Highly dispersed anodes for solid oxide fuel cells using NiO/YSZ/BZY triple-phase composite powders prepared by spray pyrolysis

NiO/Y₂O₃-stabilized ZrO₂ (YSZ)/Y-doped BaZrO₃ (BZY) triple-phase composite powders were prepared by spray pyrolysis and evaluated for Ni/YSZ/BZY cermet anodes, which are considered effective for dry CH₄ operation in solid oxide fuel cells. The structure of the particles in these powders was fine crystal fragments, and the individual material phases were clearly separated and highly dispersed within the particles. The Ni/YSZ/BZY cermet anodes fabricated with these composite powders maintained a fine electrode microstructure equivalent to that in a simple Ni/YSZ cermet anode manufactured using a composite powder prepared by spray pyrolysis. Furthermore, the addition of BZY improved the anode performance in humidified H₂ and dry CH₄ operation.     

Electrochemical properties of nanostructured lanthanum strontium manganite cathode fabricated by electrostatic spray deposition

Electrostatic spray deposition was applied to prepare nanoporous lanthanum strontium manganite (LSM) films with high specific surface area (37.34 m²/g) for the cathode application in solid oxide fuel cell (SOFC). The electrochemical characteristics were investigated at a temperature range from 546 to 777 °C and oxygen partial pressure from 0.01 to 1.0 atm. The diffusion of atomic oxygen and oxygen ion transfer from three-phase boundary to the YSZ electrolyte were found to be the rate-determining steps for oxygen reduction reaction on LSM cathode. The polarization resistance of the LSM prepared using electrostatic spray deposition decreased from 15 to 1.2 Ωcm² with increasing temperature from 546 to 777 °C and the activation energy was 0.81 eV. It was demonstrated that the ESD method offers a promising approach for the preparation of electrochemically active nanoporous layers, particularly applicable for solid oxide fuel cells.     

Nitrogen-doped carbon nanotubes with tunable structure and high yield produced by ultrasonic spray pyrolysis

Nitrogen-doped carbon nanotubes (CN_x) were prepared by ultrasonic spray pyrolysis from mixtures of imidazole and acetonitrile. Imidazole, as an additive, was used to control the structure and nitrogen doping in CN_x by adjusting its concentration in the mixtures. Scanning electron microscopy observation showed that the addition of imidazole increased the nanotube growth rate and yield, while decreased the nanotube diameter. Transmission electron microscopy study indicated that the addition of imidazole promoted the formation of a dense bamboo-like structure in CN_x. X-ray photoelectron spectroscopy analysis demonstrated that the nitrogen content varied from 3.2 to 5.2 at.% in CN_x obtained with different imidazole concentrations. Raman spectra study showed that the intensity ratio of D to G bands gradually increased, while that of 2D to G bands decreased, due to increasing imidazole concentration. The yield of CN_x made from mixtures of imidazole and acetonitrile can reach 192 mg in 24 min, which is 15 times that of CN_x prepared from only acetonitrile. The aligned CN_x, with controlled nitrogen doping, tunable structure and high yield, may find applications in developing non-noble catalysts and novel catalyst supports for fuel cells.     

Effect of Sn particle size on the intermetallic compound formations of cold sprayed Sn-Ni coatings

Comparative studies on the intermetallic compound (IMC) formations of small (aggregated) and large Sn (irregular) with Ni and Cu in cold gas dynamic sprayed coatings were carried out. The Sn with high purity were selected and prepared as raw materials mixture in order to be sprayed onto Ni and Cu plate-shape substrates. The small particles of Sn (<1 μm) were successfully coated under conventional coating parameters when they are mixed with larger powder materials. And microstructural observation regards to compound formation similarly worked out for both small and large Sn mixture. However, the intermetallic formation behavior was turned out to be different. After post-annealing, the larger Sn particles in the composite coating formed larger amount of IMC with Ni than small Sn although, owing to larger interfacial area, more intensive reactivities were expected. Also, there were significant differences in the size and distribution of eutectic pores as well.     

CTAB assisted growth and characterization of nanocrystalline CuO films by ultrasonic spray pyrolysis technique

An aqueous solution of cupric nitrate trihydrate (Cu(NO₃)₂·3H₂O) modified with cetyltrimetylammonium bromide (CTAB) is used to deposit CuO films on glass substrate by chemical spray pyrolysis technique. The thermal analysis shows that the dried CTAB doped precursor decomposes by an exothermic reaction and suggests that minimum substrate temperature for film deposition should be greater than 270 °C. X-ray diffraction (XRD) studies indicate the formation of monoclinic CuO with preferential orientation along (0 0 2) plane for all film samples. The CTAB used as cationic surfactant in precursor results in the suppression of grain growth in films along the (1 1 0), (0 2 0) and (2 2 0) crystal planes of CuO. Surfactant modified films showed an increase in crystallite size of 14 nm at substrate temperature of 300 °C. The scanning electron micrographs (FESEM) confirm the uniform distribution of facets like grains on the entire area of substrate. CTAB modified films show a significant reduction in the particle agglomeration. Electrical studies of the CuO films deposited at substrate temperature of 300 °C with and without surfactant reveal that the CTAB doping increase the activation energy of conduction by 0.217 eV and room temperature response to ammonia by 9%. The kinetics of the ammonia gas adsorption on the film surface follows the Elovich and Diffusion models.     

