Enhancement of photovoltaic performance of polyaniline/graphene composite-based dye-sensitized solar cells by adding TiO2 nanoparticles

Polyaniline (PANi)-graphene composites and polyaniline-graphene/TiO₂ composites were prepared by ex-situ approach. Systematic investigation was carried out to explore photovoltaic (PV) properties of PANi-graphene and PANi-graphene/TiO₂ composite. The prepared composites were characterized using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Raman Spectroscopy and Ultraviolet–Visible (UV–Vis) Spectroscopy. The PV properties of dye-sensitized solar cells (DSSCs) prepared composites investigated by assembling materials in ITO/PANi-graphene/Al and ITO/PANi-graphene/TiO₂/Al architecture. Different PV parameters such as short circuit current, open circuit voltage, fill factor and power conversion efficiency were determined from the (Current-Voltage) IV characteristics of PV cell. The 15 wt% PANi loaded graphene composite based PV cell shows optimized power conversion efficiency of the order 6.47%. The main accomplishment of present work is that efficiency associated with 15 wt% PANi loaded graphene composite, improved further by addition of TiO₂ nanoparticles. The composite system between PANi-graphene/TiO₂ for 1 wt% of TiO₂ nanoparticles shows optimized power conversion efficiency of the order 8.63%.     

Improvement of hardness and anti-corrosion behavior of mild steel by plasma sprayed coating of Al2O3/GO composite

A robust and fast non-transferred plasma torch method was employed for developing coating of alumina (A₂O₃) and alumina/graphene oxide (A₂O₃/GO) on mild steel. Micro Raman analysis of GO confirms its spectroscopic behavior. The energy band gap of GO was determined as 3.44 eV. The successful coating formation of A₂O₃ and A₂O₃/GO (0.5 wt%) on mild steel was confirmed by X-ray diffraction analysis. Microhardness of mild steel was found to increase about 43.75% after coating with A₂O₃/GO (0.5 wt%) composite. The microstructure of A₂O₃/GO (0.5 wt%) coated mild steel represents better quality of coating and improved structural behavior. Mild steel becomes more corrosive resistance by reduction of corrosion potential (less negative than −0.05 V) after A₂O₃/GO (0.5 wt%) coating on it.     

Hydrothermal synthesis of reduced graphene sheets/Fe2O3 nanorods composites and their enhanced electrochemical performance for supercapacitors

Reduced graphene nanosheets/Fe₂O₃ nanorods (GNS/Fe₂O₃) composite has been fabricated by a hydrothermal route for supercapacitor electrode materials. The obtained GNS/Fe₂O₃ composite formed a uniform structure with the Fe₂O₃ nanorods grew on the graphene surface and/or filled between the graphene sheets. The electrochemical performances of the GNS/Fe₂O₃ hybrid supercapacitor were tested by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge tests in 6 M KOH electrolyte. Comparing with the pure Fe₂O₃ electrode, GNS/Fe₂O₃ composite electrode exhibits an enhanced specific capacitance of 320 F g⁻¹ at 10 mA cm⁻² and an excellent cycle-ability with capacity retention of about 97% after 500 cycles. The simple and cost-effective preparation technique of this composite with good capacitive behavior encourages its potential commercial application.     

Thermal characterization of NaNO3/KNO3 with different concentrations of Al2O3 and TiO2 nanoparticles

Journal of Thermal Analysis and Calorimetry - The thermo-physical properties of NaNO3/KNO3 (solar salt) added with Al2O3 and TiO2 nanoparticles as phase change material in thermal energy storage...     

Synthesis and formation mechanism of TiO2/Al2O3 nanobelts by electrospinning

Poly(vinyl pyrrolidone) (PVP)/[Ti(SO₄)₂ + Al(NO₃)₃] composite nanobelts were prepared via electrospinning technology, and TiO₂/Al₂O₃ nanobelts were fabricated by calcination of the prepared composite nanobelts. The samples were characterized by thermogravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). XRD results show that the composite nanobelts were amorphous in structure, and pure phase TiO₂/Al₂O₃ nanobelts were obtained by calcination of the relevant composite nanobelts at 950°C for 8 h. SEM analysis indicates that the surface of as-prepared composite nanobelts was smooth, the widths of the composite fibers were in narrow range, and the mean width was ca. 8.9 ± 2.1 μm, thickness was about 255 nm, and there is no cross-linking among nanobelts. The width of TiO₂/Al₂O₃ nanobelts was ca. 1.3 ± 0.1 μm and the thickness was about 105 nm. TG-DTA analysis reveals that the N,N-dimethylformamide (DMF), organic compounds and inorganic salts in the composite nanobelts were decomposed and volatilized totally, and the weight of the sample kept constant when sintering temperature was above 900°C, and the total weight loss percentage was 81%. FTIR analysis manifests that crystalline TiO₂/Al₂O₃ nanobelts were formed at 950°C. The possible formation mechanism of the TiO₂/Al₂O₃ nanobelts was preliminarily discussed.     

