New titanium (III) phosphite structure and its application as anode for lithium ion batteries

A new titanium (III) phosphite Ti₂(HPO₃)₃, has been synthesized under hydrothermal conditions. The solid-state structure of this material was solved using single-crystal X-ray diffraction. The anionic inorganic skeleton has a three-dimensional structure, which is built up by TiO₆ octahedral units linked together via bridging HPO₃ pseudo pyramids, giving rise to tunnels along the three crystallographic axes. This new compound displays a high thermal stability limit of 625 °C. IR and Raman spectroscopies show the vibrational modes of the (HPO₃)²⁻oxoanions. Electrochemical activity of this phase toward reversible insertion of Li ion was studied for the first time by galvanostatic charge-discharge measurements, an insertion host for reversible accommodation of Li⁺ was observed.     

MoS2-mesoporous LaFeO3 hybrid photocatalyst: Highly efficient visible-light driven photocatalyst

Perovskite type materials have high potential photocatalytic application towards both hydrogen energy generation and organic dye degradation due to their high stability and good reusability. Here, it is the first analysis of photocatalytic degradation of RhB and hydrogen energy evolution under visible light over MoS₂/LaFeO₃ nanocomposite. The physicochemical properties of the materials were characterized using a range of techniques such as XRD, TEM, XPS, FTIR, PL, photocurrent, etc. The optical properties of the nanocomposite show good absorption in UV-Vis spectra as compared to the bare LaFeO₃. In this study, MoS₂/LaFeO₃ nanocomposite was synthesized through single step in situ hydrothermal processes with a narrow bandgap, enhanced photocatalytic application under visible light. This novel MoS₂/LaFeO₃ nanocomposite is an efficient and promising photocatalyst for both hydrogen energy evolution and organic dye degradation.     

Characterization of boron nitride nanosheets synthesized by boron-ammonia reaction

Boron nitride nanosheets (BNNS) with thickness 5–11 nm were successfully produced when pure boron powder (1–2 μm) interacted with ammonia gas in chemical vapour deposition set up. Under the optimized parameters, at 1200 °C and for uninterrupted 1 h of reaction duration, 2D BNNS with thickness of ca.11 nm were synthesized. BNNS were characterized by X-ray diffraction (XRD) for crystal structure, scanning electron microscopy for dimensions and morphology, energy dispersive X-ray analysis for chemical composition and Fourier transform infrared spectroscopy for sp² BN bond detection. The thickness of BNNS determined from both XRD data (using Scherrer equation) and atomic force microscopic analysis confirmed the stated product thickness. The BNNS obtained at 1200 °C had high crystallinity, purity and yield.     

Synthesis of photoluminescent SiC-SiOx nanowires using coal tar pitch as carbon source

SiC-SiOx nanowires (NWs) with core-shell and chain-bead structures were synthesized via a catalyst-free chemical vapor deposition (CVD) route without Ar gas, using silicon and coal tar pitch powders as raw materials. The SiC-SiOx NWs with sharp tips formed by solid-vapor between Si (s) and CO (g) or C (s) and SiO (g), liquid-vapor between Si (l) and CO (g), and vapor-vapor between SiO (g) and CO (g) growth process along the [111] direction. The NWs were several millimeters in length, and the average diameters of the chains and beads were 40–90 nm and 325 nm, respectively. The obtained NWs had good blue-green photoluminescence property owing to the stacking faults and amorphous SiOx. This novel CVD route is simple, low cost and suitable for large-scale production.     

Facile synthesis of Co0.5Zn0.5Fe2O4 nanoparticles decorated reduced graphene oxide hybrid nanocomposites with enhanced electromagnetic wave absorption properties

Herein, reduced graphene oxide/cobalt-zinc ferrite (RGO/Co_0.5Zn_0.5Fe₂O₄) hybrid nanocomposites were fabricated by a facile hydrothermal strategy. Results revealed that the contents of RGO could affect the micromorphology, electromagnetic parameters and electromagnetic wave absorption properties. As the contents of RGO increased in the as-synthesized hybrid nanocomposites, the dispersibility of the particles was improved. Meanwhile, numerously ferromagnetic Co_0.5Zn_0.5Fe₂O₄ particles were evenly anchored on the wrinkled surfaces of flaky RGO. Besides, the obtained hybrid nanocomposites exhibited superior electromagnetic absorption in both X and Ku bands, which was achieved by adjusting the RGO contents and matching thicknesses. Significantly, when the content of RGO was 7.4 wt%, the binary nanocomposites showed the optimal reflection loss of -73.9 dB at a thickness of 2.2 mm and broadest effective absorption bandwidth of 6.0 GHz (12.0–18.0 GHz) at a thin thickness of merely 2.0 mm. The enhanced electromagnetic absorption performance was primarily attributed to the multiple polarization effects, improved conduction loss caused by electron migration, and magnetic loss derived from ferromagnetic Co_0.5Zn_0.5Fe₂O₄ nanoparticles. Our results could provide inspiration for manufacturing graphene-based hybrid nanocomposites as high-efficient electromagnetic wave absorbers.     

Impact behavior and fractographic study of carbon nanotubes grafted carbon fiber-reinforced epoxy matrix multi-scale hybrid composites

Carbon nanotubes are the most promising reinforcement for high performance composites. Multiwall carbon nanotubes were directly grown onto the carbon fiber surface by catalytic thermal chemical vapor deposition technique. Multi-scale hybrid composites were fabricated using the carbon nanotubes grown fibers with epoxy matrix. Morphology of the grown carbon nanotubes was investigated using field emission scanning electron microscopy and transmission electron microscopy. The fabricated composites were subjected to impact tests which showed 48.7% and 42.2% higher energy absorption in Charpy and Izod impact tests respectively. Fractographic analysis of the impact tested specimens revealed the presence of carbon nanotubes both at the fiber surface and within the matrix which explained the reason for improved energy absorption capability of these composites. Carbon nanotubes presence at various cracks formed during loading provided a direct evidence of micro crack bridging. Thus the enhanced fracture strength of these composites is attributed to stronger fiber–matrix interfacial bonding and simultaneous matrix strengthening due to the grown carbon nanotubes.     

