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Friedreich's ataxia (FRDA) is the most common inherited form of ataxia in humans. It is caused by severe downregulation of frataxin (FXN) expression instigated by hyperexpansion of the GAA repeats located in intron 1 of the FXN gene. Despite numerous studies focused on identifying compounds capable of stimulating FXN expression, current knowledge regarding cis-regulatory elements involved in FXN gene expression is lacking. Using a combination of episomal and genome-integrated constructs, we defined a minimal endogenous promoter sequence required to efficiently drive FXN expression in human cells. We generated 19 constructs varying in length of the DNA sequences upstream and downstream of the ATG start codon. Using transient transfection, we evaluated the capability of these constructs to drive FXN expression. These analyses allowed us to identify a region of the gene indispensable for FXN expression. Subsequently, selected constructs containing the FXN expression control regions of varying lengths were site specifically integrated into the genome of HEK293T and human-induced pluripotent stem cells (iPSCs). FXN expression was detected in iPSCs and persisted after differentiation to neuronal and cardiac cells, indicating lineage independent function of defined regulatory DNA sequences. Finally, based on these results, we generated AAV encoding miniFXN genes and demonstrated in vivo FXN expression in mice. Results of these studies identified FXN sequences necessary to express FXN in human and mouse cells and provided rationale for potential use of endogenous FXN sequence in gene therapy strategies for FRDA. [ABSTRACT FROM AUTHOR]

In order to develop an effective and environment‐friendly method for selective adsorption of Li+, a recyclable polysulfone surface graft 4'‐aminobenzo‐12‐crown‐4‐ether (PSf‐sg‐AB12 C4) membrane was prepared via non‐solvent induced phase separation method and in situ surface grafting through nucleophilic substitution. The surface chemical compositions and the morphologies of the PSf‐sg‐AB12 C4 were systematically verified by X‐ray photoelectron spectra (XPS) and scanning electron microscopy (SEM). The dynamic adsorption process of PSf‐sg‐AB12 C4 for Li+ was well described by the pseudo‐second‐order kinetics model, and the maximum equilibrium adsorption capability was 51.99 mg⋅g‐1. Moreover, the PSf‐sg‐AB12 C4 membrane displayed good selectivity for Li+, meanwhile the selective separation factors (α) of Li+ to K+, Na+, Ca2+ and Mg2+ were 38.43, 33.13, 27.11 and 3.42, respectively. These selective adsorption results were verified by the density functional theory (DFT) calculations. Additionally, the regenerated adsorption amount of the PSf‐sg‐AB12 C4 toward Li+ after 10 cycles of adsorption/desorption was 90.37% of initial adsorption cycle. [ABSTRACT FROM AUTHOR]

Abstract: Hexagonal WO3 nanorods of 5–50 nm in diameter and 150–250 nm in length have been synthesised in gram quantities by a low temperature hydrothermal route using citric acid as a structural modifier and hexadecylamine as a templating agent. The ratio of [A]/[W] play an important role on WO3 nanorods formation. These WO3 nanorods were found highly suitable as a precursor for the synthesis of a good yield of multiwalled WS2 nanotubes by reducing them with H2S at 840 °C for 30 min. The length and the wall thickness of the WS2 nanotubes could be altered by controlled reduction of the oxide precursor. The morphology, structure and the composition of the WO3 nanorods and WS2 nanotubes were characterised by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX) and by selected area electron diffraction techniques (SAED). [Copyright &y& Elsevier]

