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Made available in DSpace on 2020-12-12T00:57:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-01 Abstract: Dielectric Barrier Discharge (DBD) can be used to produce a large volume of non-thermal plasma at atmospheric pressure. Such plasmas are sources of highly reactive species (radicals, ozone, atoms, ions and excited molecules). Due to its characteristics, the DBD plasma can be applied for the pretreatment of lignocellulosic materials, in order to extract lignin that prevents the access to remained fermentable sugars in the biomass. In this context, an alternative method for pretreatment of lignocellulosic material in an in-liquid DBD plasma reactor using non-contact electrodes, working with atmospheric air, has been proposed. After the pretreatment, the solids were washed and submitted to enzymatic hydrolysis with a commercial enzyme complex, at 10 FPU/g of pretreated biomass and 50 g/L solids concentration (dry basis), for 72 h. The release of fermentable sugars was measured, comparing the samples obtained with and without plasma treatment. The highest sugar release was achieved using the plasma-in-liquid pretreatment in a single step, with glucose and xylose yields of 51.3 and 38.5%, respectively, after enzymatic hydrolysis. Thus, an effective pretreatment was developed to be applied to biomass such as: corn cob, sugarcane bagasse, bamboo, eucalyptus, etc., in order to reduce the environmental impact and, at the same time, produce biofuels. Graphic Abstract: [Figure not available: see fulltext.] Technological Institute of Aeronautics LPP/ITA IP&D/UNIVAP University of Paraiba Valley Brazilian Bioethanol Science and Technology Laboratory Department of Bioprocesses and Biotechnology College of Agricultural Sciences São Paulo State University (UNESP) Science and Technology Institute - Biochemical Engineering Group - Unifesp Department of Bioprocesses and Biotechnology College of Agricultural Sciences São Paulo State University (UNESP)

Hollow cathode discharge (HCD) is widely used in material processing and plasma emission spectroscopy due to several advantages over other plasma sources. Basically, the HCD consists of a cathode with a hollow structure (cavity, hole, or parallel faces) and an anode of arbitrary shape. In this investigation, experimental studies on low-pressure plane-parallel HCD operated at different process conditions are reported. Herein, we investigate the dependence of the discharge current on the product of the gas pressure and inter-cathode distance (pD). In addition, the electron temperature and density were inferred from the current-voltage characteristics of a single cylindrical Langmuir probe positioned between the cathodes, on the discharge axis. The measurements were carried out at different gas pressures, magnetic field intensities, working gases, inter-cathode distances, cathode materials, and discharge voltages. The results showed that, at different gas pressures, the maximum discharge current (Id,max) is not only a function of the product pD, but also of the pressure itself. Application of a uniform longitudinal magnetic field improved plasma confinement between cathodes, leading to a substantial increase in Id,max in most of the situations considered in this study. However, for oxygen discharge, a strong discharge current reduction after the application of the magnetic field was observed. In relation to the Langmuir probe studies, it was observed that the uniform longitudinal magnetic field reduced the electron temperature, but this behavior depends strictly on pD. The typical values of electron density and electron temperature in the case of the nitrogen discharge were ne = 1017 m−3 and Te = 2.5 eV, respectively. Finally, our experiments showed that the pD range for hollow cathode effects was between 0.2–5 Pa m.

The grid-assisted magnetron sputtering is a variation of the magnetron sputtering commonly used for thin film deposition. In this work, Langmuir probe measurements were performed in such a system by using the grid under two basic and practical electrical conditions, i.e., floating and grounded. The results show that grounding the grid leads to an enhancement of the plasma confinement and to increases in both floating and plasma potential, as inferred from the probe characteristics. The grounded grid drains electrons from the plasma, acting as an auxiliary anode and reducing the plasma diffusion toward the chamber walls. For the same discharge current, the improved confinement results in a lower electron temperature when compared to floating condition, although the electron densities are comparable in both cases.

Camphor was incorporated in diamond-like carbon (DLC) films to prevent the Candida albicans yeasts fouling on polyurethane substrates, which is a material commonly used for catheter manufacturing. The camphor:DLC and DLC film for this investigation was produced by plasma enhanced chemical vapor deposition (PECVD), using an apparatus based on the flash evaporation of organic liquid (hexane) containing diluted camphor for camphor:DLC and hexane/methane, mixture for DLC films. The film was deposited at a low temperature of less than 25°C. We obtained very adherent camphor:DLC and DLC films that accompanied the substrate flexibility without delamination. The adherence of camphor:DLC and DLC films on polyurethane segments were evaluated by scratching test and bending polyurethane segments at 180°. The polyurethane samples, with and without camphor:DLC and DLC films were characterized by Raman spectroscopy, scanning electron microscopy, atomic force microscopy, and optical profilometry. Candida albicans biofilm formation on polyurethane, with and without camphor:DLC and DLC, was assessed. The camphor:DLC and DLC films reduced the biofilm growth by 99.0% and 91.0% of Candida albicans, respectively, compared to bare polyurethane. These results open the doors to studies of functionalized DLC coatings with biofilm inhibition properties used in the production of catheters or other biomedical applications.

