articles+ search results

Solar collectors, Heat pipes, Aluminum plates, Surface preparation, Thermal resistance, and Heat transfer

Micro-grooved aluminum flat plate heat pipes (MFPHPs), fabricated by hot extrusion and subsequent inner surface treatment via chemical corrosion, were developed to improve the thermal efficiency and reduce the costs of solar collectors. Thermal performances of MFPHPs, including temperature distribution, maximum heat transfer capability, and thermal resistance, were experimentally conducted. The effects of treatment time and solution concentration on the thermal performance enhancement of MFPHPs were also investigated. The experimental results show that inner surface treatment can substantially enhance the thermal performance of MFPHPs, and different treatment morphologies of inner surfaces result in differences in thermal performance enhancement. The optimal treatment parameters were determined to be a treatment time of 10 min with a solution concentration of 1.5 moL/l. This resulted in the optimal thermal performance enhancement: an increase of approximately 80% in heat transfer capability and a decrease of more than 44% in thermal resistance, compared to the untreated MFPHP. This study provides a convenient, effective, and low-cost method to enhance the thermal performance of MFPHPs applied in solar collectors. • MFPHPs with inner surface treatment were developed to improve the thermal efficiency of solar collectors. • Thermal performances of MFPHPs are subsequently enhanced by inner surface treatment. • Optimum inner surface treatment parameters for MFPHP were determined. [ABSTRACT FROM AUTHOR]

Surface preparation, Biopolymers, Rotational molding of plastics, Agaves, and Polylactic acid

In this work, agave fibers were surface treated using maleated PLA (MAPLA) in order to increase the fiber content (from 10 up to 40% wt.) in polylactic acid (PLA) biocomposites produced by rotational molding and to study the effect of the agave fiber and its treatment on the physical, mechanical and thermal properties of the biocomposites. This chemical modification between agave fibers and MAPLA was evaluated by FTIR spectroscopy. In general the results indicate that MAPLA surface treatment produces a more homogeneous morphology with lower interfacial gaps and overall porosity, especially at higher agave contents. This improved compatibility promoted better stress transfer leading to increased mechanical properties. For example, the tensile strength and modulus of treated fiber composites increased by up to 68% (from 25 to 41 MPa) and 32% (from 1.30 to 1.74 GPa) respectively, in comparison with untreated fiber composites. Fiber surface treatment also decreases hydrophilicity, lowering water absorption and diffusion coefficient. From thermo-mechanical analyses, the damping behavior of the biocomposites decreased with MAPLA treatment since a stronger interface is able to sustain higher stresses and dissipates less energy. Finally, the thermal stability was also improved as a result of better interfacial chemical bonding leading to a 12 °C increase in thermal stability (from 254 to 266 °C). [ABSTRACT FROM AUTHOR]

Biofilms, Bagasse, Biopolymers, Scanning electron microscopy, and X-ray diffraction

Bagasse fibers reinforced poly(vinyl alcohol) (PVA) composite films were successfully prepared by solution casting method. To enhance the dispersing effect of the fillers, alkali treatment of the plant fibers was adopted before the fabrication of composites. The structure and properties of the resulting composites were characterized by scanning electron microscopy (SEM), X-ray diffraction, differential scanning calorimetry, mechanical tests, water uptake and thermal stability in detail. The results showed that bagasse fibers after surface modification exhibited good compatibility with PVA matrix. The increased polarity as well as the roughness would be beneficial to the interaction and mechanical interlocking between the fiber and matrix. Acting as the heterogeneous nucleation agents, the fibers could enhance the degree of crystallization and decrease the supercooling degrees of PVA matrix. The fibers exhibited dramatically reinforcing effect in the matrix, and with the increase of fiber, the Young’s modulus and tensile yield stress increased. The Young’s modulus and tensile yield stress of composites with 8% filler would be 3 and 2 times compared with neat PVA films. The thermal stability decreased a little and the water uptake increased with the increase of filler content. These composite films would find wide applications in green packaging areas for their fine mechanical and thermal properties. [ABSTRACT FROM AUTHOR]

Arrowroot, Polylactic acid, Surface preparation, Thermal analysis, and Natural fibers

