Spark plasma sintering of Al-doped ZrB2–SiC composite (original) (raw)
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Journal of the Ceramic Society of Japan, 2018
ZrB 2 SiC composite ceramics were fabricated by spark plasma sintering SiC powders with various mixtures of ZrB 2 , Zr, Al and graphite components, toughening the ceramics through the in-situ synthesis of ZrAlC microstructures. Different microstructures of ZrAlC toughened ZrB 2 SiC (ZSA) composite ceramics were formed during the sintering process by varying the components ball milled with the ZrB 2 powders prior to sintering. When the milled ZrB 2-based powders contained Al, the major ZrAlC phase changed into Zr 3 Al 4 C 6 from the designed Zr 2 Al 4 C 5 , and the layered ZrAlC grains formed with a large aspect ratio in the ZSA ceramics due to the formation of an Al-based coating layer covering the ZrB 2 powders during milling process. The Zr and Al co-milled ZrB 2-based powders further improved the toughness of composite ceramics through a more uniform distribution and the larger aspect ratio of ZrAlC grains. As a result, the ZSA ceramic made using the milled powders of ZrB 2 , Zr and Al showed the highest fracture toughness of 5.96 MPa•m 1/2 , about 10% higher than that of the ceramic made using milled ZrB 2 and Zr powders. The toughening mechanisms are shown to be crack deflection and bridging caused by ZrAlC grains. This work points to a possible pathway to control the microstructure of ZrAlC grains for toughening ZrB 2 SiC composite ceramics.
Scripta Materialia, 2007
Four kinds of composites, ZrB 2 -SiC, ZrB 2 -SiC-ZrC, ZrB 2 -SiC-ZrN and ZrB 2 -SiC-AlN, were synthesized in situ via reactive hot pressing (RHP) and reactive spark plasma sintering (R-SPS), using Zr, Si, B 4 C, BN and Al as raw materials. The synthesis process plays a critical role in the microstructural features of the composites obtained. The R-SPS process can lead to a more homogeneous and finer microstructure due to its high heating rates and short holding time, while the RHP process is likely to result in coarse microstructures due to a long enough holding time for grains growth.
Journal of the European Ceramic Society, 2010
ZrB 2-SiC composites were fabricated by spark plasma sintering (SPS) using TaSi 2 as sintering additive. The volume content of SiC was in a range of 10-30% and that of TaSi 2 was 10-20% in the initial compositions. The composites could be densified at 1600 • C and the core-shell structure with the core being ZrB 2 and the shell containing both Ta and Zr as (Zr,Ta)B 2 appeared in the samples. When the sintering temperature was increased up to 1800 • C, only (Zr,Ta)B 2 and SiC phases could be detected in the samples and the core-shell structure disappeared. Generally, the composites with core-shell structure and fine-grained microstructure showed the higher electrical conductivity and Vickers hardness. The completely solid soluted composites with coarse-grained microstructure had the higher thermal conductivity and Young's modulus.
Mechanical and oxidation behavior of spark plasma sintered ZrB2–ZrC–SiC composites
Journal of the Ceramic Society of Japan, 2012
ZrB 2 ZrCSiC composites were prepared by spark plasma sintering (SPS) at temperatures of 1750°C for 300 s under a pressure of 40 MPa. Densification, microstructural, mechanical properties and oxidation behavior of the composites were investigated. Fully dense ZrB 2 ZrCSiC composites with a relative density of more than 99% were obtained at 1750°C for 300 s. Vickers hardness of ZrB 2 ZrCSiC composites decreased with increasing ZrC content from 20 to 40 vol %, and composite containing 60 vol % ZrB 2 , 20 vol % ZrC and SiC sintered at 1750°C for 300 s had the highest value of 21.1 GPa. The crack mode for the same composite was zigzag, and resulted in remarkable crack deflections and the highest fracture toughness value of 5.5 MPa•m 1/2. Oxidation of composites resulted in formation of protective layered oxide structures consisted of ZrO 2 and SiO rich layer in the form of SiO 2 or SiO, and normalized mass change results increased with increasing oxidation temperature.
Journal of the Ceramic Society of Japan, 2010
Dense ZrB 2 SiC and HfB 2 SiC composites were fabricated at 1800°C by spark plasma sintering (SPS) using TaSi 2 as sintering aid. The volume content of SiC was 530% and that of TaSi 2 was 5% in the initial compositions. The additive of TaSi 2 contributed to the densification of composites by the decomposition and simultaneous solid solution of Ta atoms into boride grains which was probably associated with the decrease of activation energy of boride grain boundaries. With increasing SiC content, the electrical conductivity of ZrB 2 SiC and HfB 2 SiC composites decreased from 19.89 to 11.99 and 22.29 to 13.42 © 10 5 ³ ¹1 •m ¹1 respectively. Generally, the thermal conductivity of composites showed an increasing tendency with increasing SiC content, indicating the maximum values of 49.93 and 118.39 W/m•K respectively for ZrB 2 SiC and HfB 2 SiC composites produced with 30 vol % SiC content in the initial compositions. Additionally, the Vickers hardness of composites increased with the increment of SiC content from 16.9 to 20.2 and 24.0 to 28.5 GPa for ZrB 2 SiC and HfB 2 SiC composites respectively. The fracture toughness of ZrB 2 SiC composites showed an increasing tendency from 3.70 to 4.44 MPa•m 1/2 with increasing SiC content while those of HfB 2 SiC composites did not show a changing tendency and was in a range of 3.28 3.54 MPa•m 1/2. The elastic moduli of composites declined from 464.8 to 453.2 and 494.4 to 481.9 GPa for ZrB 2 SiC and HfB 2 SiC composites respectively with increasing SiC content.
