Publications by authors named "Yu-Chen Karen Chen-Wiegart"

28 Publications

  • Page 1 of 1

Formation of three-dimensional bicontinuous structures via molten salt dealloying studied in real-time by in situ synchrotron X-ray nano-tomography.

Nat Commun 2021 Jun 9;12(1):3441. Epub 2021 Jun 9.

Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, NY, USA.

Three-dimensional bicontinuous porous materials formed by dealloying contribute significantly to various applications including catalysis, sensor development and energy storage. This work studies a method of molten salt dealloying via real-time in situ synchrotron three-dimensional X-ray nano-tomography. Quantification of morphological parameters determined that long-range diffusion is the rate-determining step for the dealloying process. The subsequent coarsening rate was primarily surface diffusion controlled, with Rayleigh instability leading to ligament pinch-off and creating isolated bubbles in ligaments, while bulk diffusion leads to a slight densification. Chemical environments characterized by X-ray absorption near edge structure spectroscopic imaging show that molten salt dealloying prevents surface oxidation of the metal. In this work, gaining a fundamental mechanistic understanding of the molten salt dealloying process in forming porous structures provides a nontoxic, tunable dealloying technique and has important implications for molten salt corrosion processes, which is one of the major challenges in molten salt reactors and concentrated solar power plants.
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http://dx.doi.org/10.1038/s41467-021-23598-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8190292PMC
June 2021

Unraveling the Formation Mechanism of a Hybrid Zr-Based Chemical Conversion Coating with Organic and Copper Compounds for Corrosion Inhibition.

ACS Appl Mater Interfaces 2021 Feb 19;13(4):5518-5528. Epub 2021 Jan 19.

Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, New York 11794, United States.

Environmentally friendly chromate-free, zirconium (Zr)-based conversion coating is a promising green technology for corrosion protection. Additives in the surface treatment provide critical functionalities and performance improvements; however, mechanistic understanding as to how the additives influence the coatings remains unclear. In this study, a new organic-inorganic hybrid Zr-based conversion coating combines copper (Cu) compounds and polyamidoamine (PAMAM), taking advantage of the complementary nature of organic and inorganic additives. A multimodal approach combining electron and X-ray characterization is applied to study the interaction of Cu and PAMAM and the resulting impacts on coating formation. Adding PAMAM changed the surface morphology, thickness, distribution of Cu in the clusters, and void formation of the coatings. High PAMAM (100-200 ppm) leads to little conversion coating formation, and low PAMAM (0-25 ppm) shows voids formation under the coatings. Moreover, PAMAM incorporates in the coating in the form of a PAMAM-Cu complex with a higher concentration toward the surface, providing an organic layer at the surface of the coating. X-ray absorption near-edge structure (XANES) spectroscopy shows the difference between the conventional and the hybrid coating treatments in an alkaline solution to simulate the E-coat process, suggesting the contribution of PAMAM in the enhanced chemical stability in an alkaline environment. Therefore, an intermediate range of addition of PAMAM (50 ppm) is optimal to (1) avoid excessive voids formation, (2) promote some Cu cluster formation and thus enhance the Zr-based coating formation, and (3) incorporate organic components into the coating to improve the adhesion of the subsequent coatings. Overall, this work furthers our knowledge on the formation mechanism of an effective and environmentally friendly hybrid conversion coating for corrosion inhibition, demonstrating a critical processing-structure-property relationship. This study will benefit future development of green and effective surface treatment technology.
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http://dx.doi.org/10.1021/acsami.0c19203DOI Listing
February 2021

Nano- to microscale three-dimensional morphology relevant to transport properties in reactive porous composite paint films.

Sci Rep 2020 Oct 27;10(1):18320. Epub 2020 Oct 27.

Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA.

The quantitative evaluation of the three-dimensional (3D) morphology of porous composite materials is important for understanding mass transport phenomena, which further impact their functionalities and durability. Reactive porous paint materials are composites in nature and widely used in arts and technological applications. In artistic oil paintings, ambient moisture and water and organic solvents used in conservation treatments are known to trigger multiple physical and chemical degradation processes; however, there is no complete physical model that can quantitatively describe their transport in the paint films. In the present study, model oil paints with lead white (2PbCO·Pb(OH)) and zinc white (ZnO) pigments, which are frequently found in artistic oil paintings and are associated with the widespread heavy metal soap deterioration, were studied using synchrotron X-ray nano-tomography and unilateral nuclear magnetic resonance. This study aims to establish a relationship among the paints' compositions, the 3D morphological properties and degradation. This connection is crucial for establishing reliable models that can predict transport properties of solvents used in conservation treatments and of species involved in deterioration reactions, such as soap formation.
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http://dx.doi.org/10.1038/s41598-020-75040-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7591493PMC
October 2020

Future trends in synchrotron science at NSLS-II.

