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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.


Macropore size distribution of the dried ZrO2 monolith with various PEO contents evaluated by mercury porosimetry.
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Figure 4: Macropore size distribution of the dried ZrO2 monolith with various PEO contents evaluated by mercury porosimetry.

Mentions: The macropore size distributions of P7, P8 and P9 dried gels with interconnected macropores and co-continuous skeletons are shown in figure 4. Mercury porosimetry analysis indicates that the gels possess a narrow pore size distribution, reflecting the macrostructure formed via the spinodal decomposition [25]. The macropore size of the dried gels is distributed roughly between 0.3 and 1 μm, and the median macropore sizes of P7, P8 and P9 dried gels are 0.68, 0.55 and 0.55 μm, respectively. The macropore size distribution of the sample with 0.105 g PEO (P8) is narrower than the two others, indicating ideal macroporous structure. The bulk densities of the three dried gels are 1.21, 1.08 and 1.01 g · cm−3, corresponding to 20.5%, 18.3% and 17.1% of the theoretical density (5.89 g · cm−3); the total pore volumes are 0.399, 0.473 and 0.524 cm3 · g−1; and the total porosities are 48.4%, 51.2% and 52.9%, respectively. It indicates that the pore size, pore volume and porosity increase, and the bulk density of dried gels decreases with the increase of PEO content. The results agree well with the SEM morphology.


Preparation of macroporous zirconia monoliths from ionic precursors via an epoxide-mediated sol-gel process accompanied by phase separation
Macropore size distribution of the dried ZrO2 monolith with various PEO contents evaluated by mercury porosimetry.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Macropore size distribution of the dried ZrO2 monolith with various PEO contents evaluated by mercury porosimetry.
Mentions: The macropore size distributions of P7, P8 and P9 dried gels with interconnected macropores and co-continuous skeletons are shown in figure 4. Mercury porosimetry analysis indicates that the gels possess a narrow pore size distribution, reflecting the macrostructure formed via the spinodal decomposition [25]. The macropore size of the dried gels is distributed roughly between 0.3 and 1 μm, and the median macropore sizes of P7, P8 and P9 dried gels are 0.68, 0.55 and 0.55 μm, respectively. The macropore size distribution of the sample with 0.105 g PEO (P8) is narrower than the two others, indicating ideal macroporous structure. The bulk densities of the three dried gels are 1.21, 1.08 and 1.01 g · cm−3, corresponding to 20.5%, 18.3% and 17.1% of the theoretical density (5.89 g · cm−3); the total pore volumes are 0.399, 0.473 and 0.524 cm3 · g−1; and the total porosities are 48.4%, 51.2% and 52.9%, respectively. It indicates that the pore size, pore volume and porosity increase, and the bulk density of dried gels decreases with the increase of PEO content. The results agree well with the SEM morphology.

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.