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1
Li, Xiang, Xu Zhao, Fang Lv, Fang Liu und Yuxin Wang. „Improved corrosion resistance of new Fe-based amorphous alloys“. International Journal of Modern Physics B 31, Nr. 16-19 (26.07.2017): 1744010. http://dx.doi.org/10.1142/s0217979217440106.
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Developing amorphous alloys with good corrosion resistance has attracted wide interests recently. In this work, a series of Fe[Formula: see text]Ni[Formula: see text]Cu1Nb3Si[Formula: see text]B9 ([Formula: see text], 1, 2, 3 and 4 at.%) amorphous alloys are fabricated. The influence of Ni addition on the structure and corrosion resistance of the alloys in KNO3 solution was investigated. The amorphous ribbons showed excellent corrosion resistance due to the formation of a stable passive film that ensured a very large passivation plateau. The corrosion resistance is sensitive to the minor addition of Ni ([Formula: see text]4 at.%), which significantly improved the corrosion resistance according to the results of electrochemical measurements.
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Li, Jiayin, Xinping Ma, Caixian Zhao, Datang Li und Jianting Tang. „Co4I3O24H15⋅3H2O: A new amorphous semiconductor with intrinsical photocatalytic performance in organic dye degradation driven by visible light“. Functional Materials Letters 10, Nr. 02 (April 2017): 1750008. http://dx.doi.org/10.1142/s1793604717500084.
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Amorphous semiconductor photocatalysts are highly desirable because they are facile and low-cost to prepare in comparison with the crystalline ones. The amorphous semiconductor with photocatalytic activity has been rarely reported. In this work, a new amorphous semiconductor photocatalyst, Co4I3O[Formula: see text]H[Formula: see text][Formula: see text][Formula: see text][Formula: see text]3H2O, was successfully developed. Its microstructure is composed of irregular particles with size of 2–20[Formula: see text][Formula: see text]m. In photocatalytic degradation of rhodamine B (RhB), or methylene blue (MB) dyes driven by visible light, the Co4I3O[Formula: see text]H[Formula: see text][Formula: see text][Formula: see text][Formula: see text]3H2O sample exhibited pronounced activity. Its activity is higher than Degussa P25 (commercial TiO[Formula: see text] in RhB degradation. It was testified that the degradation of RhB is due to the intrinsical photocatalytic role of Co4I3O[Formula: see text]H[Formula: see text][Formula: see text][Formula: see text][Formula: see text]3H2O. The reusability of the Co4I3O[Formula: see text]H[Formula: see text][Formula: see text][Formula: see text][Formula: see text]3H2O photocatalyst was also investigated.
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Caffaro, M. A. Grado, und M. Grado Caffaro. „Some New Results on Vibrational Properties of Amorphous Group IV Semiconductors“. Active and Passive Electronic Components 16, Nr. 1 (1993): 65–68. http://dx.doi.org/10.1155/1993/43719.
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For neutron scattering, an interesting formula is derived from the coherent one-phonon dynamic structure factor. In this derivation, phonon density of states is involved; this density is related to spectra due to structural disorder, which is investigated. Our considerations refer to amorphous Group IV semiconductors.
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Shen, Junyao, Yongtao Yao, Yanju Liu und Jinsong Leng. „Amorphous Bimetallic Nanowires with High-Performance Microwave Absorption: A Case for FeCo Nanowires“. Nano 14, Nr. 04 (April 2019): 1950041. http://dx.doi.org/10.1142/s1793292019500413.
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Amorphous FeCo nanowires (NWs) with the average diameter of 120[Formula: see text]nm were successfully prepared with a magnetic-field-assisted (MFA) hydrothermal method. Rapid reaction time was adopted to obtain amorphous FeCo NWs, being checked by XRD and TEM. Tuning the stoichiometric ratio of Fe/Co content meets the optimal impedance matching under different absorption frequency, making both improved intensities and frequency ranges of microwave absorption. For example, under 3[Formula: see text]mm coating thickness, the reflection loss (RL) peaks of Fe3Co7, Fe5Co5 and Fe7Co3 NWs are [Formula: see text]25.88[Formula: see text]dB at 4[Formula: see text]GHz, [Formula: see text]19.06[Formula: see text]dB at 4.24[Formula: see text]GHz and [Formula: see text]21.98[Formula: see text]dB at 5.44[Formula: see text]GHz. The related efficient absorption bandwidths ([Formula: see text]10 dB) of Fe3Co7 NWs, Fe5Co5 NWs and Fe7Co3 NWs are 5.40[Formula: see text]GHz, 3.52[Formula: see text]GHz and 4.91[Formula: see text]GHz, respectively. It is ascribed to integrating enhanced dielectric/conductive losses, negligible damages from eddy current effect and good impedance matching for high-performance FeCo NWs absorbers. This work paves a new path on synthesizing bimetallic wire-like nanostructures for microwave absorption demands.
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Zhu, Yuanyuan, Aiguo Zhou, Jin Jia, Junjun Wang, Jiang Liu, Baolin Xing und Chuanxiang Zhang. „Synthesis and Gas Adsorption Properties of Carbide-Derived Carbons from Titanium Tin Carbide“. Nano 11, Nr. 04 (April 2016): 1650040. http://dx.doi.org/10.1142/s1793292016500405.
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Here we reported the synthesis of nanoporous carbide-derived carbons (CDCs) from a new precursor, titanium tin carbides (Ti2SnC), via chlorination at 400–1100[Formula: see text]C. At low chlorination temperature (400–500[Formula: see text]C), as-synthesized CDCs mainly consisted of amorphous carbon and chlorides. As the chlorination temperature increased up to 600[Formula: see text]C, chlorides disappeared, and the main composition of CDCs was amorphous carbon. At high chlorination temperature, there was a trend of graphitization. The microstructure of CDCs was observed and characterized by scanning electron microscopy and transmission electron microscopy. Some graphite-like sheet structures in CDCs were found. Specific surface area (SSA) and pore volume of CDCs increased with chlorination temperature, except an abnormal decrease of the CDC chlorinated at 900[Formula: see text]C. CDC chlorinated at 1100[Formula: see text]C had the largest SSA, 1580[Formula: see text]m2/g. In order to apply these materials as novel hydrogen/methane storage media in the area of energy efficient transport, gas adsorption properties of CDCs were measured. For CDC chlorinated at 1100[Formula: see text]C, pore volume uptakes are [Formula: see text][Formula: see text]cm3/g at 60 bar (25[Formula: see text]C) for methane, and [Formula: see text][Formula: see text]cm3/g at 35 bar ([Formula: see text]C) for hydrogen, respectively. It was suggested that CDCs from Ti2SnC are promising materials for hydrogen/methane adsorptive storage.
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Wen, Quanwu, Shaohua Zhang, Mingwei Sun und Rencheng Jin. „Fabrication of MnFe2O4 and MnCO3 Nanoparticles Anchored on Amorphous Carbon-Coated Carbon Nanotubes for High-Performance Lithium Batteries and Supercapacitors“. Nano 13, Nr. 05 (Mai 2018): 1850050. http://dx.doi.org/10.1142/s1793292018500509.
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Transition metal oxides as Li-ion batteries (LIBs) anodes have attracted much attention because of their high theoretical capacity. However, the large volume change and low electrical conductivity still hinder their application in LIBs. In this work, a new strategy is proposed to enhance the electrochemical performance by anchoring ultrafine MnFe2O4 and MnCO3 ([Formula: see text][Formula: see text]nm) on amorphous carbon-coated carbon nanotubes. Benefiting from the unique structure, the electrode displays excellent cyclability with a reversible specific capacity of 1012[Formula: see text]mAh g[Formula: see text] at 0.1[Formula: see text]A g[Formula: see text] after 100 cycles and outstanding rate performance accompanied by a high specific capacity of 568[Formula: see text]mAh g[Formula: see text] at 5[Formula: see text]A g[Formula: see text] as anode for lithium batteries. When evaluated as supercapacitors, the electrode delivers the specific capacitance of 588.9[Formula: see text]F g[Formula: see text] at a current density of 1[Formula: see text]A g[Formula: see text] and maintains the capacitance retention 94.7% after 4000 cycles at 5[Formula: see text]A g[Formula: see text].
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Huseynov, Elchin M. „Permittivity-Frequency Dependencies Study of Neutron-Irradiated Nanocrystalline Silicon Carbide (3C-SiC)“. Nano 12, Nr. 06 (04.04.2017): 1750068. http://dx.doi.org/10.1142/s1793292017500680.
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Nanocrystalline 3C-SiC was irradiated by neutron flux ([Formula: see text] n[Formula: see text][Formula: see text][Formula: see text]cm[Formula: see text]s[Formula: see text] up to 20[Formula: see text]h in the TRIGA Mark II type research reactor. The experiments have been conducted in the 0.1[Formula: see text]Hz–2.5[Formula: see text]MHz frequency and 100–400[Formula: see text]K temperature ranges. The frequency dependencies of real and imaginary parts of the permittivity of nanomaterial were analyzed comparatively before and after neutron irradiation. After neutron irradiation, there was increase in dopant element concentration in the nanocrystalline 3C-SiC particles. Concentration of new dopant elements in the 3C-SiC nanomaterial directly affects dielectric polarization and leads to increased permittivity. Simultaneously, after neutron irradiation, agglomeration and amorphous transformation influence on the polarization of nanocrystalline 3C-SiC. Moreover, 3C-SiC nanoparticle interface polarization gives rise to dispersion. It was found that ionic polarization was dominant in the nanocrystalline 3C-SiC particles.
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Nath, K. V. Surendra, und S. N. Tandon. „Synthesis and characterization of a new crystalline tin(IV) arsenophosphate ion exchanger“. Canadian Journal of Chemistry 68, Nr. 2 (01.02.1990): 346–49. http://dx.doi.org/10.1139/v90-050.
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A new crystalline layered inorganic ion exchanger tin(IV) arsenophosphate with the formula Sn(HAsO4)(HPO4)•H2O has been prepared by refluxing the amorphous precursor. This exchanger has been characterized by X-ray powder pattern, chemical analysis, IR spectra, and thermal dehydration. Its ion exchange behaviour towards sodium ions is reported. The exchanger has an exchange capacity of 5.36 mequiv./g for Na+. The performance of tin(IV) arsenophosphate is compared with crystalline tin(IV) phosphate and arsenate. Keywords: cation exchanger, crystalline tin(IV) arsenophosphate, ion exchange, thermal behaviour, X-ray studies.
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Toraya, Hideo, und Kazuhiko Omote. „Quantitative phase analysis of amorphous components in mixtures by using the direct-derivation method“. Journal of Applied Crystallography 52, Nr. 1 (01.02.2019): 13–22. http://dx.doi.org/10.1107/s1600576718016394.