J Phys Condens Matter 2020 Jun 22;32(37):374008. Epub 2020 Jun 22.

National Synchrotron Light Source II (NSLS-II), Brookhaven National Laboratory, Upton, NY, United States of America.

In this paper, we summarize briefly some of the future trends in synchrotron science as seen at the National Synchrotron Light Source II, a new, low emittance source recently commissioned at Brookhaven National Laboratory. We touch upon imaging techniques, the study of dynamics, the increasing use of multimodal approaches, the vital importance of data science, and other enabling technologies. Each are presently undergoing a time of rapid change, driving the field of synchrotron science forward at an ever increasing pace. It is truly an exciting time and one in which Roger Cowley, to whom this journal issue is dedicated, would surely be both invigorated by, and at the heart of.
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http://dx.doi.org/10.1088/1361-648X/ab7b19DOI Listing
June 2020

Versatile compact heater design for in situ nano-tomography by transmission X-ray microscopy.

J Synchrotron Radiat 2020 May 16;27(Pt 3):746-752. Epub 2020 Apr 16.

National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY 11973, USA.

A versatile, compact heater designed at National Synchrotron Light Source-II for in situ X-ray nano-imaging in a full-field transmission X-ray microscope is presented. Heater design for nano-imaging is challenging, combining tight spatial constraints with stringent design requirements for the temperature range and stability. Finite-element modeling and analytical calculations were used to determine the heater design parameters. Performance tests demonstrated reliable and stable performance, including maintaining the exterior casing close to room temperature while the heater is operating at above 1100°C, a homogenous heating zone and small temperature fluctuations. Two scientific experiments are presented to demonstrate the heater capabilities: (i) in situ 3D nano-tomography including a study of metal dealloying in a liquid molten salt extreme environment, and (ii) a study of pore formation in icosahedral quasicrystals. The progression of structural changes in both studies were clearly resolved in 3D, showing that the new heater enables powerful capabilities to directly visualize and quantify 3D morphological evolution of materials under real conditions by X-ray nano-imaging at elevated temperature during synthesis, fabrication and operation processes. This heater design concept can be applied to other applications where a precise, compact heater design is required.
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http://dx.doi.org/10.1107/S1600577520004567DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7285687PMC
May 2020

Revealing 3D Morphological and Chemical Evolution Mechanisms of Metals in Molten Salt by Multimodal Microscopy.

ACS Appl Mater Interfaces 2020 Apr 3;12(15):17321-17333. Epub 2020 Apr 3.

Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, New York 11794, United States.

Growing interest in molten salts as effective high-temperature heat-transfer fluids for sustainable energy systems drives a critical need to fundamentally understand the interactions between metals and molten salts. This work utilizes the multimodal microscopy methods of synchrotron X-ray nanotomography and electron microscopy to investigate the 3D morphological and chemical evolution of two-model systems, pure nickel metal and Ni-20Cr binary alloy, in a representative molten salt (KCl-MgCl 50-50 mol %, 800 °C). In both systems, unexpected shell-like structures formed because of the presence of more noble tungsten, suggesting a potential route of using Ni-W alloys for enhanced molten-salt corrosion resistance. The binary alloy Ni-20Cr developed a bicontinuous porous structure, reassembling functional porous metals manufactured by dealloying. This work elucidates better mechanistic understanding of corrosion in molten salts, which can contribute to the design of more reliable alloys for molten salt applications including next-generation nuclear and solar power plants and opens the possibility of using molten salts to fabricate functional porous materials.
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http://dx.doi.org/10.1021/acsami.9b19099DOI Listing
April 2020

Systems-level investigation of aqueous batteries for understanding the benefit of water-in-salt electrolyte by synchrotron nanoimaging.

Sci Adv 2020 Mar 6;6(10):eaay7129. Epub 2020 Mar 6.

Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, NY 11794, USA.

