Synthesis and Characterization of Nanostructured Cerium Dioxide Thin Films Deposited by Ultrasonic Spray Pyrolysis

Nanostructured thin films of cerium dioxide have been prepared on single-crystalline silicon substrates by ultrasonic spray pyrolysis using cerium acetylacetonate as a metal–organic precursor dissolved in anhydrous methanol and acetic acid as an additive. The morphology, structure, optical index, and electrical properties were studied by X-ray diffraction, scanning electron microscopy, atomic force microscopy, ellipsometry, and impedance spectroscopy. The use of additives is very important to obtain crack-free films. The substrate temperature and flow rate was optimized for obtaining smooth ( R _a<0.4 nm), dense ( n >2), and homogeneous nanocrystalline films with grain sizes as small as 10 nm. The influence of thermal annealing on the structural properties of films was studied. The low activation energy calculated for total conductivity (0.133 eV) is attributed to the nanometric size of the grains.     

Ultrasonic Spray Pyrolysis for Synthesis of Spherical Zirconia Particles

This paper presents new findings on ultrasonic spray pyrolysis of zirconium hydroxyl acetate precursor drops whose sizes were precisely measured using laser light diffraction technique. Precursor concentration plays a predominant role in determination of product particle size. At 0.01 wt% precursor concentration, conventional spray pyrolysis at 750°C using precursor drops 5–8 μm in diameter, generated by an ultrasonic nebulizer at 2.66 MHz, yielded uniform spherical yttria-stabilized zirconia (YSZ) particles 73 nm in diameter measured by scanning electron microscopy. The YSZ particle diameters were much smaller than those predicted by the one-particle-per-drop mechanism. Under similar reaction conditions, the high-throughput ultrasound-modulated two-fluid (UMTF) spray pyrolysis of larger precursor drops (28-μm peak diameter) also yielded spherical dense particles; they were significantly smaller in size than those produced by the low-throughput conventional ultrasonic spray pyrolysis of smaller drops (6.8-μm peak diameter).     

Synthesis of (La,Sr)MnO3–YSZ Composite Particles by Spray Pyrolysis

(La_0.8Sr_0.2)_0.9MnO₃–YSZ composite particles were synthesized by spray pyrolysis. The mean particle size of the synthesized powders was about 1 pm and the particle size distribution was very narrow. The synthesized powders were composed of the perovskite (La,Sr)MnO₃ and cubic phase YSZ. Each particle synthesized consisted of uniform and well-dispersed line primary particles of (La,Sr)MnO₃ and YSZ (0.1 μm particle size).     

Synthesis of Ultrafine β"-Alumina Powders via Flame Spray Pyrolysis of Polymeric Precursors

Flame spray pyrolysis of a polymeric precursor is used to prepare ultrafine powders that, when sintered, convert to essentially pure phase lithium-doped sodium β"-alumina. The precursor Na_1.67 Al_10.67 Li_0.33 [N(CH₂CH₂O)₃]_10.67-[OCH₂CH₂O]·x(HOCH₂CH₂OH) has been synthesized from stoichiometric amounts of metal hydroxides and tri-ethanolamine (N(CH₂CH₂OH)₃, TEA) in excess ethylene glycol. The precursor is dissolved in ethanol, and an atom-ized spray of the solution is combusted in a specially con-structed flame spray apparatus. Combustion occurs at ∼2000°C, followed by immediate quenching. This proce-dure provides for a measure of kinetic control over the process. The resulting nanopowder particles are 50–150 nm in diameter and exhibit powder X-ray diffractometry pat-terns similar to β"-alumina. Heating the nanopowder at 30°C/min to 1200°C with a 1 hisotherm converts it to pure β"-alumina. In preliminary sintering studies, green powder compacts (∼65% theoretical density) sintered at 1600°C for 12 min densify to 3.0 ± 0.1 g/cm 3 (∼92% theoretical density) with minimal loss of Na₂O. This procedure offers several processing and cost advantages over conventional β"-alumina syntheses.     

Synthesis of Lithium-Cobalt Oxide Nanoparticles by Flame Spray Pyrolysis

Crystalline LiCoO2nanoparticles were synthesized from an aqueous solution of acetate compounds of lithium and cobalt by a flame spray pyrolysis, and characterized by TEM, XRD, and BET method. We investigated the evolution of LiCoO2nanoparticles from liquid droplets sprayed along the flame and observed disintegration of aqueous precursor droplets about 10μm into smaller fragments around 50 nm in the high temperature flame, as well as decomposition/oxidation of the precursor and coalescence/coagulation. We also examined effects of process variables such as molar concentrations of the precursors and flow rates of combustible gases on the particle size and crystal structure. The average particle diameter increased with an increase in the molar concentration of the precursor. Raising the maximum flame temperature by controlling the gas flow rates also led to an increase in the average diameter of the particles. The crystalline nanoparticles synthesized were nearly spherical, and their average primary particle diameters ranged from 11 to 35 nm.     

