Characteristic Diffraction Peaks Research Articles

Spark Plasma Sintering of Aluminum-Based Powders Reinforced with Carbon Nanotubes: Investigation of Electrical Conductivity and Hardness Properties.

This paper focuses on reporting results obtained by the spark plasma sintering (SPS) consolidation and characterization of aluminum-based nanocomposites reinforced with concentrations of 0.5 wt%, 1 wt% and 2 wt% of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Experimental characterization performed by SEM shows uniform carbon nanotube (CNT) dispersion as well as carbon clusters located in the grain boundary of the Al matrix. The structural analysis and crystallite size calculation were performed by X-ray diffraction tests, detecting the characteristic CNT diffraction peak only for the composites reinforced with MWCNTs. Furthermore, a considerable increment in the crystallite size value for those Al samples reinforced and sintered with 1 wt% of CNTs was observed. Hardness tests show an improvement in the composite surface hardness of about 11% and 18% for those samples reinforced with 2 wt% of SWNCTs and MWCNTs, respectively. Conductivity measurements show that the Al samples reinforced with 2 wt% of MWCNTs and with 0.5 wt% SWCNTs reach the highest IACS values of 50% and 34%, respectively.

Research on the gradual process of the structure and mechanical properties of NanoZnO-coated veneer

In this paper, Pinus sylvestris L. var. mongholica Litv veneer was used as the research object, and nanoZnO-coated veneer was prepared by magnetron sputtering. Based on XRD and nanoindenter, energy-dispersive spectroscopy and fluorescence microscope, the structure and mechanical properties, surface elements and fluorescence effect of the materials were characterized, and the gradual process of the structure and mechanical properties of nanoZnO-coated veneer was explored. The deposition of ZnO film on the surface of wood caused the main diffraction peaks (101) and (002) of cellulose to decrease in intensity, and the reduction in (002) characteristic peaks exceeded 10%. With the increase in the coating time, the characteristic diffraction peaks of ZnO gradually appeared. For the sample with a sputtering time of 75 min (200 °C), the film growth has a high degree of C-axis preferred orientation. The prepared nanoZnO-coated veneers have the common structural characteristics of wood and ZnO. With the increase in coating time, the load displacement of the sample sustained to decrease, the elastic modulus and hardness gradually increased. Among them, the sample with a coating time of 75 min (200 °C) reduced the loading displacement by 50%, the elastic modulus and hardness increased by 4.45 times and 5.8 times, respectively. It can be seen that the deposition of ZnO thin film on the surface of wood by magnetron sputtering has changed the microstructure of the wood surface, enhanced the wood resistance to elastic deformation, and improved the mechanical properties of the wood surface.

Enhanced Optical and Electrical Properties of Ti Doped In<sub>2</sub>O<sub>3</sub> thin Films Treated by Post-deposition Electron Beam Irradiation

Transparent and conductive Ti doped In<sub>2</sub>O<sub>3</sub> (TIO) films were prepared on slide glass substrate using a radio frequency (RF) magnetron sputter and then subjected to Transparent and conductive Ti doped In<sub>2</sub>O<sub>3</sub> (TIO) films were prepared on a glass slide substrate using radio frequency (RF) magnetron sputter. The film surface was then subjected to intense electron beam irradiation, to study the influence of incident energy on the visible transmittance and electrical resistivity of the films. All x-ray diffraction plots exhibited some diffraction peaks of the cubic bixbyite In<sub>2</sub>O<sub>3</sub> (222), (400), (332), (431), (440), and (444) planes regardless of the electron irradiation energy, while the characteristic diffraction peak for crystalline TiO<sub>2</sub> did not appear even when irradiated at 1500 eV. In atomic force microscope analysis, the surface roughness of the as deposited TIO films was found to be 0.63 nm. As the electron irradiation energy was increased up to 1500 eV, the root mean square roughness decreased down to 0.36 nm. The films electron irradiated at 1500 eV showed higher visible transmittance of 83.2% and the lower resistivity of 6.4 × 10<sup>-4</sup> Ωcm compared to the other films. From the electrical properties and optical band gap observation, it is supposed that the band gap shift is related to the carrier density. The band gap enlarged from 4.013 to 4.108 eV, along with an increase in carrier density from 9.82 × 10<sup>19</sup> to 3.22 × 10<sup>20</sup> cm<sup>-3</sup>.