Optimizing the mechanical and surface topography of hydroxyapatite/Gd2O3/graphene oxide nanocomposites for medical applications

A ternary nanocomposite (TNC) was fabricated for introducing multifunctional properties for various biomedical applications. The nanocomposites consist of hydroxyapatite (HAP) combined with/without graphene oxide (GO) and gadolinium oxide (Gd₂O₃). The lattice constants of HAP were around 9.4285 and 6.7476 Å, while for Gd₂O₃ was around 10.8441 Å. The morphological investigation detected the nanosheets of GO, and nanorods of HAP/Gd₂O₃ with length of 27 nm. Moreover, the topological study based on a field emission scanning electron microscope (FESEM) showed that HAP/GO had average roughness (R_a) of 4.8 nm, and the root mean square value (R_q) with a value of 7 nm. Furthermore, the average pore size reached 7.99 nm for the NC of HAP/GO. In addition, the cumulative surface area using the density functional theory (DFT) method was calculated at around 44.61 m²/g for TNC. The cell viability in vitro of osteoblast cell line improved from 95.6 ± 0.6% to 96.7 ± 0.5% which indicates the biocompatibility of the implants to be used in biomedical applications.     

Impact of graphene on the enhancement of electrochemical and photocatalytic performance of Gd2O3 - Graphene nanocomposites

Gadolinium oxide - Graphene (Gd₂O₃-G) nanocomposites were prepared with different weight ratio of graphene using low temperature solution process. The structural, morphological, electrochemical and photocatalytic properties of the composites were investigated by X-ray diffraction, Raman, FE-SEM, HRTEM, Cyclic voltammetric and photo-degradation analysis. The chemical composition of the composites was studied by elemental mapping analysis using EPMA. The binding states of various elements present in the composites were analyzed by XPS. Cyclic voltammetric studies revealed that the nanocomposite with 5% graphene exhibits the specific capacitance of 26 F g⁻¹, which is higher than that of pure Gd₂O₃ (18 F g⁻¹). The presence of graphene has greatly enhanced the photocatalytic performance of Gd₂O₃G composites as the rate of degradation of MB dye is relatively higher in the composites compared to pure Gd₂O₃. The significant increase in the specific capacitance and rate of degradation of dye suggest that the Gd₂O₃G is a promising material for energy storage and environmental applications.     

Influence of surface properties on the interfacial adhesion in carbon fiber/epoxy composites

A polyacrylonitrile‐based carbon fiber was electrochemically oxidized in an aqueous ammonium bicarbonate solution with current density of up to 2.76 A/m² at room temperature. X‐ray photoelectron spectroscopy revealed that the oxygen content increased with increasing current density before approaching saturation. The increase can be divided into two regions, the rapid increase region (0–1.78 A/m²) and a plateau region (1.78–2.76 A/m²). The surface chemistry analysis showed that the interlaminar shear strength (ILSS) value of the carbon fiber/epoxy composite could be improved by 24.7%. The carbon structure was examined using Raman spectroscopy in terms of order/disorder in the graphite structure and the results indicated that the relative percentage of graphite carbon in the form of sp² hybridization increased above a current density of 1.39 A/m². The increasing non‐polar graphite carbon on the carbon fiber surface decreased the surface energy. As a result, both the surface free energy () and its polar component () decreased when current density increased above 1.78 A/m². The ILSS value had no direct relationship with the nature and surface density of the oxygen‐containing functional groups nor with the carbon structure. It is the surface free energy (), especially the polar component (), which played a critical role in affecting the interfacial adhesion of carbon fiber/epoxy composites. The ILSS value changed with increasing current density and could be divided into three distinct regions, as chemical interaction region (I), anchor force region (II) and matrix damage region (III). Copyright © 2013 John Wiley & Sons, Ltd.     

