ABSTRACTS
The following is a list of the abstracts for papers which will be presented in the SECOND INTERNATIONAL SYMPOSIUM ON ADHESION ASPECTS OF THIN FILMS(INCLUDING ADHESION MEASUREMENT AND METALLIZED PLASTICS). The listing is alphabetical by presenting author. This list is updated continually to add abstracts as they become available and make appropriate corrections. This list may be conveniently searched by using the editor provided with most popular browsers (e.g. Microsoft Explorer, Netscape, ... etc.)
1) Laboratoire de Thermodynamique et Physico-Chimie Métallurgiques, (UMR 5614, CNRS - UJF - INPG) ENSEEG, BP 75, 38402 Saint Martin d'Hères Cedex, FRANCE.
2) Centre des Matériaux de l'Ecole des Mines de Paris /C2P, (CNRS UMR 7633), B.P.87, 91003 Evry Cedex, FRANCE.
3) Laboratoire de Combustion et de Détonique, (CNRS UPR 9028), B.P.109, ENSMA, 1 Av. Clément Ader, 86961 Chasseneuil Futuroscope Cedex, FRANCE.
4) Laboratoire d'Application des Lasers de Puissance, (CNRS UPR 1578), 16 bis avenue Prieur de la Côte d'Or, 94114 Arcueil Cedex, FRANCE.
Adherence Comparison of Plasma Sprayed Copper Coatings on Aluminium 2017 Substrates, Estimated with Three Testing Methods (ASTM C633 - (Laser Adhesion Test) - Bulge and Blister Test)
This study compares three adhesion tests carried out on plasma sprayed copper coatings deposited on aluminium 2017 substrates. The first test is the ASTM C633 pull test, involving uniaxial static stress applied on the entire interface and currently used in the coating industry. The second test, LASAT (LASer Adhesion Test), is an emerging technique based on spallation phenomena provoked by laser induced shock waves, in which stresses involved are mostly high strain rate uniaxial loading (1-D-dynamic). The loaded interface area is rather small so that the test can be considered as local. The last test, the bulge and blister test, offers a quasi-static measurement of the crack propagation energy at the coating/substrate interface by propagating a pre-existing interfacial crack. Stresses involved are in mixed modes. These testing methods bring into place different loading modes (local versus global, mixed modes versus single mode) and different strain rates (quasi-static versus dynamic) and their numerical results are expressed in different units. They are applied to samples prepared with different process parameters such as interface roughness (0.1 µm and 5.15 µm), substrate preheating before coating (between 205 °C and 255 °C) and plasma spray conditions (inert gas or air). Adhesion discrimination are compared and discussed and pros and cons of each test are proposed.
Simulation of Adhesion Failure in Transit Scratches in Ultra-Thin Solar Control Coatings on Glass
The major in-service failure mechanisms of modern solar control coatings for the architectural glass can be mechanical (e.g. scratch damage). Many of these coatings are multilayer structures of less than 100nm thickness and different coating architectures are possible (i.e. different layer materials, thickness and stacking order). For high performance solar control coatings deposited by physical vapour deposition processes the active layer is a thin silver coating (~8nm thick) surrounded by anti-reflection coatings (e.g. ZnO, SnO2) and barrier layers (e.g. TiOxNy). Scratches are often found during delivery of the coated glass (called transit scratches) and it has been determined that the cause of the scratches was the polymer balls sprayed onto the glass to separate sheets while in transportation. This study has developed a simulation test for the transit scratches and has determined that the adhesion of layers within the multilayer stack is critical in determining performance. To test the adhesion of the coatings coated samples have been subjected to scratch tests using a range of indenters and the most visible damage has been characterised. Through thickness cracks were observed and it was seen that the coating was stripped by the balls at the weakest point in the coating stack. Microanalysis reveals that this is the silver/zinc oxide interface in the materials analysed in this study.
Different Solutions for Composite Sandwich Cryogenic Tank Design Using Coated Aramid Papers
Different solutions for preventing permeation of gas and debonding in composite sandwich cryogenic tank are presented. A number of aramid fiber paper sheets as potential barrier films in sandwich structure have been coated and tested for helium permeability. The structure incorporates nanoparticles for properties modifications and developing additional barrier agents, and resin systems compatible to laminate and core materials in order to improve adhesion. Results are discussed with emphasis on the question of how to distinguish between the different permeability mechanism and rate in the thin coated papers. We compare the rate of permeability and long-term stability in the cryogenic temperature and some further properties of similar coatings. The difficulties encountered in producing a high quality and uniform coated papers are explained in terms of inappropriate choice of the coating conditions and/or behavior of resin system.
and Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218
Development of Intrinsic Thin Film Stresses
Almost all well adhered films on solid substrates are deposited in a state of stress. How this intrinsic stress is developed can depend on the method of deposition and associated deposition conditions, the thin film material, and the type of substrate. The nature of the real time stress evolution for various deposition methods will be discussed. Electrochemical deposition will be discussed in some detail, as it has recently become important for many applications, including metal interconnects and nanostructured materials. This will then be followed by a survey of the various models that have been proposed to explain the different stress behaviors observed. Finally a discussion will be given suggesting further avenues for experimental study and for modeling.
