Articoli di riviste: "Scanning electron microscopy (MEB)"

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Rong, Yun Long, Shao Fei Wang, Dan Dan Jia, Chun Liu, Lei Cao, Hong Yan Tian, Xue Fang Zheng, Lu Liu e Dong Jun Wang. "Preparation of Porous Carbon Material by Carbonizing Polyacrylonitrile Microspheres". Applied Mechanics and Materials 253-255 (dicembre 2012): 884–87. http://dx.doi.org/10.4028/www.scientific.net/amm.253-255.884.

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PAN microspheres were crosslinked with divinyl benzene (DVB) and styrene (St), and then pre-oxidized under atmospheric pressure, porous carbon microspheres were produced by carbonizing the pretreated microspheres under nitrogen protection. Morphology and structure characterizations of the materials were performed by employing scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption test, etc. The results show that the primitive PAN microspheres display flower-like structures, while the carbonized pretreated PAN microspheres exhibit a high porosity as well as specific surface area and have a good adsorption of methylene blue (MeB) dye.

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Naggar, Ahmed H., Ahmed Kotb, Ahmed A. Gahlan, Mahmoud H. Mahross, Abd El-Aziz Y. El-Sayed e Adel A. Abdelwahab. "Graphite Studded with Facile-Synthesized Cu2O Nanoparticle-Based Cubes as a Novel Electrochemical Sensor for Highly Sensitive Voltametric Determination of Mebeverine Hydrochloride". Chemosensors 9, n. 2 (9 febbraio 2021): 35. http://dx.doi.org/10.3390/chemosensors9020035.

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Herein, a feasible chemical reduction method followed by intensive mixing was applied for the preparation of an attractive material based on graphite studded with cuprous oxide nanoparticle-based cubes (Cu2ONPs–C@G). Transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV) were utilized for characterization. Cuprous oxide nanoparticles (Cu2ONPs), with a diameter range mainly distributed from 4 to 20 nm, aggregate to form microcubes (Cu2ONPs–C) with an average diameter of about 367 nm. Paste electrode was prepared using Cu2ONPs–C@G (Cu2ONPs–C@G/PE) for voltametric quantification of the musculotropic antispasmodic drug: mebeverine hydrochloride (MEB). The electrochemical behavior of MEB was studied using CV, and the optimum analytical parameters were investigated using square wave adsorptive anodic stripping voltammetry (SWAdASV). Moreover, density functional theory (DFT) was used to emphasize the ability of MEB to form a complex with Cu2+, confirming the suggested electrochemical behavior of MEB at Cu2ONPs–C@G/PE. With good stability and high reproducibility, SWAdASV of Cu2ONPs–C@G/PE shows successful quantification of MEB over the concentration range of 5.00 × 10−11–1.10 × 10−9 M with lower limit of detection (LOD) and lower limit of quantification (LOQ) values of 2.41 × 10−11 M and 8.05 × 10−11 M, respectively. Finally, accurate quantification of MEB in dosage forms (tablets) and biological fluids (spiked human urine and plasma samples) was achieved using Cu2ONPs-C@G/PE.

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Vanfleet, R. R., D. Muller, H. J. Gossmann e J. Silcox. "Antimony Delta Doping by Scanning Transmission Electron Microscopy and Electron Energy Loss Spectroscopy". Microscopy and Microanalysis 5, S2 (agosto 1999): 614–15. http://dx.doi.org/10.1017/s1431927600016391.

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MBE techniques allow the fabrication of exceptionally sharp compositional changes such as delta doped layers in semiconductors. Producing these spatially confined doped layers is critical to many innovative device designs. The spatial confinement of these delta doped structures can be less than the measurement resolution of the currently standard SIMS and RBS techniques. This allows only the upper limits on the layer width to be measured. These SIMS and RBS methods are also inadequate for the two dimensional information desired for future device design and development. More recently developed techniques such as Scanning Capacitance Microscopy and spreading resistance measurement give two dimensional information but have similar spatial resolution issues. The Z-contrast nature of Annular Dark Field (ADF) imaging with the complimentary technique of Electron Energy Loss Spectroscopy (EELS) in the Scanning Transmission Electron Microscope (STEM) shows promise for two dimensional dopant profiling with spatial resolution on the atomic scale.

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Guerrero, Gabriela Peñuelas, Ingrid Jiménez Cosme, Pilar Tapia López, José Luis Ruvalcaba Sil, Jesús Arenas, Aurore Lemoine, Jannen Contreras Vargas, Patricia Ruiz Portilla e Sonia Rivero Torres. "Technical Study of a set of Metallic Artifacts from the Maya Site of Lagartero, Chiapas, Mexico". MRS Proceedings 1374 (2012): 125–35. http://dx.doi.org/10.1557/opl.2012.1383.

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ABSTRACTDuring the excavations made at a burial of the post-Classic Mayan period (1220-1521 A.D.) in the pyramid number 2 of the pre-Hispanic site of Lagartero, Chiapas, Mexico, a set of four small metallic artifacts depicting reptile’s heads, were recovered. The objects were in poor conservation conditions and were taken to the Metal Conservation Laboratory of the National School of Conservation (ENCRyM- INAH) for suitable cleaning and conservation treatments.Analyses allowed identifying important technological features such as gilding remains. The analytical techniques included optical microscopy followed by X-Ray Fluorescence Spectroscopy (XRF), and Scanning Electron Microscope-coupled with Energy Dispersive Spectrometer (MEB-EDS). For the elemental depth profile a combined Particle X-Ray Emission Spectroscopy and Rutherford Backscattering Spectrometry (PIXE–RBS) analysis was carried out.The results indicate that the objects are made of a copper alloy, and then gilded probably using electrochemical replacement gilding (thickness has less than 1 μm). This technology has been observed in other metallic objects recovered from the Chichen-Itza Cenote in Yucatan, but it was not available in Mesoamerican areas so far. So, it could imply that these artifacts might have been imported from South American areas.

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TANAHASHI, Katsuto, Yuichi KAWAMURA, Naohisa INOUE e Yoshikazu HOMMA. "Three Dimensional Growth in GaAs MBE Studied by in-situ Scanning Electron Microscopy." Hyomen Kagaku 19, n. 11 (1998): 747–51. http://dx.doi.org/10.1380/jsssj.19.747.

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Tanahashi, K., Y. Kawamura, N. Inoue, Y. Homma e J. Osaka. "Surface-roughening processes in GaAs MBE studied by in situ scanning electron microscopy". Journal of Crystal Growth 188, n. 1-4 (giugno 1998): 205–10. http://dx.doi.org/10.1016/s0022-0248(98)00066-9.

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Lloret, Fernando, D. Araujo, M. P. Villar, L. Liu e Konstantinos Zekentes. "Si NWs Conversion to Si-SiC Core-Shell NWs by MBE". Materials Science Forum 821-823 (giugno 2015): 965–69. http://dx.doi.org/10.4028/www.scientific.net/msf.821-823.965.

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Si nanowires (NWs) samples have been converted to silicon carbide (SiC) NWs at different conditions of substrate temperature in an ultra-high vacuum using a molecular beam epitaxy (MBE) set-up. Auger electron spectroscopy (AES) and reflection high-energy electron diffraction (RHEED) have been in-situ carried out to control the growth process. Scanning electron microscopy (SEM) and conventional transmission electron microscopy (CTEM) have been used to characterize the resulting nanostructures. In addition, the samples have been prepared by focused ion beam (FIB) in order to have electron-transparently lamellas for TEM with the interface nanowire-substrate. SiC/Si shell/core NWs free of planar defects have been obtained for conversion tmpratures lower than 800oC.

