality. Accounting for the Rayleigh limit of charged droplets, leads to acceleration of their evaporation when high substrate temperatures or small droplet diameters are employed.     

Aerosol deposition for post-LTCC

Embedded capacitor technology is one of the most promising methods to achieve miniaturization, reduced costs and higher performance in rf wireless communication products. Much R&D on embedded capacitors has been conducted using different circuit board technologies; however, none of the circuit boards developed to date satisfy all of the requirements of embedded passive integration with high performance at low cost. Our unique method of aerosol deposition (ASD) can provide passive ceramic elements embedded in the resin substrate because it can produce ceramic dielectric film by accelerated ceramic nanoparticle aerosol bombardment at room temperature.We present our novel ASD approach to embedded capacitors in FR-4 resin and discuss the correlation between the microstructure and dielectric properties of ASD dielectric films deposited under various conditions. We confirmed that dense BaTiO₃ dielectric films with a dielectric constant of 400, tan δ of less than 2%, and a higher breakdown voltage, exceeding 80 kV/mm, could be formed on the resin substrates. The embedded capacitors on the FR-4 substrate, fabricated as a prototype using this ASD film, demonstrated a capacitance density of 300 nF/cm². We also clarified that variations in ASD film dielectric properties after thermal cycle testing between −55 and 160 °C for 2000 cycles was within 10% compared with as-deposited film.     

High-speed deposition of silicon nitride thick films via halide laser chemical vapor deposition

Silicon nitride shows significant potential in the field of surface protection for electronic devices owing to its excellent insulation performance and mechanical properties. In this study, silicon nitride films were fabricated via halide laser chemical vapor deposition (LCVD). The effects of deposition parameters on the crystallinity, microstructure, deposition rate (R_dep), Vickers microhardness, nano-hardness and electrical resistivity were investigated. The maximum R_dep of the silicon nitride thick films was 972 µm/h at T_dep of 1573 K and P_tot of 10 kPa, which is the highest value compared with those obtained via conventional CVD. As T_dep increased, the Vickers microhardness and nano-hardness of the films increased to the highest value of 25.1 GPa and 34.8 GPa at 1573 K, respectively. The electrical resistivity of the films decreased with increasing T_dep and showed a maximum value of 1.49 × 10¹⁴ Ω·cm at T_dep of 1273 K.     

Electrophoretic deposition of polyetherimide from an aqueous emulsion: optimisation of some deposition parameters

A systematic study was carried out to investigate the cataphoretic electrodeposition of polyetherimide from an aqueous medium onto an electrically conductive support (aluminum, steel mesh). The subsequent re‐imidisation steps were also investigated. The yield and quality of deposited polyetherimide were found to be strongly dependent upon a number of formulation variables that are closely related to the emulsion composition and electrodeposition conditions. A polymer modified to 70% with methylpiperazine and quaternised to 50% with lactic acid gave a stable emulsion at 6% w/w (seven days at 4–5 °C). Maximum rate of deposition was obtained with an initial current density of 10 mA cm⁻² in the voltage range of 40–68 V. © 1999 Society of Chemical Industry     

化学沉积纳米晶Co-P合金及其沉积速率影响因素的研究

化学沉积可得到均匀、致密的纳米晶薄膜,是一种较为理想的纳米晶制备方法。采用正交实验优化了化学沉积纳米晶钴磷合金的工艺配方,研究了正交实验5因素如硫酸钴、柠檬酸三钠、硼酸、次磷酸钠和温度及负载因子、沉积时间对沉积速度的影响。研究获得的优化工艺配方和参数为:0 06～0 12mol/LCoSO4·7H2O,0 40～0 55mol/LNaH2PO2·H2O,0 15～0 3mol/LNa3C6H5O7·2H2O,0 3～0 6mol/LH3BO3,50～80℃,负载因子0 4～0 8dm2/L。     

Influence of deposition temperature on the properties of hydroxyapatite obtained by electrochemical assisted deposition

