共查询到20条相似文献,搜索用时 15 毫秒
1.
Glauciane N. Barbosa Tatiana C. O. Mac Leod Débora F. C. Guedes Marilda D. Assis Herenilton P. Oliveira 《Journal of Sol-Gel Science and Technology》2008,46(1):99-105
In this work, we report the synthesis, characterization and catalytic properties of a vanadium oxide–silicon oxide composite
xerogel prepared by a soft chemistry approach. In order to obtain such material, we submitted a vanadium pentoxide gel previously
synthesized via protonation of metavanadate species to an “in situ” progressive polycondensation into silica gel. The material
has been characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy.
Further, the catalytic activity of this material was evaluated for the epoxidation of styrene and cyclooctene using iodosylbenzene,
hydrogen peroxide and m-chloroperbenzoic acid as the oxidizing agent. 相似文献
2.
I. Prakash N. Nallamuthu P. Muralidharan M. Venkateswarlu Manjusri Misra Amar Mohanty N. Satyanarayana 《Journal of Sol-Gel Science and Technology》2011,58(1):24-32
In situ base catalyst assisted sol–gel process is used for the synthesis of nanocrystalline CoFe2O4 deposition on SiO2 particles. The SiO2 particles were prepared using base catalyst assisted sol–gel process and the consecutive formation and deposition of nanocrystalline
CoFe2O4 on SiO2 particles was monitored using Powder X ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermo Gravimetric
And Differential Thermal Analysis (TG/DTA), Scanning Electron Microscopy and Energy Dispersive X ray Spectroscopy (SEM–EDS)
and High Resolution Transmission Electron Microscopy (HRTEM). The crystallite size of CoFe2O4 is calculated using Scherrer’s formula and it is found to be 8 nm. The HRTEM images and selective area electron diffraction
(SAED) results confirmed the formation of nanocrystalline CoFe2O4 particles deposited over SiO2 spheres. 相似文献
3.
Aiju Zhang Zhihong Li Zicheng Li Yumei Zhu 《Journal of Sol-Gel Science and Technology》2009,49(1):6-11
SiO2–Al2O3–Na2O glass coated cubic boron nitride (cBN) abrasive particles were prepared by sol–gel technique. The results indicated that
SiO2–Al2O3–Na2O glass was excellent material for oxidation protection of cBN abrasive grains because coefficient of thermal expansion of
this glass closely matched that of cBN materials. The single particle compressive strength and impact toughness of this glass
coated cBN abrasive particles were significantly increased. For the application of glass coated cBN abrasives to vitrified
grinding wheels, it was evident that the glass coating provided high bonding strength between cBN abrasive grains and vitrified
bond system. 相似文献
4.
N. B. Kondrashova A. S. Starostin V. A. Val’tsifer V. Ya. Mitrofanov S. A. Uporov E. Bormashenko 《Russian Journal of Applied Chemistry》2016,89(12):1960-1968
Ways to obtain Fe2O3–SiO2 iron-containing silica composites with organized mesoporous structure (MCM-41) and large specific surface area (up to 1476 m2 g–1) were considered. The influence exerted by the method used to synthesize the materials on their structure, texture characteristics, particle size, and magnetic properties were studied. The aggregative stability of samples was examined. It was shown that treatment of the resulting composites with compounds from the chlorosilane group affects their hydrophobic properties. 相似文献
5.
