Diamond-like carbon thin film with controlled zeta potential for medical material application

With the purpose of applying diamond-like carbon (DLC) thin films as a biocompatible material, we experimented with introducing functional groups such as amino and carboxyl groups to the surface of DLC thin films by plasma surface treatment. From the results, it was found that the contact angle values of the DLC thin films surface were decreased with increasing in the OCO bonded network on the surface. Measurement of the zeta potential when the amounts of the functional groups were varied showed that this successfully varied the zeta potential over the wide range of − 48 mV to + 12 mV. It was found that when carboxyl groups are introduced by O₂ plasma modification of the DLC thin films surface, the zeta potential was lower than that of untreated DLC thin films sample. It was also found that amino groups can be introduced to the DLC thin films surface by NH₃ plasma treatment, the zeta potential was higher than that of untreated DLC thin films sample. This means that zeta potential of the DLC thin films can also be controlled by controlling these two functional groups. Therefore, we have succeeded in developing a multifunctional DLC thin films that does not use polymers and is suitable as a biocompatible material.     

Diamond-like carbon applications in high density hard disc recording heads

Between 1965 and 1993 areal bit density in hard disc recording heads grew at a rate of 45% per year. Subsequently the rate of growth increased to 65% through 1998. In the past 2 years, the density growth has increased yet again to an amazing 100% per year. Increasing areal density requires growth in both track and linear density. Products currently in production have areal density in the range of 10 to 15 Gbit/inch². At a continuing density growth rate of 100% per year, 100 Gbit/inch² production will become a reality in year 2003, less than 3 years hence. Reduction in head-to-media magnetic spacing follows areal density growth. Protective coatings on both the heads and the media contribute to spacing. One of the clear challenges going forward is reduction of the coating thickness while maintaining the functional properties of corrosion protection and tribology enhancement. Traditional direct ion beam DLC deposition coatings do not have the required properties at thickness below 30 Å. New coating technology is required to meet the needs of the recording head industry. This paper will address the coating requirements as well as the test methods used to evaluate coatings.     

Electrochemical behavior of centrifuged cast and heat treated Ti-Cu alloys for medical applications

The aim of this study was to evaluate the general electrochemical corrosion resistance of Ti-5, 7.1 and 15 wt.% Cu alloys with a view to medical applications. A centrifuged casting set-up and a solution heat treatment at 900 °C for 2 h were used to prepare the samples. Electrochemical impedance spectroscopy (EIS) and potentiodynamic anodic polarization techniques were used to analyze the corrosion resistance in a 0.15 M NaCl solution at 25 °C. An equivalent circuit analyses was also conducted. It was found that the corrosion rate increased with increasing Cu content. The results have shown that the addition of Cu has not stabilized the β phase. Martensite and Ti₂Cu intermetallic particles provided by casting and heat treatment processes, respectively, have important roles on the resulting impedance parameters and passive current densities of the Ti-Cu alloys.     

Greener synthesis and medical applications of metal oxide nanoparticles

Over the past decade, the subject of “greener chemistry" and chemical processes has been emphasized. The “greener chemistry” improves environmental efficiency in reducing the consumption of resources and energy and achieving a stable economic development of the environment. Nanotechnology is investigating nanoscale materials that have applications in the area of biotechnology and nanomedicine alongside several other significant applications such as cosmetics, drug delivery, and biosensors. The different shapes and sizes of nanoparticles can be synthesized with physical, chemical, or biological methods. The tendency to produce nanomaterials, especially metal oxides, and use them, is increasing because of their exciting properties in the nanoscale. However, metal oxide nanoparticles produced by chemical methods have significant concerns due to hazardous and toxic chemicals and their environmental damage. The production of metal oxide nanoparticles using the principles of greener chemistry has found a special place in research. Increased awareness of greener chemistry and biological processes has necessitated using environmentally friendly methods for the production of non-toxic nanomaterials. Plants and polymeric materials as renewable and inexpensive sources have received particular attention to prepare nano biomaterials. The use of plants to synthesize metal oxide nanoparticles because of the non-use toxic pollutants is one of the environmentally friendly methods, and that's why this type of synthesis is called greener synthesis. In this review, we exhibit a total sight of greener synthesis methods for producing metal oxide nanoparticles and their medical applications.     

Diamond-like carbon: state of the art

Diamond-like carbon films, amorphous hydrogenated or non-hydrogenated forms of carbon, are metastable amorphous materials characterized by attractive mechanical, optical, electrical, chemical and tribological properties. The films can be prepared at low temperatures by different techniques using a large variety of precursors and can be modified by incorporation of different elements such as N, F, Si or metals. The diversity of methods used for the deposition of diamond-like carbon films provides the flexibility to tailor their properties according to specific needs and potential applications. The hydrogenated form of DLC appears to reach a maturity in understanding its properties and finding old and new practical applications for it. The non-hydrogenated diamond-like carbon, or tetrahedral carbon, is at a much younger state of preparation and characterization and practical applications have yet to be proven. The paper will review the state of the art of the preparation of the different types of diamond-like carbon films, the characterization and understanding of their properties, and their practical applications.     

