Showing papers on "Coating published in 2008"

The design of a LiFePO4/carbon nanocomposite with a core-shell structure and its synthesis by an in situ polymerization restriction method.

Abstract: Nano-sized electrode materials for lithium-ion batteries have attracted much attention recently because their reduced dimensions enable much higher power. However, the large electrolyte/electrode interface arising from their size leads to more undesired reactions, which result in poor cycling performance. Moreover, some nano-sized cathode materials synthesized by low-temperature methods are poorly crystalline, which also reduces their electrochemical stability. The synthesis of highly crystalline nanomaterials completely coated with conductive carbon (or a carbon shell) would be an effective means of eliminating these problems. Such a synthesis is a significant challenge, however, as the highly crystalline structure and its subsequent coating with conductive carbon have to be achieved at high temperature, where larger crystallite sizes are almost inevitable. Olivine (LiFePO4) is considered to be one of the most promising cathode materials for the next generation of lithium batteries due to its low toxicity, low cost, and high safety. However, its power performance is greatly limited by slow diffusion of lithium ions across the two-phase boundary and/or low conductivity. Many efforts have been made over the past few years to improve the power performance of LiFePO4 by using low-temperature routes to obtain tailored particles or carbon painting to improve the conductivity of the solid phase. However, these previous studies have always focused on the “nano-size” or the “coating with conductive carbon” separately, rather than considering both of them together. Various low-temperature methods (synthesis temperature below 600 8C), such as lowtemperature ceramic routes or hydrothermal syntheses, have been developed to lower the particle size of LiFePO4, although none of them have been able to ensure the conductivity of the carbon coating. Furthermore, some lowtemperature routes are not able to produce the required highly crystalline olivine structure, thus reducing the electrochemical stability of LiFePO4. The high surface area arising from the nano-size of the products also greatly increases the undesirable electrode/electrolyte reactions, which leads to a poor cycling performance From a review of previous studies of nano-sized LiFePO4 (less than 100 nm), we can see that a “perfect” cycle-life (> 200 cycles) at high charge/ discharge depth (90%) is almost unheard of. Approaches based on the thermal decomposition of carbon-containing precursors have also been widely studied for the preparation of carbon-coated LiFePO4 particles. [16–23] However, these methods generally involve a high-temperature treatment, during which an increase in crystallite size is inevitable, to ensure the conductivity of the resulting carbon materials. Accordingly, those approaches based on the thermal decomposition of carbon-containing precursors can only produce LiFePO4 particles with a partial coating of carbon (Figure 1a). As shown in Figure 1a, during the intercalation process, the electrons cannot reach all the positions where Li ion intercalation takes place, thus resulting in polarization of the electrode. In view of the one-dimensional Li ion mobility in the framework, full coating with carbon, which ensures LiFePO4 particles get electrons from all directions, could further alleviate this polarization phenomenon. According to our analysis of previous studies, the ideal structure for high-performance LiFePO4 should contain nano-size particles completely coated with conductive carbon (Figure 1b). It should be noted that many previous studies involving the synthesis of nano-sized LiFePO4 employ Fe 2+ salts as precursors. 11–13,21] However, these salts are much more expensive and unstable than Fe salts, therefore the synthesis of a nano-sized LiFePO4/carbon composite with a core–shell structure from Fe salts would be of great interest. Herein we report an in situ polymerization restriction method for the synthesis of a LiFePO4/carbon composite formed from a highly crystalline LiFePO4 core with a size of about 20–40 nm and a semi-graphitic carbon shell with a thickness of about 1–2 nm. As shown in Figure 1c, our strategy includes one in situ polymerization reaction and two typical restriction processes. The first of these restriction processes involves the addition of Fe ions to a solution containing PO4 3 ions and aniline, where it acts as both a precipitator for PO4 3 and oxidant for aniline. The reaction during this process can be summarized as Equations (1) and (2).

Carbon nanotube coating improves neuronal recordings.

