Magnetic response of CVD and PECVD iron filled multi-walled carbon nanotubes

Plasma enhanced chemical vapour deposition (PECVD) and injection chemical vapour deposition (CVD) methods have been used to produce superparamagnetic iron nanoparticles (NPs) encapsulated in carbon nanostructures (core@shell). Morphological and structural properties of the Fe-filled CNTs synthesized by PECVD and CVD were carried out using a scanning and transmission electron microscope (SEM, TEM), high resolution electron microscopy (HRTEM) and selected area electron diffraction (SAED). Magnetometry results and electron microscopy observations reveal magnetic responses with different characteristics associated to the iron particles depending on the deposition method. The magnetic properties of these samples have been described in terms of the carbon nanotube anisotropic structural effects. This magnetic behaviour has potential for biomedical applications.     

Plasma-Assisted Synthesis of Carbon Nanotubes

The application of plasma-enhanced chemical vapour deposition (PECVD) in the production and modification of carbon nanotubes (CNTs) will be reviewed. The challenges of PECVD methods to grow CNTs include low temperature synthesis, ion bombardment effects and directional growth of CNT within the plasma sheath. New strategies have been developed for low temperature synthesis of single-walled CNTs based the understanding of plasma chemistry and modelling. The modification of CNT surface properties and synthesis of CNT hybrid materials are possible with the utilization of plasma.     

Thermo-mechanical characterization of carbon fiber reinforced silicon carbide composites having boron nitride as an interphase material

The carbon fiber reinforced silicon carbide composites were prepared by an isothermal chemical vapour infiltration process. In order to achieve the required density, the carbon fiber preforms in the form of rectangular panels were infiltrated by silicon carbide (SiC) matrix. Prior to the matrix infiltration, a thin coating of boron nitride, as an interphase, was applied on the fiber preform. The test samples were subjected to seal coating of silicon carbide by chemical vapour deposition process. The effect of protective SiC seal coating was examined by testing (3-point bend test) the uncoated and the seal coated samples at different temperatures. Higher value of the flexural strength was observed for the seal coated samples as compared to the uncoated samples, when got tested at high temperature (up to 1400?°C). The detailed analysis of the fractured surfaces of the tested samples was carried out.     

Probing the tribochemical degradation of hydrogenated amorphous carbon using mechanically stimulated gas emission spectroscopy

Mechanically Stimulated Gas Emission (MSGE) spectroscopy was used for investigation into tribochemical reactions and gas emission for four types of amorphous hydrogenated carbon (a-C:H) coatings, which were obtained by either ion beam deposition (IBD) or plasma enhanced chemical vapour deposition (PECVD). The results of statistical analysis, which was employed to identify the components of the emitted gases from the mass-spectrometry data, argue against the hypothesis that considerable amount of CH₃ could be present in the emitted gases. For the IBD coatings the main components of the emitted gases were methane and/or argon, whereas for the PECVD coatings they were mainly methane and hydrogen. Noticeable emission of ethane, propane, carbon mono- and dioxides was also detected under sliding of PECVD coatings deposited with the lowest ion energy. While frictional heating has been definitely ruled out as the driving mechanism for MSGE, there are experimental evidences that MSGE has to be associated with structural degradation of the coating.     

Plasma-Enhanced Chemical Vapor Deposition of Boron Nitride Using Polymeric Cyanoborane as Source

The plasma-enhanced chemical vapor deposition (PECVD) of boron nitride films was studied using polymeric cyanoborane, (CNBH₂) n , a material previously examined by thermally activated CVD. The PECVD procedure yields boron nitride coatings containing ≅20 wt% paracyanogen as a contaminant. This impurity can be removed by heat treatment under vacuum or in an ammonia atmosphere. The boron nitride coatings are hexagonal and appear to be boron deficient. The PECVD process takes place at 300°C, measured at the backside of the substrate, as compared with 600°C in the thermally activated CVD process.     

