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Preparation of macroporous zirconia monoliths from ionic precursors via an epoxide-mediated sol-gel process accompanied by phase separation

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ABSTRACT

Monolithic macroporous zirconia (ZrO2) derived from ionic precursors has been successfully fabricated via the epoxide-mediated sol-gel route accompanied by phase separation in the presence of propylene oxide (PO) and poly(ethylene oxide) (PEO). The addition of PO used as an acid scavenger mediates the gelation, whereas PEO enhances the polymerization-induced phase separation. The appropriate choice of the starting compositions allows the production of a macroporous zirconia monolith with a porosity of 52.9% and a Brunauer–Emmett–Teller (BET) surface area of 171.9 m2 · g−1. The resultant dried gel is amorphous, whereas tetragonal ZrO2 and monoclinic ZrO2 are precipitated at 400 and 600 °C, respectively, without spoiling the macroporous morphology. After solvothermal treatment with an ethanol solution of ammonia, tetragonal ZrO2 monoliths with smooth skeletons and well-defined mesopores can be obtained, and the BET surface area is enhanced to 583.8 m2 · g−1.

No MeSH data available.


N2 adsorption–desorption isotherms (a), BET surface area (b) of ZrO2 monoliths heat-treated at various temperatures.
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Figure 8: N2 adsorption–desorption isotherms (a), BET surface area (b) of ZrO2 monoliths heat-treated at various temperatures.

Mentions: Figure 8 shows the N2 adsorption−desorption isotherms and BET surface area of gels heat-treated at various temperatures. The as-dried and 600 °C heat-treated gels exhibit isotherms of type-IV, while the gels heat-treated at 700 and 800 °C show isotherms of type-I (figure 8(a)). The results indicate that the elevating temperature of heat treatment can exterminate the mesopores of monoliths. It is also confirmed by the corresponding BET surface area (figure 8(b)). The BET surface area decreases from 172 to 13 m2·g−1 after being heat-treated at 800 °C due to the disappearance of mesopores, caused by phase transformation, and the aggregation of nanoparticles due to sintering.


Preparation of macroporous zirconia monoliths from ionic precursors via an epoxide-mediated sol-gel process accompanied by phase separation
N2 adsorption–desorption isotherms (a), BET surface area (b) of ZrO2 monoliths heat-treated at various temperatures.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036470&req=5

Figure 8: N2 adsorption–desorption isotherms (a), BET surface area (b) of ZrO2 monoliths heat-treated at various temperatures.
Mentions: Figure 8 shows the N2 adsorption−desorption isotherms and BET surface area of gels heat-treated at various temperatures. The as-dried and 600 °C heat-treated gels exhibit isotherms of type-IV, while the gels heat-treated at 700 and 800 °C show isotherms of type-I (figure 8(a)). The results indicate that the elevating temperature of heat treatment can exterminate the mesopores of monoliths. It is also confirmed by the corresponding BET surface area (figure 8(b)). The BET surface area decreases from 172 to 13 m2·g−1 after being heat-treated at 800 °C due to the disappearance of mesopores, caused by phase transformation, and the aggregation of nanoparticles due to sintering.

View Article: PubMed Central - PubMed

ABSTRACT

Monolithic macroporous zirconia (ZrO2) derived from ionic precursors has been successfully fabricated via the epoxide-mediated sol-gel route accompanied by phase separation in the presence of propylene oxide (PO) and poly(ethylene oxide) (PEO). The addition of PO used as an acid scavenger mediates the gelation, whereas PEO enhances the polymerization-induced phase separation. The appropriate choice of the starting compositions allows the production of a macroporous zirconia monolith with a porosity of 52.9% and a Brunauer–Emmett–Teller (BET) surface area of 171.9 m2 · g−1. The resultant dried gel is amorphous, whereas tetragonal ZrO2 and monoclinic ZrO2 are precipitated at 400 and 600 °C, respectively, without spoiling the macroporous morphology. After solvothermal treatment with an ethanol solution of ammonia, tetragonal ZrO2 monoliths with smooth skeletons and well-defined mesopores can be obtained, and the BET surface area is enhanced to 583.8 m2 · g−1.

No MeSH data available.