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Title: The mechanical properties of as-grown noncubic organic molecular crystals assessed by nanoindentation

Organic molecular crystals are often noncubic and contain significant steric hindrance within their structure to resist dislocation motion. Plastic deformation in these systems can be imparted during processing (tableting and comminution of powders), and the defect density impacts subsequent properties and performance. This paper measured the elastic and plastic properties of representative monoclinic, orthorhombic, and triclinic molecular crystalline structures using nanoindentation of as-grown sub-mm single crystals. The variation in modulus due to in-plane rotational orientation, relative to a Berkovich tip, was approximately equal to the variation of a given crystal at a fixed orientation. The onset of plasticity occurs consistently at shear stresses between 1 and 5% of the elastic modulus in all three crystal systems, and the hardness to modulus ratio suggests conventional Berkovich tips do not generate fully self-similar plastic zones in these materials. Finally, this provides guidance for mechanical models of tableting, machining, and property assessment of molecular crystals.
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [1]
  1. Purdue Univ., West Lafayette, IN (United States). School of Materials Engineering
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Purdue Univ., West Lafayette, IN (United States). School of Agricultural and Biological Engineering
Publication Date:
Report Number(s):
LA-UR-17-21569
Journal ID: ISSN 0884-2914
Grant/Contract Number:
AC52-06NA25396; FA9550-16-1-0101
Type:
Accepted Manuscript
Journal Name:
Journal of Materials Research
Additional Journal Information:
Journal Volume: 32; Journal Issue: 14; Journal ID: ISSN 0884-2914
Publisher:
Materials Research Society
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA); US Air Force Office of Scientific Research (AFOSR)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; nanoindentation; explosive; mechanical properties
OSTI Identifier:
1369202

Taw, Matthew R., Yeager, John D., Hooks, Daniel E., Carvajal, Teresa M., and Bahr, David F.. The mechanical properties of as-grown noncubic organic molecular crystals assessed by nanoindentation. United States: N. p., Web. doi:10.1557/jmr.2017.219.
Taw, Matthew R., Yeager, John D., Hooks, Daniel E., Carvajal, Teresa M., & Bahr, David F.. The mechanical properties of as-grown noncubic organic molecular crystals assessed by nanoindentation. United States. doi:10.1557/jmr.2017.219.
Taw, Matthew R., Yeager, John D., Hooks, Daniel E., Carvajal, Teresa M., and Bahr, David F.. 2017. "The mechanical properties of as-grown noncubic organic molecular crystals assessed by nanoindentation". United States. doi:10.1557/jmr.2017.219. https://www.osti.gov/servlets/purl/1369202.
@article{osti_1369202,
title = {The mechanical properties of as-grown noncubic organic molecular crystals assessed by nanoindentation},
author = {Taw, Matthew R. and Yeager, John D. and Hooks, Daniel E. and Carvajal, Teresa M. and Bahr, David F.},
abstractNote = {Organic molecular crystals are often noncubic and contain significant steric hindrance within their structure to resist dislocation motion. Plastic deformation in these systems can be imparted during processing (tableting and comminution of powders), and the defect density impacts subsequent properties and performance. This paper measured the elastic and plastic properties of representative monoclinic, orthorhombic, and triclinic molecular crystalline structures using nanoindentation of as-grown sub-mm single crystals. The variation in modulus due to in-plane rotational orientation, relative to a Berkovich tip, was approximately equal to the variation of a given crystal at a fixed orientation. The onset of plasticity occurs consistently at shear stresses between 1 and 5% of the elastic modulus in all three crystal systems, and the hardness to modulus ratio suggests conventional Berkovich tips do not generate fully self-similar plastic zones in these materials. Finally, this provides guidance for mechanical models of tableting, machining, and property assessment of molecular crystals.},
doi = {10.1557/jmr.2017.219},
journal = {Journal of Materials Research},
number = 14,
volume = 32,
place = {United States},
year = {2017},
month = {6}
}

Works referenced in this record:

An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments
journal, June 1992
  • Oliver, W. C.; Pharr, G. M.
  • Journal of Materials Research, Vol. 7, Issue 06, p. 1564-1583
  • DOI: 10.1557/JMR.1992.1564