Abstract The phase transformation of β-glycine to α-glycine in a water/ethanol media was investigated in terms of its polymorphism in pure media and in the presence of an additive. Lauric acid was used as the additive, and the experiments were conducted in three different concentrations. First, the polymorphic phase transformation was continuously monitored by in-line measuring of the ultrasonic velocity. Next, the X-ray diffraction (XRD) technique was applied for the solid phase analysis of the crystals to confirm the polymorphic transformation of β-glycine to α-glycine. Based on the combination of scanning electron microscopy (SEM) and morphology analyses, it was found that not only the shape but also the size of the crystals obtained were significantly affected by the additive. The crystals obtained were further characterized by means of thermogravimetric analyzer, elemental analyzer and Fourier-transform infrared (FTIR) spectrometer. The attained thermal data were utilized to calculate the activation energy using various kinetic models based on the isoconversional method. The kinetic results revealed that the addition of lauric acid led to an increase of around 10% in the average activation energy of the glycine crystals during decomposition process. As suggested by the elemental and FTIR analyses conducted, this increase could be related to lauric acid adsorption on the crystal surface.

中文翻译：

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月桂酸存在下甘氨酸的动力学分析和多晶型相变

摘要 研究了 β-甘氨酸在水/乙醇介质中相变到 α-甘氨酸的相变，研究了其在纯介质和添加剂存在下的多态性。使用月桂酸作为添加剂，并以三种不同的浓度进行实验。首先，通过在线测量超声速度连续监测多晶型相变。接下来，将 X 射线衍射 (XRD) 技术应用于晶体的固相分析，以确认 β-甘氨酸向 α-甘氨酸的多晶型转变。基于扫描电子显微镜（SEM）和形态分析的结合，发现不仅形状而且获得的晶体尺寸都受到添加剂的显着影响。所得晶体通过热重分析仪、元素分析仪和傅里叶变换红外（FTIR）光谱仪进一步表征。使用基于等转化方法的各种动力学模型，利用获得的热数据来计算活化能。动力学结果表明，月桂酸的加入使甘氨酸晶体在分解过程中的平均活化能增加了约 10%。正如所进行的元素分析和 FTIR 分析所表明的那样，这种增加可能与月桂酸在晶体表面的吸附有关。动力学结果表明，月桂酸的加入使甘氨酸晶体在分解过程中的平均活化能增加了约 10%。正如所进行的元素分析和 FTIR 分析所表明的那样，这种增加可能与月桂酸在晶体表面的吸附有关。动力学结果表明，月桂酸的加入使甘氨酸晶体在分解过程中的平均活化能增加了约 10%。正如所进行的元素分析和 FTIR 分析所表明的那样，这种增加可能与月桂酸在晶体表面的吸附有关。