1) The Singapore-MIT Alliance Program (Innovation in Manufacturing Systems and Technology Program), Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, SINGAPORE
2) The Biological and Chemical Processing Laboratory, School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, SINGAPORE
3) School of Chemical and Biomedical Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, SINGAPORE
Electroless Nickel Deposition on Silicone-rich UV Micro-Embossing
Polymeric microstructures with high aspect ratio are of great interest due to their increased sensitivity or throughput. They are important for diverse applications such as sensors, flat panel displays, microfluidics, microarrays, tissue engineering and micro-optical elements. For many applications, the surfaces of the microstructures must be inert or metallic or chemically tailored. Electroless metallization of three-dimensional (3D) high aspect ratio microstructures is attractive for surface customization. UV embossing and electroless nickel plating are employed in our lab to fabricate the metallized polymeric microstructures. UV embossing, a microreplication method using UV curable resins, has large latitude of resin selection and involves only ambient temperature and low pressure. Once optimized, the process is quick and usually reliable and trouble-free. Electroless nickel plating was used for metallization since the process is applicable to non-conductive surfaces and does not require sophisticated equipment. After surface nickel metallization, the metal layer can act as a diffusion barrier.
A formulation of UV embossing typically contains silicone acrylate as release additive to facilitate demolding. Despite the small amount added, the embossing surface is silicone-rich which complicates the task of firmly adhering a metal film. In this paper, the optimum processing parameters of the metallization were set up and, then, the metallized 3D microstructures were developed.
1) Laboratoire de Sciences et Ingénierie des Surfaces, Bâtiment Raulin, Université Claude Bernard - LYON 1, 69622 Villeurbanne Cedex, FRANCE
2) UMR CNRS 5180 des Sciences Analytique, Bâtiment Raulin, Université Claude Bernard - LYON 1, 69622 Villeurbanne Cedex, FRANCE
Ni or Cu Electroless Metallization of Polymer Substrates With or Without Pd-based Catalysis Processes
Conventionally, Ni or Cu electroless plating of polymer substrates and other insulating materials requires the adsorption of a catalyst (usually a Pd-based catalyst) onto the surface to be metallized. Once the electroless reaction is initiated, it continues through the catalytic action of the deposit itself. Indeed, Ni and Cu, in their zero oxidation state, are able to catalyse the reduction of their own ions. A simplified tin-free process, developed in our laboratory in the recent years, allows to graft Pd(+2) ions directly on insulating surfaces when they are previously grafted with nitrogen-containing species via an ammonia or nitrogen plasma treatment. When industrial plating baths are used, the Pd(+2) species reduction to Pd(0) is a necessary operation to initiate the electroless redox reaction. The various steps of this process are described and the adhesion results of Ni films deposited on various substrates are given.
The principle of another electroless metallization process (a Pd-free process), based on the auto-catalytic property of Ni and Cu to initiate the electroless reaction is also presented in this work. It consists in depositing, on the surface to be metallized, Ni(+2) or Cu(+2) ions from organometallic precursors solutions and in reducing them via various chemical and physical routes in order to obtain a surface seeded with Ni(0) or Cu(0) species. Under these conditions, these species are able both to initiate and perform the corresponding electroless deposition. The various steps of this process are detailed and the adhesion results of Ni or Cu films deposited on various substrates are given.
Pretreatment Processes and Film Property Requirements for Adhesion Control in Different Applications of Pvd-Coatings
(abstract not yet available)
Adhesion Aspects of Amino Functionalization for Attachment of Biomolecules and Adhesion-promotion of Copper Films
Coating and non-coating plasma-based approaches for the generation of primary amino groups on polymer surfaces were studied systematically. Yield and selectivity of coating and non-coating plasma modification processes will be reported together with the stability of resulting amino groups towards oxidation at exposure to ambient air.
