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Benchmarking of graphene-based materials: real commercial products vs. ideal graphene
摘要： There are tens of industrial producers claiming to sell graphene and related materials (GRM), mostly as solid powders. Recently the quality of commercial GRM has been questioned, and procedures for GRM quality control were suggested using Raman Spectroscopy or Atomic Force Microscopy. Such techniques require dissolving the sample in solvents, possibly introducing artefacts. A more pragmatic approach is needed, based on fast measurements and not requiring any assumption on GRM solubility. To this aim, we report here an overview of the properties of commercial GRM produced by selected companies in Europe, USA and Asia. We benchmark: A) size, B) exfoliation grade and C) oxidation grade of each GRM vs. the ones of 'ideal' graphene and, most importantly, vs. what reported by the producer. In contrast to previous works, we report explicitly the names of the GRM producers and we do not re-dissolve the GRM in solvents, but only use techniques compatible with industrial powder metrology. A general common trend is observed: products having low defectivity (%sp2 bonds >95%) feature low surface area (<200 m2/g), while highly exfoliated GRM show a lower sp2 content, demonstrating that it is still challenging to exfoliate GRM at industrial level without adding defects.
关键词： industrial materials,metrology,graphene,X-rays photoelectron spectroscopy,materials characterization
更新于2025-09-23 15:23:52
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Transmission Electron Microscopy of Halide Perovskite Materials and Devices
摘要： Transmission electron microscopy (TEM)-based techniques are uniquely suited for site-specific structural and analytical characterization of halide perovskites (HPs) at atomic, nanometer, and micrometer length scales. TEM-based studies hold the key to understanding the nature and functionality of these fascinating materials that are at the heart of emerging solar cells and (opto)electronic devices. While TEM-based techniques have made several groundbreaking discoveries that have resulted in astonishing advancements in the field of materials science in general over the past decades, their application to HPs has been relatively sparse. Here, we provide a perspective on TEM-based studies of HPs that have been conducted so far and project a vision for how these powerful characterization techniques can be brought to bear on research problems in the field of HPs. An outlook discussing important challenges and opportunities that lay ahead is also presented.
关键词： Halide Perovskites,Optoelectronics,Materials Characterization,Solar Cells,Transmission Electron Microscopy
更新于2025-09-23 15:22:29
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Powder Bed Based Laser Additive Manufacturing Process of Stainless Steel: A Review
摘要： This study presents a review on powder bed laser additive manufacturing of stainless steel. The powder bed laser additive manufacturing processes that are presented in this paper are the selective laser sintering and selective laser melting. The powder bed laser additive manufacturing process of stainless steel are reviewed in this paper. The process parameters was found to plat an important role in the evolving properties of the powder bed based laser additive manufacturing process. The paper ends with the perspective of future research directions.
关键词： Materials characterization,laser additive manufacturing,selective laser sintering,Additive manufacturing,selective laser melting
更新于2025-09-12 10:27:22
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Light transmission and internal scattering in pulsed laser-etched partially-transparent silicon wafers
摘要： Continuing trend in silicon wafer thickness directed at cost reduction approaches basic boundaries created by: (a) mismatch between Al paste and Si wafer thermal expansion and (b) incomplete optical absorption. With its symmetrical front and back electrical contacts, the bifacial solar cell setup reduces stress due to mismatch thermal expansion, decreases metal use and increases high temperature efficiency. Efficiency improvement is accomplished in bifacial solar cells by capturing light from the back surface. Partially transparent wafers provide an option to improve near-infrared radiation absorption within Si wafer. To fully absorb optical radiation, three-dimensional texture of these kinds of wafers is essential. Pulsed laser interactions, thermal oxidation, and wet chemical etching are included in this research. A feature of its energy and pattern setup is the interaction of pulsed laser with Si, running at 1.064 μm wavelength and micro-second length. Two experimental settings were explored: (a) post-laser chemical etching with potassium hydro-oxide etching with thermal oxide as etching mask and (b) post-laser heat Si surface oxidation. Due to fast melting and recrystallization, laser pulsed processing inherently produces its own texture. Some of these spherically-shaped, randomly focused characteristics improve inner scattering and boost near-infrared absorption within the wafer. These characteristics are separated during chemical etching with the thermally-grown oxide layer as an etch mask. Comparison of optical absorption in both surfaces shows almost a rise in the magnitude of absorption in non-etched surfaces. Detailed optical (optical microscope and IR absorption), morphological (field emission scanning electron microscope) and heat imaging (far IR camera) analyses were performed to comprehend physical processes that contribute to near-IR absorption improvement. Such kinds of partially-transparent, three-dimensional textured Si wafers are anticipated to discover applications for bifacial solar cells as substrates.
关键词： Thru-holes,Optics,Silicon wafer,Materials physics,Thermal image,Partial transparent,Nanotechnology,Trench,Energy,IR transmission,Materials characterization
更新于2025-09-11 14:15:04
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Structural Optimization For Accurate Characterization Of Urban Areas In Hyperspectral Datasets
摘要： Accurately estimating the urbanization process is a key-factor for the actual implementation of the sustainable development goals identified by transnational institutions and agencies. In order to retrieve precise characterization of the anthropogenic extents and a sound human-environment interaction assessment, the analysis of Earth observations (EOs) plays a crucial role. Especially, the use of nonlinear spectral investigation can improve the description of geometrically and morphologically complex scenes, so that anthropogenic settlements and dynamics can be properly outlined. In this paper, we propose a novel method for directly assessing the distribution of materials and elements in hyperspectral images by means of a structural optimization approach. Experimental results show how the proposed approach is able to deliver accurate and reliable characterization of urban materials and extents.
关键词： nonlinear spectral investigation,structural optimization,hyperspectral imaging,urban materials characterization
更新于2025-09-10 09:29:36
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On-the-Fly Fast X-Ray Tomography Using a CdTe Pixelated Detector – Application in Mechanical Testing
摘要： Fast tomography measurements are still done almost exclusively within the domain of synchrotrons. However, recent progress in X-ray imaging instrumentation has enabled researchers to perform time-lapse computed tomography (4D-CT) even under laboratory conditions with standard X-Ray sources. Thus, fast time-dependent processes within materials with relatively high X-Ray attenuation can be monitored. The article describes the in-situ tomographic monitoring of crack formation and propagation in a quasi-brittle silicate matrix composite subjected to three point bending. A three-dimensional CT volume containing the region of interest (ROI) in the specimen is imaged over a period of time while the continuously increasing load causes crack initiation and propagation, creating a dynamic volume dataset. An acquisition time of 50 seconds for one full angle tomography with 400 projections makes this tomographic system one of the fastest systems in the world. The resulting visualizations provide qualitative information concerning progressive crack propagation within areas of lower material density. Differential images then allow displaying the spatial orientation of the crack over time. The results were further processed for a quantitative analysis of image quality using various methods of beam hardening correction.
关键词： X-ray imaging techniques,X-ray tomography,Materials characterization,Mechanical testing,Quasi-brittle material,Fracture mechanics,CdTe detectors
更新于2025-09-10 09:29:36