The influence of Al on iron oxides. Part III. Preparation of Al goethites in M KOH

Clay Minerals ◽  
1979 ◽  
Vol 14 (2) ◽  
pp. 115-126 ◽  
Author(s):  
D. G. Lewis ◽  
U. Schwertmann
Keyword(s):  
Iron Oxides ◽  
Linear Correlation ◽  
Room Temperature ◽  
Degree Of Substitution ◽  
Starting Material ◽  
Aluminate Solution ◽  
Al Substitution

AbstractAluminium substituted goethites (Fe, Al)OOH were synthesized from Fe(III), Al systems (ferrihydrites) in m KOH at room temperature. A linear correlation existed between degree of Al substitution and log[Al] in solution. Incorporation of up to 12 mole % Al was obtained. The rate of conversion of ferrihydrite to goethite decreased as [Al] increased. The goethite consisted of thin elongated plates approximately 0·1 µm long with serrated edges and reduced growth in the crystallographic X-direction. The presence of salts and the nature of the starting material either an Al-ferrihydrite or a ferrihydrite in aluminate solution did not influence the degree of substitution, but only the rate of formation of the goethite.

Aluminium influence on iron oxides: XVIII. The effect of Al substitution and crystal size on magnetic hyperfine fields of natural goethites

Clay Minerals ◽  
1996 ◽  
Vol 31 (4) ◽  
pp. 455-464 ◽  
Author(s):  
J. Friedl ◽  
U. Schwertmann
Keyword(s):  
Iron Oxides ◽  
Room Temperature ◽  
Crystal Size ◽  
Tropical Soil ◽  
Iron Ores ◽  
Hyperfine Fields ◽  
Al Substitution ◽  
Subtropical Soils ◽  
Crystallization Conditions ◽  
The Mean

AbstractTwo sets of natural Al-substituted goethites from contrasting surface environments (24 tropical and subtropical soils vs. ten lake iron ores from Finland) were characterized by Mössbauer spectra obtained at room temperature and 4.2 K. A negative correlation between Bhf and Al substitution (R2 = 0.751) was found by combining the data of all the samples, which was slightly improved (R2 = 0.779) by taking the mean coherence length perpendicular to 111 (MCL111) into account. The effect of Al on lowering Bhf was, however, stronger for the tropical soil goethites than for those of the lake ores. This is parallelled by a corresponding difference in the unit-cell decrease per unit Al substitution. These differences are believed to result from the crystallization conditions in the two different environments.

Selective oxidation of aniline into azoxybenzene catalyzed by Nb-peroxo@iron oxides at room temperature

2020 ◽  
Vol 44 (21) ◽  
pp. 8710-8717
Author(s):  
André L. D. Lima ◽  
Humberto V. Fajardo ◽  
André E. Nogueira ◽  
Márcio C. Pereira ◽  
Luiz C. A. Oliveira ◽  
...  
Keyword(s):  
Iron Oxides ◽  
Selective Oxidation ◽  
Room Temperature ◽  
High Selectivity

Nb-peroxo@iron oxides show high selectivity and activity in aniline conversion to azoxybenzene.

scholarly journals Impurity-Induced Spin-State Crossover in La0.8Sr0.2Co1−xAlxO3

Crystals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 411 ◽  
Author(s):  
Ichiro Terasaki ◽  
Masamichi Ikuta ◽  
Takafumi Yamamoto ◽  
Hiroki Taniguchi
Keyword(s):  
Magnetic Field ◽  
Saturation Magnetization ◽  
Spin State ◽  
Room Temperature ◽  
Significant Fraction ◽  
Al Substitution ◽  
Spin Number ◽  
Average Spin ◽  
Heikes Formula ◽  
Temperature Susceptibility

We have prepared a set of polycrystalline samples of La 0.8 Sr 0.2 Co 1 − x Al x O 3 ( 0 ≤ x ≤ 0.2 ), and have measured the magnetization as functions of temperature and magnetic field. We find that the average spin number per Co ion ( S Co ) evaluated from the room-temperature susceptibility is around 1.2–1.3 and independent of x. However, we further find that S Co evaluated from the saturation magnetization at 2 K is around 0.3–0.7, and decreases dramatically with x. This naturally indicates that a significant fraction of the Co 3 + ions experience a spin-state crossover from the intermediate- to low-spin state with decreasing temperature in the Al-substituted samples. This spin-state crossover also explains the resistivity and the thermopower consistently. In particular, we find that the thermopower is anomalously enhanced by the Al substitution, which can be consistently explained in terms of an extended Heikes formula.