Nanotribological study of PECVD DLC and reactively sputtered Ti containing carbon films

Amorphous carbon film, also known as DLC film, is a promising material for tribological application. It is noted that properties relevant to tribological application change significantly depending on the method of preparation of these films. These properties are also altered by the compositions of these films. DLC films are well known for their self-lubricating properties, as well. In view of this, the objective of the present work is to compare the tribological properties of diamond like carbon (DLC) film obtained by plasma enhanced chemical vapour deposition (PECVD) with the Ti containing nanocrystalline carbon (Ti/a-C:H) film obtained by unbalanced magnetron sputter deposition (UMSD) in nN load range. Towards that purpose, DLC and Ti/a-C:H films are deposited on silicon substrate by PECVD and UMSD processes respectively. The microstructural features and the mechanical properties of these films are determined by scanning electron microscope (SEM), transmission electron microscope (TEM) and nano indenter. The surface topographies and the friction force surfaces of these films are evaluated by means of an atomic force microscope (AFM). The results show that although PECVD DLC film has higher elastic modulus and higher hardness than UMSD Ti/a-C:H film, the surface roughness and the friction coefficient of PECVD film is significantly higher than that of UMSD Ti/a-C:H film.     

Deposition of diamond-like carbon coatings: Conventional to non-conventional approaches for emerging markets

Diamond-like carbon (DLC) coatings are recognized for a broad range of industrial applications due to their superior mechanical properties such as high hardness, low friction, and promising wear resistance. DLC coatings are commonly produced with physical vapour deposition (PVD) and plasma-enhanced chemical vapour deposition (PECVD) methods. New DLC markets are emerging in electronics, biomedical, additive manufacturing and textiles sectors with industrial transformations. The conventional PVD and PECVD methods may have limited usage for depositing emerging DLC products due to their elevated thermal and high vacuum environment, lack of localized deposition function, and production throughput restrictions.This review begins by briefly describing DLC coatings background, the volume of research outcomes and the global revenue in the past decade and projections for the future. DLC structural designs made with conventional deposition methods and corresponding operational parameters are then discussed in detail and enhancement in conventional methods to improve DLC coating quality and to resolve unaddressed problems are summarized. The emerging DLC applications and potential of non-conventional methods to produce DLC coatings are critically analysed with specific attention to scientific, technological and economical aspects. Representative investigations suggest that DLC coatings can be produced with hardness values up to ~20 GPa using dielectric-barrier-discharge deposition, hydrophobicity up to ~167° with electrospray assisted plasma jet coating, high deposition rates up to ~6 μm/min with microwave resonator deposition, and critical load of ~30 N with a friction coefficient of ~0.1 when deposited with the plasma gun technique. The review concludes by recommending systematic investigations to optimize geometric and operational parameters of non-conventional DLC deposition methods which can produce high-quality DLC coatings at low temperatures and atmospheric pressures with scalability to meet emerging market demands.     

Low friction and protective diamond-like carbon coatings deposited by asymmetric bipolar pulsed plasma

Diamond-like carbon (DLC) thin films have been prepared at room temperature by plasma-enhanced chemical vapour deposition (PECVD) using pulsed-DC power and CH₄ as precursor. Tribological tests of these DLC films have been carried out with a nanotribometer and a calotest instrument adapted for wear measurements. Friction coefficients ranged from 0.15 to 0.20, which differ from values obtained by other techniques. In this study we have systematically measured the abrasive wear rate and friction coefficient of DLC films deposited at different conditions (pulse frequency and peak voltage), and we have discussed the results in terms of DLC structure and surface morphology. These films could find application as ultrathin anti-friction and anti-wear protective coatings, hydrophobic coatings, gas diffusion barriers and dielectric layers in electronic devices.     

