N.N. Thadhani

N.N. Thadhani
Georgia Institute of Technology | GT · School of Materials Science and Engineering

Ph.D.

About

379
Publications
24,878
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
5,219
Citations
Citations since 2017
47 Research Items
2245 Citations
20172018201920202021202220230100200300400
20172018201920202021202220230100200300400
20172018201920202021202220230100200300400
20172018201920202021202220230100200300400

Publications

Publications (379)
Article
This paper reports on spall damage mechanisms in laser powder bed fusion (LPBF) fabricated stainless steel 316L (SS316L) subjected to uniaxial, strain plate-impact loading and explores failure evolution with increasing impact velocity and peak pressure. Analysis of velocimetry profiles reveals a heterogeneous failure response with several different...
Article
This study explores the benefits of utilizing recently developed protocols for microstructure quantification and the multiresolution mechanical characterization of Ti-based bulk metallic glass matrix composites. Four alloys with different compositions and amorphous (glass) fractions were studied. Microstructure quantification of the amorphous and c...
Article
Fully dense structures of high solids loaded polymer composites printed via material extrusion additive manufacturing are of interest across many applications, including biomedical scaffolds and energetic materials. It is common to observe defects such as interfilament voids in space-filling structures, particularly during material extrusion printi...
Article
Nanoparticle-mediated photoporation is a novel delivery platform for intracellular molecule delivery. We studied the dependence of macromolecular delivery on molecular weight and sought to enhance delivery efficiency. DU145 prostate cancer cells were exposed to pulsed laser beam in the presence of carbon-black nanoparticles. Intracellular uptake of...
Article
Full-text available
Introduction: Intracellular delivery of molecules is central to applications in biotechnology, medicine, and basic research. Nanoparticle-mediated photoporation using carbon black nanoparticles exposed to pulsed, near-infrared laser irradiation offers a physical route to create transient cell membrane pores, enabling intracellular delivery. Howeve...
Article
When a system comprised of cells, carbon black nanoparticles, and delivery molecules is irradiated with a laser beam, the nanoparticles can absorb and dissipate the laser-delivered energy, producing thermal and acoustic output and fluid mechanical forces. These can then interact with the nearby cell membrane, forming membrane pores that exogenous m...
Conference Paper
The effect of bulk initial density (ρ00) on the dynamic densification behavior of a brittle granular system, cerium dioxide (CeO2), is investigated. Specifically, the consolidation behavior of pressed powder compacts at three initial bulk densities, 33, 55, and 63% of theoretical maximum density (TMD), is examined at shock compressed densities with...
Article
Luminescent semiconductor nanocrystals are a fascinating class of materials because of their size‐dependent emission. Multitudes of past studies have demonstrated that semiconductor nanoparticles with radii smaller than their Bohr radius experience quantum confinement and thus size‐dependent emission. Exerting pressure to these nanoparticles repres...
Article
This Minireview summarizes the pressure‐dependence of the optical properties of all‐inorganic and organolead perovskite, II–VI, III–V, and IV–VI semiconductor nanocrystals. Obtaining a better understanding of the optical behavior of semiconductors under pressure provides insight into the interplay of quantum confinement and mechanical effects. Abs...
Article
The performance of energetic materials subjected to dynamic loading significantly depends on their micro- and meso-scale structural morphology. The geometric versatility offered by additive manufacturing opens new pathways to tailor the performance of these materials. Additively manufactured energetic materials (AMEMs) have a wide range of structur...
Chapter
The response of heterogeneous materials subjected to extreme dynamic loads is complicated by meso-scale phenomena which manifests a bulk response to the percolating dynamic event. The microstructural arrangement of phases, the extrinsic properties of microconstituents, and the property contrasts and various length scales affect the ability of stres...
Article
The generation of three-dimensional (3D) microstructures with multiple constituents is an important part of multiscale computational simulation and design for a wide range of materials including heterogeneous polycrystalline metals, ceramics, composites, and energetics. Realistic 3D microstructures for multiphase materials are difficult to obtain e...
