CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 40 (2014) 7235–7244 Low temperature, spark plasma sintering behavior of zirconia added by a novel type of alumina nanofibers Nikolai Voltsihhin a,n , Miguel Rodríguez b , Irina Hussainova a , Marina Aghayan a a Department of Materials Engineering, Tallinn University of Technology, Ehitajate 5, 19086 Tallinn, Estonia b Instituto de Ceramica y Vidrio (CSIC), Campus Cantoblanco, 28049 Madrid, Spain Received 20 August 2013; received in revised form 27 November 2013; accepted 16 December 2013 Available online 27 December 2013 Abstract A novel type of alumina nanofibers has been used for fabrication of the alumina toughened zirconia composites and the effect of different sintering techniques on the characteristics of the material was studied. ZrO 2 –10 vol% Al 2 O 3 composite was consolidated by spark plasma sintering (SPS) in a temperature range from 1000 1C to 1200 1C and by pressureless sintering in air at 1300 1C. Dilatometry sintering of the said composite material was performed in order to assess its sinterability. Al 2 O 3 used in fabrication of the composite is a novel type of alumina nanofibers and thus the effect of different sintering techniques on the formation of the material was investigated. Microstructural analysis has revealed that Al 2 O 3 nanofibers partially retained their fiber states after being sintered at 1100 1C under SPS conditions while some of the fibers turned into rounded inclusions. Specimens produced by the SPS routine at temperatures of 1100 1C and 1200 1C were consolidated 93% of theoretical density while the same material sintered with the conventional PM method in air had a densification degree of 74%. & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Spark plasma sintering; Ceramic composite; Microstructure; Fibers 1. Introduction Zirconia toughened alumina (ZTA) is one of the most known and widely used ceramic composite materials (CMC) yet produced. This is a material based on alumina which contains different amounts of zirconia added to it as a sintering aid, toughening agent or as both [1–3]. It is also called as the alumina–zirconia composite and is designated as AZ. In the previous decade, a considerable amount of work has been done on the alumina zirconia ceramic composite system with a particular emphasis on improving the mechanical properties, utilizing the recognized toughening mechanisms [4]. Noted for their mechanical properties, AZ composites are commonly used in structural applications, such as cutting tools, grinding media and in many medical applications. Additionally, AZ composites feature high strength, fracture toughness, elasticity, hardness, and wear resistance, and one of the main properties of this ceramic is biocompatibility. Usually AZ composites contain 80–95% of alumina and 5– 20% zirconia, and this material is called ZTA. However, there are cases where zirconia is used as the main phase and alumina is a doping additive for increasing properties [5]. In this case, the composite is called alumina toughened zirconia (ATZ). It seems that so much is already done and those composites are depleted for scientific studies. However, using new approaches for well-known materials compositions is always of a scientific interest, whether the approach is a new production technique or an improved type of the same constituent material or combination of both. There are some research already done with this family of materials reinforced by whiskers [6,7]. In order to deepen the understanding of the movement of siliceous phase in YSZ compacts with alumina single crystal rods and facilitate the improvement of grain-boundary conductivity in SOFC elec- trolytes Knibbe et al. experimented and discussed the mechanism that alumina plays on the sintering behavior of zirconia. www.elsevier.com/locate/ceramint 0272-8842/$ - see front matter & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. http://dx.doi.org/10.1016/j.ceramint.2013.12.063 n Corresponding author. Mobile: +372 58451639. E-mail address: nikolai.voltsihhin@ttu.ee (N. Voltsihhin).