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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.


DTA/TG curves and FTIR spectra of dried ZrO2 gels with and without PEO.
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Figure 5: DTA/TG curves and FTIR spectra of dried ZrO2 gels with and without PEO.

Mentions: To clarify the distribution of PEO between the gel phase and liquid phase, thermal and infrared analyses were carried out, as shown in figure 5. There is an exothermal peak that resulted from the decomposition of PEO between 300 and 400 °C in the gels prepared with PEO; this peak does not appear in the DTA curve of the gels prepared without PEO. In the FTIR spectra two new peaks appear around 1252 and 943 cm−1 in the gel prepared with PEO. They correspond to the asymmetric torsional vibration and to the rocking vibration of the CH2 group [43, 44], respectively. The peak around 1124 cm−1, which originates from stretching of the C–O–C bond [45], is stronger in the gel prepared with PEO than in the PEO-free gel. These results confirm the presence of PEO in the dried gel fabricated with PEO. They suggest that in this ZrO2 system, similar to the PEO-incorporated alkoxy-derived SiO2 sol-gel [26], PEO is absorbed on the surface of ZrO2 oligomers through hydrogen bonds [46–48], which can increase the hydrophobic–hydrophilic repulsive interaction with solvent mixtures and finally cause phase separation.


Preparation of macroporous zirconia monoliths from ionic precursors via an epoxide-mediated sol-gel process accompanied by phase separation
DTA/TG curves and FTIR spectra of dried ZrO2 gels with and without PEO.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: DTA/TG curves and FTIR spectra of dried ZrO2 gels with and without PEO.
Mentions: To clarify the distribution of PEO between the gel phase and liquid phase, thermal and infrared analyses were carried out, as shown in figure 5. There is an exothermal peak that resulted from the decomposition of PEO between 300 and 400 °C in the gels prepared with PEO; this peak does not appear in the DTA curve of the gels prepared without PEO. In the FTIR spectra two new peaks appear around 1252 and 943 cm−1 in the gel prepared with PEO. They correspond to the asymmetric torsional vibration and to the rocking vibration of the CH2 group [43, 44], respectively. The peak around 1124 cm−1, which originates from stretching of the C–O–C bond [45], is stronger in the gel prepared with PEO than in the PEO-free gel. These results confirm the presence of PEO in the dried gel fabricated with PEO. They suggest that in this ZrO2 system, similar to the PEO-incorporated alkoxy-derived SiO2 sol-gel [26], PEO is absorbed on the surface of ZrO2 oligomers through hydrogen bonds [46–48], which can increase the hydrophobic–hydrophilic repulsive interaction with solvent mixtures and finally cause phase separation.

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.