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The direct-derivation (DD) method is a new technique for quantitative phase analysis (QPA) [Toraya (2016). J. Appl. Cryst. 49, 1508–1516]. A simple equation, called the intensity–composition (IC) formula, is used to derive weight fractions of individual components (w k ; k = 1–K) in a mixture. Two kinds of parameters are required as input data of the formula. One is the parameter S k , which is the sum of observed powder diffraction intensities for each component, measured in a wide 2θ range and corrected for the Lorentz–polarization factor. The other is the parameter a k −1, defined by a k −1 = M k −1∑nik 2, where M k is the chemical formula weight and n ik is the number of electrons belonging to the ith atom in the chemical formula unit. The parameter a k −1 was originally derived by using the relationship between the peak height and the integrated value of the peak at the origin of the Patterson function, implicitly assuming the presence of periodic structures like crystals. In this study, the formula has been derived theoretically from a general assemblage of atoms resembling amorphous material, and the same expression as the original formula has been obtained. The physical meaning of a k −1, which represents `the total scattering power per chemical formula weight', has been reconfirmed in the present formulation. The IC formula has been tested experimentally by using two-, three- and four-component mixtures containing SiO2 or GeO2 glass powder. In the whole-powder-pattern fitting (WPPF) procedure, incorporated into the DD method, a background-subtracted halo pattern is directly fitted as one of the components in the mixture, together with profile models for crystalline components. In the WPPF, an interaction was observed between the parameters of the background function (BGF) and the parameter for scaling the halo pattern, and this resulted in systematic deviations of w k from weighed values. The deviations were ≤0.7% in the case of binary mixtures when the BGF was fixed at the correct background height, supporting the hypothesis that the DD method is applicable to the QPA of amorphous components.
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Bernard, Samuel, Markus Weinmann, David Cornu und Philippe Miele. „A New Generation of Boron-Based Ceramic Fibers: Design, Processing and Properties of SilicoBoron CarboNitride (SiBCN) Fibers from Boron-Modified Polyvinylsilazanes“. Advances in Science and Technology 50 (Oktober 2006): 9–16. http://dx.doi.org/10.4028/www.scientific.net/ast.50.9.
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Boron-modified polyvinylsilazanes have been studied for suitability as fiber precursor. A melt-tractable polymer displaying Si- and N-bonded methyl groups was successfully processed into green fibers ~18μm in diameter via a melt-spinning process. After the shaping process, the use of an ammonia curing atmosphere at 200°C allowed to increase the ceramic yield of the polymer, then avoid inter-fiber fusion during the further increase of the temperature. As-cured fibers were annealed in the temperature range 1000-1800°C in a nitrogen atmosphere to provide SiBCN ceramic fibers black colored, of flexible form and ~12μm in diameter in different crystallinity states going from totally amorphous below 1600°C to well-crystallized at 1800°C. The excellent strength retention after heat-treatment at 1600°C (1.3-1.5GPa) is clearly related to the high amorphous stability of fibers. Elemental compositions of such amorphous fibers showed a typical chemical formula of Si3.0B1.0C5.0N2.4. Between 1600°C and 1700°C, the fiber strength decreased to 0.9GPa then dropped to about one-quarter the original value at 1800°C while structural changes were evident by XRD analysis.
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LU, YI-MIN, GUO-JUN HUANG, YAN-LONG GUO und SHU-YUN WANG. „OPTICAL PROPERTIES OF THE RAPID ANNEALED OXYGEN-DOPED DIAMOND-LIKE CARBON FILM“. Surface Review and Letters 26, Nr. 01 (Januar 2019): 1850129. http://dx.doi.org/10.1142/s0218625x18501299.
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The amorphous oxygen-doped diamond-like carbon films were prepared by pulsed laser deposition. Compared with the pure diamond-like carbon film, there were much less graphite clusters on the surfaces of the oxygen-doped diamond-like carbon films, and the average transmission of the oxygen-doped diamond-like carbon films in the medium infrared band increased. However, some new absorption peaks in the infrared spectra of the oxygen-doped diamond-like carbon film were generated. Rapid annealing was experimented to remove the absorption peaks. XPS analysis showed that the fractions of the C–O and C=O bonds that generated the new absorption peaks were reduced more than the fractions of [Formula: see text] bonds by rapid annealing at 400[Formula: see text]C, and the absorption peaks in the medium infrared spectra decreased. It indicated that rapid annealing at right temperature during the right time could reduce greatly the absorption in the medium infrared band of oxygen-doped diamond-like carbon films.
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Nikmah, Ainun, Ahmad Taufiq, Arif Hidayat, Sunaryono und Hendra Susanto. „Excellent Antimicrobial Activity of Fe3O4/SiO2/Ag Nanocomposites“. Nano 16, Nr. 05 (21.04.2021): 2150049. http://dx.doi.org/10.1142/s1793292021500491.
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In this study, a new antimicrobial agent was developed through a synthesis of Fe3O4/SiO2/Ag double nanocomposites using the sol–gel method. The prepared samples were characterized using XRD, SEM, FTIR, UV-Vis, VSM, and antibacterial test. The data analysis results for the Fe3O4/SiO2/Ag composites showed that Fe3O4, SiO2, and Ag constructed respective spinel cubic, orthorhombic, and amorphous structures in nanometric size. The saturation magnetization of Fe3O4/SiO2/Ag nanocomposites decreased due to the increase in the Ag content. Interestingly, the Fe3O4/SiO2/Ag nanocomposites presented excellent microbial activity. Ag deposition on the Fe3O4/SiO2 surface enhanced the antimicrobial activity of nanocomposites because Ag oxidized to Ag[Formula: see text] ion to produce a toxic effect in the cells of microorganisms. Furthermore, the Ag[Formula: see text] ion created the –S–Ag bond chain and deactivated the microorganism cells. Furthermore, surface plasmon resonance of Ag had an impact on the formation of photo-induced electrons, which produced superoxide radical anions, [Formula: see text] generating a collapsing force that causes the death of microorganisms.
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Bulus, Ibrahim, S. A. Dalhatu, R. Hussin, W. N. Wan Shamsuri und Y. A. Yamusa. „The role of dysprosium ions on the physical and optical properties of lithium-borosulfophosphate glasses“. International Journal of Modern Physics B 31, Nr. 13 (07.03.2017): 1750101. http://dx.doi.org/10.1142/s0217979217501016.
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Achieving outstanding physical and optical properties of borosulfophosphate glasses via controlled doping of rare earth ions is the key issue in the fabrication of new and highly-efficient glass material for diverse optical applications. Thus, the effect of replacing P2O5 by Dy2O3 on the physical and optical properties of Dy[Formula: see text]-doped lithium-borosulfophosphate glasses with chemical composition of 15Li2O–30B2O3–15SO3–[Formula: see text]P2O5–[Formula: see text]Dy2O3 (where 0.0 mol.% [Formula: see text] mol.%) has been investigated. The glass samples were synthesized from high-purity raw materials via convectional melt-quenching technique and characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDX), density and UV–vis–NIR absorption measurements. The amorphous nature of the prepared glass samples was confirmed by XRD patterns whereas the EDX spectrum depicts elemental traces of O, C, B, S, P and Dy. The physical parameters such as density, refractive index, molar volume, polaron radius and field strength were found to vary nonlinearly with increasing Dy2O3 concentration. UV–vis–NIR absorption spectra revealed seven absorption bands with most dominant peak at 1269 nm (6H[Formula: see text]F[Formula: see text]H[Formula: see text]). From the optical absorption spectra, the optical bandgap and Urbach’s energy have been determined and are related with the structural changes occurring in these glasses with increase in Dy2O3 content. Meanwhile, the bonding parameters ([Formula: see text]) evaluated from the optical absorption spectra were found to be ionic in nature. The superior features exhibited by the current glasses nominate them as potential candidate for nonlinear optical applications.
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Wang, Zhongwu, und T. Yagi. „Incorporation of ferric iron in CaSiO3 perovskite at high pressure“. Mineralogical Magazine 62, Nr. 5 (Oktober 1998): 719–23. http://dx.doi.org/10.1180/002646198547963.
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AbstractSynthetic andradite (Ca3Fe2Si3O12) has been compressed to loading pressures >21 GPa and heated to ∼1000°C by a YAG laser in a Diamond Anvil Cell (DAC). After quenching to room temperature, X-ray diffraction of the sample, still held at 21 GPa, showed that andradite had transformed to a cubic perovskite type polymorph with a = 3.460(4) Å. Upon decompression the perovskite phase transformed into an amorphous phase. The density of the perovskite polymorph (Ca3Fe2Si3O12) is ∼13.6% greater than that of isochemical andradite at 21 GPa. Ferric iron replaces Ca2+ and Si4+ in the perovskite structure (Fe3+ + Fe3+ = Si4+ + Ca2+), giving a formula unit: (Ca,Fe3+)(Si,Fe3+)O3. The new Fe3+-rich Ca-perovskite may provide new insight into the controls on the electrical conductivity of the lower mantle.
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Malakhov, V. V. „Stoichiography: New Ways Determining Chemical Composition and Real Structure of Materials“. Eurasian Chemico-Technological Journal 3, Nr. 3 (05.07.2017): 141. http://dx.doi.org/10.18321/ectj557.
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The principles of stoichiography and novel reference-free methods of molecular and phase analysis for complex unknown mixtures are considered. The stoichiography can be inferred from stoichiometry of mass transfer of unsteady homo- and heterophase processes and joins both operations: separation of mixture by means of chromatography, electromigration, dissolution or others and determination of stoichiometry of a substance flow with time. The stoichiography allows a chemical compound to be determined by its primary property, namely, by stoichiometry of elemental composition. Stoichiograms provided a basis for such type of information. They are time variances of molar ratio for mass transfer rates of chemical elements from multielement substances. Invariancy to concentration and temperature of solvents, hydrodynamic regime is a fundamental property of the stoichiograms in the case of individual compounds. Therefore the stoichiograms are kept constant and are equal to formula stoichiometric coefficients of the individual compound. Theory and methodology of new stoichographic methods, differential dissolution and ion-chromato-stoichiography are presented. New equipment, stoichiograph, and a new procedure of differential dissolution, stoichiographic titration, are discussed here in details. Applications of differential dissolution to analyze multielement and<br />polyphase crystalline and amorphous samples are given.
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Parthé, Erwin. „New examples of crystallized and amorphous borates where the ratio of BO3 triangles to BO4 tetrahedra can be calculated from the chemical formula“. Journal of Alloys and Compounds 367, Nr. 1-2 (März 2004): 126–31. http://dx.doi.org/10.1016/j.jallcom.2003.08.023.
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Buljan, Maja, Uroš V. Desnica, Nikola Radić, Goran Dražić, Zdeněk Matěj, Václav Valeš und Václav Holý. „Crystal structure of defect-containing semiconductor nanocrystals – an X-ray diffraction study“. Journal of Applied Crystallography 42, Nr. 4 (13.06.2009): 660–72. http://dx.doi.org/10.1107/s0021889809017476.
