Showing papers in "Materials Science and Engineering B-advanced Functional Solid-state Materials in 2018"
TL;DR: In this paper, a detailed study of semiconductor metal oxide (SMO) gas sensors is provided for a detailed comparison of SMO gas sensors with other gas sensors, especially for ammonia gas sensing.
Abstract: This review paper encompasses a detailed study of semiconductor metal oxide (SMO) gas sensors. It provides for a detailed comparison of SMO gas sensors with other gas sensors, especially for ammonia gas sensing. Different parameters which affect the performance (sensitivity, selectivity and stability) of SMO gas sensors are discussed here under. This paper also gives an insight about the dopant or impurity induced variations in the SMO materials used for gas sensing. It is concluded that dopants enhance the properties of SMOs for gas sensing applications by changing their microstructure and morphology, activation energy, electronic structure or band gap of the metal oxides. In some cases, dopants create defects in SMOs by generating oxygen vacancy or by forming solid solutions. These defects enhance the gas sensing properties. Different nanostructures (nanowires, nanotubes, heterojunctions), other than nanopowders have also been studied in this review. At the end, examples of SMOs are given to illustrate the potential use of different SMO materials for gas sensing.
1,296 citations
TL;DR: In this paper, the structural and morphological properties of resulting materials were characterized by X-ray diffraction (XRD), micro Raman, high-resolution transmission electron microscope (HRTEM) and scanning electron microscopy (SEM) respectively.
Abstract: Pure ZnO nanoparticles (NPs), ZnO/CuO and Al-ZnO/CuO nanocomposites (NCs) were prepared using co-precipitation followed by sol–gel method. The structural and morphological properties of resulting materials were characterized by X-ray diffraction (XRD), micro Raman, high-resolution transmission electron microscope (HRTEM) and scanning electron microscope (SEM) respectively. The XRD results confirmed that the ZnO-CuO composite is formed without the presence of any ZnO-CuO alloy. The gas sensing performance of pure ZnO, ZnO/CuO and Al-ZnO/CuO nanocomposites towards ammonia gas at room temperature was investigated. The gas sensing results revealed that the Al-ZnO/CuO nanocomposite based gas sensor has superior gas sensing properties like, high response, good stability, and fast response (14 s) and recovery (9 s) time towards 500 ppm (parts per million) ammonia gas at room temperature compared to pure ZnO and ZnO/CuO based sensors. Further the gas sensing performance of Al-ZnO/CuO sensor towards different volatile organic compound (VOC) gases was tested.
176 citations
TL;DR: In this paper, the authors discuss the emission characteristics of visible light by a monolithically integrated poly-Si diode under reverse bias and show that the dominant role of nonradiative recombination at the N+ and P+ contacts is diminished by confining the injected carriers around the PN junction's interface in which avalanche takes place.
Abstract: Development work was conducted on N+PN+PN+ Poly silicon light-emitting devices which are compatible with silicon-based integrated circuit technology. We discuss the emission characteristics of visible light by a monolithically integrated Poly-Si diode under reverse bias. With the structure of modified PN junctions, the carriers injection occurs through silicon slabs of only a few nanometer thick. The dominant role of non-radiative recombination at the N+ and P+ contacts is diminished by confining the injected carriers around the PN junction’s interface in which avalanche takes place. The current-dependent optical radiation presents a broad spectrum in the 400- to 900-nm range. Although the emission efficiency is low due to silicon’s indirect bandgap, it is advantageous to utilize these devices in all-silicon optoelectronic integrated circuits (OIC’s).
126 citations
TL;DR: In this article, two types of g-C3N4/Bi4Ti3O12 p-n heterostructures were prepared by a simple mixing-calcining method.
Abstract: Two types of g-C3N4/Bi4Ti3O12 p-n heterostructures were prepared by a simple mixing–calcining method. One is constructed from Bi4Ti3O12 (BTO) nanoparticles and g-C3N4 nanosheets (NS), and the other is constructed from BTO nanoparticles and g-C3N4 nanoparticles (NP). The structures, morphologies, optical and electrochemical properties of the samples were systematically characterized. PL spectra, EIS spectra and photocurrent responses demonstrate an effective separation of photogenerated electron-hole pairs for the composites. The photocatalytic performance of the composites was evaluated by the degradation of rhodamine B (RhB) under simulated-sunlight irradiation, revealing that they exhibit an enhanced photocatalytic activity compared to bare BTO and g-C3N4. The highest photocatalytic activity is observed for the composites with g-C3N4 content centered around 10%. Furthermore, g-C3N4(NP)/BTO composites integrated from BTO and g-C3N4 nanoparticles possess a superior photocatalytic activity compared to those integrated from BTO nanoparticles and g-C3N4 nanosheents.
