Scanning And Transmission Electron Microscopy Research Articles

Effectiveness of strontium zinc phosphosilicate on the corrosion protection of AA2198-T851 aluminium alloy in sodium chloride solution

The effectiveness of strontium zinc phosphosilicate (SZP 391) as a corrosion inhibitor for the protection of Al–Cu–Li alloy in 0.5 M NaCl solution was evaluated using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation (PDP). The morphology of substrates were characterised with scanning and transmission electron microscopy (SEM) and (TEM). The corrosion rate of the substrates exposed to uninhibited solution increases with immersion time while those in inhibited solution showed significant reduction of corrosion rate. SEM and TEM revealed presence of film formed on the substrates’ surface which serves as a barrier for blocking the access of aggressive ions.

Fossilization of Precambrian microfossils in the Volyn pegmatite, Ukraine

Abstract. We report on Precambrian microfossils from igneous rocks of the Volyn pegmatite district, associated with the Paleoproterozoic Korosten pluton, northwestern Ukraine. The fossils were recovered from meter-sized miarolitic cavities and show a well-preserved 3D morphology, mostly filamentous but with a large variety of types and also in irregular, flaky shapes reminiscent of former biofilms, as well as rare spherical objects. Based on literature data, pyrolysis experiments, and reflected light microscopy results, the organic matter (OM) is characterized as (oxy-)kerite. Further investigations with microscopic techniques, including scanning and transmission electron microscopy, and electron microprobe analysis show that fossilization likely occurred during a hydrothermal, post-pegmatitic event by silicification dominantly in the outermost 1–2 µm of the microfossils. The hydrothermal fluid, derived from the pegmatitic environment, was enriched in SiF4, Al, Ca, Na, K, Cl, and S. The OM shows O enrichment in which N and S content is low, indicating simultaneous N and S loss during anaerobic oxidation. Mineralization with Al silicates starts at the rim of the microfossils, continuing in its outer parts into identifiable encrustations and intergrowths of clay minerals, feldspar, Ca sulfate, Ca phosphate, Fe sulfide, and fluorite. Breccias, formed during collapse of some the miarolitic cavities, contain decaying OM, which released high concentrations of dissolved NH4+, responsible for the late-stage formation of tobelite-rich muscovite and buddingtonite. The age of the fossils can be restricted to the time between the pegmatite formation, at ∼1.760 Ga, and the breccia formation at ∼1.49 Ga. As the geological environment for the growth of the microorganisms and fossilization, we assume a geyser system in which the essential biological components C, N, S, and P for growth of the organisms in the miarolitic cavities were derived from microorganisms at the surface. Fossilization was induced by magmatic SiF4-rich fluids. The Volyn occurrence is a distinct and uncommon example of Precambrian fossils, and the results underline the importance of cavities in granitic rocks as a possible habitat for microorganisms preserved in the deep biosphere.

Preparation of GO/GOH/MOFs ternary blend membrane and its application for enhanced dye wastewater purification

A graphene oxide (GO)/hydroxylated graphene (GOH)/MOFs porous layered cross-flow membrane was constructed using a simple vacuum filtration method. Bimetallic MOFs (FeCuBDC) was inserted into the GO nanosheets to facilitate the expansion of adjacent GO layers in the aqueous solution, which increased the interlayer spacing of the composite films. Furthermore, successful loading of GOH not only increased the interlayer spacing of the composite membrane but also improved the self-cleaning catalytic degradation effect. The blend membrane was further characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM). Loading ratios of FeCuBDC and GOH were optimized and the results showed that the GO0.8/GOH0.2/(FeCuBDC)4 membrane had a water flux 9.5 times higher than GO membrane and 1.43 times higher than GO1/FeCuBDC4 membrane. Importantly, the separation efficiency of the GO0.8/GOH0.2/(FeCuBDC)4 membrane was very high (Rhodamine B(RhB) membrane separation efficiency was 99.98%), and the interception and flux remained almost constant even after seven RhB separation cycles. This membrane can be directly used for the degradation of pollutants through persulfate activation, and showed the high degradation efficiencies of RhB(99.89%) and methylene blue (MB) (99.87%). Overall, the GO/GOH/FeCuBDC porous layered cross-flow membrane exhibited excellent separation performance, stability, and catalytic activity, and can be used as a potential membrane for water purification and environmental protection.

