Glass Fiber Substrate Research Articles

Novel TiO 2 thin films/glass fiber photocatalytic reactors in the removal of bioaerosols

The photocatalytic disinfection of aerosolized Escherichia coli, a pathogenic microorganism was investigated. The air disinfection system is a novel TiO 2 thin films/glass reactor filter and ultraviolet (UV) radiation air purification system, operating at a flow rate of 20 L/min. A special glass fiber reactor design allowed the UV lamp to be located in the center of the reactor. The photocatalyst reactor was then filled with TiO 2 coated glass fiber substrates to examine the photocatalytic efficiency of the TiO 2 filled reactor against aerosolized E. coli in cell concentrations of 10 5 CFU/mL. A slow sol–gel technique hydrolysis was used in this study to acquire fine and uniform TiO 2 nanoparticles of 10–30 nm. The TiO 2 thin films were obtained on glass fiber substrates by dipping method followed by thermal treatment. In an attempt to understand the structure and the morphology of TiO 2 sol–gel thin films, analyses by X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed. The SEM images showed that uniform anatase TiO 2 thin films were coated on fiber surfaces. A neublizer was applied to yield E. coli bioaerosol at a controlled humidity of 72%. Disinfection of E. coli under 254 and 365 nm light illumination was conducted to evaluate the photocatalytic ability of the TiO 2 thin films. The nano-TiO 2/glass fibers gel catalyst prepared in the laboratory showed good photocatalytic performance with the high degradation efficiency above 95% at both wavelengths. With the UV illumination switched off, the degradation efficiency dropped to below 60%. The improvement of the photocatalytic activity was ascribed to the fibers-based reactor with a screen mechanism which provided a huge surface area of TiO 2 thin films. These results will be useful and assist engineers to design photocatalyst reactors for the industrial applications of bioaerosol removal.

Synthesis and characterization of silver-nanoparticle-impregnated fiberglass and utility inwater disinfection

A number of researchers have deployed silver (Ag) nanoparticles through a number oftechniques on various substrates including carbon, zeolites and polymers for waterdisinfection applications. However, Ag impregnated on an inorganic fiberglass surfacethrough a simple electroless process was only recently reported for the first time. Fiberglassimpregnated with Ag nanoparticles displays superior performance over carbon-based silversupport systems but little is known about the factors that affect the architecture of thesystem, its interfacial properties and its consequent bactericidal activity. In this study, Agcontent and particle size on a fiberglass substrate were manipulated by adjusting theAgNO3 concentration, immersion time, temperature, solution pH and reduction temperature. Thereduction chemistry of the Ag-nanoparticle-impregnated fiberglass is described andsupported with thermal gravimetric analysis (TGA) and photoelectron spectroscopy (XPS)measurements. The Ag content along with the particle size and particle size distributionwere characterized with scanning electron microscopy (SEM), transmission electronmicroscopy (TEM), energy dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD).The Ag content on the fiberglass mats ranged from 0.04 to 4.7 wt% Ag/g-fiber with a sizedistribution of 10–900 nm under standard processing conditions. Inductively coupled plasmamass spectrometry (ICP-MS) was used to analyze the Ag desorption from the fiberglasssubstrate, while the bactericidal properties were evaluated against Escherichia coli (E. coli).

Analysis of Pulsed THz Imaging Using Optical Character Recognition

Using a reflection-based pulsed THz imaging system built upon our ErAs:GaAs photoconductive switch and a gated receiver, we quantify image quality at different detection bands (centered at 100, 400, and 600 GHz). Zero-bias Schottky diode detectors mounted in various waveguide sizes are used to tune the operational frequency bands of the imaging system, while the rest of the imaging system remains unchanged. The image quality is quantified by applying an optical character recognition (OCR) algorithm on THz images of 8-by-10 mm copper letters on a fiberglass substrate. Using the OCR success rate as a metric, we see a fivefold improvement in image quality from a 400 GHz to a 600 GHz imaging system, while our 100 GHz images do not produce any correct OCR results. In a comparison experiment performed at 600 GHz, the image signal-to-noise ratio (SNR) is degraded by placing increasing numbers of denim sheets (5.4 dB decrease in signal per layer) into the beam path. We find that the OCR success rate is roughly constant from one sheet to four sheets of denim (33-25 dB SNR) and then drops off sharply starting at five denim sheets.