Article
Full-text available
Molecular dynamics (MD) simulations are carried out to investigate the effects of the type and spacing of FCC/BCC interfaces on the deformation and spall behavior. The simulations are carried out using model Cu/Ta multilayers with six different types of interfaces. The results suggest that interface type can significantly affect the structure and i...
Article
Full-text available
The past few years have witnessed rapid advances in the synthesis of high-quality perovskite nanocrystals (PNCs). However, despite the impressive developments, the stability of PNCs remains a substantial challenge. The ability to reliably improve stability of PNCs while retaining their individual nanometer size represents a critical step that under...
Article
Additive manufacturing is a promising approach to prepare highly specifically defined materials with unique dimensions, gradients in material attributes and on‐demand properties. For energetic materials applications, it is particularly exciting for its potential to create lattice and cellular structures and gradient solids to focus or dissipate ene...
Article
Full-text available
Instability of perovskite quantum dots (QDs) toward humidity remains one of the major obstacles for their long‐term use in optoelectronic devices. Herein, a general amphiphilic star‐like block copolymer nanoreactor strategy for in situ crafting a set of hairy perovskite QDs with precisely tunable size and exceptionally high water and colloidal stab...
Article
The chiral auxetic cellular structures are fabricated using SEBM (selective electron beam melting) method and tested under compressive loading. The results of experimental testing are used for validation of the computational model in LS‐DYNA. Furthermore, ballistic velocity and deformation behaviour of monolithic aluminium (Al 7075‐T651) and titani...
Article
We investigate localized strains in polymer-based composites subjected to varying strain-rates and strains. Research on composites is often focused on their bulk mechanical behavior. However, many material phenomena are influenced by their microstructure, such as the mixing and reaction mechanisms of constituents in structural energetic materials....
Article
The deformation and failure (spallation) behavior of Cu/Ta multilayered systems with Kurdjumov–Sachs (KS) orientation relationship is investigated at the atomic scales under shock loading conditions. Molecular dynamics (MD) simulations investigate the role of spacing between KS interfaces on the nucleation, evolution and interaction of defect struc...
Article
We report a simple, robust and inexpensive strategy to enable all-inorganic CsPbX3 perovskite nanocrystals (NCs) with a set of markedly improved stabilities, that is, water stability, compositional stability, phase stability, and phase segregation stability via impregnating them in solid organic salt matrices (i.e., metal stearate; MSt). In additio...
Article
Laser shock compression studies on Ce3Al metallic glass performed using a 3 J Nd:YAG laser indicate shock-induced crystallization, evidenced by the presence of a two-wave/stepped particle velocity profile and structural changes observed via X-ray Diffraction (XRD) analysis of recovered material. A direct shock-compression setup was designed with 25...
Conference Paper
The effect of grain size and moisture content on the dynamic response of high purity, Oklahoma #1, sand was explored by performing uniaxial planar impact experiments on samples sieved to either fine (0.075 – 0.150 mm) or coarse (0.425 – 0.500 mm) grain sizes in either dry or fully water-saturated conditions. Sand samples were dynamically loaded to...
Conference Paper
The uniaxial strain dynamic densification behavior of cerium dioxide powders as a function of powder compact green density is investigated in this work. Cerium dioxide powders of two particle morphologies (rod-like and equiaxed) and two green densities (55% and 62.5% TMD) are shock compressed using the gas gun with specifically designed fixtures an...
Article
Intracellular delivery of molecules can be increased by laser-exposure of carbon black nanoparticles to cause photoporation of the cells. Here we sought to determine effects of multiple laser exposure parameters on intracellular uptake and cell viability with the goal of determining a single unifying parameter that predicts cellular bioeffects. DU1...
Article
Full-text available
The time-resolved spectral responses of three asymmetrical optical microcavity (AOMC) structures under laser-driven shock compression were investigated. The objective was to compare the performance of these multilayer structures and explore the potential in dynamic shock “pressure” sensing, given their unique ability to capture spatially heterogene...
