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Capsula de radio. Programa 2 de 4 del mes de octubre. En esta emision se habla de una trampa para... more Capsula de radio. Programa 2 de 4 del mes de octubre. En esta emision se habla de una trampa para gases contaminantes.

ACS Symposium Series, 2010

Greenhouse Gases: Science and Technology, 2015

Journal of the Mexican Chemical Society

This work presents the structural characterization and electrical evaluation of Zn x-1 Cu x Mn 2 ... more This work presents the structural characterization and electrical evaluation of Zn x-1 Cu x Mn 2 O 4 spinels, which are materials presented as secondary phases into the varistor ceramic systems. Samples were analyzed by X-ray diffraction, solid-state nuclear magnetic resonance, infrared spectroscopy, scanning electron microscopy and impedance spectroscopy. Although, the addition of copper to the ZnMn 2 O 4 spinel did not produce morphological changes, the structure and electrical behaviors changed considerably. Structurally, copper addition induced the formation of partial inverse spinels, and its addition increases significantly the electrical conductivity. Therefore, the formation of Zn x-1 Cu x Mn 2 O 4 spinels, as secondary phases into the varistor materials, may compromise significantly the varistor efficiency.

Este trabajo presenta avances en la preparación de TiO2 y TiO2 soportado en membranas de óxido de... more Este trabajo presenta avances en la preparación de TiO2 y TiO2 soportado en membranas de óxido de aluminio anodizado (AAO) por la técnica sol-gel. La preparación de TiO2 soprtado implicó la obtención de un sol polimérico utilizando soluciones alcohólicas de isopropóxido de titanio y HCl como catalizador. El depósito sobre AAO se hizo mediante la recirculación del sol controlando la humedad y tiempo de recirculado. Las membranas AAO/TiO2 se calentaron a 450 °C por una hora y se caracterizaron por XRD para determinar la cristalinidad de TiO2 y verificar si el TiO2 penetró en los poros del AAO. Se considero una ventaja que el AAO presenta poros ordenados y uniformes a escala nanométrica y puede ser utilizado como plantilla para obtener membranas de nanotubos y nanoalambres de TiO2. De manera alterna se prepararon geles de los soles poliméricos. Mediante evaporación lenta se eliminó el alcohol obteniéndose monolitos los cuales se calentaron a 450 ºC por una hora y caracterizaron por XRD. Los resultados en los análisis de XRD mostraron relación entre el aumento del tamaño de grano y el tiempo de recirculación y entre el pH y el tamaño de grano en el TiO2 soportado.

Physical Review Applied, 2015

ABSTRACT The electronic structural and phonon properties of Na2−αMαZrO3 (M ¼ Li,K, α ¼ 0.0,0.5,1.... more ABSTRACT The electronic structural and phonon properties of Na2−αMαZrO3 (M ¼ Li,K, α ¼ 0.0,0.5,1.0,1.5,2.0) are investigated by first-principles density-functional theory and phonon dynamics. The thermodynamic properties of CO2 absorption and desorption in these materials are also analyzed. With increasing doping level α, the binding energies of Na2−αLiαZrO3 are increased while the binding energies of Na2−αKαZrO3 are decreased to destabilize the structures. The calculated band structures and density of states also show that, at the same doping level, the doping sites play a significant role in the electronic properties. The phonon dispersion results show that few soft modes are found in several doped configurations, which indicates that these structures are less stable than other configurations with different doping levels. From the calculated relationships among the chemical-potential change, the CO2 pressure, and the temperature of the CO2 capture reactions by Na2−αMαZrO3, and from thermogravimetric-analysis experimental measurements, the Li- and K-doped mixtures Na2−αMαZrO3 have lower turnover temperatures (Tt) and higher CO2 capture capacities, compared to pure Na2ZrO3. The Li-doped systems have a larger Tt decrease than the K-doped systems. When increasing the Li-doping level α, the Tt of the corresponding mixture Na2−αLiαZrO3 decreases further to a low-temperature range. However, in the case of K-doped systems Na2−αKαZrO3, although doping K into Na2ZrO3 initially shifts its Tt to lower temperatures, further increases of the K-doping level α causes Tt to increase. Therefore, doping Li into Na2ZrO3 has a larger influence on its CO2 capture performance than the K-doped Na2ZrO3. Compared with pure solidsM2ZrO3, after doping with other elements, these doped systems’ CO2 capture performances are improved.