Effect of Different Kinds of Zinc (II) on Early Hydration of Calcium Aluminate Cement

The early hydration of calcium aluminate cement (CAC) with different kinds of zinc (II), such as ZnSO4·7H2O, ZnO, Zn(NO3)2·6H2O and ZnCl2, was analyzed. Changes in consistency, setting time, hydration heat flow, hydration heat amount, ion concentration in solution, and hydration products were found upon the addition of different Zn2+. The water consumption of standard consistency of CAC is decreased with different Zn2+. Zn2+ can delay the initial hydration of CAC. The induction period of cement with Zn2+ is longer than that of CAC, especially the reaction time of the acceleration period is extended. Zn2+ can promote hydration hydrate of CAC at 24 h. The characteristic diffraction peaks of CA and CA2 in CAC with different Zn2+ are significantly reduced. It can inhibit the formation of CAH10 and promote the formation C3AH6 and AH3 in hydration products at 24 h.

Visible-light-driven photocatalytic degradation of ofloxacin (OFL) antibiotic and Rhodamine B (RhB) dye by solvothermally grown ZnO/Bi2MoO6 heterojunction

The 3D hierarchical ZnO/Bi2MoO6 heterojunctions were fabricated via an in-situ solvothermal method. To the best of our knowledge, this is the first report based on synthesis of ZnO/Bi2MoO6 heterojunction by decoration of ZnO nanoparticles on the surface of the flower-like Bi2MoO6 superstructures. The prepared ZnO/Bi2MoO6 heterojunctions exhibited the characteristic diffraction peaks of ZnO and Bi2MoO6 with the band gap energy of 3.25 eV and 2.76 eV, respectively. The PL intensity of the 10 wt% ZnO/ Bi2MoO6 heterojunction (denoted as 0.10Zn–Bi) is much lower than that of the bare Bi2MoO6, indicating much more effective separation of photo-generated electrons and holes at the interface which in turn results in greater expected photocatalytic performance. The 0.10Zn–Bi heterojunction showed the highest efficiency of 100% and 92% toward photodegradation of OFL antibiotic and RhB dye, respectively, due to the greatest surface area and the lowest electron-hole recombination rate. The photodegradation of the pollutants followed pseudo-first order kinetics with a very high rate constant of 0.0196 min−1. The chemical structure of photocatalyst remained stable after five cycles of use. The photogenerated electron (e−) and hole (h+) are two major reactive species involved in photodegradation of both OFL antibiotic and RhB dye. The present work demonstrates a very high potential of the 3D hierarchical ZnO/Bi2MoO6 heterojunctions for environmental remediation.

Catalytic Pyrolysis of Waste Plastics into Liquid Hydrocarbon using Mesoporous Kaolin Clay

