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Mechanical response of a Laser Cladding repaired structure: localization of plastic strain due to microstructure gradient
摘要： Laser Cladding is an additive manufacturing technology enabling to repair complex metallic components by removing the worn region and reconstructing locally the initial geometry. The aim of this work is to study the mechanical response of Inconel 718 repaired thin walls. More precisely, we perform an EBSD imaging and in-situ SEM tensile tests on specimen whose gauge section contains the interface between base material and repaired area. We observe the multiaxial strain patterns until failure at the grain level using a Digital Image Correlation method and superpose this pattern with the microstructure gradient induced by repair. The observations highlight a strain localization phenomenon in repaired structures mainly due to grain size effect.
关键词： SEM tensile tests,Laser Cladding,Inconel 718,strain localization,EBSD,microstructure gradient,Digital Image Correlation
更新于2025-09-23 15:19:57
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Studies on structural, surface morphology and optical properties of Zinc sulphide (ZnS) thin films prepared by chemical bath deposition
摘要： Zinc sulphide (ZnS) thin films have been prepared by chemical bath deposition method. X-ray diffraction (XRD) is used to analyze the structure and crystallite size and scanning electron microscopy is used to study the particle size and morphology of ZnS thin film. Optical studies have been carried out using UV-Visible-NIR absorbance spectrum. The band gap value of the film is calculated and it is found to be 3.45 eV. The dielectric properties of ZnS thin films have been studied in the different frequency at different temperatures.
关键词： scanning electron microscopy (SEM),Zinc sulphide (ZnS) thin films,dielectric studies,X-ray diffraction (XRD)
更新于2025-09-23 15:19:57
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A Beginners' Guide to Scanning Electron Microscopy || Components of the SEM
摘要： The primary components of the SEM are electron column, specimen chamber, and computer control system as shown in the photograph of Fig. 2.1. These components are used to carry out various functions of microscopy and microchemical analysis. The SEM instrumentation may include secondary and backscattered electron detectors, energy-dispersive x-ray spectrometer (EDS), low vacuum detector, electron backscattered diffraction (EBSD) detector, etc. Some of this instrumentation may not be necessary for basic imaging but play an increasingly important role in more demanding microscopy applications. A user has a continual interaction with the primary components of the SEM, which has a direct bearing on the quality of images and analyses obtained. In addition to these components, secondary/miscellaneous equipment such as vacuum pumps, water chiller, and electronics form an essential part of the overall system without which the SEM cannot function. However, this equipment runs seamlessly in the background and hardly needs any input from the user. Modern day SEMs are controlled with computers. However, the quality of images obtained largely depends on the input parameters as determined by the operator. This necessitates the study of SEM and its various components and the way it can be used to produce high-quality images and reliable analytical data.
关键词： microchemical analysis,electron column,energy-dispersive x-ray spectrometer,specimen chamber,backscattered electron detectors,computer control system,secondary electron detectors,SEM,microscopy,EBSD detector
更新于2025-09-23 15:19:57
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A Beginners' Guide to Scanning Electron Microscopy || Imaging with the SEM
摘要： The scanning electron microscope is routinely used to characterize wide-ranging materials due to its ease of operation and relatively straightforward sample preparation as well as due to simple image interpretation. New users can readily obtain images after little practice. However, high-resolution microscopy and examination of “difficult” samples require experience and know-how of the principles of image formation in the SEM. This chapter describes the role of various operational parameters used during microscopy in more detail. The effect of these parameters on contrast, resolution, and depth of field depicted by images is discussed. Pros and cons of microscopy conditions that have a direct bearing on the quality of images, type of information obtained, and image interpretation are elaborated. Guidelines for operation and upkeep of the SEM instrument are also summarized in this chapter.