96 citations
TL;DR: In this article, the state-of-the-art research activities related to the materials and assembly techniques developed for polymer-based electrochromic devices are reviewed, and an overview of the whole fabrication process including transparent conductive substrate, processing of electro-chromic polymer, electrolyte formulation, as well as edge sealant materials and possible encapsulation methods.
Abstract: The demand for polymer based electrochromic device is increasing in recent years due to not only the advantages of conjugated electrochromic polymers such as high color versatility, large optical contrasts, but also their potential applications in flexible devices. In this review, we focus on the state-of-the-art research activities related to the materials and assembly techniques developed for polymer based electrochromic devices. More specifically, we will give an overview of the whole fabrication process including transparent conductive substrate, processing of electrochromic polymer, electrolyte formulation, as well as edge sealant materials and possible encapsulation methods.
74 citations
TL;DR: In this paper, a low-cost sol-gel spin coating technique on a glass substrate was used to develop a ZnO thin-film sensor for gas sensing in the presence of NO2 gas.
Abstract: The ZnO thin film sensor is developed by a low-cost sol–gel spin coating technique on a glass substrate. The structural, morphological, surface compositional, optical and electrical properties of the ZnO thin film were studied using XRD, FESEM, XPS, HRTEM, FTIR and UV–VIS techniques. The gas sensing performance of ZnO thin film is studied at different operating temperature for various gases like NO2, NH3, CH3OH, Cl2 and H2S. The ZnO thin film sensor was highly selective towards NO2 gas with a maximum response of 12.3 at 100 ppm concentration at 200 °C operating temperature. ZnO film sensor can also detect low concentration of NO2 gas up to 5 ppm with the response of 4.1. The ZnO thin film sensor shows excellent repeatability, high stability and moderate response and recovery time, for NO2 gas in the 5–100 ppm concentration range.
73 citations
TL;DR: In this paper, the authors focused on the surfactant mediated synthesis of ZnAl2O4 nanoparticles (1−3) using sol-gel method and showed that the particle size of these nanoparticles can be reduced to half (12nm in 1, 6nm in 2 and 3nm in 3).
Abstract: The present work focuses on the surfactant mediated synthesis of ZnAl2O4 nanoparticles (1−3) using sol–gel method. 1 has been synthesized without any surfactant and during the synthesis of 2 and 3 cationic (cetyltrimethylammonium bromide) and anionic (sodium lauryl sulfate) surfactant, respectively, have been added. 1–3 have been characterized by P-XRD, FT-IR, SEM, SAED, TEM and BET techniques which suggest that surfactant reduces the particle size of ZnAl2O4 nanoparticles to half (12 nm in 1, 6 nm in 2 and 3). Zeta (ζ) potential measurements have been performed to determine the surface charges of all the samples. Moreover, the photocatalytic activities of these ZnAl2O4 nanoparticles have also been investigated. 2 exhibits better adsorption (28–41%) and degradation (97–99%) efficiency for anionic dyes due to high surface area (129.62 m2 g−1) and positively charged surface (ζ potential 30.06 mV). Radical trapping experiments suggest O2 − and OH to be the major reactive species for the degradation of dyes.
63 citations
TL;DR: In this article, composite nanofibers of magnesium oxide (MgO), poly(e-caprolactone) (PCL) and chitosan (CS) with diameters in the range of 0.7-1.3 µm were fabricated by electrospinning their blend solutions in trifluroethanol and water.
