Showing papers on "Coating published in 2003"

Single layer and multilayer wear resistant coatings of (Ti,Al)N: a review

Abstract: We review the status of (Ti,Al)N based coatings obtained by various physical vapor deposition (PVD) techniques and compare their properties. PVD techniques based on sputtering and cathodic arc methods are widely used to deposit wear resistant (Ti,Al)N coatings. These techniques were further modified to improve the metal ionization rate and to eliminate macrodroplets from plasma streams. We summarize manufacture of target/cathode, substrate materials for deposition of coatings, deposition parameters, and the effect of deposition parameters on the physical and mechanical properties of (Ti,Al)N coatings. It is shown that (Ti,Al)N coatings by PVD enhance the wear, thermal, and oxidation resistance of a wide variety of tool materials. We discuss the wear resistant properties of (Ti,Al)N for various machining applications as compared with coatings such as TiN, Ti(C,N) and (Ti,Zr)N. High hardness (∼28–32 GPa), relatively low residual stress (∼5 GPa), superior oxidation resistance, high hot hardness, and low thermal conductivity make (Ti,Al)N coatings most desirable in dry machining and machining of abrasive alloys at high speeds. Multicomponent coatings based on different metallic and nonmetallic elements combine the benefit of individual components leading to a further refinement of coating properties. Alloying additions such as Cr and Y drastically improve the oxidation resistance, Zr and V improve the wear resistance, whereas, Si increases the hardness and resistance to chemical reactivity of the film. Addition of boron improves the abrasive wear behavior of Ti–Al based coatings due to the formation of TiB2 and BN phases depending on the deposition conditions. Hafnium based nitrides and carbides have potential for resistance to flank and crater wear. The presence of a large number of interfaces between individual layers of a multilayered structure results in a drastic increase in hardness and strength. (Ti,Al)N multilayer super lattice coatings with lattice periodicity of 5–10 nm allow creation of coatings with different properties than PVD deposited single layered thick coatings with columnar grain structure. A range of (Ti,Al)N based multilayers containing layers of (Ti,Al)CN, (Ti,Nb)N, TiN, AlN/TiN, CrN, Mo and WC are also reviewed. It is now possible to design new wear resistant or functional coatings based on a multilayer or a multicomponent system to meet the demanding applications of advanced materials.

Energetically-controlled delivery of biologically active material from an implanted medical device

Abstract: A medical device and system capable of providing on-demand delivery of biologically active material to a body lumen patient, and a method of making such medical device. A first coating layer comprising a biologically active material and optionally a polymeric material is disposed on the surface of the medical device. A second coating layer comprising magnetic particles and a polymeric material is disposed on the first coating layer. The second coating layer, which is substantially free of a biologically active material, protects the biologically active material prior to delivery. The system includes the medical device and a source of energy, such as an electromagnetic or mechanical vibrational energy. When the patient is exposed to the energy source, the magnetic particles move out of the second coating layer and create channels therein through which the biologically active material can be released.

Medical devices having durable and lubricious polymeric coating

Abstract: A medical device having a contact surface exposed repeatedly to bodily tissue is disclosed. The contact surface is coated with a silicone polymer and one or more non-silicone hydrophobic polymers. The preferred medical device is a surgical needle, and the preferred coating is a polydimethylsiloxane and polypropylene wax hydrocarbon mixture. The incorporation of the non-silicone hydrophobic polymer increases the durability of the coating on the device without sacrificing lubricity.

Mechanisms underlying the formation of thick alumina coatings through the MAO coating technology

Abstract: Thick alumina coatings were synthesized on 7075 Al-alloy substrates through the microarc oxidation (MAO) route. Different oxidation times namely 1, 3, 5, 10, 20 and 30 min were employed and the coated samples were subjected to coating thickness and surface roughness measurements. Phase composition of the surface layers of the coatings was evaluated through X-ray diffraction. In addition, the surface features of the coatings were studied using scanning electron microscopy. Influence of coating time on the kinetics of coating formation, surface roughness, microhardness, number and size of the microarc discharge channels was investigated. On the basis of the experimental results, a phenomenological mechanism for the formation of the alumina-based ceramic coatings during the MAO process has been proposed.

