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Surface Micro patterning of Aluminium Reinforced Composite for Aerospace Applications through High Energy Pulse Laser Peening
摘要： Aluminium (Al) Composites have universal engineering applications because of their higher strength to weight ratio, ductility, and formability. However, in diverse applications, mechanical properties such as hardness, corrosion, wear, and fatigue resistance are the prerequisite at closer surface regions. Such localised changes without impacting various surface treatment approaches can attempt the bulk phase. Laser shock peening is an advanced surface engineering technique, which has been successfully applied to improve the surface morphology and microstructure of the material. In this work, we are focusing on improving the surface properties of Al7075 reinforced with SiC and Zirconia through laser peening technique. The hardened layer was evaluated using surface integrity with optical microscopy, energy dispersive spectroscopy, scanning electron microscope (SEM) and analysis of microhardness. Process parameters and resulting microstructures of Aluminium composite are summarised, along with the impact of laser peening on surface properties. Research results indicated that laser peening shows a significant influence on the final condition of the surface layer of Aluminium composite.
关键词： Zirconia,Aluminium Metal Matrix Composites,SiC,SEM,Laser peening
更新于2025-09-12 10:27:22
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Micromachining on Al-Sic Based Metal Matrix Composite Using DPSS Laser
摘要： Aluminum silicon carbide is a metal matrix composite largely used where strength to weight ratio and high thermal conductivity is primary in design criteria. It has wide application in Aerospace components, Automobiles & electronics industries. Present work deals in micro-grooving of this hard to machine material is carried out by diode pumped solid state pulsed Nd:YAG Laser. The experimental plan is carried out by CCD (central composite design) based on RSM (response surface methodology).Also the analysis of variance test is carried out to check the adequacy of the fitted regression mathematical models. Proper ranges of process parameters such as pulse width, pulse frequency, amount of current, assist air pressure were purposed. Screening test shows O2 as assist gas when used 0.2 to 1 kgf/cm2 pressure range gives best result because of its advantage during laser material interaction. The responses are taken as upper width deviation, lower width & depth deviation of micro-groove produced on Al-SiC material. The interaction effects of different parameters on responses are analyzed through surface plots generated. Optimal process parametric conditions are found out by utilizing meta-heuristic based search algorithm MOPSO (multi objective particle swamp optimization) technique.
关键词： MMC,ANOVA,Nd:YAG,RSM,SEM
更新于2025-09-12 10:27:22
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Influence of the buffer layers on growth and quality of graphene films grown by pulsed laser deposition
摘要： Graphene films were grown onto two different thickness levels of SiO2/Si substrates, with the help of Ni film from highly ordered pyrolytic graphite through pulsed laser deposition. In this work, the influence of thickness of buffer layer of SiO2 on quality, growth, and crystallinity of graphene films in terms of substrate temperatures has been studied. All graphene samples were characterized by using Raman spectroscopy, Scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The micro-Raman spectroscopic results clearly reveal that carbon bond strength increased while defects reduced on SiO2 (100 nm)/Si substrates with the increment in substrate temperature from 700 °C to 800 °C. Moreover, it was also observed from the Raman spectra that the number of graphene layers continuously improved over commercially available SiO2 substrates with the increase growth temperature from 700 °C to 800 °C. Thus, the presented study provides a facile, rapid, and effective technique to control the quality, growth, and crystallite size of graphene films onto different thickness SiO2 layer on Si.
关键词： Raman Spectroscopy,SEM,Graphene,PLD,XPS
更新于2025-09-12 10:27:22
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Structural and optical study of CZTS-reduced graphene oxide composite towards photovoltaic device application
摘要： The deficit in obtaining targeted photo conversion efficiency for (Cu2ZnSnS4) CZTS based photovoltaic cell results either from insufficient photo charge carrier generation or e-/h+ pair transportation towards the end of electrodes, which lowers the device Voc and Jsc. On this regard, semiconducting absorber material merged with highly mobile reduced graphene oxide (rGO) as filler form a bridging network within active layer facilitates both improvement in charge carrier separation as well as transportation to electrodes before recombination occurs. A simple solution casting approach for CZTS nanoparticle anchored rGO composite for photovoltaic device application is reported here. The presence and distribution of CZTS nanoparticles over the surface of rGO sheet is confirmed from XRD, Raman, SEM and UV-Visible analysis.
