Pore Modification in Porous Ceramic Membranes With Sol-Gel Process and Determination of Gas Permeability and Selectivity

2010 ◽  
Vol 287 (1) ◽  
pp. 135-142 ◽  
Author(s):  
F. Nihal Tüzün ◽  
Ersel Arçevik
Keyword(s):  
Gas Permeability ◽  
Porous Ceramic ◽  
Sol Gel ◽  
Ceramic Membranes ◽  
Sol Gel Process

Stochastic Reconstruction and Permeation of Ceramic Membranes Prepared by the Sol-Gel Method

2002 ◽  
Vol 752 ◽  
Author(s):  
E. S. Kikkinides ◽  
V. T. Zaspalis ◽  
V. N. Burganos
Keyword(s):  
Mechanical Stability ◽  
Sol Gel ◽  
Three Dimensional ◽  
Ceramic Membranes ◽  
Momentum Equation ◽  
Void Space ◽  
Sol Gel Process ◽  
Mesoporous Membranes ◽  
Permeation Properties ◽  
Good Agreement

ABSTRACTIn the present work we study the relation between structural and permeation properties of ceramic membranes made by the sol-gel process. For this purpose, we have developed γ-Al2O3 mesoporous membranes via the sol-gel route, on top of multi-layer asymmetric α-Al2O3 macroporous supports, to induce mechanical stability. Subsequently, we employ stochastic techniques to generate three-dimensional reconstructions of the membrane and the support that share the basic structural properties of the original materials determined directly from SEM and TEM studies. The permeability of each material is estimated by solving numerically the momentum equation in the void space of the reconstructed images. The very good agreement between predicted and experimentally measured permeability values, without the need to resort to any fitting parameter, renders the proposed reconstruction methodology quite promising for reliable characterization and representation of the pore structure of this type of membranes.

Voltammetric determination of aluminum(III) using a reagentless sensor fabricated by sol–gel process

2004 ◽  
Vol 99 (2-3) ◽  
pp. 468-473 ◽  
Author(s):  
Junwei Di ◽  
Shuping Bi ◽  
Tianyu Yang ◽  
Ming Zhang
Keyword(s):  
Sol Gel ◽  
Voltammetric Determination ◽  
Sol Gel Process

Inorganic-Organic Hybrid Composites

2005 ◽  
Author(s):  
James E. Mark ◽  
Harry R. Allcock ◽  
Robert West
Keyword(s):  
Low Temperatures ◽  
Hybrid Composites ◽  
Porous Ceramic ◽  
Sol Gel ◽  
Average Diameter ◽  
Ceramic Coatings ◽  
Organic Hybrid ◽  
Sol Gel Process ◽  
The One ◽  
Hydrolysis Of

A relatively new area that involves silicon-containing materials is the synthesis of “ultrastructure” materials, that is materials in which structure can be controlled at the level of around 100 Å. An example of such a synthesis is the “sol-gel” hydrolysis of alkoxysilanes (organosilicates) to give silica, SiO2. The reaction is complicated, involving polymerization and branching, but a typical overall reaction may be written . . . Si(OR)4 + 2H2O → SiO2 + 4ROH (1) . . . where the Si(OR)4 organometallic species is typically tetraethoxysilane (tetraethylorthosilicate) (TEOS, with R being C2H5). In this application, the precursor compound is hydrolyzed and then condensed to polymeric chains, the chains become more and more branched, and finally a continuous highly swollen gel is formed. It is first dried at moderately low temperatures to remove volatile species, and then is fired into a porous ceramic object. It can then be densified, if desired, and machined into a final ceramic part. Not surprisingly, the production of ceramics by this novel route has generated a great deal of interest. Its advantages, over the usual “heat-and-beat” (e.g., sintering) approach to ceramics, is (i) the higher purity of the starting materials, (ii) the relatively low temperatures required, (iii) the possibility of controlling the ultrastructure of the ceramic (to reduce the number of microscopic flaws that lead to brittleness), (iv) the ease with which ceramic coatings can be formed, and (v) the ease with which ceramic alloys can be prepared (for example, by hydrolyzing solutions of both silicates and titanates). This approach has been used to form ceramic-like phases in a wide variety of polymers. The one which has been studied the most in this regard is poly(dimethylsiloxane) (PDMS), the semi-inorganic polymer featured extensively in Chapter 4. This is due to PDMS being in the class of relatively weak elastomers most in need of reinforcement, and being capable of easily absorbing the precursor materials generally used in the sol-gel process. The same hydrolyses can be carried out within a polymeric matrix to generate particles of the ceramic material, typically with an average diameter of a few hundred angstroms. The polymer typically has end groups, such as hydroxyls, that can participate in the hydrolysis-condensation reactions.

COTTON FABRIC PROPERTIES WITH WATER-REPELLENT FINISHING VIA SOL–GEL PROCESS

2008 ◽  
Vol 15 (06) ◽  
pp. 833-839 ◽  
Author(s):  
CHAOXIA WANG ◽  
MAO LI ◽  
MIN WU ◽  
LI CHEN
Keyword(s):  
Tensile Strength ◽  
Cotton Fabric ◽  
Abrasion Resistance ◽  
Gas Permeability ◽  
Sol Gel ◽  
Cotton Fabrics ◽  
Water Repellent ◽  
Sol Gel Process ◽  
Dyed Fabrics ◽  
Water Repellence

The properties of the cotton fabric with water-repellence finishing by sol method with the hexadecyltrimethoxysilane as additive were observed. The cotton fabrics were immersed in the prepared sols with double dip and double nip dried at 90°C, annealed at 160°C for 3 min. The water repellence and the physical properties such as gas permeability, bending properties, beetling properties, tensile strength, elongation at break, abrasion resistance, and anti-crease properties of the cotton fabrics were investigated. The results showed that anti-crease and tensile strength were improved. However, the abrasion resistance of the cotton fabrics decreased in some way. Both the bending and beetling properties measurement proved that the handle of the treated cotton fabrics changed stiffness. For the dyed fabrics by the water-repellent finishing, the hue was slightly changed, the deeper color was achieved. There is no adverse effect for treated fabric by water-repellent finishing on the fastness.