The structural, thermal, mechanical, and biodegradable properties of composite materials made from polylactide (PLA) and agricultural residues (arrowroot (Maranta arundinacea) fibre, AF) were evaluated. Melt blended glycidyl methacrylate-grafted polylactide (PLA-g-GMA) and coupling agent-treated arrowroot fibre (TAF) formed the PLA-g-GMA/TAF composite, which had better properties than the PLA/AF composite. The water resistance of the PLA-g-GMA/TAF composite was greater than that of the PLA/AF composite; the release of PLA in water from the PLA/AF and PLA-g-GMA/TAF composites indicated good biological activity. The PLA-g-GMA/TAF material had better mechanical properties than PLA/AF. This behaviour was attributed to better compatibility between the grafted polymer and TAF. The results indicated that the Tg of PLA was increased by the addition of fibre, which may have improved the heat resistance of PLA. Furthermore, the mass losses following burial in soil compost indicated that both materials were biodegradable, especially at high levels of AF or TAF substitution. [ABSTRACT FROM AUTHOR]

Carbon, Microbial fuel cells, Polyanilines, Electrochemical analysis, Graphite, and Nanocomposite materials

Modification of electrode material from the environmental point of view and scale-up is as important as increasing the power density in benthic microbial fuel cells (BMFC). Here, we examined two different materials for an anode and their modification via surface treatment and surface coating. Polyaniline incorporated carbon cloth (PANI/CC), acid-treated carbon cloth (CC), grooved and acid treated graphite plate (GGP), and polyaniline coated graphite plate (PANI/GP) are used in this study. Modified anodes were compared through electrochemical techniques. It was observed that kinetic activity of PANI/CC was 376 times higher than CC anode, while PANI/GP possesses 1.8 times more kinetic activity than GGP. Power density was recorded and observed decreasing order as follows PANi/CC>CC> PANI/GP > GGP. A mechanism of electron transport model is proposed based on the structural properties of polyaniline coated carbon nanocomposites that enhances the electron flow efficiently for the generation of power with high degree. Polyaniline coated anode materials show greater wettability than their respective surface treated counterparts. Further enhancement in power generation was successfully achieved by recharging with acetate. The study tried to compare the different material and their modifications in the same environment and helps to optimize the system further based on the results obtained. [ABSTRACT FROM AUTHOR]

Microbial fuel cells, Surface preparation, Polyanilines, Surface coatings, Electrodes, and Power density

• Surface treated and surface coated electrodes were compared. • Grooved and acid treated anode and polyaniline coated anode were compared. • Kinetic activity of PANI/CC was 376 times higher than CC, while PANI/GP possesses 1.8 times more kinetic activity than GGP. • Enhancement in power generation was successfully achieved by recharging with acetate. Modification of electrode material from the environmental point of view and scale-up is as important as increasing the power density in benthic microbial fuel cells (BMFC). Here, we examined two different materials for an anode and their modification via surface treatment and surface coating. Polyaniline incorporated carbon cloth (PANI/CC), acid-treated carbon cloth (CC), grooved and acid treated graphite plate (GGP), and polyaniline coated graphite plate (PANI/GP) are used in this study. Modified anodes were compared through electrochemical techniques. It was observed that kinetic activity of PANI/CC was 376 times higher than CC anode, while PANI/GP possesses 1.8 times more kinetic activity than GGP. Power density was recorded and observed decreasing order as follows PANI/CC > CC > PANI/GP > GGP. A mechanism of electron transport model is proposed based on the structural properties of polyaniline coated carbon nanocomposites that enhances the electron flow efficiently for the generation of power with high degree. Polyaniline coated anode materials show greater wettability than their respective surface treated counterparts. Further enhancement in power generation was successfully achieved by recharging with acetate. The study tried to compare the different material and their modifications in the same environment and helps to optimize the system further based on the results obtained. [ABSTRACT FROM AUTHOR]

Air conditioning & the environment, Energy consumption & the environment, Refrigeration & refrigerating machinery & the environment, Magnetic field effects, and Humidity control

Frost formation is inevitable in refrigeration and air conditioning fields. Frosting heavily impacts on the operating efficiency of equipments, and leads to considerable energy consumption for defrosting. This study reviewed anti-frosting techniques in refrigeration and air conditioning fields, including air dehumidification by solid/liquid desiccant, ultrasonic vibration, external electric/magnetic field, surface treatment, etc. Although air dehumidification is an effective method to delay frost formation, the problem of desiccant regeneration prevents this method from practical application. The methods of ultrasonic vibration and external electric/magnetic field are not suitable for large or medium-sized fin-tube evaporator, which result in additional investment and energy input. Besides, the anti-frosting effect of electric/magnetic field is not obvious and needs to be verified by more experiments. However, surface treatment has advantages of high efficient, low cost, environmental protection and practicability. In particular, the superhydrophobic surface shows excellent performance in frosting prevention and defrosting improvement. This is of great significance for energy saving in refrigeration and air conditioning fields. If the strength problem can be further improved by simple preparation methods, it will be a promising anti-frosting technique to deal with the phenomenon of frost formation in refrigeration and air conditioning fields. [ABSTRACT FROM AUTHOR]

