共查询到20条相似文献,搜索用时 25 毫秒
1.
The metals-doped silica-pillared clay (SPC) materials with ordered pore structure in the gallery were obtained by a surfactant-directed assembly of silica species in the interlayer space of natural montmorillonite (MMT). The novel method afforded SPC derivatives with basal spacings of 4.4-4.5 nm, BET specific surface areas of 382.4-472.6 m2/g, pore volumes of 0.64-0.71 cm3 g−1 and uniform pores (3.6 nm) between the layers. The main nickel and cobalt species was tetrahedrally coordinated Ni2+ or Co2+ in the gallery silica framework. Our results indicate that surfactant plays a decisive role in pore formation, because in acts as a micelle-like template during the hydrolysis of TEOS. In particular, the formation of metal-ammonia complex and rapid adsorption by surfactant in galleries controls metal species outflow from interlayers and contributes to the formation of metal species containing firm silica-pillars. 相似文献
2.
Zr0.85Ce0.15O2 nanopowders synthesised by gel-combustion and spray-pyrolysis methods were comparatively studied by means of X-ray diffraction, Raman spectroscopy, thermogravimetric and differential thermal analyses, specific surface area measurements, scanning and transmission electron microscopies and chemical analysis. Fully tetragonal powders were obtained by both methods, as determined by X-ray diffraction and Raman spectroscopy. Both materials exhibited extremely small crystallite sizes (about 6 nm) and high specific surface areas (93 m2/g and 42 m2/g for gel-combustion and spray-pyrolysis powders, respectively). In both cases, no tetragonal-to-monoclinic transition was observed in the whole temperature range up to 1300 °C by differential thermal analysis. The amounts of the expected impurities (Si, B, C) were acceptable and comparable in both cases. 相似文献
3.
Mesoporous carbon spheres serving as electrode materials for supercapacitors were synthesized by a facile polymerization-induced colloid aggregation method using melamines as a carbon precursor and commercial colloidal silica as a silica source for hard template. After the carbonization of as-formed resins-template composites at 1000 °C and the removal of the silica template by hydrofluoric acid, the resulting mesoporous carbon spheres with a diameter size of ∼5 μm, specific surface area (up to 1280 m2/g) and uniform pore size as large as 30 nm could be obtained. Due to the enriched nitrogen content and the large pore size of the mesoporous carbon spheres affecting the surface wettability, resistance, and ion diffusion process in the pores, the mesoporous carbon spheres showed a high specific capacitance of 196 F/g in 5 mol/l H2SO4 electrolytes at a discharge current density of 1 A/g. 相似文献
4.
SiO2/Al2O3 composite microspheres with SiO2 core/Al2O3 shell structure and high surface area were prepared by depositing Al2O3 colloid particles on the surface of monodispersed microporous silica microspheres using a simple electrostatic attraction and heterogeneous nucleation strategy, and then calcined at 600 °C for 4 h. The prepared products were characterized with differential thermal analysis and thermogravimetric analysis (DTA/TG), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption and X-ray photoelectron spectroscopy (XPS). It was found that uniform alumina coating could be deposited on the surface of silica microspheres by adjusting the pH values of the reaction solution to an optimal pH value of about 6.0. The specific surface area and pore volume of the SiO2/Al2O3 composite microspheres calcined at 600 °C were 653 m2 g−1 and 0.34 ml g−1, respectively. 相似文献
5.
Synthesis and characterization of NiO-YSZ for SOFCs 总被引:1,自引:0,他引:1
Nickel oxide and yttria-stabilized zirconia ceramic materials were prepared by three methods: physical mixture, a modified Pechini route, and impregnation with Ni(NO3)2·6H2O. Temperature-programmed reduction (TPR) analysis showed the presence of different reduction peaks for each sample and that the reduction temperature was influenced by the employed preparation procedure. Nickel oxide species are completely reduced at temperatures up to 1000 °C and their temperature-programmed reduction profiles indicated that a higher temperature reduction corresponds to a higher calcination temperature. Furthermore, the composites synthesized through impregnation presented nickel oxide species more easily reducible than those prepared by the two other methods. Scanning electron microscopy and X-ray photoelectron spectroscopy (XPS) evidenced a larger nickel oxide coating on yttria-stabilized zirconia for the composite synthesized through the impregnation method. The electrical conductivity of impregnation sample was 117 S cm−1 at 850 °C, a value three times higher than that of the physical mixture. 相似文献
6.
