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Showing papers on "Transmission electron microscopy published in 2019"


Journal ArticleDOI
TL;DR: In this article, back scattered scanning and transmission electron microscopy combined with energy dispersive X-ray spectroscopy mapping of (0.7 − x)BiFeO3−0.3BaTiO3-xNd(Zn0.5Zr0.10) ceramics revealed a core-shell grain structure which switched from a bright to dark contrast as x increased.
Abstract: Ultrahigh discharge energy density (Wdis = 10.5 J cm−3) and efficiency (η = 87%) have been obtained in doped BiFeO3–BaTiO3 ceramic multilayers by achieving an electrically rather than chemically homogeneous microstructure. Back scattered scanning and transmission electron microscopy combined with energy dispersive X-ray spectroscopy mapping of (0.7 − x)BiFeO3–0.3BaTiO3–xNd(Zn0.5Zr0.5)O3 (0.05 ≤ x ≤ 0.10) ceramics revealed a core–shell grain structure which switched from a bright to dark contrast as x increased. Compositions with x = 0.08 were at the point of cross over between these two manifestations of core–shell contrast. Dielectric measurements together with the absence of macrodomains in diffraction contrast TEM images suggested that compositions with x = 0.08 exhibited relaxor behaviour within both the core and shell regions. Impedance spectroscopy demonstrated that, despite being chemical dissimilar, the grains were electrically homogeneous and insulating with little evidence of conductive cores. Multilayers of x = 0.08 had enhanced breakdown strength, EBDS > 700 kV cm−1 and a slim hysteresis loop which resulted in large Wdis and high η which were temperature stable to <15% from 25 to 150 °C.

346 citations


Journal ArticleDOI
TL;DR: In this paper, a two-step hydrothermal method was used to synthesize a novel In2O3/In2S3 microsphere heterostructures for efficient fixation of N2 to NH3 under mild conditions.
Abstract: The synthesis of a novel In2O3/In2S3 microsphere heterostructures is conducted through a well-designed two-step hydrothermal method. These composites are first applied for efficient fixation of N2 to NH3 under mild conditions without any organic scavengers and precious-metal cocatalysts. Here the In2S3 flakes are in situ generated and uniformly assembled on In2O3 microsphere. The phase structures, morphologies and oxygen vacancies of the samples are systematically characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse-reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL), Raman, electron spin resonance (ESR) spectroscopy and photoelectrochemistry. Meanwhile, the investigation of photocatalytic performance can confirm that the nitrogen fixation rate of In2O3/In2S3 (III) heterostructure is 40.04 μmol g−1 h−1, which is about 4.7 and 6.0 times higher than that of pure In2O3 and In2S3, respectively.

162 citations


Journal ArticleDOI
TL;DR: One-dimensional (1D) ZnO nanorods were synthesized by a facile and effective hydrothermal method using the mixture of sodium dodecyl sulfate (SDS) and polyethylene glycol 400 (PEG400) with a molar ratio of 1:1 as the complex surfactant as mentioned in this paper.
Abstract: One-dimensional (1D) ZnO nanorods (ZNRs) were synthesized by a facile and effective hydrothermal method using the mixture of sodium dodecyl sulfate (SDS) and polyethylene glycol 400 (PEG400) with a molar ratio of 1:1 as the complex surfactant. The microstructure and morphology were characterized using of X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results demonstrated that the ZNRs are of a single crystal hexagonal wurtzite structure, having a larger length-to-diameter ratio with more regular surface morphology compared with the ZnO products obtained in the presence of only SDS or PEG400. A possible growth mechanism was proposed based the mediation reaction of the complex surfactant. Gas sensing measurements indicated that the ZNRs assisted by the complex surfactant demonstrated excellent ethanol sensing properties at an optimal operating temperature of 300 °C, which could be ascribed to their large length-to-diameter ratio, one-dimensional structure, and numerous surface defects of oxygen vacancies.

