Alloy effects in consolidated binary mixtures of nanometer-sized crystals investigated by Mössbauer spectroscopy

Herr, U.; Jing, J.; Gonser, U.; Gleiter, H.

doi:10.1016/0038-1098(90)90542-j

Cited by 88 publications

(24 citation statements)

References 10 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: 85%

“…In certain cases, the formation of a Ag-Fe alloy solid solution is favored even though the constituents are immiscible in the crystalline and molten state (e.g. Fe and Ag) [32]. Nanocrystalline materials can be classified into several groups according to their dimensionality: zero-dimensional atom clusters, one-dimensional modulated multilayers, two-dimensional ultra-finegrained overlayers, and three-dimensional nanocrystalline structures (Fig.…”

Section: Nanostructurementioning

confidence: 99%

“…In the first family, all crystallites and interfacial regions have the same chemical composition. The second [32] with permission from Elsevier). Fig.…”

Section: Nanostructurementioning

confidence: 99%

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Nanocrystalline materials and coatings

Tjong

Chen

2004

Materials Science and Engineering: R: Reports

844

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respect, dislocation pile-ups cannot form, and the Hall-Petch relationship for conventional coarse-grained materials is no longer valid.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: 85%

Section: Nanostructurementioning

confidence: 99%

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Nanocrystalline materials and coatings

Tjong

Chen

2004

Materials Science and Engineering: R: Reports

844

345

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“…TambiŽn que, en aleaciones nanoestructuradas, la solubilidad en las regiones interfaciales puede variar con respecto a la de los cristalitos de una manera significativa. As' por ejemplo, la Ag y el Fe que no son miscibles ni en estado fundido, forman soluciones s-lidas en las regiones interfaciales de nanocompuestos Ag-Fe (16).…”

Section: Estructura De Los Materiales Nanocrista-linos Y Su Efecto Sounclassified

El procesado de polvos cerámicos nanoparticulados

Durán¹

1999

Bol. Soc. Esp. Ceram. Vidr.

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Los materiales cer ‡micos nanof ‡sicos, caracterizados por un tama-o de grano ultrafino (< 100 nm), han despertado un gran interŽs en los oeltimos a-os debido a sus inusuales propiedades mec ‡nicas, elŽctricas, -pticas y magnŽticas. Los polvos cer ‡-micos nanoparticulados pueden prepararse mediante el uso de diversas rutas qu'micas como sol-gel, coprecipitaci-n, hidrotermal, etc., y rutas termof'sicas como condensaci-n en fase vapor, ablaci-n l ‡ser, evaporaci-n por bombardeo electr-nico, etc. El autor cree que para la producci-n de grandes cantidades de polvos nanoparticulados con uno o varios componentes, las rutas de s'ntesis qu'micas sol-gel y/o gel-precipitaci-n son las m ‡s adecuadas y, sobre esta base, se analizan las caracter'sticas m ‡s relevantes de los polvos nanoparticulados de Y-TZP as' preparados, como tama-o de part'cula y de aglomerados de los polvos calcinados, su morfolog'a y comportamiento en la compactaci-n, estructura de los compactos y su comportamiento mediante densificaci-n convencional que conducen a la obtenci-n de materiales densos (> 99% densidad te-rica), reteniendo el tama-o de grano dentro de la escala nanomŽtrica. DespuŽs de hacer una breve revisi-n de algunas tŽcnicas no convencionales como sinterizaci-n activada mediante plasma, forjado en caliente o prensado isost ‡tico en caliente, para la producci-n de materiales cer ‡micos densos y nanoestructurados, el autor concluye dando un resumen de las caracter'sticas que deben reunir los polvos cer ‡micos nanoparticulados para la fabricaci-n de materiales cer ‡micos completamente densos y nanoestructurados de Y-TZP mediante sinterizaci-n convencional.Palabras clave: Nanopart'culas, polvos cer ‡micos, procesado. Processing of nanocrystalline ceramic powdersNanophase materials, characterized by an ultra fine grain size (< 100 nm) have created a high interest in the last years owing to their unusual mechanical, electrical, optical and magnetic properties. The nanoparticulate ceramic powders can be prepared using several chemical synthesis routes as for example, sol-gel, gel-precipitation, hydrothermal, etc, and other thermophisics ones as gas phase condensation, laser ablation, electron beam evaporation, etc. The author believes that for the production of sufficient quantities of nanocrystalline ceramic powders chemical synthesis routes as sol-gel and/or gel-precipitation are the most adequate and, on that basis, the characteristics of the as prepared Y-TZP nanocrystalline powders, as particle and agglomerate sizes, morphology and compaction behaviour, green compacts structure, and conventional densification behaviour leading to achieve almost fully dense (>99% theoretical) ceramics with a grain size within the nanoscale, are evaluated. After reviewing briefly some no conventional techniques as plasma activated sintering, hot pressing, sinter-forging, etc, for processing nanocrystalline powders into nanostructured ceramics, a summary of the best nanocrystalline Y-TZP ceramic powder characteristics required to achieve nanostructured mater...

