Search results for "Particles"
showing 10 items of 8085 documents
The influence of the anatase nanoparticles boundaries on the titania activity performance
2014
Metal oxides structures, formed by ordered self-assembling of crystalline nanoparticles aggregates, are attracting growing attention in fields such as catalysis or solar cells. The properties of these structures are influenced not only by their morphology and nanoparticles composition but also by the assembled particles boundaries. In order to determine the influence of these boundaries on the structures properties, the present investigation has been devoted to study the characteristics of anatase nanoparticles boundaries in titania aggregates prepared by TiCl4 hydrolysis at low temperature. Proton magic angle spinning nuclear magnetic resonance and high resolution transmission electron mic…
Study of surface layers and ejected powder formed by oxidation of titanium substrates with a pulsed Nd:YAG laser beam.
2009
Laser treatment of a titanium surface at certain conditions initiates the formation of titanium oxide layers as well as micro (nano) scale powder ejected from the surface of the substrate. The resultant morphology of the surface as well as the size and the structure of the particles are all strongly dependent on the treatment parameters (laser fluence, pulse frequency, overlap parameter, etc.). In this study, titanium substrates were treated with an industrial pulsed Nd:YAG laser in air, with varying parameters. Surface layers and ejected materials were compared using scanning and transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The rutile phase of TiO(2) dominate…
Preparation, Characterization, and Photoactivity of Polycrystalline Nanostructured TiO2 Catalysts.
2004
Various preparations of nanostructured TiO2 starting from Ti(iso-OC3H7)4 or TiCl4 are reported. The samples were characterized by X-ray diffractometry, specific surface area and porosity determinations, scanning and transmission electron microscopy, and diffuse reflectance spectroscopy. 4-Nitrophenol photodegradation in aqueous medium was employed as a probe reaction to test the photoactivity of the catalysts. The photoactivity of some samples derived from Ti(iso-OC3H7)4 was found comparable with that of commercial powders. Calcination after the hydrolysis process was necessary to achieve crystallization of the particles before using them as photocatalysts for the reaction studied. The samp…
Reversible Photodoping of TiO2 Nanoparticles for Photochromic Applications
2018
Financial support from the Estonian Research Council (IUT2-25, IUT2-26, and PUTJD680) is gratefully acknowledged. This work was supported by the Academy of Finland (decision numbers 141481 and 286713) and by the EU through the European Regional Development Fund (Center of Excellence for Zero Energy and Resource Efficient Smart Buildings and Districts-ZEBE, 2014-2020.4.01.15-0016). Work is supported by the Latvian Academy of Sciences in the framework of FLPP (Plasmonic oxide quantum dots for energy saving smart windows, lzp-2018/1-0187).
Nanostructured Pt–TiO2 composite thin films obtained by direct liquid injection metal organic chemical vapor deposition: Control of chemical state by…
2015
Abstract Nanostructured Pt–TiO 2 composite thin films were synthesized by direct liquid injection metal organic chemical vapor deposition process, using trimethyl(methylcyclopentadienyl)platinum and titanium isopropoxide as precursors. Surface and cross-sectional morphologies obtained by scanning electron microscopy and transmission electron microscopy evidenced the uniform distribution of platinum nanoparticles in the TiO 2 matrix. At higher Pt content, the X-ray diffraction analysis showed that the face-centered cubic phase of platinum appeared together with an anatase TiO 2 structure. In addition, as far as the platinum chemical state is concerned, the co-deposition of TiO 2 and Pt allow…
Anatase nanoparticles boundaries resulting from titanium tetrachloride hydrolysis
2017
An important factor that governs solar energy transformation into electrical or chemical energy, when using nanoparticles-based devices, is the spatial location of traps limiting electron transport. Evidences have been presented indicating that the electron diffusion is strongly influenced by nanoparticle boundaries, whose characteristics depend on the particles preparation. In the present work we have studied the role of hydrated excess proton structures in the formation of anatase nanoparticles boundaries in samples prepared by TiCl4 hydrolysis at low temperature and strong acidic conditions. The samples, constituted by anatase nanocrystals but, mainly, by amorphous titania, are studied b…
Preparation and photoactivity of nanostructured anatase, rutile and brookite TiO2 thin films
2006
Photoactive films consisting of pure anatase, brookite or rutile TiO2 were prepared by dip coating from water dispersions obtained by using TiCl4 as the precursor under similar mild experimental conditions
A study of the effect of molecular and aerosol conditions in the atmosphere on air fluorescence measurements at the Pierre Auger Observatory
2010
The air fluorescence detector of the Pierre Auger Observatory is designed to perforin calorimetric measurements of extensive air showers created by Cosmic rays of above 10(18) eV. To correct these measurements for the effects introduced by atmospheric fluctuations, the Observatory contains a group Of monitoring instruments to record atmospheric conditions across the detector site, ail area exceeding 3000 km(2). The atmospheric data are used extensively in the reconstruction of air showers, and are particularly important for the correct determination of shower energies and the depths of shower maxima. This paper contains a summary of the molecular and aerosol conditions measured at the Pierr…
On the timing properties of SAX J1808.4-3658 during its 2015 outburst
2017
We present a timing analysis of the 2015 outburst of the accreting millisecond X-ray pulsar SAX J1808.4-3658, using non-simultaneous XMM-Newton and NuStar observations. We estimate the pulsar spin frequency and update the system orbital solution. Combining the average spin frequency from the previous observed, we confirm the long-term spin down at an average rate $\dot{\nu}_{\text{SD}}=1.5(2)\times 10^{-15}$ Hz s$^{-1}$. We also discuss possible corrections to the spin down rate accounting for mass accretion onto the compact object when the system is X-ray active. Finally, combining the updated ephemerides with those of the previous outbursts, we find a long-term orbital evolution compatibl…
Gravity Probe Spin: Prospects for measuring general-relativistic precession of intrinsic spin using a ferromagnetic gyroscope
2020
An experimental test at the intersection of quantum physics and general relativity is proposed: measurement of relativistic frame dragging and geodetic precession using intrinsic spin of electrons. The behavior of intrinsic spin in spacetime dragged and warped by a massive rotating body is an experimentally open question, hence the results of such a measurement could have important theoretical consequences. Such a measurement is possible by using mm-scale ferromagnetic gyroscopes in orbit around the Earth. Under conditions where the rotational angular momentum of a ferromagnet is sufficiently small, a ferromagnet's angular momentum is dominated by atomic electron spins and is predicted to e…