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The deposition rates of protective coatings resembling polydimethylsiloxane (PDMS) were measured with numerous sensors placed at different positions on the walls of a plasma-enhanced chemical vapor deposition (PECVD) reactor with a volume of approximately 5 m3. The plasma was maintained by an asymmetric capacitively coupled radiofrequency (RF) discharge using a generator with a frequency 40 kHz and an adjustable power of up to 8 kW. Hexamethyldisiloxane (HMDSO) was leaked into the reactor at 130 sccm with continuous pumping using roots pumps with a nominal pumping speed of 8800 m3 h−1 backed by rotary pumps with a nominal pumping speed of 1260 m3 h−1. Deposition rates were measured versus the discharge power in an empty reactor and a reactor loaded with samples. The highest deposition rate of approximately 15 nm min–1 was observed in an empty reactor close to the powered electrodes and the lowest of approximately 1 nm min–1 was observed close to the precursor inlet. The deposition rate was about an order of magnitude lower if the reactor was fully loaded with the samples, and the ratio between deposition rates in an empty reactor and loaded reactor was the largest far from the powered electrodes. The results were explained by the loss of plasma radicals on the surfaces of the materials facing the plasma and by the peculiarities of the gas-phase reactions typical for asymmetric RF discharges.

Cellulose is a promising biomass material suitable for high volume applications. Its potential lies in sustainability, which is becoming one of the leading trends in industry. However, there are certain drawbacks of cellulose materials which limit their use, especially their high wettability and low barrier properties, which can be overcome by applying thin coatings. Plasma technologies present a high potential for deposition of thin environmentally friendly and recyclable coatings. In this paper, two different plasma reactors were used for coating two types of cellulose-based substrates with hexamethyldisiloxane (HMDSO). The changes in surface characteristics were measured by atomic force microscopy (AFM), scanning electron microscopy (SEM), surface free energy and contact angles measurements, X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS). Successful oleofobization was observed for an industrial scale reactor where pure HMDSO was used in the absence of oxygen.

An extremely asymmetric low-pressure discharge was used to study the composition of thin films prepared by PECVD using HMDSO as a precursor. The metallic chamber was grounded, while the powered electrode was connected to an RF generator. The ratio between the surface area of the powered and grounded electrode was about 0.03. Plasma and thin films were characterised by optical spectroscopy and XPS depth profiling, respectively. Dense luminous plasma expanded about 1 cm from the powered electrode while a visually uniform diffusing plasma of low luminosity occupied the entire volume of the discharge chamber. Experiments were performed at HMDSO partial pressure of 10 Pa and various oxygen partial pressures. At low discharge power and small oxygen concentration, a rather uniform film was deposited at different treatment times up to a minute. In these conditions, the film composition depended on both parameters. At high powers and oxygen partial pressures, the films exhibited rather unusual behaviour since the depletion of carbon was observed at prolonged deposition times. The results were explained by spontaneous changing of plasma parameters, which was in turn explained by the formation of dust in the gas phase and corresponding interaction of plasma radicals with dust particles.

Residual stress measurements of thin films are common practice in device technology and are extremely important in particular for the characterization of thin film coatings. A largely ignored stress contribution is the difference in coefficient of hygroscopic expansion between the coating and substrate. This paper presents a rather novel approach to accurately evaluate the residual stress and coefficient of hygroscopic expansion of strongly curved specimens. Silicon-containing plasma polymer coatings with different carbon contents were deposited using hollow cathode arc discharge based PECVD. Samples of different layer composition were produced comprising silicon-containing plasma-polymer layers with a high carbon concentration and more ""inorganic"" SiO2 like layers with lower carbon concentration. All coatings show a compressive stress state. The highest stress was measured in the coating with the highest carbon content (239 ± 6 MPa) and decreases to 94 ± 31 MPa at lower carbon contents. Variation of the humidity showed that all coatings expand under influence of increasing relative humidity. The most inorganic coatings exhibits the highest expansion coefficient of 29.2 ± 2·10−6 (% r.h.)−1. The results obtained were compared with the results from contact angle measurements. An increase in the hygroscopic expansion corresponds with an increasing hydrophilicity of the coatings.

