The Experts below are selected from a list of 156 Experts worldwide ranked by ideXlab platform
V. H. Grassian - One of the best experts on this subject based on the ideXlab platform.
-
phase transitions in Magnesium Nitrate thin films a transmission ft ir study of the deliquescence and efflorescence of nitric acid reacted Magnesium oxide interfaces
Journal of Physical Chemistry B, 2003Co-Authors: Hind Alabadleh A And, V. H. GrassianAbstract:In this study, transmission FT-IR spectroscopy is used to investigate the role of water in nitric acid uptake on MgO(100) and water uptake on nitric acid reacted MgO(100) at 296 K. Under dry conditions, nitric acid uptake is limited to the topmost surface layer and saturates at a Nitrate coverage of (2.3 ± 0.1) × 1015 ions cm-2 to form a single layer of Magnesium Nitrate. In the presence of water vapor at 25% relative humidity (RH), subsurface layers can react and the extent of nitric acid uptake and the formation of Magnesium Nitrate is significantly enhanced on MgO(100) without evidence of saturation. Following reaction with nitric acid, water adsorption/desorption isotherms have been measured in the presence of 0.2−20 Torr water vapor pressure corresponding to 1−95% RH on surfaces with varying Nitrate coverages. The infrared spectra clearly show two phase transitions in these thin Nitrate films as a function of increasing RH. One transition occurs at low relative humidity, <10% RH, corresponding to the...
-
Phase Transitions in Magnesium Nitrate Thin Films: A Transmission FT-IR Study of the Deliquescence and Efflorescence of Nitric Acid Reacted Magnesium Oxide Interfaces
The Journal of Physical Chemistry B, 2003Co-Authors: Hind A. Al-abadleh And, V. H. GrassianAbstract:In this study, transmission FT-IR spectroscopy is used to investigate the role of water in nitric acid uptake on MgO(100) and water uptake on nitric acid reacted MgO(100) at 296 K. Under dry conditions, nitric acid uptake is limited to the topmost surface layer and saturates at a Nitrate coverage of (2.3 ± 0.1) × 1015 ions cm-2 to form a single layer of Magnesium Nitrate. In the presence of water vapor at 25% relative humidity (RH), subsurface layers can react and the extent of nitric acid uptake and the formation of Magnesium Nitrate is significantly enhanced on MgO(100) without evidence of saturation. Following reaction with nitric acid, water adsorption/desorption isotherms have been measured in the presence of 0.2−20 Torr water vapor pressure corresponding to 1−95% RH on surfaces with varying Nitrate coverages. The infrared spectra clearly show two phase transitions in these thin Nitrate films as a function of increasing RH. One transition occurs at low relative humidity,
Daniel Honc - One of the best experts on this subject based on the ideXlab platform.
-
Suppressing supercooling in Magnesium Nitrate hexahydrate and evaluating corrosion of aluminium alloy container for latent heat storage application
Journal of Thermal Analysis and Calorimetry, 2017Co-Authors: Pavla Honcova, Galina Sadovska, Radim Pilar, Vladimír Danielik, Peter Soska, Daniel HoncAbstract:The repeating of heating/cooling cycle (75 times) simulating the heat energy storage in Magnesium Nitrate hexahydrate confirmed supercooling of 27 K, and thus many non-isostructural nucleating agents were tested in concentration of 1 mass% in four charge/discharge cycles. From the whole group, four promising nucleating salts were subjected to detailed study with addition of 0.5, 1, and 2 mass% of nucleating salt. The results show that the addition of Mg(OH)2, BaO, MgO and Sr(OH)2 suppressed supercooling below 5 K during 50 melting/crystallization cycles. At the similar conditions (temperature range and repeating of heating and cooling), MNH and MNH with 0.5 mass% Mg(OH)2 or Sr(OH)2 underwent corrosion tests in aluminium alloy tubes to discover applicability of this material for the containers or capsules for heat storage. The long-term contact (>49 days) of aluminium alloy with melted heat storage material for 664 h provided information about suitability of alloy for storing of Magnesium Nitrate hexahydrate with nucleating agent.
