Ultra-high temperature ceramics (UHTCs)
Ultra-high temperature ceramics (UHTCs) are a class of a specialized class of materials engineered to endure harsh environments for prolonged periods, particularly at elevated temperatures. These materials possess exceptional properties such as high melting points, chemical stability, hardness, and abrasion and corrosion resistance. They are typically composed of compounds involving boron, carbon, or nitrogen combined with early transition metals like Ti, Zr, Nb, Hf, and Ta. Their distinctive properties enables UHTCs to withstand extreme temperatures, heat fluxes, radiation levels, mechanical loads, chemical reactivity, and other harsh conditions that surpass the capabilities of existing structural materials.
MAX and MAB phases
MAX phases are a fascinating class of layered carbide, nitride, or carbonitride materials that exhibit a unique combination of metallic and ceramic properties. The name “MAX” stands for “M” representing an early transition metal, “A” representing a group A element, and “X” representing carbon or nitrogen. These compounds possess a three-dimensional layered structure, where metal atoms are sandwiched between layers of carbon or nitrogen atoms. Similarly, MAB phases represent a class of layered ternary transition metal borides with varying formulas, where “B” stands for boron. MAX and MAB phases are fascinating materials that exhibit good thermal and electrical conductivity, machinability, high strength, thermal shock and resistance, and exceptional damage tolerance. They also demonstrate remarkable thermal stability and oxidation resistance making them suitable for high-temperature applications. Their versatile properties have attracted significant attention in fields such as aerospace, energy production, electronics, and coatings.
MXenes
MXenes are a class of two-dimensional (2D) materials that have gained significant attention in the field of materials science. MXenes are derived from layered MAX phases, where the A-layer is selectively etched to obtain a transition metal carbide or nitride with surface terminations of various possible functional groups. These 2D materials possess a unique combination of metallic conductivity and hydrophilicity. MXenes exhibit exceptional electrical conductivity, high mechanical strength, and good chemical stability. They also demonstrate remarkable potential in various applications, including energy storage, catalysis, sensors, and electromagnetic shielding. MXenes can be easily synthesized and their properties can be modified by altering their composition and surface chemistry. Ongoing research in MXenes continues to unveil their promising properties and their potential for advancing numerous technological fields.
Nanocomposites
Nanocomposites represent a significant advancement in materials science, where nanoscale reinforcements are incorporated into a matrix to enhance mechanical, electrical, thermal, and other properties. A promising class of nanocomposites involves the integration of MAX phases and MXene into ceramic or metallic materials. MAX phases are layered nanolaminates known for their unique combination of metallic and ceramic characteristics. MXenes, derived from MAX phases, are two-dimensional transition metal carbides or nitrides with excellent electrical conductivity and surface chemistry. By combining the unique properties of MAX phases and MXenes, composites with enhanced strength, toughness, damage tolerance, electrical conductivity, thermal conductivity and shock resistance, and corrosion resistance can be achieved. These nanocomposites hold potential for various applications in energy, electronics, sensors, and structural materials, and opening new avenues in nanocomposite research.
Advanced sintering methods
Sintering is a process in which compacted powdered materials are heated below their melting point to bond and form a solid object. This process is instrumental in the field of materials processing for producing a wide range of materials, especially from those with high melting points such as ceramics. Advanced sintering methods allow for enhanced control and optimization of material properties. Conventional sintering techniques involve the application of heat and pressure to consolidate and densify powder particles. However, advanced sintering methods offer additional benefits and capabilities.
Spark plasma sintering (SPS) is a popular technique that applies pulsed direct current to promote rapid heating and sintering while maintaining fine-grained microstructures. This method enables the production of materials with improved density, enhanced mechanical properties, and reduced grain growth. SPS has become the gold standard of sintering systems for research purposes and larger and hybrid systems are being developed for industrial use.