Abstract: The ability to produce composite nanofibers of inorganic particles and synthetic polymers represents a significant advancement in the development of composite materials for potential biomedical applications. In this study, composite nanofibers of magnesium oxide (MgO), poly(e-caprolactone) (PCL) and chitosan (CS) with diameters in the range of 0.7–1.3 µm were fabricated by electrospinning their blend solutions in trifluroethanol and water. To support the potential use of these nanofibrous membranes for biomedical applications their physicochemical properties such as morphology, mechanical strength, and integrity in aqueous medium, were studied. Cellular compatibility was determined using cell viability assays and microscopy imaging, with the results showing that the nanofibrous membranes support 3T3 cell viability and attachments. The new composite nanofibrous membranes developed in this study have the ability to mimic the physical structure and function of tissue extracellular matrix (ECM) and thus have potential for many tissue engineering applications.
59 citations
TL;DR: In this paper, core-shell structured hexagonal boron nitride coated hollow glass microsphere (HGM@hBN) particles were prepared using an electrostatic assembly process and incorporated into poly(tetrafluoroethylene) (PTFE).
Abstract: Porous polymer materials have been widely used for the preparation of low dielectric constant materials, but they also suffer from high moisture absorption and decreased thermal conductivity. In this study, core–shell structured hexagonal boron nitride coated hollow glass microsphere (HGM@hBN) particles were prepared using an electrostatic-assembly process and incorporated into poly(tetrafluoroethylene) (PTFE). The composites exhibited decreased dielectric constants due to the implantation of air, which is mainly encapsulated in HGM. The hBN layer on the surface of HGM effectively enhanced composite thermal conductivity due to its special core-shell form. The 30 vol% HGM@hBN/PTFE composites had a low dielectric constant of 1.68, low moisture absorption of 0.11%, and thermal conductivity (0.276 W/mK) was improved by 43% compared with that of 30 vol% HGM/PTFE composites. This study provides a facile and cost-effective strategy for fabricating polymer composites with low dielectric constant, low moisture absorption and no deteriorated thermal conductivity simultaneously.
51 citations
TL;DR: In this paper, the visible light photocatalytic ability of bismuth ferrite-zinc oxide composites with different molar ratios was investigated for conversion of CO2 in the gas phase.
Abstract: The visible light photocatalytic ability of bismuth ferrite-zinc oxide composites with different molar ratios was investigated for conversion of CO2 in the gas phase. The catalysts were successfully synthesized by hydrothermal method, and characterized by XRD, EDS, FESEM, UV–vis, and PL analyses. Also, the gaseous products were identified by FTIR technique. The FESEM illustrated the well crystalline particles of ZnO and BiFeO3. The UV–vis and PL analyses revealed that by increasing BiFeO3 content, the composites showed higher optical response in visible region and higher efficiency of charge separation, respectively. Compared with the pure ZnO and BiFeO3, which had poor performances under visible light irradiation, the as-synthesized photocatalysts showed the enhanced visible light photocatalytic activity for CO2 reduction. The highest photocatalytic conversion of CO2, 21%, was achieved by the as-synthesized photocatalyst with molar ratio of 1:1 under visible light. The enhanced visible light photocatalytic activity of BiFeO3-ZnO was assigned to the synergistic effect of p-n heterojunction and visible light sensitive property of perovskite structure of BiFeO3.
48 citations
TL;DR: In this paper, the electronic properties of monolayer aluminene nanosheet and adsorption properties of CO and NO gas molecules were investigated using first-principles studies for the first time.
Abstract: The electronic properties of monolayer aluminene nanosheet and adsorption properties of CO and NO gas molecules on aluminene nanosheet are investigated using first-principles studies for the first time. The density of states spectrum gives a clear picture regarding the transfer of charge upon adsorption of CO and NO gas molecules on aluminene nanosheet. The adsorption properties of CO and NO molecules on aluminene base material are explored in terms of average energy gap variation, natural bond orbital, HOMO-LUMO gap and adsorption energy. The most prominent adsorption sites of CO and NO molecules on aluminene are studied at an atomistic level. The state-of-the-art of aluminene base material gives the information regarding the development of chemical nanosensor. The findings of the present work suggest the use of monolayer aluminene nanosheet for the detection of CO and NO gas molecules.
TL;DR: In this article, a scalable single-step synthesis protocol for obtaining Ni/Mn-1,3,5-benzenetricarboxylate BMOF from which interconnected multi-faceted particles of NiMn2O4 spinel could be derived by thermal calcination at 800°C.
