Showing papers on "Coating published in 1999"

Plasma electrolysis for surface engineering

Abstract: This paper overviews the relatively new surface engineering discipline of plasma electrolysis, the main derivative of this being plasma electrolytic deposition (PED), which includes techniques such as plasma electrolytic oxidation (PEO) and plasma electrolytic saturation (PES) processes such as plasma electrolytic nitriding/carburizing (PEN/PEC). In PED technology, spark or arc plasma micro-discharges in an aqueous solution are utilised to ionise gaseous media from the solution such that complex compounds are synthesised on the metal surface through the plasma chemical interactions. The physical and chemical fundamentals of plasma electrolysis are discussed here. The equipment and deposition procedures for coating production are described, and the effects of electrolyte composition and temperature on ignition voltage, discharge intensity and deposited layer thickness and composition are outlined. AC-pulse PEO treatment of aluminium in a suitable passivating electrolyte allows the formation of relatively thick (up to 500 μm) and hard (up to 23 GPa) surface layers with excellent adhesion to the substrate. A 10–20 μm thick surface compound layer (1200HV) and 200–300 μm inner diffusion layer with very good mechanical and corrosion-resistant properties can also be formed on steel substrates in only 3–5 min by use of the PEN/PEC saturation techniques. Details are given of the basic operational characteristics of the various techniques, and the physical, mechanical and tribological characteristics of coatings produced by plasma electrolytic treatments are presented.

Process for coating stents

Abstract: A process is provided for coating stents having a first and second surface with passages there between to avoid blockage and bridging of the passages. The process comprises contacting the stent with a liquid coating solution containing a film forming biocompatible polymer under conditions suitable to allow the film forming biocompatible polymer to coat at least one surface of the stent while maintaining a fluid flow through said passages sufficient prevent the film forming biocompatible polymer from substantially blocking said passages. Also described are stents coated by this process.

Nanophase-Separated Polymer Films as High-Performance Antireflection Coatings

Abstract: Optical surfaces coated with a thin layer to improve light transmission are ubiquitous in everyday optical applications as well as in industrial and scientific instruments. Discovered first in 1817 by Fraunhofer, the coating of lenses became standard practice in the 1930s. In spite of intensive research, broad-band antireflection coatings are still limited by the lack of materials with low refractive indices. A method based on the phase separation of a macromolecular liquid to generate nanoporous polymer films is demonstrated that creates surfaces with high optical transmission.

Thin Polymer Layers Formed by Polyelectrolyte Multilayer Techniques on Biological Surfaces

Abstract: Thin polymer films were formed on models of tissue surfaces using polyelectrolyte multilayer techniques, to evaluate the feasibility of using such techniques to build barrier materials onto the surfaces of tissues to improve postsurgical healing, or on the surfaces of tissue-engineered implants. By incubating heterogeneous surfaces with a polycation, followed by a polyanion, layers of polyelectrolyte were deposited onto the surfaces, as confirmed by ellipsometry and water contact angle measurement. Particularly favorable properties were found using the polyelectrolytes polylysine and alginate, which are capable of forming complex gels at physiologic pH; whereas others have demonstrated linear growth in film thickness, with this system, exponential growth was observed under certain conditions, which may be very useful in the coating of heterogeneous surfaces. Surfaces that were treated with multilayer techniques included gelatin, fibroblast extracellular matrix, and fibrillar type I collagen. All surfaces ...

Bioactive agent release coating

Abstract: A coating composition for use in coating implantable medical devices to improve their ability to release bioactive agents in vivo. The coating composition is particularly adapted for use with devices that undergo significant flexion and/or expansion in the course of their delivery and/or use, such as stents and catheters. The composition includes the bioactive agent in combination with a mixture of a first polymer component such as poly(butyl methacrylate) and a second polymer component such as poly(ethylene-co-vinyl acetate).

