Showing papers on "Coating published in 2005"

Recent Developments in Microencapsulation of Food Ingredients

Abstract: Microencapsulation involves the incorporation of food ingredients, enzymes, cells, or other materials in small capsules. Microcapsules offer food processors a means with which to protect sensitive food components, ensure against nutritional loss, utilize otherwise sensitive ingredients, incorporate unusual or time-release mechanisms into the formulation, mask or preserve flavors and aromas, and transform liquids into easily handled solid ingredients. Various techniques are employed to form microcapsules, including spray drying, spray chilling or spray cooling, extrusion coating, fluidized-bed coating, liposome entrapment, coacervation, inclusion complexation, centrifugal extrusion, and rotational suspension separation. Recent developments in each of these techniques are discussed in this review. Controlled release of food ingredients at the right place and the right time is a key functionality that can be provided by microencapsulation. A timely and targeted release improves the effectiveness of ...

Copper Nanoparticle/Polymer Composites with Antifungal and Bacteriostatic Properties

Abstract: A spinnable coating capable of releasing metal species to a broth of living organisms in a controlled manner is an extremely interesting material for a number of biotechnological applications. Poly...

A generalized approach to the modification of solid surfaces

Abstract: Interfacial interactions underpin phenomena ranging from adhesion to surface wetting Here, we describe a simple, rapid, and robust approach to modifying solid surfaces, based on an ultrathin cross-linkable film of a random copolymer, which does not rely on specific surface chemistries Specifically, thin films of benzocyclobutene-functionalized random copolymers of styrene and methyl methacrylate were spin coated or transferred, then thermally cross-linked on a wide variety of metal, metal oxide, semiconductor, and polymeric surfaces, producing a coating with a controlled thickness and well-defined surface energy The process described can be easily implemented and adapted to other systems

Surface coated cutting tool

Abstract: Provided is a surface-coated cutting tool combining superior heat resistance, superior wear resistance, and superior lubricity. A surface-coated cutting tool of the present invention includes a substrate and a coating formed on the substrate, and the coating is characterized in that the coating is formed by physical vapor deposition and includes one or more layers, that at least one of the one or more layers is a first coating layer, and that the first coating layer contains aluminum and nitrogen, has a thermal effusivity of 2,000 to 5,000 J·sec −1/2 ·m −2 ·K −1 , has a thickness of 0.2 to 5 μm, and has a crystal structure including a hexagonal structure.

Role of Alumina Coating on Li−Ni−Co−Mn−O Particles as Positive Electrode Material for Lithium-Ion Batteries

Abstract: The interface reaction between Al2O3-coated Li[Li0.05Ni0.4Co0.15Mn0.4]O2 and liquid electrolyte was investigated. The Al2O3-coated Li[Li0.05Ni0.4Co0.15Mn0.4]O2 showed no large difference in the bulk structure, comparing to bare Li[Li0.05Ni0.4Co0.15Mn0.4]O2. The coated Al2O3 was found to have an amorphous structure from X-ray diffraction study. A small amount of Al2O3 coating (0.25 wt % in the final composition) showed that a uniform mesoporous Al2O3-coating layer whose thickness is of about 5 nm covers Li[Li0.05Ni0.4Co0.15Mn0.4]O2 particles, as confirmed by transmission electron microscopy. At higher concentration (2.5 wt % in the final composition), the irregular tens of nanometer-sized Al2O3 powders were observed on the surface of the active material instead of the uniform coating layer. Despite the insulating nature of Al2O3, the thin coating was effective to improve the battery performances, depending on the thickness of the Al2O3-coating layer, and used electrolytic salt. The Al2O3 coating resulted i...

