Development of multiple-droplet drop-casting method for the fabrication of coatings and thin solid films

Spray coating is a commercial and low-cost technique for the fabrication of large-area coatings and thin films, but it is a stochastic process that is hard to control, as far as the fabrication of thin coatings and solid films is concerned. On the other hand, drop-casting is a facile and more controllable coating technique than spray coating, but its application is limited to small-area thin solid films and coatings. The objective of this work is, therefore, to study the feasibility of impinging an array of droplets, rather than just one droplet, to fabricate polymeric and other solution-processed thin films with larger surface areas than those produced by conventional drop-casting. To this end, in this study, four droplets of poly(3,4-ethylenedioxythiophene)–polystyrene sulfonate (PEDOT:PSS) solution are released simultaneously and impinged on the four vertices of a square on a wettable solid surface to make a thin film. The effect of the substrate texture on the spreading and the film formation process is studied. As a novel idea, the substrate is excited by ultrasonic vibration to improve the droplet spreading and coalescence. It is shown that as time elapses, the impinged droplets successfully coalesce and make a thin film. Surface morphology and roughness of the resulting PEDOT:PSS thin solid films show that, except on the edges, the resulting thin solid films are uniform. This leads us to conclude that the application of equal-sized and equally-spaced multiple droplets released simultaneously and impinged on vibrating substrates could be considered as a new coating technique, which has some of the benefits of the spray coating, but it is much more controllable than spray coating.     

机械涂覆技术在光催化材料制备中的应用进展

机械球磨技术因工艺简单、成本低廉而受到广泛关注,特别在粉体材料的混合、细化及合金化等领域有着广阔的应用前景。综述了由机械球磨原理发展而成机械涂覆技术的应用现状,包括用于材料表面改性的功能涂层和光催化降解的薄膜材料制备。分析了工艺参数、涂覆材料及涂覆基底等因素对涂覆效果（厚度）的影响规律,并对该技术在薄膜制备中表现出的简便、廉价且可在球形等形状复杂基底上成膜的独特优势做了讨论。基于当前机械涂覆技术制备的薄膜形貌、厚度不可控且成膜基底材质受限等现状,指出今后应该向拓展成膜基底材料类型和加快推进光催化薄膜材料的实际应用方向发展。     

Methods for studying the mechanical and tribological properties of hard and soft coatings with a nano-indenter

This study illustrates the capabilities of a nanoindentation/nanoscratch tester to assess mechanical and tribological properties of coating films. Properties such as hardness, elastic modulus, mar and scratch resistance, and critical force for cracking can be accurately measured. Operation of the Nano-Indenter is described in detail. A scanning probe microscope (SPM) is shown to be a valuable supplement to the Nano-Indenter. Well-characterized thermoset acrylic clearcoats and thermoplastic latex films were studied. For the first time, operating parameters are described for measurement of relatively soft coatings, such as films cast from a latex with a glass transition temperature (T_g) of 8°C. Thus, the method is made available for study of most types of coatings. The method can easily discriminate between coatings with different T_gs and crosslink densities. Once operating parameters are established, it takes about 10 minutes for an indentation test and 10 minutes for a scratch test with the Nano-Indenter, and with further automation this time could be reduced. Each indentation test accurately measures hardness and elastic modulus as a function of depth within the coating, and each scratch test provides additional insight into the material’s behavior. The method is sensitive to small changes in polymer composition and formulation, and results are highly reproducible. Presented at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 12–14, 2003, in Philadelphia, PA.     

Low friction and protective diamond-like carbon coatings deposited by asymmetric bipolar pulsed plasma

Diamond-like carbon (DLC) thin films have been prepared at room temperature by plasma-enhanced chemical vapour deposition (PECVD) using pulsed-DC power and CH₄ as precursor. Tribological tests of these DLC films have been carried out with a nanotribometer and a calotest instrument adapted for wear measurements. Friction coefficients ranged from 0.15 to 0.20, which differ from values obtained by other techniques. In this study we have systematically measured the abrasive wear rate and friction coefficient of DLC films deposited at different conditions (pulse frequency and peak voltage), and we have discussed the results in terms of DLC structure and surface morphology. These films could find application as ultrathin anti-friction and anti-wear protective coatings, hydrophobic coatings, gas diffusion barriers and dielectric layers in electronic devices.     

