Сушка краплин водних суспензій багатошарових вуглецевих нанотрубок в присутності катіонної поверхнево-активної речовини ЦТАБ

The effect of cetyltrimethylammonium bromide (CTAB) on drying patterns of aqueous suspension of multiwalled carbon nanotubes (NTs) has been studied. The sessile droplets were dried on glass substrates in an air bath chamber (295±0.1 K) with fixation of changes in transparency using an optical microscope CAM-03 (Sigeta, China). The relative humidity in the chamber was of 40 ± 5%. The concentrations of NTs and CTAB were changed in the ranges of C n = 0.005-0.1% and C s = 0.0-0.1%, respectively. The final drying patterns were tested using analysis of radial distribution of optical transparency, and the topographies of patterns were investigated using an atomic force microscope (AFM) NanoScope IIIa Dimension 3000 (Digital Instruments, Bruker, USA). In bulk aqueous suspensions addition of CTAB improved dispersion of NTs and at x=C s /C n >=0.1 the size of NT aggregates progressively decreased. The formation of drying patterns with four different morphological types was observed as dependent on the concentrations of NTs and CTAB. The increase of CTAB concentration resulted in increase of the thickness of a “coffee ring”. For different concentrations of NTs the similar correlations in the behaviour of total transparency of drying pattern and thickness of the "coffee ring" layer were observed. The data obtained using the AFM technique indicated the possibility of formation of quite thick bundles of NTs located inside the "coffee ring" layer.