Showing papers on "Coating published in 2007"

Anticorrosion Coatings with Self-Healing Effect Based on Nanocontainers Impregnated with Corrosion Inhibitor

Abstract: The development of active corrosion protection systems for metallic substrates is an issue of prime importance for many industrial applications. The present work shows a new contribution to the development of a new protective system with self-healing ability composed of hybrid sol−gel films doped with nanocontainers that release entrapped corrosion inhibitor in response to pH changes caused by corrosion process. A silica−zirconia based hybrid film was used in this work as an anticorrosion coating deposited on 2024 aluminum alloy. Silica nanoparticles covered layer-by-layer with polyelectrolyte layers and layers of inhibitor (benzotriazole) were randomly introduced into the hybrid films. The hybrid film with the nanocontainers reveals enhanced long-term corrosion protection in comparison with the undoped hybrid film. The scanning vibrating electrode technique also shows an effective self-healing ability of the defects. This effect is obtained due to regulated release of the corrosion inhibitor triggered by...

Apparatus and method for depositing a coating onto a surface of a prosthesis

Abstract: A patterned coating on a prosthesis, for example a stent, and a method for forming the coating are disclosed. Additionally, an apparatus for forming the patterned coating is disclosed.

Wafer level phosphor coating method and devices fabricated utilizing method

Abstract: Methods for fabricating light emitting diode (LED) chips comprising providing a plurality of LEDs typically on a substrate. Pedestals are deposited on the LEDs with each of the pedestals in electrical contact with one of the LEDs. A coating is formed over the LEDs with the coating burying at least some of the pedestals. The coating is then planarized to expose at least some of the buried pedestals while leaving at least some of said coating on said LEDs. The exposed pedestals can then be contacted such as by wire bonds. The present invention discloses similar methods used for fabricating LED chips having LEDs that are flip-chip bonded on a carrier substrate and for fabricating other semiconductor devices. LED chip wafers and LED chips are also disclosed that are fabricated using the disclosed methods.

Biomedical applications of diamond-like carbon coatings : A review

Abstract: Owing to its superior tribological and mechanical properties with corrosion resistance, biocompatibility, and hemocompatibility, diamond-like carbon (DLC) has emerged as a promising material for biomedical applications. DLC films with various atomic bond structures and compositions are finding places in orthopedic, cardiovascular, and dental applications. Cells grew on to DLC coating without any cytotoxity and inflammation. DLC coatings in orthopedic applications reduced wear, corrosion, and debris formation. DLC coating also reduced thrombogenicity by minimizing the platelet adhesion and activation. However, some contradictory results (Airoldi et al., Am J Cardiol 2004;93:474-477, Taeger et al., Mat-wiss u Werkstofftech 2003;34:1094-1100) were also reported that no significant improvement was observed in the performance of DLC-coated stainless stent or DLC-coated femoral head. This controversy should be discussed based on the detailed information of the coating such as atomic bond structure, composition, and/or electronic structure. In addition, instability of the DLC coating caused by its high level of residual stress and poor adhesion in aqueous environment should be carefully considered. Further in vitro and in vivo studies are thus required to confirm its use for medical devices.

Enhancement of carrier mobility in semiconductor nanostructures by dielectric engineering.

Abstract: We propose a technique for achieving large improvements in carrier mobilities in 2- and 1-dimensional semiconductor nanostructures by modifying their dielectric environments. We show that by coating the nanostructures with high-kappa dielectrics, scattering from Coulombic impurities can be strongly damped. Though screening is also weakened, the damping of Coulombic scattering is much larger, and the resulting improvement in mobilities of carriers can be as much as an order of magnitude for thin 2D semiconductor membranes, and more for semiconductor nanowires.