Abstract: Ternary transition metal oxides offer several advantageous features compared to the binary analogs due to presence of hetero transition metals with multiple valence states and the possible synergistic effects. Recently, metal organic frameworks have emerged as exotic template for synthesis of morphologically pre-designed metal oxide nanostructures. Nonetheless, synthesis of heteroatom ternary metal oxides through bi-metal organic framework (BMOF) route has proved to be challenging. Herein, we report a scalable single-step synthesis protocol for obtaining Ni/Mn-1,3,5-benzenetricarboxylate BMOF from which interconnected multi-faceted particles of NiMn2O4 spinel could be derived by thermal calcination at 800 °C. When applied as an anode for lithium-ion battery, the BMOF-derived mesoporous NiMn2O4 delivered a high reversible capacity (1049 mAh g−1), good rate performance (413 and 258 mAh g−1 at 503 and 1257 mA g−1) and good electrochemical stability highlighting the MOF-derived morphological advantages. The present results would help designing ternary metal oxide nanostructures for electrochemical energy storage application.
TL;DR: In this article, a smart-removal magnetic nanocomposites are developed in an attempt to decrease the band gap energy of the catalyst and to enable separation of the catalysts from the wastewater after the process.
Abstract: In this study smart-removal magnetic nanocomposites are developed in an attempt to decrease the band gap energy of the catalyst and to enable separation of the catalyst from the wastewater after the process. Ferrite magnetic nanoparticles Co0.5Zn0.25M0.25Fe2O4 (M = Ni, Cu, Mn, Mg) (MNPs) are obtained by the co-precipitation method using carboxymethyl cellulose (CMC) as surfactant and NaOH as precipitation agent. Further, the magnetic nanocomposites Co0.5Zn0.25M0.25Fe2O4-TiO2 (anatase) (MNPs-TiO2) are obtained by the TiO2 deposition onto the MNPs using Pluronic P123 as template and tetra butyl titanate (TBOT) as titanium source. This type of photocatalyst can be used under solar light irradiation because of the activation of TiO2 with MNPs in visible light range and can be very easily recovered due to their strong magnetic properties. The MNPs-TiO2 have proven to be very active for the degradation of different dyes, such as methyl orange and methylene blue, under solar light irradiation.
TL;DR: In this paper, the PbS-NiO nanocomposite had better photocatalytic activities for the photodegradation of methyl orange (MO) compared to that of pure pbS and NiO nanopowders.
Abstract: PbS, NiO and PbS-NiO nanocomposites were synthesized by a cost effective chemical route and characterized by techniques like TG-DTA, XRD, SEM, TEM, EDX, FTIR and PL. XRD studies reveal the presence of diffraction peaks related to PbS and NiO in the composite. The visible light photocatalytic tests showed that the PbS-NiO nanocomposite had better photocatalytic activities for the photodegradation of methyl orange (MO) compared to that of pure PbS and NiO nanopowders. Within 210 min of reaction time, nearly 89% decolorization efficiency of MO was achieved by the PbS-NiO photocatalyst, which is higher than that of pure PbS and NiO. The high photocatalytic efficiency of the composite was due to the extended photoresponse range and efficient separation of the electron-hole pairs in the PbS-NiO heterojunction. In addition, the composite also possess excellent antifungal efficiency against A. niger fungus strain. Enhanced magnetic properties were observed for the composite.
TL;DR: In this article, the first time, the authors test hematite either from natural goethite calcination and compared with synthetic hematites prepared by citrate or traditional precipitation method.
Abstract: 4 nitrophenol (4-NP) is a recalcitrant water pollutant. It reduces to 4 aminophenol (4-AP), which is a less harmful compound. Typically, a noble metal catalyzes this reaction. However, its preparation is complex and expensive. Here, for the first time, we test hematite either from natural goethite calcination and compared with a synthetic hematite prepared by citrate or traditional precipitation method. We characterize the catalysts by thermo gravimetric analysis (TGA), X-ray fluorescence (XRF), X-ray diffraction (XRD) transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), particle size distribution (PSD), and nitrogen adsorption desorption at 77 K. 4-NP reacted in presence of NaBH4 as the reducing agent to 4-AP. Kinetic study and catalyst stability were performed. Particle morphology played an important role in the reaction. All samples exhibited high catalytic activity with first order kinetic constants of 0.024, 0.027, 0.037 s−1 for natural α-Fe2O3, hematite prepared by precipitation, and citrate method, respectively.