Many strategies have been developed for the synthesis of silicon carbide (SiC) thin films on silicon (Si) substrates by plasma-based deposition techniques, especially plasma enhanced chemical vapor deposition (PECVD) and magnetron sputtering, due to the importance of these materials for microelectronics and related fields. A drawback is the large lattice mismatch between SiC and Si. The insertion of an aluminum nitride (AlN) intermediate layer between them has been shown useful to overcome this problem. Herein, the high-power impulse magnetron sputtering (HiPIMS) technique was used to grow SiC thin films on AlN/Si substrates. Furthermore, SiC films were also grown on Si substrates. A comparison of the structural and chemical properties of SiC thin films grown on the two types of substrate allowed us to evaluate the influence of the AlN layer on such properties. The chemical composition and stoichiometry of the samples were investigated by Rutherford backscattering spectrometry (RBS) and Raman spectroscopy, while the crystallinity was characterized by grazing incidence X-ray diffraction (GIXRD). Our set of results evidenced the versatility of the HiPIMS technique to produce polycrystalline SiC thin films at near-room temperature by only varying the discharge power. In addition, this study opens up a feasible route for the deposition of crystalline SiC films with good structural quality using an AlN intermediate layer.

Titanium dioxide (TiO2) and aluminum oxide (Al2O3) coatings have been investigated in a wide range of bio-applications due to their biodegradation and biocompatibility properties, that are key parameters for their use in the food packaging and biomedical devices fields. The present study evaluates and compares the electrochemical behavior of the non-coated, commercial resin-coated, TiO2-coated and Al2O3-coated aluminum in commercial beer electrolyte. For this, TiO2 and Al2O3 thin films were deposited on aluminum (Al) substrates using atomic layer deposition (ALD). The evaluation of the corrosion barrier layer properties was performed by linear sweep voltammetry (LSV) during 10 min and electrochemical impedance spectroscopy (EIS). In addition, profilometry, grazing incidence X-ray diffractometry (GIXRD), scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FT-IR) analyses were performed to investigate the physical and chemical properties of the pristine and / or corroded samples. TiO2 and Al2O3 films presented an amorphous structure, a morphology that follows Al substrate surface, and a thickness of around 100 nm. Analysis of LSV data showed that ALD coatings promoted a considerable increase in corrosion barrier efficiency being 86.3% for TiO2-coated Al and 80% for Al2O3-coated Al in comparison with 7.1% of commercial resin-coated Al. This is mainly due to the lower electrochemical porosity, 11.4% for TiO2-coated Al and 20.4% for Al2O3-coated Al in comparison with 96% of the resin-coated Al, i.e. an increase of up to twofold in the protection of Al when coated with TiO2 compared to Al2O3. The EIS results allow us to complement the discussions about the reduced corrosion barrier efficiency of the Al2O3 film for beer electrolyte once SEM and FT-IR analyzes did not show drastic changes in both investigated ALD films after the corrosion assays. The above results indicate that ALD TiO2 and Al2O3 films may be a viable alternative to replace the synthetic resin coatings frequently used in aluminum cans of use in the food industry.

Many strategies have been developed for the synthesis of silicon carbide (SiC) thin films on silicon (Si) substrates by plasma-based deposition techniques, especially plasma enhanced chemical vapor deposition (PECVD) and magnetron sputtering, due to importance of these materials for microelectronics and related fields. A drawback is the large lattice mismatch between SiC and Si. The insertion of a thin aluminum nitride (AlN) buffer layer between them has been shown useful to overcome this problem. Herein, the high-power impulse magnetron sputtering (HiPIMS) technique was used to grow SiC thin films on AlN/Si substrates. Furthermore, the SiC films were also grown on Si substrates. Comparisons of the structural and chemical properties of SiC thin films grown on the two types of substrates allowed us to evaluate the influence of AlN buffer layer on such properties. The chemical composition and stoichiometry of the samples were investigated by Rutherford backscattering spectrometry (RBS) and Raman spectroscopy, while the crystallinity was characterized by grazing incidence X-ray diffraction (GIXRD). Our set of results evidenced the versatility of HiPIMS technique to produce polycrystalline SiC thin films at near room temperature only varying the discharge power. In addition, this study opens up a feasible route for the deposition of crystalline SiC films with a good structural quality using AlN buffer layer.

The chemical, structural, morphological, and optical properties of Al-doped TiO2 thin films, called TiO2/Al2O3 nanolaminates, grown by plasma-enhanced atomic layer deposition (PEALD) on p-type Si &lt, 100&gt, and commercial SLG glass were discussed. High-quality PEALD TiO2/Al2O3 nanolaminates were produced in the amorphous and crystalline phases. All crystalline nanolaminates have an overabundance of oxygen, while amorphous ones lack oxygen. The superabundance of oxygen on the crystalline film surface was illustrated by a schematic representation that described this phenomenon observed for PEALD TiO2/Al2O3 nanolaminates. The transition from crystalline to amorphous phase increased the surface hardness and the optical gap and decreased the refractive index. Therefore, the doping effect of TiO2 by the insertion of Al2O3 monolayers showed that it is possible to adjust different parameters of the thin-film material and to control, for example, the mobility of the hole-electron pair in the metal-insulator-devices semiconductors, corrosion protection, and optical properties, which are crucial for application in a wide range of technological areas, such as those used to manufacture fluorescence biosensors, photodetectors, and solar cells, among other devices.

The effects of a non-steady state plasma discharge on flammability limits and flame structure of air–natural gas mixtures are investigated. As plasma power increases, flame structure is changed and flammable range is extended. In the absence of a visible flame, a higher hydrogen production is observed, revealing that the discharge is a source of molecular hydrogen. The reduction on hydrogen production inside the flammable range suggests a burning of hydrogen in the flame.

The success of the ozone sterilization process depends on some variables: gas concentration, temperature and humidity. When these variables are monitored and stored remotely, the data redundancy and operational safety are increased. For this purpose, the use of wireless sensor networks is a technological alternative with benefits. This paper studies the implementation and analysis of data from a wireless sensor network configuration in monitoring the ozone sterilization process, where critical variables can be monitored and their records stored away. Additionally the Received Signal Strength Indication is checked to serve as the network performance indicator. The result showed that the wireless sensor network sensors not only improved the monitoring process as it allowed redundancy records, collaborating with process safety.