Techniques for filtering graphite macroparticles in the cathodic vacuum arc deposition of tetrahedral amorphous carbon films

Filtered cathodic vacuum arc (FCVA) deposition has been found to be a reliable technique for the production of high quality tetrahedral amorphous carbon films (ta-C). These coatings can be used as protective coatings for different applications ranging from cutting tools to human hip joint prosthesis. The FCVA technique is widely used in different laboratories around the world with somewhat different technical implementations. A serious disadvantage in the FCVA technique is the graphite particles that are emitted from the solid graphite cathode during the arc-discharge. A variety of different techniques exist to diminish their production and transport. However, some of the magnetic filtering designs that are used to reduce the macroparticle transport into the substrate do not work well with high melting point cathode materials such as graphite. Although the influence of graphite particles for the ta-C coating performance in some applications is controversial, many applications demand that the produced ta-C film is practically particle-free. This is especially important in corrosion resistance, electrical and optical applications. In this paper an introduction to different FCVA devices is presented. Different magnetic filtering designs together with control techniques for macroparticle generation have been reviewed and their advantages and disadvantages in the plasma transport and particle filtering efficiency have been discussed.     

微弧氧化技术的研究进展

微弧氧化技术是一种针对Al,Mg,Ti等阀金属及其合金进行表面陶瓷化的新技术.利用该技术制成的氧化膜结构致密,结合好,具有优良的综合力学性能,特别适用于处在高速运动、并且对耐磨耐蚀性要求较高的零部件的表面处理,近年来该领域的研究一直较为活跃.文中综述了国内外微弧氧化技术的研究现状,概括了微弧氧化的基本原理、过程、制备方法和工艺特点,总结了微弧氧化膜的组织结构和性能特点,介绍了该技术在几种常见金属中的研究进展,并展望了该技术的应用前景.     

Thin fluoropolymer films and nanoparticle coatings from the rapid expansion of supercritical carbon dioxide solutions with electrostatic collection

Application of nanometer thick fluoropolymer films onto metal and semiconducting substrates is described. In the first step, nanometer-sized polymer particles are generated by a process of homogeneous nucleation during the rapid expansion of supercritical fluid solutions. These gas-phase particles are then charged as they are being formed by application of a high voltage to the expansion nozzle. In this way the charged nanoparticles can be collected on a solid surface forming uniform coatings with thicknesses from tens of nanometers to several micrometers thick. Supercritical carbon dioxide solutions of three different fluoropolymers were used to generate different types of coatings. This represents a ‘green’ process for film deposition. A further unique aspect of this process is that the small charged nanoparticles can be deposited to electrically conducting microscopic regions with a spatial resolution better than 50 nm.     

Effect of electrode geometry on the uniformity of plasma-polymerized methyl methacrylate coatings

Plasma polymerization is widely used to deposit functionalized coatings which properties can be tuned by different operational parameters. Although plasma-deposited coatings have many interesting properties, the influence of these parameters on the polymerization process is not yet well understood. In this study, plasma-polymerized methyl methacrylate (MMA) coatings are produced and carefully planned experiments are conducted to evaluate the influence of discharge power and electrode geometry on the chemical composition and thickness of the deposited films. For this purpose, polymerization processes are carried out in two plasma reactors with different electrode geometries (parallel plate versus mesh-to-plate) and the influence of discharge power is examined for both reactor types. This study reveals that the chemical composition of the deposited films is strongly influenced by the power of the discharge: at high powers, the coatings contain less ester functional groups, which is most likely due to monomer fragmentation at these elevated powers. It is also shown in this work that the reactor set-up strongly determines the uniformity of the deposited films: in the parallel plate reactor, film thickness, surface morphology and chemical composition depend on the location of the substrate in the discharge region, while in the mesh-to-plate reactor the deposited films are physically and chemically uniform. Taking into account the latter statement, the mesh-to-plate reactor might have important industrial applications.     