M. Baikousi S. Agathopoulos I. Panagiotopoulos A. D. Georgoulis M. Louloudi M. A. Karakassides 《Journal of Sol-Gel Science and Technology》2008,47(1):95-101
Magnetic bioglasses in the system CaO–SiO2–P2O5 were prepared by interaction of acetic acid vapors with iron nitrate dispersed on the surface of sol–gel derived porous silicate
network. Upon pyrolysis, the created iron acetate species transform into magnetic iron oxide nanoparticles. X-ray diffraction
(XRD), FT-infrared (FT-IR) spectroscopy and surface area measurements (BET) were employed to monitor the evolution of glass
structural features during the synthetic pathway as well as the structure and the texture of the resultant glasses. XRD, Raman
spectroscopy and vibration magnetic measurements (VSM) revealed the features of magnetic phases, developed in the form of
γ-Fe2O3 and magnetite. The obtained glasses exhibit in vitro bioactivity, expressed by spontaneous formation of hydroxyapatite on
their surface after immersion in SBF at 37 °C, confirmed with μ-Raman and FT-IR spectroscopies. 相似文献
6.
Mesoporous SiO2–TiO2 was synthesized by the sol–gel method using Si(OC2H5)4, Ti(OC2H5)4, and stearyltrimethylammonium chloride. By using acetylacetone as the capping agent of Ti(OC2H5)4, homogeneous SiO2–TiO2 composite was obtained. Spherical mesoporous SiO2–TiO2 was also synthesized by the sol–gel method using W/O emulsion under microwave irradiation. The specific surface area of these
mesoporous SiO2–TiO2 materials decreased when the Ti/Si molar ratio was higher than 0.1, which indicated that Ti was homogeneously distributed
in mesoporous SiO2 matrix at Ti/Si ≦ 0.1. The photocatalytic activity of mesoporous SiO2–TiO2 materials was investigated by the degradation of methylene-blue in water under UV light irradiation. Mesoporous SiO2–TiO2 was effective for the adsorption–decomposition of methylene-blue. 相似文献
7.
SiO2–ZrO2 xerogel was prepared via a sol–gel method followed by ambient pressure drying. The xerogel was characterized by X-ray diffraction, thermal analysis, fourier transform infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption/desorption analysis. The results showed that the SiO2–ZrO2 xerogel was amorphous and possessed a three-dimensional network structure with a narrow distribution of pore size. Its specific surface area reached up to 525.6?m2/g after 600?°C heat treatment, with a pore volume of 1.16?cm3/g and an average pore size of 8.5?nm. In order to explore the potential application of the SiO2–ZrO2 xerogel for the removal of organic dyes, its adsorption capacity was studied by removal of Rhodamine B (RhB) from aqueous solution through batch experiments. The results showed that the adsorption process of RhB onto SiO2–ZrO2 xerogel was slightly promoted under acidic conditions and significantly inhibited under strong alkaline conditions. And adsorption equilibrium can be achieved in 30?min. The kinetic data of the adsorption were analyzed using pseudo-first-order and pseudo-second-order models. The results indicated that the pseudo-second-order model described the adsorption mechanism better. The sorption behavior was evaluated by Langmuir and Freundlich isotherm models. The results suggested that the Langmuir model could accurately describe the experimental data and the adsorption capacity qmax was 177.7?mg/g. Thermodynamic analysis revealed that the adsorption of RhB onto the SiO2–ZrO2 xerogel was both spontaneous and exothermic in nature. Thus, the as-prepared SiO2–ZrO2 xerogel might be used as an adsorbent for wastewater treatment, especially for the removal of dyes. 相似文献
8.
A. B. Shishmakov L. S. Molochnikov D. O. Antonov Yu. V. Mikushina O. V. Koryakova L. A. Petrov 《Russian Journal of Inorganic Chemistry》2016,61(9):1085-1091
ZrO2–SiO2 xerogels have been synthesized through hydrolysis of a mixture of tetrabutoxyzirconium and tetraethoxysilane in a desiccator in a vapor of a 15% aqueous NH3 atmosphere. ZrO2–SiO2–Cu(II) xerogels were synthethized analogously through joint hydrolysis of a mixture of the organometallic precursors and copper(II) chloride. The effect of synthesis conditions on the physical and chemical properties of the resulting material has been studied. 相似文献
9.
