Preparation of Nanocomposite GDC/LSCF Cathode Material for IT-SOFC by Induction Plasma Spraying

Homogeneous mixtures of Ce_0.8Gd_0.2O_1.9 (GDC) and La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) nanopowders were successfully synthesized using induction plasma by axial injection of a solution. The resulting nanocomposite powders consisted of two kinds of nanopowders with different mass ratio of GDC/LSCF, such as 3/7 and 6/4. The morphological features, crystallinity, and the phases of the synthesized powders were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), local energy-dispersive x-ray spectroscopy (EDS) analysis, and x-ray diffraction (XRD). The nanopowders are almost globular in shape with a diameter smaller than 100 nm and their BET specific areas are around 20 m² g^?1. The GDC and LSCF phases are well distributed in the nanopowders. In addition, suspensions, made with the as-synthesized composite nanopowders and ethanol, were used to deposit cathode coatings using suspension plasma spray (SPS). Micro-nanostructures of the coatings are discussed. The coatings are homogeneous and porous (51% porosity) with cauliflower structures.     

The 400 °C Isothermal Section of the La-Co-Mg Ternary System

The isothermal section of the La-Co-Mg system at 400 °C was determined by characterization of about thirty ternary alloys synthesised by induction melting in sealed Ta crucibles and then annealed. Scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDXS) and x-ray powder diffraction (XRPD) were used to analyze microstructures, identify phases, measure their compositions and determine their crystal structures. Phase equilibria are characterized by the absence of ternary solid solutions and by the presence of three ternary phases. The existence and the crystal structure of the La_4?x CoMg_1 + x (τ₁, 0 ≤ x ≤0.15, cF96-Gd₄RhIn) were confirmed and its homogeneity region determined; the new phases La_23?x Co₇Mg_4 + x (τ₂, ?0.50≤ x ≤0.60, hP68-Pr₂₃Ir₇Mg₄) and ~La₃₈Co₅₅Mg₇ (τ₃, unknown crystal structure) were detected.     

Synthetically Controlled,Carbon-Coated Co<Subscript>2</Subscript>SnO<Subscript>4</Subscript>/SnO<Subscript>2</Subscript> Composite Anode for Lithium-ion Batteries

The inherent drawbacks of Co₂SnO₄ in demonstrating the closer-to-theoretical capacity value behavior and the inadmissible volume-expansion-related capacity fade behavior have been surpassed by choosing a tailor-made material composition of Co₂SnO₄/SnO₂, prepared at two different temperatures such as 400°C and 600°C to obtain residual carbon-containing and carbon-free compositions, respectively. Among the products, carbon-coated Co₂SnO₄/SnO₂ composite exhibits better electrochemical performance compared with that of the carbon-free product mainly because of the beneficial effect of carbon in accommodating the volume-expansion-related issues arising from the alloying/de-alloying mechanism. A combination of conversion reaction and alloying/de-alloying mechanism is found to play a vital role in exhibiting closer-to-theoretical capacity values. In other words, an appreciable specific capacity value of 834 mAh g^?1 has been exhibited by Co₂SnO₄/SnO₂ anode containing carbon coating, thus, demonstrating the possibility to improve the electrochemical performance of the title anode through carbon coating, which is realized as a result of the addition of carefully manipulated synthesis conditions.     

Formation and Study of the Nanostructured CuAl0.5Ga0.5Te2 Synthesized by Mechanical Alloying Processing

Nanostructured chalcopyrite CuAl_0.5Ga_0.5Te₂ has been prepared by milling a mixture of reactants, copper, aluminum, gallium, and tellurium. The crystal structure, morphology, and composition of the prepared samples have been characterized by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and transmission electron microscopy (TEM). X-ray diffraction has revealed the presence of the characteristic peaks of the chalcopyrite phase for the CuAl_0.5Ga_0.5Te₂-milled powders. The crystallite size and internal strain have been evaluated by XRD patterns using the Williamson–Hall method. The average particle size decreases as the milling time is prolonged, while the lattice parameters and internal strain increase. The TEM confirmed the formation of CuAl_0.5Ga_0.5Te_e nanoparticles. The bandgap has been found to increase from 1.42 eV up to 1.45 eV as the process time varies, respectively, from 60 min to 360 min.     

