To compare the different effects under different excitation methods during the measurement on the particle size of silicon carbide (SiC), an experimental system has been established to get different signal excitations of burst wave, continuous wave and pulsed wave. Variable sound path method is adopted during the measurement to obtain the ultrasonic attenuation spectrum of SiC suspensions with two immersion transducers at four different mass concentrations under the same experimental condition. It is found that the ultrasonic attenuation coefficients excited by three different waves increase with increasing frequency and the tendency is approaching the same. The result calculated by a normalized spectrum of the optimal regularization methods shows that SiC particle size distribution under the three excitation methods is similar, which indicate that the different excitation methods on particle size characterization have almost no influence to result.
SiO2/TiO2 composite mesoporous materials prepared by sol-gel method with bacterial cellulose(BC)as a surface esterification agent and porous template was as photocatalyst in the degradation of methyl orange(MO)in water under UV- irradiation. The results show that the best heat treatment condition is at 600°Cfor 3 h and the optimum content of SiO2 is 30% (30 denotes the weight percent of SiO2). The photoactivity of 30SiO2/TiO2 catalyst prepared with BC was much better than that of reference catalyst prepared with no BC. An addition of BC not only raises the adsorbability of the photocatalyst, but also effectively inhibits anatase-rutile transformation and effectively induce amorphous-anatase transformation of TiO2. The BET surface area of 30%SiO2/TiO2 composite mesoporous materials was the largest. The resulting mesoporous materials showed a high photocatalytic activity for the photodegradation of methyl orange in the UV-irradiation.
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