The layer silicate Cs2SnIVSi6O15

Single crystals of Cs2SnSi6O15, dicaesium tin(IV) hexasilicate, were serendipitously obtained from a CsCl/NaCl flux at 923 K, starting from mixtures of CaO, SnO and TeO2 in a closed silica ampoule. The crystal structure of Cs2SnSi6O15 is constructed from {Si6O15}6– layers extending parallel to (101), and CsI cations with a coordination number of eleven as well as isolated [SnO6] octahedra situated between the silicate layers. Each of the nine different SiO4 tetrahedra in the silicate layer has a connectedness of Q 3 (three bridging and one terminal O atom), which leads to the formation of five- and eight-membered rings. The same type of silicate layer is found in the crystal structure of the mineral zeravshanite. Comparison with other silicates of the type Cs2 M IVSi6O15 (M IV = Ti, Zr, Th, U) revealed a klassengleiche group–subgroup relationship of index 2 between Cs2ZrSi6O15 (Z = 6, space group C2/m) and Cs2SnSi6O15 (Z = 12, space group I2/c).

The Synthesis of Biodegradable Poly(L-Lactic Acid)-Polyethylene Glycols Copolymer/Montmorillonite Nanocomposites and Analysis of the Crystallization Properties

This study makes use of polycondensation to produce poly (L-lactic acid)-(polyethylene glycols), a biodegradable copolymer, then puts it with organically modified montmorillonite (o-MMT) going through an intercalation process to produce a series of nanocomposites of PLLA-PEG/o-MMT. The exfoliation and intercalation of the montmorillonite-layered structure could be found through X-ray diffraction and transmission electron microscopy. The lower the molecular weight of poly (ethylene glycol), the more obvious the exfoliation and dispersion. The nanocomposites were investigated under non-isothermal crystallization and isothermal crystallization separately via differential scanning calorimetry (DSC). After the adding of o-MMT to PLLA-PEG copolymers, it was found that the PLLA-PEG nanocomposites crystallized slowly and the crystallization peak tended to become broader during the non-isothermal crystallization process. Furthermore, the thermal curve of the non-isothermal melt crystallization process of PLLA-PEG copolymers with different proportions of o-MMT showed that the melting point decreased gradually with the increase of o-MMT content. In the measurement of isothermal crystallization, increasing the o-MMT of the PLLA-PEG copolymers would increase the t1/2 (crystallization half time) for crystallization and decrease the value of ΔHc. However, the present study results suggest that adding o-MMT could affect the crystallization rate of PLLA-PEG copolymers. The o-MMT silicate layer was uniformly dispersed in the PLLA-PEG copolymers, forming a nucleating agent. The crystallization rate and the regularity of the crystals changed with the increase of the o-MMT content, which further affected the crystallization enthalpies.

The Effect of Nanosilicates on the Performance of Polyethylene Terephthalate Films Prepared by Twin-Screw Extrusion

Polyethylene terephthalate (PET) films were prepared by cast extrusion using a twin-screw extruder with a severe screw profile. The effect of an organically modified montmorillonite on thermal, mechanical, optical, and barrier properties of the PET films were investigated. Morphological characterization of the nanocomposite films was performed by employing wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) followed by image analysis. The results unfold a mixed morphology for the nanocomposite films with more than 95% exfoliated and intercalated silicate layer structures, depending on the screw rotation speed. The remarkable dispersion of the organoclay particles at the nano-level is discussed in terms of solubility parameter and favorable interactions between PET macromolecules and organic modifier of the nanoclay. The crystal content of the nanocomposite films and their cold and hot crystallization temperatures confirmed the role of silicate nanolayers as a heterogeneous nucleating agent. While all nanocomposite films exhibit higher haze values in comparison to the neat PET samples, incorporation of 2 wt% nanoclay brought about 25% increase in tensile modulus and barrier properties. A range of screw rotation speeds with optimized properties in terms of haze, morphology, thermal, mechanical, and barrier properties is suggested.

Nanoclay and Its Importance

Clays are the one of the most important minerals and have numerous applications in nanotechnology, helps in improvise the product quality, cost effective and protect the environment from pollution. This review explained about the key characters of nanoclay particles and classification of nanoclay based on the sheets arrangements in their structural unit called layer. Nano clay major groups are kaoline-serpentine, smectite, mica, vermiculite, pyrophyllite talc and chlorite. The physicho-chemical and morphological properties of halloystite and mantmorillonite clay represents the 1:1 and 2:1 layer groups respectively. Nano clays are the group which is naturally present in the soil fraction of clay and most important nano clay material present in the soil are montmorillonite and allophone. Montmorillonite is a characteristically crystalline, phyllosilicate and hydrous silicate layer. Organo clays are the organically modified forms of the montmorillonite and formed from quaternary ammonium ions intercalation process and which have been used in inks, rheomodifiers, cosmetics, greases, as a additives in paints and also used in controlled release of drugs in delivery systems. Largest usage of nanoclaysis being practiced in polymer-clay nanocomposites. Organo clays are most importantly using in water treatment and pollution control. Allophane is formed by weathering of volcanic ash; it is non crystalline alluminium silicate derivative. Agricultural lands in Chile mostly formed by the allophane clay fraction. It is most suitable for enzyme mobilization. It also very useful in abortion of phenolic compounds, mill effluent colours and phosphates from waste water.