改进溶剂热法制备锂离子电池负极材料用多级孔Co3O4微球

将溶剂热法与高温煅烧法相结合制备多级孔Co3O4微球,采用XRD、SEM、TEM和电化学测试等技术研究该多级孔Co3O4微球的结构和性能.结果表明:当煅烧温度为700℃时,所合成的Co3O4(Co3O4-700)是由丰富的纳米颗粒(50～200 nm)和大量孔洞(～100 nm)构成的微米级微球(1～2μm);该Co3...     

The Systems Tantalum (Niobium)-Cobalt-Boron

Constitution of the ternary systems Nb-Co-B and Ta-Co-B was studied, employing optical and electron microscopy, x-ray powder, single crystal diffraction, electron probe microanalysis, DTA and Pirani melting point measurements. Ternary phase equilibria were determined within an isothermal section at 1100 °C. For the Co-rich part (≥50 at.% Co) of the system, a liquidus surface projection and a corresponding Schulz-Scheil reaction scheme were constructed in combination with data for primary crystallization from as-cast samples determined by SEM and EPMA measurements. The crystal structures of novel ternary compounds have been elucidated by x-ray powder and single crystal diffraction and were supported by TEM. {Nb,Ta}CoB with NbCoB-type exhibits a high temperature modification (ZrAlNi-type, a = 0.5953 nm, c = 0.3248 nm; a = 0.5926 nm, c = 0.3247 nm for Nb and Ta respectively), which was only present in as-cast alloys, but found to be stabilized by the addition of Fe to annealing temperatures of 1400 °C. Ta₃Co₄B₇ (a = 0.3189 nm, b = 1.8333 nm, c = 0.8881 nm) was proven to be isotypic with Nb₃Co₄B₇. The novel orthorhombic compounds {Nb,Ta}Co₂B₃ (TaCo₂B₃-type with space group Pnma; a = 0.53628 nm, b = 0.32408 nm, c = 1.24121 nm for TaCo₂B₃; a = 0.53713 nm, b = 0.32442 nm, c = 1.2415 nm for NbCo₂B₃) adopt unique structure types with branched boron zig-zag chains. {Nb,Ta}Co₂B were found to crystallize in a unique monoclinic structure type (space group P2 ₁/c; a = 0.9190 nm, b = 0.64263 nm, c = 0.63144 nm; β = 109.954°, for Nb) very close to an orthorhombic setting (Cmce, a = 0.63162 nm, b = 1.72810 nm, c = 0.64270 nm, for Nb). Substitution of Co by Ni stabilizes a smaller orthorhombic lattice with Re₃B-type structure (Cmcm) although no homologue compound in the Ni-system exists. The crystallographic relations among the structure types of Re₃B and pseudo-orthorhombic as well as monoclinic {Nb,Ta}Co₂B were defined in terms of a Bärnighausen scheme. DFT calculations revealed very close stabilities for the three competing structure types for {Nb,Ta}Co₂B. Detailed transmission electron microscopy (TEM) for Nb(Co,Fe)B, {Nb,Ta}Co₂B,  {Nb,Ta}(Co,Ni)₂B, and Ta₃Co₄B₇ confirmed lattice geometries and crystal symmetry. Vickers hardness was measured for {Nb,Ta}Co₂B, {Nb,Ta}(Co,Ni)₂B, {Nb,Ta}_2?x Co_21+x B₆ and {Nb,Ta}Co₂B₃ exhibiting the highest value of hardness of HV = 22.4 ± 1.1 GPa for TaCo₂B₃. Magnetic, specific heat and electrical resistivity measurements on the compounds TaCo₂B and Ta₂Co₂₁B₆ reveal paramagnetic and ferromagnetic metallic ground states, respectively.     