Complete oxidation of isopropanol over Cu4O3 (paramelaconite) coating deposited on fiberglass by CVD

Thin films of paramelaconite, tenorite and their mixtures were deposited on fiberglass substrate by chemical vapor deposition and catalytically evaluated by isopropanol oxidation at low temperatures between 150 and 275 °C. Copper oxides were deposited using bis(2,4-pentanedionato)copper(II) as a precursor and oxygen as carrier-reactant gas. Original crystalline phases deposited on fiberglass at different temperatures or formed subsequently were characterized by several analytical techniques. Films gave crystallite sizes from 6.5 to 8.4 nm and a thickness around 230 nm. The fiberglass with a paramelaconite film showed a relatively high catalytic activity, more than 40%, at 250 °C. Nevertheless, the fiberglass with a tenorite film exhibited a catalytic activity of only 10% at the same temperature. Above 250 °C the paramelaconite experienced a notable deactivation after which the catalytic activity decreased to 6.7% at 350 °C and after this, the catalyst could not be reused. This activity loss was probably due to changes in the chemical phases on fiberglass by effect of temperatures above 250 °C.

Development of a Pulsed Radio Frequency Glow Discharge for Three-Dimensional Elemental Surface Imaging. 1. Application to Biopolymer Analysis

Glow discharge optical emission spectrometry has cemented itself as an important surface elemental analysis technique in part because of its superb depth resolution (on the order of single nanometers). However, very few studies have explored the ability of the glow discharge to provide laterally resolved elemental information. In the present study, an end-on-viewed pulsed radio frequency glow discharge is coupled to a monochromatic imaging spectrometer to provide lateral surface imaging. The performance of the technique is demonstrated with etched copper circuits on fiber-glass substrates, and it is shown how several operating parameters including pressure, pulsed mode operation, and time-resolved detection affect the lateral surface resolution. In addition, because a pulsed radio frequency glow discharge offers elemental information on nonconducting samples, the technique is applied to the three-dimensional elemental analysis of proteins on blotting substrates. Several alternative sample types are also examined, including photographic film and glass.

Mould release potential of polydimethylsiloxane coatings using photoinitiated polymerisation

Cycloaliphatic epoxide-functionalised polydimethylsiloxanes were coated onto a gel-coated fibreglass substrate and cured using two different light sources: UV light and visible light. Curing was accomplished through the use of an acid-generating photoinitiator, and a photosensitiser was used to shift the initiating wavelength into the visible region. The release potential, mechanical properties, surface tension, and contact angle of the cross-linked polymer were measured. The contact angle and surface tension of the UV-cured coatings were found to be 103° ± 0.05 and 10.93 ± 0.05mJ/m2, respectively. The contact angle and surface tension of the visible light-cured coatings were 102° and 11.42 ± 0.05mJ/m2, respectively. Pull-off adhesion tests revealed that a consistent 0.2MPa of normal force was required to remove the mould from both the UV- and visible light-cured coatings even after 30 releases. Both methods of cure offered the same release properties, but the visible light sample required a much longer cure time.