金属--浸塑涂装技术

叙述了粉末流化床浸塑涂装金属的技术。     

Diamond-like carbon films in multilayered interference coatings for IR optical elements

In the majority of modern IR interference multilayer coatings (MLC), conventional film-forming materials (FFM) of fluoride and chalcogenide types are used. Such coatings are characterized by relatively low mechanical strength and stability against enhanced humidity and, therefore, require surface protection. Our present results support the view that mechanical strength of these MLCs can be improved by applying a diamond-like carbon (DLC) film as an external layer. Nanoindentation measurements show that the addition of a DLC film to ZnSe/BaF₂/Y₂O₃ IR antireflection MLC increases the combined hardness of the coatings from 0.5 to 3.6 GPa. The formation of an indent on the upper and subsequent layers of MLC has been studied by SEM and X-ray spectrum microanalysis. The resistance of DLC films applied onto MLC against light irradiation, organic solvents as well as against environmental factors was also studied. Atomic force microscopy (AFM) was used to study variations of the surface morphology of the initial MLC components before and after DLC film deposition.     

Self-repairing coating for corrosion protection of aluminum alloys

The development of effective anticorrosion pre-treatments for metallic substrates is an issue of great importance for durability of metal structures and components. In this work, we proposed and demonstrated the concept of self-repairing coating for corrosion protection of aluminum alloys, using cagelike oil core/silica gel shell particles. These micron-scale, cagelike smart microspheres with opened and closed pores were successfully fabricated, and at the same time encapsulated repairing agent (methyl methacrylate) and catalysts (potassium persulfate and sodium thiosulfate) into the microspheres, respectively. Such smart particle composites (SPCs) were prepared based on an interfacial self-assembly process and sol–gel reaction. They were then self-assembled on the AA2024 aluminum alloy surface, followed by the application of a sol–gel film. The hybrid film worked as a primer coating featuring the self-repairing property. Both the EIS and SEM/EDS data demonstrated that the encapsulated repairing agent was released as a response to external stimulus (scratches) and polymerized to repair the coating defects. By comparing the corrosion rate of AA2024 in three coating systems, the self-repairing effect is quantified to be 22% after 2 h immersion in deoxidized 3% NaCl solution.     

Novel hyperbranched resins for coating applications

Hyperbranched polycondensates derived from AB_x-type monomers have been generally recognized as the cheaper and economically more feasible counterparts of the well-known other members of the dendritic macromolecule family, the perfectly branched dendrimers. Since they can be manufactured more quickly and easily in a one-step polymerization procedure, their significantly lower cost price puts them in a much more favourable position to be industrially applied as coating resins. The conceptual design of a branched macromolecule is ideally outlined for film forming applications. The viscosity in relation to their molecular weight is kept low due to their compact morphology hampering chain entanglements, while on the other hand, the large number of functional end groups enable efficient cross-linking.

Standing apart from the standard AB_x approaches, optionally employing a B_x starter molecule, DSM has now developed a new type of hyperbranched polyesteramides derived from cyclic carboxylic anhydrides and dialkanolamines. In a one-pot procedure, the dialkanolamine molecules react preferentially via the secondary amine group with the cyclic anhydride, forming in situ a bis(hydroxyalkyl)amide group (AB₂) containing carboxylic acid. Because of the known high reactivity of 2-hydroxyalkylamide groups towards esterification with carboxylic acids, a fast and efficient polycondensation at temperatures of 140–200°C without the addition of a catalyst can be performed. Using the dialkanolamine component in molar excess over the anhydride, gel formation is excluded and a predictable and stable melt viscosity is obtained.

The resulting hydroxyl functional resins have been applied successfully as powder coatings binder components. In addition, the presence of the reactive hydroxyl groups makes these hyperbranched polymers very suitable materials for further modifications. By letting them react with aliphatic and/or aromatic monoacids, for example, polymers with different properties could be synthesized which have been found very suitable for a number of coating applications, for example, air drying topcoats and primers and two-pack urethane lacquers. A combination of favourable properties, including high hardness and early drying, high solids content and weatherability was observed.     

Bio-based semi-aromatic polyesters for coating applications

Linear and branched bio-based semi-aromatic (co)polyesters were evaluated as resins for solvent-based and powder coatings. Dimethyl-2,5-furandicarboxylate (DMF), 2,3-butanediol and various multifunctional comonomers were used to synthesize amorphous hydroxyl-end-capped (co)polyesters. The resins were cross-linked using the ?-caprolactam blocked trimer of isophorone diisocyanate. Both the solvent-based and powder coatings proved to be hard but brittle, which was a result of the very stiff molecular structure of the formed network. This was corroborated by the T_g values obtained for the coatings, which exceeded 100 °C for both the solvent-based and powder coatings. The poly(ester urethane) coatings prepared from the branched copolyesters show a reasonable solvent resistance. However, swelling occurred during the solvent treatment, indicating an insufficient network formation. The solvent-based and powder coatings exhibit similar mechanical and physical performance, showing that in this study there was no significant influence of the preparation method. In view of the obtained results it can be concluded that DMF-based branched polyesters are interesting candidates for solvent-based and powder coating applications.     