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Aguilera Mandujano, A., e J. Serrato Rodriguez. "Synthesis and characterization of titania/graphene nanocomposite for application in photocatalysis". Revista Mexicana de Física 66, n. 5 Sept-Oct (1 settembre 2020): 610. http://dx.doi.org/10.31349/revmexfis.66.610.

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Titanium dioxide has been extensively investigated as a photocatalyst for water purification, presenting limitations such as recombination of electron-hole pairs generated by photons. The titania / graphene nanocomposites are promising materials to overcome these limitations due to the high specific area of graphene and unique electronic properties. In this work, an anatase-graphene nanocomposite was synthesized by a simple mixture assisted by ultrasound. Graphene was obtained by electrochemical exfoliation of graphite using the electrolysis technique. On the other hand, anatase was synthesized using the sol gel method. The obtained graphene, anatase and the nanocomposite material, were characterized with the X-ray diffraction technique (DRX), scanning electron microscopy (MEB) and transmission electron microscopy (MET). Using Raman spectroscopy, it was possible to verify that the graphite exfoliated correctly producing few layer-graphene. The lamellar nano-structure of the exfoliated graphite has crystallographic planes characteristic of graphite, graphene and graphene oxide. The presence of the anatase phase is shown in the diffraction spectrum of titania. The images obtained with SEM and TEM of the graphene sample show a layered lamellar structure and the TiO2 images show agglomerates of ellipsoidal nanoparticles. Obtained titania nanoparticles have a size of about 6 nm. Band gap value for such extremely low particle size nanocomposite is around 3.6 eV and presumably corresponds to the TiO2 (anatase) phase that completely surrounds the graphene. A nanocomposite model based on HRTEM observations is proposed. Considering the graphene electrical properties and the photocatalytic properties of TiO2, this nanocomposite promises to have applications in photocatalysis.

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Zsebök, Otto, Jan V. Thordson, Qingxiang Zhao, Ulf Södervall, Lars Ilver e Thorvald G. Andersson. "The Effect of Al in Plasma-assisted MBE-grown GaN". MRS Internet Journal of Nitride Semiconductor Research 5, S1 (2000): 209–15. http://dx.doi.org/10.1557/s1092578300004294.

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We have grown GaN, with addition of a 0.10 to 0.33 % Al, on sapphire(0001) substrates by solid-source RF-plasma assisted MBE. The Al-concentration was determined by secondary ion-mass spectrometry and Auger-electron spectroscopy, while the layer quality was assessed by photoluminescence and high-resolution scanning electron microscopy. Microscopy revealed a meandering pattern and a surface roughness varying with Al-content. The smallest surface roughness was obtained at 0.10 % Al. Photoluminescence revealed two main peaks attributed to the neutral donor-bound exciton. Its energy increased slightly with Al-concentration, which established a correlation between the Al-concentration and the band gap.

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Fan, Yunan, e Fugang Qi. "Effect of rapid cold stamping on the precipitation and mechanical properties of Al–Cu–Mg alloy". Materials Express 12, n. 2 (1 febbraio 2022): 355–61. http://dx.doi.org/10.1166/mex.2022.2142.

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High-angle annular dark-field scanning transmission electron microscopy, scanning electron microscopy, and tensile tests were used to investigate the effects of rapid cold stamping deformation on the precipitation and mechanical properties of spray-formed fine-grained Al–Cu–Mg alloy during aging. The number of longplate S′ phases in peak-aged samples evidently increases with increasing number of rapid cold stamping passes. After two passes of rapid cold stamping, the distribution of long-plate S′ phases in the samples is evidently uneven, with high density in some areas and low density in some areas. The S′ phases are refined, the number is further increased, and the distribution is uniform after four passes of rapid cold stamping deformation. The overall performance of the material is excellent. The tensile strength, yield strength, and elongation are 512 MPa, 453 MPa, and 11.2%, respectively.

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Osaka, J., N. Inque, Y. Mada, K. Yamada e K. Wada. "In-situ observation of roughening process of MBE GaAs surface by scanning reflection electron microscopy". Journal of Crystal Growth 99, n. 1-4 (gennaio 1990): 120–23. http://dx.doi.org/10.1016/0022-0248(90)90496-8.

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Ling, Zicheng, Weiping Chen, Weiye Xu, Xianman Zhang, Tiwen Lu e Jian Liu. "The Influence of A Mo Addition on the Interfacial Morphologies and Corrosion Resistances of Novel Fe-Cr-B Alloys Immersed in Molten Aluminum". Materials 12, n. 2 (14 gennaio 2019): 256. http://dx.doi.org/10.3390/ma12020256.

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The influence of a Mo addition on the interfacial morphologies and corrosion resistances of novel Fe-Cr-B alloys in molten aluminum at 750 °C was systematically investigated using scanning electron microscopy, X-ray diffractometer, electron probe microanalysis, and transmission electron microscopy. The results indicated that Mo could not only strengthen the matrix but also facilitate the formation of borides. Furthermore, the microstructures of Mo-rich M2B boride changed from a local eutectic net-like structure to a typical coarse dendritic structure and a blocky hypereutectic structure with increasing Mo addition. This was true of the blocky Mo-rich M2B boride, rod-like Cr-rich M2B boride and the corrosion products, which had a synergistic effect on retarding of the diffusion of molten aluminum. Notably, the corrosion resistance of the Fe-Cr-B-Mo alloy, with an 8.3 wt.% Mo addition, was 3.8 times higher than that of H13 steel.

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Lazo, A., C. Paucarchuco e H. Loro. "SÍNTESIS DE YAIO3 (YAP) POLICRISTALINO POR EL MÉTODO DE COMBUSTIÓN EN SOLUCIÓN". Revista Cientifica TECNIA 27, n. 1 (4 gennaio 2018): 61. http://dx.doi.org/10.21754/tecnia.v27i1.126.

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Se presenta el método de combustión en solución y su aplicación para la síntesis de YAlO3 (YAP), fueron usados como combustibles para la reacción de combustión y síntesis la urea y glicina, del YAP. Usando las técnicas de difracción de rayos X (XRD) por el método del polvo y microscopia electrónica de barrido (MEB) fueron analizadas la parte estructural y morfológica de las muestras obtenidas. Los difractogramas de Rayos X muestran una excelente correspondencia con lo reportado en la literatura para este material. Se suministran también los resultados de las muestras de material YAlxCrx‐1O3, dopado con Cr3+ con x = 0.001, 0.01, que exhiben picos de difracción dominantes debidos a la fase ortorrómbica de YAlO3 Palabras clave.- YAP, YAlO3, Combustion method. ABSTRACT The solution‐combustion process is presented, as well as its application to the synthesis of YAlO3 (YAP). Urea and glycine were used as fuel for the combustion reaction and synthesis of the YAP. The structure and morphology of the obtained sample were analyzed using the X‐ray diffraction (XRD) powder method and scanning electron microscopy (SEM). The X‐ray patterns showed an excellent agreement with data reported in the literature for this material. Results are also given for samples of YAlxCrx‐1O3 doped with Cr3+, with x = 0.001, 0.01, which showed dominant diffraction peaks due to the orthorhombic phase of YAlO3. Keywords.- YAP, YAlO3, combustion method.