Water-in-salt (WIS) electrolytes provide a promising path toward aqueous battery systems with enlarged operating voltage windows for better safety and environmental sustainability. In this work, a new electrode couple, LiVO-LiMnO, for aqueous Li-ion batteries is investigated to understand the mechanism by which the WIS electrolyte improves the cycling stability at an extended voltage window. Operando synchrotron transmission x-ray microscopy on the LiMnO cathode reveals that the WIS electrolyte suppresses the mechanical damage to the electrode network and dissolution of the electrode particles, in addition to delaying the water decomposition process. Because the viscosity of WIS is notably higher, the reaction heterogeneity of the electrodes is quantified with x-ray absorption spectroscopic imaging, visualizing the kinetic limitations of the WIS electrolyte. This work furthers the mechanistic understanding of electrode-WIS electrolyte interactions and paves the way to explore the strategy to mitigate their possible kinetic limitations in three-dimensional architectures.
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http://dx.doi.org/10.1126/sciadv.aay7129DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7060054PMC
March 2020

Designing Multiscale Porous Metal by Simple Dealloying with 3D Morphological Evolution Mechanism Revealed via X-ray Nano-tomography.

ACS Appl Mater Interfaces 2020 Jan 2;12(2):2793-2804. Epub 2020 Jan 2.

Department of Materials Science and Chemical Engineering , Stony Brook University , Stony Brook , New York 11794 , United States.

Designing materials with multiscale, hierarchical structure is critical to drive the advancement of new technology. Specifically, porous metals with multiscale porosity from nanometer to micrometer sizes would lead to enhanced physical and chemical properties-the micron-sized pores can increase the effective diffusivity of ion transport within the porous media, and the nano-sized pores provide high specific surface area, enabling functionalities that are unique to nanoporous metals. A new ternary precursor alloy selection concept utilizing the different mixing enthalpies is demonstrated in this work for the design of multiscale, bimodal porous copper from a simple, one-step dealloying of Cu-Fe-Al ternary alloy. The nanoporosity in the bimodal porous structure is formed from dealloying of the Cu-rich phase, whereas the microporosity is controlled by dissolving the Fe-rich phase, determined by both the initial Fe particle size and sintering profile. In addition to advancing the materials design method, the multiscale pore formation during dealloying was directly visualized and quantified via an interrupted in situ synchrotron X-ray nano-tomography. The 3D morphological analysis on tortuosity showed that the presence of the microporosity can compensate the increase of the diffusion path length due to nanoporosity, which facilitates diffusion within the porous structure. Overall the focus of the work is to introduce a new strategy to design multiscale porous metals with enhanced transport properties, and sheds light on the fundamental mechanisms on the 3D morphological evolution of the system using advanced synchrotron X-ray nano-tomography for future materials development and applications.
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http://dx.doi.org/10.1021/acsami.9b16392DOI Listing
January 2020

Cationic Ordering Coupled to Reconstruction of Basic Building Units during Synthesis of High-Ni Layered Oxides.

J Am Chem Soc 2018 Oct 19;140(39):12484-12492. Epub 2018 Sep 19.

Sustainable Energy Technologies Department , Brookhaven National Laboratory , Upton , New York 11973 , United States.

Metal (M) oxides are one of the most interesting and widely used solids, and many of their properties can be directly correlated to the local structural ordering within basic building units (BBUs). One particular example is the high-Ni transition metal layered oxides, potential cathode materials for Li-ion batteries whose electrochemical activity is largely determined by the cationic ordering in octahedra (e.g., the BBUs in such systems). Yet to be firmly established is how the BBUs are inherited from precursors and subsequently evolve into the desired ordering during synthesis. Herein, a multimodal in situ X-ray characterization approach is employed to investigate the synthesis process in preparing LiNiMnCoO from its hydroxide counterpart, at scales varying from the long-range to local individual octahedral units. Real-time observation corroborated by first-principles calculations reveals a topotactic transformation throughout the entire process, during which the layered framework is retained; however, due to preferential oxidation of Co and Mn over Ni, significant changes happen locally within NiO octahedra. Specifically, oxygen loss and the associated symmetry breaking occur in NiO; as a consequence, Ni ions become highly mobile and tend to mix with Li, causing high cationic disordering upon formation of the layered oxides. Only through high-temperature heat treatment, Ni is further oxidized, thereby inducing symmetry reconstruction and, concomitantly, cationic ordering within NiO octahedra. Findings from this study shed light on designing high-Ni layered oxide cathodes and, more broadly, various functional materials through synthetic control of the constituent BBUs.
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http://dx.doi.org/10.1021/jacs.8b06150DOI Listing
October 2018

New aspects of longitudinal instabilities in electron storage rings.

