𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Contribution to the Determination of Kinetic Parameters of the Sol–Gel Transformation by Rheological Measurements

✍ Scribed by Wolfram Vogelsberger; Andreas Seidel; Rolf Fuchs

Publisher
Elsevier Science
Year
2000
Tongue
English
Weight
71 KB
Volume
230
Category
Article
ISSN
0021-9797

No coin nor oath required. For personal study only.

✦ Synopsis

The system tetraethoxysilane(TEOS)-water-ethanol has been studied by rheological measurements. Different molar ratios of TEOS : water (1 : 4, 1 : 10, and 1 : 20) are studied at different temperatures (30, 40, and 50 • C). The dynamic viscosity (rotating mode) at a constant shear rate (100 s -1 ) and the elastic and viscous moduli (oscillating mode) at a constant frequency (1 Hz) are determined. The viscosity-time curves are evaluated by application of a nucleation and particle growth model. Good agreement between experiments and theory is observed. The model allows the determination of the complex rate constant of silica precipitation. The temperature-dependent measurements gave the possibility to determine the apparent energy of activation by common methods. The results are in agreement with data from the literature. The gel time defined as intersection point of elastic and plastic moduli and its dependence on temperature are evaluated by the Smoluchowski model. The energy of activation for the coagulation was determined and found to be in the correct order of magnitude.

📜 SIMILAR VOLUMES

Contribution of HRTEM to the characteriz
Contribution of HRTEM to the characterization of silica-incorporated copper-oxide catalysts prepared by the Sol-Gel technique
✍ Benaïssa, M.; Diaz, G. 📂 Article 📅 1998 🏛 John Wiley and Sons 🌐 English ⚖ 458 KB

The aim of the present work is a structural characterization study of silicaincorporated copper-oxide (CuO-SiO 2 ) catalysts using HRTEM. The catalysts were prepared by the sol-gel synthetic route. Two calcined catalysts (at 400°C and 800°C, respectively) were analyzed before and after the ''NO x ϩ

Kinetics of the 1,5-dipolar cyclization
Kinetics of the 1,5-dipolar cyclization of 2-Vinylpyridinium ylides to Indolizines. Determination of rate parameters by laser flash photolysis
✍ Michael T. H. Liu; Yuri N. Romashin; Roland Bonneau 📂 Article 📅 1994 🏛 John Wiley and Sons 🌐 English ⚖ 354 KB

Nanosecond laser flash photolysis (A = 355 nm) of an aqueous solution of 3-chloro-3-p-chlorophenyldiazirine in isooctane produces a transient absorption at 310 nm due to the formation of the carbene. In the presence of 2-vinylpyridine, a second transient with a broad absorption band peaking at 520 n

Determination of kinetic parameters of f
Determination of kinetic parameters of fermentation processes by a continuous unsteady-state method: Application to the alcoholic fermentation of D-xylose by Pichia stipitis
✍ H. Domínguez; M. N. Núñez; R. Chamy; J. M. Lema 📂 Article 📅 1993 🏛 John Wiley and Sons 🌐 English ⚖ 325 KB 👁 3 views

A quick technique for determination of kinetic parameters of fermentation processes is proposed and applied to the transformation of D-xylose into ethanol by Pichia stipitis. The commonly used method to evaluate these parameters is based on achieving several steady states. In the proposed procedure,

An Isothermal Titration Calorimetric Met
An Isothermal Titration Calorimetric Method to Determine the Kinetic Parameters of Enzyme Catalytic Reaction by Employing the Product Inhibition as Probe
✍ Lifeng Cai; Aoneng Cao; Luhua Lai 📂 Article 📅 2001 🏛 Elsevier Science 🌐 English ⚖ 68 KB

An isothermal titration calorimetric (ITC) method was developed to measure the kinetic parameters of ribonuclease A catalytic hydrolysis of cytidine 2',3'-cyclic monophosphate. Employing the inhibition of product as a probe, the K(m), K(i), k(c), and DeltaH(m) can be determined by two simple calorim

Fourier transform ion cyclotron resonanc
Fourier transform ion cyclotron resonance determination of lithium cation basicities by the kinetic method: upward extension of the scale to phosphoryl compounds
✍ Buncel, Erwin; Chen, Austin; Decouzon, Michèle; Fancy, Sally Ann; Gal, Jean-Fran 📂 Article 📅 1998 🏛 John Wiley and Sons 🌐 English ⚖ 275 KB 👁 2 views

Lithium cation basicities (LCBs) are reported for a series of 16 phosphoryl compounds, including phosphine oxides, phosphinates, phosphonates and phosphates. The experiments were carried out using the kinetic method applied to Fourier transform ion cyclotron resonance mass spectrometry. Two di †eren