Journal articles: 'Silicatées'

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Baraček, Jan, Martin Palou, Jiří Másilko, Jaromír Wasserbauer, František Šoukal, Tomáš Opravil, and Martin Boháč. "Application of Sol-Gel Method to Investigate the Influence of P₂O₅ on the Course of Reactions in CaO-SiO₂ System." Materials Science Forum 851 (April 2016): 92–97. http://dx.doi.org/10.4028/www.scientific.net/msf.851.92.

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The effect of P2O5 addition on the calcium silicate phase equilibrium during the sol-gel synthesis of dicalcium silicate was investigated using Scanning electron microscope and X-ray diffraction. It is established that phosphorous oxide can form solid solution with dicalcium silicate, but its causes the formation of phosphatic calcium silicate phases such as Ca14.92 (PO4)2.35(SiO4)5.65 and 5CaO.SiO2.P2O5 also. Local analysis has demonstrated the presence of calcium phosphate epicenters containing silicon oxide and calcium silicate zones with minimum content of phosphorous oxide and intermediary areas of various phosphatic calcium silicates. The formation of two distinct islets of calcium silicate and calcium phosphate is due to the affinity between acid oxides (SiO2, P2O5) and basic one (CaO) during sol-gel process. Then, the formation of various phosphatic calcium silicates result from the diffusion of P2O5 towards calcium silicate and that of SiO2 towards calcium phosphate.

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Wooden, Diane H. "Cometary Silicates: Interstellar and Nebular Materials." Highlights of Astronomy 13 (2005): 495–97. http://dx.doi.org/10.1017/s1539299600016403.

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AbstractEvidence for interstellar material in comets is deduced from IR spectra, in situ measurements of Comet Halley, and chondritic porous interplanetary dust particles (CP IDPs). IR spectra of comets reveal the spectrally active minerals: amorphous carbon, amorphous silicates, and (in some comets) crystalline silicates. Evidence suggests amorphous silicates are of interstellar origin while crystalline silicates are of nebular origin.10 μm spectra of comets and sub-micron amorphous silicate spherules in CP IDPs have shapes similar to absorption spectra through lines-of-sight in the ISM. Thermal emission models of cometary IR spectra require Fe-bearing amorphous silicates. Fe-bearing amorphous silicates may be Fe-bearing crystalline silicates formed in AGB outflows that are amorphized through He+ ion bombardment in supernova shocks in the ISM.Crystalline silicates in comets, as revealed by IR spectra, and their apparent absence in the ISM, argues for their nebular origin. The high temperatures (>1000 K) at which crystals form or are annealed occur in the inner nebula or in nebular shocks in the 5 – 10 AU region. Oxygen isotope studies of CP IDPs show only 1% by mass of the silicate crystals are of AGB origin. Together this suggests crystalline silicates in comets are probably primitive grains from the early solar nebula.

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Liang, Jian-Jie, Alexandra Navrotsky, Thomas Ludwig, Hans J. Seifert, and Fritz Aldinger. "Enthalpy of Formation of Rare-earth Silicates Y2SiO5 and Yb2SiO5 and N-containing Silicate Y10(SiO4)6N2." Journal of Materials Research 14, no. 4 (April 1999): 1181–85. http://dx.doi.org/10.1557/jmr.1999.0158.

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The enthalpies of formation of two rare-earth silicates (Y2SiO5 and Yb2SiO5) and a N-containing rare-earth silicate Y10(SiO4)6N2 have been determined using high-temperature drop solution calorimetry. Alkali borate (52 wt% LiBO2·48 wt% NaBO2) solvent was used at 800 °C, and oxygen gas was bubbled through the melt. The nitrogen-containing silicate was oxidized during dissolution. The standard enthalpies of formation are for Y2SiO5, Yb2SiO5, and Y10(SiO4)6N2, respectively, –22868.54 ± 5.34, –22774.75 ± 8.21, and –14145.20 ± 16.48 kJ/mol from elements, and –52.53 ± 4.83, –49.45 6 ± 8.35, and –94.53 ± 11.66 kJ/mol from oxides (Y2O3 or Yb2O3, SiO2) and nitride (Si3N4). The silicates and N-containing silicate are energetically stable with respect to binary oxides and Si3N4, but the N-containing silicate may be metastable with respect to assemblages containing Y2SiO5, Si3N4, and SiO2. A linear relationship was found between the enthalpy of formation of a series of M2SiO5 silicates from binary oxides and the ionic potential (z/r) of the metal cation.

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Kozasa, Takashi, and Hisato Sogawa. "Formation of crystalline silicate around oxygen–rich AGB stars." Symposium - International Astronomical Union 191 (1999): 239–44. http://dx.doi.org/10.1017/s0074180900203124.

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Crystallization of silicate has been investigated within the framework of dust formation in steady state gas outflows around oxygen–rich AGB stars, where silicates are locked not only into homogeneous silicate grains but also into the mantles of heterogeneous grains. Based on the thermal history of dust grains after their formation, the crystallization calculation results in no crystalline silicate for the mass loss rate Ṁ ≤ 2 × 10−5M⊙ yr−1. Only silicate in the mantles of heterogeneous grains can be crystallized for Ṁ ≥ 3 × 10−5M⊙ yr−1, while homogeneous silicate grains remain amorphous. The mass fraction of crystalline silicate increases with increasing Ṁ. The radiation transfer calculations confirm the appearance of an emission feature around 33.5 μm, taking olivine as a representative of crystalline silicates. On the other hand, the 10μm feature appears in absorption, being dominated by homogeneous silicate grains. These trends are consistent with the observations. Thus the crystalline silicate is a diagnostics of high mass loss rate at the late stage of AGB stellar evolution, reflecting the formation process of dust grains.

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DERRIEN, RICHARD, ETHAN MICHAEL SULLIVAN, STEPHEN LIU, ELODIE MOINE, and FRANCIS BRIAND. "Silicate Island Formation in Gas Metal Arc Welding." Welding Journal 100, no. 01 (January 1, 2021): 13–26. http://dx.doi.org/10.29391/2021.100.002.

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Because formation of silicate islands during gas metal arc welding is undesirable due to decreased productivity and decreased quality of welds, it is important to understand the mechanism of the formation of these silicate islands to mitigate their presence in the weld. The effects of welding parameters on the silicate formation rate were studied. Results showed that the applied voltage and oxidizing potential of the shielding gas were the parameters that most strongly influenced the amount of silicates formed on the surface of the weld bead. High-speed video was used to observe the formation of silicate islands during the welding process, which showed that the silicates were present at each stage of the welding process, including the initial melting of the wire electrode, and grew by coalescence. A flow pattern of the silicate islands was also proposed based on video analysis. An electromagnetic levitation system was used to study the growth kinetics of the silicate islands. Silicate coverage rate was found to increase with increasing oxidizing time, increasing oxidizing potential of the atmosphere, and increasing content of alloying elements except for Ti.

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Niciu, H., Dorel Radu, C. Onose, A. Ioncea, Daniela Niciu, H. Stroescu, and C. S. Onose. "The Permanently Bonded Glass Decor from Chemical Precursors." Advanced Materials Research 39-40 (April 2008): 579–82. http://dx.doi.org/10.4028/www.scientific.net/amr.39-40.579.

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Alkaline earth metal silicates as well as many polyvalent metals silicates can be obtained through aqueous solutions reactions between an alkaline silicate solution and the solutions of metal salts. The vitrifiation of the oxide compositions, established by the necessary molar ratios for the projected glass, is realised by calculating the concentration of chemical precursors, through their reaction directly on the substrate. The sodium silicate viscosity in aqueous solution and the viscosity of nitrogenated compounds or oxalates necessary in the silicates synthesis is compatible with the necessary viscosity for ink-jet cartridges. The necessary silicates forming reactions were studied directly on the deposition support, so that the functional characteristics of the multicompartment ink-jet cartridges were used. Compositions were realised, in which the colouring effect was obtained with ionic colorants. The vitrifiation and the quality of the obtained thin films were studied through Optical Microscopy and Scanning Electron Microscopy.