Novel Low-Temperature Synthesis of Disodium Dimolybdate by Ultrasonic Spray Pyrolysis

A new method for the synthesis of disodium dimolybdate (Na₂Mo₂O₇) in the process of ultrasonic spray pyrolysis using acidified aqueous solutions of thermodynamically stable molybdenum (VI) oxide clusters as a precursor is described. Na₂Mo₂O₇ particles were collected in alcohols (ethanol, 2-propanol, isobutyl alcohol), and ultracentrifugation was used to isolate solid material from solution. Scanning electron microscopy revealed the formation of uniform spherical Na₂Mo₂O₇ particles with an average diameter of about 0.25 μm. The X-ray diffraction analysis undoubtedly confirmed the formation of orthorhombic Na₂Mo₂O₇ for samples synthesized at a temperature as low as 300°C.     

Synthesis of Solid, Spherical Zirconia Particles by Spray Pyrolysis

A model is used to predict solid particle formation during spray pyrolysis by correlating droplet shrinkage before salt precipitation with its relative solution saturation. For the rapid drying conditions and droplet size of ∼ 10 μm, which are characteristic of conventional spray pyrolysis, solid salt particles are formed when a droplet's initial relative solution saturation is ∼ 10⁻² and the precipitated salt is sufficiently permeable to permit evolution of the remaining solvent after precipitation. It is proposed that this concentration allows the drying droplet more time and a shorter diffusion distance in which to maintain chemical homogeneity before precipitation. Using these concepts it is demonstrated that zirconyl chloride (ZrOCI₂· 8H₂O) and zirconyl hydroxychloride (ZrO(OH)CI) are excellent zirconium salts for solid zirconia particle synthesis by spray pyrolysis.     

Preparation of YAG:Europium Red Phosphors by Spray Pyrolysis Using a Filter-Expansion Aerosol Generator

Europium-doped yttrium aluminum garnet (YAG) phosphor particles were prepared from mixed nitrate solutions by the FEAG (filter expansion aerosol generator) process. The crystallinity, morphology, and luminescence of the YAG:Eu particles were investigated. The prepared particles had an amorphous phase, which turned into phase-pure YAG particles after annealing above 1000°C. A cubic-structure YAG phase was formed by the reaction of crystalline Y₂O₃ and the aluminum component. The prepared particles had spherical morphology. The mean size of the YAG:Eu particles increased from 0.45 to 1.0 µm when the overall solution concentrations were increased from 0.02 to 1.2 mol/L. The optimum doping concentration of europium for the maximum brightness of phosphor particles was 1.3 at.%. The cathodoluminescence (CL) intensity was strongly affected by the annealing temperatures. The maximum CL value of the particles was 55 cd/m².     

Preparation of Matrix-Type Nickel Oxide/Samarium-Doped Ceria Composite Particles by Spray Pyrolysis

Matrix-type nickel oxide (NiO)/samarium-doped ceria (SDC) composite particles, in which NiO and SDC nano-particles were homogeneously dispersed, were synthesized by spray pyrolysis (SP) for an anode precursor of intermediate-temperature solid oxide fuel cells (IT-SOFCs). SP of an aqueous solution containing Ni, Ce, and Sm salts resulted in capsule-type composite particles that had NiO enveloped with SDC. The capsule-type composite particles actually prevent Ni aggregation between particles, but they cannot have a large contact area between nickel (Ni) and SDC. A matrix-type composite particle is expected to have a large contact area because the matrix-type composite is comprised of nanometer-sized Ni and SDC particles. An adequate addition of ethylene glycol successfully resulted in matrix-type NiO/SDC composite particles. The matrix-type composite particles also showed higher anode performance than the capsule-type composite particles in these experiments and they were effective as precursors of high-performance IT-SOFC anodes.     

Synthesis of Titanium Dioxide Aerosol Gels in a Buoyancy-Opposed Flame Reactor

Aerosol gels are a novel class of materials with potential to serve in various energy and environmental applications. In this work, we demonstrate the synthesis of titanium dioxide (TiO₂) aerosol gels using a methane-oxygen coflow diffusion flame reactor operated in down-fired configuration (fuel flow in the direction opposite to buoyancy forces). Titanium tetraisopropoxide was fed as a precursor to the flame under different operating conditions. Control of the monomer size and crystalline phase of TiO₂ gel particles was achieved by adjusting the flame operating conditions, specifically the flame temperature, which was shown to significantly influence the phase transformation and rate of particle growth and sintering. The resulting materials were characterized for their physical and optical properties. Results showed that the TiO₂ aerosol gels had effective densities in the range 0.021–0.025 g/cm³, which is 2 orders of magnitude less than the theoretical mass density of TiO₂. The monomer size distribution, crystalline phase, and UV-Vis absorbance spectra of the gels showed distinct characteristics as a function of flame temperature.