158 citations


Journal ArticleDOI
TL;DR: Liquid phase transmission electron microscopy reveals the growth pathway of 2D cobalt oxide and cobalt nickel oxide, in which 3D nanoparticles are formed first and then spread and transform into 2D nanosheets.
Abstract: Two-dimensional (2D) materials have attracted significant interest because of their large surface-to-volume ratios and electron confinement. Compared to common 2D materials such as graphene or metal hydroxides, with their intrinsic layered atomic structures, the formation mechanisms of 2D metal oxides with a rocksalt structure are not well understood. Here, we report the formation process for 2D cobalt oxide and cobalt nickel oxide nanosheets, after analysis by in situ liquid-phase transmission electron microscopy. Our observations reveal that three-dimensional (3D) nanoparticles are initially formed from the molecular precursor solution and then transform into 2D nanosheets. Ab initio calculations show that a small nanocrystal is dominated by positive edge energy, but when it grows to a certain size, the negative surface energy becomes dominant, driving the transformation of the 3D nanocrystal into a 2D structure. Uncovering these growth pathways, including the 3D-to-2D transition, provides opportunities for future material design and synthesis in solution. Liquid phase transmission electron microscopy reveals the growth pathway of 2D cobalt oxide and cobalt nickel oxide, in which 3D nanoparticles are formed first and then spread and transform into 2D nanosheets.

157 citations


Journal ArticleDOI
TL;DR: In this article, the phase composition of high-entropy alloy (HEA) coatings of AlCoCrFeNiTiTix was investigated using X-Ray diffraction.
Abstract: High-entropy alloy (HEA) coatings of AlCoCrFeNiTix (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were fabricated on AISI1045 steel by laser cladding. X-Ray diffraction (XRD) was used to investigate the phase composition of the coatings. The microstructure of coatings was analyzed using a scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-Ray diffraction (XRD) was used to investigate the phase composition of the coatings. The potentiodynamic polarization behaviour of coatings and substrate was studied. The composition of passive film on the corroded surface of the coating was identified by X-Ray photoelectron spectroscopy (XPS). The phase composition analysis showed that the coating was mainly composed of disordered body-centered cubic (BCC) solid solution phase (Fe-Cr) and ordered BCC phase (Al-Ni). The microstructure of the coatings was mainly composed of equiaxed polygonal grains, micro-nano particles of TiC and nanoparticles of Al2O3. The spinodal decomposition structure of Fe-Cr enrichment and Al-Ni-Ti enrichment was found in grains. The introduction of Ti led to passivation behavior of the coating during corrosion process. The components of the passive film were Al2O3, TiO2, Ti2O3, Cr2O3 and Cr(OH)3. The AlCoCrFeNiTi HEA coating showed the best corrosion resistance.

125 citations


Journal ArticleDOI
TL;DR: The laser phase plate provides a stable and tunable phase shift without electrostatic charging or unwanted electron scattering and is suggested for dose-efficient imaging of unstained biological macromolecules and cells.
Abstract: Transmission electron microscopy (TEM) of rapidly frozen biological specimens, or cryo-EM, would benefit from the development of a phase plate for in-focus phase contrast imaging. Several types of phase plates have been investigated, but rapid electrostatic charging of all such devices has hindered these efforts. Here, we demonstrate electron phase manipulation with a high-intensity continuous-wave laser beam, and use it as a phase plate for TEM. We demonstrate the laser phase plate by imaging an amorphous carbon film. The laser phase plate provides a stable and tunable phase shift without electrostatic charging or unwanted electron scattering. These results suggest the possibility for dose-efficient imaging of unstained biological macromolecules and cells.

120 citations


Journal ArticleDOI
TL;DR: In this paper, a gas sensor based on CuO has been fabricated to detect an ultra-trace H2S gas, which achieved a ppb level detection limit and showed outstanding selectivity and high sensitivity.

118 citations


Journal ArticleDOI
TL;DR: In this paper, the authors survey the competing factors that determine spatial and temporal resolution for transmission electron microscopy and scanning transmission electron microscope of liquids and discuss the effects of sample thickness, stability and dose sensitivity on spatial and time resolution.
Abstract: Liquid cell electron microscopy possesses a combination of spatial and temporal resolution that provides a unique view of static structures and dynamic processes in liquids. Optimizing the resolution in liquids requires consideration of both the microscope performance and the properties of the sample. In this Review, we survey the competing factors that determine spatial and temporal resolution for transmission electron microscopy and scanning transmission electron microscopy of liquids. We discuss the effects of sample thickness, stability and dose sensitivity on spatial and temporal resolution. We show that for some liquid samples, spatial resolution can be improved by spherical and chromatic aberration correction. However, other benefits offered by aberration correction may be even more useful for liquid samples. We consider the greater image interpretability offered by spherical aberration correction and the improved dose efficiency for thicker samples offered by chromatic aberration correction. Finally, we discuss the importance of detector and sample parameters for higher resolution in future experiments. Liquid cell electron microscopy provides a unique combination of spatial and temporal resolution, which is useful for imaging static and dynamic processes in liquids. In this Review, we discuss the resolution expected when imaging liquid specimens in transmission electron microscopy and scanning transmission electron microscopy and consider the benefits of spherical and chromatic aberration for resolution, image interpretability and dose efficiency.