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Defects of crystal structure in semiconductor nanocrystals embedded in an amorphous matrix are studied by X-ray diffraction and a full-profile analysis of the diffraction curves based on the Debye formula. A new theoretical model is proposed, describing the diffraction from randomly distributed intrinsic and extrinsic stacking faults and twin blocks in the nanocrystals. The application of the model to full-profile analysis of experimental diffraction curves enables the determination of the concentrations of individual defect types in the nanocrystals. The method has been applied for the investigation of self-organized Ge nanocrystals in an SiO2matrix, and the dependence of the structure quality of the nanocrystals on their deposition and annealing parameters was obtained.
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Wang, Xiao-Hong, Yue-Wei Guo, Emad Tolba, Maria Kokkinopoulou, Matthias Wiens, Heinz C. Schröder und Werner E. G. Müller. „Two-Armed Activation of Bone Mineral Deposition by the Flavones Baicalin and Baicalein, Encapsulated in Polyphosphate Microparticles“. American Journal of Chinese Medicine 45, Nr. 03 (Januar 2017): 533–55. http://dx.doi.org/10.1142/s0192415x1750032x.
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In this study, we investigated the effect of the two flavonoids, baicalin (baicalein 7-O-[Formula: see text]- d-glucuronic acid) and its aglycone, baicalein (5,6,7-trihydroxyflavone), after encapsulation into amorphous calcium polyphosphate (Ca-polyP) microparticles on mineralization of primary human osteoblasts (phOSB). Both flavonoids, which come from root extracts of Scutellaria baicalensis Georgi, are used in Traditional Chinese Medicine, and are nontoxic in cells up to a concentration of 3[Formula: see text][Formula: see text]g/ml. The morphogenetically active, energy-rich Ca-polyP particles with a stoichiometric P:Ca ratio of 1:2 are degraded by cellular alkaline phosphatase (ALP) to ortho-phosphate used for bone hydroxyapatite formation. Here we show that the flavone-loaded Ca-polyP microparticles are readily taken up by phOSB, resulting in the accumulation of polyP around the nuclei and the formation of intracellular vesicles containing the ALP. In addition, we demonstrate that baicalin/baicalein causes a rise of the intracellular calcium [Ca[Formula: see text]]i a level which markedly is augmented after encapsulation into Ca-polyP, through activation of the phospholipase C. Moreover, both flavones, either alone or associated with Ca-polyP microparticles, upregulate the expression of the osteoblast calcium efflux channel, the plasma membrane Ca[Formula: see text]-ATPase (PMCA), while the expression of ALP, which promotes bone mineralization, is induced by Ca-polyP and by the flavones only if present in the Ca-polyP-microparticle-associated form. As a result, the extent of bone mineralization is markedly enhanced. Based on the two-armed activating function, new applications of baicalin/baicalein as a component of nutriceuticals for osteoporosis prevention or bone implants can be envisaged.
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Al-Khateeb, Khalid A. S., Ammar A. Mustafa, Ahmad Faris und Agus Geter Edy Sutjipto. „Use of Porous Alumina Bioceramic to Increase Implant Osseointegration to Surrounding Bone“. Advanced Materials Research 445 (Januar 2012): 554–59. http://dx.doi.org/10.4028/www.scientific.net/amr.445.554.
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A new experimental porous glass ceramic coating for dental implants was prepared with a new formula consisted of a sintered glass ceramic based on alumina, silica glass and boron trioxide. The resultant sintered objects were anodized by one step anodization method at a constant potential of 40V and at a temperature of 22°C. X-ray diffraction analysis was performed to investigate the phase structure of the new material in addition to SEM investigation for surface texture and pores size and distribution. The new experimental material was subjected to failure under universal testing machine for compressive strength. The results showed a promising material to use as coating for implants as X-ray diffraction exhibited an amorphous phase diagram for the material structure whereas SEM results revealed that the pores in the specimens prepared by anodization method were highly ordered and the mean average pore size was 6.5-8.5 nm. The compressive strength test showed that the test-porous glass ceramic coating has a mean numerical value of up to 7.5 MPa which indicates an ambitious result for the new material.
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Campostrini, Italo, Francesco Demartin und Marco Scavini. „Russoite, NH4ClAs23+O3(H2O)0.5, a new phylloarsenite mineral from Solfatara Di Pozzuoli, Napoli, Italy“. Mineralogical Magazine 83, Nr. 1 (15.05.2018): 89–94. http://dx.doi.org/10.1180/minmag.2017.081.097.
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AbstractThe new mineral russoite (IMA2015-105), NH4ClAs23+O3(H2O)0.5, was found at the Solfatara di Pozzuoli, Pozzuoli, Napoli, Italy, as a fumarolic phase associated with alacránite, dimorphite, realgar, mascagnite, salammoniac and an amorphous arsenic sulfide. It occurs as hexagonal plates up to ~300 µm in diameter and 15 µm thick, in rosette-like intergrowths. On the basis of powder X-ray diffraction measurements and chemical analysis, the mineral was recognised to be identical to the corresponding synthetic phase NH4ClAs2O3(H2O)0.5. Crystals are transparent and colourless, with vitreous lustre and white streak. Tenacity is brittle and fracture is irregular. Cleavage is perfect on {001}. The measured density is 2.89(1) g/cm3; the calculated density is 2.911 g/cm3. The empirical formula, (based on 4.5 anions per formula unit) is [(NH4)0.94,K0.06]Σ1.00(Cl0.91,Br0.01)Σ0.92As2.02O3(H2O)0.5. Russoite is hexagonal, space group P622, with a = 5.2411(7), c = 12.5948(25) Å, V = 299.62(8) Å3 and Z = 2. The eight strongest X-ray powder diffraction lines are [dobs Å(I)(hkl)]: 12.63(19)(001), 6.32(100)(002), 4.547(75)(100), 4.218(47)(003), 3.094(45)(103), 2.627(46)(110), 2.428(31)(112) and 1.820(28)(115). The structure, was refined to R = 0.0518 for 311 reflections with I > 2σ(I) and shows a different location of the ammonium cation and water molecules with respect to that reported for the synthetic analogue. The mineral belongs to a small group of phylloarsenite minerals (lucabindiite, torrecillasite and gajardoite). It contains electrically neutral As2O3 layers, topologically identical to those found in lucabindiite and gajardoite between which are ammonium cations and outside of which Cl– anions. Water molecules and additional ammonium cations are located in a layer between two levels of chloride anions.
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Kushnerov, O. I., und V. F. Bashev. „Structure, thermal and electrical properties of Fe-B-Co-Nb-Ni-Si high-entropy metallic glass“. Journal of Physics and Electronics 28, Nr. 1 (10.09.2020): 49–54. http://dx.doi.org/10.15421/332009.
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New nanostructured Fe25B17.5Co21.35Nb3.65Ni25Si7.5 high-entropy metallic glass is synthesized by dint of splat-quenching technique. The estimated cooling rate is ~106 K/s. The coherently scattering domain size (crystallite size) of films of Fe 25B17.5Co21.35Nb3.65Ni25Si7.5 high-entropy metallic glass estimated by the Sherer formula is ~ 3 nm. The high-entropy metallic glass shows a high temperature of glass transition Tg ~ 800 K and the initial temperature of crystallization Tx ~ 863 K. After annealing to ~ 1010 K (above the crystallization temperature) and subsequent slow cooling, the amorphous films crystallize with the formation of several crystalline phases. The temperature dependencies of electrical resistivity of the Fe25B17.5Co21.35Nb3.65Ni25Si7.5 films indicate the occurrence of phase transformations. The phase transformation temperature (temperature of crystallization) is ~ 869 K. This value agrees well with the value obtained from the differential thermal analysis.
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Li, Jing, Raghda A. M. Attia, Mostafa M. A. Khater und Dianchen Lu. „The new structure of analytical and semi-analytical solutions of the longitudinal plasma wave equation in a magneto-electro-elastic circular rod“. Modern Physics Letters B 34, Nr. 12 (05.03.2020): 2050123. http://dx.doi.org/10.1142/s0217984920501237.
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This research paper extracts novel analytical and semi-analytical wave solutions of the longitudinal wave equation in a magneto-electro-elastic circular rod by using the modified Khater method as one of the most novel and general computational methods and the Adomian decomposition method as a semi-analytical method. The longitudinal waves in metallic thin films are explained for the first time by Nilsson and Lindau, who used the visual evidence. They noted subdued anomalies in the ports of thin ([Formula: see text]100 Å) Ag layers deposited on amorphous silica for p-polarized light at frequencies padlock to the dynamic plasma frequency. These properties are studied by our two suggested methods and are explained by sketching some of our obtained solutions. Moreover, the stability property is tested for our obtained solutions by using the features of the Hamiltonian system. The performance of our used methods shows the power and effectiveness of these methods and their ability to apply on many different forms of nonlinear partial differential equations.
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Sammour, Rana, Muhammad Taher, Bappaditya Chatterjee, Aliasgar Shahiwala und Syed Mahmood. „Optimization of Aceclofenac Proniosomes by Using Different Carriers, Part 1: Development and Characterization“. Pharmaceutics 11, Nr. 7 (18.07.2019): 350. http://dx.doi.org/10.3390/pharmaceutics11070350.
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In the contemporary medical model world, the proniosomal system has been serving as a new drug delivery system that is considered to significantly enhance the bioavailability of drugs with low water solubility. The application of this system can improve the bioavailability of aceclofenac that is used for the relief of pain and inflammation in osteoarthritis, rheumatoid arthritis, and ankylosing spondylitis. The present study is intended to develop an optimized proniosomal aceclofenac formula by the use of different carriers. Aceclofenac proniosomes have been prepared by slurry method, and different carriers such as maltodextrin, mannitol, and glucose were tried. Prepared proniosomes characterized by differential scanning calorimetry (DSC) analysis and Fourier transform infrared (FTIR) analysis revealed the compatibility of the drug chosen with the ingredient added, powder X-ray diffractometry (XRD) confirmed the amorphous phase of the prepared proniosomes, and finally, the surfactant layer was observed by scanning electron microscopy (SEM). Aceclofenac physical state transformations were confirmed with all formulas but maltodextrin proniosomes exhibited solubility more than other formulations. HPLC method has been used to analyze the niosomes derived from proniosomes in terms of their entrapment capability and drug content. The obtained results revealed that aceclofenac proniosomes can be successfully prepared by using different carriers.
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Pei, Liefei, Xiangyun Zhang und Zizhou Yuan. „Reduction and Immobilization of Movable Cu2+ Ions in Soils by Fe78Si9B13 Amorphous Alloy“. Metals 11, Nr. 2 (10.02.2021): 310. http://dx.doi.org/10.3390/met11020310.
