Tantalum coating bores of steel tubes e.g. for chromatography - by thermal decompsn. of tantalum chloride in hydrogen

摘要

Parent patent describes coating the bores of tubular objects with tantalum using chemical vapour deposition in which a current of H2 contg. TaCl5 is drawn through tubes which are zone-heated to a deposition temp. above 600 degrees C. In the addition, several tubes are simultaneously zone-heated by an induction coil, the tubes being arranged symmetrically w.r.t. each other on a concentric circle inside the induction coil. Each Tube is pref. fed with 0.5-1.5 litres H2/minute to which TaCl5 is added, with heating in zones to 900-1050 degrees C by an induction coil travelling at 1-20 mm/minute along the tubes, esp. using 3 mm/minute and 950 degrees C. Method is e.g. used for coating the bores of tubes made of steels V2A or V4A, with Ta for use in liq. and gas chromatography in chemical analysis. The cost of coating is reduced by the simultaneous treatment of several tubes. Attempts to reduce costs by increasing temp. or speed were unsuccessful.