The Role of H in Superconducting HxYBa2Cu3O7

1987 ◽  
Vol 99 ◽  
Author(s):  
C. Y. Yang ◽  
S. M. Heald ◽  
J. J. Reilly ◽  
M. Suenaga

ABSTRACTWe have examined the role of H on the superconductivity properties, the atomic structure, and the electronic state in the HxYBa2Cu3O7. The hydrogen solid solution phase (up to ×≃O.2) exhibits a superconducting transition at 94 K, which was usually slightly higher than the starting oxide (YBa2Cu3O7, while the hydride phases (H rich) are not superconducting. Infrared (IR), x-ray diffraction, and x-ray absorption spectroscopy (XAS) measurements indicate that H is located interstitially only near Cu sites.

2013 ◽  
Vol 747-748 ◽  
pp. 765-771 ◽  
Author(s):  
Jian Sheng Yao ◽  
Ding Zhong Tang ◽  
Xiao Guang Liu ◽  
Cheng Bo Xiao ◽  
Xin Li ◽  
...  

The interfacial reactions between ceramic moulds and DZ417G and DZ125 superalloys were investigated. The microstructure and composition of the interface region were observed by optical microscope, X-ray diffraction and scanning electron microscope with energy dispersive spectroscopy. The results showed that (Al1-xCrx)2O3solid solution phase with pink color was formed from the dissolution of Cr2O3and Al2O3and vapour phase, which was transferred to the reaction surfaces. The reaction layer thicknesses of DZ417G and DZ125 alloys were about in the range of 40-50μm. The interface reaction product between DZ417G alloy and ceramic mould was TiO2and the product between DZ125 alloy and ceramic mould was HfO2.


Author(s):  
Xuehong Cui ◽  
Jinming Zhu ◽  
Ketong Luo ◽  
Jianlie Liang

Abstract Phase relationships in the Ce-Nd-B ternary system at 773 K were investigated by means of X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy techniques. Six borides, i. e. CeB4, CeB6, NdB4, NdB6, NdB66 and Nd2B5 are confirmed in this work. No ternary compound was observed. CeB4 and NdB4 were discovered to form the continuous solid solution phase (Ce,Nd)B4, CeB6 and NdB6 also form the solid solution phase (Ce,Nd)B6. The maximum solid solubility of Ce in (Ce,Nd)2B5 phase is 46.5 at.%. The isothermal section of the Ce-Nd-B ternary system at 773 K consists of 3 three-phase regions, 7 two-phase regions and 7 single- phase regions.


2008 ◽  
Vol 104 (11) ◽  
pp. 113527 ◽  
Author(s):  
L. Alves ◽  
T. P. A. Hase ◽  
M. R. C. Hunt ◽  
A. C. Brieva ◽  
L. Šiller

2007 ◽  
Vol 280-283 ◽  
pp. 1441-1444 ◽  
Author(s):  
Qiang Xu ◽  
Xing Hong Zhang ◽  
Jie Cai Han ◽  
Xiao Dong He

Large-scale (Ti,Cr)B2-Cu composite from Ti, Cr, B and Cu powders was produced by combining combustion synthesis with Pseudo Hot Isostatic Pressing. The diameter of the synthesized product is 240 millimeter. The product was identified using X-ray diffraction and the result showed that only (Ti,Cr)B2 and Cu phases, without other phases, existed in the product. The analysis of the microstructure indicated that the skeletal structure had been formed in the (Ti,Cr)B2 solid solution phase. Fine (Ti,Cr)B2 reinforcement grew in near equivalent axis-like shape and some sintering neckings were found between the solid solution phases. The relative density of the synthesized product was 93.6% because the skeletal structure baffled the densification of the composite. The bending strength and fracture toughness of the product were 476 MPa and 6.8 MPa·m1/2 respectively.


Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1620
Author(s):  
Xiaomin Yuan ◽  
Haonan Zhu ◽  
Huiling Ji ◽  
Yiwei Zhang

Carbon nanotubes (CNTs), dispersed in absolute ethanol, were evenly mixed into Ti/MgH2 powders by wet milling. Then, we applied the vacuum hot-pressed sinteringmethod to the CNTs/TiMg composite materials. An optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and a field emission scanning electron microscope (FESEM) were used for the microstructure observation and phase analysis of samples. The mechanical properties were measured via the micro-vickers hardness. The results show that the main phases in the composites were Ti, Mg and C. Meanwhile, a small amount of Ti-Mg solid solution phase was also found. The cross-section morphology of the composites shows that the melted magnesium fills the grain interface during extrusion and that the composites have a better compactness.The microstructures of the composites have been greatly refined as the CNT contents increased. The structure of the composites was further refined when 0.5 wt.% CNTs were added. The fracture surface is obviously a ductile fracture. The microhardness increases obviously with the CNT content increasing. When the content of the CNTs is 1.0 wt.%, the microhardness of the composites reaches 232 HV, which is 24% higher than that of the matrix.


