Hydrolysis Of FeCl3 Solutions Research Articles

Morphology control of rutile TiO2 with tunable bandgap by preformed β-FeOOH nanoparticles

Rutile TiO2 are widely used for applications of coatings, cosmetics, photoelectric devices and so on. However, effective control of well-defined morphology, size and composition of rutile TiO2 nanoparticles from agglomeration has always been a challenge. A new synthesis strategy was proposed to prepare rutile TiO2 with controllable morphology varied from flower-like structures to single-separated nanorods. The β-FeOOH nanoparticles were generated by the hydrolysis of FeCl3 solution and could prevent the aggregation of TiO2 nanocrystals at early stages of the reaction; thus, could control the morphology of rutile nanoparticles. The morphology of rutile TiO2 nanoparticles could be controllably regulated from flower-like structures to individually separated nanorods. Meanwhile, the preformed β-FeOOH also played a role of dopant. Fe ions were substitutionally doped into the bulk lattice of TiO2 nanocrystals and reduced the bandgap, which extended the solar radiation absorption range of rutile TiO2. The prepared TiO2 may be suitable for novel UV-blue light shielding agents and many other applications in photoelectric devices, photocatalysis, and so on due to its small size, unprecedented discrete rod-like structure and unique UV–vis light permeability.

THE EFFECT OF SODIUM DODECYL SULPHATE ON THE FORCED HYDROLYSIS OF FeCl3 SOLUTIONS

Precipitations by the forced hydrolysis of 0.2 M FeCl3 aqueous solutions between 2 and 72 hours in the presence of 1% sodium dodecyl sulphate (SDS) were investigated. In the absence of SDS a direct phase transformation ß-FeOOH → α-Fe2O3 via dissolution/recrystallization occured in the precipitation system. In the presence of SDS, α-FeOOH as an intermediate phase precipitated and, with a prolonged time of forced hydrolysis, also transformed to α-Fe2O3 via the dissolution/recrystallization mechanism. On the basis of Mössbauer spectra it was concluded that in the presence of SDS, α-Fe2O3 phase possessed a lower degree of crystallinity. In this precipitation process the competition between the stability of Fe(III)-dodecyl sulphate, on one side, and the formation of iron oxide phases, on the other, also played an important role. FE SEM revealed that the big α-Fe2O3 particles possessed the substructure. The elongation of primary α-Fe2O3 particles produced in the presence of SDS was noticed. This effect can be assigned to the preferential adsorption of dodecyl sulphate groups on nuclei and crystallites of FeOOH and α-Fe2O3 phase during the forced hydrolysis of FeCl3 solutions.

Bromate Ion-Exchange Properties of Crystalline Akaganéite

We synthesized crystalline akaganéite (β-FeOOH; Cl− type) by hydrolysis of FeCl3 solution at 100 °C and examined the ion-exchange properties with BrO3−. The uptake rate of BrO3− was so fast that equilibrium was attained in 60 min. The uptake was significantly dependent on pH, showing a maximum uptake at pH ≈ 4. From distribution coefficients (Kd) determined with a mixed solution (BrO3−, Cl−, CO32−, and SO42−; each concentration = 0.1 mmol/dm3), crystalline akaganéite showed the highest selectivity toward BrO3−. The BrO3− uptake was fitted well with the Langmuir model.

TG/DSC analysis of Fe8(OOH)16Cl1.3 nanospindles

The thermal analysis of Fe8(OOH)16Cl1.3 (Akaganeite-M) nanospindles prepared by the hydrolysis of FeCl3 solutions are determined by thermogravimetric analyses and differential scanning calorimetry (TG/DSC), in conjunction with field-emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD). Different products are formed after Fe8(OOH)16Cl1.3 nanospindles are calcined at different temperatures for 30min in N2 atmosphere: Fe1.833(OH)0.5O2.5 and magnetite obtained at 250°C; pure magnetite (Fe3O4) obtained at 630°C; and magnetite containing some iron nitrides (Fe2N and Fe4N) obtained at 800°C. The calcination of Fe8(OOH)16Cl1.3 provides a new method to prepare pure magnetite.

