P. Niedzielski

Diamond-like carbon coatings for biomedical applications

Abstract The results of experimental studies on amorphous diamond carbon layers obtained by a new method of r.f. dense plasma chemical vapour deposition onto orthopaedic pins and screws are presented. Research on this subject which has been carried out over many years allows us to draw optimistic conclusions concerning the biomedical applications of diamond-like carbon (DLC). In particular, preliminary medical research on a new DLC-steel substrate system developed in 1992, which has just been concluded, is extremely promising.

Nanocrystalline Diamond Coatings

Abstract Carbon—in the form of diamond coatings (nanocrystalline diamond—NCD) on suitable substrates—has attractive properties for biomedical applications. The excellent chemical inertness of NCD films makes them a promising material for medical implants, cardiovascular surgery and for coating of certain components of artificial heart valves. The medical applications of carbon films impose some special requirements on their quality, purity, phase content and the state of the surface. Of particular importance is the smoothness of the surface and good adhesion of the coatings to the substrate. We have investigated carbon films which were synthesized by Radio Frequency Plasma Chemical Vapour Deposition (RF–PCVD). The specimens obtained have been tested to show their structure and their biological, mechanical and chemical resistance. Additional investigations of the NCD films were carried out by micro-X-ray spectroscopy, Raman spectroscopy, AFM, Auger spectroscopy, corrosion tests, breakdown tests and clinical investigations. Nanocrystalline diamond (NCD) layers obtained by a new method of RF dense plasma CVD onto AISI-316L steel used in surgery were investigated to determine their suitability as biomaterials.

Single and Multilayer Growth of Graphene from the Liquid Phase

The preparation of poly crystalline graphene from the liquid phase has been discussed.The mechanism of graphene growth from the liquid phaseon the Cu-Ni alloy and the type of atmosphere, used inthe graphene fabrication-acetylene, ethylene, hydrogen has been presented. Stages of nucleation and poly crystalline growth of graphene were identified. The paper presents theresults of a single-and multi-layered graphene growth phase.It is assumed the final result will mean the optimization of the industrial-scale production of low-cost poly crystalline graphene.

Amorphous carbon — Biomaterial for implant coatings

Abstract Thin, hard amorphous carbon (a-C) layers were the object of investigations, in particular the microstructure of the layer in the carbon layer-steel substrate system with the aim of optimization of the synthesis and applicability of this new system for medical implants. The results of Auger electron spectroscopy studies show that the composition of the layer is complex. It consists of carbon and a transitional layer containing both carbides and carbon regions. The structure of the coatings ensures a high mechanical strength and very good adhesion to steel. The studies were aimed at investigations of the biological resistance of implants in the oral cavity. Human saliva is an aqueous solution of salts (organic compounds) and contains small amounts of organic substances and gases. The results of the investigations have shown very good resistance of a-C to elements of the oral cavity environment.

Influence of carbon coatings origin on the properties important for biomedical application

Abstract The purpose of the present study was to investigate the properties of a carbon layer depending of the origin of applied methods. Quasiamorphous carbon coatings prepared by ion beam methane decomposition by RF dense plasma and vacuum pulsed arc deposition were applied to stainless steel implants used in surgery. The studies of carbon films as coatings for implants in surgery were aimed on the investigations of biological resistance of implants, histopathological investigations using laboratory animals, tests of corrosion resistance, measurements of mechanical properties and a breakdown test in Tyrod solution. The comparison of the properties of the coating produced by these methods shows very good biotolerance and biocompatibility of all of the coatings. They are not corroded in physiological fluids. From the other side they have different properties, especially electrical and optical, and are not influenced on medical applications. The obtained results prove that the implants coated by all the methods mentioned are a very good material for medical use.