Onshore applications for intumescent coating systems

Conclusions  1. Thin-film intumescents are virtually unaffected by dry interior environments. 2. Exterior durable intumescents can give long term fire protection to structural steelwork in an exterior environment provided they are overcoated with suitable finishing coats. 3. Thin-film intumescents are not suitable for hot condensing environments. Caution has to be exercised in using exterior exposure data obtained in the UK for intumescents that are going to be exposed in hot humid climates. 4. Infrared analysis can be used to monitor the durability of intumescent coatings in situ.     

Rheology of plastisol formulations for coating applications

A plastisol is a suspension of PVC particles and mineral fillers in a liquid phase composed of plasticizer and adjuvants. Plastisol formulations are commonly used in coating processes for flooring application. In the knife‐over‐roll process, they are subjected to a wide range of shear rates (0–10⁵ s^?1). They are adjusted in order to fulfil the target end‐use properties but their processability depends on their rheology. Plastisol based on three PVC resins with or without mineral filler have been investigated using a Couette device and a capillary rheometer. Results show a high impact of PVC particle content, particle sizes and distribution on rheology: a polydisperse formulation displays a shear‐thinning behavior in the whole shear rates range and exhibits yield stress; a monodisperse formulation shows a shear thinning behavior at low shear rate, followed by a Newtonian plateau, then a more or less pronounced dilatancy peak depending on plasticizer rate and finally another shear‐thinning behavior; a bidisperse resin stands in between. Filler content also impacts the rheology: shear thickening effects at intermediate shear rates decrease or even disappear; however, the viscosity increase is important for low shear rates and depends on the filler particle size and particle size distribution. POLYM. ENG. SCI., 57:982–988, 2017. © 2016 Society of Plastics Engineers     

Electrochemical characteristics of lithium metal anodes with diamond like carbon film coating layer

To overcome the poor electrochemical characteristics of lithium metal anodes due to the dendrite formations, diamond like carbon (DLC) films were deposited onto the surface of lithium metal by radio frequency-plasma enhanced chemical vapor deposition (CVD) technique using acetylene gas as carbon precursor. The substrate temperature was selected as the main experimental parameter to control the bonding characteristic (sp²/sp³ ratio) of the films. The presence of diamond like structures was confirmed by Raman and Fourier transform infra red spectroscopy. The DLC coated lithium metal was then characterized as an anode material for lithium secondary batteries. The results showed that the DLC coated lithium metal anodes exhibited better electrochemical characteristics in terms of higher specific capacity and smaller interfacial impedance. These improved characteristics were attributed to the presence of DLC film coating which might suppress the dendrite's formation by protecting the lithium metal surface from the direct contact with the electrolyte.     

Compounding for medical applications

The use of plastics for medical applications is expected to top US$ 4 billion in the next two years — and that is just the American market. To give an approximate value for the world market, by all precedents the figure can be at least doubled and possibly trebled. Plastics are used for medical products and components of equipment, and for packaging of products and pharmaceuticals. John Murphy looks at the market and the role that plastics additives play, as well as some of the compounds available for medical applications.     

Smart self-healing anti-corrosion vanadia coating for magnesium alloys

Eco-friendly vanadia based chemical conversion coating was applied for improving the corrosion resistance of a newly developed magnesium AZ31 HP-O alloy. The effect of vanadia solution concentrations (10, 30 and 50 g/l) and pH (neutral pH 7 and pH 9) on the corrosion protection performance of a magnesium substrate were investigated. EIS and linear polarization techniques were used to evaluate the electrochemical behavior in 3.5% NaCl. The results showed a marked increase in the localized corrosion resistance after applying vanadia surface treatment of 50 g/l due to self-healing effect. The optimum conditions to obtain protective coatings for AZ31 HP-O with a self-healing ability were determined. Changes in surface morphology, composition and microstructure of the conversion coatings were followed by SEM-EDS and macroscopic imaging techniques.     

Plasma interface engineered coating systems for magnesium alloys

In this study, a dc low-temperature plasma technique, including plasma treatment and plasma polymerization, was used to create interface engineered coating systems with a structure of Mg/plasma interlayer/cathodic electrocoating (E-coat) for machined AZ31B magnesium (Mg) alloy panels. The plasma interlayer deposited from trimethylsilane (TMS) precursor had a nano-scale thickness of ∼65 nm and well-controlled surface properties through subsequent plasma treatments in order to achieve different level of interfacial adhesion between the E-coat and the Mg substrates. The surface wettability of the plasma interlayer was monitored by water surface contact angle measurement. The interface adhesion of the coating system was evaluated using N-methylpyrrolidinone (NMP) paint removal test and ASTM tape test conducted under dry and wet conditions. Electrochemical impedance spectroscopy (EIS) was employed to investigate the effects of plasma interlayer properties including surface wettability and adhesion enhancement on corrosion protection properties of the coating systems. It was found that a more wettable interface enhanced the electrolyte penetration through the coating and thus reduced the corrosion resistance of the coating system. On the other hands, the improved interface adhesion had little effects on EIS results mainly due to the high chemical reactivity of the Mg alloy substrates.