Catalytic pyrolysis of waste plastics into liquid hydrocarbon was conducted in a locally-made stainless steel reactor. Mesoporous kaolin clay treated with sulfuric acid in the concentration range of 3-7 M was used as a catalyst and waste polyethylene was the plastic feed. The X-ray powder diffraction (XRPD) pattern showed that the raw kaolin clay is crystalline. However, XRPD patterns of H2SO4 acid treated kaolin and Ni and Ru metal impregnated H2SO4 treated kaolin did not exhibit any characteristic diffraction peaks of kaolin. The acid treatment of kaolin causes leaching of Al3+ and results in disintegration of layered structure of kaolin, leading to the formation of Al2(SO4)3, SiO2, and amorphous phase. After 5 M H2SO4 acid treatment, the content of Al2O3 decreased significantly to 18.62%. The Si/Al ratio and specific surface area were found to increase after 5 M sulfuric acid treatment from 1.79 to 3.48 and 6.85 m2/g to 17.92 m2/g, respectively. The nitrogen adsorption-desorption isotherms of the 5 M H2SO4 acid treated kaolin clay showed the isotherm to be of type IV typical for mesoporous structure. Among 3, 5, and 7 M H2SO4 treated kaolin catalysts, the 3 M H2SO4 treated kaolin (at a catalyst to plastic feed ratio of 1:5) exhibited the highest activity with the yield of 83% liquid hydrocarbon. The Ru- and Ni-impregnated 5 M H2SO4 treated kaolin catalyst provided 76% and 79% yield, respectively of liquid hydrocarbon at a catalyst to plastic ratio of 1:5. The gas chromatography-mass spectrometry (GC-MS), 1H NMR, and FTIR spectral analysis confirmed the presence of linear and branched alkanes and alkenes (C9-C20) in the end product obtained with 5 M H2SO4 treated kaolin catalyst. The produced liquid hydrocarbon was found to be free from aromatic compounds importantly polycyclic aromatic hydrocarbons which are potent mutagenic and carcinogenic.
 Journal of Bangladesh Academy of Sciences, Vol. 44, No. 1, 1-12, 2020

Entangled cellulose nanofibrils/nanosheets derived from native mexican agave for lead(II) ion removal

Cellulose nanofibrils (CNFs) produced from waste lignocellulosic biomass have emerged as a sustainable source material for high value-added applications. In the current study, previously unreported entangled cellulose nanofibril and nanosheet (CNF/CNS) were obtained using Agave Tequilana Weber var. Azul leaves by means of a microfluidization process. These nanomaterials were investigated as potential biosorbents of Pb2+, for which three adsorption mechanisms were identified by XPS. At low initial concentrations of Pb2+ (C0 < 100 ppm), the adsorption-mechanism is governed by electrostatic interactions between carboxylate groups and Pb2+; meanwhile, at (C0 = 1000 ppm) mono and bi-dentate complexes dominate the adsorption-mechanism. Finally, when 110 < C0 < 1000 ppm, both mechanisms co-exist. The maximum adsorption capacity was 43.55 mg/g, according to the Langmuir model, while CNF/CNS showed the characteristic diffraction peaks of cellulose type II. Our results highlight the high potential of these novel CNF/CNS biosorbents in the treatment of wastewater contaminated with toxic metals and afford new insights on adsorption mechanisms.

Synthesis and evaluation of cationic flocculant P(DAC-PAPTAC-AM) for flocculation of coal chemical wastewater

In this study, a high-efficiency cationic flocculant, P(DAC-MAPTAC-AM), was successfully prepared using UV-induced polymerization technology. The monomer Acrylamide (AM): Acryloxyethyl Trimethyl ammonium chloride (DAC): methacrylamido propyl trimethyl ammonium chloride (MAPTAC) ratio, monomer concentration, photoinitiator concentration, urea content, and cationic monomer DAC:MAPTAC ratio, light time, and power of high-pressure mercury lamp were studied. The characteristic groups, characteristic diffraction peaks, and characteristic proton peaks of P(DAC-MAPTAC-AM) were confirmed by fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), 1H nuclear magnetic resonance spectrometer (1H NMR), and scanning electron microscopy (SEM). The effects of dosage, pH value, and velocity gradient (G) value on the removal efficiencies of turbidity, COD, ammonia nitrogen, and total phenol by poly aluminum ferric chloride (PAFC), P(DAC-MAPTAC-AM), and PAFC/P(DAC-MAPTAC-AM) in the flocculation treatment of coal chemical wastewater were investigated. Results showed that the optimal conditions for the flocculation of coal chemical wastewater using P(DAC-MAPTAC-AM) alone are as follows: dosage of 8–12 mg/L, G value of 100–250 s − 1, and pH value of 4–8. The optimal dosage of PAFC is 90–150 mg/L with a pH of 2–12. The optimal dosage for PAFC/P(DAC-MAPTAC-AM) is as follows: PAFC dosage of 90–150 mg/L, P(DAC-MAPTAC-AM) dosage of 8–12 mg/L, and pH range of 2–6. When P(DAC-MAPTAC-AM) was used alone, the optimal removal efficiencies of turbidity, COD, ammonia nitrogen, and total phenol were 81.0%, 35.0%, 75.0%, and 80.3%, respectively. PAFC has good tolerance to wastewater pH and good pH buffering. Thus, the flocculation treatment of coal chemical wastewater using the PAFC/P(DAC-MAPTAC-AM) compound also exhibits excellent resistance and buffering capacity.