Copyright © 2015 American Association for Aerosol Research     

喷雾阀按钮注塑模具设计

在喷雾阀按钮塑件结构分析的基础上,确定了该塑件注塑模具的结构设计方案。该方案通过设置潜伏式浇口解决多腔模具后处理工作量大的问题,并安装了先复位机构以避免活动型芯与推杆产生干涉。实践证明:该模具工艺性好、动作可靠,可为类似结构的注塑模具设计提供借鉴。     

A One-Step Ultrasonic Spray Pyrolysis Approach to Large-Scale Synthesis of Silica Microspheres

This paper proposes a novel and simple one-step ultrasonic spray pyrolysis (USP) approach to prepare silica (SiO2) microspheres, in which only one chemical     

机械力化学法制备复合钛白粉研究进展

机械力化学是一门新兴交叉学科,在此基础上发展起来的机械力化学技术,已成为制备无机复合材料的一种重要方法.近年来,其在无机粉体改性与复合材料制备上的应用更加广泛.本文主要综述了近几年来利用机械力化学法在制备复合钛白粉方面的研究现状,并总结了其优势和不足,进而展望了其发展趋势.     

Electrochemical Performance of a Ni and YSZ Composite Synthesised by Ultrasonic Spray Pyrolysis as an Anode for SOFCs

The electrochemical performance of an anode material for a solid oxide fuel cell (SOFC) depends highly on microstructure in addition to composition. In this study, a NiO–yttria‐stabilised zirconia (NiO–YSZ) composite with a highly dispersed microstructure and large pore volume/surface area has been synthesised by ultrasonic spray pyrolysis (USP) and its electrochemical characteristics has been investigated. For comparison, the electrochemical performance of a conventional NiO–YSZ is also evaluated. The power density of the zirconia electrolyte‐supported SOFC with the synthesised anode is ∼392 mW cm^–2 at 900 °C and that of the SOFC with the conventional NiO–YSZ anode is ∼315 mW cm^–2. The improvement is ∼24%. This result demonstrates that the synthesised NiO–YSZ is a potential alternative anode material for SOFCs fabricated with a zirconia solid electrolyte.     

Synthesis of Spherical β-Silicon Carbide Particles by Ultrasonic Spray Pyrolysis

Fine agglomerate-free spherical β-SiC powder was synthesized from a dispersion of colloidal silica, saccharose, and boric acid, by means of an ultrasonic spray pyrolysis method. Droplets of 2.2 μm were formed with an aerosol generator, operated at 2.5 MHz, and carried into a reaction furnace at 900°C with argon. Spherical X-ray amorphous gel particles of 1.1 μm were obtained. β-SiC particles with a mean diameter of 0.79 μm and spherical shape resulted when the SiC gel precursor particles were heated at 1500°C in argon.     

Synthesis of Submicrometer Mullite Powder via High-Temperature Aerosol Decomposition

High-purity mullite powders (3Al₂O₃.2SiO₂) have been prepared using a high-temperature aerosol decomposition technique yielding submicrometer (0.6 μm average) particles of spherical morphology with no hard agglomerates using aluminum nitrate and fumed silica as precursors. Depending upon the reaction conditions used, the powders range from amorphous to crystalline with no evidence of secondary-phase formation. This mullite synthesis approach has the advantages of not requiring postsynthesis milling, the ability to use a wide range of precursor systems, and enhanced control over chemical homogeneity and particle size/shape.     

A Spray Pyrolysis Approach for the Generation of Patchy Particles

Copyright 2013 American Association for Aerosol Research     

改进的Williamson醚化法合成葡萄糖衍生物

以葡萄糖衍生物、碱金属氢氧化物、氯化苄为原料,以正辛烷为带水剂,经Williamson醚化反应合成了3个苄醚化葡萄糖衍生物。考察了带水剂、碱、苄醚化试剂及投料比对反应的影响,得到优化的反应条件为:n(底物羟基)∶n(氢氧化钾或氢氧化钠)∶n(氯化苄)=1.00∶(1.10~1.15)∶(1.10~1.15),正辛烷为带水剂,125~130℃保温回流脱水反应4 h,在该条件下产物产率为96.8%~98.2%。产物结构经FTIR、UPLC-MASS、1HNMR确证。     

Spray Pyrolysis of Fe3O4–BaTiO3 Composite Particles

Fe₃O₄–BaTiO₃ composite particles were successfully prepared by ultrasonic spray pyrolysis. A mixture of iron(III) nitrate, barium acetate and titanium tetrachloride aqueous solution were atomized into the mist, and the mist was dried and pyrolyzed in N₂ (90%) and H₂ (10%) atmosphere. Fe₃O₄–BaTiO₃ composite particle was obtained between 900° and 950°C while the coexistence of FeO was detected at 1000°C. Transmission electron microscope observation revealed that the composite particle is consisted of nanocrystalline having primary particle size of 35 nm. Lattice parameter of the Fe₃O₄–BaTiO₃ nanocomposite particle was 0.8404 nm that is larger than that of pure Fe₃O₄. Coercivity of the nanocomposite particle (390 Oe) was much larger than that of pure Fe₃O₄ (140 Oe). These results suggest that slight diffusion of Ba into Fe₃O₄ occurred.