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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.


SEM images of dried ZrO2 gels prepared with various WPEO: (a) 0.060 g (P5), (b) 0.075 g (P6), (c) 0.090 g (P7), (d) 0.105 g (P8), (e) 0.120 g (P9) and (f) 0.135 g (P10); the insect picture in (d) is the appearance of the dried monolith of the P8 sample.
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Figure 2: SEM images of dried ZrO2 gels prepared with various WPEO: (a) 0.060 g (P5), (b) 0.075 g (P6), (c) 0.090 g (P7), (d) 0.105 g (P8), (e) 0.120 g (P9) and (f) 0.135 g (P10); the insect picture in (d) is the appearance of the dried monolith of the P8 sample.

Mentions: Figure 2 presents the morphologies of dried gels prepared with different WPEO. With the increasing WPEO, the morphology of gels changes from nanopores (figure 2(a)), through co-continuous skeletons and pores (figures 2(b)–(e)), to particles (figure 2(f)), indicating the rising phase separation tendency. An appropriate proportion of PO and PEO can lead to a concurrent sol-gel transition and phase separation, producing co-continuous porous structures. The system is divided into the co-continuous gels phase and the fluid phase. The fluid phase is transformed into macropores after evaporation drying. As a result, monolithic dried gels with interconnected macropores and co-continuous skeletons are obtained.


Preparation of macroporous zirconia monoliths from ionic precursors via an epoxide-mediated sol-gel process accompanied by phase separation
SEM images of dried ZrO2 gels prepared with various WPEO: (a) 0.060 g (P5), (b) 0.075 g (P6), (c) 0.090 g (P7), (d) 0.105 g (P8), (e) 0.120 g (P9) and (f) 0.135 g (P10); the insect picture in (d) is the appearance of the dried monolith of the P8 sample.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: SEM images of dried ZrO2 gels prepared with various WPEO: (a) 0.060 g (P5), (b) 0.075 g (P6), (c) 0.090 g (P7), (d) 0.105 g (P8), (e) 0.120 g (P9) and (f) 0.135 g (P10); the insect picture in (d) is the appearance of the dried monolith of the P8 sample.
Mentions: Figure 2 presents the morphologies of dried gels prepared with different WPEO. With the increasing WPEO, the morphology of gels changes from nanopores (figure 2(a)), through co-continuous skeletons and pores (figures 2(b)–(e)), to particles (figure 2(f)), indicating the rising phase separation tendency. An appropriate proportion of PO and PEO can lead to a concurrent sol-gel transition and phase separation, producing co-continuous porous structures. The system is divided into the co-continuous gels phase and the fluid phase. The fluid phase is transformed into macropores after evaporation drying. As a result, monolithic dried gels with interconnected macropores and co-continuous skeletons are obtained.

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.