Sci Rep 2018 Aug 9;8(1):11918. Epub 2018 Aug 9.

Brookhaven National Laboratory, Upton, NY, 11973, USA.

Novel features of the longitudinal instability of a single electron bunch circulating in a low-emittance electron storage ring are discussed. Measurements and numerical simulations, performed both in time and frequency domain, show a non-monotonic increase of the electron beam energy spread as a function of single bunch current, characterized by the presence of local minima and maxima, where a local minimum of the energy spread is interpreted as a higher-order microwave instability threshold. It is also shown that thresholds related to the same zero-intensity bunch length depend linearly on the accelerating radio frequency voltage. The observed intensity-dependent features of the energy spread, confirmed by measurements with two independent diagnostics methods, i.e. horizontal beam profile measurements by a synchrotron light monitor and photon energy spectrum measurements of undulator radiation, are given a theoretical interpretation by applying a novel eigenvalue analysis based on the linearized Vlasov equation.
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http://dx.doi.org/10.1038/s41598-018-30306-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6085323PMC
August 2018

Operando Multi-modal Synchrotron Investigation for Structural and Chemical Evolution of Cupric Sulfide (CuS) Additive in Li-S battery.

Sci Rep 2017 10 11;7(1):12976. Epub 2017 Oct 11.

Sustainable Energy Technologies Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.

Conductive metal sulfides are promising multi-functional additives for future lithium-sulfur (Li-S) batteries. These can increase the sulfur cathode's electrical conductivity to improve the battery's power capability, as well as contribute to the overall cell-discharge capacity. This multi-functional electrode design showed initial promise; however, complicated interactions at the system level are accompanied by some detrimental side effects. The metal sulfide additives with a chemical conversion as the reaction mechanism, e.g., CuS and FeS, can increase the theoretical capacity of the Li-S system. However, these additives may cause undesired parasitic reactions, such as the dissolution of the additive in the electrolyte. Studying such complex reactions presents a challenge because it requires experimental methods that can track the chemical and structural evolution of the system during an electrochemical process. To address the fundamental mechanisms in these systems, we employed an operando multimodal x-ray characterization approach to study the structural and chemical evolution of the metal sulfide-utilizing powder diffraction and fluorescence imaging to resolve the former and absorption spectroscopy the latter-during lithiation and de-lithiation of a Li-S battery with CuS as the multi-functional cathode additive. The resulting elucidation of the structural and chemical evolution of the system leads to a new description of the reaction mechanism.
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http://dx.doi.org/10.1038/s41598-017-12738-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5636834PMC
October 2017

Elemental and Molecular Segregation in Oil Paintings due to Lead Soap Degradation.

Sci Rep 2017 09 14;7(1):11656. Epub 2017 Sep 14.

National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York, USA.

The formation of Pb, Zn, and Cu carboxylates (soaps) has caused visible deterioration in hundreds of oil paintings dating from the 15th century to the present. Through transport phenomena not yet understood, free fatty acids in the oil binding medium migrate through the paint and react with pigments containing heavy metals to form soaps. To investigate the complex correlation among the elemental segregation, types of chemical compounds formed, and possible mechanisms of the reactions, a paint sample cross-section from a 15th century oil painting was examined by synchrotron X-ray techniques. X-ray fluorescence (XRF) microscopy, quantified with elemental correlation density distribution, showed Pb and Sn segregation in the soap-affected areas. X-ray absorption near edge structure (XANES) around the Pb-L3 absorption edge showed that Pb pigments and Pb soaps can be distinguished while micro-XANES gave further information on the chemical heterogeneity in the paint film. The advantages and limitations of these synchrotron-based techniques are discussed and compared to those of methods routinely used to analyze paint samples. The results presented set the stage for improving the information extracted from samples removed from works of art and for correlating observations in model paint samples to those in the naturally aged samples, to shed light onto the mechanism of soap formation.
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http://dx.doi.org/10.1038/s41598-017-11525-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5599643PMC
September 2017

Three-Dimensional Morphological and Chemical Evolution of Nanoporous Stainless Steel by Liquid Metal Dealloying.

ACS Appl Mater Interfaces 2017 Oct 19;9(39):34172-34184. Epub 2017 Sep 19.

Department of Materials Science and Chemical Engineering, Stony Brook University , Stony Brook, New York 11794, United States.

