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Nanotechnology ; 31(49): 494001, 2020 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-32990260


The present paper describes the improvement of the performances of boron powder obtained applying the freeze-drying process (FDP) for the nanostructuration and doping of B2O3, which is here used as boron precursor. After the nanostructuration process, B2O3 is reduced to elemental nanoboron (nB) through magnesiothermic reaction with Mg. For this work, the usefulness of the process was tested focusing on the carbon-doping (C-doping), using Cblack, inulin and haemoglobin as C sources. The choice of these molecules, their concentration, size and shape, aims at producing improvements in the final compound of boron: in this case the superconductive magnesium diboride, which has been prepared and characterized both as powder and wire. The characteristics of B2O3, B and MgB2 powder, as well as MgB2 wire were tested and compared with that obtained using the best commercial precursors: H. C. Starck micrometric boron and Pavezyum nanometric boron. Both the FDP and the magnesiothermic reaction were carried out with simplicity and a great variety of doping sources, i.e. elements or compounds, which can be organic or inorganic and soluble or insoluble. The FDP allows to produce nB suitable for numerous applications. This process is also very competitive in terms of scalability and production costs if compared to the via gas technique adopted by nanoboron producers currently available on the world market.

Adv Mater ; 25(44): 6430-5, 2013 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-24038351


A programmable micromechanical resonator based on a VO2 thin film is reported. Multiple mechanical eigenfrequency states are programmed using Joule heating as local power source, gradually driving the phase transition of VO2 around its Metal-Insulator transition temperature. Phase coexistence of domains is used to tune the stiffness of the device via local control of internal stresses and mechanical properties. This study opens perspectives for developing mechanically configurable nanostructure arrays.

Adv Mater ; 24(21): 2929-34, 2012 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-22528823


Two-terminal multistate memory elements based on VO(2)/TiO(2) thin film microcantilevers are reported. Volatile and non-volatile multiple resistance states are programmed by current pulses at temperatures within the hysteretic region of the metal-insulator transition of VO(2). The memory mechanism is based on current-induced creation of metallic clusters by self-heating of micrometric suspended regions and resistive reading via percolation.

Semicondutores , Titânio/química , Compostos de Vanádio/química , Condutividade Elétrica , Temperatura