Instrumentation colloidal silica

Photomultipliers are used to measure the intensity of the scattered light. The output is compared to that of a second photocell located in the light trap which measures the intensity of the incident beam. In this way the ratio [J q is measured directly with built-in compensation for any variations in the source. When filters are used for measuring depolarization, their effect on the sensitivity of the photomultiplier and its output must also be considered. Instrument calibration can be accomplished using well-characterized polymer solutions, dispersions of colloidal silica, or opalescent glass as standards. 

The characterization of colloidal silica has been the subject of numerous studies involving both physical and chemical methods. Iler (I) summarized many of the available methods, with particular emphasis on chemical approaches. Other more recent reviews (2-4) featured instrumental methods that are useful for characterizing silica sols and other colloids. This chapter describes some of the relatively new separations... 

Cheang-Wong, J.C. Morales, U. Resendiz, E. Lopez-Suarez, A. Rodriguez-Femandez, L. 2008. Dependence of the MeV ion-induced deformation of colloidal silica particles on the irradiation angle. Nuclear Instruments and Methods in Physics Research, Section B, 266(12-13) 3162—3165. 

The instrument response function, sometimes called the lamp function, is the resp( ise of the instrument to a zero-lifetime san le. This curve is typically collected using a tUlute scattering solution such as colloidal silica (Ludox) and no emission filtor. This decay represents the shortest time jnrofile which can be measured by the instrument. The lamp function in Hgure 4.8 is quite narrow. 

During the last two decades, dynamic light scattering has evolved into a major characterisation technique for colloidal suspensions. A recent interlaboratory study into the characterisation of colloidal silica (Braun et al. 2011) showed that state-of-the-art DLS instrumentation facilitate a highly reproducible and very reliable acquisition of correlation function and corresponding mean particle size cum-... 

Claesson and Ohman (137) described an automatic recording light-scattering instrument which was standardized with colloidal silica. 

The high resolution of SdFFF permits excellent discrimination between particle sizes. Narrow particle-size distributions with a 10-15% difference in size produce bands that can be resolved to baseline. This high level of resolution produces accurate size measurements. Computer-con-trolled SdFFF instruments are capable of data with excellent reproducibility—results with < 5% deviation (relative) are common. A typical analysis time for a silica sol is about 0.5 h. The SdFFF method can be applied to a wide range of colloidal particles, both inorganic and organic. 

Carraher CE Jr (2005) General topics silica aerogels-properties and uses. Polymer News, 30(12), 386-388 Carraher CE Jr (2005) Silica aerogels - synthesis and history. Polymer News, 30 62-64 Pajonk GM (2003) Some applications of silica aerogels. Colloid and Polymer Science, 281 637—651 Akimov YK (2003) Fields of Application of Aerogels (Review) Instruments and Experimental Techniques (Translation of Pribory i Tekhnika Eksperimenta), 46 287-299... 

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