以Au和Au-Cu为衬底的Si/DLC薄膜的机械性能

通过纳米划痕测试技术(nano-scratch)研究了以Au和Au-Cu(xAu=93%, xCu=7%)为衬底, 多晶硅Si为基片的类金刚石(DLC)薄膜的机械性能, 其中DLC薄膜厚度约为10 nm. 研究结果表明, Au-Cu衬底对Si/DLC薄膜的结合力比Au衬底对Si/DLC薄膜的结合力要好. 紫外(244 nm)为激发光源的拉曼光谱测试结果显示在相同薄膜制备条件下Au-Cu衬底比Au衬底含有更多的sp3成分, 同时也意味着以Au-Cu为衬底的Si/DLC薄膜具有更高的硬度和密度. 通过对研究结果的分析讨论可以得出, 由于具有较好的结合力和高硬度, Au-Cu是磁记录磁头保护膜Si/DLC薄膜的更好lead材料.     

表面抗菌功能涂层的构建及在生物医用材料中的应用研究

近年来,生物医用材料在使用过程中产生的医源性感染问题层出不穷,对人们健康和生命造成严重威胁.表面抗菌涂层构建是解决该类医源性感染问题最有效的策略之一.目前,按照作用机制和功能不同将表面抗菌涂层分为接触式抗菌涂层、抗黏附抑菌涂层、抗黏附杀菌涂层以及智能抗菌涂层.表面抗菌涂层的构建不仅赋予了生物医用材料抗菌性能,有效解决了上述医源性感染问题,还可以提高材料的生物相容性,赋予其抗黏附、抗氧化、生物识别、传感等功能.本文旨在对目前表面抗菌涂层的种类、构建方法以及其在生物医用材料领域中的应用做一全面论述,为进一步开发高性能表面抗菌涂层并扩展其应用提供新思路.     

How can H content influence the tribological behaviour of W-containing DLC coatings

In this paper, the influence of the addition of W and H to pure DLC coatings on the structural, mechanical and tribological properties will be presented. The coatings were deposited by r.f. magnetron sputtering from a C target embedded with different numbers of W pellets. Working in non-reactive or reactive atmosphere allowed to deposit H-free or H-containing coatings, respectively, on steel and Si substrates. A Cr adhesion interlayer was interposed between the films and the substrate. Films with W content from 0 to 12 at.% and H incorporated up to a maximum value close to 40 at.% were deposited. All coatings had an amorphous structure, although vestiges of crystallinity could be detected in W-containing films. The addition of W led to a significant hardening of the DLC coating (from ～10 to 18 GPa); inversely, with H incorporation the hardness drop down to values even lower than that of pure DLC films. It was possible to establish a good correlation between the hardness and the residual stresses. In spite of decreasing friction and wear coefficients when alloying DLC with W, almost no difference was found among the W–DLC films whatever the W content was. A similar trend was achieved with the H addition. However, in this case a decrease in the friction coefficient was registered whereas the wear rate increased. The best performance concerning the friction was obtained for an H-containing coating (0.05) whereas, for the wear resistance, H-free W–DLC films were better performing (0.3 × 10^?16 m³ N^?1 m^?1).     

The high‐temperature tribological properties of Si‐DLC films

The tribological properties of Silicon‐containing diamond‐like‐carbon (Si‐DLC) films, deposited by magnetron sputtering Si target in methane/argon atmosphere, were studied in comparison with diamond‐like‐carbon (DLC) films. The DLC films disappeared because of the oxidation in the air at 500 °C, whereas the Si‐DLC films still remained, implying that the addition of Si improved significantly the thermal stability of DLC films. Retarded hydrogen release from DLC film at high temperature and silicon oxide on the surface might have contributed to lower friction coefficient of the Si‐DLC films both after annealing treatment and in situ high‐temperature environment. Copyright © 2012 John Wiley & Sons, Ltd.     

Contact angles of diiodomethane on silicon-doped diamond-like carbon coatings in electrolyte solutions

The influence of surrounding electrolyte type and concentration on the contact angle of hydrophobic diiodomethane on silicon-doped diamond-like carbon (DLC) coatings was examined to provide insight into how the presence of electrolytes in the solution influences adhesion of hydrophobic material to doped DLC surfaces. There was a small but statistically significant increase of contact angle with increasing electrolyte concentration over the range from 0 to approximately 0.01 M, after which the contact angle was virtually unaffected by further increase in the concentration of electrolyte. It was shown that CaCl(2) has a stronger influence on the change of the contact angle than NaCl, and that an increase in Si content in the DLC coatings increased the change in the contact angle of diiodomethane for all types of electrolyte. These observations suggest that the adhesion to the Si-doped DLC surfaces is reduced by addition of the electrolytes to the surrounding solvent. This could be explained by increased ion adsorption on the DLC surface with increase in silicon doping, causing the surfaces to be more hydrophilic.     

