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1.
A. A. Malkov E. N. Korytkova T. P. Maslennikova A. M. Shtykhova V. V. Gusarov 《Russian Journal of Applied Chemistry》2009,82(12):2079-2086
The structural-chemical transformations in nanotubular magnesium hydrosilicate of composition Mg3Si2O5(OH)4 (chrysotile) obtained by hydrothermal synthesis were studied in heating to 1200°C. 相似文献
2.
E. N. Korytkova L. N. Pivovarova I. A. Drosdova V. V. Gusarov 《Russian Journal of General Chemistry》2007,77(10):1669-1676
Nanotubes of the chrysotile structure were obtained under hydrothermal conditions in the series of hydrosilicates of the Mg3Si2O5(OH)4-Co3Si2O5(OH)4 system. Substitution of cobalt ions for magnesium ions affects the conditions of formation, morphology, and size of the nanotubes. The formation of nanotubes on hydrothermal treatment of the starting mixtures of cobalt metasilicate and magnesium, cobalt, and, silicon oxides and hydroxides occurs in stages, and the stage of nanotube formation is always preceded by the formation of a lammellar structure. 相似文献
3.
T. P. Maslennikova E. N. Korytkova V. V. Gusarov 《Russian Journal of Applied Chemistry》2008,81(3):375-379
Interaction of Mg3Si2O5(OH)4 nanotubes with aqueous solutions of potassium hydroxide in various temperature-time treatment modes was studied. 相似文献
4.
E. N. Korytkova L. N. Pivovarova O. E. Semenova I. A. Drozdova V. F. Povinich V. V. Gusarov 《Russian Journal of Inorganic Chemistry》2007,52(3):338-344
Magnesium iron hydrosilicate nanotubes with a chrysotile ((Mg,Fe)3Si2O5(OH)4) structure have been synthesized hydrothermally at t = 250–450°C and p = 30–100 MPa. In the hydrothermal synthesis of (Mg,Fe)3Si2O5(OH)4 chrysotile, part of the Fe2+ ions oxidize to Fe3+ and are incorporated into the octahedron and tetrahedron layers of the chrysotile structure. The limiting iron content of chrysotile has been determined up to which cylindrically rolled layers can form to yield nanotubes. The hydrothermal treatment of precursors richer in FeO yields platelike hydrosilicates. The iron ions present in the starting components affect the synthesis parameters, morphology, size, optical properties, and thermal stability of the nanotubes. 相似文献
5.
G. N. Gubanova S. V. Kononova M. E. Vylegzhanina T. E. Sukhanova A. I. Grigor’ev K. A. Romashkova V. M. Svetlichnyi E. N. Korytkova M. Christi D. Timpu V. Harabagiu 《Russian Journal of Applied Chemistry》2010,83(12):2175-2181
New nanocomposites based on heat-resistant poly[(diphenyl oxide)amido-N-phenylphthalimide] with Mg3Si2O5(OH)4 hydrosilicate nanoparticles of tubular structure were prepared. The structure, morphology, and thermal properties of the nanocomposites were studied in relation to the content of hydrosilicate nanotubes. 相似文献
6.
T. Zaremba A. Krząkała J. Piotrowski D. Garczorz 《Journal of Thermal Analysis and Calorimetry》2010,101(2):479-485
This article reports the possibility of detoxification of chrysotile asbestos through a low temperature heating and grinding
treatment. The effect of thermal treatment at different temperatures in the range from 500 to 725 °C for 3 h on raw natural
asbestos was characterized by thermal analysis, X-ray diffraction, and scanning electron microscopy. It was found that an
isothermal treatment at 650 °C caused the complete dehydroxylation of chrysotile Mg3Si2O5(OH)4. Transformation of the dehydroxylated phase to forsterite Mg2SiO4 was obtained by heat treatment in the range 650–725 °C. The study of microstructure changes of heated asbestos show the destruction
of characteristic fibers of chrysotile and formation of strips of forsterite. It is easily milled to pulverulent-shape material
by mechanical milling in vibratory mill. 相似文献
7.
V. V. Voitylov A. V. Voitylov E. N. Korytkova V. P. Romanov S. V. Ul’yanov V. V. Gusarov 《Russian Journal of Applied Chemistry》2008,81(2):207-211
Behavior of hydrosilicate nanotubes of composition Mg3Si2O5(OH)4 in aqueous dispersions was studied. Experiments devoted to observation of steady-state and relaxation electro-optical effects demonstrated that, irrespective of their initial concentration in water, nanotubes form stable bulk aggregates with weak anisotropy, rather than a homogeneous system of separate suspended nanosize cylinders. 相似文献
8.
