2. Experimental procedureAnalytical grade (PA ACS) MgðNO3Þ2:6H2O from Vetec Química
Fina and polyvinyl alcohol from Isofar were used as received without
further purification. An appropriate amount of metal nitrate
and PVA were first dissolved in deionized water. The PVA solution
(10 wt.%) was heated to 60 5 C for 0:5 h. The nitrate solution
was then slowly added to the PVA solution with constant stirring,
at a molar ratio of 1 : 2 nitrate to monomer unit. The final mixed
solution was concentrated at 70 5 C until it became a viscous liquid
with a slight yellow color liquid, and then it was dried at
80 5 C to form the gel. The gel precursor was then burned under
controlled conditions to produce nanoscale MgO powder.