Brucite Structure Research Articles

Equation of state of phase E

AbstractThe isothermal equation of state (EoS) of phase E, Mg1.96(7)Fe0.072(5)Si1.04(5)H3.7(8)O6, has been determined using high-pressure single-crystal X-ray diffraction. A third-order Birch Murnaghan EoS fit to pressue-volume data collected from room pressure and temperature to 6.7 GPa reveals that phase E has the lowest bulk modulus, KT = 92.9(7) GPa, and highest pressure derivative of the bulk modulus, K' = 7.3(2), for any dense hydrous magnesium silicate (DHMS) yet measured. A parameterized third-order Birch-Murnaghan EoS was also fit to the unit-cell parameters which display significant curvature with increasing pressure. This analysis shows that the c-axis (Kc = 89.1(10) GPa) is 6% more compressible than the a-axis (Ka = 94.8(6) GPa), with little of the anisotropy commonly observed in other layered structures. The high K' is indicative of the similarity to layers of the brucite structure. The introduction of interlayer cation polyhedra to the structure serves to reduce both the anisotropy, by reducing the compressibility perpendicular to the sheets, and the ability to shear, by increasing the coherence between layers.

Large metal clusters and lattices with analogues to biology

The magnetic properties of two types of material derived from the brucite lattice, M(OH) 2 are described. The structure-directing effects of simple templates on the brucite lattice parallels the processes seen in nature in the formation of biominerals. The first type exemplified by Fe 17 /Fe 19 aggregates models the structural features of the iron storage protein ferritin. The magnetic behaviour also reveals some interesting parallels with the magnetic phenomena reported previously on ferritins. We have used a combination of experimental techniques including DC, AC and RF susceptibility measurements on powders and a microSQUID on single crystals. The second type is based on an extended-defect brucite structure with stoichiometry M 2 (OH) 2 (ox) for M = Fe 2+ , Co 2+ . They show long-range ordering to antiferromagnetic phases and then, at much lower temperatures, undergo a phase transition to canted antiferromagnetic states. Symmetry arguments are used to predict the spin configurations in these extended materials.

Low-Temperature Structure and Dynamics of Brucite

Structural refinements of time-of-flight neutron powder diffraction data for Mg(OD)2 and inelastic neutron scattering measurements for Mg(OH)2 demonstrate that the mechanism of thermal contraction ...

Influence of drying temperature on properties of Ni-MgO catalysts

The interaction between Ni 2+ and Mg 2+ species in Ni/MgO catalyst precursors prepared by impregnation of MgO with aqueous solutions of Ni(NO 3) 2 · 6H 2O, and the mechanism that produces Ni 2+ cations of very low reducibility after thermal treatments of the samples at low temperature are studied by temperature programmed methods (TPD, TPR) and DRIFTS and EXAFS spectroscopies. Results clearly demonstrate that during the impregnation and mild drying steps ( T ≤ 120 °C) a bulk reaction between MgO and the aqueous Ni 2+ solution yields a mixed hydroxide, where Mg 2+ and Ni 2+ cations occupy the same type of positions in a M(OH) 2 lattice with the brucite structure. NiO/MgO solid solutions are formed by decomposition of this mixed hydroxide after thermal treatments in the 250–400 °C range.

Electron diffractometry and crystal structure of brucite

Electron diffractometry and crystal structure of brucite

High-pressure phase transition in brucite, Mg(OH)2

High-pressure phase transition in brucite, Mg(OH)₂

The structure and morphology of the corrosion products formed on the surfaces of a rapidly solidified Mg3.5Al alloy

The effect of a saline environment on the surfaces of rapidly solidified Mg−.5wt.%Al alloy splats has been studied by different surface analysis techniques keeping in perspective the depth and spatial resolution of each technique. The surface of the as-splat alloy consists of an admixture of magnesium hydroxide and oxide with hydroxide depleting with depth. The corrosion products are acicular and voluminous. Hydrolysis of the cubic oxide to the hexagonal brucite causes the formation of a microporous brucite structure. Hydromagnesite is formed on excess of magnesium hydroxide with chlorine ion incorporated between the hydroxide (brucite) layers.

