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1.
Yutang Fang Xueqing Li Xianghui Liang Shuangfeng Wang Xuenong Gao Zhengguo Zhang 《Journal of Porous Materials》2017,24(2):315-325
With a characteristic of S-shaped water sorption isotherms, AlPO4-5 molecular sieves have been considered as up-and-coming adsorbents for the utilization in adsorptive cooling and heating systems. In order to avoid toxicity and corrosion of fluoride, this paper introduced a fluorine-free microwave hydrothermal synthesis strategy of pure AlPO4-5 crystals. The effects of hydrothermal conditions including template agent, crystallization temperature and time on the performances of AlPO4-5 adsorbents were systematically investigated. Fourier transform infrared spectroscopy, X-ray diffraction (XRD), 27Al and 31P solid state magic angle spinning nuclear magnetic resonance (MAS NMR), pore size analyzer and Scanning electron microscopy (SEM) were used to determine the chemical structure, crystalloid phase, framework, pore structure and the morphology. Adsorption and desorption performances were measured by static adsorption, thermogravimetry and temperature programmed desorption. XRD results indicated that both triethylamine and tetraethylammonium hydroxide as templates, AlPO4-5 crystals could quickly be synthesized within 30–45 min under fluorine-free microwave irradiation. By comparison, the adsorption and desorption performance of the former (recorded as AlPO4-5A) was superior to that of the latter (recorded as AlPO4-5H). FT-IR, MAS NMR and SEM results revealed that AlPO4-5 crystals have the frameworks of alternating AlO4 and PO4 units and typical hexagonal rod-like morphologies. 相似文献
2.
Large, high quality, perfect hexagonally shaped AlPO4-5 crystals have been crystallized using hydrothermal synthesis. The crystallization was carried out at 447 or 457 K with a crystallization time from one to four days and tripropylamine (TPA) molecules as template. The morphology of the crystals was observed with SEM. For the first time, the structure of the AlPO4-5 crystal together with TPA template molecules has been successfully refined in space group P6cc by single crystal X-ray diffraction. The parameters are a = b = 13.725(3) Å, c = 8.473(3) Å, and = 120.0. The size of some crystals is up to 2.2 mm in c direction, or up to 0.31 mm in a or b direction. All observed angles and distances are within acceptable ranges: P–O = 1.50–1.54 Å, Al–O = 1.62–1.72 Å, O–P–O = 107–111, O–Al–O = 103–113 and P–O–Al = 147–150. 相似文献
3.
The electrochemical properties and stability during storage of pristine and AlPO4-coated LiCoO2 thin films were characterized. The wide and smooth surface of the thin film electrode might provide an opportunity for one
to observe surface reactions with an electrolyte. The rate capability and cyclic performance of the LiCoO2 thin film were enhanced by AlPO4 surface coating. Based on secondary ion mass spectrometry analysis and scanning electron microscopy images of the surface,
it was confirmed that the coating layer was successfully protected from the reactive electrolyte during storage at 90°C. In
contrast, the surface of the pristine sample was severely damaged after storage. 相似文献
4.
5.
Cobalt oxide [Co3O4] anode materials were synthesized by a simple hydrothermal process, and the reaction conditions were optimized to provide
good electrochemical properties. The effect of various synthetic reaction and heat treatment conditions on the structure and
electrochemical properties of Co3O4 powder was also studied. Physical characterizations of Co3O4 are investigated by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller [BET] method. The BET surface
area decreased with values at 131.8 m2/g, 76.1 m2/g, and 55.2 m2/g with the increasing calcination temperature at 200°C, 300°C, and 400°C, respectively. The Co3O4 particle calcinated at 200°C for 3 h has a higher surface area and uniform particle size distribution which may result in
better sites to accommodate Li+ and electrical contact and to give a good electrochemical property. The cell composed of Super P as a carbon conductor shows
better electrochemical properties than that composed of acetylene black. Among the samples prepared under different reaction
conditions, Co3O4 prepared at 200°C for 10 h showed a better cycling performance than the other samples. It gave an initial discharge capacity
of 1,330 mAh/g, decreased to 779 mAh/g after 10 cycles, and then showed a steady discharge capacity of 606 mAh/g after 60
cycles. 相似文献
6.
The magnetite nanoparticles and nanocomposite “Nanotube of hydrosilicate Mg—magnetite nanoparticles—Mg-ChR-NT/Fe3O4-NP” were obtained by coprecipitation. The composition of the synthesized samples has been established by X-ray diffraction. Using transmission electron microscopy, the presence of magnetite nanoparticles has been detected both inside the NTs and at the external surface of the NT walls. The specific surface of the NTs, nanoparticles, and composite is determined. 相似文献
7.