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Bayon, Nicole Nazario, Nithin Krisshna Gunasekaran, Prathima Prabhu Tumkur, Babu R. Lamani, Jessica E. Koehne, Wondwossen D. Arasho, Krishnan Prabhakaran, Joseph C. Hall e Govindarajan T. Ramesh. "Synthesis and characterization of titanium nitride nanoparticles". Materials Express 12, n. 9 (1 settembre 2022): 1211–15. http://dx.doi.org/10.1166/mex.2022.2241.

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Titanium nitride (TiN) materials have gained an interest over the past years due to their unique characteristics, such as thermal stability, extreme hardness, low production cost, and comparable optical properties to gold. In the present study, TiN nanoparticles were synthesized via a thermal benzene route to obtain black nanoparticles. Scanning electron microscopy (SEM) was carried out to examine the morphology. Further microscopic characterization was done where the final product was drop cast onto double-sided conductive carbon tape and sputter-coated with gold/palladium at a thickness of 4 nm for characterization by field emission scanning electron microscopy (FE-SEM) with energy dispersive X-Ray spectroscopy (EDS) that revealed they are spherical. ImageJ software was used to measure the average size of the particles to be 79 nm in diameter. EDS was used to determine the elements present in the sample and concluded that there were no impurities. Further characterization by Fourier Transform infrared (FTIR) spectroscopy was carried out to identify the characteristic peaks of TiN. X-ray diffraction (XRD) revealed typical peaks of cubic phase titanium nitride, and crystallite size was determined to be 14 nm using the Debye-Scherrer method. Dynamic light scattering (DLS) analysis revealed the size distribution of the TiN nanoparticles, with nanoparticles averaging at 154 nm in diameter. Zeta potential concluded the surface of the TiN nanoparticles is negatively charged.

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Weng, Shuo, Hongchang Cai, Lihui Zhao e Songlin Zheng. "Microstructural change and corrosion variation of SAPH440 steel induced by pre-deformation". Materials Express 9, n. 6 (1 settembre 2019): 610–15. http://dx.doi.org/10.1166/mex.2019.1546.

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The influence of microstructural variation on corrosion of SAPH440 steel induced by pre-deformation has been investigated in the corrosive solution. The microstructure observation was carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The corrosion was characterized by weight loss method (WLM), open circuit potential (OCP) and potentiodynamic polarization curve (PPC) measurements. The results show that compared to the as-received specimens, the corrosion potential moves to the negative direction and corrosion current density increases after pre-deformation. The corrosion susceptibility is enhanced by the pre-deformation behavior, which is attributed to the increase in dislocation density with the increasing tensile elongation.

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Yang, Zhiguang, Chaosheng Zhu, Zhiqiang Hou e Peng Peng. "Effect of oxygen vacancies on the surface morphology and structural properties of WO3– x nanoparticles". Materials Express 9, n. 7 (1 ottobre 2019): 773–77. http://dx.doi.org/10.1166/mex.2019.1567.

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WO3 is an essential material for energy storage and catalytical technology, the oxygen vacancies level will play an essential role in its potential application. In this paper, porous tungsten oxide (WO3–x) with various oxygen contents was quickly fabricated by a microwave plasma-enhanced chemical vapor deposition method. A detailed characterization of structure and morphology features with the plasma handling process was recorded by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy, respectively. The etching mechanism of porous WO3–x under H2 plasma was discussed based on the systemically characterization. These results will help us to design the active sites or structure in the metal oxide materials.

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Fan, Caihe, Liuxin Ding, Yumeng Ni, Jiangxiong Gao, Jianjun Yang e Guixiang Long. "Effect of different precoating cleaning processes on the corrosion resistance of WC-Co hard alloy matrix". Materials Express 13, n. 9 (1 settembre 2023): 1570–81. http://dx.doi.org/10.1166/mex.2023.2488.

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Taking a WC-Co cemented carbide substrate as the research object, this study analyzes the roles of pH value and temperature in the corrosion action of the alloy substrate by electrochemical test. The surface morphology of the samples before and after retest was observed by scanning electron microscope. Comparative research on the corrosion behavior of different pH values at room temperature demonstrates that the alloy matrix has the best self-corrosion potential when the solution pH is 11, and the charge transfer resistance Rct is an order of magnitude higher than that in other pH solutions. Therefore, the best corrosion stability of the alloy matrix is realized at pH = 11. Comparative research on the corrosion behavior of different immersion liquid temperatures under the condition of pH = 11 is also conducted. The results show that the sample has the highest corrosion potential at 50 °C, suggesting the best corrosion stability of the alloy. The measurement results of scanning electron microscopy and atomic absorption spectrometry show that galvanic corrosion occurs. The binder phase Co is used as the anode for corrosion, and the corrosion product is mainly Co(OH)2.

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Zhang, Yu, Ruijian Song e Xiang Zhang. "Preparation of electrochemically deposited nickel—cobalt nanocomposite coating and research on its corrosion resistance". Materials Express 11, n. 12 (1 dicembre 2021): 2039–46. http://dx.doi.org/10.1166/mex.2021.2110.

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Alloying as a way of improving material properties has really gained a lot of global attention over the past few years. Alloying majorly improves physicochemical, electrochemical, thermal, and mechanical and corrosion resistance of a parent material. In this work, electrodeposition using a sulphamate electrolytic cell under varied concentrations of the secondary phase of cobalt. Characterization of the alloy was achieved using scanning electron microscopy (SEM), optical microscopy (OM), and X-ray diffraction (XRD) techniques. Corrosion resistance was investigated using potentiometric and impedance tests, reported, and well explained.

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Higashino, T., J. Osaka, K. Tanahashi, M. Kikuchi, Y. Kawamura, N. Inoue e Y. Homma. "The measurement of work function on GaAs (001) surface during MBE growth by scanning electron microscopy". Journal of Crystal Growth 209, n. 2-3 (febbraio 2000): 431–34. http://dx.doi.org/10.1016/s0022-0248(99)00585-0.

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Maiti, Paramita, Arijit Mitra, R. R. Juluri, Ashutosh Rath e Parlapalli V. Satyam. "Growth of Molybdenum Trioxide Nanoribbons on Oriented Ag and Au Nanostructures: A Scanning Electron Microscopy (SEM) Study". Microscopy and Microanalysis 25, n. 6 (18 giugno 2019): 1449–56. http://dx.doi.org/10.1017/s1431927619014648.

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AbstractWe report the growth of molybdenum trioxide (MoO3) nanoribbons (NRs) on epitaxial Ag and oriented Au nanostructures (NSs) using an ultra-high vacuum (UHV)-molecular beam epitaxy (MBE) technique at different substrate temperatures. An approximately 2 nm silver (Ag) film has been deposited at different growth temperatures (using UHV-MBE) on cleaned Si(100), Si(110), and Si(111) substrates. For faceted Au NSs, an approximately 50 nm Au film has been deposited (using high-vacuum thermal evaporation) on a Si(100) substrate with a native oxide layer at the interface and the sample was annealed in low vacuum (≈10−2) and at high temperature (≈975°C). Scanning electron microscopy measurements were performed to determine the morphology of MoO3/Ag and MoO3/Au composite films. From energy dispersive X-ray spectroscopy elemental mapping and line scans it is found that faceted Au NSs are more favorable for the growth of MoO3 NRs than epitaxial Ag microstructures.

