Refractory Materials Beyond Thermal Resistance: Engineering Functionality, System Integration, and Sustainable Evolution in Advanced High-Temperature Systems — A Comprehensive Review

Refractory materials have traditionally been used as thermally stable and chemically resistant structural linings in metallurgy, energy generation, glass production, and chemical processing. They remain essential components of high-temperature industrial systems. However, increasingly demanding operating conditions, environmental restrictions, and performance requirements have shifted refractory design from an empirical, operation-oriented approach towards multifunctional, system-integrated, and sustainable solutions. This paper critically reviews the evolution of refractory materials from conventional heat-resistant ceramics to advanced high-temperature composites with tailored functional properties and engineered microstructures. The review examines mechanical load-bearing behaviour, thermomechanical and thermochemical stability, wear and corrosion resistance, thermal-shock performance, and functional transport properties. Microstructural engineering strategies including spinel bonding, grain-boundary tailoring, carbon optimisation, fibre reinforcement, and hierarchical porosity design are discussed in relation to degradation mechanisms and service-life extension. Emerging technologies, including additive manufacturing, multiscale computational modelling, materials informatics, and digital twin-based predictive maintenance, are evaluated for their potential to accelerate materials development and improve reliability. Sustainability considerations, including life-cycle assessment, recycling, energy-efficient processing, and circular-economy strategies, are also examined as drivers of future innovation. Finally, the review identifies current challenges, knowledge gaps, and research priorities for upgrading refractories from passive thermal-barrier components to smart, performance optimised elements of integrated high-temperature engineering systems.