Improvement in Thermo-oxidative Stability and Mechanical Strength of Carbon Foams for Thermal Management of Reusable Lau
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ORIGINAL ARTICLE
Improvement in Thermo‑oxidative Stability and Mechanical Strength of Carbon Foams for Thermal Management of Reusable Launch Vehicles R. Sreeja1 · Deepa Devapal1 · N. Sreenivas2 Received: 19 May 2020 / Accepted: 22 August 2020 © Indian National Academy of Engineering 2020
Abstract Carbon foams were prepared and coated with silicon carbide (SiC) by chemical vapour infiltration (CVI) technique and tested for improvement of oxidation stability and compressive strength, compared to virgin carbon foams. Microstructural and morphological characterisation of SiC-coated carbon foam samples proved the formation of stoichiometric high strength, crystalline β-SiC over amorphous carbon which enables the ceramic foam to take high compressive loads. The final ceramic foam was successfully tested for oxidation stability up to a maximum temperature of 1650 °C under air atmosphere. The weight loss of SiC-coated carbon foam was found to depend on the final density, which depends on the SiC coating thickness. The functional property of reducing the back wall temperature of ceramic matrix composites (CMC) based light weight thermal protection systems (TPS) using SiC-coated carbon foam as the core material was validated by carrying out the plasma testing under atmospheric re-entry conditions. The process is noted for the cost-effective method of imparting desired ceramic property of SiC to less-expensive carbon foam structure. Keywords Silicon carbide · Carbon foam · Polymer infiltration and pyrolysis · Chemical vapour infiltration · Oxidation resistance · Thermal protection systems
Introduction Reticulated vitreous open cell carbon foams have unique properties of extremely light weight, high inertness up to 2000 °C under vacuum, electrically conductive, easily machinable to near-net shape, chemical resistance, resistant to thermal shock, and good thermal insulator (Sarna 2016; Alei 2019; Satish 2010; Kim et al. 2005). It finds applications in energy storage devices, as filters for metals and gas filtration, shock-absorption, catalyst support, and as thermal insulation in aerospace vehicles (Gallego 2003; Liu 2018; Dang 2018; Ribeiro 2008; Inagaki 2015; Walsh 2016; Pham 2014). However, the poor oxidation resistance and fragility * R. Sreeja [email protected] 1
Ceramic Matrix Products Division, Analytical Spectroscopy and Ceramics Group, PCM Entity, Vikram Sarabhai Space Centre, Thiruvananthapuram 695022, India
ARC Plasma Laboratory Division, Propulsion Research Group, SPRE Entity, Vikram Sarabhai Space Centre, Thiruvananthapuram 695022, India
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of the carbon foams restricts their use as thermostructural material, especially in aerospace applications (Dong 2015). Hence, the technology of providing refractory/metallic coatings on carbon foam is widely explored (Kumanek 2014; Chen 2019a, b; Ultramet 2018). Polymeric foam is pyrolyzed to form vitreous carbon foam with the required physical, thermal, and electrical properties. Refractory metals and ceramics are then infiltrated into the foam to tailor the
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