拉曼光谱研究不同风化过程中七水硫酸镁晶体相转变行为

Raman Spectral Investigations on the Phase Transition Behaviors of MgSO_4·7H_2O Crystals in Different Efflorescence Processes

通过不同的相对湿度(relative humidity,RH)调节方法,获得了MgSO4.7H2O晶体不同风化过程中的原位共聚焦拉曼光谱,实现了不同阶段相转变细节的观测。在快速和慢速风化过程中,MgSO4.7H2O晶体在RH 3%时均转变生成MgSO4.3H2O晶体。而在潮解过程中,不同风化过程形成的MgSO4.3H2O晶体的相转变行为并不相同。对应于快速风化过程,MgSO4.3H2O晶体在RH70%时转化为MgSO4.6H2O晶体,而对应于慢速风化过程,MgSO4.3H2O晶体则潮解形成过饱和MgSO4液滴。研究结果表明MgSO4不同水合晶体之间的相转变行为与RH改变路径有关。

In the present paper,the in situ confocal Raman spectra of MgSO4·7H2O crystal in different efflorescence processes were obtained through changing relative humidities in differernt ways.Thus,detailed investigation of phase transition of MgSO4·7H2O crystal was achieved.At 3% RH,the phase transition of MgSO4 crystal from MgSO4·7H2O to MgSO4·3H2O both occurred in the fast-efflorescence and slow-efflorescence processes.However,in the deliquescence process,distinct phase transition behaviors were found between the MgSO4·3H2O crystals which formed in different efflorescence processes.the MgSO4·3H2O crystals formed in fast-efflorescence process transformed to MgSO4·6H2O crystals at 70% RH in the deliquescence process.On the contrary,the MgSO4·3H2O crystals formed in slow-efflorescence process deliquesced to supersaturated MgSO4 droplet.The studies indicated that there is a correlation between the phase transition behaviors and ways of changing RH for the different MgSO4 crystal hydrates.