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Abud, Saleh H., Hassan Zainuriah, Fong Kwong Yam e Alaa J. Ghazai. "Structural and Optical Properties of In_0.27Ga_0.73N/Si (111) Film Grown Using PA-MBE Technique". Advanced Materials Research 620 (dicembre 2012): 368–72. http://dx.doi.org/10.4028/www.scientific.net/amr.620.368.

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In this paper, InGaN/GaN/AlN/Si (111) structure was grown using a plasma-assisted molecular beam epitaxy (PA-MBE) technique. The structural and optical properties of grown film have been characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), high resolution X-ray diffraction (HR-XRD) and photoluminescence (PL). Indium-mole fraction has been computed to be 0.27 using XRD data and Vegards law with high grain size and low tensile strain. Room-temperature photoluminescence revealed an intense peak at 534 nm (2.3 eV) related to our sample In0.27Ga0.73N.

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Khalili, Parastoo, e Majid Farahmandjou. "Morphology and structure study of polygon ZnO nanorods: Biomedical applications". Materials Engineering Research 3, n. 1 (2021): 125–32. http://dx.doi.org/10.25082/mer.2021.01.001.

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In this study, zinc oxide (ZnO) nanoparticles (NPs) were first synthesized using co-precipitation method in the presence of Zn(NO3)2.6H2O precursor and calcined at different temperature of 450 oC and 1000 oC. Samples were then characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The XRD study revealed the hexagonal wurtzite structure for annealed samples. SEM images showed tthat he morphology of the ZnO NPs changed from sphere-like shape to polygon shape by increasing temperature. The exact size of NPs were measured by TEM analysis about 40 nm for as-prepared samples. The EDS analysis demonstrated an increasing level of Zn element from 28.5 wt% to 50.8 wt% for as-synthesized and annealed samples, respectively.

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Cullen, David A., Haoran Yu, Michael J. Zachman, Chenzhao Li, Leiming Hu, Nancy N. Kariuki, Rangachary Mukundan, Jian Xie, K. C. Neyerlin e Deborah J. Myers. "Recreating Fuel Cell Catalyst Degradation in Aqueous Environments for Identical-Location Scanning Transmission Electron Microscopy Studies". ECS Meeting Abstracts MA2022-01, n. 35 (7 luglio 2022): 1452. http://dx.doi.org/10.1149/ma2022-01351452mtgabs.

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Proton exchange membrane fuel cells (PEMFCs) have long been studied for applications in sustainable transportation. The recent shift in focus from passenger vehicle to heavy duty applications places increased demand on the efficiency and durability of the components used in membrane electrode assemblies (MEAs).[1] Of particular interest are the oxygen reduction reaction electrocatalysts used in the fuel cell cathode. While the relaxed capital cost requirements for heavy duty applications allows for increased precious metal loadings, the four-fold increase in operating lifetime requires improved catalysts which can express their high activity not only at beginning-of-life, but also after 25k-hour equivalent accelerated stress tests (ASTs). This paradigm shift prioritizes efforts aimed at understanding and subsequently controlling catalyst degradation. In situ characterization methods can be instrumental in this effort, but it is critical that the operating conditions in these studies reliably replicate the type and degree of degradation observed in the operating fuel cell.[2,3] In this study, identical-location scanning transmission electron microscopy (IL-STEM) is used to compare catalyst degradation in an aqueous environment to degradation observed ex situ in MEAs following AST cycling.[4] For traditional catalysts, the aqueous environment appears to replicate the dissolution and coalescence mechanisms observed for Pt catalysts with small starting particle sizes (<3nm) supported primarily on the surfaces of graphitized carbon supports. In evaluating more stable alloy catalysts (4-5nm) supported on high surface area carbon supports, the large discrepancy between degradation in the aqueous and MEA environment was observed. In particular, the Ostwald ripening mechanism, which is more dominate in these high surface area carbons, seemed absent in the aqueous environment.[5] To better replicate the type and degree of degradation in the MEA environment, various experimental parameters such as temperature, acid type/concentration, and upper and lower potential limits were explored. By extending the cycling potential window from 0.6-0.95 Vvs . to 0.4-1.0 Vvs . RHE in an sulfuric acid electrolyte containing Pt ions, the Ostwald ripening mechanism was enhanced, resulting in an end-of-test particle size distribution and composition which better match MEA tests. These refined conditions can now be used to perform in situ and identical-location experiments that will play an important role in the development of robust catalysts for heavy-duty vehicle applications.[6] References [1] D. A. Cullen, et al. Nat. Energy 2021, 6 (5), 462–474. [2] J. A. Gilbert, et al. Electrochim. Acta 2015, 173, 223–234. [3] I. Martens, et al. ACS Energy Lett. 2021, 6 (8), 2742–2749. [4] S. Rasouli, et al. Nano Lett. 2019, 19 (1), 46–53. [5] E. Padgett, et al. J. Electrochem. Soc. 2019, 166 (4), F198–F207 [6] This material is primarily based on work performed by the Million Mile Fuel Cell Truck (M2FCT) Consortium (https://millionmilefuelcelltruck.org), technology manager Greg Kleen, which is supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office. Electron microscopy was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

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Khalili, Parastoo, e Majid Farahmandjou. "Study of α-Fe2O3@ ZnO nanoleaves: Morphological and optical study". Materials Engineering Research 2, n. 1 (2020): 118–24. http://dx.doi.org/10.25082/mer.2020.01.004.

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In this paper, α-Fe2O4@ZnO nanoparticles (NPs) were synthesized by coprecipitation method in the presence of PVP and EG surfactants. The samples were charactrized by x-ray fluorescence (XRF), x-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and fourier transform infrared spectroscopy (FTIR). The XRD results exhibited rhombohedral α-Fe2O3 and wurtzite structure of ZnO. The SEM images showed that the NPs changed from rod-shape to nanoleaves particles after heat treatment. The TEM studies displayed the formation of Fe2O3@ZnO core-shell of as-synthesized NPs. The stretching vibrations peaks in FTIR in the wavenumber of 532 cm-1 and 473 cm-1 ascribed to the Fe and Zn groups. The XRF data indicated decreasing of the Fe weight percent from 22 %Wt. to 25 %Wt., after heat treatment.

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KAZAKOV, I. P., V. I. KOZLOVSKY, V. P. MARTOVITSKY, YA K. SKASYRSKY, M. D. TIBERI, A. O. ZABEZHAYLOV e E. M. DIANOV. "MBE GROWN ZnSSe/ZnMgSSe MQW STRUCTURE FOR BLUE VCSEL". International Journal of Nanoscience 06, n. 05 (ottobre 2007): 407–10. http://dx.doi.org/10.1142/s0219581x07004493.

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ZnSSe / ZnMgSSe MQW structures were grown by molecular beam epitaxy on GaAs substrates. The band gap of ZnMgSSe barriers was approximately 3 eV at room temperature. Cathodoluminescence, X-ray diffraction, optical, scanning electron beam, and atomic force microscopy were all used for structure characterization. Decay of the ZnMgSSe solid solution in at least two phases was observed. Improvement in the quality of the crystal lattice and surface morphology was achieved by mismatching the ZnMgSSe from the GaAs substrate by increasing the lattice period by 0.24%.

