Protective coatings for stainless steel for SOFC applications

In this paper, a coating procedure based on spin coating of metal oxide polymer precursors on stainless steel, which decreases the oxide scale growth rate, is evaluated. The yttrium and cobalt solutions were used as polymer precursors, while a ferritic stainless steel Crofer 22 APU was used for the deposition of protective coatings. The thickness of deposited protective film was about ~500 nm. The effectiveness of protective layer was evaluated by cyclic thermogravimetry, oxide scale electrical conductivity, and X-ray diffractometry. The results show that steel coated with yttrium polymer precursor has better properties than uncoated or cobalt-coated sample.     

XPS depth profiling investigations on La2Zr2O7 layers prepared by chemical solution deposition

La₂Zr₂O₇ (LZO) layers have been recently investigated as potential buffer layers for superconducting YBa₂Cu₃O_7–x coated conductors deposited on Ni tapes. Chemical solution deposition was used for LZO layer preparation. X-ray photoelectron spectroscopy (XPS) depth profiling is demonstrated to be an important method for layer characterization in addition to X-ray diffraction techniques. XPS measurements revealed layers that are homogeneous in depth, very smooth, and have no significant impurities. A slight difference to the nominal La:Zr stoichimetry is discussed in combination with structural defects that are suspected from spectral changes during ion sputtering.     

Fabrication and electrochemical investigation of layer-by-layer deposited titanium phosphate/Prussian blue composite films

Composite films of titanium phosphate (TiPS)/Prussian blue (PB) were fabricated by the alternative deposition of TiPS layer and PB nanocrystals. The layer of TiPS was fabricated by adsorption of hydrated titanium from aqueous Ti(SO4)2 solution and subsequent reaction with phosphate groups. The layer of PB nanocrystals was fabricated by sequential adsorption of FeCl3 solution and K4[Fe(CN)6] solution. Regular deposition of TiPS/PB composite films were verified by UV-vis absorption spectroscopy and quartz crystal microbalance measurements. The successful fabrication of the TiPS/PB composite films was further confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. Instead of producing films of TiPS layers alternating with PB nanocrystal layers, the TiPS/PB composite films have a structure in which the interstices of the PB nanocrystal films are filled with TiPS component. TiPS/PB composite films show enhanced electrochemical properties and improved stability in comparison with pure PB films prepared by the multiple sequential adsorption process. TiPS/PB composite films have the capability to catalyze the electrochemical reduction of H2O2 and can be used as a biosensor for detecting H2O2.     

Synthesis of highly textured superconducting NdBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7-<Emphasis Type="Italic">y</Emphasis></Subscript> thin films by two aqueous sol-gel dip coating techniques

Today, the deposition of coated conductors on a variety of substrates is often performed using a vacuum or low pressure technique. However, obtaining uninterrupted deposition at high speed, increasing flexibility in composition and attaining independence of geometric constraints of the substrates are areas in which vacuum techniques will need sustained development in order to answer industrial demands. The development of the next generation of deposition methods, based on deposition under atmospheric environment and from aqueous precursor solutions is a real challenge. This work describes the deposition of thin NdBa₂Cu₃O_7-y layers on SrTiO₃ single crystals based on a new sol-gel dip coating process using aqueous precursor solutions. Two inorganic aqueous sol-gel routes were investigated, a metal nitrate–citric acid based and a metal acetate–triethanol amine based solution. Using detailed thermal analysis, it is shown that adjusting the different parameters during thermal treatment can be used to control the morphology of the films. Also special attention is given to the microstructure of the thin film because of its relevance to the superconducting transport properties of the coated conductor system.     

Inkjet printing of Ce<Subscript>0.8</Subscript>Gd<Subscript>0.2</Subscript>O<Subscript>2</Subscript> thin films on Ni-5%W flexible substrates

The successful inkjet printing of a cerium gadolinium oxide (Ce_0.8Gd_0.2O₂) precursor solution on highly textured Ni-5%W is reported. A stable ink was synthesised from metal acetates and propionic acid with rheological properties suitable for inkjet printing and also the development of solid–liquid interface comparable with thin film formation by dip coating. Two different drop-on-demand print heads were used for deposition: a 16-nozzle piezoelectric cartridge and a single electromagnetic nozzle. Two different rastering patterns with different droplet sizes and spacing were compared. Thermogravimetry and X-ray diffractometry were used to study the thermal decomposition of the metal oxide precursors and to determine the shortest possible heat treatment of the deposited layers, potentially suitable for continuous large scale production. The results from X-ray diffraction show that the single phase Ce_0.8Gd_0.2O₂ was obtained in all cases, but only piezoelectric inkjet printing with optimised drop overlapping produces a highly textured buffer layer. Optical micrographs and atomic force microscopy also indicate the good quality of deposited films after heat treatment.     

