Structure,Composition, Mechanical,and Tribological Properties of BCN Films Deposited by Plasma Enhanced Chemical Vapor Deposition

In this work thin BCN films were deposited by plasma enhanced chemical vapor deposition (PECVD) using chloridic precursors. Through adjusting the BCl₃ content in the inlet gas mixture the chemical composition of the deposited films was changed from carbon rich to boron rich. Based on optical emission spectroscopy (OES) measurements, a correlation between film composition and precursor species concentration in the plasma was established. The films were amorphous as detected by grazing incidence X-ray diffraction (GIXRD). The hardness and the elastic modulus have maximal values of 25.5±1.2 and 191±6 GPa, respectively, for the films with a boron concentration of 45.2 at.%. GIXRD data suggest that a depletion in boron content may initiate the formation of graphitic domains in the amorphous matrix. The observed degradation of the mechanical properties is associated with the graphitization. The tribological behavior was studied with a tribometer operated in pin-on-plate configuration at the temperatures 25 and 400°C. The wear mechanisms were discussed with respect to the formation of a boric acid surface layer which was detected by reflection electron energy loss spectroscopy (REELS) analysis.     

Influence of the composition of BCN films deposited by reactive magnetron sputtering on their properties

Compounds of the B--C--N system are very promising to produce superhard coatings with good tribological, chemical, and thermal properties. To investigate the influence of the composition of BCN films on their properties, films with five different compositions at nearly constant nitrogen content were deposited on silicon wafers by magnetron sputtering from hexagonal boron nitride and graphite targets operated in RF and DC mode, respectively. The compositions and binding states of the films were determined by XPS. The nitrogen content was found to be almost constant for all films at about a 40 at-%, whereas boron and carbon compositions ranged between 15-35 and 25-50 at-%, respectively. The electronic and bonding structure of the coatings were analyzed by REELS using three different electron beam energies to obtain information at different depths. An increase of the carbon content of the films resulted in a significant shift of the pi-pi* interband transition with respect to the energy loss corresponding to h-BN. The absence of the pi-pi* transition in the energy loss spectra acquired at a beam energy of 1900 eV indicates the existence of a very thin overlayer mostly sp(2) bonded and probably with a distorted hexagonal structure. The position of the bulk plasmon losses corresponded to the hexagonal phase for the overlayer and presented a shift of more than 1.5 eV to the higher energy loss direction for the spectra obtained at 1900 eV beam energy. This shift and the absence of the sp(2)-bond fingerprint induced the possibility of an underlying disordered structure with a majority of sp(3) bonds.     

Bioactivity and mechanical properties of nickel‐incorporated hydrogenated carbon nanocomposite thin films

In this paper, the influence of nickel incorporation on the mechanical properties and the in vitro bioactivity of hydrogenated carbon thin films were investigated in detail. Amorphous hydrogenated carbon (a‐C:H) and nickel‐incorporated hydrogenated carbon (Ni/a‐C:H) thin films were deposited onto the Si substrates by using reactive biased target ion beam deposition technique. The films' chemical composition, surface roughness, microstructure and mechanical properties were investigated by using XPS, AFM, TEM, nanoindentation and nanoscratch test, respectively. XPS results have shown that the film surface is mainly composed of nickel, nickel oxide and nickel hydroxide, whereas at the core is nickel carbide (Ni₃C) only. The presence of Ni₃C has increased the sp² carbon content and as a result, the mechanical hardness of the film was decreased. However, Ni/a‐C:H films shows very low friction coefficient with higher scratch‐resistance behavior than that of pure a‐C:H film. In addition, in vitro bioactivity study has confirmed that it is possible to grow dense bone‐like apatite layer on Ni/a‐C:H films. Thus, the results have indicated the suitability of the films for bone‐related implant coating applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Structure and composition studies of chemical vapour-deposited BCN fibre coatings

The composition and structure of boron carbonitride (BCN) films were studied. The films were continuously deposited on fibres by atmospheric pressure CVD. The precursors were ammonia, trimethyl borate and toluene. The composition was determined by photoelectron spectra of boron 1s, nitrogen 1s, carbon 1s and oxygen 1s. By fixing the C 1s peak at 285 eV, the position of the B 1s peak and the N 1s peak in the BCN films was equal to BN films. The C content of the films increases from about 6 at% to 60 at%, leaving the stoichiometric boron/nitrogen ratio as well as the oxygen content below 10 at% unchanged. Generally, the carbon content in the films is lower than predicted by the precursor ratios. Obviously, the insertion of carbon into the film is decreased in the presence of ammonia, which is known to etch carbon. With a decreasing ammonia/toluene ratio, the undesired effect in the reaction is suppressed and the carbon deposition becomes considerable. Transmission electron microscopic studies were performed on cross-sections of the coated fibres. High-resolution images generally show a hexagonal turbostratic structure with different orientation preferences of the atomic lamellae similar to hexagonal turbostratic boron nitride and pyrolytic carbon. When a noticeable carbon concentration (20 at%) is reached, the atomic sheets become uniformly distributed in all directions in space.     

