www.afm-journal.de FULL PAPER © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 2567 www.MaterialsViews.com wileyonlinelibrary.com Adv. Funct. Mater. 2012, 22, 2567–2570 Jun-Qiang Wang,* Yan-Hui Liu,* Ming-Wei Chen, Guo-Qiang Xie, Dmitri V. Louzguine-Luzgin, Akihisa Inoue, and John H. Perepezko 1. Introduction Colorants and dyes are among the mostly utilized organic chem- icals in modern industries for decorations and other purposes. But their applications often result in severe water pollution. [1–5] Current approaches to degrade and detoxify the contaminants include reduction reaction by zero-valence metals, [1–3] bacte- rial degradation [4] and carbon sorbent absorption. [5] Among the options, the zero valent metals have attracted a heightened industrial interest because of their low cost, efficient degrada- tion capability and simple operations. Zero valent iron (ZVI), or crystalline elemental iron, in the form of powders, is the typical metal for water purification by decomposing the con- taminants, [1–3,6–8] but its fast corrosion leads to rapid decay of the efficiency. [9] Noble metals have been combined with ZVI to improve the chemical stability and activity. [7] The increased cost, however, limits their wide applications. Consequently, it is important to explore low cost, abundant materials that have high efficiency in degrading the water contaminants. The metallic glasses, unlike the crystal- line metals in which the constituent atoms reside at thermodynamic equilibrium, are metastable materials in far-from-equilib- rium states. [10–12] The far-from-equilib- rium nature is responsible for many excel- lent properties of metallic glasses that are unachievable in crystalline alloys. [13,14] For example, the good chemical and catalytic properties of metallic glasses are well known. [9,15–17] More interestingly, the compositions of the metallic glasses can be widely tuned to improve their properties, especially when the glass forming ability is not the major concern. The intrinsic brittleness of some metallic glasses facilitates their subdivision into fine powders. The combination of metastable character- istics, widely tunable compositions, and intrinsic brittleness makes some of the metallic glasses very interesting catalytic materials for degrading the water contaminants. In this paper, we report the excellent performance of a Fe- based metallic glass (hereafter, we denote it as G-ZVI) powders in degrading organic chemicals, by evaluating the decoloriza- tion capability in a Direct Blue Azo Dye C 32 H 20 N 6 Na 4 O 14 S 4 aqueous solution. Different from the conventional wisdom, the G-ZVI powders were found to exhibit higher reaction activity than pure Fe, even though they contain 24 at.% metalloid elements such as Si and B. Our results are expected to open new opportunities for the functional applications of metallic glasses. 2. Results and Discussion Two types of G-ZVI powders were prepared. One was fabricated using a high pressure argon gas atomization (GA) method. The other was prepared by ball-milling (BM) the glassy ribbon under Ar gas atmosphere. The morphologies of the GA and BM powders are shown in Figure 1a and b. It is evident that the particles are well dispersed and no aggregation can be observed in both types of powders. Compared with the GA powder par- ticles whose surfaces are rounded and smooth (see the inset of Figure 1a), the BM particles appear to be rather irregular and many corrugations can be seen on their surfaces (see the inset of Figure 1b). The size distributions of the powders are presented in Figure 1c and d, respectively. For both powders, the distribution is narrow and the average diameter of the GA Rapid Degradation of Azo Dye by Fe-Based Metallic Glass Powder The outstanding efficiency of Fe-based metallic glass powders in degrading organic water contaminants is reported. While the glassy alloy contains 24% chemically inactive metalloid elements, the powders are capable to com- pletely decompose the C 32 H 20 N 6 Na 4 O 14 S 4 azo dye in aqueous solution in short time, about 200 times faster than the conventional Fe powders. The metastable thermodynamic nature and the particle surface topography are the major factors controlling the chemical performance of the metallic glass. Our findings may open a new opportunity for functional applications of metallic glasses. DOI: 10.1002/adfm.201103015 Dr. J. Q. Wang, Dr. Y. H. Liu, Prof. M. W. Chen, Prof. D. V. Louzguine-Luzgin, Prof. A. Inoue, Prof. J. H. Perepezko WPI Advanced Institute of Materials Research Tohoku University Sendai 980-8577, Japan E-mail: junqiangwang@wpi-aimr.tohoku.ac.jp; yhliu78@gmail.com Prof. G. Q. Xie, Prof. A. Inoue Institute for Materials Research Tohoku University Sendai 980-8577, Japan Prof. J. H. Perepezko Department of Materials Science and Engineering University of Wisconsin-Madison 1509 University Avenue, Madison, WI 53706, USA