Effect of TiO 2 Addition on Grain Growth, Anodic Bubble Evolution and Anodic Overvoltage of NiFe 2 O 4 -Based Composite
- PDF / 1,134,596 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 91 Downloads / 154 Views
JMEPEG (2017) 26:5610–5619 DOI: 10.1007/s11665-017-3006-y
Effect of TiO2 Addition on Grain Growth, Anodic Bubble Evolution and Anodic Overvoltage of NiFe2O4-Based Composite Inert Anodes Bin Wang, Jinjing Du, Yihan Liu, Zhao Fang, and Ping Hu (Submitted May 13, 2016; in revised form May 14, 2017; published online October 17, 2017) A two-step powder compaction and sintering process was employed to fabricate TiO2-doped NiFe2O4 ceramic-based inert anodes. Grain growth during isothermal sintering was analyzed using Brook grain growth model. The bubble behavior of NiFe2O4 ceramic-based inert anodes was investigated in a twocompartment see-through quartz cell for aluminum electrolysis process. Anodic overvoltage and potential decay curves of the inert anodes were measured by using the steady state and current interruption technique. The results showed that the kinetic index of grain growth decreased with an increase in temperature. The average activation energy of grain growth for 1.0 wt.% TiO2-doped NiFe2O4 ceramic samples with a sintering temperature range from 1373 to 1673 K dropped from 675.30 to 183.47 kJ/mol. The diameter size of bubbles before releasing from the bottom surface of the anodes was reduced with increasing the current density, and the larger average releasing bubble size for carbon anode at the same current density could be obtained, which was compared to the NiFe2O4 inert anodes. Besides, the cell voltage of carbon anodes fluctuated much more violently under the same experimental conditions. After adding small amount of TiO2, a minor reduction in anodic overvoltage of NiFe2O4-based anodes can be observed. Keywords
bubble behavior, NiFe2O4 ferrite, overpotential, synthesis mechanism, titanium dioxide
1. Introduction The novel technique of inert anodes for aluminum electrolysis, despite years of study, is still an important research topic (Ref 1, 2). For the environmental and energy issues of important significance, continual development of green anode materials for aluminum production has been obtained in recent years (Ref 3). At present, carbon anodes are still widely applied in aluminum electrolysis industry. Although the current efficiency of aluminum electrolysis is as high as 96%, the anode products are mainly CO2 and CO, also along with fluorocarbons, which is harmful to the environment (Ref 4). So it is urgent to figure out some new anode materials as potential candidate. Up to now, numerous researches have been focused on new materials as inert anodes, such as metal anodes, ceramic anodes and cermet anodes, which will be likely to replace the commonly used carbon-based anodes. The advantages of inert anodes should contribute significantly to solving numerous ecological and economical problems. Also it can produce environment-friendly O2 to increase additional value of aluminum electrolysis (Ref 5, 6). And, much research has shown that NiFe2O4 with cubic inverse spinel structure can provide a Bin Wang, Jinjing Du, Zhao Fang, and Ping Hu, School of Metallurgy Engineering, XiÕan University of Architect
Data Loading...
