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Saint Petersburg, Russia

Tatte T.,University of Tartu | Kolesnikova A.L.,Institute of Problems of Mechanical Engineering | Hussainov M.,University of Tartu | Talviste R.,University of Tartu | And 6 more authors.
Journal of Nanoscience and Nanotechnology

We report on the method of Ti0 2 nano- and microfibres preparation and their cracking during processing and post-treatment. Nano- and microfibres were fabricated by drawing from viscous alkoxide based oligomeric concentrate precursors with the following exposure into an atmosphere of 30-50% humidity. The fibres microstructure was analyzed with TEM, solid state NMR, X-ray diffraction tools, and AFM. Experiments on crack formation in Ti0 2 microfibres proved that fibres with diameter larger than 10 micron are fractured for chosen post-treatment regimes. In theoretical considerations sol-gel produced and thermally treated microfibres are modeled as core/shell structures. It is suggested that the formation of fibres starts via solidification of liquid jet through the appearance of a rigid solid shell, which reveals tensile mechanical stresses because of material shrinkage. The effect of post-treatment is taken into account by additional densification of the fibre surface layer. The stress intensity factor K 1 is calculated for the model core/shell structures and the dependence of K 1 on the fibre diameter is demonstrated. The results of modeling qualitatively confirm experimental data of microfibre cracking above a certain threshold diameter. © 2010 American Scientific Publishers. Source

Aleksenskiy A.E.,Loffe Physical Technical Institute | Eydelman E.D.,Loffe Physical Technical Institute | Vul A.Ya.,Loffe Physical Technical Institute
Nanoscience and Nanotechnology Letters

It is well known that a commercial powder of detonation nanodiamonds (DND) and their aqueous suspensions consist of agglomerates of 4-5 nm crystalline diamond grains . We have submitted a method for production of stable mono-disperse hydrosol of 4 nm isolated DND particles . The method includes deep purification commercial DND from metal impurities and appropriate control of its residual amount by electronic spin resonance, annealing of purified DND in air and centrifugation The main result of the study demonstrates that centrifuging of a DND hydrosol of particles with a high negative zeta potential produced by deep purification and air annealing results into breakup of the agglomerates. A model explained high strength of the DND agglomerates has been discussed Copyright © 2011 American Scientific Publishers. All rights reserved. Source

Saveliev A.N.,Loffe Physical Technical Institute | Irzak M.A.,Loffe Physical Technical Institute | Shcherbinin O.N.,Loffe Physical Technical Institute
38th EPS Conference on Plasma Physics 2011, EPS 2011 - Europhysics Conference Abstracts

Simulations predict LH driven current about 100 kA for existing Globus-M plasma parameters and poloidal grill orientation. Increased magnetic field, plasma current and temperature in modernized Globus-M will permit to drive LH current about 200 kA for poloidal grill orientation and about 460 kA for toroidal one. Both grill orientations will be possible in the future experiments. Self-consistent "LHCD + transport" simulations should be performed on the basis of future experimental electron heat conductivity measured during LH pulses. Source

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