Prediction of the transparency in the visible range of x-ray absorbing nanocomposites built upon the assembly of LaF_3 or LaPO_4 nanoparticles with poly(methyl methacrylate)

Abstract

A theoretical multiscale approach combining density functional theory and four-flux calculations based on the radiative transfer theory is used to prospect the optical properties of nanocomposite materials composed of inorganic nanoparticles of lanthanum-containing compounds (LaF 3 or LaPO 4 ) embedded in Poly(methyl methacrylate) (PMMA). This theoretical investigation shows that a potential route to produce lead-free x-ray shielding screens with high transparency in the visible range (>70% of incident light) may consist in incorporating colorless LaF 3 or LaPO 4 spherical particles with a diameter lower than 6 nm in a PMMA panel from a minimum thickness of 3 mm with a volumetric fraction of at least 10%. In terms of x-ray attenuation, this would lead to lead equivalency of 0.1 mm (lead foil).

NMR parameters in alkali, alkaline earth and rare earth fluorides from first principle calculations

“…For example, a recent theoretical investigation has shown that it is necessary to add an on-site Hubbard correction (U eff = 10.3 eV) on the 4f(La) orbitals to properly describe their localizations and then their energy positions, allowing the XPS/BIS and reflectance experimental spectra of LaF 3 to be properly simulated. 118 In our case, the very large deviation observed for LaF 3 (Fig. 3(a)) shows that the La 3+ ion (4f 0 ) has a similar symptomatic behaviour as Ca 2+ and Sc 3+ ions.…”

“…Another striking point is that the slope obtained here, which is relatively close to that obtained by Griffin et al, 26 differs significantly from the slope reported by Zheng et al 56 This difference arises mainly from the consideration of the calculated s iso values for LaF 3 , ScF 3 and CaF 2 , two of these compounds containing cations (Ca 2+ and La 3+ ) already known to be inaccurately described with PBE-DFT. 60,118 In the work of Griffin et al, two of these three compounds (CaF 2 and LaF 3 ) were considered while only CaF 2 was studied by Zheng et al leading to a larger absolute slope.…”

Laser ablation of lanthanum phosphate for pulsed laser deposition

“…This article is protected by copyright. All rights reserved Mass density ρ (gm cm -3 ) 4.93 [14] Absorption coefficient α (cm -1 ) at 532nm 2.362X10 3 [24] Reflectivity used in model R 0.9 [25] Melting point T m (K) 1853 [1] Boiling point T b (K) 2500 [26] Heat of phase transition ΔH lv (J gm -1 ) 5.89 X 10 4 [27] Laser attenuation parameters in ablation plume, (i) a (cm -1 ) and (ii) b (cm 2 /J) (i) a=3000…”

Transfer matrix method for four-flux radiative transfer

“…In principle, four-flux models are more accurate for thin films in which there is a substantial unscattered component. Four-flux models have been applied recently to design thermal barrier coatings [29], x-ray shielding [30], dental composites [31], and nanotechnology for energy applications [32]. However, a major drawback of the current formalism is that it cannot be easily extended to multiple layers [33].…”