Preparation and characterization of TiO<Subscript>2</Subscript> sol–gel modified nanocomposite films
In this study, the role of TiO2 MT-150A loading in the polymeric sol was investigated for the synthesis of immobilized TiO2 nanocomposite films on glass substrate using the MT-150A nanoparticles-modified sol–gel method. The nanocomposite film properties
were examined using different material characterization techniques including X-ray diffraction, X-ray photoelectron spectroscopy,
field emission scanning electron microscopy, UV–Vis spectrophotometer, Scotch tape test and pencil hardness test. The hydrophilicity
of films during UV/Vis irradiation and storage in a dark place were evaluated by a contact angle analyzer. The MT-150A loading
had a significant effect on the amount of crystallite phases in the films. However, increasing the MT-150A loading in the
sol resulted in an increase in rutile phase content. In addition, increasing MT-150A loading in the sol yielded films with
higher hydrophilicity but a concentration of 10–30 g/L MT-150A in the sol was found as the maximum for obtaining films with
good adherence on the glass substrate. 相似文献
10.
Haiyan Xia Yunzhe Ye Longgang Yan Qingfang Liu Jianbo Wang Desheng Xue 《Journal of Sol-Gel Science and Technology》2012,61(1):39-43
Ba2Co2Fe12O22 (Co2Y) was synthesized by sol–gel method using glucose as chelating agent. X-Ray diffraction studies indicate that sintering temperature
as low as 950 °C is sufficient to produce Co2Y ferrites. Co2Y ferrites calcined at 1,000 °C exhibit good magnetic prosperities in high frequency, with the resonance frequency up to 11 GHz
and intrinsic permeability about 5 even at 6 GHz. The heat-treated temperature dependence of coercivity, initial permeability
and resonance frequency is close related to the particle shape and size. 相似文献
11.
Mazyar Ahmadi Golsefidi Bijan Sarkhosh 《Journal of the Iranian Chemical Society》2017,14(5):1089-1098
Effective procedure to synthesize Fe3O4@SiO2@TiO2–Sn magnetically separable photocatalyst by a combination of co-precipitation, sol–gel and photodeposition methods was introduced. Products were characterized by XRD, SEM, VSM, EDS, DRS, TEM, ICP-OES and IR techniques. The dimensions of catalyst particle size were evaluated by scanning electron microscopy, and results approved nanoscale size for product. In addition, studying the magnetic nature by VSM analysis showed superparamagnetic properties for all samples. XRD pattern indicates that TiO2 coated on Fe3O4@SiO2 core well crystallized at 400 °C in anatase phase. Synthesized photocatalyst shows good photocatalytic performance in decolorization of rhodamine B aqueous solution. The composite nanoparticles showed high recycling efficiency and stability over five separation cycles. 相似文献
12.
Magdalena Leśniak Marcin Gajek Janusz Partyka Maciej Sitarz 《Journal of Thermal Analysis and Calorimetry》2017,130(1):165-176
In this work, the structure and thermal properties of aluminosilicate fritted glazes in SiO2–Al2O3–CaO–MgO–Na2O–K2O–ZnO system with (4.0 mol%) and without addition of ZnO were examined by GIXRD, FTIR, MAS-NMR and thermal methods (DTA, DIL). It has been found that the all experimental glazes are amorphous material (transparent glazes). On the base of spectroscopic investigations, it was found that zinc ions exist in the network glazes in the octahedral coordination—Zn2+ ions play a network modifier role in structure of glazes. An analysis of the data obtained from thermal tests showed that addition of ZnO into chemical composition results in decrease in glass transition temperature value (T g) for all glazes (DTA, DIL). The coefficient of thermal expansion (α) is decreased as the whole measurement range for one series of fritted glazes. 相似文献
13.
