title: Environmentally friendly gamma-MnO2 hexagon-based nanoarchitectures: structural understanding and their energy-saving applications.
abstract: Although about 200,000 metric tons of gamma-MnO(2) are used annually worldwide for industrial applications, the gamma-MnO(2) structure is still known to possess a highly ambiguous crystal lattice. To better understand the gamma-MnO(2) atomic structure, hexagon-based nanoarchitectures were successfully synthesized and used to elucidate its internal structure for the present work. The structural analysis results, obtained from the hexagon-based nanoarchitectures, clearly show the coexistence of akhtenskite (epsilon-MnO(2)), pyrolusite (beta-MnO(2)), and ramsdellite in the so-called gamma-MnO(2) phase and verified the heterogeneous phase assembly of the gamma-MnO(2) state, which violates the well-known "De Wolff" model and derivative models, but partially accords with Heuer's results. Furthermore, heterogeneous gamma-MnO(2) assembly was found to be a metastable structure under hydrothermal conditions, and the individual components of the heterogeneous gamma-MnO(2) system have structural similarities and a high lattice matches with pyrolusite (beta-MnO(2)). The as-obtained gamma-MnO(2) nanoarchitectures are nontoxic and environmentally friendly, and the application of such nanoarchitectures as support matrices successfully mitigates the common problems for phase-change materials of inorganic salts, such as phase separation and supercooling-effects, thereby showing prospect in energy-saving applications in future "smart-house" systems.
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale, University of Science & Technology of China, Hefei, Anhui 230026, PR China.
authors.forename: Changzheng
authors.initials: C
authors.lastname: Wu
authors.forename: Wei
authors.initials: W
authors.lastname: Xie
authors.forename: Miao
authors.initials: M
authors.lastname: Zhang
authors.forename: Liangfei
authors.initials: L
authors.lastname: Bai
authors.forename: Jinlong
authors.initials: J
authors.lastname: Yang
authors.forename: Yi
authors.initials: Y
authors.lastname: Xie
mesh_terms: D045744:Cell Line, Tumor; D003246:Conservation of Energy Resources; D018360:Crystallography, X-Ray; D055772:Green Chemistry Technology / Q000379:methods*; D006801:Humans; D017895:Manganese Compounds / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D012449:Safety
chemical_list: D017895:Manganese Compounds; D010087:Oxides; C016552:manganese dioxide