The effect of rolling temperature on the precursor of aluminum foam sandwich (AFS) prepared by powder metallurgy through Pack Rolling method is investigated in this work. The cross-section along rolling direction of the precursors was observed. It was found that periodic corrugated morphology with micro-cracks on the composite interface as well as cracks and micro-holes among core powder particles emerged abundantly at room temperature rolling. These defects degraded with increasing rolling temperature and completely disappeared when the rolling temperature reached 400 °C. Combining with foaming ability of these precursors, the densification mechanism of core powders was discussed. Powder particles deformed with difficulty at low rolling temperature; the gap between them cannot be effectively filled through their plastic deformation. Fracture occurred in powder core layer during co-extension with the outer panel and was partly embedded by it, resulting in corrugated composite morphology at the interface. The precursors of high density and excellent bonding interface were prepared at the rolling temperature of 400 °C. A more suitable foaming condition was determined.
To realize the utilization of the valorization of buckwheat waste (BW), a two-stage thermal-chemical process was explored and evaluated to produce saccharides and biochar. During the first stage, BW underwent a hydrothermal extraction (HTE) of varying severity to explore the feasibility of saccharides production; then, the sum of saccharides yields in the liquid sample were compared. A higher sum of saccharides yields of 4.10 % was obtained at a relatively lower severity factor (SF) of 3.24 with a byproducts yield of 1.92 %. During the second stage, the contents of cellulose, hemicellulose, and lignin were analyzed in the residue after HTE. Enzymatic hydrolysis from the residue of HTE was inhibited. Thus, enzymatic hydrolysis for saccharides is not suitable for utilizing the residue after HTE of BW. These residues with an SF of 3.24 were treated by pyrolysis to produce biochar, providing a higher biochar yield of 34.45 % and a higher adsorption ability (based on methyl orange) of 31.11 % compared with pyrolysis of the raw BW. Meanwhile, the surface morphology and biomass conversion were analyzed in this study. These results demonstrate that the two-stage thermal-chemical process is efficient for treating BW and producing saccharides and biochar. This work lays a foundation for the industrial application of BW, and for improving the economic benefits of buckwheat cultivation.
Conversion of livestock manure into organic fertilizer is a sustainable strategy in crop production. In contrast to composted manure, the agronomic characteristics of an anaerobic digestion by-product, digestate, have not been well characterized. This study aimed to investigate the effects of digestate and compost, derived from a pilot-scale livestock waste recycling system, on bioactive compounds in tomato fruits. Both field and greenhouse experiments were conducted to compare the effects of these two organic fertilizers with the application of chemical fertilizer. These comparisons were made by evaluating their influence on tomato yield and bioactive compound contents and antioxidant activity of fruits. The experiment included a control (no fertilizer) and three fertilization treatments with the same nitrogen dose: chemical fertilizer, digestate, and compost. The results revealed that the application of digestate and compost yielded similar results in terms of tomato production, surpassing both the chemical fertilizer application and the control group under both field and greenhouse conditions. Fertilization exhibited a significant influence on the bioactive compound contents and antioxidant capacity of the fruits. Furthermore, the application of digestate and compost led to an increase in the concentration of sugars, phenolic compounds, and several organic acids in the fruits while simultaneously reducing the citric acid levels in comparison to the chemical fertilizer treatment. Moreover, the application of both organic fertilizers improved the total phenol and total flavonoid contents in tomato fruits, and the antioxidant capacity in fruits was significantly higher than that of the chemical fertilizer treatment. In conclusion, the application of digestate or compost derived from the livestock waste recycling system reduced use of chemical fertilizers and resulted in higher tomato yields and fruit with considerably superior bioactive compounds. The results suggested that using digestate or compost as an alternative to inorganic fertilizers for tomato cultivation could assist farmers in increasing productivity, improving the content of bioactive compounds in tomato fruit, and promoting agricultural waste management.
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