Non-coating plasma processes for equipping polymer surfaces with primary amino groups included ammonia and nitrogen/hydrogen radio-frequency excited plasmas. Maximum yields in amino groups amounted to 3 amino groups per 100 C atoms. Admixture of hydrogen did not improve the yield in NH2 groups in the sense of Le Chatelier's principle but enhanced selectivity for NH2 with respect to other nitrogen functional groups.
Coating plasma polymerization processes compared diaminocyclohexane precursor gas to allylamine. In cw mode, diaminocyclohexane plasma polymer layers contained about 5 primary amino groups per 100 C atoms. Whereas pulsed plasma-initiated gas phase polymerization of the chemically polymerizable monomer allylamine significantly improved amino selectivity and the yield in NH2 groups to 18 NH2/100 C.
Primary amino groups at polymer surfaces exhibited good performance as anchoring points for graft synthesis when consumption reactions of amino groups with aldehydes and isocyanates were applied.
In metallization applications, polymer surfaces equipped with amino groups are known to be chemically reactive candidates for copper adhesion via formation of complexes. Due to the rather noble metal character of copper, chemical interactions to other than amino functional groups are less efficient. Peel-strength results will be reported of electron-beam evaporated copper films on amino-functionalized polypropylene surfaces.
The Adhesion of TiO2 and Al2O3 Thin Layers Deposited by Atomic Layer Deposition (ALD) on a Polycarbonate Substrate
The mechanical stability and adhesion behaviour of single and two-layered coatings fabricated by atomic layer deposition was investigated by using tensile experiments. The systems consisted of titania and alumina layers ,deposited on polycarbonate substrates. The tensile tests were conducted in a micromechanical tester positioned under an optical microscope allowing in-situ viewing of cracking damage. The strain to initiate first cracking and the crack density as a function of strain were obtained. Moreover: the rupture strength, the fracture toughness and the interfacial adhesion of the films on the substrate, were deduced from analytical models, in which the experimentally determined parameters were included.
A special interest was devoted to analyse the effect induced by a prior water plasma treatement of the polycarbonate substrate surface, on the mechanical stability of the investigated systems. As a matter of fact, it is shown that this treatment will improve their mechanical response, delaying the initiation of the cracking and the debonding, when it occurs
Stress and Young's Modulus Properties of Some Metallic Thin Films
In this paper, I shall summarize all the results from our recent studies on the stress and Young's modulus properties of some metallic thin films. Those films include the Pd, Au, Cu, Ag, Ni, Fe-Ni, and Co-Ni films. The film thickness (tf) ranges from 500 to 2000 Å. Film stress (S) was measured by the strain-gauge and cantilever system, and/or estimated from the amount of peak shifting of the (111) x-ray diffraction line. Young's modulus (Ef) of each film was measured by the nano-indentation technique, using a Berkovich tip. Regarding the Pd and Ni films, we find that when 25 < TS < 100 , S is tensile (i.e. S > 0), and when 100 < TS < 200 , S is compressive (i.e. S < 0). However, regarding the Au, Cu, and Ag films, S is always tensile; independent of TS. In general, Ef is a function of tf. The tf dependence of Ef is due to the different degrees of texturing in the films. Moreover, it is found that even when TS, tf, deposition rate (R), and vacuum base pressure (p) are all kept the same, the magnetic deposition field (h) is still another important factor which can affect S and Ef in the case of the Permalloy (Fe21Ni79) film. Finally, I like to make a brief comment about the stress and the nano-indentation measurements. In particular, a few empirical guiding rules are raised (or discussed) when employing these techniques on a thin-film sample.
Contributions of Substrate and Film to Scratch Test Performance
The scratch test is an easy to use, fast, and inexpensive test that has found wide spread use for assessment of the quality of hard-coated steels. Unfortunately, the scratch test is not very successful in quantitatively determining characteristic properties of film, substrate, or interface, because these properties are entangled in the parameters obtained from the scratch test: the so-called critical loads. The separate contributions of substrate and film to the scratch resistance of hard CrNx coatings (various compositions x) sputter deposited on hot work tool steel (HWTS) and high speed steel (HSS) in an industrial PVD reactor will be discussed. Two different failure mechanisms were investigated: chipping and complete coating removal. For all specimens, the coating-to-substrate adhesion was that good that adhesion did not limit the scratch resistance. Therefore the minimum loads at which a given type of failure was initiated were not a measure for the coating-to-substrate adhesion. The scratch resistance was better for coatings on HSS than for coatings on HWTS due to the higher hardness of the HSS. Substrate independent measures for the scratch resistance of the coating were obtained by considering critical track widths instead of critical loads. CrN1.0 coatings outperformed CrN0.6 coatings in scratch tests both on HSS and on HWTS, which will be explained by means of detailed transmission electron microscopy investigations to the failure in the coatings.