DNA-decorated carbon nanotubes for chemical sensing

Abstract: We demonstrate a new, versatile class of nanoscale chemical sensors based on single-stranded DNA (ss-DNA) as the chemical sensors recognition site and single-walled carbon nanotube field effect transistors (swCN-FET) as the electronic read-out component. swCN-FETs with a nanoscale coating of ss-DNA respond to gas odors that do not cause a detectable conductivity change in bare devices. Responses of ss-DNA/swCN-FETs differ in sign and magnitude for different gases, and can be tuned by choosing the base sequence of the ss-DNA. ss-DNA/swCN-FET sensors detect a variety of odors, with rapid response and recovery times on the scale of seconds. The sensor surface is self-regenerating: samples maintain a constant response with no need for sensor refreshing through at least 50 gas exposure cycles. This very remarkable set of attributes makes sensors based on ss-DNA decorated nanotubes very promising for "electronic nose" and "electronic tongue" applications ranging from homeland security to disease diagnosis.

Analysis of coaxial laser cladding processing conditions

Abstract: The formation of thick Ni-based coating on a steel substrate by coaxial laser cladding using the Nd:YAG 2 kW continuous laser was studied both from a theoretical and experimental point of view. The theoretical analysis concentrated on the transfer of laser irradiation and powder particles using a simple model of heat transfer to the substrate. This approach provides predictions of the laser power required for melting powder particles and substrate, respectively. For an appropriate experimental analysis of the main process parameters involved, a method based on a gradual change of a single processing parameter was examined. Correlations between the main processing parameters and geometrical characteristics of an individual laser track have been found and are discussed.

Review paper: surface modification for bioimplants: the role of laser surface engineering.

Abstract: Often hard implants undergo detachment from the host tissue due to inadequate biocompatibility and poor osteointegration. Changing surface chemistry and physical topography of the surface influences biocompatibility. At present, the understanding of biocompatibility of both virgin and modified surfaces of bioimplant materials is limited and a great deal of research is being dedicated to this aspect. In view of this, the current review casts new light on research related to the surface modification of biomaterials, especially materials for prosthetic applications. A brief overview of the major surface modification techniques has been presented, followed by an in-depth discussion on laser surface modifications that have been explored so far along with those that hold tremendous potential for bioimplant applications.

High Flux Filtration Medium Based on Nanofibrous Substrate with Hydrophilic Nanocomposite Coating

Abstract: A novel high flux filtration medium, consisting of a three-tier composite structure, i.e., a nonporous hydrophilic nanocomposite coating top layer, an electrospun nanofibrous substrate midlayer, and a conventional nonwoven microfibrous support, was demonstrated for oil/water emulsion separations for the first time. The nanofibrous substrate was prepared by electrospinning of poly(vinyl alcohol) (PVA) followed by chemical cross-linking with glutaraldehyde (GA) in acetone. The resulting cross-linked PVA substrates showed excellent water resistance and good mechanical properties. The top coating was based on a nanocomposite layer containing hydrophilic polyether-b-polyamide copolymer or a cross-linked PVA hydrogel incorporated with surface-oxidized multiwalled carbon nanotubes (MWNTs). Scanning electron microscopy (SEM) examinations indicated that the nanocomposite layer was nonporous within the instrumental resolution and MWNTs were well dispersed in the polymer matrix. Oil/ water emulsion tests showed that this unique type of filtration media exhibited a high flux rate (up to 330 L/m2-h at the feed pressure of 100 psi) and an excellent total organic solute rejection rate (99.8%) without appreciable fouling. The increase in the concentration of surface-oxidized MWNT in the coating layer generally improves the flux rate, which can be attributed to the generation of more effective hydrophilic nanochannels for water passage in the composite membranes.

Functionalisation of textiles by inorganic sol–gel coatings

Abstract: The maintenance and improvement of current properties and the creation of new material properties are the most important reasons for the functionalisation of textiles. The coating of textiles with chemically or physically modified silica sols with particle diameters smaller than 50 nm (“nanosols”) enables the manifold alteration of their physico-mechanical, optical, electrical and biological properties. Thus the protection of textiles against destruction and the creation of new advantageous functions can be realised. Prospective new products to be developed include textiles with water, oil and soil repellency and with antimicrobial properties. This article discusses recent results from applying modified silica nanosols to the functionalisation of textiles.