TL;DR: In this paper, the effect of annealing on the physical properties of ZnO nanowires was investigated by field-emission scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction.
Abstract: ZnO nanowires were grown by hydrothermal synthesis and the effect of annealing on their physical properties was investigated by field-emission scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, spectrophotometry and Hall effect measurements. The nanowires adopted the c-axis [0 0 1] growth orientation of the underlying gallium and aluminium co-doped ZnO seed layer and their vertical alignment improved with annealing temperature up to 250 °C, above which it became random at 350 °C. This was attributed to the improvement in crystallinity up to 250 °C and its deterioration at 350 °C. Energy dispersive spectroscopy confirmed that the Zn:O atomic ratios for all samples were nearly stoichiometric. Average optical transmittances around 50–70% were observed in the visible region. The optimum electrical properties for transparent electrode fabrication were achieved at 250 °C, where the carrier concentration was maximum (5.5 × 1020 cm−3) and electrical resistivity was minimum (1.1 × 10−2 Ω cm).
TL;DR: A green route for the synthesis of PbS nanoparticles in an imidazolium based ionic liquid (IL) using single source and dual source precursor methods was reported in this paper.
Abstract: We report a green route for the synthesis of PbS nanoparticles in an imidazolium based ionic liquid (IL) (1-ethyl-3-methylimidazolium methanesulfonate) using single source and dual source precursor methods. Lead ethyl xanthogenate complex was used as single source molecular precursor for the synthesis of PbS nanoparticles, whereas in dual source approach organic sulfur (1-dodecanethiol) and inorganic sulfur (sodium sulfide) sources were used to observe the suitability of different sulfur sources on formation of PbS nanoparticles. The results showed that the temperature has an effect on the as prepared nanoparticles for both routes. X-ray diffraction (XRD) studies confirmed formation of cubic phase of PbS from both routes. Electron microscopy techniques showed that the nanoparticle morphologies differed significantly depending on the synthetic factors such as temperature, nature of precursors and ranged from spherical to cubic shapes.
TL;DR: In this paper, a CdO:ZnO (1:3) nanostructure was obtained that has a 25'nm grain size with a 4.870'A lattice constant.
Abstract: CdO:ZnO nanocomposite were synthesized via sol-gel technique and optimized for oxygen sensing. The transport properties of the CdO:ZnO thin films were analyzed for enhancing the gas sensing properties at low operating temperatures. CdO:ZnO (1:3) nanostructure was obtained that has a 25 nm grain size with a 4.870 A lattice constant. A highly transparent thin film of CdO:ZnO (3:1) with hollow sphere morphology and band gap of 2.4 eV was found to be less resistive. The sensing parameters such as sensor response, response time, recovery time, selectivity and stability of sensor were analyzed for different operating temperatures based on resistivity measurements. CdO:ZnO thin films of volume ratio 3:1 has the best sensitivity of 98.96 at an operating temperature of 150 °C. The present studies are encouraging for the realization of CdO:ZnO nanocomposite based sensor for efficient oxygen sensing properties at low temperatures fabricated with a low cost simple spin coating technique.
TL;DR: A series of Nickel-Zinc ferrite samples were synthesized by low-energy ball milling with subsequent thermal treatment in air at 1200 °C for 12 h.
Abstract: A series of Nickel-Zinc ferrite samples were synthesized by low-energy ball milling with subsequent thermal treatment in air at 1200 °C for 12 h. X-ray Diffraction patterns confirm the formation of the ferrite phases. Lattice parameters were found to increase almost linearly from 8.3366 A to 8.4387 A with the increment of zinc substitution. The oxygen parameters also increased and were found to closely follow an earlier proposed power law equation. The cation-oxygen bond lengths, suggest a gradual tetrahedral expansion and octahedral contraction with increasing Zn content. Additionally, the occupation of Zn2+ and Ni2+ ions in all samples has been determined by using the line intensity ratios of diffraction peaks together with a proposed general chemical formula. From the calculated cation distributions, it was found that the theoretical lattice parameters agree with the experimental ones. By using, the Williamson-Hall method, an average crystallite size of ∼36 nm was found.
TL;DR: In this paper, a simple, low cost and industrial scalable ball milling procedure for the eco-friendly synthesis of nanostructured CFTS powder without the need for organic solvents, amines or catalysts was developed.