Vapor deposition polymerization of synthetic rubber thin film in a plasma enhanced chemical vapor deposition reactor

Rubber is one of the most commonly used industrial materials worldwide. However, there is a gap in the literature on the production of rubber thin films in nanoscale. When the rubber thin films are produced in nanoscale, they can be used in high-tech applications where bulk rubbers have never been used before. This study is one of the first investigations to focus on the vapor-based production of the polyisoprene (PI), which is an important member of the synthetic rubber class. For this purpose, a single-step, rapid and environmentally friendly method based on plasma enhanced chemical vapor deposition (PECVD) was employed to produce PI thin films using 2-methyl-1,3-butadiene (isoprene). The high-vapor pressure of isoprene makes it a promising monomer for the production of chemical vapor deposition polymers. The effect of plasma processing parameters on the PI deposition rate was investigated. The deposition rate of PI thin film as high as 40 nm/min was achieved and the contact angle of PI coated bamboo surface was found to be 146.8°. The mechanical durability and laundering tests of PI thin films were performed. Based on this study results, PI thin films produced by PECVD can be used in a number of potential applications.     

Chemical and electrochemical intercalation of lithium into boronated carbons

Boron-substituted carbons have been produced by chemical vapour deposition from acetylene and boron trichloride precursors at 1140°C. Li intercalation was investigated, chemically from the Li vapour and electrochemically in Li–carbon cells. In both cases, the amount of intercalated Li increases with the boron content of the carbon, up to a value of 13 at.% boron. Above this value, the intercalation of lithium is not so efficient. This behaviour is understood by assuming that boron, which acts as an electron acceptor and hence favours the intercalation of electron donors like lithium, can enter substitutionally into the carbon lattice up to a certain limit, which is close to 13 at.% for the materials deposited at 1140°C.     

Atomic layer deposition of ZnO thin films on boron-doped nanocrystalline diamond

ZnO thin films were successfully prepared on boron-doped nanocrystalline diamond NCD by means of atomic layer chemical vapour deposition. Their growth and properties are similar to the layers grown by the same technique on glass. The layers thickness can be easily monitored by the number of precursors pulses. The ZnO layers are uniform and have perfect adhesion to NCD. Electrical measurements show that there is no current rectification if highly doped NCD and low resistance ALCVD ZnO are used. On the contrary, a rectifying behaviour can be obtained if lightly boron-doped NCD and resistive hydrothermally prepared ZnO are used.     

Wetting angles and photocatalytic activities of illuminated TiO2 thin films

TiO₂ thin films have been prepared by physical vapour deposition (PVD) and plasma enhanced chemical vapour deposition (PECVD) to study the UV-induced photo-activity of this material. Wetting angle variations and photo-catalytic activity for the degradation of dyes upon UV illumination have been compared for thin films with different crystalline structure (amorphous, rutile and anatase), microstructure (columnar, compact, etc.) and porosities as estimated from the values of their refraction indices and their direct assessment with a quartz crystal monitor. The surface of the thin films became superhydrophilic upon UV light irradiation and then it recovered its original state by keeping the samples in the dark. Wetting angle decays follow very similar kinetics for amorphous and crystalline films, independently of their actual porosities. By contrast the photo-catalytic activity was very dependent on the crystalline structure of the films (anatase > rutile > amorphous) and on their porosities. The different behaviour depicted by the films with regard to these two properties suggests that they respond to different though related mechanisms and that they cannot be considered as equivalent when trying to prove the photo-activity of TiO₂.     

类金刚石薄膜在模拟体液中的电化学阻抗

利用双放电腔微波等离子体源全方位离子注入设备,分别采用等离子体增强化学气相沉积技术、等离子体源离子注入和等离子体增强化学气相沉积复合技术两种工艺对医用3161,不锈钢进行类会刚石薄膜表面改性。利用电化学阻抗谱法考察了两种工艺制备的类金刚石薄膜在模拟体液中的抗腐蚀性能。结果表明：与采用等离子体增强化学气相沉积技术制备的类金刚石薄膜相比,在72h的浸泡时间内,采用等离子体源离子注入和等离子体增强化学气相沉积复合技术制备的类金刚石薄膜防腐蚀性能明显增高,腐蚀阻抗较高,碳注入层可有效抑制溶液渗入薄膜和基体之间的界面,起到了腐蚀防护层的作用。动电位极化测试表明：采用复合技术制备的类金刚石薄膜在模拟体液中的腐蚀倾向性更低,钝态稳定性更好。     