Yttrium tris-propionate monohydrate: Synthesis,crystal structure,and thermal stability

The complex [Y(Prop)₃(H₂O)]_∞ (I) was prepared by treating yttrium carbonate, acetate, or acetylacetonate hydrates with propionic acid and characterized by the data of elemental analysis, IR spectroscopy, X-ray diffraction, and thermal analysis in air. Complex I has a polymeric layered structure with clear-cut structure-forming dimeric groups bridged by bidentate ligands. Only van der Waals interactions occur between the adjacent polymeric layers. In air, yttrium propionate monohydrate I is completely converted to the oxide at 600°C.     

Synthesis and structure of tridentate bis(phosphinic amide)-phosphine oxide complexes of yttrium nitrate. Applications of 31P,89Y NMR methods in structural elucidation in solution

The synthesis and characterisation of a tridentate ligand containing two diphenylphosphinic amide side-arms connected through the ortho position to a phenylphosphine oxide moiety and the 1:1 and 2:1 complexes formed with yttrium nitrate are reported for the first time. The free ligand (R(P1)*,S(P3)*)-11 is obtained diastereoselectively by reaction of ortho-lithiated N,N-diisopropyl-P,P-diphenylphosphinic amide with phenylphosphonic dichloride. Complexes [Y((R(P1)*,S(P3)*)-11)(NO(3))(3)] and [Y((R(P1)*,S(P3)*)-11)(2)(NO(3))](NO(3))(2) were isolated by mixing ligand 11 with Y(NO(3))(3)·6H(2)O in acetonitrile at room temperature in a ligand to metal molar ratio of 1:1 and 2:1, respectively. The 1:1 derivative is the product of thermodynamic control when a molar ratio of ligand to yttrium salt of 1:1 is used. The new compounds have been characterised both as the solid (X-ray diffraction) and in solution (multinuclear magnetic resonance). In both yttrium complexes the ligand acts as a tridentate chelate. The arrangement of the two ligands in the 2:1 complex affords a pseudo-meso structure. Tridentate chelation of yttrium(III) in both complexes is retained in solution as evidenced by (89)Y NMR data obtained via(31)P,(89)Y-HMQC, and (89)Y,(31)P-DEPT experiments. The investigation of the solution behaviour of the Y(III) complexes through PGSE NMR diffusion measurements showed that average structures in agreement with the 1:1 and 1:2 stoichiometries are retained in acetonitrile.     

高纯氧化钇的感耦等离子体发射光谱分析及基体效应的研究

以高纯氧化钇中稀土杂质的ICP-AES测定为例, 研究了基体对分析元素谱线强度的影响及基体效应与工作条件的关系, 指出基体效应除主要来自分析物进样效率的降低外, 大量基体进入ICP降低了激发温度并对分析物的电离产生抑制作用, 提出用Se内标法代替通常的基体匹配法来补偿基体效应。进行了折衷条件选择及联样量确定等研究。实样分析表明, 内标法和基体匹配法所得结果一致, 加入回收率为87-120%, 精度也符合分析要求。     

Ultrathin silica films immobilized on gold supports: fabrication, characterization, and modification

A novel method for covalent attachment of ultrathin silica films (thickness <10 nm) to gold substrates is reported. Silica layers were prepared using spin-coating of sol-gel precursor solutions onto gold substrates that were cleaned and oxidized using UV photo-oxidation in an ozone atmosphere. The gold oxide layer resulting from this process acts as a wetting control and adhesive agent for the ultrathin silica layer. Control of silica layer thickness between approximately 6 and 60 nm through modification of precursor solution composition or by repetitive deposition is demonstrated. Films were characterized using infrared spectroscopy, ellipsometry, atomic force microscopy, and cyclic voltammetry. For the standard deposition parameters developed here, films were determined to be 5.5 +/- 0.75 nm thick, and were stable in aqueous solutions ranging in pH from 2 to 10 for at least 30 min. Films contained nanoscopic defects with radii of 相似文献   