Analysis of the Surface Treatments Effect on the Creep Behavior of Ti-6Al-4V Alloy

Abstract This paper compares the creep behavior of Ti-6Al-4V alloy after different surface treatments, the plasma nitriding using Plasma Enhanced Chemical Vapor Deposition (PECVD), and the deposition of SiC thin films with Cr interlayer using High Power Impulse Magnetron Sputtering (HiPIMS). A microstructural characterization was performed with Scanning Electron Microscopy (SEM), Scanning and Transmission Electron Microscopy (STEM), and Energy Dispersive Spectroscopy (EDS) techniques. The creep test was performed at a constant load from 500 to 600 °C and 125 to 319 MPa, and a fractographic analysis was performed. The EDS analysis of the plasma nitrided layer indicated the nitrogen presence of the compounds TiN and Ti2N and an increase in the iron concentration. Creep test results in both conditions indicated an increase in the creep resistance. Plasma nitrided condition indicated the lowest creep rate and lesser elongation, making it the most suitable in applications that require a low dimensional distortion.

Tensile Properties of a Cast Al-Si-Mg Alloy with Reduced Si Content and Cr Addition at High Temperature

Tensile properties of an Al-Si-Mg casting alloy with reduced Si content and Cr addition were investigated at room and high temperatures. It was found that the studied alloy exhibits a remarkable performance up to 200 °C, with comparable or slightly higher strength than typical values for Al-Si-Mg-Cu alloys, commonly used for high-temperature applications, and good elongation. This is due to the choice of proper heat treatment and to the formation of dispersoids containing Cr during heat treatment, which are stable at the considered temperatures, as demonstrated by scanning and transmission electron microscopy (STEM) analysis. Interestingly, exposure to 300 °C during tensile tests enhanced an additional formation of dispersoids. It is believed that heating the material in T6 condition led to such observed dispersoids formation since precursors were already present in the Al matrix. This is not sufficient to avoid material softening at 300 °C, but it represents an interesting point in order to develop alternative heat treatment routes for dispersion-strengthened Al alloys.

Nanostructural characterization of sputter deposited Ti-Nb coatings byautomated crystallographic orientation mapping

AISI 316 L stainless steel (SS) and CrCo alloys are commonly used for manufacturing biomedical implants due to their reasonably adequate bulk properties. Commercially pure (CP) Ti and its alloys are more biocompatible, but also significantly more expensive, than SS and CoCr alloys; they have an additional advantage compared to SS and CoCr alloys: their elastic modulus values are more compatible with those of the human bones (10–40 GPa). An interesting option would be to coat an implant with a TiNb thin film having adequate composition and thickness so that the coating would enhance the material biocompatibility. In this work, TiNb coatings were deposited on AISI 316L stainless steel and silicon substrates by magnetron sputtering and then were characterized by scanning and transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) coupled with automatic crystal orientation mapping (ACOM). The results show that films form a homogenous solid solution and that the growth modes are not modified by the Nb content and substrate material. Also, the texture changes together with the grain growth morphology with the increase in the niobium content. For a columnar structure characteristic of zone II of the zone structure diagram (SZD) there are strongly marked textures in {113} for the x-axis, {110} for the y-axis, and {111} for the z axis. These are suppressed when the growth type changes for the T zone with the variation in the alloying element content, and that could be due to the high mobility generated during the deposition process.

