A review on molten sulfate salts induced hot corrosion

Hot corrosion has been extensively observed in various high temperature applications,which might cause large economic losses.To deepen the insight and understanding of hot corrosion,herein,we provide a detailed discussion on hot corrosion induced by molten sulfate salt,in which Na_(2)SO_(4)is the main chemical reactant.The hot corrosion is triggered and sustained by the negative solubility gradient of protective oxide from the oxide/salt interface to salt/gas interface.In this work,we reviewed several key factors,including temperature,gas composition,molten salt composition,alloy element and external stress,influencing the hot corrosion of alloy beneath the molten salt.The application of anti-corrosion coating seems to be the most effective and commercial mothed to mitigate hot corrosion.Therefore,the progress of the development of effective coatings,e.g.,Ni-Cr coatings,aluminide coatings,silicide coatings and MCrAlY(X)coatings,has also been summarized.

An experimental study of salt expansion in sodium saline soils under transient conditions

Salt expansion in sulfate saline soils that are widely distributed in northwestern China causes serious infrastructural damages under low-temperature conditions. However, the mechanism of salt expansion under low temperatures is not clear. In this study, we conducted a series of cooling experiments combined with salt crystallization to study this mechanism, and employed an ionic model to calculate the supersaturation ratio of the solution. During the experiments, the strength and the process of salt expansion were examined under different cooling rates and various crystal morphologies. The relationship between temperature and supersaturation ratio under transient conditions was also considered. Results indicate that the initial supersaturation ratio of a sodium sulfate solution is closely related to environmental conditions, and that this ratio decreases with slowing the cooling rates and stabilizing the crystal forms. Higher initial supersaturation ratios lead to an increased non-steady-state zone, resulting in less salt expansion. On the other hand, chloride ion content has a distinct influence on the crystallization supersaturation ratio of the sodium sulfate solution, and higher chloride ion content can inhibit salt expansion in sodium saline soils. These findings help explain salt expansion mechanisms in complex conditions such as seasonally frozen soils, and thus help search for improved methods of preventing salt expansion in sulfate saline soils.

Mild hydrothermal preparation of a layered metal hydroxide salt with microtube/rod morphology

Microtubes/rods of the layered metal hydroxide salt compound Cd2（OH）3（DS）·nH2O, where DS stands for dodecyl sulfate sandwiched between two adjacent inorganic sheets, have been synthesized for the first time through a mild hydrothermal reaction route. The microtubes/rods have a diameter of about 1 μm and a length ranging from several microns to 20μm. The growth process of microtubes/rods under the experimental conditions employed follows a dissolution-recrystallization route.

Characteristics of dry deposited mineral particles associated with weather conditions in the adjacent sea areas of East China during a cruise in spring 2011

Dry deposited particles, larger than 1.3 μm, were collected under clear, cloudy, and foggy conditions during a cruise, traversing the Yellow Sea and the East China Sea from 23 March to 8 April 2011. In these areas, air masses are influenced by pollution outflows from the Asian continent. The size and elemental composition of dry deposited particles were investigated using a scanning electron microscope. Number-size distributions of these particles were approximately lognormal. Under clear conditions, the mode size was about 5.0 μm, with a mean diameter of 6.9 μm. Under cloudy and foggy conditions, the mean diameters were 5.7 and 6.0 μm, respectively, but the mode sizes were vague. Non-mixed mineral particles, sea salt, and mixed mineral-sea salt particles were the major particle types. Correspondingly, Al and Si were the most frequently detected elements. Frequencies of K-, Ca-, and S-containing particles were highest under foggy conditions, while the frequency of Na-containing particles was lowest. These results indicate that fog favored sulfate production on the particles and led to the deposited mineral particles more abundant in secondary salt, suggesting the importance to consider the dependence of the comoosition of deoosited mineral narticles on weather as well as narticle size.