Design of composite porous cermets synthesized by hydrothermal treatment of CrAl powder followed by calcination Serguei Tikhov • Vladimir Usoltsev • Aleksey Salanov • Sergey Tsybulya • Yurii Chesalov • Galina Kustova • Vladislav Sadykov • Galina Golubkova • Oleg Lomovskii Received: 30 June 2009 / Accepted: 13 February 2010 / Published online: 4 March 2010 Ó Springer Science+Business Media, LLC 2010 Abstract The microstructure of the porous Cr–Al metal– oxide cermet was studied by means of XRD, SEM, EDX as well as IR and Raman spectroscopy. This cermet was synthesized by mechanical alloying of Cr–Al powders in an AGO-2 planetary ball mill followed by hydrothermal treatment in a special stainless steel die and calcination in air. As a result, a highly porous monolith comprised of metal-like particles randomly distributed in the oxide matrix (Cr 2 O 3 and Al 2 O 3 ) was formed. Two types of the composite cores were found in cermets. The first one consisted of chromium phase containing nanoparticles sized from 50 to 140 nm and Al-enriched phase at the interfaces. The second one consisted of new chromium oxide phases with hexagonal Cr 2 N-like and fcc CrN-like structures probably with Cr 2 O and CrO stoichiometry. These new phases were stabilized within aggregates of the nanocomposite particles containing inclusions of alumina. The relations between different preparation stages and the cermet microstructure are discussed. Introduction Oxide matrix cermets are used in various sectors of industry due to their thermomechanical and dielectric properties [1]. Highly porous cermets prepared from powder CrAl alloys are promising materials for catalyst supports, membranes and filter materials. Synthesis of cermets includes a number of unusual steps. First, powder alloys were prepared by high-energy mechanical alloying of aluminium and chromium mixture under air. Mechanical treatment provide interaction between chromium and alu- minium eventually leading to formation of amorphous Cr 4 Al and Cr 2 Al phases with alloying time increasing [2]. Then, powdered alloys were partially oxidized under hydrothermal conditions. Strong porous monoliths were formed after calcination in air. In general, thermal treat- ment conditions used for synthesis of cermets are much milder than are essential for porometals preparation by hot pressing and high-temperature sintering [1]. Cermets have developed macroporous structure with pore sizes from 1 to 100 lm. However, unlike porometals that have similar macroporous structure, cermets additionally have devel- oped mesoporous structure located in their oxide compo- nent. Furthermore, the metal particles are evenly distributed in this mesoporous matrix. So, the contacts between particles of the porous materials are oxide-like rather than metal-like. Their mechanical, thermo-physical and textural properties are largely determined by the ratio between ceramic and metal components, requiring addi- tional studies. The textural and catalytic properties of cermets based on powder CrAl alloys prepared by hydrothermal treat- ment followed by calcination were described earlier [3]. Meanwhile, problems of the ceramic component type in cermet, quantitative relations between ceramic and metal S. Tikhov (&)  V. Usoltsev  A. Salanov  S. Tsybulya  Y. Chesalov  G. Kustova  V. Sadykov Boreskov Institute of Catalysis SB RAS, Lavrentieva Str., 5, Novosibirsk, Russia 630090 e-mail: tikhov@catalysis.ru S. Tsybulya  V. Sadykov  O. Lomovskii Novosibirsk State University, Pirogova Str., 2, Novosibirsk, Russia 630090 G. Golubkova  O. Lomovskii Institute of Solid State Chemistry and Mechanochemistry SB RAS, Kutateladze Str., 18, Novosibirsk, Russia 630128 123 J Mater Sci (2010) 45:3160–3168 DOI 10.1007/s10853-010-4322-x