Exafs studies of nanocrystalline materials exhibiting a new solid state structure with randomly arranged atoms

Haubold, T.; Birringer, R.; Lengeler, B.; Gleiter, H.

doi:10.1016/0375-9601(89)90049-2

Cited by 167 publications

(47 citation statements)

References 8 publications

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“…structure is similar to that in coarser-grained materials [20][21][22][23][24][25][26][27][28][29][30], while others proposed a frozen 'gaslike' structure of the grain boundaries in which the atomic arrangement at interfacial region lacks short-or long-range order [31][32][33]. In nanocrystalline solids a large fraction of atoms are located near grain boundaries.…”

Section: Nanostructurementioning

confidence: 83%

Nanocrystalline materials and coatings

Tjong

Chen

2004

Materials Science and Engineering: R: Reports

842

345

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In recent years, near-nano (submicron) and nanostructured materials have attracted increasingly more attention from the materials community. Nanocrystalline materials are characterized by a microstructural length or grain size of up to about 100 nm. Materials having grain size of $0.1 to 0.3 mm are classified as submicron materials. Nanocrystalline materials exhibit various shapes or forms, and possess unique chemical, physical or mechanical properties. When the grain size is below a critical value ($10-20 nm), more than 50 vol.% of atoms is associated with grain boundaries or interfacial boundaries. In this respect, dislocation pile-ups cannot form, and the Hall-Petch relationship for conventional coarse-grained materials is no longer valid. Therefore, grain boundaries play a major role in the deformation of nanocrystalline materials. Nanocrystalline materials exhibit creep and super plasticity at lower temperatures than conventional micro-grained counterparts. Similarly, plastic deformation of nanocrystalline coatings is considered to be associated with grain boundary sliding assisted by grain boundary diffusion or rotation. In this review paper, current developments in fabrication, microstructure, physical and mechanical properties of nanocrystalline materials and coatings will be addressed. Particular attention is paid to the properties of transition metal nitride nanocrystalline films formed by ion beam assisted deposition process. #

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Section: Nanostructurementioning

confidence: 83%

Nanocrystalline materials and coatings

Tjong

Chen

2004

Materials Science and Engineering: R: Reports

842

345

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“…Several other researchers believe grain boundaries in nanocrystalline state to be more disordered than in the conventional microcrystalline materials. [19][20][21][22][23] Though the 'grains' and 'grain boundaries' in nanocrystalline state have been visualized in a way which is remarkably different from the traditional concept of large grains separated by considerably thin boundaries in the case of conventional microcrystalline materials, in this review, the terms 'grains' and 'grain boundaries' will continue to be used in the traditional sense. However, it is important to reflect that the structure of nc-materials is visualized as consisting of two components: a crystalline component (CC), which is formed by small equiaxed single crystals and the intercrystalline component (IC), [12,24] as shown in Figure 1.…”

Section: Structure and Properties Of Nanocrystalline Alloysmentioning

confidence: 99%

Role of Nanostructure in Electrochemical Corrosion and High Temperature Oxidation: A Review

Mahesh

Raman

2014

Metall Mater Trans A

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The extremely fine grain size of nanocrystalline (nc) metallic alloys results in significantly different mechanical, electrochemical and oxidation properties as compared to the coarse-grained alloys of the same composition. Although the synthesis and attractive mechanical properties of nanocrystalline materials have been investigated and reviewed in great depth, the high temperature oxidation and electrochemical corrosion of these materials has received limited attention. The difference in the active dissolution and passivation behavior of nc alloys as compared to their microcrystalline counterparts varies for each alloy system. However, a unified theory explaining these phenomena still eludes us. In this context, this article reviews the progress in the electrochemical corrosion behavior of different nanocrystalline alloys, and hence, develops a better understanding of the effect of grain size, composition, interfacial phenomena and selective dissolution on corrosion of nanocrystalline alloys. This review also presents the role of nanometric grain size and the associated increase in grain boundary diffusion on the high temperature oxidation of nc alloys. The attractive possibility of enhanced oxidation resistance at lower alloying additions as compared to the coarse-grained alloys has been discussed. Although the primary focus of the article is on ferrous alloy systems, however, the lead studies on the role of ultrafine grain size in oxidation/corrosion behavior of other alloys systems have also been reviewed.

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“…These different atomic arrangements can be attributed to the presence of interfacial region and crystalline region [51]. Similarly, EXFAS investigation of nanocrystalline Fe and Pd indicated a large reduction in the atomic coordination number, supporting the idea of a very disordered structure at the interfaces [52][53][54][55][56]. Positron-lifetime spectroscopy measurements showed a large density of vacancy-like defects in grain boundaries and relatively large free volume at the triple points arising from misorientationinduced atomic instability of these sites [57].…”

Section: Dual Phase Modelmentioning

confidence: 80%