Grain boundary complexions in ceramics and metals: An overview

Dillon, Shen J.; Harmer, Martin P.; Luo, Jian

doi:10.1007/s11837-009-0179-3

Cited by 77 publications

(53 citation statements)

References 58 publications

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“…Furthermore, it is worth noting that nanometer-thick IGFs investigated in this study only represent one of several types of GB complexions discovered recently [23,51e53]; such GB complexions (a.k.a. interfacial phases that are thermodynamically 2-D) exist ubiquitously in both metallic and ceramic materials, where they can often critically influence or even control a board range of transport, mechanical, and physical properties [23,25,27,43,51,54e71] beyond sintering.…”

Section: Further Discussion Of Activated Sintering Mechanisms and Beyondmentioning

confidence: 99%

Probing the densification mechanisms during flash sintering of ZnO

et al. 2017

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a b s t r a c tThe eutectic temperature and composition of the TiO 2 -CuO system were carefully measured to be 1010 ± 10 C and 83CuO:17TiO 2 , respectively. Subsequently, a TiO 2 -CuO phase diagram was computed, representing a correction and major improvement from the phase diagram available in literature. Dilatometry measurements and isothermal sintering experiments unequivocally demonstrated the activated (enhanced) sintering of TiO 2 with the addition of CuO, occurring at as low as >300 C below the eutectic temperature. High resolution transmission electron microscopy (HRTEM) characterization of waterquenched specimens revealed the formation of nanometer-thick, liquid-like, intergranular films (IGFs), a type of grain boundary (GB) complexion (a.k.a. 2-D interfacial phase), concurrently with accelerated densification and well below the bulk eutectic temperature. Consequently, activated sintering is explained from the enhanced mass transport in this premelting-like complexion. An interfacial thermodynamic model was used to quantitatively explain and justify the stabilization of liquid-like IGFs below the eutectic temperature and the temperature-dependent IGF thicknesses measured by HRTEM. A GB l diagram was computed, for the first time for a ceramic system, to represent the thermodynamic tendency for general GBs in CuO-doped TiO 2 to disorder.

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Section: Further Discussion Of Activated Sintering Mechanisms and Beyondmentioning

confidence: 99%

Probing the densification mechanisms during flash sintering of ZnO

et al. 2017

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“…Diffuse-interface models have demonstrated the existence of abrupt (first-order) interfacial "phase" transitions at GBs. 7,34,54 Furthermore, phenomenological models 12,28,32,55 showed that an atomic-size effect can produce a series of discrete GB phases (which are called Dillon-Harmer complexions) 5,10,11,55-57 : namely, intrinsic/clean GBs, monolayers, bilayers, trilayers, nanoscale IGFs (with a continuous equilibrium thickness on the order of 1 nm), and complete wetting films (with an arbitrary thickness). The origin of this series of discrete GB "phases" can be well understood via an analogy to layering transitions in a case of multilayer surface adsorption on attractive/inert substrates.…”

Section: E Rigorous Gb "Phase" Diagrams and Dillon-harmer Complexionsmentioning

confidence: 99%

Developing grain boundary diagrams as a materials science tool: A case study of nickel-doped molybdenum

2011

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Impurity-based, premelting-like, grain boundary (GB) "phases" (complexions) can form in alloys and influence sintering, creep, and microstructural development. Calculation of Phase Diagrams (CalPhaD) methods and Miedema-type statistical interfacial thermodynamic models are combined to forecast the formation and stability of subsolidus quasiliquid GB phases in binary alloys. This work supports a long-range scientific goal of developing "GB (phase) diagrams" as a new materials science tool to help controlling the materials fabrication processing and resultant materials properties. Using nickel-doped molybdenum as a model system, a type of GB diagram (called "λ diagram") is computed to represent the temperature-and composition-dependent thermodynamic tendency for general GBs to disorder. Subsequently, controlled sintering experiments are conducted to estimate the GB diffusivity as a function of temperature and overall composition, and the experimental results correlate well with the computed GB diagram. Although they are not yet rigorous GB-phase diagrams with well-defined transition lines, the predictability and usefulness of such λ diagrams are demonstrated. Related interfacial thermodynamic models and computational approaches are discussed.

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“…The term "complexion" has been suggested to separate these interfacial phases from ordinary bulk phases. 7,8 The equilibrium complexion is determined by intensive thermodynamic variables as temperature T and chemical potentials μ i , but also by the boundaries provided by the adjoining bulk phases.…”

Section: Introductionmentioning

confidence: 99%

“…[7][8][9] In some cases, kinetic rates associated with different interfacial complexions may span several orders of magnitude, exemplified by, e.g., activated sintering in several W-metal systems caused by premelting in grain boundaries, 6,10 and changes in grain boundary mobility in doped alumina. 7 Knowledge of how to control interfacial structure and thereby atomic transport rate is thus key for performing "interfacial kinetic engineering" 9 as a means to tailor a microstructure for a specific application.…”

Section: Introductionmentioning

confidence: 99%

First-principles study of an interfacial phase diagram in the V-doped WC-Co system

Johansson

Wahnström

2012

Phys. Rev. B

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We present a method of determining an interfacial phase diagram using density functional theory calculations for interface energetics. Cluster expansions based on these calculations are used in Monte Carlo simulations to obtain configurational free energies. The method is applied to study the segregation of V to the WC(0001)/Co interface and to construct the corresponding interface diagram, a "complexion" phase diagram. By CALPHADtype analysis for the adjoining bulk phases, a connection with real materials is made. We find that, in equilibrium, the interface contains a thin V-rich film for a wide range of temperatures and chemical potentials of V corresponding to V additions below the (V,W)C x solubility limit. The results are compared with available experimental data, and implications of the strong segregation of V for the sintering process of V-doped WC-Co are discussed.

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Grain boundary complexions in ceramics and metals: An overview

Cited by 77 publications

References 58 publications

Probing the densification mechanisms during flash sintering of ZnO

Probing the densification mechanisms during flash sintering of ZnO

Developing grain boundary diagrams as a materials science tool: A case study of nickel-doped molybdenum

First-principles study of an interfacial phase diagram in the V-doped WC-Co system

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