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“…Such an enhancement of the solute solubility in the space charge region was, indeed, experimentally revealed. 15) The Moessbauer spectrum (shown in Fig. 8), together with the results of X-ray diffraction experiments, indicates that in a region (about 4 atomic layers thick) on both sides of the interphase boundaries between the Ag and the Fe crystals, a Ag-Fe solid solution is formed (Fig.…”

Section: Electronic Tuning Of the Chemical And Physical Properties Ofmentioning

confidence: 99%

Is there a Hidden World of New Materials and Effects “between” the Elements of the Periodic Table?

Gleiter

2003

Mater. Trans.

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A constrained state of solid matter is known to exist in the cores of crystal defects -for example -in the cores of intercrystalline interfaces. This constrained state of solid matter differs structurally and propertywise from other (unconstrained) solid states such as perfect crystals, glasses etc. in terms of its atomic and electronic structure as well as in its chemical composition. It is the basic idea of nanocrystalline solids to generate a novel type of materials by incorporating such a high density of defect cores into a -formerly -perfect crystal that the total volume of these defect cores becomes comparable to the total volume of the residual lattice regions between the defect cores. The resulting solids are called nanocrystalline solids. Due to the large volume fraction of defect cores, nanocrystalline solids differ from other forms of solids (e.g. single crystals, coarse-grained polycrystals, glasses) in terms of their atomic and electronic structure, their chemical composition and by the fact that the size of the crystalline regions between neighbouring defects is reduced to a few interatomic spacings. As the properties of solids depend on exactly those four parameters (atomic structure, electronic structure, chemical composition and crystal size), the properties of nanocrystalline solids deviate from the ones of crystalline or glassy materials. In this paper attention will be focused on the tuning of the electronic structure of solids by means of their nanostructure. In fact, solids with nanometer-sized microstructures may open the way to generate materials with an excess or a deficit of electrons or holes of up to 0.3 electrons/holes per atom i.e. elements that are electronically ''between'' the (electrically neutral) elements of the periodic table. Large deviations from charge neutrality may be achieved either by means of an externally applied voltage or by the space charges at interfaces between materials with mobile charge carriers (such as metals or semiconductors) and with different chemical compositions (or combinations of both). As many properties of solid materials depend on their electronic structure, significant deviations from charge neutrality may lead the way into a world of materials with new, yet mostly unexplored properties such as modified electric, ferromagnetic, optical etc. properties. Some existing and conceivable new technological applications of solids deviation from charge neutrality are briefly discussed.

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Alloy effects in consolidated binary mixtures of nanometer-sized crystals investigated by Mössbauer spectroscopy

Cited by 88 publications

References 10 publications

Nanocrystalline materials and coatings

Nanocrystalline materials and coatings

El procesado de polvos cerámicos nanoparticulados

Is there a Hidden World of New Materials and Effects “between” the Elements of the Periodic Table?

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Alloy effects in consolidated binary mixtures of nanometer-sized crystals investigated by Mössbauer spectroscopy

Cited by 88 publications

References 10 publications

Nanocrystalline materials and coatings

Nanocrystalline materials and coatings

El procesado de polvos cerámicos nanoparticulados

Is there a Hidden World of New Materials and Effects &ldquo;between&rdquo; the Elements of the Periodic Table?

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Product

Resources

About

Is there a Hidden World of New Materials and Effects “between” the Elements of the Periodic Table?