Microstructural evolution and mechanical properties of in situ nano Ta4HfC5 reinforced SiBCN composite ceramics

Abstract

The in situ nano Ta4HfC5 reinforced SiBCN-Ta4HfC5 composite ceramics were prepared by a combination of two-step mechanical alloying and reactive hot-pressing sintering. The microstructural evolution and mechanical properties of the resulting SiBCN-Ta4HfC5 were studied. After the first-step milling of 30 h, the raw materials of TaC and HfC underwent crushing, cold sintering, and short-range interdiffusion to finally obtain the high pure nano Ta4HfC5. A hybrid structure of amorphous SiBCN and nano Ta4HfC5 was obtained by adopting a second-step ball-milling. After reactive hot-pressing sintering, amorphous SiBCN has crystallized to 3C-SiC, 6H-SiC, and turbostratic BN(C) phases and Ta4HfC5 retained the form of the nanostructure. With the in situ generations of 2.5 wt% Ta4HfC5, Ta4HfC5 is preferentially distributed within the turbostratic BN(C); however, as Ta4HfC5 content further raised to 10 wt%, it mainly distributed in the grain-boundary of BN(C) and SiC. The introduction of Ta4HfC5 nanocrystals can effectively improve the flexural strength and fracture toughness of SiBCN ceramics, reaching to 344.1 MPa and 4.52 MPa·m1/2, respectively. This work has solved the problems of uneven distribution of ultra-high temperature phases in the ceramic matrix, which is beneficial to the real applications of SiBCN ceramics.

Mechanical and thermal shock properties of Cf/SiBCN composite: Effect of sintering densification and fiber coating

“…The toughness can be improved by adding reinforcements such as fibers, whiskers, particles, graphenes, and carbon nanotubes. [10][11][12][13][14] Among them, the carbon fiber toughening effect is the most significant: through fiber debonding, fracture, and pull-out, composites show pseudo-plasticity rather than brittle fracture, and their mechanical properties are not sensitive to microdefects, which greatly improves damage tolerance and service reliability. 10 According to the source of SiBCN matrix, the preparation of carbon fiber-reinforced SiBCN (C f /SiBCN) composites can be divided into organic method and inorganic method.…”

“…[10][11][12][13][14] Among them, the carbon fiber toughening effect is the most significant: through fiber debonding, fracture, and pull-out, composites show pseudo-plasticity rather than brittle fracture, and their mechanical properties are not sensitive to microdefects, which greatly improves damage tolerance and service reliability. 10 According to the source of SiBCN matrix, the preparation of carbon fiber-reinforced SiBCN (C f /SiBCN) composites can be divided into organic method and inorganic method. Based on the organic method, C f /SiBCN composites are prepared via densifying carbon fiber preform through repeated precursor infiltration pyrolysis (PIP).…”

“…Based on the organic method, C f /SiBCN composites are prepared via densifying carbon fiber preform through repeated precursor infiltration pyrolysis (PIP). 10,15,16 However, precursor preparation involves high requirements and cost, and the repeated PIP process (up to 12 times) requires long preparation cycle. 16 Using inorganic powders (such as Si, C, B, BN, etc.)…”

Mechanical /thermal Shock Properties and Failure Mechanisms of Cf/SiBCN Composites Effect of Sintering Densification and Fiber Coating

“…However, like most ceramics, the brittleness and poor reliability of SiBCN ceramics hinder its practical application. The toughness can be improved by adding reinforcements such as bers, whiskers, particles, graphenes and carbon nanotubes [10][11][12][13][14]. Among them, the carbon ber toughening effect is the most signi cant: through ber debonding, fracture and pull-out, composites show pseudo-plasticity rather than brittle fracture, and their mechanical properties are not sensitive to micro-defects, which greatly improves damage tolerance and service reliability [10].…”

“…At present, C f /SiBCN composites are mainly prepared via densifying carbon ber preform through repeated precursor in ltration pyrolysis (PIP) [10,[15][16]. However, precursor preparation involves high requirements and cost and repeated PIP process (up to 12 times) requires long preparation cycle [16].…”