Henrik Schulz* and Anita Horn, Archäomertrie-Labor der HAWK ...

Manuscript, H. Schulz and A. Horn, Hildesheim, henrik.schulz@archaeometrielabor.com 19
This plot gives a good impression of the sensitive influence of the interaction parameter φ
which is causing by the different test liquids. The test liquids No. 1 and No. 2 are strongly
ionic (CaCl2/H2O) rather than the more polar and hydrogen bonding liquids No. 3 – 9
(water/ethylene glycol mixtures). If we consider only the latter series we receive an expected
value of ∆π between 1 and 7 mNm -1 for the sample of spruce wood. In the same way we have
estimated the value for the sample of beech wood: ∆π between 8 and 14 mNm -1 . These two
value are compiled into the table 6 (last right column). If we compare the values of ∆π with
those of ∆γc,max they correspond in good agreement for both wood species. The reliability of
the equation of state (eq. (7)) and the adsorption therm (eq. (8)) is given in practice an we set
∆γc,max = ∆π . If we do so, finally we can estimate the number ∆N of activated functional
groups onto the wooden surface that are created by the plasma treatment. We use eq. (6):
⎛ 1 ⎞ ⎛ ∆π
⎞
∆N = ⎜
⎟ ⎜ ⎟ λ 0 ⋅ λ 1
⎝ hc
⎠ ⎝ ∆λ
⎠
With the data given in the tables 5. and 6. the following values of ∆N were calculated and are
summarized in table 7.
Table 7: Summary of the experimental data (see table 5 and 6) for the estimation of the
increase of the number of activated surface groups ∆N by plasma treatment
(beech and spruce wood)
wood λ0 [nm] λ1 [nm] ∆λ [nm] ∆π [mNm -1 ] ∆N [cm -2 ]
beech 599 588 11 8 1,3 10 14
(6)
14 2,3 10 14
spruce 591 567 24 1 7,1 10 12
7 5,0 10 13
The magnitude of the estimated ∆N is of reasonable order for surface groups of isolators [20].
Unfortunately no details about the number of hydroxy groups onto the surface of cellulose or
wood were given or found in literature resp. We found in the literature for the number of
hydroxy groups onto surfaces of SiO2 5⋅10 14 cm -2 and Al2O3 8⋅10 14 cm -2 [21].