Reducing implant-related infections: active release strategies

Despite sterilization and aseptic procedures, bacterial infection remains a major impediment to the utility of medical implants including catheters, artificial prosthetics, and subcutaneous sensors. Indwelling devices are responsible for over half of all nosocomial infections, with an estimate of 1 million cases per year (2004) in the United States alone. Device-associated infections are the result of bacterial adhesion and subsequent biofilm formation at the implantation site. Although useful for relieving associated systemic infections, conventional antibiotic therapies remain ineffective against biofilms. Unfortunately, the lack of a suitable treatment often leaves extraction of the contaminated device as the only viable option for eliminating the biofilm. Much research has focused on developing polymers that resist bacterial adhesion for use as medical device coatings. This tutorial review focuses on coatings that release antimicrobial agents (i.e., active release strategies) for reducing the incidence of implant-associated infection. Following a brief introduction to bacteria, biofilms, and infection, the development and study of coatings that slowly release antimicrobial agents such as antibiotics, silver ions, antibodies, and nitric oxide are covered. The success and limitations of these strategies are highlighted.     

Impact of high N2 flow ratio on the chemical and morphological characteristics of sputtered N‐DLC films

Because of their outstanding characteristics, diamond‐like carbon (DLC) thin films have been recognized as interesting materials for a variety of applications. For this reason, the effects of the incorporation of different elements on their fundamental properties have been the focus of many studies. In this work, nitrogen‐incorporated DLC films were deposited on Si (100) substrates by DC magnetron sputtering of a graphite target under a variable N₂ gas flow rate in CH₄ + N₂ + Ar gas mixtures. The influence of high N₂ flow ratios (20, 40 and 60%) on the chemical, structural and morphological properties of N‐DLC films was investigated. Different techniques including field emission gun‐equipped scanning electron microscope (FEG‐SEM), energy‐dispersive X‐ray spectroscopy (EDS), atomic force microscopy (AFM), profilometry, Rutherford backscattering spectrometry (RBS) and Raman spectroscopy (325‐nm and 514‐nm excitation) were used to examine the properties of the N‐DLC films. Thus, the incorporation of nitrogen was correlated with the morphology, roughness, thickness, structure and chemical bonding of the films. Overall, the results obtained indicate that the fundamental properties of N‐DLC films are not only related to the nitrogen content in the film but also to the type of chemical bonds formed. Copyright © 2016 John Wiley & Sons, Ltd.     

Low energy X-ray radiation impact on coated Si constructions

Low energy X-ray radiation impact on the coated Si structures is discussed in this paper. Experimental sandwich structures consisting of amorphous hydrogenated a:C–H or SiO_x-containing DLC films were synthesized on Si 〈1 1 1〉 wafers using direct ion deposition method and exposed to low energy (medical diagnostic range) X-ray photons. Irradiation of samples was performed continuously or in sequences and protective characteristics of the irradiated DLC films were investigated. Experimental data were used as the input data for Monte Carlo modelling of X-ray scattering effects in the coated silicon constructions, which affect significantly the “signal to noise ratio” in DLC-coated Si structures proposed for their application in medical radiation detectors. Modelling results obtained in the case of DLC coatings were compared to the results of calculations performed for other commonly used combinations coating–detector material.The evaluation method of coated structures for their possible application in medical radiation detector constructions has been proposed in this paper. It is based on the best achieved compatibility between the appropriate mechanical characteristics, coating’s resistance against the radiation damage and the lowest estimated scattering to total dose ratio in the coated radiation sensitive volume.     

