Method and equipment for measuring diffusion spectrum in non-ergodic system with high-speed charge coupled imaging system
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A charge-coupled imaging and diffusion spectroscopy technology, which can be used in measurement devices, scattering characteristics measurement, radiation control devices, etc., and can solve problems such as the inapplicability of single-mode fibers
Inactive Publication Date: 2003-10-22
FUDAN UNIV
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However, for the electrorheological fluid under the electric field, which is non-ergodic and has a very fast structural response (on the order of milliseconds), the ensemble averaging includes not only time averaging, but also spatial averaging. Therefore, the single-mode fiber method has been not applicable anymore
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Embodiment 1
[0021] Example 1: Light source
[0022] Nd: YAG laser (CrystaLaser LC GCL-150-S): Power 150mW, TEM 00 The mode and wavelength are 532nm, the coherence length exceeds 100m, the output power is stable (power fluctuation within 24 hours<=0.25%), and the laser diameter is 6mm after beam expansion. Sample and sample cell
[0023] Glass microspheres / silicone oil system, the glass microspheres are dehydrated (160° C. / 24 hours), and the volume fraction is 2%.
[0024] The sample cell is composed of two sides of conductive glass and two sides of ordinary glass, and the distance between the conductive glasses is 2mm. experiment
[0025] When no electric field is applied, the particle interaction is weak and the volume fraction is small, which can be regarded as an ergodic system, and the autocorrelation function can be detected by ALV. The autocorrelation function is measured by the single-mode fiber method and the CCD method respectively, and the attenuation time τ is obtained. as...
Embodiment 2
[0026] Embodiment 2: The light source is the same as Embodiment 1. sample
[0027] carbon doped TiO2 / Silicone oil system, TiO 2 With a very high dielectric constant (80-100), organic carbon is doped into TiO at 400°C 2 , can be changed by changing the TiO 2 The content of DDA in the powder changes the TiO 2 conductivity. The volume fraction of the system is 0.33%. Experiment 1. Static measurement
[0028] When the DC electric field is 600V / mm and the AC electric field is 3000V / mm, the different conductivity (TiO 2 Diffusion coefficient D of samples with different carbon content) changes with time, as shown in the attached image 3 and 4 . Figure 5 is the variation of the diffusion coefficient with time under different DC electric fields. image 3 and Figure 5 Each curve contains a peak and a valley, and the peak can be considered to be caused by dipole interaction. As the electric field increases, the peaks gradually disappear and the valleys remain, which is du...
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Abstract
The invention is a method for observing the dynamic structure evolution process of a non-ergodic system with a high volume fraction under a strong electric field by using a high-speed charge-coupled imaging system to measure a diffusion spectrum. The single-mode optical fiber detection method in the existing technology is no longer suitable for measuring the non-ergodic system, and there is no suitable method to measure the structural evolution process of the system. The present invention observes the structure formation of the electrorheological fluid system under dynamic and static conditions by measuring the autocorrelation function and diffusion transmittance of the sample, thereby drawing a conclusion that at least two factors play an important role in the electrorheological process, One is the net charge interaction and the other is the dipole interaction. Under low DC electric field, the two effects are equivalent, while under high DC electric field, the former plays a dominant role. In contrast, under an alternating electric field, the latter plays a decisive role, thus providing a better explanation for the electrorheological mechanism. Under the condition of no electric field, the results of this method are compared with those of the single-mode fiber method, and they are in good agreement, which proves the reliability of this method. The device of the invention is simple and convenient, and is suitable for various ergodic and non-ergodic soft matter systems with fast structural response, such as electrorheological fluid, magnetorheological fluid and blood.
Description
technical field [0001] The present invention uses a high-speed charge-coupled imaging system (CCD, Charge-Coupled Device) to measure a diffusion spectrum (DWS, Diffusing Wave Spectroscopy) method to observe a non-ergodic system with a higher volume fraction under a strong electric field, such as an electrorheological fluid system. Dynamic Structural Evolution Process. Background technique [0002] Traditional DWS experiments are probed using single-mode fiber (SMF). After the laser beam passes through the sample, the scattered light at a certain point is received by the optical fiber, and the signal is received by the photomultiplier tube (ALV's single photon detector, SPD) and enters the correlator. The software provided by ALV can measure the autocorrelation function. There are certain applications in various ergodic systems such as colloidal suspensions, sand piles and foams. For ergodic systems, the time average means the ensemble average of the whole. However, for th...
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