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26

XIE, M. H., S. H. CHEUNG, L. X. ZHENG, S. Y. TONG, B. S. ZHANG e H. YANG. "GROWTH AND STRUCTURAL PROPERTIES OF GaN FILMS ON FLAT AND VICINAL SiC(0001) SUBSTRATES". International Journal of Modern Physics B 16, n. 01n02 (20 gennaio 2002): 165–72. http://dx.doi.org/10.1142/s0217979202009603.

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Abstract (sommario):

Initial stage GaN growth by molecular-beam (MBE) on SiC (0001) substrate is followed by in situ scanning tunneling microscopy. Comparison is made between growth on nominally flat and vicinal substrate surfaces and the results reveal characteristic differences between the two. Ex situ transmission electron microscopy (TEM) and X-ray diffraction (XRD) rocking curve measurements of the films show lower density of defects and better structural quality of the vicinal film. We suggest the improved structural quality of the vicinal film is related to the characteristic difference in its initial stage nucleation and coalescence processes than that of the flat film.

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27

Perovic, D. D., e J. H. Paterson. "High-angle annular dark-field STEM imaging of doped semiconductor layers". Proceedings, annual meeting, Electron Microscopy Society of America 49 (agosto 1991): 704–5. http://dx.doi.org/10.1017/s0424820100087835.

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Abstract (sommario):

With the development of crystal growth techniques such as molecular beam epitaxy (MBE), it is now possible to fabricate modulation-doped superlattices consisting of alternating ultrathin layers of n-and/or p-type material abruptly separated by undoped material. At sufficiently high dopant concentrations these abrupt layers may be imaged in cross section by electron microscopy. Pennycook et al. and Treacy et al. have used high angle annular dark-field (HAAD) imaging in the scanning transmission electron microscope (STEM) to image low levels of dopants (∼1 at. %) in semiconductors. This work is concerned with imaging boron and arsenic doped layers in silicon at levels « 1 at.%.Fig. 1 shows a HAAD image of a B-Si superlattice at the <110> zone-axis orientation taken at 100 kV using a VG HB501UX STEM. The bright vertical layers are the B-doped regions, containing ∼4 x 1020 B/cm3. The horizontal lines are due to beam instability while the image was recorded. Fig.2 shows a line scan across the same superlattice, recorded by scanning the beam across the specimen in a direction perpendicular to the layers.

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28

DVURECHENSKII, A. V., J. V. SMAGINA, V. A. ZINOVYEV, S. A. TEYS, A. K. GUTAKOVSKII e R. GROETZSCHEL. "MODIFICATION OF GROWTH MODE OF Ge ON Si BY PULSED LOW-ENERGY ION-BEAM IRRADIATION". International Journal of Nanoscience 03, n. 01n02 (febbraio 2004): 19–27. http://dx.doi.org/10.1142/s0219581x04001778.

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Abstract (sommario):

Scanning tunneling microscopy (STM) and reflection high-energy electron diffraction (RHEED) experiments were performed to study growth modes induced by hyperthermal Ge + ion action during molecular beam epitaxy (MBE) of Ge on Si (100). The continuous and pulsed ion beams were used. These studies have shown that ion-beam bombardment during heteroepitaxy leads to decrease in critical film thickness for transition from two-dimensional (2D) to three-dimensional (3D) growth modes, enhancement of 3D island density and narrowing of island size distribution, as compared with conventional MBE experiments. The crystal perfection of Ge / Si structures with Ge islands embedded in Si was analyzed by Rutherford backscattering/channeling technique (RBS) and transmission electron microscopy (TEM). The results of Kinetic Monte Carlo (KMC) simulation have shown that two mechanisms of ion beam action can be responsible for stimulation of 2D–3D transition. They are: (1) surface defect generation by ion impacts and (2) enhancement of surface diffusion.

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29

Łapiński, Marcin, Piotr Dróżdż, Mariusz Gołębiowski, Piotr Okoczuk, Jakub Karczewski, Marta Sobanska, Aleksiej Pietruczik et al. "Thermal Instability of Gold Thin Films". Coatings 13, n. 8 (25 luglio 2023): 1306. http://dx.doi.org/10.3390/coatings13081306.

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Abstract (sommario):

The disintegration of a continuous metallic thin film leads to the formation of isolated islands, which can be used for the preparation of plasmonic structures. The transformation mechanism is driven by a thermally accelerated diffusion that leads to the minimalization of surface free energy in the system. In this paper, we report the results of our study on the disintegration of gold thin film and the formation of nanoislands on silicon substrates, both pure and with native silicon dioxide film. To study the processes leading to the formation of gold nanostructures and to investigate the effect of the oxide layer on silicon diffusion, metallic film with a thickness of 3 nm was deposited by molecular beam epitaxy (MBE) technique on both pure and oxidized silicon substrates. Transformation of the thin film was observed by low-energy electron microscopy (LEEM) and a scanning electron microscope (SEM), while the nanostructures formed were observed by atomic force microscope (AFM) method. Structural investigations were performed by low-energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS) methods. Our experiments confirmed a strong correlation between the formation of nanoislands and the presence of native oxide on silicon substrates.

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30

Nadzirah, Sharipah, e Uda Hashim. "Synthesis and Film Investigation of Titania". Advanced Materials Research 832 (novembre 2013): 128–31. http://dx.doi.org/10.4028/www.scientific.net/amr.832.128.

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Abstract (sommario):

Titania or titanium dioxide (TiO2) thin film has been synthesized via sol-gel method with monoethanolamine (MEA) as a catalyst. The mixing of titanium butoxide as a precursor, ethanol as a solvent and MEA were stirred using magnetic stirrer under ambient temperature [. The TiO2solution prepared then was deposited on SiO2substrates using spin-coater and the coated films were annealed at 600°C. Finally, both before and after annealed TiO2thin films were characterized using Field Emission Scanning Electron Microscopy (FESEM). The obtained results show the different TiO2particles formation before and after annealed.

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31

Chen, Zixuan, Xudong Li, Jie Xie, Jianzhong Pei, Chengchao Wang e Rui Li. "Preparation and performance characteristics of reduced graphene oxide modified asphalt". Materials Express 11, n. 9 (1 settembre 2021): 1579–86. http://dx.doi.org/10.1166/mex.2021.2046.

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Abstract (sommario):

Reduced graphene oxide (RGO) was self-prepared by the oxidation reduction method and then characterized by several tests known as Fourier Transform Infrared Spectroscopy (FTIR) test, scanning electron microscopy (SEM) test, transmission electron microscopy (TEM) test, elemental analysis, raman measurement and thermogravimetry (TG) analysis to evaluate the properties of RGO. Additionally, RGO modified asphalt was prepared in this research to study the influence of RGO on matrix asphalt. Some of the normal performances of RGO modified asphalt were studied in terms of penetration at medium temperature, penetration index (PI), softening point, equivalent softening point T800 at high temperature and ductility at low temperature. Results showed that the prepared RGO has obvious layer structures and good properties and the performance of RGO modified asphalt at high temperature has increased significantly while the performance at low temperature decreased slightly. This research can provide an insight for the further study of RGO modified asphalt to enhance its road performance.

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32

Inoue, N., Y. Homma, J. Osaka e T. Araki. "Behavior of monolayer holes on MBE grown GaAs surfaces during annealing revealed by in situ scanning electron microscopy". Journal of Crystal Growth 164, n. 1-4 (luglio 1996): 88–91. http://dx.doi.org/10.1016/0022-0248(95)01064-5.