Crystallization determines the programming speed of phase‐change memory devices; while, the nucleation phenomenon of many phase‐change materials (PCMs) is not entirely understood, especially concerning the atomic structures and dynamic behaviors of the subcritical nuclei. This is undoubtedly an insurmountable challenge for scandium antimony telluride (ScxSb2Te3) PCM as its subnanosecond‐crystallization nature impedes the real‐time observation of the transient nucleation process. To solve the puzzle, atomic probe tomography and transmission electron microscopy are employed to circumvent the technical difficulties; for the first time, the atomistic information of the heterogeneous nuclei in ScxSb2Te3 is unveiled, such as enriched Sc ≈ 25 at% in core composition, ≈1.0 nm in geometric size, and ≈1023–1024 m−3 in spatial density. The unique nanoscale chemical inhomogeneity ensures the unusual stabilities and dynamics of the early‐stage nuclei, reinforcing them to survive the melt‐quenching action and greatly suppressing the nucleating randomness, thereby facilitating simultaneous and prompt crystal growth throughout the amorphous phase to achieve ultrafast crystallization. The present study offers a new insight into the nonclassical pathways, which will improve understanding and promote better regulation of the nucleation phenomenon in functional materials. [ABSTRACT FROM AUTHOR]

Based on the selectively complexing properties of crown ethers for metal ions, a chitosan-graft-benzo-15-crown-5 ether (CTS-g-B15C5)/non-woven fabric (NWF) composite membrane with sponge-like pore structure was prepared. A flow-through dynamic adsorption method was used to investigate the adsorptive separation performance for Pd2+. The thermodynamic analysis revealed that Pd2+ adsorption on the composite membrane was a spontaneous procedure in which the high temperature would benefit the adsorption. Moreover, the composite membrane showed excellent reusability after regeneration, and there was no obvious loss of adsorption amount after five cycles. Finally, the CTS-g-B15C5/NWF composite membrane retained high selectivity for Pd2+ in simulated nuclear wastewater. [ABSTRACT FROM AUTHOR]

Fourier ptychographic microscopy is a simple and effective computational imaging method that improves the spatial bandwidth product of the system. Its principle is to realize the aperture expansion by using a phase retrieval algorithm to splice a set of low-resolution images under different illumination angles in the Fourier domain. However, the long periods of time required for the data acquisition limit its application. Therefore, we propose a new adaptive FP algorithm to significantly reduce the volume of data acquired using the information entropy of the image as a judgment function, and a special separation strategy as a judgment method to estimate the information distribution of a high-resolution sample from a specific low-resolution image. Further, the effectiveness and superiority of our method are verified via simulations and experiments. The results show that the volume of data acquired can be reduced by more than 60% without any deterioration in resolution and quality of the recovered image. [ABSTRACT FROM AUTHOR]

The enhanced mechanical properties of Ni-based single-crystal superalloys induced by refractory elements such as Re, Wo, Mo, etc. are essential for the manufacture of advanced aero engines' turbine blades. Whereas these elements could promote the formation of the topologically close-packed (TCP) phases, and their growth would have a deleterious effect on the creep rupture life of single-crystal superalloys. Concomitantly, the formation of the brittle phase of the internal nitrides, especially the aluminium nitride (AlN), would be detrimental to superalloys as well. Nonetheless, the formation relationship between AlN and TCP phases has maintained opaque. In this study, the relationship between the TCP phase and AlN phase was analysed by microscopic methods, such as BSE, TEM and EDS. An AlN phase located near the TCP phase in the deep surface of the superalloy was found, and its formation was suggested to be related to nitrogen penetration during the thermal exposure. This accompanying growth of the AlN phase and TCP phase in the deep surface could provide a new perspective on the formation mechanism of these brittle phases in the Ni-based single-crystal superalloys. [ABSTRACT FROM AUTHOR]

