Rapid heating thermal shock study of ultra high temperature ceramics using an in situ testing method

Kong

Int J Applied Ceramic Tech

et al. 2019

The quasi-static, dynamic compression experiments and micromechanical model were employed to declare the dynamic compressive response of ZrB 2 -20%SiC composite at high-strain rates. The quasi-static compressive strengths were measured to determine the range of initial microcrack length in ZrB 2 -20%SiC composite. The effects of the strain rate on dynamic compressive strength, critical stain, as well as fracture mechanisms were discussed based on experimental results. Dynamic mechanical properties of ZrB 2 -based composites display obvious strain rate dependence. The dynamic increase factor in the compressive strength shows a rapid increase above a transition strain rate of 1228 s −1 . Moreover, a micromechanical model considering initial microcrack lengths is used to predict dynamic compressive strengths, which agree with the experimental results. Additionally, the critical strain has a linear increase tendency with the increase of strain rate. The dynamic compressive fracture mechanism of ZrB 2 -20%SiC composite is relative to the combination effect between strain rate and microstructure. The size of flaw distribution is critical below the transition strain rate resulting in bigger fragments, whereas the flaw density is primary with more and smaller fragments above the transition strain rate. K E Y W O R D Sdynamic compressive strength, fracture mechanism, micromechanical model, strain rate, ZrB 2 -20%SiC composite How to cite this article: Wang M, Kong D, Wang L, Li Y, Cai T. Dynamic compressive response of zirconium diboride-silicon carbide composites at highstrain rates. Int J Appl Ceram Technol. 2019;16:2206-2213. https ://doi.

Section: Introductionmentioning

confidence: 99%

Dynamic compressive response of zirconium diboride‐silicon carbide composites at high‐strain rates

Kong

Int J Applied Ceramic Tech

et al. 2019

“…A GKZ-II servohydraulic testing machine with the indenter and holder made of dense SiC material equipped with a split furnace attachment was conducted to study the temperature dependence of mechanical properties of the obtained composites [1,37]. The load is recorded by the attached weighting sensor, at the same time, displacement sensor is used to record the displacement of material under stress, and the accuracy for both data is ±1%.…”

Section: Characterization Of the Mosi 2 (Cr 5 Si 3 )-Rsic Compositesmentioning

confidence: 99%

High temperature mechanical retention characteristics and oxidation behaviors of the MoSi2(Cr5Si3)—RSiC composites prepared via a PIP—AAMI combined process

et al. 2019

In the present paper, MoSi 2 (Cr 5 Si 3)-RSiC composites were prepared via a combination of precursor impregnation pyrolysis (PIP) and MoSi 2 −Si−Cr alloy active melt infiltration (AAMI) process. Composition, microstructure, mechanical retention characteristics, and oxidation behaviors of the composites at elevated temperature were studied. X-ray diffraction (XRD) pattern confirms that the composites mainly compose of 6H-SiC, hexagonal MoSi 2 , and tetragonal Cr 5 Si 3. Scanning electron microscopy (SEM) image reveals that nearly dense MoSi 2 (Cr 5 Si 3)-RSiC composites exhibiting three-dimensionally (3D) interpenetrated network structure are obtained when infiltrated at 2173 K, and the interface combination of the composites mainly depends on the composition ratio of infiltrated phases. Oxidation weight gain rate of the composites is much lower than that of RSiC matrix, where MoSiCr2 possesses the lowest value of 0.1630 mg⋅cm −2 , about 78% lower than that of RSiC after oxidation at 1773 K for 100 h. Also, it possesses the highest mechanical values of 139.54 MPa (flexural strength σ f and RT) and 276.77 GPa (elastic modulus E f and RT), improvement of 73.73% and 29.77% as compared with that of RSiC, respectively. Mechanical properties of the composites increase first and then decrease with the extension of oxidation time at 1773 K, due to the cooperation effect of surface defect reduction via oxidation reaction and thermal stress relaxation in the composites, crystal growth, and thickness increase of the oxide film. Fracture toughness of MoSiCr2 reaches 2.24 MPa•m 1/2 (1673 K), showing the highest improvement of 31.70% as compared to the RT value.

“…Ultra-high temperature ceramics (UHTCs) are a class of nonmetallic and inorganic materials that have melting point over 3000 ℃ and are typically borides, carbides, and nitrides of early transition metals (e.g., Zr, Hf, Nb, Ta) [1][2][3][4][5][6][7][8]. Due to the combination of series of excellent physical and chemical properties, such as high hardness, good high-temperature stability, and excellent solid-phase stability, UHTCs are considered as promising candidate materials for high-temperature structural applications, including engines, hypersonic vehicles, plasma arc electrode, cutting tools, furnace elements, and high-temperature shielding [7,[9][10][11][12][13]. UHTCs are difficult to densify without sintering additives and external pressure.…”

Section: Introductionmentioning

confidence: 99%

Sol-gel derived porous ultra-high temperature ceramics

et al. 2020

Ultra-high temperature ceramics (UHTCs) are considered as a family of nonmetallic and inorganic materials that have melting point over 3000 ℃. Chemically, nearly all UHTCs are borides, carbides, and nitrides of early transition metals (e.g., Zr, Hf, Nb, Ta). Within the last two decades, except for the great achievements in the densification, microstructure tailoring, and mechanical property improvements of UHTCs, many methods have been established for the preparation of porous UHTCs, aiming to develop high-temperature resistant, sintering resistant, and lightweight materials that will withstand temperatures as high as 2000 ℃ for long periods of time. Amongst the synthesis methods for porous UHTCs, sol-gel methods enable the preparation of porous UHTCs with pore sizes from 1 to 500 μm and porosity within the range of 60%-95% at relatively low temperature. In this article, we review the currently available sol-gel methods for the preparation of porous UHTCs. Templating, foaming, and solvent evaporation methods are described and compared in terms of processing-microstructure relations. The properties and high temperature resistance of sol-gel derived porous UHTCs are discussed. Finally, directions to future investigations on the processing and applications of porous UHTCs are proposed.