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Heckmann, W., F. Ramsteiner, and Ch Mehler. "Morphology of Poly Amide Nanocomposites Characterized by Transmission Electron Microscopy (TEM) and Electron Spectroscopic Imaging (ESI)." Microscopy and Microanalysis 7, S2 (August 2001): 502–3. http://dx.doi.org/10.1017/s1431927600028580.

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The introduction of organophilic layered silicates into a polyamide matrix significantly improves stiffness and strength [1,2]. Two methods are known to prepare such nanocomposites. For both methods cations such as sodium, potassium, magnesium or calcium, located in the interlayer galleries of the layered silicates must be exchanged by quaternary alkyl ammonium ions containing at least one alkyl chain and so rendering the originally hydrophilic into an organophilic silicate. in the insitu-method monomeric caprolactam is intercalated between the modified silicate interlayers and subsequently polycondensated to polyamide. By this method the silicates can be broken down into their nanoscale building blocks as can be shown by TEM and ESI (Fig. 1). Another more direct possibility to delaminate the silicates is melt mixing in an extruder. with both methods similar degrees of delamination can be achieved.This paper presents some of our morphological results on polyamide containing organically modified montmorillonite.

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Lii, Kwang-Hwa. "High-T, High-P Hydrothermal Synthesis of Uranium Silicates and Germanates." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C759. http://dx.doi.org/10.1107/s2053273314092407.

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Most uranium minerals can be classified as oxidized species in which U is fully oxidized to U(VI), and reduced species, in which U occurs primarily as U(IV). Uranyl silicates are an important group of uranium(VI) minerals in the altered zones of many uranium deposits [1]. Uranyl silicates have also received attention because they form when spent nuclear fuel interacts with water containing silicon under oxidizing conditions. One naturally occurring uranium(IV) silicate exists, namely coffinite (USiO4), which is the most important ore mineral for uranium after uraninite. Numerous synthetic uranium(VI) silicates and germanates containing organic amines or alkali metals as countercations have also been reported [2]. In contrast to the uranium(VI) compounds, the chemistry of materials containing uranium(V) is considerably less developed owing to the tendency of U(V) to either oxidize to U(VI) or disproportionate to U(IV) and U(VI). We have synthesized a pentavalent-uranium silicate and a germanate by a high-temperature, high-pressure hydrothermal method in gold ampoules contained in a high-pressure reaction vessel at ca. 600 °C and 170 MPa [3a,b]. Following the synthesis of the U(V) compounds, a number of mixed-valence uranium silicates and germanates have been synthesized, for example, a mixed-valence uranium(IV,V) silicate, Cs2K(UO)2Si4O12 [3c], a uranium(IV,VI) germanate, Cs8U(UO2)3(Ge3O9)3·3H2O [3d], uranium(V,VI) silicates and germanates, A3(U2O4)Ge2O7 (A = Rb, Cs) and [Na9F2][(UO2)3(Si2O7)2] [3e,f], and a uranium(IV,V,VI) silicate, Na7UO2(UO)2(UO2)2Si4O16 [3g] in which three oxidation states of uranium co-exist in one compound. In addition, tetravalent-uranium compounds, Cs2USi6O15 and Cs4UGe8O20 [3h,i], were also synthesized. All members in the family of uranium silicates and germanates with the oxidation states of uranium from +4 to +6 have been observed. In this presentation the high-temperature, high-pressure hydrothermal synthesis, crystal structures, and XPS spectroscopy of these interesting compounds will be reported.

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Jakobsen, U. H. "A hydrated barium silicate in unmetamorphosed sedimentary rocks of central North Greenland." Mineralogical Magazine 54, no. 374 (March 1990): 81–89. http://dx.doi.org/10.1180/minmag.1990.054.374.08.

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AbstractA new occurrence of barium silicates has been found in unmetamorphosed sedimentary rocks of central North Greenland. Two different barium minerals have been identified, the Ba-feldspar hyalophane, and an unknown and hitherto undescribed hydrated Ba-silicate with an anhydrous chemical composition identical to cymrite but with about 4 moles of water in the mineral structure. Both silicates are found in a black organic-rich chert sequence in close association with baryte. No replacement textures are observed between the three Ba-minerals.The hydrated Ba-silicate in the unmetamorphosed rock sequence of the Navarana Fjord area is considered to represent a member in a sequence of Ba-silicates from the unknown Ba-silicate with four H2O in the structure (BaAl2Si2O8·4H2O), through cymrite with one H2O (BaAl2Si2O2O8·H2O) to celsian with none (BaAl2Si2O8). This sequence might reflect the continuous release of water during prograde diagenesis and metamorphism. The association between chert and Ba minerals in the sedimentary rocks of the Navarana Fjord area is believed to reflect an addition of silica and barium by hydrothermal solutions.

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P. C. Bennett, J. R. Rogers, W. J. "Silicates, Silicate Weathering, and Microbial Ecology." Geomicrobiology Journal 18, no. 1 (January 2001): 3–19. http://dx.doi.org/10.1080/01490450151079734.

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11

Okamoto, Tamami, and Shigeru Ida. "Monte Carlo Simulation of Dust Particles in a Protoplanetary Disk: Crystalline to Amorphous Silicate Ratio in Comets." Astrophysical Journal 928, no. 2 (April 1, 2022): 171. http://dx.doi.org/10.3847/1538-4357/ac4bc1.

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Abstract The observationally inferred crystalline abundance in silicates in comets, which should have been formed in the outer region of a protoplanetary disk, is relatively high (∼10%–60%), although crystalline silicates would be formed by the annealing of amorphous precursors in the inner disk region. In order to quantitatively address this puzzle, we performed a Monte Carlo simulation of the advection/diffusion of silicate particles in a turbulent disk in a setting based on the pebble accretion model: pebbles consisting of many small amorphous silicates embedded in an icy mantle are formed in the outer disk region, silicate particles are released at the snow line, crystalline silicate particles are produced at the annealing line, silicate particles diffuse beyond the snow line, and they eventually stick to drifting pebbles to return to the snow line. In the simple case without sticking and with steady pebble flux, we show through the simulations and analytical arguments that the crystalline components in silicate materials beyond the snow line are robustly and uniformly ≃5%. On the other hand, in a more realistic case with sticking and with a decaying pebble flux, the crystalline abundance increases to ∼20%–25%, depending on the ratio of the decay to diffusion timescales. This abundance is consistent with the observations. In this investigation, we assume a simple steady-accretion disk. The simulations coupled with the disk evolution are needed for a more detailed comparison with observed data.

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Borrmann, Thomas, Anton Dominis, Andrew J. McFarlane, James H. Johnston, Michael J. Richardson, Leon A. P. Kane-Maguire, and Gordon G. Wallace. "Immobilisation of Fully Sulfonated Polyaniline on Nanostructured Calcium Silicate." Journal of Nanoscience and Nanotechnology 7, no. 12 (December 1, 2007): 4303–10. http://dx.doi.org/10.1166/jnn.2007.879.

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Up to 7.4% (w/w) of the sulfonated polyaniline, poly(2-methoxyaniline-5-sulfonic acid) (PMAS) can be absorbed onto nanostructured calcium silicates. Spectroscopic and leaching studies on the novel PMAS-silicate nanocomposites obtained indicate that attachment of the PMAS occurs via electrostatic binding of PMAS sulfonate groups to Ca2+ sites on the silicates. The surface area and pore volume of the nanocomposites are comparable to those of pure silicate and increase the surface area of the PMAS polymer by several orders of magnitude. The PMAS emeraldine salt in the nanocomposites retains its chemical reactivity, being readily oxidised and reduced to its pernigraniline and leucoemeraldine forms, respectively. The conductivity of the composite is comparable to that of the pure PMAS, several orders of magnitude higher than that of dried nanostructured calcium silicate.