RSC Adv., 2015

was evaluated as a CO 2 captor at moderate temperatures, using water vapor in the gas flow.

Chemical Engineering Journal, 2015

Processing and Application of Ceramics, 2011

A single dynamic kinetic analysis, describing the surface decomposition of Li 4 Ti 5 O 12 pellets... more A single dynamic kinetic analysis, describing the surface decomposition of Li 4 Ti 5 O 12 pellets, has been performed. Samples were analyzed by X-ray diffraction and scanning electron microscopy. The analyses were performed between 1000 and 1100°C and different times, perceiving the Li 4 Ti 5 O 12 decomposition to Li 2 Ti 3 O 7 , with a loss of lithium. As expected, more rapid decomposition behaviour was found at higher temperatures. Finally, the activation energy for this decomposition of Li 4 Ti 5 O 12 to Li 2 Ti 3 O 7 was estimated to be equal to 383 kJ/mol.

New J. Chem., 2015

From a binary equimolar gas-mixture of CO 2 and CH 4 , NOTT-400 shows CO 2 separation from CH 4 .... more From a binary equimolar gas-mixture of CO 2 and CH 4 , NOTT-400 shows CO 2 separation from CH 4 . By kinetic uptake experiments, this material confirms a maximum of 4.3 wt% CO 2 capture at 30 8C and a significant 2-fold increase (B9.3 wt%) in CO 2 capture under 40% relative humidity of water vapour.

Thermochimica Acta, 2011

... Permissions & Reprints. Thermokinetic analysis of the MgO surface carbonation pro... more ... Permissions & Reprints. Thermokinetic analysis of the MgO surface carbonation process in the presence of water vapor. Daniela A. Torres-Rodríguez a and Heriberto Pfeiffer Corresponding Author Contact Information , a , E-mail The Corresponding Author. ...

Thermochimica Acta, 2011

Magnesium hydroxide (Mg(OH)2) is widely used in different applications, including as a magnesium ... more Magnesium hydroxide (Mg(OH)2) is widely used in different applications, including as a magnesium oxide precursor. Therefore, understanding the different physicochemical properties as a function of pressure is important. In this work, a systematic thermal analysis was performed at high pressure using differential scanning calorimetry. The dehydroxylation enthalpy (ΔH) of Mg(OH)2 was determined at different pressures. The results showed that between atmospheric pressure and a pressure of 500psi, ΔH increases due to a reaction equilibrium shift. However, at pressures higher than 500psi, ΔH decreases significantly. At these high pressures, the reaction occurs at temperatures above the critical temperature, resulting in the production of overheated steam.

Nanoscale Research Letters, 2010

Porous silicon (PSi) is a nanostructured material possessing a huge surface area per unit volume.... more Porous silicon (PSi) is a nanostructured material possessing a huge surface area per unit volume. In consequence, the adsorption and diffusion of oxygen in PSi are particularly important phenomena and frequently cause significant changes in its properties. In this paper, we study the thermal oxidation of p ? -type free-standing PSi fabricated by anodic electrochemical etching. These freestanding samples were characterized by nitrogen adsorption, thermogravimetry, atomic force microscopy and powder X-ray diffraction. The results show a structural phase transition from crystalline silicon to a combination of cristobalite and quartz, passing through amorphous silicon and amorphous silicon-oxide structures, when the thermal oxidation temperature increases from 400 to 900°C. Moreover, we observe some evidence of a sinterization at 400°C and an optimal oxygen-absorption temperature about 700°C. Finally, the UV/Visible spectrophotometry reveals a red and a blue shift of the optical transmittance spectra for samples with oxidation temperatures lower and higher than 700°C, respectively.