Study on the preparation and mechanical properties of alumina ceramic coating reinforced by graphene and multi-walled carbon nanotube

The paper investigates preparation and mechanical performances of a composite ceramic coating reinforced by graphene and multi-walled carbon nanotube. The carbon nanotube is functionalized with the carboxyl functional group (–COOH) and un-functionalized with sodium dodecyl benzene sulfonate (SDBS). The structure of the functionalized and hybrid-functionalized carbon nanotube is identified using infrared spectroscopy (FTIR analysis). The coating is brushed on the matrix and then cures under temperature lower than 250°C. The morphological and cross section features are studied by scanning electron microscopy (SEM). The distributions of hardness and fracture toughness are determined using a microhardness tester. The adhesive strength is evaluated using a universal tensile tester. The tribological properties are detected using friction wear testing machine. The experimental results show that the structure of the composite coating is compact, and both graphene and hybridtreated carbon nanotube are well dispersed. Addition of 0.2 wt % graphene and 0.2 wt % hybrid-functionalized carbon nanotube results in a prominent increase in hardness and fracture toughness. Meanwhile, the adhesive strength between the composite coating and the metallic substrate is well improved due to the high tensile strength of both graphene and carbon nanotube. Compared with pure alumina coating, the friction coefficient as well as the wear depth and width of grinding crack of the composite coating is much lower.

     

Structural,chemical and nanomechanical investigations of SiC/polymeric a-C:H films deposited by reactive RF unbalanced magnetron sputtering

Amorphous carbon (or diamond-like carbon, DLC) films have shown a number of important properties usable for a wide range of applications for very thin coatings with low friction and good wear resistance. DLC films alloyed with (semi-)metals show some improved properties and can be deposited by various methods. Among those, the widely used magnetron sputtering of carbon targets is known to increase the number of defects in the films. Therefore, in this paper an alternative approach of depositing silicon-carbide-containing polymeric hydrogenated DLC films using unbalanced magnetron sputtering was investigated. The influence of the C₂H₂ precursor concentration in the deposition chamber on the chemical and structural properties of the deposited films was investigated by Raman spectroscopy, X-ray photoelectron spectroscopy and elastic recoil detection analysis. Roughness, mechanical properties and scratch response of the films were evaluated with the help of atomic force microscopy and nanoindentation. The Raman spectra revealed a strong correlation of the film structure with the C₂H₂ concentration during deposition. A higher C₂H₂ flow rate results in an increase in SiC content and decrease in hydrogen content in the film. This in turn increases hardness and elastic modulus and decreases the ratio H/E and H³/E². The highest scratch resistance is exhibited by the film with the highest hardness, and the film having the highest overall sp³ bond content shows the highest elastic recovery during scratching.     

The effect of thermal annealing on the microstructure and mechanical properties of magnetron sputtered hydrogenated amorphous carbon films

Hydrogenated amorphous carbon films were deposited by magnetron sputtering of a carbon target in a methane/argon atmosphere. A postdeposition annealing at 300 °C was performed and the microstructure, bonding structure and mechanical properties of the as‐deposited and annealed films were analyzed and compared directly by high‐resolution transmission electron microscopy, micro‐Raman spectroscopy, XPS, and nanoindentation. The results showed that the carbon films are quite stable upon annealing, since there are only minor changes in microstructure and chemical bonding in the amorphous matrix. The hardness of the films remained unaffected, but the elastic properties were somewhat deteriorated. In comparison to the outcomes of our previous work on the growth of fullerene‐like hydrogenated carbon films, we can state that the formation of fullerene‐like carbon structures requires different sputtering process conditions, such as a higher ion energy and/or different sputtering target. Copyright © 2011 John Wiley & Sons, Ltd.     

