²³Na Nuclear Magnetic Resonance Study of the Structure and Dynamic of Natrolite

Abstract

The temperature dependences of nuclear magnetic resonance (NMR) and magic angle spinning (MAS) NMR spectra of 23 Na nuclei in natrolite (Na 2 Al 2 Si 3 O 10 ·2H 2 O) have been studied. The temperature dependences of the spin-lattice relaxation times T 1 in natrolite have also been studied. It has been shown that the spin-lattice relaxation of the 23 Na is governed by the electric quadrupole interaction with the crystal electric field gradients modulated by translational motion of H 2 O molecules in the natrolite pores. The dipolar interactions with paramagnetic impurities become significant as a relaxation mechanism of the 23 Na nuclei only at low temperature (<270 K).

Proton Dipolar Spin–Lattice Relaxation in Nano-channels of Natrolite

“…From our experimental T 1 and T 1ρ data, it follows that at T > 250 K, the diffusion of water molecules in parallel and perpendicular to the c-axis channels of natrolite is observed [ 15 ]. Our 23 Na and 27 Al NMR investigations show that in temperature range up to 573 K, the phase transitions in natrolite, connected with modifications of the aluminosilicate framework or the structure of pores, are not observed [ 13 , 16 , 17 ]. It follows also from these data that the diffusions of sodium cations in natrolite are absent.…”