Stress Reduction and Improved Adhesion in Sputter Deposited Thin Films Using Nanostructured Compliant Layers
We present a new strategy of stress reduction in sputter deposited films by a nano-compliant layer at the substrate using physically self-assembled nanostructures obtained either by an oblique angle deposition technique or by a high working-gas pressure process prior to the deposition of a continuous film. This technique is all in-situ, and the nanostructures are made of the same material as the deposited thin film and require no lithography process. The nanostructured layer has a lower material density and can act as a compliant layer to reduce the stress of the subsequently deposited continuous film. By using this approach we were able to reduce stress values significantly in sputter deposited tungsten and ruthenium films. In addition, these lower-stress thin films also exhibit strong adhesion to the substrate, which retards delamination buckling.
Hard Coatings for Polymers
Within the presented investigations the deposition of hard coatings on thermoplastic substrates were examined. The substrate materials were polyamide (PA6), polycarbonate (PC), polybutylene terephthalate (PBT) and poly ether ether ketone (PEEK). As hard coatings alumina and titanium nitride were deposited by different physical vapor deposition (PVD) technologies. The coating technologies were magnetron sputtering (MS), pulsed magnetron sputtering (PMS) and high ionization sputtering (HIS).
The aims of these investigations were to determine the effects of different deposition techniques on the material compound coating/polymer. Special attention was directed to the coating structure and the adhesion between coating and polymer substrate. The coating structure was observed by cross-sectional areas of fractured samples by scanning electron microscope (SEM). The adhesion was evaluated by scratch, Scotch tape and lattice cut tests. Further, the functionality of the coating was proved by ball-on-disk tests.
The investigations showed that the choice of deposition technology influenced clearly the material compound characteristics. By use of high ionization sputtering and pulsed magnetron sputtering the coating structure developed more fine-crystalline compared to magnetron sputtering. The adhesion between coating and polymer substrate was even improved by pulsed magnetron sputtering and high ionization sputtering. The lattice cut tests showed an increase from adhesion class 4 (MS) to adhesion class 1 (PMS, HIS). The functionality of the hard coatings depended both on the coating technology and on the kind of polymer. Slight improvements in wear resistance were determined at coatings deposited with PMS or HIS. The main influence was the substrate material. An improvement of wear resistance by hard coatings was ascertained for PC, PA and PEEK.
1) Advanced Materials Science Research and Development Laboratory, Hakusan, JAPAN
2) Olympus Co., Ltd., Hachioji, JAPAN
Control of Internal Stress of Coatings by Inductively-coupled-plasma Assisted Pulsed Magnetron Sputtering -Deposition of Low Stress and High Density Ta2o5 Films
Internal stress in coatings reduces reliability of the devices in which coatings are used by adhesion failure. In the sputter deposition internal stress results from the bombardment of the surface of growing films by highly energetic particles. Internal stress can be reduced by lowering energy of the particles, e.g., by increasing discharge pressure and thermalizing sputtered particles. However, low stress films deposited under the low energy particle bombardment generally show a voided fibrous structure, resulting in poor stabilities of properties. In this paper, to explore conditions to deposit low-stress and high-density films, relationship between stress and optical index of Ta2O5 films has been studied for various combinations of energy flux intensity and discharge pressure by using dc magnetron, pulsed magnetron, and inductively-coupled-plasma (ICP) assisted pulsed magnetron sputtering. For all of dc, pulsed, and ICP assisting pulsed magnetron sputtering, compressive stress decreases with increasing discharge pressure. Optical index decreases with increasing discharge pressure for dc and pulsed magnetron sputtering while it increases with increasing discharge pressure for ICP assisted pulsed magnetron sputtering. Film structure observed by cross sectional scanning electron microscopy changes from columnar to granular by increasing energy of incident particle. Energy flux arriving to substrate or growing film in ICP assisted pulsed magnetron sputtering is about two orders higher than that in dc magnetron sputtering. The high energy flux results in the structure change of Ta2O5 films in ICP assisted pulsed magnetron sputtering and induces the abnormal stress-optical index relationship in the film deposited by ICP assisted pulsed magnetron sputtering. It is concluded that the flexibility in control of the intensity of energy flux arriving to the substrate in ICP assisted pulsed magnetron sputtering enables us to control film density and stress independently.
1) Materials and Engineering Science, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW, 2234. AUSTRALIA.