Via in situ transmission electron microscopy, we observed on nanoscale unconventional structural evolution during two-dimensional (2D) phase transitions in a Sb 2 Te 3 /TiTe 2 phase-change heterostructure (PCH), which reduces amorphous relxation and crystallization stochasiticity to facilitate rapid and reliable memory programming. [Display omitted] Phase-change heterostructure (PCH) holds great promise for overcoming the low-precision bottleneck that limits multibit storage and parallel computing in conventional phase-change random-access memory. However, the origin of high-accuracy control of electrical resistance achieved in programming PCH memory devices has yet to be established. Via in situ transmission electron microscopy, here we unveil the unusual microscopic processes during the order–disorder phase transitions driven by electrical pulse in a Sb 2 Te 3 /TiTe 2 PCH architecture. The template-modulated phase transition is confirmed to be two-dimensional (2D) in nature. The structural transformation path and dynamics in the confined Sb 2 Te 3 sublayers are found to be profoundly changed with respect to those in bulk monolithic Sb 2 Te 3 , leading to markedly suppressed amorphous relaxation and substantially reduced crystallization stochasticity, both highly desirable for swift and accurate device operations. Our atomic-scale observations provide direct evidence of, and much-needed insight into, the working mechanisms that may enable superior 2D phase-change electronic devices. [ABSTRACT FROM AUTHOR]

Both Sn addition and pre-ageing are known to be effective in maintaining the artificial ageing potential after natural ageing of Al–Mg–Si alloys. In this study, the combined effects of Sn addition and pre-ageing at 100 °C or 180 °C on natural secondary ageing and subsequent artificial ageing of an alloy AA6014 were investigated using hardness, electrical resistivity, differential scanning calorimetry and transmission electron microscopy characterizations. It is found that pre-ageing can suppress natural secondary ageing and improve the artificial ageing hardening kinetics and response after 1 week of natural secondary ageing in both alloys with and without Sn addition. The effect of pre-ageing at 100 °C is more pronounced in the Sn-free alloy while the combination of pre-ageing at 180 °C and adding Sn shows superiority in suppressing natural secondary ageing and thus avoiding the undesired hardening before artificial ageing. Moreover, when natural ageing steps up to 8 h are applied before pre-ageing at 100 °C, the effect of pre-ageing in Sn-added alloy can be further improved. The influence of Sn on vacancies at different ageing temperatures is discussed to explain the observed phenomena. [ABSTRACT FROM AUTHOR]

Abstract: High-purity zirconium trisulfide (ZrS3) and hafnium trisulfide (HfS3) nanobelts with maximal length of 2–5 mm have been successfully synthesized through a chemical vapor transport (CVT) process. XRD results show that ZrS3 and HfS3 crystallize in the monoclinic system. SEM images reveal that ZrS3 and HfS3 nanobelts have thickness ranging from 60 to 120 nm, and HRTEM images and ED patterns confirm that [100] is the dilated direction and [010] is the elongated direction for both the trisulfide nanobelts. The formation of these trisulfide nanobelts is interpreted by a vapor-solid mechanism. The results of Raman scattering show that a slight red shift and peak broadening are observed relative to those of large crystals, which may be induced by the phonon confinement effect. [Copyright &y& Elsevier]

Abstract: Crystalline ZrO2 nanoparticles were prepared from zirconium isopropoxide by slow hydrolysis and subsequent hydrothermal treatment of solutions containing various amounts of sodium hydroxide at 180°C. Whereas moderately basic solutions lead to the formation of nanoparticles of monoclinic ZrO2 with plate-like morphology, and nanoparticles of the cubic ZrO2 high-temperature polymorph with diameters of approx. 5nm were obtained from strongly basic solutions. The morphology, structure and properties of as-synthesized nanoparticles were characterized using HRTEM, XRD, Raman spectroscopy, UV–vis, PL spectroscopy and BET measurements. The formation of both, the monoclinic and the cubic polymorph, was confirmed by electron microscopy and Raman spectroscopy. The crystallinity and morphology of the resulting ZrO2 nanoparticles can be adjusted by the choice of the reaction conditions. The cubic ZrO2 nanoparticles have a high surface area (300m2/g) and exhibit a strong photoluminescence in the UV region. [Copyright &y& Elsevier]