Comparative investigations of structure and properties of BCN coatings deposited by thermal and plasma-enhanced CVD

Hard BCN films were deposited by chemical vapour deposition (CVD) on Si(100) substrates. TCVD (thermal activated) and PECVD (GD or RF microwave plasma-activated, respectively) were used. The films were analysed with respect to chemical state, composition, morphology and microstructure, oxidation behaviour and hardness. Wavelength dispersive X-ray spectroscopy (EPMA), infrared spectroscopy (IR), transmission electron microscopy (TEM), differential thermal analysis (DTA) and hardness evaluation were employed for film characterization. A correlation between deposition parameters and film composition, structure and hardness could be proved in every CVD process. Parallels between TCVD and PECVD films emerged in the case of chemical composition and the correlation between carbon content and hardness values. Considerable differences exist with regard to the microstructure, especially the texture of the films. Moreover in TCVD films the carbon is preferentially incorporated between the BN basal planes, whereas in PECVD films it is incorporated preferentially in as well as between the BN basal planes.     

Synthesis and Characterization of Nanostructured a-C:H (Hydrogenated Amorphous Carbon) Thin Films by Gaseous Thermionic Vacuum Arc (G-TVA) Deposition Technique

The aim of this contribution is to present the properties of the nanostructured hydrogenated carbon thin films and to study their growth carried out in a special deposition technique based on Thermionic Vacuum Arc method. The Gaseous Thermionic Vacuum Arc (G-TVA) technology is an original deposition method performed in a special configuration, consisting of a heated thermionic cathode which provides an electron beam on the anode. The surface free energy was evaluated by contact angle and their optical properties were studied by Filmetrics F20 spectrometry system. Structure of the film has been investigated by Raman spectroscopy as well as the mechanical properties like hardness, wear resistance, film-substrate adhesion. The films showed two distinct Raman characteristic peaks located at 1,350 cm⁻¹ (D-line) and 1,550 cm⁻¹ (G-line), broad for Si and very sharp for glass substrates. The G-TVA enables to prepare soft (hardness ~6 GPa) or hard (~24 GPa) films.     

The tribological performance of fullerene‐like hydrogenated carbon films under ionic liquid lubrication

Fullerene‐like hydrogenated carbon films were deposited on Si substrate by plasma‐enhanced chemical vapor deposition. The microstructures of films were characterized by high‐resolution transmission electron microscopy and Raman spectrum. The tribological performance of films was tested by reciprocating ball‐on‐disc tester under 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ionic liquid. The surface morphology and chemical composition of wear tracks and wear rates were investigated by optical microscope, X‐ray photoelectron spectroscopy, and 3D surface profiler. The results indicated that the film with a typical fullerene‐like structure embedded into the amorphous sp² and sp³ carbon networks could be prepared successfully, and the film shows a higher hardness (26.7 GPa) and elastic recovery (89.9%) compared with the amorphous carbon film. Furthermore, the film shows a lower friction coefficient at low contact load and friction frequency, and excellent wear‐resistance performance at high load and frequency under ionic liquid lubrication. Meanwhile, the wear life of fullerene‐like hydrogenated carbon films could be improved significantly using ionic liquid as a lubrication material. Copyright © 2015 John Wiley & Sons, Ltd.     

Cluster assembled thin films of covalent materials

Cluster assembled thin films of covalent materials are studied by Raman spectroscopy. The main properties are discussed in terms of frustration through several examples (carbon, silicon, and boron nitride). Some applications such as luminescence are discussed.     

Nanoindentation testing of SiO<Subscript>2</Subscript>-PMMA hybrid films on acrylic substrates with variable coupling agent content

In this work we report the influence of the molar composition of the coupling agent, as well as the curing conditions on the mechanical properties of SiO₂-PMMA (polymethyl methacrylate) hybrid films deposited on organic acrylic substrates. The SiO₂-PMMA hybrid films were deposited by the sol–gel method from hybrid precursor solutions with fixed molar ratio of 1:0.25 for TEOS/MMA (Tetraethyl-orthosilicate/Methylmethacrylate) and TEOS/TMSPM (3-trimethoxysilyl propyl methacrylate) molar ratios ranging from 1:0.05 to 1:0.2. The organic compound TMSPM was used as coupling agent to enhance the bond between the organic and inorganic molecules. The wear resistance, hardness and elastic modulus of the hybrid films were determined by nanoindentation techniques and compared to the substrate mechanical behaviour. The chemical bonding in the hybrid films was analyzed by Fourier Transform Infrared spectroscopy and their transparency by optical transmission and reflection spectroscopy. The friction coefficient and sliding life of the hybrid films were also measured with a pin-on-disc tribometer. The surface morphology and roughness were determined from atomic force microscopy images. The hybrid films with lowest content of coupling agent showed the best mechanical performance in terms of hardness, friction coefficient and wear resistance keeping high optical transparency.     

