Showing papers by "Denis P. Dowling published in 2011"

Effect of Surface Wettability and Topography on the Adhesion of Osteosarcoma Cells on Plasma-modified Polystyrene

Abstract: Biomaterials interact with the biological environment at their surface, making accurate biophysical characterization of the surface crucially important for understanding subsequent biological effects. In this study, the surface of polystyrene (PS) was systematically altered in order to determine the effect of plasma treatment and surface roughness on cell adhesion and spreading. Surfaces with water contact angle from hydrophilic (12°) to superhydrophobic (155°) were obtained through a combination of modifying surface roughness (R (a)), the deposition of siloxane coatings and the fluorination of the PS surface. R (a) values in the range of 19-2365 nm were obtained by grinding the PS surface. The nanometer-thick siloxane coatings were deposited using an atmospheric pressure plasma system, while the fluorination of the PS was carried out using a low-pressure radio frequency (RF) plasma. The siloxane coatings were obtained using a liquid poly(dimethylsiloxane) precursor that was nebulized into helium or helium/oxygen plasmas. Water contact angles in the range of 12-122° were obtained with these coatings. Cell adhesion studies were carried out using human MG63 osteosarcoma cells. It was observed that higher polymer surface roughness enhanced cell adhesion, but had a negative effect on cell spreading. Optimum cell adhesion was observed at ∼64° for the siloxane coatings, with a decrease in adhesion observed for the more hydrophilic and hydrophobic coatings. This decrease in cell adhesion with an increase in hydrophobicity was also observed for the fluorinated PS surfaces with water contact angles in the range of 110-155°.

Influence of dc Pulsed Atmospheric Pressure Plasma Jet Processing Conditions on Polymer Activation

Abstract: Plasma treatments are widely used to activate polymer surfaces prior to adhesive bonding This study investigates the influence of plasma treatment conditions on the surface activation of a range of polymers using the PlasmaTreat (Open Air) system In this study the effect of dc pulse plasma cycle time, compressed air flow rate and the plasma jet nozzle to substrate distance on the plasma discharge was examined The influence that the dc pulse plasma cycle time parameter has on the activation of polypropylene, polystyrene and polycarbonate was also investigated The level of polymer surface activation was evaluated based on the change in water contact angle after plasma treatment The polymer surface properties were also monitored usingAFMandXPSmeasurements Theheating effect oftheplasmawas monitored using both infrared thermographic camera and thermocouple measurements Plasma diagnostics measurements were obtained using the photodiode and optical emission spectroscopy techniques From this study it was concluded that for the PlasmaTreat system the level of plasma activation was closely correlated with the dc pulsed plasma cycle time, which is a measure of the plasma intensity For example, the more intense plasma obtained with shorter cycle times gave higher levelsofpolymer activationTheoptimized pulsed plasma cycle times were found to be specific for a given polymer type and related to their thermal properties The pulsed cycle times were also found to correlate with both the substrate and plasma gas temperatures

Enhancing the Mechanical Properties of Superhydrophobic Atmospheric Pressure Plasma Deposited Siloxane Coatings

Abstract: preparedultrahydrophobic surfaces by photolithography and hydro-phobised using silane reagents. The surfaces were termedultrahydrophobic because they exhibited advancing andrecedingwatercontactanglesabove1708.Someoftheothertechniques that have been used to fabricate superhydro-phobicsurfacesincludewaxsolidification,

Application of a novel microwave plasma treatment for the sintering of nickel oxide coatings for use in dye-sensitized solar cells

Abstract: In this study the use of microwave plasma sintering of nickel oxide (NiO x ) particles for use as p -type photoelectrode coatings in dye-sensitized solar cells (DSSCs) is investigated. NiO x was chosen as the photocathode for this application due to its stability, wide band gap and p -type nature. For high light conversion efficiency DSSCs require a mesoporous structure exhibiting a high surface area. This can be achieved by sintering particles of NiO x onto a conductive substrate. In this study the use of both 2.45 GHz microwave plasma and conventional furnace sintering were compared for the sintering of the NiO x particles. Coatings 1 to 2.5 μm thick were obtained from the sintered particles (mean particle size of 50 nm) on 3 mm thick fluorine-doped tin oxide (FTO) coated glass substrates. Both the furnace and microwave plasma sintering treatments were carried out at ~ 450 °C over a 5 min period. Dye sensitization was carried out using Erythrosin B and the UV–vis absorption spectra of the NiO x coatings were compared. A 44% increase in the level of dye adsorption was obtained for the microwave plasma sintered samples as compared to that obtained through furnace treatments. While the photovoltaic performance of the DSSC fabricated using the microwave plasma treated NiO x coatings exhibited a tenfold increase in the conversion efficiency in comparison to the furnace treated samples. This enhanced performance was associated with the difference in the mesoporous structure of the sintered NiO x coatings.

