scholarly journals Control of micro/mesoporosity in non-hydrolytic hybrid silicophosphate xerogels

2015 ◽  
Vol 3 (14) ◽  
pp. 7477-7487 ◽  
Author(s):  
Ales Styskalik ◽  
David Skoda ◽  
Zdenek Moravec ◽  
Michal Babiak ◽  
Craig E. Barnes ◽  
...  
Keyword(s):  
Sol Gel ◽  
Structural Units ◽  
Phosphonic Acids ◽  
Surface Areas ◽  
Hybrid Xerogels

Non-hydrolytic sol–gel reactions of acetoxysilanes with trimethylsilyl esters of phosphoric and phosphonic acids provide hybrid xerogels with large surface areas (up to 700 m2 g−1). The presence of SiO6 structural units in bridged-phosphoryl xerogels is related to their microporosity while the absence of such moieties in bridged-acetoxysilane networks is congruent with significant mesoporosity.

Effect of Iron (III)-Doping on the Photocatalytic Activity of Titanium Dioxide Catalysts for Methylene Blue Degradation

2011 ◽  
Vol 117-119 ◽  
pp. 1088-1091
Author(s):  
Wen Churng Lin ◽  
Rui Liu ◽  
Wein Duo Yang
Keyword(s):  
Methylene Blue ◽  
Photocatalytic Activity ◽  
Visible Light ◽  
Specific Surface ◽  
Effective Means ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Surface Areas ◽  
Bet Specific Surface Area ◽  
Vis Spectroscopy

Iron-doped TiO2 photocatalyst powders were prepared by the sol–gel method and characterized by Brunauer–Emmett–Teller (BET)-specific surface area, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Ultraviolet–Visible (UV-Vis) spectroscopy. Fe3+ doping in the TiO2 decreases the crystal grain size, increases the specific surface areas of powders, extends the absorption to visible light regions (400~500 nm), and lowers the photocatalytic activity for methylene blue (MB) degradation under UV irradiation. The photocatalytic degradation of MB in water was investigated as a function of the Fe3+ content in TiO2. It was found that under the irradiation of visible light, a small amount of Fe3+ dopant in TiO22 powders could obviously enhance the photocatalytic activity. When the Fe3+ content was in the range of 0.03–0.1 mol%, the photocatalytic activity of the samples was higher than that of undoped TiO2. Appropriate content of Fe-doping is an effective means to improve the photocatalytic activity of TiO2 for MB degradation under visible light irradiation.

Microstructure and Bio-Mineralization Behavior of the Sol-Gel Derived Bioactive Materials

2007 ◽  
Vol 280-283 ◽  
pp. 1609-1612 ◽  
Author(s):  
Xiao Feng Chen ◽  
Ying Jun Wang ◽  
Na Ru Zhao ◽  
Jian Dong Ye ◽  
Yu Dong Zheng ◽  
...  
Keyword(s):  
Sol Gel ◽  
Glass Ceramics ◽  
Tissue Engineering Scaffolds ◽  
Bioactive Materials ◽  
Electrode Layer ◽  
Oh Groups ◽  
Surface Areas ◽  
Gel Layer ◽  
Double Electrode ◽  
Sbf Solution

The biomaterials in system CaO-P2O5-SiO2 were synthesized via sol-gel method. The biomaterials can be applied to bone reparation and bone tissue engineering scaffolds The nano-pore structure, degradability, bioactivity and bio-mineralization characteristic of the biomaterials were investigated in details using XRD, SEM/EDX, FTIR, BET and DSC/TG techniques. It was indicated that the sol-gel derived biomaterials have a higher bioactivity than that of the melt derived bioactive glasses or glass-ceramics. It just takes 4-8 hours for HCA to form on the surface of the sol-gel samples in SBF solution at 37°C. The spherical HCA crystal clusters formed on the surface of the sol-gel derived samples immersed in SBF for 8 hours have a low crystallinity. Owing to their interconnected nano-sized pores, the sol-gel samples possess much higher surface areas and the hydrous porous SiO2 gel layer containing a great amount of ºSi-OH groups can be rapidly formed on the biomterials’ surface through a quick ion exchange between H3O+ in the solution and Ca2+ in the surface of the materials. ºSi-OH groups can play a very important role in inducing formation of HCA. They make the material surfaces electronegative, which resulted in a double electrode layer formed between the samples surface and SBF solution. The double electrode layer is in favor of formation of HCA on the surface of the materials.

