Nanosize Mn3O4 (Hausmannite) by microwave irradiation method

The present investigation reports, the novel synthesis of nanosize Mn₃O₄ powder with nanorods using microwaves and its physicochemical characterization. The nanosize Mn₃O₄ powder has been prepared using manganese nitrate as a precursor and effect of ethanolamine and ethylenediamine on particle morphology has been studied. The microwave irradiation has been carried out in the range 50–500 W and it was observed that formation of Mn₃O₄ takes place at 50 W. TEM analysis demonstrated nanosize Mn₃O₄ powder and nanorods with an average diameter of about 10 nm. The structural study by XRD indicates that these nano-powders have pure tetragonal phase. The phase pure samples were characterized using X-Ray Photoelectron Spectroscopy (XPS) for both Mn 2p and Mn 3s levels. The values of binding energies are consistent with the relative values reported in the literature. The metallic impurity levels have been characterized using Inductively Coupled Plasma-Optical Emission Spectrophotometer (ICP-OES).     

Synthesis of silver nanoparticles using N 1, N 2-diphenylbenzamidine by microwave irradiation method

Silver nanoparticles have been prepared under microwave irradiation from a solution of silver nitrate in the presence of N ¹,N ²-diphenylbenzamidine (DPBA) or simply amidine without any stabilizing agent. Different morphologies of silver colloids with charming colors could be obtained using N ¹,N ²-diphenylbenzamidine (DPBA). The structures of silver colloids were determined by TEM. UV-Vis spectroscopy was used to follow the reaction process and to characterize the optical properties of the resultant silver colloids. The influence of unconventional reducing agent on the morphology of silver was investigated.     

Synthesis and characterization of TiO2/WO3 composite nanotubes for photocatalytic applications

TiO₂/WO₃ composite nanotubes were synthesized in an anodic aluminum oxide (AAO) template by a sol–gel method. The prepared nanotubes were characterized by transmission electron microscopy, scanning electron microscopy, powder X-ray diffraction, and Brunauer–Emmett–Teller surface area. Using the nanotubes embedded in the AAO templates as catalysts, photocatalytic degradation of methyl orange aqueous solution was carried out under UV light irradiation. The results showed that the TiO₂/WO₃ composite nanotubes with the thickness about 50 nm could be successfully synthesized by this method. TiO₂ showed anatase phase and WO₃ displayed monoclinic phase. The composite nanotubes (TiO₂/WO₃) exhibited higher photocatalytic activity than the pure nanotubes (WO₃ or TiO₂). The possible reason for improving the photocatalytic activity was also discussed.     

Synthesis of Ni-doped LaSrMnO3 nanopowders by hydrothermal method for SOFC interconnect applications

Ni-doped lanthanum strontium manganite (LSMN) nanopowders, La_0.7Sr_0.3Mn_1?xNi_xO₃ (0.05?≤?x?≤?0.3) were synthesized at 150?°C for 8?h by hydrothermal reaction as a function of Ni doping concentration. The SEM analyses suggested that the calcination treatment influenced the morphology of the nanopowders. The calcined nanopowders at 1300?°C had agglomerated spherical structure of 44–77?nm. Meanwhile, the XRD studies revealed that the nanopowders have single crystalline phase over the range x?=?0.05–0.2. In addition, the LSMN nanopowders were sintered at elevated temperatures, 1250–1350?°C to examine their electrical conductivity for solid oxide fuel cell (SOFC) interconnect applications under actual SOFC working condition. Their electrical conductivity gradually increased to 90.05?S/cm with Ni doping concentration x?=?0.2, which were sintered at 1300?°C. These results suggest La_0.7Sr_0.3Mn_0.8Ni_0.2O₃ displays a good performance as an optimal composition of the LSMN.     

制备条件对TiO2纳米管晶型影响研究

用不同TiO2作原料,在一般水热法和微波法条件下,制备TiO2纳米管,通过TEM、XRD等表征手段,研究了影响合成TiO2纳米管晶型的因素,提出了影响纳米管晶型结构的机理.结果表明,利用不同的原料在一定制备条件下可制得单一晶型的TiO2纳米管.     