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Iliushchenko, V., L. Kalina, P. Hruby, V. Bilek Jr, J. Fladr, P. Bily, and J. Bojanovsky. "The treatment of cementitious surface by selected silicate sealers." Journal of Physics: Conference Series 2341, no. 1 (September 1, 2022): 012003. http://dx.doi.org/10.1088/1742-6596/2341/1/012003.

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Over the past decades, the efficiency of the silicate-based surface treatment agents, in other words, sealers, in concrete systems has been widely investigated. The surface treatment technology protects the cementitious systems against the penetration of undesirable substances. Nevertheless, understanding of the several aspects concerning silicate-based sealers is not entirely clear. This paper studies the action mechanism of selected silicates such as potassium, sodium, lithium water glasses, and colloidal silica. The effectiveness of used sealers in terms of water absorption reduction, the ability of silicates to heal pores, and the influence on the microstructure of the cement substrate were studied. Instrumental methods such as rheology, mercury intrusion porosimetry, or scanning electron microscopy were used to achieve satisfactory results. Nuances between the unique film-forming sealers were found. Colloidal silica showed a low sealing effect compared to alkali silicates.

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Marler, Bernd, Melanie Müller, and Hermann Gies. "Structure and properties of ITQ-8: a hydrous layer silicate with microporous silicate layers." Dalton Transactions 45, no. 25 (2016): 10155–64. http://dx.doi.org/10.1039/c6dt00713a.

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Farooq, Abid, Heejin Lee, Gwang Hoon Rhee, Eun-Bum Cho, and Young-Kwon Park. "Yellow Poplar Gasification Over Ni Silicate and Ni/Silica." Journal of Nanoscience and Nanotechnology 20, no. 9 (September 1, 2020): 5667–70. http://dx.doi.org/10.1166/jnn.2020.17635.

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The activity of Ni silicates having different Ni/Si molar ratio (0.5 and 1) and Ni/silica were tested on biomass gasification. Ni silicate (Ni/Si= 0.5) and Ni/silica produced the higher gas yield than Ni silicate (Ni/Si = 1.0). The larger amount of H2 and CO were produced over Ni silicate (Ni/Si = 0.5) and Ni/silica compared those over Ni silicate (Ni/Si = 1.0). The catalysts were characterized using BET and XRD analysis. Ni silicate (Ni/Si = 0.5) showed promising activity for the production of syngas at higher temperature and can be employed in gasification.

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Hawthorne, Frank C., Yulia A. Uvarova, and Elena Sokolova. "A structure hierarchy for silicate minerals: sheet silicates." Mineralogical Magazine 83, no. 1 (November 9, 2018): 3–55. http://dx.doi.org/10.1180/mgm.2018.152.

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AbstractThe structure hierarchy hypothesis states that structures may be ordered hierarchically according to the polymerisation of coordination polyhedra of higher bond-valence. A hierarchical structural classification is developed for sheet-silicate minerals based on the connectedness of the two-dimensional polymerisations of (TO4) tetrahedra, where T = Si4+ plus As5+, Al3+, Fe3+, B3+, Be2+, Zn2+ and Mg2+. Two-dimensional nets and oikodoméic operations are used to generate the silicate (sensu lato) structural units of single-layer, double-layer and higher-layer sheet-silicate minerals, and the interstitial complexes (cation identity, coordination number and ligancy, and the types and amounts of interstitial (H2O) groups) are recorded. Key aspects of the silicate structural unit include: (1) the type of plane net on which the sheet (or parent sheet) is based; (2) the u (up) and d (down) directions of the constituent tetrahedra relative to the plane of the sheet; (3) the planar or folded nature of the sheet; (4) the layer multiplicity of the sheet (single, double or higher); and (5) the details of the oikodoméic operations for multiple-layer sheets. Simple 3-connected plane nets (such as 63, 4.82 and 4.6.12) have the stoichiometry (T2O5)n (Si:O = 1:2.5) and are the basis of most of the common rock-forming sheet-silicate minerals as well as many less-common species. Oikodoméic operations, e.g. insertion of 2- or 4-connected vertices into 3-connected plane nets, formation of double-layer sheet-structures by (topological) reflection or rotation operations, affect the connectedness of the resulting sheets and lead to both positive and negative deviations from Si:O = 1:2.5 stoichiometry. Following description of the structural units in all sheet-silicate minerals, the minerals are arranged into decreasing Si:O ratio from 3.0 to 2.0, an arrangement that reflects their increasing structural connectivity. Considering the silicate component of minerals, the range of composition of the sheet silicates completely overlaps the compositional ranges of framework silicates and most of the chain-ribbon-tube silicates.

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Vedyakov, Ivan, Vladimir Vaskalov, Nikolai Maliavski, and Mikhail Vedyakov. "Highly Efficient Glass Ceramic Thermal Insulation." E3S Web of Conferences 263 (2021): 01017. http://dx.doi.org/10.1051/e3sconf/202126301017.

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Alkali-silicate thermal insulation materials (foam silicates) belong to the group of mineral heat insulators. Their main disadvantage is insufficient water resistance, to increase which special water-strengthening additives are introduced into materials. The aim of this work was to obtain and study foam silicates in granular (FGCG) and slab (FGCS) forms using a new production technology characterized by a simple one-stage technological scheme. Natural or technogenic amorphous silica, glassy sodium silicate (with the addition of carbonate or hydroxide) and a carbon-containing foaming agent, were used as the raw materials. Some part of the silica component was included in the binder solution, which made it possible to increase the silicate modulus in the final product to 5-10. This factor together with rather high Al2O3 concentration in the silica raw, made it possible to obtain foamed materials of very high water resistance. Another feature of the applied technology was a high foaming temperature (750–900°C). This factor makes a significant contribution to improving the water resistance of foam silicates, and significantly reducing their thermal conductivity and water absorption. As a result, FGCG was obtained with a bulk density of 170-440 kg/m3 (for FGCS – 300-400 kg/m3), a compressive strength in a cylinder of 0.5-6.3 MPa, a thermal conductivity of 0.046-0.084 W/(m·K) and a water absorption of 7.8-13.5% by volume. Mass loss of the specimens in boiling water was 0.12-0.33%, which puts obtained foamed materials on a par with most waterproof foam silicates being produced today.

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Kemmitt, T., and NB Milestone. "The Ring Size Influence on 29Si N.M.R. Chemical Shifts of Some Spirocyclic Tetra- and Penta-coordinate Diolato Silicates." Australian Journal of Chemistry 48, no. 1 (1995): 93. http://dx.doi.org/10.1071/ch9950093.

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A series of tetracoordinate spirocyclic silicates has been prepared from the reaction of a range of diols with tetraethoxysilane, Si ( OEt )4. The silicates can be converted into anionic pentacoordinate silicates by reaction with KOBut/18-crown-6 in toluene. Alternatively, the pentacoordinate spirocycles can be prepared directly without prior preparation of a tetracoordinate spiro silicate. 29Si n.m.r. studies have demonstrated that the chemical shifts are sensitive to both coordination number and ring size. Ring contributions to the 29Si chemical shifts are apparent for the five- membered ring spiro silicates, those for the pentcoordinate species being less than those for the tetracoordinate species. Acyclic and six- membered ring spiro silicates are virtually indistinguishable by 29Si n.m.r. spectroscopy, which demonstrates that no ring contribution to the chemical shift is apparent for this ring size.