Study on preparation and fire-retardant mechanism analysis of intumescent flame-retardant coatings

Abstract: An intumescent flame-retardant coating was prepared by unsaturated polyester resin and epoxy resin as two-component matrix resins, ammonium polyphosphate (APP) as acid source, melamine (Mel) as the blowing agent and pentaerythritol (PER) as carbon agent, expandable graphite as synergistic agent, adding titanium dioxide (TiO2), solvent and other assistants. Results showed that such a coating had excellent physical–chemical properties. When the thickness of the coating on the wood matrix reached 2.0 mm, the limit of fire-endurance could get to 210 min. And the various component thermal characteristics, decompose processes and interactions of the flame-retardant coating system were investigated by DSC and TGA. The contribution of phosphorus to the formation of the final charring layer and their morphological structures was studied by SEM, XRD and FTIR. On the basis, the flame-retardant mechanism of the intumescent flame-retardant coating was systematically investigated.

Characterization and corrosion studies of fluoride conversion coating on degradable Mg implants

Abstract: Fluoride conversion coating was synthesized on magnesium (Mg) by immersion treatment in hydrofluoric acid (HF) at room temperature, with the aim of improving the corrosion resistance of Mg in applications as degradable implant material. After an immersion period of 24 h in 48% HF, the samples carried a bronze color, and the conversion coating was dense and free of cracks. Field-emission scanning-electron microscopy (FE-SEM) of the cross-section revealed a coating thickness of about 1.5 μm. Atomic-force microscopy (AFM) recorded an average surface roughness of ∼ 21 nm for the coated sample, similar to that of the untreated one (∼ 17 nm). The coating was mainly composed of magnesium fluoride (MgF 2 ) as identified by thin-film X-ray diffractometry (TF-XRD), consistent with compositional analysis using X-ray photoelectron spectroscopy (XPS). The MgF 2 was in the form of crystallites of a few nm. A small amount of oxygen was present inside the coating, suggesting that some F − ions are replaced by hydroxyl (OH − ) ions in the MgF 2 structure, or that a small amount of Mg(OH) 2 was present. The corrosion resistance of untreated and conversion coated Mg in Hanks' solution was studied using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization tests, and immersion tests. EIS results showed a polarization resistance of 0.18 kΩ cm 2 for the untreated Mg and 5.2 kΩ cm 2 for the coated sample, giving an improvement of about 30 times. Polarization tests also recorded a reduction in corrosion current density from 400 μA/cm 2 to 10 μA/cm 2 , showing an improvement of about 40 times. The galvanic effect between untreated and fluoride-coated Mg samples was small. Immersion tests in Hanks' solution also resulted in a much milder and more uniform corrosion damage on the fluoride-coated samples. The results of the present study showed that fluoride coating by conversion treatment is a simple and promising way of enhancing the corrosion resistance of Mg in Hanks' solution, or that it may be employed as a pretreatment step for subsequent coating.

Titania and silver-titania composite films on glass-potent antimicrobial coatings

Abstract: Titania (anatase) and Ag-doped titania (anatase) coatings were prepared on glass microscope slides by a sol - gel dip-coating method. The resultant coatings were characterised by X-ray diffraction, X-ray absorption near edge structure (XANES), Raman, scanning electron microscopy (SEM), wavelength dispersive X-ray (WDX) analysis, X-ray photoelectron spectroscopy (XPS) and UV-vis techniques and shown to consist of anatase with ca. 0.2 - 1 atom% Ag2O. Photocatalytic activity of the coatings was determined by photomineralisation of stearic acid, monitored by FT-IR spectroscopy. Photocatalytically-active coatings were screened for their antibacterial efficacy against Staphylococcus aureus (NCTC 6571), Escherichia coli ( NCTC 10418) and Bacillus cereus (CH70-2). Ag-doped titania coatings were found to be significantly more photocatalytically and antimicrobially active than a titania coating. No antimicrobial activity was observed in the dark - indicating that silver ion diffusion was not the mechanism for antimicrobial action. The mode of action was explained in terms of a charge separation model. The coatings also demonstrated significantly higher activity against the Gram-positive organisms than against the Gram-negative. The Ag2O - TiO2 coating is a potentially useful coating for hard surfaces in a hospital environment due to its robustness, stability to cleaning and reuse, and its excellent antimicrobial response.