星形支化树脂在紫外光固化粉末涂料中的应用

用可紫外光固化的星形支化树脂作主要成膜物,制成了紫外光固化粉末涂料。讨论了星形支化树脂用量对光固化粉末涂料熔融黏度、漆膜光泽度、鲜映性、耐溶剂擦洗性的影响,考察了紫外光固化粉末涂料熔融黏度随温度的变化,以及漆膜的玻璃化温度与光照时间的关系。结果表明,与紫外光固化线性树脂相比,星形支化树脂应用于粉末涂料中时,可制得熔融黏度更低、漆膜外观更好、漆膜耐溶剂性更优的紫外光固化粉末涂料。     

轿车漆膜后处理工艺中抛光对漆膜光泽度影响研究

研究了二种不同抛光膏(白色抛光膏和灰色抛光膏)分别对二种不同的漆膜(金属漆和单色漆)表面作不同时间抛光处理后的漆膜表面光泽度变化,从而讨论了抛光膏、抛光工艺对不同漆膜表面光泽度的影响,提出了最佳抛光材料和抛光工艺。     

超细粉体表面包覆技术综述

通过超细粉体的表面包覆以改善粉体的分散性及其表面性质,已经成为超细粉体制备和应用的关键技术。综述了超细粉体的表面包覆方法,包括机械化学法、气相沉积法、聚合物包裹法、液相化学法及微胶囊化法等,主要介绍了每种方法的基本原理及应用。     

Antibacterial activity of DLC and Ag–DLC films produced by PECVD technique

Diamond-like carbon (DLC) films have been the focus of extensive research in recent years due to its potential application as surface coatings on biomedical devices. Doped carbon films are also useful as biomaterials. As silver (Ag) is known to be a potent antibacterial agent, Ag–DLC films have been suggested to be potentially useful in biomedical applications. In this paper, DLC films were growth on 316L stainless steel substrates by using Plasma Enhanced Chemical Vapour Deposition (PECVD) technique with a thin amorphous silicon interlayer. Silver colloidal solution was produced by eletrodeposition of silver electrodes in distilled water and during the deposition process it was sprayed among each 25 nm thickness layer DLC film. The antibacterial activity of DLC, Ag–DLC and silver colloidal solution were evaluated by bacterial eradication tests with Escherichia coli (E. coli) at different incubation times. With the increase of silver nanoparticle layers in Ag–DLC, the total compressive stress decreased significantly. Raman spectra showed the film structure did not suffer any substantial change due to the incorporation of silver. The only alteration suffered was a slightly reduction in hardness. DLC and Ag–DLC films demonstrated good results against E. coli, meaning that DLC and Ag–DLC can be useful to produce coatings with antibacterial properties for biomedical industry.     

氧化锆涂层(薄膜)的应用与研究

重点归纳了氧化锆(Zr02)作为热障涂层材料的应用和研究内容，并对Zr02功能薄膜材料和生物涂层材料的研究进行了简单总结。对纳米氧化锆涂层的研究现状进行初步介绍。     

铝及其合金等离子微弧氧化技术

等离子微弧氧化是一种新兴的材料表面陶瓷化技术,利用该技术可在铝及其合金表面生成一层耐磨,耐蚀,耐高温以及电绝缘性能优异的陶瓷膜层,介绍了微弧氧化技术的发展及现状,基本原理,陶瓷膜的制备以及膜层结构及性能特点,并展望了其应用前景。     

A new concept for dispersing agents in aqueous coatings

After a short overview about the development of synthetic dispersing agents for solvent-borne coatings up to the actual state of technique, analogous concepts of polymeric additives for water-borne coatings are introduced. The performance of these polyfunctional dispersants will be critically reviewed and described in comparison to dispersing agents based on new concepts. With these new concepts using mono- and difunctional oleochemical agents or a combination of them it is often possible to reach better performance than with polyfunctional polymers. During our study different physicochemical methods (Zeta potential, adsorption, desorption) and paint application tests including numerous binders and pigments were done. These investigations lead to the discussion of new models for the dispersing of pigments in water-borne coatings and to more knowledge about the design of a dispersant to reach high gloss, optimal rub-out and high color-strength. Furthermore the formulation of solvent- and resin-free water-borne pigment pastes is possible using dispersing agents selected by the new concepts.     

