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1.
Farook Adam Thiam-Seng Chew Jeyashelly Andas 《Journal of Sol-Gel Science and Technology》2011,59(3):580-583
Mesoporous silica nanoparticles with a spherical morphology have been synthesized from rice husk (agricultural biomass) by
a simple, template-free synthetic approach, which was carried out via sol–gel technique at ambient condition. Transmission
electron micrographs revealed the formation of spherical silica nanoparticles with an average diameter of 50.9 nm. From the
nitrogen adsorption–desorption analysis, the rice husk silica shows a high specific BET surface area of 245 m2 g−1. The silica nanoparticles have a narrow pore size distribution of 5.6–9.6 nm. 相似文献
2.
Mesoporous titania nanoparticles (denoted as MTN) with high surface area (e.g., 252 m2 g−1) were prepared using tetrapropyl orthotitanate (TPOT) as a titania precursor and 10–20 nm or 20–30 nm silica colloids as
templates. Co-assembly of TPOT and silica colloids in an aerosol-assisted process and immediate calcination at 450 °C resulted
in anatase/silica composite nanoparticles. Subsequent removal of the silica colloids from the composite by NaOH solution created
mesopores in the TiO2 nanoparticles with pore size corresponding to that of silica colloids. Effects of silica colloids’ contents on MTN porosity
and crystallites’ growth at a higher calcination temperature (e.g., 1000 °C) were investigated. Silica colloids suppressed
the growth of TiO2 crystallites during calcination at a higher calcination temperature and controllable contents of the silica colloids in precursor
solution resulted in various atomic ratios of anatase to rutile in the calcinated materials. The mesostructure and crystalline
structure of these titania materials were characterized by transmission electron microscope (TEM), scanning electron microscope
(SEM), X-ray diffraction (XRD), differential thermal analysis (DTA)-thermo-gravimetric analysis (TGA), and N2 sorption. 相似文献
3.
Zhijie Li Wenzhong Shen Zhiguo Wang Xia Xiang Xiaotao Zu Qiangmin Wei Lumin Wang 《Journal of Sol-Gel Science and Technology》2009,49(2):196-201
SnO2/SiO2 composite nanoparticles were prepared by sol–gel-hydrothermal process and their physico-chemical structure and photocatalytic
property were investigated. The results of XRD, TEM and FT-IR indicated that SnO2 crystallites with the tetragonal rutile structure were well-developed directly during hydrothermal process. The SnO2/SiO2 composite nanoparticles owned narrow size distribution, large specific surface area, and good thermal stability. As the presence
of 25.0 wt% SiO2, the SnO2 nanoparticles were about 4.0 nm in diameter and the specific surface area was 259.0 m2/g. After calcination at 800 °C, the crystalline grain size maintained 16.2 nm and the surface area still remained 132.6 m2/g. The SnO2/SiO2 composite nanoparticles showed better photocatalytic activity than pure SnO2 nanoparticles. 相似文献
4.
Guangwu Liu Bin Zhou Xingyuan Ni Jun Shen Guangming Wu Ai Du Guoqing Zu 《Journal of Sol-Gel Science and Technology》2012,62(2):126-133
The experimental results of thermal process on the microstructural and physical properties of ambient pressure dried hydrophobic
silica aerogel monoliths are reported and discussed. With sodium silicate as precursor, ethanol/hexamethyldisiloxane/hydrochloric
acid as surface modification agent, the crack-free and high hydrophobic silica aerogel monoliths was obtained possessing the
properties as low density (0.096 g/cm3), high surface area (651 m2/g), high hydrophobicity (~147°) and low thermal conductivity (0.0217 Wm/K). Silica aerogels maintained hydrophobic behavior
up to 430 °C. After a thermal process changing from room temperature to 300 °C, the hydrophobicity remained unchanged (~128°),
of which the porosity was 95.69% and specific density about 0.094 g/cm3. After high temperature treatment (300–500 °C), the density of final product decreased from 0.094 to 0.089 g/cm3 and porosity increased to 96.33%. With surface area of 466 m2/g, porosity of 91.21% and density about 0.113 g/cm3, silica aerogels were at a good state at 800 °C. Thermal conductivities at desired temperatures were analyzed by the transient
plane heat source method. Thermal conductivity coefficients of silica aerogel monoliths changed from 0.0217 to 0.0981 Wm/K
as temperature increased to 800 °C, revealed an excellent heat insulation effect during thermal process. 相似文献
5.