-
calorimetric study of calcium Nitrate tetrahydrate and Magnesium Nitrate hexahydrate
Journal of Thermal Analysis and Calorimetry, 2016Co-Authors: Galina Sadovska, Pavla Honcova, Radim Pilař, Lucie Oravova, Daniel HoncAbstract:The heat capacity and enthalpy of fusion of calcium Nitrate tetrahydrate and Magnesium Nitrate hexahydrate were determined from 234.15 K to melting temperature by DSC. The modified stepwise method was used for heat capacity measurement, and enthalpy of fusion was determined from continuous heating by the rate of 10 K min−1 (Pilař et al. in J Therm Anal Calorim 118:485–491, 2014). Determined values were used for the calculation of entropy and Gibbs energy in the experimental temperature range. Melting point and enthalpy of fusion of calcium Nitrate tetrahydrate are 317.1 ± 0.3 K and 36.6 ± 0.2 kJ mol−1, and for the Magnesium Nitrate hexahydrate, the values are 362.9 ± 0.4 K and 40.8 ± 0.5 kJ mol−1. One solid–solid phase transformation was observed for the Magnesium salt at 345.7 ± 0.9 K with enthalpy of transition 3.1 ± 0.2 kJ mol−1. The available accumulated energy composed of sensible (heating) and latent heat (phase transformations) is 43.4 and 63.8 kJ mol−1 for the hydrated calcium and Magnesium Nitrate, respectively. The kinetics of solid–solid phase transformation for Magnesium salt was studied under non-isothermal conditions by DSC, and the process was described using autocatalytical model with parameters in the range of 0.50–0.85 for m and range of 2.58–1.48 for n, respectively.
Hind A. Al-abadleh And - One of the best experts on this subject based on the ideXlab platform.
-
Phase Transitions in Magnesium Nitrate Thin Films: A Transmission FT-IR Study of the Deliquescence and Efflorescence of Nitric Acid Reacted Magnesium Oxide Interfaces
The Journal of Physical Chemistry B, 2003Co-Authors: Hind A. Al-abadleh And, V. H. GrassianAbstract:In this study, transmission FT-IR spectroscopy is used to investigate the role of water in nitric acid uptake on MgO(100) and water uptake on nitric acid reacted MgO(100) at 296 K. Under dry conditions, nitric acid uptake is limited to the topmost surface layer and saturates at a Nitrate coverage of (2.3 ± 0.1) × 1015 ions cm-2 to form a single layer of Magnesium Nitrate. In the presence of water vapor at 25% relative humidity (RH), subsurface layers can react and the extent of nitric acid uptake and the formation of Magnesium Nitrate is significantly enhanced on MgO(100) without evidence of saturation. Following reaction with nitric acid, water adsorption/desorption isotherms have been measured in the presence of 0.2−20 Torr water vapor pressure corresponding to 1−95% RH on surfaces with varying Nitrate coverages. The infrared spectra clearly show two phase transitions in these thin Nitrate films as a function of increasing RH. One transition occurs at low relative humidity,
Hind Alabadleh A And - One of the best experts on this subject based on the ideXlab platform.
-
phase transitions in Magnesium Nitrate thin films a transmission ft ir study of the deliquescence and efflorescence of nitric acid reacted Magnesium oxide interfaces
Journal of Physical Chemistry B, 2003Co-Authors: Hind Alabadleh A And, V. H. GrassianAbstract:In this study, transmission FT-IR spectroscopy is used to investigate the role of water in nitric acid uptake on MgO(100) and water uptake on nitric acid reacted MgO(100) at 296 K. Under dry conditions, nitric acid uptake is limited to the topmost surface layer and saturates at a Nitrate coverage of (2.3 ± 0.1) × 1015 ions cm-2 to form a single layer of Magnesium Nitrate. In the presence of water vapor at 25% relative humidity (RH), subsurface layers can react and the extent of nitric acid uptake and the formation of Magnesium Nitrate is significantly enhanced on MgO(100) without evidence of saturation. Following reaction with nitric acid, water adsorption/desorption isotherms have been measured in the presence of 0.2−20 Torr water vapor pressure corresponding to 1−95% RH on surfaces with varying Nitrate coverages. The infrared spectra clearly show two phase transitions in these thin Nitrate films as a function of increasing RH. One transition occurs at low relative humidity, <10% RH, corresponding to the...
Pavla Honcova - One of the best experts on this subject based on the ideXlab platform.