Nanoporous materials, especially those fabricated by liquid metal dealloying processes, possess great potential in a wide range of applications due to their high surface area, bicontinuous structure with both open pores for transport and solid phase for conductivity or support, and low material cost. Here, we used X-ray nanotomography and X-ray fluorescence microscopy to reveal the three-dimensional (3D) morphology and elemental distribution within materials. Focusing on nanoporous stainless steel, we evaluated the 3D morphology of the dealloying front and established a quantitative processing-structure-property relationship at a later stage of dealloying. The morphological differences of samples created by liquid metal dealloying and aqueous dealloying methods were also discussed. We concluded that it is particularly important to consider the dealloying, coarsening, and densification mechanisms in influencing the performance-determining, critical 3D parameters, such as tortuosity, pore size, porosity, curvature, and interfacial shape.
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http://dx.doi.org/10.1021/acsami.7b04659DOI Listing
October 2017

Is an electric field always a promoter of wetting? Electro-dewetting of metals by electrolytes probed by in situ X-ray nanotomography.

Faraday Discuss 2017 07 28;199:101-114. Epub 2017 Apr 28.

Department of Materials Science and Engineering, Clemson University, Clemson, SC 29634, USA.

We developed a special electrochemical cell enabling quantitative analysis and in situ X-ray nanotomography of metal/electrolyte interfaces subject to corrosion. Using this cell and applying the nodoid model to describe menisci formed on tungsten wires during anodization, the evolution of the electrolyte surface tension, the concentration of reaction products, and the meniscus contact angle were studied. In contrast to the electrowetting effect, where the applied electric field decreases the contact angle of electrolytes, anodization of the tungsten wires increases the contact angle of the meniscus. Hence, an electric field favors dewetting rather than wetting of the newly formed surface. The discovered effect opens up new opportunities for the control of wetting phenomena and calls for the revision of existing theories of electrowetting.
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http://dx.doi.org/10.1039/c6fd00239kDOI Listing
July 2017

Evolution of dealloying induced strain in nanoporous gold crystals.

Nanoscale 2017 May;9(17):5686-5693

Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, NY 11794, USA.

We studied the evolution of dealloying-induced strain along the {111} in a Ag-Au nano-crystal in situ, during formation of nanoporous gold at the initial stage of dealloying using Bragg coherent X-ray diffractive imaging. The strain magnitude with maximum probability in the crystal doubled in 10 s of dealloying. Although formation of nano-pores just began at the surface, the greatest strain is located 60-80 nm deep within the crystal. Dealloying induced a compressive strain in this region, indicating volume shrinkage occurred during pore formation. The crystal interior showed a small tensile strain, which can be explained by tensile stresses induced by the non-dealloyed region upon the dealloyed region during volume reduction. A surface strain relaxation developed, attributed to atomic rearrangement during dealloying. This clearer understanding of the role of strain in the initial stages of formation of nanoporous gold by dealloying can be exploited for development of new sensors, battery electrodes, and materials for catalysis.
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http://dx.doi.org/10.1039/c6nr09635bDOI Listing
May 2017

Visualization of anisotropic-isotropic phase transformation dynamics in battery electrode particles.

Nat Commun 2016 08 12;7:12372. Epub 2016 Aug 12.

Photon Science, National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, USA.

Anisotropy, or alternatively, isotropy of phase transformations extensively exist in a number of solid-state materials, with performance depending on the three-dimensional transformation features. Fundamental insights into internal chemical phase evolution allow manipulating materials with desired functionalities, and can be developed via real-time multi-dimensional imaging methods. Here, we report a five-dimensional imaging method to track phase transformation as a function of charging time in individual lithium iron phosphate battery cathode particles during delithiation. The electrochemically driven phase transformation is initially anisotropic with a preferred boundary migration direction, but becomes isotropic as delithiation proceeds further. We also observe the expected two-phase coexistence throughout the entire charging process. We expect this five-dimensional imaging method to be broadly applicable to problems in energy, materials, environmental and life sciences.
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http://dx.doi.org/10.1038/ncomms12372DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4990630PMC
August 2016

In situ X-ray nanotomography of metal surfaces during electropolishing.

Sci Rep 2015 Oct 15;5:15257. Epub 2015 Oct 15.

Department of Materials Science and Engineering, Clemson University, Clemson, SC 29634, USA.