关键词： Raman,XRD,Cu2ZnSnS4 (CZTS),reduced graphene oxide (rGO),SEM,Photovoltaic device
更新于2025-09-12 10:27:22
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The Effects of Laser Parameters and the Ablation Mechanism in Laser Ablation of C/SiC Composite
摘要： The e?ects of laser parameters and the ablation mechanism in laser ablation of a carbon ?ber reinforced silicon carbide (C/SiC) composite are investigated in the present study. Six di?erent power densities are provided, as well as six levels of pulse numbers, and then ablation experiments are conducted for the C/SiC composite, induced by a pulsed laser. Based on the experimental results, the characteristics of surface morphology and ablation behavior are discussed. It is revealed that the surface morphology of the C/SiC composite under laser irradiation usually includes three regions: the center region, the transition region, and the border region. With the increase of laser power density, the ablation of the center region becomes severe, surface cracks occur, and more spherical SiC particles are found in the transition region. As for scenarios involving multiple pulses, the damage occurs in the center region at low power density limits, within the ?rst two layers below the surface. However, if the power density is relatively high, an ablation pit occurs in the center region when the pulse number is larger than 50. Meanwhile, the transition region and the border region diminish with increase of the pulse number. It is noted that both the power density and pulse number have noticeable e?ects on surface morphology and ablation behavior during laser ablation, which is helpful for material design and performance evaluation of C/SiC composites.
关键词： Surface morphology,C/SiC composite,Ablation mechanism,Laser ablation,Scanning electron microscopy (SEM)
更新于2025-09-12 10:27:22
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Precipitation of Silver Nanoparticles in Borate Glasses by 1064?nm Nd:YAG Nanosecond Laser Pulses: Characterization and Dielectric Studies
摘要： This work aims to present a modern process to synthesis nanoparticles in a glassy matrix. Borate glasses doped by silver nitrate (AgNO3) via the melt annealing technique were irradiated by a (1064 nm wavelength) Nd:YAG (Neodymium–doped Yttrium Aluminum Garnet) laser to yeild precipitation of silver nanoparticles (AgNPs) in borate glasses. The characterization of the irradiated glasses was investigated using ultraviolet/visible (UV/Vis.), x-ray diffraction (XRD), high resolution-transmission electron microscopy (HR-TEM), ?eld emission-scanning electron microscopy (FE-SEM), and dielectric properties. XRD patterns depict the presence of sharp diffraction peaks at 111 and 200 planes that can be attributed to the precipitated AgNPs in the borate glass sample after laser irradiation. A signi?cant change in color was observed within the borate glass after laser irradiation, which was attributed to the appearance of surface plasmon resonance and con?rmed the presence of AgNPs in the borate glass. The morphological properties and the distribution of the observed AgNPs inside the sample were performed via HR-TEM and FE-SEM. The behavior of dielectric constant and dielectric loss progressively decreased as the frequency increased. The values of AC conductivity increased as the temperature of the borate glass matrix increased.