EFFECT OF ANNEALING TEMPERATURE ON THE OPTICAL AND STRUCTURAL PROPERTIES OF DIP-COATED Al2O3 THIN FILMS PREPARED BY SOL–GEL ROUTE

2005 ◽  
Vol 12 (05n06) ◽  
pp. 793-797 ◽  
Author(s):  
F. E. GHODSI ◽  
M. MAFAKHERI ◽  
A. NOVINROOZ
Keyword(s):  
Thin Films ◽  
Structural Properties ◽  
Annealing Temperature ◽  
Sol Gel ◽  
Dip Coating ◽  
X Ray Diffraction ◽  
Glass Substrates ◽  
Sol Gel Process ◽  
Dip Coating Technique

Thin films of Al 2 O 3 were prepared by the sol–gel process. Dip-coating technique was used for deposition of the Al 2 O 3 thin films onto glass substrates. Optical and structural properties of the films were investigated with respect to the annealing temperature (100–500°C). The structure of these films was determined by X-ray diffraction (XRD). Scanning electron microscopy (SEM) was performed for the analysis of surface morphology. For determination of the optical constants of Al 2 O 3 thin films, UV-Visible spectrophotometry measurements were carried out. Annealing temperature affects the structural and optical properties of the Al 2 O 3 thin films. The refractive index and extinction coefficient of the films at 550 nm wavelength increase from 1.56 to 1.66, and from 3.41 × 10-5 to 5.54 × 10-5, respectively while optical band gap and thickness of the films decrease from 4.15 eV to 4.11 eV, and 360 nm to 260 nm, respectively, by increasing annealing temperature from 100°C to 500°C.

scholarly journals Multinuclear Magnetic Resonance Study on Aluminium Sec-butoxide Chelated with Ethyl Acetoacetate in Various Amounts

2019 ◽  
Vol 92 (1) ◽  
pp. 17-28 ◽  
Author(s):  
Stanislav Kurajica ◽  
Gregor Mali ◽  
Vilko Mandić ◽  
Iva Minga
Keyword(s):  
Ethyl Acetoacetate ◽  
Sol Gel ◽  
Gain Control ◽  
Spectroscopic Techniques ◽  
27Al Nmr ◽  
One Dimensional ◽  
Sol Gel Process ◽  
Rapid Hydrolysis ◽  
First Time

Reactive aluminum alkoxide (ASB, aluminium sec-butoxide) was chelated using β-diketone (EAA, ethyl acetoacetate) in order to gain control over rapid hydrolysis in the course of the sol-gel process. Derived chelates were analysed using several NMR spectroscopic techniques: one-dimensional 1H, 13C, 27Al NMR and two-dimensional COSY, HSQC and DOSY. The NMR analysis enabled identification of the formed chelate species, as well as determination of their quantitative relationships. Several complexation products were observed: tris-chelated monomer, Al(EAA)3, bis-chelated dimmer, Al2(OnBu)4(EAA) 2, tris-chelated dimmer, Al2(OnBu)3(EAA)3, tetra-chelated dimmer, Al2(OnBu)2(EAA)4, and monochelated trimer, Al3(OnBu)8(EAA). Of the formed oligomer compounds, this is the first evidence of Al2(OR)3L3 in any alkoxide and β-ketoester or β-diketone combination. Aluminium sec-butoxide and ethyl acetoacetate complexes Al2(OnBu)4(EAA) 2 and Al2(OnBu)2(EAA)4 were also observed for the first time. With the increase of the EAA/ASB ratio the coordination of aluminium shifts towards six, whereas above the EAA/ASB ratio of 2.5 solely six-coordinated aluminium exists.

scholarly journals Effect of coating steps on uniformity and gas permeability of mesoporous layers in ceramic membranes

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Shahram G. Pakdehi ◽  
Elham Rahimi ◽  
Korosh Shafiei
Keyword(s):  
Electron Microscopy ◽  
Pore Radius ◽  
Gas Permeability ◽  
Sol Gel ◽  
Porous Silica ◽  
Ceramic Membranes ◽  
Flow Mechanism ◽  
Sem Images ◽  
Knudsen Flow ◽  
Scanning Electron

AbstractPorous silica, silica-cobalt, silica-zirconia and zirconia membranes were synthesized by the sol-gel method. Multi-step coating (two, six, and ten steps) was used to reduce the defectiveness of the mesoporous layer. Scanning electron microscopy (SEM) images indicated that an increase in the number of coating steps improved the mesoporous layer quality. The results obtained from gas permeability tests with nitrogen and argon, however, indicated a reduction in the gas permeability with increasing coating steps. The reduction in gas permeability from two to six coating steps was more pronounced than from sixto ten- coating steps. It was found that six-step coating was economically justified in obtaining a uniform mesoporous layer. The results of pore radius calculations by Knudsen flow mechanism revealed that the pores in the silica, silica-cobalt, and zirconia membranes were in the mesoporous range. The sols with a mean particle size more than 100 nm are not recommended for synthesis of mesoporous layer free of defects. Furthermore, the type of acid used as a catalyst is also important in obtaining a layer without defectiveness.

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