Controllable synthesis of Y2O3 microstructures for application in cataluminescence gas sensing

Y(2)O(3) dumbbells, microspheres, and nanosheets were synthesized by a facile hydrothermal procedure followed by calcination. Electron microscopy, X-ray diffraction, and N(2) adsorption measurements were used to characterize the yttrium oxide microstructures. On the basis of a time-dependent study of nanostructure evolution and the effect of other processing parameters, a kinetic "homogeneous nucleation-self assembly-anisotropic growth" mechanism is proposed to explain the growth of these microstructures under hydrothermal conditions. The sensitivity of as-prepared Y(2)O(3) structures to a series of gaseous chemicals was examined by using a homemade cataluminescence sensing system. The designed cataluminescence sensor based on the yttrium oxide dumbbells shows good sensing performance for 16 common volatile organic compounds.     

Uniform Y2O3 coating on multi-component phosphor powders by modified polyol process

We have developed a method to coat the phosphors comprising of multi-component systems to prevent them from aging effect. Y2O3 was selected as a protective material because of its superior ability to resist against mercury adsorption and oxidation and its good UV transparency at the wavelength used for phosphor activation. By dispersing the phosphor particles in the polyol medium that contains the yttrium precursor, heterogeneous nucleation and growth on the particle surface were induced. This allows us to obtain a thick and uniform coating of the phosphors with amorphous Y2O3 sols. The heat-treatment condition for Y3O3 sols was carefully controlled to keep the phosphors from surface oxidation and at the same time to assure the complete crystallization and burn-out of organic impurity by XRD and TG/DTA. The surface morphology of the coated phosphors was examined by SEM as a function of reaction time and temperature and precursor concentration.     

Yttrium Acetate-Derived Particle Coatings for Mitigating Oxidation and Corrosion of Inconel 625

Sol paint that yields yttrium-based compounds was prepared by mixing four chemical ingredients, yttrium acetate tetrahydrate precursor, diethanolamine, isopropyl alcohol, and hydrochloric acid, and then applied as oxidation/corrosion resistant coatings for Inconel 625 substrates. Annealing the coatings at 500°C developed a coalescent microstructure of coarse particles consisting of amorphous yttrium carbonate as the major component and crystalline yttrium oxide (Y2O3) as the minor one. At 700°C, the yttrium carbonate was transformed into Y2O3 by decarbonation. Increasing the annealing temperature to 900°C led to the formation of the YCrO3 phase yielded by interaction between Y2O3 and the Cr2O3 which had arisen from the oxidation of the underlying Inconel; the YCrO3 phase created a particle coating with a densified microstructure. There were two key factors in mitigating the degree of oxidation of Inconel at 900°C in air: (1) an uptake of oxygen by Y2O3 in the coatings, and (2) a densified coating layer that suppresses the diffusion and permeation of oxygen through it. Furthermore, inhibiting the rate of NaCl-caused corrosion was not only due to the excellent coverage of particle coatings over the entire surfaces of the substrates, but also may be associated with a good adherence of the coatings to the substrates.     

Synthesis and characterization of volatile,fluorine-free beta-ketoiminate lanthanide MOCVD precursors and their implementation in low-temperature growth of epitaxial CeO(2) buffer layers for superconducting electronics

A new class of volatile, low-melting, fluorine-free lanthanide metal-organic chemical vapor deposition (MOCVD) precursors has been developed. The neutral, monomeric Ce, Nd, Gd, and Er complexes are coordinatively saturated by a versatile, multidentate ether-functionalized beta-ketoiminato ligand series, the melting point and volatility characteristics of which can be tuned by altering the alkyl substituents on the keto, imino, and ether sites of the ligand. Direct comparison with conventional lanthanide beta-diketonate complexes reveals that the present precursor class is a superior choice for lanthanide oxide MOCVD. Epitaxial CeO(2) buffer layer films can be grown on (001) YSZ substrates by MOCVD at significantly lower temperatures (450-650 degrees C) than previously possible by using one of the newly developed cerium beta-ketoiminate precursors. Films deposited at 540 degrees C have good out-of-plane (Deltaomega = 0.85 degrees ) and in-plane (Deltaphi = 1.65 degrees ) alignment and smooth surfaces (rms roughness approximately 4.3 A). The film growth rate decreases and the films tend to be smoother as the deposition temperature is increased. High-quality yttrium barium copper oxide (YBCO) films grown on these CeO(2) buffer layers by pulsed organometallic molecular beam epitaxy exhibit very good electrical transport properties (T(c) = 86.5 K, J(c) = 1.08 x 10(6) A/cm(2) at 77.4 K).     