Solar cell efficiency, Titanium dioxide, and Surface preparation

Herein, we studied the effect of surface treatment of compact TiO2 layer by vacuum ultraviolet (VUV) light and by TiCl4 on the I- V hysteresis of perovskite solar cells prepared on fluorine-doped tin oxide (FTO) substrates with two different surface roughnesses. Initially, the cells prepared on flat FTO substrates show better results than cells prepared on rough FTO, with slightly higher power conversion efficiency (PCE) and less hysteresis in the I- V curves. Treatment of TiO2 prepared on flat FTO has no effect on the I- V hysteresis because of better contact between TiO2/CH3NH3PbI3 layers. Treatment of TiO2 layer on rough FTO has a positive effect on the PCE and I- V hysteresis and stability. [ABSTRACT FROM AUTHOR]

Energy consumption, Refrigeration & refrigerating machinery, Electrohydrodynamics, Surface preparation, and Humidity control equipment

This study reviewed the defrosting techniques applicable for the heating, ventilation, air-conditioning, and refrigeration industry, including passive, active, and system techniques. The passive methods normally use treated surfaces by changing the surface morphology through micro-grooved, anti-frost coating, hydrophilic, hydrophilic, or superhydropholic coating. For passive defrosting techniques, the microgrooved surfaces can improve the drainage of the frost melt effectively. It is generally agreed that the superhydropholic coating can delay the initialization of frosting and provides less water adhesion during defrosting. Yet defrosting performance for hydrophobic surfaces outperforms hydrophilic and uncoated surfaces. Active and system techniques, including electrohydrodynamic (EHD), low-frequency oscillation, and ultrasonic vibration methods, hot gas reverse cycle, electric heater, desiccant dehumidifiers and controlling strategies are reviewed. The EHD defrosting method is proved to be comparatively effective in natural or laminar flow operation. Test results also indicate that utilization of alternative current source is superior to the direct current source. The electrode with negative polarity is better than positive polarity as far as frost accumulation is concerned. The low-frequency oscillation is ineffective in defrosting while ultrasonic vibration provides effective frost removal and can delay the frost growth appreciably. Test results indicate that the ultrasonic oscillation poses considerable positive influence on defrosting either operated continuously or intermittently, in direct contact or not. For system defrosting, the hot gas reverse cycle is comparatively expensive to install but the efficiency, COP, and energy consumption are superior to the other system methods. Desiccants, either solid or liquid, can be employed in association with the system defrosting methods to lower energy consumption. There were various controlling strategies to detect the frost formation and to decide the best time to initiate defrosting. However, many of them were applicable to some specific systems and environments and require further investigations to test the relevant reliability, stability, and repeatability. [ABSTRACT FROM AUTHOR]

Gas cleaning, Jet engines, Filter efficiency, Ultrasonic cleaning, and Particles

This work was performed in order to evaluate the operating conditions during the pulse jet cleaning filtration using different surface treated fibrous filters. The experiments were realized using a small flat media. The comparative studies were performed with untreated and treated (singeing/calendering and calendering/thermofixation with an eggshell type anti-pilling finish (smooth surface) on one side) polyester filters to remove micrometric particles of dolomitic limestone. Filtration tests were conducted with a superficial velocity of 4 cm/s. The stipulated maximum pressure drop was 100 Pa, the pulse time was 200 ms and pressure pulse (Pp) of 2 kgf/cm². The filters showed satisfactory performance during fifty cycles. The untreated filter presented better cleaning efficiency and lower residual pressure drop, resulting in better regeneration of the filter during fifty cycles. However, the collection efficiency of the untreated filter was lower, compared to the surface-treated filters. The findings indicate that it is important to use surface treatment of filters in order to avoid deep deposition of particles and achieve high collection efficiencies during prolonged filtration cycles. [ABSTRACT FROM AUTHOR]

Aniline, Polyethylene terephthalate, Metallic composites, Microfabrication, X-ray diffraction, Polymerization, Scanning electron microscopy, and Zinc oxide

