# E.J. GarbocziNational Institute of Standards and Technology | NIST · Material Measurement Laboratory (MML)

E.J. Garboczi

Ph.D. Physics

## About

282

Publications

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17,503

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Introduction

Additional affiliations

April 2009 - May 2016

October 1988 - June 2014

Education

September 1976 - January 1985

## Publications

Publications (282)

Modeling the electromagnetic response of carbon nanotube (CNT) reinforced composites is inherently a three-dimensional (3D) multi-scale problem that is challenging to solve in real-time for nondestructive evaluation applications. This article presents a fast and accurate full-wave electromagnetic solver based on a multi-layer dyadic Green’s functio...

The particle size distribution (PSD) and particle morphology of metal powders undoubtedly affects the quality of parts produced by additive manufacturing (AM). It is, therefore, crucial to accurately know the PSD and morphology of these powders. There exist several measurement techniques for these quantities, but since each method is based on diffe...

A novel method of detecting overlap between two irregularly shaped virtual particles whose surfaces are described by analytical functions is presented in this study. Utilizing the analytical equation that describes the surface of the particle, the first and second spatial derivatives are used to locate the major surface asperities via the surface c...

This study follows a first paper written on some three-dimensional geometrical quantities of a selection of sand particles from the United Arab Emirates (UAE), determined using a combination of X-ray microcomputed tomography (μCT) and spherical harmonic analysis, and their correlation to the properties of mortars made with these sands, with no adde...

div>Modeling the electromagnetic response of carbon nanotube (CNT) reinforced composites is inherently a three dimensional (3D) multi-scale problem that is challenging to solve in real-time for nondestructive evaluation applications. This article presents a fast and accurate full-wave electromagnetic solver based on a multi-layer dyadic Green’s fun...

div>Modeling the electromagnetic response of carbon nanotube (CNT) reinforced composites is inherently a three dimensional (3D) multi-scale problem that is challenging to solve in real-time for nondestructive evaluation applications. This article presents a fast and accurate full-wave electromagnetic solver based on a multi-layer dyadic Green’s fun...

Two-dimensional (2D) dynamic image analysis (DIA) is often used to measure particle size and shape distributions of metal powders in terms of various size and shape parameters. In this present work, five titanium alloy (Ti-6Al-4V or Ti64) powders that were previously characterized with DIA are now characterized in three dimensions (3D) using a comb...

Shape, in addition to size and material composition, has a strong effect on the optical scattering characteristics of a particle. In this work, we computationally study how the measured 3-D shapes of individual lunar regolith particles affect their optical scattering characteristics. The shapes of 25 lunar regolith particles collected during the Ap...

Insufficient data are available to fully understand the effects of metal additive manufacturing (AM) defects for widespread adoption of the emerging technology. Characterization of failure processes of complex internal geometries and defects in metal AM can significantly enhance this understanding. We aim to demonstrate a complete experimental meas...

In all prior electromagnetic modeling studies of carbon nanotube (CNT) composites, the exact three-dimensional (3D) shape and spatial distribution of the CNTs in the composite were unknown. Therefore, simplifying assumptions had to be made regarding the CNT distributions. The effect of such assumptions on the electromagnetic response of CNT composi...

All scanning electron microscopic (SEM) examinations of mortars are based on 2D slices through the true 3D microstructure. There are many artifacts that can be seen in such 2D slices that are different from 3D reality, even if the sand were perfectly monosize and spherical. A mortar containing a size distribution of randomly-shaped sand grains, sur...

Plasmonic nano-antennas are typically designed with RF-inspired rigorous parametric optimization processes that lack proper physical insights. In this study, we demonstrate a systematic optimization approach for nano-antennas based on characteristic mode analysis (CMA). A complex geometry, designated as split-ring two-wire antenna (SRA), is selecte...

There has been a long partnership in the materials science of building materials between the National Institute of Standards and Technology (NIST) in the United States and the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM). This paper discusses on the technical contributions NIST has made t...

