Dislocations in Ceramics

Mitchell, T. E.

doi:10.1002/9783527631940.ch21

Cited by 3 publications

(3 citation statements)

References 171 publications

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“…Due to strong ionic and covalent bond-ing, most ceramics are plastically deformable only at high temperatures through uniaxial compression tests or creep tests. [7][8][9] In fact, high-temperature deformation has been so far one of the most commonly adopted methods to engineer dislocations in oxides and harness the functionality. 1,4,10 Under such circumstances, the combination of external mechanical loading and thermal heating during deformation makes it challenging to pinpoint the thermal effect on the dislocation structure evolution.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, much less is known about the thermal effect on the evolution of pre‐engineered, room‐temperature (RT) dislocations in ceramics. Due to strong ionic and covalent bonding, most ceramics are plastically deformable only at high temperatures through uniaxial compression tests or creep tests 7–9 . In fact, high‐temperature deformation has been so far one of the most commonly adopted methods to engineer dislocations in oxides and harness the functionality 1,4,10 .…”

Section: Introductionmentioning

confidence: 99%

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Thermally enhanced dislocation density improves both hardness and fracture toughness in single‐crystal SrTiO₃

et al. 2022

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Dislocation‐tuned functionality in ceramic oxides for potential versatile applications gains increasing attention. As the widespread chemical doping suffers from poor temperature stability, dislocations in well‐controlled mesoscopic structure may be an alternative to thermally stable intrinsic doping features. To this end, the dislocation density in plastic zones introduced by cyclic Brinell indentation is considered under thermal annealing conditions. The considerably enhanced dislocation density due to thermal treatment is found to impact both microhardness and fracture toughness, albeit only to a modest degree. The mechanistic understanding centers around enhanced mobility and multiplication of the pre‐engineered dislocations at elevated temperatures driven by the residual indentation stress, as well as the strengthened interaction of point defects and dislocations at high temperature.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermally enhanced dislocation density improves both hardness and fracture toughness in single‐crystal SrTiO₃

et al. 2022

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“…The strong resistance to plastic deformation in most ceramic materials originates from the character of the chemical bonds and the limited density of dislocation slip planes which do not allow for appreciable nucleation and mobility of dislocations under normal conditions . Grain size refinement, with the resulting expansion of the grain boundary network, may act as an additional effective barrier for dislocations, further reducing plasticity and increasing hardness—often referred to as Hall‐Petch relation .…”

Section: Introductionmentioning

confidence: 99%

Size‐induced grain boundary energy increase may cause softening of nanocrystalline yttria‐stabilized zirconia

et al. 2019

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An increase in hardness with reducing grain sizes is commonly observed in oxide ceramics in particular for grain sizes below 100 nm. The inverse behavior, meaning a decrease in hardness below a critically small grain size, may also exist consistently with observations in metal alloys, but the causing mechanisms in ceramics are still under debate. Here we report direct thermodynamic data on grain boundary energies as a function of grain size that suggest that the inverse relation is intimately related to a size‐induced increase in the excess energies. Microcalorimetry combined with nano and microstructural analyses reveal an increase in grain boundary excess energy in yttria‐stabilized zirconia (10YSZ) when grain sizes are below 36 nm. The onset of the energy increase coincides with the observed decrease in Vickers indentation hardness. Since grain boundary energy is an excess energy related to boundary strength/stability, the results suggest that softening is driven by the activation of grain boundary mediated processes facilitated by the relatively weakened boundaries at the ultra‐fine nanoscale which ultimately induce the formation of an energy dissipating subsurface crack network during indentation.

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Effects of Al3Ni compound on localized plastic deformation and creep strain of Al/Si hypoeutectic material

Alsowidy,

Al-Asry

2024

Sci Rep

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The mechanical resistance of AS10/xNi hypoeutectic alloy with (x = 0.05% and 0.1%) has been investigated. Vickers hardness (HV) was determined for the samples before and after sintering. All samples were subjected to a compressive creep test at a constant temperature of 298 K and a constant load of 45 MPa. Creep parameters, such as creep rate, sensitivity (m), time exponent (n), β, and ɣ have been calculated and related to the Ni content. Microstructure investigation was conducted using the scanning electron microscope technique (SEMT). After sintering, the results showed that there was a significant improvement in the hardness with the addition of nickel. There is an increase in creep resistance as a result of the distribution of Al3Ni chemical compound across grain boundaries, which stops additional dislocation movement and hence reduces the creep rate.

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Dislocations in Ceramics

Cited by 3 publications

References 171 publications

Thermally enhanced dislocation density improves both hardness and fracture toughness in single‐crystal SrTiO₃

Thermally enhanced dislocation density improves both hardness and fracture toughness in single‐crystal SrTiO₃

Size‐induced grain boundary energy increase may cause softening of nanocrystalline yttria‐stabilized zirconia

Effects of Al3Ni compound on localized plastic deformation and creep strain of Al/Si hypoeutectic material

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Dislocations in Ceramics

Cited by 3 publications

References 171 publications

Thermally enhanced dislocation density improves both hardness and fracture toughness in single‐crystal SrTiO3

Thermally enhanced dislocation density improves both hardness and fracture toughness in single‐crystal SrTiO3

Size‐induced grain boundary energy increase may cause softening of nanocrystalline yttria‐stabilized zirconia

Effects of Al3Ni compound on localized plastic deformation and creep strain of Al/Si hypoeutectic material

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Thermally enhanced dislocation density improves both hardness and fracture toughness in single‐crystal SrTiO₃

Thermally enhanced dislocation density improves both hardness and fracture toughness in single‐crystal SrTiO₃