Parametric studies on iron-carbon composite nanoparticles synthesized by laser pyrolysis for increased passivation and high iron content

Iron/iron carbide core and carbon shell nanoparticles with improved magnetic properties were successfully synthesized by laser pyrolysis. As iron and carbon precursors, iron pentacarbonyl and pure or argon-diluted acetylene/ethylene mixtures, respectively, were used. The aim of the present optimization is the improvement of the magnetic properties of the nanomaterials by the increase of the iron percent in powders simultaneously to the maintaining of the protective character of the carbon coverage of nanoparticles. The chemical content and the crystalline structure were monitored by EDX, XRD and TEM techniques. In the first study, the content of acetylene as carbon source was diminished from 75% to 0%. Consequently the percent iron increased from 10 at.% to 28 at.% while oxygen remained relatively constant (around 5 at.%). In the second step, only diluted ethylene was used (maximum 87.5 vol.% Ar). In this case, an increase of iron to 46 at.% is observed. An optimum 50% carbon source dilution was found. Above this value, the carbon content increases and below it, superficial oxidation increases through the diminishing of the carbon shell. The magnetic properties and the Fe phase composition of the Fe-C samples were analyzed by temperature dependent Mössbauer spectroscopy.     

溶液液滴在热等离子体射流中的运动和蒸发

为考察溶液注入热等离子体喷涂过程中喷雾参数对涂层质量的影响,本文建立了溶液液滴在热等离子体中运动蒸发的数学模型。模拟了液滴在不同参数下的运动和蒸发的过程,考虑了液滴、热等离子气流及液滴表面气体混合物随温度及组分的物性变化以及斯蒂芬流的影响,得到液滴的运动轨迹,蒸发速率以及半径和表面温度的变化。结果表明在一定范围内增大液...     

Studies on multistep thermal decomposition behavior of polytriazole polyethylene oxide‐tetrahydrofuran elastomer

Polytriazole polyethylene oxide‐tetrahydrofuran (PTPET) is an energetic propellant elastomer that is prepared using glycidyl azide polymer and trifunctional alkynyl‐terminated polyethylene oxide‐tetrahydrofuran. Its thermal decomposition, determined using thermogravimetic analysis, showed two mass‐loss peaks largely related to the decomposition of azide groups and the main chain. Flynn‐Wall‐Ozawa and Kissinger‐Akahira‐Sunose methods were deployed to obtain kinetic triplet parameters of PTPET thermal decomposition by the traditional model‐free method; the Coats‐Redfern approach was used as the model‐fitting method. Kinetics analysis indicated that the mechanism of the two‐step reactions were the primary‐reaction of first order and the power‐law phase reaction of the 2/3 order. The first decomposition stage of PTPET had an activation energy (E_a) of 113 to 116 kJ/mol while the second was 196 to 210 kJ/mol. The thermal decomposition of PTPET with different heating rates and mechanisms showed good kinetic compensation effects, the gas products being further studied with TG‐FTIR.     

Thermal degradation and pyrolysis study of brominated butyl rubber‐based damping material

This paper deals with the thermal stability and decomposition behavior of brominated butyl rubber‐based damping material (BRP). The raw materials, butyl rubber matrix (IIR) and brominated phenolic resin (PF), were also investigated as control. IIR shows one decomposition stage, while PF shows four weight loss stages. Flynn‐Wall‐Ozawa calculation indicates that BRP has thermal stability between IIR and PF. Thermogravimetric analysis–Fourier transform infrared (TGA‐FTIR) and pyrolysis–gas chromatography/mass spectrometry (GC/MS) were used to investigate the volatile products under nitrogen atmosphere. As expected, BRP shows combined thermal decomposition behavior of both IIR and PF. The degradation mechanism of BRP was proposed, which is not significantly influenced by the incorporation of PF. The application stability of BRP is worth to be noticed since the post‐cure effect, that is, the free radicals remained from vulcanization would cause additional cross‐linking when stored at 80°C to 120°C.     

Silver spray deposition for AgLDI imaging MS of cholesterol and other olefins on thin tissue sections

Olefins such as cholesterol and unsaturated fatty acids play important biological roles. Silver‐assisted laser desorption ionization (AgLDI) takes advantage of the strong affinity of silver to conjugate with double bonds to selectively ionize these molecules for imaging mass spectrometry (IMS) experiments. For IMS studies, two main approaches for silver deposition have been described in the literature: fine coating by silver sputtering and spray deposition of silver nanoparticles. While these approaches allow for extremely high resolution IMS experiments to be conducted, they are not readily available to all laboratories. Herein, we present a silver nitrate spray deposition approach as an alternative to silver sputtering and nanoparticle deposition for routine IMS analysis. The silver nitrate spray has the same level of specificity and sensitivity for olefins, particularly cholesterol, and has shown to be capable of IMS experiments down to 10‐μm spatial resolution. Minimal sample preparation and the affordability of silver nitrate make this a convenient and accessible technique worth considering.