简介概要

低温电解质[K3AlF6/Na3AlF6]-AlF3-Al2O3熔体中 TiB2-C复合阴极的耐腐蚀性能

来源期刊:中南大学学报(自然科学版)2011年第3期

论文作者:张凯 方钊 吕晓军 赖延清 李劼

文章页码:588 - 594

关键词:铝电解;低温电解;黏结剂;TiB2-C复合阴极;耐腐蚀性能

Key words:aluminum electrolysis; low temperature electrolysis; binder; TiB2-C cathode composites; corrosion resistance

摘    要:采用模压-焙烧技术制备沥青、呋喃、酚醛和环氧基TiB2-C复合阴极,研究其在[K3AlF6/Na3AlF6]-AlF3- Al2O3熔体中的低温电解腐蚀行为。研究结果表明:TiB2-C复合阴极均有着良好的铝液润湿性;沥青基TiB2-C复合阴极耐腐蚀性能较差,其腐蚀率和碱金属(K和Na)渗透速率分别为8.09 mm/a和10.6 mm/h;相比之下,酚醛基TiB2-C复合阴极的耐腐蚀性能最好,其腐蚀率和碱金属的渗透速率分别为3.05 mm/a和4.72 mm/h,分别比沥青基TiB2-C复合阴极下降62.3%和55.5%;树脂基TiB2-C复合阴极的抗碱金属渗透能力较好,其中又以酚醛基TiB2-C复合阴极的抗碱金属渗透能力最强;树脂黏结剂的使用可以在一定程度上改善TiB2-C复合阴极的耐腐蚀性能。

Abstract: Pitch, furan, phenolic aldehyde and Epoxy based TiB2-C cathode composites were prepared in the mould pressing-baking process, and their corrosion resistance in [K3AlF6/Na3AlF6]-AlF3-Al2O3 melts was studied. The results show that no matter what kind of binder is used, TiB2-C cathode composites have the good wetting property by liquid aluminum. Pitch based TiB2-C cathode composite has the poor corrosion resistance, and its corrosion rate and penetration rate of alkali metals(K, Na) is 8.09 mm/a and 10.6 mm/h respectively. In contrast, phenolic aldehyde based TiB2-C cathode composite has the stronger corrosion resistance, and its corrosion rate and penetration rate of alkali metal is 3.05 mm/a and 4.72 mm/h, respectively, which decreases by 62.3% and 55.5%. Compared with pitch, resin based TiB2-C cathode composites have stronger resistance ability to penetration of alkali metals. Among them, phenolic aldehyde based TiB2-C cathode composite exhibits the strongest resistance ability to penetration of alkali metals. The use of resin as adhesive can improve the corrosion resistance of TiB2-C cathode composites to some extent.



详情信息展示

低温电解质[K3AlF6/Na3AlF6]-AlF3-Al2O3熔体中

TiB2-C复合阴极的耐腐蚀性能

张凯,方钊,吕晓军,赖延清,李劼

(中南大学 冶金科学与工程学院,湖南 长沙,410083)

摘要:采用模压-焙烧技术制备沥青、呋喃、酚醛和环氧基TiB2-C复合阴极,研究其在[K3AlF6/Na3AlF6]-AlF3- Al2O3熔体中的低温电解腐蚀行为。研究结果表明:TiB2-C复合阴极均有着良好的铝液润湿性;沥青基TiB2-C复合阴极耐腐蚀性能较差,其腐蚀率和碱金属(K和Na)渗透速率分别为8.09 mm/a和10.6 mm/h;相比之下,酚醛基TiB2-C复合阴极的耐腐蚀性能最好,其腐蚀率和碱金属的渗透速率分别为3.05 mm/a和4.72 mm/h,分别比沥青基TiB2-C复合阴极下降62.3%和55.5%;树脂基TiB2-C复合阴极的抗碱金属渗透能力较好,其中又以酚醛基TiB2-C复合阴极的抗碱金属渗透能力最强;树脂黏结剂的使用可以在一定程度上改善TiB2-C复合阴极的耐腐蚀性能。

关键词:铝电解;低温电解;黏结剂;TiB2-C复合阴极;耐腐蚀性能

中图分类号:TF821           文献标志码:A         文章编号:1672-7207(2011)03-0588-07

Corrosion resistance of TiB2-C cathode composites for aluminum electrolysis in [K3AlF6/Na3AlF6]-AlF3-Al2O3 melts

ZHANG Kai, FANG Zhao, L? Xiao-jun, LAI Yan-qing, LI Jie

(School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China)

Abstract: Pitch, furan, phenolic aldehyde and Epoxy based TiB2-C cathode composites were prepared in the mould pressing-baking process, and their corrosion resistance in [K3AlF6/Na3AlF6]-AlF3-Al2O3 melts was studied. The results show that no matter what kind of binder is used, TiB2-C cathode composites have the good wetting property by liquid aluminum. Pitch based TiB2-C cathode composite has the poor corrosion resistance, and its corrosion rate and penetration rate of alkali metals(K, Na) is 8.09 mm/a and 10.6 mm/h respectively. In contrast, phenolic aldehyde based TiB2-C cathode composite has the stronger corrosion resistance, and its corrosion rate and penetration rate of alkali metal is 3.05 mm/a and 4.72 mm/h, respectively, which decreases by 62.3% and 55.5%. Compared with pitch, resin based TiB2-C cathode composites have stronger resistance ability to penetration of alkali metals. Among them, phenolic aldehyde based TiB2-C cathode composite exhibits the strongest resistance ability to penetration of alkali metals. The use of resin as adhesive can improve the corrosion resistance of TiB2-C cathode composites to some extent.

