Effects of Citric Acid on Hydration Process and Mechanical Properties of Thermal Decomposed Magnesium Oxychloride Cement

In order to make full use of salt lake magnesium resources and improve the strength of the thermal decomposed magnesium oxychloride cement （TDMOC）, the effects of citric acid on the hydration process and mechanical properties of TDMOC was studied. The hydration heat release at initial 24 h and strengths at 3, 7, and 28 days of TDMOC specimens were conducted. The hydration products and paste microstructure were analyzed by XRD, FT-IR and SEM, respectively. The results showed that citric acid can not only reduce the 24 h hydration heat release and delay the occurring time of second peak of TDMOC, but also produce more 5Mg（OH）z.MgC12.SH20 and less Mg（OH）2 in hydration process of TDMOC. More perfect and slender crystals were observed in the microstructure of the TDMOC pastes with citric acid. The results demonstrated that citric acid as an additive of TDMOC can decrease the hydration heat release and increase the compressive strength and flexural strength of TDMOC. The possible mechanism for the strength enhancement was discussed.

Effect of the post-annealing temperature on the thermal-decomposed NiO_(x) hole contact layer for perovskite solar cells

A hysteresis-less inverted perovskite solar cell(PSC)with power conversion efficiency(PCE)of 13.57%was successfully achieved based on the thermal-decomposed NiO_(x) hole contact layer,possessing better electron blocking and hole extraction properties for its suitable work function and high-conduction band edge position.Herein,the transparent and high-crystalline NiO_(x) film is prepared by thermal-decomposing of the solution-derived Ni(OH)_(2) film in our study,which is then employed as hole transport layer(HTL)of the organic–inorganic hybrid PSCs.Reasonably,the post-annealing treatment,especially for the annealing temperature,could greatly affect the Ni(OH)_(2) decomposition process and the quality of decomposed NiO_(x) nanoparticles.The vital NiO_(x) HTLs with discrepant morphology,crystallinity and transmission certainly lead to a wide range of device performance.As a result,an annealing process of 400℃/2 h significantly promotes the photovoltaic properties of the NiO_(x) layer and the further device performance.