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Khachatryan, L. A. "Disperse Layered Silicates in Magnesium Silicate Rocks." Glass Physics and Chemistry 30, no. 1 (January 2004): 67–72. http://dx.doi.org/10.1023/b:gpac.0000016400.42044.5b.

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Sanghani, Manish N., Luc Lajaunie, Kuljeet Kaur Marhas, William D. A. Rickard, Silver Sung-Yun Hsiao, Zan Peeters, Hsien Shang, Der-Chuen Lee, José J. Calvino, and Martin Bizzarro. "Microstructural and Chemical Investigations of Presolar Silicates from Diverse Stellar Environments." Astrophysical Journal 925, no. 2 (January 31, 2022): 110. http://dx.doi.org/10.3847/1538-4357/ac3332.

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Abstract We report the structural and chemical investigation of nine presolar silicate grains from the CH3/CBb3 chondrite Isheyevo and CR2 chondrite Northwest Africa (NWA) 801. Five of these grains belong to group 1, likely condensed in low- to intermediate-mass asymptotic giant branch (AGB) stars, super-AGB stars, or core-collapse supernovae, while the remaining four grains belong to group 4 and have a supernova origin. The advanced transmission electron microscopy and associated electron spectroscopy analyses show a diverse range of chemical and structural compositions for presolar silicates. Two GEMS (glass with embedded metal and sulfide)-like silicates, each from different groups, condensed under nonequilibrium conditions in stellar outflows. Two nonstoichiometric silicates from group 1 have dissimilar formation and alteration histories. An amorphous silicate from group 1 with olivine-like [(Mg,Fe)2SiO4] composition likely formed as a crystalline olivine that subsequently amorphized in the interstellar medium. An oldhamite (CaS) grain within a stoichiometric enstatite (MgSiO3) from group 1 probably formed by heterogeneous condensation in circumstellar outflows. Of the two crystalline grains from group 4, one is an antigorite [(Mg,Fe)3Si2O5(OH)4], while the other is a nontronite [Na,Fe2(Si,Al)4O10(OH)2.nH2O], both formed as a crystalline forsterite and later altered to have hydrated silicate composition. A group-4 silicate has a chemical composition similar to a low Ca-pyroxene [(Ca,Mg)(Si,Al)2O6]. Our data imply that presolar grains from different groups can have a similar range of grain-formation conditions.

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Champness, P. E., and R. W. Devenish. "Elemental mass loss in silicate minerals during x-ray analysis." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 804–5. http://dx.doi.org/10.1017/s0424820100177155.

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It has long been recognised that silicates can suffer extensive beam damage in electron-beam instruments. The predominant damage mechanism is radiolysis. For instance, damage in quartz, SiO2, results in loss of structural order without mass loss whereas feldspars (framework silicates containing Ca, Na, K) suffer loss of structural order with accompanying mass loss. In the latter case, the alkali ions, particularly Na, are found to migrate away from the area of the beam. The aim of the present study was to investigate the loss of various elements from the common silicate structures during electron irradiation at 100 kV over a range of current densities of 104 - 109 A m−2. (The current density is defined in terms of 50% of total current in the FWHM probe). The silicates so far ivestigated are:- olivine [(Mg, Fe)SiO4], a structure that has isolated Si-O tetrahedra, garnet [(Mg, Ca, Fe)3Al2Si3AO12 another silicate with isolated tetrahedra, pyroxene [-Ca(Mg, Fe)Si2O6 a single-chain silicate; mica [margarite, -Ca2Al4Si4Al4O2O(OH)4], a sheet silicate, and plagioclase feldspar [-NaCaAl3Si5O16]. Ion- thinned samples of each mineral were examined in a VG Microscopes UHV HB501 field- emission STEM. The beam current used was typically - 0.5 nA and the current density was varied by defocussing the electron probe. Energy-dispersive X-ray spectra were collected every 10 seconds for a total of 200 seconds using a Link Systems windowless detector. The thickness of the samples in the area of analysis was normally 50-150 nm.

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JIA, FEIFEI, and SHAOXIAN SONG. "EXFOLIATION AND CHARACTERIZATION OF LAYERED SILICATE MINERALS: A REVIEW." Surface Review and Letters 21, no. 02 (April 2014): 1430001. http://dx.doi.org/10.1142/s0218625x14300019.

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Exfoliated silicate minerals have attracted great attentions because of the dramatic improvement in properties. This paper highlights the preparation of exfoliated silicate minerals, including physical, chemical, mixed physical and chemical methods. The mechanisms by which silicates are exfoliated and the important influential factors are also summarized. Finally, the instrumental techniques to characterize the exfoliated structure and exfoliation degree are presented.

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Morard, Guillaume, Jean-Alexis Hernandez, Marco Guarguaglini, Riccardo Bolis, Alessandra Benuzzi-Mounaix, Tommaso Vinci, Guillaume Fiquet, et al. "In situ X-ray diffraction of silicate liquids and glasses under dynamic and static compression to megabar pressures." Proceedings of the National Academy of Sciences 117, no. 22 (May 15, 2020): 11981–86. http://dx.doi.org/10.1073/pnas.1920470117.

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Properties of liquid silicates under high-pressure and high-temperature conditions are critical for modeling the dynamics and solidification mechanisms of the magma ocean in the early Earth, as well as for constraining entrainment of melts in the mantle and in the present-day core–mantle boundary. Here we present in situ structural measurements by X-ray diffraction of selected amorphous silicates compressed statically in diamond anvil cells (up to 157 GPa at room temperature) or dynamically by laser-generated shock compression (up to 130 GPa and 6,000 K along the MgSiO3glass Hugoniot). The X-ray diffraction patterns of silicate glasses and liquids reveal similar characteristics over a wide pressure and temperature range. Beyond the increase in Si coordination observed at 20 GPa, we find no evidence for major structural changes occurring in the silicate melts studied up to pressures and temperatures exceeding Earth’s core mantle boundary conditions. This result is supported by molecular dynamics calculations. Our findings reinforce the widely used assumption that the silicate glasses studies are appropriate structural analogs for understanding the atomic arrangement of silicate liquids at these high pressures.

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Krüger, Hannes, Peter Tropper, Udo Haefeker, Reinhard Kaindl, Martina Tribus, Volker Kahlenberg, Christoph Wikete, Martin R. Fuchs, and Vincent Olieric. "Innsbruckite, Mn33(Si2O5)14(OH)38 – a new mineral from the Tyrol, Austria." Mineralogical Magazine 78, no. 7 (December 2014): 1613–27. http://dx.doi.org/10.1180/minmag.2014.078.7.06.

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AbstractA description of the new mineral innsbruckite, Mn33(Si2O5)14(OH)38, a hydrous manganese phyllosilicate found in Tyrol, Austria is given. The crystal structure was determined by singlecrystal synchrotron radiation diffraction experiments at the X06DA beamline at the Swiss Light Source (Paul Scherrer Institute, Villigen, Switzerland). The space group is Cm and lattice parameters are a = 17.2760(19), b = 35.957(5), c = 7.2560(8) Å , β = 91.359(7)º, V = 4506.1(10) Å3, Z = 2. Innsbruckite belongs to the group of modulated 1:1 layer silicates and is chemically and structurally quite closely related to bementite, Mn7(Si2O5)3(OH)8. The chemical analysis revealed a close to ideal composition with only minor amounts of Al, Fe and Mg. Using Liebau’s nomenclature for silicate classification the silicate anion can be described as an unbranched siebener single layer. Innsbruckite shows a complex topology of the silicate sheet, exhibiting 4-, 5-, 6- and 8-membered rings. The silicate sheet is fully characterized using vertex symbols, and its topology is compared to those in other complex sheet silicates. Furthermore, the structural investigation is complemented with Raman spectroscopic studies.

