High-resolution Electron Microscopy Analysis Research Articles

Effect of simultaneous helium implantation on the microstructure evolution of Inconel X-750 superalloy during dual-beam irradiation

This study focuses on investigation into the effect of helium implantation on microstructure evolution in Inconel X-750 superalloy during dual-beam (Ni+/He+) irradiation. The 1 MeV Ni+ ions with the damage rate of 10−3 dpa/s as well as 15 keV He+ ions using rate of 200 appm/dpa were simultaneously employed to irradiate specimens at 400 °C to different doses. Microstructure characterization has been conducted using high-resolution analytical transmission electron microscopy (TEM). The TEM results show that simultaneous helium injection has significant influence on irradiation-induced microstructural changes. The disordering of γ′ (Ni3 (Al, Ti)) precipitates shows noticeable delay in dose level compared to mono heavy ion irradiation, which is attributed to the effect of helium on promoting the dynamic reordering process. In contrast to previous studies on single-beam ion irradiation, in which no cavities were reported even at high doses, very small (2–5 nm) cavities were detected after irradiation to 5 dpa, which proved that helium plays crucial role in cavity formation. TEM characterization also indicates that the helium implantation affects the development of dislocation loops during irradiation. Large 1/3 〈1 1 1〉 Frank loops in the size of 10–20 nm developed during irradiation at 400 °C, whereas similar big loops detected at higher irradiation temperature (500 °C) during sole ion irradiation. This implies that the effect of helium on trapping the vacancies can help to develop the interstitial Frank loops at lower irradiation temperatures.

The preparation of high photocatalytic activity nano-spindly Ag-BiVO4 and photoinduced carriers transfer properties

A series of nano-spindly BiVO4 and Ag-BiVO4 were synthesized by a simple solvothermal method. X-ray photoelectron spectroscopy (XPS) and high resolution electron microscopy (HRTEM) analysis indicated that the chemical state of the Ag particles was metallic Ag. Their photocatalytic activities were evaluated by the decolorization of rhodamine B (RhB) under visible light irradiation (λ>420nm). The research of photoinduced charge properties of samples studied by surface photovoltage spectroscopy (SPS) and electric field-induced surface photovoltage spectroscopy (FISPS) measurement system and the results indicated that the existence of Ag attained the enhancement of photoinduced charge carriers’ separation. This was thought to be responsible for the higher efficient photocatalytic activity of Ag-BiVO4 in the degradation of RhB.

A high-resolution analytical scanning transmission electron microscopy study of the early stages of spinodal decomposition in binary Fe–Cr

Spinodal decomposition (SD) is an important phenomenon in materials science and engineering. For example, it is considered to be responsible for the 475°C embrittlement of stainless steels comprising the bcc (ferrite) or bct (martensite) phases. Structural characterization of the evolving minute nano-scale concentration fluctuations during SD in the Fe–Cr system is, however, a notable challenge, and has mainly been considered accessible via atom probe tomography (APT) and small-angle neutron scattering. The standard tool for nanostructure characterization, viz. transmission electron microscopy (TEM), has only been successfully applied to late stages of SD when embrittlement is already severe. However, we here demonstrate that the structural evolution in the early stages of SD in binary Fe–Cr, and alloys based on the binary, are accessible via analytical scanning TEM. An Fe–36wt% Cr alloy aged at 500°C for 1, 10 and 100h is investigated using an aberration-corrected microscope and it is found that highly coherent and interconnected Cr-rich regions develop. The wavelength of decomposition is rather insensitive to the sample thickness and it is quantified to 2, 3 and 6nm after ageing for 1, 10 and 100h, which is in reasonable agreement with prior APT analysis. The concentration amplitude is more sensitive to the sample thickness and acquisition parameters but the TEM analysis is in good agreement with APT analysis for the longest ageing time. These findings open up for combinatorial TEM studies where both local crystallography and chemistry is required.

Three-Dimensional Automated Crystal Orientation and Phase Mapping Analysis of Epitaxially Grown Thin Film Interfaces by Using Transmission Electron Microscopy

As devices are miniaturized with thinner films, the electrical and magnetic properties of surfaces and interfaces in multi-layered semiconductors can affect the overall device performance (Lebedev, 2006). Therefore, it is vital to accurately analyze their interfacial properties. The absorber film adhesion and electrical properties rarely improve when they form alloys with adjacent layers (Wurz et al., 2003); however, well defined epitaxial thin films are typically uniform with steady magnetic properties (Kousuke et al., 2011). High-resolution electron microscopy (HREM) is essential for nanoscale structural characterization and chemical composition. However, HREM provides restrictive nanoscale localized information. Recently, it has been reported that a technique of automated crystal orientation and phase mapping, based on transmission electron microscopy (TEM) (similar to scanning electron microscope-electron backscatter diffraction [SEM-EBSD], TEM-EBSD), can analyze nanostructured materials for extensive structural information (Rauch et al., 2010; Moeck et al., 2011; Yoo et al., 2012). In this study, we applied a three-dimensional (3D) TEM-EBSD method to obtain more reliable structural information as a complement to energy dispersive spectroscopy (EDS) and HREM analysis combined with a tilting technique.