In-Jin Shon In-Yong Ko Hui-Soo Jun Kyung-Tae Hong Jung-Mann Doh Jin-Kook Yoon 《Research on Chemical Intermediates》2011,37(8):821-830
Rapid synthesis and sintering of nanostructured MgSiO3–Mg2SiO4 composites was investigated via a high-frequency induction heating sintering process. The advantage of this process is that
it enables very quick densification to near theoretical density and prohibition of grain growth in nanostructured materials.
High-density nanostructured MgSiO3–Mg2SiO4 composites were produced by simultaneous application of 80 MPa pressure under an induced output power of 15 kW within 2 min.
The grain sizes and hardness of MgSiO3–Mg2SiO4 composites were investigated. 相似文献
14.
Marcela Stoia Mircea Stefanescu Thomas Dippong Oana Stefanescu Paul Barvinschi 《Journal of Sol-Gel Science and Technology》2010,54(1):49-56
The paper presents a study on the preparation of Co2SiO4/SiO2 nanocomposites by a new modified sol–gel method. We have prepared gels starting from tetraethylorthosilicate (Si(OC2H5)4), cobalt nitrate Co(NO3)2·6H2O and some diols: ethylene glycol (C2H6O2), 1,2propanediol (C3H8O2) and 1,3propanediol (C3H8O2), for a final composition: 30% CoO/70% SiO2. During the heating of the gels at 140 °C, a redox reaction takes place between NO3
− ions and diol with formation of some carboxylate anions. These carboxylate anions react with the Co(II) ions to form coordination
compounds embedded in silica matrix, as evidenced by FT-IR spectrometry and thermal analysis. These Co(II) coordinative compounds
thermally decompose in the range 250–300 °C to the corresponding oxides: CoO and/or Co3O4 inside the matrices pores. When CoO results, it reacts with SiO2 at low temperature leading to Co2SiO4, which crystallizes at 700 °C. XRD patterns of the samples annealed at temperatures lower than 700 °C were characteristic
to amorphous phases. The samples annealed at temperatures ≥700 °C, contain Co2SiO4 (olivine) as unique crystalline phase inside the amorphous silica matrix, according to XRD patterns. As evidenced by TEM
images, Co2SiO4 nanoparticles are homogenously dispersed inside the silica matrix. 相似文献
15.
A porous borosilicate substrate has been coated with base catalysed SiO2 sol–gel nanoparticles. Onto these were deposited the vapour of titanium isopropoxide, where it reacted with the surface OH groups to give a TiO2-overcoat. This nanocomposite sol–gel derived TiO2/SiO2 membrane was then doped with 1%Rh giving Rh/TiO2/SiO2 membranes. These are shown to be coherent and crack-free, to have good permeability and activity in the isomerisation of butanes. It appears that sol–gel chemistry will allow such membranes to be totally engineered at a nm level. 相似文献
16.
Yan Wang Nuo Wei Qingling Feng Sha Li Chang Yang Zhiqiang Liu Wenming Zhang Qing Li 《Polymer Science Series B》2016,58(5):594-600
Novel luminescent bio-based hydrogels comprising cellulose and Y4Si2O7N2:Ce4+ (YC) were prepared in an alkali/urea aqueous system using epichlorohydrin as a cross-linker. The structure, characteristics and properties of the hydrogels were investigated by various techniques, including FTIR spectroscopy, wideangle X-ray diffraction, scanning electron microscopy, etc. The results showed that when the content of YC was less than 0.05 g, the YC particles were tightly embedded in the macro porous of cellulose matrix, which not only supplied cavities for YC immobilization, but also supplied the pore wall to protect the structure and character of YC. Hence, the cellulose–YC hybrid hydrogels exhibited strong cyan fluorescence under a UV lamp. However, excess of YC particles were enshrouded in the cellulose matrix resulted in smaller pores, weaker fluorescence intensity, lower swelling ratio and higher mechanical properties. 相似文献
17.
