Ionic liquid-assisted synthesis of tri-functional ruthenium oxide nanoplatelets for electrochemical energy applications

Journal of Materials Science - Nanostructured crystalline metal oxides are in great demand in industrial processes due to their unique physicochemical properties and ionic liquids (ILs) are...     

Characterization of dielectric barium titanate powders prepared by homogeneous precipitation chemical reaction for embedded capacitor applications

Various articles have reported that a highly pure and uniform form of barium titanate can be prepared by homogeneous precipitation. However, most of these works emphasize the mechanism of thermal decomposition of barium titanyl oxalate tetrahydrate, and only a few have discussed morphology or particle size. The morphology and particles size of barium titanyl oxalate tetrahydrate are governed by reaction temperature, pH value and solvent ratio; the barium titanate structure can be obtained by calcinating barium titanyl oxalate tetrahydrate above 600 °C or hydrothermally in a basic solution at 200 °C. The final morphology of barium titanate in this investigation was similar to that of barium titanyl oxalate tetrahydrate and the particle size of barium titanate increased with the calcination temperature. Using this barium titanate in a polymer/ceramic composite provided better dielectric characteristics than commercial ceramic powders use in embedded capacitor applications.     

Nanocrystalline indium tin oxide fabricated via sol-gel combustion for electrochemical luminescence cells

Nanoporous indium tin oxide (ITO) was synthesized via a sol-gel combustion hybrid method using Ketjenblack as a fuel. The effects of the sol-gel combustion conditions on the structures and morphology of the ITO particles were studied. The size of the nanoporous powder was found to be 20-30 nm in diameter. The layer of the nanoporous ITO electrode (-10 microm thickness) with large surface area (-360 m2/g) was fabricated for an electrochemical luminescence (ECL) cell. At 4 V bias, the ECL efficiency of the cell consisting of the nanoporous ITO layer was approximately 1050 cd/m2, which is significantly higher than the cell using only the FTO electrode (450 cd/m2). The nanoporous ITO layer was effective in increasing the ECL intensities.     

Highly conductive graphene-based segregated composites prepared by particle templating

We use capillary-driven particle level templating and hot melt pressing to disperse few-layer graphene flakes within a polystyrene matrix to enhance the electrical conductivity of the polymer. The conducting pathways provided by the graphene located at the particle surfaces through contact of the bounding surfaces allow percolation at a loading of less than 0.01 % by volume. This method of distributing graphene within a matrix overcomes the need to disperse the sheet-like conducting fillers isotropically within the polymer, and can be scaled up easily.     

表面活性剂模板法制备纳米TiO2有序薄膜

以表面活性剂吐温20为模板，乙酰丙酮修饰异丙氧醇钛的表面活性剂模板法制备了纳米多孔二氧化钛有序薄膜；并用于组装成染料敏化太阳能电池，在模拟太阳光下的光电性能测试表明：开路电压为0．715V，短路电流密度为11．99mA／cm^2，光电转换效率为5．34％。对二氧化钛有序膜的微观结构及结构特征进行了表征和讨论。     

Nano-scale islands of ruthenium oxide as an electrochemical sensor for iodate and periodate determination

In this study, a promising electrochemical sensor was fabricated by the electrodeposition of nano-scale islands of ruthenium oxide (ruthenium oxide nanoparticles, RuON) on a glassy carbon electrode (RuON–GCE). Then, the electrocatalytic oxidation of iodate and periodate was investigated on it, using cyclic voltammetry, chronoamperometry and amperometry as diagnostic techniques. The charge transfer coefficient, α, and the charge transfer rate constant, k_s, for electron transfer between RuON and GCE were calculated as 0.5 ± 0.03 and 9.0 ± 0.7 s^? 1 respectively. A comparison of the data obtained from the electrocatalytic reduction of iodate and periodate at a bare GCE (BGCE) and RuON–GCE clearly shows that the unique electronic properties of nanoparticles definitely improve the characteristics of iodate and periodate electrocatalytic reduction. The kinetic parameters such as the electron transfer coefficient, α, and the heterogeneous electron transfer rate constant, k′, for the reduction of iodate and periodate at RuON–GCE surface were determined using cyclic voltammetry. Amperometry revealed a good linear relationship between the peak current and the concentration of iodate and periodate. The detection limits of 0.9 and 0.2 μM were calculated for iodate and periodate respectively.     