Fangxia Feng Scott Paulson Jason Young Viola Birss 《Journal of Sol-Gel Science and Technology》2009,51(2):153-157
Mesoporous Ni hydroxynitrates were synthesized from a hydrothermal mixture of Ni nitrate, octylamine as the surfactant, ethanol
and water at 25–100 °C for 24 h. Mesoporous Ni oxides were obtained by calcining the Ni hydroxynitrates in air at temperatures
ranging from 200 to 500 °C for 2 h. The mesoporous Ni oxides have crystalline walls, a high surface area of 133 m2/g at 350 °C, high porosity up to 0.61 cm3/g, and a bimodal mesopore size distribution, with pores roughly 2 and 10–25 nm in diameter. With an increase in the synthesis
temperature, the size of the larger pores and the total pore volume of the mesoporous Ni oxide increase, while the surface
area decreases slightly from 133 (25 °C) to 111 m2/g (100 °C). 相似文献
6.
Silica particles with lamellar and wormhole-like bi-modal mesopores have been synthesized using anionic surfactant (N-lauroylsarcosine sodium) as the template. The particles with diameters of 300―500 nm possess bi-modal mesopores with pore sizes of 3 nm and 12 nm, which were ascribed to the disordered wormhole-like mesophase and lamellar mesophase, respectively. The BET surface area of the particles was 536 m2/g and the pore volume was 0.83 cm3/g. The lamellar mesophase and cylindrical mesophase were formed... 相似文献
7.
The multi-walled mesoporous silica nanotubes are prepared using cetyltrimethylammonium bromize (CTAB) as the surfactant micellar
template and tetraethylorthosilicate (TEOS) as the silica precursor via a one-step wet chemical approach. The synthesized
tubes are found to be double/triple walled and of amorphous nature. Their diameter and the length are about 100 nm to 1 μm
and about 0.1–20 μm, respectively. The specific surface area approaches 1,488 m2/g. Based on the transmission electron microscopy analysis, it is inferred that the formation of the double/triple walled
silica nanotubes is associated with the lamellar curling mechanism. A striking photoluminescence effect is detected in the
mesostructured silica nanotubes. These nanotubes are expected to be a promising material for various applications such as
gas storage, catalyst, or catalyst supports. 相似文献
8.
High surface area silica (500 m2/g) was synthesized by the sol-gel method from tetraethyl orthosilicate. The total porosity of the sample was 37% and most
of the pores were well below 2 nm in size. The adsorption characteristics of ethylene and ethane in the silica were measured
from 300–350 K by gravimetry, and Langmuir adsorption constants and enthalpies and entropies of adsorption were determined.
Quasielastic neutron scattering was used to determine the translation and rotational diffusivities of both adsorbates from
200–270 K. Based on the adsorption and translational diffusion characteristics of ethylene and ethane, separation factors
of 1.1–2 for olefin to paraffin are predicted. 相似文献
9.
A facile synthesis of micro- and mesoporous carbons has been proposed using colloidal silica nanoparticles with diameter of
∼24 nm and poly(vinylidene chloride-co-vinyl chloride) (Saran) as a carbon precursor. The resulting carbons possessed large
specific surface area, ∼800 m2/g, and approximately the same volume of micro- and mesopores, each about 50% of the total pore volume. While the size of
micropores was around 1 nm, the large and uniform spherical mesopores (about 24 nm) resemble the diameters of silica colloids
used. Nitrogen adsorption measurements proved that these mesopores were interconnected and accessible. The well-developed
microporosity was created mainly by decomposition of Saran copolymer during carbonization. 相似文献
10.