Shengqiang Xu Qingming Huang Yanting Xu Zhuoliang Ye Xiaohui Chen 《Research on Chemical Intermediates》2017,43(12):7055-7071
The phosphorus (P) modified MoO3–Bi2SiO5/SiO2 catalyst was prepared by a simple co-impregnation method and investigated in the epoxidation of propylene by molecular oxygen. The catalyst was characterized by X-ray diffraction (XRD), N2 adsorption–desorption analysis, NH3-temperature-programmed desorption (NH3-TPD), transmission electron microscopy, and Raman spectroscopy. It was found that the P-modified MoO3–Bi2SiO5/SiO2 catalyst with a P/Mo molar ratio of 0.5 exhibits the best catalytic performance for epoxidation of propylene by O2, the TOFs for propylene oxide (PO) formation was four times higher than that of the unmodified one at 633 K. The modification by P could promote the dispersion of MoO3 nanoparticles and increase the number of weak and moderate acid sites with respect to the phosphorus-free MoO3–Bi2SiO5/SiO2 catalyst, which were beneficial to the formation of PO. Moreover, the introduction of P also could protect the mesoporous structure by inhibiting the formation of Bi2Mo3O12, which was beneficial to the dispersion of active species. We suppose that the phosphorus, bismuth and molybdenum species of P-modified MoO3–Bi2SiO5/SiO2 catalyst play important roles for propylene epoxidation by molecular oxygen. 相似文献
18.
Hugo R. Fernandes Dilshat U. Tulyaganov Ashutosh Goel José M. F. Ferreira 《Journal of Thermal Analysis and Calorimetry》2011,103(3):827-834
This article aims to shed some light on the structure and thermo-physical properties of lithium disilicate glasses in the
system Li2O–SiO2–Al2O3–K2O. A glass with nominal composition 23Li2O–77SiO2 (mol%) (labelled as L23S77) and glasses containing Al2O3 and K2O with SiO2/Li2O molar ratios (3.13–4.88) were produced by conventional melt-quenching technique in bulk and frit forms. The glass-ceramics
(GCs) were obtained from nucleation and crystallisation of monolithic bulk glasses as well as via sintering and crystallisation
of glass powder compacts. The structure of glasses as investigated by magic angle spinning-nuclear magnetic resonance (MAS-NMR)
depict the role of Al2O3 as glass network former with four-fold coordination, i.e., Al(IV) species while silicon exists predominantly as a mixture
of Q
3
and Q
4
(Si) structural units. The qualitative as well as quantitative crystalline phase evolution in glasses was followed by differential
thermal analysis (DTA), X-ray diffraction (XRD) adjoined with Rietveld-reference intensity ratio (R.I.R.) method, Fourier
transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The possible correlation amongst structural
features of glasses, phase composition and thermo-physical properties of GCs has been discussed. 相似文献
19.
L. M. Delitsyn 《Doklady Chemistry》2017,477(1):265-270
The system LaPO4–SiO2–NaF–Nb2O5–Fe2O3 is characterized by immiscibility fields in the liquid state region. Addition of iron expands fields of immiscibility of melts and decreases the temperature of their coexistence. A fraction of 87–90% of niobium is extracted into iron silicate melt, and 92–98% of lanthanum is extracted into phosphate salt melt. 相似文献
20.
B. Li Y. Y. Wang W. Q. Luo Y. H. Zhang 《Journal of Radioanalytical and Nuclear Chemistry》2017,311(3):1619-1625
Radiation-induced degradation of the weakly and strongly 4-vinylpyridine basic ion exchange resins by gamma radiolysis was investigated in the presence of air and liquid water. This study is focused on evaluating the radiolytic gases (H2, CO, CO2 and CH4) and liquid products (water-solute TOC and NH4 +). The weakly basic resin yielded lower amounts of H2 and CO and higher amounts of CO2 than those of the strongly basic resin. Moreover, the strong basic resin tended to yield greater amounts of NH4 +. Resins were characterized by the FTIR spectroscopy technique and the results showed that the resins structures are relatively stable. 相似文献