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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Nanoscale Imaging and Measurements of Grain Boundary Thermal Resistance in Ceramics with Scanning Thermal Wave Microscopy

Material thermal conductivity is a key factor in various applications, from thermal management to energy harvesting. With microstructure engineering being a widely used method for customizing material properties, including thermal properties, understanding and controlling the role of extended phonon-scattering defects, like grain boundaries, is crucial for efficient material design. However, systematic studies are still lacking primarily due to limited tools. In this study, we demonstrate an approach for measuring grain boundary thermal resistance by probing the propagation of thermal waves across grain boundaries with a temperature-sensitive scanning probe. The method, implemented with a spatial resolution of about 100 nm on finely grained Nb-substituted SrTiO 3 ceramics, achieves a detectability of about 2 × 10 –8 K m 2 W –1 , suitable for chalcogenide-based thermoelectrics. The measurements indicated that the thermal resistance of the majority of grain boundaries in the STiO 3 ceramics is below this value. While there are challenges in improving sensitivity, considering spatial resolution and the amount of material involved in the detection, the sensitivity of the scanning probe method is comparable to that of optical thermoreflectance techniques, and the method opens up an avenue to characterize thermal resistance at the level of single grain boundaries and domain walls in a spectrum of microstructured materials.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Autonomous Experiments in Scanning Probe Microscopy and Spectroscopy: Choosing Where to Explore Polarization Dynamics in Ferroelectrics

Polarization dynamics in ferroelectric materials are explored via automated experiment in piezoresponse force microscopy/spectroscopy (PFM/S). A Bayesian optimization (BO) framework for imaging is developed, and its performance for a variety of acquisition and pathfinding functions is explored using previously acquired data. The optimized algorithm is then deployed on an operational scanning probe microscope (SPM) for finding areas of large electromechanical response in a thin film of PbTiO 3 , with results showing that, with just 20% of the area sampled, most high-response clusters were captured. Furthermore, this approach can allow performing more complex spectroscopies in SPM that were previously not possible due to time constraints and sample stability. Improvements to the framework to enable the incorporation of more prior information and improve efficiency further are modeled and discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Charge transport in CdTe solar cells revealed by conductive tomographic atomic force microscopy

Polycrystalline photovoltaics comprising cadmium telluride (CdTe) represent a growing portion of the solar cell market, yet the physical picture of charge transport through the meso-scale grain morphology remains a topic of debate. It is unknown how thin film morphology affects the transport of electron-hole pairs. Accordingly this study is the first to generate three dimensional images of photocurrent throughout a thin-film solar cell, revealing the profound influence of grain boundaries and stacking faults on device efficiency.

14 SOLAR ENERGY↗
DOE OSTI2022

3D magnetic imaging using electron vortex beam microscopy

Abstract Electron vortex beams are free-electron waves that carry orbital angular momentum. There has been growing theoretical and experimental interest in the use of electron vortex beams as a tool for the investigation of magnetic materials. However, due to the complex wavefront of the propagating waves, a deeper understanding of the interaction of electron vortex beams and the magnetic sample is needed. Here we calculate the magnetic phase shift that an electron vortex beam obtains upon transmitting through a magnetic sample. We show that this magnetic phase shift is influenced by the out-of-plane magnetization, which is a unique characteristic of incident electron vortex beams and is proportional to their orbital angular momentum. Finally, we develop a phase retrieval methodology to retrieve the out-of-plane component of magnetization. Based on our theory, we discuss suitable experimental conditions that would enable this imaging capability for magnetic materials and further extend to non-magnetic chiral materials.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Atomic Force Microscopy Study of Monodisperse Carbon Nanoparticles

Monodisperse carbon nanodots and nanodiamond particles were studied by AFM method. Particle size distributions were calculated using AFM and DLS data. The results obtained correspond to TEM measurements. It was demonstrated that AFM allows detecting nanoparticles with sizes less than 2 nm. The average size of the particles for both samples was found to be ~4 nm. It was found that PSD for CND and DND was symmetric and asymmetric, correspondingly. Such difference can be understood in terms of different crystal structure perfection and the specific aspects of nanosized carbon preparation technology.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Insights into Heterogeneous Catalysts under Reaction Conditions by In Situ/Operando Electron Microscopy