Plasma enhanced chemical vapor deposition is a promising process for the generation of tailor-made polymer coatings on medical devices in order to improve their implant/ host interaction. The ultra-thin coatings can fulfil a variety of purposes, depending on the monomers used, the process conditions and the location of the coated implants in the human body. In addition, even complex geometries can be coated easily and without the application of solvents. Particularly hydrophilic and hydrophobic plasma polymer coatings can improve biocompatibility, especially in blood contact. Furthermore, the selection of the monomers used enables the generation of specific functional groups for further surface immobilization of drugs, such as proteins, by chemical crosslinking. The release of toxic residues from polymeric implants, such as monomers, additives or degraded components, can also be avoided. The aim of our investigation was the generation of plasma polymer films, their characterization and application as coatings for biodegradable metallic biomaterials in order to retard the degradation process. Metallic biomaterials, in various forms are frequently used in orthopaedics, dentistry, cardiovascular and neurosurgical equipment, because of their tensile strength, fracture toughness, fatigue strength and electrical conductivity. Plasma polymerization was performed using the monomers hexamethyldisiloxane and allylamine. The resulting plasma polymers were analysed in an accelerated degradation test. Both plasma polymers appear to be promising, while polyHMDSO appears to degrade over time and polyallylamine indicates to be stable.

Made available in DSpace on 2020-12-12T02:30:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-11-25 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Carbon steel is the most commonly used material for sheets, plates, bars and tubes in mechanical metallurgy and construction industry. However, the susceptibility of carbon steel to oxidation under real conditions of use turns preventive and corrective repairs mandatory. Many published studies show that plasma deposited silica and organosilicon layers can be used as corrosion barriers, being the first one more efficient due to its higher chemical density and inertness. However, the performance of SiOx layers may be affected by mechanical stress, and especially by defects generated in the deposition process or by the substrate finishing. To associate the good corrosion resistance of the silicon oxide films to the flexibility of organosilicon ones, some authors created multilayered systems, intercalating organosilicon and silica layers. However, the adhesion between the organosilicon and inorganic layers in these multilayered systems is still a problem, since there is a well-defined interface between them and both layers are just slightly interconnected. In this sense, the purpose of the present work is to create, from plasma polymerization of hexamethyldisiloxane, an organosilicon-silica gradual system and to investigate its barrier and mechanical properties. SiOx/SiOxCyHz gradual films were deposited by low pressure radiofrequency (13.56 MHz) plasmas using HMDSO, Ar and O2 mixtures. The change of an organosilicon to inorganic coating or vice versa was made only by adjusting the plasma conditions without interrupting the process. The influence of the carbon steel native oxide pre-deposition treatment in O2 plasma was also evaluated. Electrochemical Impedance Spectroscopy, EIS was used to evaluate the corrosion resistance provided by the gradual system to the carbon steel. Infrared spectroscopy, FTIR, was applied to analyze the chemical composition and molecular structure. The thickness of the films was measured by profilometry. Surface wettability was assessed from contact angle measurements using an automated goniometer. The morphology of the samples was inspected by secondary electrons micrographs acquired using a scanning electron microscope while the mechanical properties of the systems were examined by nanoindentation. The oxidation treatment performed on the substrate surface prior to deposition improve the corrosion resistance of the samples. The total corrosion resistance increases six orders of magnitude when carbon steel was coated with a quaternary gradual coating of only 2 μm. Laboratory of Technological Plasmas (LaPTec) São Paulo State University (UNESP) Science and Technology Institute of Sorocaba (ICTS), Av. Três de Março, 511 Department of Chemistry University of Bari Aldo Moro, Via Orabona 4 Laboratory of Technological Plasmas (LaPTec) São Paulo State University (UNESP) Science and Technology Institute of Sorocaba (ICTS), Av. Três de Março, 511 FAPESP: 2012/14708-2 FAPESP: 2013/05012-7 FAPESP: 2014/24707-9

To overcome challenges for manufacturing of modern smart medical plastic parts by injection molding, e.g. for active implants, the optimization of the interface between electronics and the polymer component concerning adhesion and diffusion behavior is crucial. Our results indicate that a nano-sized SiOxCyHz layer formed by plasma-enhanced chemical vapour deposition (PE-CVD) via open air atmospheric pressure plasma jet (APPJ) and by use of a hexamthyldisiloxane (HMDSO) precursor can form a non-corrosive, anti-permeable and biocompatible coating. Due to the open air character of the APPJ process an inline coating before overmolding could be an easy applicable method and a promising advancement.