溶胶-凝胶法制备的Y_2O_3薄膜的光波导性质研究

用醋酸钇溶解于甲氧基乙醇的溶胶 凝胶法制备了Y2 O3光波导薄膜。通过二乙烯三胺的络合作用 ,获得了均匀和稳定的前驱液 ,并用浸渍提拉法得到了薄膜。差热分析、红外吸收光谱被用来表征Y2 O3凝胶和粉末。用XRD、扫描电子显微镜、m线法和波导荧光光谱法研究了Y2 O3光波导薄膜的结构和光波导性质。结果表明 ,Y2 O3薄膜对于光活性掺杂是一种很好的基质材料 ,预示Y2 O3薄膜在光电子方面具有巨大的应用前景。     

Y2O3包覆LiCo1/3Ni1/3Mn1/3O2的电化学性能

通过在硝酸钇水溶液浸渍并焙烧的简单工艺, 在LiCo1/3Ni1/3Mn1/3O2材料表面包覆了一层Y2O3. 采用X射线衍射(XRD), 扫描电子显微镜(SEM), 透射电子显微镜(TEM), 循环伏安(CV)和恒流充放电对包覆和未包覆的LiCo1/3Ni1/3Mn1/3O2进行了测试分析. 结果表明, Y2O3包覆并没有改变LiCo1/3Ni1/3Mn1/3O2的晶体结构, 只存在于LiCo1/3Ni1/3Mn1/3O2的表面; 与未包覆的材料相比, Y2O3包覆后的材料在高电位下具有更好的容量保持率和放电容量. CV测试表明, 包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应.     

Synthesis, crystal structure from single-crystal and powder X-ray diffraction data, and thermal behavior of mixed potassium lanthanide squarates: thermal transformations of layered [Ln(H2O)6]K(H2C4O4)(C4O4)2 into pillared LnK(C4O4)2 (Ln = Y, La, Gd, Er)

A new series of mixed potassium and rare-earth squarates, [Ln(H(2)O)(6)]K(H(2)C(4)O(4))(C(4)O(4))(2) (Ln = Y, La, Gd, Er), has been synthesized and structurally characterized from single-crystal X-ray diffraction and spectroscopic analyses. The yttrium-based compound crystallizes with a monoclinic symmetry, space group C2/c [a = 8.3341(2) A, b = 37.7094(9) A, c = 11.7195(3) A, beta = 90.3959(9) degrees , V = 3683.1(2) A(3), Z = 8]. The structure is built from layers maintained together via hydrogen bonds. Within a layer, squarate ligands act as linkers between lanthanide and potassium cations. The thermal decomposition of the precursors has been studied by powder thermodiffractometry and thermal analyses. It is shown that crystalline intermediate phases are formed during the degradation. Among them, unprecedented mixed anhydrous squarates, LnK(C(4)O(4))(2), could be isolated. The crystal structure of the Y compound has been solved ab initio from X-ray powder diffraction data, using direct-space methods [a = 6.2010(5) A, c = 11.639(1) A, V = 447.55 A(3), Z = 2]. The structure consists of layers of edge-sharing YO(8) and KO(8) antiprisms, pillared by mu(8)-squarate groups. The end of the precursor decomposition is marked by the formation of cubic sesquioxides Ln(2)O(3), including lanthanum oxide.     

Environmentally Benign Solution-Based Procedure for the Fabrication of Metal Oxide Coatings on Metallic Pigments

Aluminum pigments were coated with Fe₂O₃ and CuO by solution-based thermal decomposition of the urea nitrate compounds hexakisureairon(III)nitrate and tetrakisureacopper(II)nitrate. The deposition process was optimized to obtain homogeneously coated aluminum pigments. The growth of the surface coatings was controlled by investigation with scanning electron microscopy, energy dispersive X-ray spectroscopy and static light scattering as well as infrared, X-ray diffraction and thermogravimetric analysis. The iron precursor showed an incomplete decomposition in solution, incorporating traces of urea molecules inside the coatings while the copper precursor showed complete dissociation accompanied by in situ formation of amine complexes. The amount of organic residues resulting from ligand fragments in the final oxide coatings could be reduced to 22 % for the iron oxide and 12 % for the copper oxide by further temperature treatment in solution (259 °C). Colorimetric investigations of the obtained pigments revealed an excellent hiding power, outperforming the pigments used in current state-of-the-art formulations.     