The influence of aluminium on iron oxides: XII. High-resolution transmission electron microscopic (HRTEM) study of aluminous goethites

Clay Minerals ◽  
1985 ◽  
Vol 20 (2) ◽  
pp. 255-262 ◽  
Author(s):  
S. Mann ◽  
R. M. Cornell ◽  
U. Schwertmann
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Iron Oxides ◽  
Dissolution Kinetics ◽  
Electron Microscopic ◽  
Al Substitution ◽  
Transmission Electron ◽  
Transmission Electron Microscopic

Aluminium-substituted goethites are found in many soils and can also be synthesised readily in the laboratory. In recent years, synthetic substituted goethites have been examined by various techniques including XRD, IR, TEM and dissolution kinetics (Thiel, 1963; Jonas & Solymar, 1970; Fey & Dixon, 1981; Fysh & Fredericks, 1983; Schulze & Schwertmann, 1984; Schwertmann, 1984). Transmission electron microscopy (TEM) studies have shown that as Al substitution rises above 10%, the goethite needles become shorter and also thicker in the a direction. Furthermore, crystals which at zero substitution consist of domains parallel to the c axis become less domainic with increasing Al substitution (Schulze & Schwertmann, 1984).

scholarly journals Deposits of iron oxides in the human globus pallidus

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 291-298
Author(s):  
Helena Svobodová ◽  
Jana Hlinková ◽  
Pavol Janega ◽  
Daniel Kosnáč ◽  
Barbora Filová ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Human Brain ◽  
Iron Oxides ◽  
Globus Pallidus ◽  
Room Temperature ◽  
Hysteresis Loops ◽  
Point Of View ◽  
Zero Field ◽  
Fixed Temperature ◽  
Transmission Electron

Abstract Samples taken from the human brain (Globus Pallidus) have been investigated by physical techniques such as light microscopy, scanning electron microscopy, transmission electron microscopy, Mössbauer spectroscopy and SQUID magnetometry. SEM-EDX/TEM investigation reveals multielemental composition of hematite and magnetite nanocrystals with sizes ranging from 40 nm to 100 nm and hematite microcrystals from 3 μm to 7 μm. Room temperature Mössbauer spectra show quadrupole doublets assigning to hematite and ferrihydrite. SQUID measurements of temperature dependence of the mass magnetic susceptibility between T = 2 – 300 K at DC field B0 = 0.1 T, the field dependence of the mass magnetization taken at the fixed temperature T0 = 2.0 and 4.6 K and the zero-field cooled and field cooled magnetization experiments (ZFCM/FCM) confirm a presence of ferrimagnetic phases such as maghemite and/or magnetite with hysteresis loops surviving until the room temperature. Differences between these measurements from the point of view of iron oxides detected can indicate important processes in human brain and interactions between ferritin as a physiological source of iron and surrounding environment.

Synthesis and Characterization of Iron Oxides Nanoparticles

2006 ◽  
Vol 306-308 ◽  
pp. 1115-1120 ◽  
Author(s):  
Bee Chin Ang ◽  
Iskandar Idris Yaacob
Keyword(s):  
Iron Oxides ◽  
Room Temperature ◽  
Magnetic Particles ◽  
Aqueous Salt Solution ◽  
Gas Absorption ◽  
Microemulsion System ◽  
X Ray Diffraction ◽  
Weight Losses ◽  
Magnetite Fe3o4

Magnetic iron oxides nanoparticles were synthesized at room temperature using water in oil microemulsion process. This microemulsion system was prepared using HTAB (surfactant), noctane (oil), 1-butanol (cosurfactant) and aqueous salt solution of Fe2+ and OH-. The microemulsions were used as microreactors for controlling the growth of the particles. The nanoparticles were characterized using TGA, XRD, TEM, BET, DLS and AGM. X-ray diffraction analysis revealed that the magnetic nanoparticles could be directly formed at room temperature. It also showed that the particles were either maghemite (γ-Fe2O3) or magnetite (Fe3O4). TGA thermogram showed two significant weight losses at around 100°C and 250° C, which were caused by dehydration and burn off of the surfactant. The surface area of the magnetic particles measured using gas absorption and desorption technique was 105.43m2/g, which indicated the presence of particles of 21nm in length. The size measured by TEM and DLS was 105nm and 107.9nm respectively due to the formation of large aggregated clusters. The sample also showed strong magnetic properties with the value of Ms of 11.2 emu/g.

