E. Zhao et al., THERMAL-BEHAVIOR AND TEXTURE OF MESOPOROUS ZIRCONIA OBTAINED FROM ANIONIC SURFACTANTS, Journal of materials chemistry (Print), 8(7), 1998, pp. 1635-1640
Thermogravimetric and differential thermal analyses of mesoporous zirc
onias obtained from anionic surfactants by a scaffolding mechanism rev
eal interesting differences between the samples prepared from long-cha
in sulfates or sulfonates, which lose their hydration water in two ste
ps, and those obtained from long-chain phosphates for which dehydratio
n occurs in one step. From the temperature of the tetragonal to monocl
inic transition the molar volume of ZrO2 undergoing this transformatio
n can be calculated. From the density and from the mesoporous volume (
N-2 adsorption), the thickness of the wall separating the elemental vo
lumes of the mesoporous structure can be calculated as well as the pse
udo-length of the pores. The calculated surface area of the mesopore f
its nicely with the measured T-plot surface area for the sample calcin
ed at 500 degrees C. For the sample dried at 140 degrees C, the agreem
ent is not as good, probably because of a more disordered organization
. The alkyl chain is tilted by about 57 +/- 10 degrees with respect to
the normal to the wall. Upon calcination the thickness of the wall in
creases to a point where crystallization in monoclinic zirconia occurs
. At this point the mesoporous character is lost.