抄録
For quantitative extraction of niobium carbide from low carbon niobium steel, comparisons were made on the acid extraction method (6 N HCl or 30 N H3PO4) without stirring at room temperature, the acid extraction method under ultrasonic stirring at room temperature, the acid extraction method by heating, the potentiostatic electrolysis extraction method with 15%Na-citrate-1.2%KBr electrolyte (pH 3, adjusted with citric acid), the potentiostatic electrolysis extraction method with 5%Na-citrate-1.2%KBr electrolyte (pH 5, adjusted with citric acid) and the potentiostatic electrolysis extraction method with 7%HCl-3%FeCl3-Ethylene-glycol electrolyte were compared.
The potentiostatic electrolysis extraction method with 15%Na-citrate-1.2%KBr electrolyte (pH 3, adjusted with citric acid) was recommended, because of the highest extraction ratio of niobium carbide and the least dependence of the extraction of niobium carbide upon electrolytic potential.
The steel sample (50×25×5 mm) is suspended as an anode in about 1.3 L of 15%Na-citrate-1.2%KBr electrolyte adjusted to pH 3 by citric acid. From 0.1 to 2 g of the sample is potentiostatically electrolyzed at −400 mV vs SCE under nitrogen atmosphere. The residues attached to the sample and those in the anode cell electrolyte are collected through a Millipore filter. Niobium in the residues is determined by iso-amyl-alcohol-extraction-molybdenum-blue spectrophotometry and calculated as niobium carbide.
