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首页> 外文期刊>European Journal of Glass Science and Technology, PartB. Physics and Chemistry of Glasses >A small angle neutron scattering study of long range density fluctuations in vitreous silica
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A small angle neutron scattering study of long range density fluctuations in vitreous silica

机译：石英玻璃中长距离密度波动的小角度中子散射研究

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摘要

The magnitude of the network density fluctuations in vitreous silica,prepared by flame hydrolysis and from crystalline alpha-quartz,have been investigated by careful absolute measurements of the zero scattering vector limit of the structure factor,S(0).The data were obtained using the Dll instrument at the Institut Laue-Langevin,making a precise correction for multiple scattering followed by accurate normalisation to yield an absolute differential scattering cross section.If it is assumed that the density fluctuations present in the supercooled liquid at the glass transition temperature,T_g,are frozen in as the liquid cools,then S(0)may be calculated from the isothermal static compressibility,K(T_g),of the supercooled liquid at T_g.Any increase in the density fluctuations during or below the glass transition will lead to an excess contribution to S(0)above that predicted from K(T_g).Measurements of the neutron differential scattering cross section at small scattering vector magnitudes,Q,have been made in the region 0.004<=Q<=0.154 A~(-1),which extrapolate to an absolute value for S(0)of 0.0300(+-)0.0016,in agreement with previous small angle x-ray scattering studies and with the isothermal compressibility of the liquid at the glass transition temperature,obtained from light scattering.The results are thus consistent with a random network structure incorporating 'frozen in density fluctuations,appropriate to the liquid at the fictive temperature,and there is no evidence for the formation of crystallites on passing through the glass transition.
机译：通过仔细地绝对测量结构因子S（0）的零散射矢量极限，研究了通过火焰水解和晶体α-石英制备的石英玻璃中网络密度波动的大小。使用Laue-Langevin研究所的Dll仪器，对多次散射进行精确校正，然后进行精确归一化以产生绝对微分散射截面。如果假设在玻璃化转变温度下过冷液体中存在密度波动，则T_g在液体冷却时被冻结，则S（0）可以由T_g处的过冷液体的等温静态可压缩性K（T_g）计算得出。在玻璃化转变期间或以下，密度波动的任何增加都会导致以上是根据K（T_g）预测的对S（0）的过量贡献。在小的散射矢量幅度下测量中子微分散射截面，已在0.004 <= Q <= 0.154 A〜（-1）的范围内得出Q，并推断出S（0）的绝对值为0.0300（+-）0.0016，与先前的小角度X射线一致散射研究以及通过光散射获得的液体在玻璃化转变温度下的等温可压缩性。因此，结果与包含“冻结的密度波动”的随机网络结构相一致，该密度适合于虚拟温度下的液体，并且存在没有证据表明在通过玻璃化转变时会形成微晶。

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