Proton Spin-Spin Relaxation of Water Molecules in a Gel Binder and Ceramic Blend
P S. Wang
Water molecules interactions in a agarose gel used as a ceramic binder and ceramic blends were studied by proton spin-spin relaxation. Nuclear spin echo signals of agar powder, water/agar gels, and gel/alumina blends were measured using a (π/2)-τ-π-τ-echo pulse sequence, and the nuclear spin-spin relaxation times (T2) were calculated by Bloch equations from these echo intensities. Two types of protons with distinct relaxation times were observed from the agar powder, O-H and C-H. The 1H T2 from water molecules in the gel was found to be shorter than that for pure water due to the proton spin exchange between free water and a small fraction of water interacting with polysaccharide networks. The relaxation rate was found to be directly proportional to the agarose concentration in the gels because of increasing exchange rate. When the gel was blended with an alumina powder, the free water was adsorbed by the alumina powder surfaces resulting in a significant loss of molecular mobility, indicating a bound state with an extremely short relaxation time.
Journal of Materials Science
ceramic binder, proton relaxation, water molecules