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The Fe-based amorphous alloy (Fe78Si9B13AP) is applied to the remediation of copper contaminated soil for the first time. The dynamic process of conversion of movable Cu to immobilized forms in the soil system is analyzed. In addition, the dynamic process of form transformation of Cu2+ ions in the soil system is analyzed. The morphology and phase composition of the reaction products are characterized by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). Finally, the feasibility of recovering residual stabilizer particles and attached immobilized copper by the magnetic separation process is discussed. The results show that the apparent reaction rate constant of Fe79Si9B13AP with Cu2+ ions is higher than that of zero valent iron (ZVI) at all the experimental temperatures. According to the Arrhenius formula, the apparent activation energy of the reaction of Fe78Si9B13AP and ZVI with Cu2+ ions is 13.24 and 19.02 kJ/mol, respectively, which is controlled by the diffusion process. The lower apparent activation energy is one of the important reasons for the high reaction activity of Fe78Si9B13AP. After 7 days of reaction, a continuous extraction of the experimental soil shows that the main form of copper in the immobilized soil is Cu and copper combined with iron (hydroxide) oxide, and there is almost no soluble copper with a strong mobility, which effectively reduced the bioavailability of copper in the soil. The magnetic separation results of the treated soil show that the recovery rates of immobilized copper in Fe78Si9B13AP and soil are 47.23% and 21.56%, respectively, which reduced the content of iron and copper in the soil to a certain extent. The above experimental results show that Fe78Si9B13AP is a promising new material for the remediation of heavy metal contaminated soils, and provides more new references for the application of amorphous alloys in the field of remediation of water and soil contaminated by heavy metals and organic matter.
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Ahmina, W., M. El Moudane, M. Zriouil, M. Cherraj und M. Taibi. „Study of the mechanical and chemical properties of potassium manganese phosphate glasses“. MATEC Web of Conferences 149 (2018): 01081. http://dx.doi.org/10.1051/matecconf/201814901081.
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Homogeneous phosphate glasses having the general formula 20K2O-xMnO-(80-x)P2O5 were synthesized using a melt-quenching method. The amorphous nature of the samples was asserted by X–ray diffraction. The glasses are studied in order to evaluate the influence of MnO addition on the chemical and mechanical properties, such as, dissolution rate, average compressive strength (Rc), Young’s modulus (E) and limit strain (εlim). Some studies show that the addition of MnO significantly reduces the degradation rate (DR) of soluble phosphate glasses and enhanced chemical stability of both alkali-resistance and acid-resistance. MnO interfere with the chemical structure of the glass, and consequently improve their mechanical properties. Indeed, the mechanical measurements showed that the glass structure was modified by the addition of MnO oxide, becoming more rigid, and as a result, increasing the compressive strength (Rc), Young’s modulus (E). These new materials could be an important opportunity for applications in the fields of building, construction, civil engineering, etc…
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Grey, I. E., E. Keck, A. R. Kampf, W. G. Mumme, C. M. Macrae, R. W. Gable, A. M. Glenn und C. J. Davidson. „Steinmetzite, Zn2Fe3+(PO4)2(OH)·3H2O, a new mineral formed from alteration of phosphophyllite at the Hagendorf Süd pegmatite, Bavaria“. Mineralogical Magazine 81, Nr. 2 (April 2017): 329–38. http://dx.doi.org/10.1180/minmag.2016.080.100.
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AbstractSteinmetzite, ideally Zn2Fe3+(PO4)2(OH)·3H2O, is a new mineral from the Hagendorf-Süd pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany. Steinmetzite was found in a highly oxidized zone of the Cornelia mine at Hagendorf-Süd. It has formed by alteration of phosphophyllite, involving oxidation of the iron and some replacement of Zn by Fe. Steinmetzite lamellae co-exist with an amorphous Fe-rich phosphate in pseudomorphed phosphophyllite crystals. The lamellae are only a few μm thick and with maximum dimension ∼50 μm. The phosphophyllite pseudomorphs have a milky opaque appearance, often with a glazed yellow to orange weathering rind and with lengths ranging from sub-mm to 1 cm. Associated minerals are albite, apatite, chalcophanite, jahnsite, mitridatite, muscovite, quartz and wilhelmgümbelite.Goethite and cryptomelane are also abundant in the oxidized zone. The calculated density is 2.96 g cm–3. Steinmetzite is biaxial (–) with measured refractive indices α = 1.642(2), β = 1.659 (calc.), γ = 1.660(2) (white light). 2V(meas) = 27(1)°; orientation is Y ≈ b, X ^c ≈ 27°, with crystals flattened on {010} and elongated on [001]. Pleochroism shows shades of pale brown; Y > X ≈ Z. Electron microprobe analyses (average of seven crystals) with Fe reported as Fe2O3 and with H2O calculated from the structure gave ZnO 31.1, MnO 1.7, CaO 0.5, Fe2O3 21.9, Al2O3 0.3, P2O5 32.9, H2O 14.1 wt.%, total 102.5%. The empirical formula based on 2 P and 12 O, with all iron as ferric and OH–adjusted for charge balance is Zn1.65Fe1.193+ Mn0.112+Ca0.03Al0.023+(PO4)2(OH)1.21·2.79H2O. The simplified formula is Zn2Fe3+(PO4)2(OH)·3H2O.Steinmetzite is triclinic, P1̄, with unit-cell parameters: a = 10.438(2), b = 5.102(1), c = 10.546(2) Å, α = 91.37(2), β = 115.93(2) and γ = 94.20(2)°. V = 502.7(3) Å3, Z = 2. The strongest lines in the powder X-ray diffraction pattern are [dobs in Å (I) (hkl)] 9.313(65) (100), 5.077(38) (010), 4.726(47) (002), 4.657(100) (200), 3.365 (55) (3̄02), 3.071(54) (11̄2) and 2.735(48) (3̄1̄2). The structure is related to that of phosphophyllite.
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Rajab, Nawal Ayash. „PREPARATION AND IN VITRO EVALUATION OF LACIDIPINE ORAL LIQUID SOLID TABLET AS AN APPROACH OF SOLUBILITY AND DISSOLUTION RATE ENHANCEMENT“. International Journal of Applied Pharmaceutics 10, Nr. 1 (06.01.2018): 145. http://dx.doi.org/10.22159/ijap.2018v10i1.22313.
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Objective: The aim of the present study was to prepare a new liquid-solid tablet to enhance the dissolution and bioavailability of a poor water soluble calcium channel blocker lacidipine.Methods: Firstly, solubility study of lacidipine in different media of water-miscible non-volatile solvents as tween 20, tween 80, propylene glycol, liquid paraffin, PEG200, PEG400, and PEG600 was investigated to select the most suitable solvent. A mathematical model was applied to calculate the appropriate amount of carrier and coating material.Four liquid-solid tablets of 6 mg lacidipine were prepared by dissolving the drug in the previously chosen water miscible non-volatile solvents, then a binary mixture of the carrier (Avicel PH 102) and coating material (Aerosil 200) at a ratio of 45:1 was used in all preparation since it gave the optimal flow property. Croscarmellose and magnesium stearate were incorporated in all prepared formulas as super disintegrant and lubricant respectively. On the other hand, directly compressed lacidipine tablet of the same previous composition without the addition of any non-volatile solvent was prepared for comparism study. Both characterizations of powder mixture and post-compression tablet evaluations were done. Differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR) were investigated for the pure drug, physical mixture, and selected liquid-solid tablet to exclude any drug-excipients interaction.Results: The obtained results indicated that PEG 200 was the most suitable solvent with lacidipine solubility of 2.81 mg/ml. Flowability of all the prepared formulas was found to be within the specification limits. The liquid-solid tablet formula with PEG 200 at 10% w/w lacidipine was the most suitable one in the term of disintegration time (21±0.2 second), 100% of drug release within 10 min, and with accepted other tablet properties.DSC thermograms for both physical mixture of selected liquisolid system and its tablets illustrated the formation of lacidipine amorphous solid solution. The absence of chemical interaction between drug and other formula components was confirmed by remaining all characteristic peaks of lacidipine in all investigated FTIR spectra.Conclusion: Liquid-solid tablet was considered as a promising system to enhance solubility and dissolution rate of poor-water soluble lacidipine.
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Abou Melha, Khlood S., Gamil A. Al-Hazmi, Ismail Althagafi, Arwa Alharbi, Ali A. Keshk, Fathy Shaaban und Nashwa El-Metwaly. „Spectral, Molecular Modeling, and Biological Activity Studies on New Schiff’s Base of Acenaphthaquinone Transition Metal Complexes“. Bioinorganic Chemistry and Applications 2021 (22.03.2021): 1–17. http://dx.doi.org/10.1155/2021/6674394.
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The newly synthesized Schiff’s base derivative, N-allyl-2-(2-oxoacenaphthylen-1(2H)-ylidene)hydrazine-1-carbothioamide, has been characterized by different spectral techniques. Its reaction with Co(II), Ni(II), and Zn(II) acetate led to the formation of 1 : 1 (M:L) complexes. The IR and NMR spectral data revealed keto-thione form for the free ligand. On chelation with Co(II) and Ni(II), it behaved as mononegative and neutral tridentate via O, N1, and S donors, respectively, while it showed neutral bidentate mode via O and N1 atoms with Zn(II). The electronic spectra indicated that all the isolated complexes have an octahedral structure. The thermal gravimetric analyses confirmed the suggested formula and the presence of coordinated water molecules. The XRD pattern of the metal complexes showed that both Co(II) and Ni(II) have amorphous nature, while Zn(II) complex has monoclinic crystallinity with an average size of 9.10 nm. DFT modeling of the ligand and complexes supported the proposed structures. The calculated HOMO-LUMO energy gap, ΔEH-L, of the ligand complexes was 1.96–2.49 eV range where HAAT < Zn(II) < Ni(II) < Co(II). The antioxidant activity investigation showed that the ligand and Zn(II) complex have high activity than other complexes, 88.5 and 88.6%, respectively. Accordingly, the antitumor activity of isolated compounds was examined against the hepatocellular carcinoma cell line (HepG2), where both HAAT and Zn(II) complex exhibited very strong activity, IC50 6.45 ± 0.25 and 6.39 ± 0.18 μM, respectively.
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Elliott, P., G. Giester, R. Rowe und A. Pring. „Putnisite, SrCa4Cr83+ (CO3)8SO4(OH)16·25H2O, a new mineral from Western Australia: description and crystal structure“. Mineralogical Magazine 78, Nr. 1 (Februar 2014): 131–44. http://dx.doi.org/10.1180/minmag.2014.078.1.10.