The structure and tribological properties of aluminum/carbon nanocomposite thin films synthesized by reactive magnetron sputtering

Hydrogenated nanocomposite aluminum/carbon thin films (Al/a‐C:H) were fabricated on stainless steel and silicon wafer substrates via unbalanced reactive magnetron sputtering from an Al target in CH₄/Ar plasma. The composition and structure of Al/a‐C:H films were investigated by high‐resolution transmission electron microscope (HRTEM), XPS and micro‐Raman spectroscopy. Nanoindenter, interferometer and ball‐on‐disc tribometer were carried out to evaluate the hardness, internal stress and tribological properties of Al/a‐C:H films. HRTEM observations confirmed that the metallic Al nanocrystallites were uniformly dispersed in the amorphous carbon matrix. XPS and Raman analyses indicated that the sp² content increased with the increase of Al content in the films. Nanoindenter and interferometer tests exhibited that the uniform incorporation of Al nanocrystallites can diminish drastically the magnitude of internal stress with maintaining the higher hardness of as‐deposited films. Especially, the ball‐on‐disc tribometer measurements revealed that the nanocomposite film with 2.3 at.% Al content exhibited relatively better wear resistance and self‐lubrication performance with a friction coefficient of 0.06 and wear rate of 3.1 × 10^?16 m³/ N·m under ambient air, which can be attributed to the relatively higher hardness, the formation of continuous graphitized transfer film on counterface and the reduced reaction of oxygen with carbon. Copyright © 2010 John Wiley & Sons, Ltd.     

Surface Enhanced Raman Spectroscopy on Carbon Filaments

 A method for analysis of carbon-containing thin films by using surface enhanced Raman spectroscopy (SERS) is described. Thin films of boron nitride or silicon carbide which are deposited on carbon filaments were coated additionally with silver nanoparticles. A very thin plasma polymer film was deposited on the silver particles to give a better long time stability. Using these layers, very intensive carbon band were detected.     

Effects of UV irradiation on tribological properties of nano‐TiO2 thin films

One‐layer and two‐layer nano‐TiO₂ thin films were prepared on the surface of common glass by sol–gel processing. Water contact angle, surface morphology, tribological properties of the films before and after ultraviolet (UV) irradiation were investigated using DSA100 drop shape analyzer, scanning probe microscopy (SPM), SEM and universal micro‐materials tester (second generation) (UMT‐2MT) friction and wear tester, respectively. The stored films markedly resumed their hydrophilicity after UV irradiation. But UV irradiation worsened tribological properties of the films. After the film was irradiated by UV, the friction coefficient between the film and GCr15 steel ball increased about 10–50% and its wear life shortened about 20–90%. Abrasive wear, brittle break and adherence wear are the failure mechanisms of nano‐TiO₂ thin films. It was believed that UV irradiation increased surface energy of the film and then aggravated adherence wear of the film at initial stage of friction process leading to severe brittle fracture and abrasive wear. Copyright © 2009 John Wiley & Sons, Ltd.     

笼型倍半硅氧烷形态分析及对杂化材料相容性和机械性能的影响

采用水解缩合方法制备了八乙烯基笼型倍半硅氧烷(OVPOSS), 并将其引入到聚甲基丙烯酸甲酯(PMMA)自凝树脂中, 得到有机-无机杂化材料. 通过傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、差示扫描量热仪(DSC)、塑料球压痕硬度计、高温高速摩擦磨损测试仪和悬臂梁冲击实验等对其形貌和性能进行了研究. 结果表明, OVPOSS以晶体状态存在于PMMA树脂中. 通过DSC热性能曲线、FOX方程和Gordon-Talyor方程曲线发现, 当POSS含量较高时, PMMA-POSS杂化体系能够发生相分离, 对杂化材料的机械性能有一定的影响.     