Capsula de radio. Programa 2 de 4 del mes de octubre. En esta emision se habla de una trampa para... more Capsula de radio. Programa 2 de 4 del mes de octubre. En esta emision se habla de una trampa para gases contaminantes.

ACS Symposium Series, 2010

Greenhouse Gases: Science and Technology, 2015

Journal of the Mexican Chemical Society

This work presents the structural characterization and electrical evaluation of Zn x-1 Cu x Mn 2 ... more This work presents the structural characterization and electrical evaluation of Zn x-1 Cu x Mn 2 O 4 spinels, which are materials presented as secondary phases into the varistor ceramic systems. Samples were analyzed by X-ray diffraction, solid-state nuclear magnetic resonance, infrared spectroscopy, scanning electron microscopy and impedance spectroscopy. Although, the addition of copper to the ZnMn 2 O 4 spinel did not produce morphological changes, the structure and electrical behaviors changed considerably. Structurally, copper addition induced the formation of partial inverse spinels, and its addition increases significantly the electrical conductivity. Therefore, the formation of Zn x-1 Cu x Mn 2 O 4 spinels, as secondary phases into the varistor materials, may compromise significantly the varistor efficiency.

Este trabajo presenta avances en la preparación de TiO2 y TiO2 soportado en membranas de óxido de... more Este trabajo presenta avances en la preparación de TiO2 y TiO2 soportado en membranas de óxido de aluminio anodizado (AAO) por la técnica sol-gel. La preparación de TiO2 soprtado implicó la obtención de un sol polimérico utilizando soluciones alcohólicas de isopropóxido de titanio y HCl como catalizador. El depósito sobre AAO se hizo mediante la recirculación del sol controlando la humedad y tiempo de recirculado. Las membranas AAO/TiO2 se calentaron a 450 °C por una hora y se caracterizaron por XRD para determinar la cristalinidad de TiO2 y verificar si el TiO2 penetró en los poros del AAO. Se considero una ventaja que el AAO presenta poros ordenados y uniformes a escala nanométrica y puede ser utilizado como plantilla para obtener membranas de nanotubos y nanoalambres de TiO2. De manera alterna se prepararon geles de los soles poliméricos. Mediante evaporación lenta se eliminó el alcohol obteniéndose monolitos los cuales se calentaron a 450 ºC por una hora y caracterizaron por XRD. Los resultados en los análisis de XRD mostraron relación entre el aumento del tamaño de grano y el tiempo de recirculación y entre el pH y el tamaño de grano en el TiO2 soportado.

Physical Review Applied, 2015

ABSTRACT The electronic structural and phonon properties of Na2−αMαZrO3 (M ¼ Li,K, α ¼ 0.0,0.5,1.... more ABSTRACT The electronic structural and phonon properties of Na2−αMαZrO3 (M ¼ Li,K, α ¼ 0.0,0.5,1.0,1.5,2.0) are investigated by first-principles density-functional theory and phonon dynamics. The thermodynamic properties of CO2 absorption and desorption in these materials are also analyzed. With increasing doping level α, the binding energies of Na2−αLiαZrO3 are increased while the binding energies of Na2−αKαZrO3 are decreased to destabilize the structures. The calculated band structures and density of states also show that, at the same doping level, the doping sites play a significant role in the electronic properties. The phonon dispersion results show that few soft modes are found in several doped configurations, which indicates that these structures are less stable than other configurations with different doping levels. From the calculated relationships among the chemical-potential change, the CO2 pressure, and the temperature of the CO2 capture reactions by Na2−αMαZrO3, and from thermogravimetric-analysis experimental measurements, the Li- and K-doped mixtures Na2−αMαZrO3 have lower turnover temperatures (Tt) and higher CO2 capture capacities, compared to pure Na2ZrO3. The Li-doped systems have a larger Tt decrease than the K-doped systems. When increasing the Li-doping level α, the Tt of the corresponding mixture Na2−αLiαZrO3 decreases further to a low-temperature range. However, in the case of K-doped systems Na2−αKαZrO3, although doping K into Na2ZrO3 initially shifts its Tt to lower temperatures, further increases of the K-doping level α causes Tt to increase. Therefore, doping Li into Na2ZrO3 has a larger influence on its CO2 capture performance than the K-doped Na2ZrO3. Compared with pure solidsM2ZrO3, after doping with other elements, these doped systems’ CO2 capture performances are improved.