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AbstractPutnisite, SrCa4Cr83+ (CO7)8SO4(OH)16·25H2O, is a new mineral from the Polar Bear peninsula, Southern Lake Cowan, Western Australia, Australia. The mineral forms isolated pseudocubic crystals up to 0.5 mm in size in a matrix composed of quartz and a near amorphous Cr silicate. Putnisite is translucent, with a pink streak and vitreous lustre. It is brittle and shows one excellent and two good cleavages parallel to {100}, {010} and {001}. The fracture is uneven and the Mohs hardness 1½−2. The measured density is 2.20(3) g/cm3 and the calculated density based on the empirical formula is 2.23 g/cm3. Optically, putnisite is biaxial negative, with α = 1.552(3), β = 1.583(3) and γ = 1.599(3) (measured in white light). The optical orientation is uncertain and pleochroism is distinct: X pale bluish grey, Y pale purple, Z pale purple. Putnisite is orthorhombic, space group Pnma, with a = 15.351(3), b = 20.421(4) Å, c = 18.270(4) Å, V = 5727(2) Å3 (single-crystal data), and Z = 4. The strongest five lines in the X-ray powder diffraction pattern are [d(Å)(I)(hkl)]: 13.577 (100) (011), 7.659 (80) (200), 6.667 (43) (211), 5.084 (19) (222, 230), 3.689 (16) (411). Electron microprobe analysis (EMPA) gave (wt.%): Na2O 0.17, MgO 0.08, CaO 10.81, SrO 5.72, BaO 0.12, CuO 0.29, Cr2O3 31.13, SO3 3.95, SiO2 0.08, Cl− 0.28, CO2calc 17.94, H2Ocalc 30.30, O=Cl−0.06, total 100.81. The empirical formula, based on O + Cl = 69, is: Cr8.023+Ca3.78Sr1.08Na0.11Cu0.072+Mg0.04Ba0.02[(SO4)0.96(SiO4)0.03]0.99 (CO3)7.98(OH)16.19Cl0.15·24.84H2O. The crystal structure was determined from single-crystal X-ray diffraction data (MoKα, CCD area detector and refined to R1 = 5.84% for 3181 reflections with F0 > 4σF. Cr(OH)4O2 octahedra link by edge-sharing to form an eight-membered ring. A 10-coordinated Sr2+ cation lies at the centre of each ring. The rings are decorated by CO3 triangles, each of which links by corner-sharing to two Cr(OH)4O2 octahedra. Rings are linked by Ca(H2O)4O4 polyhedra to form a sheet parallel to (100). Adjacent sheets are joined along [100] by corner-sharing SO4 tetrahedra. H2O molecules occupy channels that run along [100] and interstices between slabs. Moderate to weak hydrogen bonding provides additional linkage between slabs.
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Sokolova, E., A. Genovese, A. Falqui, F. C. Hawthorne und F. Cámara. „From structure topology to chemical composition. XXIII. Revision of the crystal structure and chemical formula of zvyaginite, Na2ZnTiNb2(Si2O7)2O2(OH)2(H2O)4, a seidozerite-supergroup mineral from the Lovozero alkaline massif, Kola peninsula, Russia“. Mineralogical Magazine 81, Nr. 6 (Dezember 2017): 1533–50. http://dx.doi.org/10.1180/minmag.2017.081.015.
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AbstractThe crystal structure and chemical formula of zvyaginite, ideally Na2ZnTiNb2(Si2O7)2O2(OH)2(H2O)4, a lamprophyllite-group mineral of the seidozerite supergroup from the type locality, Mt. Malyi Punkaruaiv, Lovozero alkaline massif, Kola Peninsula, Russia have been revised. The crystal structurewas refined with a new origin in space group C1, a = 10.769(2), b = 14.276(3), c = 12.101(2) Å, α = 105.45(3), β = 95.17(3), γ = 90.04(3)°, V = 1785.3(3.2) Å3, R1 = 9.23%. The electron-microprobe analysis gave the following empirical formula [calculated on 22 (O + F)]: (Na0.75Ca0.09K0.04□1.12)Σ2 (Na1.12Zn0.88Mn0.17Fe2+0.04□0.79)Σ3 (Nb1.68Ti1.25Al0.07)Σ3 (Si4.03O14)O2 [(OH)1.11F0.89]Σ2(H2O)4, Z = 4. Electron-diffraction patterns have prominent streaking along c* and HRTEM images show an intergrowth of crystalline zvyaginite with two distinct phases, both of which are partially amorphous. The crystal structure of zvyaginite is an array of TS (Titanium-Silicate) blocks connected via hydrogen bonds between H2O groups. The TS block consists of HOH sheets (H = heteropolyhedral, O = octahedral) parallel to (001). In the O sheet, the [6]MO(1,4,5) sites are occupied mainly by Ti, Zn and Na and the [6]MO(2,3) sites are occupied by Na at less than 50%. In the H sheet, the [6]MH(1,2) sites are occupied mainly by Nb and the [8]AP(1) and [8]AP(2) sites are occupied mainly by Na and □. The MH and AP polyhedra and Si2O7 groups constitute the H sheet. The ideal structural formula is Na□Nb2NaZn□Ti(Si2O7)2O2(OH)2(H2O)4. Zvyaginite is a Zn-bearing and Na-poor analogue of epistolite, ideally (Na□)Nb2Na3Ti(Si2O7)2O2(OH)2(H2O)4. Epistolite and zvyaginite are related by the following substitution in the O sheet of the TS-block: (Naþ 2 )epi↔Zn2+ zvy +□zvy. The doubling of the t1 and t2 translations of zvyaginite relative to those of epistolite is due to the order of Zn and Na along a (t1) and b (t2) in the O sheet of zvyaginite.
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Roberts, Andrew C., T. Scott Ercit, Alan J. Criddle, Gary C. Jones, R. Scott Williams, Forrest F. Cureton und Martin C. Jensen. „Mcalpineite, Cu3TeO6·H2O, a new mineral from the McAlpine mine, Tuolumne County, California, and from the Centennial Eureka mine, Juab County, Utah“. Mineralogical Magazine 58, Nr. 392 (September 1994): 417–24. http://dx.doi.org/10.1180/minmag.1994.058.392.07.
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AbstractMcalpineite, ideally Cu3TeO6·H2O, occurs as isolated 0.5 mm-sized emerald green cryptocrystalline crusts on white quartz at the long-abandoned McAlpine mine, Tuolumne County, California, U.S.A. Associated nonmetallic phases are muscovite (mariposite), calcite, goethite, hematite, chlorargyrite, choloalite, keystoneite, mimetite, malachite, azurite, annabergite and a host of unidentified crusts, both crystalline and amorphous. Associated metallic minerals include pyrite, acanthite, hessite, electrum, altaite, native silver, galena, pyrargyrite, sphalerite and owyheeite. The mineral has also been identified at the Centennial Eureka mine, Juab County, Utah, U.S.A., where it occurs as interstitial olive-green coatings and as millimetre-sized dark green-black cryptocrystalline nodules lining drusy quartz vugs. Associated minerals are xocomecatlite, hinsdalite-svanbergite, goethite and several new species including two hydrated copper tellurates, a hydrated copper-zinc tellurate/tellurite, and a hydrated copper-zinc tellurate/tellurite-arsenate-chloride. Mcalpineite is cubic, P-lattice (space group unknown), a = 9.555(2) Å, V = 872.4(4) Å. The strongest six lines in the X-ray powder-diffraction pattern [d in Å (I) (hkl)] are: 4.26(40)(210), 2.763(100)(222), 2.384(70)(400), 1.873(40)(431,510), 1.689(80)(440) and 1.440(60)(622). The average of four electron-microprobe analyses (McAlpine mine) is CuO 50.84, NiO 0.17, PbO 4.68, SiO2 0.65, TeO3 39.05, H2O (calc.) [4.51], total [100.00] wt. %. With O = 7, the empirical formula is (Cu2.79Pb0.09Ni0.01)∑2.89(Te0.97Si0.05)∑1.02O5.90·1.10H2O. This gives a calculated density of 6.65. g/cm3 for Z = 8. The average of two electron-microprobe analyses (Centennial Eureka mine) is CuO 51.2, ZnO 3.1, TeO3 39.0, SiO2 0.2, As2O5 0.8, H2O (by CHN elemental analyser) 7, total 101.3 wt. %, leading to the empirical formula (Cu2.56Zn0.15)∑2.71 (Te0.88Si0.02As0.02)∑0.92O5.47·1.53H2O. The infrared absorption spectrum shows definite bands for structural H2O with an O-H stretching frequency centred at 3320 cm−1 and a H-O-H flexing frequency centred at 1600 cm−1. In reflected light Mcalpineite is isotropic, nondescript grey, with ubiquitous brilliant apple to lime green internal reflections. The refractive index calculated from Fresnel equations is 2.01. Measured reflectance values in air and in oil are tabulated. Reflectance study also shows that cryptocrystalline aggregates are composed of micron-sized sheaves of fibrous or prismatic crystals. Other physical properties include: adamantine lustre; light green streak; brittle; uneven fracture; translucent to transparent and nonfluorescent under both long- and short-wave ultraviolet light. The name is for the first known locality, the McAlpine mine.
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Yıldız Yorgun, Nergiz. „Gamma-ray shielding parameters of Li2B4O7 glasses: undoped and doped with magnetite, siderite and Zinc-Borate minerals cases“. Radiochimica Acta 107, Nr. 8 (26.07.2019): 755–65. http://dx.doi.org/10.1515/ract-2019-0014.
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Abstract Designing new shielding materials and calculating their shielding parameters are important task to keep living in safe from hazardous effects of radiation. In this study, the lithium borate glasses with chemical formula (Li2B4O7)(100−x)Yx (x = 0, 10, 20, 30 and 40 wt % and Y = magnetite, siderite and zinc-borate) were fabricated via melt quenching technique. X-ray diffraction method was employed to confirm amorphous structure of fabricated glass samples. The glass sample’s shielding parameters such as mass attenuation coefficient, effective atomic number, and half value layer were measured experimentally by the narrow beam transmission method for 81, 276, 302, 356, and 383 keV of incident photon energies. Also, WinXCom software was used to calculate theoretical shielding parameters from 1 keV to 105 MeV photon energy. Moreover, Geometric Progression (G–P) method was used to calculate exposure buildup factor (EBF) values for incident photon energy 0.015 MeV–15 MeV up to penetration depths of 40 mfp (mean free path). Among the obtained results, while Li2B4O7 glass with magnetite 40 % has the highest mass attenuation and effective atomic number, it has the lowest half value layer and exposure buildup factor. The results show that the fabricated glass systems could be considered as a good candidate for radiation safety.
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Dkhilalli, F., S. Megdiche Borchani, M. Rasheed, R. Barille, S. Shihab, K. Guidara und M. Megdiche. „Characterizations and morphology of sodium tungstate particles“. Royal Society Open Science 5, Nr. 8 (August 2018): 172214. http://dx.doi.org/10.1098/rsos.172214.