Chapter
Strain rate sensitivity of sheet steels affects their formability and crashworthiness. This contribution reports strain rate sensitivity and effects of strain rate on fracture micro-mechanisms in a commercial dual phase sheet steel (DP590). Uniaxial tensile tests were performed at strain rates of 10⁻⁴/s, 1/s and 3200/s to characterize effects of st...
Article
Exposure of carbon-black (CB) nanoparticles to near-infrared nanosecond-pulsed laser energy can cause efficient intracellular delivery of molecules by photoporation. Here, cellular bioeffects of multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs) are compared to those of CB nanoparticles. In DU145 prostate-cancer cell...
Article
A novel 2D-surface shock pressure sensor is designed and tested based on 1D-Photonic Crystal, i.e., Distributed Bragg Reflector Multilayer (DBR/ML) structures. The fast opto-mechanical response of these structures to changes in layer thicknesses and refractive indices are ideally suited for dynamic pressure sensing. They offer the potential to mini...
Article
Sternförmige Triblockcopolymere, die durch radikalische Atomtransferpolymerisation erhalten wurden, wurden als Nanoreaktoren für die Synthese hohler Halbleiter-Nanopartikel verwendet, die mit herkömmlichen Verfahren nicht herzustellen sind. In ihrer Zuschrift (DOI: 10.1002/ange.201706182) beschreiben Z. Lin et al. die Synthese gleichmäßiger hohler...
Article
Rationally designed star-like triblock copolymers that were prepared by atom transfer radical polymerization were used as nanoreactors for the synthesis of semiconducting hollow nanoparticles that are inaccessible by conventional synthetic approaches. In their Communication (DOI: 10.1002/anie.201706182), Z. Lin and co-workers describe the preparati...
Article
Despite recent impressive advances in synthesizing lead chalcogenide solid nanoparticles, there are no demonstrations of lead chalcogenide hollow nanoparticles (HNPs) with controlled hollow diameter and shell thickness as current synthetic approaches for HNPs have inherent limitations associated with inability to precisely control the dimensions an...
Article
Despite recent impressive advances in synthesizing lead chalcogenide solid nanoparticles, there are no demonstrations of lead chalcogenide hollow nanoparticles (HNPs) with controlled hollow diameter and shell thickness as current synthetic approaches for HNPs have inherent limitations associated with inability to precisely control the dimensions an...
Article
The effect of grain size and moisture content on the dynamic macroscopic response of granular geological materials was explored by performing uniaxial planar impact experiments on high purity, Oklahoma #1, sand samples composed of either fine (75–150 μm) or coarse (425–500 μm) grain sizes in either dry or fully water-saturated conditions. Oklahoma...
Article
Exposure of cells and nanoparticles to near-infrared nanosecond pulsed laser light can lead to efficient intracellular delivery of molecules while maintaining high cell viability by a photoacoustic phenomenon known as transient nanoparticle energy transduction (TNET). Here, we examined the influence of cytoskeletal mechanics and plasma membrane flu...
Article
Previous studies have shown that exposure of carbon black nanoparticles to nanosecond pulsed near-infrared laser causes intracellular delivery of molecules through hypothesized transient breaks in the cell membrane. The goal of this study is to determine the underlying mechanisms of sequential energy transfer from laser light to nanoparticle to flu...
Conference Paper
Taylor rod-on-anvil impact experiments have been performed on a range of polyolefins. At impact velocity greater than ~250 m/s there are significant differences observed in the deformation behavior between the four polymers, which cannot be explained based on current understanding. During the initial stages of impact, mechno-luminescence is observe...
Conference Paper
Shock compression experiments were performed on amorphous Ce3Al melt-spun ribbons using the 50 J laser shock loading system at the Omega laser facility. A multi-layered sample of 2mm total thickness with 1 mm × 1.5 mm width and 40 µm thick ribbons sandwiched with 6 µm epoxy was used as the target in order to study the effects of varying pressures (...
Conference Paper
Full-text available
Distributed Bragg Reflectors and optical microcavities are multilayer optical structures with spectral properties that are intrinsically sensitive to external perturbations. With nanometer to micrometer dimensions and near instantaneous optical response, these structures show filigficant potential as the basis for meso-scale time-resolved diagnosti...