Electrochemical synthesis: a novel technique for processing multi-functional coatings

Electrochemical synthesis is a powerful tool for surface modification, substrate cleaning and formulation of thin films and bulk materials. It is especially suited for surface modification of fibers, metals and films. In the past decade electrochemical method has become the preferred technique for in situ passivation, and coating of commodity metals such as aluminum, zinc, copper and steel.

We have successfully synthesized different kinds of conducting polymers, including polypyrrole (PPy)–polyaniline (PANi) composites. The processability and corrosion performance of PPy/PANi, composite coatings are significantly better than those for either PPy or PANi, coatings.

In this paper, we will discuss the use of electrochemical technique in the synthesis and characterization of multi-functional corrosion resistant conducting polymer coatings for aerospace and automotive applications.     

Impact of the coating process on the molecular structure of starch‐based barrier coatings

Molecular analysis of starch structure can be used to explain and predict changes in physical properties, such as water vapor and oxygen barrier properties in packaging materials. Solution casting is a widely used technique to create films from starch formulations. This study compared the molecular properties of these standard films with those of experimental coatings applied to paper in laboratory‐scale and pilot‐scale trials, with all three techniques using the same starch formulation. The results revealed large differences in molecular structure, i.e., cross‐linking and hydrolysis, between films and coatings. The main differences were due to the shorter drying time allowed to laboratory‐scale coatings and the accelerated drying process in pilot trials owing to the high energy output of infrared dryers. Furthermore, surface morphology was highly affected by the coating technique used, with a rougher surface and many pinholes occurring in pilot‐scale coatings, giving lower water vapor permeability than laboratory‐scale coatings. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41190.     

Physicochemical and biological properties of electrodeposited graphene oxide/chitosan films with drug-eluting capacity

In this study, novel graphene oxide/chitosan nanocomposite coatings with long term drug-eluting potential are presented. The coatings are fabricated by the facile and reproducible electrophoretic deposition technique. Analysis of the prepared films shows that the graphene oxide nanosheets are exfoliated in the chitosan matrix. Fourier-transform infrared spectrometry reveals polymer attachment to the carboxylic bonds of graphene oxide, providing a strong interaction and exfoliation of the nanolayers. In vitro viability assay by human osteosarcoma cells (MG-63) demonstrates that the nanocomposite films are highly biocompatible up to 30 wt% graphene oxide, but at higher concentrations a slight cytotoxicity is noticed. Alkaline phosphates enzyme assay also reveals that the presence of graphene oxide nanosheets moderately hampers osteogenesis of the cultured cells. It is shown that vancomycin-loaded nanocomposite coatings gradually release the drug macromolecules for relatively long period of time (up to 4 weeks). The electrodeposited films also exhibit a high bactericidal potential against Gram-positive Staphylococcus aureus. Effects of graphene oxide nanosheets on the physicochemical, biological, antimicrobial and drug-eluting properties of electrodeposited chitosan films are presented and discussed. It is shown that the GO/CS films support the initial attachment, proliferation and growth of osteoblast-like cells.     

水性木器漆的施工

水性木器是现今涂料研发和生产的热点，本文介绍了水性木器漆的组成，涂装施工及其注意事项，强调了施工工艺的重要性以及如何克服施工中可能造成的弊病。     

环保型芳烃含量低的聚氨酯涂料及其应用

环保型低芳烃双组分聚氨酯涂料是一种兼顾了性能和环境保护的新型涂料体系,近年来在国外已取得较快的发展,在中国尚属首次推向市场。本文概述了该涂料的研究进展、涂料的组成、制备,及其在建筑外墙涂料、塑料涂料中的应用,讨论了助剂、溶剂、颜填料的选择对性能的影响,研究了涂料的应用性能。