Cryptomelane型材料的制备和表征

The Synthesis and Characterization of Cryptomelane like Material

ＭｎＯ－４和Ｍｎ２＋在酸性条件和一定温度下，用氧化还原方法制得了高结晶度的Ｃｒｙｐｔｏｍｅｌａｎｅ型锰氧化物．用Ｘ射线粉末衍射法（ＸＲＤ）、傅里叶红外光谱法（ＦＴ－ＩＲ）、热重－微商热重差热分析法（ＴＧ－ＤＴＧ／ＤＴＡ）、透射电子显微镜法（ＴＥＭ）等方法对它进行了表征．研究表明，该Ｃｒｙｐｔｏｍｅｌａｎｅ中可能存在两种不同热力学性质的Ｃｒｙｐｔｏｍｅｌａｎｅ，加热Ｃｒｙｐｔｏｍｅｌａｎｅ到６００℃时，热稳定性较差的那部分转化为Ｍｎ２Ｏ３；在６００～８７０℃，Ｃｒｙｐｔｏｍｅ－ｌａｎｅ和Ｍｎ２Ｏ３共同存在；８７０℃，样品完全转化为Ｍｎ２Ｏ３；到９４０℃则Ｍｎ２Ｏ３再度失氧生成Ｍｎ３Ｏ４．另在Ｃｒｙｐ－ｔｏｍｅｌａｎｅ中存在Ｌ酸和Ｂ酸，且Ｂ酸强于Ｌ酸．

A well crystallized Cryptomelane like material has been synthesized by redox reaction between Mn 2+ and MnO - 4 under acid conditions at certain temperature. XRD,FT IR,TG DATA/DTG,TEM were used to characterize the material. There are probably two types of Cryptomelane with different thermodynamic properties in our synthesized material. At 600℃,part of the Cryptomelane with worse thermal stability transformed into Mn 2O 3,the Mn 2O 3 coexisted with the another part of Cryptomelane between 600℃ and 800℃,at 870℃,the remainder completely transformed into Mn 2O 3.Both Lewis and Bronsted acid sites have been observed in Cryptomelane and the Bronsted acid is stronger than the Lewis acid.