Abstract:
For more than 40 decades, research has been widespread in the field of increasing the fracture toughness (KIc) of ceramic materials. Since carbon nanotubes (CNT) were announced in 1991, several studies have been published showing the potential of these nanomaterials in improving the fracture toughness of ceramic materials, mainly alumina. However, there is several controversies in the literature regarding the values of KIc for Al2O3/CNT composite. The divergent results arise from several variables involved in the processing of this composite, such as: the dispersion process of carbon nanotube in the ceramic matrix, the type of pressing of the green compact (uniaxial, cold and hot isostatic), the sintering method (spark plasma sintering, hot pressing, pressureless, microwave-assisted sintering), the characteristics of the raw materials (particle size, diameter and length of CNT, surface area, single- or multi-walled nanotubes) and the experimental technique used for measuring KIc: Vickers indentation fracture (VIF) crack length and single-edge notched beam (SENB). The objective of this review was to select works with some variables such as: sintering only by SPS, multiwalled nanotubes, fine alumina (30 nm to 500 nm), and indirect indentation method (VIF) for measuring KIc in which the Anstis and Evans & Charles equations were used. Even with the attempt to isolate certain variables, comparing results among them was not simple. There is variation in KIc results even for pure alumina (2.32 MPam1/2 to 4.3 MPam1/2), the same happening with Al2O3/CNT composites. KIc values, for example, for composites with the same CNT content (1 wt %) ranged from 3.77 MPam1/2 to 7 MPam1/2. Despite the differences, it was possible to verify that there is an increase in the fracture toughness of the nanotube/alumina composite in relation to pure alumina.
Referência:
FREDERICCI, Catia; PRADA, Ivan Mauricio Daza. The effect of nanotube on the fracture toughness of alumina composite; a review. In: OLIVEIRA, Aline Mara; GUIMARÃES, Osvaldo Sena. Engenharia, Gestão e Inovação. Belo Horizonte: Ed.Poisson, 2024. v.13, Cap.2, p.14-25.
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