Development of active packaging containing natural antioxidants

Abstract: Two active packagings, consisting of PET trays sprayed with citrus fruit extract and α-tocopherol, were developed and tested. A comparison of the antioxidant activity of the two packagings was carried out on cooked meat stored at 4 °C. Lipid oxidation in citrus fruit extract-coated trays, measured with TBARS analysis, was significantly lower (p<0.01) than in uncoated (control) trays. Trays coated with α-tocopherol did not show any antioxidant activity. Morphology examination showed a more irregular coating for citrus fruit extract. Different orientations of the active phenolic groups on the PET surface could explain the differences in antioxidant efficacy of the two packagings.

Influence of the physical, structural and chemical properties on the photoresponse property of magnetron sputtered TiO2 for the application of water splitting.

Abstract: The production of hydrogen from water (called "water splitting"), utilises sunlight as an energy source (solar-hydrogen) in a photoelectrochemical (PEC) solar cell, is a promising source of green energy. In this work, a PEC was used, for evaluating the photoactivity of a thin film TiO2 based photoanode by measuring photocurrent (which is comparable to hydrogen production rate by water splitting process in PEC). The main focus of this work is to study the effect of the TiO2 nanosurface and bulk properties on the photoresponse properties of the photoanode. The TiO2 coatings (360-400 nm) were deposited using a closed field reactive magnetron sputtering system. The structure and morphology of the TiO2 coatings were systematically altered by varying the deposition pressure between 5 x 10(-4) to 1 x 10(-2) mbar. The properties of the deposited nano-coatings were determined using Ellipsometry, SEM, AFM, profilometry, XPS, Raman and X-ray diffraction (XRD). Coating properties were correlated with the light absorption and photocurrent performance which were evaluated using UV-Vis spectroscopy and tri-electrode potentiostat measurements respectively. It was concluded from this study that the coating deposition pressure has a pronounced effect on the TiO2 photoanode properties leading to a significant enhancement in the photoactivity in PEC cell. Over a six fold increase in photocurrent at applied potential 0 V was observed for TiO2 photoanode prepared at 4 x 10(-3) mbar as compared to 5 x 10(-4) mbar. A correlation has been established between the deposition pressure, nano surface morphology and bulk properties, UV-Vis light absorbance and bandgap value, and the consequently higher (i) photocurrent density, (ii) negative flat band, and (iii) open circuit potential measured in Photoelectrochemical (PEC) cell.

Correlation Between the Electrical and Optical Properties of an Atmospheric Pressure Plasma During Siloxane Coating Deposition

Abstract: The effect of varying process parameters on atmospheric plasma characteristics and properties of nanometre thick siloxane coatings is investigated in a reel-to-reel deposition process. Varying plasma operation modes were observed with increasing applied power for helium and helium/oxygen plasmas. The electrical and optical behaviour of the dielectric barrier discharge were determined from current/voltage, emission spectroscopy and time resolved light emission measurements. As applied power increased, multiple discharge events occurred, producing a uniform multi-peak pseudoglow discharge, resulting in an increase in the discharge gas temperature. The effects of different operating modes on coating oxidation and growth rates were examined by injecting hexamethyldisiloxane liquid precursor into the chamber under varying operating conditions. A quenching effect on the plasma was observed, causing a decrease in plasma input power and emission intensity. Siloxane coatings deposited in helium plasmas had a higher organic component and higher growth rates than those deposited in helium/oxygen plasmas.

Deposition of hybrid organic-inorganic composite coatings using an atmospheric plasma jet system.