2) Laboratoire de Thermodynamique et de Physico-Chimie Métallurgique, associé au CNRS, E.N.S.E.E.G., BP 75, F-38402 Saint Martin d'Hères, FRANCE.
Fracture And Adhesion of Thin Films on Ductile Substrates
A simple tensile test procedure has been used to investigate the fracture and adhesion behaviour of sol-gel derived silica and atomic layer deposited titania and alumina thin films on metallic and polymeric substrates. Experiments were performed on the film-substrate systems using small flat dogbone samples, to enable in situ observation during tensile testing. These types of tests are used to quantify the onset of film cracking and to probe film damage/delamination. Initially tensile-driven parallel cracks occur at defined strains and the density increases dramatically to a saturation level, with no further cracks generated. At this point, film delamination from the substrate may occur as small, regular shaped debonded zones. For elastic-brittle films, cracks are continuous and regularly spaced with differing degrees of delamination whereas in viscoelastic films, cracks are usually small and irregular and little or no delamination is observed. The critical strains for film cracking and debonding were measured and used to extract film properties and apparent interfacial fracture energies, respectively. Results show adhesion of the film to the substrate is strongly influenced by surface conditioning, processing temperature and by the nature of the constituent material. The effect of these conditions on mechanical properties and the implications of the findings will be discussed.
1) Laboratory for Biomaterials and Bioengineering, Laval University, Quebec City, G1K 7P4, CANADA
2) Quebec University Hospital Center, Quebec City, G1K 7P4, CANADA
Development of a Method to Evaluate the Adhesion of Thin Polymer Films on Metallic Substrates for Long-term Stable Drug Eluting Stents
Metallic intravascular stents are medical devices mainly made of stainless steel 316L generally used to scaffold a biological lumen, most often diseased arteries, after balloon angioplasty. Stenting procedures consist of the stent deployment (expansion in the arterial wall) after having been delivered in situ under radiological observation. These procedures reduce the risk of restenosis, but do not eliminate it completely; indeed, restenosis remains the principal cause of clinical complications, leading to up to 30 % of failure after 3 months of implantation. In the last years, several works were focused on the development of an appropriate coating able to act as a carrier for specific anti-restenosis drugs. Moreover, this coating would act as a barrier, thus inhibiting potentially toxic ions release. However, the coating of a 316L stainless steel surface is not a trivial task, especially in regard to its stability and adhesion after the stent deployment. The aim of this research project was therefore to propose a specific method to evaluate the adhesion of thin (from tens to hundreds nanometers) polymer films deposed by radio-frequency plasma polymerization on metallic substrates. Specific experimental methods were used to extract appropriate information on the adhesion of the polymeric coating onto the metallic substrates. Results for flat polymeric-coated metallic substrates will be presented in order to evaluate the thin polymer film adhesion before and after the stent deployment.
Water-resistant Hard Coating on Plastics Surface by Photo-Oxidation of Silicone Oil
A hard coating method of single crystalline porous silica film is widely used for high power laser optics in the air. There is, however, no protective hard coating method for the elements to survive high power laser irradiance while in the water. Here, we developed a new method for waterproof coating by using photo-excited silicone oil. The silicone oil1 was spin-coated onto the surface of optical elements, consisting of a plastic lens and a laser mirror, and then irradiated with a xenon excimer lamp in the air, which transformed the organic silicone oil into an amorphous glass film. This technique has enabled an optical thin film to transmit ultraviolet rays of wavelengths under 200 nm and possess the characteristics of homogeneity, high density, resistance to environment, resistance to water, and Mohs' scale of 5, which is comparable to apatite.
1) School of Materials Science and Engineering, Georgia Institute of
Technology, 771 Ferst Dr NW, Atlanta, GA 30332-0245, USA
2) National Institute for Lasers, Plasma and Radiation Physics, P.O. Box
MG-36, RO-077125, Bucharest-Magurele, ROMANIA
3) School of Chemistry and Biochemistry, Georgia Institute of Technology,
Atlanta, GA 30332-0400, USA
4) Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084, USA
5) University of Bucharest, Faculty of Physics, P.O. Box MG-11, 3Nano-SAE,
Bucharest-Magurele, ROMANIA
6) US Naval Research Laboratory, Washington, D.C. 20375-5345, USA
Laser Processing of Mussel Adhesive Protein and Mussel Adhesive Protein Analog Thin Films
We have demonstrated thin film growth of mussel adhesive proteins and DOPA modified- PEO-PPO-PEO block copolymer mussel adhesive protein analogs using matrix assisted pulsed laser evaporation. The MAPLE-deposited thin films were examined using Fourier transformed infrared spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle measurements. We have demonstrated that the main functional groups of the mussel adhesive protein analog are present in the transferred film. The effect of increasing the mussel adhesive protein analog chain length on film structure was also examined. These materials have numerous medical, electronic, and marine applications.
