Advances in ultra-high temperature ceramics, composites, and coatings

TLDR

Ultra‑high temperature ceramics (UHTCs), mainly Zr, Hf carbides/nitrides and TaC, possess ultra‑high melting points, superior mechanical strength, and ablation resistance, making them attractive for extreme‑temperature aerospace components, while UHTC coatings and composites are pursued to overcome brittleness and thermal shock, and high‑entropy variants are rapidly emerging. This review aims to survey the state of the art in processing, microstructure design, and properties of UHTCs across bulk, composite, and coating forms, and to outline future research directions. The authors compile and analyze recent processing approaches, microstructural strategies, and property data for UHTCs, drawing comparisons across bulk materials, composites, and coatings to identify trends and gaps.

Abstract

Abstract Ultra-high temperature ceramics (UHTCs) are generally referred to the carbides, nitrides, and borides of the transition metals, with the Group IVB compounds (Zr & Hf) and TaC as the main focus. The UHTCs are endowed with ultra-high melting points, excellent mechanical properties, and ablation resistance at elevated temperatures. These unique combinations of properties make them promising materials for extremely environmental structural applications in rocket and hypersonic vehicles, particularly nozzles, leading edges, and engine components, etc. In addition to bulk UHTCs, UHTC coatings and fiber reinforced UHTC composites are extensively developed and applied to avoid the intrinsic brittleness and poor thermal shock resistance of bulk ceramics. Recently, highentropy UHTCs are developed rapidly and attract a lot of attention as an emerging direction for ultra-high temperature materials. This review presents the state of the art of processing approaches, microstructure design and properties of UHTCs from bulk materials to composites and coatings, as well as the future directions.