Please cite this article in press as: B. Matovi ´ c, et al., Monolithic nanocrystalline SiC ceramics, J Eur Ceram Soc (2015), http://dx.doi.org/10.1016/j.jeurceramsoc.2015.10.031 ARTICLE IN PRESS G Model JECS-10337; No. of Pages 6 Journal of the European Ceramic Society xxx (2015) xxx–xxx Contents lists available at www.sciencedirect.com Journal of the European Ceramic Society jo ur nal home p ag e: www. elsevier.com/locate/jeurceramsoc Monolithic nanocrystalline SiC ceramics Branko Matovi ´ c a,∗ , Dusan Buˇ cevac a , Vladimir Urbanovi ´ c b , Nadezda Stankovi ´ c a,c , Nina Daneu c , Tatjana Volkov-Husovi ´ c d , Biljana Babic a a Institute of Nuclear Sciences “Vinca”, Materials Science Laboratory, University Belgrade, Serbia b Scientific-Practical and Materials Research Center, NAS of Belarus, Minsk, Belarus c Department for Nanostructured Materials, Jozef Stefan Institute, Ljubljana, Slovenia d Faculty of Technology and Metallurgy, Belgrade University, Serbia a r t i c l e i n f o Article history: Received 29 July 2015 Received in revised form 9 October 2015 Accepted 21 October 2015 Available online xxx Keywords: SiC High-pressure densification Balk nanomaterial Microstructure Mechanical properties a b s t r a c t Additive-free -SiC nanopowders were densified by using high-pressure “anvil-type with hollows” appa- ratus at the pressure of 4 GPa in the range of 1500–1900 ◦ C. The starting powder with average particle size of 10 nm was synthesized by a sol–gel process. Crystallite size and lattice parameters of the samples have been studied at room temperature by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the size of the crystallites gradually increases from 16 to 51 nm with increas- ing sintering temperature (1500 to 1900 ◦ C). Fully densified sample (>99%) was obtained at a sintering temperature of 1900 ◦ C for 60 s. This sample exhibits nano-hardness and Young’s modulus of elasticity of 35 GPa and 450 GPa, respectively. Modified vibratory cavitation test method was used for laboratory testing of the cavitation resistance. A very low erosion level with mass loss 0.1% after 10 h was exhibited during the cavitation test. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Ceramic carbides such as silicon carbide (SiC) possess an attrac- tive combination of thermo-mechanical and chemical properties due to their high covalency, making them one of the most use- ful materials for high temperature structural applications. SiC has low thermal expansion coefficient, good thermal conductivity and high fracture strength at low and high temperatures. Its good ther- mal and chemical stability, excellent oxidation, corrosion and wear resistance and relatively good resistance to high neutron irradia- tion make SiC promising material for harsh environments [1–5]. It is believed that these properties can be exploited at even higher temperature, i.e., above 2000 ◦ C, if SiC is protected by ultra-high temperature ceramics (UHTCs) [6,7]. Materials with grain size in the nanoscale show improved hardness and fracture strength, there- fore there is interest in obtaining nanstructured bulk SiC ceramic [8,9]. On the other hand, the covalent nature of the Si C bond and low self-diffusion coefficients require very high sintering tempera- tures and pressures [10]. Sintering of SiC with boron (B) and carbon (C) additives is regarded to take place by solid-state diffusion ∗ Corresponding author. Tel.: +381 648505080; fax: +381 113408224. E-mail address: mato@vinca.rs (B. Matovi ´ c). process. This approach requires sintering temperatures of more than 2100 ◦ C and very often results in exaggerated grain growth, which is detrimental to the mechanical properties [11]. Liquid phase sintering allows densification of SiC at temperatures about 1900 ◦ C, which is much lower compared to the conventional solid- state sintering [10]. However, there are two drawbacks associated with sintering of SiC in the presence liquid-phase forming oxide additives like yttria and other rare-earth oxides, alumina or AlN. First, the reaction between SiC and the oxide additives results in weight loss due to the formation of gaseous products. Sec- ond, the final microstructure consists of SiC grains surrounded by secondary crystalline phases and amorphous grain boundary layers and these grain boundary phases start to soften already at lower temperatures [12]. Depending on the composition and the amount of grain boundary phases, various processes, such as diffusion, creep, slow crack growth, oxidation and corrosion, may occur at elevated temperatures with the consequence that a new defect population is generated, which determines the fail- ure behavior and limits the lifetime. The extent to which these processes occur is mainly influenced by the softening point and viscosity of the amorphous grain boundary phase. This fact clearly limits the possible applications under extreme conditions. Fully dense nanostructured SiC ceramics with a grain size of 40 nm were prepeared by two-step sintering using CaO, Al 2 O 3 and Y 2 O 3 powders. In spite of good results, this processing requires http://dx.doi.org/10.1016/j.jeurceramsoc.2015.10.031 0955-2219/© 2015 Elsevier Ltd. All rights reserved.