The sequence of phase formation in the oxidation of ASD-4 aluminum powder modified by vanadium pentoxide during heating in air in the temperature range 873–1073 K has been studied by synchrotron radiation x-ray diffraction. It has been shown that the sharp acceleration of the oxidation of the modified powder is related to the loss of the protective properties of the oxide shell on the particle surface due to the polyvalence of vanadium, which provides structural and phase changes on the surface and in the depth of the oxidized metal. 相似文献
8.
Glass and glass-ceramics, which are important bioceramics, have established an essential group of silicon-based materials having wide applications in medicine. Bioactive glass-ceramics have proved to be able to chemically bond to living bones due to forming an apatite-like layer on their surfaces. In this study, bioactive glass-ceramics of (64-X) SiO2- 31 CaO- 5 P2O5- X ZnO based on mol% were synthesized by the sol–gel process. The bioactive glass-ceramics were analyzed using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) before and after being exposed to simulated body fluid (SBF) solution. The results show that an increase in ZnO will cause the ability of calcium phosphate apatite formation on the glass-ceramic surfaces to first rise by 8 % but subsequently to decline by 12 %. The bioactivity of synthesized glass-ceramics can be confirmed by SEM and XRD due to the presence of a rich bone-like apatite layer. 相似文献
9.
Ho-Sung Yoon Kyung Woo Chung Chul-Joo Kim Jin-Ho Kim Hyung-Seop Lee Seok-Jong Kim Se-Il Lee Seung-Joon Yoo Byung-Chul Lim 《Korean Journal of Chemical Engineering》2018,35(2):470-478
Ferric hydroxide adsorbent was prepared by a chemical treatment process with H2O2, NaOH, and aeration from a Fe2(SO4)3 aqueous solution as a side product discharged from the hydrometallurgical process used to extract neodymium. The ferric hydroxide was used as an adsorbent to prevent eutrophication in water. At the time of synthesis, the most important process variable is the pH condition, which, in this experiment, was changed from pH 3 to 13. The cost of synthesizing ferric hydroxide was sharply reduced by using ferric sulfate, which is considered a side product of the aforementioned hydrometallurgical process, as a starting material, and an adsorbent with high adsorption ability was prepared by controlling the pH level. Microstructural characterization of the synthesized ferric hydroxide revealed particles with a specific surface area of 194.2 m2/g and an average pore diameter of 2.66 nm at pH 6 and 298 K. A column-type packed-bed adsorption experiment was conducted under the following conditions: a flow rate of 0.567 BV/min (3.2 mL/min), 298 K, and atmospheric pressure. The results of the adsorption performance test indicated that the adsorption efficiency of phosphate at concentrations of 10 ppm was 100% at a flow rate of 0.567 BV/min within a contact time of 2 min, and the maximum adsorption capacity for phosphate ions was 65 mg/g. 相似文献
10.
T. P. Maslennikova E. N. Korytkova O. M. Kuznetsova L. N. Pivovarova 《Glass Physics and Chemistry》2016,42(3):288-294
The interaction of an aqueous solution of silver nitrate with Mg3Si2O5(OH)4 hydrosilicate nanotubes under atmospheric conditions at 50 and 80°C and under dynamic conditions with subsequent annealing at 300°C has been investigated. The intercalation of AgNO3 solutions into the internal channel and interlayer spaces of the nanotube structure and the crystallization of the silver particles of the spherical shapes on the nanotube surface have been established. 相似文献
11.
The quaternary glasses of mixed divalent oxides including ZnO, MgO, CdO within a phosphate network former were prepared. Vanadium pentoxide was introduced as a dopant in the range from 0.5 to 3%. Optical and infrared absorption studies for all glass samples were carried out. The optical spectra reveal the presence of both V3+ and V4+ ions in the studied host mixed divalent oxides phosphate glass. Fourier transform infrared absorption spectral analysis indicates the appearance of distinct vibrational bands due to the presence of characteristic phosphate groups depending on the glass composition and the ratio of V2O5 content. The optical band gap and Urbach energy were calculated and discussed in relation to the effect of V2O5 content. Finally, the glasses were optically and structurally examined affter gamma irradiation with a dose of 80 KGy. 相似文献
12.
The crystal structure of a low-temperature modification of the Li12Zn4(P2O7)5 compound has been determined by full-profile analysis from the X-ray powder diffraction data. The compound crystallizes in the monoclinic crystal system (a = 5.130(1) Å, b = 13.454(1) Å, c = 8.205(1) Å, β = 90.36(1)°, space group P21/n, Z = 4) and has a framework structure in which the zinc and lithium atoms statistically occupy equivalent positions. 相似文献
13.