Abstract: Environmentally benign Cu-based multinary chalcogenidessuch as Cu2FeSnS4 (CFTS) are fascinating growing attention owing to their outstanding opto-electronics properties. Here we developed a simple, low cost and industrial scalable ball milling procedure for the eco-friendly synthesis of nanostructured CFTS powder without the need for organic solvents, amines or catalysts. The nanostructured CFTS powder were characterized by various techniques. The phase pure CFTS structure of the product was confirmed by XRD, Raman spectroscopy and EDX analysis. The TEM images confirmed its nanostructured form with particle size around 30 nm. The band gap of the nanostructured CFTS powder was found to be 1.42 eV, which is suitable for multiple applications including photo-catalysis. Further, the synthesized nanocrystalline CFTS powder were used as a solar photocatalyst to explore the degradation of Rhodamine B dye under visible-light. The dye significantly degraded within 120 min under sun light irradiation.
TL;DR: In this article, Ni3N nanoparticles with spherical structure were successfully synthesized by urea glass route and the morphology and structure of the as-prepared nanoparticles were characterized by scanning electron microscopy and X-ray diffraction.
Abstract: In this paper, nickel nitride (Ni3N) nanoparticles with spherical structure are successfully synthesized by urea glass route. The morphology and structure of the as-prepared nanoparticles are characterized by scanning electron microscopy and X-ray diffraction. The electrocatalytic properties of the synthesized Ni3N for ethanol and methanol oxidation in alkaline media were investigated using cyclic voltammetry and chronoamperometry. A peak current of about 200 µA for ethanol and 100 µA for methanol oxidation was recorded during ethanol and methanol oxidation under the test condition of adding 1.0 M alcohols in 0.1 M NaOH solution. The stability of the catalyst was investigated using steady state chronoamperometry for 1000 s. The results show that the nickel nitride exhibits excellent electrocatalytic activity that is very promising catalyst for fuel cell application.
TL;DR: In this article, the influence of Gd ion doping on resistive switching and magnetic properties of NiFe2O4 (NiFe2−xGdxO4, NFG-x) thin films prepared by chemical solution deposition method was investigated.
Abstract: Influence of Gd ion doping on resistive switching (RS) and magnetic properties of NiFe2O4 (NiFe2−xGdxO4, NFG-x) thin films prepared by chemical solution deposition method was investigated. The 0.075 Gd-doped NiFe2O4 based devices exhibited much reliable repeatability, endurance (>500 switching cycles), and good data retention (105 s at 25 and 100 °C) without any significant degradation in their RS performance. Dominant conduction mechanisms in devices were Ohmic conduction at low resistance state and at lower voltage region of high resistance state, while Schottky emission dominated at higher voltage region in high resistance state. The physical mechanism of resistive switching was linked with the formation and rupture of conducting filaments, and the improved stability of the switching parameters for Pt/NFG/Pt devices was attributed to appropriate concentration of oxygen vacancies which can easily minimize randomness for formation/rupture of conductive filaments. Due to variation in concentration of oxygen vacancies, saturation magnetization of the RS device at high resistance state was higher than those at virgin state and low resistance state, and changes of saturation magnetization maintained a stable value of 40% between HRS and LRS of Pt/NFG-0.075/Pt device. Our study indicates that doping rare earth element into ferrite thin films is a viable approach for enhancing resistance switching and magnetic properties.
TL;DR: In this paper, a comprehensive review of the FeS2 nanostructures, including the preparation methods, properties and applications, is provided, and the application prospects of FeS 2 nanostructure in plentiful novel devices are introduced.
Abstract: Nanostructured metal sulfides have been widely studied due to their unique electrical, chemical, magnetic and optical properties and the promising application prospects. Pyrite iron disulfide (FeS2) receives high attention because of its suitable band gap, exceptionally high optical absorption coefficient in the visible region and the advantages of earth abundance, nontoxicity and low fabrication cost. It exhibits promising applications in photovoltaics, rechargeable batteries, dye-sensitized solar cells, photodetectors, photocapacitors and photocatalysis. This paper provides a comprehensive review of the FeS2 nanostructures, including the preparation methods, properties and applications. We begin from a short background of FeS2, describing the structure, fundamental physical, chemical and electronic properties. Then a detailed investigation of FeS2 nanostructures with different shapes and the corresponding methods are described. Finally, the application prospects of FeS2 nanostructures in plentiful novel devices are introduced.