International audience; This work aims at studying the impact of silane-based coatings, generated by atmospheric pressure plasma spraying (APPS) of a liquid precursor (hexamethydisiloxane – HMDSO), on dairy antifouling and antibacterial properties of food-grade 316L stainless steel. The influence of the manufacturing parameters (precursor flow rate, nozzle-to-substrate distance and scanning speed) on the coatings properties was investigated using a wide range of characterization techniques (drop shape analysis, X-Ray Mappings, Scanning Electron Microscopy, Fourier-Transformed Infrared Spectroscopy, Atomic Force Microscopy). Coating’s roughness in particular was shown to strongly increase when precursor flow rate increases. A pilot pasteurizer, fed with a model foulant solution (whey protein and calcium), allowed performing two consecutive industrial-like isothermal dairy fouling tests, revealing the promising anti-fouling properties of the HMDSO-coated steel. A fouling reduction of up to 90% compared to bare stainless steel was achieved after first cycle for all samples. The second fouling run allowed to select the best-performing sample, which kept the same antifouling properties as in the first test. Its mechanism of action was investigated, which revealed that a nanostructured, Si-O-Si rich surface was efficient to prevent isothermal dairy fouling. The adhesion of the pathogenic bacterium Staphylococcus aureus also proved to be impacted by this plasma coating, with a significant decrease of adhered cells (−30% compared to native stainless steel).

Made available in DSpace on 2018-12-11T17:30:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-02-15 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Films were produced on stainless-steel substrates by radiofrequency Plasma Enhanced Chemical Vapor Deposition (RF-PECVD) of mixtures containing 70% hexamethyldisiloxane, 20% oxygen and 10% argon. While the plasma excitation power was varied from 15 to 75 W, the deposition time and total gas pressure were kept constant at 1800 s and 8.0 Pa, respectively. The influences of the plasma power on the plasma kinetics and the ion bombardment of the growing film are discussed. Film composition and chemical structure were determined using X-ray photoelectron- and infrared reflectance-absorbance spectroscopy, respectively. Profilometry was used to measure the thicknesses of the resulting layers. The root mean square roughness was evaluated from surface topographic profiles acquired by atomic force microscopy. Scanning electron microscopy and energy dispersive spectroscopy were employed to evaluate the morphology and elemental composition of the coatings. Electrochemical impedance spectroscopy and potentiodynamic polarization tests were used to derive the corrosion resistance of the samples to a saline solution. Substantial changes in the material structure and progressive increases in film thickness were observed with increasing applied power. The resulting material was an organosilicon layer composed of Si[sbnd]O backbones surrounded by methyl groups, very similar to conventional polydimethylsiloxane. Increases in the proportions of Si[sbnd]O and methylsilyl groups in the structure were observed at greater plasma excitation powers, indicating densification of the structure owing to greater ion bombardment. The surface morphology and roughness were also dependent on the treatment power. Independently of the deposition conditions, application of the film increased the corrosion resistance of the stainless steel. A 10,000-fold elevation in the total system resistance under electrochemical testing was achieved for the film prepared with the greatest ion bombardment intensity. Film thickness was observed to be a key parameter but the coating structure had a major effect on this result. Laboratory of Technological Plasmas UNESP Brazilian Bioethanol Science and Technology Laboratory CTBE Department of Materials Engineering UNICAMP Laboratory of Technological Plasmas UNESP FAPESP: 2010/12240-8 FAPESP: 2012/14708-2 FAPESP: 2014/21594-9 CNPq: 301622/2012-4 CNPq: 302446/2012-5

Made available in DSpace on 2020-12-12T02:36:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 The possibility of controlling the density of organosilicon films was investigated by tuning the plasma activation degree without providing extra energy to the structure, as usually reported in the literature. For this purpose, thin films were deposited in plasmas fed with hexamethyldisiloxane/Ar mixtures at a total pressure of 9.5 Pa. The power of the radiofrequency excitation signal, P, ranged from 50 to 300W to alter the average energy of the plasma species while the electrical configuration was chosen to avoid direct ion bombardment of the growing films. In this way, it was possible to evaluate the effect of P on the film properties. Thickness and deposition rate were derived from profilometry data. X-ray energy dispersive and infrared spectroscopies were, respectively, applied to analyze the chemical composition and molecular structure of the layers. Surface topography and roughness were determined by atomic force microscopy while nanoindentation was used to evaluate the mechanical properties of the films. From electrochemical impedance spectroscopy the total resistance to the flow of electrolyte species was derived. The main alteration observed in the structure with changing P is related to the proportion of the methyl functional which remains connected to the Si backbone. Chain crosslinking and film density are affected by this structural modification induced by homogeneous and heterogeneous plasma reactions. The density increase resulted in a film with hardness comparable to that of the silica and more resistant to the permeation of oxidative species, but preserving the organosilicon nature of the structure. Laboratory of Technological Plasmas (LaPTec) São Paulo State University (UNESP) Science and Technology Institute of Sorocaba (ICTS), Av. Três de Março, 511 Laboratory of Technological Plasmas (LaPTec) São Paulo State University (UNESP) Science and Technology Institute of Sorocaba (ICTS), Av. Três de Março, 511

