摘要 :
Diamond-like nanocomposite (DLN) coatings (a-C:H/a-Si:O) are a particular class of modifieddiamond-like carbon coatings, which can be predominantly described as two interpenetratingamorphous networks, one network being a diamond-l...
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Diamond-like nanocomposite (DLN) coatings (a-C:H/a-Si:O) are a particular class of modifieddiamond-like carbon coatings, which can be predominantly described as two interpenetratingamorphous networks, one network being a diamond-like a-C:H network and the other a glass-likea-Si:O network. Structural studies have been performed using X-ray diffraction (XRD) and X-rayphotoelectron spectroscopy (XPS). The two-network description of the atomic bonding state isinvestigated by analysing the C-C, C-Si and Si-O contributions to the C 1s and Si 2p XPS photolines.Tribological properties have been measured using standard ball-on-disk tests against a steelcounterbody at 10 N load, yielding a typical wear factor between 0.5 and 4×10{sup}-7mm{sup}3 Nm{sup}-1. The coefficient of friction against steel is typically between 0.05 and 0.15,even in humid air and under water. The low-friction and low-wear DLN coatings, combined with lowinternal stress and good adhesion, make this type of coatings an excellent candidate for manytribological applications in the automotive, textile, chemical or biomedical industry.
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Hydrogen-free diamond-like carbon (DLC) thin films are attractive for a wide range of industrial applications. One of the challenges related to the use of hard DLC lies in the high intrinsic compressive stresses that limit the fil...
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Hydrogen-free diamond-like carbon (DLC) thin films are attractive for a wide range of industrial applications. One of the challenges related to the use of hard DLC lies in the high intrinsic compressive stresses that limit the film adhesion. Here, we report on the mechanical and tribological properties of DLC films deposited by High Power Impulse Magnetron Sputtering (HiPIMS) with Ne as the process gas. In contrast to standard magnetron sputtering as well as standard Ar-based HiPIMS process, the Ne-HiPIMS lead to dense DLC films with increased mass density (up to 2.65 g/cm3) and a hardness of 23 GPa when deposited on steel with a Cr + CrN adhesion interlayer. Tribological testing by the pin-on-disk method revealed a friction coefficient of 0.22 against steel and a wear rate of 2 × 10?17 m3/Nm. The wear rate is about an order of magnitude lower than that of the films deposited using Ar. The differences in the film properties are attributed to an enhanced C ionization in the Ne-HiPIMS discharge.
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The structure of diamond-like carbon (DLC) features an amorphous topology with a high fraction of sp~3 bonds, which increases with density and reaches over 80% at 3.0 g/cm~3. To perform large-scale simulations of DLC using interat...
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The structure of diamond-like carbon (DLC) features an amorphous topology with a high fraction of sp~3 bonds, which increases with density and reaches over 80% at 3.0 g/cm~3. To perform large-scale simulations of DLC using interatomic potentials one should be able to generate this structure using a melting and quenching procedure. In the present work, we evaluate the accuracy of different bond order interatomic potentials developed for carbon and hydrocarbons to describe the properties of DLC, in particular its structure. The potentials include the reactive empirical bond order (REBO) and variants of the Tersoff potentials (standard, ZBL, extended cutoff). Results indicate that Tersoff potential with extended cutoff of 2.45 ? is the most accurate in reproducing the experimental structure and mechanical properties of DLC and DLCH (hydrogenated diamond-like carbon). The calculated sp~3 fraction as a function of density, pair correlation functions, and Young's modulus as a function of density show excellent agreement with experimental data. Our findings suggest that the Tersoff potential with extended cutoff is a reliable interatomic potential for large-scale atomistic simulations of both DLC and DLCH.
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Diamond-like carbon (DLC) and fluorinated DLC (F-DLC) films were deposited on SUS316L guidewires using radio frequency (RF) plasma enhanced chemical vapor deposition (CVD), and the lubrication performance of DLC- or F-DLC-coated g...
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Diamond-like carbon (DLC) and fluorinated DLC (F-DLC) films were deposited on SUS316L guidewires using radio frequency (RF) plasma enhanced chemical vapor deposition (CVD), and the lubrication performance of DLC- or F-DLC-coated guidewires was then evaluated under in vitro conditions using a novel friction simulator developed for this study. Scanning electron microscopy (SEM) demonstrated that DLC or F-DLC film completely coated the specimens (SUS316L guidewires) and that polishing scars were substantially reduced. In the torturous vessel model, DLC- or F-DLC-coated guidewires exhibited significantly improved lubrication performance (by approximately 30 percent over that of uncoated wires). DLC and F-DLC films are thus promising candidates for lubricious coating of intravascular guidewires.
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The purpose of this paper is to show the production and characterization of diamond-like carbon (DLC) films with incorporated crystalline diamond (CD), produced by plasma enhanced chemical vapor deposition. CDDLC films were charac...
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The purpose of this paper is to show the production and characterization of diamond-like carbon (DLC) films with incorporated crystalline diamond (CD), produced by plasma enhanced chemical vapor deposition. CDDLC films were characterized by scanning electron microscopy, X-ray diffraction, atomic force microscopy and Raman scattering spectroscopy. Wetting contact angle, stress and friction coefficient were also evaluated. Our results demonstrated CD-DLC films are more hydrogenated and hydrophobic, with higher fiction coefficient. The stress values kept almost constantly.