Lithographic printing plate precursor

Abstract: A lithographic printing plate precursor containing: an aluminum support; and a photosensitive layer containing a water-insoluble and alkali-soluble resin and an infrared absorber, wherein the photosensitive layer has a coating weight of 05 to 3 g/m 2 and a thickness distribution with a relative standard deviation of 20% or less

Corrosion Inhibition of Aluminum and Aluminum Alloys by Soluble Chromates, Chromate Coatings, and Chromate-Free Coatings

Abstract: This review covers the aqueous chemistry of chromium and the origins of chromium toxicity. Evidence from older and more recent studies is presented showing that inhibition of Al corrosion is derived from both inhibition of oxygen reduction and inhibition of metal dissolution reactions mainly due to a delay in the onset of pitting. Inhibition of corrosion by chromates appears to be closely linked to their ability to irreversibly adsorb on to metal and oxide surfaces. With respect to chromate conversion coatings (CCCs), the evolution of modern coating formulations is presented with a focus on key advances that led to process simplification and improved coating performance. The current understanding of CCC formation, protection, and aging is presented. In the last section of the paper, processing and properties of selected chromate-free conversion coating chemistries is discussed. This discussion focuses on coatings that offer particularly attractive attributes such as self-healing and excellent adh...

Coating composition for multiple hydrophilic applications

Abstract: A coating composition is disclosed which comprises an aqueous polymeric matrix, a hydrophilic polymer, a colloidal metal oxide and a crosslinker. The coating composition when applied on medical devices is hydrophilic, shows improved lubricity, abrasion resistance and substrate adhesion on metallic or plastic substrates. The coating also shows improved water sheeting thus providing the coated substrates with anti-fog properties. The coating absorbs aqueous dye or stain solutions making the substrate suitable for printing.

Photocatalytic activity, antibacterial effect, and photoinduced hydrophilicity of TiO2 films coated on a stainless steel substrate.

Abstract: Transparent TiO2 films on stainless steel prepared by dip coating in a nonionic microemulsions solution have been shown to have much higher photocatalytic activity than those coatings on glass. Fe3+ and Fe2+ ions, diffusing from stainless steel substrate into TiO2 films during high-temperature calcination, behave as dopants to significantly affect the films' photocatalytic activity. An optimum calcination condition, under which the amount of diffused Fe3+ and the ratio of Fe3+ to Fe2+ ions favor the film's photocatalytic reaction, was obtained. In addition, this TiO2 films also exhibits excellent photoinduced hydrophilicity and antibacterial effect for the sterilization of Bacillus pumilus. As stainless steel is a very common material, practical systems for pollution treatment and disinfection may be designed based on this enhanced coating.

Advances in Coating Design for High-Performance Gas Turbines

Abstract: Surface engineering is now a key materials technology in the design of future advanced gas-turbine engines. This article focuses on coating systems for hot-gas-path components, which can vary from low-cost aluminide diffusion coatings to the more exotic, and therefore expensive, thermal-barrier coatings. Available coating systems and their relative benefits are reviewed in terms of performance against manufacturing complexity and cost. Future trends in the design of environmental- and thermal-protection coatings are discussed, including the addition of multiple reactive elements, modified aluminide coatings, diffusion-barrier concepts, the design of “smart” corrosion-resistant coatings, and the development of structurally modified, low-thermal-conductivity thermal-barrier coatings.

Coating Single-Walled Carbon Nanotubes with Tin Oxide

Abstract: Single-walled carbon nanotubes coated with crystalline tin oxide by a simple chemical-solution route are reported. The room-temperature chemical treatment results in a nominally complete and unifor...

Electroless alloy/composite coatings: A review

Abstract: Since the inception of electroless coating by Brenner & Riddell in 1946, it has been the subject of research interest and, in the past two decades, emphasis has shifted to the studies of its properties and applications. The co-deposition of paniculate matter or substance within the growing film has led to a new generation of electroless composite coatings, many of which possess excellent wear and corrosion resistance. This valuable process can coat not only electrically conductive materials including graphite but also fabrics, insulators like plastics, rubber etc. The low coating rates with these can provide better reflectivity of plated surfaces and many more applications. Coatings can be tailored for desired properties by selecting the composition of the coating alloy/composite/metallic to suit specific requirements. The market for these coatings is expanding fast as the potential applications are on the rise. In the present article, an attempt has been made to review different electroless alloy/composite coatings with respect to bath types and their composition, properties and applications. Different characterisation studies have been conducted on various electroless nickel-based coatings with emphasis on wear and corrosion properties.