This study reports on the deposition of a hydrophobic coating on polyurethane (PU)-based synthetic leather through a plasma polymerization method and investigates the hydrophobic behavior of the plasma-coated substrate. The silicon compound of hexamethyldisiloxane (HMDSO), inactive gas argon (Ar), and toluene were used to impart surface hydrophobicity to a PU-based substrate. Surface hydrophobicity was analyzed by water contact angle measurements. Surface hydrophobicity was increased by deposition of compositions of 100% HMDSO, 3:1 HMDSO/toluene, and 1:1 HMDSO/toluene. Optimum conditions of 40 W, 30 s plasma treatment resulted in essentially the same initial contact angle results of approximately 100 for all three treatment compositions. The initial water contact angle for untreated material was about 73. A water droplet took 1800 s to spread out on the plasma-treated sample after it had been placed on the sample surface. An increase in plasma power also led to a decrease in contact angle, which may be attributed to oxidization of HMDSO during plasma deposition. XPS analysis showed that plasma polymerization of HMDSO/toluene compositions led to a significant increase in atomic percentage of Si compound responsible for the hydrophobic surface. The easy clean results for the treated and untreated PU-based synthetic leather samples clearly showed that the remaining stain on the plasma-polymerized sample was less than that of untreated sample. The plasma-formed coating was both hydrophobic and formed a physical barrier against water and stain. © 2013 American Coatings Association & Oil and Colour Chemists' Association.

The development of thermoplastic materials based on starch has become a promising alternative for reducing plastic waste. To this end, plasma treatments were used to enhance the hydrophobicity of cornstarch films. Cornstarch films plasticized using glycerol and distilled water were prepared by casting. A surface modification method was employed using different precursor gases, HMDSO and SF(6), and a combined treatment using HMDSO followed by SF(6) (HMDSO/SF(6)) and then the reverse, using SF(6) first followed by HMDSO (SF(6)/HMDSO). The results indicated that the induced surface morphology determines the contact angle. It was observed that all films became hydrophobic, and films that were initially treated with SF(6) showed the greatest hydrophobicity if no further coating was applied, or if the treated surface was further coated using HMDSO. Under both of these treatment conditions the contact angle was greater than 110°.

The mass sensitivity of thin aluminum nitride (AlN) film S0 Lamb wave resonators is theoretically and experimentally studied. Theoretical predictions based on modal and finite elements method analysis are experimentally verified. Here, two-port 888 MHz synchronous FPARs are micromachined and subsequently coated with hexamethyl-disiloxane(HMDSO)-plasma-polymerized thin films of various thicknesses. Systematic data on frequency shift and insertion loss versus film thickness are presented. FPARs demonstrate high mass-loading sensitivity as well as good tolerance towards the HMDSO viscous losses. Initial measurements in gas phase environment are further presented. VR "Thin Film Guided Microacoustic Waves in Periodical Systems: Theory and Applications"

HMDSO plasma polymer films are known to reduce the resulting surface free energy and the permeation rate of water vapour and oxygen through the treated polymer substrates. In this work, plasma polymer films were deposited from hexamethyldisiloxane (HMDSO) on polyethylene terephthalate surfaces under different operating conditions and the resulting surface properties were investigated. The structure and bondings in the deposited films were studied by means of IR spectroscopy. The thickness of the deposited films was deduced observing images acquired with a focused ion beam (FIB). Hydrophobic performances were investigated by means of water droplet contact angle measurements. Correlation between operating deposition conditions and resulting structure and surface properties of the films were also discussed.

