Ps. Wang et al., NMR CHARACTERIZATION OF INJECTION-MOLDED ALUMINA GREEN COMPACTS .1. NUCLEAR SPIN-SPIN RELAXATION, Journal of Materials Science, 30(4), 1995, pp. 1059-1064
Development of proton nuclear magnetic resonance (H-1 NMR) analysis at
400 MHz has been initiated to evaluate the binder in green injection-
moulded alumina compacts. The nuclear spin-spin relaxation times, T-2,
of protons in the binder components (paraffin wax, polypropylene, and
stearic acid) were measured to allow comparison with those in the inj
ection-moulded green compacts. H-1 nuclear spin echo signals were obse
rved by a (pi/2)-tau-pi-tau-echo pulse sequence. Bloch's equations wer
e used to calculate the spin-spin relaxation times from these echo int
ensities. The T-2 for paraffin wax and polypropylene we re in the 30-3
3 mu s range and their intensity decay behaviours were very similar. H
owever, the T-2 value for stearic acid was found to be only 17 mu s an
d its echo signal intensity decayed more rapidly than those for paraff
in wax and polypropylene. Binder content variations in three green com
pacts moulded from the same nominal blend composition were detected. A
nalysis of the moulded compacts also showed the presence of a species
with a T-2 value near 300 mu s This unexpected species may be the resu
lt of reaction during processing or the presence of moisture. The widt
h of r.f. pulses used to measure echoes did not have a significant eff
ect on relaxation times but should be considered in calculation of ech
o intensities at equilibrium and, hence, binder composition. This tech
nique development is expected to allow analysis of both binder content
and distribution in moulded components with application in process mo
dels.