In this work, a series of Mn-based borohydrides were synthesized by mechanochemical milling of ABH\(_4\)-MnCl\(_2\) (where A=Li, Na, K) under argon. Samples prepared by milling xLiBH\(_4\)-MnCl\(_2\) (where x = 2 or 3) resulted in the formation of Mn(BH\(_4\))\(_2\) and LiCl in a stoichiometric ratio. Thermal decomposition of Mn(BH\(_4\))\(_2\) was observed between 105 and 180°C with the concurrent evolution of hydrogen and diborane. Analysis of the decomposition products suggested the presence of amorphous B, Mn and LiCl. When NaBH\(_4\) was used as a reagent, Mn(BH\(_4\))\(_2\) was also observed, however instead of NaCl, a solid solution of NaCl\(_x\)(BH\(_4\))\(_1\)\(_-\)\(_x\) and Na\(_6\)MnCl\(_8\) were formed. Mn(BH\(_4\))\(_2\) decomposed between 110 and 170°C for xNaBH\(_4\)-MnCl\(_2\) with the concurrent evolution of hydrogen and diborane. Analysis of the decomposed samples showed that amorphous B and Mn formed (110 to 170°C) and NaCl\(_x\)(BH\(_4\))\(_1\)\(_-\)\(_x\) reacted with Na\(6\)MnCl\(_8\) to produce NaCl (250 to 475°C). When KBH\(_4\) was used as a reagent, Mn(BH\(_4\))\(_2\) was not observed. Rather, K\(_2\)Mn(BH\(_4\))\(_4\), KMnCl\(_3\) and unreacted KBH\(_4\) were observed. The mass losses for the milled sample were observed between 100 to 160°C with a release of hydrogen and trace diborane, forming KBH\(_4\), B, and Mn, and between 165 to 260°C with only hydrogen release, giving KCl, B and Mn.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:573512 |
| Date | January 2012 |
| Creators | Liu, Ruixia |
| Publisher | University of Birmingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.bham.ac.uk//id/eprint/4301/ |
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