Efficient linear phase contrast in scanning transmission electron microscopy with matched illumination and detector interferometry

Transmission electron microscopy studies of nanofibers formed on Fe7C3-carbide

Interaction of Nickel Deposits with Catalytic Metals on CoMo/Al 2O 3 Hydrodemetalation Catalysts

The Ni-Mn-Ga Ferromagnetic shape memory alloys are becoming an important element of sensor and actuator materials due to their large magnetic-field-induced strain and shape memory effect in recent years. The martensitic transformation temperature of the Heusler alloy system has been intensively studied. The Ni54.8Mn23.2Ga21.7 irregular agglomerated nanoparticles were prepared by ball milling method, and characterized by x-ray diffraction, differential scanning calorimetry and transmission electron microscopy techniques. These particles reveal a disordered non modulated face centered tetragonal structure. For the first time, nanopowder has been found to undergo a sequence of temperature-induced intermartensitic transformation in addition to the martensitic transformation on cooling. It is believed that relaxation of internal stresses is the main issue in this case. The resistivity of the material has been measured on cooling from 450 K to 300 K. It is observed that the resistivity is maximum in the nano crystalline state and it decreases substantially with decrease of the temperature. Both amorphous and nanocrystalline material coexisted in the ball-milled sample, such a nanomagnetic structure is considered to be ideal for soft nanomagnetic material.

A facile synthesis of silver nanowires and their evaluation in the mitochondrial membrane potential.

The effect of temperature on the sequence of hardening precipitates in Al–1?15Mg2Si–0?34Cu– 0?21Cr (wt-%) balanced and Al–1?14Mg2Si–0?34Cu–0?21Cr (wt-%) alloys with excess Si has been investigated by hardness measurement (HV), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) techniques. The values of microhardness which are corresponding to the hardening precipitated particles in the alloy containing excess Si are higher than that in the alloy without Si. The results showed that, the difference in the hardening precipitation peak positions may match the fact that, the excess Si increases the density of b’’ metastable phase and also, reduces the Mg/Si ratios in the early stage of GP zones and cocluster formation. After the complete formation of the metastable needle shaped precipitates b’’ takes place, the strengthening of the alloy would take place as a result of the formation of the semicoherent rod shaped precipitates b’ and/or Q’ phases.

Large‐scale high‐quality BaMoO4 nanocrystals have been synthesized in aqueous solutions under mild conditions with citrate as a simple additive. The crystals have bone‐like, spindle‐like and wheatear‐like morphologies assembled from nanoparticles, nanofibers and have been characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. The results showed that experimental parameters had great influences on the shape evolution of products. The adjustment of these parameters such as room temperature stirring time, reaction temperature and reaction time of hydrothermal reaction, can lead to obvious morphology changes of products, and the growth mechanism has been proposed. Room‐temperature photoluminescence indicated that the as‐prepared BaMoO4 nanocrystals had a strong blue emission peak at 481.5 nm. This facile route could be employed to synthesize more promising nanomaterials with interesting self‐assembly structures. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The coprecipitation technique has been used to prepare ZrO2 (Y2O3 3 mol %) nanopowder. The influence of residual NH4Cl and pH value on the crystallization of ZrO2 (Y2O3 3 mol %) nanopowder have been investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), x-ray diffraction (XRD), infrared spectrometry (IR), and transmission electron microscopy (TEM) techniques. The IR spectra proved that the presence of residual NH4Cl increased the amount of the hydroxo group. This led to serious gel agglomerate and free enthalpy decrease. Therefore, the crystallization of ZrO2 (Y2O3 3 mol%) nanopowder is greatly influenced by the residual NH4Cl. While there is no residual NH4Cl, the crystallization takes place at 445 °C and is an exothermic process. On the contrary, with NH4Cl the crystallization takes place at 376 °C and is an endothermic process. However, the pH value does not influence the crystallization of ZrO2 (Y2O3 3 mol%) nanopowder.

Gold nanoparticles (AuNPs) and reduced graphene oxide (RGO) composite modified carbon paste electrode (CPE) was prepared by electrodepositing AuNPs over the reduced graphene oxide (RGO) modified carbon paste electrode. The composite material was characterised using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques. The nano composite modified electrode was applied for the determination of total As and for the inorganic speciation of As(III) and As(V) in environmental samples. The linear dynamic range was obtained for the determination of As(III) in the present method from 1μgL−1 to 20 μgL−1 and the limit of detection(LOD) in the standard solution was found to be 0.13 μgL−1 for the 300 sec deposition time in 10 mL supporting electrolyte solution. This method was applied for the determination of As (III) in water and soil samples. The results were agreed well with the result obtained from the hydride generation atomic absorption spectrometry.