Abstract: The objective of this study is to investigate the influence of alcohol addition on the incorporation of metal oxide nanoparticles into nm thick siloxane coatings. Titanium oxide (TiO2) nanoparticles with diameters of 30-80 nm were incorporated into an atmospheric plasma deposited tetramethylorthosilicate (TMOS) siloxane coating. The TMOS/TiO2 coating was deposited using the atmospheric plasma jet system known as PlasmaStream. In this system the liquid precursor/nanoparticle mixture is nebulised into the plasma. It was observed that prior to being nebulised the TiO2 particles agglomerated and settled over time in the TMOS/TiO2 mixture. In order to obtain a more stable nanoparticle/TMOS suspension the addition of the alcohols methanol, octanol and pentanol to this mixture was investigated. The addition of each of these alcohols was found to stabilise the nanoparticle suspension. The effect of the alcohol was therefore assessed with respect to the properties of the deposited coatings. It was observed that coatings deposited from TMOS/TiO2, with and without the addition of methanol were broadly similar. In contrast the coatings deposited with octanol and pentanol addition to the TMOS/TiO2 mixture were significantly thicker, for a given set of deposition parameters and were also more homogeneous. This would indicate that the alcohol precursor was incorporated into the plasma polymerised siloxane. The incorporation of the organic functionality from the alcohols was confirmed from FTIR spectra of the coatings. The difference in behaviour with alcohol type is likely to be due to the lower boiling point of methanol (65 degrees C), which is lower than the maximum plasma temperature measured at the jet orifice (77 degrees C). This temperature is significantly lower than the 196 degrees C and 136 degrees C boiling points of octanol and pentanol respectively. The friction of the coatings was determined using the Pin-on-disc technique. The more organic coatings deposited with octanol and pentanol exhibited friction values of 0.2, compared with approx. 0.8 for the coatings deposited from TMOS/TiO2 mixture (with and without methanol). Wear performance comparison between the two types of coating again indicated a significant organic component in the coatings deposited from the higher boiling point alcohols.

A Comparison between Gas and Atomized Liquid Precursor States in the Deposition of Functional Coatings by Pin Corona Plasma

Abstract: This work directly compares vapour and liquid aerosol states for the deposition of perfluorocarbon coatings using an atmospheric pressure, non-thermal equilibrium plasma jet system. The objective of the study is to evaluate how the physical state of the precursor (gas or liquid), influences the fragmentation of the monomer molecules in the plasma and the subsequent coating properties. Specifically the effect of gas or liquid aerosol precursor feed on the ability to achieve a soft plasma polymerization (SPP) is assessed with a view to producing a coating that exhibits minimal fragmentation, while being well cross-linked. The precursor (perfluoro-1decene) was introduced into a helium plasma and coatings deposited at rates of up to

Novel, Nanoporous Silica and Titania Layers Fabricated by Magnetron Sputtering

Abstract: Composite asymmetric membranes are fabricated through the deposition of submicrometer thick (100 nm) silica (SiO(2)) and titania (TiO(2)) films onto flat nanoporous silica and zirconia substrates by magnetron sputtering. The deposition conditions for both coating types were systematically altered to determine their influence on the deposited coating morphology and thickness. Ideal He/N(2) gas selectivity was measured for all of the membranes. The TiO(2) coatings, when deposited onto a ZrO(2) support layer with a pore size of 3 nm, formed a long columnar grain structure with average column diameter of 38 nm. A similar columnar structure was observed for TiO(2) coatings deposited onto a SiO(2) support layer with a pore size of 1 nm. Under the same conditions, SiO(2) coatings, deposited onto the same SiO(2) supports, formed a closely packed spherical grain structure whereas, when deposited onto ZrO(2) supports, the SiO(2) coatings formed an open grain structure. The average SiO(2) grain diameter was 36 nm in both cases. This preliminary investigation was aimed at studying the effect of sputtering parameters on the density and morphology of the deposited coatings. For the depositions carried out, the coating material was found to be very dense. However, the presence of grain boundaries resulted in poor ideal He/N(2) separation efficiencies.

