Characterization of iron(III) oxide/hydroxide nanostructured materials produced by sol–gel technology based on the Fe(NO3)3·9H2O–C2H5OH–CH3CHCH2O system

Effect of additives on the properties of silica based aerogels synthesized from methyltrimethoxysilane (MTMS)

“…After aging, the samples were dried by a continuous Low Temperature Supercritical Fluids Drying (LTSCD) stage using CO 2 as supercritical solvent, with a layout/strategy similar to an older system already applied by the authors in an earlier work [12]. The new system was designed and built by Paralab (Portugal) and consists of several parts, namely: (i) the liquid CO 2 feeding part, with a CO 2 bottle and a cooling bath; (ii) two pumps for the pressurization of liquid CO 2 and organic solvents; (iii) a 50 cm 3 stainless steel extraction cell to contain the sample; (iv) an oven, to increase the temperature above the critical temperature of CO 2 (31 • C); (v) a flow meter and several regulating valves and pressure transducers, for pressure and flow measuring/regulation; (vi) a back-pressure regulator, to stabilize pressure; (vii) an acquisition and automatic control system for registry and following/setting the pressurization/depressurization stages and flow conditions.…”

Controlled phase formation of nanocrystalline iron oxides/hydroxides in solution – An insight on the phase transformation mechanisms

“…Transmittance bands between 400 and 700 cm À1 are characteristic of FeeO bonds [28]. In particular, sample S3 presents a broad peak at 636 cm À1 , and samples S5 and S6 a broad double peak with minima at 633 and 581 cm À1 , for sample S5, and at 633 and 577 cm À1 , for sample S6.…”

“…They are attributed to the absorption of radiation by CO 2 existing in the analysis atmosphere [27]. Sample S3 presents two sharp peaks around 800 and 900 cm À1 attributed to the bending vibration of the group eOH … O in iron oxyhydroxides [28]. This spectral feature is typical of goethite [1].…”

Biopolymers - Carbon Sources for Composite Materials Used as Adsorbents for As (V)

“…During this process, the formation of iron water complexes is followed by their deprotonation. Simultaneously are formed iron hydroxyl aqua complexes which represent the intermediates which may participate at condensation reactions leading at Fe -O -Fe bonds [10].…”