TiO 2 thin films were deposited on FTO glass by ALD technique using titanium tetrachloride and water as precursors. A thorough investigation of the TiO 2 /FTO film properties was carried on, varying the process temperature in the range (150–400) °C and keeping fixed at 2000 the number of reaction cycles. TiO 2 films were also grown on Si(100) and glass substrates for some comparisons. RBS, GIXRD, Raman spectroscopy, SEM, AFM and spectrophotometry analyses were performed to investigate the growth per cycle (GPC), composition, structure, morphology and optical properties of the as-deposited films. Through elemental composition analysis was possible to observe that amorphous and rutile films have a deficiency of oxygen. Pure-anatase TiO 2 films can be obtained at process temperatures in the range 250–300 °C, while for temperatures higher than 300 °C rutile phase starts to appear which turns to unique crystalline phase at temperature higher than 350 °C. AFM results shows that FTO substrate tends to restrict the size of crystallite growth, and therefore, the grain size in TiO 2 film. The optical parameters of ALD TiO 2 films showed very dependent of the change of crystal phase and roughness, allowing to obtain films with distinct properties for dye-sensitized and perovskite-based solar cells.

Titanium dioxide (TiO2) and aluminum oxide (Al2O3) thin films, with thicknesses around 100 nm, were grown on commercial pure- and resin-coated Al substrates using the atomic layer deposition (ALD). A comprehensive and comparative study of corrosion protection was carried out by linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) measurements for a set of six samples: two reference samples (Al-bare and Al-resin), and four ALD coated samples ( Al-TiO2, Al-Al2O3, Al-resin-TiO2, and Al-resin-Al2O3). The LSV and EIS results display good mutual agreement, indicating a higher protection efficiency of all ALD-coated samples after immersion in NaCl. When compared to Al-bare, all ALD coated samples (TiO2 or Al2O3) showed a corrosion inhibition enhancement factor of 99%. Besides, our results demonstrated that Al-resin+Al2O3 has 24.95% and 33.40% more corrosion inhibition than Al-Al2O3 and Al-resin, respectively. EIS data were fitted by an equivalent electric circuit (EEC). The Nyquist and Bode plots from the experiments showed that ALD films are a potential candidate for altering/improving commercial resin-coated Al cans.

In this paper, we report the plasma-enhanced atomic layer deposition (PEALD) of TiO2 and TiO2/Al2O3 nanolaminate films on p-Si(100) to fabricate metal-oxide-semiconductor (MOS) capacitors. In the PEALD process, we used titanium tetraisopropoxide (TTIP) as a titanium precursor, trimethyl aluminum (TMA) as an aluminum precursor and O2 plasma as an oxidant, keeping the process temperature at 250 &deg, C. The effects of PEALD process parameters, such as RF power, substrate exposure mode (direct or remote plasma exposure) and Al2O3 partial-monolayer insertion (generating a nanolaminate structure) on the physical and chemical properties of the TiO2 films were investigated by Rutherford backscattering spectroscopy (RBS), Raman spectroscopy, grazing incidence X-ray diffraction (GIXRD), and field emission scanning electron microscopy (FESEM) techniques. The MOS capacitor structures were fabricated by evaporation of Al gates through mechanical mask on PEALD TiO2 thin film, followed by evaporation of an Al layer on the back side of the Si substrate. The capacitors were characterized by current density-voltage (J-V), capacitance-voltage (C-V) and conductance-voltage (G-V) measurements. Our results indicate that RF power and exposure mode promoted significant modifications on the characteristics of the PEALD TiO2 films, while the insertion of Al2O3 partial monolayers allows the synthesis of TiO2/Al2O3 nanolaminate with well-spaced crystalline TiO2 grains in an amorphous structure. The electrical characterization of the MOS structures evidenced a significant leakage current in the accumulation region in the PEALD TiO2 films, which could be reduced by the addition of partial-monolayers of Al2O3 in the bulk of TiO2 films or by reducing RF power.

Made available in DSpace on 2018-12-11T17:21:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-09-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Metallic materials are the most widely used for orthopedic applications and, their corrosion resistance is one of the main prerequisites for avoiding impairment of the material properties due to degradation. Ti-6Al-4V is one of the main medical titanium alloys. However, for permanent implant applications, this alloy may cause toxic effect due to release of vanadium and aluminum. Nanolaminates of alternatively ordered thin films of transition metal oxides with nanoscale thickness are known to have distinct properties of a single layer film. Atomic layer deposition (ALD) is a promising method for fabrication of thin sealing coatings for corrosion protection. These films can also be used as in vivo sensors to antedate the detection of diseases such as cancer, to inform the best treatments, and to understand the response to therapies. The ideal in vivo sensor should be non-toxic, biocompatible, stable, and very sensitive. In this work, TiO2/Al2O3 nanolaminate, Al2O3 and TiO2 thin films were deposited on Ti-6Al-4V substrates by using ALD and their structure, adhesion and tribocorrosion properties were analyzed. The tribocorrosion tests were performed in Ringer's solution. The coatings showed to protect the sample surface evidenced by the increase on the OCP both in static mode and in dynamic mode. The TiO2/Al2O3 nanolaminates presented lower friction coefficient. Plasma and Processes Laboratory Aeronautics Institute of Technology (ITA) Centro de Ciência e Tecnologia de Plasmas e Materiais (PlasMat) Nanotechnology and Plasmas Processes Laboratory (NanoTecPlasma) University of Paraíba Valley (UNIVAP) University Center SOCIESC - UNISOCIESC São Paulo State University (UNESP) Faculty of Sciences of Bauru Physics Department Brazilan Branch of the Institute of Biomaterials Tribocorrosion and Nanomedicine (IBTN/Br) Center for MicroElectroMechanical Systems (CMEMS) Universidade do Minho, Azurém São Paulo State University (UNESP) Faculty of Sciences of Bauru Physics Department CAPES: 005/2014 Capes/ITA FAPESP: 2003/13373-8 FAPESP: 2004/10856-0 FAPESP: 2008/05533-9 FAPESP: 2011/50773-0 CNPq: 313280/2014-2