Macrochondrules in Some Chondrites: 1. Structural-Mineralogical Characteristics

The results of structural, mineralogical and chemical study of rare structural units of chondrites, macrochondrules and their fragments, found in five chondrites of different chemical groups and petrological types (Allende CV3, Krymka LL3.1, Saratov L4, "Velyka Balka" L4-5, Château-Renard L6), are given. Most of them are generally similar to ordinary chondrules and previously studied macrochondrules. They have a radial and porphyritic texture, consist of olivine and pyroxene, and are covered by a silicate rim, which is fine-grained in the macrochondrules of unequilibrated chondrites and coarse-grained in equilibrated ones. Only two macrochondrules among studied one’s are extraordinary and indicate specific conditions for their formation in the protoplanetary nebula. The first one, separated directly from the Allende chondrite, is characterized by the presence of a thin amorphous shell with a porous structure and with unambiguous sculpture features of instantaneous melting and solidification of its surface silicate layer. The second one, studied in a polished section of the Krymka meteorite, is characterized by a zonal structure and the presence of graphite grains and possibly bitumen inclusions. According to the SiO2/MgO ratio, its fine-grained silicate rim with rare graphite crystals and possibly bitumen inclusions corresponds to the fine-grained rims of ordinary chondrules, but is different from the carbonaceous material of meteorites.

Ионный синтез структур кремний на изоляторе" со свинцово-силикатным изолирующим слоем

The process of ionic synthesis of “silicon-on-insulator” structures based on the sequential implantation of oxygen ions and a glass former into silicon substrates has been investigated. Lead ions were used as a glass former. The features of the formation of a buried silicate layer during post-implantation annealing are considered. The current-voltage characteristics of the synthesized structures, as well as the specific electrical resistances of the insulator and the device silicon layer, have been measured.

Lanthanum Role in the Graphite Formation in Gray Cast Irons

The present paper reviews original data obtained by the authors from recent separate publications with additional unpublished data, specifically concerning the Lanthanum (La)’s role in the solidification pattern and graphite formation in gray cast irons. Iron melting at 0.018–0.056%S, a 3.7–4.1% carbon equivalent (CE) and less than 0.005%Alresidual are inoculated with La-bearing FeSi alloys at different associations with other inoculating elements. Complex Al-La small inclusions as possible better nucleation sites for (Mn,X)S compounds and La-Ca presence in the body of these sulfides, which possibly provide better nucleation sites for flake graphite, are identified in 0.026%S cast iron. At a lower sulfur content (0.018%S), La,Ca,Al-FeSi alloy still has a high efficiency, but more complex La-bearing alloys are recommended for a higher dendritic austenite amount (LaBaZrTi–FeSi) or for lower eutectic recalescence (LaBaZr–FeSi). La has limited but specific benefits at 0.05–0.06%S irons, including favorable graphitizing factors (a higher amount of graphite precipitated at the end of solidification), lower eutectic recalescence, and a lower value of the first derivative at the end of solidification. When La,Ca,Ba,Al,Zr,S-FeSi treatment (0.035%S base iron) is used, Scanning Electron Microscopy (SEM) analysis finds that the first formed micro-compound is a complex Al-silicate (Zr,La,Ca,Ba presence), which supports the nucleation of the second compound (Mn,Ca,La)S type. At the sulfide-graphite interface, there is a visible thin (nano size) Al-silicate layer (O-Al-Si-Ca-La system), which is more favorable for graphite nucleation (it has better crystallographic compatibility). La is identified in all three important areas of nucleants (the first is formed oxidic nucleus, the second is nucleated Mn-sulfide and the third is a sulfide-graphite interface), thereby increasing the efficiency of graphite nucleation sites.

A new equation of state applied to planetary impacts

Observed FeO/MgO ratios in the Moon and Earth are inconsistent with simulations done with a single homogeneous silicate layer. In this paper we use a newly developed equation of state to perform smoothed particle hydrodynamics simulations on the lunar-forming impact, testing the effect of a primordial magma ocean on Earth. This is investigated using the impact parameters of both the canonical case, in which a Mars-sized impactor hits a non-rotating Earth at an oblate angle, and the fast-rotating case, in which a half-sized Mars impactor hits a fast-spinning Earth head-on. We find that the inclusion of a magma ocean results in a less massive Moon and leads to slightly more mixing. Additionally, we test how an icy Theia would affect the results and find that this reduces the probability of a successful Moon formation. Simulations of the fast-spinning case are found to be unable to form a massive-enough Moon.

Preparation and Characterization of Poly Methyl Methacrylate/Clay Nanocomposite Powders by Microwave-Assisted In-Situ Suspension Polymerization

The PMMA (poly methyl methacrylate)/clay nanocomposite powders were synthesized by In-Situ suspension polymerizations using microwave heating. The PMMA/clay nanocomposites were also sampled using injection moulding to make specimens for material characterization. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) indicated the formation of a highly intercalated clay layer in the nanocomposites. It was found that the microstructure of PMMA/clay nanocomposites was strongly dependent of content of clay. Thermo gravimetric analysis (TGA) indicated an improvement in the thermal stability of nanocomposites compared to that of the pure PMMA. Differential scanning calorimetry (DSC) showed that the nanocomposites had a higher glass transition (Tg) temperature than the PMMA. Fourier-transform infrared (FT-IR) spectroscopy indicated an interaction between the carbonyl group of PMMA and hydroxyl group of the clay. Therefore, a possible reason in enhanced material properties of nanocomposites is that the chemical interaction and nanostructure of PMMA polymer and intercalated inorganic silicate layer has increased the thermal stability of the PMMA/clay nanocomposites.