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33

Hu, H., M. Zheng, J. N. Eckstein e J. Zuo. "Scanning Transmission Electron Microscopy Evidences Of Interstitial And Substitutional Oxygen In MBE Grown Fe1+xTe Thin Films And Emergence Of Superconductivity". Microscopy and Microanalysis 18, S2 (luglio 2012): 1456–57. http://dx.doi.org/10.1017/s1431927612009130.

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34

Xie, M. H., S. M. Seutter, L. X. Zheng, S. H. Cheung, Y. F. Ng, Huasheng Wu e S. Y. Tong. "Surface Morphology of GaN: Flat versus Vicinal Surfaces". MRS Internet Journal of Nitride Semiconductor Research 5, S1 (2000): 174–80. http://dx.doi.org/10.1557/s1092578300004245.

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Abstract (sommario):

The surface morphology of GaN films grown by molecular beam epitaxy (MBE) is investigated by scanning tunneling microscopy (STM). A comparison is made between flat and vicinal surfaces. The wurtzite structure of GaN leads to special morphological features such as step pairing and triangularly shaped islands. Spiral mounds due to growth at screw threading dislocations are dominant on flat surfaces, whereas for vicinal GaN, the surfaces show no spiral mound but evenly spaced steps. This observation suggests an effective suppression of screw threading dislocations in the vicinal films. This finding is confirmed by transmission electron microscopy (TEM) studies. Continued growth of the vicinal surface leads to step bunching that is attributed to the effect of electromigration.

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35

Coats, Matthew, Samantha Medina, Jonathan Braaton, Lei Cheng, Nathan Craig, Christina Johnston e Svitlana Pylypenko. "Quantitative Analysis of Fuel Cell Cathode Catalyst Layer Degradation Using Scanning Transmission Electron Microscopy and Energy Dispersive Spectroscopy". ECS Meeting Abstracts MA2022-02, n. 39 (9 ottobre 2022): 1434. http://dx.doi.org/10.1149/ma2022-02391434mtgabs.

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Abstract (sommario):

Proton exchange membrane fuel cells (PEMFCs) are a central technology for the electrification of the heavy-duty automotive fleet, ultimately enabling reduced carbon emissions. However, improvements in lifetime and cost are necessary before mass adoption of PEMFC vehicles is achieved. Significant research into analyzing and mitigating degradation of catalyst layers (CLs) is ongoing and this work highlights a transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) approach aimed at quantifying electrochemically active surface area (ECSA) loss through the thickness of CLs resulting from electrochemical-applied, catalyst-specific accelerated stress tests or ASTs. Several mechanisms contribute to degradation of the catalysts in PEMFCs, including Ostwald ripening, coalescence, and formation of a Pt band within the membrane, which result in decreased active surface area throughout the CL. TEM has often been used in conjunction with electrochemical testing to infer changes in the catalyst nanoparticle size, distribution, and changes to the support materials within the catalyst layer (CL) to investigate catalyst. Typically, high-magnification TEM with high-resolution are used to infer localized changes within the CL by examining shape and size to provide information concerning the degradation mechanism. Low-magnification TEM is typically used to observe changes in the support, ionomer, and catalyst distribution. Here we use a quantitative approach to show elemental differences within the CL by using scanning transmission electron microscopy and energy dispersive spectroscopy maps (STEM/EDS) for a given MEA that underwent catalyst-specific ASTs. This approach uses the fluorine to platinum ratio (F/Pt) from a fresh sample as a benchmark to track loss of Pt through the thickness of the CL of aged samples. This information can then be used to compare differences in various locations on the MEA in relationship to gas inlets and outlets as well as changes induced by different stressors during the catalyst ASTs. This analysis complements studies using bulk techniques, such as electrochemical ECSA via cyclic voltammetry and micro-X-ray diffraction (µ-XRD), to confirm trends in CL degradation.

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36

Xiao, H. Z., R. Tsu, I. M. Robertson, H. K. Birnbaum e J. E. Greene. "Growth of Si on Ge(001)2×l by gas-source molecular beam epitaxy". Proceedings, annual meeting, Electron Microscopy Society of America 51 (1 agosto 1993): 806–7. http://dx.doi.org/10.1017/s0424820100149866.

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Abstract (sommario):

The growth of SiGe strained-layer superlattices (SLS) has been received considerable attention due to the electronic and optoelectronic properties of these layers. In addition, these structures offer tantalizing possibilities for "band gap engineering" through the use of strain and chemically ordered alloys. The remaining barriers to grow the SiGe SLS structures with high quality result from the generation of large densities of defects, such as dislocations, twins, stacking faults, etc., at the heterointerfaces arising from the misfit strain relaxation. Other problems associated with the growth of the SiGe SLS structures are segregation and low incorporation of the dopants and inter-diffusion of Si and Ge. In the present study, the inter-mixing of Si and Ge and the generation of the defects in Si epilayers grown on Ge(001)2×1 at 550 °C by gas-source molecular beam epitaxy (MBE) from Si2H6 were studied using transmission electron microscopy (TEM), in-situ reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM) and electron energy-loss spectroscopy (EELS).

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37

Christoffersen, R., S. Kim, Y. L. Yang e A. J. Jacobson. "Analytical TEM and EPMA Study of Decomposition Reactions in an Oxygen-Separation Membrane Material". Microscopy and Microanalysis 3, S2 (agosto 1997): 745–46. http://dx.doi.org/10.1017/s1431927600010618.

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Abstract (sommario):

Mixed-conducting oxides with appropriate values of electronic and ionic conductivity have the potential to be used as ceramic “membranes” for the separation of oxygen from other gases. The separation is based on oxygen transport from an O2-rich, and hence oxidizing, gas reservoir on one side of the membrane to an O2-lean, and hence reducing, take-up reservoir on the membrane's other side. The oxide Sr(Co1-xFex)O3-δ (SCFO), which has a cubic perovskite structure, is one such potential membrane material. Although the permeation flux of oxygen through SCFO membranes has been mea-sured, the microstructural evolution of SCFO membranes during permeation has been little studied in comparison to other potential membrane oxides. Several of these other systems do show segregation and/or decomposition phenomena that potentially may affect membrane properties. Here we report preliminary results of a systematic microanalytical study of SCFO membranes using scanning electron microscopy and microanalysis in an electron probe microanalyzer (EPMA), as well as transmission electron microscopy in an analytical TEM.

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38

Lian, Brenda Lim Ai, Steven Lim, Pang Ling Yean, Siew Hoong Shuit e Huei Wong Kam. "Biomass Wastes as Precursor For The Synthesis of Carbon Nanoparticle". IOP Conference Series: Earth and Environmental Science 945, n. 1 (1 dicembre 2021): 012035. http://dx.doi.org/10.1088/1755-1315/945/1/012035.

