Search results for "XAFS"

Effects of capping agent on cobalt nanoparticles

2009

The achievement of high information density and fast recording rate in memory devices crucially depends on the structure of magnetic domains. In this paper cobalt nanoparticles are synthesised using two capping agents (TOA, ODA) and two different preparation routes: thermal decomposition (TD) and Solvated Metal Atom Dispersion (SMAD). The interaction of capping agents with free metal clusters and their influence on Co nanoparticles size, atomic structure and oxidation state is investigated by means of X-ray diffraction and X-ray absorption spectroscopy.

Silver ions mediated photochemical synthesis of water soluble gold nanoparticles with control over size and morphology

2007

The role of silver in the growth of Au nanorods

2009

Photochemical Synthesis of Shape Controlled Gold Nanoparticles: A Deeper Insight on the Growth Mechanism

2007

Synthesis and structural analysis of novel proton conductors RE1-xBa1+xGaO4-x/2 (RE = La, Nd)

2009

NiO režģa dinamikas pētījumi ar apgriezto Monte-Karlo metodi

2022

NiO režģa dinamika tika izpētīta pie septiņām temperatūrām no 10K līdz 300K, izmantojot Ni K malas rentgenabsorbcijas spektroskopiju apvienojumā ar apgrieztā Monte Carlo simulācijām. Salīdzinājumam veica režģa dinamikas aprēķinus ar empīrisko potenciālu. Potenciāla modeli apstiprināja, salīdzinot eksperimentālos NiO Ni K malas izstieptās rentgenabsorbcijas sīkstruktūras (EXAFS) spektrus ar molekulārās dinamikas modelēšanas rezultātiem pie 300 K. Ni-O un Ni-Ni atomu pāru vidējās kvadrātiskās relatīvās nobīdes (MSRD) noteica ar divām metodēm un salīdzināja ar literatūrā pieejamajiem datiem.

Režģa dinamikas rentgenabsorbcijas spektroskopija metālos ar kubiskām un heksagonālām struktūrām

2022

Režģa dinamikas rentgenabsorbcijas spektroskopija metālos ar kubiskām un heksagonālām struktūrām. Dimitrijevs. V., Darba vadītāji Dr. phys. Aleksejs Kuzmins un pētniece Mg. chem Aina Semjonova. Bakalaura darbs, 41 lappuses, 26 attēli, 5 tabulas 35 literatūras avoti, 7 pielikumi. Latviešu valodā. Darbā ir analizēta kadmija, molibdēna un cinka režģa dinamika, izmantojot apgrieztas Monte-Karlo un Molekulāras Dinamikas metodes. Analizējot kadmija, molibdēna un cinka K malas rentgenabsorbcijas spektra sīksturktūru (EXAFS) ar apgrieztas Monte-Karlo metodi, tika iegūti relatīvi vidēji kvadrātiski novietojumi (MSRD) atomu pāriem Cd-Cd, Mo-Mo un Zn-Zn. Tika iegūta MSRD atkarība no temperatūras un st…

Indium doping of proton-conducting solid oxides

2008

Solid oxides protonic conductors are prepared by doping the pure matrix compounds with cationic species. Barium cerate and barium zirconate are perovskite-like compounds, characterized by a network of corner-sharing MeO6 octahedra (Me=Ce, Zr). Barium lies in the cavities between octahedra. Insertion of trivalent species in the octahedral site involves the formation of charge- compensating oxygen vacancies, that can be filled by hydroxyls coming from dissociative water absorption. Then, proton delocalization among structural oxygens ensures conductivity. The most effective conductors are obtained by yttrium doping that, on the other hand, enters only in limited amounts in both BaZrO3 and BaC…

The Role of the Local Atomic Order and Boundary Effects on the Electrical Transport of Ceria

2014

Heavily acceptor doped ceria is a material of great relevance for applications in solid oxide fuel cells and oxygen membranes. Depending on the operation temperature, dopant concentration and microstructure (e.g. nanocrystalline vs. microcrystalline), the ionic transport properties of ceria can be mostly hindered by (i) grain boundaries or (ii) local atomic disorder in the bulk. Here, we present a selection of examples (ranging from thin films to ceramics) of how and to which extent these effects can affect the electrical transport properties. Emphasis will be given to the case of heavily doped nanocrystalline and microcrystalline ceria doped with samarium, erbium and ytterbium (dopant conc…

The fate of silver ions in the photochemical synthesis of gold nanorods: an Extended X-ray Absorption Fine Structure analysis

2009

Water-soluble gold nanorods (Au NRs) were synthesized using a silver-ion mediated photochemical route under UV irradiation. Extended X-ray Absorption Fine Structure (EXAFS) measurements on the Ag K-edge were performed on samples obtained at different Ag/Au ratios and at increasing irradiation times in order to investigate the fate of silver ions during the growth of Au NRs. EXAFS measurements allowed to probe the chemical state and the local environment of silver in the final product. Experimental data suggest that Ag atoms are placed on top of the Au particles as metallic Ag(0), while no significant contribution to the EXAFS spectra comes from AgBr or other Ag(+) based species. The reporte…