Chemically activated carbon on a fiberglass substrate for removal of trace atrazine from water

Chemically activated fiber (CAF) for removal of trace atrazine from water was prepared by coating fiberglass assemblies with a phenolic resin along with a chemical activation agent of ZnCl2, then stabilization and heat treatment in N2 at 500 °C. The carbon on the CAF shows similar BET surface area and volumes of narrow micropores (<10 A), higher volumes of wide micropores (10–20 A) and narrow mesopores (20–50 A), as compared with a commercially available GAC F-400. Adsorption isotherm data show that the CAF has a higher adsorption capacity for atrazine than the GAC, primarily because the CAF has an increased pore (10–50 A) volume. The breakthrough tests show that the CAF filter is ten times more effective over the GAC filter in removing the atrazine to below the current USEPA standard of 3 ppb. The CAF filter also shows a better competitive adsorption of atrazine over the GAC filter in the presence of 50 times higher concentration of humic acid. Such a filter can be regenerated to 90% of its original activity by heating at 350 °C in air.

The photocatalytic application and regeneration of anatase thin films with embedded commercial TiO2 particles deposited on glass microrods

Anatase thin films (<200 nm in thickness) embedding Degussa P25 TiO2 were prepared by sol–gel method. TiO2-anatase thin films were deposited on a fiberglass substrate and then ground to obtain glass microrods containing the composite films. The film structure was characterized using Raman spectroscopy, atomic absorption and UV–vis spectrophotometry, and atomic force microscopy. The photocatalytic activity of the composite films, calcined at 450 °C, and the regeneration of the activity under the same experimental conditions, were assessed using gas chromatography to study the photodegradation of phenol, an industrial pollutant, in water under 365 nm irradiation. The film with 15.0 wt.% of P25 TiO2 was found to be more photoactive (54 ppm of degraded phenol at 6 h of illumination) than the other ones.

Electroforming of metallic bipolar plates with micro-featured flow field

In addition to mechanical properties, uniform fuel dispersion, efficient removal of water and high electric conductivity are also important functions of a bipolar plate. The capillary effect of micro-featured flow field may attract water from the carbonic diffusion layer and promote more evenly dispersion of fuels into the diffusion layer. Thus, it may improve the performance of proton exchange membrane (PEM) fuel cells. In this research, the Lithography Galvanik Abformung (LIGA) manufacturing processes with electroforming technology are investigated for the production of micro-featured flow field of the metallic bipolar plates. The micro-features are designed in conjunction with the existing flow channel to form an integrated flow field system. Instead of silicon wafer, a 4 in. wafer size SS304 stainless steel plate is used as the substrate. The LIGA processes of photo masking, spin coating, exposure and development are employed to create electric conducting die with flow field pattern. Electroforming of this metallic plate coated with flow field patterned photo resist will result in the main flow channel on the SS304 plate. The same processes were conducted for the second iteration to form micro-features. Thus, metallic bipolar plates with micro-features are produced using the electroforming technology. A single cell with total cell area of 16 cm 2 and reaction area of 4 cm 2 was produced. It has micro-features of 100 and 200 μm width and of 50 μm depth. The dimensions of the main flow channel were 300 μm in width and 200 μm in depth. Single cell tests were conducted to evaluate its performance. The cell performance of the single cell with SS304 metallic bipolar plates exceeds similar size single cell with silicon or glass fiber substrates. The electroforming is a promising technology for metallic bipolar plates with micro-features and micro-fuel cell.

Elucidating the porous and chemical structures of ZnCl2-activated polyacrylonitrile on a fiberglass substrate

ZnCl2-activated polyacrylonitrile (PAN) coated onto a fiberglass substrate was prepared in N2 at 450 °C. The porous and chemical structures were characterized by using N2 adsorption at 77 K, XPS, FTIR, competitive adsorption of CO2/CH4 and the adsorption of Cs+, Sr2+ and Ag+. The activated PAN displays a high BET surface area up to 1012 m2 g−1, a broad mesopore size distribution as well as a major micropore size distribution. Up to 19.3 wt% of nitrogen, which is probably in the form of pyridinic and pyrrolic structures, is incorporated in the chemically activated PAN. HCl uptake results show that such a material has a higher amount of weakly basic functional groups compared to a commercially available ACF15. The activated PAN also exhibits a higher selectivity coefficient for CO2/CH4 at STP and higher adsorption amounts for Cs+, Sr2+ and Ag+ than ACF15. It is proposed that nitrogen-containing, weakly basic functional groups positioned on the suitable-sized pore walls improve the adsorption ability of the activated PAN toward CO2, Cs+, Sr2+ and Ag+.

