Synthesis of Ramsdellite by Refluxing Process and Its Influencing Factors

Nanosized ramsdellite was synthesized by oxidizing 30 mmol Manganese(II) sulfate dissolved in different amounts of hydrochloride(0,10,20 and 40 mmol) with adding 60 mmol sodium hypochlorite solution at constant velocity of 1 mL/min minute using a refluxing process at atmospheric pressure at different temperatures(60,80 and 100℃).The products were characterized by XRD diffraction,scanning electron microscope and automated surface area analyzer.The effects of reflux temperature,time and amount of hydrochloric acid on the crystal structures,micromorphologies and yield of products were investigated.It was observed that nano-particles of conglobated ramsdellite was prepared at 60℃,and particle size increased with elevating the refluxing temperature.Both aggregate level and particle size of ramsdellite decrease after adding hydrochloric acid into the reaction solution.When the reflux reaction was carried out at 100℃ with adding different amount of hydrochloric acid,nano-size particles of ramsdellite were formed firstly,and then needle-like fibers of products came into being formed.The concentration of hydrochloric acid in the reaction system plays an important role in the morphologies of ramsdellite crystal,which acts more remarkably at higher temperatures.It is favorable to the formation of needle-like ramsdellite in nano size and aggregation with loose structures by addition of no less than 10 mmol hydrochloric acid into the reaction solution at 100℃.Ramsdellite particles with high specific surface area(maximum of 66.32 m2/g) are more prone to be formed by adding hydrochloric acid into the reaction solution at lower refluxing temperature.Product yield increases firstly and then decreases with the increase of the amount of hydrochloric acid and refluxing temperature,and the highest yield can be as high as 97.5%.