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Differential Multi-probe Thermal Transport Measurements of Multi-walled Carbon Nanotubes grown by Chemical Vapor Deposition

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arXiv 2023年

作者： Jia, Qianru Zhou, Yuanyuan Li, Xun Lindsay, Lucas Shi, Li Walker Department of Mechanical Engineering The University of Texas at Austin AustinTX78712 United States Materials Science and Technology Division Oak Ridge National Laboratory Oak RidgeTN37831 United States

Carbon nanotubes (CNTs) are quasi-one dimensional nanostructures that display both high thermal conductivity for potential thermal management applications and intriguing low-dimensional phonon transport phenomena. In comparison to the advances made in the theoretical calculation of the lattice thermal conductivity of CNTs, thermal transport measurements of CNTs have been limited by either the poor temperature sensitivity of Raman thermometry technique or the presence of contact thermal resistance errors in sensitive two-probe resistance thermometry measurements. Here we report advances in a multi-probe measurement of the intrinsic thermal conductivity of individual multi-walled CNT samples that are transferred from the growth substrate onto the measurement device. The sample-thermometer thermal interface resistance is directly measured by this multi-probe method and used to model the temperature distribution along the contacted sample segment. The detailed temperature profile helps to eliminate the contact thermal resistance error in the obtained thermal conductivity of the suspended sample segment. A differential electro-thermal bridge measurement method is established to enhance the signal-to-noise ratio and reduce the measurement uncertainty by over 40%. The obtained thermal resistances of multiple suspended segments of the same MWCNT samples increase nearly linearly with increasing length, revealing diffusive phonon transport as a result of phonon-defect scattering in these MWCNT samples. The measured thermal conductivity increases with temperature and reaches up to 390 ± 20 W m-1 K-1 at room temperature for a 9-walled MWCNT. Theoretical analysis of the measurement results suggests submicron phonon mean free paths due to extrinsic phonon scattering by extended defects such as grain boundaries. The obtained thermal conductivity is decreased by a factor of 3 upon electron beam damage and surface contamination of the CNT sample. © 2023, CC BY-NC-ND.

关键词： Probes

Packing fraction related transport in disordered quantum dot arrays

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arXiv 2024年

作者： Eshraghi, K. Natani, S. Bandaru, P. Program in Materials Science University of California La Jolla San DiegoCA92093 United States Department of Mechanical Engineering University of California La Jolla San DiegoCA92093 United States

Models to describe electrical conduction in quantum dot (QD) constituted films often overlook the effects of geometric disorder. We address related issues by examining the influence of the QD packing fraction (PF) on the charge transport and transmission in QD arrays. Using transfer matrix based algorithms and Monte Carlo simulations, we quantify the transmission across disordered QD assemblies. Our results indicate a critical packing fraction (PFc) of ∼ 0.64, marking a transition from a non-conducting to a conducting state, aligning well with experimental observations and analytical predictions. This study enhances the understanding of transport in QD arrays, with implications for designing efficient electronic devices based on disordered nanoscale systems. © 2024, CC BY-NC-SA.

关键词： Semiconductor quantum dots

Effect of surface segregation on the oxidation resistance of Cu3Pt(100)

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Physical Review materials 2022年第2期6卷 025801-025801页

作者： Chaoran Li Yaguang Zhu Dongxiang Wu Jorge Anibal Boscoboinik Guangwen Zhou Department of Mechanical Engineering and Materials Science and Engineering Program State University of New York at Binghamton New York 13902 USA Center for Functional Nanomaterials Brookhaven National Laboratory Upton New York 11973 USA

Alloying element segregation often occurs under a reactive environment but its interplay with the subsequent surface oxidation of the alloy remains unclear. Using synchrotron-based ambient-pressure x-ray photoelectron spectroscopy, we dynamically monitor the surface segregation in Cu3Pt(100) in response to temperature and oxygen gas. Vacuum annealing leads to surface segregation of Cu along with the enrichment of Pt in the subsurface region. Upon switching to the O2 atmosphere, dissociative chemisorption of oxygen does not change the surface segregation profile from that under the vacuum annealing condition. A stepwise increase in the oxygen pressure results in the transformation pathway of Cu→Cu2O→CuO, in which the selective oxidation of Cu gives rise to further accumulation of Pt underneath the oxide/alloy interface that hinders the supply of Cu from the bulk to the oxide/alloy interface, thereby leading to the termination of the surface oxidation after the Cu2O→CuO conversion is completed. This differs from the transformation pathway of Cu→Cu2O→Cu2O/CuO for the oxidation of pure Cu and Cu-Au alloys, in which the oxidation of Cu continues and the Cu2O/CuO bilayer growth is constantly maintained. These key differences provide useful insight into alloy design for controlling the surface properties such as corrosion resistance and catalytic performance of Cu base alloys.