Analysis of nitrated polycyclic aromatic hydrocarbons by liquid chromatography with fluorescence and mass spectrometry detection: air particulate matter, soot, and reaction product studies.

Polycyclic aromatic hydrocarbons (PAH) and their nitrated derivatives (nitro-PAH) are environmental pollutants which pose a threat to human health even at low concentration levels. In this study, efficient analytical methods for the analysis of nitro-PAH and PAH (extraction, clean-up, chromatographic separation, and spectrometric detection) have been developed, characterized, and applied to aerosol samples. The separation and quantification of 12 nitro-PAH was carried out by reversed-phase high performance liquid chromatography (HPLC), on-line reduction, and fluorescence detection. The detection limits were in the range of 0.03-0.5 microg L(-1) (6-100 pg in the investigated sample aliquots), and the recovery rates from soot samples were 70-90%. Nitro-PAH and PAH concentrations have been determined for different types of soot and for urban, rural, and alpine fine air particulate matter (PM2.5). For the first time, trace amounts of nitro-PAH have been detected in a high-alpine clean air environment. The on-line reduction and fluorescence technique has been complemented by atmospheric pressure chemical ionization time-of-flight mass spectrometry (APCI-TOF-MS). The MS detection allowed the analysis of partially nitrated and oxygenated PAH in laboratory studies of the heterogeneous reaction of PAH on soot and glass fiber substrates with gaseous nitrogen oxides and ozone. It led to the tentative identification of a previously unknown nitrated derivative of the particularly toxic PAH benzo[ a]pyrene (BaP-nitroquinone), and provides the first experimental evidence that PAH-nitroquinones can be formed by reaction of PAH with atmospheric photooxidants.

Anion exchange fibers for arsenate removal derived from a vinylbenzyl chloride precursor

AbstractThe preparation of anionic exchange fibers (AEFs) is described utilizing an oligomer derived from vinylbenzyl chloride as the precursor coating on a glass fiber substrate. This approach permits a significant reduction in number of synthetic steps required for commercial beads, as well as eliminating the need for solvents prior to functionalization. The amination reaction time was also substantially reduced. These fibers were characterized through a variety of techniques such as scanning electron microscopy (SEM), analytical titration, and diffuse reflectance fourier transform infrared spectroscopy (DRIFTS) of the copolymer. With respect to ion exchange properties the fibers could be regenerated for over 20 cycles with no capacity loss or physical degradation of the coating. Particular emphasis was placed on establishing conditions for the removal of arsenate from water. The design and testing of AEF filters for breakthrough experiments were carried out and compared to commercially available beads. The results indicate that AEF have a significant kinetic advantage over the anionic exchange beads, which approaches an order of magnitude improvement in lowering effluent contaminants. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Novel polymeric chelating fibers for selective removal of mercury and cesium from water.

We report here the synthesis and characterization of two new classes of chelating fibers, namely, (1) polymercaptopropylsilsesquioxane (PMPS) and (2) copper(II) ferrocyanide complexed with poly[1-(2-aminoethyl)-3-aminopropyl]silsesquioxane (Cu-FC-PAEAPS) fibers. These fibers were evaluated for selective removal of trace amount of mercury and cesium ions respectively in the presence of competing metal ions from water. The PMPS and Cu-FC-PAEAPS fibers were prepared by coating their corresponding soluble prepolymers, which are derived from mercaptopropyltrimethoxysilane and [1-(2-aminoethyl)-3-aminopropyl]trimethoxysilane monomers, respectively, on a glass fiber substrate, followed by a cross-linking step at 120 degrees C. The fibers were characterized through infrared spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). These novel materials are extremely efficient in removing low concentrations of mercury and cesium ions from water in the presence of high concentrations of sodium or potassium ions. They were shown to remove trace mercury and cesium contaminants effectively to well below parts per billion concentrations under a variety of conditions.