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Liu, Yongjun, Wenping Luo, Jiali Wu, Yewen Fang, Yan Li, Xiaoping Jin, Li Zhang, Zongyong Zhang, Fenfen Xu, and Chan Du. "Radical addition-polar termination cascade: efficient strategy for photoredox-neutral-catalysed cyclopropanation and Giese-type reactions of alkenyl N-methyliminodiacetyl boronates." Organic Chemistry Frontiers 7, no. 13 (2020): 1588–92. http://dx.doi.org/10.1039/d0qo00349b.

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Silicate meets boronate: efficient cyclopropanation and Giese-type reactions of alkenyl N-methyliminodiacetyl boronates with alkyl silicates have been realized via a photoredox-neutral-catalysed radical-polar crossover process.

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Li, Chao-Feng, Lian-Jun Feng, Xuan-Ce Wang, Simon-A. Wilde, Zhu-Yin Chu, and Jing-Hui Guo. "A low-blank two-column chromatography separation strategy based on a KMnO4 oxidizing reagent for Cr isotope determination in micro-silicate samples by thermal ionization mass spectrometry." Journal of Analytical Atomic Spectrometry 32, no. 10 (2017): 1938–45. http://dx.doi.org/10.1039/c7ja00225d.

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27

Peñaflor Galindo, Tania Guadalupe, Kazuto Sugimoto, Shota Yamada, Taito Sugibuchi, Zizhen Liu, and Motohiro Tagaya. "Investigation of Inclusion States of Silicate and Carbonate Ions in Hydroxyapatite Particles Prepared under the Presence of Sodium Silicate." Biomimetics 7, no. 2 (April 1, 2022): 40. http://dx.doi.org/10.3390/biomimetics7020040.

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Biological hydroxyapatite (HA) contains the different minor ions which favour its bio-reactivity in vivo. In this study, the preparation of HA particles containing both silicate and carbonate ions under the presence of sodium silicate was investigated, and the physicochemical properties were evaluated according to the contents and states of silicate and carbonate ions. The increment in the silicate ion reduced the crystallinity and expanded the crystalline size along with a-axis. Solid-state 29Si–NMR spectra indicated the increase in the adsorption of oligomeric silicate species on the HA particle surfaces in addition to the substitution state of silicate ions, suggesting the occurrence of the surface coating of silicates on the surfaces. The possible states of carbonate and silicate ions at the HA surfaces will provide the bioactivity.

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Mosser, Chr, J. C. Leprun, and A. Blot. "Les éléments traces des fractions < 2 μm à kaolinite et smectite formées par altération de roches silicatées acides en Afrique de l'Ouest (Sénégal et Haute-Volta)." Chemical Geology 48, no. 1-4 (March 1985): 165–81. http://dx.doi.org/10.1016/0009-2541(85)90044-0.

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Wagh, Arun S., and Victor E. Douse. "Silicate bonded unsintered ceramics of Bayer process waste." Journal of Materials Research 6, no. 5 (May 1991): 1094–102. http://dx.doi.org/10.1557/jmr.1991.1094.

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Sodium silicates are investigated to enhance the strengths of Bayer process muds and develop structural ceramics without sintering. With an impregnation of sodium silicate from 2% to 10% concentration in red mud, the fracture toughness is enhanced from 0.2 to 0.9 MPa. Compression strengths of 25.1 MPa (3628 psi) have been attained with red mud at 10% silicate concentration. Similar enhancements by a factor of 4 to 5 have been obtained for modulus of rupture and Brinell hardness number. It is shown that these properties do not deteriorate in acidic and neutral environment in water, implying stability to weathering conditions. SEM investigations reveal elongated crystal formation, possibly of aluminum and iron silicates in the aggregate. These crystals act like whiskers enhancing the strength. The process is applicable for development of low-cost construction components.

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Ganter, Markus, Wolfram Gronski, Peter Reichert, and Rolf Mülhaupt. "Rubber Nanocomposites: Morphology and Mechanical Properties of BR and SBR Vulcanizates Reinforced by Organophilic Layered Silicates." Rubber Chemistry and Technology 74, no. 2 (May 1, 2001): 221–35. http://dx.doi.org/10.5254/1.3544946.

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Abstract Rubber compounds based on butadiene rubber (BR) or styrene—butadiene rubber (SBR) containing organophilic layered silicates were prepared. Organophilic silicates were swollen in a rubber/toluene solution. Matrix—filler reactive bonding was performed by adding bis(triethoxysilylpropyl)-tetrasulfan (TESPT) during swelling. Excellent dispersion of organoclay nanofillers in rubber matrices was demonstrated by transmission electron microscopy (TEM) and atomic force microscopy (AFM) exhibiting intercalated and partially exfoliated silicate layers. Matrix—filler interfacial coupling by TESPT led to reduced strain at break and reduced hysteresis for both organoclay and silica-based vulcanizates as expected for successful matrix filler coupling. Organoclay vulcanizates exhibited enhanced hysteresis when compared to silica compounds. This is related to orientation and sliding of anisotropic silicate layers, as determined by online wide-angle X-ray scattering (WAXS) measurements during cyclic tensile testing.

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Reddy, P. Manohar, Ravy Lakshmi, Febin Prabhu Dass, and Swamiappan Sasikumar. "Synthesis, characterization and formulation of sodium calcium silicate bioceramic for drug delivery applications." Science and Engineering of Composite Materials 23, no. 4 (July 1, 2016): 375–80. http://dx.doi.org/10.1515/secm-2014-0057.

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AbstractSodium calcium silicate (Na2CaSiO4) is a bioactive silicate with Na2O, CaO and SiO2 as its basic components, which is similar to that of the composition of bioactive glasses. In the present study, pure sodium calcium silicate was synthesized by rapid combustion technique, and the synthesized sample was characterized by powder X-ray diffraction to check the phase purity. The scaffolds were prepared by varying the ratio of sodium calcium silicate and polyvinyl alcohol, and the apatite-formation ability of the scaffolds was examined by soaking them in a simulated body fluid. The results revealed the formation of hydroxyapatite on the surface of the scaffold after 5 days, which is found to be rapid when compared with the bioactivity of the calcium silicates and calcium magnesium silicates. The scaffolds were also loaded with ciprofloxacin as a model drug and analyzed for its drug release profile using UV spectrophotometer. The release profile did not vary with the change in bioceramic-to-biopolymer ratio, and 60% of the drug was released in 10 days, which is within the appreciable range for a targeted drug delivery system. Moreover, the experimental and simulated values of the release kinetics were compared by applying the existing mathematical model.

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Simachev, A. S., T. N. Oskolkova, A. A. Umanskii, and A. V. Golovatenko. "Non-metallic inclusions in different zones of crystallization of E90KhAF rail steel." Izvestiya. Ferrous Metallurgy 64, no. 2 (April 2, 2021): 135–42. http://dx.doi.org/10.17073/0368-0797-2021-2-135-142.

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Metallographic and X-ray studies of continuously cast billets of E90KhAF rail steel have been carried out. We have established the regularities of non-metallic inclusions distribution over the crystallization zones before and after billets deformation. It was revealed that in crustal zone the main non-metallic inclusions are point oxides, aluminum nitrides, iron silicates (FeO·SiO2) and alumosilicates (Al2O3·SiO2). They were identified in the zone of columnar crystals. In central zone of the billet, manganese sulfides (MnS), manganese silicates (MnO·SiO2), alumosilicates (Al2O3·SiO2), iron silicates (FeO·SiO2), and point oxides were found. It has been determined that concentration and size of nonmetallic inclusions tend to increase from the surface to central zone of continuously cast billets, which is consistent with generally accepted ideas about mechanisms of billet formation during crystallization. The mechanism of deformation of two-phase silicate non-metallic inclusions and their influence on quality of rail products was disclosed. It is shown that inhomogeneous deformability of complex silicate inclusions aggravates their harmful effect on rail products quality. In this case, additional stresses appear in addition to inclusion-matrix deformation and contact stresses existing at interphase boundaries. This pattern also holds for non-deformed silicate inclusions. Such a distribution of inclusions in the billets volume somewhat reduces their negative effect on rails quality, since near-contact layers of the billet undergo more intense deformation during rolling, and as the axial zone of a billet is approached, deformation rate decreases.

