Microstructure and mechanical properties of nucleant-free Li2O-CaO-SiO2 glass-ceramics
Microstructure and mechanical properties of nucleant-free Li2O-CaO-SiO2 glass-ceramics
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DOI：
10.1016/j.actamat.2017.03.010
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发表时间：
2017-05
期刊：
影响因子：
9.4
通讯作者：
G. G. Santos-G.;F. Serbena;V. Fokin;Edgar Dutra Zanotto
中科院分区：
文献类型：
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作者：
G. G. Santos-G.;F. Serbena;V. Fokin;Edgar Dutra Zanotto
Li 2 O-CaO-SiO2玻璃形成系统的一个吸引人的特征是获得具有细长形态的内部成核晶相-CaSiO 3和Li 2SiO 3-的可能性，这可能导致坚韧玻璃-陶瓷。该系统的另一个巨大优点是它不需要成核剂来内部结晶。在这项研究工作中，制备了三种组成在30-50摩尔% CaSiO 3/70-50摩尔% Li 2SiO 3范围内系统变化的玻璃，对其进行热处理，并评估了它们的微观结构和机械性能。在两阶段处理中应用加热循环。基于先前的DSC分析选择温度。采用XRD和SEM对晶化后的样品进行了表征，考察了其晶体的性质、尺寸和形貌。测定了显微结构对微晶玻璃的维氏硬度（Hv）和压痕断裂韧性（Kc）的影响。弹性模量（E），双轴向强度（σm）和断裂韧性（KDTIC）分别由纳米压痕，球对三球和双扭转测试。用X射线衍射法测定了残余应力的大小。当CaSiO 3含量为44 mol%时，在498 °C下热处理24 h以形成晶核，在700 °C下热处理2 h以形成晶体，其力学性能最佳。该组成产生具有以下显微结构特征和性质的玻璃-陶瓷：平均Li 2SiO 3（LS）晶体尺寸为8.5 μm，围绕LS晶体的硅灰石（CS）相具有约50%LS结晶体积分数，KDTIC= 2.3 ± 0.5MPa m1/2，σm =270 ± 20 MPa，HV= 8.4 ± 0.7GPa和E = 146 ± 8 GPa。这些是用于承载应用的玻璃陶瓷的令人兴奋的机械性能。
An attractive characteristic of the Li2O-CaO-SiO2glass-forming system is the possibility of obtaining internally nucleated crystal phases – CaSiO3and Li2SiO3– having elongated morphologies that can potentially lead to tough glass-ceramics. Another great advantage of this system is that it does not need a nucleating agent to crystallize internally. In this research work, three glasses with systematic compositional variations within the range of 30–50 mol% CaSiO3/70-50 mol% Li2SiO3were prepared, heat-treated and their microstructures and mechanical properties evaluated. Heating cycles were applied in two-stage treatments. The temperatures were selected based on previous DSC analyses. The crystallized samples were characterized by XRD and SEM to examine the nature, size and morphology of their crystals. The effect of microstructure on the Vickers hardness (Hv) and indentation fracture toughness (Kc) of the glass-ceramics was determined. Elastic modulus (E), biaxial strength (σm) and fracture toughness (KDTIC) were determined from nanoindentation, ball-on-three-balls and double torsion tests, respectively. The level of internal residual stresses was evaluated by X-rays diffraction. The best mechanical properties were exhibited by a composition containing 44 mol% CaSiO3heat-treated at 498 °C for 24 h for nucleation and at 700 °C for 2 h for crystal growth. This composition resulted in a glass-ceramic with the following microstructural features and properties: average Li2SiO3(LS) crystal size of 8.5 μm, wollastonite (CS) phase surrounding the LS crystals with approximately 50% LS crystallized volume fraction, KDTIC= 2.3 ± 0.5 MPa m1/2, σm =270 ± 20 MPa, HV= 8.4 ± 0.7 GPa and E = 146 ± 8 GPa. These are exciting mechanical properties for glass-ceramics intended for load bearing applications.