Phase Equilibria of the Co-Mo-Zr Ternary System at 1100 °C

The isothermal section of the Co-Mo-Zr ternary system at 1100 °C was constructed experimentally. A series of phases including their crystal structures and compositions were obtained by examining the annealed specimens through x-ray diffraction (XRD), optical microscopy (OM), and electron probe microanalysis (EPMA). It was confirmed that two ternary phases, λ₁ (Co_0.5-1.5Mo_1.5-0.5Zr, hP12-MgZn₂) and ? (CoMo₄Zr₉, hP28-Hf₉Mo₄B), exist in the Co-Mo-Zr ternary system at 1100 °C. And the experimental results also indicated that there are fourteen three-phase regions at 1100 °C. Ten of them were well determined in the present work: (1) (γCo) + Co₁₁Zr₂ + Co₂₃Zr₆, (2) (γCo) + Co₂₃Zr₆ + θ-Co₉Mo₂, (3) Co₂₃Zr₆ + θ-Co₉Mo₂ + μ-Co₇Mo₆, (4) (Mo) + μ-Co₇Mo₆ + Co₂Zr, (5) (Mo) + Co₂Zr + λ₁, (6) (Mo) + Mo₂Zr + λ₁, (7) λ₁ + Mo₂Zr + CoZr, (8) Co₂Zr + CoZr + λ₁, (9) Mo₂Zr + CoZr + liquid and (10) ? + Mo₂Zr + (βZr). The maximum solubilities of Zr in μ-Co₇Mo₆ phase, Mo in Co₂Zr phase and Co in Mo₂Zr phase were determined to be 5.89, 12.57 and 9.95 at.%, respectively. While the solubilities of Zr in θ-Co₉Mo₂ and (γCo) phases, Mo in Co₁₁Zr₂ and CoZr phases were detected to be extremely small. According to this work, the Co₂₃Zr₆ phase contained 21.61 at.% Mo and 8.32 at.% Zr. In addition, the maximum solubilities of Co and Zr in (Mo) phase and Mo in (γCo) phase were measured to be 3.61, 5.60 and 11.20 at.%, respectively.     

Influence of Nd-Co Substitution on Structural,Electrical, and Dielectric Properties of X-Type Hexagonal Nanoferrites

A series of single phase X-type hexagonal ferrites with concentration Sr_2?x Nd _x Ni₂Fe_28?y Co _y O₄₆ (x = 0.02, 0.04, 0.06, 0.08, 0.10 and y = 0.1, 0.2, 0.3, 0.4, 0.5) has been prepared by sol-gel method sintered at 1250 °C for 6 h. The x-ray diffraction analysis reveals the single phase of X-type hexagonal ferrites. The particle size was calculated by using SEM and TEM. The ferrite substituted with Nd³⁺ and Co²⁺ has average particle size in the range of 40-50 nm. The room temperature electrical resistivity experiences the significant enhancement from a value of 1.1 × 10⁷ to 2.03 × 10⁸ Ωcm with the increase in Nd³⁺ and Co²⁺ concentration. The dielectric constant exhibits high value at low frequencies and decreases with the increase of frequency. The tangent dielectric loss shows the abnormal behavior which can be explained on the basis of hopping between the Fe²⁺ and Fe³⁺ ions on octahedral sites. The maximum value of tangent loss at low frequencies reflects the application of these materials in medium frequency devices (MF).     

Role of Superficially Applied SnO2 Inhibitor in Controlling High Temperature Corrosion of Some Fe-, Co- and Ni-Base Superalloys

