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A Focus on Dynamic Modulus: Effects of External and Internal Morphological Features. METALS 2020. [DOI: 10.3390/met11010040] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The present work examines the effects of external and internal morphological features on the dynamic elastic modulus and its measure. It consists of two parts. The first part considers the effect of geometrical features of probes and shows the key role of roughness as source of a systematic error leading to the underestimation of the Young’s modulus. The second one is focused on the effect of porosity. Several models which consider the porosity as an ideal regular microstructure and the relative equations describing the Young’s modulus vs. porosity have been reviewed and critically discussed. The values of the relative modulus Er predicted by different models are similar for materials with low porosity (p < 0.2) and isolated pores whereas they strongly diverge if p > 0.2 and interconnected pores are present. Moreover, such models fail to describe the elastic behavior of materials correctly also with low porosity (p ≈ 0.1) such as sintered steels in the case of pores with a preferred orientation and an irregular shape.
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Apte A, Mozaffari K, Samghabadi FS, Hachtel JA, Chang L, Susarla S, Idrobo JC, Moore DC, Glavin NR, Litvinov D, Sharma P, Puthirath AB, Ajayan PM. 2D Electrets of Ultrathin MoO 2 with Apparent Piezoelectricity. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2000006. [PMID: 32374432 DOI: 10.1002/adma.202000006] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Revised: 04/06/2020] [Accepted: 04/07/2020] [Indexed: 06/11/2023]
Abstract
Since graphene, a variety of 2D materials have been fabricated in a quest for a tantalizing combination of properties and desired physiochemical behavior. 2D materials that are piezoelectric, i.e., that allow for a facile conversion of electrical energy into mechanical and vice versa, offer applications for sensors, actuators, energy harvesting, stretchable and flexible electronics, and energy storage, among others. Unfortunately, materials must satisfy stringent symmetry requirements to be classified as piezoelectric. Here, 2D ultrathin single-crystal molybdenum oxide (MoO2 ) flakes that exhibit unexpected piezoelectric-like response are fabricated, as MoO2 is centrosymmetric and should not exhibit intrinsic piezoelectricity. However, it is demonstrated that the apparent piezoelectricity in 2D MoO2 emerges from an electret-like behavior induced by the trapping and stabilization of charges around defects in the material. Arguably, the material represents the first 2D electret material and suggests a route to artificially engineer piezoelectricity in 2D crystals. Specifically, it is found that the maximum out-of-plane piezoresponse is 0.56 pm V-1 , which is as strong as that observed in conventional 2D piezoelectric materials. The charges are found to be highly stable at room temperature with a trapping energy barrier of ≈2 eV.
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Affiliation(s)
- Amey Apte
- Department of Materials Science and NanoEngineering, Rice University, 6100 Main Street, Houston, TX, 77005, USA
| | - Kosar Mozaffari
- Department of Mechanical Engineering, University of Houston, 4726 Calhoun Road, Houston, TX, 77204, USA
| | - Farnaz Safi Samghabadi
- Materials Science and Engineering Program, University of Houston, 4726 Calhoun Rd, Houston, TX, 77204, USA
| | - Jordan A Hachtel
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Long Chang
- Department of Electrical and Computer Engineering, University of Houston, Houston, TX, 77204, USA
| | - Sandhya Susarla
- Department of Materials Science and NanoEngineering, Rice University, 6100 Main Street, Houston, TX, 77005, USA
| | - Juan Carlos Idrobo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - David C Moore
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, OH, 45433, USA
| | - Nicholas R Glavin
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, OH, 45433, USA
| | - Dmitri Litvinov
- Materials Science and Engineering Program, University of Houston, 4726 Calhoun Rd, Houston, TX, 77204, USA
- Department of Electrical and Computer Engineering, University of Houston, Houston, TX, 77204, USA
| | - Pradeep Sharma
- Department of Mechanical Engineering, University of Houston, 4726 Calhoun Road, Houston, TX, 77204, USA
- Department of Physics, University of Houston, 3507 Cullen Blvd, Houston, TX, 77204, USA
| | - Anand B Puthirath
- Department of Materials Science and NanoEngineering, Rice University, 6100 Main Street, Houston, TX, 77005, USA
| | - Pulickel M Ajayan
- Department of Materials Science and NanoEngineering, Rice University, 6100 Main Street, Houston, TX, 77005, USA
