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Journal of Ceramic Science and Technology 2/2012
Vol. 3, No. 2 · July 2012
Formation, Decomposition and Thermal Stability of Al2TiO5 Ceramics
I.J. Kim, L.G. Gauckler
Pages 49-60 · DOI: 10.4416/JCST2011-00049
The thermal instability of Al2TiO5 can be mitigated using solid solutions of MgO, Fe2O3, TiO2, and ZrO2 in the Al2TiO5 lattice or grain boundary solutions with additives such as SiO2, ZrO2, ZrTiO4, or mullite, most of which do not form solid solutions with Al2TiO5 but rather restrain the tendency of Al2TiO5 toward decomposition. The additives SiO2 and ZrO2 do not have a significant effect on the thermal stability of Al2TiO5, even after long annealing at the critical temperature of 1100 °C. Mullite retarded decomposition and increased thermal stability between 750 and 1300 °C. Literature regard …
Laser Synthesis of Al2TiO5 Ceramics from Al2O3-TiO2 Powder Mixtures
M. Vlasova, B. Sosa Coeto, M. Kakazey, P. A. Marquez Aguilar, , A. Escobar Martinez, V. Stetsenko, A. Bykov
Pages 61-68 · DOI: 10.4416/JCST2012-00005
The phase formation process in the zone of laser irradiation of Al2O3-TiO2 compacts with different contents of components has been investigated with XRD, electron microscopy, and atomic force microscopy methods. The distinctive feature of laser synthesis is the simultaneous formation of α- and β-Al2TiO5, which is caused by the non-uniform heating of the material in the irradiation zone. The motion of the eutectic melt under the action of hydrodynamic forces is the motive force for texturing of precipitating crystalline phases during fast cooling. The degree of texturing of Al2O3 and Al2TiO5 cr …
Degradation of Sealing Glasses for SOFC under Electrical Load and Dual Atmosphere
A. Rost, J. Schilm, M. Kusnezoff, A. Michaelis
Pages 69-80 · DOI: 10.4416/JCST2012-00002
For reliable operation of planar solid oxide fuel cells (SOFC), long-term stability of the sealing materials, including gas tightness and bonding to the joined materials, is essential. Failures induced by thermal cycling, slight stack deformation or degradation of the sealing material can lead to leakages and undesired combustion of fuel gas, causing hot spots and severe damage of stacks or whole systems. Suitable partially crystallizing SOFC sealing glasses are presented and characterized in terms of their softening properties, viscosity, thermal expansion and crystallization behaviour. Howev …
Robocasting of aqueous colloidal α-Al2O3 gels for manufacturing cellular ceramics with periodical lattice truss structures was investigated. Coagulation of gels loaded with 48 vol% α-Al2O3 was induced by adding CH3COONH4. The gels exhibit shear-thinning behavior, shear elastic moduli ranging from 6.7 to 390 kPa and yield-stresses from 25 to 570 Pa. Continuous filaments with a diameter of 0.5 mm were extruded with a deposition speed of up to 35 mm/s on a high-precision six-axis robotic system equipped with a single-screw micro-extruder. The lattice structures consist of alternating layers forme …
The temperature dependence of the thermal oxidation of sintered silicon carbide (SiC) used for diesel particulate filter walls (DPF) is investigated. Silicon carbide samples are heated at temperatures between 770 K and 1470 K for different annealing times to study the effect of both the temperature and the duration on the oxidation kinetics. The thickness and composition of the oxide layers are characterized by means of XPS and RBS. Silicon oxycarbides (SiCxOy) are first formed and then silicon dioxide (SiO2) appears above 770 K. Different types of SiO2 layers can be identified. The compounds …
Effects of Copper Oxide Content in AgCuO Braze Alloy on Microstructure and Mechanical Properties of Reactive-Air-Brazed Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF)
A. Kaletsch, A. Bezold, E.M. Pfaff, C. Broeckmann
Pages 95-104 · DOI: 10.4416/JCST2012-00001
For the joining of ceramic materials as well as ceramics and metals, reactive air brazing (RAB) is an important improvement compared to existing brazing technologies. In contrast to commonly used active brazing processes, no vacuum atmosphere is needed in RAB. This is a crucial factor for certain materials, such as some functional ceramics, which cannot be brazed in vacuum easily because they are thermodynamically unstable in atmospheres of low oxygen partial pressure. Sometimes for those materials, RAB is the only possibility to obtain a gas-tight sealing, which works safely up to high temper …
