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Abstract

Owing to poor bonding between coarse fly ash particles and hydration products, gap-graded blended cements with fly ash usually show lower compressive strengths than Portland cement. Surface cementitious properties of coarse fly ash were improved by dehydration and rehydration processes in the present study. The results show that during the calcination at 750 °C, C–S–H gel is mainly transformed into a new nesosilicate, which is similar to a less crystalline C2S. The formation of melilite from hydration products is also noticed at 900 °C, however, this will not contribute to rehydration of calcined fly ash. Rehydration of new generated nesosilicate on the surface of coarse fly ash leads to a better bonding between coarse fly ash particles and hydration products. As a result, both early and late mechanical properties of gap-graded blended cements containing 25% cement clinker and 39% calcined coarse fly ash are higher than those of 100% Portland cements.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Wang Tieshan
,
Li Qiang
,
Zhang Baoguo
,
Wang Zhusheng
,
Cao Zhiyuan
, and
Zhang Peixin

Abstract  

The radio-voltaic effect is investigated to be applied radioisotopic batteries in this work. The collection rates of the electron-hole pairs are 94 percent for the alpha particles emitted by239Pu source and 65 percent for the beta particles emitted by90Sr-90Y source. The maximum energy conversion efficiency got by the silicon element is about 16%. A prototype radioisotopic battery with147Pm beta sources is constructed. Its maximum short-circuit current and off voltage are about 2 A and 190 mV respectively. The experimental data suggest that the life of the prototype battery may be more than three years.

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