Conference Paper
Determining stress and temperature distributions of dynamically compacted particles is of interest to the geophysical and astrological research communities. However, the researcher cannot easily observe particle interactions during a planar shock experiment. By using mesoscale simulations, we can unravel granular particle interactions. Unlike homog...
Article
Uniaxial strain, plate-on-plate impact experiments were performed on cold-rolled Ni/Al multilayer composites and the resulting Hugoniot was determined through time-resolved measurements combined with impedance matching. The experimental Hugoniot agreed with that previously predicted by two dimensional (2D) meso-scale calculations [Specht et al., J....
Conference Paper
Hugoniot states achieved in heterogeneous materials have shown oscillations in particle velocity about an averaged state for both experimental and simulated data. These oscillations arise from the scattering of the transmitted shock wave due to the presence of internal interfaces within heterogeneous materials. The goal of this work is to determine...
Conference Paper
Highly heterogeneous reactive powder mixtures containing Ti+2B (Stoichiometric 1:2) are studied to ascertain the shock compression response and potential reaction behavior. The transit time through the pressed powder mixture compacts is monitored using poly-vinylidene fluoride (PVDF) stress gauges and used to compute a wave speed through the compac...
Article
The influence of interfacial density, structure, and strength in addition to material strengths on the dispersion and dissipation of a shock wave traveling parallel to the layers in a laminar, multilayer composite was investigated using two-dimensional, meso-scale simulations incorporating a real, heterogeneous microstructure. Optimum interfacial d...
Article
Optical microcavity (OMC) structures have spectral properties that are directly related to their physical dimensions and material refractive indices. Their intrinsically fast optical response to mechanically-induced changes in these parameters makes OMCs uniquely suited for dynamic sensing when paired with a suitably fast streak camera and spectrog...
Article
The mechanism of destruction of a material by high-speed impact is known to be complex, and it is hard to analyze the inner state of the material during the destruction process. In particular, it is difficult to measure the temperature changes within a material during a high-speed impact. In this study, we propose a new method for estimating this t...
Article
The nanometer size of CdTe quantum dots (QDs) and their unique optical properties, including size-tunable narrow photoluminescent emission, broad absorption, fast photoluminescence decay, and negligible light scattering, are ideal features for spectrally tagging the shock response of localized regions in highly heterogeneous materials such as parti...
Article
Transparent glass ceramics with embedded light-emitting nanocrystals show great potential as low-cost nanocomposite scintillators in comparison to single crystal and transparent ceramic scintillators. In this study, cubic structure BaGdF5:Tb nanocrystals embedded in an aluminosilicate glass matrix are reported for potential high performance MeV ima...
Article
The initiation of aluminized fluorinated acrylic (AlFA) nanocomposites during modified Taylor impact tests was investigated. Samples were impacted against a steel or sapphire anvil at a nominal velocity of 150 m/s. A framing camera was used to capture head-on and side-profile impact images for the sapphire window and steel plate rigid anvils, respe...
Article
The dynamic yielding and fracture (spalling) of commercially pure (grade 4) titanium are investigated using symmetric plate impact experiments for a peak stress range of 5.6 GPa–12.5 GPa. Velocity interferometry system for any reflector rear free surfacevelocity profiles display both a Hugoniot elastic limit (HEL) and a velocity pullback, which are...
Article
The shock-compression response of Ni + Al multilayered thin foils is investigated using laser-accelerated thin-foil plate-impact experiments over the pressure range of 2 to 11 GPa. The foils contain alternating Ni and Al layers (parallel but not flat) of nominally 50 nm bilayer spacing. The goal is to determine the equation of state and shock-induc...
Article
Laser-driven shock compression experiments and corresponding finite element method simulations are carried out to investigate the blueshift in the optical emission spectra under continuous laser excitation of a dilute composite consisting of 0.15% CdTequantum dots by weight embedded in polyvinyl alcohol polymer. This material is a potential candida...