Titanium dioxide (TiO( 2 ) thin films were deposited on conductive (titanium and fluorine tin oxide glass), insulant (mica, cover glass and thermal SiO( 2 thin film on silicon) and semiconductive (silicon (100) and 4H-SiC) substrates by atomic layer deposition (ALD) technique. The metal and ligand precursors used were titanium tetrachloride and water, respectively. Grazing incidence x-ray diffraction (GIXRD) analysis was performed to investigate the dependence of crystalline phase of the as-deposited thin films on different substrates for process temperatures ranging from $150-450 ^{\circ}\mathrm{C}$. Results indicate that the ALD TiO( 2 crystalline phase is dependent on the substrate nature which modifies the required temperature for phase change, i.e. from amorphous to anatase to rutile. For example, for conductive substrates the temperature for formation of rutile phase is around $350 ^{\circ}\mathrm{C}$ while for semiconductor substrates it was observed only from $400 ^{\circ}\mathrm{C}$. By other hand, when the substrate has an amorphous structure there is not a common rule, i.e. for mica and thermal SiO( 2 thin film on silicon only anatase phase was formed in all temperature range investigated while, for cover glass, it was possible to observe all stages of TiO( 2 phase change, highlighting the formation of brookite phase for temperatures between 300 and $350 ^{\circ}\mathrm{C}$. Moreover, it is shown that rutile phase can be obtained, in pure phase, at temperatures higher than $400 ^{\circ}\mathrm{C}$, however only for glass and titanium substrates. These results allow us to infer that less expensive Ti thin film could act as a good seed layer for growth of good quality rutile TiO( 2 phase, by using ALD process on Si substrate and using precursors such as TiCl 4 and H 2 O.

This article reports a novel and efficient method to synthesize graphene by thermal decomposition process. In this method, silicon carbide (SiC) thin films grown on Si(100) wafers with an AlN buffer layer were used as substrates. A CO2 laser beam heating without vacuum or controlled atmosphere was applied for SiC thermal decomposition. The physical, chemical, morphological, and electrical properties of the laser-produced graphene were investigated for different laser energy densities. The results demonstrate that graphene was produced in form of small islands with quality, density and properties depending on the applied laser energy density. Furthermore, the produced graphene exhibits a sheet resistance characteristic similar to graphene grown on mono-crystalline SiC wafer, which indicates its potential for electronic device applications.

Atomic layer deposition (ALD) is a surface reaction limited method of depositing conformal, pinhole-free, and high-quality ultrathin films with uniform thickness onto planar or three-dimensional structures. Research on ALD is contributing to progress in the synthesis of high-efficient and low-cost ceramic nanomaterials for a sustainable future based on clean energy. In the search for sustainable energy materials, ultrathin ALD metal oxide films emerge as a promising class that combines functional properties and atomic precision that can be applied in energy conversion and storage systems. An outstanding application for these materials is as an electrolyte in fuel cells, because ceramic membranes produced by ALD exhibit improved surface exchange kinetics and reduced ohmic losses, consequently enhancing fuel cell performance at a low operating temperature. This chapter assesses the overall prospects of ultrathin metal oxide films on fuel cells based on requirements such as the material, efficiency, and development perspectives. It focuses on the key advantages that the use of ALD metal oxide films can offer to existing fuel cell technologies. A brief overview is presented on ultrathin metal oxide films for fuel cells outlining potential future opportunities based on three points: the ALD film process, material properties, and membranes for solid oxide fuel cell (SOFC) development. Because the work in this field is increasing rapidly, the main goal is to assist researchers and students to better understanding basic processes involved in the development of SOFC devices, which provide an attractive alternative to conventional thermal energy conversion by combusting fossil-derived fuels.

The effect of process temperature and reaction cycle number on atomic layer-deposited TiO2 thin films onto Si(100) using TiCl4 and H2O precursors was investigated in order to discuss the correlation between the growth per cycle (GPC), film structure (crystallinity), and surface roughness as well as the dependence of some of these properties with gas phase environment such as HCl by-product. In this work, these correlations were studied for two conditions: (i) process temperatures in the range of 100–500 °C during 1000 reaction cycles and (ii) number of cycles in the range of 100–2000 for a fixed temperature of 250 °C. To investigate the material properties, Rutherford backscattering spectrometry (RBS), grazing incidence X-ray diffraction (GIXRD), and atomic force microscopy (AFM) techniques were used. Mass spectrometry technique was used to investigate the time evolution of gas phase species HCl and H2O during ALD process. Results indicate that the GPC does not correlate well with film crystallinity and surface roughness for the evaluated process parameters. Basically, the film crystallinity relies solely on grain growth kinetics of the material. This occurs due to higher HCl by-product content during each purge step. Furthermore, for films deposited at variable cycle number, the evolution of film thickness and elemental composition is altered from an initial amorphous structure to a near stoichiometric TiO2-x and, subsequently, becomes fully stoichiometric TiO2 at 400 cycles or above. At this cycle value, the GIXRD spectrum indicates the formation of (101) anatase orientation.

