Characterization of corrosion resistance of C/C–SiC composite in molten chloride mixture MgCl2/NaCl/KCl at 700 °C

Abstract

Due to their high thermal stability and low cost, molten chlorides are promising high-temperature fluids for example for thermal energy storage (TES) and heat transfer fluid (HTF) materials in concentrated solar power (CSP) plants and other applications. However, the commercial application of molten chlorides is strongly limited due to their strong corrosivity against commercial alloys at high temperatures. The work addresses on a fundamental level whether carbon based composite ceramics could be potentially utilized for some corrosion critical components. Liquid silicon infiltration (LSI) based carbon fiber reinforced silicon carbide (called C/C-SiC) composite is immersed in a molten chloride salt (MgCl 2 /NaCl/KCl 60/20/20 mole%) at 700°C for 500 h under argon atmosphere. The material properties and microstructure of the C/C-SiC composite with and without exposure in the molten chloride salt have been investigated through mechanical testing and analysis with scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) scanning. The results reveal that the C/C-SiC composite maintains its mechanical properties after exposure in the strongly corrosive molten chloride salt. The oxidizing impurities in the molten salt react only with residual elemental silicon (Si) in the area of the C/C-SiC matrix. In comparison, no indication of reaction between the molten chloride salt and carbon fiber or SiC in the matrix is observed. In conclusion, the investigated C/C-SiC composite has a sound application potential as a structural material for high-temperature TES and HTF with molten chlorides due to its excellent corrosion resistance and favorable mechanical properties at high temperatures.

Experimental evaluation and theoretical prediction of elastic properties and failure of C/C‐SiC composite

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Due to its excellent mechanical properties, favorable damage tolerance and comparatively low density, continuous carbon fiber reinforced carbon silicon carbide (C/C-SiC) composite fabricated by Liquid Silicon Infiltration (LSI) process has been successfully used in aerospace, energy, and transport technology. [1][2][3][4][5][6][7][8] The preliminary investigation of siliconization in German Aerospace Center Stuttgart started in the late 1980s and the manufacturing process of LSI-based C/C-SiC was developed in the beginning of 2000s. 9 Since then, material properties of the composite have been characterized intensively.

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Compatibility of 3D-Printed Oxide Ceramics with Molten Chloride Salts for High-Temperature Thermal Energy Storage in Next-Generation CSP Plants

“…Moreover, their extreme hardness and brittleness lead to extremely difficult machining of ceramic components and thus limit their applications [15]. One way to improve the applicability of ceramics is via ceramic composites technology [16]. Compared to ceramics, ceramic composites have much better fracture toughness because of their composite structure, leading to easier machining [16].…”

“…One way to improve the applicability of ceramics is via ceramic composites technology [16]. Compared to ceramics, ceramic composites have much better fracture toughness because of their composite structure, leading to easier machining [16]. In our previous work [16], we confirmed the excellent corrosion resistance of a carbon-fiber-reinforced silicon carbide composite (C/C-SiC composite) in molten chlorides (MgCl 2 /NaCl/KCl 60/20/20 mole%) under argon atmosphere via immersion test at 700 • C for 500 h. Besides ceramic composites, the introduction of 3D printing, also referred to as additive manufacturing (AM), into the manufacturing of ceramic components offers new possibilities for addressing the aforementioned challenges, and extends their applications [15].…”

“…Compared to ceramics, ceramic composites have much better fracture toughness because of their composite structure, leading to easier machining [16]. In our previous work [16], we confirmed the excellent corrosion resistance of a carbon-fiber-reinforced silicon carbide composite (C/C-SiC composite) in molten chlorides (MgCl 2 /NaCl/KCl 60/20/20 mole%) under argon atmosphere via immersion test at 700 • C for 500 h. Besides ceramic composites, the introduction of 3D printing, also referred to as additive manufacturing (AM), into the manufacturing of ceramic components offers new possibilities for addressing the aforementioned challenges, and extends their applications [15]. For instance, 3D-printed oxide ceramic components with highly complex geometries [15,17], such as high-performance ceramic heat exchangers [17] and sample holders used in our other works for molten salt corrosion tests (see Figure 1) have become available.…”

C/C‐SiC component for metallic phase change materials

“…Due to their favorable mechanical properties at high temperature, corrosion resistance, and comparatively low density, Ceramic Matrix Composites (CMCs) have received considerable attention in aerospace and other applications in recent years. [13][14][15] Based on the results of previous studies for mechanical response and corrosion behavior, 16,17 carbon fiber reinforced silicon carbide (C/C-SiC) composite could be a promising candidate CMC for vehicle thermal storage applications due to its excellent corrosion resistance, low density, high damage resistance, and thermal shock resistance.…”