Surface functionalization of pure titanium (cp-Ti) with hydroxyapatite (HAp) was successfully achieved by means of electrochemical deposition (ED) in a solution containing calcium nitrate and ammonium dihydrogen phosphate. The aim of this study is to evaluate the influence of the deposition temperature on the elemental and phase composition, chemical bonds, morphology, and in vitro electrochemical behaviour in biological simulated media (simulated body fluid - SBF). The roughness and wettability of the developed coatings are also investigated. By increasing the deposition temperature from 50 °C to 75 °C, the HAp coatings present a well-crystalized structure, denser and a nobler behaviour in terms of electrochemical behaviour in SBF at 37 °C. Also, by increasing the deposition temperature from 50 °C to 75 °C, the contact angle has decreased from 76.1° to 27.4°, exhibiting a highly hydrophilic surface. Taking into consideration all the obtained data, electrodeposition of HAp at 75 °C was found preferable when compared to 50 °C. The characteristics of the HAp coatings can be easily adjusted by optimizing the electrochemical deposition parameters and/or controlling specific features like pH, temperature, or ionic concentration of electrolyte, etc.     

Fabrication of SiC/diamond composite coatings by electrophoretic deposition and chemical vapor deposition

In this research, SiC/diamond composite coatings were fabricated by a novel procedure that consisted of the electrophoretic deposition (EPD) of diamond particles onto graphite substrates followed by chemical vapor deposition (CVD) of SiC. Various concentrations of MgCl₂ were employed to increase the deposition rate and uniformity of the deposits during the EPD process by giving a positive charge to diamond particles. The CVD of SiC was found to have a tightly connected diamond‐graphite interface and spherical texture. With higher weight fraction of diamond particles deposits, the wear of steel ball increased, while the wear of SiC coating decreased.     

无磷粉的灰分沉积

介绍了洗涤过程中因无磷粉形成的灰分以及一种无磷粉灰色沉积性能的测定方法，实验测定了4种无磷助剂的灰分沉积和在高分子聚合物存在时的灰分沉积，并利用X射线荧光光谱仪对灰分进行全元素分析，分析了灰分的具体组成，考察各种助剂对灰分的贡献及高分子聚合物对无磷粉灰分沉积性能的影响。     

Carbon deposition from irradiated methane

Carbon-14 tracer techniques have been used to measure directly the carbon deposition resulting from the radiolysis of methane by itself and in the presence of carbon dioxide, oxygen and graphite. It is shown that carbon deposition is increased in the presence of carbon dioxide and decreased in the presence of oxygen. at high carbon dioxide pressures (40 cm Hg) and high doses (>100 Mrad), the majority of the methane is decomposed to deposit. Irradiation of methane by itself produces less deposit than in the presence of graphite and there is an enhancement of the surface deposit compared with that within the bulk of the graphite. The results of the analyses for light hydrocarbons produced during methane radiolysis over a range of conditions are also briefly discussed.     

Electrophoretic deposition of carbon nanotubes

Electrophoretic deposition (EPD) has been gaining increasing interest as an economical and versatile processing technique for the production of novel coatings or films of carbon nanotubes (CNTs) on conductive substrates. The purpose of the paper is to present an up-to-date comprehensive overview of current research progress in the field of EPD of CNTs. The paper specifically reviews the preparation and characterisation of stable CNT suspensions, and the mechanism of the EPD process; it includes discussion of pure CNT coatings and CNT/nanoparticle composite films. A complete discussion of the EPD parameters is presented, including electrode materials, deposition time, electrode separation, deposition voltage and resultant electric field. The paper highlights potential applications of the resulting CNT and CNT/composite structures, in areas such as field emission devices, fuel cells, and supercapacitors.     