Au-TUD-1: A new catalyst for aerobic oxidation of cyclohexene

A new, gold-containing the 3-D amorphous mesoporous TUD-1 with different Si/Au ratios (100 and 200) was synthesized by one-step hydrothermal synthesis technique by using triethanolamine as a template. Two samples (denoted as Au-TUD-1) were characterized by means of X-ray diffraction (XRD), UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), high-resolution transition electron microscopy (HR-TEM), nitrogen physisorption and elemental analysis. The obtained characterization data confirm the formation of Au nanoparticles inside the mesopores of TUD-1 matrix. The catalytic activity of Au-TUD-1 was evaluated in the aerobic oxidation of cyclohexene at 343 K in the presence of TBHP as an initiator. The results showed that Au-TUD-1 is an active, stable and reusable catalyst; moreover, the small nanoparticles (i.e. 2–4 nm) are more catalytically efficient than the bigger nanoparticles of 6–8 nm size.

Strain study of gold nanomaterials as HR-TEM calibration standard

This work presents the use of high resolution electron microscopy (HREM) and geometric phase analysis (GPA) to measure the interplanar spacing and strain distribution of three gold nanomaterials, respectively. The results showed that the {111} strain was smaller than the {002} strain for any kind of gold materials at the condition of same measuring method. The 0.65% of {111} strain in gold film measured by HREM (0.26% measured by GPA) was smaller than the {111} strains in two gold particles. The presence of lattice strain was interpreted according to the growth mechanism of metallic thin film. It is deduced that the {111} interplanar spacing of the gold thin film is suitable for high magnification calibration of transmission electron microscopy (TEM) and the gold film is potential to be a new calibration standard of TEM.

Ultrafine Grained Structures Resulting from SPD‐Induced Phase Transformation in Al–Zn Alloys

Three different Al–Zn alloys (2, 10, 30 wt% Zn) have been processed by severe plastic deformation (SPD) in the solutionized state to investigate the concomitant mechanisms of grain refinement and phase separation. The data of high resolution analytical transmission electron microscopy clearly reveal the key role of grain boundaries that promote Zn segregation and fast diffusion. Surprisingly, it is also shown that SPD carried out at 150 °C could give rise to a finer multiphase structure comparing to room temperature processing. Our observations seem to indicate that it resulted from a competition between the classical discontinuous precipitation of Zn and SPD‐induced dynamic precipitation.

Synthesis and photoluminescence study of zinc sulfide–poly(arylene ether ketone) nanocomposite materials

Zinc sulfide (ZnS)–poly (arylene ether ketone) (PAEK) nanocomposites (NCs) were synthesized in dimethylformamide solution by carboxylic-functionalized hyperbranched PAEK (ACA-HPAEK) as surface modifier without ligand exchange. The changes in the photoluminescence (PL) of ZnS-PAEK NCs with different reaction times, zinc ion (Zn2+)/thiourea ratios, and ZnS/ACA-HPAEK ratios were investigated, aiming at producing the novel NC with distinct luminescence properties. Fourier transform infrared spectroscopy and high-resolution analytical transmission electron microscopy were used to confirm the formation of ZnS quantum dots with small particle size. Ultraviolet–visible spectroscopy and PL spectroscopy were used to characterize the luminescence properties of NCs. The results of differential scanning calorimetry and thermogravimetric analysis showed that the NCs exhibited excellent heat resistance. At last, the novel ZnS-PAEK NCs with distinct luminescence properties and excellent heat resistance were obtained.

