Irreversible hydrogen bonding is the most widely recognized mechanism of fiber hornification, and NaOH/urea aqueous solution can break the inter-and intramolecular hydrogen bonds of cellulose. In order to investigate whether or not this solution system reverses the hornification of fibers that repeatedly underwent wetting and drying, we studied the degree of hornification of repaired fibers, which have been treated with NaOH/urea aqueous solution and regenerated in H 2 SO 4 /Na 2 SO 4 aqueous solution, and we analyzed the physical properties of the resulting paper sheets. The water retention value (WRV) of the repaired fibers was equivalent to that of virgin pulp, and the hornification has been thoroughly reversed. The physical properties of the resulting paper sheets have improved, especially the tear and burst indexes, which have approximately doubled. Moreover, the dissolution/regeneration process slightly inhibited the degree of fiber hornification and increased the cycle number of the recycled fibers.

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In this paper, the effects of reduction temperature and carbon content on the preparation of silicon-aluminum alloy by carbothermal reduction coal fly ash were studied. The reduction products were characterized by XRD. The results showed that when carbon content was 1.15 or 1.3 times and reduction temperature was 1900°C, Al4C3 was formed in the reduction products and Al2O3 was not completely reacted; when carbon content was 1.15 times and reduction temperature was 2000°C, Al6Fe, SiC, Al8Fe2Si, Si and Al were produced by carbon reduction coal fly ash. When carbon content was 1.3 times and reduction temperature was 2000°C, reduction product had many impurities. When carbon content was 1.15 times and reduction temperature was 2000°C, siliconaluminum alloy was obtained, impurities of the reduction products were less, the effect of carbon reduction coal fly ash on the preparation of silicon-aluminum alloy was the best.

The effect of carbothermal reduction of fly ash on the preparation of silicon and aluminium at different reaction temperatures was studied. XRD was used to analyze the phase of the reduction products at different reaction temperatures. The results showed that the products of carbothermal reduction fly ash included Al2O3, SiC, Al2SiO5, FeSiO3 and FeSi at 2073K. At 2123K, the products of carbon reduction fly ash were Al2O3, Al2SiO5, SiC, FeSi, Si and Al4.5FeSi. At 2173K, the main products of carbon reduction fly ash were Al2O3, Si, Al, SiC, FeSi and Al4.5FeSi. The diffraction peak intensity of silicon at 2173K was higher than that at 2123K, which indicated that increasing the reaction temperature was beneficial to the formation of silicon. Under the reaction conditions of 2223K and 2273K, the kinds of reduction products were the same, which were Al4.5FeSi, Si, Al, SiC and FeSi. The intensity of the diffraction peak of aluminium at 2273K was higher than that of aluminium at 2223K, which indicated that increasing the reaction temperature was beneficial to the formation of aluminium. In this experiment, with the increase of temperature, the degree of carbon reduction fly ash was more sufficient and 2273K was the optimum reaction temperature for preparing silicon-aluminium alloy from carbon reduction fly ash.

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