TL;DR: In this article, mesoporous carbon spheres (MCSs) with tunable porosity are prepared by a mass-producible spray-drying process using chitosan as carbon precursor with ethanol as porosity tuning agent.
Abstract: Mesoporous carbon spheres (MCS) with tunable porosity are prepared by a mass-producible spray-drying process using chitosan as carbon precursor with ethanol as porosity tuning agent. By this template-free method, MCSs with different porosity are deduced by manipulating the volume ratio of ethanol in the solvent for chitosan. The resulted MCSs show controllable surface areas, pore volumes and bimodal pore size distribution. They are employed as substrates for the preparation of sulfur/carbon composite cathode. Electrochemical performance of the MCSs with 50 wt% sulfur loading is investigated. One of the S/MCS composite cathodes displays initial discharge capacity of 1163 mAhg −1 , excellent rate capability of 510 mAhg −1 at 2 C and good cycling stability of 715 mAhg −1 after 100 cycles at 0.2 C. The sulfur loading content could reach as high as 60%, while it still could deliver a capacity of 642 mAhg −1 after 100 cycles at 0.2 C.
TL;DR: In this article, NiO rich Ni/NiO nanocomposites in amorphous carbon matrix was synthesized using solution combustion method and characterized with XRD, FTIR, Raman, SEM, TEM, SAED and XPS.
Abstract: NiO rich Ni/NiO nanocomposites in amorphous carbon matrix was synthesized using solution combustion method and characterized with XRD, FTIR, Raman, SEM, TEM, SAED and XPS. Presence of amorphous carbon (sp2 hybridized) matrix was confirmed from the Raman spectra since compounds were having ID/IG ratio higher than 1. Electrical conductivity of the NiO rich Ni/NiO increased with temperature which corresponds to semiconductor nature. Thermal activation energy increased with respect to Ni content in NiO rich Ni/NiO nanocomposites. Sample with higher Ni content showed better photodegradation efficiency in methylene blue which was contributed by surface plasmon resonance (SPR) of nickel nanoparticles. Higher value of room temperature magnetic coercivity of NiO rich Ni/NiO nanocomposites were due to less magnetic interactions between the nanoparticles attributed to decrease of Ni content in the sample. Blocking temperature of Ni/NiO nanocomposites was close to room temperature and it exhibited ferromagnetism.
TL;DR: In this article, the effects of hybrid extrusion and solution treatment on the microstructure and corrosion behavior of Mg-0.1Cu alloy in Hanks' solution are studied.
Abstract: Effects of hybrid extrusion and solution treatment on the microstructure and corrosion behavior of Mg-0.1Cu alloy in Hanks’ solution are studied. The applied processing treatment is noted to alter the alloy microstructure. The amount of Mg2Cu precipitation is significantly reduced by the solution treatment. The decrease of secondary phases relieves occurrence of galvanic corrosion and the lowest corrosion rate achieved for the as-solutionized alloy at 510 °C is approximately 1/53 of that of the as-cast alloy. Grain refinement after extrusion results in better corrosion resistance compared with the as-cast alloy. However, the as-extruded Mg-0.1Cu alloy after the solution treatment shows higher degradation rate than the as-solutionized alloy. It is due to the uniformity of recrystallized grain size may play prominent role on the corrosion compared with the dissolution of the Mg2Cu phase by solution treatment.
TL;DR: In this article, a simple and facile strategy has been applied to improve the photoelectrochemical (PEC) water splitting performance of ZnO nanowire arrays by the optimization of Na2SO4 and Na 2SO3 electrolytes.
Abstract: In this work, a simple and facile strategy has been applied to improve the photoelectrochemical (PEC) water splitting performance of ZnO nanowire arrays by the optimization of Na2SO4 and Na2SO3 electrolytes. The ZnO nanowire array electrode exhibits significant PEC water splitting enhancement in Na2SO3 electrolyte solution compared to in Na2SO4 electrolyte solution. The photocurrent density of ZnO nanowire array photoanode in Na2SO3 electrolyte solution is 6 times higher than that in Na2SO4 electrolyte solution at 0.5 V vs. Ag/AgCl. Mott-Schottky (MS) and electrochemical impedance spectroscopy (EIS) studies of ZnO nanowire array electrodes in Na2SO4 and Na2SO3 electrolyte solutions reveal that SO32− anions consume the holes and efficiently improve the separation of photogenerated electron-hole pairs, leading to significant improvement for PEC water splitting performance in Na2SO3 electrolyte solution. This work provides a promising strategy to improve the PEC water splitting performance of photoanode materials by the optimization of electrolytes.