Negative magnetoresistance of polycrystalline thin Bi1−xSbx alloy films in quantizing magnetic fields

We have investigated the magnetoresistance of thin polycrystalline semiconductor Bi1−xSbx films prepared on a flat fibreglass substrate at a temperature of 77 K using pulsed magnetic fields up to 50 T. For these investigations we used films exposed to different thermal annealing and having different grain structures. Negative magnetoresistance was obtained in semiconductor polycrystalline thin films affected by longitudinal magnetic fields to fields in excess of 20 T. This phenomenon has been qualitatively explained in terms of microcrystallites, which are energy band structure changes induced by strong magnetic fields. It is shown that, by measuring the magnetoresistance in strong and quantizing magnetic fields, we can determine the composition and quality of thin Bi–Sb films.

Design of polyvinyl alcohol mercaptyl fibers for arsenite chelation

The work described here entails the synthesis and characterization of polyvinyl alcohol mercaptyl fibers, coated on a fiberglass substrate, for the purpose of removing arsenite (As 3+) from water. Because thiols are chemically the most active functional groups found in cells and are capable of forming very stable complexes with metal ions, this functional group was selected as an excellent candidate for arsenite removal from water. The fibers were characterized through infrared spectroscopy, elemental analysis, analytical titration, scanning electron microscopy, and environmental scanning microscopy. The ability of these systems to chelate arsenite was measured using equilibrium adsorption isotherms at initial concentrations of 10 and 100 ppm. The ability to regenerate these systems is also described. The fibrous mercaptyl system’s performance is compared to the commercial product, Duolite’s GT-73, a macroreticular polystyrene–divinylbenzene resin with chelating thiol functional groups.

Polymeric Ion-Exchange Fibers

This work explores the design of new ion-exchange materials in the form of fibers that yield a number of important advantages over conventional ion-exchange beads. In this approach, ion-exchange fibers are prepared by (1) coating low-cost glass fiber substrates with an appropriate oligomer, (2) cross-linking, and (3) functionalizing the coating to produce either anionic or cationic capability. As a result of the thin coatings, the use of solvents prior to both functionalization and preswelling of the finished product prior to end-use was eliminated, representing a significant simplification of current synthesis methods. Kinetic experiments showed that the contact efficiencies of these systems were greatly improved over the traditional beads because of the higher surface-to-volume ratio and shorter diffusion path lengths. This improvement translated into an order of magnitude increase in both ion-exchange and regeneration rates. Another advantage is the excellent resistance of the fibers to osmotic shock even after multiple regenerations. Finally, these systems were shown to remove heavy metal contaminants effectively to well below part per billion concentrations.

Cyclohexane oxidation over Cu 2O–CuO and CuO thin films deposited by CVD process on fiberglass

Cu 2O–CuO and CuO thin films on a fiberglass substrate were prepared by chemical vapor deposition (CVD) and then catalytically evaluated by cyclohexane oxidation. The fiber with a Cu 2O–CuO film showed a high catalytic activity at low temperatures, for example 43% at 350 °C, and a good selectivity to cyclohexanol production (37% at 300 °C). The fiber with a CuO film exhibited a higher catalytic activity, for example 48% at 350 °C, with a high yield of cyclohexanone (37% at 250 °C). A CuO/SiO 2 catalyst with the same CuO content gave a result similar to the CuO/fiberglass system under the same conditions examined but, on the other hand cyclohexane was cleaved giving a higher selectivity to hexenes, 30% at 250 °C. The effect of reaction temperature on the catalytic activity and selectivity of cyclohexane oxidation were investigated. At 300 °C the steady-state catalytic performance of the CuO/fiberglass experienced a slight deactivation after 4 h time-on stream from 40% to 38% of conversion, after which, the catalyst could be reused apparently without any activity loss.