Evaluation of bias voltage effect on diamond‐like carbon coating properties deposited on tungsten carbide cobalt

Diamond‐like carbon (DLC) coatings are getting new trends for cutting tool applications. In this research work, the DLC coatings were deposited on 15 × 15 × 5‐mm tungsten carbide cobalt substrates with variation of bias voltage from 0 to 500 V. The DLC films of 400 nm were deposited using filter cathode vacuum arc system, and 100‐nm chromium interlayer was deposited by sputtering. The optimized conditions for plasma pretreatment at different argon flow rates and deposition rates with bias variation were found. The effect of bias voltage on microstructure, tribology, adhesion, and mechanical properties were evaluated. The characterization techniques employed were field emission electron microscopy, Raman spectroscopy, wear test, SEM, scratch test, and nano‐indentation. The effect of substrate pretreatment on film adhesion was also evaluated. It was observed that etching rate increased with the increase in Ar flow rate while DLC deposition and sputtering rates decreased with increase in the bias voltage. The characterization suggests the DLC coatings deposited at 0 V bias as optimum condition because of showing the best results among all other conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

The influence of Ti plasma etching pre-treatment on mechanical properties of DLC film on cemented carbide

The pre-treatment of substrate surface had been a key part of DLC film preparation to improve mechanical and tribological properties. Ti plasma etching pre-treatment was investigated in this paper as a new effective surface pre-treatment method to substitute transition layer. This pre-treatment used high-energy Ti plasma to impact substrate surface. Ti plasma etched the substrate to a depth of 407 nm and increased the roughness from 1.36 to 40.39 nm. A trace layer of substrate, together with cobalt, oxides, and other impurities, was removed. Ti plasma broke some top WC crystals and combined with the free carbon ions separating from the substrate. A DLC film was deposited on the etched surface. Compared with DLC films deposited on the untreated substrate and Ti transition layer, the DLC film on the Ti plasma etched substrate had best adhesion strength of 34.14 N. The three DLC films had the same sp³ bonding carbon content, but Ti plasma etching treatment could promote the formation of sp³ bonds on the interface of substrate and DLC film. This DLC film had low friction coefficient of 0.12 and low wear rate of 5.11 × 10⁻⁷ mm³/m·N. In summary, Ti plasma etching pre-treatment could significantly improve the adhesion of DLC film and keep its excellent tribological properties.     

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.     

Effect of temperature on the surface free energy of amorphous carbon films

Diamond-like carbon (DLC) and tetrahedral amorphous carbon (ta-C) have attracted much attention recently for biomedical and antifouling applications due to their excellent biocompatibility and inherent nonstick properties. It has been demonstrated that the solid surface free energy is a dominant factor in cellular or fouling adhesion. However, few data for the surface free energy of DLC and ta-C coatings at temperatures in the range 37-95 degrees C are available. In this study DLC and ta-C coatings on stainless steel 304 sheets were prepared using an unbalanced magnetron sputtering system and a filtered cathodic vacuum arc system, respectively. The contact angles of water, diiodomethane and ethylene glycol on the coated surfaces at temperatures in the range 20-95 degrees C were measured using a Dataphysics OCA-20 contact angle analyzer. The surface free energy of the coatings and their components (e.g., dispersion, polar or acid/base portions) were calculated using various methods. The experimental results showed that the total surface free energy and dispersive surface free energy of the ta-C coatings, DLC coatings, stainless steel 304 and titanium decreased with increasing surface temperature, while the acid-base SFE component increased with increasing temperature.     

Effect of Platinum and Ruthenium Incorporation on Voltammetric Behavior of Nitrogen Doped Diamond‐Like Carbon Thin Films

Nitrogen doped diamond‐like carbon thin films with or without platinum and ruthenium incorporation (N‐DLC or PtRuN‐DLC) were deposited on highly conductive p‐Si substrates by DC magnetron sputtering to study the effect of Pt and Ru doping on the voltammetric performance of the N‐DLC films. The potential windows of these film electrodes were measured in different electrolytic solutions, such as H₂SO₄, HCl and KCl. The cyclic voltammograms obtained from the N‐DLC film electrodes in these solutions showed wide potential windows while the introduction of Pt and Ru into the film electrodes apparently narrowed down the potential windows due to their catalytic activities.     

Thin films of discotic liquid crystals and their applications

ABSTRACT

Discotic liquid crystals (DLCs) are considered as fascinating systems due to their unique property of self-assembly to yield different columnar structures. DLCs are organic semiconductors and create pathways for the development of numerous optical and electrical devices. The thin films of DLCs can be considered as low dimensional system which can exhibit remarkable optical and physical properties. In this article, we present a review on ultrathin films of some interesting DLC molecules at air–water and air–solid interfaces. The Langmuir monolayer and Langmuir–Blodgett films of DLC molecules are extensively studied. The ultrathin films of DLC molecules can yield highly anisotropic layer wherein the molecular orientation and aggregation can have large impact on the physicochemical properties of the film. Different surface phases with different molecular orientations as function of surface density and temperature can be obtained by forming the Langmuir monolayer of the DLC molecules at the air–water interface. The Langmuir monolayer in a particular phase can be deposited onto the active area of a device layer-by-layer by employing a highly controlled Langmuir–Blodgett technique. Here, we report some interesting results related on molecular orientation of the DLC molecules at different interfaces. Such aggregation of DLC molecules in ultrathin films may find applications in thin film-based electro-optical devices.     

