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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Crystallization Kinetics of Bioactive Glasses in the ZnO-Na2O-CaO-SiO2 System
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Crystallization Kinetics of Bioactive Glasses in the ZnO-Na2O-CaO-SiO2 System

机译：ZnO-Na2O-CaO-SiO2系统中生物活性玻璃的结晶动力学

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摘要

The crystallization kinetics of Na2O·CaO·2SiO2(x=0)and 0.68ZnO·Na2O·CaO·2SiO2(x=0.68,where x is the ZnO stoichiometric coefficient in the glass formula)bioactive glasses have been studied using both nonisothermal and isothermal methods.The results obtained from isothermal XRPD analyses have showed that the first glass crystallizes into the isochemical Na2CaSi2O6 phase,whereas the Na2ZnSiO4 crystalline phase is obtained from the Zn-rich glass,in addition to Na2CaSi2O6.The activation energy(E_a)for the crystallization of the Na2O·CaO·2SiO2 glass is 193+-10 and 203+-5 kJ/mol from the isothermal in situ XRPD and nonisothermal DSC experiments,respectively.The Avrami exponent n determined from the isothermal method is 1 at low temperature(530 deg C),and its value increases linearly with temperature increase up to 2 at 607 deg C.For the crystallization of Na2CaSi2O6 from the Zn-containing glass,higher values of both the crystallization temperature(667 and 661 deg C)and E_a(223+-10 and 211+-5 kJ/mol)have been found from the isothermal and nonisothermal methods,respectively.The Na2ZnSiO4 crystalline phase crystallizes at lower temperature with respect to Na2CaSi2O6,and the E_a value is 266+-20 and 245+-15 kJ/mol from the isothermal and nonisothermal methods,respectively.The results of this work show that the addition of Zn favors the crystallization from the glass at lower temperature with respect to the Zn-free glass.In fact,it causes an increase of E_a for the Na diffusion process,determined using MD simulations,and consequently an overall increase of E_a for the crystallization process of Na2CaSi2O6.Our results show good agreement between the E_a and n values obtained with the two different methods and confirm the reliability of the nonisothermal method applied to kinetic crystallization of glassy systems.This study allows the determination of the temperature stability field of the crystalline phases with the view of creating a different glass ceramic useful in the field of bioactive materials.
机译：利用非等温和等温研究了Na2O·CaO·2SiO2（x = 0）和0.68ZnO·Na2O·CaO·2SiO2（x = 0.68，其中x为玻璃配方中的ZnO化学计量系数）的结晶动力学通过等温XRPD分析获得的结果表明，第一个玻璃结晶为等化学Na2CaSi2O6相，然后除Na2CaSi2O6之外，还从富锌玻璃中获得Na2ZnSiO4晶相。结晶的活化能（E_a）根据等温原位XRPD和非等温DSC实验，Na2O·CaO·2SiO2玻璃的玻璃化温度分别为193 + -10和203 + -5 kJ / mol。在低温下，等温法测定的Avrami指数n为1（530）在607摄氏度时，其值随温度的升高而线性增加，直至温度升高至2.对于从含锌玻璃中结晶Na2CaSi2O6而言，较高的结晶温度（667和661摄氏度）和E_a（223 + -10和211 + -5分别从等温和非等温方法中发现（kJ / mol）.Na2ZnSiO4结晶相相对于Na2CaSi2O6在较低的温度下结晶，从等温和热力学角度来看，E_a值为266 + -20和245 + -15 kJ / mol。这项工作的结果表明，相对于无锌玻璃，锌的添加有利于在较低温度下从玻璃中结晶。事实上，这导致钠扩散过程中的E_a升高，确定使用MD模拟，因此Na_CaSi2O6的结晶过程中E_a总体增加。我们的结果表明，用两种不同方法获得的E_a和n值之间有很好的一致性，并证实了用于玻璃系统动力学结晶的非等温方法的可靠性这项研究可以确定结晶相的温度稳定性场，以期创建可用于该领域的不同玻璃陶瓷生物活性材料。

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