Papers by Keyword: FCVA

Abstract: This paper presents results of the application of Ti/ta-C films to micro drilling operation for machining. Tetrahedral amorphous carbon (ta-C) films were successfully deposited on WC-Co substrates by a filtered cathodic vacuum arc (FCVA) system. The mechanical and flexion properties of Ti/ta-C films were systematically investigated. The experimental results show that the Ti/ta-C coated micro drills have the excellent microhardness, adhesion and flexion properties and represent the optimal coatings for micro drilling applications. The role of the Ti –sublayer on a sintered powder tungsten carbide substrate is not only limited by the adhesion improvement, but it is mainly used to neutralise the grain boundary microcracks on a surface. The results of drilling tests carried out on PCB boards showed that the durability and drilling efficiency of tools coated by Ti/ta-C films are significantly higher than that of uncoated ones.

Abstract: Abstract：(Ti, Al)N films were deposited on high-speed steel (HSS) by filtered cathodic vacuum arc (FCVA) technique under a nitrogen atmosphere. X-ray diffraction was used to characterize the structure of the films .The micro-hardness was tested. The result shows that the crystal structure and mechanical properties of (Ti,Al)N films are strongly dependent on the nitrogen partial pressure. The structure of (Ti,Al)N films is composed of Ti2N phase, TiN phase and TixAly phase. The hardness increases to a maximum at the nitrogen partial pressure of 8•0×10-2Pa, then decreases with increasing nitrogen partial pressure.

Abstract: One of the key factors to obtain large displacements and high efficiency with dielectric electroactive polymer (DEAPs) actuators is to have compliant electrodes. Attempts to scale DEAPs down to the mm or micrometer range have encountered major difficulties, mostly due to the challenge of micropatterning sufficiently compliant electrodes. Simply evaporating or sputtering thin metallic films on elastomer membranes produces DEAPs whose stiffness is dominated by the metallic film. Low energy metal ion implantation for fabricating compliant electrodes in DEAPs presents several advantages: a) it is clean to work with, b) it does not add thick passive layers, and c) it can be easily patterned. We use this technology to fabricate DEAPs micro-actuators whose relative displacement is the same as for macro-scale DEAPs. With transmission electron microscope (TEM) we observed the formation of metallic clusters within the elastomer (PDMS) matrix, forming a nano-composite. We focus our studies on relating the properties of this nano-composite to the implantation parameters. We identified the optimal implantation parameters for which an implanted electrode presents an exceptional combination of high electrical conductivity and low compliance.

Abstract: Tetrahedral amorphous carbon (ta-C) films were deposited onto Si(100) wafers by using filtered cathodic vacuum arc technique (FCVA). The influence of the negative bias voltage applied to substrates on film structures was studied by Raman spectroscopy, X-ray photoemission spectroscopy (XPS). The ta-C films showed maximal sp3 fractions 87%, the hardness and elastic modulus of the ta-C film is 72 and 480 GPa, respectively. In vitro measurements of contact angle and platelet adhesion were applied to evaluate the biocompatibility of the ta-C films in comparison with that of NiTi, 316L and pure titanium. The results show that the ta-C films have hydrophobicity and exhibit better hemocompatibility which are very suitable for biomedical applications.

Abstract: Amorphous silicon-carbon films have been successfully deposited by the filtered cathodic vacuum arc techniques. One set of films was deposited from varying silicon-carbon composition in the targets and another set of films was deposited at different various substrate bias voltages from 5 at.% silicon target. The properties of the film were investigated by using atomic force microscopy (AFM), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS) and contact angle measurement. The first set of the samples exhibit atomic smooth surface morphology with RMS roughness below 0.26 nm. The silicon composition in the films determined by XPS varies from 0 to 61 at.%. The Raman results show that at low silicon composition, the G peak position of C-C bond shifts to a low wavenumber, that demonstrates the silicon atom predominantly substitutes for the carbon atom. As the silicon composition increase, the G peak disappeared and a strong broad peak corresponding to the amorphous silicon carbide cluster appears around 800 cm-1. For the second set, the Raman results show the ID/IG ratio increased from 0.24 to 0.67 with using the high bias voltages during the deposition. That indicates the disorder of C-C bond within the films increased. While, both the silicon concentration in the films and contact angles remain relatively constant with the change of bias voltage.

Abstract: Nanocomposite Si containing amorphous carbon (a-C:Si) and metal containing amorphous carbon (a-C:Me) films including a-C:Al, a-C:Ti, and a-C:Ni were prepared by the filtered cathodic vacuum arc (FCVA) technique The metal-carbon (5 at.% metal) composite targets were used. The VCA Optima system was used to measure the contact angle. Three types of liquid were used to study the changes in the surface energy. X-ray photoelectron spectroscopy (XPS) was employed to analyze the composition and chemical state of the films. The surface morphology and roughness of the films were determined by atomic force microscopy (AFM). The Al containing films show the highest contact angle with water, which reaches as high as 101.26°. The Si containing films show the lowest contact angle around 64°. The contact angles of Ni, and Ti containing films are around 83°, 96.5°, respectively. The absorption of oxygen on the surface play an important role on the polar component of the a-C:Me films. The formation of Al-O, and Ti-O bonds is responsible for the lower polar component. The metal state Ni results in higher polar component. The Si-O bond contributes to the high polar component of a-C:Si film. As all films are atomic scale smooth, the RMS roughness is below 0.5 nm, the roughness does not have obvious effect on the surface energy.

Abstract: Zirconium oxide thin films were deposited at room temperature by using off-plane filtered cathodic vacuum arc (FCVA). Deposition rate, film structure, compositional analysis and optical properties are studied as a function of working pressure. Deposition rate as high as 53 nm/min could be achieved. As increasing working pressure, the film structure changes from Zr-O solid solution, to monoclinic structure with preferred orientation and finally to randomly oriented nanocrystalline structure. The averaged crystal size increases with working pressure and is less than 15 nm. The ratio of O/Zr increases with working pressure as well as transmittance and good stoichiometric film could be achieved with high transmittance of 91% at high working pressure.