Creep behavior evaluation and characterization of SiC film with Cr interlayer deposited by HiPIMS in Ti-6Al-4V alloy

This paper presents a study about creep behavior of SiC thin films with Cr interlayer deposited by High Power Impulse Magnetron Sputtering (HiPIMS) on Ti-6Al-4V alloys with Widmanstätten microstructure. After SiC/Cr film depositions, a microstructural characterization was performed using Scratching Test, Scanning Electron Microscopy (SEM), Scanning and Transmission Electron Microscopy (STEM), and Energy Dispersive Spectroscopy (EDS) techniques. Scratching tests showed that the film was well adhered to the substrate, which proves that the Cr interlayer is closely related to the strength of adhesion between SiC film and the substrate. The SiC film surface morphology has columnar shape according to STEM images. Creep test results were compared with earlier Ti-6Al-4V Widmanstätten microstructure studies, and they showed an increased lifetime for the Ti-6Al-4V Widmanstätten microstructure with SiC/Cr film, which indicates a higher creep resistance than the specimen without the SiC/Cr film. The SiC/Cr film deposited by HiPIMS improved the creep behavior of the Ti-6Al-4V Widmanstätten microstructure.

Analytical Electron Microscopy Investigation of Topologically Close-Packed Phases in CMSX-4 Single Crystal Superalloy

In this work the topologically close-packed phases precipitated during annealing of CMSX-4 single-crystal superalloy at temperature 1100 C were investigated. Microstructural analyses were carried out by means of scanningand transmission electron microscopy as well as scanning-transmission electron microscopy in high angle annular dark field mode. Chemical composition in nanoareas was determined using energy dispersive X-ray spectroscopy. Scanning electron microscopy investigation has shown that the topologically close-packed precipitates were formed already after 50 h of annealing at temperature 1000 C. With prolongation of the annealing time up to 2500 h the change of the morphology of topologically close-packed particles from blocky to needle-like occurred. Selected area electron diraction analysis indicated that the topologically close-packed precipitates are the orthorhombic

The Effects of Silica and A Nature Polymer on the Size and Properties of Nano-Hydroxyapatite

In this study, we compared the effects of silica and gelatin in nano hydroxyapatite (nHA) composite with pure hydroxyapatite. We have synthesized hydrothermal nHA gelatin template and silica. They (The obtained samples) were investigated by x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Scanning and transmission electron microscopy (SEM) was used for characterization of particle size and morphology of the samples. The percentage of elements in the prepared composite was determined using energy-dispersive x-ray spectroscopy (EDS). We have identified that the use of gelatin and silica as a coating agent for nHA contributes to the increase in the size of the particles.

Influence of functionalized polypropylene on polypropylene/graphene oxide nanocomposite properties

Graphene oxide (GO) derived from oxidation of natural graphite contains many active groups that can interact with a great variety of polar moieties. In this work, polypropylene (PP)/graphene oxide nanocomposites using polypropylene (PP) grafted with amine‐alcohol (PPgDMAE) as compatibilizer were prepared by two different methods. Maleic anhydride grafted PP (PPgMA) was reacted with 2‐[2‐(dimethylamine)‐ethoxy] ethanol (DMAE) in the melt for forming amine‐alcohol functionalized polypropylene (PPgDMAE). Nanocomposites were prepared by two methods. In one method, PP/GO nanocomposite was prepared by direct melt mixing in an internal batch mixer using PPgDMAE as compatibilizer. In another method, a previous mixing of PPgDMAE with GO in hot Xilene was done and then, once the solvent was evaporated, it was incorporated into PP by melt‐mixing. The microstructure and interface enhancement of the prepared composites were analyzed by Fourier transform infrared spectroscopy (FTIR), Raman, X‐ray difraction (DRX) contact angle, scanning and transmission electron microscopy (STEM), mechanical, thermal, and electrical properties measurements. Fourier transform infrared spectroscopy (FTIR) revealed the interaction between GO and PPgDMAE. The loading of GO conducted to enhance the composite mechanical properties attributed to the strong interfacial interactions between GO and PPgDMAE. A significant improvement in mechanical thermal stability and electrical properties was observed when nanocomposites were prepared by the solution blending method compared with melt mixing method. This work suggests a potential application of GO in preparation of high performance PP composites. POLYM. COMPOS., 39:1361–1369, 2018. © 2016 Society of Plastics Engineers