Key words: aluminum electrolysis; low temperature electrolysis; binder; TiB2-C cathode composites; corrosion resistance

我国是全球最大的原铝生产与消费国,铝电解工业已经成为我国国民经济的重要支柱产业之一。但目前工业中唯一的炼铝方法即Hall-Heroult法存在着能耗高、优质碳素消耗量大、温室气体排放量大、单位生产面积产能低和成本高等弊端,严重制约着铝电解工业的进一步发展[1-2]。基于惰性电极的铝电解新工艺将有望变革铝电解工业,实现电解过程温室气体零排放和大幅度节能。惰性电极系统的研发主要包括3个方面的内容:惰性阳极、低温电解工艺和可润湿阴    极[3-4]。研究表明:在现行电解工艺条件下,惰性阳极的耐高温熔盐腐蚀性能和抗热震性能还难以满足要求,不能获取高品质原铝。此外,使用惰性阳极电解时,Al2O3的理论分解电压比使用碳素阳极电解时高1.03 V,这将直接导致铝电解生产能耗上升[5-6]。可见:惰性阳极必须与低温铝电解工艺和可润湿性阴极配合使用才能真正实现节能减排的目的。由于[K3AlF6/Na3AlF6]-AlF3-Al2O3熔体具有电解温度低、Al2O3溶解度高、运行稳定性良好等优点,已成为低温铝电解工艺的研究热点和关注焦点[7-8]。然而,与普通电解质体系中的Na相比,该体系中所含K的离子势更低,在电解过程中更加容易渗透进入阴极内部,形成相应的CxK插层化合物,对阴极产生强烈的破坏作用,严重影响铝电解槽的使用寿命和正常的工业生产。因此,针对含钾低温电解质体系,迫切需要开发出一种具有高耐腐蚀性能的铝电解阴极。研究结果表明:TiB2基可润湿性阴极由于具有良好的铝液润湿性,在电解过程中,铝液可以对阴极起到很好的保护作用,因而成为一种很有潜力的能够抵御含钾低温电解质熔体强腐蚀性的铝电解惰性电极系统用阴极材料[9-11]。然而,就已研究的TiB2基可润湿性阴极而言,其使用寿命短的问题仍未得到根本解决,不能满足惰性电极系统对阴极材料性能的要求。因此,有必要深入研究低温电解质[K3AlF6/Na3AlF6]-AlF3-Al2O3熔体中TiB2基可润湿性阴极的耐腐蚀性能。Lü等[12]测试了以改性沥青为黏结剂所制备的TiB2-C复合阴极的电解膨胀性能。结果表明:以改性沥青为黏结剂,可以在一定程度上有效降低TiB2-C复合阴极的电解膨胀率。Ibrahiem等[13]的研究表明:与沥青基TiB2-C复合阴极涂层相比,呋喃基TiB2-C复合阴极涂层有着更强的抗碱金属渗透侵蚀能力。可见,黏结剂的性能对TiB2基可润湿性阴极的耐腐蚀性能有着显著的影响。在此,本文作者分别采用沥青、呋喃、酚醛和环氧为黏结剂,制备不同种类的TiB2-C复合阴极,考察其在低温电解质[K3AlF6/Na3AlF6]-AlF3- Al2O3熔体中的耐腐蚀性能,并对电解后阴极剖面不同区域对元素微区进行分析。

1  实验

1.1  实验原料

TiB2-C复合阴极配方(质量分数)如表1所示。TiB2粉末平均粒径为12 μm;碳质骨料平均粒径为10 μm;

表1  沥青、呋喃、酚醛和环氧基TiB2-C复合阴极配方

Table 1  Formula of pitch, funan, phenolic aldehyde based TiB2-C composite cathodes            %

黏结剂分别为沥青、呋喃、酚醛和环氧。

电解实验所用的化学试剂为:K3AlF6(分析纯)、Na3AlF6(分析纯)、Al2O3(分析纯)和AlF3(工业纯)。电解质的分子比(ρCR)为1.6,钾冰晶石含量(质量分数,下同)与钾冰晶石和钠冰晶石总含量之比(ρKR)为0.3。

1.2  制备方法

将一定配比的TiB2粉末、石墨和碳纤维置于三维运动捏合机内充分混合均匀,再在自制混捏锅内与相应的黏结剂充分混合。原料称量后在万能液压试验机上模压成形,成形压力为150 MPa,所获得的阴极生坯尺寸(直径×高)为100×(40~52) mm。最后将试样装入刚玉坩埚内,采用焦粉填埋,置于程序控制箱式电阻炉内,按图1所示升温制度焙烧,获得相应的TiB2-C复合阴极。

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