1) Department of Chemistry, Center for Materials Science and Engineering, Rochester Institute of Technology, Rochester, NY 14623
2) Department of Physics, RIT, Rochester, NY 14623
3) Xerox Corporation, Webster, NY 14580
Cohesive Failure of Sputtered Cu to Teflon® FEP Modified with VUV Helium Excimer Radiation
Excimer vacuum ultraviolet (VUV) irradiation at wavelengths of 50-110 nm from a high pressure (400 Torr) helium DC arc plasma was used to alter the physiochemical surface properties of Teflon® FEP prior to metallization. X-ray photoelectron spectroscopy (XPS) analysis revealed the formation of the hydrophilic groups C-O, O-C=O and C=O upon exposure to air. The increased wettability of the modified polymer was observed by contact angle measurements. FT-IR showed the appearance of a strong band at 1884 cm-1 indicating the formation of the carbonyl fluoride, -CF2C(O)F, group. SEM analysis showed an increase in surface roughness upon treatment. Copper was sputter coated onto the modified FEP surface. When a tape test was applied, XPS analysis showed that cohesive failure occurred within the modified FEP and not at the Cu-FEP interface probably due to an improvement of interfacial adhesion with a simultaneous weakening of the mechanical properties within the polymer resulting from photochemical chain scission. A high degree of modification was achieved within a few minutes of treatment time using VUV excimer radiation in contrast to longer treatment times needed for VUV exposure of FEP downstream from low pressure Ar microwave plasma [1].
[1] W. Dasilva, A. Entenberg, B. Kahn, T. Debies and G. A. Takacs, J. Adhesion Sci. Technol., 18, 1465 - 1481 (2004).
*To whom correspondence should be addressed. Tel.: (1-585) 475-2047, Fax: (1-585) 475-7800. E-mail: gatsch@rit.edu
® Teflon is a registered trademark of E. I. duPont de Nemours & Co., Wilmington, DE.
Investigation of Miscibilty in Guest-host Monolayer by Surface Pressure And Absorption Spectroscopic Study
Langmuir (L) monolayers have been widely used as mimetic systems to investigate the self-organization and the nature of intermolecular interactions, either at the air-water interface or in the films transferred onto solid supports by Langmuir-Blodgett (LB) technique.
In an attempt to fabricate stable 2,2'-Biquiboline film, (BQ) is successfully incorporated in different host matrices stearic acid (SA) and poly methyl methacrylate.The miscibility of BQ molecule in each of the host monolayer is demonstrated by standard analysis of the surface pressure-area isotherm, using the two dimensional phase rule and the additivity rule for the average molecular areas.
The formation of stable BQ-PMMA and BQ-SA mixed Langmuir monolayer at the air-water interface is confirmed by the isotherm characteristics study.
From the area per molecule versus molefraction curves for both PMMA and SA matrices at different surface pressure, it is observed that the experimental data points almost coincides with the ideality curve as predicted by the additivity rule [1]. This may be due to ideal mixing or complete demixing of the binary components. However, UV-Vis absorption spectroscopic study confirms the complete demixing of molecules, which lead to the formation of aggregates of BQ molecules.
Reference:
[1] N. Sadrzadeh, Hyuk Yu, G. Zografi, Langmuir, 14 (1998) 151.
