HEATS OF ADSORPTION ON EVAPORATED NICKEL FILMS

Journal Article · Tue Jan 14 04:00:00 EST 1958 · Proc. Royal Soc. (London)

DOI:https://doi.org/10.1098/rspa.1958.0006· OSTI ID:4313776

Klemperer, D F; Stone, F S

The adsorption of oxygen, hydrogen, and carbon monoxide has been studied on evaporated films of nickel prepared under varied conditions with a view to defining more precisely the differences in behavior between nickel films and nickel powder. Heats of adsorption on the films have be epsilon 'determined at room temperature using a resistancethermometer calorimeter. The extent of the adsorption with oxygen and hydrogen has been assessed by means of krypton isotherms at 77 deg K, and by means of established correlations between activity and weight for equivalent films. The coverage with oxygen reaches a complete monolayer, but with hydrogen at 0.1 mm pressure, the coverage is estimated at 40%. Curves of differential heat versus coverage have been approximated by maklng heat measurements for small increments. With oxygen, a study over 15 increments shows a heat of adsorption which is constant near 150 kcal/mole for 80% of the uptake, but which falls ultimately to a value well below 50 kcal/mole. With hydrogen, there is a continuous, almost linear fall with coverage from an initial heat near 40 kcal/mole to a final heat near 10 kcal/mole. The reversibllity of the hydrogen adsorption has been specifically examined. The films as originally prepared are porous with surface areas of 30 m//sup 2/g or higher, but the act of chemisorption appears to initiate sintering. The integral heats with each gas studied are, without exception, greater than those reported for nickel powders. From the collated results, it is suggested that the enchancement of the heat is related to the degree of disorder of the metal specimen, and attention is drawn to the possibility of release of stored energy from films on rapid chemisorption of gases. Heats of adsorption have also been measured on oxided'' films obtained by heat treatment in vacuo of oxygenated surfaces. It is apparent that the behavior of the nickel films approaches that of powders at high coverages of chemisorbed gases, or, equally, after sintering. (auth)

• Research Organization: Univ. of Bristol, Eng.
• Sponsoring Organization: USDOE
• NSA Number: NSA-12-004127
• OSTI ID: 4313776
• Journal Information: Proc. Royal Soc. (London), Journal Name: Proc. Royal Soc. (London) Vol. Vol: A243
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ADSORPTION
CARBON MONOXIDE
CHEMICAL REACTIONS
CHEMISTRY
DIAGRAMS
EVAPORATION
FILMS
GASES
HYDROGEN
KRYPTON
NICKEL
OXIDATION
OXYGEN
POROSITY
POWDERS
PRESSURE
SINTERING
SPECIFIC HEAT
SURFACES