Showing papers on "Coating published in 2006"

End effector coatings for electrosurgical instruments

Abstract: An electrosurgical stapling instrument includes an end effector capable of applying bipolar RF energy into tissue. The end effector has a first pole electrode and a second pole electrode for forming an RF contact circuit with tissue. At least one of the electrodes may have a dielectric coating thereon to create a RF circuit with tissue. The dielectric coating can cover one of the electrodes to create a capacitive coupling circuit with tissue, or can have at least one open passageway extending through the dielectric coating to enable tissue contact with the electrode and the passage of RF energy therethrough. The dielectric coating on the electrode can be masked to create passageways through the dielectric, or the dielectric coating can be locally removed with a variety of techniques to form passageways. The dielectric coating may provide a barrier to prevent shorting between the dielectrically coated electrode and a conductive fastener embedded within tissue. Alternately, a cartridge coating can be used to reduce an electric surface sheet charge on the cartridge thermoplastic that can occur during the application of RF energy to tissue.

Layer‐by‐Layer Assembled Nanocontainers for Self‐Healing Corrosion Protection

Abstract: The corrosion of metals is one of the main destructive processes that leads to huge economic losses. Polymer coating systems are normally applied on a metal surface to provide a dense barrier against the corrosive species in order to protect metal structures from corrosive attack. When the barrier is damaged and the corrosive agents penetrate to the metal surface the coating system can not stop the corrosion process. The most effective solution so far for designing anticorrosion coatings for active protection of metals is to employ chromate-containing conversion coatings. However, hexavalent chromium species are responsible for several diseases, including DNA damage and cancer, which is the main reason for banning Cr-containing anticorrosion coatings in Europe from 2007. The deposition of thin inorganic or hybrid films on metallic surfaces has been suggested as a pretreatment to provide an additional barrier against the corrosion species and mainly to improve adhesion between the metal and polymer coating system. The films are usually deposited by the plasma polymerization technique or the sol–gel route. Sol–gel-derived thin films that contain either inorganic (phosphates, vanadates, borates, and cerium and molybdenum compounds) or organic (phenylphosphonic acid, mercaptobenzothiazole, mercaptobenzoimidazole, triazole) inhibitors are investigated as substitutes for chromates. Among them, the highest activity is shown for sol–gel coatings with a cerium dopant of a critical concentration in the 0.2–0.6 wt % range. However, the negative effect of the free inhibitor occluded in the sol–gel matrix on the stability of the protective film is observed for all types of inhibitors (for instance, a higher concentration of Ce leads to the formation of microholes in the sol–gel film). This shortcoming calls for the development of nanometer-scale reservoirs to isolate an inhibitor inside and prevent its direct interaction with the sol–gel matrix. Nanoreservoirs should be homogeneously distributed in the film matrix and should possess controlled and corrosion-stimulated inhibitor release to cure corrosion defects. Mixed-oxide nanoparticles (e.g. ZrO2/CeO2), [4] b-cyclodextrin-inhibitor complexes, hollow polypropylene fibers, and conducting polyaniline have been explored as prospective reservoirs for corrosion inhibitors to be incorporated in the protective film. The common mechanism of the nanoreservoir activity is based on the slow release of inhibitor triggered by corrosion processes. Ion exchangers have also been investigated as ‘smart’ reservoirs for corrosion inhibitors. Chemically synthesized hydrocalmite behaves as an anion exchanger: adsorbing corrosive chloride ions and releasing corrosion-inhibiting nitrite anions. Despite considerable efforts devoted to the development of new, complex anticorrosion systems, practically no single solution is able to fulfill the requirements of sufficient corrosion protection while avoiding chromates in the coating, especially in the case of aluminum alloys used for aerospace applications. The recently developed technology of layer-by-layer (LbL) deposition of oppositely charged species (polyelectrolytes, nanoparticles, enzymes, dendrimers) from their solutions on the substrate surface represents an interesting approach to prepare reservoirs with regulated storage/release properties assembled with nanometer-thickness precision. LbL coatings are of practical interest in photonics (optical filters, luminescent coatings), electrocatalysis (electrodes for DNA transfer, enzyme-catalyzed oxidation), as membranes, and chemical reactors. LbL-assembled polyelectrolyte multilayers reveal controlled permeability properties. Depending on the nature of the assembled monolayers, the permeability of multilayer films can be controlled by changing pH, ionic strength, and temperature, or by applying magnetic or electromagnetic fields. Polyelectrolyte assemblies have never been used in corrosion-protection coatings, although storage of corrosion inhibitors in polyelectrolyte multilayers can confer several advantages: they can prevent a negative effect of the corrosion inhibitor on the stability of the coating, decrease the influence of the coating polymerization on the inhibitor, and provide intelligent release of the corrosion inhibitor, as the permeability C O M M U N IC A TI O N S