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A solid-state reaction technique was used to synthesize polycrystalline Na 2 WO 4 . Preliminary X-ray studies revealed that the compound has a cubic structure at room temperature. The formation of the compound has been confirmed by X-ray powder diffraction studies and Raman spectroscopy. Electrical and dielectric properties of the compound have been studied using complex impedance spectroscopy in the frequency range 209 Hz–1 MHz and temperature range 586–679 K. The impedance data were modellized by an equivalent circuit consisting of series of a combination of grains and grains boundary. We use complex electrical modulus M * at various temperatures to analyse dielectric data. The modulus plots are characterized by the presence of two relaxation peaks thermally activated. The morphologies and the average particle size of the resultant sodium tungstate sample were demonstrated by atomic force microscopy, scanning electron microscopy and transmission electron microscopy. The thicknesses and optical constants of the sample have been calculated using ellipsometric measurements in the range of 200–22 000 nm by means of new amorphous dispersion formula which is the objective of the present work. The results were obtained for Na 2 WO 4 particles from experimental (EXP) and measured (FIT) data showed an excellent agreement. In addition, the energy gap of the Na 2 WO 4 sample has been determined using ellipsometry and confirmed by spectrophotometry measurements.
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Ivanyuk, Gregory Yu, Victor N. Yakovenchuk, Taras L. Panikorovskii, Nataliya Konoplyova, Yakov A. Pakhomovsky, Ayya V. Bazai, Vladimir N. Bocharov und Sergey V. Krivovichev. „Hydroxynatropyrochlore, (Na,Сa,Ce)2Nb2O6(OH), a new member of the pyrochlore group from the Kovdor phoscorite–carbonatite pipe, Kola Peninsula, Russia“. Mineralogical Magazine 83, Nr. 1 (15.05.2018): 107–13. http://dx.doi.org/10.1180/minmag.2017.081.102.
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AbstractHydroxynatropyrochlore, (Na,Сa,Ce)2Nb2O6(OH), is a new Na–Nb–OH-dominant member of the pyrochlore supergroup from the Kovdor phoscorite–carbonatite pipe, Kola Peninsula, Russia. It is cubic, Fd$\bar{3}$m, a = 10.3211(3) Å, V = 1099.46(8) Å3 and Z = 8 (from powder diffraction data) or a = 10.3276(5) Å, V = 1101.5(2) Å3 and Z = 8 (from single-crystal diffraction data). Hydroxynatropyrochlore is a characteristic accessory mineral of the low-carbonate phoscorite in the contact zone of the phoscorite–carbonatite pipe with host foidolite as well as in the carbonate-rich phoscorite and carbonatite of the pipe axial zone. It usually forms zonal cubic or cubooctahedral crystals (up to 0.5 mm in diameter) with irregularly shaped relics of amorphous U–Ta-rich hydroxykenopyrochlore inside. Characteristic associated minerals include rock-forming calcite, dolomite, forsterite, hydroxylapatite, magnetite and phlogopite, accessory baddeleyite, baryte, barytocalcite, chalcopyrite, chamosite–clinochlore, galena, gladiusite, juonniite, ilmenite, magnesite, pyrite, pyrrhotite, quintinite, spinel, strontianite, valleriite and zirconolite. Hydroxynatropyrochlore is pale brown, with an adamantine to greasy lustre and a white streak. The cleavage is average on {111} and the fracture is conchoidal. Mohs hardness is ~5. In transmitted light, the mineral is light brown, isotropic and n = 2.10(5) (λ = 589 nm). The calculated and measured densities are 4.77 and 4.60(5) g cm−3, respectively. The mean chemical composition determined by electron microprobe is: F 0.05, Na2O 7.97, CaO 10.38, TiO2 4.71, FeO 0.42, Nb2O5 56.44, Ce2O3 3.56, Ta2O5 4.73, ThO2 5.73, UO2 3.66, total 97.65 wt.%. The empirical formula calculated on the basis of Nb + Ta + Ti = 2 apfu is (Na1.02Ca0.73Ce0.09Th0.09 U0.05${\rm Fe}_{{\rm 0}{\rm. 02}}^{2 +} $)Σ2.00(Nb1.68Ti0.23Ta0.09)Σ2.00O6.03(OH1.04F0.01)Σ1.05. The simplified formula is (Na,Ca,Ce)2Nb2O6(OH). The mineral dissolves slowly in hot HCl. The strongest X-ray powder-diffraction lines [listed as (d in Å)(I)(hkl)] are as follows: 5.96(47)(111), 3.110(30)(311), 2.580(100)(222), 2.368(19)(400), 1.9875(6)(333), 1.8257(25)(440) and 1.5561(14)(622). The crystal structure of hydroxynatropyrochlore was refined to R1 = 0.026 on the basis of 80 unique observed reflections. The mineral belongs to the pyrochlore structure type A2B2O6Y1 with octahedral framework of corner-sharing BO6 octahedra with A cations and OH groups in the interstices. The Raman spectrum of hydroxynatropyrochlore contains characteristic bands of the lattice, BO6, B–O and O–H vibrations and no characteristic bands of the H2O vibrations. Within the Kovdor phoscorite–carbonatite pipe, hydroxynatropyrochlore is the latest hydrothermal mineral of the pyrochlore supergroup, which forms external rims around grains of earlier U-rich hydroxykenopyrochlore and separated crystals in voids of dolomite carbonatite veins. The mineral is named in accordance with the pyrochlore supergroup nomenclature.
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Zhan, Bi-Zeng, Mary Anne White, James A. Pincock, Katherine N. Robertson, T. Stanley Cameron und Tsun-Kong Sham. „Oxidation of cyclohexane using a novel RuO2zeolite nanocomposite catalyst“. Canadian Journal of Chemistry 81, Nr. 6 (01.06.2003): 764–69. http://dx.doi.org/10.1139/v03-060.
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We report the synthesis, using an organic-template-free hydrothermal crystallization method, and catalysis of a new type of nanocomposite material, 1.3 nm-sized RuO2 particles confined in faujasite zeolite. The zeolite-confined RuO2 composites were fully characterized with X-ray powder diffraction, Ru K-edge X-ray absorption, and high-resolution transmission electron microscopy. XRD and X-ray fluorescence analysis indicate that the framework is faujasite zeolite with a Si:Al ratio of 1.25. Ru K-edge X-ray absorption near-edge structures indicate that the ruthenium species in the zeolite is Ru(IV) with nearest-neighbor octahedral environments similar to hydrous RuO2, i.e., distorted "RuO6". The k2-weighted extended X-ray absorption fine structure indicates that the Ru(IV) species anchored in the zeolite likely form amorphous RuO2 with a 2D-chain structure, in which RuO6 units are connected together by two shared oxygen atoms. TEM shows that the particle size of RuO2 encapsulated inside the supercages of FAU is about 1.3 nm. The RuO2FAU composites display significant catalytic activity in the oxidation of cyclohexane with tBHP under mild (room temperature and 1 atm (1 atm [Formula: see text] 101.325 kPa)) conditions. The ketone and alcohol concentration can be as high as 0.26 mol L1 in 5 h with 48% peroxide efficiency. The catalyst is stable and reusable. Possible oxidation mechanisms are also discussed.Key words: nanocomposite, ruthenium oxide, catalysis, oxidation, zeolite.
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Hocking, Martin B., und Francies W. Van Der Voort Maarschalk. „X-ray structures of adducts of 1,2,5-triphenylphosphole with dimethyl acetylenedicarboxylate: a confirmation, a revision, and a new structure“. Canadian Journal of Chemistry 71, Nr. 11 (01.11.1993): 1873–89. http://dx.doi.org/10.1139/v93-235.
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Dimethyl acetylenedicarboxylate was reacted with 1,2,5-triphenylphosphole under mild conditions, and four products isolated. Regardless of conditions used, every preparation gave low yields of dimethyl 3,6-diphenylphthalate coincident with loss of the phosphorus bridge. NMR data and X-ray crystal structures are provided for a yellow, and a red, 2:1 adduct. The yellow adduct, tetramethyl 1,6,7-triphenyl-6-phospha(V)-tricyclo[7.3.1.01,9]nona-3,5,7-triene-2,3,4,5-tetracarboxylate 6, crystallized in the triclinic space group [Formula: see text] (No. 2) with two molecules in the unit cell. Refinement (a = 11.259(1) Å, b = 12.947(3) Å, c = 13.784(3) Å, α = 112.25(2)°, β = 103.44(1)°, and γ = 101.80(1)°) converged at R = 0.0453 (Rw = 0.0453) for 537 parameters using 2880 reflections with I > 2σ(I). The red adduct, trimethyl 1,2,5-triphenylphosphoranylidene-4-methoxycyclopent-2-ene-5-one-2,3,4-tricarboxylate, an exocyclic phosphorane 8, crystallized in the monoclinic space group P21/c (No. 14) with four molecules in the unit cell. Refinement of this structure (a = 13.233(5) Å, b = 15.712(5) Å, c = 17.191(7) Å, α = 90°, β = 110.35(4)°, and γ = 90°) converged at R = 0.0916 (Rw = 0.0937) for 400 parameters using 2052 reflections with I > 2.5σ(I). Small amounts of a white or buff amorphous material, which could represent a polymeric product from the lost phosphorus bridge, were also obtained. Thermal rearrangement of the yellow adduct gave a colourless 6,5,3 tricyclic isomer 11, possibly via the isomeric cyclopropyl derivative 15 or the nine-membered phosphonin 7. The structure of 11 was confirmed by mild oxidation of the colourless rearrangement product to its P-oxide. This product, tetramethyl 2,3,6-triphenyl-2-phosphatricyclo[6.1.01,8.05,9]-2-oxonona-3,6-diene-1,7,8,9-tetracarboxylate 12, was also colourless. It crystallized in the orthorhombic space group Pbc21 (No. 29) with four pairs of molecules in the unit cell. Refinement of this structure (a = 8.918(1) Å, b = 22.605(4) Å, and c = 30.169(6) Å) converged at R = 0.0747 (Rw = 0.0757) for 321 parameters using 3255 reflections with I > 3σ(I). Unequivocal structures for these adducts and derivatives finally confirms, and establishes further understanding of, the complex reactions of the triphenylphosphole with dimethyl acetylenedicarboxylate.
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Wang, Sue-Lein. „Mesoporous Metal Phosphites with 3D Crystalline Frameworks“. Acta Crystallographica Section A Foundations and Advances 70, a1 (05.08.2014): C1119. http://dx.doi.org/10.1107/s2053273314088809.