Self-repairing coatings containing active nanoreservoirs.

Abstract: Nanocontainers with the ability to release encapsulated active materials in a controlled way can be employed to develop a new family of self-repairing multifunctional coatings, which possess not only passive functionality but also rapid feedback activity in response to changes in local environment. Several approaches to fabricate self-repairing coatings on plastic and metal substrates were surveyed. The release of the active materials occurs only when triggered, which prevents leakage of the active component out of the coating and increases coating durability. This Review also covers some principles and recent developments in the fabrication of nanocontainers with good compatibility with the coating components, the possibility to encapsulate and upkeep active material, and permeability properties of the shell controlled by external stimuli. Depending on the nature of the sensitive components introduced into the container shell, reversible and irreversible changes of the shell permeability can be induced by various stimuli. Different responses can be then observed varying from fine effects like tunable permeability to more drastic ones like total rupture of the container shell.

Investigation of Al-Al 2 O 3 Cold Spray Coating Formation and Properties

Abstract: Coating build-up mechanisms and properties of cold-sprayed aluminum-alumina cermets were investigated using two spherical aluminum powders having average diameters of 36 and 81 μm. Those powders were blended with alumina at several concentrations. Coatings were produced using a commercial low-pressure cold spray system. Powders and coatings were characterized by electronic microscopy and microhardness measurements. In-flight particle velocities were monitored for all powders. The deposition efficiency was measured for all experimental conditions. Coating performance and properties were investigated by performing bond strength test, abrasion test, and corrosion tests, namely, salt spray and alternated immersion in saltwater tests. These coating properties were correlated to the alumina fraction either in the starting powder or in the coating.

Coating Formulations for Microneedles

Abstract: Purpose To develop a rational basis for designing coating solution formulations for uniform and thick coatings on microneedles and to identify coating strategies to form composite coatings, deliver liquid formulations, and control the mass deposited on microneedles.

Nano graphene platelet-based composite anode compositions for lithium ion batteries

Abstract: The present invention provides a nano-scaled graphene platelet-based composite material composition for use as an electrode, particularly as an anode of a lithium ion battery. The composition comprises: (a) micron- or nanometer-scaled particles or coating which are capable of absorbing and desorbing lithium ions; and (b) a plurality of nano-scaled graphene platelets (NGPs), wherein a platelet comprises a graphene sheet or a stack of graphene sheets having a platelet thickness less than 100 nm; wherein at least one of the particles or coating is physically attached or chemically bonded to at least one of the graphene platelets and the amount of platelets is in the range of 2% to 90% by weight and the amount of particles or coating in the range of 98% to 10% by weight. Also provided is a lithium secondary battery comprising such a negative electrode (anode). The battery exhibits an exceptional specific capacity, an excellent reversible capacity, and a long cycle life.

Cracking in drying colloidal films.

Abstract: It has long been known that thick films of colloidal dispersions such as wet clays, paints, and coatings crack under drying. Although capillary stresses generated during drying have been recently identified as the cause for cracking, the existence of a maximum crack-free film thickness that depends on particle size, rigidity, and packing has not been understood. Here, we identify two distinct regimes for crack-free films based on the magnitude of compressive strain at the maximum attainable capillary pressure and show remarkable agreement of measurements with our theory. We anticipate our results to not only form the basis for design of coating formulations for the paints, coatings, and ceramics industry but also assist in the production of crack-free photonic band gap crystals.