Evaluation of the sensitivity of electro-acoustic measurements for process monitoring and control of an atmospheric pressure plasma jet system

Abstract: The development of non-invasive process diagnostic techniques for the control of atmospheric plasmas is a critical issue for the wider adoption of this technology. This paper evaluates the use of a frequency-domain deconvolution of an electro-acoustic emission as a means to monitor and control the plasma formed using an atmospheric pressure plasma jet (APPJ) system. The air plasma system investigated was formed using a PlasmaTreat? OpenAir applicator. Change was observed in the electro-acoustic signal with changes in substrate type (ceramic, steel, polymer). APPJ nozzle to substrate distance and substrate feature size were monitored. The decoding of the electro-acoustic emission yields three subdatasets that are described by three separate emission mechanisms. The three emissions are associated with the power supply fundamental drive frequency and its harmonics, the APPJ nozzle longitudinal mode acoustic emission and its odd overtones, and the acoustic surface reflection that is produced by the impedance mismatch between the discharge and the surface. Incorporating this knowledge into a LabVIEW program facilitated the continuous deconvolution of the electro-acoustic data. This enabled the use of specific frequency band test limits to control the APPJ treatment process which is sensitive to both plasma processing conditions and substrate type and features.

Wear resistance enhancement of the titanium alloy Ti–6Al–4V via a novel co-incident microblasting process

Abstract: In this study a room temperature coating deposition technology was investigated as a means of enhancing wear resistance of the titanium alloy Ti–6Al–4V. This process, termed CoBlast™, consists of co-incident particle streams of abrasive and coating materials which impact a substrate to create a modified surface. Al2O3 powder was chosen as the abrasive, while Teflon, SiC and B4C powders were investigated as coating precursors. Ti–6Al–4V surfaces modified via CoBlast using either Al2O3–SiC or Al2O3–B4C powder mixtures both demonstrated increased hardness compared with the unmodified alloy, however, wear testing performed using a pin-on-disc tribometer revealed that this did not translate to an appreciable improvement in wear resistance performance. In contrast, under the same wear test conditions, Al2O3–Teflon CoBlast modified Ti–6Al–4V demonstrated a significantly reduced friction coefficient and average pin-on-disc wear track widths and depths of 68 and 90% less than those which formed on the unmodified alloy. Through the deposition of either SiC or B4C coatings in combination with a Teflon top layer a further improvement in wear resistance was confirmed by a 81/97% reduction in wear track width/depth. In conclusion, the deposition of Teflon coatings onto unmodified, SiC modified or B4C modified Ti–6Al–4V using the CoBlast process yielded surfaces with significantly enhanced wear performance.

Conversion of amorphous TiO2 coatings into their crystalline form using a novel microwave plasma treatment

Abstract: Crystalline titanium dioxide (TiO 2 ) coatings have been widely used in photo-electrochemical solar cell applications. In this study, TiO 2 and carbon-doped TiO 2 coatings were deposited onto unheated titanium and silicon wafer substrates using a DC closed-field magnetron sputtering system. The resultant coatings had an amorphous structure and a post-deposition heat treatment is required to convert this amorphous structure into the photoactive crystalline phase(s) of TiO 2 . This study investigates the use of a microwave plasma heat treatment as a means of achieving this crystalline conversion. The treatment involved placing the sputtered coatings into a 2.45 GHz microwave-induced nitrogen plasma where they were heated to approximately 550 °C. It was observed that for treatment times as short as 1 min, the 0.25-μm thick coatings were converted into the anatase crystalline phase of TiO 2 . The coatings were further transformed into the rutile crystalline phase after treatments at higher temperatures. The doping of TiO 2 with carbon was found to result in a reduction in this phase transformation temperature, with higher level of doping (up to 5.8% in this study) leading to lower anatase-to-rutile transition temperature. The photoactivity performance of both doped and un-doped coatings heat-treated using both furnace and microwave plasma was compared. The carbon-doped TiO 2 exhibited a 29% increase in photocurrent density compared to that observed for the un-doped coating. Comparing carbon-doped coatings heat-treated using the furnace and microwave plasma, it was observed that the latter yielded a 19% increase in photocurrent density. This enhanced performance may be correlated to the differences in the coatings' surface morphology and band gap energy, both of which influence the coatings' photoabsorption efficiency.