Chronic neural recordings using silicon microelectrode arrays electrochemically deposited with a poly(3,4-ethylenedioxythiophene) (PEDOT) film

Abstract: Conductive polymer coatings can be used to modify traditional electrode recording sites with the intent of improving the long-term performance of cortical microelectrodes. Conductive polymers can drastically decrease recording site impedance, which in turn is hypothesized to reduce thermal noise and signal loss through shunt pathways. Moreover, conductive polymers can be seeded with agents aimed at promoting neural growth toward the recording sites or minimizing the inherent immune response. The end goal of these efforts is to generate an ideal long-term interface between the recording electrode and surrounding tissue. The goal of this study was to refine a method to electrochemically deposit surfactant-templated ordered poly(3,4-ethylenedioxythiophene) (PEDOT) films on the recording sites of standard 'Michigan' probes and to evaluate the efficacy of these modified sites in recording chronic neural activity. PEDOT-coated site performance was compared to control sites over a six-week evaluation period in terms of impedance spectroscopy, signal-to-noise ratio, number of viable unit potentials recorded and local field potential recordings. PEDOT sites were found to outperform control sites with respect to signal-to-noise ratio and number of viable unit potentials. The benefit of reduced initial impedance, however, was mitigated by the impedance contribution of typical silicon electrode encapsulation. Coating sites with PEDOT also reduced the amount of low-frequency drift evident in local field potential recordings. These findings indicate that electrode sites electrochemically deposited with PEDOT films are suitable for recording neural activity in vivo for extended periods. This study also provided a unique opportunity to monitor how neural recording characteristics develop over the six weeks following implantation.

Review on methods to deposit catalysts on structured surfaces

Abstract: The methods used to deposit a catalyst on structured surfaces are reviewed. Physical methods such as PVD and chemical methods (sol–gel, CVD, direct synthesis, etc.) are described. The coating of catalysts based on oxide, zeolite or carbon support is detailed on various surfaces such as silicon or steel microstructured reactors, cordierite monoliths or foams, fibres, tubes, etc.

Nanowire single-photon detector with an integrated optical cavity and anti-reflection coating

Abstract: We have fabricated and tested superconducting single-photon detectors and demonstrated detection efficiencies of 57% at 1550-nm wavelength and 67% at 1064 nm. In addition to the peak detection efficiency, a median detection efficiency of 47.7% was measured over 132 devices at 1550 nm. These measurements were made at 1.8K, with each device biased to 97.5% of its critical current. The high detection efficiencies resulted from the addition of an optical cavity and anti-reflection coating to a nanowire photodetector, creating an integrated nanoelectrophotonic device with enhanced performance relative to the original device. Here, the testing apparatus and the fabrication process are presented. The detection efficiency of devices before and after the addition of optical elements is also reported.

Thermochemical Interaction of Thermal Barrier Coatings with Molten CaO–MgO–Al2O3–SiO2 (CMAS) Deposits

Abstract: Thermal barrier coatings (TBCs) are increasingly susceptible to degradation by molten calcium–magnesium alumino silicate (CMAS) deposits in advanced engines that operate at higher temperatures and in environments laden with siliceous debris. This paper investigates the thermochemical aspects of the degradation phenomena using a model CMAS composition and ZrO2–7.6%YO1.5 (7YSZ) grown by vapor deposition on alumina substrates. The changes in microstructure and chemistry are characterized after isothermal treatments of 4 h at 1200°–1400°C. It is found that CMAS rapidly penetrates the open structure of the coating as soon as melting occurs, whereupon the original 7YSZ dissolves in the CMAS and reprecipitates with a different morphology and composition that depends on the local melt chemistry. The attack is minimal in the bulk of the coating but severe near the surface and the interface with the substrate, which is also partially dissolved by the melt. The phase evolution is discussed in terms of available thermodynamic information.