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Zohdi TI. An upper bound on the particle-laden dependency of shear stresses at solid–fluid interfaces. Proc Math Phys Eng Sci 2018. [DOI: 10.1098/rspa.2017.0332] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
In modern advanced manufacturing processes, such as three-dimensional printing of electronics, fine-scale particles are added to a base fluid yielding a modified fluid. For example, in three-dimensional printing, particle-functionalized inks are created by adding particles to freely flowing solvents forming a mixture, which is then deposited onto a surface, which upon curing yields desirable solid properties, such as thermal conductivity, electrical permittivity and magnetic permeability. However, wear at solid–fluid interfaces within the machinery walls that deliver such particle-laden fluids is typically attributed to the fluid-induced shear stresses, which increase with the volume fraction of added particles. The objective of this work is to develop a rigorous
strict upper bound
for the tolerable volume fraction of particles that can be added, while remaining below a given stress threshold at a fluid–solid interface. To illustrate the bound’s utility, the expression is applied to a series of classical flow regimes.
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Kushch VI, Sevostianov I, Giraud A. Local fields and effective conductivity tensor of ellipsoidal particle composite with anisotropic constituents. Proc Math Phys Eng Sci 2017. [DOI: 10.1098/rspa.2017.0472] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
An accurate semi-analytical solution of the conductivity problem for a composite with anisotropic matrix and arbitrarily oriented anisotropic ellipsoidal inhomogeneities has been obtained. The developed approach combines the superposition principle with the multipole expansion of perturbation fields of inhomogeneities in terms of ellipsoidal harmonics and reduces the boundary value problem to an infinite system of linear algebraic equations for the induced multipole moments of inhomogeneities. A complete full-field solution is obtained for the multi-particle models comprising inhomogeneities of diverse shape, size, orientation and properties which enables an adequate account for the microstructure parameters. The solution is valid for the general-type anisotropy of constituents and arbitrary orientation of the orthotropy axes. The effective conductivity tensor of the particulate composite with anisotropic constituents is evaluated in the framework of the generalized Maxwell homogenization scheme. Application of the developed method to composites with imperfect ellipsoidal interfaces is straightforward. Their incorporation yields probably the most general model of a composite that may be considered in the framework of analytical approach.
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Affiliation(s)
- Volodymyr I. Kushch
- Institute for Superhard Materials of the National Academy of Sciences, 04074 Kiev, Ukraine
| | - Igor Sevostianov
- Department of Mechanical Engineering, New Mexico State University, PO Box 30001, Las Cruces, NM 88003, USA
| | - Albert Giraud
- Universite de Lorraine/CNRS/CREGU, Georessources Laboratory, BP 40, 54501 Vandoeuvre-les-Nancy, France
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Xu J, Wang S, Wang GJN, Zhu C, Luo S, Jin L, Gu X, Chen S, Feig VR, To JWF, Rondeau-Gagné S, Park J, Schroeder BC, Lu C, Oh JY, Wang Y, Kim YH, Yan H, Sinclair R, Zhou D, Xue G, Murmann B, Linder C, Cai W, Tok JBH, Chung JW, Bao Z. Highly stretchable polymer semiconductor films through the nanoconfinement effect. Science 2017; 355:59-64. [DOI: 10.1126/science.aah4496] [Citation(s) in RCA: 677] [Impact Index Per Article: 96.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 12/02/2016] [Indexed: 12/24/2022]
Abstract
Soft and conformable wearable electronics require stretchable semiconductors, but existing ones typically sacrifice charge transport mobility to achieve stretchability. We explore a concept based on the nanoconfinement of polymers to substantially improve the stretchability of polymer semiconductors, without affecting charge transport mobility. The increased polymer chain dynamics under nanoconfinement significantly reduces the modulus of the conjugated polymer and largely delays the onset of crack formation under strain. As a result, our fabricated semiconducting film can be stretched up to 100% strain without affecting mobility, retaining values comparable to that of amorphous silicon. The fully stretchable transistors exhibit high biaxial stretchability with minimal change in on current even when poked with a sharp object. We demonstrate a skinlike finger-wearable driver for a light-emitting diode.
