Chemical Department, Saint Petersburg State University, Saint Petersburg, Russia.
Rapid Commun Mass Spectrom. 2013 Jul 15;27(13):1559-66. doi: 10.1002/rcm.6606.
The unique properties of the PbO-B2O3-SiO2 system, especially its extensive range of glass-forming compositions, make it valuable for various practical applications. The thermodynamic properties and vaporization of PbO-B2O3-SiO2 melts are not well established so far and the data obtained on these will be useful for optimization of technology and thermodynamic modeling of glasses.
High-temperature Knudsen effusion mass spectrometry was used to study vaporization processes and to determine the partial pressures of components of the PbO-B2O3-SiO2 melts. Measurements were performed with a MS-1301 mass spectrometer. Vaporization was carried out using two quartz effusion cells containing the sample under study and pure PbO (reference substance). Ions were produced by electron ionization at an energy of 25 eV. To facilitate interpretation of the mass spectra, the appearance energies of ions were also measured.
Pb, PbO and O2 were found to be the main vapor species over the samples studied at 1100 K. The PbO activities as a function of the composition of the system were derived from the measured PbO partial pressures. The B2O3 and SiO2 activities, the Gibbs energy of formation, the excess Gibbs energy of formation and mass losses in the samples studied were calculated.
Partial pressures of the vapor species over PbO-B2O3-SiO2 melts were measured at 1100 K in the wide range of compositions using the Knudsen mass spectrometric method. The data enabled the PbO, B2O3, and SiO2 activities in these melts to be derived and provided evidence of their negative deviations from ideal behavior.
PbO-B2O3-SiO2 系统的独特性质，尤其是其广泛的玻璃形成成分范围，使其在各种实际应用中具有价值。迄今为止，PbO-B2O3-SiO2 熔体的热力学性质和蒸发尚未得到很好的确立，而获得的这些数据将有助于优化技术和玻璃的热力学建模。
高温 Knudsen 扩散质谱法用于研究蒸发过程，并确定 PbO-B2O3-SiO2 熔体各成分的分压。使用 MS-1301 质谱仪进行测量。蒸发是在两个石英扩散池中进行的，其中一个含有研究样品，另一个含有纯 PbO（参比物质）。离子是通过 25eV 的电子电离产生的。为了便于解释质谱，还测量了离子的出现能。
在 1100K 下，研究发现 Pb、PbO 和 O2 是研究样品上的主要蒸汽物种。从测量的 PbO 分压中得出了系统组成的 PbO 活度。计算了 B2O3 和 SiO2 的活度、形成吉布斯自由能、形成过剩吉布斯自由能和研究样品的质量损失。
使用 Knudsen 质谱法在宽组成范围内测量了 1100K 下 PbO-B2O3-SiO2 熔体的蒸汽物种分压。这些数据使我们能够推导出这些熔体中的 PbO、B2O3 和 SiO2 的活度，并提供了它们偏离理想行为的负偏差的证据。
