Based On The Ultrasonic Frequency Spectrum Analysis And Study The Formation Process Of Soft Matter Gel

Soft material has been widely used in all aspects of their lives. The application of gelatin gel and acrylamide gel which are the typical representative of soft matter gel has shown an impressive increase. The mechanism of the gelation of gel has been concerned for the researchers. Numerous theory researches and experiment researches have been done by researchers. How to use a nondestructive method to detect the gelation of gel dynamically and online? The ultrasonic measurements are operated simply and don’t damage the sample. Comparing with the optical detection method, ultrasonic testing method can penetrate optically opaque mixtures and provide useful information up to high concentrations. Ultrasonic spectrum analysis method extracts rich information from internal structure of material in frequency domain which was contained in the ultrasonic wave, the information has no obvious difference in time domain. The gelation of gelatin and acrylamide was studied using ultrasound reflection method, the experimental data was processed using ultrasonic spectrum analysis method, which can deduce the changes of internal microstructure and molecular conformation in the solution. The main works and results were described as follows:(1) The gelation of glutaraldehyde cross-linked gelatin was tested using ultrasound reflection method. The influence factors of the concentration of the gelatin solution, the volume of crosslinking agent,the frequency of the probe and the pH value of gelatin have been studied in gelation. The curves with time of the peak value of frequency spectrum and the offsets of the center frequency were acquired. The influence of temperature was studied in gelation with different volumes of NIPAM adding in the solution. The curves with temperature of the peak values of frequency spectrums and the offset of center frequencies were acquired. The conclusion from the experiment as follows:the ultrasonic velocities weren’t changed in gelation of the same gelatin solution. The ultrasonic velocities didn’t change when the concentration of the gelatin solution, the volume of the crosslinking agent were changed. The bigger the concentration of the gelatin solution is, the sooner of gelation and the greater of the ultrasonic attenuation. The more volume of glutaraldehyde, the smaller the peak value of frequency spectrum and the bigger the offset of the central frequency is. The concentration of gelatin solution and the volume of crosslinking agent are important factors in gel gelation, which decides the quality and property of gelatin gel. The central frequencies of detection probe have influences on gelation. The probe with1.25MHz central frequency wasn’t sensitive to gelation. The ultrasonic attenuation is larger when the probe with5.0MHz is used. The detection effect is optimum when the probe with2.5MHz was used. The pH value of the gelatin solution also has influences to gel gelation. The higher the pH value of gelatin solution is, the larger the peak values of ultrasonic echo signal frequency spectrum. The offset of frequency spectrum is small and the molecules in gelatin solution have a open coil conformation. When the pH value of the gelatin solution was low, the peak values of ultrasonic echo signal frequency spectrum were small. The offsets of frequency spectrum were large and the molecules in gelatin solution have a compact coil conformation. The change of gel which was added NIPAM solution versus temperature was detected. The larger the volume of NIPAM solution, the stronger the phase transition temperature sensitivity is. This phase transition is a gradual process. The pure gelatin gel has no phase change with temperature.(2) The gelation of acrylamide gel was detected by using ultrasonic frequency spectrum analysis method, which the acrylamide solution was affected by ammonium persulfate solution and crosslinking agent glutaraldehyde. The influence factors of the concentration of the acrylamide solution, the volume of crosslinking agent and the frequency of the probe were studied in gelation. The conclusion from the experiment as follows:the bigger the concentration of acrylamide solution is, the smaller the peak value of ultrasonic echo signal frequency spectrum in the gelation. The greater the volume of crosslinking agent is, the larger the offset of ultrasonic echo signal spectrum center frequency, the greater the ultrasonic attenuation. The bigger the frequency of the ultrasonic testing probe is, the greater the variation of the peak value of frequency spectrum.