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Molster, F. J. "Astromineralogy: Crystalline silicates." Symposium - International Astronomical Union 209 (2003): 291–98. http://dx.doi.org/10.1017/s0074180900208796.

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Silicates are the most abundant dust component in our Universe. For a long time it was generally assumed that around evolved stars only amorphous silicates were present. The infrared space observatory (ISO; Kessler et al. 1996) discovered that the abundance of crystalline silicates can be quite significant. Thanks to ISO it is now for the first time possible to determine the exact chemical composition of the silicates, and in contrast to the amorphous silicates, the crystalline silicates turned out to be very Fe-poor (i.e. forsterite and enstatite). Careful investigations of the spectra of crystalline silicates in several conditions, both in laboratory and in space, have taken place. It was found that not only the abundance of the crystalline silicates is related to the spatial distribution of the circumstellar dust, but also the shape of the features differs between sources with and without a disk-like dust distribution. Because of the many spectral features of the crystalline silicates one can easily determine temperatures and mass ratios for enstatite and forsterite. But even single features contain interesting information. The position and FWHM of the 69.0 micron forsterite feature, might be used as a new diagnostic of characteristic temperatures of (crystalline) silicate dust, while the 33.6 micron forsterite feature bears evidence for its formation history.

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Plášil, Jakub. "Mineralogy, Crystallography and Structural Complexity of Natural Uranyl Silicates." Minerals 8, no. 12 (November 27, 2018): 551. http://dx.doi.org/10.3390/min8120551.

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Naturally occurring uranyl silicates are common constituents of the oxidized parts (i.e., supergene zone) of various types of uranium deposits. Their abundance reflects the widespread distribution of Si4+ in the Earth’s crust and, therefore, in groundwaters. Up to date, 16 uranyl silicate minerals are known. Noteworthy is that the natural uranyl silicates are not extremely diverse regarding their crystal structures; it is a result of possible concentrations (activity) of Si4+ in aqueous solutions derived from dissolution of primary Si minerals or the composition of late hydrothermal fluids. Therefore, in natural systems, we distinguish in fact among two groups of uranyl silicate minerals: uranophane and weeksite-group. They differ in U:Si ratio (uranophane, 1:1; weeksite, 2:5) and they form under different conditions, reflected in distinctive mineral associations. An overview of crystal-chemistry is provided in this paper, along with the new structure data for few members of the uranophane group. Calculations of the structural complexity parameters for natural uranyl silicates are commented about as well as other groups of uranyl minerals; these calculations are also presented from the point of view of the mineral paragenesis and associations.

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Garbalińska, Halina, Jarosław Strzałkowski, and Agata Stolarska. "Moisture Influence on Compressive Strength of Calcium Silicate Masonry Units–Experimental Assessment and Normative Calculations." Materials 13, no. 17 (August 29, 2020): 3817. http://dx.doi.org/10.3390/ma13173817.

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This paper primarily assesses the scale of adverse changes to the compressive strength of different types of silicates due to the influence of moisture. The study covers three groups of silicate units of different strength classes—15, 20 and 25—obtained from three different manufacturers. It was demonstrated that in all studied groups, moisture significantly decreased the compressive strength by about 30–40%. In addition, microstructural studies were conducted to analyze the relationship between the specific porosity structure of each group of silicate bricks and their compressive strength. On the basis of SEM (Scanning Electron Microscopy) and EDS (Electron Dispersive Spectroscopy) analysis, the elemental composition of individual silicates was determined and the contact zone between the aggregate and the binder was determined, which largely influenced the obtained compressive strength of each silicates. Next, the study referred to the utility of the normative procedure used to determine the strength class of samples with different geometries and at different moisture concentrations. The results of the calculations showed the high accuracy of the normative-based assessment of strength class, regardless of the manufacturer and the moisture values during examination.

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Borrmann, Thomas, Andrew McFarlane, Uwe Ritter, and James Johnston. "Rhodium catalysts build into the structure of a silicate support in the hydroformylation of alkenes." Open Chemistry 11, no. 4 (April 1, 2013): 561–68. http://dx.doi.org/10.2478/s11532-012-0186-z.

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AbstractRhodium is build into a nano-structured calcium silicate during the synthesis of the silicate. Thereby, it was desired to create a robust heterogeneous catalyst, which does not suffer from catalyst leaching like rhodium impregnated on a pre-formed silicate. While this was achieved, the silicate structure was adversely affected by the incorporation of rhodium — the surface area and pore volume of the material were found to be comparatively low. Alcohol and acid washing were tested to address this issue. The alcohol treatment proved detrimental as catalytic material was leached from the silicate. The acid washed rhodium containing calcium silicate was quite active in the hydroformylation of alkenes and did not suffer loss of catalyst into the product phase. Acid treated rhodium containing silicates were more active than their untreated counterparts but less selective due to access to the rhodium centers being opened.

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Dunn, Pete J. "The lead silicates from Franklin, New Jersey: occurrence and composition." Mineralogical Magazine 49, no. 354 (December 1985): 721–27. http://dx.doi.org/10.1180/minmag.1985.049.354.12.

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AbstractThe lead silicate minerals from Franklin, New Jersey, occurred in two separate assemblages. One of these is characterized by esperite associated with hardystonite and occasional larsenite. The second assemblage can be considered as two parts: one consists of margarosanite, barysilite, nasonite, and ganomalite; the other contains roeblingite and hancockite, together with a number of highly hydrated phases. Chemical analyses indicate that these species conform to their theoretical compositions. There are no simple lead silicates at Franklin; all are compound silicates of Pb with Mn, Zn, and Ca.

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38

Rachmadani Rambe, Sakinah, Irvina Nurachmi, and Syahril Nedi. "CONTENTS OF NITRATES, PHOSPHATES, SILICATES AND MISTAKES DIATOMS (Epiphytic) IN SEAGRASSES (Thalassia hemprichii) WATERS NIRWANA BEACH KECAMATAN TELUK NIBUNG KOTA PADANG SUMATERA BARAT PROVINCE." Asian Journal of Aquatic Sciences 2, no. 1 (January 10, 2020): 39–48. http://dx.doi.org/10.31258/ajoas.2.1.39-48.

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Epiphytic diatoms are diatoms whose lives are associated with plants, one of which is seagrass. Nitrates, phosphates and silicates are needed to support growth and development, especially epiphytic which attaches to seagrass leaves. The research was conducted in May 2018 in the waters of Nirwana Beach, Teluk Nibung Subdistrict, Padang City, West Sumatra Province. The aim of this study was to determine the relationship of nitrate, phosphate, and silicate content to the abundance of diatoms. The method used in this study is the survey method. Taking diatom samples is done by grinding the surface of seagrass leaves using a brush, while sampling nitrates, phosphates and silicates is done using a water sampler. The results of this study indicate that nitrate concentrations ranged from 1,250-1,255 mg / l, phosphate 0,031-0,570 mg / l and silicate 1,180-1,700 mg/l. The total abundance of diatoms ranges from 459-3446 ind / cm2, where the diatom genus that dominates at each station is Navicula, Isthmia, and Stephanopyxis. Based on statistical analysis shows that the content of nitrate, phosphate, and silicate has a positive relationship to the abundance of epiphytic diatoms.

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Vereshchagin, V. I., and T. S. Petrovskaya. "TRADITIONS AND PERSPECTIVES OF THE TECHNOLOGY OF SILICATES AND NANOMATERIALS DEPARTMENT." Steklo i Keramika, no. 13 (January 2023): 47–50. http://dx.doi.org/10.14489/glc.2023.01.pp.047-050.