Abstract: Implanting electrical devices in the nervous system to treat neural diseases is becoming very common. The success of these brain-machine interfaces depends on the electrodes that come into contact with the neural tissue. Here we show that conventional tungsten and stainless steel wire electrodes can be coated with carbon nanotubes using electrochemical techniques under ambient conditions. The carbon nanotube coating enhanced both recording and electrical stimulation of neurons in culture, rats and monkeys by decreasing the electrode impedance and increasing charge transfer. Carbon nanotube-coated electrodes are expected to improve current electrophysiological techniques and to facilitate the development of long-lasting brain-machine interface devices.

A Simple, One-Step Approach to Durable and Robust Superhydrophobic Textiles**

Abstract: Superhydrophobic textile fabrics are prepared by a simple, one-step gas phase coating procedure by which a layer of polymethylsilsesquioxane nanofilaments is grown onto the individual textile fibers. A total of 11 textile fabrics made from natural and man made fibers are successfully coated and their superhydrophobic properties evaluated by the water shedding angle technique. A thorough investigation of the commercially relevant poly(ethylene terephthalate) fabric reveals an unparalleled long-term water resistance and stability of the superhydrophobic effect. Because of the special surface geometry generated by the nanoscopic, fibrous coating on the microscopic, fibrous textiles, the coated fabric remains completely dry even after two months of full immersion in water and stays superhydrophobic even after continuous rubbing with a skin simulating friction partner under significant load. Furthermore, important textile parameters such as tensile strength, color, and haptics are unaffected by the silicone nanofilament coating. For the first time, an in-depth characterization of the wetting properties, beyond simple contact angle measurements, as well as a thorough evaluation of the most important textile parameters is performed on a superhydrophobic fabric, which reveals a true potential for application.

Single-Step Coating of Mesoporous Silica on Cetyltrimethyl Ammonium Bromide-Capped Nanoparticles

Abstract: A generalized, single-step synthesis procedure to coat individual cetyltrimethyl ammonium bromide- (CTAB) capped nanoparticles with a thin layer of mesoporous silica is outlined. This coating method was demonstrated on CTAB-capped Au nanorods and CTAB-transferred CdSe/ZnS quantum dots with silica coatings ∼15 nm thick containing pores ∼4 nm in diameter. This porous silica coating can serve as a platform for further surface modification to facilitate the rapid translation of nanoparticles to a wide range of end applications.

Fabrication of “Roll-off” and “Sticky” Superhydrophobic Cellulose Surfaces via Plasma Processing

Abstract: Most of the artificial superhydrophobic surfaces that have been fabricated to date are not biodegradable, renewable, or mechanically flexible and are often expensive, which limits their potential applications. In contrast, cellulose, a biodegradable, renewable, flexible, inexpensive, biopolymer which is abundantly present in nature, satisfies all the above requirements, but it is not superhydrophobic. Superhydrophobicity on cellulose paper was obtained by domain-selective etching of amorphous portions of the cellulose in an oxygen plasma and subsequently coating the etched surface with a thin fluorocarbon film deposited via plasma-enhanced chemical vapor deposition using pentafluoroethane as a precursor. Variation of plasma treatment yielded two types of superhydrophobicity : "roll-off" (contact angle (CA), 166.7 degrees +/- 0.9 degrees ; CA hysteresis, 3.4 degrees +/- 0.1 degrees ) and "sticky" (CA, 144.8 degrees +/- 5.7 degrees ; CA hysteresis, 79.1 degrees +/- 15.8 degrees ) near superhydrophobicity. The nanometer scale roughness obtained by delineating the internal roughness of each fiber and the micrometer scale roughness which is inherent to a cellulose paper surface are robust when compared to roughened structures created by traditional polymer grafting, nanoparticle deposition, or other artificial means.

Nitridation-Driven Conductive Li4Ti5O12 for Lithium Ion Batteries

Abstract: To modify oxide structure and introduce a thin conductive film on Li4Ti5O12, thermal nitridation was adopted for the first time. NH3 decomposes surface Li4Ti5O12 to conductive TiN at high temperature, and surprisingly, it also modifies the surface structure in a way to accommodate the single phase Li insertion and extraction. The electrochemically induced Li4+δTi5O12 with a TiN coating layer shows great electrochemical properties at high current densities.

