Accession Number : AD0715914

Title :   On the Anodized Aluminium Humidity Sensor.

Descriptive Note : Final rept. 1 Jul 67-30 Jun 70,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF METEOROLOGY

Personal Author(s) : Sze,Min-nan

Report Date : 30 JUN 1970

Pagination or Media Count : 294

Abstract : The objectives of the study was to understand: (1) the formation and the physical characteristics of an anodized aluminium film and (2) the sorption equilibrium and kinetics of water vapor on anodized aluminium. The results of a study of sorption equilibrium and kinetics of water vapor on anodized aluminium indicate that (1) the adsorption mechanism of water vapor on anodized aluminium film consists of monomolecular, multimolecular and condensation adsorption; (2) sorption hysteresis is evident if condensation occurs, otherwise sorption is reversible; (3) aging reduces the water vapor adsorption capacity of anodized aluminium and probably forms a hydroxide; (4) a small temperature coefficient on a relative humidity basis is observed; (5) reproducibility in sorption is excellent; (6) at low air velocities, external mass transfer plays an important role in the sorption rate; and (7) sorption rate depends on the slope of the adsorption isotherms. An analysis of response time was conducted from the standpoint of diffusion and sorption. In general, the slow response is associated with condensation absorption of water which seals off the pore, otherwise the sorption rate is very rapid (for 63% change). (Author)

Descriptors :   (*HYGROMETERS, DESIGN), (*ALUMINUM, ADSORPTION), (*ALUMINA, *ADSORPTION), FOILS(MATERIALS), WATER VAPOR, HUMIDITY, REACTION KINETICS, CHEMICAL EQUILIBRIUM, SURFACES, ANODIC COATINGS, POROSITY

Subject Categories : Physical Chemistry
      Test Facilities, Equipment and Methods

Distribution Statement : APPROVED FOR PUBLIC RELEASE