Role of acid-base interactions in synthesis of cordierite from talc and sillimanite group minerals

It has been found that the mechanical activation of mixtures of sillimanite group minerals with talc and silica additives in grinding-activating devices with periodic and flow action provides significant acceleration of their interaction with formation of cordierite at the subsequent high-temperature treatment. It is shown that the output of cordierite depends on nature of mineral: in mixture with a sillimanite it is considerably higher, than with an andalusite and kyanite, while the rate of mullitization of these minerals has opposite character. It means that the formation of mullite during heat treatment is not a limiting step in synthesis of cordierite. It is shown that the rate of reaction is determined by the difference in the acid-base properties of these minerals, which depend on the coordination of aluminum cations by oxygen ions, different for each of the modifications

Conducting materials based on nanodispersed titanium monoxide

The possibility of obtaining the TiO compound during mechanical activation of rutile and titanium in a planetary mill was studied depending on ball size and the activation time. The initial substances, TiO2 (rutile) and Ti (metal), were shown to change into TiO almost completely during grinding as early as after ten minutes. In this case the cubic modification of TiO formed, with the lattice parameter a=4.185(7) Å and particles of 1-3 μm, which consisted of units about 10 nm in size. The other subject of our research was the dependence of the conductivity of the products on the conditions under which they were moulded and sintered under argon. The conductivity of the samples was in the range 300 to 600 S cm-1. Their chemical resistance equaled that of Ti4O7 samples

Low-temperature synthesis of ZrO2-8 mol.% Y2O3 nanopowder with high sinterability

The possibility of low-temperature synthesis of yttrium-stabilized (8 mol.%) zirconium dioxide nanopowder from a mixture of hydrated zirconium oxynitrate and yttrium carbonate mechanically activated in a continuous-type mill is examined. It is demonstrated that the powder formed at as low temperature as 600°C and then subjected to a disaggregation procedure can be easily compacted by dry pressing and achieves nearly full density on sintering

Synthesis of Ti4O7 magneli phase using mechanical activation

The processes of phase formation by heating of a mechanically activated mixture of Ti + TiO2 in different atmospheres (air, argon, hydrogen) were investigated. The Ti4O7 compound was obtained by annealing of the mixture in hydrogen atmosphere in the interval of temperatures of 900-1200ºC, the Ti2O3 oxide formed at 800ºC in argon atmosphere and TiO2 formed in air atmosphere Conductivity and morphology of Ti4O7 samples obtained in hydrogen were studied

Ceramic electrodes based on Magneli phases of titanium oxides

Monophase and polyphase ceramic materials based on Magneli phases of titanium oxides of composition Ti3O5, Ti4O7, Ti5O9, and Ti6O11 were synthesized. The materials were obtained by mechanical activation of rutile with titanium and additives of niobium, vanadium, and iron, with subsequent sintering both in reductive atmosphere (hydrogen) and in neutral atmosphere (argon) in the temperature interval of 1060-1080°C. The dependences of the potentials of the obtained ceramic samples on time and composition during anodic polarization at current density of 5A/dm2 in a 1M solution of sulfuric acid were investigated. We developed a technique for manufacturing anodes in the form of hollow cylinders 60 mm in diameter with a wall 5 mm thick, and flat discs more than 60 mm in diameter