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Only open minds can push the limits......

Date: 2017-01-06Browse: 191

Summary of Gleiter's three contribution

  During his work at Harvard and MIT (1968 - 71) Herbert Gleiter- in cooperation with B.Chalmers, M.Ashby and M. Weins- discovered the existence of dislocations in inter-crystalline interfaces and proposed the “structural unit model” of grain boundaries describing grain boundaries as a two-dimensional array of low energy groups of atoms (structural units) the composition of which is controlled by the orientation relationship of the crystals forming the interface and the interface inclination. This model provides the basis for all of today’s grain boundary models and was cited many thousand times.

  In 1979, Herbert Gleiter and his associates invented and subsequently pioneered a new class of materials called nano-crystalline materials. The new concept of these materials was to create solids consisting of a large (50% or more) volume fraction of inter-crystalline boundaries between crystallites with the same or with different chemical compositions (single phase or multi-phase nano-crystalline materials). As the arrangements of atoms in these interfaces differ from the ones in crystals and glasses, nano-crystalline materials opened the way to solids with new atomic structures and hence new properties. Today, more than 800 papers are published annually in this area, about 6 international conferences on nano-materials are organized every year and most conferences on Materials Science have one or several sessions on nano-materials.The field of nano-materials keeps expanding at a remarkable rate: In 2011 more than 60 000 publications in this field were retrieved by the Web of Science, and according to a recent study of the German Government, the annual value of the products based on nano-materials is beyond 2 billion US$ with a growth rate of about 15 to 20% per year.

  Starting in 1989, Herbert Gleiter began to pioneer a new concept of non-crystalline materials, called nano-glasses. Contrary to today’s glassy materials with a homogeneous structure, nano-glasses consist of nanometer-sized glassy regions connected by glass/glass interfaces with new kinds of non-crystalline structures (different from today’s glasses). By varying the sizes and/or the chemical compositions of the glassy regions, the properties of nano-glasses can be changed in partially spectacular ways. For example, FeScnano-glasses were revealed to be strong ferro-magnets although melt-quenched glasses (with the same chemical compositions) were paramagnetic. Similar variations were noted for other properties. For example, nano-glasses were discovered to be highly ductile and biocompatible. In fact, cells (e.g. osteoblast cells) were revealed to grow almost one hundred times faster on titanium-based-nano-glasses than on chemically identical glasses or on comparable crystalline materials. This effect opens the door to insert implants (ceramic teeth or bones) into the human body within a few hours.The analogy between the microstructures of today’s crystalline materials on which our present technologies are based and the microstructures of nano-glasses suggests that nano-glasses may open the door to a new age of technologies, a kind of a ”glass age”. The technologies characterizing this “glass age” would be based on the new properties of nano-glasses similar to the bronze or iron age that were based on the new properties of bronze or iron when they were discovered.

Figure showing the analogy between the defect and the chemical microstructures of nano-crystalline materials and ofnano-glasses. The defect microstructure (c) and the chemical microstructure (d) of nano-crystalline materials are compared in (g)and (h) with the corresponding defect microstructure (g) and the corresponding chemical microstructure (h) of nano-glasses.