Academic literature on the topic 'Hydrated crystalline oxides'

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Journal articles on the topic "Hydrated crystalline oxides"

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Gaponov, Yu A., L. G. Karakchiev, N. Z. Lyakhov, B. P. Tolochko, K. Ito, and Y. Amemiya. "Structure changes in the sol–gel systems of hydrated oxides." Journal of Synchrotron Radiation 5, no. 3 (May 1, 1998): 962–63. http://dx.doi.org/10.1107/s0909049597015677.

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Sols of hydrated aluminium oxide, hydrated zirconium oxide and their mixtures were investigated during the xerogel–amorphous-product–crystalline-product transition by SAXS using synchrotron radiation. In the different temperature regions certain changes in structure and morphology were observed. Some correlation between the characteristics of the initial sols and their mixtures (the size and shape of the pores) was observed. In the temperature region 298–1173 K the characteristics of the mixed sol are defined by the characteristics of the initial sols.
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Wang, Ruocun, Ching-Chang Chung, Yang Liu, Jacob L. Jones, and Veronica Augustyn. "Electrochemical Intercalation of Mg2+ into Anhydrous and Hydrated Crystalline Tungsten Oxides." Langmuir 33, no. 37 (July 27, 2017): 9314–23. http://dx.doi.org/10.1021/acs.langmuir.7b00705.

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Ferenc, Wieslawa, Agnieszka Walkóv-Dziewulska, and Janusz Chrusciel. "Spectral and thermal behaviors of rare earth element complexes with 3,5-dimethoxybenzoic acid." Journal of the Serbian Chemical Society 68, no. 10 (2003): 751–63. http://dx.doi.org/10.2298/jsc0310751f.

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The conditions for the formation of rare earth element 3,5-dimethytoxybenzoates were studied and their quantitative composition and solubilities in water at 293 K were determined. The complexes are anhydrous or hydrated salts and their solubilities are of the orders of 10-5 ? 10-4 mol dm-3. Their FTIR, FIR and X-ray spectra were recorded. The compounds were also characterized by thermogravimetric studies in air and nitrogen atmospheres and by magnetic measurements. All complexes are crystalline compounds. The carboxylate group in these complexes is a bidentate chelating ligand. On heating in air to 1173 K, the 3,5-dimethoxybenzoates of rare earth elements decompose in various ways. The hydrated complexes first dehydrate to form anhydrous salts which then decompose in air to the oxides of the respective metals while in nitrogen to mixtures of carbon and oxides of the respective metals. The complexes are more stable in air than in nitrogen.
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Ferenc, W., K. Czapla, J. Sarzynski, and A. Zwolinska. "Comparison of some properties of 2,3 – and 3,4 – dimethoxybenzoates of Cu(II), Co(II) and Nd(III)." Eclética Química Journal 33, no. 2 (February 5, 2018): 07. http://dx.doi.org/10.26850/1678-4618eqj.v33.2.2008.p07-12.

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The physicochemical properties of 2,4-, and 3,4-dimethoxybenzoates of Cu(II), Co(II) and Nd(III) were studied and compared to observe the -OCH3 substituent positions in benzene ring on the character of complexes. The analysed compounds are crystalline hydrated or anhydrous salts with colours depending on the kind of central ions: blue for Cu(II), pink for Co(II) and violet for Nd(III) complexes. The carboxylate groups bind as monodentate, bidentate bridging or chelating and even tridentate ligands. Their thermal stabilities were studied in air at 293-1173K. When heated the hydrated complexes release the water molecules and form anhydrous compounds which are then decomposed to the oxides of respective metals. Their magnetic moment values were determined in the range of 76-303K. The results reveal the compounds of Nd(III) and Co(II) to be the high-spin and that of Cu(II) forms dimer. The various positions of -OCH3 groups in benzene ring influence some of physicochemical properties of analysed compounds.
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Firsova, Olga A., Elena M. Filonenko, Yulia A. Lupitskaya, Hurshid N. Bozorov, and Anatoly V. Butakov. "Ion-exchange properties of solid solutions based on hydrated forms of monovalent metals antimonate-tungstates." Butlerov Communications 62, no. 6 (June 30, 2020): 74–79. http://dx.doi.org/10.37952/roi-jbc-01/20-62-6-74.

