Porosity evaluation and positron annihilation study of mesoporous aluminum oxy-hydroxide ceramics
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Porosity evaluation and positron annihilation study of mesoporous aluminum oxy‑hydroxide ceramics M. Ghasemifard1 · M. Ghamari1 · S. Samarin2 · J. F. Williams2 Received: 9 March 2020 / Accepted: 20 May 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The pore size and type of aluminum oxy-hydroxide (boehmite) obtained using an optimized sol–gel method was investigated as a mesoporous material with the calcination temperature varied from 150 to 550 °C. Structural features were characterized by XRD, SEM, TEM, BET. Molecular interactions were identified by using PALS (positron annihilation lifetime spectroscopy) and CDBS (coincidence Doppler broadening spectroscopy). The XRD pattern showed that the sample synthesized at 250 °C has an orthorhombic phase characterizing the boehmite structure. All the samples prepared from pure aluminum metal were mesoporous according to BET results with a strong relationship between microstructure properties and temperature. The highest values of specific surface area and pore volume assigned to the sample prepared at 250 °C with 268.3 m2·g−1 and 0.313 cm3·g−1, respectively. The results of PAL-spectroscopy show that, the lifetime of positrons annihilating at pores of the boehmite at 350 °C increased as the average pore size growths because the free-volume defects in the samples increased. Keywords Mesoporous · AlO(OH) · Orthorhombic · BET · Positron annihilation spectroscopy
1 Introduction The development of science and technology of porous materials is experiencing a historical period. What has made these materials prone to a lot of research in various sciences? Based on what features have these materials been able to work in a variety of industries? The answers to these questions can be obtained from the perspective of relying on structural defects. Materials with a porous structure have unique chemical and physical properties due to the volume of the pores. Recent interest concerns the production of nanoscale minerals with specific morphologies in various fields of materials science, especially mesoporous materials [1] and inorganic nano-porous materials with a large variety of structural and dimensions of nanoscale pores. The most important features of these materials are high-surface size and shape selectivity which have been catalytically, refined and isolated to enhance their role in nanotechnology. Their * M. Ghasemifard [email protected] 1
Department of Engineering, New Modern Energy Lab, Esfarayen University of Technology, Esfarayen, Iran
Department of Physics, The University of Western Australia, Perth, WA 6009, Australia
2
progress depends on the fabrication of engineered and controlled nano-porous materials for a desired application [2, 3]. One of the most widely used materials is aluminum oxyhydroxide or gamma AlOOH (boehmite) as a reinforcement [4], membrane, refractory, abrasive and binder material in the ceramic industry, as well as in industries such as oil and petrochemicals as catalyst, catalyst support, and moisture
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