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LDHs can be seen as derived from hydroxides of divalent cations (d) with the brucite (Mg(OH) 2) layer structure [AdB AdB] n, by cation (c) replacement (Mg 2+ → Al 3+), or by cation oxidation (Fe 2+ → Fe 3+ in the case of green rust, Fe(OH) 2), in the metallic divalent (d) cation layers, so as to give them an excess positive electric charge; and intercalation of extra anion layers (Z ...
AFm phases belong to the class of layered double hydroxides (LDH). LDHs are hydroxides with a double layer structure. The main cation is divalent (M 2+) and its electrical charge is compensated by 2 OH − anions: M(OH) 2. Some M 2+ cations are replaced by a trivalent one (N 3+). This creates an excess of positive electrical charges which needs ...
Hydrotalcite, or formerly also völknerite, [6] is a layered double hydroxide (LDH) of general formula Mg 6 Al 2 CO 3 (OH) 16 ·4 H 2 O, whose name is derived from its resemblance with talc and its high water content. Multiple structures containing loosely bound carbonate ions exist.
A number of mixed hydroxides are known with stoichiometry A 3 M III (OH) 6, A 2 M IV (OH) 6, and AM V (OH) 6. As the formula suggests these substances contain M(OH) 6 octahedral structural units. [46] Layered double hydroxides may be represented by the formula [M z+ 1−x M 3+ x (OH) 2] q+ (X n−) q ⁄ n ·yH 2 O.
Titanium disulfide is an example of a layered material. The individual sheets are interconnected by van der Waals forces between the sulfide centers.. In material science, layered materials are solids with highly anisotropic bonding, in which two-dimensional sheets are internally strongly bonded, but only weakly bonded to adjacent layers. [1]
The different symmetry of gibbsite and brucite is due to the different way that the layers are stacked. It is the gibbsite layer that in a way forms the "floor plan" for the mineral corundum, Al 2 O 3. The basic structure of corundum is identical to gibbsite except the hydroxides are replaced by oxygen. Since oxygen has a charge of −2 the ...
The reaction of magnesium carbonate with the free alkali hydroxides present in the cement porewater also leads to the formation of expansive brucite. MgCO 3 + 2 NaOH → Mg(OH) 2 + Na 2 CO 3. This reaction, one of the two main alkali–aggregate reaction (AAR) is also known as alkali–carbonate reaction.
the loss of two water molecules from the iron(II) and iron(III) hydroxides giving rise to its dehydration and to the formation of a thermodynamically more stable phase iron(II,III) oxide. The global reaction can thus be decomposed in half redox reactions as follows: 2 (Fe 2+ → Fe 3+ + e −) (oxidation of 2 iron(II) ions)