Study of Mechanical Properties and Fracture Mode of Alumina-Silicon Carbide Nanocomposites (original) (raw)
Related papers
Materials & Design, 2012
In this study Al 2 O 3-SiC micro/nanocomposites have been fabricated by mixing alumina nanopowders and silicon carbide micro/nanopowders, followed by hot pressing at 1550, 1600, 1650 and 1700°C. The density, mechanical properties and fracture mode of Al 2 O 3-SiC composites containing different volume fractions (2.5%, 5%, 7.5%, 10% and 15%) of micro/nanoscale SiC particles were investigated and compared with those of alumina. The relative density of composites could reach values very close to theoretical density, especially after sintering at 1700°C. However, relative density declined by increasing the SiC fraction at the same sintering temperature. The flexural strength of composites was best for sintering temperature of 1700°C and showed a maximum of 545 MPa for Alumina-10%SiC sintered at 1700°C. Hardness showed a remarkable increase by adding SiC and reached a pick of 22.6 GPa for Alumina-15%SiC. Fracture toughness and fracture mode of alumina and composites with 5%, 10% and 15% SiC sintered at 1700°C were also investigated. Composites were tougher than alumina and the scanning electron microscopy observations showed that fracture mode changes from intergranular for alumina to transgranular for composites. Finally X-ray diffraction analysis could not detect any chemical reactions between Al 2 O 3 and SiC particles.
Effects of Additives on Microstructure and Properties of Alumina-Silicon Carbide Nanocomposites
Journal of the American Ceramic Society, 2004
ABSTRACT Al2O3/5-vol%-SiC nanocomposites have been fabricated by using pressureless sintering with MgO and/or Y2O3 sintering aids and post-hot isostatic pressing (HIPing), which circumvents the limitations of hot pressing. Al2O3/SiC nanocomposites that have been doped with 0.1 wt% MgO and 0.1 wt% MgO + 0.1 wt% Y2O3 show an increased sintering density and a homogeneous microstructure, as well as a high fracture strength (1 GPa) after HIPing. In contrast, using Y2O3 as a dopant has a negative impact on the microstructure and the fracture strength. The results suggest that MgO, as a sintering additive, has a key role in improving the densification and controlling the microstructure of Al2O3/SiC nanocomposites.
Silicon carbide particle size effects in alumina-based nanocomposites
Acta Materialia, 1996
AhOJSiC nanocomposites with a systematic variation in their SIC particle size together with monolithic alumina were produced using conventional powder processing, polymer pyrolysis and hot-pressing. The microstructures of the materials were investigated by means of transmission and scanning electron microscopy and correlated to their mechanical properties. All nanocomposites showed a clear increase in strength over similar grain size alumina but no clear dependence on the size of the Sic nano-reinforcement. However, the fracture toughness of the nanocomposites seems to increase with the Sic particle size but with values little changed from the toughness of monolithic alumina as measured by the Vickers indentation technique. The surface and bulk flaw populations were characterised using a Hertzian indentation technique and a Griffith flaw size analysis of strength data. The investigations revealed a significant difference between the monolithic alumina and nanocomposites. The strength increase in the nanocomposites is explained by the observed decrease in both the surface and processing flaw sizes, which further decreased with decreasing Sic particle size. CopJlright 0 1996 Acta Metallurgica Inc.
Journal of The European Ceramic Society, 2007
Al 2 O 3 -SiC nanocomposites containing 3-8 vol.% SiC were prepared from fine ␣-alumina powder and a poly(allyl)carbosilane precursor of SiC by polymer infiltration of porous alumina matrix (composites IP), or by warm pressing of polymer-coated alumina powder (composites CW). The polymer was converted to SiC by careful heating of green specimens in inert atmosphere (Ar). The residual porosity was eliminated to less than 10% by pressureless sintering (PS) at temperatures between 1700 and 1850 • C. The post-sintering hot isostatic pressing (HIP) at 1700 • C eliminated the residual porosity to less than 1%, but also resulted in coarsening of the alumina matrix grains, and the inter-and intragranular SiC inclusions. The Vickers hardness of IP specimens sintered at T < 1850 • C increased by 1-10%, which is attributed to elimination of residual porosity. The hardness and indentation fracture toughness of specimens IP sintered at 1850 • C decreased after HIP by 6 and 15%, respectively. The HIP of CW composites increased their hardness and fracture toughness by approximately 10%. The maximum fracture toughness of 5.2 ± 0.2 MPa m 1/2 was measured for the materials containing 8 vol.% of SiC. A correlation was found between the fracture toughness, and the mean size and volume fraction of intergranular SiC inclusions in composites CW.
