Origin of macrostrains and microstrains in diamond-SiC nanocomposites based on the core-shell model

Pałosz, B.; Stelmakh, S.; Grzanka, Ewa; Gierlotka, S.; Nauyoks, S.; Żerda, T. W.; Pałosz, W.

doi:10.1063/1.2785025

Cited by 12 publications

(6 citation statements)

References 16 publications

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“…These nanoparticles can be conveniently described by the core-shell model, where the unit-cell parameters are assumed to change in a step-wise manner from the central core of the particle to the surface shell. It is well known that this is a significant simplification: the actual distribution of unit-cell constants within the particle can be significantly more complicated and, in addition, depend on lattice directions (Palosz et al, 2003(Palosz et al, , 2007(Palosz et al, , 2010Harder et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Average and local strain fields in nanocrystals

2019

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This article presents a rigorous and self-consistent comparison of lattice distortion and deformation fields existing in energy-optimized pseudo-spherical gold nanoparticles obtained from real-space and powder diffraction strain analysis techniques. The changes in atomic positions resulting from energy optimization (relaxation) of ideally perfect gold nanoparticles were obtained using molecular dynamics modeling. The relaxed atomic coordinates were then used to compute the displacement, rotation and strain components in all unit cells within the energy-optimized (relaxed) particles. It was seen that all of these terms were distributed heterogeneously along the radial and tangential directions within the nanospheroids. The heterogeneity was largest in the first few atomic shells adjacent to the nanoparticle surface, where the continuity of crystal lattice vectors originating from the interior layers was broken because of local lattice rotations. These layers also exhibited maximum shear and normal strains. These (real-space) strain values were then compared with the average lattice strains obtained by refining the computed diffraction patterns of such particles. The results show that (i) relying solely on full-pattern refinement techniques for lattice strain analysis might lead to erroneous conclusions about the dimensionality and symmetry of deformation within relaxed nanoparticles; (ii) the lattice strains within such relaxed particles should be considered 'eigenstrains' ('inherent strains') as defined by Mura [Micromechanics of Defects in Solids, (1991), 2nd ed., Springer]; and (iii) the stress/strain state within relaxed nanoparticles cannot be analyzed rigorously using the constitutive equations of linear elasticity.

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Section: Introductionmentioning

confidence: 99%

Average and local strain fields in nanocrystals

2019

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“…Both plots can be used for examination of the core-shell structure of a nanocrystal. While alp-Q dependencies were already used for evaluation of core-shell models of nanocrystals [9][10][11][12][13], we are not aware of any earlier attempt to use PDF analysis for examination of the core-shell structure of nanocrystals; although plots of relative changes Dr i =r i have been measured experimentally for diamond and SiC [18], they were not used for evaluation of core-shell models.…”

Section: Distribution Of Individual Inter-atomic Distances At Pdf Plotmentioning

confidence: 99%

“…The solution might be in the analysis of the experimental alp-Q relation through seeking a model which gives theoretical alp-Q dependence similar to the experimental one. We used this approach for evaluation of the core-shell structure of nanocrystalline diamond and SiC [10][11][12][13]; the methodology of doing such an alp-Q analysis has been published previously [9] and is not discussed here.…”

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confidence: 99%

Nanocrystals: Breaking limitations of data analysis

Pałosz¹,

Grzanka

Gierlotka

et al. 2010

Zeitschrift für Kristallographie

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Abstract. A series of "virtual powder diffraction experiments" was made on models of small single crystals and nanocrystals with the core-shell structure. The results of those experiments were elaborated with application of standard methods of data analysis routinely used for reciprocal and real space analyses of polycrystalline materials. It is shown that the assumption of a uniform crystal structure of nano-materials is not justified and, therefore, application of routine procedures of collection and elaboration of diffraction data may lead to misinterpretation of the experiments and to incorrect conclusions about their structure. Tentative ways of using powder diffraction data to learn about the structure of nanocrystals with different atomic architecture of the core and of the surface of the grains are discussed. A need for elaboration of a model of the atomic structure of an individual nanograin with a non-uniform structure is discussed. An alternative approach to diffraction studies of nanocrystals by presenting the "footprints" of materials under study in the form of plots showing distribution of the experimental apparent lattice parameters as a function of diffraction vector Q, or bond length distribution as a function of r-distances derived from PDF function is suggested.

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“…For example, nanocrystalline metals and metal oxides are significantly stiffer than their bulk counterparts. The physical origin of the grain/particle size-dependent stiffness have been attributed to dislocations, , diffusion, , core–shell structures, , grain boundary shearing, and competition between energy-density gain and cohesive-energy remnant . Isolated nanocrystals (NCs) are not only stiffer than their corresponding bulk material, but their mechanical properties also exhibit unexpected size-dependent trends.…”

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confidence: 99%

The Strongest Particle: Size-Dependent Elastic Strength and Debye Temperature of PbS Nanocrystals

Bian

Bassett

Wang

et al. 2014

J. Phys. Chem. Lett.

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We investigated the elastic compressibility of PbS nanocrystals (NCs) pressurized in a diamond anvil cell and simultaneously probed the structure using synchrotron-based X-ray diffraction. The compressibility of PbS NCs exhibits bimodal size dependence. The elastic modulus of small NCs increases with increasing diameter and peaks near a particle diameter of approximately 7 nm. For large NCs the elastic modulus decreases toward the bulk value with increasing NC diameter. We explain the bimodal size-dependence of the elastic modulus in terms of a core-shell model based on distinct elasticity of the crystal near the surface and in the core of the particle. We combined insights into the size-dependent elasticity and lattice spacing to determine the Debye temperature of PbS NCs as a function of particle diameter. Understanding the size-dependent elasticity of defect-free colloidal NCs provides new insights into their crystal structure and mechanical properties.

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Origin of macrostrains and microstrains in diamond-SiC nanocomposites based on the core-shell model

Cited by 12 publications

References 16 publications

Average and local strain fields in nanocrystals

Average and local strain fields in nanocrystals

Nanocrystals: Breaking limitations of data analysis

The Strongest Particle: Size-Dependent Elastic Strength and Debye Temperature of PbS Nanocrystals

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