The pore morphology of fluoride catalyzed xerogels

1989 ◽  
Vol 4 (3) ◽  
pp. 693-697 ◽  
Author(s):  
J-B. Chan ◽  
D-W. Hua ◽  
R. Winter ◽  
J. Jonas
Keyword(s):  
Pore Size ◽  
Heating Temperature ◽  
Average Pore Size ◽  
Sol Gel ◽  
Fluoride Concentration ◽  
Silica Gels ◽  
Fluoride Anion ◽  
Average Pore ◽  
Host Materials ◽  
Wide Range

The fluoride anion has been shown to be one of the most effective catalysts in accelerating the polycondensation of alkoxide-derived silica gels. A detailed pore analysis study has been employed to investigate the effect of NaF on the pore structure of the resulting xerogels and its evolution during thermal heat treatment up to 800 °C. Addition of NaF to tetramethylorthosilicate-sols leads to an increase in average pore size, and the pore size distribution becomes narrower. By changing the fluoride concentration and the heating temperature, the surface properties of the xerogels can be tuned over a wide range. The possible application of the F− anion catalyzed sol gel process to prepare porous host materials for the studies of fluids in restricted geometries is also discussed.

Synthesis, characterization, and photocatalytic activity of silver and zinc co-doped TiO2 nanoparticle for photodegradation of methyl orange dye in aqueous solution

2019 ◽  
Vol 97 (9) ◽  
pp. 642-650 ◽  
Author(s):  
Gabriel O. Oladipo ◽  
Akinola K. Akinlabi ◽  
Samson O. Alayande ◽  
Titus A.M. Msagati ◽  
Hlengilizwe H. Nyoni ◽  
...  
Keyword(s):  
Methyl Orange ◽  
Pore Size ◽  
Average Pore Size ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Rutile Phase ◽  
Absorption Bands ◽  
Average Pore ◽  
Methyl Orange Dye ◽  
Co Doped

In this study, TiO2 nanocrystals, 1 mol% Ag-doped TiO2, and 1 mol% Ag and 0.6 mol% Zn co-doped TiO2 powders were synthesized by the sol–gel route. Their photocatalytic activities on methyl orange dye under visible irradiation were investigated. The powders were characterized by X-ray diffraction (XRD), UV–visible spectroscopy (UV–vis), Brunauer–Emmett–Teller (BET), and Fourier transform infrared spectroscopy (FTIR). The XRD results revealed the presence of a rutile phase with an average crystallite size of 9 and 11 nm. The UV–vis spectra showed a red-shift towards a longer wavelength with the corresponding decrease in band gap from 2.9 to 2.5 eV. The BET surface areas of the nanoparticles ranged from 4.7 to 11.8 m2 g−1 with an average pore size between 18.9 and 56.6 nm. The Ag-doped TiO2 has the largest surface area of 11.8 m2 g−1, whereas the Ag–Zn co-doped TiO2 was found to have the highest pore size and volume. The absorption bands at 750–500 cm−1 were attributed to the –O–Ti–O– bond in the TiO2 lattice. The photocatalytic efficiency was highest at an optimum pH of 4.1 for Ag–Zn co-doped TiO2. The results confirmed that Ag-doped and Ag–Zn co-doped TiO2 were more effective than pure TiO2. The kinetic data were fitted into a pseudo first-order equation using a Langmuir–Hinshelwood kinetic model.

Highly Ordered Nanoporous Alumina Films: Effect of Pore Size and Uniformity on Sensing Performance

2002 ◽  
Vol 17 (5) ◽  
pp. 1162-1171 ◽  
Author(s):  
Oomman K. arghese ◽  
Dawei Gong ◽  
Maggie Paulose ◽  
Keat G. Ong ◽  
Craig A. Grimes ◽  
...  
Keyword(s):  
Pore Size ◽  
Average Pore Size ◽  
High Sensitivity ◽  
Water Layer ◽  
Adsorbed Water ◽  
Average Pore ◽  
Nanoporous Alumina ◽  
Wide Range ◽  
Anodization Process ◽  
Measured Impedance