Inhibitors and fuel additives have been used with varying success to combat high temperature corrosion of metals and alloys. In this work, the role of a superficially applied SnO₂ coating to combat high temperature corrosion of some superalloys viz Superfer 800H (Alloy A), Superco 605 (Alloy B) and Superni 75 (Alloy C) has been investigated. Accelerated corrosion testing of the coated as well as bare superalloys was done in a molten salt environment (Na₂SO₄–60 %V₂O_5?) at 900 °C for 50 cycles. Each cycle consisted of 1 h heating in a silicon carbide tube furnace followed by 20 min cooling in ambient air. Weight change measurements after each cycle were taken by an electronic balance having an accuracy of 0.01 mg. XRD, SEM and EPMA analyses of the exposed specimens were carried out to characterize the oxide scales. The bare superalloys showed more overall weight gains, in general, in comparison with their SnO₂ coated counterparts. The corrosion rate for the bare Co-base alloy was found to be highest, whereas that for the Fe-base Superfer 800H a lowest. The percentage decrease in the weight gain in alloys A, B and C with superficially applied SnO₂ was found to be 17.2, 66 and 50 % respectively after 30 cycles. The effectiveness of the SnO₂ was perhaps due to its non-reactive nature with the corroding species and high melting point (1630 °C).     

Investigation of Co-Substituted Nanosized Mn2Y-Hexaferrites Synthesized by Sol-Gel Autocombustion Method

The structural and electrical properties of Co-substituted and nano-sized Y-type hexagonal ferrites have been investigated in the present work. The samples with chemical composition Ba₂Co _x Mn_2?x Fe₁₂O₂₂ (x = 0.0, 0.5, 1.0, 1.5, 2.0) were prepared by sol-gel autocombustion method. The powdered samples and pellets were sintered simultaneously at 1000 °C for 5 h and characterized by means of DTA/TGA, FTIR spectroscopy, x-ray diffraction (XRD), field emission gun scanning electron microscopy, and energy dispersive x-ray spectroscopy. The XRD analysis confirms that the investigated ferrites have single phased Y-type hexagonal structure without showing any impurity phase. Lattice constants (a and c), cell volume (V), crystallite size (D), and x-ray density (ρ _x ) have also been calculated from the XRD data. DC electrical resistivity is measured within the temperature range of 30-100 °C for each sample and is observed to increase with increasing Co-substitution. The dielectric constant (∈) has also been measured which is observed to decrease with Co-substitution. Thus, high electrical resistivity and low dielectric constant make these materials suitable for multi-layer chip inductors and also for RF components and circuits.     

水热法批量制备粒径可控SnO2纳米粉体（英文）

以SnCl4·5H2O为前驱体、NH3·H2O为矿化剂,通过水热还原技术制备平均粒径在5～30nm的SnO2纳米粉末。系统研究小批量生产(1kg/批)条件下,工艺条件包括溶液浓度、反应温度、压力、时间和pH值对SnO2粒径、形貌和晶型的影响,并采用XRD、TEM等测试手段对样品进行表征。结果表明,在保持SnO2粉末晶型和形貌不变的前提下,通过调节反应温度、反应时间等工艺参数,粉末的粒径尺寸可以有效地控制在5～30nm范围内。不同于之前的报道,SnO2粒径尺寸随着反应时间(反应温度)的变化存在新的变化趋势,并推测解释了此晶粒异常生长的机理。     

Preparation and microstructure characterization of a nano-sized Ti<Superscript>4+</Superscript>-doped AgSnO<Subscript>2</Subscript> electrical contact material

A Ti⁴⁺-doped nano-structured AgSnO₂ material was prepared using sol-gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results show that Ti⁴⁺ cations are successfully doped into the crystal lattice of SnO₂, and thus significantly improve the electrical conductivity of the sample. Furthermore, the coating of Ag on Ti⁴⁺-doped SnO₂ nano-sized particles enhances the surface wettability and enables the resulting AgSnO₂ material to have better mechanical properties.     

Synthesis and characterization of SnO2/polyaniline nanocomposites by sol–gel technique and microemulsion polymerization

Nanostructured SnO₂ was prepared based on the sol–gel method. Aniline monomer was polymerized by microemulsion polymerization in the presence of nanocrystalline SnO₂ to form inorganic–organic nanocomposite materials, in which SnO₂ nanoparticles were embedded within porous polyaniline (PANI). Structural and morphological characterization of SnO₂ and SnO₂/PANI was carried out using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The XRD pattern suggested that PANI did not modify the crystal structure of SnO₂. FT-IR spectrum proved that aniline was successfully composited with the nanostructured SnO₂. TEM analysis showed that the SnO₂ nanoparticles with a diameter of ca. 15 nm were embedded well in the porous PANI. Conductivity analysis indicated that the SnO₂/PANI nanocomposites had a higher conductivity than that of the pure SnO₂ nanopowders.     