We report on the preparation and structural characterization of CdSe nanocrystals, which are covered by a multishell structure from CdS and ZnS. By using the newly developed successive ion layer adhesion and reaction (SILAR) technique, we could gradually change the shell composition from CdS to ZnS in the radial direction. Because of the stepwise adjustment of the lattice parameters in the radial direction, the resulting nanocrystals show a high crystallinity and are almost perfectly spherical, as was investigated by X-ray diffraction and electron microscopy. Also, due to the radial increase of the respective valence- and conduction-band offsets, the nanocrystals are well electronically passivated. This leads to a high fluorescence quantum yield of 70-85% for the amine terminated multishell particles in organic solvents and a quantum yield of up to 50% for mercapto propionic acid-covered particles in water. Finally, we present experimental results that substantiate the superior photochemical and colloidal stability of the multishell particles. [ABSTRACT FROM AUTHOR]

Power level control is one of the critical functions in the instrument and control system of nuclear power plants (NPPs). In most power level control systems of NPPs, the power level or average neutron flux in reactor cores provided by out-of-core neutron sensors are usually measured as feedback of power control systems, while, as critical measuring devices, there is a risk of damage to out-of-core neutron sensors. For improving the operation reliability of NPPs under the neutron sensors' failure, a power control system based on power observer is developed in this work. The simulation based on NPP simulator shows the power control system based on the observer is effective when neutron sensors fail. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) transition metal dichalcogenides (TMDs) possess a variety of polymorphs that exhibit distinctive atomic and electronic structures and the consequent material properties. Hence, exploiting the dynamics of phase transition between different polymorphs will lay a foundation toward controlled phase engineering based applications. In this Letter, we reported a solid-state approach to realize the H to T′ transition in monolayer molybdenum disulfide in situ inside a transmission electron microscope. The release of lithium ions and the subsequent lithiation were driven by energetic electron beam irradiation, both of which in turn triggered the H to T′ phase transition of the object monolayer MoS2. The as-formed T′ phase domains showed a random nucleation behavior. Interestingly, the reverse process, i.e., T′ back to H phase transition, caused by prolonged e-beam illumination, was also captured in situ. During both phase transformation processes, i.e., H → T′ and T′ → H, we did not observe any large area T phase existing in monolayer MoS2. Our results will be instructive to elucidate the microscopic mechanisms of the phase transition and should also be extendable to other 2D TMD materials. [ABSTRACT FROM AUTHOR]

The development of new materials with hierarchical frameworks and tailored band structures is an attractive approach to efficiently photocatalytic hydrogen evolution. Here, we report a visible-light active calcium titanate (CaTiO 3) photocatalyst with a hierarchical architecture constructed from single crystal nanowires, which was prepared by a one-pot hydrothermal reaction using polyvinyl alcohol (PVA) as structure directing agent. The hierarchical structure of the CaTiO 3 samples involved single-crystal nanowires growing respectively along the [110], [1 1 ¯ 0] and [001] direction and intersecting each other perpendicularly which further featured a high specific surface area and oxygen vacancies. This material was able to split water into H 2 under visible light irradiation. It was found that oxygen vacancies formed an impurity level at an energy level 0.95 eV below the conduction band acted as electron donors and promoted charge transport and separation. • A visible-light active CaTiO 3 photocatalyst was prepared by hydrothermal way • The bandgap of CaTiO 3 photocatalyst was narrowed by oxygen vacancies • The sample showed a hierarchical single-crystal like structure formed by nanowires [ABSTRACT FROM AUTHOR]

Technologically important mechanical properties of engineering materials often degrade at low temperatures. One class of materials that defy this trend are CrCoNi-based medium- and high-entropy alloys, as they display enhanced strength, ductility, and toughness with decreasing temperature. Here we show, using in situ straining in the transmission electron microscope at 93 K (−180 °C) that their exceptional damage tolerance involves a synergy of deformation mechanisms, including twinning, glide of partials and full dislocations, extensive cross-slip, and multiple slip activated by dislocation and grain-boundary interactions. In particular, massive cross-slip occurs at the early stages of plastic deformation, thereby promoting multiple slip and dislocation interactions. These results indicate that the reduced intensity of thermal activation of defects at low temperatures and the required increase of applied stress for continued plastic flow, together with high lattice resistance, play a pivotal role in promoting the concurrent operation of multiple deformation mechanisms, which collectively enable the outstanding mechanical properties of these alloys. [ABSTRACT FROM AUTHOR]