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The synthesis of crystalline porous solids is of great importance in the area of materials chemistry. Naturally occurring zeolites are mostly crystalline; however, they possess pores/channels that only allow small species smaller than 1 nm in diameter to pass through. One exception is the mineral cacoxenite, containing 36-membered ring (36R) channels that allow guest species of up to 1.41 nm in diameter to pass through. In the past, much effort has been devoted to the development of zeolitic materials. Even though multi-faceted design strategies were utilized, the discovery of larger inorganic channels was often accidental. Compared with amorphous mesoporous silicates that contain synthetically tunable pores, zeolitic crystalline structures lack rational synthesis routes. In general, molecular templating leads to crystalline frameworks whereas organized assemblies that are able to produce much larger pores lead to noncrystalline frameworks. Synthetic methods that generate crystallinity from both discrete and organized templates represent a viable design strategy for the development of crystalline porous inorganic frameworks spanning both the micro and the meso regimes. We show by integrating templating mechanisms for both zeolites and mesoporous silica in a single system, the channel size for gallium zincophosphites can be tuned systematically up to 64R and 72R. With apertures of 3.5 nm, the new compounds represent the first non-disordered structures for mesoporous solids. Through the use of long straight-chain alkyl monoamines as templates, three common building blocks are induced that repeatedly self assemble into two isotypic porous frameworks with the ability to increasingly enlarge channel size. The rational design of crystalline porous metal oxides is achieved for the first time. A general formula was derived to predict new members with even larger channels along with their individual space group symmetry.
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Zagórska, Urszula, und Sylwia Kowalska. „Crystallization of simonkolleite (Zn5Cl2(OH)8 ∙ H2O) in powder samples prepared for mineral composition analysis by quantitative X-ray diffraction (QXRD)“. Nafta-Gaz 77, Nr. 5 (Mai 2021): 293–98. http://dx.doi.org/10.18668/ng.2021.05.02.
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The analysis of mineralogical composition by quantitative X-ray diffraction (QXRD) is one of the standard research methods used in hydrocarbon exploration. In order to improve it and to obtain better results, the methodology of quantitative analysis used at Well Logging Department is being periodically (more or less) modified. After the introduction of the improvements, comparative analyses were performed on archival samples. Reflections from an unidentified phase which did not occur in the tested Rotliegend sandstone samples were noticed on X-ray diffractograms of archival samples. Reflections of a mineral called simonkolleite were identified in the X-ray diffraction database. Chemically it is a hydrated zinc chloride of the formula: Zn5Cl2(OH)8 × H2O. Analysis of the composition of samples in which simonkolleite crystallised, indicated that the mineral is being formed in the result of the slow reaction of zinc oxide with halite (NaCl) and water vapour. An attempt was made to determine the influence of the presence of this mineral on the results of the quantitative analysis of mineralogical composition. The above methodology was applied on a group of ten samples. The results of the quantitative analysis conducted for archival samples stored with added zincite standard containing simonkolleite and for new, freshly grinded (without artifact) samples were compared. The comparison of the obtained results showed a slight influence of this mineral on the quantitative composition of the remaining components. The difference between the results usually did not exceed the method error. At the same time a significant difference in the calculated content of the internal standard was noted – on average 1% less in archival than in new samples. This shows that the reaction occurring in the archival samples will affect the evaluation of the quality of the obtained quantitative analysis, at the same time excluding the possibility of determining the rock’s amorphous substance content with the internal standard method.
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Septiansyah, Sy Indra, und Maya Santi. „Pemanfaatan Alumina Waste dari Tailing Bauksit Menjadi Zeolit Adsorben“. EKSPLORIUM 39, Nr. 2 (31.01.2019): 123. http://dx.doi.org/10.17146/eksplorium.2018.39.2.4982.
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ABSTRAK Alumina waste dari tailing bauksit merupakan produk samping yang berasal dari hasil benefisiasi bijih bauksit. Proses benefisiasi dilakukan dengan cara memisahkan partikel-partikel yang ada seperti lumpur atau clay, akar-akar, butiran bijih bauksit berkisar 2 mm yang dibuang atau menjadi waste product atau disebut sebagai limbah tailing. Tingginya kadar alumina dan silika dalam tailing bauksit menjadi salah satu alasan mengapa tailingini dapat dimanfaatkan sebagai bahan dasar dalam pembuatan produk baru yaitu zeolit sintetis. Zeolit sintetis dipilih karena zeolit merupakan produk impor, harganya mahal dan memiliki sifat yang seragam serta >150 jenis zeolit sintetis dapat dibuat secara komersial dan bahkan di industri zeolit dapat dimanfaatkan secara luas sebagai adsorben, penukar ion, membrane, katalis, dan lain-lain.Hasil analisis kimia tailing bauksit menunjukkan komposisi: alumina (Al2O3) sekitar 49,41%, silika (SiO2) sekitar 12,58%, hematit (Fe2O3) sekitar 10,6% dan beberapa oksida anorganik lainnya dalam jumlah yang kecil. Proses konversi tailing bauksit menjadi zeolit adsorben dilakukan dengan metode fusi kaustik untuk mendapatkan ekstrak fusi (mother liquor) kemudian dilanjutkan dengan penambahan prekursor natrium silikat dengan formula sintesis Si/Al(1:1). Kristalisasi produk dilakukan dengan menggunakan metode hidrotermal pada suhu rendah dengan variable waktu inkubasi yang ditentukan. Reaksi sodium aluminat dan sodium silikat telah mentransformasi fasa amorf gel menjadi fasa kristalin zeolit yang berbentuk serbuk putih halus.ABSTRACTA lumina waste from bauxite tailings is the by products derived from bauxite ore beneficiation. The beneficiation process is done by separating the particles that exist such as mud or clay, roots, grain, bauxite ore ranges from 2 mm are discarded or be referred to as a waste product or tailings. High concentration of alumina and silica in bauxite tailings considered as one of the reasons why these tailings can be used as base material in the making new products, namely synthetic zeolites. Zeolites synthetic is selected because zeolites are imported, expensive and have uniform properties and >150 types of synthetic zeolites can be made commercially and even in industrial zeolite can be used widely as an adsorbent, ion exchange, membranes, catalysts, etc. The chemical analysis of bauxite tailings showed the composition of alumina (Al2O3) is approximately 49.41% silica (SiO2) is about 12.58%, hematite (Fe2O3) is approximately 10.6% and some other inorganic oxides are small amounts. The conversion process bauxite tailings into zeolite is carried out by caustic fusion method to extract the fusion (alumina precursor) followed by the addition of sodium silicate precursor with synthesis formula 1.2Na2O.0.5SiO2.0.5Al2O3.10H2O and crystallization products is carried out by the hydrothermal method at low temperatures with variable incubation period specified. The results showed that the zeolite synthesis of bauxite tailings using caustic fusion and followed by crystallization at low temperature and under atmospheric pressure has succeeded in transforming the product into an amorphous phase to the crystalline phase product zeolite adsorbent.
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Elshazly, Noha, Abdelaziz Khalil, Manal Saad, Marco Patruno, Jui Chakraborty und Mona Marei. „Efficacy of Bioactive Glass Nanofibers Tested for Oral Mucosal Regeneration in Rabbits with Induced Diabetes“. Materials 13, Nr. 11 (07.06.2020): 2603. http://dx.doi.org/10.3390/ma13112603.
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The healing of oral lesions that are associated with diabetes mellitus is a matter of great concern. Bioactive glass is a highly recommended bioceramic scaffold for bone and soft tissue regeneration. In this study, we aimed to assess the efficacy of a novel formula of bioactive glass nanofibers in enhancing oral mucosal wound regeneration in diabetes mellitus. Bioactive glass nanofibres (BGnf) of composition (1–2) mol% of B2O3, (68–69) mol% of SiO2, and (29–30) mol% of CaO were synthesized via the low-temperature sol-gel technique followed by mixing with polymer solution, then electrospinning of the glass sol to produce nanofibers, which were then subjected to heat treatment. X-Ray Diffraction analysis of the prepared nanofibers confirmed its amorphous nature. Microstructure of BGnf simulated that of the fibrin clot with cross-linked nanofibers having a varying range of diameter (500–900 nm). The in-vitro degradation profile of BGnf confirmed its high dissolution rate, which proved the glass bioactivity. Following fibers preparation and characterization, 12 healthy New Zealand male rabbits were successfully subjected to type I diabetic induction using a single dose of intravenous injection of alloxan monohydrate. Two weeks after diabetes confirmation, the rabbits were randomly divided into two groups (control and experimental groups). Bilateral elliptical oral mucosal defects of 10 × 3.5 mm were created in the maxillary mucobuccal fold of both groups. The defects of the experimental group were grafted with BGnf, while the other group of defects considered as a control group. Clinical, histological, and immune-histochemical assessment of both groups of wounds were performed after one, two and three weeks’ time interval. The results of the clinical evaluation of BGnf treated defects showed complete wound closure with the absence of inflammation signs starting from one week postoperative. Control defects, on the other hand, showed an open wound with suppurative exudate. On histological and immunohistochemical level, the BGnf treated defects revealed increasing in cell activity and vascularization with the absence of inflammation signs starting from one week time interval, while the control defects showed signs of suppurative inflammation at one week time interval with diminished vascularization. The results advocated the suitability of BGnf as bioscaffold to be used in a wet environment as the oral cavity that is full of microorganisms and also for an immune-compromised condition as diabetes mellitus.
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Ruiz-Pérez, Juan José, und Emilio Márquez Navarro. „Optical Transmittance for Strongly-Wedge-Shaped Semiconductor Films: Appearance of Envelope-Crossover Points in Amorphous As-Based Chalcogenide Materials“. Coatings 10, Nr. 11 (05.11.2020): 1063. http://dx.doi.org/10.3390/coatings10111063.
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In this work, we study the influence of the geometry of a thin film on its transmission spectrum, as measured on amorphous As-based chalcogenide layers grown onto 1-mm-thick soda-lime-silica glass substrates. A new method is suggested for a comprehensive optical characterization of the film-on-substrate specimen, which is based upon some novel formulae for the normal-incidence transmittance of such a specimen. It has to be emphasized that they are not limited to the usual cases, where the refractive index, n, of the film and that of the thick transparent substrate, s, must obey: n2>>k2 and s2>>k2, respectively, where k stands for the extinction coefficient of the semiconductor. New expressions for the top and bottom envelopes of the transmission spectrum are also obtained. The geometry limitation usually found when characterizing strongly-wedge-shaped films, has been eliminated with the introduction of an appropriate parameter into the corresponding equations. The presence of crossover points in the top and bottom envelopes of the transmission spectrum, for these strongly-wedge-shaped chalcogenide samples, has been both theoretically predicted and experimentally confirmed.
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ANGELONI, SILVIA, ELVIRA M. BAUER, CLAUDIO ERCOLANI, IRINA A. POPKOVA und PAVEL A. STUZHIN. „Tetrakis(selenodiazole)porphyrazines. 2: Metal complexes with Mn(II), Co(II), Ni(II), and Zn(II)“. Journal of Porphyrins and Phthalocyanines 05, Nr. 12 (Dezember 2001): 881–88. http://dx.doi.org/10.1002/jpp.558.