Influence of Gas Type on the Thermal Efficiency of Microwave Plasmas for the Sintering of Metal Powders

Abstract: Microwave plasmas have enormous potential as a rapid and energy efficient sintering technology. This paper evaluates the influence of both plasma atmosphere and metal powder type on the sintering temperatures achieved and the properties of the sintered powder metal compacts. The sintering is carried out using a 2.45 GHz microwave-plasma process called rapid discharge sintering (RDS). The sintering of three types of metal powder are evaluated in this study: nickel (Ni), copper (Cu) and 316L stainless steel (SS). An in-depth study of the effects of the plasma processing parameters on the sintered powder compacts are investigated. These parameters are correlated with the mechanical performance of the sintered compacts to help understand the effect of the plasma heating process. The substrate materials are sintered in four different gas discharges, namely hydrogen, nitrogen oxygen and argon. Thermocouple, pyrometer and emission spectroscopy measurements were taken to determine the substrate and the discharge temperatures. The morphology and structure were examined using scanning electron microscopy and X-ray diffraction. The density and hardness of the sintered compacts were correlated with the plasma processing conditions. As expected higher densities were obtained with powders with lower sintering temperatures i.e. nickel and copper when compared with stainless steel. Under the power input and pressure conditions used, the highest substrate temperature attained was 1,100°C for Cu powder sintered in a nitrogen atmosphere. In contrast under the same processing conditions but in an argon plasma, the temperature achieved with SS was only 500°C. The effect of the plasma gas type on the sintered powder compact chemistry was also monitored, both hydrogen and nitrogen yielded a reducing effect for the metal in contrast with the oxidising effect observed in an oxygen plasma.

Decoding of atmospheric pressure plasma emission signals for process control

Abstract: low-temperature, non-thermal atmospheric pressure plasmas (APP) are being developed for surface treatment of biomedical devices, sterilisation, and therapeutic techniques, such as wound sterilisation and cancer treatment. In addition to these medical applications, APP are now routinely employed in the automotive (car head lamps) and aerospace (fuselage and wing components) industry for surface activation of polymer prior to bonding. The impact of this technology offers enhanced quality of care at reduced cost and will be of immense societal and commercial value. The invited plenary talk shall focus on the emerging plasma optical and electro-acoustic metrology that is being developed for these atmospheric pressure plasmas. In particular the requirement for extraction of information that describes the tempo-spatial heterogeneous processes, presently this technology is in its infancy when compared to low pressure plasma metrology. The new metrology multivariate analysis tools for the deconvolution and compression of single observables such as time-vary electrical current and electro-acoustic signals are presented for three different and contrasting plasma processes. The APP metrology will pertain to: the hand held plasma jet (needle) (1) reel-to reel APP (2, and 3), and CNC controlled plasma jets (4, and 5).

Comparison between the SBF Response of Hydroxyapatite Coatings Deposited Using both a Plasma-Spray and a Novel Co-Incident Micro-Blasting Technique

Abstract: This paper reports on the response of hydroxyapatite (HA) coatings, fabricated using two deposition technologies, to immersion in simulated body fluid (SBF). The deposition methods used were: plasma spray, a commercial standard, and CoBlast, a novel low temperature microblast technique. In the case of the latter, HA coatings are deposited by simultaneous blasting HA and abrasive powders concentrically at a metallic substrate, resulting in a thin layer of HA (approx. 2.5 µm thick). Groups of the CoBlast and plasma spray HA coatings were immersed in 7 ml of SBF solution for 1, 2, 4, 7, 14 and 28 days, and were subsequently removed and examined for any alterations caused by the SBF solution. It was noted from this study that the CoBlast HA coatings appeared to undergo a two step calcium phosphate recrystallisation process; initial homogenous nucleation and subsequent heterogeneous nucleation. Conversely recrystallisation on the plasma spray coatings appeared to proceed largely through a heterogeneous nucleation process. Two factors that may influence the differences in HA recrystallisation is the presence of amorphous HA resulting in rapid dissolution, and/or the significantly lower surface area (roughness) offered to the SBF solution by the CoBlast coatings. The interpretation of recrystallisation mechanisms from this preliminary study is limited however by the differences in coating morphology and thickness (27 versus 2 µm) for the plasma spray and CoBlast HA coatings respectively.