Synthesis of AlFe Intermetallic Nanoparticles by High-Energy Ball Milling

ABSTRACTIn this investigation, the chemical and microstructural characteristics of nanostructured AlFe intermetallic produced by high-energy ball milling have been explored. High purity elemental powders were used as the starting material. The ball milling was carried out at room temperature using a SPEX-8000 mixer/mill. The structure, morphology and compositions of the powders were obtained using X-ray diffraction patterns (XRD), scanning and transmission electron microscopy (STEM). High resolution electron microscopy observations have been used in the nanostructured materials characterization. The structural configurations have been explored through comparisons between experimental HREM images and theoretically simulated images obtained with the multislice method of the dynamical theory of electron diffraction.

The Study of Co-Doped NbC / Cr<sub>3</sub>C<sub>2</sub> on the Application of Ultrafine WC-10%Co Cemented Carbides

In this paper, ultrafine WC-10%Co cemented carbides were prepared by vacuum sintering. For inhibition of growth of WC grains during sintering, NbC and Cr3C2 were used as inhibitors. With the transformation of co-doped inhibitors content, the grain growth is inhibited and the grain size achieves 490 nm at 0.4% Cr3C2 / 0.3% NbC. The mechanism that co-doped NbC / Cr3C2 on the effective reduction of ultrafine WC-10%Co cemented carbides was analyzed. The 0.4% Cr3C2 / 0.3% NbC addition equipped with the best integrated mechanical properties was obtained in this study. And sintered samples were investigated with scanning and transmission electron microscopy (SEM).

Single-step synthesis of 3D nanostructured TiO2 as a scattering layer for vertically aligned 1D nanorod photoanodes and their dye-sensitized solar cell properties

In the present investigation we have successfully synthesized 1D vertically aligned rutile TiO2 nanorods (TNR) and 3D TiO2 nanostars (TNS) as a scattering layer by a single step hydrothermal route. The synthesized nanostructures were characterized by X-ray diffraction, scanning-and transmission electron microscopy and X-ray photoelectron spectroscopy. The 1D TiO2 nanorod and 3D TiO2 nanostar samples were further used for N-719 dye sensitized solar cells (DSSC) application. Compared to a nanorod based cell, the photovoltaic performance of the nanostars/nanorods TiO2 cell exhibits excellent DSSC performance, including superior light scattering, rapid electron transport and lower electron recombination rate. The 3D/1D TNS/TNR based DSSC cell exhibits 5.39% power conversion efficiency, which is remarkably higher than that of the bare 1D nanorod based (3.74%) photoelectrode. The detailed interface and transient properties of these nanorod and nanostar based photoanodes in DSSCs were analyzed by electrochemical impedance spectroscopy measurements and open circuit voltage decay measurements in order to understand the critical factors contributing to such high power conversion efficiency. The enhancement of the efficiency for the 3D/1D TNS/TNR photoanode based cell compared to the 1D TNR is mainly attributed to better light scattering capability, faster electron transport and lower electron recombination.

Hessian flyAvirulencegene loss-of-function defeats plant resistance without compromising the larva's ability to induce a gall tissue