The effect of active sites’ nature on the photo-catalytic performance of Cr-TUD-1 in the oxidation of C1–C3 hydrocarbons

Chromium-incorporating mesoporous material denoted as Cr-TUD-1 was synthesized by using a surfactant-free one-pot synthesis procedure. Samples with different chromium loading were prepared and extensively characterized by means of X-ray diffraction (XRD), UV–vis and Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), 29Si MAS NMR, high-resolution transition electron microscopy (HR-TEM), nitrogen physisorption and elemental analysis. Characterization results show that as a function of Cr loading, Cr exists in different morphological structures such as isolated tetrahedrally coordinated Cr6+, nano-particulates, and finally bulky crystalline Cr2O3. The catalytic performance of the Cr-TUD-1 samples was investigated in the gas phase photo-catalytic oxidation of a mixture of light hydrocarbons i.e. methane, ethylene, ethane, propylene, and propane by molecular oxygen. Isolated Cr6+ species were found to be more active than Cr3+. The sample with 5wt.% Cr loading which contains a mixture of Cr6+ and Cr3+ moieties was found to be the most active sample. A mechanism is proposed to show the synergy between Cr6+ and Cr3+. Cr-TUD-1 was found to be stable under dry conditions, the photocatalytic oxidation rates of the different hydrocarbons were almost the same up to six runs, however, the presence of water vapour in the reaction mixture causes serious deactivation to the catalyst. The activity of Cr-TUD-1 was superior to other metals-incorporated TUD-1 (e.g. Ti, V, and Mo) or other Cr-containing mesoporous materials (e.g. Cr-MCM-41 and Cr–SiO2) under the same reaction conditions.

Nanotextured pillars of electrosprayed bismuth vanadate for efficient photoelectrochemical water splitting.

We demonstrate, for the first time, electrostatically sprayed bismuth vanadate (BiVO4) thin films for photoelectrochemical water splitting. Characterization of these films by X-ray diffraction, Raman scattering, and high-resolution scanning electron microscopy analyses revealed the formation of nanotextured pillar-like structures of highly photoactive monoclinic scheelite BiVO4. Electrosprayed BiVO4 nanostructured films yielded a photocurrent density of 1.30 and 1.95 mA/cm(2) for water and sulfite oxidation, respectively, under 100 mW/cm(2) illumination. The optimal film thickness was 3 μm, with an optimal postannealing temperature of 550 °C. The enhanced photocurrent is facilitated by formation of pillar-like structures in the deposit. We show through modeling that these structures result from the electrically-driven motion of submicron particles in the direction parallel to the substrate, as they approach the substrate, along with Brownian diffusion. At the same time, opposing thermophoretic forces slow their approach to the surface. The model of these processes proposed here is in good agreement with the experimental observations.

Room Temperature Ferromagnetism of Magnetically Recyclable Photocatalyst of Cu1−x Mn x Fe2O4-TiO2 (0.0 ≤ x ≤ 0.5) Nanocomposites

Magnetically recyclable spinel Cu1−xMnxFe2O4 (0.0 ≤ x ≤ 0.5) ferrite nanophotocatalysts were synthesized by a simple one-pot microwave combustion method using glycine as the fuel. The synthesis process only took a few minutes to obtain CuFe2O4 nanopowders. The formation of nanocrystalline single-phase cubic spinel structure was confirmed by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), energy dispersive X-ray (EDX) and selected area electron diffraction pattern (SAED) analyses. The surface morphology of the samples consists of nearly spherical shaped nanoparticles (NPs) with agglomeration, which was confirmed by high-resolution scanning electron microscopy (HR-SEM) and high resolution transmission electron microscope (HR-TEM) analyses. The optical band gap energy (E g) was confirmed by UV-Vis diffuse reflectance spectrum (DRS) study, and the E g of undoped CuFe2O4 sample is 2.39 eV and it is increased from 2.51–2.81 eV with increasing the amount of Mn2+ content (x = 0.1–0.5), due to the decrease of particle size. The magnetic hysteresis (M– H) curve showed ferromagnetic behavior for all compositions. The magnetization (M s) of the samples monotonically increased with increasing Mn content x = 0.0–0.5. Smaller values of coercivity showed soft magnetic nature of Cu1−xMnxFe2O4 NPs. The photocatalytic degradation (PCD) of 4-chlorophenol (4-CP) under visible light using the spinel CuFe2O4 catalysts shows poor activity. Therefore, the present study leads to enhance the photocatalytic (PC) activity of spinel Cu1−xMnxFe2O4 NPs with the addition of TiO2 catalyst using the PCD of 4-CP under visible light. It was found that the coupled Cu1−xMnxFe2O4-TiO2 nanocomposite (NCs) photocatalysts exhibit excellent PC activity than that of Cu1−xMnxFe2O4 and TiO2 catalysts. The sample Cu0.5Mn0.5Fe2O4-TiO2 NCs showed greater performance than the other NCs. The enhanced PC ability of Cu1−xMnxFe2O4-TiO2 NCs could be ascribed to the interconnected heterojunction of spinel Cu1−xMnxFe2O4 and TiO2 catalysts.