scholarly journals Hydrocracking of Polyethylene to Jet Fuel Range Hydrocarbons over Bifunctional Catalysts Containing Pt- and Al-Modified MCM-48

Reactions ◽  
2020 ◽  
Vol 1 (2) ◽  
pp. 195-209
Author(s):  
Yanyong Liu
Keyword(s):  
Mesoporous Silica ◽  
Sol Gel ◽  
Mesoporous Structure ◽  
Jet Fuel ◽  
Magic Angle Spinning ◽  
High Yield ◽  
Magic Angle ◽  
Surface Areas ◽  
Angle Spinning ◽  
Post Modification

A low-density polyethylene was hydrocracked to liquid hydrocarbons in autoclave reactors over catalysts containing Pt- and Al-modified MCM-48. Two kinds of Al-modified MCM-48 were synthesized for the reaction: Al-MCM-48 was synthesized using a sol–gel method by mixing Al(iso-OC3H7)3 with Si(OC2H5)4 and surfactant in a basic aqueous solution before hydrothermal synthesis, and Al/MCM-48 was synthesized using a post-modification method by grafting Al3+ ions on the surface of calcined Al/MCM-48. X-ray diffraction (XRD) patterns indicated that both Al-MCM-48 and Al/MCM-48 had a cubic mesoporous structure. The Brunauer–Emmett–Teller (BET) surface areas of Al-MCM-48 and Al/MCM-48 were larger than 1000 m2/g. 27Al Magic Angle Spinning-NMR (MAS NMR) indicated that Al3+ in Al-MCM-48 was located inside the framework of mesoporous silica, but Al3+ in Al/MCM-48 was located outside the framework of mesoporous silica. The results of ammonia temperature-programmed desorption (NH3-TPD) showed that the acidic strength of various samples was in the order of H-Y > Al/MCM-48 > Al-MCM-48 > MCM-48. After 4 MPa H2 was charged in the autoclave at room temperature, 1 wt % Pt/Al/MCM-48 catalyst showed a high yield of C9−C15 jet fuel range hydrocarbons of 85.9% in the hydrocracking of polyethylene at 573 K for 4 h. Compared with the reaction results of Pt/Al/MCM-48, the yield of light hydrocarbons (C1−C8) increased over Pt/H-Y, and the yield of heavy hydrocarbons (C16−C21) increased over Pt/Al-MCM-48 in the hydrocracking of polyethylene. The yield of C9−C15 jet fuel range hydrocarbons over the used catalyst did not decrease compared to the fresh catalyst in the hydrocracking of polyethylene to jet fuel range hydrocarbons over Pt/Al/MCM-48.

scholarly journals A Structural Comparison of Ordered and Non-Ordered Ion Doped Silicate Bioactive Glasses

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 992
Author(s):  
Seray Schmitz ◽  
Ana M. Beltrán ◽  
Mark Cresswell ◽  
Aldo R. Boccaccini
Keyword(s):  
Metal Ion ◽  
Sol Gel ◽  
Glass Network ◽  
Textural Properties ◽  
Mesoporous Structure ◽  
Structure Directing Agent ◽  
Surface Areas ◽  
Pluronic P123 ◽  
Gel Glasses ◽  
The One

One of the key benefits of sol-gel-derived glasses is the presence of a mesoporous structure and the resulting increase in surface area. This enhancement in textural properties has a significant effect on the physicochemical properties of the materials. In this context the aim of this study was to investigate how sol-gel synthesis parameters can influence the textural and structural properties of mesoporous silicate glasses. We report the synthesis and characterization of metal ion doped sol-gel derived glasses with different dopants in the presence or absence of a surfactant (Pluronic P123) used as structure-directing templating agent. Characterization was done by several methods. Using a structure directing agent led to larger surface areas and highly ordered mesoporous structures. The chemical structure of the non-ordered glasses was modified to a larger extent than the one of the ordered glasses due to increased incorporation of dopant ions into the glass network. The results will help to further understand how the properties of sol-gel glasses can be controlled by incorporation of metal dopants, in conjunction with control over the textural properties, and will be important to optimize the properties of sol-gel glasses for specific applications, e.g., drug delivery, bone regeneration, wound healing, and antibacterial materials.