Gliding arc discharges have been utilized in plasma-assisted combustion processes, among various other applications, due to their chemical properties. In this paper, an ac-powered gliding arc discharge having a reverse vortex flow configuration (tornado) was experimentally studied in air and in air–natural gas mixtures. A new method is proposed for the generalization of power characteristics of this type of discharge, based on similarity theory. The application of this method is demonstrated to be efficient for gliding arc discharges with tornado effect, using dimensional numbers. Regression dependences for discharges in air and in mixtures of air and natural gas were obtained in a form of simple power function equations (using the concept of equivalence ratio), which can be applied for the design of different gliding arc equipments for plasma-assisted combustion and related technologies.

In solar energy harvesting research, there is growing interest in the study of photoelectrochemical (PEC) properties of the following classes of semiconductor materials: metal oxides and silicon-based compounds. The motivation is that such materials are being successfully used as photoelectrode in PEC cells. Special attention has been given to the wide band gap materials. This review discusses, from the material science perspective, the recent literature relating to two wide band gap semiconductor materials: one metal oxide, titanium dioxide (TiO 2 ), and one silicon-based compound, silicon carbide (SiC). Emphasis is placed on TiO 2 and SiC thin films for PEC applications. Materials characteristics, synthesis methods and recent photocatalytic applications are presented. Finally, the interesting effect of the efficiency increase of PEC devices developed from a hetero-junction of TiO 2 and SiC is discussed.

Scratch testing is a fast and effective method for the measurement of critical loads in order to determine the adhesion properties of coatings and their behavior in tribological applications. Kelvin probe force microscopy (KPFM) provides a means of monitoring electrostatic charging on the surfaces of materials. In this paper, we describe the use of a combination of scratch testing and KPFM analysis to evaluate the electrostatic effect induced by silver nanoparticles incorporated as clusters in diamond-like carbon (DLC) films, as well as its correlation with the rubbing process. KPFM was used for mapping of the potentials on the surfaces of DLC–Ag films subjected to nanoscale scratching. The procedure was also conducted at the microscale in order to analyze the way in which silver nanoparticles were spread in the track. After scratching, the track was analyzed using backscattered electrons (BSE) and energy dispersive X-ray diffraction (EDX). The BSE images highlighted bright domains of metallic nanoparticles dispersed in the amorphous coating and EDX confirmed the presence of silver nanoparticles in the scratched track. Micro Raman spectroscopy was used to check the DLC signature. The electric potentials of DLC films with and without silver nanoparticles were also analyzed. The results indicated that the incorporation of silver nanoparticles in amorphous materials could offer new option for electrostatic energy storage on the surfaces of materials.

In this work plasma-enhanced atomic layer deposition (PEALD) using trimetylaluminum (TMA) and oxygen plasma was used to deposit aluminum oxide (Al 2 O 3 ) thin film on anodic titanium dioxide (TiO 2 ) nanotube array with mean internal diameter of 100 nm. The effect of plasma power was investigated in order to found a better condition of covering of TiO 2 nanotubes for water splitting application. The reactor geometry is an asymmetric capacitive coupled (CCP) radio frequency (13.56 MHz) discharge, and the pressure investigated was fixed at 1 mbar and the discharge power varied in the range of 10-200 W. The total reaction cycle number was fixed on 200 cycles and the process temperature at $100 ^{\circ}\mathrm {C}$. These are typical conditions for PEALD process 1. SEM measurements were performed for investigate the covering process. Moreover, Raman spectroscopy was performed for investigate the structure change of material. Results indicate that the increase of RF power increase the growth rate in up to 10%, characterizing a possibility of fine adjustment of the coating of the nanotubes. SEM micrographs show that the PEALD of Al 2 O 3 were very conformal for wide range of RF power investigated, allowing to obtain a good coverage of TiO 2 nanotubes. Finally, Raman spectroscopy evidence that the increase of RF power caused a change on TiO 2 phase from amorphous to anatase.

The measurement of ion flux to the bias-electrode in contact with the plasma is an important parameter for characterization of processes assisted by energetic reactive ions [1]. However, the experimental determination of this flux is not a trivial task causing it to be theoretically estimated in most cases. In this work, the ion flux in the bias-electrode of an asymmetric capacitive discharge was estimated by three different methods: i) a non-invasive experimental method proposed by Mateev et al. Where the ion flux is estimated from a theory that uses the radio-frequency (rf) power versus V dc curve data [2]; ii) an invasive method through Langmuir probe measurement, which are determined the ion density at the sheath edge of self-polarized electrode and the electron temperature and subsequently they are replaced in the expression of ion flux: ${\Gamma _{i}}= \mathrm {n_{s}}\sqrt {\mathrm{{kT}_{e}}/\mathrm{{m}_{i}}}$ and iii) theoretically through estimates by global model based in theory presented by Thorsteinsson et al. [3]. The gases used in this investigation were the Ar and SF 6 . Also, we consider the effect of variation of gas pressure (5–100 mTorr), mass flow rate (1–100 sccm) and rf power (10–200 W). The results show a good agreement between the methods (i) and (iii) for both gases investigated. The method (ii) gives overestimated ion flux values at low powers, probably due to errors arising from the Langmuir probe ion theory used to determine the n + since at these conditions the generated plasmas presented non-Maxwellian EEDFs.