R. S. Bubnova J. E. Anderson M. G. Krzhizhanovskaya S. K. Filatov 《Glass Physics and Chemistry》2010,36(3):369-375
Anhydrous ammonium pentaborate NH4B5O8 has been synthesized by thermal dehydration of larderellite NH4[B5O7(OH)2] · H2O at a temperature of 290°C for 7 h. The crystal structure has been determined from the X-ray powder diffraction data: a = 7.58667(5) Å, b = 12.00354(8) Å, c = 14.71199(8) Å, R p = 6.23, R wp = 7.98, R B = 12.7, R F = 8.95, and β-KB5O8 structure type. The double interpenetrating framework is formed by pentaborate groups, each consisting of a boron-oxygen tetrahedron and four triangles, in which all oxygen atoms are bridging. The thermal behavior of the NH4B5O8 compound has been investigated using thermal X-ray diffraction. As for other pentaborates of this type, the thermal expansion of the NH4B5O8 compound is anisotropic and reaches a maximum along the a axis. The thermal expansion coefficients are as follows: α a = 39 × 10?6, α b = 6 × 10?6, α c = 20 × 10?6, and α V = 65 × 10?6 °C?1. 相似文献
14.
Zhenping Cheng Xiulin Zhu Lifen Zhang Nianchen Zhou Xinrong Xue 《Polymer Bulletin》2003,49(5):363-369
Summary
Reverse atom transfer radical polymerization (RATRP) of methyl methacrylate (MMA) under microwave irradiation (MI), using
azobisisobutyronitrile (AIBN) /FeC13/triphenylphosphine (PPh3) as the initiating system, was successfully carried out in N, N-dimethylformamide (DMF) at 69°C. Plots of In ([MI0/[M]) vs. time and molecular weight evolution vs. conversion showed a linear dependence. A polymer for reaching 82% conversion,
with molecular weight (Mn) 34,000 and polydispersity index (PDI) 1.37, was obtained under MI (90U') with the ratio of [MMA]0/[AIBN]0/[FeCl3]0/[PPh3]0 = 1600/2/4/8 in only 60 min; while 840 min was required under conventional heating (CH) process for reaching 82 % conversion
(Mn = 48,000 and PDI = 1.31) at identical polymerization conditions, indicating a significant enhancement of the polymerization
rates and apparent initiator efficiencies under MI.
Received: 2 September 2002/Revised version: 3 October 2002/Accepted: 10 December 2002
Correspondence to Xiulin Zhu 相似文献
15.
Yongfa Zhang Meng Zhang Guojie Zhang Huirong Zhang 《Frontiers of Chemical Science and Engineering》2010,4(4):481-485
An investigation was made using a continuous fixed bed reactor to understand the influence of carbon deposition obtained under different conditions on CH4-CO2 reforming. Thermogravimetry (TG) and X-ray diffraction (XRD) were employed to study the characteristics of carbon deposition. It was found that the carbonaceous catalyst is an efficient catalyst in methane decomposition and CH4-CO2 reforming. The trend of methane decomposition at lower temperatures is similar to that at higher temperatures. The methane conversion is high during the initial of stage of the reaction, and then decays to a relatively fixed value after about 30 min. With temperature increase, the methane decomposition rate increases quickly. The reaction temperature has significant influence on methane decomposition, whereas the carbon deposition does not affect methane decomposition significantly. Different types of carbon deposition were formed at different methane decomposition reaction temperatures. The carbon deposition Type I generated at 900°C has a minor effect on CH4-CO2 reforming and it easily reacts with carbon dioxide, but the carbon deposition Type II generated at 1000°C and 1100°C clearly inhibits CH4-CO2 reforming and it is difficult to react with carbon dioxide. The results of XRD showed that some graphite structures were found in carbon deposition Type II. 相似文献
16.
The temperature-concentration dependence of the electrical conductivity of glasses in the Na2SO4-NaPO3 and Na2O-P2O5 systems has been investigated. Based on the obtained experimental data (IR spectra, density, microhardness, sound velocity,
and paper chromatography), it has been demonstrated that SO42− ions form terminal groups through the incorporation into polyphosphate fragments of the structure of glasses in the Na2SO4-NaPO3 system. An increase in the electrical conductivity of glasses in this system by a factor of ∼1000 (as compared to NaPO3) at 25°C and a decrease in the activation energy for electrical conduction from 1.40 to 1.10 eV have been interpreted from
the viewpoint of the decrease in the dissociation energy E
d of polar sulfate phosphate structural chemical fragments formed in the glass bulk upon introduction into sodium metaphosphate
Na2SO4. This leads to an increase in the number of dissociated sodium ions, which are charge carriers, and to a decrease in the
energy (E
a) of their activation shift in the sublattice formed by sulfate phosphate fragments of the structure. 相似文献
17.