Enhancement of charge transfer rate at mixed morphology TiO2/graphene interface by Al3+

Applying conductive coatings on the surface of non-conductive materials can effectively reduce the hazards caused by static electricity during the production process. However, commercially available TiO₂ conductive powder relies on rare minerals and produces waste acids and bases. Therefore, we prepared Al-doped TiO₂/graphene composites, which combine the advantages of TiO₂ homojunction, ion doping, heterojunction, and rod morphology with excellent electrical conductivity (0.161 Ω·cm). In particular, the doping of Al³⁺ doubles its conductivity. This is due to the introduction of Al³⁺, which generates oxygen vacancies and so increases the carrier concentration. Furthermore, the introduction of Al³⁺ generates new conductive pathways (Al–O–C) and increases the content of highly electrochemically active oxygen-containing functional groups, leading to a significant enhancement of carrier transfer efficiency. Accordingly, the enhanced carrier concentration and transfer efficiency enhance the conductive properties of T-G-Al and provide new ideas for the preparation of conductive coatings.     

Preparation of Crack-free 3Y-TZP/Al2O3 Composite Ceramic Fiber by Electrolysis-sol-gel Method

Polycrystalline 3Y-TZP/Al2O3 tetragonal zirconia fiber was obtained by the pyrolysis of gel fibers using zirconium oxychloride octahydrate(ZOC)as the raw material.The spinnable zirconia sol was prepared by electrolyzing the zirconium oxychloride octahydrate(ZOC)solution in the presence of acetic acid and sugar(sucrose,glucrose or fructose),in which the molar ratios of CH3COOH/ZOC and sugar/ZOC were 1.0-4.0 and 0.2-0.4,respectively.The prepared tetragonal zirconia fibers sintered at different temperatures showed smooth and crack-free surfaces with diameters of 5-10 μm.The addition of Al2O3 enhanced the sintering process and prevented the crystals from growing.Thermogravimetric analysis(TG),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),and scanning electron microscope(SEM)techniques were used to characterize the prepared fibers.     

Improvement of interfacial adhesion in PP/PS blends enhanced with supersonic atmosphere plasma spraying surface‐treated carbon fiber

The effects of surface treatment of a carbon fiber (CF) by supersonic atmosphere plasma spraying (SAPS) on the interfacial adhesion behavior and morphology of polypropylene/polystyrene (PP/PS) matrix blends filled CF composites were investigated. Effects of surface treated a commercial CF on mechanical properties are studied. Contact angle was measured to examine the changes in wettability of the CF. The chemical and morphological changes were characterized by using X‐ray photoelectron spectroscopy and scanning electron microscopy. PP/PS/CF composites were fabricated with and without SAPS treatment, and their interlaminar fracture toughnesses were compared. The results showed that the interlaminar shear strength of composites has been greatly improved filled SAPS modification CF. The water contact angle of resin sample decreased 50% after addition of SAPS surface‐treated CF. Scanning electron microscopy results on the fractured surface exhibited PP/PS blends adhered well around the CFs of the SAPS‐treated specimen compared with that of the untreated specimen. This attributed to the CF interlock, and it improves the wetting between fibers and resins. Copyright © 2017 John Wiley & Sons, Ltd.     

Synergistic modification by mercapto hyperbranched polysiloxane and functionalized graphene oxide on the surface of aramid fiber

With the purpose of improving the interfacial properties of aramid fibers reinforced rubber composites and enhancing the tensile strength of aramid fibers simultaneously, mercapto hyperbranched polysiloxane (HPSi) and functionalized graphene oxide (GO) were used to modify the surface of aramid fibers. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and other characterization methods were performed to confirm the process of synergistic modification. Judging from the results of mechanical property tests, it could be acquired that the tensile strength of modified aramid fiber was increased by 16.8%, which could be ascribed to the wrapping effect of GO sheets. The interfacial properties were assessed by the pull-out tests of composites, and the results showed that the maximum pull-out force after synergistic surface modification was increased by 99.3%, which could be mainly related to additive reaction between double bonds and mercapto groups and the promotion of surface energy. More critically, during pull-out test, aramid fiber bundles might bring a part of shear stress into the grafted GO sheets, namely, GO sheets could convert fracture energy into interfacial energy, which would improve interfacial properties dramatically.     

化学沉积Ni-P-Al2O3和Ni-P-SiC复合材料的微观组织与物理性能

采用化学沉积方法,可以制备以镍磷合金为基质的复合硬质相粒子的复合材料［１］．镍磷合金颇受青睐之处在于可以调整成分和时效处理温度来改变其组织结构,进而获得广泛变化的性能［２,３］．本文报道化学沉积获得的ＮｉＰ氧化铝和ＮｉＰ碳化硅复合材料的微观组织与...     

