Walnuts are one of nature's more waste-heavy products. 67% of the nut is shell and husk, low value by-products that are rich in phenolic compounds. The phenolic compounds extracted from walnut shells are potentially good natural sources of antioxidants for the food and pharmaceutical industries. In this study, phenolic compounds were extracted using an ultrasonic bath, an ultrasonic probe and a standard shaking method. The extraction yield achieved with an ultrasonic probe was 51.2 mg GAE/g DW, two times higher than both the shaking method and the ultrasonic bath method which were 20.6 mg GAE/g DW and 25.8 mg GAE/g DW, respectively. Phenolic extraction was further improved by a size reduction of the walnut shells. The best extraction yield of 52.8 mg GAE/g DW was attained when the particle size was between 45-100 mesh. The ultrasonic probe treatment is the best method for extraction of phenolic compounds from walnut shells. Scanning electron microscopy (SEM) imaging indicated that the ultrasonic probe treatment could better rupture the hard structure of the cells, increasing the penetration of solvents and thus the extraction yield.

Ultrasonic shot peening (USP) is acknowledged as an effective surface treatment method to enhance the mechanical performance of materials by inducing compressive residual stress in solid metals and alloys. This article overviews recent researches from our group at Purdue University on the USP in the aspects of modelling the kinetics of the shots, predicting the surface topography of the peened samples and producing the nanostructured grains on the solid metals and alloys. Research results suggest that finite element method and the developed calculation algorithm can be used for the surface morphology prediction and the USP is capable of surface nanocrystallisation and grain refinement on solid metals. For instance, the topic of the biological enhancement for metallic bio-implant materials via the USP was discussed as well according to our preliminary investigations. The related researches in these topics are discussed and some possible addresses for future study in these fields are drawn and underlined.

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This research investigated the effects of high-intensity ultrasound on the combustion synthesis of TiC particles in Al-Ti-C system. The process involved that high-intensity ultrasound was applied on the surface of a compacted Al-Ti-C pellet directly through a Nb probe during the thermal explosion reaction. By comparing with the sample without ultrasonic treatment, it was found that the thermal explosion reaction for synthesizing TiC phase could take place thoroughly in the ultrasonically treated sample. During the process of synthesizing TiC phase, the dissolution of solid graphite particles into the Al-Ti melt, as well as the nucleation and growth of TiC particles could be promoted effectively due to the effects of ultrasound, leading to an enhancement of the formation of TiC particles. Ultrasound assisted combustion synthesis as a simple and effective approach was proposed for synthesizing materials in this research.