Article
α″-Fe16N2 has been suggested as a promising candidate for future rare-earth-free magnets. In this paper, a unique technical route including a ball milling approach and shock compaction is experimentally demonstrated as a promising way to produce an α″-Fe16N2 magnet. Firstly, α″-Fe16N2 powder is prepared by ball milling, in which ammonium nitrate (N...
Data
The field of dynamic behavior of materials comprises diverse phenomena such as deformation, fracture, fragmentation, shear localization, damage dissipation, and chemical reactions occurring under extreme conditions, as well as processing via shock compaction, explosive welding and forming, and reaction synthesis of novel materials. It has evolved c...
Article
There is an interest in producing accurate and reliable computer simulations to predict the dynamic behavior of heterogeneous materials and to use these simulations to gain further insight into experimental results. In so doing, a more complete understanding of the multiple-length scale involved in heterogeneous material compaction can be obtained....
Article
A computational study of Distributed Bragg Reflectors (DBR) and Optical Microcavities (OMC) was conducted to ascertain their potential as time-resolved mesoscale sensors due to their unique structure-driven spectral characteristics. Shock wave propagation simulations of polymer-based DBRs and glass/ceramic-based OMCs were coupled with spectral resp...
Article
Efficient intracellular delivery of molecules is needed to modulate cellular behavior for laboratory and medical applications, but is often limited by trade-offs between achieving high intracellular delivery and maintaining high cell viability. Here, we studied photoacoustic delivery of molecules into cells by exposing DU145 human prostrate carcino...
Article
Powder processing of materials typically uses uniaxial compression in the powder-compaction step and might thereby make anisotropic compacts out of initially isotropic powders. Our objective in this study was to ascertain and quantitatively characterize this possible anisotropy in green compacts of Al–Ti–B powder mixtures of three compositions, pre...
Article
The dynamic yielding and tensile fracture (spalling) behavior of an annealed aluminum–magnesium alloy is investigated using symmetric plate impact experiments. The Hugoniot elastic limit displays upper and lower yield points, with the lower yield point remaining constant near 0.33 GPa and the upper yield point increasing from 0.38 to 0.48 GPa with...
Article
Full-text available
The shock compression response of Ti+2B (1:2 Ti:B stoichiometric ratio) reactive powder mixtures at ~50% theoretical material density (TMD) is investigated for shock pressures up to 5 GPa to investigate the possible shock-induced chemical reactivity of this highly exothermic mixture. The shock adiabat is produced from instrumented parallel-plate ga...
Article
Full-text available
Fragmentation results for structural energetic materials based on intermetallic forming mixtures are reviewed and the implications of the fragment populations are discussed. Cold sprayed Ni+Al and explosively compacted mixtures of Ni+Al+W and Ni+Al+W+Zr powders were fabricated into ring shaped samples and explosively fragmented. Ring velocity was m...
Article
Full-text available
The dissipative particle dynamics with energy conservation (DPDE) method is extended to simulate the shock response of high energetic (HE) materials at micron length scales. The symmetrical impact of an RDX impactor and target plates with 1μm diameter spheres is simulated at planar impact velocities of 208 m/s and 876 m/s with a Lennard-Jones-like...
Article
Full-text available
The impact initiation of as-received and mechanically activated aluminum powder compacts is investigated through uniaxial stress rod-on-anvil impact experiments. The compacts reveal light emission due to combustion reaction at velocities greater than 165 m/s. Mechanical pre-activation, such as that achieved via high-energy ball milling (HEBM) or hi...
Article
Full-text available
The mechanisms of stress relaxation in metallic glasses under high strain rates are an area of active study. The lack of extended structure forces strain accommodation through alternative modes to slip For example, amorphous Ce3Al has been shown to undergo a phase transition to the crystalline FCC Ce3Al at 25 GPa under quasistatic loading. Whether...
Article
Full-text available
The results of FE simulations are presented, correlating the continuum and mesoscale shock response of a particulate system with particle surface stresses-strains. The objective of this work is to gain insight into how the complex responses at the meso/sub-mesoscale manifest to quantities that could be experimentally measured without perturbing the...
