3D Reconstruction and Corrosion Resistance of Porous Zr-Al Intermetallic via Thermally-regulated Rapid Self-exothermic Reaction

The efficient treatment of industrial chemical waste liquids/gases is an urgent need in the chemical and metallurgical industries, and such pollutant pose a serious challenge to the corrosion resistance, pore size controllability, and long-term stability of traditional filtration materials due to their high pH value, complex composition, and the presence of fine-particle pollutants. Currently widely used metal porous materials are prone to corrosion and pore clogging, resulting in a decline in filtration efficiency and an increase in maintenance costs. In recent years, intermetallic compound with both metal and ceramic properties have become a promising candidate for new filtration materials due to their unique performance advantages. Despite the potential of intermetallic porous materials in chemical catalysis and high-temperature gas filtration, the corrosion resistance and stability under long-term corrosion in chemical wastewater, as well as simplicity and cost optimization of the practical application, urgently need to be resolved.

For multiple Al-based binary systems, the maximum reaction temperature of the Al-based samples will surpass its melting point, leading to the melting of the samples, which is not conducive to maintain the original shape. The pre-heating process reduces the thermal effect of the exothermic reaction by modulating the initial solid-phase diffusion, decreasing the direct contact area of the metal powders and lowering the enthalpy of mixture formation, thus improving the conformality and structural homogeneity of the samples. Zr-Al intermetallics with high melting points and stabilization properties are less susceptible to deformation thus increasing research and application potential[28]. Typically, the stable ZrAl2 has a similar crystal structure to the typical Laves phase (type of MgZn2) as it has topologically close-packed structure, which have been used in applications such as high-temperature structural materials. And the Zr5Al3 phase has been shown to have remarkable compression properties. However, for Zr-Al intermetallic compounds, most research has focused on powder materials or theoretical analysis. For example, Duan et al. investigated the structural properties and phase stability of Zr-Al compounds by using first-principles calculations. Polk et al. used arrested reactive ball milling in hexane to demonstrate the effect of varying Zr-Al chemistry on powder microstructure, intermetallic reactions, and ignition temperature. Moreover, further investigation is needed on the controllable synthesis in thermal regulation, pore formation mechanism, and pore structure analysis of porous Zr-Al intermetallic compounds. The mechanical properties and corrosion resistance of porous Zr-Al are influenced by the pore morphology and pore size distribution. Therefore, it is urgent to utilize 3D reconstruction to achieve the multi-faceted display of the pore structure, and to clarify the mechanism by which thermal regulation affects the pore structure and corrosion resistance/mechanical properties of porous Zr-Al.

In this study, porous Zr-Al intermetallic compounds were prepared by rapid self-exothermic reaction combined with pre-heating treatment. pre-heating process enables the Zr-Al compounds to construct high porosity while maintaining a uniform pore structure by modulating atomic diffusion and exothermic behavior. The effects of the pre-heating treatment for thermal-adjustment on pore structure and composition evolution were explored, subsequently the corresponding action mechanism of mechanical properties/anti-corrosion behavior were analyzed. 3D reconstruction of porous Zr-Al compounds was carried out using the 3D-XRM technique, which is combined with modeling to quantitatively and qualitatively analyze the porosity, pore connectivity, and permeability properties. In-situ high-temperature synchrotron XRD (HT-SXRD) presents the phase transformation at different temperature stages and confirms the disappearance of the unreacted Zr phase by holdinging stage. This work provides a novel intermetallic binary system and cost-effective way with high filtration precision, superior corrosion resistance, and excellent mechanical properties for industrial alkaline waste liquid treatment.

The relevant research results are published in a paper titled “3D Reconstruction and Corrosion Resistance of Porous Zr-Al Intermetallic via Thermally-regulated Rapid Self-exothermic Reaction” in Journal of Alloys and Compounds.

Fig. 3. (a) XRD patterns of all Zr-Al samples. (b) The open porosity of all Zr-Al samples (inset: The actual macro morphology of sintered Zr-Al samples).

Fig. 4. In-situ synchrotron XRD characterization. Heating procedure: Heat to 570 ℃, holding for 0.5 h, then directly heat to 700 ℃.

Fig. 9. The result of threshold segmentation (a-c) and the velocity streamline distribution (d-f) of sample 570/700. The distribution of all pores on (a) the slice, and (b) the reconstructed model. (c) The total porosity by collecting XY slices perpendicular to the Z direction. (d) The total velocity streamline distribution. The streamline distribution of a plane extracted from the reconstructed model along (e) the XY direction and (f) the Z direction.

Fig. 10. (a,b) The curve of gas flow rate and pressure difference of the porous Zr-Al samples. (c) The connected pore size distribution curve of sample 570/700. (d) The largest pore size histogram of porous Zr-Al sample.

Fig. 12. Porous Zr-Al samples immersed in 1 M KOH solution: (a) the open-circuit potential curves, (b) the EIS curves, (c) the bode phase, and (d) the bode magnitude.

Title: 3D Reconstruction and Corrosion Resistance of Porous Zr-Al Intermetallic via Thermally-regulated Rapid Self-exothermic Reaction

Co-authors: Weijia Guo, Zixuan Pang, Xiaoping Cai, Chaoqun Xie, Baojing Zhang, Farid Akhtar, Peizhong Feng*

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