Lithium-ion batteries: runaway risk of forming toxic compounds.

Abstract: Lithium-ion batteries are stabilized by an ultrathin protective film that is 10-50 nanometers thick and coats both electrodes. Here we artificially simulate the 'thermal-runaway' conditions that would arise should this coating be destroyed, which could happen in a battery large enough to overheat beyond 80 degrees C. We find that under these conditions the reaction of the battery electrolyte with the material of the unprotected positive electrode results in the formation of toxic fluoro-organic compounds. Although not a concern for the small units used in today's portable devices, this unexpected chemical hazard should be taken into account as larger and larger lithium-ion batteries are developed, for example for incorporation into electric-powered vehicles.

Synthesis and magnetic characterization of Mn and Co spinel ferrite-silica nanoparticles with tunable magnetic core

Abstract: A method for coating silica on CoFe2O4 and MnFe2O4 spinel ferrite nanoparticles has been developed by using a reverse micelle microemulsion approach. The ability to controllably synthesize magnetic nanoparticulate cores independent of encapsulation provides great flexibility in tuning the magnetic properties of this magnetic nanocomposite system by controlling the magnetic properties of nanoparticulate cores. For these spinel ferrite nanoparticles, the saturation and remnant magnetizations decrease upon silica coating. The coercivity of silica-coated CoFe2O4 nanoparticles does not show any change after coating, while the coercivity of MnFe2O4 nanoparticles decreases by 10% after they have been coated with silica.

Deposition characteristics of titanium coating in cold spraying

Abstract: Titanium coating was deposited by cold spraying process using nitrogen and helium gases under different temperatures and pressures. The deposition characteristics of the particle in cold spray were studied by the examination of the microstructure evolution of the deposited spot and coating. The effects of the gas type and temperature on the deposition behavior were examined. The microstructure was examined using optical microscopy and scanning electron microscopy. It was found that the pattern of a sprayed spot in cold spray presents a conical shape. The deposition efficiency of spray particles increases with the increase in gas temperature. Two distinguishable top and inner regions exist in the spot deposit and coating, which are characterized by the porous and dense microstructures. The dense microstructure results from the accumulative effect of tamping on the top porous region by the successive impact of following particles. The tamping effect has great influence on the microstructure of the coating in cold spray.

Diffusion barrier coatings having graded compositions and devices incorporating the same

Abstract: A composite article comprises a substrate having at least a substrate surface and a graded-composition coating disposed on a substrate surface. The composition of the coating material varies substantially continuously across its thickness. The coating reduces the transmission rates of oxygen, water vapor, and other chemical species through the substrate such that the composite article can be used effectively as a diffusion barrier to protect chemically sensitive devices or materials. An organic light-emitting device incorporates such a composite article to provide an extended life thereto.

Polyurethane Adhesive Nanocomposites as Gas Permeation Barrier

Abstract: Adhesive nanocomposites of organically modified montmorillonite (OM) and polyurethane have been synthesized and their permeability to oxygen and water vapor has been measured. The gas permeation through the composites was correlated to the volume fraction of the impermeable inorganic part of the OM. The incorporation of small volume fractions of the platelike nanoparticles in the polymer matrix decreased the gas transmission rate, when the interface between the two heterogeneous phases was properly designed. The oxygen transmission rate decayed asymptotically with increasing aluminosilicate volume fraction and a 30% reduction was achieved at 3 vol %, when the clay was coated with bis(2-hydroxyethyl) hydrogenated tallow ammonium or alkylbenzyldimethylammonium ions. In contrast, coating the clay surface with dimethyl dihydrogenated tallow ammonium ions leads to an increase in the gas transmission rate with augmenting inorganic fraction. This was attributed to a probable change in morphology resulting from phase separation at the interface between the apolar pure hydrocarbon clay coating and the relatively polar PU. The water vapor permeation through the PU nanocomposites was more strongly reduced than oxygen and a 50% reduction was observed at 3 vol % silicate fraction. This was attributed to stronger interactions and hydrogen bonding of the water molecules with the PU matrix as well as to their clustering. Differences in the hydrophobicity of the clay coating influenced the water transmission rate. No spectroscopic evidence could be obtained for a reaction between the hydroxyl groups of the clay organic coating and the isocyanate groups of the prepolymer. A mixed morphology, that is, exfoliated layers and intercalated particles was observed in all composites. WAXRD and TEM gave a qualitative picture of the microstructure of the nanocomposites but no conclusive information. Some of the problems to be solved before a correlation between the nanocomposite properties and their microstructure can be established have been outlined.