Hydrothermal synthesis of nanocrystalline VO2 from poly(diallyldimethylammonium) chloride and V2O5 总被引:1,自引:0,他引:1
Fernando J. Quites 《Materials Research Bulletin》2010,45(7):892-896
Novel vanadium dioxide nanorods were fabricated from V2O5 in the presence of a reducing agent, the poly(diallyldimethylammonium chloride) (PDDA) via a hydrothermal method at 180 °C for 48 h. The samples produced were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (FTIR), nitrogen adsorption (BET) and thermogravimetry (TG/DTG). The nanorods obtained are approximately 50 nm wide and from 300 to 500 nm long and presents high surface area (42 m2 g−1). The nanocrystalline B phase VO2 is not produced by hydrothermal treatment in the absence of the PDDA polyelectrolyte. 相似文献
7.
Synthesis of amorphous supermicroporous zirconium phosphate materials by nonionic surfactant templating 总被引:1,自引:0,他引:1
Supermicroporous zirconium phosphate materials possessing wormhole-like pores in the size range 1.3-1.8 nm were synthesized by using nonionic poly(ethylene oxide) surfactant (e.g., C16H33(EO)10, C18H35(EO)10) as a structure directing agent. The textural and structural properties were characterized by powder X-ray diffraction, N2 adsorption analysis, differential thermal analysis, scanning and transmission electron microscopy, 31P MAS NMR and infrared spectroscopy. The synthesized materials are amorphous, exhibiting high surface areas, narrow pore size distributions, excellent thermal stabilities (over 800 °C) and acidic properties. The supermicropore size of the synthesized zirconium phosphate may be tunable by the variation of alkyl chain length of the surfactant. 相似文献
8.
Liaoyuan Xia Mingqiu Zhang Minzhi Rong Kunkun Guo Yunchu Hu Yiqiang Wu Tibor Czigany 《Composites Science and Technology》2012
Wormhole-like mesoporous tungsten carbide/carbon (WC/C) composites can be prepared by an easy method that combines emulsion processing with triblock copolymer self-assembly strategy, followed by a high-temperature carbothermal reduction. X-ray diffraction, transmission electron microscopy, X-ray spectroscopy, thermogravimetric analysis and N2 sorption techniques were employed to characterize the mesoporous WC/C composites. The results show that the resultant materials have a wormhole-like mesostructure containing nanoscale (∼40 nm) tungsten carbide particles, and high surface areas (up to 314.9 cm2/g). It is proposed that a general assemble procedures are responsible for the wormhole-like mesoporous WC/C composites. 相似文献
9.
Spindle porous iron nanoparticles were firstly synthesized by reducing the pre-synthesized hematite (α-Fe2O3) spindle particles with hydrogen gas. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption/desorption isotherms and vibrating sample magnetometry (VSM). A lattice shrinkage mechanism was employed to explain the formation process of the porous structure, and the adsorbed phosphate was proposed as a protective shell in the reduction process. N2 adsorption/desorption result showed a Brunauer-Emmett-Teller (BET) surface area of 29.7 m2/g and a continuous pore size distribution from 2 nm to 100 nm. The magnetic hysteresis loop of the synthesized iron particles showed a saturation magnetization of 84.65 emu/g and a coercivity of 442.36 Oe at room temperature. 相似文献
10.
In this paper, we report the successful synthesis of NiTiO3 microtubes constructed by nearly spherical nanoparticles via a simple solution-combusting method employing a mixture of ethanol and ethyleneglycol (V/V = 60/40) as the solvent, nickel acetate as the nickel source, tetra-n-butyl titanate as the titanium source and oxygen gas in the atmosphere as the oxygen source. The as-obtained product was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometry (EDS). The UV-vis absorption spectrum of the product showed two absorption peaks centered at 258.6 and 350.1 nm, respectively. The Brunauer-Emmett-Teller (BET) surface area of the product was 14.06 m2/g and the pore size distribution mainly located from 20 to 30 nm. The photocatalytic degradation property of the product for organic dyes showed that the as-obtained porous NiTiO3 microtubes could strongly promote the degradation of organic dyes including Pyronine B, Safranine T and Fluorescein. 相似文献
11.