Room Temperature Impact Consolidation (RTIC) of Fine Ceramic Powder by Aerosol Deposition Method and Applications to Microdevices

Abstract: Ceramic integration technology requires downsizing and/or improvement of device performance in many applications, such as in the fabrication of microelectromechanical systems, display devises, fuel cells, optical devices, and RF components. For these applications, realization of high-speed deposition rate, low process temperature, and fine patterning in ceramic coating are very important. The aerosol deposition (AD) method has many advantages for above requirements in comparison with conventional thin-film method or thermal spray coating technology. In this article, advantages of the AD method are highlighted by realizing a comparison with conventional thin-film methods and thermal spray technology. Challenges associated with AD method are also highlighted. At the end, examples of integration of AD method in the fabrication of electronic components are also given to show the easiness in usage and in integration of this method in the device process flow.

Calcium as the superior coating metal in functionalization of carbon fullerenes for high-capacity hydrogen storage.

Abstract: We explore theoretically the feasibility of functionalizing carbon nanostructures for hydrogen storage, focusing on the coating of C60 fullerenes with light alkaline-earth metals. Our first-principles density functional theory studies show that both Ca and Sr can bind strongly to the C60 surface, and highly prefer monolayer coating, thereby explaining existing experimental observations. The strong binding is attributed to an intriguing charge transfer mechanism involving the empty d levels of the metal elements. The charge redistribution, in turn, gives rise to electric fields surrounding the coated fullerenes, which can now function as ideal molecular hydrogen attractors. With a hydrogen uptake of >8.4 wt % on Ca32C60, Ca is superior to all the recently suggested metal coating elements.

Coating for a Stent and a Method of Forming the Same

Abstract: A coating for a stent and methods for coating a stent are provided. The coating may be used for the sustained delivery of an active ingredient or a combination of active ingredients.

Prospects of microwave processing: An overview

Abstract: Microwave processing has been emerging as an innovative sintering method for many traditional ceramics, advanced ceramics, specialty ceramics and ceramic composites as well as polymer and polymer composites. Development of functionally gradient materials: joining; melting; fibre drawing; reaction synthesis of ceramics; synthesis of ceramic powder, phosphor materials, whiskers, microtubes and nanotubes; sintering of zinc oxide varistors; glazing of coating surface and coating development have been performed using microwave heating. In addition, microwave energy is being explored for the sintering of metal powders also. Ceramic and metal nanopowders have been sintered in microwave. Furthermore, initiatives have been taken to process the amorphous materials (e.g. glass) by microwave heating. Besides this, attempt has been made to study the heating behaviour of materials in the electric and magnetic fields at microwave frequencies. The research is now focused on the use of microwave processing for industrial applications.

Active Anticorrosion Coatings with Halloysite Nanocontainers

Abstract: This work contributes to the development of a new generation of active corrosion protection coatings composed of hybrid sol−gel films doped with halloysite nanotubes able to release entrapped corrosion inhibitors in a controllable way. A silica-zirconia-based hybrid film was used in this work as an anticorrosion coating deposited on 2024 aluminum alloy. Halloysite nanotubes with inner voids loaded by corrosion inhibitors (2-mercaptobenzothiazole) and outer surfaces layer-by-layer covered with polyelectrolyte multilayers were introduced into the hybrid films. The sol−gel film with the nanocontainers reveals enhanced long-term corrosion protection in comparison with the undoped sol−gel film. This effect is obtained because of the self-controlled release of the corrosion inhibitor triggered by the corrosion processes. Utilization of the inner halloysite nanotube lumen as a storage medium for the corrosion inhibitor offers a novel way of fabricating composite core−shell type nanomaterials with their further a...

