Fusion Engineering and Design 89 (2014) 2738–2742 Contents lists available at ScienceDirect Fusion Engineering and Design jo u r n al homep age: www.elsevier.com/locate/fusengdes Thermogravimetric study of the kinetics of lithium titanate reduction by hydrogen Sagar Sonak a,∗ , R. Rakesh b , Uttam Jain a , Abhishek Mukherjee a , Sanjay Kumar a , Nagaiyar Krishnamurthy a a Fusion Reactor Materials Section, Bhabha Atomic Research Centre Mumbai 400085, India b Metallic Fuel Division, Bhabha Atomic Research Centre, Mumbai 400085, India h i g h l i g h t s • Li 2 TiO 3 powder is synthesized by the gel combustion route. • Activation energy of reduction of Li 2 TiO 3 by H 2 found out to be 27.45 kJ/mol H 2 . • Non-stoichiometric phase of Li 2 TiO 3 is formed in hydrogen atmosphere. • One-dimensional diffusion appears to be the most probable mechanism of reduction. a r t i c l e i n f o Article history: Received 13 January 2014 Received in revised form 14 July 2014 Accepted 22 July 2014 Available online 18 August 2014 Keywords: Lithium titanate Hydrogen reduction Kinetics Activation energy a b s t r a c t The lithium titanate powder was synthesized by gel-combustion route. The mechanism and the kinetics of hydrogen interaction with lithium titanate powder were studied using non-isothermal thermogravi- metric technique. Lithium titanate underwent reduction in hydrogen atmosphere which led to the formation of oxygen deficient non-stoichiometric compound in lithium titanate. One-dimensional diffu- sion appeared to be the most probable reaction mechanism. The activation energy for reduction of lithium titanate under hydrogen atmosphere was found to be 27.4 kJ/mol/K. Structural changes after hydrogen reduction in lithium titanate were observed in X-ray diffraction analysis. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Lithium based ceramics such as LiAlO 2 , Li 4 SiO 4 , Li 2 ZrO 3 , Li 2 TiO 3 in the form of ceramic pebbles are the candidate tritium breeding materials in upcoming International Thermonuclear Experimental Reactor (ITER) [1–4]. Among various tritium breeding materials, lithium titanate in the form of ceramic pebbles is the most promis- ing candidate material because of its high thermal conductivity, low moisture absorption, resistance to high neutron flux and better tri- tium release properties [5]. The tritium will be generated in the test blanket module during the reactor operation by (n, ˛) reaction with lithium [6]. The tritium thus released is likely to interact with the lithium titanate and cause structural, compositional and functional changes [7]. Therefore tritium interaction with lithium titanate is an important aspect to be investigated. ∗ Corresponding author. Tel.: +91 22 2559 2422. E-mail addresses: sagarsonak@gmail.com, sonaks@barc.gov.in (S. Sonak). Tritium being the isotope of hydrogen behaves more or less sim- ilar to that of hydrogen and hence the studies on the mechanism of hydrogen interaction with solid Li 2 TiO 3 are equally valid for tritium as well. It has been reported earlier that in case of Li 2 TiO 3 pebbles exposed to hydrogen atmosphere, multiple micro cracks were gen- erated on the surface. The reduction in the theoretical density was also observed [7–9]. The structural changes have been explained on the basis of reduction Ti 4+ to Ti 3+ which led to the formation of oxygen deficient phase: Li 2 TiO 3-x [10]. However, the knowledge on the mechanism and kinetics of hydrogen reduction of Li 2 TiO 3 is very limited. Evaluation of kinetic parameters and identification of reaction mechanism will help to understand long term effects of hydrogen on lithium titanate pebbles. In the present study, the mechanism and kinetics of hydro- gen interaction with Li 2 TiO 3 powder has been investigated. The lithium titanate powder used in the present investigation was synthesized by gel-combustion technique. The kinetics of the reac- tion of synthesized lithium titanate with hydrogen is studied by non-isothermal thermo-gravimetric technique at different heating http://dx.doi.org/10.1016/j.fusengdes.2014.07.017 0920-3796/© 2014 Elsevier B.V. All rights reserved.