Article
Full-text available
The spall strength and Hugoniot Elastic Limit (HEL) of aluminum alloy 5083 (Al 5083) are compared for plates fabricated using equi-channel angular pressing (ECAP) and rolling. Al 5083 is a light-weight and strain-hardenable aluminum alloy used for armor plating in military transport vehicles, thus requiring the highest achievable spall strength and...
Article
The impact initiated reaction response of a Ta + Bi2O3 thermite powder mixture encapsulated in two different maraging steel geometric structures was investigated. Experiments were performed on the Ta + Bi2O3 mixture initially compressed to ∼40% theoretical maximum density in a hollow cylinder and 9-Cell linear cellular alloy (LCA) structure, both o...
Article
Conventional physical and chemical methods that efficiently deliver molecules into cells are often associated with low cell viability. In this study, we evaluated the cellular effects of carbon nanoparticles believed to emit photoacoustic waves due to nanosecond-pulse laser activation to test the hypothesis that this method could achieve efficient...
Article
The initiation of chemical reaction in cold-rolled Ni/Al multilayered composites by shock compression is investigated numerically. A simplified approach is adopted that exploits the disparity between the reaction and shock loading timescales. The impact of shock compression is modeled using CTH simulations that yield pressure, strain, and temperatu...
Conference Paper
The cell membrane is a challenging barrier to cross because of its structure and composition. Endocytotic processes can be inefficient, especially for molecules that have therapeutic value such as siRNA, plasmids, etc. So it is a challenging task to come up with a method that can address the issue of intracellular delivery. Various methods have be...
Article
In this paper, a methodology has been developed to accurately predict the elastic properties of multi-constituent particulate composites by accounting for irreversible effects, such as energy loss that arises due to internal friction. The complex dependence on loading density and particle properties (i.e., size, shape, morphology, etc.) is investig...
Article
Full-text available
The spall properties of rolled Al 5083-H116 plate are investigated using symmetric plate impact experiments over the stress range 1.5–6.2 GPa. Rear free surface velocity measurements made employing Velocity Interferometer System for Any Reflector interferometry reveal velocity profiles with clear signals of the Hugoniot elastic limit (HEL) and velo...
Article
Full-text available
A model framework for predicting the dynamic shock-compression response of heterogeneous powder mixtures using readily obtained measurements from quasi-static tests is presented. Low-strain-rate compression data are first analyzed to determine the region of the bulk response over which particle rearrangement does not contribute to compaction. This...
Article
Full-text available
Nanoscale Nd-Fe-B particles were fabricated with room temperature coercivity of 4.9 kOe by attrition (stirred media) milling. For longer milling times, more than 80% of the particles were less than 500 nm diameter, and 50–200 nm particles can be selected by a decanting process. Anisotropy was demonstrated by field alignment, as shown by creation of...
Article
The mechanisms influencing impact initiation of reactions in structural energetic materials formed by explosive compaction of pure Ni, Ta, or W powders mixed with Al powder are investigated in this work. High speed images of rod-on-anvil impact tests indicate that the energy requirements for initiating reaction in Ta+Al compacts are lower than thos...
Article
Impact initiation of reactions in various aluminum-based intermolecular composites in the form of powder mixture compacts and cold-rolled laminates are being investigated using instrumented gas-gun impact experiments under conditions of uniaxial-strain and uniaxial-stress loading. Time-resolved stress and particle velocity measurements as well as h...
Article
The shock consolidation response of recently obtained data for a powder mixture of Ta + Bi2O3 with previously published results for mixtures of Ni + Al, Mo + Si, and Ti + Si are investigated within the context of the P-α and P-λ models to determine the applicability of these models to highly heterogeneous powder mixtures. The mixtures were found to...
Article
Heterogeneities at the meso-scale strongly influence the shock compression response of composite materials. Laminated geometries with full density and intimate particle contacts provide a unique system to investigate the influence of microstructure on a propagating shock wave. Computational analysis is used to understand the effects of layer orient...