Abstract It is very challenging to synthesize perovskite oxides with controlled morphology and defect states at the same time. In this work, the BaZrO 3 hollow nanostructures with oxygen vacancies were facilely synthesized through one-step solvothermal method using ethylenediamine (EDA) as solvent. The as-synthesized BaZrO 3 could split pure water into H 2 without addition of sacrificial agent under UV light irradiation. The photocatalytic H 2 production rate is about 15 times than that of the commercial BaZrO 3 (BZO-C). It is believed that the presence of oxygen vacancies and the hollow morphology made contribution to the improvement of photocatalytic performance. This work provides a reference for microstructure and defect modification of photocatalysts at the same time to enhance the photocatalytic performance. Highlights • The BaZrO 3 with hollow structures and oxygen defects was one-step synthesized. • The as-obtained BaZrO 3 shows increased photocatalytic activities in pure water. • The special morphology and defects contribute to the improvement of properties. • The hollow structures and defects result from the presence of EDA in the reaction. • This work provides a reference for microstructure and defect modification. [ABSTRACT FROM AUTHOR]

Facet engineering to expose specific surfaces has received rapid growth attention to promote the photocatalytic performance. In this work, we reported that BaZrO3 nanocrystals with {001}/{011} facets and corresponding higher reducing capacity could effectively improve the photocatalytic hydrogen evolution in pure water. The tuned electronic band structure arising from exposed specific {001}/{011} facets and the higher surface area are the main reasons to promote photocatalytic activity. The conduction band bottom for BaZrO3 nanocrystals with {001}/{011} facets synthesized by solvothermal method (denoted as BZO-HT) is about 0.31 eV higher than that of sample prepared by hydrothermal reaction (denoted as BZO-H). During the evaluation of photocatalytic activity in pure water, the H2 production rate for BZO-HT (27.80 μmol/g/h) is 9.4 times and six times higher than BZO-H and commercial BaZrO3 (denoted as BZO-C), respectively. This work provides a reference for other facets-related photocatalysts’ design for pure water reduction or splitting. [ABSTRACT FROM AUTHOR]

Highlights • A simple and efficient approach to acquire the charge distribution in TEM • Direct inspection of charge and fast response to charge variations • Mapping charge density in quantitative way with a high sensitivity Abstract Mapping the charge distribution in nano scale systems still is a difficult task, but is important to provide fundamental insights into the properties of materials. We demonstrate how in-line holography in transmission electron microscopy can be used to extract the charge distribution in the nanowire in a quantitative way. This technique can realize a fast acquisition of delicate charge variations. By taking advantage of the possibilities of in-situ electron microscopy, variations of the external field can be used to modulate the charge distribution. Because of the fast response to charge variations, this method provides an efficient probing tool for detecting dynamic charge redistribution. [ABSTRACT FROM AUTHOR]

The distribution of Rhenium (Re) in a Ni-based single-crystal superalloy is studied by sub-angstrom resolution transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). It is found that Re atoms segregate at the tensile stress regions near the interfacial dislocation cores, forming the “Cottrell atmosphere”, and the segregation process is facilitated by dislocation pipe diffusion. In situ TEM and scanning electron microscopy (SEM) straining studies reveal that the Re-decorated dislocation networks along the phase boundaries act as mechanical walls that effectively block dislocation motion and crack propagation. Furthermore, the degree of Re segregation can be regulated by thermal treatment. Theoretical analysis demonstrates that this remarkable alloying effect originated mainly from the interactions between the local composition strain of Re and the dislocation strains, leading to significantly stabilized interfacial dislocation networks. These results provide a new perspective on understanding the origin of the Re effect on mechanical properties in Ni-based superalloys and will be beneficial to both improving creep properties of Ni-based superalloys and designing high-performance Re-free superalloys. [ABSTRACT FROM AUTHOR]

