Review on ultra-high temperature boride ceramics

The oxidation behaviour of transition metal diboride ceramics is reviewed with emphasis on the performance of zirconium diboride and hafnium diboride. First, the oxidation behaviour of nominally pure diborides is discussed, focusing on the transition to linear mass gain kinetics at temperatures above ∼1100°C. Next, the use of SiC and other additives that produce silica based scales when oxidised is reviewed. These additives improve oxidation protection due to the formation/stability of the outer layer of borosilicate glass that acts as a barrier to diffusion of oxygen to the substrate. However, elevated temperatures (>1650°C) and/or the combination of aerodynamic flow, high heat flux and reactive atmosphere associated with hypersonic flight destabilises the outer oxide and decreases oxidation protection. Other additives that affect the composition and structure of the crystalline oxide scale without forming an outer glassy layer are a promising approach to improving oxidation behaviour of diboride...

Oxidation of ultra-high temperature transition metal diboride ceramics

Zirconium diboride is a strategic material, finding applications as thermal protection system in reentry vehicles, high temperature electrode, thermowell tubes, etc. Solid state reactions require high temperature and thus result in coarse powders which are difficult to sinter. Densification of ZrB2 is extremely difficult due to its refractory nature. Sinter additives help in densification but deteriorate the high temperature properties. In the recent past, various researchers have made attempts to improve the existing methods and also invented new processes for synthesis of pure and fine powders as well as for densification of ZrB2. All the techniques on synthesis and consolidation of ZrB2 are discussed in detail and critically reviewed in this article.

Synthesis and consolidation of zirconium diboride: review

Zirconium diboride and boron carbide particles were used to improve the ablation resistance of carbon–carbon (C–C) composites at high temperature (1500 °C). Our approach combines using a precursor to ZrB 2 and processing them with B 4 C particles as filler material within the C–C composite. An oxyacetylene torch test facility was used to determine ablation rates for carbon black, B 4 C, and ZrB 2 –B 4 C filled C–C composites from 800 to 1500 °C. Ablation rates decreased by 30% when C–C composites were filled with a combination of ZrB 2 –B 4 C particles over carbon black and B 4 C filled C–C composites. We also investigated using a sol–gel precursor method as an alternative processing route to incorporate ZrB 2 particles within C–C composites. We successfully converted ZrB 2 particles within C–C composites at relatively low temperatures (1200 °C). Our ablation results suggest that a combination of ZrB 2 –B 4 C particles is effective in inhibiting the oxidation of C–C composites at temperatures greater than 1500 °C.

Improved ablation resistance of C–C composites using zirconium diboride and boron carbide

Effect of graphite flake on microstructure as well as mechanical properties and thermal shock resistance of ZrB2―SiC matrix ultrahigh temperature ceramics

Gang Li

Papers

Microstructure evolution and mechanical properties of friction stir spot welded dissimilar aluminum-copper joint

Effect of AlN as sintering aid on hot-pressed ZrB2–SiC ceramic composite

Ablation resistance of ZrB2–SiC–AlN ceramic composites