2010
Starting from a ZrB 2 matrix, composites containing 10, 20 vol% of SiC whiskers and 20 vol% of SiC-chopped fibers were sintered by spark plasma sintering at 15001C. The addition of whiskers allowed both strengthening (740-770 MPa) and toughening (5.1-5.7 MPa . m 1/2 ) compared with the reference material. In the fiber-reinforced composite, the increase in fracture toughness (5.5 MPa . m 1/2 ) was accompanied by a decrease of strength (370 MPa). Toughening mechanisms were explored through the analysis of crack propagation. Crack deflection, crack pinning, and thermal residual stresses were the most important mechanisms identified. The experimental toughness increase was successfully compared with the values predicted by theoretical models. Compared with the baseline material, the reinforced composites showed an increased strength at 12001C in air. The highest value, 450 MPa, was for the fiber-reinforced composite.
Ceramics International, 2018
ZrB 2-based ceramics, reinforced with 25 vol% SiC whiskers (SiC w) as well as 0, 2.5, 5 and 7.5 wt% carbon nanoparticles (C np), were prepared by spark plasma sintering (SPS) at 1900 ºC under 40 MPa for 7 min in a vacuum environment. The influences of C np content on densification behavior, microstructure evolution, hardness and fracture toughness of ZrB 2-SiC w ceramics were investigated. Compared to the carbon-free sample, the grain growth of ZrB 2 matrix was moderately decreased (~20%) after the addition of C np. The in-situ formation of B 4 C and ZrC phases was attributed to the elimination of surface oxide impurities through their chemical reactions with the C np additive. All composite samples approached their theoretical densities. A hardness of 21.9 GPa was obtained for ZrB 2-SiC w sample, but the hardness values linearly decreased by the addition of soft carbon additives and reached 14.6 GPa for the composite doped with 7.5 wt% C np. The fracture toughness showed another trend and increased from 4.7 MPa m ½ for the carbon-free sample to 7.1 MPa m ½ for 5 wt% C np-reinforced composite. The formation of new carbides and the presence of unreacted C np resulted in toughness improvement. Various toughening mechanisms such as crack branching, bridging, and deflection were detected and discussed.
Phase stability, hardness and oxidation behaviour of spark plasma sintered ZrB2-SiC-Si3N4 composites
Ceramics International, 2019
Despite significant efforts to develop ultrahigh temperature ceramics, the phase stability together with high hardness and oxidation resistance remains to be addressed in ZrB 2-SiC based ceramics. ZrB 2-20vol.% SiC (ZS20) ceramics with varying amounts of Si 3 N 4 (2.5, 5 and 10vol.%) were processed by multi stage Spark Plasma Sintering (SPS) over a range of temperature (1800-1900 °C) for 3 min under 50 MPa. All the ZS20-Si 3 N 4 composites could be densified to more than 98% theoretical density (ρ th) after SPS at 1900 °C. The XRD, SEM-EDS analysis of the ZS20-Si 3 N 4 composites revealed the presence of reaction product phases (ZrO 2 , BN, ZrN) along with SiC and ZrB 2 major phases. Sintering reactions were proposed to explain the existence of such new phases and extinction of Si 3 N 4. Thermo-Calc software was also used to further confirm the formation of these new phases in the ZS20-Si 3 N 4 samples. The hardness of ZS20-Si 3 N 4 composites varied between 25.50 to 30.56 GPa, in particular, ZrB 2-20vol.% SiC-5vol.% Si 3 N 4 measured with the maximum hardness. In fact, it is the highest ever reported hardness for the ZrB 2 composites. Considering oxidation resistance, the weight gain of ZrB 2-20vol.%SiC composites decreased (from 13.84 to 9.84 mg/cm 2) and oxide layer thickness increased (64-128 µm) after oxidation at 1500°C for 10 h * * *
Effect of composition on spark plasma sintering of ZrB2–SiC–ZrC nanocomposite synthesized by MASPSyn
Ceramics International, 2017
ZrB 2-SiC-ZrC nanocomposites containing different contents of ZrC (6-20 wt%) were fabricated by spark plasma synthesizing and sintering method. Sintering mechanism was investigated by studying the displacement-temperature-time (DTT) diagrams which were obtained during spark plasma cycles. The flexural strength, hardness and fracture toughness were measured. The mean crystallite size of 77, 62 and 56 nm were calculated respectively for ZrB 2 , SiC and ZrC phases based on the Rietveld method. The maximum relative density (99.8 ± 0.1 %), flexural strength (620 ± 24 MPa), Vickers hardness (19.3 ± 0.4 GPa) and fracture toughness (5.7 ± 0.2 MPa.m 1/2) were measured for the composite containing 15 wt% ZrC.