Synthesis and Photocatalytic Properties of ZnO-Volcanics Composites

2013 ◽  
Vol 331 ◽  
pp. 497-502
Author(s):  
Ai Hua Wang ◽  
Ping Che ◽  
Jie Min Liu ◽  
Gui Hua Wang
Keyword(s):  
Calcination Temperature ◽  
Physical Adsorption ◽  
Sol Gel ◽  
Degradation Efficiency ◽  
X Ray Diffraction ◽  
Photocatalytic Reactor ◽  
Decolorization Rate ◽  
Surface Areas ◽  
Transmission Electron ◽  
Average Grain Size

in this paper, nano-ZnO were synthesized via a sol-gel method, and ZnO-volcanics composites (ZVCs) were prepared via physical adsorption process. The morphology and structure of ZnO/ ZnO-volcanics composites (ZVCs) samples were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM).BET surface areas of the catalysts were determined by N2 adsorption (BET). According the data of XRD, the average grain size of ZnO is 15.1 nm consistent with the result observed by TEM (16.3 nm). Photocatalytic performance of ZnO and ZVCs were carried out in sprinkling photocatalytic reactor, with methylene blue (MB) as pollutants model. Decolorization rate is select as the evaluation parameters for the degradation effect. The effect of catalyst dosage, MB initial concentration, calcination temperature and pH on the degradation efficiency have been investigated. The MB degradation efficiency was 99.2% when the concentration of MB, the ZVCs, the pH and the calcination temperature were 10 mg/L, 20 g/L, and 10.03, 500 oC respectively. In the catalysts recycle experiments, the decolorization rate of MB using ZVCs is 90.2% after utilization for six times, overwhelmingly higher than that of ZnO (22.6%), indicating immobilization is efficient.

Crystallization Behavior of Chemically Prepared and Rapidly Solidified PbTiO3

1988 ◽  
Vol 121 ◽  
Author(s):  
Robert W. Schwartz ◽  
D. A. Payne
Keyword(s):  
Crystallization Behavior ◽  
Fine Particles ◽  
Sol Gel ◽  
Free Energies ◽  
X Ray Diffraction ◽  
Surface Areas ◽  
Treatment Conditions ◽  
Polymeric Sol ◽  
Co Precipitation ◽  
Rapidly Solidified

ABSTRACTThe crystallization behavior of chemically prepared and rapidly solidified PbTiO3 was investigated. Chemical methods were (i) polymeric sol-gel processing and (ii) co-precipitation of fine particles. Rapid solidification was obtained by a twin-roller quencher. Details are reported for the processing methods and the characteristics of the materials. X-ray diffraction and electron microscopy confirmed the amorphous nature of the prepared materials. Crystallization was examined as a function of heat-treatment conditions. Non-isothermal DSC was used to determine the kinetics of crystallization. Activation energies and frequency factors were determined. Co-precipitated PbTiO3 crystallized at the lowest temperature of 375 C, followed by sol-gel at 425 C, and rapidly solidified at 475 C. The results are interpreted in terms of processing routes, structural free-energies, available surface areas and fractional free volumes.

Synthesis of Monolithic Macroporous Carbon Xerogels from Phenol, m-Cresol, Furfural and Phosphoric Acid by Sol-Gel Approach

2013 ◽  
Vol 750-752 ◽  
pp. 1804-1811
Author(s):  
Rui Zhang ◽  
Zi Jun Hu ◽  
Shuang Ling Jin ◽  
Xia Shao ◽  
Ming Lin Jin
Keyword(s):  
Phosphoric Acid ◽  
Ambient Pressure ◽  
Sol Gel ◽  
Nitrogen Atmosphere ◽  
Molar Ratio ◽  
Surface Areas ◽  
Carbon Xerogels ◽  
Porous Properties ◽  
Macroporous Carbon