Amorphous La2O-TiO2 powders were synthesized by the polymerized complex (PC) method. The activation energies for crystallization and grain growth
of La2Ti2O7 from these precursors were determined from results of XRD and DTA and compared with those for La2Ti2O7 precursors by the conventional solid-state reaction (SSR). Activation energy of grain growth of La2Ti2O7 in PC-sample was determined to be 7.1 kJ/mol while that of SSR sample was 14.8 kJ/mol. The energy required for the phase
transformation from amorphous PC sample to layered perovskite was 432 kJ/mol, while the SSR sample did not show this transition
below 900‡C. It was clearly demonstrated that the La2Ti2O7 crystals were formed at a lower temperature and they grew in size faster in the sample prepared by the PC method relative
to the sample prepared by the SSR method. Mixing of elements in molecular level in PC preparation appeared responsible for
these differences. 相似文献
18.
Yu. K. Startsev A. A. Pronkin I. A. Sokolov I. V. Murin 《Glass Physics and Chemistry》2011,37(3):263-282
The glasses, in which oxygen was partially replaced with sulfur, have been synthesized in the Na2O-P2O5-Na2S system. The chemical and chromatographic analyses of the glasses synthesized have been performed. The temperature-concentration
dependences of electrical conductivity of the glasses have been studied over a wide temperature range; the glass transition
temperatures and the nature of charge carriers have been determined. The IR spectra and Raman spectra have been recorded at
room temperature; the density and microhardness of the glasses and ultrasound velocity have been measured. A comparison of
the electrical conductivities of the investigated glasses with those of the earlier studied glasses in the Na2O-P2O5 system has shown their fair coincidence. The introduction of sodium sulfide into the Na2O-P2O5 system is accompanied by an approximately threefold increase in electrical conductivity, although the concentrations of charge
carriers (sodium ions) in the glasses amount to ∼17 and ∼26 mmol/cm3, respectively. The rise in electrical conductivity has been assumed to be caused by the increase in the degree of dissociation
of polar structural chemical units including sulfide ions and by the higher mobility of sodium ions in the oxygen-free matrix. 相似文献
19.
One of the most promising anode materials for Li-ion batteries, Li4Ti5O12, has attracted attention because it is a zero-strain Li insertion host having a stable insertion potential. In this study,
we suggest two different synthetic processes to prepare Li4Ti5O12 using anatase TiO2 nanoprecursors. TiO2 powders, which have extraordinarily large surface areas of more than 250 m2 g-1, were initially prepared through the urea-forced hydrolysis/precipitation route below 100°C. For the synthesis of Li4Ti5O12, LiOH and Li2CO3 were added to TiO2 solutions prepared in water and ethanol media, respectively. The powders were subsequently dried and calcined at various
temperatures. The phase and morphological transitions from TiO2 to Li4Ti5O12 were characterized using X-ray powder diffraction and transmission electron microscopy. The electrochemical performance of
nanosized Li4Ti5O12 was evaluated in detail by cyclic voltammetry and galvanostatic cycling. Furthermore, the high-rate performance and long-term
cycle stability of Li4Ti5O12 anodes for use in Li-ion batteries were discussed. 相似文献
20.
N. A. Sennova R. S. Bubnova S. K. Filatov I. G. Polyakova 《Glass Physics and Chemistry》2007,33(3):217-225
The thermal expansion of two layered sodium borates is investigated using high-temperature X-ray powder diffraction. It is established that both compounds are characterized by strong anisotropy of thermal expansion due to the hinge mechanism. Special (singular) points are revealed in the temperature dependences of the angular lattice parameters for the α-Na2B4O7 compound. The temperature of manifestation of these singularities corresponds to the glass transition temperature of the melt of the same chemical composition. The assumption is made that the angular lattice parameters (angles between atomic rows) in compounds with a considerable degree of ionic bonding are more sensitive to variations in temperature as compared to the linear lattice parameters (interatomic distances). It is experimentally in situ demonstrated with high-temperature X-ray diffraction that the β-NaB3O5 borate is peritectically melted at a temperature of 725 ± 10°C with the formation of the α-Na2B8O13 octaborate. 相似文献