Stents with hybrid coating for medical devices

Abstract: A device such as a stent is provided with a hybrid coating including a time released, restenosis inhibiting coating and a non-thrombogenic coating to prevent clotting on the device. One first coat or layer includes a polymer, a crosslinking agent, and pacitaxel, analogues, or derivatives thereof. The first coat preferably includes a polymer having Taxol admixed therein so as to be releasable over time. The first coat preferably includes a polyfunctional aziridine as the crosslinking agent. The second coat preferably includes heparin to inhibit clot formation on the device. The crosslinking agent can covalently bond to both the first coat polymer and the second coat heparin. A stent can be provided with a first coat including an aqueous dispersion or emulsion of a polymer and an excess of crosslinking agent. The first coating can be dried, leaving a water insoluble polymer coating. A second aqueous coating including a solution or dispersion of heparin can be applied over the first coating, the heparin becoming covalently bound to the crosslinking agent on the first coating surface. The resulting stent can inhibit restenosis while preventing blood clot formation on the stent.

Medical device coated with interpenetrating network of hydrogel polymers

Abstract: A medical device comprising an organic polymer substrate material having a coating thereon, the coating comprising an interpenetrating network of two different hydrogel polymers, one of which is a polyurethane/polyurea hydrogel polymer, the polyurethane/polyurea hydrogel polymer being linked to the substrate material by covalent urea linkages.

Implant Surfaces and Interface Processes

Abstract: The past decades and current R&D of biomaterials and medical implants show some general trends. One major trend is an increased degree of functionalization of the material surface, better to meet the demands of the biological host system. While the biomaterials of the past and those in current use are essentially bulk materials (metals, ceramics, polymers) or special compounds (bioglasses), possibly with some additional coating (e.g., hydroxyapatite), the current R&D on surface modifications points toward much more complex and multifunctional surfaces for the future. Such surface modifications can be divided into three classes, one aiming toward an optimized three-dimensional physical microarchitecture of the surface (pore size distributions, "roughness", etc.), the second one focusing on the (bio) chemical properties of surface coatings and impregnations (ion release, multi-layer coatings, coatings with biomolecules, controlled drug release, etc.), and the third one dealing with the viscoelastic properties (or more generally the micromechanical properties) of material surfaces. These properties are expected to affect the interfacial processes cooperatively, i.e., there are likely synergistic effects between and among them: The surface is "recognized" by the biological system through the combined chemical and topographic pattern of the surface, and the viscoelastic properties. In this presentation, the development indicated above is discussed briefly, and current R&D in this area is illustrated with a number of examples from our own research. The latter include micro- and nanofabrication of surface patterns and topographies by the use of laser machining, photolithographic techniques, and electron beam and colloidal lithographies to produce controlled structures on implant surfaces in the size range 10 nm to 100 microns. Examples of biochemical modifications include mono- or lipid membranes and protein coatings on different surfaces. A new method to evaluate, e.g., biomaterial-protein and biomaterial-cell interactions--the Quartz Crystal Microbalance--is described briefly.

Stent with smooth ends

Abstract: A stent having at least one smooth end is disclosed. The stent may include a coating or coatings on one or both end portions to provide a smooth finish to reduce possible damage to body passages when the stent is deployed and delivered. The stent may also contain drugs or surgical adhesives or a combination thereof in or on the coated portion of the stent. The stent may also be of the type where the materials of the stent may be treated to have a smooth flexible end or ends. The stent may also be of a configuration such that at least one end is more flexible than the middle portion of the stent.

Method and apparatus for ionized physical vapor deposition

Abstract: Ionized Physical Vapor Deposition (IPVD) is provided by a method of apparatus (500) particularly useful for sputtering conductive metal coating material from an annular magnetron sputterin target (10). The sputtered material is ionized in a processing space between the target (10) and a substrate (100) by generating a dense plasma in the space with energy coupled from a coil (39) located outside of the vacuum chamber (501) behind a dielectric window (33) in the chamber wall (502) at the center of the opening (421) in the sputtering target. A Faraday type shield (26) physically shields the window to prevent coating material from coating the window, while allowing the inductive coupling of energy from the coil into the processing space. The location of the coil in the plane of the target or behind the target allows the target-to-wafer spacing to be chosen to optimize film deposition rate and uniformity, and also provides for the advantages of a ring-shaped source without the problems associated with unwanted deposition in the opening at the target center.