关键词： high-resolution microscopy,operational parameters,resolution,scanning electron microscope,SEM,image formation,contrast,microscopy conditions,image interpretation,depth of field
更新于2025-09-23 15:19:57
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Combined microscopy and spectroscopy techniques to characterize a fossilized feather with minimal damage to the specimen
摘要： The study of fossil feathers has been revitalized in the last few decades and has contributed significantly to paleontological studies of dinosaurs and birds. Specific morphological and physicochemical characteristics of the microscale structures of feathers and the protein keratin are key targets when preserved during the fossilization process. Keratin is a fibrous protein that composes some hard tissues such as hair, nails and feathers. It is part of the so called intermediate filaments inside keratinocyte cells and is rich in sulfur containing amino acid cysteine. To date, different microscopy and analytical methods have been used for the analysis and detailed characterization and classification of feathers. However, in this work we showed that analytical optical and electron microscopies can be quick and precise methods with minimal effects on the sample during analysis. This association of different approaches on the same sample results in correlative data albeit in different length scales. Intracellular bodies called melanosomes originally present in melanocyte cells were identified with Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), and had well-defined orientation and a mean aspect ratio comparable to melanosomes extant in dark feathers. The detection of sulphur in melanosomes via Energy Dispersive Spectroscopy both in SEM and TEM shows that, along the fossilization process, sulphur from the degraded keratin matrix could have been trapped inside the melanosomes. Chemical groups that make up keratin and melanin in the fossil sample were detected via FT-IR Spectroscopy and Confocal Laser Scanning Microscopy (CLSM). The use of combined analytical microscopy techniques can contribute significantly to the study of fossils generating precise results with minimum damage to the original sample.
关键词： EDS,Crato Formation,TEM,CLSM,FT-IR Spectroscopy,SEM
更新于2025-09-19 17:15:36
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Morphology of CdSe-Based Coatings Formed on Polyamide Substrate
摘要： Cadmium selenide (CdSe)-based layers were formed on the surface of polyamide 6 (PA) substrate film by treating PA film samples with potassium selenotrithionate (K2SeS2O6) solution (seleniumization) and then with cadmium(II) acetate, Cd(CH3COO)2, solution (cadmiumization). The morphology of CdSe-based layers was investigated by atomic force and scanning electron microscopies. It was determined that the formation of CdSe-based layers proceeds unevenly in the form of islands, which later tends to agglomerate. Therefore the surface of the layers formed is relatively uneven and rather rough. After seleniumization and cadmiumization procedures the average height of this layer have tendency to decrease from 337 after 1 h of seleniumization to 153 nm at 2.5 and 3.5 h of seleniumization. It was also determined that the RMS of formed layers slightly increases (from 32 to 42 nm) with the prolongation of PA seleniumization (from 1 to 2.5 hours) and it decreases (from 43 to 22 nm) with the increase of the temperature (from 50 °C to 70 °C) of seleniumized PA treatment by the solution containing Cd(II) salt. XPS data show that in coatings, substantial amounts of both cadmium hydroxide (Cd(OH)2) and cadmium oxide (CdO) are formed on the surface and within deeper layers of formed coatings. It was also determined that only a small fraction (～0.1%–2%) of cadmium selenide is present on the surface of formed coating after seleniumization and cadmiumization, while within in the deeper layers the concentrations of both Cd and Se were much higher and the fractions of Cd(OH)2 and CdO decreased.
关键词： SEM,Polyamide,Potassium Selenotrithionate,AFM,Morphology,CdSe-Based Layers
更新于2025-09-19 17:15:36
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Electrical Properties of Metal-Porous GaAs Structure at Water Adsorption
摘要： This paper reports the morphological, optical, luminescent and electrical properties of electrochemically made porous GaAs in order to evaluate their humidity sensing performance. The obtained porous GaAs exhibits non-homogenous surface morphology, which consists of pyramid-shaped crystallites and micropores. Photoluminescent and FTIR study shows that the surface of such material is covered by an oxide of As and Ga. The impedance spectroscopy was applied to analyze the influence of water vapor on electrical properties of metal-porous GaAs. It was shown that water adsorption results in the Nyquist plots shift to the region of higher frequencies. In humid atmosphere resistance Rv and characteristic time of charge accumulation s are decreased by 1.4 times and 5 times, respectively; resistance Rb and capacity Cb decreased by 1.4 times and 4.4 times, respectively. The response of the metal-porous GaAs structure to the adsorption of water is attributed to the decreasing of the bulk resistivity and potential barrier height. The formed oxide layer on the surface of porous GaAs plays a dual role—it increases the ability to adsorb water molecules and prevents the surface from receiving structural degradation.
