Structure of lithium aluminum hydroxide dihydrate (LiAl2(OH)7.2H2O)

Abstract

The room-temperature reaction of lithium hydroxide with aluminum hydroxide (bayerite) in the ratio of 1:2 produces lithium dialuminate, LiA12(OH),*2H20. Rietveld refinement of X-ray and neutron powder diffraction patterns indicate that the structure is composed of [LiAlZ-(OH),]+ layers separated by water molecules and hydroxide ions. Disorder in the stacking sequence leads to indexing the diffraction pattern on a hexagonal cell (a = 5.0972(3) A, c = 7.5524(9) A X 3n layers); however, the structure is better described by a C-centered monoclinic cell with the constraints the b = a d 3 and cos / 3 = -a/3c ( a = 5.097 A, b = 8.829 A, c = 7.741 A, and /3 = 103.0'). The diffraction patterns were refined using a model of up to 54 layers (-400 A). The layer stacking vector, which defines the angle between layers, is less than expected based on the position of the diffraction peaks. The structural complexities present in lithium dialuminate have their origins in the conditions of synthesis and the layered nature of the material.

Corrosive effect of lithium nitrate trihydrate on common heat exchanger materials

“…We attribute these peaks to corrosion products on the surface. The peak near 10.6° 2θ cannot be assigned to common aluminum oxide or hydroxide phases, but corresponds to a low angle peak for LiAl 2 (OH) 7 ­ · 2H 2 O, a previously observed reaction product of LNH and aluminum . The other peak (20.6° 2θ) could potentially be related to the same phase, although it also overlaps potential Al(OH) 3 (gibbsite) peaks.…”

New Separation Science Using Shape-Selective Ion Exchange Intercalation Chemistry

“…The unique Li/Al cation ordering exhibited by [LiAl 2 (OH) 6 ] + layers [9,10] may be a significant factor as other cation-disordered LDHs do not show such pronounced selectivities. However, cation ordering cannot account for the strong solvent dependence of the ion-exchange intercalation preferences of the various isomers.…”

Well‐Crystallized CO32–‐Type LiAl–LDH from Urea Hydrolysis of an Aqueous Chloride Solution

“…LiAl-LDH Crystallites Figure 1 shows the XRD patterns of the products synthesized at increasing temperature for 48 h. Below 160°C [ Figure 1(d)], all diffraction peaks can be attributed to a single-phase monoclinic LiAl-CO 3 -LDH [ Figure 1(a)-(e)] as proposed by Thiel et al [21] The absence of impurities represents an improvement with regard to, for example, the known synthetic route of Britto et al [16] based on urea hydrolysis in reflux, where bayerite [monoclinic Al(OH) 3 ] was always present. It is also clear that the higher the temperature the sharper the peaks, i.e.…”

“…19°to 32°in 2θ, i.e. by Thiel et al [21] ), and the three-layer hexagonal model starts being approximate. Moreover, the simulated intensity of (002) is low relative to (001).…”

“…It can clearly be seen that the model does not fully agree with the data, and in particular a wide set of peaks are missing in the experimental pattern. In fact, in fully dehydrated [LiAl 2 (OH) 6 ]X where X = Cl, Br, NO 3 , the Li + cations have been shown to occupy the vacant octahedral sites within the Al(OH) 3 layers; [21,30] the structure is regular and shows a stacking sequence of type aAXAaBXBa (where a is the metal layer, A and B are hydroxide layers and X the anion layer) with the occurrence of Li + ···X -···Li + ··· chains. 19°to 32°in 2θ, i.e.…”