《Solid State Sciences》1999,1(6):381-393
The synthetic layered 1:1 phyllosilicate, Co2.3Al0.7Si1.3Al0.7O5(OH)4, and 2:1 phyllosilicates Co3Si4O10(OH)0.7F1.3, Co3Si4O10(OH)1.2F0.8(Co(CH3COO)2)0.24, Co3Si4O10(OH)1.3F0.7 (TAEAH)0.12 and Co3Si4O10(OH)1.3F0.7 (TAEAH)0.24 have been obtained under hydrothermal conditions at ca. 200 °C (TAEA : (tris-aminoethyl)-amine). The compounds are characterized by interplanar distances of 7.0, 9.5, 11.1, 13.3 and 14.3 Å, respectively. They show long range magnetic ordering below 16 K, characterized by positive Weiss constants, imaginary component in the ac-susceptibility, spontaneous magnetisation in small applied field and coercive fields in the range 400 to 700 Oe. The magnetisation in field of 3 Tesla classifies them as 3D ferromagnet. 相似文献
9.
Triniobium hydroxide heptaoxide, Nb3O7(OH), was prepared hydrothermally by treating niobic acid or triniobium chloride heptaoxide with 3.0 mol/dm3 sulfuric acid at 250–350°C and 15 MPa. The hydroxide oxide was isomorphous with the low-pressure form of triniobium fluoride heptaoxide which is built up of 3 X ∞ blocks of the ReO3 structure with crystallographic shear in one dimension. When heated in air, Nb3O7(OH) dehydrated up to 460°C to give poorly crystallized Nb2O5, which, on further heating, changed slowly into a less ordered precursor of M? Nb2O5(1). Hydrothermal treatment of Nb3O7(OH) with pure water at 400–500°C afforded P? and R? Nb2O5; the conversion of Nb3O7(OH) is explained in terms of the close structural relation among these three forms. 相似文献
10.
Kaiwen Zhou Wenwei Wu Yongni Li Xuehang Wu Sen Liao 《Journal of Thermal Analysis and Calorimetry》2013,114(1):205-212
The spinel Mn0.5Mg0.5Fe2O4 was obtained via calcining Mn0.5Mg0.5Fe2(C2O4)3·5H2O above 400 °C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform FT-IR, X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray spectrometer, and vibrating sample magnetometer. The results showed that Mn0.5Mg0.5Fe2O4 obtained at 600 °C had a specific saturation magnetization of 46.2 emu g–1. The thermal decomposition of Mn0.5Mg0.5Fe2(C2O4)3·5H2O below 450 °C experienced two steps which involved, at first, the dehydration of five water molecules and then decomposition of Mn0.5Mg0.5Fe2(C2O4)3 into spinel Mn0.5Mg0.5Fe2O4 in air. Based on Starink equation, the values of the activation energies associated with the thermal decomposition of Mn0.5Mg0.5Fe2(C2O4)3·5H2O were determined. 相似文献
11.
L. P. Ogorodova I. A. Kiseleva L. V. Mel’chakova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(2):315-316
A thermochemical study of partheite of composition (Ca1.96Mg0.04Na0.01K0.01) · [(Al4.04Fe 0.01 3+ )Si3.95O14.97(OH)2.03] · 4.2H2O, a natural calcium zeolite extracted from gabbro pegmatites of the Denezhkin Kamen’ deposit (North Ural, Russia), was performed. The enthalpies of formation of partheite from the constituent oxides, (Δf H°ox(298.15 K) = ?359 ± 21), and elements, (Δf H°el(298.15 K) = ?10108 ± 21), were determined by means of high-temperature in-melt-dissolution calorimetry. On the basis of the experimental data obtained, the enthalpy of formation of partheite of theoretical composition Ca2[Al4Si4O15(OH)2] · 4H2O from the elements was evaluated, ?10052 ± 21 kJ/mol. 相似文献
12.