Alumina/IO wt% Sic nanocomposites were prepared by using a number of processing techniques, in order to produce d@erent microstructures while keeping a uniform distribution of the Sic particles in the alumina matrix. Basically, this study used three techniques, i. e. mechanical mixture qf powders, the use of an inorganic precursor for alumina precipitated onto Sic particles and the use of dIrerent polymeric precursors for Sic precipitated on alumina particles. Hot pressing at 1700°C was necessary to produce fully dense nanocomposites. The alumina precursor route produced the smallest matrix grain size and the Sic precursor route produced the smallest reinfbrcement particle size. Despite the d$erences in microstructure between the nanocomposites, the flexure strength remained the same, and no distinct improvement over the monolithic alumina was observed. The fracture mode, however, changed from intergranular to transgranular with the presence of the Sic particles. 0 1997 Elsevier Science Limited. All rights reserved.
Microstructure and Properties of Al2O3–SiC Nanomaterials
The relationship between densification, microstructure and mechanical properties of Silicon carbide reinforced Alumina matrix were investigated. The composites were prepared from nano-powders in an attempt to produce composites with nanostructured grains and as a result improved hardness and fracture toughness values. The composite powders were sintered using a Spark Plasma Sintering (SPS) furnace which allows for high heating and cooling rates to be implemented. For the Al 2 O 3-SiC composites it was evident that the densification of the materials containing 30% and 50% (by volume) of the reinforcing component was below 97%, whereas for the lower additions of the reinforcing components full densification was observed. The oxygen content of the starting powder was seen to strongly affect the densification behaviour of the Al 2 O 3-SiC nano-composites and is also assumed to have resulted in deterioration of the mechanical properties in the Al 2 O 3-SiC composites. The hardness values of the Al 2 O 3-SiC nano-composite materials were up to 20.7GPa, while the fracture toughness was up to 4.7MPa.m 0.5 .
International Journal of Applied Ceramic Technology, 2019
The hot pressing process of monolithic Al2O3 and Al2O3‐SiC composites with 0‐25 wt% of submicrometer silicon carbide was done in this paper. The presence of SiC particles prohibited the grain growth of the Al2O3 matrix during sintering at the temperatures of 1450°C and 1550°C for 1 h and under the pressure of 30 MPa in vacuum. The effect of SiC reinforcement on the mechanical properties of composite specimens like fracture toughness, flexural strength, and hardness was discussed. The results showed that the maximum values of fracture toughness (5.9 ± 0.5 MPa.m1/2) and hardness (20.8 ± 0.4 GPa) were obtained for the Al2O3‐5 wt% SiC composite specimens. The significant improvement in fracture toughness of composite specimens in comparison with the monolithic alumina (3.1 ± 0.4 MPa.m1/2) could be attributed to crack deflection as one of the toughening mechanisms with regard to the presence of SiC particles. In addition, the flexural strength was improved by increasing SiC value up to 2...
Journal of the Korean Ceramic Society, 2019
In this research, some mechanical properties of Al 2 O 3-based composites containing nanoSiC and nanoMgO additives, including elasticity modulus, hardness, and fracture toughness, have been evaluated. Micron-sized Al 2 O 3 powders containing 0.08 wt.% nanoMgO particles have been mixed with different volume fractions of nanoSiC particles (2.5 to 15 vol.%). Untreated samples have been sintered by using hot-press technique at temperatures of 1600 to 1750°C. The results show significant increases in the mechanical characteristics with increases in the sintering temperature and amount of nanoSiC particles, with the result that the elasticity modulus, hardness, and fracture toughness were obtained as 426 GPa, 21 GPa, and 4.5 MPa.m 1/2 , respectively.
International Journal of Applied Ceramic Technology, 2019
The hot pressing process of monolithic Al 2 O 3 and Al 2 O 3-SiC composites with 0-25 wt.% of submicron silicon carbide was done in this paper. The presence of SiC particles prohibited the grain growth of the Al 2 O 3 matrix during the sintering at the temperatures of 1450 °C and 1550 °C for 1 h and under the pressure of 30 MPa in vacuum. The effect of SiC reinforcement on the mechanical properties of composite specimens like fracture toughness, flexural strength and hardness was discussed. The results showed that the maximum values of fracture toughness (5.9 ± 0.5 MPa.m 1/2) and hardness (20.8 ± 0.4 GPa) were obtained for the Al 2 O 3-5 wt.% SiC composite specimens. The significant improvement in fracture toughness of composite specimens in comparison with the monolithic alumina (3.1 ± 0.4 MPa.m 1/2) could be attributed to crack deflection as one of the toughening mechanisms regarding to the presence of SiC particles. In addition, the flexural strength was improved by increasing SiC value up to 25 wt.% and reached 395 ± 1.4 MPa. The SEM observations verified that the increasing of flexural strength was related to the fine-grained microstructure.