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[[alternative]]Ultrasonics research in the phase separation of the Alkali s

By [[author]]王富民, [[author]]Wang,Fu Min, 王富民 and Wang,Fu Min

Abstract

[[abstract]]由於物質的超聲波的性質,可直接反應其空間的彈性係數。其彈性係數依 據Kul'bitskaya的凍結理論,可以合理解釋超聲波在矽氧玻璃之聲速變化 情形。在矽氧玻璃中我們加入鹼金屬氧化物,發現在180K至室溫間其聲速 變化對溫度呈線性關係;且溫度係數和鹼金屬氧化物莫耳百分比亦是線性 關係。在Li■O- nSiO■玻璃中,其聲速的溫度係數和Li■O 莫耳百分比 的關係,以25% 為界,呈現兩不同斜率的直線,此乃因Li■O 的分布情形 不同。本文對照前人以SEM 方法分析鋰原子團大小的研究結果,可推論鋰 玻璃25% Li■O 莫耳百分比以下者為二相玻璃,而在此之上者轉為單相玻 璃。根據玻璃凍結理論的分析,可推知當鹼金屬氧化物莫耳濃度甚低時, 玻璃聲速變化的溫度係數,主要取決於因矽氧鍵被破壞而形成單鍵氧的莫 耳濃度。比照鋰玻璃的相位分離情形,我們推測鹼金屬氧化物矽氧玻璃中 ,Na■O-nSiO■ 及 K■O-nSiO■玻璃結構為單相;而 Cs■O -nSiO■則 為二相分離。 Ultrasonic measurments of a series of R■O-nSiO■ (R=Li ,Na,K, Cs) glasses samples are presented. In term of the model of frozen-in thermal fluctuations in glasses, the analysis of the relationship of temperature coefficient of ultrasonic velocity change versus Li■O molar frac- tion provides evidence of the existence of two-phase separation phenomenon in lithium oxide less than 0.25. It also provides some information about the structural change of the glasses from a system of two phase to a single phase. A comparison of the temperature coeffi- cient of lithium glass with those of Na,K and Cs glass- es reveals some interesting feature of structure. The structured feature of Na or K glasses is single phase; The structured feature of Cs glass is two phase separa- tion. Ultrasonic measurments of a series of R■O-nSiO■ (R=Li ,Na,K,

Topics: 相位分離;矽氧玻璃;超聲波, phase separation; silicate glasses; ultrasonics., [[classification]]38
Year: 2010
OAI identifier: oai:ir.lib.ntnu.edu.tw:309250000Q/7997
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