Sara J. Palmer H. J. Spratt R. L. Frost 《Journal of Thermal Analysis and Calorimetry》2009,95(1):123-129
Thermal analysis complimented with evolved gas mass spectrometry has been applied to hydrotalcites containing carbonate prepared
by coprecipitation and with varying divalent/trivalent cation ratios. The resulting materials were characterised by XRD, and
TG/DTG to determine the stability of the hydrotalcites synthesised. Hydrotalcites of formula Mg4(Fe,Al)2(OH)12(CO3)·4H2O, Mg6(Fe,Al)2(OH)16(CO3)·5H2O, and Mg8(Fe,Al)2(OH)20(CO3)·8H2O were formed by intercalation with the carbonate anion as a function of the divalent/trivalent cationic ratio.
XRD showed slight variations in the d-spacing between the hydrotalcites. The thermal decomposition of carbonate hydrotalcites
consists of two decomposition steps between 300 and 400°C, attributed to the simultaneous dehydroxylation and decarbonation
of the hydrotalcite lattice. Water loss ascribed to dehydroxylation occurs in two decomposition steps, where the first step
is due to the partial dehydroxylation of the lattice, while the second step is due to the loss of water interacting with the
interlayer anions. Dehydroxylation results in the collapse of the hydrotalcite structure to that of its corresponding metal
oxides and spinels, including MgO, MgAl2O4, and MgFeAlO4. 相似文献
13.
V2O3(OH)4(g), Proof of Existence, Thermochemical Characterization, and Chemical Vapor Transport Calculations for V2O5(s) in the Presence of Water By use of the Knudsen-cell mass spectrometry the existence of V2O3(OH)4(g) is shown. For the molecules V2O3(OH)4(g), V4O10(g), and V4O8(g) thermodynamic properties were calculated by known Literatur data. The influence of V2O3(OH)4(g) for chemical vapor transport reactions of V2O5(s) with water ist discussed. ΔBH°(V2O3(OH)4(g), 298) = –1920 kJ · mol–1 and S°(V2O3(OH)4(g), 298) = 557 J · K–1 · mol–1, ΔBH°(V4O10(g), 298) = –2865,6 kJ · mol–1 and S°(V4O10(g), 298) = 323.7 J · K–1 · mol–1, ΔBH°(V4O8(g), 298) = –2465 kJ · mol–1 and S°(V4O8(g), 298) = 360 J · K–1 · mol–1. 相似文献
14.
The effect of the treatment of magnesium hydrosilicate (Mg3Si2O5(OH)4) fibers with an aqueous 5% ammonium chloride solution at 37?40 and 57?60°C on their electrokinetic potential (ζ potential) is studied. The maximum time of exposure in the NH4Cl solution was 100 min, while the ζ potential was measured every 20 min. It is shown that the treatment of the initial magnesium hydrosilicate fibers with the NH4Cl solution leads to a reversal of their surface charge and a rise in the absolute value of the negative charge, which is explained by magnesium leaching out of the surface layer of the fibers. Washing of the treated fibers with distilled water leads again to the sign reversal of the ζ potential. Therewith, the character of the dependences of the fiber ζ potential on the time of the treatment with the 5% NH4Cl solution at T = 37?40°C is the same before and after washing. 相似文献
15.
Dr. Xue-Rui Tian Zhi-Yu Jiang Sheng-Li Hou Assoc. Prof. Han-Shi Hu Prof. Jun Li Prof. Bin Zhao 《Angewandte Chemie (International ed. in English)》2023,62(23):e202301764
Utilization of N,N-dimethylformamide (DMF) as an amine source and reductant for synthesizing tertiary amines is a promising way to replace the substrates formaldehyde and dimethylamine, and it is desirable to seek porous acid-resistant catalysts for heterogeneous catalysis of this reaction. Herein, a robust metal–organic framework (MOF) {[Th6O4(OH)4(H2O)6(BCP)3]⋅10 DMF}n ( 1 ) containing stacked nanocages with a diameter of 1.55 nm was constructed. Compound 1 can maintain its single-crystal structure even kept in air at 400 °C for 3 h, and in DMF or water at 200 °C for 7 days. Density functional theory (DFT) calculations suggested that the high interaction energy between the [Th6O4(OH)4(H2O)6]12+ clusters and ligands was responsible for the excellent stability of 1 . Catalytic investigations revealed that 1 can effectively and size-selectively catalyze the reductive amination of aldehydes with DMF, and it can be reused at least five times without obvious loss in catalytic activity. 相似文献
16.