微波照射凝胶-溶胶法制备均分散纺锤形α-Fe2O3超细粒子

以Fe(OH)3凝胶为前驱物经微波照射凝胶-溶胶法制备了均分散纺锤形a-Fe2O3超细粒子，该法具有反应时间短、产率高的优点。采用TEM、XRD、IR等手段对产物进行了表征，同时对a-Fe2O3的形成过程进行了初步探讨。     

Synthesis of ZnOAl2O3 core-shell nanocomposite materials by fast and facile microwave irradiation method and investigation of their optical properties

Alumina (Al₂O₃) coated ZnO core-shell structures were synthesized by a novel, fast, and facile route utilizing microwave (MW) irradiation to control photocatalytic property of ZnO. The phase analysis and the core–shell structure development were corroborated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray fluorescence (XRF), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) analysis and Fourier transform infrared spectroscopy (FT-IR). The XPS results affirmed that elements on the coated surface were Al and O. Zeta potential analysis predicted the presence of Al₂O₃ layer on ZnO due to almost similar zeta potential curve for pure Al₂O₃ and Al₂O₃ coated ZnO nanoparticles. There was no significant change in band gap energy of ZnO after amorphous Al₂O₃ coating as obtained from derived data of the reflectance spectra but gradual decreasing of reflectance in the visible range, measured by UV–vis spectroscopy, of the prepared core-shell nanoparticle may be due to the coating of amorphous Al₂O₃ on ZnO. The photocatalytic efficiency of ZnO was reduced after amorphous Al₂O₃ layer as confirmed by the photodegradation of methylene blue under UV irradiation.     

Synthesis of amorphous Fe2O3 nanoparticles by microwave irradiation

Amorphous Fe₂O₃ nanoparticles of about 3–5 nm in size have been synthesized by microwave irradiation heating of an aqueous solution, containing ferric chloride, polyethylene glycol-2000 and urea. The Fe₂O₃ nanoparticles were characterized by the techniques of TEM, XRD, DSC, TGA and magnetization measurements.     

Synthesis of nanosize BPO4 under microwave irradiation

Nanosize BPO₄ was synthesized using H₃BO₃ and H₃PO₄ (85%) as raw materials under microwave irradiation. This reaction was performed at powers lower than 640 W and irradiation time ranging from 2.5 min to 5 min, which were only a fraction of the time required for conventional synthetic procedures. The structure of the as-prepared BPO₄ is analogous to that of a high cristobalite. The particle sizes of the samples irradiated at 640 and 400 W range from 40 nm to 90 nm and 30 nm to 60 nm, respectively. The effects of different conditions on the experimental outcome are also discussed.     

Synthesis of KNbO3 nanostructures by a microwave assisted hydrothermal method

One-dimensional nanostructures of KNbO₃ have attracted a great interest in the scientific community, mainly because of their promising application as nanoelectromechanical systems (NEMS). However, the synthesis of KNbO₃ structures becomes complex due to the natural tendency to form non-stoichiometric potassium niobates. In this context, we report on the crystallization of one-dimensional KNbO₃ nanostructures through the reaction between Nb₂O₅ and KOH under microwave-assisted hydrothermal synthesis (M-H). The use of this synthesis method made possible a very fast synthesis of singlecrystalline powders. Based on SEM, TEM and XRD characterizations, the influence of the synthesis time and the reactants concentration in the structure and morphology of the resultant KNbO₃ was established. The conditions that favor the crystallization of nanofingers were determined to be small amounts of Nb₂O₅ and short reaction times.     

Facile microwave synthesis of Sn-doped WO3 for pseudocapacitor applications

In the present work, we have successfully synthesized pure tungsten oxide (WO₃) and Sn (3 and 5 wt%)-doped WO₃ nanoparticles using facile microwave irradiation method and studied about the electrochemical performances for supercapacitor electrode material. Structural and morphological studies of the prepared nanomaterials were investigated systematically. The powder XRD analysis reveals that pure WO₃ and Sn-doped WO₃ have monoclinic crystal structure and also crystallite size of the material decreases from 38 to 30 nm with increasing dopant concentration. Micro-Raman analysis confirms the formation of monoclinic phase with υ(O–W–O) stretching and δ(O–W–O) bending mode of vibration. SEM and micrographs show the elongation of the plate-like nanostructure of WO₃ for the doping of Sn. High-resolution transmission electron microscope images depict the morphological change and increased porosity in doped samples. The supercapacitive performance and the electrochemical conductivity of the samples were analysed using cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy measurements. The results demonstrate that the 5 wt% Sn-doped WO₃ electrode has the enhanced electrochemical performance in 1 M KOH with a maximum specific capacitance of 418 F g^?1 at low current density of 1 A g^?1. Also, it shows the increase in energy density from 4.88 to 11.77 Wh kg^?1 with respect to the Sn concentration at the power density of 225 W kg^?1_.

