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首页> 外文会议>International Symposium on State-of-the-Art Application of Surface and Interface Analysis Methods to Environmental Material Interactions: in Honor of James E.Castle's 65th Year, Mar 26-27, 2001, Washington D.C. >RELATIONSHIP OF AN EQUIVALENT ELECTRICAL CIRCUIT TO STRUCTURE OF SETTING CALCIUM PHOSPHATE BIOCEMENTS
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RELATIONSHIP OF AN EQUIVALENT ELECTRICAL CIRCUIT TO STRUCTURE OF SETTING CALCIUM PHOSPHATE BIOCEMENTS

机译：等效电路与设定磷酸钙生物结构的关系

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Electrochemical impedance spectroscopy (EIS) was used to characterize the setting of calcium phosphate cements (CPC) unexposed and exposed to H_2O during setting. X-ray diffraction (XRD), scanning electron microscopy (SEM), and penetration tests were also used. Results showed that the EIS of setting CPC was characterized by higher frequency bulk CPC behavior and by lower frequency bulk-electrode interfacial behavior. Accelerating or retarding the setting kinetics of CPC, in the same order as revealed from the penetration hardening behavior, affected the EIS. A series equivalent circuit with three time constants (ι) was used to model bulk CPC at times up to 1 day for water exposed and water unexposed material. For water mixed and water unexposed CPC, ι_2 increased by (4 to 7) orders of magnitude after 10 h with respect to water exposed CPC, while ι_1 and ι_3 increased up to two orders after 5 h. Acid mixed CPC also increased but at shorter times during setting. For all mixes unexposed to water during setting, XRD did not detect hydroxyapatite (OHAp), while OHAp was detected for water exposed CPC. Platelet crystals were detected by SEM for water exposed CPC, while a sheath of reaction products overlying the reactant particles mainly occurred for water unexposed CPC. It is concluded that the water content and its form affects the EIS in setting CPC. Precursor and intermediary calcium phosphate phases in addition to OHAp are required to interpret an equivalent circuit model. Three-probe guarded experiments are needed to eliminate possible short circuiting surface currents from adsorbed water. EIS is a useful technique to monitor the reactivity of different batches of material.
机译：电化学阻抗谱（EIS）用于表征未固化和在固化过程中暴露于H_2O的磷酸钙水泥（CPC）的固化。还使用了X射线衍射（XRD），扫描电子显微镜（SEM）和渗透测试。结果表明，设置CPC的EIS具有较高频率的体CPC行为和较低频率的体电极界面行为。以与渗透硬化行为相同的顺序加速或延迟CPC的凝固动力学会影响EIS。具有三个时间常数（η）的串联等效电路用于对暴露于水和未暴露于水的材料进行高达1天的总体CPC建模。对于水混合和水未暴露的CPC，相对于水暴露的CPC，l_2在10 h后增加了（4到7）个数量级，而l_1和ι_3在5 h后增加了两个数量级。酸混合CPC也增加，但是在凝固过程中时间较短。对于凝固期间未暴露于水的所有混合物，XRD均未检测到羟基磷灰石（OHAp），而水分暴露的CPC则检测到OHAp。通过SEM检测暴露于水的CPC的血小板晶体，而覆盖反应物颗粒的反应产物的鞘主要发生于暴露于水的CPC。得出的结论是，水分含量及其形式会影响设置CPC的EIS。除OHAp外，还需要前体和中间磷酸钙相来解释等效电路模型。需要三探针保护的实验，以消除吸附水可能产生的短路表面电流。 EIS是监视不同批次材料的反应性的有用技术。

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