In this work plasma polymerized coatings for anti-pilling purposes were deposited on knitted wool fabrics by means of a capacitively coupled RF discharge reactor using hexamethyldisiloxane as precursor. Their resistance to dry and wet cleaning was investigated and compared to that of a wet chemically deposited coating. Different gas mixtures and pre-treatment steps were tested to adjust the plasma process and to improve the film adhesion. An evaluation of the silica-like coatings behaviour to the washing stresses was performed by means of Fourier transform infrared and x-ray photoelectron spectroscopy. Anti-pilling performances of untreated, plasma-treated, and wet chemically treated wool fabrics were assessed.

Thin film chemical vapour deposition technique has been used for more than 50 years. Introducing organosilicones as precursors, e.g. hexamethyldisiloxane (HMDSO) or tetraethylorthosilicate (TEOS), brought new possibilities to this method. Barrier properties of thin films have become an important issue, especially for army and emergency services as well as for food and drink manufacturers. Our work is focused on protective HMDSO thin films for encapsulating cleaned archaeological artefacts, preventing the corrosion from destroying these historical items. Thin films are deposited via plasma enhanced chemical vapour deposition (PECVD) technique using low pressure capacitively coupled plasma in flow regime. Oxygen transmission rate (OTR) measurement was chosen as the most important one for characterization of barrier properties of deposited thin films. Lowest OTR reached for 50 nm thin film thickness was 120 cm3 m-2 atm-1 day-1. Samples were also analyzed by Fourier Transform Infrared Spectrometry (FTIR) to determine their composition. Optical emission spectra and thin film thickness were measured during the deposition process. We optimized the deposition parameters for barrier layers by implementation of pulsed mode of plasma and argon plasma pre-treatment into the process. Chemická depozice z plynné fáze se používá pro přípravu tenkých vrstev už více než 50 let. Použití organokřemičitanů jako prekurzorů, např. hexamethyldisiloxanu (HMDSO) nebo tetraethoxysilanu (TEOS), přineslo této metodě nové možnosti. Bariérové vlastnosti tenkých vrstev se staly velmi aktuálním tématem, zejména pro armádu a bezpečnostní složky stejně tak jako pro výrobce potravin a nápojů. Tato práce je zaměřena na ochranné tenké vrstvy na bázi HMDSO pro zapouzdření očištěných archeologických nálezů. Vrstvy by měly nálezy chránit před korozí, která by mohla tyto artefakty zničit. Tenké vrstvy byly deponovány pomocí chemické depozice z plynné fáze iniciované plazmatem (PECVD) za použití nízkotlakého kapacitně vázaného plazmatu v průtočném režimu. Měření rychlosti prostupu kyslíku (OTR) bylo zvoleno jako nejdůležitější pro charakterizaci bariérových vlastností tenkých vrstev. Nejnižší dosažené OTR pro vrstvy o tloušťce 50 nm bylo 120 cm3 m-2 atm-1 den-1.Vzorky byly rovněž analyzovány infračervenou spektrometrií za účelem zjištění složení tenké vrstev. Optická emisní spektra a tloušťky vrstev byly měřeny v průběhu depozice. Podařilo se nám optimalizovat depoziční proces pro bariérové vrstvy implementací pulzního módu plazmatu a předčištění vzorků před depozicí argonovým plazmatem.

The variation of power, pressure and O2/HMDSO ratio in an RF plasma was carried out to examine deposition rates and to optimize SiOx film properties for the coating of polymers. The deposition rate can mainly be increased with monomer gas flow, whereas it is independent of pressure. Pure HMDSO plasmas reveal different internal conditions and deposition rates compared to gas mixtures of O2 and HMDSO. Empirically obtained deposition models for the used symmetrical plasma reactor are given. Investigations on the three-dimensional (3D) uniformity of quartz-like coatings on polycarbonate blocks with and without recesses were performed. The deposition rate depends on the dimensions of the 3D-formed parts when depositing in front of the RF electrode. A higher pressure and use of power modulation can improve the coating uniformity in fissures.

In situ Fourier transform infrared spectroscopy was used to study the powder formation of hexamethyldisiloxane/O-2 plasmas. The spectra show that oxygen plays an important role at the beginning of the process. A large amount of oxygen is responsible for intense powder formation. The admixture of inert or non-reactant gases, such as AT or N-2, into the plasma promotes polymerization of the monomer. The formation of the particulates, the evolution of their size, and chemical characteristics give evidence of a multistep growth process. The size, as well as the production rate, undergoes a reduction once the Ar or N-2 amount is increased in the plasma admixture.