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61.
Garegin R. Karagedov Svetlana S. Shatskaya Nikolai Z. Lyakhov 《Journal of Materials Science》2007,42(18):7964-7971
Reasons for a phase transition in zirconia subjected to intensive mechanical treatment in planetary mill have been considered.
If steel balls and vials are used for milling the comminution is accompanied by oxidation of wear metal particles and successive
mechanochemical reaction with ZrO2. Aluminum has been shown to behave similarly and, being deliberately added to zirconia powder, to form solid solutions. Foreign
metal cations introduced into the lattice stabilize a modification with higher crystal symmetry thus increasing the threshold
size above which the monoclinic modification is stable. An increase of surface energy contribution to the Gibbs’ energy of
zirconia plays an important role in phase transformation at the initial stages of mechanical treatment, while henceforth thermodynamic
stability is more and more determined by the stabilizing effect of the impurity cations. Under the conditions that rule out
contamination of ZrO2 with wear material or other metal additives, dynamic equilibrium sets in between the direct transition to the tetragonal
phase and the reverse transition to the monoclinic form. 相似文献
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Minoru Furukawa Patrick B. Berbon Terence G. Langdon Zenji Horita Minoru Nemoto Nikolai K. Tsenev Ruslan Z. Valiev 《Metallurgical and Materials Transactions A》1998,29(1):169-177
Experiments were conducted to determine the age-hardening characteristics and the mechanical properties of an Al-5.5 pct Mg-2.2
pct Li-0.12 pct Zr alloy processed by equal-channel angular (ECA) pressing to give a very fine grain size of ∼1.2 μm. The results show that peak aging occurs more rapidly when the grain size is very fine, and this effect is interpreted in
terms of the higher volume of precipitate-free zones in the fine-grained material. Mechanical testing demonstrates that the
ECA-pressed material exhibits high strength and good ductility at room temperature compared to conventional Al alloys containing
Li. Elongations of up to ∼550 pct may be achieved at an elevated temperature of 603 K in the ECA-pressed condition, thereby
confirming that, in this condition, the alloy may be a suitable candidate material for use in superplastic forming operations. 相似文献
69.
Lydia K. Muranova Vladislav M. Shatov Andrey V. Slushchev Nikolai B. Gusev 《International journal of molecular sciences》2021,22(15)
In this study, a reliable and simple method of untagged recombinant human HspB7 preparation was developed. Recombinant HspB7 is presented in two oligomeric forms with an apparent molecular weight of 36 kDa (probably dimers) and oligomers with an apparent molecular weight of more than 600 kDa. By using hydrophobic and size-exclusion chromatography, we succeeded in preparation of HspB7 dimers. Mild oxidation promoted the formation of large oligomers, whereas the modification of Cys 126 by iodoacetamide prevented it. The deletion of the first 13 residues or deletion of the polySer motif (residues 17–29) also prevented the formation of large oligomers of HspB7. Cys-mutants of HspB6 and HspB8 containing a single-Cys residue in the central part of the β7 strand in a position homologous to that of Cys137 in HspB1 can be crosslinked to the wild-type HspB7 through a disulfide bond. Immobilized on monoclonal antibodies, the wild-type HspB6 interacted with the wild-type HspB7. We suppose that formation of heterodimers of HspB7 with HspB6 and HspB8 may be important for the functional activity of these small heat shock proteins. 相似文献
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