The viscoelastic/viscoplastic behavior of cement paste may occur due to intrinsic calcium silicate hydrate (C-S-H) viscoelasticity/viscoplasticity and cement grain dissolution during the hydration process. A numerical model that combines a microstructure model and a finite element calculation model has been developed to predict the time-dependent b...

The success of computational materials science models for cement and concrete, at the micrometer-to-millimeter scale, is based on careful characterization of the two main starting materials – cement and aggregates. Concrete is a complex material, and models based on over-simplified chemical, geometrical, and topological assumptions have limits on t...

Pore structures of additively manufactured metal parts were investigated with X-ray Computed Tomography (XCT). Disks made of a cobalt-chrome alloy were produced using laser-based powder bed fusion (PBF) processes. The additive manufacturing processing parameters (scan speed and hatch spacing) were varied in order to have porosities varying from 0.1...

Virtually every corrosion detection method reports only the presence of a material phase that denotes probable corrosion, not its spectral signature. A signature specific to the type of iron oxide corrosion product would not only confirm the presence of corrosion but also provide insight into the environment of its formation. To identify the unique...

When cementitious materials are dried, internal stresses are generated that lead to desiccation shrinkage, a portion of which is irreversible. Previous research has indicated that, while a cementitious composite is subjected to a state of stress, dissolution of cement grains and precipitation of hydrates can yield irreversible creep strains, and it...

We studied the 3-D shape of concrete aggregate fines with particle sizes between 3 μm and 250 μm produced by high-speed vertical shaft impact (VSI) crushing of rock types from 10 different quarries representing a wide range of local Norwegian geology with respect to mineralogy and mechanical properties. This included igneous (intrusive and extrusiv...

To compute any physical quantity for a random particle, one needs to know the mathematical shape of the particle. For regular particles like spheres and ellipsoids, the mathematics are straightforward. For random particles, with realistic shapes, mathematically characterizing the shape had not been generally done. But since about the year 2002, a m...

We present a free-space measurement technique for nondestructive noncontact electrical and dielectric characterization of nanocarbon composites in the Q-band frequency range of 30-50 GHz. The experimental system and error correction model accurately reconstruct the conductivity of composite materials that are either thicker than the wave penetratio...

Carbon nanotube composites are lightweight, multifunctional materials with readily adjustable me-chanical and electrical properties-relevant to the aerospace,[1] automotive,[2] and sporting goods[3] indus-tries as high-performance structural materials.[4,5] Here, we combine well-established and newly-developed characterization techniques[6,7] to de...

Metal Additive Manufacturing (AM) has great potential to revolutionize manufacturing industries, but a reliable method to detect defects in AM-produced parts with complex internal structures must be developed prior to its widespread adoption. In this research, defects occurring in additively manufactured metal parts are characterized with X-ray Com...

Near real-time visualization of complex two-phase flow in a porous medium was demonstrated with dynamic 4-dimensional (4D) (3D + time) imaging at the 2-BM beam line of the Advanced Photon Source (APS) at Argonne National Laboratory. Advancing fluid fronts through tortuous flow paths and their interactions with sand grains were clearly captured, and...

In composites, carbon nanotubes (CNTs) are rarely perfectly straight and they usually exhibit complex shapes. In this paper, we employ the method-of-moments formulation for arbitrary thin wires to study the electromagnetic scattering characteristics of CNTs with realistic shapes. More than 800 different CNT shapes were simulated in this work. These...

The importance of particle shape in terms of its effects on the behaviour of powders and other particulate systems has long been recognised, but particle shape information has been rather difficult to obtain and use until fairly recently, unlike its better-known counterpart, particle size. However, advances in computing power and 3D image acquisiti...

The composite geometrical structure of mortar composites can be represented by a model consisting of sand embedded in a cement paste matrix and the structure of concrete by gravel embedded in a mortar matrix. Traditionally, spheres have often been used to represent aggregates (sand and gravel), although the accuracy of properties computed for struc...

