THE LOW-TEMPERATURE SORPTION BEHAVIOUR OF CRYOSORBENT MATERIALS

摘要

This paper presents low-temperature sorption data (experimental and correlated values) of gases that are of particular relevance to cryosorption vacuum pumping, e.g. nitrogen, helium, hydrogen, and deuterium. The parametric measurements were performed using a granular coconut-charcoal (CHEMVIRON SC-Ⅱ), which was shown to have an excellent vacuum pumping performance. Moreover, a porous non-evaporable getter material was investigated for comparison. Nitrogen isotherms at 77 K were used for benchmarking the measurement device. The DFT approach is employed to derive pore size distributions from the 77 K data for nitrogen on charcoal; Toth's Ψ-function is also applied. The Langmuir model is found to satisfactorily represent the hydrogen data. It is highlighted how the accessible pore size and volume depend on the adsorptive under investigation.