Effect of annealing on the structural and optical properties of laser ablated nanostructured barium tungstate thin films

High quality BaWO₄ thin films are successfully deposited on quartz substrate for a duration of 30 min using pulsed laser ablation technique and using a laser radiation of wavelength 355 nm and the effect of thermal annealing on the structural and optical properties is studied by using techniques like X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy, micro-Raman, FTIR and UV–visible spectroscopy. All the films show monoclinic crystalline structure with (2 0 2) plane as the preferred orientation of crystal growth. From the XRD analysis it is found that the optimum annealing temperature for better crystallization of the BaWO₄ film is 700 °C and there is no phase change observed with annealing temperature. The presence of the characteristic bands for the BaWO₄ in the Raman spectra of the films suggests the formation of BaWO₄ crystalline phase in all the films. SEM and AFM analyses show that as the annealing temperature increases the connectivity between individual grains increases and shows an ordered packing. The geometrical optimization and energy calculation of the title compound were done using the Gaussian 09 software package and the calculations were carried out using the CAM-B3LYP functional combined with standard Lanl2Dz basis set. The thickness of the films was calculated using lateral SEM images and also from optical transmission spectral data using PUMA software.     

Enhanced hollow fiber membrane performance via semi-dynamic layer-by-layer polyelectrolyte inner surface deposition for nanofiltration and forward osmosis applications

The layer-by-layer (LBL) polyelectrolyte deposited membranes have drawn increasing attention in various applications due to the ease of selective layer formation and their stability and versatility. In this study, the LBL deposition was performed at the inner surface of the polyethersulfone (PES) hollow fiber substrate to form composite nanofiltration (NF) membrane. The semi-dynamic deposition procedure was adopted with the aid of syringes. The newly developed inner deposited (id-LBL) membranes were then tested in NF and forward osmosis (FO) applications and the performance were compared with outer surface deposition as well as some literature data. The id-LBL membranes could not only withstand higher operating pressure but also possess superior hardness rejection especially in high concentration mixed salt solutions (more than 95% rejection to Mg²⁺ and Ca²⁺ in a 5000 ppm total dissolved salt (TDS) mixture under 4.8 bar). As for the FO process, with only two layer deposition, the id-LBL membranes also demonstrated significant performance improvement with increased water flux (up to 70 L/m² h using 0.5 M MgCl₂ as draw solution in active layer facing draw solution configuration) and reduced salt leakage (around 0.5 g/m² h using 1 M MgCl₂ draw solution in active layer facing feed water configuration). This study suggests that for hollow fiber substrate, the inner surface is more suitable for the formation of the selective layer via LBL deposition than the outer surface.     

Effects of CaO addition on Ni/CeO2–ZrO2–Al2O3 coated monolith catalysts for steam reforming of N-decane

A series of 10 wt%Ni/CeO₂–ZrO₂–Al₂O₃ (10%Ni/CZA) coated monolith catalysts modified by CaO with the addition amount of 1 wt%~7 wt% are prepared by incipient-wetness co-impregnation method. Effects of CaO promoter on the catalytic activity and anti-coking ability of 10%Ni/CZA for steam reforming of n-decane are investigated. The catalysts are characterized by N₂ adsorption-desorption, XRD, SEM-EDS, TEM, NH₃-TPD, XPS, H₂-TPR and Raman. The results show that specific surface area and pore volume of as-prepared catalysts decrease to some extent with the increasing addition of CaO. However, the proper amounts of CaO (≤3 wt%) significantly enhance the catalytic activity in terms of n-decane conversion and H₂ selectivity mainly due to the improved dispersion of NiO particles (precursor of Ni particles). As for anti-coking performance, reducibility of CeO₂ in composite oxide support CZA is promoted by CaO resulting in providing more lattice oxygen, which favors suppressing coke formation. Moreover, the addition of CaO reduces the acidity of 10%Ni/CZA, especially the medium and strong acidity. But far more importantly, a better dispersion of NiO particles obtained by proper amounts of CaO addition is dominant for the lower carbon formation, as well as the higher catalytic activity. For the spent catalysts, amorphous carbon is the main type of coke over 10%Ni–3%CaO/CZA, while abundant filamentous carbon is found over the others.     

析湿工况下翅片管式换热器表面粉尘沉积过程的数值模型

空调器采用翅片管式换热器作为蒸发器，在制冷工况下换热器表面发生析湿及粉尘沉积，导致性能衰减。建立湿翅片表面粉尘颗粒物沉积过程的数学模型，模拟冷凝水捕集颗粒物以及湿积灰层黏附颗粒物的过程。被冷凝水捕集的颗粒物数量等于运动轨迹与水表面轮廓会出现相交的入射颗粒物的数量；后续的入射颗粒物与湿积灰层碰撞时，部分入射颗粒物会发生沉积且部分被碰撞的已沉积湿颗粒物会发生移除，这两部分的颗粒物数量相减即为被湿积灰层黏附的颗粒物数量。模拟与实验结果的对比表明，预测的湿积灰层形状与实验照片的吻合度较好，预测的单位面积颗粒物沉积质量与91%的实验数据之间的误差在±20%之间，平均误差为11.8%。