Production of Sols from Aggregated Titania Precipitates

1992 ◽  
Vol 271 ◽  
Author(s):  
John. R Bartlett ◽  
James L. Woolfrey
Keyword(s):  
Hydrodynamic Radius ◽  
Dlvo Theory ◽  
Correlation Spectroscopy ◽  
Radius Of Gyration ◽  
Chemical Methods ◽  
Photon Correlation ◽  
Solids Loading ◽  
Solids Concentration ◽  
Colloidal Species ◽  
Hydrolysis Of

ABSTRACTTitania and titania/zirconia sols, with solids loadings exceeding 1000 g dm3, have been prepared on a 10 kg scale by chemical methods involving the hydrolysis of an appropriate mixture of alkoxides, followed by peptisation with dilute nitric acid. The rate of peptisation of the hydrolysates was determined by static light-scattering and photon-correlation spectroscopy, enabling the hydrodynamic radius, the radius of gyration and the fractal dimension of colloidal species to be monitored as a function of peptisation time.The peptisation kinetics were influenced by a range of factors including the initial solids loading, the acid concentration, the reaction temperature and the age of the alkoxide hydrolysate. Hydrolysate peptisation is first order with respect to concentration of acid and exhibited a non-integer reaction rate order (complex mechanism) with respect to solids concentration. Sols produced from freshly-precipitated hydrolysate peptised at a faster rate than aged precipitates but slowly re-aggregated after peptising, yielding “equilibrium” aggregate sizes often exceeding 100 nm. This effect was not observed in sols produced from aged hydrolysate. These differences are interpreted using DLVO theory.

scholarly journals SYNTHESIS OF BIOLOGICALLY ACTIVE COPPER SOLS IN PRESENCE OF NITRILOTRI(METHYLENE)PHOSPHONIC ACID

2018 ◽  
Vol 59 (6) ◽  
pp. 112
Author(s):  
Ekaterina V. Erokhina ◽  
Valentina N. Galashina ◽  
Tatiana N. Bogachkova ◽  
Natalia S. Dymnikova ◽  
Andrei P. Moryganov
Keyword(s):  
Copper Nanoparticles ◽  
Phosphonic Acid ◽  
Hydrodynamic Radius ◽  
Photon Correlation Spectroscopy ◽  
Sodium Tetrahydroborate ◽  
Correlation Spectroscopy ◽  
Biologically Active ◽  
Photon Correlation ◽  
Favorable Conditions ◽  
Titratable Alkalinity

In this work the conditions for synthesis of copper nanoparticles by sodium tetrahydroborate in the presence of NTF are optimized. It is proved that the most favorable conditions for the reduction of copper in the solutions with its concentration of 2.0∙10-2 mol/l, are created when the concentration of tetrahydroborate sodium is three to four- fold exceeded, the titratable alkalinity is 5.3∙10-2-10.3∙10-2 mol/l, the temperature is 60 °C and the ratio of cation and chelate is equimolar. The method of photon correlation spectroscopy has confirmed the obtaining of copper nanoparticles with hydrodynamic radius of 25 nm, including shell stabilizers. The immutability of the size of bass for at least 72 h has been revealed.

scholarly journals The effect of guanidinium chloride on the behaviour of human cervical-mucus glycoproteins. Evidence for unfolding regions of ordered structure in 6M-guanidinium chloride

1984 ◽  
Vol 221 (2) ◽  
pp. 499-504 ◽  
Author(s):  
J K Sheehan ◽  
I Carlstedt
Keyword(s):  
Frictional Coefficient ◽  
Correlation Spectroscopy ◽  
Cervical Mucus ◽  
Random Coil ◽  
Radius Of Gyration ◽  
Ordered Structure ◽  
Guanidinium Chloride ◽  
Photon Correlation ◽  
The Individual ◽  
Mucus Glycoproteins