Kinetic spray coatings

Abstract: Coatings have been produced by entraining metal powders in an air flow which is accelerated by a de Laval type of nozzle. The particles are not melted or thermally softened prior to impingement onto the substrate. The coating process depends primarily on the kinetic energy of the incident powders. The coatings have low oxide content and low thermal stress, and can exhibit relatively low porosity and high adhesion. The mechanism by which the coatings are formed is not well understood, and it is the goal of this work to provide some insights into this mechanism. We have produced a new high-velocity spray apparatus which allows the spray parameters to be controlled and monitored for the first time. This, together with our simulations of air and particle velocities and temperatures, has provided new information on the coating process. Al, Cu, and Fe powders were sprayed onto Al, brass, Cu, and steel substrates. A threshold behavior was observed for coating deposition as a function of nozzle inlet air temperature, with a roughly linear behavior above the threshold. Results are obtained as a function of nozzle inlet air pressure and temperature, powder feed rate, and nozzle–substrate stand-off distance. The effect of the choice of substrate metal was relatively weak in our experiments. Results seem consistent with necessary inelastic processes such as plastic deformation and/or partial melting of the powder particles upon collision with the substrate. More research is needed to define the relative importance of these phenomena or of other possible mechanisms.

Nanocomposite tribological coatings for aerospace applications

Abstract: Challenges in aerospace tribology and composite coatings for aerospace applications are briefly reviewed. Attention is given to nanocomposite coatings made of carbide, diamond-like carbon (DLC) and transition-metal dichalcogenide phases. The preparation of such coatings within the W–C–S material system using a hybrid of magnetron sputtering and pulsed laser deposition is described. Coatings consist of 1–2 nm WC and 5–10 nm WS2 grains embedded in an amorphous DLC matrix. These WC/DLC/WS2 nanocomposites demonstrate low friction and wear in tests performed in high vacuum, dry nitrogen and humid air. Coatings are found to adapt to the test conditions, which results in: (1) crystallization and reorientation of initially nanocrystalline and randomly oriented WS2 grains; (2) graphitization of the initially amorphous DLC matrix; (3) reversible regulation of the composition of the transfer film between WS2 and graphite with environmental cycling from dry to humid; and (4) possible DLC/WS2 synergistic effects, providing friction reduction in oxidizing environments. These adaptive mechanisms achieve low friction coefficients of 0.02–0.05 and an endurance above two million cycles in space simulation tests. This also provides stable coating performance and recovery of low friction in tests simulating ambient/space environmental cycling. Correlations among WC/DLC/WS2 chemistry, structure, hardness, friction and wear are discussed. The tremendous potential of such composites for aerospace tribology is demonstrated.

A Mechanistic Investigation of Polyaniline Corrosion Protection Using the Scanning Reference Electrode Technique

Abstract: Growing environmental concerns regarding the use of heavy metals in coating formulations have lead to a new coating strategy employing inherently conducting polymers (ICPs), such as polyaniline (PANI), as a key component. The principal potential advantage offered by the ICP coating technology is toleration of pinholes and minor scratches. This paper describes the application of the scanning reference electrode technique (SRET) to the study of PANI coatings on carbon steel. SRET results demonstrate that conductive PANI passivates pinhole defects in coatings on carbon steel. In addition, it is shown that phosphonic acid salts of PANI are more effective for corrosion protection than sulfonic acid salts. A model is proposed which entails passivation of the metal surface through anodization of the metal by PANI and formation of an insoluble iron-dopant salt at the metal surface.

Sputtering apparatus and process for high rate coatings

Abstract: A sputtering apparatus and method for high rate deposition of electrically insulating and semiconducting coatings with substantially uniform stoichiometry. At least one set of vertically mounted, dual and triple rotatable cylindrical (or planar) magnetrons with associated vacuum pumps, form semi-isolated sputtering modules. The sputtering modules can be independently controlled for the sequential deposition of layers of similar or different materials. Constant voltage operation of AC power with an optional reactive gas flow feedback loop maintains constant coating stoichiometry during small changes in pumping speed caused by substrate motion. The coating method is extremely stable over long periods (days) of operation, with the film stoichiometry being selectable by the voltage control point. The apparatus may take the form of a circular arrangement of modules for batch coating of wafer-like substrates, or the modules may be arranged linearly for the coating of large planar substrates

PVD coatings as an environmentally clean alternative to electroplating and electroless processes

