TY  - JOUR
AU  - Olguin, Gianni
AU  - Yacou, Christelle
AU  - Motuzas, J.
AU  - Butterling, Maik
AU  - Meulenberg, Wilhelm A.
AU  - Smart, Simon
AU  - Diniz da Costa, João C.
TI  - Surfactant functionalised cobalt silica membranes – Gas permeation and thin film positron annihilation lifetime spectroscopy characterisation
JO  - Journal of membrane science
VL  - 664
SN  - 0376-7388
CY  - New York, NY [u.a.]
PB  - Elsevier
M1  - FZJ-2022-03634
SP  - 121040 -
PY  - 2022
AB  - This work investigates the use of positron annihilation lifetime spectroscopy (PALS) for the in-situ structural characterisation of silica derived thin film membranes. By using a quantified maximum entropy method, PALS allowed for the measurement of a pore size distribution depth profile. PALS measurements were carried out on a series of silica derived membranes where alumina supports were coated with four layers of cationic HTBA surfactant cobalt silica sols wherein the surfactant/cobalt molar ratio loading varied from 0 to 3. PALS results showed that the coated layers adjacent to the porous alumina substrate were characterised by micropores and broad mesopores, a clear indication that the porosity of the substrate affected the pore size at the substrate and thin film interface. The last coated layer resulted in a high concentration of ultra-micropores (dp < 6 Å). This was attributed to the surface smoothness conferred by three previous coated layers. Higher surfactant loadings resulted in an increase in gas permeation and reduction of He/CO2 permselectivity from 91.5 to 3.8. A strong correlation with R2 up to 0.999 was found between the ultra-micropores in the top layer and gas permselectivity, a clear indication that gas separation is controlled by small pore sizes. In this work, PALS showed to be a powerful tool for the characterisation of the structural features of thin films.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000967940300007
DO  - DOI:10.1016/j.memsci.2022.121040
UR  - https://juser.fz-juelich.de/record/910145
ER  -