Improvement of the Mo/TiO2-Al2O3 Catalyst by the Control of the Sol-Gel Synthesis

Traditional hydrotreating catalysts are constituted by molybdenum deposited on Al₂O₃ promoted by nickel and phosphorous. Several studies have shown that TiO₂-Al₂O₃ mixed oxides are excellent supports for the active phases. Results concerning the preparation, characterization and testing of molybdenum catalyst supported on titania-alumina are presented. The support was prepared by sol-gel route using titanium and aluminum isopropoxides, the titanium one chelated with acetylacetone (acac) to promote similar hydrolysis ratio for both the alcoxides. The effect of nominal molar ratio [Ti]/[Ti+Al] on the microstructural features of nanometric particles was analyzed by X-Ray Diffraction, N₂ Adsorption Isotherms and Transmission Electron Microscopy. The catalytic activity of Mo impregnated supports was evaluated using the thiophene hydrodesulfurization at different temperatures and atmospheric pressure. The pores size distribution curve moves from the micropores to the mesopores by increasing the Ti contents, allowing the fine tuning of average size from 2.5 to 6 nm. Maximal (367 m²·g^?1) and minimal (127 m²·g^?1) surface area were found for support containing [Ti]/[Ti+Al] ratio equal to 0.1 and 1, respectively. The good mesopore texture of alumina-titania support with [Ti]/[Ti+Al] molar ratio between 0.3 and 0.5 was found particularly valuable for the preparation of well dispersed MoS₂ active phase, leading to HDS catalyst with somewhat higher activity than that prepared using a commercial alumina support.     

High reversible capacity and rate capability of ZnCo2O4/graphene nanocomposite anode for high performance lithium ion batteries

A facile and straightforward method was adopted to synthesize ZnCo₂O₄/graphene nanocomposite anode. In the first step, pure ZnCo₂O₄ nanoparticles were synthesized using urea-assisted auto-combustion synthesis followed by annealing at a low temperature of 400 °C. In the second step, in order to synthesize ZnCo₂O₄/graphene nanocomposite, the obtained pure ZnCo₂O₄ nanoparticles were milled with 10 wt% reduced graphene nanosheets using high energy spex mill for 30 s. The ZnCo₂O₄ nanoparticles, with particle sizes of 25–50 nm, were uniformly dispersed and anchored on the reduced graphene nanosheets. Compared with pure ZnCo₂O₄ nanoparticles anode, significant improvements in the electrochemical performance of the nanocomposite anode were obtained. The resulting nanocomposite delivered a reversible capacity of 1124.8 mAh g⁻¹ at 0.1 C after 90 cycles with 98% Coulombic efficiency and high rate capability of 515.9 mAh g⁻¹ at 4.5 C, thus exhibiting one of the best lithium storage properties among the reported ZnCo₂O₄ anodes. The significant enhancement of the electrochemical performance of the nanocomposite anode could be credited to the strong synergy between ZnCo₂O₄ and graphene nanosheets, which maintain excellent electronic contact and accommodate the large volume changes during the lithiation/delithiation process.     

Co3O4/聚吡咯/石墨烯碱性溶液中电化学还原氧

燃料电池具有较高的能量密度和发电效率,以清洁能源为原料,零污染排放,是一种具有发展前景的能量储存和转化装置.阴极氧还原反应(ORR)在燃料电池中起着关键作用.ORR广泛采用贵金属铂基催化剂,但是它们价格昂贵,电子动力学转移速率慢,碱性条件下易团聚,这些亟需解决的问题阻碍了燃料电池商业化进程.近期,一些非贵金属催化剂被广泛研究,例如氮掺杂碳材料、Fe/N/C和Co/N/C材料等,它们有可能在未来替代铂基催化剂.我们的目标是合成新型高催化活性的Co/N/C及其衍生非贵金属材料,用于ORR催化反应.由于石墨烯具有独特的形貌、较大的比表面积和良好的导电性,其表面含有功能化的官能团,所以我们选择石墨烯作为碳载体.首先,用改性休克尔方法合成了氧化石墨烯(GO),为了提高其催化活性,采用聚吡咯作为氮源对其进行了氮掺杂,制备了聚吡咯/氧化石墨烯(Ppy/GO).通过ORR催化性能测试发现,GO对ORR具有一定的催化活性,它的起始电位和阴极电流电位分别为–0.31 V vs SCE和–0.38 V vs SCE;Ppy/GO的起始电位和阴极电流电位分别为–0.20 V vs SCE和–0.38 V vs SCE,氮掺杂对GO的催化活性有所提高.采用水热法沉积氧化钴合成了Co3O4/聚吡咯/氧化石墨烯(Co3O4/Ppy/GO).其形貌为Co3O4分散在氮掺杂GO表面.在KOH电解质(0.1 mol/L)中测试,Co3O4/Ppy/GO的起始电位和阴极电流电位分别为–0.20 V和–0.38 V vs SCE.经过800℃高温煅烧处理后,Co3O4/Ppy/GO-800的催化活性明显提高,起始电位和阴极电流电位分别达到–0.10 V和–0.18 V vs SCE.ORR电子转移数为3.4,接近于4电子反应途径.Co3O4/Ppy/GO对ORR的催化活性及4电子催化选择性较高,可能是由于纳米形态的Co3O4和Ppy/GO之间具有较强的表面作用力,聚吡咯掺杂的氧化石墨烯具有较强的电子储存及释放能力.综上,我们通过水热法制备了钴、氮共掺杂的GO,并研究了其对ORR的催化活性和电子转移选择性.结果表明Co3O4/Ppy/GO是一种高效的非贵金属电催化剂,在碱性电解质中具有很高的ORR催化活性,在燃料电池阴极催化剂方面很有前景.     

