We propose a method for the evaluation of stability of the corrosion products of zirconium in melts of different compositions. The method is based on the analysis of the dependence of the equilibrium ...potential of zirconium electrode on the initial concentration of its compounds in the oxidation state 4+. It is discovered that zirconium compounds in the oxidation state 2+ are in equilibrium with the metal in all investigated systems and their stability depends on the composition of the melt and decreases in the following order: (NaBr–KBr) > KBr ≥ KCl > (LiCl–KCl). It is also established that, parallel with zirconium compounds in the oxidation state 2+, the investigated systems contain its compounds in the other oxidation states. The stability of these compounds in bromide melts decreases in the following order: Zr(II) (NaBr–KBr) > Zr(IV) (NaBr–KBr) > Zr(II) (KBr) > Zr(IV) (KBr). In chloride melts, the observed sequence has a somewhat different form: Zr(II) (KCl) > Zr(IV) (KCl) > Zr(II) (LiCl–KCl). Lithium is present among the corrosion products in LiCl–KCl melts. We also determined the thermodynamic characteristics (Δ
H
and Δ
S
) of equilibria of the corrosion products of zirconium with the investigated melts.
In this paper, we propose a theoretical model that takes into account Vegard strains and performs a detailed quantitative comparison of the theoretical results with experimental ones for ...quasispherical KTa sub(1-x) Nbx O sub(3) nanoparticles (average radius 25 nm), which reveal the essential (about 100 K) increase of the transition temperature in spherical nanoparticles in comparison with bulk crystals. We determined the dependence of Vegard strains on the content of Nb and reconstructed the Curie temperature dependence on the content of Nb using this dependence. The dependence of the Curie temperature on the Nb content becomes a nonmonotonic one for the small (<20 nm) elongated KTa sub(1-x) Nbx O sub(3) nanoparticles. We established that the accumulation of intrinsic and extrinsic defects near the surface can play a key role in the physical origin of extrinsic size effects in ferroelectric nanoparticles and govern its main features.
Discharge-ionization of hydrogen on carbon nanotube (CNT) electrodes in H3PO4 aqueous solution has been investigated and the effect of catalysts (Pt and polynuclear complexes 2Co–Ni with aminoethanol ...ligands) has been studied. It was found that the most probable mechanism contains the slow step of hydrogen atoms recombination on highly energetically nonuniform surface of CNT when the polarization is low. Increasing the polarization for more than −300 to −350 mV vs silver chloride reference electrode results in the operation of the CNT as a porous gas electrode with linear current-potential dependence. The influence of catalysts consists in the, first, decrease of the ohmic resistance of this electrode and, second, increase of the coulomb efficiency of charge (reduction of H+ ions) to discharge (oxidation of stored H2) from 70 to 80–90%. As follows from the results, the complexes 2Co–Ni can be used instead of Pt in the CNT-based hydrogen storage materials.
► Discharge-ionization of hydrogen on CNT electrodes in H3PO4 solutions. ► The hydrogen atoms recombination is the rate determining step. ► The catalytic effects of Pt and 2Co–Ni aminoethanol complex have been studied. ► Both catalysts decrease the resistance and increase the efficiency of the process. ► 2Co–Ni aminoethanol complex can be used instead of Pt as the catalyst.
A condensed overview about the forefathers’ and Mendeleev’s contribution to the compilation of the Periodic Table of Chemical Elements is presented. Milestones en route to the modern Periodic Table ...are ‘electrification’ of the Periodic Law, discovery of the rare-earth elements and the noble gases, investigation of the atomic structure and discovery of the transuranic elements. Then the contribution focuses on the Table’s short form as toolbox for learning the basics of inorganic chemistry. Similarities and differences in the chemical behavior of elements on the basis of full, close and approximate electronic analogies and the kainosymmetric sublevels (1
s
, 2
p
, 3
d
, 4
f
) are described. A question/answer section completes the article.
Inner complex compound of cobalt(III) with diaminoethanol, Co(DetmHdetm), and polynuclear complex compound 2Co-Ni with diaminoethanol, Ni(CoDetmHdetm)2(NO3)2, were synthesized. Stabilities of the ...obtained compounds were investigated in non-aqueous (dimethylformamide) solutions at different values of pH (from acid to alkaline). Methods of potentiometric titration and electron absorption spectra were used to determine the range of pH values where the compounds do not decompose. As a result of these studies, we found that at the upper value of pH=7, the coordination surrounding of the metals (Co(III), Ni(II)) does not change. When the pH value becomes lower than 7 (with adding HCl acide), the inner complex of Co(III) begins to decompose. The ligand H2detm is replaced by Cland partial protonization of diethanolamine occurs. Also, transformation of N,Ncis isomer of inner complex compound of cobalt(III) to N,N-trans isomer takes place, thus reducing the symmetry of the complex. As for the polynuclear complex compound 2Co-Ni, when pH value becomes lower than 7, molecules of solvent begin to react with the products of partially destroyed complex. As a result, new complex compound is formed with the increase of coordination number of nickel(II) from 4 to 6. However, in alkaline solutions where pH values are up to 10, the heterometal complex compound of 2Co-Ni remains stable. Only partial hydrolysis of the solvent occurs in these conditions. The schemes of transformations of Co(DetmHdetm) and Ni(CoDetmHdetm)2(NO3)2 occuring in non-aqueous (dimethylformamide) solutions at different values of pH (from acid to alkaline) are presented in the paper. The results of this study can be used for the preparation of precursor solution for the technology of catalytic materials production. Evidently, the range of pH from 7 to 10 must be maintained in order to avoid the contamination of the final products by the decomposed wastes of complexes and solvent.
The synthesis method of lithiated d-metal oxides using molten formate mixtures as precursors has been developed and the isothermal (800 °C) cross section of pseudo ternary Li–Mn–Co oxide system under ...ambient oxygen pressure has been investigated by XRD,
7
Li NMR, and galvanostatic electrochemical methods. Special attention has been paid to the compositions inside the quadrangle restricted by solid solutions LiCoO
2
–LiCo
0.85
Mn
0.15
O
2
with the layered structure of α-NaFeO
2
and solid solutions LiMn
2
O
4
–LiMnCoO
4
with the structure of spinel. It was found that, depending on the composition, three types of equilibrium phases could be formed: spinels LiLi,Mn,Co
2
O
4
with a part of Li atoms in octahedral sites, cation-deficit layered compounds Li
1 −
δ
Co,MnO
2
, and Li
2
MnO
3
. Areas of (co)existence of these phases were plotted on the composition plane of the pseudo-ternary Li–Mn–Co system. Electrochemical properties of the compositions inside the quadrangle LiCoO
2
–LiCo
0.85
Mn
0.15
O
2
–LiMn
2
O
4
–LiMnCoO
4
are determined by the content and average oxidation number of Mn atoms, which is higher than in the normal spinels LiMn,Co
2
O
4
. Thus, the specific capacities of the polyphase compositions are lower in comparison with the binary solid solutions LiMn,Co
2
O
4
or pure LiCoO
2
.
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