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The article provides a brief historical outline of the activities of the Technology of Silicates and Nanomaterials Department of the National Research Tomsk Polytechnic University which is the first technical university in the Asian part of Russia. Initially, the Laboratory of Chemical Technology of Mineral Substances, since 1929 the Silicate Technology Department, since 2007 the Technology of Silicates and Nanomaterials Department, nowdays it is one of the leading scientific and educational centers of the country for the study of silicate raw materials, the development of advanced technologies for ceramics, binders and glass materials, and the training of engineers and scientists specializing in the relevant fields. Research areas of the team embrases now the development of materials and technologies for nanostructured technical and building ceramics with enhanced functional properties, foam glass-ceramic materials, proppants for oil and gas production, biomedical ceramics, magnesian binders with increased strength and water resistance.

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Malhis, Abeer A., Sharif H. Arar, Manar K. Fayyad, and Hamdallah A. Hodali. "Amino- and thiol-modified microporous silicalite-1 and mesoporous MCM-48 materials as potential effective adsorbents for Pb(II) in polluted aquatic systems." Adsorption Science & Technology 36, no. 1-2 (January 25, 2017): 270–86. http://dx.doi.org/10.1177/0263617416689270.

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Aluminum-free zeolite silicalite-1 and the ordered mesoporous silicates Mobile Crystalline Material No. 48 (MCM-48) were prepared and functionalized with 3-aminopropyltriethoxysilane (APTES) and 3-mercaptopropyltrimethoxysilane (MPTMS) for the enhancement of adsorption capacity. Functionalization via post synthesis grafting method was adopted and the functionalized silicate systems were denoted as silicalite-1-NH2, silcalite-1-SH, MCM-48-NH2 and MCM-48-SH. Functionalization, that was confirmed by XRD, FT-IR and surface area measurements, indicated no structural changes on the silicate materials. The adsorption of Pb(II) ions into these modified silicates was investigated in aqueous solutions with optimized pH at 5.5 where adsorption influencing factors including contact time, adsorbent dose and metal ion initial concentration were studied. Adsorption experimental data for silicalite-1-NH2, MCM-48-NH2 and MCM-48-SH showed satisfactory correlation with Langmuir and Freundlich models. According to Langmuir isotherm, the maximum capacities for the above three modified silicate systems, for 100 ppm Pb(II) dose, are 43.5, 75.2 and 31.2 mg/g and with Kf constant values of 16.9, 44.4 and 12.0 L/mg from Freundlich isotherm, respectively. The three modified silicate systems exhibited complete sequestration of Pb(II) ion concentrations in the range 0.48–1.7 ppm from samples collected from Zarqa River in four seasons of the year 2013.

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Spoon, H. W. W., A. Hernán-Caballero, D. Rupke, L. B. F. M. Waters, V. Lebouteiller, A. G. G. M. Tielens, T. Loredo, Y. Su, and V. Viola. "The Infrared Database of Extragalactic Observables from Spitzer. II. The Database and Diagnostic Power of Crystalline Silicate Features in Galaxy Spectra." Astrophysical Journal Supplement Series 259, no. 2 (March 22, 2022): 37. http://dx.doi.org/10.3847/1538-4365/ac4989.

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Abstract We present the Infrared Database of Extragalactic Observables from Spitzer (IDEOS), a homogeneous, publicly available, database of 77 fitted mid-infrared observables in the 5.4–36 μm range, comprising measurements for 3335 galaxies observed in the low-resolution staring mode of the Infrared Spectrometer on board the Spitzer Space Telescope. Among the included observables are polycyclic aromatic hydrocarbon fluxes and their equivalent widths, the strength of the 9.8 μm silicate feature, emission-line fluxes, solid-state features, rest-frame continuum fluxes, synthetic photometry, and a mid-infrared spectral classification. The IDEOS spectra were selected from the Cornell Atlas of Spitzer-IRS Sources. To our surprise, we have detected at a >95% confidence level crystalline silicates in the spectra of 786 IDEOS galaxies. The detections range from single-band detections to detections of all fitted crystalline bands (16, 19, 23, 28, and 33 μm). We find the strength of the crystalline silicate bands to correlate with the amorphous silicate strength and the change from an emission to an absorption feature to occur at higher obscuration as the wavelength of the crystalline silicate band is longer. These observed characteristics are consistent with an origin for the amorphous and crystalline silicate features in a centrally heated dust geometry, either an edge-on disk or a cocoon. We find the 23 and 33 μm crystalline silicate bands to be well suited to classify the obscuration level of galactic nuclei, even in the presence of strong circumnuclear star formation. Based on our detection statistics, we conclude that crystalline silicates are a common component of the interstellar medium of galactic nuclei.

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Mihailova, Irena, and Dimitar Mehandjiev. "Catalytic activity of Co-åkermanite and Co-pyroxene in oxidation reactions." Canadian Journal of Chemistry 89, no. 8 (August 2011): 939–47. http://dx.doi.org/10.1139/v11-061.

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Two calcium–cobalt silicates were synthesized in which cobalt occupies different structural positions. The crystal phases belong to two main structural silicate types. In the Co-åkermanite structure (Ca2CoSi2O7), cobalt cations take tetrahedral coordination toward oxygen atoms. In the Co-pyroxene structure of CaCoSi2O6, cobalt displays octahedral coordination. Ca2CoSi2O7 was prepared by solid-phase synthesis and CaCoSi2O6 was prepared by sol–gel method. The synthesis of the phases was confirmed by XRD, FTIR, and EPR data. On the basis of the XPS analysis, it can be concluded that Co2+ cations exist in the studied silicates. Thus, it is possible to study the catalytic activity of two silicate phases containing Co2+ cations in different coordinations: tetrahedral and octahedral. It was found that cobalt silicates with crystal structures corresponding to pyroxene and åkermanite possess catalytic activity in the reactions of complete oxidation of CO and toluene. Co-pyroxene exhibits higher catalytic activity than Co-åkermanite, but the higher cobalt content on the surface of Co-pyroxene should also be taken into account. Then, it turns out that catalytically active complexes with Со2+ ions in tetrahedral coordination are more efficient than those with such ions in octahedral coordination when equal concentrations of cobalt were used on the surface of the catalysts.

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Almeida Streitwieser, Daniela, Arturo Arteaga, Alvaro Gallo-Cordova, Alexis Hidrobo, and Sebastian Ponce. "Chemical Recycling of Used Motor Oil by Catalytic Cracking with Metal-Doped Aluminum Silicate Catalysts." Sustainability 15, no. 13 (July 4, 2023): 10522. http://dx.doi.org/10.3390/su151310522.

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The chemical recycling of used motor oil via catalytic cracking to convert it into secondary diesel-like fuels is a sustainable and technically attractive solution for managing environmental concerns associated with traditional disposal. In this context, this study was conducted to screen basic and acidic-aluminum silicate catalysts doped with different metals, including Mg, Zn, Cu, and Ni. The catalysts were thoroughly characterized using various techniques such as N2 adsorption–desorption isotherms, FT-IR spectroscopy, and TG analysis. The liquid and gaseous products were identified using GC, and their characteristics were compared with acceptable ranges from ASTM characterization methods for diesel fuel. The results showed that metal doping improved the performance of the catalysts, resulting in higher conversion rates of up to 65%, compared to thermal (15%) and aluminum silicates (≈20%). Among all catalysts, basic aluminum silicates doped with Ni showed the best catalytic performance, with conversions and yields three times higher than aluminum silicate catalysts. These findings significantly contribute to developing efficient and eco-friendly processes for the chemical recycling of used motor oil. This study highlights the potential of basic aluminum silicates doped with Ni as a promising catalyst for catalytic cracking and encourages further research in this area.