110 citations


Journal ArticleDOI
TL;DR: Scanning electron nanobeam diffraction is used to monitor the morphology of organic thin films with nanometre resolution, revealing information on the arrangement of crystalline domains useful for structure–property relationship understanding.
Abstract: The properties of organic solids depend on their structure and morphology, yet direct imaging using conventional electron microscopy methods is hampered by the complex internal structure of these materials and their sensitivity to electron beams. Here, we manage to observe the nanocrystalline structure of two organic molecular thin-film systems using transmission electron microscopy by employing a scanning nanodiffraction method that allows for full access to reciprocal space over the size of a spatially localized probe (~2 nm). The morphologies revealed by this technique vary from grains with pronounced segmentation of the structure-characterized by sharp grain boundaries and overlapping domains-to liquid-crystal structures with crystalline orientations varying smoothly over all possible rotations that contain disclinations representing singularities in the director field. The results show how structure-property relationships can be visualized in organic systems using techniques previously only available for hard materials such as metals and ceramics.

101 citations


Journal ArticleDOI
TL;DR: The results showed that Fe3O4@GO@MIL-100(Fe) exhibited excellent photo-Fenton catalytic activity, achieving almost 100% of 2,4-DCP degradation within 40 min at reaction condition of 3 mmol/L H2O2, 50 mg/L 2, 4-D CP, pH 5.5 and irradiation intensity of 500 W.

97 citations


Journal ArticleDOI
TL;DR: The results show that the gap between nanorods is reduced by adding spinning carbon nitride, and the photocatalytic performance of the composite is stronger than that of single material.

Journal ArticleDOI
TL;DR: The first design and development of a low-leaching bionanostructure, easy separation and reusability of the nanocatalyst, simple work-up procedure, mild, green and environmentally friendly conditions are some important features and advantages of the present work.

Journal ArticleDOI
TL;DR: In this article, magnetic separable CoFe2O4/ZnO/Ag nanocomposites were successfully synthesized using CoFeO4 nanoparticle as core by a simple precipitate route.

Journal ArticleDOI
TL;DR: In this paper, the precipitates found in the 300 grade maraging steel built by Selective Laser Melting (SLM), which is globally one of the fastest-growing additive manufacturing (AM) technology, were investigated.

Journal ArticleDOI
TL;DR: In this article, the in-situ TiB2 reinforcement particles were prepared by the exothermic reaction of K2TiF6 and KBF4 salts in melted aluminium copper alloy which improved the hardness, yield, and tensile strengths to the extent of ∼ 89 VHN, ∼ 236 MPa and ∼ 295 MPa, respectively.

Journal ArticleDOI
TL;DR: Alkaline fuel cells and electrolyzers have attracted increasing attention from the electrochemical community, and one of their supposed advantages is their greater electrode material stability in c... as discussed by the authors.
Abstract: Alkaline fuel cells and electrolyzers have attracted increasing attention from the electrochemical community, and one of their supposed advantages is their greater electrode material stability in c...


Journal ArticleDOI
TL;DR: In this article, the peroxidase biomimetic activity of Si-CoO nanorods was investigated and a new biosensor for detection of H2O2 and reduced glutathione (GSH) in the range of 1-100 uM with a limit of 0.22 and 0.45 uM, respectively.
Abstract: Si doped CoO nanorods (denoted as Si-CoO) were prepared by the hydrothermal method. The Si-CoO composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectra (XPS), etc. The results suggest that Si element uniformly distributed onto CoO nanorods with a diameter of 50–100 nm. The as-prepared Si-CoO nanocomposite possessed an excellent peroxidase-like activity as well as quickly catalyzed the colorless substrate 3,3,5,5-tetramethylbenzidine (TMB) to be oxidized into blue oxTMB by H2O2 only in 20 s, which was easily visually observed. The electron spin resonance (ESR) data confirms that superoxide radicals (•O2–) play a key function in catalytic reaction. On the basis of the peroxidase biomimetic activity of Si-CoO, we constructed a new biosensor for detection of H2O2 and reduced glutathione (GSH) in the range of 1–100 uM with a limit of 0.22 and 0.45 uM, respectively.