P. R. Aravind P. Shajesh P. Mukundan K. G. K. Warrier 《Journal of Sol-Gel Science and Technology》2009,52(3):328-334
Ambient pressure drying has been carried out for the synthesis of silica–titania aerogel monoliths. The prepared aerogels
show densities in the range 0.34–0.38 g/cm3. The surface area and pore volume of these mixed oxide aerogels are comparable to those of the supercritically dried ones.
The surface area for 5wt% titania aerogel has been found to be as high as 685 m2/g with a pore volume of 2.34 cm3/g and the 10wt% titania aerogel has a surface area of 620 m2/g with a pore volume of 2.36 cm3/g. Some gels were also made hydrophobic by a surface treatment with methyltrimethoxysilane and trimethylchlorosilane. The
surface modified aerogels possess high surface areas in the range of 540–640 m2/g, and are thermally stable in terms of retaining hydrophobicity up to a temperature of 520 °C. The pore size distribution
of the aerogels clearly indicates the preservation of the aerogel structure. High Resolution Transmission Electron microscopy
has been employed to characterise the aerogels and Fourier Transform infrared spectroscopy to study the effect of titania
addition to silica and the surface modification. X-ray diffraction patterns were recorded to verify the molecular homogeneity
of the aerogel. 相似文献
11.
Influence of surfactant surface coverage and aging time on physical properties of silica nanoparticles 总被引:1,自引:0,他引:1
Gui-Mei Gao Hai-Feng Zou Da-Rui Liu Li-Na Miao Gui-Juan Ji Shu-Cai Gan 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,350(1-3):33-37
The experimental results on the influence of surfactant surface coverage and aging time on physical properties of silica nanoparticles were reported. The spherical silica nanoparticles have been synthesized using polyethylene glycol (PEG) as the surfactant and oil shale ash (OSA) as a new silica source. In order to identify the optimal condition for producing the best quality silica nanoparticles with the good dispersion and uniformity, the effects of surfactant surface coverage and aging time were investigated. It was found that the particle size and distribution of silica nanoparticles depend on the concentration of PEG in dispersion. At relatively low concentration, 0–2 wt.%, the existing PEG is not sufficient to prevent further growth of the initially formed silica nanoparticles, leading to large aggregates of silica particles. When the PEG concentration increases to 3 wt.%, self-assembled PEG layer on the surface stabilizes the initially formed silica nanoparticles and the silica particles with average diameter of 10 nm are uniformly distributed. With further increasing the concentration of PEG, the number of PEG aggregates increases and silica nanoparticles are mainly formed inside the entangled PEG chains, resulting in an observation of clusters of silica nanoparticles. Moreover, it was found that as the aging time increased, the shape of silica nanoparticles becomes regular and the particle size distribution becomes narrow. 相似文献
12.
G. Abelln A.I. Carrillo N. Linares E. Serrano J. García-Martínez 《Journal of solid state chemistry》2009,182(8):2141-2148
Bimodal macro-mesoporous silica networks have been prepared in a simple one-pot synthesis using an inexpensive tetramine surfactant and tetraethoxysilane as a silica precursor. These novel materials show high pore volumes and templated mesopores (average pore size 3.0 nm) embedded in 20 nm thick walls forming interparticle large meso/macropores. The judicious control of the pH during the silica formation allows for the precise control of the interparticle condensation, likely due to the change in the interaction between the tetramine surfactant and the silica precursors. Finally, a highly porous carbon replica with bimodal porosity was prepared by using the bimodal silica as a hard sacrificial template. The microstructure of the silica template was accurately transferred to the carbon material obtaining high surface areas (up to 1300 m2 g−1) and total pore volumes ≥2 cm3 g−1. 相似文献
13.