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The present report describes two series of new porphyrazine macrocycles derived from tetrakis(selenodiazole)porphyrazine, TSeDPzH 2, having the formulae [ TSeDPzM ]( CH 3 COOH )( H 2 O )x M = Mn (II), Co (II), Ni (II), Zn (II); x = 4–6) and [ TSeDPzM ( py )]( CH 3 COOH )( H 2 O )x ( M = Mn (II), Co (II), Ni (II); x = 1–5), obtained by reaction of the free ligand with the appropriate metal acetate in dimethyl (DMSO), and, respectively, pyridine. All the species isolated are stable-to-air substantially amorphous materials, almost completely insoluble in the usual organic solvents and N -donors (pyridine etc.), and only slightly soluble in CF3COOH or 96% H 2 SO 4. The complexes have been investigated by IR, Raman, and UV-vis spectra, and magnetic susceptibility measurements. Their properties in terms of electronic structure and reactivity towards N -bases are discussed in comparison with their S-containing analogs and the class of the structurally similar metal phthalocyanines.
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Deltuva, Juozas, und Žymantas Rudžionis. „THE ESTIMATION METHODS OF MICROFILLERS INFLUENCE ON CEMENT STONE PROPERTIES/MIKROUŽPILDŲ ĮTAKOS CEMENTINIO AKMENS SAVYBĖMS ANALITINIO ĮVERTINIMO PRINCIPAI“. JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 3, Nr. 10 (30.06.1997): 69–75. http://dx.doi.org/10.3846/13921525.1997.10531686.
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The concrete and cement microfillers are materials of different fineness, such as wastes of production or pulverized rocks. According to their influence on cement hardening process, they may be classified into inert microfillers or chemically active ones. The chemically active microfillers, such as silica fume, fly ashes and others, have more then 50% amorphous SiO2, that takes part in cement hardening process. Inert microfillers, such as granite, dolomite, sand dust and others, in most cases have no influence on the cement hydration. The usage of microfillers in concrete is common, but so far no clear dependence between the quantity of added microfillers and properties of concrete has been established. One of possible ways to estimate the microfillers influence on the products with cement binder is the structural element method. The structural element is the smallest cell, approximated to a spatial figure of regular form, that has all components with the same proportions, as in all the volume of heterogeneous material. The essence of this method is to divide the mix in to bigger particles, that are named “nuclei” of structural elements and take 50% of all mix volume, and smaller particles, that form cover layers of the nuclei and make up the rest of the volume of the mix. The dependence between the relative density of loose materials and relation (1) between the diameters of the bigger and smaller particles of the structural element has been estimated. This relation is changed when microfillers are added to the cement. There is a possibility to optimize relative density by (2), (3) and (4) relations, if the granulometric composition of the cement and microfillier is known. The experimental and calculated results of this optimization are shown in Table 1. The properties of pressed cement stone with inert microfillers admixture are presented in Table 2. Formulae for calculating the relative density (8) and compressive strength (11) of hardening cement have been estimated. The chemically active microfillers, such as silica fume, interact with Ca(OH)2 and form new CSH. The density and strength of cement stone increased after this interaction. The influence of chemically active microfillers on the relative density of the cement stone is given in (12). The density of cement stone increases to 4.5% and strength increases to 40.2%, if the quantity of inert microfillers in the cement paste reaches 10%. The density of cement stone increases to 7.4% and strength increases to 54.7%, if the quantity of chemically active microfillers in the cement paste reaches 10%.
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Oner, Yildirhan, und Cihat Boyraz. „A successive multi-phase transitions in polycrystalline BaFe2As2: Emergence of C4 phase“. International Journal of Modern Physics B, 23.09.2021, 2150277. http://dx.doi.org/10.1142/s0217979221502775.
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We report magnetization and resistivity studies on polycrystalline BaFe2As2 prepared by solid-state reaction, in the temperature range of 5–350 K, upto the field of 9 T. Low-field susceptibility exhibits multi-phase transitions with two new magnetic phase transitions beside the well-known transition at [Formula: see text] K from paramagnetic/antiferromagnetic-tetragonal/orthorhombic transitions. The phase at [Formula: see text] K is attributed to the phase transition from antiferromagnetic-orthorhombic (C2-phase) to antiferromagnetic-tetragonal phase (C4-phase), while the phase transition at higher temperatures remains unsolved. Making an analogy to the antiferromagnetic nanosized particles, we suggest that BaFe2As2 consists of smaller but similar nanosized clusters. We have analyzed the magnetization data using the modified Langevin function on the basis of thermally activated induced uncompensated spins (thermoinduced moments). The nanosized clustering in this compound is evidenced by the exchange bias and coercivity stemming from the exchange coupling interactions between weak ferromagnetic bulk magnetization in clusters and spin-glass-like phase interface layers surrounding the clusters. We also observe that annealing enhances the superconductivity, similar to the effect of pressure on the superconductivity. We find that an exponential term well describes the resistivity of this compound due to magnon-assisted interband electron–phonon scattering between the bands with [Formula: see text] and [Formula: see text] orbitals forming two-hole pockets around the zone center and one electron pocket around the zone corner. We have also obtained the Kadowaki–Woods ratio ([Formula: see text] cm (K mol/mJ)[Formula: see text] and the Sommerfeld–Wilson ratio ([Formula: see text]) for BaFe2As2, both ratios are much larger than those ([Formula: see text]/[Formula: see text] cm (K mol/mJ)2, [Formula: see text]) for Kondo lattice systems, indicating the existence of a weak ferromagnetic correlation between Fe moments. It appears that magnon-mediated pairing is responsible for superconductivity. Finally, we observe zero resistance at [Formula: see text] K in amorphous BaFe2As2, which gives a new insight into the superconductivity under very high pressure.
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Shur, Michael, und Michael Hack. „Determination of Density of Localized States in Amorphous Silicon Alloys From the Low Field Conductance of Thin N-I-N Diodes“. MRS Proceedings 49 (1985). http://dx.doi.org/10.1557/proc-49-69.
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AbstractWe describe a new technique to determine the bulk density of localized states in the energy gap of amorphous silicon alloys from the temperature dependence of the low field conductance of n-i-n diodes. This new technique allows us to determine the bulk density of states in the centre of a device, and is very straightforward, involving fewer assumptions than other established techniques. Varying the intrinsic layer thickness allows us to measure the,density of states within approximately 400 meV of midgap.We measured the temperature dependence of the low field conductance of an amorphous silicon alloy n-i-n diode with an intrinsic layer thjckness of 0.45 microns and deduced the density of localised states to be 3xlO16cm−3 eV−1 at approximately 0.5 eV below the bottom of the conduction band. We have also considered the high bias region (the space charge limited current regime) and proposed an interpolation formula which describes the current-voltage characteristics of these structures at all biases and agrees well with our computer simulation based on the solution of the complete system of transport equations.
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Hatert, Frédéric, Fabrice Dal Bo, Yannick Bruni, Nicolas Meisser, Pietro Vignola, Andrea Risplendente, François-Xavier Châtenet und Julien Lebocey. „Limousinite, BaCa[Be4P4O16]·6H2O, a New Beryllophosphate Mineral with a Phillipsite-Type Framework“. Canadian Mineralogist, 17.12.2020. http://dx.doi.org/10.3749/canmin.2000007.
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Abstract Limousinite, ideally BaCa[Be4P4O16]·6H2O, is a new beryllophosphate mineral discovered in the Vilatte-Haute pegmatite, Chanteloube near Razès, Limousin, Haute-Vienne, France. The new mineral is intimately associated with microcrystalline pale brown greifensteinite, black amorphous vitreous Mn-oxyhydroxide, triplite, and quartz. It forms isolated, partly corroded, colorless to snow-white crystals up to 0.9 mm long, showing rhombic cross sections. Limousinite is transparent with a vitreous luster, non-fluorescent, without cleavage planes; its calculated density is 2.58 g/cm3. Optically, the mineral is biaxial negative, α = 1.532(2), β = 1.553(3), γ = 1.558(2) (measured under 589 nm wavelength light), 2Vcalc. = 18°, non-dispersive, with Z parallel to the elongation of the prismatic crystals. Electron-microprobe analyses indicate an empirical formula of (Ba0.91K0.07)Σ0.98(Ca0.87Na0.05)Σ0.92[(Be3.87Al0.13)Σ4P4O16]·5.56H2O, calculated on the basis of 4 P atoms per formula unit, assuming 4 (Be + Al) pfu and a water content calculated from refined site-occupancy factors. A single-crystal structure refinement was performed to R1 = 4.90%, in the P21/c space group, with a = 9.4958(4), b = 13.6758(4), c = 13.4696(4) Å, β = 90.398(3)°, V = 1749.15(10) Å3, Z = 4. The crystal structure is characterized by a beryllophosphate framework similar to that of phillipsite-group zeolites, based on corner-sharing BeO4 and PO4 tetrahedra forming interconnected four- and eight-membered rings. Large cages within this zeolite framework contain Ba, Ca, and water molecules. Limousinite is the third known natural zeolite-type beryllophosphate, together with pahasapaite and wilancookite; it is also the first phosphate with a framework identical to that of a natural zeolite silicate.
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Kamei, Toshihiro, und Akihisa Matsuda. „Development of Ultra-Clean Plasma Deposition Process“. MRS Proceedings 557 (1999). http://dx.doi.org/10.1557/proc-557-19.
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AbstractWe have developed a new type of ultra-high vacuum plasma-enhanced chemical vapor deposition (UHV/PECVD) system. According to high sensitivity secondary ion mass spectrometry, device quality hydrogenated amorphous silicon (a-Si:H) films deposited at 250°C at a deposition rate of 1 Å/s contains 1015 cm-3 of O, 1015 cm-3 of C, and 1014 cm-3 of N impurities, while low defect hydrogenated microcrystalline silicon (μc-Si:H) films deposited at 200°C at a very low rate of 0.1 Å/s include 1016 cm-3 of O, 1015 cm-3 of C and 1016 cm-3 of N. These are the lowest concentrations of atmospheric contaminants for these kinds of materials observed so far. The essential features of the present UHV/PECVD system are an extremely low outgassing rate of 8×10-9 Torr·s, extremely low partial pressure of contaminant gas species <10-12 Torn, and purification of feed gas SiH4 at “point of use”. These efforts are quite important not only for clarifying the microscopic mechanism of photo-induced degradation in a-Si:H, but also for enlarging the crystalline grain size in μc-Si:H. μc-Si:H with a grain size of ≍1000 Å as determined by Scherrer's formula can be obtained at the higher rate of 1.5 Å/s by utilizing a VHF (Very High Frequency) plasma. The specific origins of impurities in the films are also discussed.