Plant pathogen effectors encoded by Avirulence (Avr) genes benefit the pathogen by promoting colonization and benefit plants that have a matching resistance (R) gene by constituting a signal that triggers resistance. The Hessian fly,Mayetiola destructor (Say) (Diptera: Cecidomyiidae), resembles a plant pathogen in showing R/Avr interactions. Because of these interactions, a wheat plant with the H13 resistance gene can be resistant or susceptible depending on the genotype of the larva that attacks the plant, being resistant if attack comes from a larva with a functional vH13 gene, but susceptible if attack comes froma larva with a non-functional vH13 gene. In this study we asked: does this susceptible interaction involving plants with H13 look like susceptible interactions with plants lacking H13? Possibly, the H13 plant attacked by a larva with a non-functional vH13 is induced to partial rather than complete resistance. Or the larva, lacking its vH13-encoded effector, is compromised in its ability to induce susceptibility, which includes forcing the plant to create a gall nutritive tissue. Responses of epidermal cells to larval attack were explored using imaging techniques (light microscopy, scanning and transmission electron microscopy). Whole-organism responses were investigated by measuring the growth of plants and larvae.No evidence was found for partial resistance responses by H13 plants or for a compromise in the ability of vH13 loss-of-function larvae to induce susceptibility. It appears that disrupting vH13 function is sufficient for overcoming the induced resistance mediated by the H13 gene.

Synthesis, Growth Mechanism and Characterization of Single Crystalline α-Fe2O3 Spherical Nanoparticles

In the present report, we proposed a simple and efficient method for synthesizing single crystalline alpha-Fe2O3 spherical nanoparticles array into hexagonal dipyramid (HGDP) hierarchical structures using urea as a surface-active agent to control the growth and nucleation of the iron species. Growth mechanisms for the formation of HGDP hierarchical structures have been also proposed. Single crystalline feature, structural morphology and size of the nanoparticles were investigated by X-ray diffraction (XRD), Scanning and Transmission electron microscopy (SEM). The spectroscopic techniques such as; FT-IR, UV-VIS absorption and Raman spectroscopy were used to investigate optical response of the synthesized nanoparticles. Optical energy band gap was calculated to be 2.57 eV and 2.21 eV corresponding to direct and indirect transitions, respectively. The magnetic properties of the single crystalline nanoparticle were also investigated by Vibrating sample magnetometer (VSM) and found that they are weak ferromagnetic in nature. The values of saturation magnetization, remanent magnetization and coercivity were found to be 0.5925 emu/g and 0.1642 emu/g and approximately 1650 Oe, respectively.

Substrate Effects on the Growth of Multiwalled Carbon Nanotubes by Thermal Chemical Vapor Deposition

Chemical and Materials Engineering Department, University of Alberta, Edmonton, Alberta T6G 2V4, CanadaDifferent shapes and sizes of multiwalled carbon nanotubes (MWCNTs) were prepared by the thermal chemicalvapor deposition (CVD) process using ferrocene and toluene on conducting (cobalt/silicon), semiconducting(silicon) and insulating (quartz) substrates to investigate the change in surface morphology, microstructure andelectron “eld emission properties. The lengths and diameters of the MWCNTs were estimated from the scanningand transmission electron microscopy, revealing that although the lengths were not identical, changing withinm, there was no signi“cant change in diameter. The I

Long term cycling studies of electrospun TiO2nanostructures and their composites with MWCNTs for rechargeable Li-ion batteries

Nanofiber- and rice grain-shaped TiO2 nanostructures and their composites with functionalized multiwalled carbon nanotubes were fabricated by electrospinning and subsequent sintering process for applications in Lithium ion batteries. The fabricated nanostructures were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning-and transmission electron microscopy and surface area measurements. All nanostructured materials showed average discharge-charge plateaux of 1.75 to 1.95V. The nanofibrous- and rice grain-shaped TiO2 nanomaterials showed stable performances of 136 (± 3) mAh g−1 and 140 (± 3) mAh g−1, respectively, at the end of 800 cycles in the cycling range of 1.0–2.8 V vs.Li at a current rate of 150 mA g−1. TiO2–CNT (4 wt.%) composites showed a slightly lower capacity value but better capacity retention (8% capacity loss between 10–800 cycles). We believe that the present long term cycling materials would have wide interests in lithium ion batteries research.