The effect of pore size and uniformity on the humidity response of nanoporous alumina, formed on aluminum thick films through an anodization process, is reported. Pore sizes examined range from approximately 13 to 45 nm, with a pore size standard deviations ranging from 2.6 to 7.8 nm. The response of the material to humidity is a strong function of pore size and operating frequency. At 5 kHz an alumina sensor with an average pore size of 13.6 nm (standard deviation 2.6 nm) exhibits a well-behaved change in impedance magnitude of 103 over 20% to 90% relative humidity. Increasing pore size decreases the humidity range over which the sensors have high sensitivity and shifts the operating range to higher humidity values. Cole–Cole plots of 5 to 13 MHz measured impedance spectra, modeled using equivalent circuits, are used to resolve the effects of water adsorption and ion migration within the adsorbed water layer. The presence of impurity ions within the highly ordered nano-dimensional pores, accumulated during the anodization process, appear highly beneficial for obtaining a substantial variation in measured impedance over a wide range of humidity values.

scholarly journals Sol–Gel Synthesis and Characterization of a Quaternary Bioglass for Bone Regeneration and Tissue Engineering

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4515
Author(s):  
Ricardo Bento ◽  
Anuraag Gaddam ◽  
José M. F. Ferreira
Keyword(s):  
Tissue Engineering ◽  
Bone Regeneration ◽  
Pore Size ◽  
Average Pore Size ◽  
Glass Structure ◽  
Sol Gel ◽  
Atomic Scale ◽  
Average Pore ◽  
Hydrolysis And Condensation ◽  
Sol Gel Synthesis

Sol–gel synthesis using inorganic and/or organic precursors that undergo hydrolysis and condensation at room temperature is a very attractive and less energetic method for preparing bioactive glass (BG) compositions, as an alternative to the melt-quenching process. When properly conducted, sol–gel synthesis might result in amorphous structures, with all of the components intimately mixed at the atomic scale. Moreover, developing new and better performing materials for bone tissue engineering is a growing concern, as the aging of the world’s population leads to lower bone density and osteoporosis. This work describes the sol–gel synthesis of a novel quaternary silicate-based BG with the composition 60 SiO2–34 CaO–4 MgO–2 P2O5 (mol%), which was prepared using acidified distilled water as a single solvent. By controlling the kinetics of the hydrolysis and condensation steps, an amorphous glass structure could be obtained. The XRD results of samples calcined within the temperature range of 600–900 °C demonstrated that the amorphous nature was maintained until 800 °C, followed by partial crystallization at 900 °C. The specific surface area—an important factor in osteoconduction—was also evaluated over different temperatures, ranging from 160.6 ± 0.8 m2/g at 600 °C to 2.2 ± 0.1 m2/g at 900 °C, accompanied by consistent changes in average pore size and pore size distribution. The immersion of the BG particles in simulated body fluid (SBF) led to the formation of an extensive apatite layer on its surface. These overall results indicate that the proposed material is very promising for biomedical applications in bone regeneration and tissue engineering.

Structural Characterization of MMT Modified by Acrylamide

2011 ◽  
Vol 689 ◽  
pp. 425-431
Author(s):  
Zeng Zhi Zhang ◽  
Dan Dan Ma
Keyword(s):  
Pore Size ◽  
Lamellar Structure ◽  
Heating Temperature ◽  
Average Pore Size ◽  
Lamellar Spacing ◽  
Treatment Temperature ◽  
Carbonization Temperature ◽  
Average Pore ◽  
Heating Treatment

Carbon pillared MMT was prepared from Na-MMT modified by acrylamide. The structural behavior of the MMT and AM/modified MMT were characterized by TG-DTA and DSC. The analysis of modified MMT showed that: the lamellar structure of carbon pillared MMT increases clearly with the carbonization temperature. In the experiment temperature range, the higher the heating temperature, the more significantly carbonization properties of MMT exhibited, and the more apertures of Pillared MMT developed. In the test MMT lamellar spacing of the carbide change with the heating treatment temperature, d001 value of the MMT augmented to the largest when carbonization temperature reach 200°C; the average pore size of treated MMT was larger than untreated MMT, the pore size became the largest average at 400 °C.