The addition of carbon nanotubes (CNTs) and graphene sheets (GSs) into polymeric materials can greatly enhance the conductivity and alter the electromagnetic response of the resulting nanocomposite material. The extent of these property modifications strongly depends on the structural parameters describing the CNTs and GSs, such as their shape and...

Abstract A microstructure model has been applied to simulate near-surface degradation of portland cement paste in contact with a sodium sulfate solution. This new model uses thermodynamic equilibrium calculations to guide both compositional and microstructure changes. It predicts localized deformation and the onset of damage by coupling the confine...

The overlapping sphere (OS) percolation model gives a two-phase microstructure (matrix plus inclusions) that is useful for testing composite material ideas and other applications, as well as serving as a paradigm of overlapping object percolation and phase transitions. Real materials often have more than two phases, so it is of interest to extend t...

Carbon Nanotube (CNT) and Graphene Sheets (GS) dispersed in composites exhibit a variety of shapes that are controlled by many factors such as how the CNT/GS are fabricated, how they are dispersed, and the material in which the CNT/GS are embedded. The goal of this work is to study how the shape of the CNT and GS affects their electromagnetic prope...

Carbon Nanotubes (CNT) in composites exhibit a wide variety of complex shapes and are rarely perfectly straight even when they are highly aligned. Moreover, fabrication capabilities have advanced enough to allow the synthesis of CNT with specific three-dimensional shapes, e.g. helixes, rings, and Y-shaped junctions. The shape of the CNT has a profo...

Electromagnetic scattering from Carbon Nanotubes (CNT) has received wide interest in the past decade. Many different CNT configurations have been computationally investigated such as single CNTs, infinite planar arrays of CNTs, finite arrays with simple distributions, and bundles of CNTs. In all of the previously reported configurations, the CNTs w...

A combined computational/experimental technique was developed to analyze the compressive elastic properties of a rigid organic foam. This technique combines X-ray computed tomography, image analysis, and large-scale finite element computations utilizing a new numerical technique. Predictions of Young’s modulus were validated with uniaxial compressi...

Construction aggregate particles, fine or coarse, can be scanned by X-ray computed tomography and mathematically characterized using spherical harmonic series, and can then be used to simulate random parking of irregular aggregates to form a virtual mortar or concrete using the Anm model. Any other similar composite system of irregular (star-shaped...

With advances in anisotropic particle synthesis, particle shape is now a feasible parameter for tuning suspension properties. However, there is a need to determine how these newly synthesized particles with prescribed shapes affect suspension properties and to solve the inverse problem of inferring the shape of particles from property measurements....

Additive manufacturing (AM) processes can produce highly complex and customized parts without the need for dedicated tooling and can produce parts directly from the part design information. These types of processes are poised to revolutionize the manufacturing industry, yet several challenges are currently preventing more widespread adoption of AM...

A computational model has been developed that combines finite element methods with microstructure development simulations to quantitatively predict the viscoelastic/viscoplastic relaxation of cement paste due to intrinsic calcium silicate hydrate viscoelasticity/viscoplasticity and cement grain dissolution associated with the hydration process. The...

A free-space transmission-reflection measurement method for the non-destructive electrical characterization of carbon nanotube based composites was developed. Specifically, this versatile method measures the dielectric properties of the sample in the Q-band, corresponding to a frequency range of 30 GHz to 50 GHz, and can be used with specimens that...

A real multiphase microstructure, Anm model, with irregular shape particles has been proposed. The Anm model places multiple irregular shape particles into a pre-defined empty box according to the real parking density to build up particles embedded in matrix material model in all scales from nano to macro. However, the packing accuracy and efficien...

An analytical full wave model of parallel, randomly centered carbon nanotubes (CNTs) embedded in a dielectric slab was developed to calculate the electromagnetic scattering from CNT composites. The model simulates empty and metal-filled single walled CNTs as infinitesimally thin wires, parallel and infinitely long in the z direction, but randomly l...