Structure, morphology, adhesion and in vitro biological evaluation of antibacterial multi-layer HA-Ag/SiO2/TiN/Ti coatings obtained by RF magnetron sputtering for biomedical applications.

Biocompatible and antibacterial multi-layer coatings of hydroxyapatite (HA)-Ag/SiO2/TiN/Ti were obtained on the Ti-6Al-4V alloy, by means of the magnetron sputtering technique. During characterization of the coatings, the chemical composition was evaluated by energy dispersive X-ray spectroscopy and the phase analysis was carried out by X-ray diffraction. The morphology of the coatings was observed by field emission scanning electron microscopy, while transmission electron microscopy was used to appreciate their structure. The adhesion of the coatings to the substrate was evaluated by micro scratch test. The in vitro biological response was evaluated in terms of cytotoxicity, adhesion and differentiation of mouse mesenchymal stem cells, as well as adhesion and bacterial viability of Staphylococcus aureus strain. Through the compositional study carried out, the deposition of the HA phase was verified, with a Ca/P ratio close to 1.67 and the characteristic diffraction peaks of this compound. The structural study of the coatings evidenced the obtention of multi-layer architectures. The use of an intermediate SiO2/TiN/Ti trilayer was found to improve adhesion between HA-Ag and the substrate by 84%. Finally, the in vitro biological tests carried out indicated a potentially non-toxic character in the coatings. Additionally, an antibacterial effect was registered at low concentrations of Ag (<0.25mg/L).

Morphological variations in Bi2S3 nanoparticles synthesized by using a single source precursor

A simple solvothermal decomposition of bismuth dithiocarbamate complex in oleylamine, oleic acid, and hexadecylamine at 180 °C, yielded bismuth sulphide nanomaterials of different morphologies represented as Bi2S3(OAm), Bi2S3(OAc) and Bi2S3(HDA) respectively. The bismuth complex, used as the single source precursor, was synthesized and characterised by elemental analysis, FTIR, and NMR spectroscopic techniques. The spectroscopic and micro analysis confirmed the proposed compound, while the as-prepared nanoparticles were characterized using UV-visible spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectrometer (EDS). The effects of the different solvent media on the structural properties of the obtained Bi2S3 were investigated. An orthorhombic phase bismuthinite of varying intensities were obtained, with an indication that a bias of orientations existed in the (2 1 1) crystallographic planes in the Bi2S3(OAm) compared to the characteristic (1 3 0) diffraction peak of Bi2S3. The microscopic analysis showed a correlation between the nanoparticles' morphology and the type of solvent used, which also implied that the properties of Bi2S3 were affected by the solvent medium.

Study on Magnetic Properties of Na-Doped rGO Prepared from Coconut Shells

Na-doped reduced graphene oxide (Na-rGO) was prepared by wet mixing process of the reduced graphene oxide (rGO) in NaOH solution. The results showed that the rGO doped with Na ions can increase its magnetization approximately 2 times greater than that in rGO without doping. Saturation magnetization (Ms) for rGO and Na-rGO samples are 0.017 emu/g and 0.037 emu/g, respectively. The increasing value of magnetization is suggested to be due to defect presented in the Na-rGO samples. Both samples, rGO and Na-rGO, have the similar XRD (X-ray Diffraction) spectra that is marked by two characteristic diffraction peaks of rGO, which are associated with [002] and [10] planes, followed by the increasing inter-planar distance in Na-rGO samples which might be due to Na ions intercalation into rGO sheets, confirmed by the energy-dispersive X-ray (EDX) result revealing the presence of Na atoms in rGO.

