S. QI
,
N. M. POROTNIKOVA
,
M. V. ANANYEV
,
A. V. KUZMIN
,
V. A. EREMIN
,
A. A. PANKRATOV
,
N. G. MOLCHANOVA
,
O. G. REZNITSKIKH
,
A. S. FARLENKOV
,
E. G. VOVKOTRUB
,
Yu. P. ZAIKOV
中国有色金属学报(英文版)
doi:10.1016/S1003-6326(16)64421-7
制备了在燃料电池中作为密封剂使用的操作温度可达700~900°C 的 SiO2?Al2O3?BaO?MgO 和SiO2?Al2O3?ZrO2?CaO?Na2O 系玻璃陶瓷。采用同步热分析和高温膨胀测量技术，对所研究的玻璃陶瓷的热性能和其与燃料电池用材料(YSZ 电解质，合金连接器 Crofer22APU,15Х25Т)的匹配性能进行研究。采用原子发射光谱对玻璃陶瓷的元素成分进行分析。结果表明，45%SiO2?15%Al2O3?25%BaO?15%MgO 陶瓷的线膨胀系数为10.0×10?6°C?1，60%SiO2?10%Al2O3?10%ZrO2?5%CaO?15%Na2O 的为9.5×10?6°C ?1。采用扫描电镜对 YSZ/玻璃陶瓷/Crofer22APU 的界面结构进行分析。SiO2?Al2O3?BaO?MgO 玻璃中的硅酸盐相发生了晶化，采用拉曼光谱和X 射线衍射对晶化产物进行了分析。与非晶玻璃相比，所研究的玻璃陶瓷作为电化学或氧传感器中的密封剂使用时具有更佳的性能指标。而 SiO2?Al2O3?ZrO2?CaO?Na2O 低温非晶陶瓷可以作为燃料电池中的密封剂使用。
关键词:
玻璃陶瓷密封剂
,
燃料电池
,
YSZ
,
Crofer22APU
,
硅酸镁
Journal of Nanoparticle Research
Cobalt ferrite (CoFe(2)O(4)) nanoparticles were synthesized by using the hydrothermal route with the addition of trisodium citrate dihydrate (Na(3)CA center dot 2H(2)O). The formation of CoFe(2)O(4) nanoparticles with size ranging from 13 to 19 nm was confirmed by X-ray diffraction, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy; the clear-cut sharp of the nanoparticles was observed by transmission electron microscopy. By these characterization methods, the evolution of lattice constant and morphologies of the nanoparticles with the addition of Na(3)CA center dot 2H(2)O is observed. Furthermore, the magnetic hysteresis loops measured at room temperature indicate that the magnetic properties of the products also show clear relationship with the masses of Na(3)CA center dot 2H(2)O. For example, coercivity and high-field paramagnetic susceptibility increase with the increasing masses of Na(3)CA center dot 2H(2)O, whereas the saturation magnetization and the effective magnetic anisotropy constant have the maximum values as the mass of Na(3)CA center dot 2H(2)O is 1 g. This change of magnetic properties is related with the expanded lattice and the varied size and shape because of the addition of Na(3)CA center dot 2H(2)O.
关键词:
Cobalt ferrite;Nanoparticles;Hydrothermal method;Magnetism;nanocomposite;nanocrystals;temperature;particles;size
International Journal of Modern Physics B
The perturbation formulae of EPR parameters g factors g(x), g(y) and g(z) for the lowest Kramers doublet of 4f(1) ion in orthorhombic symmetry are established. In these formulae, the contributions of the covalency effects, the admixture between J = 7/2 and J = 5/2 states as well as the second-order perturbation (which is not considered in the previous works) via crystal-field and orbital angular momentum interactions are all included. According to these formulae, and by using the superposition model, the g-factors g., g(y) and g(z) for Ce3+ center in YBa2CU3O6+x superconductor are calculated. The results are discussed.
关键词:
YBa2Cu3O6+x;EPR;superposition model;Ce3+;crystal-field
Superconductor Science & Technology
The EPR g factors for the tetragonal NdBa2CU3O7-delta high-T-c superconductor are theoretically investigated on the basis of the perturbation formulae of the g factors for a 4f(3) ion in tetragonal symmetry. The contributions to the g factors arising from the second-order perturbation terms, the admixture of various states and the covalency effect are included in these formulae. The relevant crystal-field parameters are determined from the superposition model and the local structural data of the tetragonal Nd3+ site in NdBa2CU3O7-delta. The calculated g factors are in reasonable agreement with the observed values. The validity of the results is discussed.
关键词:
crystal-field parameters;superposition-model;oxygen-deficient;nd;temperature;dependence;spectra;ndbacuo
European Physical Journal-Applied Physics
The local structures and the EPR g factors g(parallel to) and g(perpendicular to) are theoretically studied for the tetragonal Ti(3+)-V(O) centers in BaTiO(3) bulks and thin films using the perturbation formulas of the g factors for a 3d(1) ion in tetragonally elongated octahedra and compressed tetrahedra, respectively, based on the cluster approach. For the Ti(3+)-V(O) center in BaTiO(3) bulks, the impurity Ti(3+) suffers the displacement away from the oxygen vacancy V(O) by about 0.15 angstrom along the C(4) axis due to the electrostatic repulsion of the V(O). Nevertheless, the Ti(3+)-V(O) center in BaTiO(3) thin films may exhibit the tetragonally compressed tetrahedron, characterized by the bond angle 55.88 degrees larger than that (approximate to 54.74 degrees) of an ideal tetrahedron. The quite different g factors (especially g anisotropies Delta g = g(parallel to) - g(perpendicular to)) for the two kinds of samples are discussed, in view of the dissimilar bonding or coordination environments (i.e., incomplete bonding in the thin films may lead to the lower coordination number).
关键词:
electron-paramagnetic resonance;atomic screening constants;superposition model;spin-resonance;scf functions;crystals;epr
International Journal of Modern Physics B
The EPR g factors g(//) and g(perpendicular to) for the six-coordinated Cu2+(1) site in YBa2Cu3O6+x are theoretically investigated from the perturbation formulas for a 3d(9) ion in tetragonally elongated octahedra. The related tetragonal crystal-field parameters Ds and Dt are determined from the superposition model and the structural data for the Cu2+(1) site, by considering the effective elongation of the oxygen octahedron due to the Jahn-Teller effect of the Cu2+ cluster. Based on the calculations, the effective elongation (= 15%) of the ligand octahedron is obtained for the signals at 100K. As for the EPR signals at room temperature, the elongation declines to merely 4%, corresponding to the smaller anisotropy Delta g (=g(//) - g(perpendicular to)). The theoretical results for the g factors are in good agreement with the observed values, and the local tetragonal distortion due to the Jahn-Teller effect is discussed.
关键词:
crystal fields and spin hamiltonians;electron paramagnetic resonance;Cu2+;YBa2Cu3O6+x;single-crystals;yba2cu3o7-delta;evolution;esr