-
Suppressing supercooling in Magnesium Nitrate hexahydrate and evaluating corrosion of aluminium alloy container for latent heat storage application
Journal of Thermal Analysis and Calorimetry, 2017Co-Authors: Pavla Honcova, Galina Sadovska, Radim Pilar, Vladimír Danielik, Peter Soska, Daniel HoncAbstract:The repeating of heating/cooling cycle (75 times) simulating the heat energy storage in Magnesium Nitrate hexahydrate confirmed supercooling of 27 K, and thus many non-isostructural nucleating agents were tested in concentration of 1 mass% in four charge/discharge cycles. From the whole group, four promising nucleating salts were subjected to detailed study with addition of 0.5, 1, and 2 mass% of nucleating salt. The results show that the addition of Mg(OH)2, BaO, MgO and Sr(OH)2 suppressed supercooling below 5 K during 50 melting/crystallization cycles. At the similar conditions (temperature range and repeating of heating and cooling), MNH and MNH with 0.5 mass% Mg(OH)2 or Sr(OH)2 underwent corrosion tests in aluminium alloy tubes to discover applicability of this material for the containers or capsules for heat storage. The long-term contact (>49 days) of aluminium alloy with melted heat storage material for 664 h provided information about suitability of alloy for storing of Magnesium Nitrate hexahydrate with nucleating agent.
-
calorimetric study of calcium Nitrate tetrahydrate and Magnesium Nitrate hexahydrate
Journal of Thermal Analysis and Calorimetry, 2016Co-Authors: Galina Sadovska, Pavla Honcova, Radim Pilař, Lucie Oravova, Daniel HoncAbstract:The heat capacity and enthalpy of fusion of calcium Nitrate tetrahydrate and Magnesium Nitrate hexahydrate were determined from 234.15 K to melting temperature by DSC. The modified stepwise method was used for heat capacity measurement, and enthalpy of fusion was determined from continuous heating by the rate of 10 K min−1 (Pilař et al. in J Therm Anal Calorim 118:485–491, 2014). Determined values were used for the calculation of entropy and Gibbs energy in the experimental temperature range. Melting point and enthalpy of fusion of calcium Nitrate tetrahydrate are 317.1 ± 0.3 K and 36.6 ± 0.2 kJ mol−1, and for the Magnesium Nitrate hexahydrate, the values are 362.9 ± 0.4 K and 40.8 ± 0.5 kJ mol−1. One solid–solid phase transformation was observed for the Magnesium salt at 345.7 ± 0.9 K with enthalpy of transition 3.1 ± 0.2 kJ mol−1. The available accumulated energy composed of sensible (heating) and latent heat (phase transformations) is 43.4 and 63.8 kJ mol−1 for the hydrated calcium and Magnesium Nitrate, respectively. The kinetics of solid–solid phase transformation for Magnesium salt was studied under non-isothermal conditions by DSC, and the process was described using autocatalytical model with parameters in the range of 0.50–0.85 for m and range of 2.58–1.48 for n, respectively.
-
Improvement of thermal energy accumulation by incorporation of carbon nanomaterial into Magnesium chloride hexahydrate and Magnesium Nitrate hexahydrate
Renewable Energy, 1Co-Authors: Pavla Honcova, Galina Sadovska, Jana Pastvova, Petr Koštál, Jürgen Seidel, Petr Sazama, Radim PilařAbstract:Abstract Magnesium chloride hexahydrate and Magnesium Nitrate hexahydrate were tested for their thermal energy storage in a mixture with carbon materials. The graphite, graphene and zeolite-templated carbon replicas were used as a nucleating agent to supress supercooling. The addition of any type of carbon into Magnesium chloride hexahydrate did not lead to a decrease in the supercooling and a significant decrease of the enthalpy of fusion and crystallisation was observed. The mixtures after cycling were apparently wet, indicating that some of the Magnesium chloride was dissolved in its structural water. In the case of Magnesium Nitrate hexahydrate, the addition of carbon replicas of zeolite beta, mordenite or faujasite lead to a decrease in supercooling. Nevertheless, graphite and graphene provided the highest supercooling suppression from about 30 to 2.2 K within the fifty cycles. The thermal conductivity measurement of pressed tablets of Magnesium Nitrate hexahydrate with carbon materials at 2 MPa showed a significant increase of 9% and 15% for the addition of 3 mass% of graphene and 3 mass% of graphite, respectively. Mixing of Magnesium Nitrate hexahydrate with graphene or graphite improved heat transfer and significantly reduced unwanted supercooling, which is necessary for its use in thermal energy accumulation.