Diamond-like carbon films with End-Hall ion source enhanced chemical vapour deposition

A custom-designed End-Hall ion source was used to deposit diamond-like carbon (DLC) films in a plasma enhanced chemical vapour deposition (PECVD) mode. The deposition system was characterised and optimised for infrared transmission enhancement applications and large area deposition onto silicon or germanium substrates. Ion bombardment energy (in eV) on substrate was found to scale about 60% of the discharge voltage. Uniformity was about 2.5% and 5% for substrate diameters of 20 cm and 40 cm respectively. For the infrared enhancement applications the optimised ion bombardment energy was about 54 eV with a high deposition rate approximate 30 nm/min. Coating the DLC onto a single side of double-sided polished silicon wafers resulted in a transmission of 69.5% in the wavelength of about 4 μm, very close to the ideal value. Mechanical and reliability properties of the DLC films on silicon wafers were analysed at different environmental conditions. It was found that the DLC films produced in the ion source PECVD deposition system were satisfied with the requirements for the infrared transmission enhancement applications.     

Cubic boron nitride films for industrial applications

The effects of kinetic energy, chemical nature of substrates and temperature on the synthesis of cBN films are explored to obtain cBN films with industrial quality. Carbon including amorphous carbon, nanocrystalline and polycrystalline diamond enables deposition of stable, thick and adherent cBN films with characteristic Raman signature. Although temperature has been designated as an unimportant parameter, the deposition at higher temperatures yields higher quality of cBN films. The higher temperature (800 °C) was also employed at cBN deposition on diamond coated tungsten carbide (WC) cutting inserts using plasma enhanced chemical vapor deposition (PECVD). The quality of cBN films grown by PECVD significantly overcomes that prepared by physical vapor deposition (PVD) which is affected in large extent by the lower kinetic energies of particles used in PECVD. The low kinetic energy of particles induces surface growth mechanism which differs from the growth models previously proposed.     

Identification of carbon phases and analysis of diamond/substrate interfaces by Raman spectroscopy

Raman spectroscopy is employed to characterize thin diamond and diamond-like carbon films deposited by hot filament chemical vapour deposition (HFCVD). A method is proposed and experimentally verified for a contact-less measurement of the actual substrate temperature by Raman spectroscopy.     

Preparation of boron nitride-based coatings through thermal diffusion process

ABSTRACT

Preparation of boron nitride (BN)-based coatings for friction and corrosion conditions has been proposed and made through the thermal diffusion process following chemical vapour deposition principles. It includes the formation of gaseous B- and N-based species due to high-temperature reactions (decomposition) in the B- and N-rich powders with consequent deposition of B and N onto the heated substrate and their diffusion into the substrate with formation and consolidation of a thin BN layer. The proposed process can be used for complex-shape components employing simple production equipment.     

Hydrogenated Silicon Carbonitride Thin Film Nanostructuring Using SF6 Plasma: Structural and Optical Analysis

Silicon - Hydrogenated silicon carbonitride thin films have been deposited on silicon substrates in a plasma enhanced chemical vapor deposition (PECVD) system using hexamethyldisilazane (HMDSN:...     

Growth of bent carbon nanotubes by in-situ control of cantilever bending

A new and simple method for in-situ control of the growth direction of carbon nanotubes (CNTs) on cantilevers has been developed using plasma enhanced chemical vapor deposition (PECVD). Plasma-induced surface stresses in PECVD processes tend to cause bending of the cantilevers, which significantly changes the electric field distribution near the free-end of the cantilever. By adjusting the flow ratio of the feed gases during CNT growth, the degree of cantilever bending can be controlled due to the change in the plasma-induced surface stress, and in doing so manipulating the field line direction, as well as the growth direction of CNTs. Combining this in-situ tunable CNT growth technique with electron beam induced deposition of catalyst patterns, we have fabricated a bent CNT on a cantilever in one single, continuous deposition run.