Alkali-resistant performance of V2O5-MoO3/TiO2 catalyst modified by SiO2

以陶瓷为骨架,用溶胶凝胶法和浸渍法制备了V2O5-MoO3/TiO2催化剂,并用SiO2进行改性.采用浸渍法模拟碱K中毒,研究了SiO2改性前后催化剂中毒脱硝效率的变化,并通过BET、H2-TPR、NH3-TPD等技术手段对催化剂进行了表征.结果表明,加入SiO2后,催化剂的比表面积明显提高.SiO2改性后新鲜催化剂还原温度向低温方向迁移10℃左右,氧化还原能力得到了提高,其表面酸强度和酸量也得到较大的提高.反应评价结果表明,SiO2改性可以提高催化剂抗碱中毒的件能.     

Preparation of Al2O3/TiO2 composite sol-gel fiber for headspace solid-phase microextraction of chlorinated organic solvents from urine

A new solid-phase microextraction fiber based on alumina/titania sol-gel-coated on copper wire for headspace sampling of chlorinated organic solvents (chloroform, carbon tetrachloride, trichloroethene, and tetrachloroethene) from urine samples is introduced. The influences of fiber coating composition and microextraction conditions (extraction temperature, extraction time, and ionic strength of the sample matrix) on the fiber performance were investigated. Also, the influence of temperature and time on desorption of analytes from fiber was studied. The proposed fiber has high capacity and demonstrates fast sampling of chlorinated organic solvents from urine samples with high sensitivity. The relative standard deviation (RSD, n=5) for all analytes was below 6.5%.     

Improvement of surface wettability and interfacial adhesion ability of poly(p-phenylene benzobisoxazole) (PBO) fiber by incorporation of 2,5-dihydroxyterephthalic acid (DHTA)

By introducing 2,5-dihydroxyterephthalic acid (DHTA) into poly(p-phenylene benzoxazole) (PBO) macromolecular chains, dihydroxy poly(p-phenylene benzobisoxazole) (DHPBO) was synthesized and then DHPBO fibers were prepared by dry-jet wet-spinning method. Effects of hydroxyl polar groups on surface wettability and interfacial adhesion ability of PBO fiber were investigated. With the incorporation of double hydroxyl polar groups, contact angle on PBO fiber for water can decrease from 71.4° to 50.70°, and contact angle for ethanol can decrease from 37.2° to 27.40°. The wetting time on DHPBO fibers for water can be as short as 650 ms, which is half of that of PBO fibers. The interfacial shearing strength (IFSS) between DHPBO (10% mol content DHTA) fibers and epoxy resin is 18.87 MPa, 92.55% higher than that of PBO fibers. SEM images indicate that the PBO/epoxy composite failure mode may change from fiber/matrix adhesive failure to partially cohesive failure.     

Improvement of the Pd/Al2O3 Catalyst by the Control of the Sol-Gel Preparative Parameters

In this work, the metal dispersion of the Pd/Al₂O₃ catalyst prepared by sol-gel method is improved by an adequate optimisation of the preparative variables. First, the gelation temperature and the ageing time are selected, in order to avoid the reduction of the metal precursor (palladium acetylacetonate, Pd(acac)₂) by the solvent (sec-butanol, sB). The metal sintering effect on the catalysts treated in oxygen at 500°C is then minimized when the alumina pore size is controlled by the variation of the alumium alkoxide (AsB) concentration and the acetic acid amount ([AcA]/[AsB]). The appearance of new palladium particles on the alumina surface and the matching between the particle diameters and the pore sizes were also effective for the metallic surface area improvement on the samples treated in oxygen at 800°C. Compared to the reference catalysts, the higher metal dispersion obtained on the sol-gel ones was the determinant factor for their higher catalytic activity in methane combustion.