Tribological performance of fluoroalkylsilane modification of sol–gel TiO<Subscript>2</Subscript> coating

This paper explores the possibility of making coatings with super friction-reducing and wear protection properties by using both sol–gel and self-assembling techniques. The thin film of TiO₂ was firstly prepared on glass substrates via a sol–gel method, followed by sintering at 480°C. The self-assembled monolayer of Fluoroalkylsilane (FAS) were then prepared on TiO₂ thin film to obtain TiO₂–FAS dual-layer film. The contact angle measurement and X-ray photoelectron spectroscopy were used to determine the wetting behavior and chemical structure of films, respectively. The friction behavior of films sliding against a steel ball was examined on a macro friction and wear tester. It is shown that FAS is strongly adsorbed on sol–gel derived TiO₂ thin film, making it strongly hydrophobic. Good friction-reducing and wear protection behavior is observed for the glass substrate after duplex surface-modification with sol–gel TiO₂ and top layer of FAS.     

Mechanical and tribological properties of DLC coatings deposited by plasma-based ion implantation and deposition method on polyoxymethylene

Polyoxymethylene (POM, polyacetal) is one of the most popular plastics for machine elements, especially in Japan. However, it is difficult to use it under severe operating conditions such as high speed and high contact pressure. Diamond-like carbon (DLC) coatings were well known to be tribological and functional coatings. However, both POM and DLC coatings are difficult to adhere them each other. In the present paper, DLC coatings are deposited by plasma-based ion implantation and deposition (PBIID) method on POM substrate, and validity of DLC coatings on POM was investigated through friction and mechanical tests. When gas pressure was 0.2 and 0.8 Pa, hardness and adhesion properties of DLC coating deposited under gas pressure of 0.5 Pa were lower compared with under 0.2 and 0.8 Pa. For preparing DLC coatings having hard and good adhesion properties, relatively thin substrate was suitable. A correlation between relative humidity in the laboratory and friction coefficient was confirmed while DLC coatings remain on the substrate.     

Nanoindentation and optical properties of poly(4,4′-oxydiphenylene p-phenylene pyromellitimide) copolyimide thin films according to the p-phenylene diamine content

Poly(p-phenylene pyromellitimide) (PMDA-PDA), poly(oxydiphenylene pyromellitimide) (PMDA-ODA), and poly(4,4′-oxydiphenylene p-phenylene pyromellitimide) random copolyimide thin films with different p-phenylene diamine (PDA) contents were prepared. Nanoindentation was used to characterize the mechanical properties (hardness and modulus), and a prism coupler was used for measuring the optical properties (refractive index and birefringence). The hardness and modulus were calculated from curves of the nanoindentation load versus the displacement. The effect of the PDA content on the hardness and modulus was studied. The hardness of the polyimide thin films varied from 0.248 to 0.613 GPa, and the modulus varied from 3.78 to 6.75 GPa at a load of 0.127 mN. The hardness and modulus increased with increasing PDA content, whereas the penetration depth and plastic deformation decreased. As the load increased, the penetration depth increased. The hardness of PMDA-ODA films remained constant, whereas that of PMDA-PDA and PMDA-ODA/PDA films decreased with increasing load. The in-plane refractive index varied from 1.7219 to 1.8244, and the out-of-plane refractive index varied from 1.6390 to 1.5827, as a function of the PDA content. The birefringence varied with the PDA content from 0.0829 to 0.2417. The morphological structure of the prepared polyimide thin films was investigated with wide-angle X-ray diffraction. The mechanical properties and optical properties of the polyimide thin films were strongly dependent on the changes in the morphological structure, which originated from the variation of the composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2202–2214, 2004     

纳米二氧化钒薄膜的制备及红外光学性能

采用双离子束溅射方法在Si3N4/SiO2/Si基底表面沉积氧化钒薄膜, 在氮气气氛下热处理获得二氧化钒薄膜. 利用X射线衍射(XRD)、扫描电子显微镜(SEM)和X射线光电子能谱(XPS)研究了热处理温度对氧化钒薄膜晶体结构、表面形貌和组分的影响, 利用傅里叶变换红外光谱(FT-IR)对二氧化钒薄膜的红外透射性能进行了测试分析. 结果表明, 所制备的氧化钒薄膜以非晶态V2O5和四方金红石结构VO2为主, 经400 ℃、2 h热处理后获得了(011)择优取向的单斜金红石结构纳米VO2薄膜, 提高热处理温度至450 ℃, 纳米结构VO2薄膜的晶粒尺寸减小. FT-IR结果显示,纳米VO2薄膜透射率对比因子超过0.99, 高温关闭状态下透射率接近0. 小晶粒尺寸纳米VO2薄膜更适合在热光开关器件领域应用.