deboora bezerra - Academia.edu (original) (raw)

Uploads

Papers by deboora bezerra

Materials Characterization, 2017

Layered double hydroxides are anionic clays with formula [M II 1-x M III x (OH) 2 ] q+ [A n-.] q/... more Layered double hydroxides are anionic clays with formula [M II 1-x M III x (OH) 2 ] q+ [A n-.] q/n. mH 2 O, finding possible uses as catalyst support, adsorbents and so on. In this paper, we address the phase formation of layered double hydroxides containing Ni 2+ , Zn 2+ , Al 3+ and Zr 4+ cations, namely, NiZn-Al, NiZn-AlZr and NiZn-Zr compositions obtained by the coprecipitation method. Such systems were characterized by X-ray diffraction, confirming the phase formation for NiZn-Al and NiZn-AlZr samples. Infrared/Raman spectroscopies elucidated the anion and water molecules occurrence in the interlayer. Nitrogen physisorption (BET method) determined the presence of pores and specific surface area. The isotherm shapes were Type IV, according to the IUPAC, and represent a mesoporous structure. A morphological study was performed by means of scanning and transmission electron microscopies, and particle size values of 120, 131 and 235 nm for NiZn-Al, NiZn-AlZr and NiZn-Zr, respectively, were determined. Thermogravimetric analysis of the decomposition of the systems revealed that their complete disintegration occurred at ~ 550°C and resulted in mixed oxides.

Materials Research Bulletin, 2018

Highlights 1) The oxides mixture containing NiO, ZnO, Al 2 O 3 , NiAl 2 O 4 and ZnAl 2 O 4 was de... more Highlights 1) The oxides mixture containing NiO, ZnO, Al 2 O 3 , NiAl 2 O 4 and ZnAl 2 O 4 was detected. 2) The results exhibited intermediate interactions between Ni 0 and other phases. 3) Dry reforming of methane was applied to production of synthesis gas. 4) Deposition of the carbon filamentous on the catalysts surface was observed.

Materials Characterization, 2019

Abstract The low stability of Si-MCM-41 limits its usage in the presence of water. The loss of st... more Abstract The low stability of Si-MCM-41 limits its usage in the presence of water. The loss of structural order is mainly due to H2O physisorption and hydrolysis of the ≡Si-O-Si≡ bonds. In this work, it was demonstrated that water molecules could cause destruction of the pore walls. X-ray diffraction experiments revealed the effect of physisorbed water on the intensity of the diffraction peaks. In addition, partial regeneration of the hydrated samples was observed after thermal treatment. Evaluation was made of the structural stability of mesoporous silicas (Si-MCM-41) synthesized at different temperatures (30, 60, and 90 °C), as a function of time, when placed in a controlled humidity atmosphere. The materials were characterized by X-ray diffraction, which confirmed formation of the hexagonal phase at all the temperatures used. Furthermore, loss of long-range structural organization was observed when the calcined mesoporous silicas were conditioned in humid environments. In situ investigation was made of the thermal treatment of the hydrated silicas, with thermogravimetric quantification of silanols after the hydration and heating process. Transmission electron microscopy analysis revealed partial loss and/or reduction of the walls of some pores, caused by hydrolysis of the siloxane bonds (≡Si-O-Si≡). This resulted in decrease of the mean diameter of the pores that were resistant to wall degradation. X-ray diffraction analyses, as a function of temperature, showed that there was recovery of peak intensity and a shift of the diffraction peaks towards greater angles, as the duration of exposure to the heating increased, evidencing a decrease in the interplanar spacing.

The low stability of Si-MCM-41 limits its usage in the presence of water. The loss of structural ... more The low stability of Si-MCM-41 limits its usage in the presence of water. The loss of structural order is mainly due to H 2 O physisorption and hydrolysis of the ≡Si-O-Si≡ bonds. In this work, it was demonstrated that water molecules could cause destruction of the pore walls. X-ray diffraction experiments revealed the effect of physisorbed water on the intensity of the diffraction peaks. In addition, partial regeneration of the hydrated samples was observed after thermal treatment. Evaluation was made of the structural stability of mesoporous silicas (Si-MCM-41) synthesized at different temperatures (30, 60, and 90°C), as a function of time, when placed in a controlled humidity atmosphere. The materials were characterized by X-ray diffraction, which confirmed formation of the hexagonal phase at all the temperatures used. Furthermore, loss of long-range structural organization was observed when the calcined mesoporous silicas were conditioned in humid environments. In situ investigation was made of the thermal treatment of the hydrated silicas, with thermogravimetric quantification of silanols after the hydration and heating process. Transmission electron microscopy analysis revealed partial loss and/or reduction of the walls of some pores, caused by hydrolysis of the siloxane bonds (≡Si-O-Si≡). This resulted in decrease of the mean diameter of the pores that were resistant to wall degradation. X-ray diffraction analyses, as a function of temperature, showed that there was recovery of peak intensity and a shift of the diffraction peaks towards greater angles, as the duration of exposure to the heating increased, evidencing a decrease in the interplanar spacing.

Materials Characterization, 2017

Materials Research Bulletin, 2018

Materials Characterization, 2019