| The novel technology of aluminum electrlysis with inert anode and wettable cathode is major development trends to achieve energy saving, emissions reduction and efficiency increasing. Much progress has been made on the research of inert anode, but it still can not meet the requirement of corrosion resistance under the condition of current electrolytes and electrolysis process, which will hinder seriously inert anode to accomplish industrialization. Low temperature aluminum electrolysis technique has seductive energy saving potential, and it also is an important way to solve the problem of corrosion resistance of inert anode.This thesis is conducted with the support from the Major State Basic Research and Development Program of China (2005CB623703). In order to develop the technology of low temperature aluminum electrolysis and to resolve the problem of corrosion resistance of NiFe2O4 based inert anode, by combining document surveys with corrosion resistant exploration of 5Cu/(NiFe2O4-10NiO) cermet inert anode in low temperature aluminum electrolytes, K3AlF6-Na3AlF6-AlF3 system is chosen. Liquidus temperature and dissolving ability (solubility and dissolution rate) of Al2O3 are studied systematically in K3AlF6-Na3AlF6-AlF3 system, the aim is to provide a certain amount theoretical datum for designing low temperature aluminum electrolyte system and optimize the aluminium electrolytic technology. Based on these, a promising low temperature electrolyte is chosen, and it is with the composition 23.4wt.%K3AlF6-54.6wt.%Na3AlF6-22wt.%AlF3, electrolytic corrosion behavior of NiF2O4 based inert anodes are done, the purpose is to provide basis for improving preparation technique of inert anode and building up low temperature electrolytic technology. The main results of the thesis are as follows.(1) When AlF3 content is 0-30wt.%, K3AlF6/(K3AlF6+Na3AlF-6) is 0-50wt.%, the liquidus temperature of K3AlF6-Na3AlF6-AlF3 system is measured systematically. The influence law of AlF3 content, K3AlF6/(K3AlF6+Na3AlF6) percentage and CR on liquidus temperature is gained, an empirical formula with correlation coefficient 0.987 and average error 0.00167℃for calculating liquidus temperature of K3AlF6-Na3AlF6-AlF3 ternary system is put forward, it is as follow, T=1003.508-0.081[AlF3]2.3159-5.87[K/(K+Na)]0.657-0.024[AlF3]2.22[K/(K+ Na)]1.14+0.035[AlF3]2.17[K/(K+Na)]1.084, ternary isotherm diagram of K3AlF6-Na3AlF6-AlF3 system is drawn, by which the liquidus temperature with various electrolytes compositions can be obtained in K3AlF6-Na3AlF6-AlF3 low temperature electrolytes, and series of K3AlF6-Na3AlF6-AlF3 low temperature electrolytes compositions under certain liquidus temperature also can be determined quickly.(2) When AlF3 content is 23-29wt.%, K3AlF6/(K3AlF6+Na3AlF6) is 0-50wt.%, the dissolving ability of Al2O3 is researched systematically in K3AlF-6-Na3AlF6-AlF3 ternary system. The influence law of melt composition, temperature (690-940℃), and superheat degree (0-60℃) on Al2O3 solubility is indicated. An empirical formula with correlation coefficient 0.988 and average error -0.00406wt.% shows relationship between Al2O3 solubility and melt composition and temperature is built, it is as follow.Among it,And the equivalent solubility lines of alumina in K3AlF6-Na3AlF6-AlF3 ternary system are drawn, from it, Al2O3 solubility with various electrolytes compositions can be obtained, and series of electrolytes compositions with certain Al2O3 solubility also can be determined. A numerical representation method using Q factor to reflect dissolution rate of Al-2O3 is proposed, and the influence law of melt composition, temperature (690-940℃), and superheat degree (0-60℃) on Q factor is indicated. It is found and explained, when industrial grade AlF3 take the place of high purity AlF3 as raw material, the solubility and dissolution rate of Al2O3 became higher obviously in Na3AlF6-K3AlF6-AlF3, and the empirical formula with correlation coefficient 0.998 shows solubility of two kinds of Al2O3 is set up, it is as follows, [Al2O3]Industrial AlF3= 2.266 +0.997×[Al2O3]High impurty Alf3.(3) When electrolysis temperature is 900℃(liquidus temperature of bath is 890℃and superheat degree is 10℃), the effect of metallic composition (Cu content and Ni content is 5wt.% and 17wt.% respectively) and CaO sintering agent on the electrolytic corrosion behavior of M/(NiFe2O4-10NiO) based cermet inert anodes in the low temperature electrolyte 23.4K3AlF6-54.6Na3AlF6-22AlF3 are studied systematically. Research results show that, the annual corrosion rate of 5Cu/(NiFe2O4-10NiO), 5Ni/(NiFe2O4-10NiO)and 17Cu/(NiFe2O4-10NiO) is 0.41cm, 0.64cm and 1.06cm respectively, they are far lower than those (1.23cm, 3.8cm and 2.76cm) in the traditional electrolytes (Na3AlF6-AlF3, CR=2.3, 5wt.%Al2O3+5wt.%CaF2, superheat degree is 15℃), it decrases by about 60%. Although CaO sintering agent can effectively promote the densification and strengthening of NiFe2O4 inert anodes, residual CaO in grain boundary and reaction products will have negative effect on corrosion resistant properties of anodes. Cu/(NiFe2O4-10NiO) anodes with 2wt.% CaO doped are all swollen with different degrees, when CaO doped content are 0wt.%, 1wt.%, 2wt% and 4wt.%, annual corrosion rate of NiFe2O4-10NiO andeds are 1.1cm, 2.8cm, 4.2cm and 10.7cm respectively.
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