The mechanics of coating delamination in thermal gradients

Abstract: Oxide coatings used for various components in the hot section of aero-turbine engines experience temperature gradients at various stages during their flight cycle. One gradient exists during steady-state, due to the combination of the combustion environment next to the free surface and internal cooling of the underlying superalloy substrate. Other gradients develop during cooling of the surface when engine power is reduced. It will be argued that delaminations, when observed within the oxide layer, can only be explained by the presence of a significant stress gradient in the coating, governed by these thermal circumstances. Two extreme cool-down scenarios are envisaged. In one, the surface is cooled suddenly to a lower temperature, followed by slow uniform cooling. In the other, the entire system reduces its temperature uniformly before the temperature gradient in the TBC is eliminated. Criteria for guarding against delaminations within the oxide layer and along the interface with the substrate are provided and the outcome visualized in the form of delamination maps. A comparison with engine experience provides a preliminary assessment of the relevant thermal scenarios, as well as pathways for continuing research.

Significant Improvement of Electrochemical Performance of AlF3-Coated Li [ Ni0.8Co0.1Mn0.1 ] O2 Cathode Materials

Abstract: The particle surface of Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2 was modified with AlF 3 as a coating material to improve the electrochemical properties. The effect of AlF 3 coating on Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2 cathode was extensively studied with respect to the structural and electrochemical properties, and thermal stability. The AlF 3 coating on Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2 particles improved the overall electrochemical properties, such as the cyclability, rate capability, and thermal stability, compared to pristine Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2 . Electrochemical impedance spectroscopy and transmission electron microscopy showed that the AlF 3 coating on Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2 particles played an important role in stabilizing the interface between the cathode and electrolyte.

Coating thickness of magnetic iron oxide nanoparticles affects R2 relaxivity.

Abstract: Purpose To evaluate the effect of coating thickness on the relaxivity of iron oxide nanoparticles. Materials and Methods Monocrystalline superparamagnetic iron oxide nanoparticles (MIONs), coated with a polyethylene glycol (PEG)-modified, phospholipid micelle coating, with different PEG molecular weights, were prepared. The particle diameters were measured with dynamic light scattering (DLS) and electron microscopy (EM). The R1 and R2 of MIONs were measured using a bench-top nuclear magnetic resonance (NMR) relaxometer. pH was varied for some measurements. Monte Carlo simulations of proton movement in a field with nanometer-sized magnetic inhomogeneities were performed. Results Increasing the molecular weight of the PEG portion of the micelle coating increased overall particle diameter. As coating thickness increases, the R2 decreases and the R1 increases. Changing pH has no effect on relaxivity. The Monte Carlo simulations suggest that the effect of coating size on R2 relaxivity is determined by two competing factors: the physical exclusion of protons from the magnetic field and the residence time for protons within the coating zone. Conclusion Coating thickness can significantly impact the R2, and the R2/R1 ratio, of a MION contrast agent. An understanding of the relationship between coating properties and changes in relaxivity is critical for designing magnetic nanoparticle probes for molecular imaging applications using MRI. J. Magn. Reson. Imaging 2007. © 2007 Wiley-Liss, Inc.

Apparatus and method for coating implantable devices

Abstract: A coating for implantable devices, such as stents, and a method of making the same is disclosed. Moreover, an apparatus for depositing the coating is disclosed.

XPS Study on Al2O3- and AlPO4-Coated LiCoO2 Cathode Material for High-Capacity Li Ion Batteries

Abstract: The impact of aluminum oxide coatings on LiCoO2 materials for commercial lithium ion batteries has been investigated by X-ray photoelectron spectroscopy (XPS). A low binding energy component in the Al 2p core peak spectra was observed and attributed to the formation of a LiAlx Co(1-x) O2 solid solution interphase for both Al2 O3 - and AlPO4 -coated LiCoO2. The surface chemistry of pristine and Al2 O3 -coated LiCoO2 cathodes and graphite anodes have been investigated after cycling up to 4.2 V or 4.4 V cutoff voltage and after various levels of capacity fade. The Al2 O3 coating enhances the capacity retention at both 4.2 V and 4.4 V cutoff voltages. XPS analyses provided evidence of the inhibition of cobalt dissolution from the LiCoO2 positive electrode by the aluminum coatings. Moreover, the Al2 O3 coating lowers the kinetics of degradation of electrolyte species, especially the LiPF6 salt. © 2007 The Electrochemical Society.