Lattice distortions in hydroxyapatites with size as follows from the electronic relaxation time measurements

Thermal EOR International Workshop III: "Thermal Methods for Enhanced Oil Recovery: Laboratory Testing, Simulation and Oilfields Applications"

Shurtakova, D.^1 ; Mamin, G.^1 ; Gafurov, M.^1 ; Kuznetsova, L.^2 ; Putlayev, V.^3^4 ; Klimashina, E.^3^4 ; Orlinskii, S.^1

Kazan Federal University, Kazan

420008, Russia^1

Kazan State University for Architecture and Engineering, Kazan

420043, Russia^2

M.V.Lomonosov Moscow State University, Chemistry Department, Moscow

119991, Russia^3

M.V.Lomonosov Moscow State University, Faculty of Materials Science, Moscow

119991, Russia^4

关键词: Average particle size;    Electronic relaxation;    Electronic relaxation time;    Lattice distortions;    Modified debye models;    Molecular transformation;    Selective reactions;    Substituted hydroxyapatites;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/282/1/012019/pdf
DOI  :  10.1088/1755-1315/282/1/012019

来源: IOP

【 摘 要 】

Pure and substituted hydroxyapatites (Ca10(PO4)6(OH)2, HAp) have been recently gaining special importance in catalysis for selective reactions where the synergetic functioning of acid-base active site pair facilitates the molecular transformations. Transition to the nanostructured HAp materials and ion incorporation can cause lattice distortions and influence physicochemical properties of HAp. We have investigated powders of HAp synthesized by wet techniques from the nitrogen-containing solutions with the average particle sizes of 30 (nanosized) and 1000 nm (microsized) with pulsed electron paramagnetic resonance (EPR). Electronic relaxation times (T1e) for the stable impurity paramagnetic NO32- centers were measured in the temperature range of 10-300 K. It is revealed that T1e shortens with the size reduction of factor two in the whole temperature range. The results are discussed in the framework of the modified Debye model taking into account non-Debye HAp phonon density. The obtained results show the feasibility of pulsed EPR techniques for characterization HAp based materials.