Zaoxue Yan Hui Meng Lei Shi Zihui Li Pei Kang Shen 《Electrochemistry communications》2010,12(5):689-692
The synthesis procedure of the highly mesoporous hollow carbon hemispheres (HCHs) using glucose as carbon source and solid core mesoporous shell silica (SCMSS) as template and the formation mechanism of the HCHs have been presented. The HCHs show an ultrahigh surface area of 1095.59 m2 g?1 and an average mesopore size of 9.38 nm. The hemispherical structure with large mesopores also results in the improvement in the mass transfer and therefore more concentrated ethanol solution can be used to increase the energy density. The additional advantage of the HCHs compared to the hollow carbon spheres is that they can provide the similar surface area at reduced volume. The current densities of ethanol oxidation on Pd nanoparticles supported on HCH (Pd/HCH) electrocatalyst are three times as many as on Pd/C at the same Pd loadings. 相似文献
14.
Zi Le Hua Jian Hua Gao Wen Bo Bu Ling Xia Zhang Hang Rong Chen Jian Lin Shi 《Journal of Sol-Gel Science and Technology》2009,50(1):22-27
Under typical dilute reactant compositions (3 ~ 5 wt% of surfactant template concentration) and conventional hydrothermal
conditions for mesoporous materials synthesis, successful preparation of hierarchically macro/mesoporous silica monoliths
was reported in this paper. The resultant materials were characterized by a series of techniques including powder X-ray diffraction,
N2 adsorption–desorption, SEM, TEM/EDS, and Hg porosimetry. A new kind of stable and hierarchically porous pure silica monoliths
was confirmed, which are featured with highly ordered mesoporous structures, rod-shaped unit particles, large specific surface
area of 492 m2/g, continuous macropores of about 4.0 μm in size and high macropore volume of about 13.1 cm3/g. Moreover, using the resultant silica monoliths as hard templates, carbon monoliths have been successfully replicated,
which inherit the structural characters of parent silica materials.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
P. Padmaja K. G. K. Warrier M. Padmanabhan W. Wunderlich 《Journal of Sol-Gel Science and Technology》2009,52(1):88-96
Alumina–titania mixed oxide nanocatalysts with molar ratios = 1:0.5, 1:1, 1:2, 1:5 have been synthesized by adopting a hybrid
sol–gel route using boehmite sol as the precursor for alumina and titanium isopropoxide as the precursor for titania. The
thermal properties, XRD phase analysis, specific surface area, adsorption isotherms and pore size details along with temperature
programmed desorption of ammonia are presented. A specific surface area as high as 291 m2/g is observed for 1:5 Al2O3/TiO2 composition calcined at 400 °C, but the same composition when calcined at 1,000 °C, resulted in a surface area of 4 m2/g, while 1:0.5 composition shows a specific surface area of 41 m2/g at 1,000 °C. Temperature programmed desorption (of ammonia) results show more acidic nature for the titania rich mixed
oxide compositions. Transmission electron microscopy of low and high titania content samples calcined at 400 °C, shows homogeneous
distribution of phases in the nano range. In the mixed oxide, the particle size ranges between 10–20 nm depending on titania
content. The detailed porosity data analysis contributes very much in designing alumina–titania mixed oxide nanocatalysts. 相似文献
16.
D. A. Zherebtsov 《Colloid Journal》2012,74(1):45-50
Being exposed to hydrochloric acid vapor, solutions of a surfactant and sodium tungstate form tungstic-acid-based materials
with a structure representing a system of interpenetrating hollow spheres 2–8 μm in diameter constructed from lamellar H2WO4 crystals with a thickness of 80–200 nm. The reduction of the tungstic-acid-based material with hydrogen gives rise to the
formation of a material based on tungsten(IV) oxide (WO2), which retains the initial structure. The adsorption capacity of the tungstic-acid-based materials is determined with respect
to benzene. The specific surface area of the obtained materials is 60–110 m2/g. 相似文献
17.