Journal ArticleDOI
TL;DR: In this article, the phase structure, micro-structure and morphology of the as-prepared samples were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscope (FESEM) and the transmission electron microscopy (TEM) respectively.
Abstract: MoO3 gas-sensing materials with different Ni2+ doping concentration were prepared by a simple one-step solvothermal method. The phase structure, micro-structure and morphology of the as-prepared samples were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscope (FESEM) and the transmission electron microscope (TEM) etc., respectively. The morphology can be changed by adjusting the doping concentration of Ni2+. Among them, the 5 mol% Ni-doped MoO3 sample with a pompon-like morphology improved gas accessibility significantly. Prominently, the response of the sensors on xylene was increased 18 times from 3.48 to 62.6, the response time was about 1 s and the best selectivity was obtained at the optimum temperature of 250 °C. These breakthroughs are attributed to the increase of surface-active sites and the improvement of micro-morphology caused by Ni2+ doping.

Journal ArticleDOI
TL;DR: In this article, pure and 2% Mn, Fe and Zn doped NiO nanoparticles were synthesized by co-precipitation method at calcination temperature 550°C.

Journal ArticleDOI
07 Nov 2019
TL;DR: It can be concluded that the adsorbent proposed herein possessed high-speed and high-adsorption capacity and can be considered as promising in removing the reported dye pollutants.
Abstract: A novel mesoporous carbon nanostructured material was prepared and characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, thermogravimetry, and X-ray d...

Journal ArticleDOI
TL;DR: Hybrid ZrB2-based composite having 10% nano-sized carbon black and 20% SiC was fabricated by vacuum hot pressing at 1850'°C under 20'MPa for 60'min this article.

Journal ArticleDOI
TL;DR: The catalyst has ability to successfully convert substituted nitroarenes into desired products keeping many functionalities intact and can be stored for long time without any sign of aggregation and used multiple times without any significant loss in its catalytic activity.

Journal ArticleDOI
TL;DR: In this paper, the one dimension (1D) TiO2 nanotubes and nanorods were successfully prepared via a one-step hydrothermal method, and the structure and properties of the catalysts were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), XPS, Electron paramagnetic resonance (EPR), N2 adsorption-desorption, UV-vis diffuse reflectance and photoluminescence (PL) spectroscopy

Journal ArticleDOI
TL;DR: In this paper, a 3D net-like structure of nano-scale Fe3O4@C nanoparticles was synthesized via a facile and scalable one-pot co-precipitation followed by a subsequent carbonization in an Ar atmosphere.
Abstract: Fe3O4@C nanoparticles with a 3D net-like structure were synthesized via a facile and scalable one-pot co-precipitation followed by a subsequent carbonization in an Ar atmosphere. Verified by scanning and transmission electron microscopy characterization, it can be seen that Fe3O4 nanoparticles with the size of 10–15 nm were embedded in a uniform carbon shell with a thickness of around 2 nm. Furthermore, the corresponding XRD and EDS analysis combined with TEM images also proved that the thin carbon layer on the nano-scale Fe3O4 was amorphous. The charge/discharge tests showed that Fe3O4@C composite delivered an excellent reversible capacity of 980 mAh g−1 after 100 cycles at a current density of 92.4 mA g−1, which was much higher than that of the pure Fe3O4 (170 mAh g−1) synthesized by the same method. The outstanding reversible capacity is attributed to the small size of Fe3O4 particles and the high conductivity and mechanical strength of the amorphous carbon layer, which accelerates the electron transfer and relieves structure collapse caused by mechanical stress, thus maintaining a superior electrochemical stability.