关键词： Surface & interfacial phenomena Alloys X-ray photoelectron spectroscopy

Customizable wave tailoring materials enabled by nonlinear bilevel inverse design

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arXiv 2024年

作者： MacNider, Brianna Xiu, Haning Qian, Kai Frankel, Ian Kim, Hyunsun Alicia Boechler, Nicholas Department of Mechanical and Aerospace Engineering University of California La Jolla San DiegoCA92093 United States Department of Structural Engineering University of California La Jolla San DiegoCA92093 United States Program in Materials Science and Engineering University of California La Jolla San DiegoCA92093 United States

Passive transformation of waves via nonlinear systems is ubiquitous in settings ranging from acoustics to optics and electromagnetics. Passivity is of particular importance for responding rapidly to stimuli and nonlinearity enormously expands signal transformability compared to linear systems due to the breaking of superposition. It is well known that different types of nonlinearity yield vastly different effects on propagating signals, which raises the question of "what precise nonlinearity is the best for a given wave tailoring application?" Considering a one-dimensional spring-mass chain as a testbed, we couple the shape optimization of structures for tailored nonlinear constitutive responses with reduced-order nonlinear dynamical inverse design. Using minimization of peak kinetic energy transmission from impact as a case study, we identify ideal nonlinear constitutive responses and the geometries needed to achieve them. As part of this, we show the large sensitivity of this metric to small changes in nonlinearity, and thus the need for high precision, free-form nonlinearity tailoring. We validate our predictions using impact experiments in a chain of nonlinear springs and masses. This work sets the foundation for broader passive nonlinear mechanical wave tailoring material design, with applications to computing, signal processing, shock mitigation, and autonomous materials. © 2024, CC BY-NC-ND.

关键词： Kinetic energy

Atomistic mechanisms of the initial oxidation of stepped Cu3Au(100)

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Physical Review B 2022年第7期105卷 075422-075422页

作者： Yaguang Zhu Dongxiang Wu Chaoran Li Xiao Tong J. Anibal Boscoboinik Jerzy T. Sadowski Guangwen Zhou Department of Mechanical Engineering & Materials Science and Engineering Program State University of New York Binghamton New York 13902 USA Center for Functional Nanomaterials Brookhaven National Laboratory Upton New York 11973 USA

Alloy oxidation is complex and involves several critical processes that lack understanding on the atomic level. Here, we report an atomistic picture of the initial-stage oxidation of stepped Cu3Au(100) using a combination of surface science tools and modeling to illuminate the microscopic processes underlying oxygen-adsorption-induced structural and compositional changes. Pristine Cu3Au(100) consists of wide CuAu-terminated terraces and narrow Cu-terminated terraces separated by monatomic steps. Counterintuitive to the common expectations of the adsorbate-induced surface segregation of the more reactive alloy component, our observations demonstrate that the oxygen adsorption leads to the exfoliation of the outermost CuAu layer, thereby exposing the inner Cu plane to O attack. This occurs via the oxygen-assisted abstraction of Au and Cu atoms from step edges and CuAu terraces, which generates many Cu adatoms aggregating into Cu clusters and Au adatoms dissolving into the bulk. The oxygen adsorption onto fourfold hollow sites of the exposed Cu plane results in nucleation and growth of the c(2×2)−O superstructure, which can be fit well by the Johnson-Mehl-Avrami-Kolmogorov theory with a site-saturated nucleation mechanism.

关键词： Surface & interfacial phenomena Alloys Surfaces Density functional theory Ion beam analysis Scanning tunneling microscopy X-ray photoelectron spectroscopy

A Sparse DAE Solver in Maple

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arXiv 2022年

作者： Jang, Taejin Uppaluri, Maitri Subramanian, Venkat R. Materials Science and Engineering Program Texas Materials Institute The University of Texas at Austin AustinTX78712 United States Walker Department of Mechanical Engineering The University of Texas at Austin AustinTX78712 United States Oden Institute for Computational Science and Engineering The University of Texas at Austin AustinTX United States

In this paper, some adaptive single-step methods like Trapezoid (TR), Implicit-mid point (IMP), Euler-backward (EB), and Radau IIA (Rad) methods are implemented in Maple to solve index-1 nonlinear Differential Algebraic Equations (DAEs). Maple's robust and efficient ability to search within a list/set is exploited to identify the sparsity pattern and the analytic Jacobian. The algorithm and implementation were found to be robust and efficient for index-1 DAE problems and scales well for finite difference/finite element discretization of two-dimensional models with system size up to 10,000 nonlinear DAEs and solves the same in few seconds. © 2022, CC BY-NC-ND.

