Investigation of sodium sulfate phase transitions in a porous material using humidity- and temperature-controlled X-ray diffraction.

摘要: Crystals growing in confined spaces can generate stress and are a major cause of damage porous materials. To investigate such deleterious processes, appropriate situ techniques required. This paper describes the use X-ray diffractometry under controlled conditions temperature relative humidity (RH-XRD) for direct observation phase transition reactions substrate. An improved environmental chamber without gradients is presented applied to investigation transformations system Na2SO4 + H2O. salt generally considered as particularly damaging frequently used accelerated weathering tests. It demonstrated that RH-XRD be successfully several relevant transitions glass frits substrates. The conversion Na2SO4(III) Na2SO4(V) hydration both proceed fairly rapidly true solid-state deliquescence educt phases. In contrast, crystallization from solution kinetically hindered there strong tendency aqueous form supersaturated solutions also narrow pores. important implications this behavior briefly discussed paper.