A low voltage electropolishing of metal wires is attractive for nanotechnology because it provides centimeter long and micrometer thick probes with the tip radius of tens of nanometers. Using X-ray nanotomography we studied morphological transformations of the surface of tungsten wires in a specially designed electrochemical cell where the wire is vertically submersed into the KOH electrolyte. It is shown that stability and uniformity of the probe span is supported by a porous shell growing at the surface of tungsten oxide and shielding the wire surface from flowing electrolyte. It is discovered that the kinetics of shell growth at the triple line, where meniscus meets the wire, is very different from that of the bulk of electrolyte. Many metals follow similar electrochemical transformations hence the discovered morphological transformations of metal surfaces are expected to play significant role in many natural and technological applications.
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http://dx.doi.org/10.1038/srep15257DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4606789PMC
October 2015

Quantified abundance of magnetofossils at the Paleocene-Eocene boundary from synchrotron-based transmission X-ray microscopy.

Proc Natl Acad Sci U S A 2015 Oct 29;112(41):12598-603. Epub 2015 Sep 29.

Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854; Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964

The Paleocene-Eocene boundary (∼55.8 million years ago) is marked by an abrupt negative carbon isotope excursion (CIE) that coincides with an oxygen isotope decrease interpreted as the Paleocene-Eocene thermal maximum. Biogenic magnetite (Fe3O4) in the form of giant (micron-sized) spearhead-like and spindle-like magnetofossils, as well as nano-sized magnetotactic bacteria magnetosome chains, have been reported in clay-rich sediments in the New Jersey Atlantic Coastal Plain and were thought to account for the distinctive single-domain magnetic properties of these sediments. Uncalibrated strong field magnet extraction techniques have been typically used to provide material for scanning and transmission electron microscopic imaging of these magnetic particles, whose concentration in the natural sediment is thus difficult to quantify. In this study, we use a recently developed ultrahigh-resolution, synchrotron-based, full-field transmission X-ray microscope to study the iron-rich minerals within the clay sediment in their bulk state. We are able to estimate the total magnetization concentration of the giant biogenic magnetofossils to be only ∼10% of whole sediment. Along with previous rock magnetic studies on the CIE clay, we suggest that most of the magnetite in the clay occurs as isolated, near-equidimensional nanoparticles, a suggestion that points to a nonbiogenic origin, such as comet impact plume condensates in what may be very rapidly deposited CIE clays.
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http://dx.doi.org/10.1073/pnas.1517475112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4611651PMC
October 2015

Precipitation and surface adsorption of metal complexes during electropolishing. Theory and characterization with X-ray nanotomography and surface tension isotherms.

Phys Chem Chem Phys 2015 Sep 17;17(35):23121-31. Epub 2015 Aug 17.

Department of Materials Science and Engineering, Clemson University, Clemson, SC 29634, USA.

Electropolishing of metals often leads to supersaturation conditions resulting in precipitation of complex compounds. The solubility diagrams and Gibbs adsorption isotherms of the electropolishing products are thus very important to understand the thermodynamic mechanism of precipitation of reaction products. Electropolishing of tungsten wires in aqueous solutions of potassium hydroxide is used as an example illustrating the different thermodynamic scenarios of electropolishing. Electropolishing products are able to form highly viscous films immiscible with the surrounding electrolyte or porous shells adhered to the wire surface. Using X-ray nanotomography, we discovered a gel-like phase formed at the tungsten surface during electropolishing. The results of these studies suggest that the electropolishing products can form a rich library of compounds. The surface tension of the electrolyte depends on the metal oxide ions and alkali-metal complexes.
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http://dx.doi.org/10.1039/c5cp03431kDOI Listing
September 2015

Probing three-dimensional sodiation-desodiation equilibrium in sodium-ion batteries by in situ hard X-ray nanotomography.

Nat Commun 2015 Jun 26;6:7496. Epub 2015 Jun 26.

National Synchrotron Light Source II, Brookhaven National Laboratory, Building 743 Ring Road, Upton, New York 11973, USA.

Materials degradation-the main limiting factor for widespread application of alloy anodes in battery systems-was assumed to be worse in sodium alloys than in lithium analogues due to the larger sodium-ion radius. Efforts to relieve this problem are reliant on the understanding of electrochemical and structural degradation. Here we track three-dimensional structural and chemical evolution of tin anodes in sodium-ion batteries with in situ synchrotron hard X-ray nanotomography. We find an unusual (de)sodiation equilibrium during multi-electrochemical cycles. The superior structural reversibility during 10 electrochemical cycles and the significantly different morphological change features from comparable lithium-ion systems suggest untapped potential in sodium-ion batteries. These findings differ from the conventional thought that sodium ions always lead to more severe fractures in the electrode than lithium ions, which could have impact in advancing development of sodium-ion batteries.
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http://dx.doi.org/10.1038/ncomms8496DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4491187PMC
June 2015

Visualization of electrochemically driven solid-state phase transformations using operando hard X-ray spectro-imaging.