The possibility of using silver nanoparticles (AgNPs) to enhance the plants growth, crop production, and control of plant diseases is currently being researched. One of the most effective approaches for the production of AgNPs is green synthesis. Herein, we report a green and phytogenic synthesis of AgNPs by using aqueous extract of strawberry waste (solid waste after fruit juice extraction) as a novel bioresource, which is a non-hazardous and inexpensive that can act as a reducing, capping, and stabilizing agent. Successful biosynthesis of AgNPs was monitored by UV-visible spectroscopy showing a surface plasmon resonance (SPR) peak at ~415 nm. The X-ray diffraction studies confirm the face-centered cubic crystalline AgNPs. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques confirm the rectangular shape with an average size of ~55 nm. The antibacterial and antifungal efficacy and inhibitory impact of the biosynthesized AgNPs were tested against nematode, Meloidogyne incognita, plant pathogenic bacterium, Ralstonia solanacearum and fungus, Fusarium oxysporum. These results confirm that biosynthesized AgNPs can significantly control these plant pathogens.

With the aim of promoting the Ni/Ce0.8Gd0.2O2-δ (Ni/GDC20) cermet anodic performance of low temperature solid oxide fuel cell (LT-SOFC) [1], nanostructuring platinum nanoparticles on NiO/GDC composite was done by single-step wet-infiltration of hexachloroplatinic acid hexahydrate (H2PtCl6.6H2O) precursor on NiO/GDC20 composite. The anodic polarization resistance was measured using symmetric Ni–GDC20|GDC20|Pt electrolyte-supported cell at a temperature range of 400 to 600 °C. Microstructural refinement was studied by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) techniques in comparison to the bare anode before and after hydrogen reduction at 600 °C and also after anodic performance test. Nanostructuring Pt-nanoparticles with an average particle size of 12.5 nm on Ni/GDC20 anode indicated the lack of electrocatalytic enhancement with the addition of platinum for H2 oxidation reaction in LT-SOFC.

Structure and phase transformation behaviour of electroless Ni–W–P on aluminium alloy

The effect of a small addition of silicon (Si) was studied to increase the mechanical properties of Mg–Al–Sn alloys. Test specimens were produced by a vacuum die casting process which makes it possible to perform various heat treatments on the alloy which was not possible with conventional high pressure die casting (HPDC). The addition of Si leads to the formation of a binary Mg2Si phase which contributes to an increase in strength in the as-cast condition. Artificial aging treatments were performed to further increase the strength of the alloys by precipitation of fine Mg2Sn, Mg2Si, and Mg17Al12 phases. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques were used to observe these fine precipitates at different stages of the heat treatment and mechanical testing was performed to compare strength and ductility to previous magnesium alloys.

This paper presents the effects of multi‐walled carbon nanotube (MWCNT) as reinforcing agent on some properties of natural fiber/polypropylene composites. In the sample preparation, MWCNT contents and fiber types (bagasse stalk and poplar) were used as variable parameters. The composites with different MWCNT contents were fabricated by melt compounding in a twin‐screw extruder and then by injection molding. The mass ratio of the wood flour to polymer was 40/60 (w/w). The mechanical properties of composites in terms of tensile, flexural, and Izod impact strength were evaluated. The morphology of the specimens was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Based on the findings of this study, it appears that mechanical properties reached the maximum when 2.5 wt% MWCNT were used. However, addition of 3.5 wt% MWCNT could not enhance the mechanical properties considerably. TEM micrographs showed that at high level of MWCNT loading (3.5 wt%) increased population of MWCNT leads to agglomeration and stress transfer gets blocked. The mechanical properties of composites filled with poplar fibers were generally greater than bagasse stalk composites. POLYM. COMPOS., 37:3269–3274, 2016. © 2015 Society of Plastics Engineers