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Abstract (sommario):

Abstract The development of technology and the growth in human population had resulted in a surge in energy demand and biomass waste production. Metal-air battery (MAB) is a potential energy storage technology with high theoretical energy density and safety. However, the conventional air cathode material synthesized from carbon nanotube (CNT) is rather costly. In this study, several biomass wastes such as oil palm empty fruit bunch (OPEFB), garlic peel (GP) and oil palm frond (OPF) were investigated to identify a suitable greener and efficient precursor to syntheelesize carbon nanoparticle as air electrode material for MAB. The carbon materials were synthesized through carbonization of precursor at different temperatures of 450 °C, 600 °C, and 700 °C before activation with potassium hydroxide (KOH) through wet impregnation method. The materials synthesized were evaluated based on its chemical and physical properties through characterization using thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersion x-ray (SEM-EDX), field emission scanning electron microscopy (FESEM) and Brunauer-Emmet-Teller (BET) analysis. Based on the experiments conducted, it was found that the suitable precursor was the OPF as it displayed a better tunability for enhanced electrical conductivity as it was able to achieve smaller sized particles with higher specific surface area of 548.26 m2/g and hierarchical porous structure at 700 °C compared to OPEFB and GP. This study proved that OPF could be a promising alternative to CNT as an electrode material which is more sustainable and cost efficient for energy storage application such as MAB.

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39

He, Xiaoqing, Lin Gu, Changbao Zhu, Yan Yu, Chilin Li, Yong-Sheng Hu, Hong Li et al. "Direct Imaging of Lithium Ions Using Aberration-Corrected Annular-Bright-Field Scanning Transmission Electron Microscopy and Associated Contrast Mechanisms". Materials Express 1, n. 1 (1 marzo 2011): 43–50. http://dx.doi.org/10.1166/mex.2011.1006.

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40

Bourqui, B., P. A. Buffat, J. D. Ganière e F. K. Reinhart. "Characterization of zinc diffusion induced disordering in GaAs/AlGaAs multiquantum well structures by Transmission Electron Microscopy". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 4 (agosto 1990): 734–35. http://dx.doi.org/10.1017/s0424820100176800.

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Abstract (sommario):

Diffusion of impurities, such as zinc or silicon, enhances the intermixing of Ga-Al atoms at GaAs/AlGaAs interfaces. This process is useful to modify the bandedge properties of multilayered structures such as (AlxGa1-xAs/GaAs). Important technological applications are due to this effect. Information about electronic states of the disordered structure is directly obtained by photoluminescence. The impurity induced disordering depth is, usually, estimated either by scanning electron microscopy (SEM) or by secondary ion mass spectroscopy (SIMS). We used transmission electron microscopy on wedge shaped specimen (WTEM) is used to obtain local information on the disordering depth and to check the chemical homogeneities of the diffused samples.The multiquantum well structures (MQW) were grown by molecular beam epitaxy (MBE) on n doped [001] substrate at surface temperature of 600 °C. A specimen structure is given in Figure 1. Zinc diffusions were performed by using the sealed quartz tube method at 575°C. The ZnAs2 source provide sufficient partial pressure of arsine to maintain the surface at equilibrium.

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41

Tamizhanban, S., e D. Jegatheeswaran. "Multiscale analysis, mechanical properties and strength of hydrophobic paper sludge". Materials Express 12, n. 9 (1 settembre 2022): 1231–40. http://dx.doi.org/10.1166/mex.2022.2267.

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Abstract (sommario):

In order to combat the damaging environmental effects of cement production and the depletion of natural resources, a sustainable concrete company must develop alternative binders. This study investigates the use of hydrophobic paper sludge ash as a partial cement substitute in new concrete. The primary chemical components of the hydrophobic paper sludge ash were determined using energy dispersive X-ray microanalysis and Fourier transforms infrared. Differential scanning calorimetry and thermogravimetry are used to analyse the hydration and pozzolanic reaction in concrete in relation to the amount of hydrophobic paper sludge ash substituted for cement. Scanning electron microscopy and X-ray diffraction techniques were used to examine the microstructures of concrete mixtures. There is also discussion of how the properties of hydrophobic paper sludge ash concrete affect its usability, mechanical strength, sorptivity, and water absorption.

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42

Wang, Guofeng, Minghui Liu, Lizhong Wang e Hongbo Liu. "Preparation and study of Fe–Co–Zr–B nano-soft magnetic alloy". Materials Express 9, n. 6 (1 settembre 2019): 686–89. http://dx.doi.org/10.1166/mex.2019.1541.

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Abstract (sommario):

The mechanical alloying of Fe–Co–Zr–B mixed powder has been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and other test methods. The results show that the Fe–Co–Zr–B nanocrystalline alloy can be produced by mechanical alloying from the elements powders by ball milling of 50 h. With the increase in Co content, the grain size increases correspondingly, and the size of composite particles decreases continuously. The mechanical alloying process of Fe–Co–Zr–B alloy system is slowed down by the addition of Co.

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Dixon, R. H., P. Kidd e P. J. Goodhew. "Defect morphology in thick relaxed layers of InGaAs on GaAs". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 4 (agosto 1990): 668–69. http://dx.doi.org/10.1017/s0424820100176472.

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Abstract (sommario):

Thick relaxed InGaAs layers grown epitaxially on GaAs are potentially useful substrates for growing high indium percentage strained layers. It is important that these relaxed layers are defect free and have a good surface morphology for the subsequent growth of device structures.3μm relaxed layers of InxGa1-xAs were grown on semi - insulating GaAs substrates by Molecular Beam Epitaxy (MBE), where the indium composition ranged from x=0.1 to 1.0. The interface, bulk and surface of the layers have been examined in planar view and cross-section by Transmission Electron Microscopy (TEM). The surface morphologies have been characterised by Scanning Electron Microscopy (SEM), and the bulk lattice perfection of the layers assessed using Double Crystal X-ray Diffraction (DCXRD).The surface morphology has been found to correlate with the growth conditions, with the type of defects grown-in to the layer (e.g. stacking faults, microtwins), and with the nature and density of dislocations in the interface.

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44

CHEN, XIAODONG, WILLIAM J. SCHAFF e LESTER F. EASTMAN. "FOCUSED THERMAL BEAM DIRECT PATTERNING ON INGAN DURING MOLECULAR BEAM EPITAXY". International Journal of High Speed Electronics and Systems 17, n. 01 (marzo 2007): 97–101. http://dx.doi.org/10.1142/s0129156407004291.

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Abstract (sommario):

During InGaN Molecular Beam Epitaxy (MBE) growth, the material surface is exposed to a small diameter pulse laser beam that is controlled by scanning mirrors. Local heating effects are observed at the points of exposure. The materials are characterized by Wavelength Dispersive Spectroscopy (WDS), Scanning Electron Microscopy (SEM), and Photoluminescence (PL). Indium mole fraction of materials is reduced where laser exposure takes place. The effect of local thermal heating appears to enhance surface diffusion while not causing ablation or evaporation under the conditions studied. PL efficiency is significantly increased by focused thermal beam exposure. Laser written regions have 7 times higher PL intensity compared to non-written areas, which might be due to surface texturing that causes higher extraction efficiency.

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45

Gas, Katarzyna, Slawomir Kret, Wojciech Zaleszczyk, Eliana Kamińska, Maciej Sawicki, Tomasz Wojtowicz e Wojciech Szuszkiewicz. "Oxidation of MBE-Grown ZnTe and ZnTe/Zn Nanowires and Their Structural Properties". Materials 14, n. 18 (13 settembre 2021): 5252. http://dx.doi.org/10.3390/ma14185252.

