Search results for "NANOCRYSTALLINE"
showing 10 items of 145 documents
Acid versus base peptization of mesoporous nanocrystalline TiO2 films: functional studies in dye sensitized solar cells
2005
We report an analysis of the influence of acid/base conditions employed in the synthesis of TiO2 nanoparticles upon the performance of dye sensitised photoelectrochemical solar cells fabricated from these particles. The functional properties of the TiO2 nanoparticles in these devices are investigated by potential step chronoamperometry, transient laser spectroscopy, and photovoltaic device characterisation. We find that base peptization conditions employed in the sol–gel fabrication of the TiO2 nanoparticles result in a reduction in film electron density under negative applied bias, correlated with slower interfacial recombination losses and a higher device open circuit voltage.
Mechanical properties and accommodation processes on metallic interfaces
1998
Bimetallic joints Al/Pb, Al/Sn, Pb/Sn, Pb/Pb, etc. with clean interfaces, obtained by a special cold welding method, are used as a model of phase boundaries for investigation of accommodation processes and strength properties of interfaces. To reduce the volume diffusion-induced relaxation processes, investigations were carried out at relatively low temperatures 0.1-0.5 T m . The role of surface diffusion and the effect of phase boundary energy on the healing of micropore ensembles on interfaces was investigated. The accommodation processes on the phase boundaries are considered as a result of mechanoactivation of both the interaction and structure formation of such non-equilibrium systems.…
Luminescence of ZrO<sub>2</sub> Nanocrystals
2005
The luminescence of nanocrystalline tetragonal and cubic ZrO2 has been investigated. The tetragonal undoped ZrO2 revealed two luminescence bands, at ~2.0 eV and 2.7 eV , but only one band at ~2.7 eV was observed from cubic ZrO2. This luminescence was shown to be intrinsic. The regular zirconium-oxygen complex excited state is suggested as being responsible for intrinsic luminescence.
Extraction–Pyrolytic Method for TiO2 Polymorphs Production
2021
The authors thank V. Kuzovkov, A. Lushchik and M. Lushchik for many useful discussions. The research was (partly) performed in the Institute of Solid State Physics, University of Latvia ISSP UL. ISSP UL as the Center of Excellence is supported through the Framework Program for European universities Union Horizon 2020, H2020-WIDESPREAD-01–2016–2017-TeamingPhase2 under Grant Agreement No. 739508, CAMART2 project.
Nanocrystalline ZnCO3—A novel sorbent for low-temperature removal of H2S
2013
Abstract The reactivity of a nanocrystalline ZnCO 3 toward H 2 S (0.2 vol% in N 2 /H 2 mixture) at 140–180 °C was characterized by thermal gravimetric analysis and by breakthrough curves measurements. We have found that under used conditions transformation of ZnCO 3 into ZnS is complete and the rate determining step of the sulfidation is the surface reaction. Such behavior is in strike contrast with that of ZnO whose sulfidation is severely limited by diffusion. The higher reactivity of ZnCO 3 in comparison with ZnO is attributed to the different microstructure of ZnS layer formed in these materials after a partial sulfidation. As in ZnO–ZnS transformation the molar volume increases (from 1…
A study of electron transfer in Ru(dcbpy)2(NCS)2 sensitized nanocrystalline TiO2 and SnO2 films induced by red-wing excitation.
2008
Excited state dynamics and electron transfer from the Ru(dcbpy)2(NCS)2 (RuN3) sensitizer to semiconductor nanoparticles were studied using time-resolved femtosecond absorption spectroscopy. We found that excitation of the red wing of the absorption spectrum of the sensitizer populates the (3)MLCT state directly, both in solution and attached on semiconductor nanoparticle films. Electron injection is slowed down and becomes gradually less efficient as excitation moves towards red from the absorption maximum at 535 nm. At 675 nm the injection is non-exponential and characterized by 5, 30 and 180 ps time constants. The non-exponential electron injection observed is assigned to injection from a…
Polystyrene nanoparticle-templated hollow titania nanosphere monolayers as ordered scaffolds
2018
We report a novel multi-step method for the preparation of ordered mesoporous titania scaffolds and show an illustrative example of their application to solar cells. The method is based on (monolayer) colloidal nanosphere lithography that makes use of polystyrene nanoparticles organised at a water–air interface and subsequently transferred onto a solid substrate. A titania precursor solution (titanium(IV) isopropoxide in ethanol) is then drop-cast onto the monolayer and left to “incubate” overnight. Surprisingly, instead of the expected inverse monolayer-structure, a subsequent calcination step of the precursor yields an ordered monolayer of hollow titania nanospheres with a wall thickness …
XAS, XRD, AFM and Raman studies of nickel tungstate electrochromic thin films
2001
Abstract Systematic studies of nanocrystalline nickel tungstate, NiWO 4 , thin films were performed by several experimental techniques such as Ni K- and W L 1,3 -edges X-ray absorption spectroscopy, X-ray diffraction, Raman spectroscopy, atomic force microscopy and cyclic voltammetry measurements. We found that the NiWO 4 thin films exhibit electrochromic properties similar to that of amorphous tungsten trioxide films, but show better structural stability upon multiple colouring/bleaching cycling. It was observed that a nanocrystallinity of the thin films results in strong modifications of the NiO and WO interactions, which affect both local atomic and vibrational structures.
<title>Iridium L<formula><inf><roman>3</roman></inf></formula>-edge and oxygen K-edge x-ray absorption spec…
2003
Structural investigations of the short range order around iridium and oxygen ions in nanocrystalline iridium oxide thin films, prepared by dc magnetron sputtering technique, were performed by x-ray absorption spectroscopy. The Ir L3-edge extended x-ray absorption fine structure and the O K-edge x-ray absorption near edge structure signals were measured at room temperature and analyzed within ab initio multiple-scattering and full-multiple-scattering approaches, respectively. The x-ray absorption spectroscopy results indicate the presence in the films of orderd regions - nanocrystals, having a size of about 10 angstrom and a structure rather close to that in crystalline iridium oxide IrO2. S…
Novel nanocrystalline cores for EMI suppression in cables: characterization methodology and performance study
2021
El control de las interferencias electromagnéticas (EMI) en dispositivos electrónicos es un problema cada vez mayor al que se enfrentan los diseñadores para garantizar que los dispositivos cumplan con los requisitos de compatibilidad electromagnética (EMC) para operar simultáneamente sin inferir entre sí. Este hecho se debe a la tendencia hacia una mayor integración de componentes, la reducción del tamaño y grosor de las placas de circuito impreso (PCB) y la miniaturización de las carcasas de los dispositivos. Además, otros factores como el empleo de frecuencias de conmutación más altas en los convertidores de potencia y las velocidades de datos de comunicación en los circuitos digitales. C…