Morphometric and high resolution scanning electron microscopy analysis of low-level laser therapy and latex protein (Hevea brasiliensis) administration following a crush injury of the sciatic nerve in rats

This study evaluated the effect of low-level laser therapy (LLLT; 15J/cm2) and a latex protein (F1) on a crush injury of the sciatic (ischiadicus) nerve. Seventy-two rats (male, 250g) were divided into 6 groups: CG, control; EG, exposed nerve; IG, injured nerve without treatment; LG, injured nerve with LLLT; HG, injured nerve with F1; and LHG, injured nerve with LLLT and F1. After 4 or 8weeks, the animals were euthanized and samples of the sciatic nerve were collected for morphometric and high-resolution scanning electron microscopy (HRSEM) analysis. After 4weeks, the morphometry revealed improvements in the treated animals, and the HG appeared to be the most similar to the CG; after 8weeks, the injured groups showed improvements compared to the previous period, and the results of the treatment groups were more similar to one another. At HRSEM after 4weeks, the treated groups were similar and showed improvement compared to the IG; after 8weeks, the LHG and HG had the best results. In conclusion, the treatments resulted in improvement after the nerve injury, and this recovery was time-dependent. In addition, the use of the F1 resulted in the best morphometric and ultrastructural findings.

Smart rose flower like bioceramic/metal oxide dual layer coating with enhanced anti-bacterial, anti-cancer, anti-corrosive and biocompatible properties for improved orthopedic applications

The flower like Se,Mn-HAP/ZrO2 dual layer coating on AZ91 magnesium alloy satisfies the requirements in bone cancer treatment and signifies progress in the field of implant materials.

A facile synthesis of a novel three‐phase nanocomposite: Single‐wall carbon nanotube/silver nanohybrid fibers embedded in sulfonated polyaniline

ABSTRACTA three‐phase water‐soluble nanocomposite of single wall carbon nanotube/silver nanoparticle hybrid fibers embedded in sulfonated polyaniline has been synthesized by a simple chemical solution mixing process. The nanocomposite has been characterized by high resolution electron microscopy, X‐ray diffractometry, FTIR spectroscopy, Raman spectroscopy, and thermogravimetric analysis. Optical and electrical characteristics of the nanocomposite have been determined by UV–vis absorption spectroscopy, photoluminescence spectroscopy, and four‐probe electrical conductivity measurement. A surface plasmon absorption band obtained around 460 nm indicates the presence of silver nanoparticles in the composite. The optical band gap calculation for sulfonated polyaniline vis‐a‐vis the nanocomposite supported the conductivity measurement. Over 1300 times increase in DC electrical conductivity has been observed for the three‐phase nanocomposite, with a filler loading of 20 wt %, at 306 K. This observation could be explained by Mott's variable range hopping model considering a three‐dimensional conduction. Such a nanocomposite has immense potential for use as a cathode material in lithium‐ion batteries and supercapacitors. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41692.

Preparation of nanopowders of carbides and hard-alloy mixtures applying low-temperature plasma

The preparation of nanodimensional powders of tungsten carbides, as well as other transitionmetal carbides, using plasma-chemical reduction synthesis are investigated. The main regularities of preparing powders of specified dispersity and composition are revealed. Characteristic particle sizes of carbides are 40–80 nm. In order to prepare a homogeneous mixture of WC-Co nanoparticles with an exact weight content, the procedure of deposition of cobalt on the tungsten carbide powder with the simultaneous introduction of an additive of inhibitor carbides such as carbides of chromium, vanadium, and tantalum is developed. The prepared powders were investigated using modern methods, including high-resolution scanning electron microscopy and fractional gas analysis.

New insights into the early stages of silica-controlled barium carbonate crystallisation.

Recent work has demonstrated that the dynamic interplay between silica and carbonate during co-precipitation can result in the self-assembly of unusual, highly complex crystal architectures with morphologies and textures resembling those typically displayed by biogenic minerals. These so-called biomorphs were shown to be composed of uniform elongated carbonate nanoparticles that are arranged according to a specific order over mesoscopic scales. In the present study, we have investigated the circumstances leading to the continuous formation and stabilisation of such well-defined nanometric building units in these inorganic systems. For this purpose, in situ potentiometric titration measurements were carried out in order to monitor and quantify the influence of silica on both the nucleation and early growth stages of barium carbonate crystallisation in alkaline media at constant pH. Complementarily, the nature and composition of particles occurring at different times in samples under various conditions were characterised ex situ by means of high-resolution electron microscopy and elemental analysis. The collected data clearly evidence that added silica affects carbonate crystallisation from the very beginning (i.e. already prior to, during, and shortly after nucleation), eventually arresting growth on the nanoscale by cementation of BaCO3 particles within a siliceous matrix. Our findings thus shed light on the fundamental processes driving bottom-up self-organisation in silica-carbonate materials and, for the first time, provide direct experimental proof that silicate species are responsible for the miniaturisation of carbonate crystals during growth of biomorphs, hence confirming previously discussed theoretical models for their formation mechanism.