TL;DR: In this paper, three-dimensional porous nitrogen-doped graphene aerogels (NGAs) were synthesized via a facile and green hydrothermal process by using graphene oxide and different amino acids as nitrogen source.
Abstract: Three-dimensional porous nitrogen-doped graphene aerogels (NGAs) were synthesized via a facile and green hydrothermal process by using graphene oxide and different amino acids as nitrogen source. The morphology and structure of the as-prepared NGAs were characterized by means of FESEM, XRD, FTIR, Raman and XPS spectroscopy. The microstructure, nitrogen content and doping configuration of NGAs could be facilely controlled by selecting different amino acids. The formation mechanism of different nitrogen doping configurations was proposed. It has been proved that the NGAs prepared with amino acids as nitrogen doping source had enhanced electrochemical performance than pristine graphene aerogels. The pyrrolic N as main doping configuration plays important role in determining the electrochemical performance of NGAs. The NGA with pyrrolic N (content up to 13.82 at.%) exhibited a high specific capacitance, superior rate capability and excellent cycling life. This study gives inspiration to fabricate NGAs for a broad range of technological applications.
TL;DR: In this article, thermal conductivities of general carbon nanotube reinforced polymer nanocomposites are predicted using the effective medium approach using both straight and wavy and also aligned, 2-dimensinal (2D) and 3-dimensional (3D) randomly oriented CNTs.
Abstract: Overall thermal conductivities of general carbon nanotube (CNT) reinforced polymer nanocomposites are predicted using the effective medium approach. Both straight and wavy and also aligned, 2-dimensinal (2D) and 3-dimensional (3D) randomly oriented CNTs are included in the analysis. The CNT/polymer interface thermal resistance and temperature dependency of the constituent's properties are taken into account. The effects of volume fraction, diameter and non-straight shape of CNTs, interfacial thermal resistance and temperature are investigated on the nanocomposite overall heat transfer behavior. Generally, a good agreement is observed between the results of the presented model and experimental data. The results emphasize that the consideration of the proper waviness and 3D random orientation of CNTs together with the interfacial thermal resistance into the analysis is essential for a more realistic prediction. Effective conducting response of the 3D randomly oriented wavy CNT-reinforced nanocomposites is considerably higher than those of 3D randomly oriented straight CNT-reinforced nanocomposites.
TL;DR: In this article, the gas-sensing properties of NiGa2O4 nanofibers were investigated, and it was found that the sensor based on NiGa 2O4 (600°C, 2´h) exhibited good response and good selectivity to trimethylamine (TMA) vapor at room temperature.
Abstract: NiGa2O4 nanofibers were prepared by a single spinneret electrospinning method. The precursor was analyzed by TG-DSC. The as-prepared samples were characterized by XRD, SEM, N2 adsorption–desorption, FTIR, XPS and UV–Vis DRS, respectively. The gas-sensing properties of NiGa2O4 nanofibers were investigated. The characterization results demonstrated that the one-dimensional NiGa2O4 nanofibers consisted of about 10–15 nm nanocrystals after calcinations. It was found that the sensor based on NiGa2O4 nanofibers (600 °C, 2 h) exhibited good response and good selectivity to trimethylamine (TMA) vapor at room temperature. When operating at room temperature, the responses of the sensor based on NiGa2O4 nanofiber (600 °C, 2 h) to 1 ppm trimethylamine reached 1.05; the detection limit for trimethylamine was 1 ppm; especially, the response time and the recovery time for 1000 ppm trimethylamine were 14 s and 2 s, respectively; the response time and the recovery time for 1 ppm trimethylamine were all shorter than 2 s. If the long-term gas sensing stability is improved, the sensor based on NiGa2O4 nanofibers (600 °C, 2 h) can be used as trimethylamine-sensing gas sensor in practice.