NiO-改性活性炭电极电化学电容器研究

为提高普通活性炭材料的电化学性能,用Ni(NO3)2溶液浸渍法和高温热解对活性炭进行改性处理.分别采用氮气吸附法、SEM、XPS等方法分析研究改性炭材料的比表面积、孔结构、形貌和组成;用循环伏安、恒流充放电等电化学方法研究改性活性炭电极构成的电化学电容器性能.结果表明,由Ni(NO3)2热解产生的NiO有准电容效应,与活性炭原有的双电层电容构成了复合电容,因而改性炭的电容量有明显的提高,其质量比电容达到246.1 F/g,比原样炭的130.1 F/g提高了89.2%,表观体积比电容和面积比电容分别高达169.7 F/cm3和30.1 μF/cm2,均显著优于普通炭材料.     

Thin film ferroelectrics for capacitor applications

Pulsed laser deposition (PLD) has been used to fabricate simple thin film capacitor structures with a variety of ferroelectric materials. Thin film capacitors using the conventional ferroelectric material BaxSr1-xTiO3(BSTO) have been made across the entire compositional series. Electrical characterization shows that in thin film form these ferroelectrics display Curie point behaviour which is largely independent of composition. This contrasts sharply with bulk behaviour. The thin film fabrication and characterization of relaxor ferroelectric ceramics, such as Pb(Mg1/3Nb2/3)O3 (PMN) and Pb(Zn1/3Nb2/3)O3-BaTiO3(PZN-BT), is also reported. © 1998 Chapman & Hall     

Enhanced formation of ruthenium oxide nanoparticles through green synthesis for highly efficient supercapacitor applications

Ruthenium oxide nanoparticles (RuO₂ NPs) are one of the most promising materials at nanoscale, for energy storage devices. In the present work, a bottom up approach was utilized to synthesize RuO₂ NPs using biological resources, as reducing agent. Root extract of traditionally important medicinal plant, Akarkara (Anacyclus pyrethrum), was used in this study as the reducing agent. The investigation was carried out without the addition of any external reaction catalyzing agent. The Characterization studies were performed to analyze the conformational nature of the nanoparticles through XRD, SEM, TEM with SAED and FTIR spectroscopy was done to assess the functional moieties. Cyclic voltammetric (CV) studies were carried out to investigate the electrochemical potential of the synthesized RuO₂ NPs using the extract. The results demonstrated that the biologically reduced nanoparticles were crystalline, spherical and with an average size of 13 nm. The RuO₂ NPs were observed to be highly stable even after repeated usage. CV analysis revealed that capacitance behavior was reversible in nature and the specific capacitance of RuO₂ NPs using Akarkara (Anacyclus pyrethrum) coated over carbon sheet was 209 Fg⁻¹ at a scan rate of 5 mV/s. These results proved that green biosynthesis of RuO₂ can be used for supercapacitor applications.     

杂质离子对非晶态水合氧化钌电化学超电容性能的影响

采用化学沉淀法(在RuCl_3溶液中滴加NaOH)制备非晶态水合氧化钌,用去离子水对非晶态水合氧化钌沉淀充分洗涤,获得了Na、Cl杂质含量不同、而非晶态结构、水含量和显微相貌都相同的两种氧化钌样品.X射线光电子能谱分析表明,样品中的Na和Cl杂质分别以水合Na~+、水合Cl~-的形式存在.去离子水充分洗涤5次的样品(W-5)与不充分洗涤1次的样品(W-1)相比,前者的Na~+、Cl~-杂质含量低.循环伏安测试表明,W-5的比电容和功率性能都优于W-1 Na~+、Cl~-杂质不仅降低了氧化钉的比电容,也降低了氧化钌的功率性能.在非晶态水合氧化钌的制备过程中杂质含量的控制对获得高超电容性能十分重要.文中还分析了Na~+、Cl~-杂质对电容性能不利影响的机理.     

Study of YSZ-based electrochemical sensors with oxide electrodes for high temperature applications

Potentiometric sensors based on yttria stabilized zirconia (YSZ) with WO₃ as sensing electrode were fabricated using either Pt or Au electrodes. The sensors were studied in the temperature range 550–700°C in the presence of different concentrations (300-1000 ppm) of NO₂ and CO in air. The response to NO₂ was very stable with fast response time (20-40 s). The best sensitivity (18.8 mV/decade) using Pt electrodes was observed at 600°C. At the same temperature a cross-sensitivity (-15 mV/decade) to CO gas was also noticed. The response to CO was decreased (-4 mV/decade) using Au electrode. The role played by WO₃ on the sensing electrode was discussed.     