The cold spray process and its potential for industrial applications

Abstract: Cold spraying has attracted serious attention since unique coating properties can be obtained by the process that are not achievable by conventional thermal spraying This uniqueness is due to the fact that coating deposition takes place without exposing the spray or subtrate material to high temperatures and, in particular, without melting the sprayed particles Thus, oxidation and other undesired reactions can be avoided Spryy particles adhere to the substrate only because of their high kinetic energy on impact For successful bonding, powder particles have to exceed a critical velocity on impact, which is dependent on the properties of the particular spray material This requires new concepts for the description of coating formation but also indicates applications beyond the market for typical thermal spray coatings The present contribution summarizes the current “state of the art” in cold spraying and demonstrates concepts for process optimization

Light emitting apparatus and method of manufacturing the same

Abstract: A light emitting apparatus comprising a light emitting device ( 101 ) disposed on a supporting body ( 105 ), and coating layers (( 108, 109 ) that bind a fluorescent substance that absorbs light emitted by the light emitting device ( 101 ) and emits light of a different wavelength and secures the fluorescent substance onto the surface of the light emitting device ( 101 ). The coating layers ( 108, 109 ) are made of an inorganic material including an oxide and a hydroxide, each containing at least one element selected from the group consisting of Si, Al, Ga, Ti, Ge, P, B, Zr, Y, Sn, Pb and alkali earth metals. Also an adhesive layer ( 110 ) is made of the same inorganic material as that of the coating layers ( 108, 109 ).

Electrodeposition of hydroxyapatite onto nanotubular TiO2 for implant applications

Abstract: Titanium and its alloys are being used in many orthopedic and bioimplant applications. In order to render these materials bioactive and to enhance osteointegration, the surfaces are coated with hydroxyapatite (HAp). Adhesion of bone cell to the implant surface, bond strength and durability of the implants are highly dependent upon the characteristics of the Ti substrate and the methods utilized in the hydroxyapatite coating process. In this paper we have reported an innovative method of preparation of a nanotubular titania surface and subsequent electrodeposition of hydroxyapatite nanocrystalline coating. Growth of the hydroxyapatite onto the nanotubular titania surface was accomplished by a pulsed electrodeposition process. Prior to the electrodeposition, the nanotubular titania surface was subjected to an alkaline treatment, which provided a template for nucleation of the hydroxyapatite inside the nanotubes. This process resulted in a vertical growth of the hydroxyapatite crystals and increased the bond strength of the coating. Bond strength was further improved by annealing the hydroxyapatite coated nanoporous titania in an argon atmosphere.

Hard AlTiN, AlCrN PVD coatings for machining of austenitic stainless steel

Abstract: The austenitic stainless steels in general are considered to be difficult to machine materials. This is mainly due to the high plasticity and tendency to work-harden of the austenitic stainless steel, which usually results in severe cutting conditions. Additionally, austenitic stainless steels have much lower thermal conductivity as compared to structural carbon steels; this inflicts high thermal impact within the chip-tool contact zone, which significantly increase the cutting tool wear rate. The machineability of austenitic stainless steels can be improved due to application of coated cutting tools. Hard PVD coating with low thermal conductivity and improved surface finish should be used in this case. This can result in enhancement of frictional characteristics at the tool/workpiece interface as well as chip evacuation process. In this study the stainless steel plates were machined using cemented carbide finishing end mills with four high aluminum containing PVD coatings namely: AlCrN, AlCrNbN, fine grained (fg) AlTiN and nano-crystalline (nc) AlTiN. Both AlTiN and AlCrN-based coatings have high oxidation resistances due to formation of aluminum oxide surface layers. The influence of surface post-deposition treatment on tool wear intensity was investigated. The coating surface texture before and after post-deposition treatment was analyzed by means of the Abbot-Firestone ratio curves. Minimal wear intensity after length of cut 150 m was achieved for cutting tools with the nc-AlTiN coating.

