Influence of high-pressure processing on the structure and memory effect of synthetic layered double hydroxides |
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| Authors: | Jaqueline C Rodrigues Tania Maria Haas Costa Márcia R Gallas Celso C Moro |
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| Institution: | (1) Instituto de Química, Universidade Federal do Rio Grande do Sul, P.O. Box 15003, Porto Alegre (RS), 91501-970, Brazil;(2) Instituto de Física, Universidade Federal do Rio Grande do Sul, P.O. Box 15051, Porto Alegre (RS), 91501-970, Brazil |
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| Abstract: | We investigate the structural evolution of synthetic layered double hydroxides (LDH) samples, processed at room temperature
and high-pressure (up to 7.7 GPa) in a toroidal chamber with two pressure-transmitting media, lead and graphite, using X-ray
diffraction, thermogravimetry and N2-adsorption isotherms techniques. The X-ray patterns of compacted samples show a decrease in the peak intensities. For both
pressure-transmitting media, our samples revealed a reduction of the basal d-spacing for the (003) plane when processed at
7.7 GPa. The expected high-pressure-induced amorphization was not observed. Surprisingly, we find high-pressure processing
to have a strong influence on the memory effect of the LDH, due essentially to the reduction of the surface area and pore
closing. Even when immersed in water, our samples did not recover the LDH structure, when either calcined at 450°C and compacted
at 7.7 GPa, or calcined at 700°C and immediately compacted at 2.5 and 7.7 GPa. |
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| Keywords: | Synthetic LDH High pressure Memory effect Double hydroxides |
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