Nanocrystalline CoP coatings prepared by different electrodeposition techniques

A Watts-type cobalt bath containing additives has been used to prepare magnetic nanocrystalline CoP alloys. Coatings several microns thick were obtained using galvanostatic pulse plating (PP) and direct current (DC) electrodeposition. In both cases, compact deposits with slightly different grain sizes were achieved. The CoP deposits were magnetically softer than amorphous P-richer CoP electrodeposits and also than crystalline Co and Co-alloys prepared previously by electrodeposition.     

Nanocrystalline diamond films for nanotechnology applications

Abstract

Nanocrystalline diamond films with rms roughnesses in the order of 50 nm have been prepared by microwave plasma enhanced chemical vapour deposition. Ar-CH₄ gas mixtures have been used in a coaxially bladed reactor, and Ar-H₂-CH4 gas mixtures have been used in a reactor with a dual mode microwave applicator. These films have been examined by ultraviolet and visible Raman spectroscopy. They have been subjected to nanotribological investigation, with a view to their incorporation into microelectromechanical systems (MEMS). Comparisons with other diamond and hard carbon films are made, and the advantages of nanocrystalline diamond films are discussed.     

一步模板炭化法制备新型沥青基中孔炭材料

以乙酸镁和柠檬酸镁为模板(MgO)镁源,沥青为碳前驱体,在氮气氛中950℃一步炭化制得高表面积中孔炭材料.采用1 mol/L的HCl去模,并将炭材料洗涤至中性.采用低温N2吸附测得炭材料的比表面积和孔径分布,透射电镜观察炭材料的内部结构特征.结果表明:尽管未经活化,所得炭材料中的孔大多为中孔,BET比表而积达到1295 m2/g,当以柠檬酸镁为MgO前驱体时,所得炭材料的收率可高达50%.     

Formation of bismuth oxide nanowires by simultaneous templating and electrochemical adhesion of DNA on Si/SiO2

Deoxyribonucleic acid (DNA)-templated growth of Bi/Bi₂O₃ nanowires attached to the Si surface was obtained by electrochemical reduction of Bi(III) at an n-type Si electrode in aqueous Bi(NO₃)₃/HNO₃ at pH 2.5 with calf thymus DNA. The nanowires had a mean diameter of 5 nm and a range of lengths from 1.4 μm to 6.1 μm. The composition and structure of the wires were determined by atomic force microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray photoemission spectroscopy. The dominant component of the material is Bi₂O₃ owing to the rapid re-oxidation of nanoscale Bi in the presence of air and water. Our method has the potential to construct complex architectures of Bi/Bi₂O₃ nanostrucures on high quality Si substrates.     

Developments in ferroelectric ceramics for capacitor applications

A brief overview of the materials and processes for making ceramic capacitors based on BaTiO₃ and relaxor ferroelectric compositions is presented with special emphasis on more recent developments.     

Nanocrystalline ZnSe thin films prepared by solution growth technique for photosensor application

Zinc selenide (ZnSe) thin films were deposited onto the glass substrates by solution growth technique (SGT). Triethanolamine (TEA) was used as a complexing agent for uniform deposition. Deposition parameters were optimized and elemental composition was confirmed by energy dispersive X-ray analysis technique (EDAX). The SEM, AFM and XRD pattern revealed that as-deposited thin films were uniformly deposited by nanocrystalline grains distributed over the entire glass substrate. Transmission spectra showed high transmission (∼55%) with direct optical band gap energy equal to 2.71 eV. The I–V characteristic showed good photoresponse, suitable for photosensor applications.     

Nanocrystalline nickel ferrites prepared by doping with niobium ions

Doping of nickel ferrites by suitable aliovalent ions was explored in order to synthesize nanocrystalline ferrites. With the doping of Nb₂O₅, the size of NiFe₂O₄ is reduced down to 33 nm. The substitution of Nb⁵⁺ ions essentially break up the ferrimagnetically active oxygen polyhedra and the size of the grains are confined. An increase of coercive field and a decrease of magnetization is observed as the size of NiFe₂O₄ is reduced. This behavior can be explained introducing core-shell model of magnetic nanoparticles. Mössbauer spectra shows superparamagnetic doublet that supports the presence of smaller sized particles in the specimens. The DC resistivity of the doped specimens decreases by at least five orders of magnitude compared to pure sample. This is ascribed to the presence of an interfacial amorphous phase between the sites.