Abstract: Today the development of clean technologies in all spheres of industrial manufacturing is an essential task, not only for material and metal finishing but also for plasma surface engineering. Among the most critical group of technologies which needs to be replaced by alternative technologies are processes used to produce functional galvanic and decorative coatings. The electroplating of finishes, such as hard chromium, cadmium and nickel in metal finishing is today recognized as a major source of environmental pollution in every country. Therefore wet bath technologies have started to lose favour compared with high performance dry coating methods such as physical vapour deposition (PVD), plasma-assisted chemical vapour deposition, chemical vapour deposition and thermal spraying. Among these techniques, the results obtained with PVD coatings in metal cutting and forming in the last 15 years show the most promising solution of the complicated situation in which galvanic coatings seemed to be technologically and economically irreplaceable. In this paper the general situation in this field is shown. Already today it is possible to replace efficiently some of the galvanic processes in specific cases (e.g. Cr, Ni, Cd, Zn, Au). It is important to point out that PVD is considered to be a technique which can provide not only metallic, but also alloyed and ceramic coatings with a virtually unlimited range of chemical composition and therefore controlled protective, mechanical and wear-resistant properties. Entering into competition with galvanic coatings the manufacturers of PVD coaters were confronted with new requirements: a huge quantity of substrates of the same size, to be chemically and plasma cleaned and then coated at the highest possible deposition rate. For industrial mass production one can therefore use only large PVD batch systems or in-line coaters. The alternative for today's low price galvanic coatings is therefore dry and clean PVD technologies, fully supported by legislation on environmental protection. The economics depend directly on the substrate type and the quantity. The first positive results on the replacement of electrodeposited nickel on aluminium substrates and hard chrome on soft iron are also reported here. A soldering test was made on a sputtered nickel layer. Wear and corrosion tests were performed with iron cores, coated with PVD CrN coating. All tests were made in the Slovenian automotive industry. Results show that for a large number of substrates PVD clean technology is already economically competitive with galvanic coatings.

Protective coating for separators for electrochemical cells

Abstract: This invention pertains to separators for electrochemical cells which comprise (i) two microporous pseudo-boehmite layers and (ii) a protective coating layer comprising a polymer interposed between the microporous pseudo-boehmite layers; electrolyte elements comprising such separators; electrical current producing cells comprising such separators; and methods of making such separators, electrolyte elements and cells.

Transparent substrate with diffuser surface

Abstract: A transparent substrate having a glare reducing diffuser surface coating on its outer surface forms a faceplate for attachment to a screen for a cathode ray tube or other display device. The coating has a preferred resolution of at least about 3 lines per millimeter, and the substrate may include an index matching adhesive/medium for attaching said faceplate to a cathode ray tube screen. The diffuser surface coated substrate is bendable and overcoatable with functional coatings such as transparent conductor and/or abrasion resistant coatings. Alternately, the diffuser surface coating may be applied over such functional coatings which are applied to the substrate.

Tribology of thin coatings

Abstract: The fundamentals of coating tribology are presented in a generalised holistic approach to friction and wear mechanisms of coated surfaces in dry sliding contacts. This is based on a classification of the tribological contact process into macromechanical, micromechanical, tribochemical contact mechanisms and material transfer. The tribological contact process is dominated by the macromechanical mechanisms, which have been systematically analysed by using four main parameters: the coating-to-substrate hardness relationship, the film thickness, the surface roughnesses and the debris in the contact. The description covers both soft and hard coatings with thicknesses typically in the range 0.1–50 μm, where the interaction between the coating and the substrate is essential to the tribological behaviour. The concept is supported by experimental observations. The important influence of thin tribo- and transfer layers formed during the sliding action is shown. Optimal surface design both regarding friction and wear can be achieved by new multilayer techniques giving reduced stresses, improved adhesion to substrate, more flexible coatings and harder and smoother surfaces. The differences in contact mechanisms in dry, water- and oil lubricated contacts with coated surfaces is illustrated by experimental results from diamond-like coatings sliding against a steel ball. The mechanisms of the formation of dry transfer- and tribolayers and lubricated boundary and reaction films are discussed.

New hard/lubricant coating for dry machining

Abstract: Environmental and economic considerations have emphasized the trend for more dry machining. Advanced wear-resistant coatings with increased oxidation resistance such as PVD TiAlN offer an advantage for dry machining of cast iron and alloyed steel. Although some important cutting operations are still not possible without coolants, further possibilities for dry drilling and tapping of steels are enabled by the recent approach using tools with hard coating layers topped with a lubricant layer. The combination of hard/soft coating layers allows improved chip flow with a lowered coefficient of friction and reduced cutting force. In this work, the hard/soft coating consists of a low-internal-stress TiAlN (hard layer) and WC/C (lubricant layer) of medium microhardness and low coefficient of friction. Both coating types are produced economically and reproducibly in one production scale PVD coating system. Recent performance data from field tests will be presented.

