Silicon carbide particle size effects in alumina-based nanocomposites

Carroll, Laura; Sternitzke, Martin; Derby, Brian

doi:10.1016/1359-6454(96)00074-2

Cited by 127 publications

(67 citation statements)

References 10 publications

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“…Even though several models for the mechanisms of nanocomposites have been proposed [10,11], such as a steep R-curve behavior model [12], residual stress model [13], and reduction in the processing defect size model [14], several researchers remain skeptical about nanocomposites [15,16]. These skepticisms result from the fact that the previously proposed strengthening and toughening mechanisms mentioned above do not provide sufficient explanations for all of the characteristics of nanocomposites that have been observed.…”

Section: Introductionmentioning

confidence: 85%

“…Several mechanical properties were also improved, such as hardness [14,20,21], wear resistance [1,5], thermal shock resistance [1], and creep resistance [1,5]. On the other hand, Niihara observed highly developed sub-grain boundaries or dislocation networks in annealed nanocomposites [1], and several researchers have observed embryonic dislocations in the matrix grains [22].…”

Section: Characteristics Of Nanocompositesmentioning

confidence: 99%

“…Several researchers have reported a moderate enhancement of fracture toughness with improved strength in nanocomposites, for instance, Niihara [1], Davidge et al [11], Carroll et al [14], Zhao et al [19], and Gao et al [20], in spite of the well-known trade-off relations between the strength and the fracture toughness of monolithic ceramics [8]. Several mechanical properties were also improved, such as hardness [14,20,21], wear resistance [1,5], thermal shock resistance [1], and creep resistance [1,5].…”

Section: Characteristics Of Nanocompositesmentioning

confidence: 99%

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Nanocomposites—a new material design concept

Choi

Araki

2005

Science and Technology of Advanced Materials

182

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Ceramic-based nanocomposites were reviewed, emphasizing the newly developed concept of material design for ceramics. First, characteristics of the nanocomposites observed by previous researchers were summarized as, significant or moderate improvement in strength, drastic change of the fracture mode from intergranular fracture of monolithic ceramics to transgranular fracture of nanocomposites, moderate enhancement of fracture toughness, improvement of other mechanical properties, and observations of dislocations. Second, several mechanisms proposed previously to explain these characteristics were reviewed. Third, our strengthening and toughening mechanisms of nanocomposites on the basis of dislocation activities were explained. In nanocomposites, the highly localized residual stresses in the matrix grains are generated by the mismatch of thermal expansion coefficients between the matrix and the dispersed particles, and the dislocations are yielded during the cooling process after sintering. These dislocations then release the tensile residual stresses intrinsically existing in the matrix grains of sintered ceramics and improve the strength of the materials. In addition, as these dislocations cannot move at room temperature the sessile dislocations in the matrix operate as nano-crack nuclei in a frontal process zone (FPZ) ahead of the crack tip when the tip of a propagating crack approaches this area. Therefore, the size of the FPZ is expanded and as a result the fracture toughness is improved. Finally, estimation of the critical FPZ size was explained in order to clarify its toughening mechanism in nanocomposites. q

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Section: Introductionmentioning

confidence: 85%

Section: Characteristics Of Nanocompositesmentioning

confidence: 99%

Section: Characteristics Of Nanocompositesmentioning

confidence: 99%

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Nanocomposites—a new material design concept

Choi

Araki

2005

Science and Technology of Advanced Materials

182

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“…(3) would be the existence of porosity in the test specimens, as indicated by the lower density in the Al 2 O 3 /5% vol. SiC nanocomposites, where r theoretical ¼ 3.951 g/cm 3 , while r experimental ¼ 3.8970.02 g/cm 3 [24]. The lower the density, the higher the porosity, and the lower the fracture strength [25].…”

Section: Verification and Discussionmentioning

confidence: 99%

“…3 shows a comparison between the experimental data and model prediction with different nanoparticle sizes. The following data given by Wu et al [10] and Carroll et al [24] are used: Experimental data (before annealing)…”

Section: Verification and Discussionmentioning

confidence: 99%

Prediction of fracture strength in Al₂O₃/SiC_pceramic matrix nanocomposites

Zhang

Chen²

2007

Science and Technology of Advanced Materials

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Based primarily on a recent publication [S.M. Choi, H. Awaji, Sci. Tech. Adv. Mater. 6 (2005) 2-10.], where the dislocations around the nano-sized particles in the intra-granular type of ceramic matrix nanocomposites (CMNCs) were modeled, dislocation activities in Al 2 O 3 /SiC p CMNCs were discussed in relation to the processing conditions. The dislocations around the nano-sized particles, caused by the thermal mismatch between the ceramic matrix and nano-sized particles, were assumed to hold out the effect of Orowan-like strengthening, although the conventional Owowan loops induced by the movement of dislocations were unlikely in the ceramic matrix at room temperature. A model involving the yield strength of metal matrix nanocomposites (MMNCs), where the Owowan strengthening effect was taken into consideration, was thus modified and extended to predict the fracture strength of the intra-granular type of CMNCs without and with annealing. On the basis of the characteristics of dislocations in the CMNCs, the load-bearing effect and Orowan-like strengthening were considered before annealing, while the load-bearing effect and enhanced dislocation density strengthening were taken into account after annealing. The model prediction was found to be in agreement with the experimental data of Al 2 O 3 /SiC p nanocomposites reported in the literature. r

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