In the past few years, the research team of the magnetoelectric functional characteristics of amorphous alloys at the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences has carried out a series of studies on the functional characteristics of aluminum-based amorphous alloys in terms of environment and energy. The team mainly initiated two aspects: One is to develop aluminum-based amorphous alloys that can be used to clean water pollution, and the second is to explore the application of aluminum-based amorphous alloys in energy storage and hydrogen evolution.
Organic sewage such as printing and dyeing is an important source of industrial sewage. In recent years, domestic and foreign counterparts have found that amorphous alloys such as iron-based, magnesium-based, and cobalt-based have excellent performance in degrading azo dye solutions, and their fading rate can reach the corresponding crystalline alloy Dozens or even thousands of times. In the early stage, the research team introduced residual stress through the ball milling method to improve the surface energy state of the iron-based and magnesium-based amorphous alloy powders, and significantly improved the activity of degrading the azo dye. The rate of degrading the azo dye reached 200 times and 1000 times of the commercial iron powder respectively ( Adv. Funct. Mater. 22, 2567 (2012). Sci. Rep. 2, 418 (2012). "Materials China" 33 (5), 270 (2014). However, in general, the rate of discoloration decreases rapidly as the pH of the solution increases. Considering that many of the actual dye wastewater are alkaline solutions, the development of amorphous alloy systems that can quickly fade in alkaline solutions is of great significance to promote their application. In order to solve this problem, the team found that aluminum-based amorphous alloys can rapidly degrade azo dyes in a wide pH range, and degrade in alkaline (pH = 12) and acidic (pH = 2) solutions than neutral conditions. The rate is 1.5 and 189 times faster. The study of the surface structure and element composition shows that the aluminum element first undergoes a dealloying reaction, and a nickel-rich and yttrium-rich nanoporous layer is formed on the surface, thereby enhancing the role of dye adsorption and accelerating the dye fading and degradation process, as shown in Figure 1. These results indicate that aluminum-based amorphous alloys have good application prospects in the degradation of alkaline, acidic and neutral dye wastewater. The relevant results are published in J. Alloys Compounds 701, 759 (2017).
Nanoporous materials have attracted widespread attention in many technical fields such as catalysis and energy storage due to their large specific surface area and adjustable composition. On the basis of previous work, the research team continued to further study the influence of alloy composition, crystallization structure and other factors on the dealloying of AlNiCo amorphous alloy to form nanoporous structure, and studied its pseudocapacitance characteristics. It was found that the addition of 3 at.% Copper can increase the specific capacitance of nanoporous composites to 1.22 F cm2. The work was published in J. Alloys Compounds 703, 461 (2017). The team further designed a multi-level nanoporous composite structure with triple dimensions by introducing a pre-crystallization process. The nanoporous scaffold also formed a metal / oxide core-shell composite structure, which greatly improved the transport characteristics of ions and electrons. The specific capacitance increased to 3.35 F cm2, as shown in Figure 2, the article was published in J. Alloys Compounds 772, 164 (2019). Due to the good elasticity and high strength of Al-based amorphous alloys, this high energy storage density nanoporous material is expected to be applied as a flexible self-supporting supercapacitor electrode.
As the non-equilibrium material, amorphous alloy has the biggest characteristic that it can add different alloy elements in a very wide composition range to realize the multi-functionality of the material. The research team used Al-based amorphous alloy as a matrix, added a small amount of precious metal elements to control the material composition, explored and developed a hydrogen evolution catalyst with high performance activity, and successfully developed Al80Ni6Co3Mn3Y5Au3 amorphous alloy material. 70 mV @ 10 mA cm-2, with a Tafel slope of about 39 mV dec-1, comparable to commercial precious metal Pt / C electrodes (33 mV @ 10 mA cm-2, 38 mV dec-1). Through research on the microstructure and reaction mechanism, the team found that this high catalytic activity can be attributed to the multi-component high-entropy alloy nanoporous structure formed on the surface. The hydrogen conversion frequency and ion transport conductivity are shown in Figure 3. The unique uniform diffusion effect of atoms in the amorphous state causes the interface to form a gold-rich protective layer, thereby exhibiting long-term stability. And the material also has a very high yield strength, greater elasticity and good electrical conductivity, is an ideal independent catalytic electrode, related work published in J. Mater. Chem. A 8, 3246 (2020).