关键词： SEM,DRIFT spectrum,impedance spectroscopy,Nyquist plot,Porous GaAs,humidity sensor
更新于2025-09-19 17:15:36
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Deposition of p-type Al doped PbS thin films for heterostructure solar cell device using feasible nebulizer spray pyrolysis technique
摘要： Doping of metal atoms with PbS thin films can make significant influence on the structural and electron transport properties which makes it suitable for photovoltaic and other device applications. The objective of the present work is to study the structural, morphological, optical and electrical properties of PbS:Al thin films as a function of different Al doping percentage. PbS and Al doped PbS thin films were deposited using Nebulizer Spray Pyrolysis (NSP) on soda lime glass substrates by varying Al doping level from 0 wt% to 8 wt%. Polycrystalline nature with face centered cubic crystal structure was noticed for all the prepared films from XRD pattern. The orientation along (200) plane was observed for all the prepared films. From AFM analysis, the observed surface roughness values were considerably decreased on increasing the Al doping concentration. The calculated optical band gap values exhibits increasing trend and shifted from 1.54 eV to 1.66 eV on increasing Al doping concentration. The electrical resistivity value of the PbS:Al thin films were reduced from 3.08 ? 103 to 1.63 ? 103 Ωcm with raise in Al doping level. The solar cell efficiency for FTO/n-CdS/p-PbS:Al structure constructed from 6% of Al doped PbS film was about 0.44%.
关键词： SEM/AFM,Hall effect measurement,PbS:Al structure,UV visible,Solar cell,X-ray diffraction
更新于2025-09-19 17:13:59
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Interface analysis of Ag/na??type Si contacts in na??type PERT solar cells
摘要： To increase efficiencies of bifacial solar cells, emitter, back surface field (BSF), and metal patterns must be optimized. We study the influence of paste volume, through multiple prints, of two silver pastes on the contact formation at the rear side of n-type passivated emitter and rear totally diffused (n-PERT) solar cells with two BSF doping profiles. Differences in fingers' electrical properties were found between pastes. Contact resistivity shows a relative difference of 27.6%, partially explained by changes in the silver crystallites formation at the Ag/Si interface and in the crystallites' penetration depth. Variations in crystallites formation and penetration between pastes can reach 38.4% and 48.8%, respectively. Line resistance shows a difference between pastes, appearing as the main cause of an absolute efficiency difference of 2.9%. Fingers' structural and electrical properties are modified by increasing the paste volume. Microstructure analysis reveals that additional metallic printing does not only increase line cross sectional area but also increases the formation of silver crystallites, which can reach a relative increment of 23.9% between first and second prints. Further printing does not necessarily decrease contact resistivity, but reduces line resistance in up to 94.9%, which results in an absolute efficiency increase of 2.2%. In addition, the higher presence of silver oxide in the finger is related to a higher efficiency in the formation of silver crystallites. Finally, BSF doping has an influence in the open circuit voltage, short circuit current density, and contact resistivity, with differences that can reach 8.7 mV, 0.2 mA/cm2, and 6.1 mΩcm2, respectively, depending on paste and number of prints.
关键词： solar cells,FE-SEM,metallization,XPS,AFM
更新于2025-09-19 17:13:59
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Microstructural Characteristics of Cement-Based Materials Fabricated Using Multi-Mode Fiber Laser
摘要： Cement-based materials are the most prevalent construction materials, and the conventional cutting techniques are still mostly used for fabricating the materials. However, these conventional cutting methods could generate undesirable micro-cracks and remove unintentional structural sections. This experimental study aims to evaluate the e?ects of the new fabricating method using laser on the microstructural characteristics of the cement-based materials. The experimental variables are laser cutting speed, water to cement ratio and material compositions. In order to compare the microstructure before and after the laser interaction, the microstructure of the cut surface is observed through scanning electron microscopy/energy dispersive X-Ray (SEM/EDX). After the laser interaction, the Material Removed Zone (MRZ) and Heat A?ected Zone (HAZ) are observed on the cut surface. In MRZ, it is found that the glassy layer is thickened by an increasing amount of silicate-based materials in cement-based materials. In addition, it concluded that the amount of silicate-based material mixed in the cement-based materials a?ects the laser cutting quality.
关键词： microstructure,laser cutting,cement-based materials,multi-mode ?ber laser,SEM/EDX analysis
更新于2025-09-19 17:13:59