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The interest in using CVD diamond in the fabrication of microelectro-mechanical components has steadily increased over the last few years. Typical technology for manufacturing such components involves the use of molds patterned in...
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The interest in using CVD diamond in the fabrication of microelectro-mechanical components has steadily increased over the last few years. Typical technology for manufacturing such components involves the use of molds patterned in silicon or silicon dioxide, which are filled by diamond deposition. The degree of conformality of the CVD film and the characteristics of the diamond-substrate interface becomes critical for the successful fabrication and performance of such devices. We have investigated the growth of CVD diamond films on patterned substrates using a microwave plasma assisted deposition reactor. In particular, the use of seed layers to enhance nucleation on horizontal and vertical walls as well as to promote complete filling of narrow trenches is investigated. Scanning electron microscopy is used to characterize the nucleation and growth of the diamond films.
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In 2007, Andrews and Paule introduced the family of functions ?_k(n) which enumerate the number of broken k-diamond partitions for a fixed positive integer k. Since then, numerous mathematicians have considered partitions congruen...
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In 2007, Andrews and Paule introduced the family of functions ?_k(n) which enumerate the number of broken k-diamond partitions for a fixed positive integer k. Since then, numerous mathematicians have considered partitions congruences satisfied by ?_k(n) for small values of k. In this work, we focus our attention on the function ?_2(n) and explicitly identify infinitely many Ramanujan-like congruences modulo 3 which are satisfied by this function.
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A route to reducing the wear of the metal counterpart in the friction of meatal against diamond-like carbon (DLC) is to form a lubricating tribofilm on the metal counterface. However, in liquid lubricating conditions, the formatio...
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A route to reducing the wear of the metal counterpart in the friction of meatal against diamond-like carbon (DLC) is to form a lubricating tribofilm on the metal counterface. However, in liquid lubricating conditions, the formation of tribofilm can be influenced by both the lubricating medium and the counterpart material. Here we report the effect of lubricating biomolecule and doping fluorine element on the formation of tribofilm in fluorinated DLC (FDLC)-Ti6Al4V friction system. A group of ball-on-disc frictional experiments with different sliding speeds and normal loads were performed in phosphate buffer solution (PBS) and bovine serum albumin (BSA) solution. The results showed the formation of tribofilm was inhibited by the absorption of biomolecules on the frictional surface, thus improving the friction coefficient and wear of Ti6Al4V counterpart. Doping fluorine into DLC film also can restrain the formation of tribofilm on Ti6Al4V counterface. As a result, tribofilm is difficult to form when Ti6Al4V counterface slides against FDLC in BSA solution. Fluorinated DLC film should be considered carefully for the anti-wear use in body fluid containing biomolecules because it might cause severe wear of the counterpart material.
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Vacuum environments provide challenging conditions for tribological systems. MoS2 is one of the materials commonly known to provide low friction for both ambient and vacuum conditions. However, it also exhibits poor wear resistanc...
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Vacuum environments provide challenging conditions for tribological systems. MoS2 is one of the materials commonly known to provide low friction for both ambient and vacuum conditions. However, it also exhibits poor wear resistance and low ability to withstand higher contact pressures. In search of wear-resistant alternatives, superhard hydrogen-free tetrahedral amorphous carbon coatings (ta-C) are explored in this study. Although known to have excellent friction and wear properties in ambient atmospheres, their vacuum performance is limited when self-paired and with steel. In this study, the influence of the paired material on the friction behavior of ta-C is studied using counterbodies made from brass, bronze, copper, silicon carbide, and aluminum oxide, as well as from steel and ta-C coatings as reference materials. Brass was found to be the most promising counterbody material and was further tested in direct comparison to steel, as well as in long-term performance experiments. It was shown that the brass/ta-C friction pair exhibits low friction (μ < 0.1) and high wear in the short term, irrespective of ambient pressure, whereas in the long term, the friction coefficient increases due to a change in the wear mechanism. Al2O3 was identified as another promising sliding partner against ta-C, with a higher friction coefficient than that of brass (μ = 0.3), but considerably lower wear. All other pairings exhibited high friction, high wear, or both.
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This paper describes the deposition of diamond and diamond-like carbon coatings using the Circumferencial Antenna Plasma (CAP) reactor. Carbon coatings were deposited at pressures of 8000, 5000 and 3300 Pa onto silicon wafers. The...
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This paper describes the deposition of diamond and diamond-like carbon coatings using the Circumferencial Antenna Plasma (CAP) reactor. Carbon coatings were deposited at pressures of 8000, 5000 and 3300 Pa onto silicon wafers. The coatings were characterised using electron microscopy and Raman spectroscopy as a function of distance from the centre of the substrate holder. At 8000 Pa, diamond coatings were deposited up to 20 mm from the centre of the silicon wafer, while under the same deposition conditions, diamond-like carbon was observed in an annular region between 62 and 75 mm from the centre. At a deposition pressure of 5500 Pa, homogeneous free-standing diamond films, 120 #mu#m thick and 50 min in diameter were deposited.
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