Nat Commun 2015 Apr 20;6:6883. Epub 2015 Apr 20.

Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.

In situ techniques with high temporal, spatial and chemical resolution are key to understand ubiquitous solid-state phase transformations, which are crucial to many technological applications. Hard X-ray spectro-imaging can visualize electrochemically driven phase transformations but demands considerably large samples with strong absorption signal so far. Here we show a conceptually new data analysis method to enable operando visualization of mechanistically relevant weakly absorbing samples at the nanoscale and study electrochemical reaction dynamics of iron fluoride, a promising high-capacity conversion cathode material. In two specially designed samples with distinctive microstructure and porosity, we observe homogeneous phase transformations during both discharge and charge, faster and more complete Li-storage occurring in porous polycrystalline iron fluoride, and further, incomplete charge reaction following a pathway different from conventional belief. These mechanistic insights provide guidelines for designing better conversion cathode materials to realize the promise of high-capacity lithium-ion batteries.
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http://dx.doi.org/10.1038/ncomms7883DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4411298PMC
April 2015

Critical factors affecting the 3D microstructural formation in hybrid conductive adhesive materials studied by X-ray nano-tomography.

Nanoscale 2015 Jan;7(3):908-13

Photon Sciences Directorate, Brookhaven National Laboratory, Upton, NY 11973, USA.

Conductive adhesives are found favorable in a wide range of applications including a lead-free solder in micro-chips, flexible and printable electronics and enhancing the performance of energy storage devices. Composite materials comprised of metallic fillers and a polymer matrix are of great interest to be implemented as hybrid conductive adhesives. Here we investigated a cost-effective conductive adhesive material consisting of silver-coated copper as micro-fillers using synchrotron-based three-dimensional (3D) X-ray nano-tomography. The key factors affecting the quality and performance of the material were quantitatively studied in 3D on the nanometer scale for the first time. A critical characteristic parameter, defined as a shape-factor, was determined to yield a high-quality silver coating, leading to satisfactory performance. A 'stack-and-screen' mechanism was proposed to elaborate such a phenomenon. The findings and the technique developed in this work will facilitate the future advancement of conductive adhesives to have a great impact in micro-electronics and other applications.
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http://dx.doi.org/10.1039/c4nr06068gDOI Listing
January 2015

In operando tracking phase transformation evolution of lithium iron phosphate with hard X-ray microscopy.

Nat Commun 2014 Aug 4;5:4570. Epub 2014 Aug 4.

Photon Sciences Directorate, Brookhaven National Laboratory, Building 744 Ring Road, Upton, New York 11973, USA.

The delithiation reaction in lithium ion batteries is often accompanied by an electrochemically driven phase transformation process. Tracking the phase transformation process at nanoscale resolution during battery operation provides invaluable information for tailoring the kinetic barrier to optimize the physical and electrochemical properties of battery materials. Here, using hard X-ray microscopy--which offers nanoscale resolution and deep penetration of the material, and takes advantage of the elemental and chemical sensitivity--we develop an in operando approach to track the dynamic phase transformation process in olivine-type lithium iron phosphate at two size scales: a multiple-particle scale to reveal a rate-dependent intercalation pathway through the entire electrode and a single-particle scale to disclose the intraparticle two-phase coexistence mechanism. These findings uncover the underlying two-phase mechanism on the intraparticle scale and the inhomogeneous charge distribution on the multiple-particle scale. This in operando approach opens up unique opportunities for advancing high-performance energy materials.
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http://dx.doi.org/10.1038/ncomms5570DOI Listing
August 2014

Sample preparation of energy materials for X-ray nanotomography with micromanipulation.

Chemphyschem 2014 Jun 25;15(8):1587-91. Epub 2014 Mar 25.

Photon Sciences Directorate, Brookhaven National Laboratory, Upton, New York, 11973 (USA), Fax: (+1) 631 344 3238.