DC Pulsed Atmospheric-Pressure Plasma Jet Image Information

Abstract: This paper presents optical imaging and optical emission spectroscopy (OES) data of an atmospheric-pressure plasma jet. It is shown how the visual information and OES information of the air discharge are related as the blown arc extends from the nozzle (2-4 mm) with a molecular nitrogen rotational temperature on the order of 1700 K and the flowing afterglow beyond this region is dominated by the cooler (300-K) NO-O chemiluminescent reaction that produces NO2 species.

Comparison between Microwave and Microwave Plasma Sintering of Nickel Powders

Abstract: The objective of this study is to investigate the use of microwave plasma treatments as a processing technology for the sintering of metal powders. The volumetric heating process achieved with microwaves is considerably more efficient compared with resistance heating. The sintering study was carried out on 20 mm diameter by 2 mm thick compacted discs of nickel powder, with mean particle size of 1 µm. The discs were fired in a 5 cm diameter microwave plasma ball, under a hydrogen atmosphere at a pressure of 2 kPa. There was an increase in fired pellet transverse rupture strength (TRS) with plasma treatment duration. The mechanical properties of the sintered nickel discs were compared based on TRS, Rockwell hardness tests and density measurements. The morphology of the sintered discs was compared using microscopy and SEM. Comparison disc sintering studies were carried out using both a non plasma microwave and tube furnace firing. Using the microwave plasma sintering process full sintered disc strength of ≈1000 N (based on 3-point bend tests) was achieved after a 10 minute treatment time. In contrast the sintering time in the tube furnace treatment involved total processing time of up to 6 hours. The non plasma microwave system involved intermediate treatment periods of 2 hours. The degree of sintering between the individual nickel powder particles can be precisely controlled by the duration of the treatment time in the plasma.

Acoustic emission within an atmospheric helium discharge jet

Abstract: This paper describes the thermal gas effluent and ion acoustic pressure wave interaction between the fundamental drive frequency and its harmonics within an atmospheric helium discharge. Deconvolution of the acoustic signal and the electrical signals reveal that the plasma jet undergoes a change in operational mode from chaotic (where the plasma is spatially and temporally inhomogeneous at the electrode surface) to stable (periodic in nature) when the plasma expands away from the electrodes and into the reactor cylinder. This effect is strongly influence by the helium flow and input power. In addition the generated acoustic signals is found to have a frequency response to that of a closed-end cylinder column which supports antinodes of n = 1 and 3. Decoding of the acoustic signal allows the helium thermal gas temperature to be obtained: Tgas ~ 290 K. The signal allows the axial gap distance between the jet nozzle and work surface to be estimated which has technology importance in terms of plasma metrology and in the basic understanding of atmospheric pressure plasma jet physics.

Microwave-assisted rapid discharge sintering of a bioactive glass–ceramic

Abstract: Bioactive glass–ceramics have been developed as successful bone graft materials. Although conventional sintering in an electrically-heated furnace is most commonly used, an alternative microwave plasma batch processing technique, known as rapid discharge sintering (RDS), is examined to crystallise the metastable base glass to form one or more ceramic phases. Apatite-mullite glass–ceramics (AMGC) were examined to elucidate the effects of RDS on the crystallization of a bioactive glass–ceramic. By increasing the fluorine content of the glass, the fluorapatite (FAp) and mullite crystallization onset temperatures can be reduced. Samples were sintered in a hydrogen and hydrogen/nitrogen discharge at temperatures of ≈800 and 1000°C respectively with the higher sintering temperature required to form mullite. Results show that the material can be densified and crystallised using RDS in a considerably shorter time than conventional sintering due to heating and cooling rates of ≈400°C/min.

Real-Time Process Monitoring during the Plasma Treatment of Carbon Weave Composite Materials

Abstract: Carbon fibre reinforced composite materials are used widely in applications ranging from autom obiles to aircraft and sports equipment. In all of these applications plasma treatment can be used to activate the composite surface in order to enhance surface energy, prior to adhesive bonding. In this study plasma metrology is used as a means of evaluating the performance of a reel-to-reel atmospheric pressure plasma system consisting of two reactor chambers used to active a composite is investigated. A real-time electrical (current and voltage and resonant drive frequency) parametric analysis of the plasma treatment process was carried o ut as the carbon composite was passed through the plasma chamber. A reproducible correlation was obtained between the plasma parameters and the position of the composite in the two plasma reactor chambers. Key words: Atmospheric pressure plasma, electrical diagnostics, principal component analysis. 1. Introduction Atmospheric pressure plasma processing of materials is becoming wide spread in the manufacturing sector, particularly where they provide an alterative low temperature (less than 100

Atomistic simulation of the formation of nanoporous silica films via molecular chemical vapor deposition on nonporous substrates.