Additive manufacturing techniques can produce complex, high-value metal parts, with potential applications as critical metal components such as those found in aerospace engines and as customized biomedical implants. Material porosity in these parts is undesirable for aerospace parts - since porosity could lead to premature failure - and desirable f...

Additive manufacturing (AM) techniques(1) can produce complex, high-value metal parts, with potential applications as critical parts, such as those found in aerospace components. The production of AM parts with consistent and predictable properties requires input materials (e.g., metal powders) with known and repeatable characteristics, which in tu...

There are different ways to mathematically represent three-dimensional (3D) heterogeneous material microstructures. It is desirable to pick the representation that best bridges the gap between heterogeneous microstructure and computer-aided engineering finite element analysis. 3D cubic meshes of brick (voxel) elements can be generated for digital s...

Some iron oxide corrosion products exhibit antiferromagnetic magnetic resonances (AFMR) at frequencies on the order of 100 GHz at ambient temperatures. AFMR can be detected in laboratory conditions, which serves as the basis for a new non-destructive spectroscopic method for detecting early corrosion. When attempting to measure the steel corrosion...

Detecting the early corrosion of steel that is embedded in reinforced concrete (rebar) is a goal that would greatly facilitate the inspection and measurement of corrosion in the US physical infrastructure. Since 2010, the National Institute of Standards and Technology (NIST) has been working on a large project to develop an electromagnetic (EM) pro...

Systematic studies have been carried out on two different powder
materials used for additive manufacturing: stainless steel and cobalt-chrome. The characterization of these powders is important in NIST efforts to develop appropriate measurements and standards for additive materials and to document the property of powders used in a NIST-led additiv...

Systematic studies have been carried out on two different powder materials used for additive manufacturing: stainless steel and cobalt-chrome. An extensive array of characterization techniques were applied to these two powders. The physical techniques included laser-diffraction particle-size analysis, X-ray
computed tomography for size and shape a...

Some metal additive manufacturing processes can produce parts with internal porosity, either intentionally (with careful selection of the process parameters) or unintentionally (if the process is not well-controlled.) Material porosity is undesirable for aerospace parts - since porosity could lead to premature failure - and desirable for some biome...

Carbon nanotubes
(CNT) have exceptional electrical and mechanical properties that have fueled extensive research on their incorporation in advanced composite materials. The CNT density and dispersion characteristics have a strong impact on overall composite properties. Electromagnetic waves in the microwave band represent a non-contact and data-ri...

Carbon fiber reinforced polymer composites (CFRPC) are of great interest in the aerospace and automotive industries due to their exceptional mechanical properties.
Carbon fibers are typically woven and inter-laced perpendicularly in warps and wefts to form a carbon fabric that can be embedded in a binding matrix. The warps and wefts can be interla...

The Blaine fineness (Blaine) of a cement powder is a single parameter that is meant to characterize the specific surface area of a cement; Blaine is assumed to be linked to physical and mechanical properties of the hydrated cement such as strength, setting time, and rheology. However, a single parameter cannot characterize the particle-size distrib...

Truncated spherical harmonic expansions are used to approximate the shape of 3D
star-shaped particles including a wide range of axially symmetric ellipsoids, cuboids, and over 40 000
real particles drawn from seven different material sources. This mathematical procedure enables any geometric property to be calculated for these star-shaped particles...

Biofilm density, porosity, and thickness are biofilm architecture properties that are important but often difficult to measure. In this study, wet and dry biofilm densities and biofilm porosity in shredded tire biofilters were measured using a volumetric displacement method and a new porosity equation. Methods for determining the surface area and m...

Concrete service life models have proliferated in recent years due to increased interest in designing infrastructure elements with at least a 75-year service life, along with greater emphasis on life-cycle costing in general. While existing models consider a variety of concrete material and environmental factors, at varying levels of complexity, in...

Quantifying the shape of particles in three dimensions (3D) is important in particle technology. In concrete, the 3D shape of particles like sand, gravel and cement is of great interest for applications including suspension rheology, mechanical properties and realistic microstructure models. When particles are classified as star-shaped, a weaker co...