X-ray nanotomography presents an unprecedented opportunity to study energy storage/conversion materials at nanometer scales in three dimensions, with both elemental and chemical sensitivity. A critical step in obtaining high-quality X-ray nanotomography data is reliable sample preparation to ensure that the entire sample fits within the field of view of the X-ray microscope. Although focused-ion-beam lift-out has previously been used for large sample (few to tens of microns) preparation, a difficult undercut and lift-out procedure results in a time-consuming sample preparation process. Herein, we propose a much simpler and direct sample preparation method to resolve the issues that block the view of the sample base after milling and during the lift-out process. This method is applied on a solid-oxide fuel cell and a lithium-ion battery electrode, before numerous critical 3D morphological parameters are extracted, which are highly relevant to their electrochemical performance. A broad application of this method for microstructure study with X-ray nanotomography is discussed and presented.
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http://dx.doi.org/10.1002/cphc.201400023DOI Listing
June 2014

In situ three-dimensional synchrotron X-Ray nanotomography of the (de)lithiation processes in tin anodes.

Angew Chem Int Ed Engl 2014 Apr 19;53(17):4460-4. Epub 2014 Mar 19.

Photon Sciences Directorate, Brookhaven National Laboratory, Building 744, Upton, NY (USA).

The three-dimensional quantitative analysis and nanometer-scale visualization of the microstructural evolutions of a tin electrode in a lithium-ion battery during cycling is described. Newly developed synchrotron X-ray nanotomography provided an invaluable tool. Severe microstructural changes occur during the first delithiation and the subsequent second lithiation, after which the particles reach a structural equilibrium with no further significant morphological changes. This reveals that initial delithiation and subsequent lithiation play a dominant role in the structural instability that yields mechanical degradation. This in situ 3D quantitative analysis and visualization of the microstructural evolution on the nanometer scale by synchrotron X-ray nanotomography should contribute to our understanding of energy materials and improve their synthetic processing.
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http://dx.doi.org/10.1002/anie.201310402DOI Listing
April 2014

Characterization of 3D interconnected microstructural network in mixed ionic and electronic conducting ceramic composites.

Nanoscale 2014 May;6(9):4480-5

HeteroFoaM Center, a DOE Energy Frontier Research Center, USA.

The microstructure and connectivity of the ionic and electronic conductive phases in composite ceramic membranes are directly related to device performance. Transmission electron microscopy (TEM) including chemical mapping combined with X-ray nanotomography (XNT) have been used to characterize the composition and 3-D microstructure of a MIEC composite model system consisting of a Ce0.8Gd0.2O2 (GDC) oxygen ion conductive phase and a CoFe2O4 (CFO) electronic conductive phase. The microstructural data is discussed, including the composition and distribution of an emergent phase which takes the form of isolated and distinct regions. Performance implications are considered with regards to the design of new material systems which evolve under non-equilibrium operating conditions.
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http://dx.doi.org/10.1039/c3nr06684cDOI Listing
May 2014

Size-dependent surface phase change of lithium iron phosphate during carbon coating.

Nat Commun 2014 Mar 5;5:3415. Epub 2014 Mar 5.

Department of Mechanical and Materials Engineering, Western University, London, Ontario, Canada N6A 5B9.

Carbon coating is a simple, effective and common technique for improving the conductivity of active materials in lithium ion batteries. However, carbon coating provides a strong reducing atmosphere and many factors remain unclear concerning the interface nature and underlying interaction mechanism that occurs between carbon and the active materials. Here, we present a size-dependent surface phase change occurring in lithium iron phosphate during the carbon coating process. Intriguingly, nanoscale particles exhibit an extremely high stability during the carbon coating process, whereas microscale particles display a direct visualization of surface phase changes occurring at the interface at elevated temperatures. Our findings provide a comprehensive understanding of the effect of particle size during carbon coating and the interface interaction that occurs on carbon-coated battery material--allowing for further improvement in materials synthesis and manufacturing processes for advanced battery materials.
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http://dx.doi.org/10.1038/ncomms4415DOI Listing
March 2014

In situ chemical mapping of a lithium-ion battery using full-field hard X-ray spectroscopic imaging.

Chem Commun (Camb) 2013 Jul 17;49(58):6480-2. Epub 2013 May 17.

Photon Science Directorate, Brookhaven National Laboratory, 75 Brookhaven Avenue Building 725D, Upton, NY, USA.

In situ tracking of chemical phase transformation, mapping, and composition information of a battery with CuO as the anode was performed with quantitative analysis at sub-30 nm resolution with a 40 × 40 μm field of view using transmission X-ray microscopy combined with spectroscopy. A size-dependent and core-shell lithiation-delithiation mechanism was suggested for the electrochemical reaction.
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http://dx.doi.org/10.1039/c3cc42667jDOI Listing
July 2013