Thermal Decomposition of Afwillite Ca3(SiO3OH)2 · 2 H2O Using the molybdate method [1], infrared, Raman, and high resolution solid state 1H and 29Si NMR spectroscopy two intermediate phases can be identified in the process of dehydration of afwillite: At temperatures of 250 to 300°C a non-crystalline phase is formed mainly (about 80 to 90% referred to Si) with a structure similar to mineral killalaite Ca3OH(Si2O6OH) [2] and phase F [3]. Between 300 and 500°C this compound is converted to a non-crystalline kilchoanite-like phase γ-Ca2SiO4 · Ca4Si3O10 [4], consisting of ordered γ-Ca2SiO4 and disordered trisilicate layers. By a side reaction polysilicate (about 10 to 20% referred to Si) is formed. 相似文献
17.
A. A. Krasilin V. V. Panchuk V. G. Semenov V. V. Gusarov 《Russian Journal of General Chemistry》2016,86(12):2581-2588
The process of formation of iron hydrosilicates (Mg2+,Fe3+)2–3Si2O5(OH)4 was studied. It was shown that the stage of coprecipitation of magnesium and iron hydroxides in the presence of silica nanoparticles forms poorly crystallized layered Mg–Fe double hydroxides having Fe3+ ions in the octahedral sites. Hydrothermal treatment of the mixtures of coprecipitated hydroxides and silica nanoparticles gives rise to layered hydrosilicates, where Fe3+ ions occupy both the octahedral (preferentially) and tetrahedral sires. The possibility of the formation and a fairly stable existence of the variable-composition layered hydrosilicate (Mg2+,Fe3+)2–3Si2O5(OH)4 was shown to correlate with the stability range of its precursor brucite-like Mg–Fe layered double hydroxide. 相似文献
18.
L. P. Ogorodova I. A. Kiseleva E. N. Korytkova T. P. Maslennikova V. V. Gusarov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(1):44-47
Nanotubular (Mg,Fe2+,Fe3+)3Si2O5(OH)4 hydrosilicates with a chrysotile structure were synthesized under hydrothermal conditions. The phases prepared were studied
thermochemically on a high-temperature Tian-Calvet microcalorimeter by solution calorimetry. The standard enthalpies of formation
of magnesium-iron nanotubular hydrosilicates were determined. The formation of iron-containing nanotubes was shown to be lass
favorable energetically than the formation of magnesium nanotubes. 相似文献
19.
《Solid State Sciences》2000,2(4):489-493
The partial system Mg3(PO4)2Mg4Na(PO4)3Na4P2O7Mg2P2O7 in the ternary system MgONa2OP2O5 was investigated using thermal and X-ray diffraction analyses and microscopy, and its phase diagram has been determined. In this range of composition, two binary phosphates occur: Mg4Na(PO4)3 and Mg6Na8(P2O7)5. The former melts incongruently (at 1155°C) and the latter does congruently (at 808°C). In the partial system of interest, the two sections Mg4Na(PO4)3Mg2P2O7 and Mg4Na(PO4)3Mg6Na8(P2O7)5 are studied, and their phase diagrams are established. The partial system is divided into three partial ternary systems in which two ternary eutectics and one ternary peritectic occur. 相似文献
20.
The chemical species of silica in NaCl solutions of different concentrations were identified by FAB-MS (fast atom bombardment mass spectrometry). The basic structures of silica species, such as cyclic pentamer (Si5¶(OH)9O6 –), linear pentamer (Si5(OH)11O5 –), cyclic hexamer (Si6(OH)9O8 –, Si6(OH)11O7 –) and linear hexamer (Si6(OH)14O6 –), were identified, in addition to dimer (Si2(OH)5O2 –), trimer (Si3(OH)7O3 –) and cyclic tetramer (Si4(OH)7O5 –). The patterns of changes of the peak intensities of the silicate complexes relative to the dimer with increasing NaCl concentration were classified into two types: that represented by linear silicate complexes and the other by cyclic silicate complexes. The differences in the type of chemical species and their changes according to the NaCl concentration reflect the number of bonds necessary for polymerization and hydrolysis of the silica complexes. The differences between the linear and the cyclic silicate type have some implications on the dissolution mechanism of silicate complexes, the hydration of the molecules and the equilibrium between solubility, hydrolysis, polymerization and the salting-out effect in NaCl solution. 相似文献