Technical and Economical Aspects of Current Thermal Barrier Coating Systems for Gas Turbine Engines by Thermal Spray and EBPVD: A Review

Abstract: The most advanced thermal barrier coating (TBC) systems for aircraft engine and power generation hot section components consist of electron beam physical vapor deposition (EBPVD) applied yttria-stabilized zirconia and platinum modified diffusion aluminide bond coating. Thermally sprayed ceramic and MCrAlY bond coatings, however, are still used extensively for combustors and power generation blades and vanes. This article highlights the key features of plasma spray and HVOF, diffusion aluminizing, and EBPVD coating processes. The coating characteristics of thermally sprayed MCrAlY bond coat as well as low density and dense vertically cracked (DVC) Zircoat TBC are described. Essential features of a typical EBPVD TBC coating system, consisting of a diffusion aluminide and a columnar TBC, are also presented. The major coating cost elements such as material, equipment and processing are explained for the different technologies, with a performance and cost comparison given for selected examples.

Calcium phosphate-based coatings on titanium and its alloys

Abstract: Use of titanium as biomaterial is possible because of its very favorable biocompatibility with living tissue. Titanium implants having calcium phosphate coatings on their surface show good fixation to the bone. This review covers briefly the requirements of typical biomaterials and narrowly focuses on the works on titanium. Calcium phosphate ceramics for use in implants are introduced and various methods of producing calcium phosphate coating on titanium substrates are elaborated. Advantages and disadvantages of each type of coating from the view point of process simplicity, cost-effectiveness, stability of the coatings, coating integration with the bone, cell behavior, and so forth are highlighted. Taking into account all these factors, the efficient method(s) of producing these coatings are indicated finally.

Nanostructured multilayer graded-index antireflection coating for Si solar cells with broadband and omnidirectional characteristics

Abstract: Design, fabrication, and characterization of a broadband, omnidirectional, graded-index antireflection (AR) coating made using nanostructured low-refractive-index (n=1.05–1.40) silica deposited by oblique-angle deposition are reported. Averaged over wavelength range from 400 to 1100 nm and 0°–90° angle of incidence, polished Si reflects ∼37% of incident radiation. The reflection losses are reduced to only 5.9% by applying a three-layer graded-index AR coating to Si. Our experimental results are in excellent agreement with theoretical calculations. The AR coatings reported here can be optimized for photovoltaic cells made of any type of material.

Self-healing anticorrosion coatings based on pH-sensitive polyelectrolyte/inhibitor sandwichlike nanostructures

Abstract: An anticorrosion layer of a smart polymer coating is developed. The nature and properties of the coating simultaneously provide three mechanisms of corrosion protection: passivation of the metal degradation by controlled release of an inhibitor, buffering of pH changes at the corrosive area by polyelectrolyte layers, and self-curing of the film defects due to the mobility of the polyelectrolyte constituents in the layer-by-layer assembly.

Glass coating for PDMS microfluidic channels by sol–gel methods

Abstract: Soft lithography using polydimethylsiloxane (PDMS) allows one to fabricate complex microfluidic devices easily and at low cost. However, PDMS swells in the presence of many organic solvents significantly degrading the performance of the device. We present a method to coat PDMS channels with a glass-like layer using sol–gel chemistry. This coating greatly increases chemical resistance of the channels; moreover, it can be functionalized with a wide range of chemicals to precisely control interfacial properties. This method combines the ease of fabrication afforded by soft-lithography with the precision control and chemical robustness afforded by glass.

Front electrode for use in photovoltaic device and method of making same

Abstract: This invention relates to a front electrode/contact for use in an electronic device such as a photovoltaic device. In certain example embodiments, the front electrode of a photovoltaic device or the like includes a multilayer coating including at least one transparent conductive oxide (TCO) layer (e.g., of or including a material such as tin oxide, ITO, zinc oxide, or the like) and/or at least one conductive substantially metallic IR reflecting layer (e.g., based on silver, gold, or the like). In certain example instances, the multilayer front electrode coating may include one or more conductive metal(s) oxide layer(s) and one or more conductive substantially metallic IR reflecting layer(s) in order to provide for reduced visible light reflection, increased conductivity, cheaper manufacturability, and/or increased infrared (IR) reflection capability.

