Indentation Plasticity and Fracture Studies of Organic Crystals

Mannepalli, Sowjanya; Kiran, M. S. R. N.

doi:10.3390/cryst7110324

Cited by 35 publications

(32 citation statements)

References 137 publications

(227 reference statements)

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“…In fact, an efficient plastic deformation mechanism is essential in lowering the hardness of molecular crystals. When subjected to shear stress by indentation, the layers are compressed initially in an elastic regime and later plastically ,. However, the incompressible nature of a crystal beyond an absolute limit generates enormous strain.…”

Section: Resultsmentioning

confidence: 99%

“…The surface pile‐up is observed when the material reaches a point beyond which it cannot afford to absorb the induced strain. In general, initial yield stress and work‐hardening exponents are known to be major contributors in determining the pile‐up or sink‐in behavior of materials in response to indentation forces . Soft, easily hardened materials sink‐in, whereas harder, work‐hardened materials pile‐up.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Molecular Basis for the Mechanical Response of Sulfa Drug Crystals

SeethaLekshmi

Kiran

Ramamurty

et al. 2018

Chemistry A European J

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Comprehension of the nanomechanical response of crystalline materials requires the understanding of the elastic and plastic deformation mechanisms in terms of the underlying crystal structures. Nanoindentationd ata were combined with structurala nd computational inputs to derive am olecular-level understandingo ft he nanomechanical response in eight prototypical sulfa drug molecular crystals. The magnitude of the modulus, E,w as strongly connected to the non-covalent bond features, that is, the bond strength, the relative orientation with the measured crystal facet and their dispositioni nt he crystal lattice. Additional features derived from the currents tudy are the following. Firstly,r obust synthons well isolatedb yw eak andd ispersive interactions reduce the material stiffness;i nc ontrast, the interweaving of interactions with diverse energetics fortifies the crystal packing. Secondly, mereo bservation of layered structures with orthogonal distribution of strong and weak interactions is ap rerequisite, but inadequate, to attain higher plasticity.T hirdly,i nterlocked molecular arrangements preventl ong-range sliding of molecular planes and, hence, lead to enhanced E values. In ab roader perspective, the observations are remarkable in deriving am olecular basis of the mechanical properties of crystalline solids, which can be exploited through crystal engineering for thep urposeful design of materials with specific properties.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Molecular Basis for the Mechanical Response of Sulfa Drug Crystals

SeethaLekshmi

Kiran

Ramamurty

et al. 2018

Chemistry A European J

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“…In addition to the physical properties of borax crystals, the mechanical properties, which are described as the behaviors of materials under applied external forces, are important for industrial applications. The knowledge of these properties is crucial to establishing the fundamental principles for the design of molecular solids with desirable properties and to prevent failures in many engineering application areas [4]. One of the most widely studied mechanical properties of crystalline materials in the literature is hardness, which is generally defined as the resistance to deformation [5].…”

Section: Introductionmentioning

confidence: 99%

Effects of polyelectrolytes on the hardness of borax decahydrate crystals

Polat¹,

Sayan²

2019

Journal of Boron

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The hardness of borax decahydrate crystals was measured using cationic polyelectrolytes of FO4115, FO4400 and FO4990 with anionic polyelectrolytes of AN923, AN930 and AN999 as an additive. The measurements were carried out in the indentation load range of 10 g to 30 g. It was determined that the Vickers hardness (H V) decreased with increasing applied load, showing that the borax decahydrate crystals exhibited an indentation size effect. Vickers microhardness measurements revealed that pure borax decahydrate crystals had a brittle structure, yet the crystals obtained in additive media were categorized as a soft material. The proportional specimen resistance model was applied to determine the load-independent microhardness. The crystal hardness of borax decahydrate was found to change depending on the type and concentration of polyelectrolyte used. In addition to the mechanical properties, the thermal and physical characteristics of borax decahydrate crystals were investigated by thermogravimetric and Fourier transform infrared spectroscopy analysis. The characterization results confirmed that the polyelectrolytes were adsorbed on the crystal's surface.

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“…For organic molecular crystals, such as saccharin, [ 36 ] aspirin, [ 37,38 ] and cyclotrimethylenetrinitramine (RDX), [ 39 ] the largest ratio of the elastic moduli along different crystal faces is usually less than 2. [ 40–43 ] For instance, the wavelike π‐stacked energetic crystals of 1,1‐diamino‐2,2‐dinitroethylene (FOX‐7) show a mechanical anisotropy E (002) / E (020) = 1.9. [ 44 ] For a two‐component hybrid Bragg stack composed of alternating inorganic (hectorite) and polymer (polyvinylpyrrolidone) [ 13 ] layers, the elastic anisotropy ( E || / E ⊥ ) can be as high as 7 and this is the highest reported value so far for hybrid nanocomposites.…”

Section: Discussionmentioning

confidence: 99%

Extreme Elasticity Anisotropy in Molecular Glasses

Cang

Wang

Bishop

et al. 2020

Adv Funct Materials

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Glasses are generally assumed to be isotropic and there are no literature reports of elastic anisotropy for molecular glasses. However, as glasses formed by physical vapor deposition can be structurally anisotropic, it is of interest to investigate the elastic anisotropy in these materials. Micro‐Brillouin light spectroscopy is used in several experimental geometries to determine the elastic stiffness tensors of three glass films of itraconazole vapor‐deposited at substrate temperatures (Tsub) of 330, 315, and 290 K, respectively. Significant elastic anisotropy is observed and, in these glasses, the elastic anisotropy shows a strong correlation with the molecular orientation. The out‐of‐plane and in‐plane Young's moduli of the high Tsub (330 K) sample, which features a predominantly vertical molecular orientation, exhibit a high anisotropy ratio of 2.2. The observed elastic anisotropy is much larger than those previously observed in liquid crystals and even many crystalline solids.

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Indentation Plasticity and Fracture Studies of Organic Crystals

Cited by 35 publications

References 137 publications

Molecular Basis for the Mechanical Response of Sulfa Drug Crystals

Molecular Basis for the Mechanical Response of Sulfa Drug Crystals

Effects of polyelectrolytes on the hardness of borax decahydrate crystals

Extreme Elasticity Anisotropy in Molecular Glasses

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