1) INSA de Lyon, Laboratoire des Matériaux Macromoléculaires (IMP/LMM), Bâtiment Jules Verne, 17 rue Jean Capelle, 69621 VILLEURBANNE Cedex, FRANCE
2) Université des Sciences et Technologies de Lille (LSPES, UMR 8008) - UFR de Physique, 59655 Villeneuve d'Ascq Cedex, FRANCE
3) Université Claude Bernard Lyon1 (UFR DE CHIMIE BIOCHIMIE, Centre commun de Diffractométrie), Bâtiment Jules Raulin, 43 Boulevard DU 11 NOVEMBRE 1918, 69622 VILLEURBANNE Cedex, FRANCE
4) Centre d'Etude de Chimie Métallurgique, 15, rue Georges Urbain, 94407 VITRY Cedex, FRANCE
Epoxy-amine / Metal Interphases: Influences from Sharp Needle-like Crystals Formation
Epoxy-amine liquid prepolymers are extensively applied onto metallic substrates and cured to obtain painted materials or bonded joint structures. Overall performances of such systems depend on the created interphase between the organic layer and the substrate. When epoxy-amine liquid mixtures are applied onto more or less hydrated metallic oxide layer, concomitant amine chemical sorption and metallic surface dissolution appear leading to the organo-metallic complex (or) chelate formation. Using two different amines as hardener (a cycloaliphatic diamine (IPDA) and an aliphatic triamine (DETA)), we will study the interphase formation and more particularly its formation kinetic using µFTIR. The interphase thickness increases when the liquid-solid duration at room temperature before polymerization increases. If the complex (or chelate) concentration within the liquid amine or epoxy-amine prepolymer is higher than its solubility limit, complexes (or chelates) crystallize. Sharp needle-like crystals are observed with modified IPDA, in less than 5 minutes in contact with the metal, whatever the metal nature is (except gold), whereas DETA never crystallize (even after three hours in contact with any of the studied metals).
Considering the initial crystal dimensions, it was necessary to increase their size to characterize then using conventional characterization tools. So, the organo-metallic complexes were re-crystallized in deionized water. For Al-IPDA crystals, the melting point was in the range 75 - 80°C, and they were orthorhombic crystals. But unfortunately, amine may also react with carbon dioxide to form carbonates. Their melting points were determined to be about 85-90°C. We are now able to differentiate both compounds: carbonates and organo-metallic complexes. Using ICP analysis, metal ions into organo-metallic complexes were observed, but not into carbonate species. Lastly, organo-metallic crystals looked like sharp needle and carbonates were fluffy.
1) Laboratoire de Sciences et Ingénierie des Surfaces, Bâtiment Raulin, Université Claude Bernard - LYON 1, 69622 Villeurbanne Cedex, FRANCE
2) UMR CNRS 5180 des Sciences Analytique, Bâtiment Raulin, Université Claude Bernard - LYON 1, 69622 Villeurbanne Cedex, FRANCE
Practical Adhesion of Electroless Ni Thin Films on Polymer Surfaces. A New Method of Characterization
The present work deals with the electroless deposition of nickel thin films and with their adhesion to a variety of polymer substrates including poly(imide), poly(propylene), poly(carbonate) and poly(tetrafluoroethylene).
Previous studies have shown that simplified processes leading to electroless plating can be developed through new surface pretreatments of the polymer substrates. These pretreatments require the surface grafting of nitrogen containing-groups through plasma- or VUV-assisted techniques and the activation of the so-functionalized surfaces via the direct chemisorption of Pd-based species.
In the present study, the practical adhesion of the metal thin films to their substrates has been investigated. For that purpose, it is used a stretch deformation test (also known as a shear tensile or fragmentation test) and an original approach which consists in measuring the changes in the electrical resistance of the metal thin film when the metal-polymer system is placed under uniaxial tension. Let us recall the fragmentation test offers some specific advantages as it does not require the use of a third body (adhesive joint or tape) and is applicable to the case of flexible substrates.
Results show that correlations can be established between the changes in the relative electrical resistance dR/R and the development of the crack pattern observed at the surface of the metal coating. Correlations are made with the distribution of segment lengths at saturation as it can be inferred from the conventional use of the fragmentation test.
In addition, it is shown that differences in adhesion performances can be observed as a function of the nature of the polymer substrate, and the nature and duration of the plasma treatment (NH3, N2 …). Among others, the influence of the roughness and chemical nature of the surface functionalities created by the plasma treatments is emphasized.
XPS analyses and microscopic observations are carried out to contribute to the interpretation of the mechanical / electrical test data.
The Ageing Effect of Adhesion of Au Coating with Keylayer on Polymer Substrate
Polymer with metal coating has become very attractive now because of the emerging application such as flexible display. However the adhesion between metal and polymer is usually very poor. At moment this is the barrier for the applications of metallized polymer substrates. In order to improve the adhesion between metal and polymer, some special material is inserted between metal and polymer as buffer layer such as Ti and Si. In our research Au is the metal layer, the substrate is C-coated PET, and the Ti is used as buffer layer. The Ti buffer layer does improve the adhesion between Au and PET. However, the results indicted that the adhesion is aged by time. The ageing speed of adhesion also depends on the duration that substrates are kept in high vacuum before deposition. If the duration is longer the ageing speed is slower. The adhesion is measured by using Mecmesin adhesion measurement system. The delamination is at interface between Ti layer and C-coating on PET. This was confirmed by SEM analysis with EDX and DEKTEK profile measurement.