Thermal properties of organic and inorganic aerogels

1994 ◽  
Vol 9 (3) ◽  
pp. 731-738 ◽  
Author(s):  
Lawrence W. Hrubesh ◽  
Richard W. Pekala
Keyword(s):  
Thermal Conductivity ◽  
Pore Size ◽  
Average Pore Size ◽  
Sol Gel ◽  
Total Thermal Conductivity ◽  
Insulation Property ◽  
Average Pore ◽  
Thermal Insulating ◽  
Thermal Insulation Property ◽  
Infrared Extinction

Aerogels are open-cell foams that have already been shown to be among the best thermal insulating solid materials known. This paper examines the three major contributions to thermal transport through porous materials, solid, gaseous, and radiative, to identify how to reduce the thermal conductivity of air-filled aerogels. We found that significant improvements in the thermal insulation property of aerogels are possible by (i) employing materials with a low intrinsic solid conductivity, (ii) reducing the average pore size within aerogels, and (iii) affecting an increase of the infrared extinction in aerogels. Theoretically, polystyrene is the best of the organic materials and zirconia is the best inorganic material to use for the lowest achievable conductivity. Significant reduction of the thermal conductivity for all aerogel varieties is predicted with only a modest decrease of the average pore size. This might be achieved by modifying the sol-gel chemistry leading to aerogels. For example, a thermal resistance value of R = 20 per inch would be possible for an air-filled resorcinol-formaldehyde aerogel at a density of 156 kg/m3, if the average pore size was less than 35 nm. An equation is included which facilitates the calculation of the optimum density for the minimum total thermal conductivity, for all varieties of aerogels.

Nanoporous TiO2/SiO2 Composite Prepared by a Combined Sol-Gel and Hybrid Method

2008 ◽  
Vol 368-372 ◽  
pp. 1497-1499 ◽  
Author(s):  
Wen Yuan Xu ◽  
Lu Bin Wei ◽  
Ming Biao Luo
Keyword(s):  
Phase Composition ◽  
Pore Size ◽  
Hybrid Method ◽  
Average Pore Size ◽  
Sol Gel ◽  
Molar Ratio ◽  
Tetrabutyl Titanate ◽  
Average Pore ◽  
Silica Nanocomposites ◽  
Surface Areas

Titania-silica nanocomposites with different TiO2/SiO2 compositions have been prepared by a sol-gel and hybrid method from tetraethylorthosilicate (TEOS) and tetrabutyl titanate(TBT) and β-Cyclodextrin as a pore-forming template. Drying and calcining of the hybrid xerogel can lead to the formation of nanoporous particles with surface areas in the range of 298-418 m2/g. The effect of the β-cyclodextrin concentration, the molar ratio of TiO2/SiO2 and the calcining temperature on the phase composition and structural properties of TiO2/SiO2 composites were also investigated. The results show that an increase in β-cyclodextrin concentration can lead to a decrease of the surface area and an increase of average pore size, which can be controlled by the amount of β- cyclodextrin in the hybrid sol.

Characterization of TiO2 Film Prepared by Sol-Gel Method Using Ti(OC4H9)4

2011 ◽  
Vol 298 ◽  
pp. 249-252 ◽  
Author(s):  
Li Li Yang ◽  
Jia Wei Bai ◽  
Wen Jie Zhang
Keyword(s):  
Pore Size ◽  
Tio2 Film ◽  
Average Pore Size ◽  
Sol Gel ◽  
Total Pore Volume ◽  
Source Surface ◽  
Average Pore ◽  
Tio2 Particles ◽  
Sol Gel Process

TiO2 film was dip-coated on glass substrate by a sol-gel process. Ti(OC4H9)4 was used as the titanium source. Surface morphology, crystallite phase, UV-Vis transmittance spectrum and pore size distribution of TiO2 powder prepared under the same conditions of the film were investigated. Surface of TiO2 film is fairly smooth with very slight roughness. No obvious hole or pore is found on the surface of the film. The strongest diffraction peak situated at 2θ=25.3o is the characteristic of anatase TiO2. The absorption edge of the TiO2 film is around 350 nm, while the transmittance fluctuates between 50% and 90%. The average pore size of the TiO2 particles calculated by BJH method is 23 nm. The total pore volume and specific surface area are 0.16 ml/g and 27 m2/g, respectively.

