224 KB20 KB200820262011Dolinšek, Janezštevilka:5letnik:58str. 180-188ISSN:0473-7466COBISSID:25448999URN:URN:NBN:SI:doc-3S4TAPHHslDruštvo matematikov, fizikov in astronomov SlovenijeObzornik za matematiko in fizikoDanny Shechtmankemijakristalna mrežakvazikristaliNobelova nagradaShechtman, DannyNobelovo nagrado za kemijo 2011 je prejel Danny Shechtman za odkritje kvazikristalov|Quasicrystals are materials having a new type of perfect long-range order without translational periodicity. Their symmetries (icosahedral, dodecagonal, decagonal, octagonal, and pentagonal) involve symmetry elements such as 5-, 8-, 10-, and 12-fold rotation axes, which are incompatible with the periodicity of a Bravais lattice. A consequence of nonperiodicity is that quasicrystals - alloys of matallic elements (Al-Pd-Mn, Al-Cu-Fe, Al-Ni-Co, Tb-Mg-Zn, etc.) - exhibit more semimetallic to insulating-like properties. Their favourable physical and mechanical properties - high hardness, resistance to corrosion and wear, low friction coefficient, low electrical and thermal conductivity, superplasticity at elevated temperatures, ability to store large ammounts of hydrogen - make quasicrystals interesting new materials for the technological application. Quasiperiodic symmetries are observed also in self-organized soft matter. The Nobel prize 2011 for chemistry was awarded to Israel scientist Danny Shechtman for the discovery of quasicrystals. This discovery has an interesting history, showing the difficulties of accepting a new breaktrough discovery in the scientific societyKvazikristali so snovi, v katerih obstaja nov red dolgega dosega brez translacijske simetrije. Njihove simetrije vsebujejo kristalografsko "prepovedane" elemente kot so 5-, 8-, 10- in 12-števna rotacijska os. Kvazikristali so zlitine kovinskih elementov (Al-Pd-Mn, Al-Cu-Fe, Al-Ni-Co, Tb-Mg-Zn, itd.), kvaziperiodične simetrije pa najdemo tudi v samoorganizirani mehki snovi. Visokokvalitetni kvazikristali imajo veliko električno upornost in majhno toplotno prevodnost, nekateri so trši od jekel, kemijsko nereaktivni (ne korodirajo) in imajo majhen količnik trenja. V njih je možno uskladiščiti velike količine vodika. Za odkritje kvazikristalov je izraelski znanstvenik Danny Shechtman prejel Nobelovo nagrado 2011 za kemijo. Scechtmanovo odkritje kvazikristalov ima zanimivo in poučno zgodovino, ki kaže kako težko je prodreti s popolnoma novimi spoznanji v mednarodno strokovno javnostTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaDruštvo matematikov, fizikov in astronomov