【作者】 张恒；

【导师】 梁学民； 孔亚鹏；

【作者基本信息】 郑州大学 ， 材料与化工（专业学位）， 2025， 硕士

【摘要】 金属铝具有质轻、耐腐蚀、导电性强等特性,被广泛应用于交通运输、建筑、电力、包装等领域。目前,Hall-Héroult熔盐电解法是工业生产金属铝的唯一方法,该工艺采用炭素阳极,生产过程中阳极不断消耗,同时生成CO₂,存在能耗高、碳排放大、环境污染等问题。铝电解惰性阳极是实现无碳铝电解的颠覆性技术,镍铁尖晶石由于具有优异的抗氟盐侵蚀能力,在惰性阳极材料研究领域备受关注,以镍铁尖晶石和金属复合的金属陶瓷材料被认为是最具应用前景的惰性阳极材料。通常采用粉末冶金法制备上述材料,由于金属相与镍铁尖晶石润湿性差,烧结过程易造成金属相团聚、分布不均匀,烧结过程陶瓷晶粒易长大粗化,造成阳极致密度低以及电导率、耐蚀性、力学性能差等问题。针对上述问题,本文通过新型反应烧结工艺制备NiFe₂O₄基金属陶瓷材料,并掺杂添加剂进行改性,并通过焦耳热烧结（UHS）对阳极材料的微观组织进行调控,制备了适用于钾冰晶石熔盐电解质体系的惰性阳极材料,论文的主要研究结果如下:（1）通过步冷曲线热分析法和EDTA络合滴定法测定了K₃Al F₆-Na₃Al F₆-Al F₃-Li F体系的初晶温度和Al₂O₃溶解度。结果表明,在Na₃Al F₆熔盐中添加K₃Al F₆和Al F₃能够降低电解质的初晶温度,当K₃Al F₆、Na₃Al F₆、Al F₃的质量比为7:7:6时,初晶温度从1007.3℃降低至756℃;在K₃Al F₆-Na₃Al F₆-Al F₃熔盐中每添加1%的Li F,初晶温度降低约4.8℃。此外,提高过热度能够有效提高Al₂O₃溶解度,当K₃Al F₆、Na₃Al F₆、Al F₃的质量比为2:2:1、Li F添加量为1%、过热度为20℃时,Al₂O₃的饱和溶解度达到4.8%。（2）以NiO和Fe₂O₃为镍铁尖晶石前驱体与金属Ni混合,通过反应烧结制备了高致密度的NiFe₂O₄基金属陶瓷。Mn₂O₃掺杂改善了阳极烧结性能,促进陶瓷晶粒扩散传质并净化晶界、细化晶粒,掺杂量为1%的阳极致密度高达98.58%,硬度为3027.3 N·mm^-2,断裂韧性为8.7 MPa·m^1/2,抗弯强度为128.4 MPa;烧结过程中,NiO和Fe₂O₃原位反应放热,促进陶瓷相的收缩和金属相的均匀分布,在800℃下的阳极电导率为55.86 S/cm,以钾冰晶石熔盐作为电解质,电解槽电压保持在3.6 V附近,阳极腐蚀速率为3.3 cm/year。（3）采用新型超快高温焦耳热烧结（UHS）工艺制备了17Ni/（10NiO-NiFe₂O₄）金属陶瓷,大温度梯度有效改善了金属陶瓷的烧结性能,陶瓷相、金属相均匀分布,有利于实现致密化。经过2000℃、40 s的烧结处理,所制备金属陶瓷材料致密度为97.53%,硬度为856.3 N·mm^-2,断裂韧性为7.1 MPa·m^1/2,抗弯强度为118.5 MPa;快速的升/降温速率和超高温促使非平衡烧结,促进高温阶段的体积扩散与晶界扩散,改善了阳极致密度和微观组织演变,阳极在800℃下的电导率为48.9 S/cm;颗粒细小、均匀分布的金属相延缓了熔盐向阳极基体渗透,有效提高阳极的抗腐蚀性能,阳极腐蚀速率为1.5 cm/year。更多还原