A series of Ni1−xCuxFe2O4 (0 ≤ x ≤ 0.5) spinels were synthesized employing sol-gel combustion method at 400 °C. The decomposition process was monitored by thermal analysis, and the synthesized nanocrystallites were characterized by X-ray diffraction, transmission electron microscopy, infra-red and X-ray photoelectron spectroscopy. The decomposition process and ferritization occur simultaneously over the temperature range from 280 °C to 350 °C. TEM indicates the increase of lattice parameter and particle size with the increase of copper content in accordance with the XRD analysis. Cu2+ can enter the cubic spinel phase and occupy preferentially the B-sites within x = 0.3, and redundant copper forms CuO phase separately. A broadening of the O 1s region increases with the increment of copper content compared to pure NiFe2O4, showing different surface oxygen species from the spinel and CuO. Cu2+ substitution favors the occupancy of A-sites by Fe3+. 相似文献
12.
Fluoridated hydroxyapatite (FHAp) was successfully synthesized from the starting materials of CaCO3, CaHPO4·2H2O, and CaF2 via a mechanochemical-hydrothermal route. X-ray diffraction, infrared spectroscopy, surface area measurements, and scanning electron microscopy identified the resultant powders as FHAp nanocrystals with the specific surface areas of up to 114.72 m2/g. The mechanism study revealed that under such mechanochemical-hydrothermal conditions the formation reactions of FHAp were completed in two stages. The starting materials firstly reacted into a poorly crystallized calcium-deficient apatite and the complete incorporation of fluoride ions into apatite occurred in the second stage. 相似文献
13.
Ultrafine fluorite type Dy2Zr2O7 nanocrystals with cubic structure were fabricated at relatively low temperature by stearic acid method (SAM) using zirconium(IV) butoxide and dysprosium nitrate as raw materials, stearic acid as solvent and dispersant. The fabrication process was monitored by thermogravimetric analysis and differential thermal analysis (TG-DTA) and Fourier transform infrared spectroscopy (FT-IR). The obtained products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectrometer (EDS) and UV-vis absorption spectroscopy. A single phase of Dy2Zr2O7 with high crystallinity was formed at 800 °C. The interplanar distances measured from the HRTEM image were 0.284 and 0.256 nm, respectively, coinciding with the theoretical values. 相似文献
14.
A new kind of superparamagnetic luminescent nanocomposite particles has been synthesized using a modified Stöber method combined with an electrostatic assembly process. Fe3O4 superparamagnetic nanoparticles were coated with uniform silica shell, and then 3-aminopropyltrimethoxysilane was used to terminate the silica surface with amino groups. Finally, negatively charged CdSe quantum dots (QDs) were assembled onto the surface of the amino-terminated SiO2/Fe3O4 nanoparticles through electrostatic interactions. X-ray diffraction (XRD), transmission electron microscopy (TEM), microelectrophoresis, UV-vis absorption and emission spectroscopy and magnetometry were applied to characterize the nanocomposite particles. Dense CdSe QDs were immobilized on the silica surface. The thickness of silica shell was about 35 nm and the particle size of the final products was about 100 nm. The particles exhibited favorable superparamagnetic and photoluminescent properties. 相似文献
15.
Nanocrystalline LiMn2O4 powders have been synthesized by combustion process in a single step using a novel fuel, l-alanine. Thermogravimetric analysis and differential thermal analysis of the gel indicate a sharp combustion at a temperature as low as 149 °C. Quantitative phase analysis of X-ray diffraction data shows about 97% of phase purity in the as-synthesized powder, which on further calcination at 700 °C becomes single phase LiMn2O4. High Brunauer, Emmett, and Teller surface area values obtained for ash (53 m2/g) and calcined powder (23 m2/g) indicate the ultrafine nature of the powder. Average crystallite size is found to be ∼60-70 nm from X-ray diffraction analysis and transmission electron microscopy. Fourier transformed infra-red spectrum shows two strong bands at 615 and 511 cm−1 originating from asymmetrical stretching of MnO6 octahedra. A nominal composition of Li0.88 Mn2O4 is calculated from the inductive coupled plasma analysis. From UV-vis spectroscopy, an optical band gap of 1.43 eV is estimated which is assigned to a transition between t2g and eg bands of Mn 3d. Electrochemical charge-discharge profiles show typical LiMn2O4 behavior with a specific capacity of 76 mAh/g. 相似文献
16.
Uniform submicron BiMn2O5 particles were prepared via a facile one-step hydrothermal route at low temperature. Bi(NO3)3, MnCl2·4H2O and KMnO4 were used as starting materials; KOH as a pH adjustor and also as a mineralizer. Single-crystalline orthorhombic BiMn2O5 sample with controllable morphology was obtained. The microstructure strongly depends on the molar ratio of the starting materials, KOH concentration and reaction temperature. X-ray photoelectron spectroscopy shows the existence of Mn4+ state. Magnetic measurement indicates Néel temperature TN at 44 K. The susceptibility above TN obeys the Curie-Weiss law, χ = C/(T − θ), with θ = −350 K. The effective paramagnetic moment μeff = 4.66 μB/Mn, demonstrating the coexistence of mixed Mn3+ and Mn4+ valences. 相似文献
17.
