Characterization and application of porous Ti3SiC2 ceramic prepared through reactive synthesis
Graphical abstract
Introduction
The environment pollution [1] and high energy consumption [2] are closely related to the modern metallurgical industry, where fabric filters that were used for filtration often have insufficient corrosion resistance, low filtering accuracy, and poor endurance to elevated temperature. So far, the existing porous materials have been considered to replace the fabric in the hydro- and pyro-metallurgy industry. The traditional inorganic porous materials selected as the candidates can be classified into two types: porous metal and porous ceramic, which have played crucial roles in the fields of energy [3], [4], environment [5], chemical [6] and medical industries [7], [8], etc. However, the utilization of porous metals in harsh environments has not been realized due to their poor resistance to oxidation, sulfuration and corrosion in acid, alkali and salt solutions, and low strength at high temperature. Moreover, the application of porous ceramics which possess a good corrosion resistance, high microstructure stability and strength at elevated temperature, is also restricted due to their intrinsic brittleness, poor machinability, and low thermal shock resistance [9], [10]. The question among the inorganic porous materials cannot be well answered until recent years, a family of layered ternary ceramics called MAX phase were intensively investigated, where M is a transition metal, A is an A-group (mostly IIIA and IVA) element, and X is either C or N. The MAX phases combine the advantages of both metal and ceramic, making the layered ternary compounds erosion-resisting, machinable and not brittle [11], for instance Ti3SiC2.
Ti3SiC2 crystallizes in a hexagonal structure with lattice parameters a = 0.3068 nm and c = 1.7669 nm [12]. The crystalline structure shows a typical laminate characteristic [13], in which each layer of Si atoms alternates with each of the three close-packed Ti atoms with all the octahedral pores between Ti layers occupied by carbon atoms. The nanolaminate structure has two typical kinds of atom bonds [14]: covalent bond of Ti–C and metallic bond of Ti–Si. The special crystal lattice and bond structures make the material like a flexible ceramic. As common ceramic, Ti3SiC2 has excellent corrosion resistance [15] and good performance at high temperature (melting point > 2000 °C [16] and decomposed ∼2300 °C [17]). Moreover, Ti3SiC2 has merits such as pseudo plasticity [18], good thermal shock resistance, easy machinability [14], electrical conductivity (4.5 × 106 Ω−1 m−1) and good thermal conductivity (40 W/mK) [13].
Sun et al. [13] fabricated porous Ti3SiC2 compounds (∼43 vol.%) by the reactive sintering of elemental powders. Firstov et al. [17] synthesized porous Ti3SiC2 (porosity θ = 0.03–0.41) in volume of 0.9–0.95 with impurities of TiC, TiSi2 and SiC by solid-phase sintering of mixes of powders TiH2–TiC–SiC. The features of its short and long-term hardness behavior were investigated and a deformation scheme was proposed. Radhakrishnan et al. [16] synthesized Ti3SiC2 with 50% of theoretical density and a purity of better than 98 vol.% by reactive sintering of elemental reactants. Ti3SiC2 ternary compound with good pore structure and permeability will be anticipated as filtration material. However, few investigations on the pore structure and filtration property were carried out in the literatures.
In this paper, we demonstrate that porous Ti3SiC2 can be fabricated through a reactive synthesis of titanium hydride, silicon and graphite elemental powders. The pore structure and corrosion resistance of this novel porous material were investigated in detail. The application of porous Ti3SiC2 in the refined purification of zinc sulfate (ZnSO4) solution in a zinc hydrometallurgy process was also showed in this paper.
Section snippets
Preparation of porous Ti3SiC2
The reactive synthesis of porous Ti3SiC2 compound was started with elemental powders of TiH2 (median diameter, 36.5 μm, 99.5%, Chengdu Guoheng technology co., LTD), Si (median diameter, 14.6 μm, 99.5%, Beijing Xingrongyuan technology co., LTD) and graphite (median diameter, 5.5 μm, 99.0%, Qingdao Furongda graphite co., LTD). The particle sizes of the powders were cross-checked by laser particle size analyzer (Micro-Plus, Malvern, England) before the experiment. The addition of TiH2 is beneficial
Characterization of the synthesized porous Ti3SiC2
Fig. 1a and b are the different magnification SEM images of the compacts after sintering at 1350 °C for 3 h. It can be seen that a large number of pores were generated among the compacts as shown in Fig. 1a. The open porosity of this material is measured to be 48–55% according to the Archimedes method. The pore size is in the range of 3–10 μm (Fig. 1b). The resultant skeleton has a smooth surface, indicating small resistance against passed gas or liquid and good fluid permeability for this
Conclusions
Porous Ti3SiC2 ternary compound with the purity higher than 99.0 wt.% was successfully fabricated through a reactive synthesis method using TiH2, Si and graphite elemental powders as raw materials. The pore structure parameters of porous Ti3SiC2 including the maximum pore size, open porosity and air permeability obey the Hagen-Poiseuille formula with the constant G = 0.226 m−1 Pa−1 s−1. The synthesized porous Ti3SiC2 has excellent corrosion resistance in concentrated acids. Furthermore, the
Acknowledgement
This research is supported by the State Science and Technology support program of China (Grant No. 2012BAC02B05).
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