     

Mg2(Si,Sn)热电固溶体微波合成研究

为了解决传统方法制备Mg2Si1-xSnx(0≤x≤1.0)固溶体过程中带来Mg的氧化、挥发等问题,引进微波低温合成法,成功合成了Mg2Si1-xSnx热电固溶体,用XRD及SEM分析手段对合成的块体物相和形貌进行了表征,并系统研究了合成工艺对Mg2Si1-xSnx压坯制备的影响及Mg2Si1-xSnx压坯在微波场中的...     

High-sensitivity humidity sensor based on SnO2 nanoparticles synthesized by microwave irradiation method

Tin oxide hexagonal-shaped nanodiscs (SnO) and spherical nanoparticles (SnO₂) have been prepared by using a simple household microwave irradiation method with an operating frequency of 2.45 GHz. This technique permits us to produce gram quantity of homogeneous nanoparticles in just 10 min. The crystallite size was evaluated from powder X-ray diffraction (XRD) studies and was in the 20 to 25 nm range. Transmission electron microscopy (TEM) analysis showed that the as prepared SnO form as hexagonal-shaped nanodiscs and upon subsequent annealing at 500 °C for 5 h in air, the SnO gets converted to spherical-shaped nanoparticles of SnO₂. The SnO₂ sample shows good sensitivity towards the relative humidity. The calculated response and recovery time were found to be 32 s and 25 s respectively. These results indicate promising applications of SnO₂ nanoparticles in a highly sensitive environmental monitoring and humidity controlled electronic devices. The samples were further subjected to thermal analyses (TG–DTA) and UV–VIS diffusion reflectance spectroscopy (DRS) studies.     

Rapid photocatalytic destruction of pentachlorophenol in F-Si-comodified TiO(2) suspensions under microwave irradiation

A novel photocatalysis material, F-Si-comodified TiO(2) (FST) powder, was synthesized by ultrasound-assisted hydrolysis. The prepared material was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-visible absorption spectroscopy, respectively. XRD analysis indicated that the phase of FST was pure anatase and Si atoms suppressed the growth of titania crystalline, XPS spectra showed that FST was composed of Ti, O, Si and F element, the band gap energy of FST calculated according to the spectrum of UV-vis absorption was 3.26 eV. The electron spin resonance (ESR) spin-trapping technique using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as the spin-trap reagent has been applied to detect free radical intermediates generated from FST. ESR results showed the concentration of the active species (OH) on FST is higher than those on F-doping TiO(2) (FT), Si-modifying TiO(2) (ST) and P25 titania. The degradation of pentachlorophenol (PCP) in the microwave-assisted photocatalysis (MAPC) process was faster than other processes including microwave-assisted direct photolysis (MADP), microwave process alone (MP) and dark process (DP). The photocatalytic activity of FST is much higher than that of ST, FT and P25 titania. It may be attributed to its strong capacity of absorption to the UV-vis irradiation and more hydroxyl radical on surface of FST. In MPAC process, 40 mg L(-1) PCP was completely degraded in 20 min and its corresponding mineralization efficiency was 71%, the pH of solutions decreased from 10.3 to 6.47 and the dechlorination was completed in 12 min. The intermediates products of PCP in MAPC process identified by GC/MS were trichlorophenols (TCP), tetrachlorophenols (TTCP) and tetrachlorocatechol (TTCC) and the possible mechanism of PCP degradation is proposed.     

Synthesis of Ni and bimetallic FeNi nanopowders by microwave plasma method

Nickel nanopowders can be synthesized by microwave plasma synthesis method. The effect of the feeding rate of the precursor material to the average particle size and crystallinity was studied. FeNi bimetallic alloy nanopowders were also successfully synthesized by pre-mixing the respective precursor raw materials before feeding into the plasma reaction zone. The Ni and FeNi nanopowders were characterized by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD).     

微波爆聚法合成荧光性类水滑石/PMMA复合材料

利用微波爆聚法快速合成了发黄色荧光的有机/无机聚合物纳米复合材料。用红外光谱、荧光光谱、XRD、TEM、热分析等对结构和性能进行了表征。结果表明,黄光类水滑石片层已充分剥离并均匀分散于PMMA基质中,在468nm蓝光激发下,产生明亮的黄光发射,并且相较于PMMA具有更高的热稳定性。微波爆聚法为实现无机板层快速剥离并在聚合物基体中均匀分散提供了新的高效途径,有望在制备各种聚合物/层状无机物纳米复合材料中得到应用。