Diamond-like carbon coatings with Ca-O-incorporation for improved biological acceptance

Diamond-like carbon (DLC) coatings were modified by doping the thin films with Ca-O compounds. Raman spectroscopy indicates growth of sp(2)-hybridised, ordered regions in size and/or number within the amorphous carbon-hydrogen network as a result of the Ca-O-incorporation. CaCO(3) was identified by X-ray induced photoelectron spectroscopy. Proliferation and morphology of L929 mouse fibroblasts reveal improved biocompatibility of Ca-O-modified DLC.     

Prétraitements de nitruration compatibles avec les procédés MOCVD et PACVD: Influence sur l'adhérence de revêtements céramiques sur ACIER

The influence of nitriding pretreatments of steel substrates on the adhesion of representative ceramic coatings has been investigated. Vapor phase nitriding using the mixture NH₃/H₂/He has been applied before the growth by MOCVD of vanadium nitrides, carbonitrides and oxides. Similarly, microwave plasma nitriding using the mixture N₂/Ar was applied prior to the deposition by PACVD of silicon carbide based films. The nitriding pretreatment enhances the adhesion of plasma SiC(H) and MOCVD V(C,N) and V₂O₃ coatings but is not favorable to a better adhesion of MOCVD VN-type films. The different mechanical behaviors of these coatings are discussed in terms of compatibility between the combined processes.     

Structural,optical and secondary electron emission properties of diamond like carbon thin films deposited by pulsed-DC plasma CVD technique

Plasma enhanced chemical vapor deposition (PECVD) technique using pulsed-DC power supply was used to fabricate diamond like carbon (DLC) films at deposition rates as high as 110 nm/min. The DLC films deposited by pulsed-DC and DC based power supplies under different gas flow ratios were studied for their suitability as dielectric layer coatings in plasma display panels (PDPs). The effect of deposition parameters on the properties of the DLC films were studied using Fourier transform infra-red spectroscopy (FTIR) and spectroscopic ellipsometry (SE). FTIR reveals that higher hydrogen dilution in gas mixture leads to higher sp³ content. SE studies in wide spectral range were analyzed using Tauc-Lorentz model dielectric function. A rise in the extracted refractive index was seen on increasing the H₂ content in the feed gas, thus resulting in optically denser films. Secondary electron emission coefficient (γ) was measured in the films deposited by the DC and pulsed-DC based PECVD. Firing voltage in the DLC samples was found to have very low variation in the operating pressure range used in commercial PDPs, suggesting possibility of enhanced long term reliability of DLC coatings in future PDP applications.     

Development of Chitosan-Based Surfaces to Prevent Single- and Dual-Species Biofilms of Staphylococcus aureus and Pseudomonas aeruginosa

Implantable medical devices (IMDs) are susceptible to microbial adhesion and biofilm formation, which lead to several clinical complications, including the occurrence of implant-associated infections. Polylactic acid (PLA) and its composites are currently used for the construction of IMDs. In addition, chitosan (CS) is a natural polymer that has been widely used in the medical field due to its antimicrobial and antibiofilm properties, which can be dependent on molecular weight (Mw). The present study aims to evaluate the performance of CS-based surfaces of different Mw to inhibit bacterial biofilm formation. For this purpose, CS-based surfaces were produced by dip-coating and the presence of CS and its derivatives onto PLA films, as well surface homogeneity were confirmed by contact angle measurements, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The antimicrobial activity of the functionalized surfaces was evaluated against single- and dual-species biofilms of Staphylococcus aureus and Pseudomonas aeruginosa. Chitosan-based surfaces were able to inhibit the development of single- and dual-species biofilms by reducing the number of total, viable, culturable, and viable but nonculturable cells up to 79%, 90%, 81%, and 96%, respectively, being their activity dependent on chitosan Mw. The effect of CS-based surfaces on the inhibition of biofilm formation was corroborated by biofilm structure analysis using confocal laser scanning microscopy (CLSM), which revealed a decrease in the biovolume and thickness of the biofilm formed on CS-based surfaces compared to PLA. Overall, these results support the potential of low Mw CS for coating polymeric devices such as IMDs where the two bacteria tested are common colonizers and reduce their biofilm formation.