Journal ArticleDOI
TL;DR: In this article, a sol-gel synthesis of Zn doped spinel Co1-xZnxFe2O4 (where x = 0.0, 0.1,0.2, and 0.3) was reported.
Abstract: The finely controlled nanostructured cubic spinel ferrites pave the way to synthesize nanomaterials with specific properties for particular applications. In this paper, we report sol-gel synthesis of Zn doped spinel Co1-xZnxFe2O4 (where x= 0.0, 0.1, 0.2, and 0.3) ferrite nanoparticles. X-ray diffraction confirms the single phase cubic structure of nano ferrites with average particle size estimated between 55.38 to 32.87 nm and validated by Transmission electron microscopy (TEM) results (±1). The lattice parameter was found to increase with increasing Zn doping concentration. The samples exhibit normal dielectric behaviour of Maxwell-Wagner type of interfacial polarization that decreases with increasing frequency of the applied field. Temperature-dependent magnetic properties were investigated with the aid of physical property system. The hysteresis measurements of the samples show clearly enhancement in magnetic parameters as the temperature goes down to 20 K. Tuning of magnetic properties has been witnessed as a function of doping and temperature under the influence of externally applied magnetic field, has been discussed in this paper.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed an approach for the deposition of Tungsten disulfide (WS2) films down to a few monolayers while retaining a low thermal budget compatible with potential applications in electronics as well as energy production and storage.
Abstract: Tungsten disulfide (WS2) is a semiconducting 2D material, which is gaining increasing attention in the wake of graphene and MoS2 owing to its exciting properties and promising performance in a multitude of applications. Herein, the authors deposited WSx thin films by atomic layer deposition using W2(NMe2)6 and H2S as precursors. The films deposited at 150 °C were amorphous and sulfur deficient. The amorphous films crystallized as WS2 by mild postdeposition annealing in H2S/N2 atmosphere at 400 °C. Detailed structural characterization using Raman spectroscopy, x-ray diffraction, and transmission electron microscopy revealed that the annealed films consisted of small (<10 nm) disordered grains. The approach proposed by the authors enables deposition of continuous and smooth WS2 films down to a thickness of a few monolayers while retaining a low thermal budget compatible with potential applications in electronics as well as energy production and storage, for example.Tungsten disulfide (WS2) is a semiconducting 2D material, which is gaining increasing attention in the wake of graphene and MoS2 owing to its exciting properties and promising performance in a multitude of applications. Herein, the authors deposited WSx thin films by atomic layer deposition using W2(NMe2)6 and H2S as precursors. The films deposited at 150 °C were amorphous and sulfur deficient. The amorphous films crystallized as WS2 by mild postdeposition annealing in H2S/N2 atmosphere at 400 °C. Detailed structural characterization using Raman spectroscopy, x-ray diffraction, and transmission electron microscopy revealed that the annealed films consisted of small (<10 nm) disordered grains. The approach proposed by the authors enables deposition of continuous and smooth WS2 films down to a thickness of a few monolayers while retaining a low thermal budget compatible with potential applications in electronics as well as energy production and storage, for example.

Journal ArticleDOI
TL;DR: In this paper, an area-selective atomic layer deposition (ALD) of ZnO was achieved on SiO2 seed layer patterns on Hterminated silicon substrates, using diethylzinc (DEZ) as the zinc precursor and H2O as the coreactant.
Abstract: Area-selective atomic layer deposition (ALD) of ZnO was achieved on SiO2 seed layer patterns on Hterminated silicon substrates, using diethylzinc (DEZ) as the zinc precursor and H2O as the coreactant. The selectivity of the ALD process was studied using in situ spectroscopic ellipsometry and scanning electron microscopy, revealing improved selectivity for increasing deposition temperatures from 100 to 300 °C. The selectivity was also investigated using transmission electron microscopy and energy-dispersive X-ray spectroscopy. Density functional theory (DFT) calculations were performed to corroborate the experimental results obtained and to provide an atomic-level understanding of the underlying surface chemistry. A kinetically hindered proton transfer reaction from the H-terminated Si was conceived to underpin the selectivity exhibited by the ALD process. By combining the experimental and DFT results, we suggest that the trend in selectivity with temperature may be due to a strong DEZ or H2O physisorption on the H-terminated Si that hampers high selectivity at low deposition temperature. This work highlights the deposition temperature as an extra process parameter to improve the selectivity.

Journal ArticleDOI
TL;DR: Chen et al. as mentioned in this paper provided results of a detailed microstructural characterization of a series of Ta-Nb-Mo-Cr-Ti-Al derivatives and evaluate if B2-type ordering could be the origin for the observed lack of ductility.

Journal ArticleDOI
TL;DR: In this article, different concentrations of Dy3+ doped Ca3MgSi2O8 phosphors were synthesized by solid state reaction method by using X-ray diffraction, scanning electron microscopy, TEM, and photoluminescence.