Mesostructured cellular foam (MCF) silica with high surface area (>600 m2/g) and large pore volume (≈1.16 cm3/g) was synthesized via a surfactant templating method. The MCF silica was then modified by grafting 3-aminopropyl-triethoxysilane (APTES) to create a positive charge on the surface, and thus, to provide sites for the immobilization of H3PMo12O40. By taking advantage of the overall negative charge of [PMo12O40]3−, the H3PMo12O40 catalyst was chemically immobilized on the aminopropyl group of the surface modified MCF silica as a charge matching component. The mesopore structure of MCF silica was maintained even after the surface modification step and the subsequent immobilization step of H3PMo12O40. The H3PMo12O40 species were finely and molecularly dispersed on the surface modified MCF silica via chemical immobilization. 相似文献
18.
Jakkidi Krishna Reddy Machiraju Subrahmanyam Bojja Sreedhar 《Materials Research Bulletin》2009,44(7):1540-2050
Ce-Al-MCM-41, TiO2/Al-MCM-41 and TiO2/Ce-Al-MCM-41 materials with varying contents of Ce (by impregnation) and TiO2 loaded (by solid-state dispersion) on Al-MCM-41 support are prepared. The Ce modified and TiO2 loaded composite systems are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS) and X-ray photoelectron spectroscopy (XPS) techniques. The DRS and XPS of low Ce content (0.2-0.5 wt.%) modified Al-MCM-41 samples are showing more characteristic of Ce3+ species wherein cerium in interaction with Al-MCM-41 and that of high Ce (0.8, 3.0 wt.%) content modified samples are showing the characteristic of both Ce4+and Ce3+species. A series of Ce-modified Al-MCM-41 and TiO2 loaded composite catalysts are evaluated for photocatalytic degradation of phenol under UV irradiation. Low Ce content in Ce3+ state on Al-MCM-41 is showing good photoactivity in comparison with high Ce content samples and pure ceria. The composite TiO2/Ce-Al-MCM-41 is showing enhanced degradation activity due decreased rate of electron-hole recombination on TiO2 surface by the redox properties of cerium. The photocatalyst TiO2/Ce-Al-MCM-41 with an optimum of 10 wt.% TiO2 and 0.3 wt.% Ce is showing maximum phenol degradation activity. The possible mechanism of phenol degradation on the composite photocatalyst is proposed. 相似文献
19.
As yellow pigments, nanosized rutile structured Ni0.1W0.1Ti0.8O2 and priderite structured BaNiTi7O16 have been prepared through pyrolysis of precursor solution containing nickel nitrate, dimethyl tungstate, titanium oxalate, triethanolamine (TEA) for the former composition and barium nitrate, nickel nitrate, titanium oxalate, TEA for the later composition, respectively. In the reaction, TEA acts to minimize the agglomeration in the products through formation of a highly branched polymeric framework, which anchors the metal ions for producing nanocrystalline powders. The rutile and priderite structured titanates obtained on heat-treatment of the precursor powders at 800 °C and 850 °C, respectively, have been characterized by XRD, TGA-DTA, BET surface area measurement, UV-vis spectroscopy, CIE L*a*b* colour parameter measurements, TEM and HRTEM. XRD reveals the purity of the resulting rutile and priderite phases. Their crystallite sizes, average particle sizes and specific surface areas determined from XRD, TEM, and BET surface area measurement are found to be in the range between 25 nm and 30 nm, 25-45 nm and 100-120 m2/g, respectively, for both compositions. 相似文献
20.
A mesostructured tungsten disulfide (WS2) material was prepared through a solid-phase reaction utilizing ammonium tetrathiotungstate as the precursor and n-octadecylamine as the template. The as-synthesized WS2 material was characterized by X-ray powder Diffraction (XRD), Low-temperature N2 Adsorption (BET method), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). The characterization results indicate that the WS2 material has the typical mesopore structure (3.7 nm) with a high specific surface area (145.9 m2/g), and large pore volume (0.18 cm3/g). This approach is novel, green and convenient. The plausible mechanism for the formation of the mesostructured WS2 material is discussed herein. 相似文献