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The research of tungsten-antimony crystalline acid (TACA) structural transformations in the condition of ion-exchange and thermolysis of its substituted M+, H+-forms (M+ – Li, Na, K, Ag) were conducted. The data of thermogravimetric and qualitative X-ray phase analyses made it possible to conclude that the thermolysis of TACA and its derivatives proceeds in a wide temperature range from 300 to 1150 K being accompanied by the removal of crystalline water molecules with the formation of phases mixture containing complex antimony oxides of the ( -,  - Sb2O4) modification and WO3. It was shown that compounds based on hydrated forms of monovalent metal antimonates-tungstates are stable up to 1023 K with a pyrochlore-type structure. For pyrochlore-like phases, a monotonic dependence of unit cell parameter a on ion-exchange degree α and the ionic radius of metals r was revealed indicating the formation of solid solutions Мх(Н3О)1–хWSbO6 nН2О (M+ – Li, Na, K, Ag; 0.0≤х<1.0; 0.0≤n<2.0) with a limited range of solubility from the crystal chemistry point of view. Within the framework of the Fd-3m space group, based on the data of X-ray diffraction analysis (Rietveld method), the structural characteristics of TACA and its substituted M+, H+-forms were refined, and a model for populating the corresponding metal ions by crystallographic positions of the pyrochlore-type structure was proposed. Using a complex of physicochemical methods (thermogravimetric, X-ray diffraction analyses and IR spectroscopy), a correlation between the composition of the obtained compounds, structural disorder, and ion-exchange properties were determined. According to the data of thermogravimetry and IR spectroscopy, it follows that the degree of compounds hydration analyzed depends on the nature of the alkaline ion. This allows to conclude that lithium and sodium ions are located in 16d– positions, dragging neutral water molecules into the structure occupying 8b-positions. In this case, potassium ions can partially occupy both 16d- and 8b-positions of the structure.
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Ferenc, Wieslawa, and Agnieszka Walków-Dziewulska. "Complexes of light lanthanides with 2,4-dimethoxybenzoic acid." Journal of the Serbian Chemical Society 65, no. 1 (2000): 27–35. http://dx.doi.org/10.2298/jsc0001027f.

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The complexes of light lanthanides with 2,4-dimethoxybenzoic acid of the formula: Ln(C9H9O4)3.nH2O where Ln = La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(IIII), and n = 3 for La(III), Gd(III), n = 2 for Sm(III), Eu(III), and n = 0 for Ce(III), Pr(III), Nd(III) have been synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric studies and X-ray diffraction measurements. The complexes have colours typical for Ln 3+ ions (La, Ce, Eu, Gd-white, Sm-cream, Pr-green, Nd-violet). The carboxylate group in these complexes is a symmetrical, bidentate, chelating ligand. They are crystalline compounds characterized by various symmetry. On heating in air to 1273 K the 2,4-dimethoxybenzoates of the light lanthanides decompose in various ways. The hydrated complexes decompose in two or three steps while those of anhydrous ones only in one or two. The trihydrate of lanthanum 2,4-dimethoxybenzoate first dehydrates to form the anhydrous salt, which then decomposes to La2O3 via the intermediate formation of La2O2CO3. The hydrates of Sm(III), Eu(III), Gd(III) decompose in two stages. First, they dehydrate forming the anhydrous salts, which then decompose directly to the oxides of the respective metals. The anhydrous complexes of Ce(III), Pr(III) decompose in one step, while that of Nd(III) in two. The solubilities of the 2,4-dimethoxybenzoates of the light lanthanides in water and ethanol at 293 K are in the order of: 10 -3 mol dm -3 and 10 -4.10 -3 mol dm-3, respectively.
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Jung, T. H., and R. V. Subramanian. "Alkali resistance enhancement of basalt fibers by hydrated zirconia films formed by the sol-gel process." Journal of Materials Research 9, no. 4 (April 1994): 1006–13. http://dx.doi.org/10.1557/jmr.1994.1006.

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Basalt fibers were dip-coated in zirconium-n-propoxide, unstabilized or stabilized by chelation with ethyl acetoacetate. The thermal transformations of the hydrated zirconia coatings formed were investigated by dynamic x-ray diffraction and differential thermal analysis. The changes in the surface chemical compositions of coated and uncoated fibers, following alkali immersion extending to 90 days, were characterized by EDXA and IR spectral analysis. Fiber strengths were also measured after immersion in 0.1 M NaOH for different durations. It was found that the transition of the amorphous zirconia coating to the tetragonal crystalline phase is shifted to higher temperatures by chelation of the zirconium alkoxide. Alkali corrosion of the uncoated basalt fibers results in dissolution of the oxides of Si, Al, and Ca, and the formation of unsoluble hydroxides of Fe, Mg, and Ti from the chemical constituents of basalt. These reactions are suppressed by the protective zirconia coating on basalt fibers formed by the unstabilized zirconium alkoxide. However, the coating formed from zirconium propoxide stabilized by ethyl acetoacetate does not form an effective barrier against alkali attack since it is easily detached from the fiber surface during alkali immersion. The tensile strength of uncoated basalt fibers is drastically reduced by alkali attack. But the strength of zirconia-coated basalt fibers is maintained even after 90 days of alkali immersion. The vastly improved alkaline durability of the coated fibers shows the potential of zirconia-coated basalt fibers for cement reinforcement.
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Mio, Matthew J., and Jeffrey S. Moore. "Supramolecular Aufbau: Folded Polymers as Building Blocks for Adaptive Organic Materials." MRS Bulletin 25, no. 4 (April 2000): 36–41. http://dx.doi.org/10.1557/mrs2000.27.