Characterization and Synthesis of Co(ss)/WSi2-CoWSi Nanocomposite by Mechanical Alloying and Subsequent Sintering

In this study, Co_(ss)/WSi₂-CoWSi nanocomposite was synthesized via mechanical alloying and heat treatment. In order to fabricate bulk composite, 50-h-milled powders were cold pressed and subsequently sintered at 1150 °C for 4 h in Ar atmosphere. Phase development and structural changes were investigated by x-ray diffraction technique and scanning electron microscopy. After various milling times, the powders were investigated by differential thermal analysis and microhardness measurements. The starting powder mixture has two allotropic structures of Co (fcc and hcp). After 10-h milling, an allotropic transformation takes place in Co (fcc to hcp), and a composite microstructure consisting of cold-welded Co, W, and Si phases is formed. After 20 h, new peaks related to WSi₂ appeared in x-ray diffractograms. Increasing milling time to 50 h caused the formation of (Co, W, and Si) solid solution, WSi₂, and CoWSi phases. DTA analysis of 30- and 50-h-milled powders confirmed an increase in the degree of ordering. The 50-h-milled powders exhibited high microhardness value of about 1050 HV_0.1. XRD result of sintered material demonstrated that only ordered Co_(ss)/WSi₂-CoWSi nanostructured composite is present. Consolidated sample showed 12% porosity. Nanoindentation results showed that the sintered composite an exhibited a high hardness of 700 HV_0.1 with an elastic modulus of 107 GPa.     

Effects of Calcination on Structural, Photocatalytic Properties of TiO2 Nanopowders Via TiCl4 Hydrolysis

Photocatalytic degradation of methyl orange (MO) in water was examined using TiO₂ nanopowders under solar irradiation. These photocatalysts were successfully synthesized by hydrolysis of titanium tetra chloride (TiCl₄) in the temperature range of 70-95 °C and calcined at higher temperatures of between 400 and 900 °C. The samples prepared were characterized using x-ray powder diffraction, scanning electron microscope (SEM) and Fourier transform infrared spectrophotometer (FTIR). UV-Vis spectrometer was used for analyzing the concentration of MO in solution at different time intervals during the photodegradation experiment. Parameters affecting the photodegradation rate such as catalyst crystallinity, concentration of the catalyst, MO concentration, and pH of the solution have been investigated. The results indicate that TiO₂ nanopowder was antase at low calcination temperatures in the range of 400-500 °C. The sample calcined at 600 °C is composed of both anatase and rutile phase. Further increase in the temperature enhanced the intensities of diffraction peaks of the rutile phase. The size of the crystallites for all the samples prepared were found to be in the 6-13 nm range and from SEM micrographs it was in the range of 19-43 nm. The mixture of both phases exhibited a higher photoactivity in comparison with pure anatase or rutile catalysts.     

Isothermal Section of the Al-Pd-Co Phase Diagram at 850 °C Delimited by Homogeneity Ranges of Phases Epsilon,U, and F

Eight alloys with metal compositions (at.%) ranging between (68-76)Al, (9-25)Pd and (5-20)Co were investigated after annealing at 850 °C for 500 h. In the investigation, the scanning electron microscopy including energy dispersive x-ray spectroscopy and the x-ray diffraction were used. In the investigated alloys, various combinations of phases β, U, F, ε₆, ε₁₆, ε₂₈, δ, Al₅Co₂, and Al₉Co₂ were identified. Partial isothermal section at 850 °C of the Al-Pd-Co phase diagram was proposed, containing homogeneity ranges of six phases (ε_n, U, F, β, δ, and Al₅Co₂).     