scholarly journals Tandem Deoxygenative Hydrosilation of Carbon Dioxide with a Cationic Scandium Hydridoborate and B(C6F5)3

2019 ◽  
Author(s):  
Daniel W. Beh ◽  
Warren Piers ◽  
Benjamin S. Gelfand ◽  
Jian-Bin Lin
Keyword(s):  
Carbon Dioxide ◽  
Transition Metal ◽  
Room Temperature ◽  
Starting Material ◽  
Metal Component ◽  
Hydride Complex ◽  
Hydride Abstraction ◽  
Pentadentate Ligand ◽  
Hb C

A scandium hydridoborate complex supported by the dianionic pentadentate ligand B<sub>2</sub>Pz<sub>4</sub>Py is prepared via hydride abstraction from the previously reported scandium hydride complex with <i>tris</i>-pentafluorophenyl borane. Exposure of [(B<sub>2</sub>Pz<sub>4</sub>Py)Sc][HB(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>] to CO<sub>2</sub> immediately forms [(B<sub>2</sub>Pz<sub>4</sub>Py)Sc][HCOOB(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>] at room temperature. The formatoborate complex can also be synthesized directly from the starting material (B<sub>2</sub>Pz<sub>4</sub>Py)ScCl with Et<sub>3</sub>SiH and B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> while in the presence of an atmosphere of CO<sub>2</sub> in 81% yield. This compound was evaluated as the transition metal component of a tandem deoxgenative CO<sub>2</sub> hydrosilation catalyst. At 5% loadings, complete consumption of Et<sub>3</sub>SiH was observed along with CO<sub>2</sub> reduction products, but conversion to an inactive scandium complex identified as (B<sub>2</sub>Pz<sub>4</sub>Py)ScOSiEt<sub>3</sub> was observed

Concentration of iron oxides from soil clays by 5 m NaOH treatment: the complete removal of sodalite and kaolin

Clay Minerals ◽  
1991 ◽  
Vol 26 (4) ◽  
pp. 463-472 ◽  
Author(s):  
Balwant Singh ◽  
R. J. Gilkes
Keyword(s):  
Iron Oxide ◽  
Iron Oxides ◽  
Crystal Size ◽  
Complete Removal ◽  
Complete Dissolution ◽  
Al Substitution ◽  
Soil Clays ◽  
Naoh Treatment ◽  
Very High

AbstractThe Kämpf & Schwertmann (1982) procedure for concentrating iron oxides in soil clays by dissolution of kaolin and gibbsite by boiling for 1 h in 5 m NaOH may not dissolve all kaolin, and also results in the precipitation of sodalite. For the complete dissolution of kaolin in kaolin-rich soil clays a boiling time of 2 h in 5 m NaOH was required. The large amounts of sodalite produced were not removed by the prescribed single wash in 0·5 m HCl. Oxalate soluble Al contents of iron oxide concentrates were sometimes very high and dithionite Fe contents were very low both in concentrates containing sodalite, and in those for which sodalite was not detected by XRD, but where a previously unsuspected amorphous sodalite-like phase may have been present. Complete removal of precipitated sodalite was achieved by two extractions with 0·5 m HCl at 25°C for 20 min. This modified procedure does not alter the Al-substitution and crystal size of goethite, hematite and maghemite as determined by XRD measurements.

Synthesis of aenigmatite

1969 ◽  
Vol 37 (286) ◽  
pp. 253-255 ◽  
Author(s):  
R. N. Thompson ◽  
J. E. Chisholm
Keyword(s):  
Oxygen Fugacity ◽  
Room Temperature ◽  
Comparative Data ◽  
Starting Material ◽  
Powder Pattern ◽  
X Ray

SummaryAenigmatite with the formula Na4[Fe102+Ti2]Si12O14 has been synthesized hydrothermally, at 700 °C and 1000 bars PH2O, from an oxide starting material. The oxygen fugacity was controlled by means of an iron-wüstite buffer. An indexed X-ray powder pattern of synthetic aenigmatite is given, together with comparative data on two natural samples. One of the aenigmatites, from Kola, U.S.S.R., is known to be triclinic (Kelsey and McKie, 1964). The powder patterns of this and the synthetic aenigmatite are so similar that it is concluded that the latter is also triclinic, at least at room temperature.

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