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Surface analytical study of the cause of mass gain of the kilogram prototype
Author(s) -
Hashiguchi Y.,
Mizuno K.,
Nagoshi M.,
Kasamura H.,
Shiozawa K.,
Fujita D.,
Yoshihara K.
Publication year - 1993
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740200403
Subject(s) - kilogram , adsorption , iridium , x ray photoelectron spectroscopy , desorption , atmosphere (unit) , analytical chemistry (journal) , thermal desorption , chemistry , alloy , mass spectrometry , thermodynamics , chemical engineering , environmental chemistry , chromatography , physics , catalysis , body weight , organic chemistry , medicine , engineering
The International Prototype of the Kilogram, which is the only artificial material defining one of the fundamental constants, has been reported to gain mass as time elapses after it is cleaned. The surface of a Pt‐Ir alloy that has been used for the newer Kilogram prototypes was analysed by XPS and thermal desorption spectroscopy (TDS) to investigate the cause of mass gain, its time dependence and the effect of the cleaning method. The main cause of the mass gain was found to be adsorption of carbon (in the form of hydrocarbons) and oxygen (as water) from the atmosphere. The amounts of the two contaminant elements were almost saturated 6 months after sample cleaning. Cleaning methods do not make a large difference to adsorption behaviour. Although surface iridium is slightly oxidized, this effect is negligibly small.