Microwave-assisted hydrothermal synthesis of ceria (CeO2): Microstructure, sinterability and electrical properties

This work reports the microstructural (XRD/SEM), dilatometric and electrical characterization (impedance spectroscopy) of ceria (CeO2) obtained by microwave-assisted hydrothermal synthesis under mild conditions (T = 120 °C and short reaction times of 10 and 20 min). The as-prepared and calcined powders show characteristic diffraction peaks of the cubic fluorite-type structure of cerium oxide. A remarkable sinterability allows obtaining dense ceramics (relative densities exceeding 95%) with enhanced electrical properties (σt = 2.14 × 10−5 S cm−1 at 500 °C) after sintering at a temperature as low as 1200 °C.

Biomimetic chitosan against bioinspired nanohydroxyapatite for repairing enamel surfaces

In this study, chitosan was employed as a novel biomimetic mineralization model to repair damaged enamel to compare its performance with that of bioinspired zinc-doped nanohydroxyapatite. Fifty human premolar tooth slices were prepared, and artificial caries lesions were induced to produce demineralized enamel surfaces. The etched slices were randomly divided into two groups: a chitosan-hydrogel-treated group and a zinc-doped nanohydroxyapatite-treated group. In vitro assessment using energy-dispersive X-ray analysis, X-ray diffraction analysis and scanning electron microscopy was conducted at the baseline, demineralization and remineralization stages. Baseline results were matched with those for normal enamel; a marked reduction in the calcium (Ca)/phosphorus (P) ratio to 1·12 and the lack of the characteristic hydroxyapatite diffraction peaks were detected for demineralized enamel. The remineralization stage revealed evident recovery of the mineral contents (the calcium/phosphorus ratio was 1·61 for the chitosan-treated group and 1·58 for the bioinspired-nanohydroxyapatite-treated one), with apparent distinctive X-ray diffraction patterns of hydroxyapatite in both groups. Scanning electron microscopic analysis showed the absence of etched enamel porosity, with the formation of a newly formed rod-like apatite layer, similar to natural enamel, which extended over the treated enamel surfaces of both groups. Chitosan hydrogel is recommended as a biomimetic mineralization smart system for repairing demineralized carious enamel.

Temperature dependent current- and capacitance-voltage characteristics of W/n-Si structures with two-dimensional WS2 and three-dimensional WO3 interfaces deposited by RF sputtering technique

In this study, tungsten disulfide (WS2) and tungsten trioxide (WO3) thin films are deposited on n-Si by RF sputtering technique. The optical, morphological and structural characteristics of these films are investigated. The XRD patterns showed that highly crystallinity have been obtained with dominant characteristic diffraction peaks of the WS2 and WO3. The SEM images show that these films are nearly uniform and covered all surface of substrates. Furthermore, the WS2 film has two-dimensional (2D) vertical layers while the WO3 has three-dimensional (3D) structure. From the XPS spectra, it revealed that the peaks confirmed the formation of WS2 and WO3 phases. The Raman spectra presented that different vibrational modes and phases are characteristics of the WS2 and WO3 thin films. Electrical properties of W/n-Si metal-semiconductor (MS) and W/WS2/n-Si and W/WO3/n-Si metal-interfacial layer-semiconductor (MIS) diodes are investigated using current-voltage (I-V) and capacitance-voltage (C-V) characteristics at various temperatures. It was found that I-V and C-V characteristics are strongly dependent on temperature and the interfacial WS2 and WO3 layers are significant roles for the electrical properties of W/WS2/n-Si and W/WO3/n-Si devices.

