准晶材料专业用.ppt

NEWS：In recent,The Nobel Prizes are being awarded , the chemistry prize goes to Daniel Schechtman for his work on something called quasicrystals. Schechtman discovered these crystals in 1982, and they fundamentally changed the way scientists looked at solid matter. The Brief Introduction of Quasicrystal (QC:准晶)contents The Definition of QC The Structure Characteristics of QC The Properties and Applications of QCs Conclusion The Definition of QC A quasiperiodic crystal, or, in short, QC, is a structure that is ordered but not periodic. A quasicrystalline pattern can continuously fill all available space, but it lacks translational(平移的) symmetry. The first “natural quasicrystal” The Structure Characteristics of QC QCs are structural forms that are both ordered and nonperiodic.They form patterns that fill all the space but lack translational symmetry. QCs display symmetry of other orders (folds). Just like crystals,QCs produce Bragg diffraction(布拉格衍射), but where crystals have a simple repeating structure. QCs are more complex. The Structure Characteristics of QC D. Shechtman, I. Blech, D. Gratias, J.W. Cahn (1984)Al6Mn model The Properties and Applications of QCs Poor conductors of heat and electricity Nonsticking（不粘特性） Low friction coefficient（摩擦系数） Mechanical property The Properties and Applications of QCs Applications in daily life: non-stick cookware(不粘炊具) Applications in industry:auto parts ；aerospace materials；engine materials Conclusion To summarize,QCs are clearly fascinating materials:crystal structures,with their five-fold symmetry,could be remarkably useful.Of course,there are still many problems we must face.For instance, producing industrial quantities of good quality quasicrystals is not simple,and material cost is another challenge But the future is promising and the present is already bearing its fruits. Thanks!!!