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首页> 外文期刊>Zeitschrift fur Naturforschung. A, A journal of physical sciences >Heat Capacities of Thermally Treated Na_2O-3B_2O_3 Glasses Above and Below T_g
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Heat Capacities of Thermally Treated Na_2O-3B_2O_3 Glasses Above and Below T_g

机译：T_g上下的热处理过的Na_2O-3B_2O_3玻璃的热容量

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Various contributions have been obtained from the heat capacities of "as quenched" and annealed Na_2O-3 B_2O_3 glasses. It is shown that the enthalpic release gives a major contribution to the DSC curves obtained by reheating quenched glasses. Different relaxation processes are followed by comparing DSC scans of quenched and annealed samples in the vitreous state and around the glass transition temperature, T_g. As a function of the annealing time at T = T_g - 30℃, the specific heats at room temperature initially increase, due to the decrease of the exothermic contribution from quenched-in defects, which are absent in a fully annealed glass; over a month-long time scale these heat capacities drop, due to a partial ordering, which decreases the configurational contribution. Such a decrease is related with the "overshoot" which occurs above T_g and which attains a limiting value ΔH_g ≈ 14J mol~(-1) in a matter of days. The heat capacities above T_g relax towards a value of C_p of ≈ 2.3 J mol~(-1) K~(-1) after a few days of annealing, which is intermediate between the anomalously low C_p (～1.8J mol~(-1)K~(-1)) of a fast quenched (～10~3 K min~(-1)) and that (～2.9 J mol~(-1) K~(-1)) of a sample annealed for one hour. These phenomena point to complex relationships among enthalpic relaxation, entropic relaxation and temperature in these glasses.
机译：从“淬火”和退火的Na_2O-3 B_2O_3玻璃的热容量中获得了各种贡献。结果表明，焓的释放对通过再加热淬火玻璃获得的DSC曲线起主要作用。通过比较玻璃态和玻璃化转变温度T_g附近的淬火和退火样品的DSC扫描，可以得出不同的弛豫过程。根据T = T_g-30℃退火时间的函数，室温下的比热最初会增加，这是由于淬火缺陷（完全退火的玻璃中不存在）导致的放热作用减小所致。在一个月的时间内，由于部分排序，这些热容量下降，这降低了结构贡献。这种减少与“过冲”有关，该“过冲”发生在T_g之上，并在几天之内达到极限值ΔH_g≈14J mol〜（-1）。经过几天的退火，T_g之上的热容量朝着约2.3 J mol〜（-1）K〜（-1）的C_p值放松，这介于异常低的C_p（〜1.8J mol〜（- 1）快速淬火（〜10〜3 K min〜（-1））的K〜（-1））和样品（〜2.9 J mol〜（-1）K〜（-1））退火的样品一小时。这些现象表明这些眼镜的焓弛豫，熵弛豫和温度之间存在复杂的关系。

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