Synthesis and characterization of carboxylate - FeOOH nanoparticles (ferroxanes) and ferroxane-derived ceramics

A new environmentally benign process for producing Fe-based ceramics of variable properties is presented. We have demonstrated that the reaction between lepidocrocite and acetic acid (=AA) in water results in the formation of carboxylate-FeOOH nanoparticles called ferroxane-AA analogous to aluminum-based alumoxanes. The structure of the ferroxane particles consists of an FeOOH core part with the structure of the lepidocrocite (γ-FeOOH), coated with AA. FTIR and EXAFS at the Fe K edge indicates that AA is chemically adsorbed onto the FeOOH core part. The size of these ferroxanes is 0.3 μm composed of nanodomains of 20-30 Å with a γ-FeOOH structure. Thermolysis of the ferroxane-AA yields Fe oxide ceramics. The specific surface area of 134 m2/g does not increase from the initial mineral to the ferroxane while the pore size distribution becomes monodisperse and the diameter of the pore size decreases from 55 to 12 and 13 nm after the firing of the ferroxanes. Moreover, the ferroxane-AA has been successfully doped with metal to form a precursor for Fe mixed-metal oxides. Upon thermolysis the products evolve to homogeneous Fe-metal oxides. A low firing temperature for conversion to ceramic as well as the use of environmentally benign feedstock suggest that the process for creating ferroxane-derived ceramics should have minimal environmental impacts.

Duke Scholars

Author Mark Wiesner Civil and Environmental Engineering