Mixtures of phenol and m-cresol in 1-propanol were first reacted with phosphoric acid and then with furfural to form gels, which were dried under ambient pressure and pyrolyzed under nitrogen atmosphere to form monolithic macroporous carbon xerogels. The molar ratio of m-cresol to phenol (m-C/P), phenol and m-cresol to furfural ((m-C+P)/F), phenol and m-cresol to phosphoric acid ((m-C+P)/H3PO4) was fixed at 1:5, 1:2 and 4.0 respectively while the m-C+P+F in 1-propanol was changed from 18 to 30 g/100ml to investigate the effect of the m-C+P+F concentrations on the porous properties of the monolithic carbon xerogels. It is found that the surface areas of the monolithic carbon xerogels are mainly contributed by micropores and their mesopore volumes are negligible. The monolithic carbon xerogels are rich in macropores whose sizes decrease from 4 to 0.22μm with increasing m-C+P+F concentrations. Moreover, the yields of the monolithic carbon xerogels are around 60%, which is higher than previous ones without phosphoric acid.

Sol-Gel Synthesis and Preliminary Characterizations of Novel Silica Hybrid Xerogels

2013 ◽  
Vol 594-595 ◽  
pp. 1009-1014
Author(s):  
S.A. Syed Nuzul Fadzli ◽  
S. Roslinda ◽  
Z. Firuz
Keyword(s):  
Sodium Alginate ◽  
Calcium Oxide ◽  
Sol Gel ◽  
Silica Xerogel ◽  
Particle Sizes ◽  
Mesoporous Composite ◽  
Hybrid Silica ◽  
Hybrid Xerogels ◽  
Mild Temperature ◽  
Sol Gel Synthesis

Hybrid silica xerogel mesoporous composite was synthesized by a mild temperature acid catalysed sol-gel route where a natural copolymer; sodium alginate (Na-COOH) together with calcium oxide (CaO) powder were incorporated into silica sol precursor prior to gel formation. For this study, bulk xerogels samples were prepared with the amount of silica precursor and the natural copolymer was fixed meanwhile the loading of calcium oxide was varied at 10 and 20 wt%. The monolith silica was also synthesized as control parameter. The preliminary properties were investigated using XRD, FTIR and SEM together with EDS for elemental analysis. The calcium oxide powder used in this study was prepared from calcium hydroxide, CaOH compound, which was previously calcined at 1000°C for 3 hours in normal air. The component of calcium oxide and sodium alginate were found to be uniformly dispersed in matrixes without affecting the cross-linked silica formation. As the presence of the components in the silica matrixes, the synthesized hybrid xerogels were found to be crack-free, structurally amorphous and physically opaque. Furthermore, the hybrid xerogels samples were found to have denser bodies, smoother surface, and decreased in particle sizes and thus might produced less brittleness in nature compared to the monolith xerogels.

A General Nonhydrolytic Sol‐Gel Route to Oxides

1994 ◽  
Vol 346 ◽  
Author(s):  
Sylvie Acosta ◽  
Pascal Arnal ◽  
Robert J.P. Corriu ◽  
Dominique Leclercq ◽  
P. Hubert Mutin ◽  
...  
Keyword(s):  
Nucleophilic Substitution ◽  
High Surface ◽  
Sol Gel ◽  
Metal Center ◽  
Binary Oxides ◽  
Surface Areas ◽  
Sol Gel Process ◽  
Silica Alumina ◽  
The One ◽  
Oxygen Donors

ABSTRACTA nonhydrolytic sol‐gel route based on the condensation between chlorides and oxygen donors such as ethers and alkoxides is presented. Four examples, silica, alumina, titania and binary oxides in the Al/Si system show that this is a general route. The mechanism of this condensation is completely different from the one of classical sol‐gel process, since it implies nucleophilic substitution at the carbon center instead of the metal center. As a consequence, the differences in reactivity between different metals are reduced. In addition, the structure of the precursors may be retained in the gel. Thus, the nonhydrolytic sol‐gel process is very efficient for the preparation of homogeneous bicomponent oxides. Futhermore, nonhydrated gels are formed, which allowed us to prepare amorphous aluminas with high surface areas.

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