RSC Adv., 2015

was evaluated as a CO 2 captor at moderate temperatures, using water vapor in the gas flow.

Chemical Engineering Journal, 2015

Processing and Application of Ceramics, 2011

A single dynamic kinetic analysis, describing the surface decomposition of Li 4 Ti 5 O 12 pellets... more A single dynamic kinetic analysis, describing the surface decomposition of Li 4 Ti 5 O 12 pellets, has been performed. Samples were analyzed by X-ray diffraction and scanning electron microscopy. The analyses were performed between 1000 and 1100°C and different times, perceiving the Li 4 Ti 5 O 12 decomposition to Li 2 Ti 3 O 7 , with a loss of lithium. As expected, more rapid decomposition behaviour was found at higher temperatures. Finally, the activation energy for this decomposition of Li 4 Ti 5 O 12 to Li 2 Ti 3 O 7 was estimated to be equal to 383 kJ/mol.

New J. Chem., 2015

From a binary equimolar gas-mixture of CO 2 and CH 4 , NOTT-400 shows CO 2 separation from CH 4 .... more From a binary equimolar gas-mixture of CO 2 and CH 4 , NOTT-400 shows CO 2 separation from CH 4 . By kinetic uptake experiments, this material confirms a maximum of 4.3 wt% CO 2 capture at 30 8C and a significant 2-fold increase (B9.3 wt%) in CO 2 capture under 40% relative humidity of water vapour.

Thermochimica Acta, 2011

... Permissions & Reprints. Thermokinetic analysis of the MgO surface carbonation pro... more ... Permissions & Reprints. Thermokinetic analysis of the MgO surface carbonation process in the presence of water vapor. Daniela A. Torres-Rodríguez a and Heriberto Pfeiffer Corresponding Author Contact Information , a , E-mail The Corresponding Author. ...

Thermochimica Acta, 2011

Magnesium hydroxide (Mg(OH)2) is widely used in different applications, including as a magnesium ... more Magnesium hydroxide (Mg(OH)2) is widely used in different applications, including as a magnesium oxide precursor. Therefore, understanding the different physicochemical properties as a function of pressure is important. In this work, a systematic thermal analysis was performed at high pressure using differential scanning calorimetry. The dehydroxylation enthalpy (ΔH) of Mg(OH)2 was determined at different pressures. The results showed that between atmospheric pressure and a pressure of 500psi, ΔH increases due to a reaction equilibrium shift. However, at pressures higher than 500psi, ΔH decreases significantly. At these high pressures, the reaction occurs at temperatures above the critical temperature, resulting in the production of overheated steam.

Nanoscale Research Letters, 2010

Porous silicon (PSi) is a nanostructured material possessing a huge surface area per unit volume.... more Porous silicon (PSi) is a nanostructured material possessing a huge surface area per unit volume. In consequence, the adsorption and diffusion of oxygen in PSi are particularly important phenomena and frequently cause significant changes in its properties. In this paper, we study the thermal oxidation of p ? -type free-standing PSi fabricated by anodic electrochemical etching. These freestanding samples were characterized by nitrogen adsorption, thermogravimetry, atomic force microscopy and powder X-ray diffraction. The results show a structural phase transition from crystalline silicon to a combination of cristobalite and quartz, passing through amorphous silicon and amorphous silicon-oxide structures, when the thermal oxidation temperature increases from 400 to 900°C. Moreover, we observe some evidence of a sinterization at 400°C and an optimal oxygen-absorption temperature about 700°C. Finally, the UV/Visible spectrophotometry reveals a red and a blue shift of the optical transmittance spectra for samples with oxidation temperatures lower and higher than 700°C, respectively.