Sebastian Bette

9Mg(OH)2 · MgCl2 · 4H2O, a High Temperature Phase of the Magnesia Binder System

The metastable phase 9Mg(OH)(2)·MgCl(2)·4H(2)O (9-1-4 phase) was found at the extended metastable isotherm of Mg(OH)(2) in the system MgO-MgCl(2)-H(2)O at 120 °C and occurs as intermediate binder phase during setting of magnesia cement due to temperature development of the setting reaction. The crystal structure of the 9-1-4 phase was solved from high resolution laboratory X-ray powder diffraction data in space group I2/m (C2/m) (a = 22.2832(3) Å, b = 3.13501(4) Å, c = 8.1316(2) Å, β = 97.753(1)°, V = 562.86(2) Å(3), and Z = 1). Structural and characteristical relations of the phases in the system MgO-MgCl(2)-H(2)O can be derived, with which the development of the cement or concrete qualities becomes explainable.

Structure solution and refinement of stacking-faulted NiCl(OH)

Two samples of pure NiCl(OH) were produced by hydrothermal synthesis and characterized by chemical analysis, IR spectroscopy, high-resolution laboratory X-ray powder diffraction and scanning electron microscopy. Layers composed of edge-sharing distorted NiCl6x(OH)6−6x octahedra were identified as the main building blocks of the crystal structure. NiCl(OH) is isostructural to CoOOH and crystallizes in space group R \overline{{3}}m [a = 3.2606 (1), c = 17.0062 (9) A]. Each sample exhibits faults in the stacking pattern of the layers. Crystal intergrowth of (AγB)(BαC)(CβA) and (AγB)(AγB) [C6 like, β-Ni(OH)2 related] stacked layers was identified as the main feature of the microstructure of NiCl(OH) by DIFFaX simulations. A recursion routine for creating distinct stacking patterns of rigid-body-like layers in real space with distinct faults (global optimization) and a Rietveld-compatible approach (local optimization) was realized and implemented in a macro for the program TOPAS for the first time. This routine enables a recursive creation of supercells containing (AγB)(BαC)(CβA), (AγB)(AγB) and (CβA)(BαC)(AγB) stacking patterns, according to user-defined transition probabilities. Hence it is an enhancement of the few previously published Rietveld-compatible approaches. This routine was applied successfully to create and adapt a detailed microstructure model to the measured data of two stacking-faulted NiCl(OH) samples. The obtained microstructure models were supported by high-resolution scanning electron microscopy images.

Ni3Cl2.1(OH)3.9·4H2O, the Ni analogue to Mg3Cl2(OH)4·4H2O.

For the first time a basic transition-metal hydrate, Ni3Cl2.1(OH)3.9·4H2O, is found to be isostructural to a main-group metal phase, Mg3Cl2.0(OH)4.0·4H2O. The Ni phase was found as crystalline solid in the course of investigations into the formation of basic nickel(II) chloride phases at 25 and 40 °C in alkaline, concentrated nickel(II) chloride solutions. Ni3Cl2.1(OH)3.9·4H2O was characterized by thermal analysis, IR spectroscopy, scanning electron microscopy, and X-ray powder diffraction. The crystal structure was determined from high-resolution laboratory X-ray powder diffraction data. Ni3Cl2.1(OH)3.9·4H2O crystallizes in space group C2/m (12) with Z = 2, a = 14.9575(4) Å, b = 3.1413(1) Å, c = 10.4818(5) Å, β = 101.482(1)°, and V = 482.50(3) Å(3). The main building unit of the structure is an infinite triple chain of edge-linked distorted NiO6 octahedra. These chains are separated by interstitial one-dimensional zigzag chains of disordered Cl(-) ions and H2O molecules. The crystal structures of Ni3Cl2.1(OH)3.9·4H2O and the isostructural magnesium salt hydrate Mg3Cl2(OH)4·4H2O (2-1-4 phase) are compared in detail.

A solid solution series of atacamite type Ni{sub 2x}Mg{sub 2−2x}Cl(OH){sub 3}

Abstract For the first time a complete solid solution series Ni2xMg2−2xCl(OH)3 of an atacamite type alkaline main group metal chloride, Mg2Cl(OH)3, and a transition group metal chloride, Ni2Cl(OH)3, was prepared and characterized by chemical and thermal analysis as well as by Raman and IR spectroscopy, and high resolution laboratory X-ray powder diffraction. All members of the solid solution series crystallize in space group Pnam (62). The main building units of these crystal structures are distorted, edge-linked Ni/MgO4Cl2 and Ni/MgO5Cl octahedra. The distribution of Ni2+- and Mg2+-ions among these two metal-sites within the solid solution series is discussed in detail. The crystallization of the solid solution phases occurs via an intermediate solid solution series, (Ni/Mg)Cl2x(OH)2−2x, with variable Cl: OH ratio up to the 1:3 ratio according to the formula Ni2xMg2−2x Cl(OH)3. For one isolated intermediate solid solution member, Ni0.70Mg0.30Cl0.58(OH)1.42, the formation and crystal structure is presented as well.