NON-AUTOCLAVE SILICATE COMPOSITES USING NON-TRADITIONAL RAW MATERIALS AND CRYSTAL FILLER

In the construction of buildings and structures, many wall materials are used, including silicate products of various functional purposes. In traditional production technology of such materials, the hardening process occurs due to the formation of a crystal structure in the CaO-SiO2-H2O system. There are various ways to modify the crystalline growth of the cementing substance, one of which is the use of various kinds of crystal seedings, in particular the use of natural and synthetic calcium hydrosilicates. The purpose of the experiments is to study the possibility of improving the performance properties of non-autoclave silicate composites by modifying the structure formation in the "lime-non-traditional aluminosilicate raw materials" system, which consists in the crystal-chemical regulation of the structure formation processes with a synthetic crystal filler CaO-SiO2-H2O (C-S-H). The use of synthetic crystalline filler C-S-H synthesized by hydrothermal synthesis in an autoclave at a pressure of 1 MPa and a temperature of 175 °C from a mixture of Ca(OH)2 and crystalline silica in a ratio different C/S=1 in the technology of non-autoclave silicate materials on the basis of alternative aluminium raw material allows to increase the operational indicators resulting products to 18 % or more. The optimal content of CaO and crystal filler C-S-H at which the maximum strength characteristics are provided is 8 % and 2.5 %, respectively, which allows to develop optimal compositions of raw materials for the technology of producing high-density non-autoclave silicate materials based on non-traditional aluminosilicate raw materials with a compressive strength of at least 20 MPa and more, with an average product density of no more than 2000 kg /m3.

Single-crystal diffraction at the high-pressure Indo-Italian beamline Xpress at Elettra, Trieste

In this study the first in situ high-pressure single-crystal X-ray diffraction experiments at Xpress, the Indo-Italian beamline of the Elettra synchrotron, Trieste (Italy), are reported. A description of the beamline experimental setup and of the procedures for single-crystal centring, data collection and processing, using diamond anvil cells, are provided. High-pressure experiments on a synthetic crystal of clinoenstatite (MgSiO3), CaCO3 polymorphs and a natural sample of leucophoenicite [Mn7Si3O12(OH)2] validated the suitability of the beamline experimental setup to: (i) locate and characterize pressure-induced phase transitions; (ii) solve ab initio the crystal structure of high-pressure polymorphs; (iii) perform fine structural analyses at the atomic scale as a function of pressure; (iv) disclose complex symmetry and structural features undetected using conventional X-ray sources.

Ethynyl hydrogen bonds and iodoethynyl halogen bonds: a case of synthon mimicry

The common electrostatic features of ethynyl and iodoethynyl hydrogen- and halogen-bond donors, respectively, lead to synthon mimicry which can be employed in synthetic crystal engineering for the construction of identical supramolecular assemblies in the solid-state.

Applications of Spectroscopic Methods for Structural Analysis of Synthesis and Natural Crystals

Crystal is of people's favorite now. Many people had done lots of work to explore the coloration mechanism of crystals, and until now there is no complete conclusion. So, we studied the coloration mechanism of synthetic crystal and nature crystal by the Violet-Visible Spectroscopy and radio-luminescence. The results showed that coloration mechanism of color rock crystals (amethyst, citrine, smoky quartz and rose quartz) were color center coloration.

The crystal structure of parkinsonite, nominally Pb7MoO9Cl2: a naturally occurring Aurivillius phase

The crystal structure of the sheet oxychloride mineral parkinsonite, nominally Pb7MoO9Cl2, has been determined for synthetic and natural crystals of analysed compositions, (Pb7.28Mo0.72) O8.96Cl1.96 and (Pb7.23Mo0.40V0.37)O8.90Cl1.82, respectively. Parkinsonite is tetragonal, space group I4/mmm. Unit-cell parameters for synthetic and natural crystals are: asynthetic = 3.9773(4) Å, csynthetic = 22.718(4) Å, Vsynthetic = 359.38(5) Å3, and anatural = 3.9570(3) Å, cnatural = 22.634(5) Å, Vnatural = 354.40(5) Å3. Final agreement indices (R1, wR2) for refinements of the two crystals are 0.024, 0.067 (synthetic) and 0.036, 0.078 (natural). Although a superlattice has been identified by electron diffraction for crystals of both samples (Welch et al., 1996), only the substructure could be determined by X-ray diffraction. This X-ray invisibility of the superstructure has also been observed for the closely related sheet oxychlorides asisite and schwartzembergite, for both of which superstructure motifs have been identified by electron diffraction. The Pb(1) site of both parkinsonite crystals is fully occupied by Pb. Refinement of the Pb content of the Pb(2) site for the synthetic and natural crystals gives occupancies of 0.85(1) and 0.70(1) respectively, corresponding to 3.40 and 2.80 Pb(2) a.p.f.u. respectively. The substituent cation Mo (synthetic crystal) and [Mo+V] (natural crystal) was located at a distance of 0.5 Å from Pb(2), being displaced along the fourfold axis. The reduced occupancy of Pb(2) is due to substitution by Mo or [Mo+V]. No evidence for separate Mo and V sites in the substructure of natural parkinsonite was found. Refined occupancies of the Cl site are 0.84(4) and 0.91(5) for the synthetic and natural crystals, respectively, and are consistent with the 9:1 superstructure component identified by electron diffraction.