Introduction Ozonization is an alternative sterilization process for heat-sensitive medical devices. However, the side effects of this process on packaging materials should be verified. Methods Four types of commercial disposable packaging for medical devices were evaluated after undergoing ozone sterilization: crepe paper sheet, non-woven fabric sheet (SMS), medical grade paper-plastic pouch and Tyvec©-plastic pouch. For each material, the gas penetration through the microbiological barrier was measured. Other packaging properties, such as chemical composition, color, tactile and mechanical resistance, were also evaluated after sterilization, by using characterization techniques, namely microbiological indicators, infrared spectroscopy, tensile test and optical microscopy. Results All commercial disposable packaging showed good ozone penetration. Crepe paper and SMS were chemically and mechanically modified by ozone, while Tyvec© only suffered mechanical modification. Paper-plastic pouch was the packaging material which just experienced an acceptable reduction in tensile resistance, showing no variations on chemical or visual properties. Conclusion The results suggest that medical grade paper-plastic pouch is the most appropriate disposable medical device packaging to be sterilized by ozone when compared to other materials.

Os biofilmes fúngicos são uma predominante causa de infecções crônicas associadas à utilização de cateteres e próteses, conferindo resistência aos antibióticos e fatores imunológicos do hospedeiro, sendo as leveduras, do gênero Candida spp, as mais frequentemente isoladas. O plasma não-térmico, operado à pressão atmosférica, vem ganhando destaque como uma nova estratégia antimicrobiana, inclusive para erradicação de biofilmes. Este trabalho teve como objetivo avaliar a eficácia da inativação de biofilmes de Candida albicans ATCC sobre substrato de poliuretano, utilizando jatos de plasma atmosférico de 6L/min de hélio e 4L/min de ar comprimido, alternando entre sistema contínuo e pulsado, com frequência de 60Hz e distâncias de 10 a 30mm entre o bocal e substrato. Após tratamento, realizou-se a contagem das unidades formadoras de colônia e a análise morfológica da superfície do biofilme por Microscopia Eletrônica de Varredura. O melhor grupo foi o plasma de modo pulsado com distância de 30mm com redução de 92% das unidades formadoras de colônia, demonstrando ser uma tecnologia promissora para o controle de biofilmes de C. albicans.

In this work, mass spectrometry and optical emission spectroscopy techniques were used to monitor the molecular and atomic neutral species during SF6/CF4, SF6/O2 and CF4/O2 plasmas generated in a radio-frequency Hollow Cathode Reactive Ion Etching (HCRIE) reactor keeping constant the following operational conditions: total gas flow rate, gas pressure, and discharge power. The investigations were aimed to understand the chemistry behavior of plasmas generated with SF6 and CF4 mixtures or mixed separately with O2. The neutral mass spectrometry analysis showed a high concentration of gas species namely SF5+ (parent specie = SF6), SF3+ (SF4), CF3+ (CF4) and HF+ (HF) in SF6/CF4 plasmas, SF5+, SF3+, O2+ (O2), F+ (F) and HF+ in SF6/O2 plasmas and CF3+, O2+, CO2+ (CO2) and HF+ in CF4/O2 plasmas. The presence of other species was observed in quantities lower than 1% of total gas pressure. It was used the actinometry method to monitor the atomic fluorine (F) concentration during discharge operation. Higher density of F was observed in all experiments, varying from (2.8–9.5) × 1019 m−3 in SF6/CF4 plasmas, (0.2–1.7) × 1020 m−3 in SF6/O2 plasmas and (0.06–1.17) × 1020 m−3 in CF4/O2 plasmas. The addition of CF4 in SF6 plasma reduces monotonically the F concentration when compared with the SF6/O2 and CF4/O2 plasmas that promotes an increase of F for low O2 concentrations. This effect shows the importance of oxygen species in the dissociative processes of the fluorine-based plasma also for this type of plasma reactor. Moreover, it is highlighted the higher concentrations of HF in gas phase that promotes reactions paths that decrease the F species in gas/plasma phase.

The thermal decomposition of silicon carbide (SiC), with the subsequent formation of graphene, can be achieved by heating treatment. Several heating processes have been applied for this purpose by using SiC, either in form of powder particles or monocrystalline substrate. In this work, instead of using an expensive commercially available SiC wafer, a polycrystalline SiC substrate was obtained, based on powder metallurgy process, in order to explore the synthesis of graphene layers on its surface by using a CO2 laser beam as heating source. Different levels of energy density (fluence) were applied and Raman spectroscopy analyses demonstrated that graphene layers were formed on the polycrystalline SiC surface. The ratio of the integrated intensity of the D and G bands, and the crystallite size were calculated. The FWHM of the 2D band peaks are in excellent agreement with the range of values found in the literature. The samples irradiated with energy density of 138.4 J/cm2 presented lower concentration of defects and higher crystallite size, while the lowest FWHM was obtained for energy density of 188 J/cm2. The process occurred at room conditions and no gas flow was used. The results reveal a simple and cost-effective alternative for synthesis of graphene-based structures on SiC.

In this paper, the anisotropic model for the dc electric arc was expanded, which allows the obtaining of power function generalized expressions for calculating the characteristics of the electric discharge into the dc plasma torch channel without using a large number of experimental studies. The model is based on the power law approximation of temperature dependence of the plasma electrical conductivity σ with different exponents along the longitudinal and transversal coordinates. The approximation of the dependence for σ of steam plasma was obtained in simple linear forms σ = 0.221 ΔS and as the power approximation σ = 44.51 ΔS0.484 [where ΔS is increment of thermal conductivity function (TCF)]. The comparison of the obtained dependences with referenced data shows such moderate difference between the calculated approximations for σ of steam and the data of recent publications for this plasma as 15%-25% throughout the vast ranges of the plasma parameters T (temperature) and S (TCF).

