The evolution of internal energy released from nanomaterials during grain growth

Tengen, Thomas Bobga; Iwankiewicz, R.

doi:10.1002/pssc.200983364

Cited by 2 publications

(3 citation statements)

References 12 publications

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“…Due to the presence of both GBM and GRC mechanisms taking place in most typical nanomaterials, the evolution of the shape function due to the TOTAL process initially deviates away from the spherical shape and finally approaches the spherical shape. The convergence at a later/final stage is due to the fact that a larger amount of energy is required to rotate the grains at larger sizes, thus leading to a diminished GRC process at those sizes [ 10 , 21 , 22 ].…”

Section: Resultsmentioning

confidence: 99%

“…first and second) observations is that both mean grain size and grain size dispersion should simultaneously be used when designing and modelling nanomaterials' mechanical properties (i.e. grain size distribution is important) [9,10,13]. While remarkable success has been achieved on the concurrent employment of mean grain size and grain size dispersion in modelling and designing of nanomaterials' mechanical properties, it has also been, thirdly, acknowledged that nanomaterials from similar samples produced to the same mean grain size and the same dispersion may have different mechanical properties [9-11,13].…”

Section: Introductionmentioning

confidence: 99%

“…To elucidate, firstly, nanomaterials (from the same initial sample type) produced through different processing routes to the same mean grain size may have different grain size dispersion and as such may exhibit different material properties [ 9 - 11 ]. Secondly, different nanomaterials having different mean grain sizes and different grain size dispersions may possess the same material properties [ 9 , 10 ]. The conclusion following the last two (i.e.…”

Section: Introductionmentioning

confidence: 99%

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Designing nanomaterials with desired mechanical properties by constraining the evolution of their grain shapes

Tengen

2011

Nanoscale Res Lett

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Grain shapes are acknowledged to impact nanomaterials' overall properties. Research works on this issue include grain-elongation and grain-strain measurements and their impacts on nanomaterials' mechanical properties. This paper proposes a stochastic model for grain strain undergoing severe plastic deformation. Most models deal with equivalent radii assuming that nanomaterials' grains are spherical. These models neglect true grain shapes. This paper also proposes a theoretical approach of extending existing models by considering grain shape distribution during stochastic design and modelling of nanomaterials' constituent structures and mechanical properties. This is achieved by introducing grain 'form'. Example 'forms' for 2-D and 3-D grains are proposed. From the definitions of form, strain and Hall-Petch-Relationship to Reversed-Hall-Petch-Relationship, data obtained for nanomaterials' grain size and conventional materials' properties are sufficient for analysis. Proposed extended models are solved simultaneously and tested with grain growth data. It is shown that the nature of form evolution depends on form choice and dimensional space. Long-run results reveal that grain boundary migration process causes grains to become spherical, grain rotation coalescence makes them deviate away from becoming spherical and they initially deviate away from becoming spherical before converging into spherical ones due to the TOTAL process. Percentage deviations from spherical grains depend on dimensional space and form: 0% minimum and 100% maximum deviations were observed. It is shown that the plots for grain shape functions lie above the spherical (control) value of 1 in 2-D grains for all considered grain growth mechanisms. Some plots lie above the spherical value, and others approach the spherical value before deviating below it when dealing with 3-D grains. The physical interpretations of these variations are explained from elementary principles about the different grain growth mechanisms. It is observed that materials whose grains deviate further away from the spherical ones have more enhanced properties, while materials with spherical grains have lesser properties. It is observed that there exist critical states beyond which Hall-Petch Relationship changes to Reversed Hall-Petch Relationship. It can be concluded that if grain shapes in nanomaterials are constrained in the way they evolve, then nanomaterials with desired properties can be designed.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Designing nanomaterials with desired mechanical properties by constraining the evolution of their grain shapes

Tengen

2011

Nanoscale Res Lett

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The response of the statistics of the cumulative features on grains in nanomaterials to different grain growth phenomena

Tengen

2012

Int J Mech Mater Des

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Each nanomaterial grain has some number of features, such as faces or triple junctions, on it. The sum of all the features on all grains in nanomaterials, herein called cumulative feature, can be obtained. During grain growth both the number of features per grain and the cumulative features on all grain in nanomaterials evolve randomly with time. Different mechanisms are responsible for grain growth in nanomaterials. This includes Grain Boundary Migration, Grain Rotation-Coalescence, T1 and T2 events. Evolution models for number of features per grain are known already, and not model for evolution of cumulative features. The present paper uses the tools of stochastic theory given by Random Marked Point Field to propose models for the temporal and thermal evolutions of the statistics of the random cumulative features on grains in nanomaterials under different grain growth mechanisms. The resulting differential equations are solved simultaneously using data from nanocrystalline aluminium. It is observed that the mean number of features per grain increases and density of grains in nanomaterials decreases during grain growth. It is revealed that grain growth results in decrease in moments of the cumulative features. It is shown that an increase in annealing temperature results in relatively higher increase in mean number of features per grain, further decrease in grain density, relative increase in mean cumulative features on grain and variable dispersions of cumulative features. It is also observed that the evolution of the statistics of the cumulative features depends on the nature of Galzierdiffusion term, the form of the critical number of faces per grain and the type of grain growth mechanisms. For some choices of the Glazier diffusion term, the dispersion of the cumulative feature evolves in a manner similar to that of the nanomaterials mechanical properties given by the Hall-Petch to ReversedHall-Petch Relationship. The variables results are explained to be consequences of different grain growth mechanisms, temperature and the diffusion termed. Thus, it can be concluded that processing route, processing conditions and the nature of evolution of the constituents of nanomaterials are simultaneously vital when designing or characterising nanomaterials.

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The evolution of internal energy released from nanomaterials during grain growth

Cited by 2 publications

References 12 publications

Designing nanomaterials with desired mechanical properties by constraining the evolution of their grain shapes

Designing nanomaterials with desired mechanical properties by constraining the evolution of their grain shapes

The response of the statistics of the cumulative features on grains in nanomaterials to different grain growth phenomena

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