Abstract: To distinguish thin deposited film characteristics clearly from the influence of substrate morphological properties, the growth mechanism and the macroscale and nanoscale properties of nanoporous SiO(2) films deposited on nonporous silica (SiO(2)) substrates from chemical precursors Si(OH)(4) and TEOS (tetraethoxysilane) via low-pressure chemical vapor deposition are the primary targets of this study. This work employs a kinetic Monte Carlo (KMC) simulation method coupled to the Metropolis Monte Carlo method to relax the strained silica structure. The influence of the deposition temperature (473, 673, and 873 K) on the properties of the SiO(x) layers is addressed via analysis of the film growth rates, density profiles of the deposited thin films, pore size distributions, carbon depth profiles (with respect to TEOS), and voidage analysis for layers of different thicknesses (8-18 nm). A comparison of simulation with experimental results is also carried out.

Methods of manufacturing photovoltaic electrodes

Abstract: A photovoltaic electrode is made by the following steps: (a) depositing on a substrate a dispersion comprising powdered semiconductor particles in a dispersion medium; (b) removing the majority of the dispersion medium to leave the powdered semiconductor particles in a deposition layer on the substrate; (c) creating a plasma using microwave energy excitation; (d) exposing the deposition layer to said microwave-excited plasma for a sufficient time to sinter the nanoparticles thereby adhering them to the substrate; and (e) absorbing a dye into said sintered deposition layer. The electrode thus obtained exhibits improved performance relative to conventional sintered electrodes.

Use of atmospheric plasma jet treatments for the enhancement of cell adhesion to 1 mm internal diameter microwell cell arrays

Abstract: In this study a cyclic olefin copolymer (COC) is micro-injection moulded to manufacture miniature multiwell plates with biodiagnostic applications. The biological inertness of the COC polymer however hampers the cell growth. In order to address this problem, the feasibility of using both helium and air atmospheric plasma treatments for the activation of the well arrays was investigated. In addition to evaluating if the enhancement in the polymer surface energy would facilitate cell attachment onto the internal surface of the wells, a further issue was to avoid thermal damage by the plasma to the 1 mm internal diameter microwell cell arrays.

Atmospheric Pressure Plasma Acoustic Moment Analysis

Abstract: NUMERICAL ANALYSIS AND APPLIED MATHEMATICS ICNAAM 2011: International Conference on Numerical Analysis and Applied Mathematics, 19–25 September 2011, Halkidiki, (Greece)

Rapid Discharge Sintering of Powder Metallurgy Components

Abstract: A microwave circumferential antenna plasma system has been used to sinter pressed-powder metallurgy components. The rapid heat generated in the discharge once the plasma is fired is sufficient to sinter samples within minutes and to temperatures upward of 1300°C based on gas mixtures and applied powers. Images of the sintering process in hydrogen at various flow rates and applied powers are presented.

Deposition of nano and micron thick aligned fiber plasma polymerised coatings using an atmospheric plasma jet technique

Abstract: International Symposium on Plasma Chemistry (ISPC20), Philadelphia, USA, July 24 - 29, 2011

Methods of manufacturing photovoltaic electrodes for dye-sensitized solar cells

Abstract: A photovoltaic electrode is made by the following steps: (a) depositing on a substrate a dispersion comprising powdered semiconductor particles in a dispersion medium; (b) removing the majority of the dispersion medium to leave the powdered semiconductor particles in a deposition layer on the substrate; (c) creating a plasma using microwave energy excitation; (d) exposing the deposition layer to said microwave-excited plasma for a sufficient time to sinter the nanoparticles thereby adhering them to the substrate; and (e) absorbing a dye into said sintered deposition layer. The electrode thus obtained exhibits improved performance relative to conventional sintered electrodes.