Crystal‐field properties of Fe in brucite Mg(OH)2

AbstractSamples of brucite Mg(OH)2 containing iron are investigated using 57Fe Mößbauer spectroscopy. The values of the isomer shift and the quadrupole splitting, measured at room temperature, are IS = 1.15 mm/s relative to metallic iron and QS = 2.94 mm/s. From these values, iron is deduced to be in a high spin divalent state. From the magnitude of the QS it is inferred that the ground state associated with the crystal‐field splitting of the 3d levels for Fe2+ in the trigonally distorted oxygen octahedron is a singlet, in agreement with the results of calculations of this splitting. It is argued that this may lead to an increase of the trigonal distortion and provide an explanation of the anomaly in the c/a lattice parameter ratio observed in Fe(OH)2 in comparison with other compounds forming the brucite structure.

ChemInform Abstract: THE ELECTRONIC STRUCTURE OF MAGNESIUM HYDROXIDE (BRUCITE) USING X‐RAY EMISSION, X‐RAY PHOTOELECTRON, AND AUGER SPECTROSCOPY

AbstractDie Elektronenstruktur von Mg(OH)2 wird anhand der Spektren und einfacher HMO‐Berechnungen interpretiert.

The electronic structure of magnesium hydroxide (brucite) using X-ray emission, X-ray photoelectron, and auger spectroscopy

The X-ray emission spectra (Mg-Kβ1,3, Mg-L2,3 M, and O-Kα), X-ray photoelectron spectra, and O-KLL Auger spectra from brucite, Mg[OH]2, are reported. The electronic structure of brucite is discussed using these spectra and a simple Huckel molecular-orbital model. The spectra indicate that the strongest interaction exists between the oxygen and hydrogen of the hydroxide group, but that the Mg-O bond has some covalent character. An attempt to interpret the 2p–2 peak in the oxygen Auger spectrum using the O-Kα, X-ray profile has met with only limited success.

A magnesium oxide defect structure of hexagonal symmetry

When brucite, Mg(OH) 2, is carefully heated in vacuum beyond the dehydration temperature (250–270°C) the (001) x-ray intensity decreases rapidly but does not vanish. The (100) reflection persists up to 480°C. The lattice contracts by 0.2% in c -direction. The thermal expansion in a -direction slows down. This indicates the formation of a nearly anhydrous high defect MgO which retains the brucite structure: Mg(OH) 2−x O x 2 □ x 2 with x→2 (□ unoccupied anion site). This relict structure collapses progressively to the cubic MgO.

ChemInform Abstract: THE STRUCTURE AND REACTIVITY OF NICKEL HYDROXIDE

AbstractDie Beziehung zwischen Struktur und Reaktivität von Ni‐hydroxid wird durch Röntgenbeugung, DTA, IR‐Spektroskopie und gravimetrisch während der Dehydratisierung untersucht.

The Structure and Reactivity of Nickel Hydroxide

Abstract This paper examines the correlation between the structure and the reactivity of nickel hydroxide, using X-ray diffraction, DTA, IR spectroscopy, and gravimetry during dehydration. The degree of crystallization of β-nickel hydroxide depends on the preparation conditions of the hydroxide. Highly-crystallized β-nickel hydroxide has “free” hydroxyl groups, as is to be expected from its brucite structure. Poorly-crystallized β-hydroxide, however, has “hydrogen-bonded” hydroxyl groups, this finding is in disagreement with a previous result that “hydrogen-bonded” hydroxyl groups were found to exist only in α-form nickel hydroxide. The dehydration of the hydroxide is shown to take place in first-order kinetics with an activation energy which increases as the crystallization extends.

Crystal Structure of Brucite and Portlandite in Relation to Infrared Absorption

Crystal Structure of Brucite and Portlandite in Relation to Infrared Absorption