Synthetic opals composed of mesoporous SnO2 spheres were successfully fabricated from anodization of Sn opals, double templated from polystyrene opals. The mesoporous SnO2 spheres were 440 nm in diameter containing mesopores of 20–40 nm. The resultant mesoporous SnO2 opals possessed a high specific surface area of 196 m2/g and a grain size of 12 nm as estimated from XRD patterns. Such a hierarchical structure of SnO2 is a promising candidate for applications in gas sensors, catalysts, and electrode materials since the regularity of the sub-micron opal structure eases transfers of relevant chemical species within the structure while the mesoporosity of the constituent SnO2 spheres offers sufficient functioning surfaces for targeted applications. 相似文献
18.
Xueao Zhang Jianfang Wang Wenjian Wu Changli Liu Siwen Qian 《Journal of Sol-Gel Science and Technology》2007,43(3):305-311
Highly ordered amino-functionalized mesoporous silica thin films have been directly synthesized by co-condensation of tetraethoxysilane
(TEOS) and 3-aminopropyltriethoxysilane (APTES) in the presence of triblock copolymer Pluronic P123 surfactant species under
acidic conditions by sol-gel dip-coating. The effect of the sol aging on thin films organization is systematically studied,
and the optimal sol aging time is obtained. The amino-functionalized mesoporous silica thin films exhibit a long-range ordering
of 2D hexagonal (p6mm) mesostructure with a large pore size of 8.3 nm, a large Brunauer–Emmett–Teller (BET) specific surface area of 680 m2 g−1 and a large pore volume of 1.06 cm3 g−1 following surfactant extraction as demonstrated by X-ray diffraction (XRD), Transmission electron microscope (TEM), and physical
adsorption techniques. Based on BET surface area and weight loss, the surface coverage of amino-groups for the amino-functionalized
mesoporous silica thin films is calculated to be 3.2 amino-groups per nm2. Moreover, the functionalized thin films display improved properties for immobilization of cytochrome c in comparison with pure-silica mesoporous thin films. 相似文献
19.
High-quality cubic MCM-48 is successfully synthesized using a new silica source known as silatrane and cetyltrimethylammonium
bromide (CTAB) as the structure-directing agent via sol–gel process. The effects of synthesis parameters, viz. crystallization
temperature, crystallization time, surfactant concentration, quantity of NaOH, and silica source, on the product structure
are investigated. The synthesized samples are characterized using X-ray diffractometer (XRD), N2 adsorption–desorption isotherms, and electron microscopy. Optimally, this product is synthesized from samples crystallized
at 140°C for 16 h with a CTAB/SiO2 ratio of 0.3 and NaOH/SiO2 ratio of 0.5. The XRD result exhibits a well-resolved pattern, corresponding to the Ia3d space group of MCM-48. The BET surface area of this product is as high as 1,300 m2/g with a narrow pore-size distribution of 2.86 nm. The scanning electron microscopic (SEM) images also show the truncated
octahedral shape and well-ordered pore system of MCM-48 particles. 相似文献
20.
In this work we prepared the hybrid material (SG) by the sol–gel method through the reaction between tetraethylortosilicate
(TEOS) and acetylacetonatepropyltrimethoxysilane (ACACSIL). We also immobilized the acetylacetonate on silica surface (GR)
by the grafting method through the reaction between a commercial silica and ACACSIL. Infrared thermal analysis showed that
these materials were thermally stable until 200 °C. SG is a microporous material and has surface area of 500 m2 g−1, average porous volume of 0.09 cm3 g−1 and organic content of 1 mmol g−1. GR is a mesoporous material and has surface area of 300 m2 g−1, average porous volume of 0.7 cm3 g−1 and organic content of 0.4 mmol g−1. Iron(III) was coordinated to SG and GR resulting in the SG–Fe and GR–Fe silicas which were tested as catalysts on the aerobic
epoxidation of cis-cyclooctene. SG–Fe yielded 100% of conversion and 94% of selectivity in epoxide whereas GR–Fe silica led
to a maximum conversion of 50% and 100% of selectivity. 相似文献