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Abstract (sommario):

Results of comparative structural characterization of bare and Zn-covered ZnTe nanowires (NWs) before and after thermal oxidation at 300 °C are presented. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, and Raman scattering not only unambiguously confirm the conversion of the outer layer of the NWs into ZnO, but also demonstrate the influence of the oxidation process on the structure of the inner part of the NWs. Our study shows that the morphology of the resulting ZnO can be improved by the deposition of thin Zn shells on the bare ZnTe NWs prior to the oxidation. The oxidation of bare ZnTe NWs results in the formation of separated ZnO nanocrystals which decorate crystalline Te cores of the NWs. In the case of Zn-covered NWs, uniform ZnO shells are formed, however they are of a fine-crystalline structure or partially amorphous. Our study provides an important insight into the details of the oxidation processes of ZnTe nanostructures, which could be of importance for the preparation and performance of ZnTe based nano-devices operating under normal atmospheric conditions and at elevated temperatures.

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46

Zhao, Xiaoguang, Jing Ouyang, Qi Tan, Xiumin Tan e Huaming Yang. "Interfacial characteristics between mineral fillers and phenolic resin in friction materials". Materials Express 10, n. 1 (1 gennaio 2020): 70–80. http://dx.doi.org/10.1166/mex.2020.1596.

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Abstract (sommario):

Mineral fillers are indispensable constituent part of friction materials, which are capable of improving and stabilizing coefficient of friction, decreasing wear, enhancing thermal conductivity and reducing costs of friction materials, in addition, decreasing the noise in brake application. Based on their roles in the friction materials, mineral fillers are classified into abrasives, lubricants, functional fillers, and space fillers. Herein, four typical commercial mineral fillers, namely quartz, graphite, expanded vermiculite, and barite were studied for revealing their effects on the performance of friction materials. The composition, thermal stability, structural characteristics such as surface area, pore volume, and distribution of the pore size, and thermal conductivity of these mineral fillers were researched mainly by X-ray diffraction (XRD), differential scanning calorimetry and thermogravimetry (DSC-TG), N2 adsorption–desorption isotherms, and thermal conductivity tester. Moreover, in order to illustrate the interfacial characteristics of mineral-based in friction materials, four ideal brake pads only consisting of mineral filler, BaSO4 and phenolic resin were prepared. Microstructure and combination of mineral fillers and phenolic resin were investigated by scanning electron microscopy (SEM), polarizing microscope, and Fourier transformation infrared spectroscopy (FTIR). The results showed that different types of material fillers had special functions for friction materials, and they combined with phenolic resin mainly in a physical way.

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47

Zhao, Feng-Wei, Qian Zhang, Feng Hui, Jun Yuan, Su-Ning Mei, Qin-Wei Yu, Jian-Ming Yang et al. "Catalytic Behavior of Alkali Treated H-MOR in Selective Synthesis of Ethylenediamine via Condensation Amination of Monoethanolamine". Catalysts 10, n. 4 (2 aprile 2020): 386. http://dx.doi.org/10.3390/catal10040386.

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Abstract (sommario):

Catalytic behavior of alkali treated mordenite (H-MOR) in selective synthesis of ethylenediamine (EDA) via condensation amination of monoethanolamine (MEA) was investigated. Changes in the structural and acidic properties of alkali treated H-MOR were systematically investigated by N2 adsorption/desorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), temperature programmed ammonia desorption (NH3-TPD), pyridine adsorption was followed by infrared spectroscopy (Py-IR), and X-ray fluorescence (XRF) analyses. The results show that alkali treatment produces more opening mesopores on the H-MOR crystal surfaces and leads to an increase in the number of B acid sites and the strength of the acid sites. The mesopores effectively enhance the rate of diffusion in the bulk catalyst. Moreover, the B acid sites are active sites in selective synthesis of EDA. Due to improvements in the diffusion conditions and reactivities, alkali treated H-MOR shows an excellent catalytic performance under mild reaction conditions. The conversion of MEA was 52.8% and selectivity to EDA increased to 93.6%, which is the highest selectivity achieved so far. Furthermore, possible mechanism for the formation of EDA is discussed.

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48

Ji, Xiaoying, Xin Huang, Fengcheng Shi, Zongze Geng, Dongliang Li, Bang Chao Yin e Junhua Zhang. "Enhancing the water vapor barrier of eco-friendly, emulsion-coated paper via a bilayer-like structure design". Materials Express 12, n. 5 (1 maggio 2022): 726–34. http://dx.doi.org/10.1166/mex.2022.2180.

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Abstract (sommario):

To further improve the water vapor barrier of paper packaging materials, eco-friendly, polyvinyl alcohol (PVA)/glycerol tristearate (GTS) emulsions were prepared as surface coatings. The hydrophilic hydroxyl groups within the PVA chains were consumed through a crosslinking reaction to improve water resistance. Introducing the hydrophobic GTS phase into the crosslinked matrix led to the formation of a bilayer-like structure, which could be tuned by changing the GTS content and the drying temperature. The microstructural evolution was revealed via scanning electron microscopy (SEM) and atomic force microscopy (AFM). Ultimately, the water vapor transmission rate (WVTR) of the coated paper was as low as 187 g/m2/24 h, which was 85.74% lower than the base paper. The key objective of this work was to develop an eco-friendly paper coating material with a good water vapor barrier for packaging applications.

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Guy, Owen J., Amador Pérez-Tomás, Michael R. Jennings, Michal Lodzinski, A. Castaing, Philip A. Mawby, James A. Covington et al. "Investigation of Si/4H-SiC Hetero-Junction Growth and Electrical Properties". Materials Science Forum 615-617 (marzo 2009): 443–46. http://dx.doi.org/10.4028/www.scientific.net/msf.615-617.443.

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Abstract (sommario):

This paper describes the growth and characterisation of Si/SiC heterojunction structures. Heterojunction structures are of interest for low on-resistance diodes and as potential solutions to fabricating SiC MOS devices with lower interface state densities. The formation of the Si/SiC heterojunction using Chemical Vapour Deposition (CVD), Molecular Beam Epitaxy (MBE), Electron Beam Evaporation under UHV conditions (EBE-UHV) and Layer Transfer (LT) are reported. The physical nature of Si/SiC structures has been investigated using scanning electron microscopy (SEM). Results of electrical characterisation of the Si/SiC heterojunctions, are also reported. Finally, thermal oxidation of a Si / SiC heterojunction structures has been performed. The C(V) characteristics of the resulting oxides are compared to conventional thermal oxides on SiC.

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Wagner, Thomas. "High temperature epitaxial growth and structure of Nb films on α–Al2O3(0001)". Journal of Materials Research 13, n. 3 (marzo 1998): 693–702. http://dx.doi.org/10.1557/jmr.1998.0087.

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Abstract (sommario):

Epitaxial Nb thin films were grown via molecular beam epitaxy (MBE) at different substrate temperatures on α–Al2O3(0001) substrates. For temperatures of 900 °C to 1100 °C, it was found that Nb grows in the Volmer–Weber growth mode (formation of three-dimensional crystallites). Depending on the growth temperature, different epitaxial orientations of Nb films can be found. At a growth temperature of 900 °C, the Nb{111} planes are parallel to the sapphire basal plane whereas at 1100 °C the Nb grows with the {110} planes on the basal plane of sapphire. These orientations are present even in the initial stages of growth at both temperatures. The formation of two different epitaxial orientations of thick Nb films can be conclusively explained only by considering both the change in the total density of Nb islands with temperature and the influence of island size on the total energy of the islands. The Nb island growth process has been investigated in situ using reflection high energy electron diffraction (RHEED) and Auger electron spectroscopy (AES). Scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM) were employed to determine the morphology and structure of Nb islands, Nb films, and Nb/α–Al2O3 interfaces.

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