Mechanism and Kinetic Model of In-situ TiB_2/7055Al Nanocomposites Synthesized under High Intensity Ultrasonic Field

In-situ TiB2/7055Al nanocomposites are fabricated by in situ melt chemical reaction from 7055Al-K2TiF6-KBF4 system under high intensity ultrasonic field,and the mechanism and kinetic model of in-situ melt chemical reaction are investigated.X-ray diffraction （XRD） and scanning electron microscope （SEM） analyses indicate that the sizes of in-situ TiB2 nanoparticles are in the range of 80-120 nm.The results of ice-water quenched samples show that the whole process contains four stages,and the overall in-situ reaction time is 10 minutes.The in situ synthesis process is controlled mainly by chemical reaction in earlier stage （former 3 minutes）,and by the particulate diffusing in later stage.The mechanism of key reaction between Al3Ti and AlB2 under high intensity ultrasonic in the 7055Al-K2TiF6-KBF4 system is the reaction-diffusion-crack-rediffusion.Furthermore,the reactive kinetic models in 7055Al-K2TiF6-KBF4 system are established.

Ultrasound assisted electrocatalytic oxidation of 3-chlorophenol in aqueous solution

Ultrasound assisted electrocatalytic process was used for enhancing decomposition efficiency of organic compounds. In this paper, the effect of ultrasonic frequency, ultrasonic intensity and pH value on 3-chlorophenol decomposition were studied. It was found that 3-chlorophenol in aqueous solution can be markedly decomposed by ultrasound assisted electrocatalytic process. The rate of decomposition increased with the increase of frequency, and low frequency is proper in the ultrasound assisted electrocatalytic system. The removal of 3-chlorophenol increased visibly with the increase of ultrasonic intensity until the intensity of 1.56 W/cm2. Alkaline condition is beneficial to 3-chlorophenol decomposition, the rate at pH 9.08 was higher than pH 2.48 and 6.85. The major intermediate formed during 3-chlorophenol decomposition was 2-chloro-pbenzoquinone, which was readily decomposed by ultrasound assisted electrocatalytic process.

An executive review of sludge pretreatment by sonication

Ultrasonication（US）, which creates hydro-mechanical shear forces in cavitation, is an advanced technology in sludge pretreatment. However, there are many factors affecting the efficacy of cavitation and ultrasonication disintegration of sludge as a consequence.The objective of this work is to present an extensive review of evaluation approaches of sludge US pretreatment efficiency. Besides, optimization methodologies of related parameters,the differences of optimum values and the similarities of affecting trends on cavitation and sludge pretreatment efficiency were specifically pointed out, including ambient conditions,ultrasonic properties, and sludge characteristics. The research is a prerequisite for optimization of sludge US pretreatment efficiency in lab-scale and practical application. There is not-yet a comprehensive method to evaluate the efficiency of sludge US pretreatment, but some main parameters commonly used for this purpose are degree of sludge disintegration, proteins,particle size reduction, etc. Regarding US parameters, power input PUS, intensity IUS, and frequency FSseem to have significant effects. However, the magnitude of the effect of PUSand probe size in terms of IUShas not been clearly detailed. Investigating very low FSseems interesting but has not yet been taken into consideration. In addition, static pressure effect has been marginally studied only and investigation on the effect of pH prior to US process has been restricted. Their effects therefore should be varied separately and simultaneously with other related parameters, i.e. process conditions, ultrasonic properties, and sludge characteristics, to optimize sludge US pretreatment process.