Preparation and characterization of broken-rice starch nanoparticles with different sizes

Broken-rice starch nanoparticles with different mean particle diameters for 100, 200, 400 and 800 nm were prepared by nanoprecipitation, alkali freezing, cross-linking and H2SO4 hydrolysis methods respectively, and their structural, morphological and physicochemical properties were systematically characterized. The results showed that broken-rice starch nanoparticles had higher water absorption rate, and the maximum water absorption rate was obtained from the 100 nm starch granules being 91.53%, which means an increase about 2.07-fold in water absorption rate as compared with native rice starch. The stability of native rice starch is the worst, but the viscosity characteristic value is always higher than that of starch nanoparticles in the whole gelatinization process. The FT-IR spectrum showed that only starch nanoparticles prepared by cross-linking method showed the characteristic peak of secondary amide structure at 1714 cm−1, but the structure of was basically the same as native starch. The X-ray diffraction pattern revealed that there were obvious characteristic diffraction peaks near 2θ for 15°, 17°, 19° and 23° for the 800 nm starch nanoparticles and native rice starch, while the characteristic diffraction peaks of other starch nanoparticles disappeared in varying degrees due to the changed crystal structure.

MnO2-supported catalytic bodies for selective reduction of NO with NH3: Influence of NO2 and H2O

Catalytic bodies based on MnO2, TiO2 and sepiolite showed an improved behavior for selective reduction of NOx with NH3 at low temperatures. In this work, the influence of Mn %wt and NO2 and/or water vapor presence was assessed. The materials were prepared by wet equilibrium impregnation of the pre-shaped support. All the catalysts exhibited the characteristic diffraction peaks of TiO2-anatase, hexagonal MnO2and anhydrous sepiolite. According to SEM-EDX, MnO2 was preferentially deposited over TiO2.The optimum nominal content of Mn was 7.5 %wt, what may be related to an appropriate particle dispersion that confers the suitable properties: lower acid strength, and better redox properties with improved reducibility. This catalyst was then evaluated under NO2 and/or H2O presence. NO2 improved the catalytic response and the best result was obtained with 1:1 NO2:NO ratio showing 90 % NOx conversion and 97 % N2 selectivity at very low temperature, 110 °C. A higher amount of NH4NO3 seems to be formed with the increase in the NO2/NO ratio causing a modification of N2 selectivity.Although water presence affected the performance, mainly at low temperatures, the catalyst showed good resistance to water vapor at temperatures above 180 °C maintaining good activity (90 % of NO conversion and 96 % of N2 selectivity). When NO2 was co-added to the feed, a beneficial effect was again observed with 91 % of NOx and 95 % of N2 selectivity converted at 143 °C.At low temperatures, deactivation has to do with a competitive effect of H2O with NOx towards the adsorption centers, which decreases the concentration of nitrate species adsorbed on the surface. However, the adsorption of ammonia was less affected.7.5 Mn catalyst is a highly efficient system to work in real conditions, where there is water in gas stream. In this situation, co-feeding NO2 improves activity.