Silica coating of silver nanoparticles using a modified Stober method.

Abstract: Silver nanoparticles prepared through a borohydride-reduction method were directly coated with silica by means of a seeded polymerization technique based on the Stober method. Various amine catalysts were used for initialization of a sol-gel reaction of TEOS with no need for a prior surface modification. Use of dimethylamine (DMA) as a catalyst was found to be necessary to obtain a proper coating. The silica shell thickness was varied from 28 to 76 nm for TEOS concentrations of 1-15 mM at 11.1 M water and 0.8 M DMA. The optical spectra of the core-shell silver-silica composite particles show a qualitative agreement with predictions by Mie theory.

Nanoindentation of coatings

Abstract: A range of mechanical properties of a coating/substrate system may be obtained using indentation tests, and with the emergence of continuously recording indentation testing with nanometre penetration (often called nanoindentation) the mechanical properties of very thin coatings (<1 µm) and surface treated layers may be measured. This paper reviews the deformation mechanisms which occur and the methods for extracting mechanical properties of coatings from nanoindentation load–displacement curves and introduces the differences observed when compared with the testing of bulk materials. The importance of the relative hardness of coating and substrate on the response of the system is highlighted, and the use of energy-based models for the prediction of the performance of single and multilayered systems is discussed.

Super-liquid-repellent surfaces prepared by colloidal silica nanoparticles covered with fluoroalkyl groups.

Abstract: A simple and easy method to prepare super-liquid-repellent surfaces is proposed Sol-gel films were prepared by hydrolysis and condensation of alkoxysilane compounds Both surface energy and roughness were controlled using colloidal silica particles and fluoroalkylsilane When the fractional amounts of both colloidal silica and fluoroalkylsilane were optimized in the films, the film surface exhibited repellency to both water and oil Finally, it was shown that the method proposed here would be applied to a simple one-pot coating for a uniform large area, and be useful for practical use

Thermo-physical properties of plasma electrolytic oxide coatings on aluminium

Abstract: Plasma electrolytic oxide coatings appear to offer attractive combinations of hardness, wear resistance, corrosion resistance and interfacial adhesion. In order to optimise such characteristics, however, more basic thermo-physical property data are required, together with an understanding of how they are affected by processing conditions and microstructure. In the present study, coatings were produced on 6082 aluminium and characterised using profilometry, scanning electron microscopy, X-ray diffraction and nanoindentation. The in-plane thermal expansivity of detached coatings was measured by dilatometry to be about 8 microstrain K −1 . There is thus a rather substantial mismatch between the expansivities of coating and substrate, amounting to about 15 microstrain K −1 . The global in-plane Young's modulus was estimated using cantilever bending of sandwich coated substrates and also by measuring the curvature generated in a bi-material beam on cooling to low temperature. It was found to lie in the approximate range of 10–40 GPa. Values of this order, which are low compared with the figure of around 370 GPa expected for fully dense polycrystalline alumina, are thought to be associated with the presence of a network of microcracks and voids. A low value is expected to be beneficial in terms of conferring good strain tolerance, and hence resistance to spallation driven by differential thermal expansion.

A novel antibacterial titania coating: metal ion toxicity and in vitro surface colonization.

Abstract: Postoperative implant-associated infection is still an unresolved and serious complication in modern surgery. Antibacterial and biocompatible surfaces could both reduce infection rates and promote tissue integration. In this respect, a comparative study of the antibacterial as well as the biocompatible potential of different metal ions in vitro is presented. The assays used were growth inhibition tests with different metal salts carried out with tissue cells and bacteria under corresponding culture conditions. Additionally, in vitro tests in direct surface contact with tissue cells and bacteria onto a novel copper containing sol-gel derived titanium dioxide coating (Cu-TiO2) and a fourfold Cu-TiO2 coating were performed. The values were compared to a non-filled titanium dioxide coating and standard Ti6Al4V alloy. SEM-investigations were performed to approve the results of the in vitro tests. Among Ag+, Zn2+, Co2+, Al3+ and Hg2+, the growth inhibition tests revealed an outstanding position of copper ions as antibacterial but nevertheless bio-tolerant additive. These results were affirmed by the cell tests in direct surface contact and SEM-investigations, where best cell growth was found on the Cu-TiO2 coatings. Highest antibacterial properties with a tolerable cytocompatibility could be observed on the fourfold Cu-TiO2 coatings. Consequently, surfaces with custom-tailored antibacterial properties may be established and could be of particular interest in revision and tumor arthroplasty.