Synthesis,crystal structure modeling and thermal decomposition of yttrium propionate [Y2(CH3CH2COO)6·H2O]·3.5H2O

An yttrium propionate complex was synthesized and characterized for its application as precursor for Y₂O₃ based oxide thin films deposition and YBa₂Cu₃O_7 − x superconducting thin films. The TG–DTA and FT-IR analyses have revealed the formation of an yttrium propionate complex with the formula [Y₂(CH₃CH₂COO)₆·H₂O]·3.5H₂O. The molecular structure of the yttrium propionate complex was determined by modeling the FT-IR spectra. The coordination numbers for the yttrium ions are eight and nine, respectively being coordinated by bridging bimetallic triconnective and chelating bidentate propionate groups.The thermal decomposition of yttrium propionate has been investigated by thermogravimetric (TG) and differential thermal analysis (DTA) coupled with quadrupole mass spectrometry (QMS), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques.     

Synthesis and Crystal Structure of (H)2[Y(H2O)8]2(NO3)8(C36H36N24O12)?13H2O

The compound of (H)₂[Y(H₂O)₈]₂(NO₃)₈(C₃₆H₃₆N₂₄O₁₂)13H₂O composition was obtained from a nitric acid solution of yttrium nitrate and a macrocyclic cavitand cucurbituryl. According to X-ray diffraction data, the crystal structure of the compound involves alternating layers of cucurbituryl molecules and eight-coordinate yttrium aqua complexes. The structure has a complex system of hydrogen bonds involving the oxygen atoms of cucurbituryl and water molecules and the nitrate anions and linking all structural elements of the crystal.     

Low-valence triruthenium compounds via substitution of a bridging acetate in the parent Ru(3)O(OAc)(6) cluster core by 2,2'-azobispyridine (abpy) or 2,2'-azobis(5-chloropyrimidine) (abcp)

Reaction of oxo-centered Ru(3)(III,III,III) precursor [Ru(3)O(OAc)(6)(py)(2)(CH(3)OH)](PF(6)) (1) with 1 equiv of 2,2'-azobispyridine (abpy) or 2,2'-azobis(5-chloropyrimidine) (abcp) induced the formation of stable Ru(3)(III,III,II) derivatives [Ru(3)O(OAc)(5){mu-eta(1)(N),eta(2)(N,N)-L}(py)(2)](PF(6)) (L = abpy (2), abcp (3)). As established in the structure of 3 by X-ray crystallography, 2 or 3 is derived from 1 by substitution of the axial methanol and one of the bridging acetates in the parent Ru(3)O(OAc)(6) cluster core with abpy or abcp in an mu-eta(1)(N),eta(2)(N,N) bonding mode. Reduction of 3 by hydrazine induces isolation of one-electron reduced neutral Ru(3)(III,II,II) product Ru(3)O(OAc)(5){mu-eta(1)(N),eta(2)(N,N)-abcp}(py)(2) (3a). As revealed by electrochemical and spectroscopic studies, substituting one of the bridging acetates in the parent Ru(3)O(OAc)(6) cluster core by abcp or abpy modifies dramatically the electronic and redox characteristics in the triruthenium derivatives. Relative to that for the parent compound [Ru(3)O(OAc)(6)(py)(3)](PF(6)) (E(1/2) = -0.46 V), triruthenium-based redox potential in the redox process Ru(3)O(III,III,III)/Ru(3)O(III,III,II) is significantly anodic-shifted to E(1/2) = +0.36 V for 2 and E(1/2) = +0.53 V for 3. Furthermore, the anodic shifts of redox potentials are progressively enhanced with a decrease of the formal oxidation states in the triruthenium cluster cores. As a consequence of remarkable positive shifts for redox potentials, the low-valence Ru(3)(III,III,II) and Ru(3)(III,II,II) species are stabilized and accessible.