Ultrasonication is very effective in dispersing alumina and barium titanate slurries. When optimum conditions are used, very short durations (2 to 3 min) are enough to achieve well-dispersed, stable suspensions. 相似文献
The axial and radial distributions of solid and gas holdups were investigated in an air‐water‐glass bead circulating fluidized bed (GLSCFB) using a new ultrasonic technique, with a new method based on signal fluctuations. The cross‐sectional averaged gas and solid holdups measured at two axial positions appear to be similar at all studied operating conditions. The radial non‐uniformity decreases with increasing liquid velocity but does not change with an increasing solid circulating rate. The radial distribution of gas holdup was more uniform for 1.3 mm beads than for 433 µm glass beads. 相似文献
A method of measurement of solids holdup in a three-phase reactor by analyzing the shape and the phase lag or lead of an ultrasonic wave has been proposed. The solids holdup in a solids-dilute three-phase fluidized bed could be measured without being affected by the presence of gas bubbles. The experimental values of solids axial dispersivity measured by the ultrasonic technique are in reasonable agreement with an empirical correlation of previous data obtained by other methods. The possibility of the application of the ultrasonic technique to the measurement of solids holdup in a three-phase fluidized bed has been suggested. 相似文献
Summary: A new technique, ultrasonically initiated in situ emulsion polymerization, was employed to prepare intercalated polystyrene/Na+‐MMT nanocomposites. FTIR, XRD, and TEM results confirm that the hydrophobic PS can easily intercalate into the galleries of hydrophilic montmorillonite via ultrasonically initiated in situ emulsion polymerization, taking advantages of the multi‐effects of ultrasonic irradiation, such as dispersion, pulverization, activation, and initiation. Properly reducing SDS concentration is beneficial to widen the d‐spacing between clay layers. However, the Na+‐MMT amount has little effect on the d‐spacing of nanocomposites. The glass transition temperature of nanocomposites increased as the percentage of clay increased, although the average molecular weight of PS decreased, and the decomposition temperature of the 1obtained nanocomposites moves to higher temperature.
TEM of PS/Na+‐MMT nanocomposite prepared by ultrasonically initiated in situ emulsion polymerization. 相似文献
The ultrasonic velocity and density measurements of europium soaps in a mixture of benzene and methanol (3:2, vol/vol) were
used to evaluate various acoustic parameters and molar volume and to determine the critical micelle concentration. The results
showed that the ultrasonic velocity, specific acoustic impedance, molar sound velocity, and molar compressibility increase,
and intermolecular free length, adiabatic Compressibility, and relative association decrease with increasing concentration
and chainlength of the soap. The results were interpreted in terms of soap-solvent interaction. 相似文献
A novel sol–gel process is used to synthesize mesoporous silica–alumina catalysts with controlled pore size distribution without using templates or pore-regulating agents. The nitrogen sorption analysis shows that the synthesized materials have high specific surface area in the range 587–692 m2/g and similar mesoporous distribution within 2–11 nm. Ultrasound is applied to prepare precursor silica–alumina sol with narrow particle diameter distribution. By calculation, it is found that ultrasonic treatment is able to provide 22.94 kJ/mol energy, which is just in accordance with the weak bond's bonding energy. Based on the calculation result, it is proposed that the role of ultrasonic treatment followed by acid peptization is to provide energy to break down the weak bonds. After gelation, the regular and close packing of similar-sized sol particles is capable of formation of controlled-sized interstices which are the precursors of mesopores. Solid-state 27Al MAS NMR and TEM are used to characterize the samples' structure and particle morphology. They show that most of the aluminum is located in the tetrahedral position in the present materials. According to TEM results, it is shown that the synthesized materials have spherical particles with size of about 15 nm. 相似文献
An ultrasonic technique was developed to study the crystallization process of edible fats on-line. A chirp wave was used instead
of the conventional pulser signal, thus achieving a higher signal-to-noise ratio. This enabled measurements to be made in
concentrated systems [≈20% solid fat content (SFC)] through a 8.11-cm thick sample without significant signal loss. Fat samples
were crystallized at 20, 25, and 30°C at a constant agitation rate of 400 rpm for 90 min. The crystallization process was
followed by ultrasonic spectroscopy and a low-resolution pulsed nuclear magnetic resonance spectrometer. Specific relationships
were found between ultrasonic parameters [integrated response, time of flight (TF), and full width half maximum] and SFC.
TF, which is an indirect measurement of the ultrasonic velocity (v), was highly correlated to SFC (r2>0.9) in a linear fashion (v=2.601 SFC+1433.0). 相似文献