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Cheaburu, Catalina Natalia, Cornelia Vasile, Donatella Duraccio, and Sossio Cimmino. "Characterisation of the Chitosan/Layered Silicate Nanocomposites." Solid State Phenomena 151 (April 2009): 123–28. http://dx.doi.org/10.4028/www.scientific.net/ssp.151.123.

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Characterization of chitosan / layered silicate nanocomposites obtained by solution-mixing technique, having different compositions including treated and untreated montmorilonite (MMT) has been performed. The optimum amount of MMT and also the effect of nanoparticles type on nanocomposite properties by DSC, X-ray diffraction and TG measurements have been established. The chitosan chains were inserted into silicate layers to form the intercalated nanocomposites. The interlayer distance of the silicates in the nanocomposites enlarged as their amount increased. The stiffness and thermal stability enhanced.

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Shoshin, Evgeniy, Valeria Strokova, Denis Timokhin, and Alexandr Strakhov. "Effect of Calcium Synthetic Hydro Silicate Additives on the Cement Systems’ Technological Characteristics." Materials Science Forum 1011 (September 2020): 59–65. http://dx.doi.org/10.4028/www.scientific.net/msf.1011.59.

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The use of finely dispersed fillers for cement concrete is accompanied not only by the cement binder saving, but also by a change in the technological characteristics of the cement mixtures. Depending on the nature of the additive used, both a positive and a negative water-reducing effect can be observed. The nature of the synthetic calcium silicates additives’ effect obtained by the method of sucrose-modified calcium hydro silicates thermolysis on the technological properties of the cement systems is considered. The independent methods determined the polymodal nature of the calcium silicates dispersions. The effect of the various dimensional scales particles on the technological properties of the cement system is determined. Micron particles affect the powder mixture compaction, the optimal content of calcium silicate additives is 20–40%. Nanometric particles, as well as residual freely extractable sucrose, determine the plasticizing effect of the synthetic calcium silicates additives introduction, the maximum manifestation of which is observed when the additive content is 20%. The visco-plastic properties of the “cement - synthetic calcium silicates” system’s mixtures were evaluated at various additive contents.

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Zulputra, Zulputra, and Nelvia Nelvia. "KETERSEDIAAN P, SERAPAN P DAN SI OLEH TANAMAN PADI GOGO (Oryza sativa. L) PADA LAHAN ULTISOL YANG DIAPLIKASIKAN SILIKAT DAN PUPUK FOSFAT." JURNAL AGROTEKNOLOGI 8, no. 2 (February 10, 2018): 9. http://dx.doi.org/10.24014/ja.v8i2.3351.

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The research was conducted from August 2014 to Januari 2015 in the Ultisol Land, Pematang Berangan Village, Rokan Hulu Regency, Riau Province. The study aims to determine the availability of P, P and Si uptake by upland rice plants granting silicate and phosphate fertilizer on Ultisol land. The form of this research is experimental factorial completely randomized design consist of two factors. The first factor is silicate consists of four levels (0, 50, 75, and 100 kg SiO2/ha), while the second factor is phosphate fertilizer consists of four levels (0, 36, 54, and 72 kg P2O5/ha), each combination was repeated three times. The results showed that administration of silicates and phosphates increase the availability of P, P and Si uptake of upland rice crop. Giving of 100 kg SiO2 and 36 kg P2O5 per hectare increase uptake of P and Si, each respectively increased by 208 % and 218 % compared without silicates and phosphates fertilizer.

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Ramamurthy, Sundar, Brian C. Hebert, and C. Barry Carter. "Olivine-MgO interfaces produced by crystallization of glass fulms on single-crystal MgO substrates." Proceedings, annual meeting, Electron Microscopy Society of America 53 (August 13, 1995): 342–43. http://dx.doi.org/10.1017/s0424820100138087.

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Glassy silicates are present at grain boundaries in almost all liquid-phase sintered ceramic oxides. In many cases, the amorphous-crystalline interfaces in the sintered microstructure can be modified by inducing crystallization of the glassy phase. The intergranular phases in polycrystalline MgO are typically silicates with cations of calcium, magnesium and iron in the silicate network. A systematic approach to study the crystallization behavior of glass-MgO interfaces has been attempted in the present study. Following the work by Mallamaci in which crystallization of a silicate glass in contact with A12O3 was studied, devitrification of glass in contact with single-crystal MgO has been investigated. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterize the resulting microstructures.A pellet of Mg2SiO4 (forsterite) prepared by hot-pressing MgO and SiO2 powders was used as the target for depositing glass films onto single-crystal MgO substrates by pulsed-laser deposition (PLD). Glass films with the composition of olivine.

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García, Hermenegildo. "Photoresponsive porous organosilicas." Pure and Applied Chemistry 75, no. 8 (January 1, 2003): 1085–90. http://dx.doi.org/10.1351/pac200375081085.

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Novel structured functional hybrid materials can be obtained by incorporating photoresponsive organic components into the silicate walls of periodic mesoporous silicates. Two such materials are described, containing either viologens or stilbene analogs. Thermal or photochemical activation of viologen units generates the corresponding radical cations, whose lifetime can vary from months to milliseconds, depending on the surfactant content of the solid. In a second example, the porosity and tortuosity of the silicate can be modulated by irradiation of an organosilica containing a stilbene-like moiety.

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Petrov, Dmitry, Elena Zhuzhulina, and Alexander Savushkin. "Influence of the scattering particle shape on the SiO2 silicate feature." Acta Astrophysica Taurica 2, no. 1 (September 30, 2021): 26–29. http://dx.doi.org/10.31059/aat.vol2.iss1.pp26-29.

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Silicate dust particles are part of many astronomical objects such as comets and circumstellar disks. In a spectrum, silicates exhibit a number of characteristic silicate emission features. To study these features, Mie’s theory is usually used. This theory assumes that the scattering object is an ideal sphere. In this work, we investigated the contribution of non-spherical quartz particles (SiO2) to these features. We studied the influence of the deviation from sphericity on the 10-micron silicate feature of quartz. It is shown that the deviation from sphericity has a significant effect on both the scattered light intensity and the scattering factor Qsca, and this effect increases with increasing scattering particle size. The main peculiarities of the 10-micron silicate feature have been studied for both prolate and oblate spheroids.

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Ivaschenko, Yuri, Maria Kochergina, and Irina Pavlova. "Structure formation and properties of thermochemically modified silicate-sodium compositions." E3S Web of Conferences 97 (2019): 02030. http://dx.doi.org/10.1051/e3sconf/20199702030.

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Modern methods allow to improve the functional properties of silicate-sodium compositions. Increased water resistance primarily will allow their use in construction. The article presents the results of the study of modified silicate-sodium compositions by X-ray phase analysis, differential thermal analysis, thermo-gravimetric analysis. An organic zinc-containing compound, zinc acetate dihydrate, which is introduced into the binder in the form of a concentrated aqueous fluid, was used as a modifier. Using X-ray analysis, it was shown that in the hardening system “silicate-sodium binder an aqueous fluid of zinc acetate” in the temperature range 110-450°C various forms of hydroxides, silicates and zinc silicates are formed. In addition, at T = 450°C, only “traces” of ZnO were detected, and the crystalline phase of the hardly soluble zinc metasilicate ZnSiO3 prevailed. The results of the study of modified samples by thermal analysis indicate the processes of thermal decomposition of the modifying additive in the binder system and indicate the possible formation of a new crystalline phase (ZnSiO3) at a temperature of 440-450°C. It was revealed that temperature treatment of modified samples in the range of 440-450°C leads to a more significant increase in water resistance (by 25-28%) than during low-temperature curing (by 20-23%).

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Journal articles on the topic 'Silicatées'

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