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Experimental Study on Multi-parameter in Colloid and Design of Multi-channel Simultaneous Data Acqui

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Tutor: SuMingXu
School: University of Shanghai for Science and Technology
Course: Thermal Power Engineering
Keywords: Colloid,Multi-parameter,Nanoparticles,Ultrasoniccomputed tomography
CLC: TP274.2
Type: Master's thesis
Year:  2011
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Colloidal nanoparticles have been paid more and more attenation in recent years.The paricle size density and concentration of disperse phase in the colloid are showinggreat importance during the course of researing. Hence, it is significant to determineparticle size density and concentration of disperse phase in the colloid.Therefore, an approach of determining the three parameters based on ultrasound hasbeen developed in the first part of this paper. Meanwhile, an experimental system hasalso been established which contains two parts. One is hardware system, the other issoftware system.1. The multi-parameter measurement system is divided into two parts. One ishardware system, the other is software system. There are pulse ultrasonictransmitter/received device, NI-5114high-speed data acquisition boards, sample cell,ultrasonic transducers and computer in the hareware system. And the software systemincludes data acquisition, Fast Fiourier transform, curve fitting and parameterscalculation programs developed based on LabVIEW. The measurement system is stableand reliable with the measurement range of particle size is from10nm-100um, that ofconcentration is up to40%and there is no specific requirements on density.2£®Two samples, nano-ATO and sulfur, have been used in the experiments andthere are four concentrations in each sample.The results show that:1.It is feasible toobtain particle size density and concentration based on ultrasound.2. The result ofparticle size by ultrasonic attenuation spectra and the other approaches agrees very well.It shows that it is reasonable to obtain the particle size of nanoparticles using ultrasonicattenuation spectra.3The error of density is within1%. However, that of concentrationis less than10%which is much larger than error of density. It is mainly due to theconcentration dependent on the density.3£®The effects of using different excitation forms on particle size characterizationhave been discussed. The research shows that:1.The acoustic attenuation of pulsed andcontinuous excitation have the same trendence.2. The value of acoustic attenuationexcitated by continuous-wave are10%larger than that of pulsed-wave.3. The D10, D50and D90of continuous wave excitation is5%larger than that of pulsed wave excitationbecause of the complex sound field of measurement area. In summary, particle sizecharacterization by different excitation form shows a high consistency. 4£®At the same time, the role of ultrasonic dispersion in particle aggregation and thestability of colloid before and after ultrasonic dispersion have been also discussed indetails. Therefore, a real-time cacquisition program has been developed based onLabVIEW and a lot of experiments have been carried out with the program then theacoustic attenuation and particle size distribution has been determined.The results showthat: The acoustic attenuation valus after ultrasonic dispersion are less than that of pre-dispersion. And its D10, D50are smaller than that of pre-dispersion. It means that theaggregated particles have been separated by ultrasonic cavitation effect. The acousticattenuation and particle size are becoming larger and larger with the time goes by. Tosum up, ultrasonic dispersion can separate the aggregated particles. But the colloid isnot stable in thermodynamics due to a lot heat generated during ultrasonic dispersion.Hence, the particles will aggregate again.The apparatus mentioned above is fit for the static state. Howerve, There are lots ofproblems related to the two-phase flow and milti-phase flow. Tomography is consideredas a better solution of two-phase flow measurement. Hence, a mutit-channel dataacquisition system has been developed, including fan-beam ultrasonic transducer array,a weak signal amplifier and a multi-channel acquisition program, which can be used inultrasonic compted tomography.5. A transducer array has been designed which contains16fan-beam ultrasonictransducers. And it can be abtained240independent data in an experiment.6. A weak signal amplifier has also been developed to connect with the transducerarray and data acquition board which contains impedance match circuit, two-stageamplifier circuit and filter circuit.7. A multi-channel synchronous data acquition program has been developed withtwo data acquition board in this paper. A mutit-channel data acquisition system hasbeen developed with the three parts and several experiments has been carried out withthis system.
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