The advancement of clean energy and environment depends strongly on the development of efficient catalysts in a wide range of heterogeneous catalytic reactions, which has benefited from transmission electron microscopic techniques in determining the atomic-scale morphologies and structures. However, it is the morphology and structure under the catalytic reaction conditions that determine the performance of the catalyst, which has captured a surge of interest in developing and applying in situ/operando transmission electron microscopic techniques in heterogeneous catalysis. The major theme of this review is to highlight some of the most recent insights into heterogeneous catalysts under the relevant reaction conditions using in situ/operando transmission electron microscopic techniques. Rather than a comprehensive overview of the basic principles of in situ/operando techniques, this review focuses on the insights into the atomic-scale/nanoscale details of various catalysts ranging from single-component to multicomponent catalysts under heterogeneous catalytic, electrocatalytic, and photocatalytic reaction conditions involving both gas–solid and liquid–solid interfaces. Here, this focus is coupled with discussions of the correlation of the atomic, molecular, and nanoscale morphology, composition, and structure with the catalytic properties under the reaction conditions, shining light on the challenges and opportunities in design of nanostructured catalysts for clean and sustainable energy applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Polymeric spatial resolution test patterns for mass spectrometry imaging using nano-thermal analysis with atomic force microscopy

As the spatial resolution of mass spectrometry imaging technologies has begun to reach into the nanometer regime, finding readily available or easily made resolution reference materials has become particularly challenging for molecular imaging purposes. This study describes the fabrication, characterization and use of vertical line array polymeric spatial resolution test patterns for nano-thermal analysis/atomic force microscopy/mass spectrometry chemical imaging.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

High resolution for confocal fluorescence microscopy via extending zero-region of super-oscillation

Superoscillation is the phenomenon that is observed when a wave oscillates locally faster than its highest Fourier component. Although previous reports have been shown that the superoscillation is highly attractive for imaging, however, the small zero-region area of the superoscillation increases the remarkable effect of the outsidelobes. In this work, we introduce a method using a binary phase mask with radial polarization to extend the zero-region of the superoscillation for high numerical aperture objectives. We successfully design a binary phase mask combining with a radial polarization to obtain a big zero-region of the superoscillation. Evaluation methods rely on point spread function and simulation images are presented. The results demonstrate that our proposed method is very effective for suppressing the outsidelobes. In addition, we show that our technique becomes more effective by adding an amplitude mask.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Investigation of Effects of SiO{sub 2} Content and Cooling Rate on Crystallization in Fe{sub 2}O{sub 3}-CaO-SiO{sub 2} System Using In Situ Confocal Laser Scanning Microscopy

The crystallization behaviors of the Fe{sub 2}O{sub 3}-CaO-SiO{sub 2} system in a non-equilibrium state with various chemical compositions and cooling rates were investigated by confocal laser scanning. Equilibrium samples were prepared in melt states and cooled at a rate of 1 K/min to produce samples in quasi-equilibrium states. The effect of SiO{sub 2} on the phase constitution was investigated using Image Analyzer, and the changes of the phase ratios were analyzed using activity values of Fe{sub 2}O{sub 3} calculated using FactSage 7.1. The Continuous cooling transformation diagram of the Fe{sub 2}O{sub 3}-CaO-SiO{sub 2} system was obtained for various cooling rates. The temperatures at which the primary phase formed for various SiO{sub 2} contents and cooling rates differed from the equilibrium temperatures, and the phase-formation temperature ranges varied with the cooling rate. In addition, the reduction degree of each sample was measured to determine the effect of SiO{sub 2} content and cooling rate on the Fe{sub 2}O{sub 3}-CaO-SiO{sub 2} system. The reduction degree in the FeO{sub 3}-CaO-SiO{sub 2} system is dominantly influenced by the SiO{sub 2} bond-phase morphology (CF, C{sub 2}S, C{sub 3}S, or glass) rather than the cooling rate.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Correction to: Investigation of Effects of SiO{sub 2} Content and Cooling Rate on Crystallization in Fe{sub 2}O{sub 3}-CaO-SiO{sub 2} System Using In Situ Confocal Laser Scanning Microscopy

In multiple places in the text FeO{sub 3} should be replaced by Fe{sub 2}O{sub 3}. The following acknowledgments were missed: Acknowledgments: This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20172010106300).

36 MATERIALS SCIENCE↗