The Modification of Polyamide Tapes by the Conducting Copper Sulfide–Copper Selenide Layers
Keywords:selenopentathionate, polyamide, sorption–diffusion, copper sulfide layers, copper selenide layers.
The selenopentathionate anions are sorbed−diffused into a polyamide tapes if they are treated with the not acidified (or acidified) with hydrochloric acid solutions (0.025 – 0.2 mol⋅dm–3, 30 – 50 °C) of potassium selenopentathionate, K2SeS4O6. The sorption–diffusion from the acidified solutions proceeds more intensive: the concentrations of diffused from the acidified solution selenium and sulfur are about 5 times higher compared with those reached using the non acidified solution of the same concentration and at the same temperature. The concentration of sorbed selenopentathionate ions increases with the increase of temperature and concentration of a K2SeS4O6 solution, and the duration of treatment. The SeS4O62– anions diffused into polyamide gradually decompose and the decomposition products – sulfate ions and SO2 – are washed out from a polymer but elemental selenium remains in it. Therefore, the colour of polyamide tapes depending on a degree of SeS4O62– ions decomposition changes from colourless to yellow, brown or red. The copper sulfide and copper selenide layers are formed in the surface of polyamide tape if the chalcogenized polymer is treated with the water solution of copper(II/I) salt: the anionic particles containing sulfur and selenium atoms of low oxidation state react with the copper ions. The conditions of a polymer initial chalcogenation (the concentration and temperature of K2SeS4O6 solution) determine the amount of copper and the composition of chalcogenide layer: the amount of copper in the polyamide tape increases with the increase of concentration and temperature, and varies from 0.2⋅10–2 to 33.5⋅10–2 mg/cm2. The results of X−ray structural analysis confirmed the formation of mixed copper sulfide−copper selenide layers in the surface of polyamide. The phase composition of layer changes depending on the duration of initial treatment in a K2SeS4O6 solution: CuxS−CuySe layers are composed of little conductive chalcocite, Cu2S, electrically conductive digenite, Cu1.8S, djurleite, Cu1.9375S, anilite, Cu1.75S, and of copper selenides – bellidoite, Cu2Se, umangite, Cu3Se2, klockmannite, CuSe, krutaite, CuSe2 and Cu2Sex. Therefore the phase composition determines the electrical characteristics of the layers: the sheet resistance may vary from 12.2 Ω/???? to 4.8 MΩ/????. The determination of layers composition (in depth to 1 nm) studied by the method of X−ray photoelectron spectroscopy confirmed the formation of copper sulfides and selenides of various phases. The regularities determined enable formation by sorption–diffusion method of mixed copper sulfide and copper selenide layers of desirable composition and electrical conductance using the selenopentathionate as a polyamide chalcogenation agent.
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