关键词： Borate,UV/Vis.,Nd:YAG,dielectric properties,AgNPs,XRD,FE-SEM,HR-TEM
更新于2025-09-11 14:15:04
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European Microscopy Congress 2016: Proceedings || Dispersion, dose and stability of semiconductor quantum dot biomarkers
摘要： Photoluminescent semiconductor nanoparticles or quantum dots have significant potential for medical imaging. For optimum performance however, the dispersion of the nanoparticulate material when suspended in delivery or incubation media, any transformation of the particles in the media, plus the nature and degree of uptake of the nanoparticles by a particular cell or organism all need to be understood. Analytical electron microscopy can play a vital role in assessing this complex inter-relationship, and we discuss here specific methods developed for this type of analysis. First, we will review the in vitro cellular uptake of commercially available CdSe/ZnS quantum dot nanoparticles with a coating specifically targeted for endocytic uptake (Invitrogen QTracker 705), dispersed in cell culture media and exposed to human osteosarcoma (U-2 OS) cells. We have examined these nanoparticles as-dispersed in cell culture media (t = 0 h), after 1 hour exposure to cells and after a round of cell division (t = 24 h). Transmission electron microscopy (TEM) has been used to assess the dispersion state of the nanoparticles in media after rapidly freezing suspensions to avoid drying artefacts [1], and in exposed cells which have been fixed and resin embedded [2]. The resin-embedded cells have been further examined using serial block face scanning electron microscopy (SBF-SEM), which enables quantification of nanoparticle loaded organelles in whole cell volumes for quantitative correlation to imaging flow cell cytometry [2]. From this we have measured probability densities for the number of quantum dots per agglomerate when in cell culture media and following uptake by cells in vitro [3, 4 and Figure 1 a-d]. Thus, we will discuss the agglomeration processes that occur both in suspension and during endocytosis. Second and looking forward, most commercially available semiconductor quantum dots currently contain cadmium although its health and environmental risks may limit exploitation. Thus, copper indium sulfide (CIS) quantum dots have been investigated as a potential replacement [5]. Aberration corrected STEM-EELS has identified some elemental separation of Cu and In within individual quantum dots [Figure 1 e-h], which may be the origin of an In-Cu anti-site defect state known to act as a donor in the radiative recombination pathway for chalcopyrite CIS quantum dots. We will report here on further analysis using a FEI Titan cubed Themis 300 G2 S/TEM to assess elemental distribution by STEM-EDX. Such analysis will enable additional characterisation of core-shell coatings (e.g. CIS/ZnS/ZnS:Al) designed to improve photo luminescent quantum yield while enhancing environmental stability of the particles.
关键词： quantum dots,SBF-SEM,dose,TEM
更新于2025-09-11 14:15:04
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European Microscopy Congress 2016: Proceedings || SEM based electro-optical characterization of core-shell LEDs and simulation of imaging including CL and EBIC excitation inside ensembles
摘要： Three dimensional (3D) nano- and microstructures (NAMs) are attracting a lot of attention and are discussed regarding several applications, especially in optoelectronics and sensors. For example GaN based 3D light emitting diodes (LEDs) with a core-shell geometry are supposed to have substantial advantages over conventional planar LEDs: The active area along the sidewalls of hexagonal GaN pillars can considerably be increased by high aspect ratios - leading to a lower current density inside the InGaN quantum well (QW) at the same operation current per substrate area. [1] Thus related methods are requested for characterization of local electro-optical properties with a high spatial resolution on single structures as well as in ensembles. Usually, electron microscopy is employed to investigate the geometry and properties of such 3D-NAMs and for mapping of vertical features by an SEM a certain sample tilt (e.g. about 30°) is needed. Investigation of single 3D-LEDs by electron beam induced current (EBIC) using an SEM based manipulator setup proves the presence of a pn-junction and doping type of the core and shell, while cathodoluminescence (CL) gives an insight to the optical properties of the QW [2]. But in contrast to SEM on planar regions the interactions of the electron probe are significantly affected by the 3D geometry and the surrounding of the NAMs. In ensembles of 3D-NAMs a certain portion of incident electrons are scattered into neighbor structures and conventional SEM signals (SE, BSE, CL, X-ray emission) are partly shadowed. This interaction is affecting the SEM imaging contrast and the probed signal also includes