S. Begin-Colin

Influence of the nature of milling media on phase transformations induced by grinding in some oxides

Abstract Polymorphic transformations induced by dry ball milling in an argon atmosphere have been investigated in various oxides (TiO2, SnO2, Y2O3, WO3) by X-ray diffraction, Mossbauer spectroscopy and transmission electron microscopy (TEM). The transformations have been found to depend on the nature of the milling media, particularly when reduction reactions take place between grinding tools and oxide particles. When ground with steel tools, cubic yttria is transformed into a monoclinic modification as reported in the literature, while tin oxide is reduced. When ground with zirconia tools, cubic yttria with a bixbyite type structure is transformed into cubic yttria with a fluorite type structure, while monoclinic tungsten oxide is transformed into a cubic oxide with an ReO3 type structure. Plausible structural explanations are proposed. In all cases, nanometre-sized domains have been observed by TEM even after grinding times as short as some minutes.

Polymorphic transformations of titania induced by ball milling

Abstract The high-pressure modification of TiO2 with an α-PbO2-type structure is formed transiently during room-temperature grinding of anatase. Rutile is the only phase present after prolonged ball milling. These experimental results are at variance with reports of a direct transformation of anatase into rutile by room-temperature grinding.

Kinetics of formation of nanocrystalline TiO2 II by high energy ball-milling of anatase TiO2

Abstract Ball-milling is a way of inducing phase transformations, chemical reactions and changes in the reactivity of solids. The high pressure and high temperature phase of TiO2 : TiO2 II is formed transiently during room-temperature grinding of anatase TiO2-Rutile is the only phase present after prolonged ball milling. The influences of physical and of chemical processing conditions on the kinetics of phase transformations are considered.

119Sn Mössbauer spectroscopy in nanocrystalline aluminat-in composites synthesized by direct grinding and reactive ball milling

Alumina-tin nanocomposites have been synthesized by direct grinding of α-Al2O3-β-Sn powder mixtures, as well as by reactive milling of Al-SnO2 mixtures. According to the preparation method used, the composites differ from one another mainly in the amount of a disordered SnOx (x≈1.1) phase and in the structural characteristics of alumina.