Excellent Toluene Sensing Properties Based on Monodispersed WO3 Nanoparticles

Introduction Tungsten trioxide (WO3) has been demonstrated to possess high sensitivity and selectivity for gas sensing [ 1,2 ], and used to detect NOx, NH3, H2S and O3 gases. However, studies on toluene are comparatively few. It was demonstrated that smaller particles with controlled pore sizes contribute to better performance for gas detection compared with their corresponding bulk forms [3,4]. Nevertheless, the particle agglomeration during operation at elevated temperatures affects the diffusion of gases into the sensing bodies and leads to a decrease in their sensitivityWe here demonstrate the synthesis of dispersed WO3 nanoparticles with porous nanostructure through a facile solvothermal process. Gas sensing investigation indicates the sensor based on the synthesized WO3 samples with suitable hexamethylenetetramine amount and sintering at 500 °C shows remarkably superior response, outstanding selectivity and fast response/recovery time towards toluene. Experimental WO3 nanoparticles were prepared through a facile solvothermal method. Hexamethylenetetramine (HMT) with different HMT/WCl6 molar ratios (0, 0.5, 1 and 2) and WCl6 were dissolved in n-butanol solution, and the corresponding obtained samples were labelled as H0-W, H0.5-W, H1-W and H2-W, respectively. Typically, 0.79 g WCl6 was dissolved completely into a mixed solution containing 0.28 g HMT and 30 mL n-butanol under vigorous and continuous stirring using a magnetic stirrer for 20 min at room temperature accompanied by the precipitate emergence. Afterwards, the uniform solution was placed into a 45 mL Teflonlined stainless-steel autoclave, followed by tightly sealed and stored at 160 °C for 24 h in an electric oven. Then, the precipitate was gathered and washed with distilled water and absolute ethanol for six times by centrifugal separation before drying at 80°C overnight. Finally, the obtained products were calcined under various air atmospheres at 400°C, 500°C and 600°C for 2 h using a muffle furnace (2°C min− 1) and were named as 400°C-WO3, 500°C-WO3 and 600°C-WO3. Results and Conclusions Twelve main characteristic diffraction peaks of XRD patterns can be assigned to the monoclinic structure of WO3 according to JCPDS card no.72-677 (Fig. 1a). The intensity becomes stronger with the increase of sintering temperature from 400°C to 500°C due to the crystal growth, then decreases at 600°C caused by crystal distortion. XPS analyses (Fig. 1b-c) indicate that regardless of the samples synthesized at various HMT proportions or sintered at different temperatures, the H1-W nanoparticles sintered at 500°C own the least contents of surface-chemisorbed oxygen (OC). With the increase of HMT amount, the morphologies of the samples will transform from flower-like nanostructure to coagulated nanoparticles (Fig. 3) and dispersed WO3 nanoparticles can be synthesis with suitable HMT amount (Fig. 3c). The inlet in Fig. 3c clearly demonstrates that H1-W has a narrow size distribution. The morphologies of the H1-W will transform from flocculent clusters to coagulated nanoparticles after annealing at high temperature (Fig. 4). Schematic diagrams of H1-W preparation and the morphology-controlled process are shown in Fig.5. Gas investigation indicates that the sensor based on H1-W nanoparticles sintered at 500 °C possesses superior sensing properties towards toluene at the working temperature of 225 °C, including high response (132 to 100 ppm toluene) and fast response/recovery times (2 s/6 s) (Fig. 6). Generally, high gas response is accompanied with more oxygen defects, which will absorb more chemisorbed oxygen species to react with the target gas. However, this rule does not account for the explanation of the highest response of the sensor based on H1-W nanoparticles sintered at 500 °C. The sensor based on H1-W nanoparticles sintered at 500 °C possesses the highest resistance (over 300 MΩ, which is almost 20 times higher than those of other gas sensors) in air among all sensors. Thus, the resistance of the sensor will change considerably when only a spot of toluene gas reacts with the surface of the sensor. The high resistance of the sensor based on H1-W nanoparticles sintered at 500 °C can be attributed to the high crystallization as shown in the XRD results (Fig. 1a) and the grain boundary among the nanoparticles. Uniform size distribution is also very important when nanoparticles are used as the sensing materials. When the sensing body is composed by nanoparticles with a wide size distribution, the accumulation pores formed by large particles will be filled up by tiny particles. Then the sensing body will become compact which makes it difficult for the tested gas to diffuse deeply into the sensing material. The results imply that monodispersed WO3 nanoparticles with high resistance and porous nanostructure are a promising candidate for ultrafast toluene detection.