In scanning transmission electron microscopy (STEM), one can obtain a variety of STEM images such as bright‐field (BF) and annular dark‐field (ADF) STEM images by changing the shape of the scintillator. However, the intensity distribution of convergent beam electron diffraction (CBED) patterns at the detector plane is yet to be fully utilized. Meanwhile, direct electron detectors with fast frame rate have recently been commercialized and used in electron microscopy. Such detectors, when used for recording CBED pattern images for each STEM probe position, are called pixelated STEM detectors. With the obtained 4‐dimensional (4D) dataset, any shape of STEM detector can be synthesized in a post processing by a free selection of the integration area. Therefore, we can synthesize variety of STEM images such as differential phase contrast (DPC) and annular bright field (ABF) images, if we once record the image signal with a pixelated detector. The 4D dataset can also be used for the advanced image processing techniques such as ptychography, which has been shown to provide high efficiency for reconstructing the phase image of an object [1,2]. Using ptychography, not only the phase contrast can be enhanced but also the effect of lens aberrations to the image such as defocus can be corrected by the post processing using the information collected by a pixelated detector. Experiments were performed using an aberration corrected microscope (JEOL JEM‐ARM200F) equipped with a pixelated detector (pnDetector pnCCD), the fast direct electron detector, which can record images at a speed of 1,000 fps in a full frame mode (264 x 264 pixels). Binning or windowing can increase the speed. The camera was placed below the ADF detector to enable simultaneous recording. Figure 1 shows STEM images of a monolayer graphene obtained at 80 kV. Fig. 1a shows an ADF image obtained with the probe current of approximately 0.2 pA and the dwell time for a pixel of 0.5 ms. Because of a combination of low dose and residual uncorrected aberrations, the lattice contrast of graphene is almost buried in the noise originated from 50 Hz commercial frequency. Fig. 1b shows a reconstructed phase image using ptychography. The image contrast is significantly improved compared to the simultaneous ADF image, but the contrast transfer of the image (see the Fourier transform displayed in the inset) is anisotropic, resulting in uncertain positions of carbon atoms. This is because there remains large two‐fold astigmatism and defocus in the image shown in Fig. 1(b), because we could not adjust those by observation of the ADF image due to the weak image signal. Fig. 1c is a phase image in which the aberrations are corrected through post processing using the same 4D dataset by applying correction functions in the spatial frequency domain. The image is no longer anisotropic and the carbon atomic positions can be unambiguously determined. Although the same amount of electron dose is used to form the ADF and the corrected phase images, the result clearly shows the benefit of ptychographic phase reconstruction in improving image signal to noise and being able to correct aberrations through post processing. Figure 2 shows the ptychographic phase maps of the 4D dataset at a certain spatial frequency. With an aberration‐free electron probe, they would be flat phase on the two sidebands, and the phase difference between the bands be π. In Fig. 2a, the map of the original dataset, there is a phase gradient inside each sideband because the aberrations were present in the electron probe. Fig. 2b is the correction function that compensates for the aberration seen in Fig. 2a. Fig. 2c is the corrected phase map and corresponding to the image in Fig. 1c. Here, only defocus and two‐fold astigmatism are corrected but corrections of other higher order aberrations are in principle possible. Figure 3 shows through focus images created in the same way as above. As we know the full information on the electron wave at the condenser aperture plane, we can induce any aberrations such as defocus.

The influence of annealing temperature and time on solute carbon levels was investigated in four ultralow-carbon (ULC) bake-hardenable steels; two Ti-V ULC steels with different V/C levels and two Ti-Nb ULC steels with different Nb/C levels. Internal-friction and scanning transmission electron microscopy (STEM) techniques were used to understand the precipitation/dissolution behavior in the various steels. An effect of annealing time on the carbon Snoek-peak height was observed in both Ti-V steels and in the Ti-Nb steel having a lower Nb/C ratio. Despite differences between these steels resulting from their composition (and, thus, carbide solubility) differences, after cold rolling and annealing at different temperatures, the maximum Snoek-peak height was achieved after annealing for shorter times in each instance, on the order of 1 minute. The highly stabilized Ti-Nb ULC steel with a higher Nb/C ratio did not show the effect because of the absence of solute carbon. For the Ti-V steels, most of the precipitates examined using STEM contained both Ti and V. The energy-dispersive X-ray (EDX) analysis indicated that both the Ti-V steels annealed at 845 °C for 1 minute have greater Ti/V ratios compared to their corresponding Ti-V steels in the as-received (hot-rolled) condition. This behavior is consistent with dissolution of carbides causing the carbon in solution to increase, as indicated by a greater carbon Snoek-peak height for both Ti-V steels in the annealed condition. The reduction in Snoek-peak height at longer annealing times is believed to be associated with segregation to lower-energy defect sites.