1) Department of Chemistry, College of William and Mary, Williamsburg, VA 23185, U.S.A.
2) Langley Research Center, NASA, Hampton, VA 23681, U.S.A.
Novel Route to Palladium Surface-Metallized Polyimide Nanocomposite Films
Palladium surface-metallized polyimide films were prepared by an unusual macromolecular matrix mediated, single stage synthetic protocol first reported by Taylor et al. (J.A.C.S. 1980, 102, 876). Several Pd(II) complexes, [PdCl2(SMe2)2], [PdBr2(SMe2)2], and Pd(CF3COO)2 were dissolved in the poly(amic acids of BTDA/4,4¢-ODA and BPDA/4,4¢-ODA in the solvent DMAc. Films cast onto glass plates from these Pd(II)-doped resins were thermally cured to 300 °C in air which resulted in air-side surface-metallized membranes. Palladium concentrations ranged from 1.0 to 5.2% by weight. The films were characterized by both specular and diffuse reflectivity and by conductivity measurements as a function of the cure time and temperature. Maximum specular reflectivities of ca. 50% were observed at 530 nm. After achieving maximum specular reflectivities in the thermal cure cycle at 300 °C from 0.5-2 h, the film surface quickly degraded upon further curing. The surface sheet resistivities were in the range of ca. 1- 75 ohm/square. Initial Pd metal particles formed in the film were in the 3-10 nm range. The optical data coupled SEM micrographs, elemental analytical results, and X-ray diffraction observations were interpreted to support a mechanism for the formation of a reflective and conductive metallized surface which involves selective air-side surface oxidative degradation of the polyimide matrix to volatile products which then concentrates the metal nanoparticles at the surface and increases particle size via sintering. The mechanical properties of the metallized films are compromised with respect to the parent polyimide although the composite membranes are still useful for a range of applications. The tensile strength is reduced; the percent elongation and the tensile modulus are increased. Both BTDA/ODA and BPDA/ODA gave very similar results with the Pd(II) additives. Many Pd(II) compounds, e.g., PdBr2, were not useful in generating a metallized surface which suggests that the pathway to a metallized surface is extremely sensitive to experimental conditions.
Thompson1, and R. E. Southward2
1) Department of Chemistry, College of William and Mary, Williamsburg, VA 23187
2) Advanced Materials and Processing Branch, Langley Research Center, NASA
Single-stage Near-surface Silver Metallization of Fluorinated Polyimides Yielding Reflective Nanoparticulate Hybrid Membranes at Low Metal Concentrations
The synthesis of highly reflective flexible nanoparticulate polyimide films by a single-stage matrix mediated metallization process involving the (hexafluoroacetylacetonato)silver(I) complex dissolved in solutions of the poly(amic acid)s and polyimides which are formed from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropanedianhydride (6FDA) and 2,2-bis[4-(4-aminophenoxy]hexafluoropropane (4-BDAF) as well as the poly(amic acids) of traditional non-fluorinated polyimide such as BTDA/ODA is described. Thermal treatment of cast silver(I)-poly(amic acid) films leads to cycloimidization of the amic acid with concomitant Ag(I) reduction and nano-aggregation into a monolayer of closely packed ca.60 nm spherical Ag particles very near (within nanometers of) the surface. The bulk also contains nanometer-sized Ag particles which are much smaller than those near the surface. Specularly reflective films for Ag concentrations at the very low concentration of 2 wt% are realized, but the films are not electrically conductive. A 2% Ag 6FDA/4-BDAF film gives specular reflectivites from 70-80% relative to vapor deposited Ag. TEM and SEM measurements have been used to characterize the Ag particles. The formation and position of the near-surface silver layer will be analyzed in terms of the theory of Vincett and Kovacs.
Adhesion of PZT on Zr, ZrO2, Ti, and Ta
We have investigated the addition of silicon nitride thin films into standard PZT stacks and quantified the effects of various adhesion layers on the ferroelectric characteristics of these stacks. Although previous research has investigated issues related to adhesion and quality of PZT films, this research considers four specific adhesion layers deposited onto a silicon nitride coated substrate (Zr, ZrO2, Ti, and Ta) and compares results for each. Adhesion layer thicknesses of 15 nm and 25 nm were tested with pyrolysis temperatures of 600ó¬C and 650ó¬C. For many of the adhesion layers, the remnant polarization Pr and C-V characteristics are similar to conventional PZT stacks deposited onto SiO2 substrates, but only Ta withstands the thermal processing required for PZT deposition.