Plasma Spray Coating: Principles and Applications

Abstract: I. Scope and Introduction Coatings in the Industrial Environment Surface Coating Techniques Brief History of Thermal Spraying Synergistic Nature of Coatings Applications of Thermally Sprayed Coatings II. Principles of Thermal Spraying Characterization of Flame versus Plasma Spraying Concept of Energy Transfer Processes Unique Features of the Plasma Spray Process III. The First Energy Transfer Process: Electron-Gas Interaction The Plasma State Plasma Generation Design of Plasmatrons Plasma Diagnostics: Temperature, Enthalpy, and Velocity Measurements IV. The Second Energy Transfer Process: Plasma-Particle Interaction Injection of Powders Feed Material Characteristics Momentum Transfer Heat Transfer Particle Diagnostics: Velocity, Temperature, and Number Densities V. The Third Energy Transfer Process: Particle-Substrate Interaction Basic Considerations Estimation of Particle Number Density Momentum Transfer from Particles to Substrate Heat Transfer from Particles to Substrate Coating Diagnostics: Microstructure, Porosity, Adhesion, and Residual Stresses VI. Modeling and Numerical Simulation Plasma Properties Plasma-Particle Interactions Plasma-Substrate Interactions VII. Solutions to Industrial Problems (1): Structural Coatings Carbide Coatings Nitride Coatings Oxide Coatings Metallic Coatings Diamond Coatings VIII. Solutions to Industrial Problems (2): Functional Coatings Thermal and Chemical Barrier Coatings Conducting and Superconducting Coatings Dielectric Coatings Electro- and Photocatalytic Coatings IX. Solution to Medical Problems: Bioceramic Coatings Essential Properties of Bioconductive Coatings Structure and Crystal Chemistry of Hydroxyapatite Melting, Decomposition, and Solidification of Hydroxyapatite Bioinert Bond Coats In Vitro and In Vivo Performance of Coatings X. Quality Control and Assurance Procedures XI. Design of Novel Coatings XII. Future Developments and Outlook Appendices

Parameters Controlling Liquid Plasma Spraying: Solutions, Sols, or Suspensions

Abstract: This article presents what is our present knowledge in plasma spraying of suspension, sol, and solution in order to achieve finely or nano-structured coatings. First, it describes the different plasma torches used, the way liquid jet is injected, and the different measurements techniques. Then, drops or jet fragmentation is discussed with especially the influence of arc root fluctuations for direct current plasma jets. The heat treatment of drops and droplets is described successively for suspensions, sols, and solutions both in direct current or radio-frequency plasmas, with a special emphasize on the heat treatment, during spraying, of beads and passes deposited. The resulting coating morphologies are commented and finally examples of applications presented: Solid Oxide Fuel Cells, Thermal Barrier coatings, photocatalytic titania, hydroxyapatite, WC-Co, complex oxides or metastable phases, and functional materials coatings.

Study of the structure and corrosion behavior of PEO coatings on AM50 magnesium alloy by electrochemical impedance spectroscopy

Abstract: In this work coatings were developed on the surface of AM50 magnesium alloy using four different electrolytes containing 10 wt.% each of K3PO4 and Na3PO4 in combination with either potassium or sodium hydroxides. Electrolyte conductivity and breakdown voltage were measured in order to correlate the property of the coating to the nature of electrolyte. Further, the coatings were examined using scanning electron microscopy for surface morphology and cross sectional investigation, X-ray diffraction for phase determination, and electrochemical impedance spectroscopy for corrosion resistance evaluation. The effect of employing different ions in the electrolytes results in different surface morphologies, chemical phases and, consequently, the corrosion resistance of the coatings. The EIS results indicate the presence of porous and compact layers in the structure of the PEO coatings, whilst the overall coating resistance mainly results from the compact layer, the role of the porous layer as a barrier against corrosion is negligible. Finally, a correlation between the passive current density of the bare alloy and the corrosion resistance of the PEO coating is proposed.