Development and performance analysis of compound parabolic solar concentrators with reduced gap losses—‘V’ groove reflector

A system has been developed to use compound parabolic concentrators to collect solar energy and to generate steam. A CPC reflector profile with a V groove at the bottom of the reflector to reduce the gap losses was designed with a half acceptance angle of 23.5° for a tubular absorber of OD 30 mm. Five troughs fabricated with fiberglass substrate pasted over with UV stabilized self-adhesive aluminized polyester foil having high specular reflectivity joined together side by side comprise the CPC module with an aperture area of 2.04 m 2. Copper tubes coated with NALSUN selective coatings and enclosed by borosilicate glass envelope act as absorbers. The reflector absorber assembly housed in a single glass wool insulated wooden box forms the CPC collector. Using water as the heat transfer fluid efficiency tests were carried out with different inlet temperatures. In situ steam generation testing and possible application to steam cooking were also carried out. A theoretical modeling was developed by setting up different heat balancing equations and a reasonable agreement between theoretical computed values and the experimental values was observed.

Development and performance analysis of compound parabolic solar concentrators with reduced gap losses – oversized reflector

A severe energy shortage already exists in many parts of the developing world. In an attempt to find a technical solution, several solar energy collection technologies have been developed. A system has been designed to use compound parabolic concentrating collectors to collect solar energy and to generate steam. A compound parabolic concentrator (CPC) profile with oversized reflector and thereby reduced gap losses was designed with a half-acceptance angle of 23.5 o for a tubular absorber of OD 19 mm. Five troughs fabricated with a fiberglass substrate pasted over with UV stabilized self-adhesive aluminized polyester foil having high specular reflectivity joined together side by side make the CPC module with aperture area of 0.72 m 2. Copper tubes coated with NALSUN selective coatings and enclosed by borosilicate glass envelopes act as absorbers. The reflector–absorber assembly placed in a single glazed glass wool insulated wooden box forms the CPC collector. Using water as heat transfer fluid, efficiency tests were conducted with different inlet temperatures. Even at high temperature, the system operates with a reasonably high efficiency of 50%. In situ steam generation testing was also conducted. The fabricated CPC collector was used for steam cooking by connecting it to a pressure cooker. Cooking tests were conducted and the results are compared with earlier works. This cooker unites the characteristics of reflector cookers, steam cookers, pressure cookers and heat accumulating solar cookers. The fabricated CPC can be of immense and wide spread use for rural applications, such as water heating, steam cooking and sterilization.

Design of high efficiency polymeric cation exchange fibers1

AbstractIn this study, we have been exploring a new ion exchange material in the form of a fiber that could yield a number of important advantages over conventional ion exchange beads. In this approach, ion exchange fibers are prepared by 1) coating low‐cost glass fiber substrates with a polystyrene/divinylbenzene oligomer, 2) curing, and 3) sulfonating. The sulfonation process and effects of varying degrees of crosslinking were characterized through diffuse reflectance infrared spectroscopy and acid‐base neutralization titrations. Capacities of 4.7 meq/g (on a per resin basis) were easily obtained. Kinetics experiments showed the contact efficiencies of the new systems were greatly improved over the traditional beads due to greater surface associated with the film morphology and shorter diffusion lengths. This translated into an order of magnitude increase in ion exchange rate. As a result of the thin coatings, the use of solvents prior to functionalization, and preswelling of the finished product prior to end‐use were eliminated. Scanning electron microscopy was used to image the fibers and track­their mechanical integrity through various stages of­the process. Finally, repetitive regenerations proved­the long‐term stability of the spent fibers. Copyright­© 2001 John Wiley &amp; Sons, Ltd.