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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Influence of nucleation and crystallisation on the rheological properties of lithium disilicate melt
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Influence of nucleation and crystallisation on the rheological properties of lithium disilicate melt

机译：成核和结晶对二硅酸锂熔体流变性能的影响

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摘要

The rheological properties of pure, nucleated and partially crystallized lithium disilicate melts may be described by various rheological features such as Newtonian and non-Newtonian viscosity, stress generation modulus, stiffness and stiffness resistance (brittleness) and the critical deformation rate at the first high-temperature crack. These quantities are determined from the stress-strain curves of cylinder compression experiments on the basis of equal (Newtonian) equilibrium viscosities (isochomal conditions). The flow-, brittleness- and stiffness-parameters show a characteristic non-linear decrease with increasing deformation rates. This 'shear thinning' behaviour shows one step in the case of single-phase glass melt and two independent steps in the case of partially crystallized two phase-samples. This behaviour can be successfully described by a sum of two separate equations on the basis of recently developed flow equations for stress induced changes of viscosity and brittleness of glass melts, The first step of the viscosity and brittleness decrease, within the range of low deformation rates, is caused by a 'suspension effect' of the homogenously distributed crystals and the second step, at higher deformation rates, by the non-Newtonian flow behaviour of the glass melt matrix. The 'suspension effect' is due to a flow-orientation mechanism of the suspended crystals and varies with their sizes, their shapes and number, The non-Newtonian flow behaviour of the pure glass matrix is not only a consequence of viscoelasticity but is also based on the orientability of flow units because the character of the flow curves of single-phase glass melts with different degrees of structural interconnectivities is changed in a similar way as in two phase lithium disilicate melts with different degrees of deviation from the isometric spherical habit of the crystals.
机译：纯的，成核的和部分结晶的二硅酸锂熔体的流变特性可以通过各种流变特性来描述，例如牛顿和非牛顿粘度，应力产生模量，刚度和刚度（脆性），以及在第一次高温下的临界变形率。温度裂缝。这些量是根据相等（牛顿）平衡粘度（等速条件）从气缸压缩实验的应力-应变曲线确定的。流动，脆性和刚度参数显示出随变形率增加而出现的非线性特征性下降。这种“剪切稀化”行为在单相玻璃熔体的情况下显示了一个步骤，在部分结晶的两相样品的情况下显示了两个独立的步骤。在最近开发的用于应力引起的玻璃熔体粘度和脆性变化的流动方程的基础上，可以通过两个单独的方程的总和来成功地描述这种行为。在低变形速率的范围内，粘度和脆性的第一步降低是由均匀分布的晶体的“悬浮效应”引起的，第二步是在较高的变形速率下，由玻璃熔体基质的非牛顿流动行为引起的。 “悬浮效应”是由于悬浮晶体的流动方向机制所致，并且随其尺寸，形状和数量而变化。纯玻璃基体的非牛顿流动行为不仅是粘弹性的结果，而且还基于流动单元的可定向性，因为具有不同结构互连度的单相玻璃熔体的流动曲线特征的变化方式类似于两相二硅酸锂熔体，其偏离程度与球体的等距球形习惯不同晶体。

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