Effect of SnO2 intermediate layer on performance of Ti/SnO2/MnO2 electrode during electrolytic-manganese process

SnO₂ intermediate layers were coated on the titanium (Ti) substrate by thermal decomposition. Scanning electron microscope (SEM) and X-ray diffraction (XRD) results show that uniform SnO₂ intermediate layers with rutile crystal structure were successfully achieved. According to the results of linear sweep voltammetry (LSV), oxygen evolution potential (OEP) of the Ti/SnO₂/MnO₂ electrodes decreases with increasing SnO₂ content, indicating that the electro-catalytic oxidation activity of the electrode increases. Accelerated service life tests results demonstrate that SnO₂ intermediate layer can improve the service life of the Ti/SnO₂/MnO₂ electrode. As the content of SnO₂ intermediate layer increases, the cell voltage and the energy consumption decrease apparently.     

Effect of calcination temperature and atmosphere on crystal structure of BaTiO<Subscript>3</Subscript> nanofibers

Barium titanate (BaTiO₃, BT) nanofibers with a diameter range of 160 nm to 300 nm were prepared by drying electrospun BT/polyvinylpyrrolidone (BT/PVP) composite fibers for 1 h at 80 °C in vacuum with a subsequent calcination in air for 1 h at a temperature range of 650 °C to 750 °C. The morphology and crystal structure of calcined BT nanofibers were characterized with the aid of XRD, FT-IR, SEM, and TEM. The XRD and FR-IR measurements confirm that BT nanofibers with a diameter of about 160 nm and a tetragonal perovskite structure were present in the electrospun fibers after calcination for 1 h at 750 °C. The FR-IR analysis of the BT fibers reveals that the intensity level of the O-H stretching vibration bands (at 3430 cm⁻¹ and 1425 cm⁻¹) become weaker as the calcination temperature is increased and that a broad band at 570 cm⁻¹, which represents the Ti-O vibration, appears sharper and narrower after calcination at 750 °C due to the formation of metal oxide bonds. In contrast, BT fibers prepared by a refluxing process in a nitrogen atmosphere show a dramatic change in crystal structure: the tetragonal structure changes to a cubic perovskite structure, probably due to the suppression of carbonate contamination. Thus, the calcination temperature and atmosphere appear to have a significant influence on the crystal structure of BT.     

Experimental Investigation of the Isothermal Section in Fe-Gd-Pd Ternary System at 873 K

Isothermal section of Fe-Gd-Pd ternary system at 873 K has been established by means of x-ray diffraction (XRD), differential scanning calorimetry (DSC), and scanning electron microscope (SEM) with energy disperse x-ray spectroscopy (EDS) in backscattered electron imaging modes. The isothermal section consists of 14 single-phase regions, 25 two-phase regions, and 12 three-phase regions. At 873 K, no ternary compound was found and the binary inermetallic compounds Gd₃Pd and Fe₂₃Gd₆ are not stable, whereas the compound Fe₂₃Gd₆ decomposes into compounds Fe₁₇Gd₂ and Fe₃Gd. The XRD and the SEM/EDS analysis show that there is almost no solubility of Gd in the FePd and FePd₃ phases, and the solubilities of Pd in Fe₁₇Gd₂, Fe₃Gd and Fe₂Gd and Fe in GdPd₂, α-Gd₃Pd₄ and Gd₃Pd₂ are all less than 1 at.%. Meanwhile, the solubilities of Fe in GdPd₃, α-GdPd and Gd₇Pd₃ are determined to be as high as 1.37, 5.31, and 4.18 at.% Fe, respectively.     

Preparation and properties of K2NiF4-type perovskite oxides La2NiO4 catalysts for steam reforming of ethanol

The performance of La₂NiO₄ perovskite catalysts, prepared using a citric acid complexation method, for the steam reforming of ethanol was studied. The catalysts were characterized by X-ray diffractometry (XRD), specific surface area measurements (BET), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The experimental results show that the calcination temperature and the amount of citric acid (CA) have a significant influence on the characteristics of the catalysts and their catalytic activity. Among the catalysts tested, the La₂NiO₄ catalyst calcined at 700 °C with n(La):n(Ni):n(CA) of 2:1:3 exhibits the best activity and excellent stability as well as very low coke formation.