1998 ◽  
Vol 269-272 ◽  
pp. 473-478 ◽  
Author(s):  
Francsco Cardellini ◽  
Vittoria Contini ◽  
Gregorio D'Agostino ◽  
Adriano Filipponi

Author(s):  
Z.T. Zhang ◽  
H.P. Nie ◽  
K. Yan

Sb distribution in the phases of SiO2 saturated Sb-Fe-O-SiO2-CaO system has been determined for the first time through high-temperature experiment and quenching techniques, followed by Electron probe X-ray microanalysis(EPMA) in air(Ptot= 1 atm, PO2= 0.21 atm). The phases were quantified in the temperature range of 900?C-1200?C and the effects of Fe/SiO2(mass fraction) and CaO/SiO2(mass fraction) on Sb2O3 content in the Sb-Fe-O-SiO2-CaO system were investigated at 1200?C. The results indicate that the Sb-containing phase primarily existed in the solid solution phase at 1200?C. With the increase of temperature from 1100?C to 1200?C, the Sb2O3 content in the solid solution phase increased drastically from 7.52 wt% to 17.36 wt%. Lowering the values of CaO/SiO2 and Fe/SiO2 in the smelting process effectively reduced Sb2O3 content in the slag. The verification experiment results suggest that the antimony content in slag was 0.57 wt%, the crude antimony yield rate was lower than 4%,and the crude antimony grade was beyond 94 wt%, which can achieve the reduction of antimony content in the slag.


Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 640 ◽  
Author(s):  
Nikolay D. Trofimov ◽  
Alexander L. Trigub ◽  
Boris R. Tagirov ◽  
Olga N. Filimonova ◽  
Polina V. Evstigneeva ◽  
...  

The oxidation state and local atomic environment of admixtures of In, Cu, and Ag in synthetic sphalerite crystals were determined by X-ray absorption spectroscopy (XAS). The sphalerite crystals doped with In, Cu, Ag, In–Cu, and In–Ag were synthesized utilizing gas transport, salt flux, and dry synthesis techniques. Oxidation states of dopants were determined using X-ray absorption near edge structure (XANES) technique. The local atomic structure was studied by X-ray absorption fine structure spectroscopy (EXAFS). The spectra were recorded at Zn, In, Ag, and Cu K-edges. In all studied samples, In was in the 3+ oxidation state and replaced Zn in the structure of sphalerite, which occurs with the expansion of the nearest coordination shells due to the large In ionic radius. In the presence of In, the oxidation state of Cu and Ag is 1+, and both metals can form an isomorphous solid solution where they substitute for Zn according to the coupled substitution scheme 2Zn2+ ↔ Me+ + In3+. Moreover, Ag K-edges EXAFS spectra fitting, combined with the results obtained for In- and Au-bearing sphalerite shows that the Me-S distances in the first coordination shell in the solid solution state are correlated with the ionic radii and increase in the order of Cu < Ag < Au. The distortion of the atomic structure increases in the same order. The distant (second and third) coordination shells of Cu and Ag in sphalerite are split into two subshells, and the splitting is more pronounced for Ag. Analysis of the EXAFS spectra, coupled with the results of DFT (Density Function Theory) simulations, showed that the In–In and Me+–In3+ clustering is absent when the metals are present in the sphalerite solid solution. Therefore, all studied admixtures (In, Cu, Ag), as well as Au, are randomly distributed in the matrix of sphalerite, where the concentration of the elements in the “invisible” form can reach a few tens wt.%.


1988 ◽  
Vol 143 ◽  
Author(s):  
Joe Wong ◽  
Glen A. Slack

The bonding and local atomic structure of a series of 3d metal-beta boron solid solution are investigated using a combination of x-ray absorption near-edge structure (XANES) and extended fine structure (EXAFS) technique utilizing intense synchrotron radiation as a light source. The corresponding metal diborides MB2, (M = Sc, Ti, V, Cr).were also measured and used to model the coordination environment of these metal sites in beta-boron.


2018 ◽  
Vol 52 (2) ◽  
pp. 775-782 ◽  
Author(s):  
Minhua Su ◽  
Changzhong Liao ◽  
Tingshan Chan ◽  
Kaimin Shih ◽  
Tangfu Xiao ◽  
...  

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