The properties of carbon layers deposited onto titanium substrates

Abstract Thin, hard, amorphous carbon layers, deposited using a dense r.f. methane plasma onto titanium substrates, were investigated. This includes an examination of the interface between the carbon layer and the substrate and the optimization of the process and its application. The substrates coated with carbon layers were analysed by Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). Results of AES studies show that the surface layer, several thousand angstroms thick, consists of carbon. The carbon film passes smoothly into a thick layer (about 1 μm) consisting of titanium carbide. The composition varies across the transitional layer between carbon and carbide regions. This coating structure ensures a high mechanical strength and very good adhesion to Ti substrates. These coatings also protect metal implants against corrosion, and protect man from a serious illness, metallosis. Preliminary investigations in vivo and in vitro confirm the biocompatibility of the C/TiC/Ti system and its biointegration. In addition, investigations of the mechanical, anticorrosive and structural properties of the coatings, deposited using a dense methane plasma excited in an r.f. electric field, show that this can be a very good material to apply in cardiovascular surgery. The r.f. decomposition of methane seems to be a very convenient method for the production of superhard carbon coatings on Ti substrates for medical applications.

Tribological properties of NCD coated cemented carbides in contact with wood

Abstract Cemented carbides coated with diamond layers are promising materials for mills in the wood industry. Therefore, a study of the tribological properties of the contact between this material and wood is interesting and important. Wood is a specific material with a highly anisotropic structure, which causes roughness of its surface. For example, the friction coefficient (μ) of wood in contact with polished steel coated with a smooth DLC layer, has a relatively high value of μ=0.2–0.5. Cemented carbides, as manufactured for tools for wood milling purposes with roughness R z =0.66 μm, have been modified with a nanocrystalline diamond film (NCD) using the RF PACVD method. The surface of the NCD coating showed ‘sharp hills’ morphology, but the surface roughness of cemented carbide decreased slightly after coating. The friction was very high (μ=0.7–0.8 at v =1 m/s; F N =60 N) and it depended on the species of wood. When examining oak and poplar using carbides coated with the thickest NCD layer and a DLC film on top, this value decreased by 30% with respect to that of uncoated carbides. For fibreboard against NCD, the value was increased. Comparing the friction of NCD against wood to its friction against steel, titanium and aluminium alloys, we could see that the roughness of wood was the main factor which determined its tribological behaviour. Prime novelty: the tribological properties of a NCD layer deposited on cemented carbides with wood.

The corrosion tests of amorphous carbon coatings deposited by r.f. dense plasma onto steel with different chromium contents

In the paper the results of experimental studies concerning characterization of amorphous carbon layers obtained by a new method of r.f. dense plasma CVD onto steel with different chromium contents are presented. Thin, amorphous carbon layers, deposited onto these substrates, are the subject of structural and physical investigations. This refers also to the system of carbon layer-steel substrate correlated with a microstructure of the layer, and to the determination of specifications resulting from the model for optimization of the synthesis and applicability of a new system as medical implants. Amorphous carbon coatings produced by the dense r.f. CH4 plasma method from steel AISI-316L used in medicine were investigated to determine their suitability as biomaterials.

Colour carbon coatings

In this paper, the unique properties of thin diamond-like layers are presented. Diamond-like carbon (DLC) films have been developed as colour coatings for a range of substrates. They can be used in a wide variety of applications, including jewellery and other applications where colours need to be combined in a tough, hard-wearing, aesthetically appealing and biocompatible application. DLC films were synthesised by the radio frequency plasma activated chemical vapour deposition (RFPACVD) technique, running at 13.56 MHz. The possibility of the repeatable manufacturing of such coatings makes them a new possible material in jewellery. The coatings have been examined using a range of characterisation tools, including X-ray elemental microanalysis, Raman spectroscopy, atomic force microscopy, colourimetric analysis, ellipsometry and the measurement of nanohardness and adhesion. The examinations show that the technology can be applied in many fields. An example of the jewellery application is afforded by the UK Millennium Medal, created by the well-known English artist Wendy Ramshaw OBE, who worked closely with our team.

Comparison of the surface structure of carbon films deposited by different methods

Abstract Atomic force microscopy is used to estimate and compare surface morphology of the carbon coatings, prepared using radio frequency plasma chemical vapor deposition, pulsed cathodic are discharge, ion-beam deposition and hot-filament chemical vapor deposition. The difference in the surface structure was mentioned for each method of deposition. The influence of the surface morphology on the film properties is discussed.