Mesoporous Carbon Materials with Ultra‐Thin Pore Walls and Highly Dispersed Nickel Nanoparticles

AbstractMesoporous carbon materials with ultra‐thin carbon pore walls and highly dispersed Ni nanoparticles have been successfully prepared by using two different SBA‐15 silicas as hard templates and 2,3‐dihydroxynaphthalene (DHN) as a carbon precursor. The nickel precursor was a concentrated nickel nitrate hexahydrate [Ni(NO3)2·6H2O] solution in 2‐propanol, which was added to the carbon–silica nanocomposite prior to thermal treatment. The samples studied were analyzed by thermogravimetry (TG), nitrogen adsorption at –196 °C, powder X‐ray diffraction (XRD), Raman spectroscopy, scanning and transmission electron microscopy (STEM), and in situ electron diffraction X‐ray spectroscopy (EDX). While TG analysis revealed carbon contents lower than 30 wt.‐%, nitrogen adsorption provided information about the homogeneity of the carbon thin film deposited onto the mesopore walls of the ordered silica templates SBA‐15. The templates, carbon–silica nanocomposites, and carbon inverse replicas with nickel nanoparticles exhibit uniform pores, high surface areas, and large pore volumes. Partially graphitic carbon was identified by the presence of a characteristic G band in the Raman spectra, whereas the diffraction peak attributed to the stacking of graphene planes was not observed by powder XRD. The presence of ordered domains in the carbon materials studied was confirmed by small angle XRD and STEM imaging. In addition, the STEM images revealed that the nickel nanoparticles are uniform in size, ca. 3 nm, and are homogeneously dispersed on the tubular carbon walls. A few larger clusters of nickel, ca. 60 nm, present on the external surface, were identified by powder XRD as metallic Ni. The in situ EDX revealed that the small nanoparticles are largely composed of Ni with traces of NiO. Similar nanoparticle dispersions have been reported only for Ni‐containing multiwalled carbon nanotubes (CNTs), whereas previously reported ordered mesoporous carbon materials, CMK‐3, possess larger Ni/NiO nanoparticles.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Effect of Milling Condition on Properties and Microstructure of Copper Reinforced with 1% vol. NbC

Composites materials consisting of pure copper reinforced with 1 vol.% of NbC were prepared by the powder metallurgy route to determine the influence of the milling process on the mechanical and electrical properties. For comparative purpose different milling times at four different rotational speeds were used. The resulting powders were consolidated by hot uniaxial pressing under 90MPa for 2h at 923K to obtain materials with a fine microstructure without residual porosity. It was found that the microstructure and properties of composite materials could be principally related to the amount of Fe, Cr, C and O incorporated as impurities during the milling process. Therefore, the rotational speeds used for milling has an important influence on the properties of the final product. A lower energy-ball milling is accompanied by a smaller amount of impurities (Fe, C and O) incorporated during milling. Composites materials combine electrical conductivity above 40% IACS with high strength. A detailed microstructural analysis by scanning and transmission electron microscopy and X ray diffraction showed that these properties are related not only to NbC particles, but also to the presence of very fine particles of carbides and oxides.

The Effect of Hot Rolling on Room Temperature Ductility of a NiAl Intermetallic Compound

A Ni57Fe18Al25 alloy is produced by vacuum induction melting under an argon atmosphere and gravity cast into a copper chill mould. Ingots of 2 x 10 x 50 mm are re-heated at 1100 °C for 24 hours and hot rolled until a 25 % reduction is reached. Immediately, hot rolled plates are heat treated at 1100 °C for 1 hour and water cooled to room temperature. Microstructures of as cast, hot rolled and hot rolled plus heat treated specimens are characterized using scanning and transmission electron microscopy and x-ray diffraction. Specimens in the as-cast and hot rolled conditions show the presence of equiaxial and partially elongated β-grains, respectively, with the presence of a thin γ-phase decorating the grain boundaries. Hot rolled plus heat treated specimens have partially recrystallized β-grains with γ-phase and (Ni,Fe)3Al at the grain boundaries. The hot rolled specimens have a room temperature ductility of approximately 5 % in tensile testing. This enhancement in ductility is attributed to the modification of the β-grains by coexistence with a γ- phase along the grain boundaries.