Because of the scarcity of nonrenewable natural resources, such as petroleum and natural gas, the use of biofuel is needed. Gasification is a major process used to obtain renewable fuels from biomass; however, the gas cleaning system is a constraint for its broad utilization. During the pyrolysis process, a mixture of organic compounds in the gas phase is produced and must be removed from the gases before it is used in the most practical applications. In order to remove such organic compounds, which are known as tar, large, sophisticated, problematic, and expensive gas cleaning systems are added to the gasifier gas exit. Previous papers have shown that the plasma torch has the potential to destroy produced tar, being a simpler and less-expensive system than traditional gas cleaners. This work presents a qualitative and quantitative evaluation of a microwave plasma system running on tar destruction and its reforming. In order to evaluate a 1 kW microwave plasma system performance, an apparatus was develope...

Titanium dioxide (TiO2) thin films have generated considerable interest over recent years, because they are functional materials suitable for a wide range of applications. The efficient use of the outstanding functional properties of these films relies strongly on their basic characteristics, such as structure and morphology, which are affected by deposition parameters. Here, we report on the influence of plasma power and precursor chemistry on the growth kinetics, structure and morphology of TiO2 thin films grown on Si(100) by plasma-enhanced atomic layer deposition (PEALD). For this, remote capacitively coupled 13.56 MHz oxygen plasma was used to act as a co-reactant during the ALD process using two different metal precursors: titanium tetrachloride (TiCl4) and titanium tetraisopropoxide (TTIP). Furthermore, we investigate the effect of direct plasma exposure during the co-reactant pulse on the aforementioned material properties. The extensive characterization of TiO2 films using Rutherford backscattering spectroscopy, ellipsometry, x-ray diffraction (XRD), field-emission scanning electron microscopy, and atomic force microscopy (AFM) have revealed how the investigated process parameters affect their growth per cycle (GPC), crystallization and morphology. The GPC tends to increase with plasma power for both precursors, however, for the TTIP precursor, it starts decreasing when the plasma power is greater than 100 W. From XRD analysis, we found a good correlation between film crystallinity and GPC behavior, mainly for the TTIP process. The AFM images indicated the formation of films with grain size higher than film thickness (grain size/film thickness ratio ≈20) for both precursors, and plasma power analysis allows us to infer that this phenomenon can be directly related to the increase of the flux of energetic oxygen species on the substrate/growing film surface. Finally, the effect of direct plasma exposure on film structure and morphology was evidenced showing that the grid removal causes a drastic reduction in the grain size, particularly for TiO2 synthesized using TiCl4.

Introduction Various works have shown that diamond-like carbon (DLC) coatings are able to improve the cells adhesion on prosthesis material and also cause protection against the physical wear. On the other hand there are reports about the effect of substrate polishing, in evidence of that roughness can enhance cell adhesion. In order to compare and quantify the joint effects of both factors, i.e, polishing and DLC coating, a commonly prosthesis material, the Ti-6Al-4V alloy, was used as raw material for substrates in our studies of macrophage cell adhesion rate on rough and polished samples, coated and uncoated with DLC. Methods The films were produced by PECVD technique on Ti-6Al-4V substrates and characterized by optical profilometry, scanning electron microscopy and Raman spectroscopy. The amount of cells was measured by particle analysis in IMAGE J software. Cytotoxicity tests were also carried out to infer the biocompatibility of the samples. Results The results showed that higher the surface roughness of the alloy, higher are the cells fixing on the samples surface, moreover group of samples with DLC favored the cell adhesion more than their respective uncoated groups. The cytotoxity tests confirmed that all samples were biocompatible independently of being polished or coated with DLC. Conclusion From the observed results, it was found that the rougher substrate coated with DLC showed a higher cell adhesion than the polished samples, either coated or uncoated with the film. It is concluded that the roughness of the Ti-6Al-4V alloy and the DLC coating act complementary to enhance cell adhesion.

In this work is proposed the automation of a gas injection (mass flow) system in order to generate timemultiplex SF6/CH4 radiofrequency plasma applied for silicon (Si) etching process. The control of the gas injection system is important in order to better control the process anisotropy, i.e., the high-aspect-ratio of mask pattern transfer to substrate surface. In other words, this control allows the attainment of deep Si etching process. Here, the automation of the gas injection system was realized through the interface between a computer and a data acquisition board. The automation software developed allows controlling the gas flow rate switching it on and off during whole process through the use of a square waveform routine, intermittent flow, beyond the conventional condition of a fixed value for gas flow rate, continuous flow. In order to investigate the time-multiplex SF6/CH4 plasma etching of Si, the residual gas analysis was performed. The investigations were made keeping the following process parameters: flow of SF6: 10 sccm, flow of CH4: 6 sccm, 100 W rf power, wave period: 20 sec. It were monitored the partial pressure of SF+ 5 (parent neutral specie: SF6), CH+4 (CH4) and SiF+ 3 (SiF4) species as a function of time for different gas flow switching and duty cycle. The results showed that with the generation of plasma occurs a drastic change in behavior of partial pressures of SF+ 5 and CH+4 species. Moreover, it is evidenced that the interactions between the SF6 and CH4 fragments promotes a high production rate of HF molecule and consequently a decrease of atomic fluorine, mainly when plasma is on. Finally, the behavior of partial pressure of SiF+ 3 specie for alternatively intermittent SF6 and CH4 flow operation shows us that both the etching processes and the deposition of a polymer passivation layer are occurring alternatively, a desirable feature for multi-step etching process (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A DC dual magnetron sputtering system with graphite (C) and silicon (Si) targets was used to grow stoichiometric and non-stoichiometric silicon carbide (SixCy) thin films at low temperature. Two independently DC power sources were used to enable the total discharge power be shared, under certain proportions, between the Si and C magnetron cathodes. The motivation was to control the sputtering rate of each target so as to vary the stoichiometric ratio x/y of the deposited films. The species content, thickness and chemical bonds of as-deposited SixCy films were studied by Rutherford backscattering spectroscopy (RBS), profilometry analysis and Fourier transform infrared absorption (FTIR), respectively. Overall, the present work reveals a new reliable plasma sputtering technique for low temperature growth of amorphous SixCy thin films with the capability of tuning the degree of formation of a-SiC, a-Si and a-C bonds in the film bulk.