Abstract: A conductive network consisting of polyaniline (PANI) and PANI/nm-ZnO immobilized on the surfaces of poly(ethylene terephthalate) (PET) fabrics was synthesized by a route involving a wet-chemical technique and in-situ chemical oxidative polymerization procedures. Morphological, structural, thermal and electrical properties of the PET fabrics modified with PANI–ZnO composites were analyzed. X-ray diffraction (XRD) measurements of the composites revealed that the crystal structure of incorporated ZnO undergone a weak distortion during the polymerization reaction and the XRD pattern of PANI was predominate. Attenuated total reflection Fourier transform infrared spectroscopic studies indicated the presence of interaction between ZnO nanorods and molecular chains of PANI in the ZnO/PANI layers. Field emission scanning electron microscope images implied the thin composite layers showed a submicro-sized rod like network and the homogeneous distribution on the substrates. Thermogravimetric studies exhibited that the PET-ZnO/PANI composite had a higher thermal stability than anyone of PET and PET-PANI. The surface resistance of ZnO/PANI conductive films was found to be smaller than the PANI film, which was declined as aniline concentration in adsorption bath increased and reached a relatively low value when Zn(NO3)2 concentration was at 0.03mol/L in the precursor solution. [Copyright &y& Elsevier]

Polymeric composites, Sisal (Fiber), Fibrous composites, Chemical resistance, and Sodium hydroxide

In this study, effect of fibre surface treatment on tensile, flexural and chemical resistance properties were studied for sisal fibre reinforced composites. Natural ligno cellulosic sisal fibre reinforced composites were prepared by different surface treatments by hand lay-up method. Fibre surface treatments were carried out to produce good interface between the fibre and the matrix to improve the mechanical properties. Fibre surface treatments were done by boiled the sisal fibres in different % of NaOH and treated the fibres in different % of NaOH, treated in acetic acid and methanol. Unsaturated polyester resin was used as the matrix for preparing the composites. For comparison, these properties for untreated sisal fibre reinforced composites were also studied. From the results it was observed that 18% aqueous NaOH boiled sisal fibre reinforced composites have higher tensile, flexural properties than other composites. Untreated sisal fibre composites show lower properties than treated composites. Chemical resistance properties indicate that all sisal fibre reinforced composites are resistance to all chemicals except carbon tetra chloride. The tests are carried out as per the ASTM standards. [ABSTRACT FROM AUTHOR]

Metals, Plasma gases, Zinc oxide thin films, Silicon solar cells, Crystal texture, Metallic surfaces, Gas flow, Scanning electron microscopy, Microfabrication, and Plasma etching

Abstract: This paper considers texturing of ZnO:Ga (GZO) films used as back contacts in amorphous silicon (a-Si) thin film solar cells. GZO thin films are first prepared by conventional methods. The as-deposited GZO surface properties are modified so that their use as back contacts on a-Si solar cells is enhanced. Texturing is performed by simple dry plasma etching in a CVD process chamber,at power=100W, substrate temperature=190°C (temperature is held at 190°C because thin film solar cells are damaged above 200°C), pressure=400Pa and process gas H2 flow=700sccm. Conventional a-Si solar cells are fabricated with and without GZO back contact surface treatment. Comparison of the with/without texturing GZO films shows that plasma etching increases optical scattering reflectance and reflection haze. SEM and TEM are used to evaluate the morphological treatment-induced changes in the films. Comparison of the a-Si solar cells with/without texturing shows that the plasma treatment increases both the short-circuit current density and fill factor. Consequently, a-Si solar cell efficiency is relatively improved by 4.6%. [ABSTRACT FROM AUTHOR]

Photovoltaic cells, Styrene, Ultraviolet radiation, Diodes, Sulfonates, Thermal conductivity, Polyalkylthiophenes, and Surface analysis

Abstract: In this study, the effect of ultraviolet treatment on the photovoltaic property of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate)/n-type Si (PEDOT:PSS/n-Si) diodes was examined. Power conversion efficiency of the PEDOT:PSS/n-Si diodes in the light (AM 1.5G, 100mW/cm2) was improved by reducing the device series resistance by ultraviolet treatment. This study shows that conductivity of PEDOT:PSS plays an important role in PEDOT:PSS/n-Si photovoltaic devices. [ABSTRACT FROM AUTHOR]

Solar cells, Porous materials, Crystal growth, Electric properties of thin films, Electric properties of silicon crystals, Substrates (Materials science), Geometry, Crystal defects, and Transmission electron microscopy

Abstract: The effect of substrate morphology on the growth and electrical properties of single-junction microcrystalline silicon cells is investigated. A large variety of V-shaped and U-shaped substrates are characterized by scanning electron microscopy (SEM) and the growth of thin-film microcrystalline silicon (μc-Si:H) devices is observed by cross-sectional transmission electron microscopy (TEM). It is shown that enhanced electrical properties of solar cells are obtained when U-shaped substrates are used and the effect is universal, i.e. independent of the substrate or feature size. U-shaped substrates prevent the formation of two dimensional “cracks”, which are identified as zones of porous material, from propagating throughout the active part of the solar cell. A numerical growth simulation program reproduces satisfactorily these experimental observations. According to these simulations, shadowing effect due to surface morphology and low adatom surface diffusion length are responsible for the formation of cracks in μc-Si:H material. [Copyright &y& Elsevier]