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The design of inorganic and organic solids with novel structures and properties has long been the object of materials research. The classical examples of porous materials (i.e., involving reversible guest passage) are zeolites. First discovered in the mid-1700s, zeolites are hydrated, crystalline aluminosilicates that organize into stable, discrete frameworks. Basic structures employ tetrahedral atoms (silicon or aluminum) bridged by oxygen atoms, where each oxygen is shared between two metalloid tetrahedra. Resulting covalent lattices can be neutral or negatively charged (as a result of bridging oxides) and often employ alkali metal or alkalineearth counterions. As a consequence of this ordered structure, zeolites both benefit from and are limited by their highly geometrical nature: their rigid structures are inherently robust, yet they are difficult to process. In addition, while natural and unnatural zeolites have been characterized, harsh synthetic conditions are common to both and lead to limitations in design and processability. Even so, these impediments have not prevented constructing a myriad of architectures on zeolite host lattices. Strengths and weaknesses aside, zeolites demonstrate a major objective of materials chemistry: the ability to manifest macroscopic physical properties based on embedded microscopic structure.
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Dercz, Grzegorz, Lucjan Pająk, Krystian Prusik, Roman Pielaszek, Janusz J. Malinowski, and Wojciech Pudło. "Structure Analysis of Nanocrystalline MgO Aerogel Prepared by Sol-Gel Method." Solid State Phenomena 130 (December 2007): 203–6. http://dx.doi.org/10.4028/www.scientific.net/ssp.130.203.

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Wet gel obtained by sol-gel technique was dried in supercritical CO2 to prepare hydrated form of magnesium oxide. Calcination at 723 K under vacuum yielded nanocrystalline MgO aerogel. Structure studies were performed by X-ray diffraction, scanning and transmission electron microcopies. Electron microscopy images reveal rough, unfolded and ramified structure of solid skeleton. Specific surface area SBET was equal to 238 m2/g. X-ray pattern reveals the broadened diffraction lines of periclase, the only crystalline form of magnesium oxide. The gamma crystallite size distribution was determined using FW 5 4 / 5 1 M method proposed by R. Pielaszek. The obtained values of <R> and σ (measure of polydispersity) of particle size parameters are equal to 6.5 nm and 1.8 nm, respectively, whereas the average crystallite size estimated by Williamson-Hall procedure was equal to 6.0 nm. The obtained at Rietveld refinement Rwp, and S fitting parameters equal to 6.62% and 1.77, respectively, seem to be satisfactory due to the nanosize of MgO crystallites and because of the presence of amorphous phase.
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Zhao, Qiang, X. F. Pang, Le Wei Liu, and Bo Deng. "The Biological Effect of Iron Oxide and Its Hydrate Nanoparticles." Solid State Phenomena 121-123 (March 2007): 735–38. http://dx.doi.org/10.4028/www.scientific.net/ssp.121-123.735.

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Iron oxide and its hydrate nanoparticles were synthesized by hydrothermal method and confirmed by infrared and SEM (Scanning Electron Microscope) et al. The dimensions of the nanoparticles are about 50-120 nm. The crystalline form of iron oxide nanoparticles is like globosity while its hydrate rod. Amino acids intermingling with the synthesized nanoparticles were crystallized to investigate the space effect of the nanoparticles. The crystalline forms of crystal are different to that of pure amino acid. The positions and width of the nanoparticles’ peaks in the infrared spectrum are changed too. Microscope observation and infrared spectrum results indicated the nanoparticles had changed the internal structure of amino acids crystal. To considerate the toxicity of the synthesized nanoparticles, MTT (3-(4,5-dimethylthiazol 2-yl)-2,5 diphenyltetrazolium bromide) assay was used to determine their cytotoxicity. The OD value (Optical Density) was used to calculated RGR% (Relative Generation Rate) of cells, which determined the grade of cytotoxicity. The RGR of nanoparticles of iron oxide and its hydrate are about 1 to 2, which indicate they have just low toxicity.
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Dissertations / Theses on the topic "Hydrated crystalline oxides"

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Claridge, D. A. "Studies of some insertion compounds." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370311.

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