Mechanochemical synthesis of complex oxides

Mechanochemical Synthesis of Fe‐Doped Apatite‐Type Lanthanum Silicates

“…This mechanism seems also to be suitable to explain the results obtained by Rodriguez-Reyna et al [11,12] However, it is well known that MA is a complex process, with different experimental parameters such as raw materials, type of mill, rotation speed, ball-to-powder mass ratio, milling container, milling time, and type and size of the grinding media, determining final products of the activation and a mechanism of their formation. [13,14] Thus, in contrast to our and Rodriguez-Reyna et al results, data on the milling of mixtures of La 2 O 3 and SiO 2 to prepare silicates with an apatite structure obtained by Tzvetkov and Minkova include a complete amorphization of the reaction mixture after milling for 3 h and cannot be explained by the cluster-topotactic mechanism. [15] This paper is devoted to the study of the synthesis of Fe-doped ATLS by using mechanochemical activation of mixtures containing Fe 2 O 3 , FeO(OH), Fe(NO 3 ) 3 /SiO 2 , or Fe(HCOO) 3 as the iron parent compound.…”

“…The presence of LaFeO 3 perovskite seems to be caused by its formation being kinetically more preferable than Fe incorporation into the apatite during the milling of the SiO 2 -La 2 O 3 -FeO(OH) mixture in contrast to SiO 2 -La 2 O 3 -Al(OH) 3 when there is some LaAlO 3 perovskite observed in the mechanically activated products mainly due to limited solubility of Al in the apatite. [12,13] The primary incorporation of Fe into the apatite occurs only after calcination of the mechanically activated products at 1200°C, though some amount of LaFeO 3 still remains. According to microscopy data, the crystalline apatite nanoparticles of 10-70 nm form micron-sized agglomerates.…”

“…This band is rather typical for an amorphous silicate than for the crystalline apatite. [12,13,16] Besides, only one broad band at ca. 509 cm -1 is observed in the region of Si-O deformation vibrations.…”

“…[13] In so doing, the chemical interaction between solids is greatly accelerated in comparison with thermally activated reactions due to facilitating mass transfer that occurs by means of diffusion on surface of particles and the bulk of quite small defect particles of the components. [14] A number of studies are devoted to the mechanism of component interaction in the course of MA.…”

Mechanochemistry and the Other Branches of Chemistry: Similarities and Differences

“…The simple geometry also lends itself to theoretical investigations [18] and computer modeling [19]. The ing occurs across interfaces [25] or reactant particles rub against each other and either new compound grains rollers form [26] or direct mixing takes place at the interface [27].…”