Carbon, Fuel cells, Direct energy conversion, Coal-fired power plants, Activated carbon, Surface analysis, Electric generators, and Electrochemistry

Abstract: The direct carbon fuel cell (DCFC) is a promising power-generation device that has much higher efficiency (80%) and less emissions than conventional coal-fired power plants. Two commercial carbons (activated carbon and carbon black) pre-treated with HNO3, HCl or air plasma are tested in a DCFC. The correlation between the surface properties and electrochemical performance of the carbon fuels is explored. The HNO3-treated carbon fuels have the highest electrochemical reactivity in the DCFC due to the largest degree of surface oxygen functional groups. The overall effect on changing the electrochemical reactivity of carbon fuels is in the order HNO3 >air plasma≈HCl. Product gas analysis indicates that complete oxidation of carbon to CO2 can be achieved at 600–700°C. [Copyright &y& Elsevier]

Silicon solar cells, Plasma effects in semiconductors, Dielectrics, and Surface chemistry

Abstract: To lower the fabrication cost of silicon solar cells, a surface treatment using a dielectric barrier discharge (DBD) instead of a wet cleaning technique was examined on electrode surfaces on silicon solar cells. The fill factor obtained through measuring current–voltage characteristics was evaluated, and the treated surface state was characterized by energy-dispersive X-ray. It was found that the DBD effectively activated the electrode surface and the surface treatment on finger electrodes contributed greatly to improve the fill factor. [Copyright &y& Elsevier]

Chromatographic analysis, Saline waters, Thin films, Gamma-hydroxybutyrate, Colloids, Scanning electron microscopy, and Particles (Nuclear physics)

The poly(ℇ-caprolactone) (PCL) and poly[(R)-3-hydroxybutyrate] (R-PHB) films with a hydrophilic surface were prepared by the alkali treatment of their as-cast films in NaOH solutions of different concentrations. The alkali-treated PCL and R-PHB films, as well as the as-cast PCL and R-PHB films, were biodegraded in soil controlled at 25°C and the effects of alkali treatment or surface hydrophilicities on their biodegradation were investigated by the use of gravimetry, gel permeation chromatography (GPC), scanning electron microscopy (SEM), and polarization optical microscopy. It became evident that the alkali treatment enhanced the hydrophilicities and biodegradabilities of the PCL and R-PHB films in soil. The biodegradabilities of the as-cast aliphatic polyester films in controlled soil decreased in the following order: PCL > R-PHB > PLLA, in agreement with that in controlled static seawater. [ABSTRACT FROM AUTHOR]

Solar cells, Contact angle, and Stoichiometry

We treated the surface of indium–tin oxide (ITO) substrates in two ways, (i) coating of thin insulating ITO layer or (ii) irradiation of the surface with accelerated ions, and investigated the change in sheet resistance (Rsh) and the water-contact angle (WCA). Rsh increased with the thickness of the insulating ITO layer or with the ion dose. WCA dropped as a result of the surface treatment to <15°. The microstructure, the surface morphology, the optical transmittance, and the stoichiometry of CdS improved with the surface treatment. CdS/CdTe solar cells showed a better performance as a result of ITO surface treatment. [Copyright &y& Elsevier]

Solar cells, Titanium dioxide, and Metallic surfaces

Origin ofI–V hysteresis in perovskite solar cells: The cover image highlights the role of interfaces in perovskite solar cells that are strongly related to the I–V hysteresis and efficiencies of CH3NH3PbI3‐based cells. Accumulated photogenerated charges at the TiO2/CH3NH3PbI3 interface caused by contact mismatch or/and band bending at this interface are expected to give rise to a trapping and a large recombination rate. Unbalanced charge collection and transfer create the capacitance that is the main origin of the I–V hysteresis. Such capacitance observed in perovskite solar cells is related to purely interfacial contacts. Perovskite devices prepared on flat fluorinated tin oxide (FTO) substrates showed better interfacial contacts, with small I–V hysteresis compared to the rough FTO substrates. For devices prepared on rough FTO, surface treatment of the compact TiO2 layer with TiCl4 and vacuum ultraviolet radiation affected the efficiency and also the I–V hysteresis, which is related to the physical contacts at this interface. More details can be found in the Communication by Ludmila Cojocaru et al. at the University of Tokyo and SPD Laboratory, Inc, Japan on page 1762 in Issue 10, 2017 (DOI: 10.1002/ente.201700308). [ABSTRACT FROM AUTHOR]