Effects of Nanosized Iron Oxide with Different Morphology on Nanomechanical Properties of Nanocomposite Coating

The nanocomposite coatings were prepared on the surface of PVC substrate using spinning technique with attempts of introducing nanosized iron oxide particles with different morphology into the organic-inorganic hybrid matrices. The hybrid matrices were derived from 3-glycidoxypropyltrimethoxysilane (GLYMO) and tetraethoxysilane (TEOS) with a process of hydrolyzing and condensation. Nanosized iron oxide particles were synthesized by hydrolysis of FeCl3 solution at different pH value and different temperature. The effects of different additions on nanomechanical properties of the nanocomposite coatings were investigated using X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and MTS Nano Indenter XP system. It was found that the acicular α-FeOOH and spherical α-Fe2O3 particles were synthesized, both of them dispersed homogeneously. Nanoindentation and nanoscratch behaviors of the nanoindenter system showed that both of the nanocomposite coatings reinforced the nanomechanical properties of the PVC obviously. Especially, the contribution of acicular α-FeOOH was more remarkable than the spherical α-Fe2O3.

Study on the formation process of spindle beta-FeOOH particles

The formation process of spindle beta-FeOOH particles obtained through the hydrolysis of FeCl3 solutions has been investigated by means of TEM and XRD. The effect of surfactant-Hexadecyl trimethyl ammonium bromide (CTAB) on this process has also been studied. The results show that growth of the needle-like pre-particles is based on the aggregation process, when there is no CTAB in the FeCl3 solution. Once CTAB was added, [beta-FeOOH] nuclies would grow up through the diffusion mechanism. The beta-FeOOH particles were smaller and uniform under the effect of CTAB. The spindle and needle-like beta-FeOOH particles with different axis ratios can be synthesized by controlling the reaction parameters such as the concentration of the original FeCl3 solution and aging temperature.

Synthesis and Anion Exchange of Tunnel Structure Akaganeite

Akaganeite (β-FeOOH) has been prepared by the hydrolysis of FeCl3 solutions. The effects of microwave heating, pH of the solution, and addition of manganese with different valence states have been studied for the optimization of its synthesis. The nucleation and growth of akaganeite crystallites are accelerated by microwave heating. A low pH favors the crystallization of akaganeite, and a high pH favors the crystallization of hematite. Addition of manganese appears to impede crystallization at low pH but improves it at high pH. The anion exchange of Cl-akaganeite with F-, Br-, and OH- and some properties of different anion-exchanged akaganeites has been investigated. The exchange rate and capacity depend on the nature of the anions. Anion exchange significantly changes the loss of chloride and affects the decomposition of akaganeite upon being heated.

Near-Infrared Turbidity of β-FeOOH Particle Suspensions

Near-infrared transmission spectroscopy can be complicated by the light scattering from heterogeneous materials. For the examination of an evolving system exhibiting such light scattering, transmission spectra near wavenumber v = 104cm−1were obtained during the hydrolysis of FeCl3solutions. At first, the resulting turbid suspension of cigar-shaped β-FeOOH particles exhibits single-particle scattering, including a Rayleigh regime (attenuation ∞ v4). At later times, the scattering increases strongly as the particles aggregate, and becomes proportional to vα, with α ≈ 2, consistent with scattering models that interpret the structure of aggregates in terms of a fractal dimension dfroughly equal to 2. In all cases investigated, the attenuation due to scattering is spectrally smooth and increases monotonically with wavenumber. It can be written in the simple form vα with 1 ≤ α ≤ 4. While over limited spectral ranges α may be taken independent of v, over wide ranges it decreases with increasing v. This behavior is consistent with the theoretical limits of α = 4 at v = 0, and α = 0 at v = ∞. Overall, the results suggest that a useful form for simulating scattering backgrounds in near-infrared spectroscopy is Avα, with A and α fitted constants.

Preparation of monodispersed haematite particles by two-step hydrolysis of ferric chloride aqueous solutions

Monodispersed haematite particles have been synthesized by two-step hydrolysis of dilute FeCl3 aqueous solution. The first step is the hydrolysis of FeCl3 solution at 70 ∼ 90 °C, which provided β-FeO(OH) colloidal suspension, and the second step is the transformation from β-FeO(OH) to α-Fe2O3 at 100 ∼ 120 °C via a dissolution and recrystallization process. Partial neutralization with NaOH solution promotes the hydrolysis of highly concentrated FeCl3 solutions. Particle size of α-Fe2O3 can be controlled by neutralization degree, and it decreases with decreasing the electrolyte concentration.

Mössbauer study of the microcrystals formed by slow hydrolysis of FeCl3 solutions

Mössbauer study of the microcrystals formed by slow hydrolysis of FeCl3 solutions