High-sensitivity optical monitoring of a micromechanical resonator with a quantum-limited optomechanical sensor

Abstract: We experimentally demonstrate the high-sensitivity optical monitoring of a micromechanical resonator and its cooling by active control. Coating a low-loss mirror upon the resonator, we have built an optomechanical sensor based on a very high-finesse cavity (30 000). We have measured the thermal noise of the resonator with a quantum-limited sensitivity at the 10(-19) m/sqrt[Hz] level, and cooled the resonator down to 5 K by a cold-damping technique. Applications of our setup range from quantum optics experiments to the experimental demonstration of the quantum ground state of a macroscopic mechanical resonator.

Electronic-Insulating Coating of CaCO3 on TiO2 Electrode in Dye-Sensitized Solar Cells: Improvement of Electron Lifetime and Efficiency

Abstract: Electronic-insulating coating of CaCO3 on nanocrystalline TiO2 electrode for dye-sensitized solar cells was found to increase both short-circuit photocurrent (Jsc) and open-circuit photovoltage (Voc) remarkably. The significant increase in Jsc is mainly attributed to the remarkably increased dye adsorption resulting from the more basic surface of CaCO3 than TiO2, while the increase in Voc originates from suppression of charge recombination owing to the surface covering of TiO2 with an insulating coating of CaCO3, revealed by intensity-modulated photovoltage spectroscopy. A 15 μm TiO2 (23 nm) nanocrystalline electrode coated with 1 wt % CaCO3, sensitized with N719, produced power conversion efficiency of 10.2%, where N719 is cis-di(thiocyanato)-bis(2,2‘-bipyridyl-4,4‘-dicarboxylate) ruthenium(II), using an antireflective film on the cell surface.

Functional Coatings and Microencapsulation: A General Perspective

Abstract: Today, many objects that we come across in our daily lives, including the house in which we live and the materials we use (e.g., toothbrushes, pots and pans, refrigerators, televisions, computers, cars, furniture) all come under the “umbrella” of coated materials. Likewise, fields such as military applications – for example, vehicles, artilleries and invisible radars – and aerospace products such as aircraft, satellites and solar panels all involve the widespread use of coated materials. Clearly, the importance of coatings has increased hugely during the modern era of technology. Coating is defined as a material (usually a liquid) which is applied onto a surface and appears as either a continuous or discontinuous film after drying. However, the process of application and the resultant dry film is also regarded as coating [1]. Drying of the liquid coating is mostly carried out by evaporative means or curing (cross-linking) by oxidative, thermal or ultraviolet light and other available methods. Paint can be defined as a dispersion that consists of binder(s), volatile components, pigments and additives (catalyst, driers, f low modifiers) [2]. The binder (polymer or resin) is the component that forms the continuous film, adheres to the substrate, and holds the pigments and fillers in the solid film. The volatile component is the solvent that is used for adjusting the viscosity of the formulation for easy application. Depending on their compositions, paints can be divided into three groups: solvent-borne, water-borne and solvent-free (100% solid). Solvent-borne paints consist of resin, additives and pigments that are dissolved or dispersed in organic solvents. Similarly, in water-borne paints the ingredients are dispersed in water. In solvent-free compositions, the paints do not contain any solvent or water and the ingredients are dispersed directly in the resin. The properties of coating films are determined by the types of binders, pigments and miscellaneous additives used in the formulation. Moreover, types of substrates, substrate pretreatments, application methods and conditions of film formation

Thermal spraying of biomaterials

Abstract: Osteoconductive hydroxyapatite coatings for metallic endoprostheses for hip and knee joint replacement provide a state-of-the-art template for enhanced in-growth of bone cells. However, the high temperature of the plasma jet leads to large scale dehydroxylation and decomposition of the starting powder. A model is being developed to explain the formation of chemically and mechanically inhomogeneous porous calcium phosphate coatings deposited by atmospheric plasma spraying onto titanium alloy substrates. In addition the biofunctionality is being discussed of titania bond coats and their influence on the in vivo performance of hydroxyapatite-titania duplex coating systems.