contributions which are not related to the material properties at the electron beam spot. As such parasitic signals are generated quite close to the original region of the interaction most (global) SEM detectors cannot separate them from the original source. In particular scattering events occur in an enlarged volume of the sample (of the substrate and NAMs) leading to a reduced excitation density and parasitic effects, e.g. this causes a significant contribution of defect related yellow luminescence (YL) We present results of InGaN/GaN core-shell LEDs obtained with an FE-SEM which is equipped with SE, In-Beam SE, low-kV BSE, EBIC and monochromatic CL detection as well as a piezo controlled manipulator setup, see Figure 1. A modified parabolic collection mirror enables measuring luminescence from planar samples up to 4’’ in a tilted view up to 30°. For a quantitative interpretation of CL and EBIC measurement values and image contrasts, the physical modeling of SEM images and spatially resolved energy transfer by a probe spot is necessary. This is performed using the simulation program MCSEM [3]. It models the different stages of image formation and generates SEM images of complex NAM shapes using e.g. GaN as model material. Aspects of the simulation are the electron probe formation, a 3D model of the specimen structure, the interaction of electron probe and solid state by means of scattering trajectories, the emission of secondary electrons, and different types of electron detectors, see Figure 2 and Figure 3. An insight to CL and EBIC imaging is gained by evaluating the scattering energy deposited in a distinct volume inside the NAMs as an imaging signal - this is related to the generation rate of electron-hole pairs inside the respective volume of the semiconductor. Consent to the experiments this simulation reveals an edge contrast and shadowing of signals by the ensemble as well as scattering of primary electrons inside the ensemble of 3D-NAMs. A quantitative comparison is possible by the absorbed current (EBAC). Artefacts of the EBIC are also demonstrated by the simulation, in particular edge contrast by a reduced generation rate and parasitic signals by scattering from neighbor structures.
关键词： EBIC,cathodoluminescence,electron beam induced current,SEM simulation,core-shell LED
更新于2025-09-11 14:15:04
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Micron-Sized Constrictions Fabricated Using the Femtosecond Laser Technique on YBCO Thin Films
摘要： In this paper, I report on the fabrication of micron-sized constrictions in YBCO thin films using the femtosecond laser technique. The constrictions are S-shaped superconducting weak links fabricated on YBCO thin films. The constrictions show a measurable superconducting current flowing through them. Current-voltage (I–V) characteristics were used to determine the critical current IC of the constrictions at 77 K. The width of the constrictions was determined at the narrowest point using SEM (scanning electron microscope). Three micron-sized constrictions were fabricated with a width of 2.88 μm, 1.72 μm, and 1.69 μm and a length of 5 μm. Based on the width and length of these constrictions in relation to the coherence length (ξ) of the YBCO, these constrictions should conduct supercurrent by Abrikosov vortices. The SEM images show that the femtosecond laser heats the samples beyond the geometric boundary, damaging some of the superconductive phases of the YBCO constrictions. As a result, the constrictions conduct current by one-dimensional depairing.
关键词： Atomic force microscope (AFM),Abrikosov vortices,Flux pinning,YBCO thin film,Lasers,Critical currents,Scanning electron microscopy (SEM)
更新于2025-09-11 14:15:04
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Rapid synthesis of ZnO nanoparticles by waste thyme (Thymus vulgaris L.)
摘要： Synthesis of nanoparticles by utilizing microorganisms and plants in green methods is a feasible procedure. This method can be used instead of chemical procedures as an eco-friendly procedure. Antibacterial activity of zinc oxide nanoparticles as one of the best multifunctional nanoparticles is well known. In this study, ZnO nanoparticles were produced by waste thyme (Thymus vulgaris L.) extract. SEM, XRD, UV–Vis, visual analysis and FTIR spectroscopic techniques were used for characterizing ZnO nanoparticles. The absorption of wavelengths of the UV–Vis in the region of 290–320 nm confirmed the formation of zinc oxide nanoparticles. The average size of ZnO nanoparticles was estimated 10–35 nm by SEM technique. An eco-friendly method for the synthesis of ZnO nanoparticles can be used in which the waste thyme extract is used as a stabilizing agent. Therefore, the use of waste thyme extract is an alternative to the chemical methods. Biological methods are rapid, green, economical and simple to perform.
关键词： Medicinal plants,SEM,ZnO nanoparticles,UV–Vis,Green chemistry,XRD
更新于2025-09-11 14:15:04