Introduction:Candida species are responsible for about 80% of hospital fungal infections. Non-thermal plasmas operated at atmospheric pressure are increasingly used as an alternative to existing antimicrobial strategy. This work investigates the action of post-discharge region of a non-thermal atmospheric plasma jet, generated by a gliding arc reactor, on biofilms of standard strain of Candida albicans grown on polyurethane substrate. Methods Samples were divided into three groups: (i) non-treated; (ii) treated with argon plasma, and (iii) treated with argon plus air plasma. Subsequently to plasma treatment, counting of colony-forming units (CFU/ml) and cell viability tests were performed. In addition, the surface morphology of the samples was evaluated by scanning electron microscopy (SEM) and optical profilometry (OP). Results Reduction in CFU/ml of 85% and 88.1% were observed in groups ii and iii, respectively. Cell viability after treatment also showed reduction of 33% in group ii and 8% in group iii, in comparison with group i (100%). The SEM images allow observation of the effect of plasma chemistry on biofilm structure, and OP images showed a reduction of its surface roughness, which suggests a possible loss of biofilm mass. Conclusion The treatment in post-discharge region and the chemistries of plasma jet tested in this work were effective in controlling Candida albicans biofilm contamination. Finally, it was evidenced that argon plus air plasma was the most efficient to reduce cell viability.

Amorphous silicon oxycarbonitride (SiC x N y O z ) films have been deposited on Si substrates by low temperature reactive magnetron co-sputtering of silicon and graphite targets in mixed Ar/N 2 atmosphere. Our studies are focused on the influence of nitrogen incorporation on deposition rate, film composition, film structure, chemical bonds, and electrical resistivity of SiC x N y O z films investigated by profilometry, Rutherford Backscattering Spectrometry (RBS), X-ray diffraction (XRD), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), and four-point probe method. RBS results show that all samples contain significant amounts of oxygen (up to 16 at.%) which led to the formation of SiC x N y O z . Further, XPS results show that most of this oxygen is located in the film surface. With the addition of N 2 gas in the plasma, the carbon, and nitrogen contents in the films increase. The increased carbon content is due to the contribution of chemically driven sputtering of the graphite target and the reduction of the sputtering rate of the silicon target owing to poisoning by nitrogen. Raman spectra suggest that the films contain amorphous phases and that the a-C clusters suffer a graphitization with increased N 2 gas flow rate. The XRD analysis confirmed the amorphous structure of these films. According to the XPS analysis, the increase in nitrogen content leads to an increase in Si N and C N bonds, decreasing the Si C, Si Si, and C C bonds. Finally, the films electrical resistivity depends mainly on the nitrogen content, which makes it possible to obtain semiconductor or insulator SiC x N y O z films only by adjusting the N 2 concentration in the gas phase during the deposition process.

In this work, the surface of silicon etched by sulphur hexafluoride (SF6) and carbon tetrafluoride (CF4) plasma jet, pure or mixed with oxygen gas (O2), was investigated by scanning electron microscope (SEM), optical perfilometry and x-ray photoelectron spectroscopy (XPS). Through these techniques it was possible to investigate the etching rate, etched surface roughness and chemistry on Si surface as a function of O2 concentration in the SF6+O2 and CF4+O2 mixture. The results indicate high etching rates of up to 1.0 µm/min obtained for rf power and operating pressure at about 150W and 3.2 mTorr, respectively. The conditions whose etched profile showed higher anisotropy were obtained with CF4. Regarding the chemical analysis of the etched Si surface it was possible to identify elements of the sample surface such as F, C, N and O, as well as, their respective bonds with the Si.

Nitrogen doped titanium dioxide (TiO2) thin films were deposited by RF magnetron sputtering onto various substrates. The films were prepared in plasma of argon, oxygen, and nitrogen, with varying the nitrogen content, from 0% up to 70%. The resulting TiOx–Ny films were found to consist of cubic TiN osbornite and tetragonal TiO2 rutile phases. Using optical spectroscopy with large spectral range from 350 to 1000 nm, the band gap width was determined and a narrowing of the optical gap from 2.76 to 2.32 eV was observed as a function of the N-content. It was found that the optical properties of the TiOx–Ny layers are influenced by the surface morphology, roughness, surface energy and phase content. The chemical composition, the crystalline structure, the surface morphology and the surface energy were thoroughly studied by the Rutherford backscattering spectrometry (RBS), grazing-angle XRD, atomic force microscopy (AFM) and contact angle measurements (wettability), respectively.

Gliding-arc discharges have been utilized in plasma-assisted combustion processes, among various other applications, due to their properties of high electron density and chemical selectivity in a transitional regime. However, basic characteristics relative to the relations between the fundamental parameters of discharge, like mass flow rate, breakdown voltage, and frequency of repetition (number of discharge breakdowns per half cycle), have not been completely studied. In this paper, an ac-powered gliding-arc discharge having a reverse vortex flow configuration is built to carry on a basic investigation on discharges in air, natural gas, and mixture of both. Electrical measurements, optical emission spectroscopy, and mass spectrometry are the techniques used for these investigations. The results presented in this paper describe the dependence of the breakdown voltage, frequency of discharges, and conversion rates of methane and molecular oxygen with respect to the variation of the mass flow rate (directly related to the residence time) and discharge current.