Effect of rare earth Ce on the far infrared radiation property of iron ore tailings ceramics
Graphical abstract
Introduction
Far infrared ceramics, which can radiate infrared light waves with specific wavelengths, are widely used in fuel saving, air purification, health care, etc. For example, far infrared ceramics have the ability to facilitate atomization and full-combustion of fuel oil by way of reducing its surface tension [1]. Moreover, far infrared ceramic coatings have a catalytic function. It can generate OH− under the sunlight, which could effectively remove indoor formaldehyde, benzene, sulfide, ammonia, or odor material. Therefore, far infrared ceramics are considered to be good functional ceramics for nature environment.
Tailings are a kind of solid waste derived from mining, attracting more and more attention as a secondary resource recycling [2], [3], [4], [5], [6]. It can be applied to materials preparation in many fields, such as building brick, concrete, mesoporous materials, and microcrystalline glass [7], [8], [9], [10], [11], [12], [13]. Using iron ore tailings (IOT) to prepare far infrared ceramics are based on the following reasons: first, similar chemical compositions. IOT are mainly composed by SiO2, Al2O3, Fe2O3, CaO, and MgO, corresponding to the minerals of quartz, hematite, calcite, feldspar, etc. Coincidentally, far infrared ceramics with high emissivity are just composed by these materials mentioned above. Second, the lower production cost. Far infrared materials derived from purified oxides or expensive rare minerals increase the production cost, while IOT with low price are relatively easy to obtain. Furthermore, this approach has played an important role in turning waste into treasure.
Rare earths have the reputation of “industrial vitamin”, which are used in the field of ceramics in order to improve their performance. Liang et al. [14], [15], [16], [17] have reported the performances and applications of some kinds of far infrared ceramics prepared by rare earth and minerals. It was found that appropriate content of rare earth could enhance the property of far infrared ceramics. Two reasons are summarized here: (1) in the view of quantum mechanics, the decrease of multi-phonon relaxation rate can promote property of far infrared radiation ceramics [18], [19], [20]. (2) Lattice distortion and grain refinement are the main affecting factors [21], [22]. Rare earth can either cause internal defect through replacing cation in ceramic matrix [23], [24], or form independent phase at grain boundaries [25], [26], [27]. For example, rare earth La is able to enhance Fe–O vibration via replacing Fe in the perovskite [28], [29]. In addition, CeO2 and Eu2O3 can limit the crystal growth and reduce the average grain size of ceramics through moving to the grain boundaries, forming an isolating ultra-thin layer around the grains [28].
In this paper, IOT was used to replace natural minerals as the main raw materials, and Ce as additive to prepare far infrared ceramics. The effect of Ce on the far infrared radiation property was systematically studied. It is expected that this study can be a significant step in promoting the functional applications of IOT.
Section snippets
Synthesis of samples
The raw materials were IOT, CaCO3, SiO2, and Ce(NO3)3·6H2O (analytical grade, 99.0%). IOT came from Hebei province of China, which is the remaining materials derived from iron ore by crushing, sieving, grinding, and flotation. Its chemical compositions were given in the mass ratio as follows: SiO2, 30.09%; Fe2O3, 28.02%; Al2O3, 11.73%; TiO2, 10.97%; CaO, 5.64%; MgO, 4.33%; Na2O, 1.78%; loss on ignition, 5.67%; others, 1.77%. The weight percentages of Ce in the experimental group are 3, 5, 7, 9,
Far infrared radiation property
The histograms of far infrared emissivity are plotted as Fig. 1. It is important to note that with increasing doping Ce the value reaches its maximum at x = 7, and gradually decreases with a further increasing in Ce content. In our experiment, the value sequence for the far infrared emissivity is C7 > C5 > C9 > C11 > C3 > C0. The optimal doping content of Ce for the sample is 7 wt.%. The upper inset in Fig. 1 presents the far infrared emission spectrum of C7.
Phase compositions and lattice parameter
XRD patterns of the as-prepared samples are shown
Conclusions
In conclusion, we have shown how we successfully fabricated the iron ore tailings ceramics doping with 0–11 wt.% rare earth Ce. When doped with 7 wt.% Ce, the iron ore tailings ceramics showed the best far infrared radiation property and its emissivity reached 0.914. The characterization results revealed that Ce4+ oxidized Fe2+ to Fe3+ in the iron diopside, as well as formed interstitial solid solution with it. The superposed effects led to a decrease of iron diopside’s crystallite size and an
Acknowledgment
This research was supported by the Cultivation Plan for Leading Talent from the Innovation Team of the Hebei Higher Education Institutions of China (Grant No. LJRC020).
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