Method for coating an implantable device and system for performing the method

Abstract: Methods of coating an implantable device and a system for performing such methods are disclosed. An embodiment of the method includes applying a coating substance to the surface of an implantable device, and rotating the implantable device in a centrifuge. The method can uniformly coat the implantable device with the coating substance and to remove unwanted accumulations of coating substance entrained between struts or crevices in the implantable device body. This system is applicable to methods for coating intraluminal stents, synthetic grafts, and stent coverings with therapeutic compositions comprising therapeutic agents mixed with a polymeric matrix and a solvent.

Emulsion Science: Basic Principles

Abstract: Emulsions are generally made out of two immiscible fluids like oil and water, one being dispersed in the second in the presence of surface active compounds. They are used as intermediate or end products in a huge range of areas including the food, chemical, cosmetic, pharmaceutical, paint, and coating industries.....

Cu nanocrystal growth on peptide nanotubes by biomineralization: size control of Cu nanocrystals by tuning peptide conformation.

Abstract: With recent interest in seeking new biologically inspired device-fabrication methods in nanotechnology, a new biological approach was examined to fabricate Cu nanotubes by using sequenced histidine-rich peptide nanotubes as templates. The sequenced histidine-rich peptide molecules were assembled as nanotubes, and the biological recognition of the specific sequence toward Cu lead to efficient Cu coating on the nanotubes. Cu nanocrystals were uniformly coated on the histidine-incorporated nanotubes with high packing density. In addition, the diameter of Cu nanocrystal was controlled between 10 and 30 nm on the nanotube by controlling the conformation of histidine-rich peptide by means of pH changes. Those nanotubes showed significant change in electronic structure by varying the nanocrystal diameter; therefore, this system may be developed to a conductivity-tunable building block for microelectronics and biological sensors. This simple biomineralization method can be applied to fabricate various metallic and semiconductor nanotubes with peptides whose sequences are known to mineralize specific ions.

Analyte sensors and methods for making them

Abstract: Embodiments of the invention provide analyte sensors (100) having stabilized coating compositions and methods for making such sensors. Illustrative embodiments include electrochemical glucose sensors (100) having stabilized glucose oxidase coatings (110) that are generated for example, via spin coating processes.

Method for patterning carbon nanotube coating and carbon nanotube wiring

Abstract: A method for making a nanocomposite electrode or circuit pattern includes forming a continuous carbon nanotube layer impregnated with a binder and patterning the binder resin using various printing or photo imaging techniques. An alternative method includes patterning the carbon nanotube layer using various printing or imaging techniques and subsequently applying a continuous coating of binder resin to the patterned carbon nanotube layer. Articles made from these patterned nanocomposite coatings include transparent electrodes and circuits for flat panel displays, photovoltaics, touch screens, electroluminescent lamps, and EMI shielding.

Design and performance of a microcantilever-based hydrogen sensor

Abstract: This paper describes the design of, and the effects of basic environmental parameters on, a microelectromechanical (MEMS) hydrogen sensor. The sensor contains an array of 10 micromachined cantilever beams. Each cantilever is 500 μm wide×267 μm long×2 μm thick and has a capacitance readout capable of measuring cantilever deflection to within 1 nm. A 20-nm-thick coating of 90% palladium–10% nickel bends some of the cantilevers in the presence of hydrogen. The palladium–nickel coatings are deposited in ultra-high-vacuum (UHV) to ensure freedom from a “relaxation” artifact apparently caused by oxidation of the coatings. The sensor consumes 84 mW of power in continuous operation, and can detect hydrogen concentrations between 0.1 and 100% with a roughly linear response between 10 and 90% hydrogen. The response magnitude decreases with increasing temperature, humidity, and oxygen concentration, and the response time decreases with increasing temperature and hydrogen concentration. The 0–90% response time of an unheated cantilever to 1% hydrogen in air is about 90 s at 25 °C and 0% humidity.