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Modeling electrical power absorption and thermally-induced biological tissue damage. Biomech Model Mechanobiol 2013; 13:115-21. [PMID: 23589115 DOI: 10.1007/s10237-013-0489-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Accepted: 03/28/2013] [Indexed: 10/27/2022]
Abstract
This work develops a model for thermally induced damage from high current flow through biological tissue. Using the first law of thermodynamics, the balance of energy produced by the current and the energy absorbed by the tissue are investigated. The tissue damage is correlated with an evolution law that is activated upon exceeding a temperature threshold. As an example, the Fung material model is used. For certain parameter choices, the Fung material law has the ability to absorb relatively significant amounts of energy, due to its inherent exponential response character, thus, to some extent, mitigating possible tissue damage. Numerical examples are provided to illustrate the model's behavior.
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Rong Z, Feng Q. How Insoluble Particles Affect the Solutions’ Conductivity: A Theory and the Test in NaCl and Chitosan Solutions. J Phys Chem B 2011; 115:12816-21. [DOI: 10.1021/jp202432u] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ziqin Rong
- Laboratory of Advanced Material, Department of Material Science and Engineering, Tsinghua University, Beijing 100084, P.R. China
| | - Qingling Feng
- Laboratory of Advanced Material, Department of Material Science and Engineering, Tsinghua University, Beijing 100084, P.R. China
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Chowdhury A, Christov CI. Memory effects for the heat conductivity of random suspensions of spheres. Proc Math Phys Eng Sci 2010. [DOI: 10.1098/rspa.2010.0133] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The presence of a particulate phase defines the effective response of a suspension to changes of the average heat flux. Using the random-point approximation we show that within the first order in the concentration, one needs to solve the problem for the temperature field created by a single inclusion in a matrix subject to an unsteady temperature gradient at infinity. We solve this problem by means of Laplace transform and use the solution as the first-order kernel in the functional expansion. From this kernel, we find the statistical average for the heat flux, which turns out to be a memory integral of the spatially averaged time-dependent temperature gradient. Thus, we discover that the constructive relationship between the average flux and averaged temperature gradient is not local in time, but rather involves a convolution integral that represents the memory due to the heterogeneity of the system. This is a novel result, which
inter alia
gives a rigorous justification to the usage of generalizations of the heat conduction law involving fractional time derivatives. The decay of the kernel is very close to
t
−1/2
for dimensionless times lesser than one and abruptly changes to
t
−3/2
for larger times.
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Affiliation(s)
- A. Chowdhury
- Department of Mathematics, University of Louisiana, at Lafayette, LA 70504, USA
| | - C. I. Christov
- Department of Mathematics, University of Louisiana, at Lafayette, LA 70504, USA
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Sevostianov I. Explicit relations between elastic and conductive properties of materials containing annular cracks. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2003; 361:987-999. [PMID: 12804225 DOI: 10.1098/rsta.2003.1176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The impact of annular cracks on the effective elastic and conductive properties of a material is analysed. The compliance contribution tensor of an annular crack - the quantity that determines the increase in compliance of a solid due to introduction of such a crack - is derived analytically. The resistivity contribution tensor of an annular crack is calculated numerically. It is shown that an effective circular crack, i.e. a crack which yields the same change in elastic/conductive properties of a material as the given annular crack, can be chosen to match both of these tensors. Using this result, the explicit relation between elastic and conductive properties of a material containing annular cracks is obtained. The relation is derived using a non-interaction approximation. Applicability of the derived formulae to real materials (to plasma-sprayed coatings, in particular) is discussed.
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Affiliation(s)
- Igor Sevostianov
- Department of Mechanical Engineering, New Mexico State University, PO Box 30001, Las Cruces, NM 88003, USA
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