UHTC ceramics derived from B₄C and MAX phases by reactive sintering

Area of Science:

• Materials Science
• Ceramic Engineering
• Composite Materials

Background:

• Ultra-High Temperature Ceramics (UHTCs) are crucial for extreme environments.
• Boron carbide (B4C) is a UHTC with desirable properties but high sintering temperatures.
• MAX phases are a class of ternary carbides/nitrides with unique properties.

Purpose of the Study:

• To investigate the effect of three MAX phases (Ti3SiC2, Ti2AlC, Cr2AlC) on UHTC composite densification and properties.
• To evaluate the potential of MAX phases in reducing sintering temperatures of B4C-based composites.
• To analyze the phase composition and mechanical properties of the resulting composites.

Main Methods:

• Synthesis of dense UHTC composites incorporating different MAX phases.
• Analysis of phase formation through chemical reactions between B4C and MAX phases.
• Characterization of mechanical properties, including fracture resistance (KIC), Vickers hardness, and Young's Modulus.

Main Results:

• Addition of MAX phases led to secondary boride phase formation.
• Sintering temperatures were reduced by up to 800 °C compared to pure B4C.
• Fracture resistance (KIC) increased by 33-100%.
• Ti3SiC2 addition retained B4C mechanical properties, while Ti2AlC and Cr2AlC decreased hardness and Young's Modulus.

Conclusions:

• MAX phases effectively reduce sintering temperatures for B4C-based UHTCs.
• Ti3SiC2-containing composites show excellent potential for UHTC applications due to enhanced fracture toughness.
• The study highlights the role of MAX phases in tailoring the properties of advanced ceramic composites.