Binder phase strengthening of WC–Co alloy through post-sintering treatment

Due to the large mean free paths of the binder phases in extra coarse and super extra coarse cemented carbides, it is necessary to strengthen the binder phase to obtain a well-matched performance of the binder phase and the WC hard phase. A nanoindentation tester, a high-resolution analytical electron microscope and an X-ray diffractometer were used in the study of the Co-based binder phase (the Co) of WC–8.4Co alloy with a grain size of 10.2μm. Specimens with four sequential treatment states, namely, as-sintered, supersolidus liquid-phase quenched, cryogenic, and tempered were analyzed. It is shown that compared with the as sintered state, the elastic modulus (EIT) and nano-indentation Vickers hardness (HV2mN) of the Co in a tempered state increase by 20.0% and 8.7%, respectively; the EIT and HV2mN of the Co in a quenched state increase by 10.1% and 6.9%, respectively. Stable WC/amorphous Co/crystal Co (fcc) interfaces, the mixture of order and disorder structure in nano-scale in the Co accompanied by the local transition of fcc to hcp structure of the Co were observed in the alloy in a tempered state.

Electrodeposition of a porous strontium-substituted hydroxyapatite/zinc oxide duplex layer on AZ91 magnesium alloy for orthopedic applications.

Magnesium alloy is a potential biomedical implant because of its outstanding biodegradability and mechanical properties. But the poor corrosion resistance of AZ91 magnesium alloy in physiological solution limits its biomedical applications. In order to improve the corrosion resistance and biological performance of AZ91 magnesium alloy, we have fabricated a strontium-substituted porous hydroxyapatite (Sr-HAP)/zinc oxide (ZnO) duplex layer on AZ91 magnesium alloy by electrodeposition. The porous Sr-HAP/ZnO duplex-layer coating on AZ91 magnesium alloy was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, high-resolution scanning electron microscopy and energy dispersive X-ray analysis. Also, the mechanical properties of the duplex-layer coating were evaluated using adhesion and Vickers micro-hardness tests. The effects of the duplex-layer coating on the corrosion behavior of AZ91 magnesium alloy were also investigated in simulated body fluid using electrochemical studies. The potentiodynamic polarization and electrochemical impedance spectroscopy results indicated that the corrosion resistance of AZ91 magnesium alloy was significantly improved by the duplex-layer coating. The in vitro cell-material interaction of the duplex-layer coating was observed with human osteosarcoma MG63 cells for cell viability at 1, 4 and 7 days of incubation and the coating exhibited good biocompatibility. Hence, from the obtained results we believe that the duplex-layer made of ZnO together with porous Sr-HAP on AZ91 magnesium alloy could provide effective corrosion protection and enhanced bioactivity. Thus, duplex-layer-coated AZ91 magnesium alloy can serve as a promising candidate for orthopedic applications.

Segregation of anion (Cl−) impurities at transparent polycrystalline α-alumina interfaces

Small amounts of anion impurities (e.g. Cl), which are incorporated during the synthesis of ceramic powders, can affect the properties and microstructure of the final sintered ceramic. The effect of anion impurities is a little studied and poorly understood phenomenon. In this work a combination of STEM-EDX analysis and atomistic modeling approach was used to understand the segregation of Cl in transparent alumina ceramics. A high resolution analytical electron microscopy study showed the presence of Cl at the grain boundaries and especially at triple points. Atomistic simulations were carried out to understand the origins and consequences of such segregation. Segregation energy calculations predict a strong segregation of Cl at the different surfaces and grain boundaries of alumina. A higher coordination number of Cl at surfaces was observed, which indicates strong ionic bonds making it difficult to remove at low temperature, which explains the presence of Cl at triple points.

FIB serial milling and lifting out of fine inclusions in an intensively melt sheared aluminum alloy

An intensively melt sheared aluminum alloy was cast to verify the possibility of heterogeneous nucleation of aluminum grains from fine oxide particles. A novel combined technique of serial milling and lifting out using the focused ion beam has detected fine particles at the grain center of aluminum. High resolution analytical electron microscopy shows that oxides can act as substrates for the nucleation of aluminum grains. Based on the observations, the possibility of survival and nucleation potency of the oxide is discussed.