Biocompatible coating for a prosthesis and a method of forming the same

Abstract: A coating for a prosthesis, for example a stent, and a composition for forming the coating is disclosed. The coating can serve as a primer, allowing substances, such as polymers, to be effectively secured by the prosthesis. Alternatively, the coating can serve as a reservoir, allowing for the local and sustained release of a therapeutic substance to biological tissues. The composition can be formed from an ethylene vinyl alcohol copolymer and a dimethylsulfoxide solvent, with or without a therapeutic substance. Alternatively, the composition can be formed from an ethylene vinyl alcohol copolymer, a dimethylsulfoxide solvent, and a wetting fluid, with or without a therapeutic substance. The composition is applied to a surface of the prosthesis and essentially all of the dimethylsulfoxide solvent or dimethylsulfoxide solvent/wetting fluid is removed or allowed to evaporate to form the coating.

Monolith coating apparatus and method therefor

Abstract: Apparatus for coating a support such as a monolithic catalyst support (5) comprises a dispenser (1) for dispensing a predetermined quantity of coating liquid, a containment (2) for the liquid and a source of vacuum (8, 9) which can be actuated to draw the entire quantity of coating liquid into the support (5). The apparatus and method are particularly useful for coating car catalysts without wastage and with increased design options.

Method and apparatus for augmentating osteointegration of prosthetic implant devices

Abstract: Bone augmentation in a mammalian body to enhance the mechanical strength of a prosthesis is provided by reinforcement of bone in the region surrounding the implant device. A number of fibrillar wires are formed on the prosthetic implant device. Formation of the fibrillar wires comprises gauging the implant device so that the fibrillar wires are formed by peeling them from the implant device. Alternatively, formation of the fibrillar wires may comprise forming a mesh of fibrillar wires having a woolly structure, forming the mesh around the prosthetic implant device, and attaching a number of the fibrillar wires to the prosthetic implant device. A coating is formed on the fibrillar wires and an associated prosthetic implant device. The coating comprises bone morphogenetic proteins along with osteoinductive factors and osteoconductive factors that function as nutrients, anti-microbial and anti-inflammatory agents, and blood-clotting factors. The polymer is a polymer matrix component comprising lactic acid, glycolic acid, and copolymers of lactic acid and glycolic acid. The osteoinductive coating combined with the fibrillar wool or prongs should allow for optimal osteointegration and physiologic load distribution of a implant device resulting in prosthetic success when placed in the human body.

The origin and nature of flame retardance in ethylene-vinyl acetate copolymers containing hostaflam AP 750

Abstract: The aim of the study is to investigate new intumescent materials based on ethylene-vinyl acetate copolymers. Hostaflam AP 750 is used as a flame-retardant system. Fire testing and thermal analyses have shown that the incorporation of AP 750 leads to the formation of an intumescent coating which provides good fire barrier properties. Spectrochemical analyses have shown that the coating consists of polyethylenic chains issued from the polymer. Polyaromatic structures and phosphorus oxides are also observed in the coating.

Glass substrates coated with a stack of thin layers having reflective properties in the infra-red and/or solar ranges

Abstract: A transparent substrate particularly of glass, provided with a stack of thin layers having at least one metallic layer (4) having properties in the infrared range particularly having low emissivity and two coatings having a base of dielectric material located one (8) under and the other (9) over the layer having properties in the infrared range, as well as a protective metallic layer (5) place immediately over an in contact with the layer having properties in the infrared range, characterized in that in order to prevent the modification of properties of the stack, particularly optical and thermal properties, in the case where the substrate is submitted to a thermal treatment of the tempering or bending kind, firstly the second coating (9) having a base of dielectric material, includes a barrier layer for the diffusion of oxygen chosen from the following materials: components of silicon SiO2, SiOxCy, SiONNy, nitrates such as Si3N4 or AlN, carbides such as SiC, TiC, CrC, TaC of a thickness of at least 10 nanometers and preferably of at least 20 nanometers, and secondly the layer having properties in the infrared range is directly in contact with the underlying dielectric coating.