High Temperature Engineering Ceramics

Komeya, Katsutoshi; Matsui, Masanao

doi:10.1002/9783527603978.mst0126

Cited by 9 publications

(9 citation statements)

References 34 publications

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“…[9][10][11][12] Previous studies of diborides have also outlined some guidelines for the design of highly refractory ceramics with improved strength at elevated temperature. [11,[13][14][15][16][17][18] Starting from the macro scale, the ceramic should be fully dense, without microcracks or other flaws, have an average grain size between 1 and 2 µm, have grain boundaries free of low-melting temperature phases, and, possibly, contain homogeneously dispersed refractory second phases. Furthermore, another factor which seems to positively affect the elevated temperature strength is the presence of concentrated dislocation networks within the grains of the matrix phase.…”

Section: Introductionmentioning

confidence: 99%

A simple route to fabricate strong boride hierarchical composites for use at ultra-high temperature

Silvestroni

Gilli

Migliori

et al. 2020

Composites Part B: Engineering

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A simple method to obtain a highly refractory HfB 2 -based ceramic nano-composite is presented. The boride was hot pressed with additions of SiC and WC particles and subsequently annealed at 2100°C for 2 hours.The annealing procedure was beneficial for high temperature strength, which increased by about 300 MPa in the 1500°C to 1800°C temperature range compared to the as-sintered material. Peak strengths of 850 MPa at 1500°C and 650 MPa at 1800°C were achieved due to two main microstructural changes. First, rounded SiC particles that were surrounded by a silica-based glass in the as-sintered ceramics evolved into platelets with mostly clean grain boundaries after heat treatment. In addition, the (Hf,W)B 2 solid solution that formed as shells around HfB 2 grain cores during densification reached an equilibrium state after annealing that revealed nano-texturing of the shell, which constituted a nano-composite with metallic W nano-particles embedded within HfB 2 grains. These two features combined to contribute to refractoriness and increased strength at elevated temperature. The unique findings reported in this study launch significant opportunities for ceramic development, manufacturing, and applications.

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Section: Introductionmentioning

confidence: 99%

A simple route to fabricate strong boride hierarchical composites for use at ultra-high temperature

Silvestroni

Gilli

Migliori

et al. 2020

Composites Part B: Engineering

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“…However, most studies have focused on particulate composites, and recently little research has been carried out on advanced fibre-reinforced SiC/SiC composites, particularly with regards to impact and erosive wear [41,[55][56][57][58]. Continuous SiC fibre-reinforced SiC matrix (SiC f /SiC) composites are a promising candidate for a structural application, particularly under extreme conditions, such as high temperature and wear-resistant environments [55][56][57][58][59][60][61][62][63][64][65][66][67]. It is well known that SiC has one of the highest hardness of all single-phase ceramics; moreover, it performs extremely well under a wide variety of conditions [57][58][59][60][61][62][63][64][65][66][67].…”

Section: Introductionmentioning

confidence: 99%

Erosive Wear Mechanism of New SiC/SiC Composites by Solid Particles

Suh

Hinoki

2010

Tribol Lett

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A solid-particle erosive wear test by impinging silicon carbide (SiC) powders was carried out at room temperature over a range of median particle sizes of 425-600 lm, speed of 100 m/s and impact angle of 90°a nd assessed by wear measurements and scanning electron microscopy. Erosive wear behaviour was examined on newly fabricated nano-powder infiltration and transient eutectoid (NITE) SiC/SiC composites and two commercial composites by the chemical vapour infiltration (CVI) and NITE fabrication route. Microstructural observation was performed to examine the correlation between erosive wear behaviours and fabrication impurities. Conspicuous defects were observed in the prototype materials as the forms of porosity, fibre deformation, residual oxide, pyrolytic carbon (PyC) deformation, PyC cleavage, among others. Erosive wear behaviour was rather serious in the prototype of fabricated composites, which employ pre-SiC fibre and phenolic resin. Two dominant erosive wear mechanisms were observed: delamination of constituents, mainly caused by erosive crack propagation, and fragmentation and detachment of constituents, which usually resulted from erosive impact. A unit size of delamination was the most decisive factor affecting wear volume. The bonding strength of each constituent was mostly affected by various forms of porosities. Therefore, the fundamental cause and subsequent results must be carefully elucidated. The correlation of microstructural defect and wear behaviour was investigated with the aim of reducing dominant wear by improving fabrication conditions. The final product of the cost-effective composite had a 2.5-fold higher resistance than the commercial CVI composite. Consequently, by controlling fabrication impurities, we have been successful in developing and improving a new fabrication technique; consequently, the known defects are rarely observed in final product. A schematic wear model of erosive wear mechanisms is proposed for the newly fabricated SiC/SiC composites under particle erosion.

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“…The application of molecular precursors for the synthesis of silicon- based nonoxidic ceramics with outstanding properties has been investigated intensively since the early 1990s. , Nevertheless, polycarbosilanes and related polymers are still the most important among non-oxide polymer precursors, , and since the pioneering work by Yajima (SiC-nicalon), Takamizawa (first Si−B−N−C-fibers) and others, the chemical and physical properties of binary and multinary ceramics containing Si, B, N, and/or C have been optimized. − Remarkably, using molecular monomers in the relatively recent “M-to-M” (molecules-to-materials) approach, the thermal stability of the obtained materials can be increased significantly. However, the ceramic yield is lower than that of the polymer route .…”

Section: Introductionmentioning

confidence: 99%

High-Yield Molecular Borazine Precursors for Si−B−N−C Ceramics

et al. 2004

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The synthesis of Si-B-N-C ceramic materials can be accomplished via two different routes using B-tris(trichlorosilylvinyl)borazine (2) as starting material. This silyl-functionalized ethinylborazine is obtained by Pt-catalyzed hydrosilylation of B, B′, B′′-tri-ethynylborazine (1) with HSiCl 3 in quantitative yield with a selectivity of 80% β-substituted product. Amminolysis of 2 with methylamine leads to the soluble silazane polymer P3 which contains intact borazine rings connected by sCHdCHsSisNMe linkages. In a second approach, the trichlorosilyl groups of 2 are hydrogenated to yield the B-tris(hydrosilylvinyl)borazine (4). With polymer P3 or 4, a highly durable Si-B-N-C ceramic is obtained after pyrolysis under inert atmosphere. The composition SiBN 1+x C 2 of the ceramic material corresponds exactly to the backbone of the precursor molecules 2 or 4, and very compact materials are obtained in each case. The ceramic yield of approximately 94% starting from the silane precursor 4 sets a new standard for this type of ceramics using the pyrolysis of a single site molecular precursor. Conductivity measurements show a semiconductor behavior of the ceramic at about 10 2 (Ωm) -1 at room temperature. The composition of the ceramic was characterized by laser-ablation ICP-MS, which was used for that purpose for the first time. The very satisfying results demonstrate the high potential of this direct solid sampling technique.

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High Temperature Engineering Ceramics

Cited by 9 publications

References 34 publications

A simple route to fabricate strong boride hierarchical composites for use at ultra-high temperature

A simple route to fabricate strong boride hierarchical composites for use at ultra-high temperature

Erosive Wear Mechanism of New SiC/SiC Composites by Solid Particles

High-Yield Molecular Borazine Precursors for Si−B−N−C Ceramics

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