Hollow morphology, crystallization and phase transformation behavior of magnetic hollow composite materials based lignocellulose fibers via heat treatment

The hollow composite materials with unique topological structure and ideal appearance morphology were conducted via high-heat process to investigate the relationship of magnetic hollow materials between structure and performance. The hollow composite materials were characterized via scanning electron microscope (SEM), Thermo-gravimetric analyses (TGA), X-ray diffraction (XRD), vibration sample magnetic flowmeter (VSM) and X-ray photoelectron spectroscopy (XPS). The results revealed that there were no distinct effect on both the size of hollow cavity and the property of hollow structure via heat treatment. The weight loss occurred between 290 °C and 450 °C, indicating that lignocellulose fibers (LCFs) of metallization lignocellulose fibers (MLCFs) was 4.54%, 5.60%, respectively. The characteristic diffraction peaks corresponding to Ni3P had appeared. In addition, there was the crystallite size between 4.7 nm and 26.8 nm for Ni deposited on LCFs by the measurement of XRD, further indicating that particle size could be fined via high-heat treatment. The crystalline properties of the hollow composite materials via high-heat treatment at 400 °C were optimum. The mechanism of high-temperature heat treatment for Ni crystal grains growth was analyzed. Here, the magnetic parameters of saturation magnetization (Ms), coercive (HC) and remanence (Mr) were good. The coatings surface can absorb some Ni2+ ions and oxygen and the metal Ni can be oxidized NiO via heat treatment.

Influence of Sulfurization Time on the Properties of Cu2ZnSnS4 Thin Films Deposited on Mo-coated Soda Lime Glass Substrates by Co-sputtering Technique

In this work, Cu2ZnSnS4 (CZTS) absorber films were prepared by sulfurization of co-sputtered precursor films at different time periods. The influence of sulfurization time on physical characteristics of the grown films was investigated in detail. The sulfurized CZTS films exhibited the characteristic diffraction peak of the kesterite phase corresponding to the (112) crystal plane, the main Raman mode of kesterite phase at around 337 cm−1 and Cu-deficient and Zn-rich composition. From the atomic force microscopy surface and cross-sectional scanning electron microscopy images, it was revealed out that the films were uniform, compact without any cracks and consisted of micron-sized and closely packed grains. In addition, the films showed tail-to-tail, band-to-tail and band-to-band transitions at around 1.41 eV (E1), 1.45 eV (E2) and 1.51 eV (E3), respectively. Secondary ion mass spectroscopy analysis showed that the sodium ions deeply diffused through the molybdenum layer into the CZTS film from the soda lime glass substrate for all samples. All of the films exhibited an optical band gap of around 1.4 eV, an absorption coefficient over 104 cm−1, p-type conductivity with a high concentration of free holes in the order of 1017-1018 cm−3 and low mobility in the range from 0.63 cm²/V.s to 8.11 cm²/V.s.

Effects of acid etching on the structure of PtNi catalyst and total exposed active sites

The integration technology of hydrogen preparation–hydrogen storage not only can utilize hydrogen energy efficiently but also can improve the selectivity of the electrode maximally. In the present work, the structure and composition of the PtNi catalyst was characterized by X‐ray diffraction (XRD); and its electrochemical properties, morphology, and surface binding energy were analyzed by cyclic voltammetry (CV) and linear scanning voltammetry (LSV), scanning electron microscopy equipped with energy‐dispersive spectrometry (SEM‐EDS), and X‐ray photoelectron spectroscopy (XPS), respectively. The effects of different acid etching treatments (e.g., etching time, etchant concentration, and etching temperature) on the structure and surface active sites were investigated by the orthogonal experiment. The experimental results reveal that after etching with 0.5 mol/L of perchloric acid for 0.5 h at 60°C, the electrode weight loss of the PtNi catalyst is mainly attributed to the large loss of Ni atoms in film layer. This results in the reduced alloy phase in film layer and the appearance of Pt characteristic diffraction peak. The relative content of Pt on the surface of the film electrode increases significantly, and the total number of active sites also increases correspondingly. The binding energy of Pt4f7/2 decreases by 0.19 eV, and the number of active sites involved in hydrogen release decreases, indicative of the reduced promotion effect of the PtNi catalyst on hydrogen release.