Intrinsic Proton NMR Studies of Mg(OH)₂ and Ca(OH)₂

Abstract

We studied the short proton free induction decay signals and the broad 1 H NMR spectra of Mg(OH) 2 and Ca(OH) 2 powders at 77−355 K and 42 MHz using pulsed NMR techniques. Using a Gaussian-type back extrapolation procedure for the obscured data of the proton free induction decay signals, we obtained more precise values of the second moments of the Fourier-transformed broad NMR spectra than those in a previous report [Y. Itoh and M. Isobe, J. Phys. Soc. Jpn. 84, 113601 (2015)] and compared with the theoretical second moments. The decrease in the second moment could not account for the large decrease in the magnitude of the intrinsic proton spin-lattice relaxation rate 1/T 1 from Mg(OH) 2 to Ca(OH) 2 . The analysis of 1/T 1 ∝ exp(−E g /k B T ) with E g ∼ 0.01 eV points to a local hopping mechanism, and that of 1/T 1 ∝ T n with n ∼ 0.5 points to an anharmonic rattling mechanism.

On the quantification of solid phases in hydrated cement paste by 1H nuclear magnetic resonance relaxometry

“…Both materials exhibit multi-component exponential T1 recovery. A similar phenomenon has been reported for calcium [29] and magnesium hydroxides [30,31] and was attributed by these authors to separation of the particulate material into two parts: an inner crystalline core and a less well defined outer shell.…”