【Abstract】 Aluminum is widely utilized in transportation,construction,power,and packaging industries due to its lightweight,corrosion-resistant,and high electrical conductivity properties.Currently,the Hall-Héroult molten salt electrolysis process remains the sole industrial method for aluminum production.However,this process suffers from high energy consumption,substantial CO₂ emissions and environmental pollution due to continuous anode consumption.Inert anode for aluminum electrolysis is a disruptive technology for carbon-free aluminum production.Nickel-iron spinel has garnered significant attention in inert anode research owing to its exceptional resistance to fluoride salt corrosion.Cermet combining nickel-iron spinel with metallic phases are considered the most promising inert anode materials.Conventional powder metallurgy methods for fabricating such materials usually result in metallic phase agglomeration,non-uniform distribution and ceramic grain coarsening during sintering,which leading to insufficient densification,low electrical conductivity,poor corrosion resistance and inferior mechanical properties.To address these problems,this study developed NiFe₂O₄-based cermet materials through an innovative reactive sintering process with additive modification.Furthermore,ultrafast high-temperature joule heat sintering（UHS）was employed to optimize microstructure of the anode,which producing inert anode materials compatible with potassium cryolite molten salt electrolyte systems.The main findings are as follows:（1）The initial crystallization temperature and Al₂O₃ solubility of the K₃Al F₆-Na₃Al F₆-Al F₃-Li F system were determined by step-cooling curve thermal analysis and EDTA complexometric titration.The results indicated that incorporating K₃Al F₆ and Al F₃ into Na₃Al F₆ effectively reduced the initial crystallization temperature.At a mass ratio of 7:7:6（K₃Al F₆:Na₃Al F₆:Al F₃）,the initial crystallization temperature decreased from 1007.3℃to 756℃.With per 1%Li F in added to the K₃Al F₆-Na₃Al F₆-Al F₃molten salt,the initial crystallization temperature decreased by about 4.8℃.In addition,improvement of superheat increased the solubility of Al₂O₃ effectively.The saturated solubility of Al₂O₃ reached 4.8%with the mass ratio of 2:2:1（K₃Al F₆:Na₃Al F₆:Al F₃）,Li F addition of 1%and superheat of 20℃.（2）NiFe₂O₄-based cermet with high density were prepared by reactive sintering with NiO and Fe₂O₃ as nickel-iron spinel precursors mixed with metallic Ni.Sintering performance of the anode was improved by doping with Mn₂O₃,which promoted diffusion and substance transfer of ceramic grains as well as purified grain boundaries and refined grains.The anode doping with 1%of Mn₂O₃ possessed a relative density of 98.58%,a hardness of 3027.3 N·mm^-2,a fracture toughness of 8.7 MPa·m^1/2 and a flexural strength of 128.4 MPa.The exothermic of in-situ reaction between NiO and Fe₂O₃ during sintering promoted the shrinkage of the ceramic phase and homogeneous distribution of the metal phase.The anodic conductivity was 55.86 S/cm at 800℃.With potassium cryolite molten salt as the electrolyte,the cell voltage was kept at 3.6 V nearly,the rate of anodic corrosion was 3.3 cm/year.（3）The 17Ni/（10NiO-NiFe₂O₄）cermet were prepared by a novel ultrafast high-temperature Joule heat sintering（UHS）process,with a large temperature gradient effectively improving the sintering performance of the cermet,and the ceramic phase and metal phase were uniformly distributed,which was conducive to densification.With the sintering treatment at 2000℃for 40 seconds,the prepared cermet possessed a relative density of 97.53%,a hardness of 856.3 N·mm^-2,a fracture toughness of 7.1MPa·m^1/2 and a flexural strength of 118.5 MPa.The rapid ramp-up/down rates and ultra-high temperature prompted non-equilibrium sintering,facilitated volume diffusion and grain boundary diffusion at high temperature stages,to improve anodic density and microstructure evolution.The anodic conductivity was 48.9 S/cm at 800℃.The metal phase with fine particles and uniform distribution delayed the penetration of molten salt into the anode substrate,thus the corrosion resistance of the anode was effectively improved with a corrosion rate of 1.5 cm/year..更多还原