Amorphous Carbon-Coated Tin Anode Material for Lithium Secondary Battery

Abstract: A uniform amorphous carbon coating on the tin nanoparticles was prepared from aqueous glucose solutions using a hydrothermal method at 180 °C, which facilitated an enhanced dimensional stability during Li alloying/dealloying. This material showed excellent initial capacity and capacity retention, 681 mAh/g and 98% retention after 50 cycles, respectively.

Corrosion behavior of carbon nanotubes–Ni composite coating

Abstract: Ni–carbon nanotube (CNTs) composite coatings were deposited on a carbon steel by electrodeposition The effect of incorporation of CNTs into the nickel coating on the morphology of the coating surface and corrosion properties was investigated Scanning electron microscopy (SEM) showed that the CNTs appear well dispersed in the nickel layer Corrosion tests were performed in aqueous NaCl (35 wt%) using a weight loss method and electrochemical measurements for bare, pure nickel coated and CNTs–nickel coated samples The results showed that addition of CNTs in the deposition process of nickel significantly increased the resistance to corrosion The anti-corrosion mechanism of the composite coating is also discussed

Super-Water-Repellent Al2O3 Coating Films with High Transparency

Abstract: We have prepared transparent, super-water-repellent coating films of alumina on glass plates by a combination of geometric and chemical approaches. The contact angle for water in the films was 165° and the transmittance for visible light was higher than 92%. A roughness of 20 to 50 nm was obtained, which is too small to scatter visible light, while the degree of roughness was great enough to enhance the water-repellent properties together with the chemical effect of a fluorine-containing agent and gave a super-water-repellent surface. The coatings have great potential for practical applications such as eyeglasses, cover glasses for solar cells, windshields of automobiles, and so on.

Oxide ceramic coatings on aluminium alloys produced by a pulsed bipolar plasma electrolytic oxidation process

Abstract: In the paper, a modified Plasma Electrolytic Oxidation process (PEO) to produce ceramic coatings on Al alloys, suitable for tribological applications, is discussed. The process utilises bipolar current pulses in the kHz frequency range, providing better control over plasma discharges occurring at the sample surface. The coatings, formed on a 2024 series Al alloy, are characterized by means of optical microscopy, SEM, EDX, XRD and surface profilometry. Microhardness and scratch adhesion tests are performed to evaluate the coating mechanical performance. The effects of current pulse frequency on both the layer growth kinetics and the process energy efficiency are discussed. It is found that in the 1 to 3 kHz frequency range, the layer growth rate can be increased from 0.5 to 1 to 1.6 to 3.2 μm min−1 and the volume fraction of the porous outer layer can be reduced from 25 to 20% to 15 to 10% of the total layer thickness, compared to the conventional 50 Hz AC PEO process. The inner layer, despite a slight increase in porosity, preserves a relatively high hardness of 1200 to 1500 HK25 and good adhesion (LC2=60 N), which should be sufficient for many tribological applications.

Medical device with multiple coating layers

Abstract: An implantable medical device that contains two coating layers disposed above at least one of its surfaces. The first coating layer contains a biologically active material; and the second coating layer contains a polymeric material and nanomagnetic material disposed on the first coating layer; the second coating layer is substantially free of the biologically active material. The nanomagnetic material has a saturation magnetization of from about 2 to about 3000 electromagnetic units per cubic centimeter, and it contains nanomagnetic particles with an average particle size of less than about 100 nanometers; the average coherence length between adjacent nanomagnetic particles is less than 100 nanometers.