The macromolecular properties of cervical-mucus glycoproteins (mucins) were studied as a function of the concentration of guanidinium chloride with conventional light-scattering, photon-correlation spectroscopy and sedimentation-velocity centrifugation. No evidence for an association of the mucins in 0.2M-NaCl as compared with 6M-guanidinium chloride was found at mucin concentrations below approx. 0.5 mg/ml. However, an increase in the frictional coefficient and in the radius of gyration occurred with increasing concentrations of guanidinium chloride, in particular between 4 M and 6 M, suggesting an expansion of the individual macromolecule. The change in the particle-scattering function is consistent with a transition from a ‘stiff’ random coil in 0.2 M-NaCl into a more flexible one in 6 M-guanidinium chloride. We suggest that the mucins contain regions of ‘ordered’ structure which can undergo a reversible ‘unfolding’ analogous to the behaviour of a conventional globular protein exposed to a denaturing solvent. Such regions might carry sites for specific interactions between mucins and/or be decisive for their conformation and macromolecular properties in physiological solvents.

scholarly journals Adjustment of Hydrophobic Properties of Cellulose Materials

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1241
Author(s):  
Michael Ioelovich
Keyword(s):  
Ester Group ◽  
Hydroxyl Groups ◽  
Chemical Methods ◽  
Hydrophobic Properties ◽  
Cellulose Esters ◽  
Cellulose Modification ◽  
Polar Groups ◽  
Polar Substituents ◽  
Hydrolysis Of ◽  
Cellulose Materials

In this study, physicochemical and chemical methods of cellulose modification were used to increase the hydrophobicity of this natural semicrystalline biopolymer. It has been shown that acid hydrolysis of the initial cellulose increases its crystallinity, which improves hydrophobicity, but only to a small extent. A more significant hydrophobization effect was observed after chemical modification by esterification, when polar hydroxyl groups of cellulose were replaced by non-polar substituents. The esterification process was accompanied by the disruption of the crystalline structure of cellulose and its transformation into the mesomorphous structure of cellulose esters. It was found that the replacement of cellulose hydroxyls with ester groups leads to a significant increase in the hydrophobicity of the resulting polymer. Moreover, the increase of the number of non-polar groups in the ester substituent contributes to rise in hydrophobicity of cellulose derivative. Depending on the type of ester group, the hydrophobicity increased in the following order: acetate < propionate < butyrate. Therefore, tributyrate cellulose (TBC) demonstrated the most hydrophobicity among all studied samples. In addition, the mixed ester, triacetobutyrate cellulose (TAB), also showed a sufficiently high hydrophobicity. The promising performance properties of hydrophobic cellulose esters, TBC and TAB, were also demonstrated.

scholarly journals From Femtoseconds to Hours–Measuring Dynamics over 18 Orders of Magnitude with Coherent X-rays

2021 ◽  
Vol 11 (13) ◽  
pp. 6179
Author(s):  
Felix Lehmkühler ◽  
Wojciech Roseker ◽  
Gerhard Grübel
Keyword(s):  
Time Scales ◽  
Free Electron Laser ◽  
Photon Correlation Spectroscopy ◽  
Signal To Noise Ratio ◽  
Coherent Scattering ◽  
Correlation Spectroscopy ◽  
X Rays ◽  
Photon Correlation ◽  
X Ray ◽  
Scattering Technique

X-ray photon correlation spectroscopy (XPCS) enables the study of sample dynamics between micrometer and atomic length scales. As a coherent scattering technique, it benefits from the increased brilliance of the next-generation synchrotron radiation and Free-Electron Laser (FEL) sources. In this article, we will introduce the XPCS concepts and review the latest developments of XPCS with special attention on the extension of accessible time scales to sub-μs and the application of XPCS at FELs. Furthermore, we will discuss future opportunities of XPCS and the related technique X-ray speckle visibility spectroscopy (XSVS) at new X-ray sources. Due to its particular signal-to-noise ratio, the time scales accessible by XPCS scale with the square of the coherent flux, allowing to dramatically extend its applications. This will soon enable studies over more than 18 orders of magnitude in time by XPCS and XSVS.

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