关键词： Differential equations

Multiplex Magnetic Biosensor Microarrays Facilitate Personalized Vaccination Schedules for Sars-Cov-2 Variants

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SSRN

SSRN 2024年

作者： Um, Hyun-Kyung Kim, Songeun Wang, Shan X. Lee, Jung-Rok Department of Mechanical and Biomedical Engineering Ewha Womans University Seoul03760 Korea Republic of Graduate Program in Smart Factory Ewha Womans University Seoul03760 Korea Republic of Department of Materials Science and Engineering Stanford University Stanford CA94305 United States Department of Electrical Engineering Stanford University Stanford CA94305 United States

Rapid, sensitive, multiplexed antibody detection technologies are essential for assessing vaccine efficacy and recipient immunity against viruses. As severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants continue to emerge, and the fact that novel viruses may pose potential threats in the near future, personalized vaccines can be precisely tailored to an individual’s measured immunity to help mitigate the symptoms of infection and viral spread. Here, we present giant magnetoresistive (GMR) biosensor microarrays for the quantitative multiplexed detection of antibodies against SARS-CoV-2 variants. The multiplexed GMR biosensor microarrays demonstrated high sensitivity, comparable to that of the single-plex enzyme-linked immunosorbent assay, enabling multiplexed measurements using blood obtained from finger pricks. Additionally, the GMR biosensor microarrays demonstrated compatibility with clinical samples and could detect variant-specific antibodies in serum, allowing for the assessment of current immunity status. Notably, an increased concentration of antibodies against the Omicron variant was clearly observed two weeks after receiving an Omicron-based booster vaccination. These results indicate that GMR biosensor microarrays offer a practical point-of-care tool for monitoring humoral immunity and guiding personalized vaccination schedules, thereby supporting immunity management against SARS-CoV-2 and future viral threats. © 2024, The Authors. All rights reserved.

关键词： Giant magnetoresistance

Flash Sintering of Rhenium at Ambient Temperature in < 1 Minute with Electrical Current

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SSRN

SSRN 2023年

作者： Bamidele, Emmanuel A. Weimer, Alan W. Raj, Rishi Materials Science and Engineering Program University of Colorado BoulderCO80309 United States Department of Mechanical Engineering University of Colorado BoulderCO80309-0427 United States Department Chemical and Biological Engineering University of Colorado BoulderCO80309 United States

We show that rhenium can be sintered from powders to nearly full density (99.96%) by the direct injection of dc current (without a furnace) into dogbone shaped specimens in Ar atmosphere ( © 2023, The Authors. Al... 详细信息

关键词： Sintering

Gradient Design with Low-Tortuosity Overcoming Kinetic Limitations in High-Loading Solid-State Cathodes

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Angewandte Chemie 2025年

作者： Guangzeng Cheng Jinping Yu Yonghui Wang Zhengyu Ju Yue Zhu Weiqian Tian Jingwei Chen Huanlei Wang Jingyi Wu Guihua Yu School of Materials Science and Engineering Ocean University of China Qingdao 266404 China Materials Science and Engineering Program and Walker Department of Mechanical Engineering The University of Texas at Austin Austin Texas 78712 USA

The extensive commercialization of practical solid-state batteries (SSBs) necessitates the development of high-loading solid-state cathodes with fast charging capability. However, electrochemical kinetics are severely delayed in thick cathodes due to tortuous ion transport pathways and slow solid-solid ion diffusion, which limit the achievable capacity of SSBs at high current densities. In this work, we propose a conductivity gradient cathode with low-tortuosity to enable facile ion transport and counterbalance ion concentration gradient, thereby overcoming the kinetic limitations and achieving fast charging capabilities in thick cathodes. The LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathodes deliver a room-temperature (RT) capacities of 147 and 110 mAh g −1 at 5 C and 10 C, respectively, and meanwhile achieve a RT areal capacity of 3.3 mAh cm −2 at 3 C, enabling SSBs simultaneously high energy and power densities. The universality of this strategy is demonstrated in LiFePO 4 cathodes, providing a novel solution for fast charging and large-scale application of high-loading SSBs.

关键词： solid-state battery composite cathode high-loading gradient low-tortuosity