Ceramics based bismuth vanadate are conductors of oxygen ions and they are used as solid electrolytes in pressure sensors and fuel cells. The g-phase of Bi4V2O11 can be stabilized at T0 by partial substitution of V5+ ion by Cu2+ and Zn2+ ions to provide high electrical conductivity values between 100 and 400oC. Polycrystalline samples of Bi4V1.8Cu0.1Zn0.1O10.7 were obtained after 4h sintering at 800 °C. Investigations were made about densification process and electrical conductivity related to the effect of addition of Zr0.88Y0.12O1.94.
Resumo: Fração substancial (30-50%) da biomassa vegetal é constituída de nanocristais de celulose, de maneira que esses cristais são os cristais orgânicos mais abundantes da Terra. As celuloses nativas têm duas estruturas cristalinas conhecidas, denominadas Ia e Ib. Nessas estruturas, a celulose forma camadas moleculares que seguem padrões bem definidos de empilhamento. Falhas de empilhamento são prováveis defeitos dos cristas, mas, de fato, pouco se conhece sobre as imperfeições dos cristais de celulose vegetal. Dado que difração de raios-x é capaz de revelar imperfeições de cristais, este projeto fará a simulação computacional da difração de raios-x de cristais de celulose contendo falhas de empilhamento, Os resultados finais apontam caminhos para que falhas de empilhamento sejam experimentalmente detectadas e quantificadas. Dessa forma, o projeto contribui para a compreensão da celulose vegetal, esse biopolímero renovável, abundante e fascinante.
Gelatin-based protonic electrolyte for electrochromic windows
Proton-conducting gel polymer electrolytes based on gelatin plasticized with glycerol and containing acetic acid were investigated, characterized, and applied to electrochromic window. For glycerol contents varying from 7% to 48%, the conductivity of the uniform and predominantly amorphous gel electrolyte was found to follow a Vogel–Tamman–Fulcher behavior with the temperature. Typically, for the electrolyte chosen to make 7×2 cm2 electrochromic smart window with the configuration: glass/ fluor-doped tin oxide (FTO)/WO3 gelatin electrolyte/CeO2– TiO2/FTO/glass and containing 28% of glycerol, the conductivities were found to be of the order of 5×10−5S/cm at room temperature and 3.6×10−4S/cm at 80°C. The device was characterized by spectroelectrochemical techniques and was tested up to 10,000 cycles showing a fast coloring/ bleaching behavior, where the coloring process was achieved in 10 s and the bleaching in 2 s. The transmission variation at the wavelength of 550 nm was about 15%. The cyclic voltammograms showed a very good reversibility of the
cathodic/anodic processes, and the charge density was about
3.5 mC/cm2. The memory tests showed that the transmittance
in the colored state increased by 8% in 90 min after
removing the potential.
Amal Al-Kahlout, Diogo Vieira, César O. Avellaneda, Edson Roberto Leite, Michel A. Aegerter, Agnieszka Pawlicka
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