Porous Silica Nanomaterial Derived from Organic Waste Rice Husk as Highly Potential Drug Delivery Material

2019 ◽  
Vol 964 ◽  
pp. 88-96
Author(s):  
Hariyati Purwaningsih ◽  
Slamet Raharjo ◽  
Vania Mitha Pratiwi ◽  
Diah Susanti ◽  
Agung Purniawan
Keyword(s):  
Mesoporous Silica ◽  
Pore Size ◽  
Surface Area ◽  
Hydrothermal Treatment ◽  
Rice Husk ◽  
Average Pore Size ◽  
Sol Gel ◽  
Average Pore ◽  
Hydrothermal Temperature ◽  
Mcm 41

Rice became the main product of agriculture in agrarian countries including Indonesia. Rice husk is a waste of rice as one of the largest silica producers. Silica from rice husks can be used as a source of silica in the manufacture of sodium silicate as an alternative to the formation of mesoporous silica at a low price. In this research, the characterization of mesoporous silica nanoparticle (MSN) MCM-41 from rice husk (rice husk) with sol-gel method followed by hydrothermal treatment. Silica extraction was performed by titrating sodium silica using HCl method until the gel was formed. The mesoporous synthesis was performed with the addition of CTAB. The titration is then carried out using a solution of acetic acid. XRD shows silica with an amorphous structure. The FTIR results show that extraction silica and MSN MCM-41 contain pure silica displayed with Si-O-Si functional groups in the sample. The SEM results show MSN MCM-41 images such as a coral-like structure of agglomerated silica and the higher temperature hydrothermal treatment then it would be the more large size of particles. The material has a hexagonal pore structure such as a honeycomb as characteristic of MCM-41 with a pore size of 2.535 nm which includes mesoporous material. The result of nitrogen adsorption-desorption isotherms shows lower hydrothermal temperature will increase the specific surface area and decrease average pore size, where the best result with surface area value is 825.365 m2/gr and average pore size is 6.10426 nm obtained from process hydrothermal at 85°C.

Manufacturing of Porous Polydimethylsiloxane (PDMS) Plates Using Solvent Evaporation Induced Phase Separation Technique

2020 ◽  
Author(s):  
Mohammad Abshirini ◽  
M. Cengiz Altan ◽  
Yingtao Liu ◽  
Mrinal C. Saha ◽  
Laura Cummings ◽  
...  
Keyword(s):  
Phase Separation ◽  
Porous Structure ◽  
Pore Size ◽  
Average Pore Size ◽  
Solvent Evaporation ◽  
Separation Technique ◽  
Solvent Ratio ◽  
Average Pore ◽  
Wide Range ◽  
Curing Cycle

Abstract This paper presents the fabrication and characterization of porous polydimethylsiloxane (PDMS) plates. The framework for obtaining porous PDMS is based on the solvent evaporation induced phase separation technique. A mixture of PDMS, water, and tetrahydrofuran (THF) with different concentrations is prepared. The three phases are stirred to reach a highly stable and viscous solution. The THF and water phases are evaporated during a curing cycle by applying a stepping heat treatment. The porous PDMS sheets with a wide range of pore sizes are fabricated by controlling the ratio of water to THF in the mixture. The confocal microscopy images are used to characterize the average pore size and the pore size distribution in the structures. Dogbone samples following the ASTM standard D412 are cut from the porous plates by utilizing a designed cutting die and mechanical press. The specimens are tested under tensile loading to evaluate the effect of the pore size on the mechanical properties of the porous structure. The results demonstrate the ability of the proposed solvent evaporation method to control the stiffness of the porous structure by changing the non-solvent to the solvent ratio in the mixture.

Study on Environmental Materials with Pore Size and Photocatalytic Activity of Porous TiO2-Al2O3 Photocatalyst

2013 ◽  
Vol 700 ◽  
pp. 67-70 ◽  
Author(s):  
Rui Ma ◽  
Wen Jie Zhang
Keyword(s):  
Methyl Orange ◽  
Photocatalytic Degradation ◽  
Pore Size ◽  
Pore Volume ◽  
Average Pore Size ◽  
Sol Gel ◽  
Total Pore Volume ◽  
Degradation Process ◽  
Order Kinetic ◽  
Average Pore

A novel porous TiO2-Al2O3 composite as a kind of environmental material was prepared by sol-gel method. The pore size distribution is not even in the whole pore size range. When pore size is 7.049 nm, the maximum pore volume of the material is 0.06627 cm3·g-1. The average pore size for the material is 14.56 nm and the total pore volume is 0.3945 cm3·g-1, as calculated from BJH method. Photocatalytic degradation of methyl orange can be regarded as following first order kinetic reaction. After 90 min of reaction, methyl orange degradation on the material was 77.0% and the total dye decoloration rate was 95.1%, containing both adsorption and photocatalytic degradation. The intensities of both peaks in visible and UV regions decreased sharply during photocatalytic degradation process.

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