Electrophoretic deposition of zein coatings

In this study, crack free, well-adhered and transparent zein coatings were obtained on 316L stainless steel substrates by electrophoretic deposition (EPD) employing varying deposition voltages and times. Obtained films were studied by Fourier transform infrared spectroscopy and scanning electron microscopy, and it was shown that the obtained coatings exhibit homogeneous and smooth surfaces. The deposition yield was investigated at various EPD conditions; the highest yield was found at 10 V and 10 min deposition time. The deposition mechanism was discussed by considering chemical reactions occurring during EPD. The EPD method developed here is attractive for the surface modification of metal implants by zein layers aiming at functionalizing surfaces for biomedical applications.     

High-quality diamond film deposition on a titanium substrate using the hot-filament chemical vapor deposition method

Diamond film on titanium substrate has become extremely attractive because of the combined properties of these two unique materials. Diamond film can effectively improve the properties of Ti for applications as aerospace and biomedical materials, as well as electrodes. This study focuses on the effects of process parameters, including gas composition, substrate temperature, gas flow rate and reactor pressure on diamond growth on Ti substrates using the hot-filament chemical vapor deposition (HFCVD) method. The nucleation density, nuclei size as well as the diamond purity and growth tendency indices were used to quantify these effects. The crystal morphology of the material was examined with scanning electron microscopy (SEM). Micro-Raman spectroscopy provided information on the quality of the diamond films. The growth tendency of TiC and diamond film was determined by X-ray diffraction analysis. The optimal conditions were found to be: CH₄:H₂ = 1%, gas flow rate = 300 sccm, substrate temperature T_sub = 750 °C, reaction pressure = 40 mbar. Under these conditions, high-quality diamond film was deposited on Ti with a growth rate of 0.4 μm/h and sp² carbon impurity content of 1.6%.     

Diamond deposition on chromium, cobalt and nickel substrates by microwave plasma chemical vapour deposition

Only after a relatively long incubation time (which is necessary to saturate the substrate and its surface with carbon by diffusion or formation of an intermediate layer) did diamond nucleation and deposition occur on Cr, Co and Ni, Also, prior to the onset of the diamond formation, non-diamond carbon layers can be formed with too high a concentration of CH₄. However, most of the experimental facts observed during the diamond depositions on Cr, Co and Ni surfaces can be explained by interactions occurring between the reaction gases and the substrates.

Chromium substrates form an intermediate carbide layer prior to diamond deposition. Diamond nucleation did not occur readily. Cobalt has only a low solubility for C. At low CH₄ concentrations, diamond was deposited on pure Co. No deposition of amorphous carbon was observed. Nickel has a certain C solubility. Diamond nucleation occurred only after the substrate and its surface had been carbon saturated. The length of the interval until saturation was reached depended on the substrate thickness.

During the time needed to cover the substrate fully with a diamond layer, the metal vapour from substrate interacted with the diamond growth. Large growth steps developed on the diamond crystal facets. Also refractory metal substrates placed near to the Cr, Co or Ni substrates were contaminated and their diamond coatings exhibited the same growth step features.     

Continuous deposition of carbon nanotubes on a moving substrate by open-air laser-induced chemical vapor deposition

Continuous deposition of carbon nanotubes under open-air conditions on a moving fused quartz substrate is achieved by pyrolytic laser-induced chemical vapor deposition. A CO₂ laser is used to heat a traversing fused quartz rod covered with bimetallic nanoparticles. Pyrolysis of hydrocarbon precursor gas occurs and subsequently gives rise to rapid growth of a multi-wall carbon nanotube forest on the substrate surface. A “mushroom-like” nanotube pillar is observed, where a random orientation of carbon nanotubes is located at the top of the pillars while the growth is more aligned near the base. The typical carbon nanotube deposition rate achieved in this study is approximately 50 μm/s. At high power laser irradiation, various carbon microstructures are formed as a result of excessive formation of amorphous carbon on the substrate. High-resolution transmission and scanning electron microscopy, and X-ray energy-dispersive spectrometry are used to investigate the deposition rate, microstructure, and chemical composition of the deposited carbon nanotubes.