Papers by Keyword: Diamond-Like Carbon (DLC)

Abstract: DLC (Diamond Like Carbon) films show very desirable surface interactions with high hardness, low friction coefficient, and good wear-resistance properties. The friction behavior of hydrogenated DLC film is dependent on tribological environment, especially surrounding temperature. In this work, the tribological behaviors of DLC (Diamond-like carbon) films, prepared by the radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) method, were studied in elevated temperatures. The ball-on-disk tests with DLC films on steel specimens were conducted at a sliding speed of 60 rpm, a load of 10 N, and surrounding various temperatures of 25
, 40
, 55
and 75
. The results show considerable dependency of DLC tribological parameters on temperature. The friction coefficient decreased as the surrounding temperature increased. After tests the wear tracks of hydrogenated DLC film were analyzed by optical microscope, scanning electron spectroscopy (SEM) and Raman spectroscopy. The surface roughness and 3-D images of wear track were also obtained by an atomic force microscope (AFM).

Abstract: Highly compressively stressed diamond-like carbon and polymer films were used to fabricate normally closed microgrippers with diameters as small as 30~40μm. The microgrippers consisted of a DLC layer of 30-50nm, a thin Al layer of 40nm as a heater and an SU8 layer of 250~500nm, and were fabricated by a self-aligned two-mask process. Electrical tests and nonelectrical tests on a Peltier device confirmed the devices have an operation temperature of ~100°C for an opening angle of 90°, much lower than the ~400°C needed for previously fabricated Ni/DLC microgrippers. This value is consistent with finite element modelling and analytical calculation. The power needed to open the microgripper was only ~10 mW, less than half of those used for the previous Ni/DLC microgrippers. It has been successfully demonstrated that the microgrippers can be used to capture and confine micro-objects using microbeads for the tests.

Abstract: One of the surface modification methods is proposed in this report to improve the wear resistance of light metal such as aluminum alloys. At first alumite layer is formed on the surface of aluminum alloy JIS A6061 which was used as the substrate with anodic oxidation treatment method. Then thin layer of CrN is coated with sputtering method, and diamond like carbon (DLC) layer is finally coated with ion plating method. The influence of the thickness of the alumite layer on wear-resistance is experimentally investigated. The critical load of the coated aluminum alloy in scratch test is measured with the surface property tester, and the wear amount of the coated aluminum alloy is measured with the SUGA abrasion tester. The main results obtained are as follows: (1) The critical load of coated aluminum alloy with the alumite layer in the scratch test is higher than that without the alumite layer. (2) The wear amount of the coated aluminum alloy increased with the increase of the thickness of the alumite layer. (3) This combined surface treatment method can become new surface modification method because this method provided excellent adhesive strength and good wear-resistance.

Abstract: This paper presents an analysis of diamond-like carbon thin film deposited using homebuilt microwave chemical vapor deposition. Two different deposition conditions were investigated, namely, with and without microwave power. Post deposition analysis included Raman spectroscopy, scanning electron microscope (SEM), energy dispersed X-ray (EDX), four-pointprobe resistivity measurements and refractive spectroscopy. Substrate with pretreatment was observed to have thin film formation. Samples with diamond paste pretreatment show better quality compared to SiC treated samples as suggested by Raman spectral. The presences of sp3 and sp2 peaks were identified in the Raman spectral. The overall resistivity is low due to the graphite content.

Abstract: Diamond-like carbon (DLC) films were deposited onto UHMWPE and PMMA substrates using plasma CVD process. To improve adhesion of DLC films, substrates were treated plasma before DLC deposition. Samples were analyzed by ball-on disk tester, atomic force microscopy (AFM), and scratch test. Wear and scratch resistance of DLC-coated each substrates were evaluated and showed good results.

Abstract: Diamond-like carbon (DLC) coatings were deposited on titanium alloy (Ti-13Nb-13Zr) by plasma immersion process. DLC-coated Ti alloy and uncoated Ti were investigated in an animal model using the femoral condyles of rats for intervals of 4 and 12 weeks postoperatively. The interface between the implants and bones of the femoral condyles were analysed using scanning electron microscopy (SEM) by backscattering. The results showed that the DLC coatings were well tolerated in both periods.

Abstract: In this work fluorinated Diamond Like Carbon (DLC) films have been grown with different CF4 concentrations and have been studied by electrical DC measurements in a temperature range from 30 to 300 K. It was found that the samples grown with lower CF4 concentration show a small rectification, with a potential barrier lower than 0.3 V. The bulk conduction shows a trapcontrolled Space Charge Limited Current (SCLC), with characteristic trap energy between 0.08 and 0.13 eV, confirmed by the differential conductivity analysis. The activation energy (ranging from 50 to 140 meV) is also dependent on the sample fluorine concentration, decreasing with the fluorine concentration increase.

Abstract: Dry sliding wear resistance of DLC coated silicon disk with different surface roughness has been evaluated using a ball-on-disk sliding tester. It was found that the transfer layer formed on steel ball produced a low friction regime and the formation of transfer layer was more active with increasing the substrate surface roughness. The wear life of DLC coating was increased as increasing the real area of contact.

Abstract: The thick diamond-like carbon (DLC) film of good-adhesion was prepared on a stainless steel (SUS304) substrate by a hybrid process of plasma-based ion implantation and deposition using hydrocarbon gases such as methane, acetylene, and toluene. In this process, a high repetition pulsed plasma was produced by RF pulse (13.56 MHz) with the duration of 50 µs and the repetition rate of 0.5 - 1 kHz. Besides, the plasma ions were implanted to the substrate by a negative pulsed voltage of -20 kV and the pulse duration of 5 µs. Ion implantation served to produce a graded interface of carbon component in the boundary region of DLC film and substrate, and also to reduce the residual stress to several MPa, enhancing the adhesive strength of DLC film. Furthermore, the adhesive strength of DLC film was increased above the epoxy resin strength (about 65 MPa) by implantation of mixed Si and C ions.