MORPHOLOGICAL AND CHEMICAL -PHYSICAL CHARACTERIZATION OF FE DOPED SYNTHETIC CHRYSOTILE NANO-CRYSTALS

Chrysotile accounts for approximately 95% of manufactured asbestos world production and it is now well known that it may induce fibrogenesis and carcinogenesis of the respiratory system not only for the asbestiform nature of its fibres, but for its chemical and structural characteristics. The presence in mineral chrysotile of foreign elements and structural disorder affect not only their growth patterns, morphology, structure, shape, stiffness, strength, fracture characteristics, dissolution mechanisms, kinetics and surface activity, but also the biological-mineral system interaction. The toxicity and pathogenicity of chrysotile is almost certainly dependent on a combination of mechanical-dimensional and chemical properties of fibres.Stoichiometric chrysotile single nano-crystals have been recently synthesized as a unique phase with definite structure, morphology and chemical composition to be used as a reference sample to investigate the chemical, physical and biological properties of chrysotile fibers.In this work we report the morphological, structural and chemical-physical modifications induced in synthetic stoichiometric chrysotile nanocrystals by the Fe doping extent. Fe doped synthetic chrysotile nano-crystals have been obtained in the range from Fe 0.29 wt. % up to 1.37 wt. %. A partial Fe replacement for Si and Mg has been observed through the modification of FTIR absorption bands. FTIR spectroscopic, X-ray diffraction and thermogravimetric analyses provide evidence for Fe inclusion into the chrysotile crystal structure in both octahedral and tetrahedral sites. The morphological analysis (SEM, TEM and AFM) has revealed that the Fe doping affects on the stoichiometric chrysotile crystal morphology inducing a flattening of the curved brucite-like layers and affects the aggregation of the single chrysotile nanocrystals. The results obtained on synthetic chrysotile nanocrystals which can be prepared with controlled morphology and chemical-physical properties as a function of the Fe doping extent, appear interesting also in the light of the possibility of synthetic chrysotile fibres to represent an alternative to carbon nanotubes for manufacture new quantum wires.