Thermodynamics and kinetics of H[sub 2]O(v) chemisorption and solubility in nanometric and single-crystal MgO particles during sintering

Journal Article · Thu Sep 09 04:00:00 EDT 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100138a022· OSTI ID:5652106

Beruto, D; Botter, R; Giordani, M ^[1]; Searcy, A W ^[2]

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1. Univ. of Genoa (Italy)
2. Lawrence Berkeley Lab., CA (United States)

Equilibrium chemisorption of H[sub 2]O at 613 Pa on nanometric and micrometric MgO particles was measured at 549-1053 K. Degrees of coverage are calculated on the assumptions that only [100] surfaces of MgO were exposed and that each surface O[sup 2[minus]] ion reacted with H[sub 2]O to form 2OH[sup [minus]] ions. When the thermal entropy of adsorption is assumed to be equal to the correspondent value for the reaction of H[sub 2]O(v) with MgO to form Mg(OH)[sub 2], the data fit a regular solution model. The enthalpy of adsorption is calculated to be [minus]189 kJ mol[sup [minus]1] at low coverage and [minus]113 kJ mol[sup [minus]1] at 70% coverage. At temperature of 898 K and above water dissolved rapidly enough in the nanometric MgO particles to permit the equilibrium concentration to be measured. From the temperature dependence of solubility, the heat of solution is calculated to be [minus]84 kJ mol[sup [minus]1]. It is shown that if the water dissolved by reacting with O[sup 2[minus]] ions to form OH[sup [minus]] ion sites, the observed catalysis of MgO sintering by water vapor can be qualitatively explained. 22 refs., 4 figs., 1 tab.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5652106
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:36; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360200 -- Ceramics
Cermets
& Refractories
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALINE EARTH METAL COMPOUNDS
CATALYSTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISORPTION
CRYSTALS
ENTHALPY
ENTROPY
EQUILIBRIUM
FABRICATION
FLUIDS
GASES
KINETICS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MATHEMATICAL MODELS
MONOCRYSTALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
REACTION KINETICS
SEPARATION PROCESSES
SINTERING
SOLUBILITY
SORPTION
SURFACE PROPERTIES
THERMODYNAMIC PROPERTIES
THERMODYNAMICS
VAPORS
WATER VAPOR