Specific surface area and pore size distribution are determined usually from adsorption isotherms at low temperatures using
nitrogen or noble gases. These are not absolute parameters and the measuring methods are fraught with serious difficulties.
General problems of sorption measurements and recent developments are discussed. To obtain information for practical purposes
these measurements need to be supplemented by investigations of the sorbate/sorbent system used in practice. Results of the
measurement of nitrogen and water vapour adsorption on different materials are compared.
Authors:E. Robens, A. Bischoff, A. Schreiber, and K. Unger
Recently we published results of investigations of the surface properties of three lunar soil samples from the Apollo 11,
12 and 16 missions. In the present paper we summarise and supplement the results of measurements of density using a helium
pycnometer, krypton and nitrogen adsorption using volumetric techniques and of water, heptane and octane adsorption using
gravimetric techniques. We present additional diagrams and electron micrographs.
Thermogravimetry, differential thermal analysis, and IR spectroscopy were used to investigate the process of thermal destruction
of adsorbed polydimethylsiloxane (PDMS) in air. The disperse adsorbents were pristine fumed silica and modified fumed silica
whose surface contained oxygen compounds of phosphorus.
It was shown that under the given experimental conditions the thermal destruction of PDMS on the fumed silica surface was
accompanied by the complete transformation of the adsorbed PDMS to SiO2. In the case of phosphorus-containing silica, the thermal destruction proceeded in a different way. It was found that at
140–300C depolymerization of the siloxane chains of a certain part of the adsorbed polymer took place with the concurrent
removal of volatile products of the reaction. However, the remaining part of the adsorbed PDMS interacted with the modified
silica surface to form chemisorbed dimethylsilyl structures. The thermal destruction of the chemisorbed fragments of PDMS
in air was initiated at 400C or above for both types of silica investigated.
Authors:J. Poulis, E. Robens, C. Massen, and M. Barczak
introduced a method to calculate the final value of the adsorbed mass already
in a very early stage of adsorption measurements. His method was restricted
to gravimetric measurements and to adsorptions, which satisfy the simplest
molecular model. One of the advantages of his method was that when more complicated
molecular models were necessary, the curve resulting from Jntti`s calculations
showed discrepancies from the curve predicted for the simple situation. We
used such deviations to evaluate the parameters of the models necessary for
the explanation of the measurements. One of the examples we discussed concerned
the influence of the occurrence of two parallel and simultaneous adsorptions.
In the present paper we discuss the application of these results to
adsorption onto a surface where roughness could be expected to play a part.
If we consider a rough surface as the sum of two extra surfaces we can apply
Jntti’s method by using our former results of parallel adsorption.
We characterise roughness by two parameters which we evaluated with Jntti’s
method. We emphasise that the existence of roughness is not demonstrated by
Jntti’s method, but that the method is useful for the evaluation
of parameters introduced by other arguments or from other sources.
Authors:D. Sternik, P. Staszczuk, J. Pękalska, G. Grodzicka, B. Gawdzik, J. Osypiuk-Tomasik, and P. Witer
The adsorption of a polar (water)
and a non-polar (n-octane) liquid on silica
gels, modified by adsorption of proteins, has been studied by thermal analysis.
Silica gels with physically adsorbed BSA and ovalbumin layers were used. Thermodesorption
energies were determined from Q-TG and Q-DTG curves recorded under quasi-equilibrium
conditions. Significant differences in liquid desorption were observed from
the surfaces due to heterogeneous changes (energetic and geometrical) as a
result of modification. These results are compared with those obtained for
the samples heated at 160C for 1 h.
Authors:A. Dąbrowski, E. Mendyk, E. Robens, K. Skrzypiec, J. Goworek, Mariola Iwan, and Zofia Rzączyńska
We investigated lunar regolith collected during the Apollo 11, 12 and the Apollo 16 missions. The Apollo 11 and the Apollo
12 samples come from the lunar mare, whereas the Apollo 16 expedition brought back material from a highland region of the
near side of the Moon. In paper series we summarise in brief the results of measurements using photoelectron spectroscopy
(XPS), Raman spectroscopy, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), nitrogen adsorption, thermal analysis
(TG, DTA) and temperature-programmed reduction and oxidation (TPRO) method. Parts of samples were examined by means of scanning
electron (SEM/EDS) and atomic force microscopy (AFM).