As a photocatalyst, barium titanate (BaTiO 3 ) has shown a great potential in photocatalytic water splitting for hydrogen evolution. In this work, BaTiO 3 nanoparticles were synthesized at room temperature conditions under ambient pressure. The small particle size below 10 nm plays a key role in suppressing the recombination of photo-induced carriers, and thus promoting the photocatalytic activity. The photocatalytic hydrogen evolution rates of BaTiO 3 (BTO-R) synthesized at room temperature are 8 and 2.9 times that of commercial BaTiO 3 (BTO-C) in the presence and absence of triethanolamine (TEOA) as a sacrificial agent, respectively. This work provides a good example on size control, low-cost synthesis and photocatalysts' design. [ABSTRACT FROM AUTHOR]

Visible-light-responded BaZrO 3 hollow nanostructure with Fe (III) doping was prepared through facile solvothermal reaction using ethanediamine (EDA) as solvent. Fe doping in BaZrO 3 as an efficient way of reducing its wide band gap (∼4.96 eV) is realized in order to achieve visible light response. The corresponding trapping center introduced by Fe 3+ doping contributes to the lower recombination of photo-induced holes and electrons. Meanwhile, the special hollow structure with larger specific area is also a key factor to increase optical absorption, charge carrier migration rate and redox reaction sites. Hence, the participation of Fe and hollow nanostructure are responsible for the visible-light-driven photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

Most mechanisms used for strengthening crystalline materials, e.g. introducing crystalline interfaces, lead to the reduction of ductility. An additive manufacturing process – selective laser melting breaks this trade-off by introducing dislocation network, which produces a stainless steel with both significantly enhanced strength and ductility. Systematic electron microscopy characterization reveals that the pre-existing dislocation network, which maintains its configuration during the entire plastic deformation, is an ideal “modulator” that is able to slow down but not entirely block the dislocation motion. It also promotes the formation of a high density of nano-twins during plastic deformation. This finding paves the way for developing high performance metals by tailoring the microstructure through additive manufacturing processes. [ABSTRACT FROM AUTHOR]

Abstract The dynamics of oxidation of cobalt nanoparticles were directly revealed by in situ environmental transmission electron microscopy. Firstly, cobalt nanoparticles were oxidized to polycrystalline cobalt monoxide, then to polycrystalline tricobalt tetroxide, in the presence of oxygen with a low partial pressure. Numerous cavities (or voids) were formed during the oxidation, owing to the Kirkendall effect. Analysis of the oxides growth suggested that the oxidation of cobalt nanoparticles followed a parabolic rate law, which was consistent with diffusion-limited kinetics. In situ transmission electron microscopy allowed potential atomic oxidation pathways to be considered. The outward diffusion of cobalt atoms inside the oxide layer controlled the oxidation, and formed the hollow structure. Irradiation by the electron beam, which destroyed the sealing effect of graphite layer coated on the cobalt surface and resulted in fast oxidation rate, played an important role in activating and promoting the oxidations. These findings further our understanding on the microscopic kinetics of metal nanocrystal oxidation and knowledge of energetic electrons promoting oxidation reaction. [ABSTRACT FROM AUTHOR]

The rational design of catalytic materials from the reaction characteristics is expected to be a useful strategy to create highly efficient catalysts. Herein, according to a well-established reaction pathway of epoxide hydration catalyzed a dual-molecular system of Co3+/salen in which a high concentration of active sites is favorable to enhance the activity, we provide an alternative way to prepare a highly efficient heterogeneous catalyst with a high concentration of Co3+/salen from the polymerization of vinyl-functionalized salen monomers followed by the loading of Co3+ species (Co3+/POL-salen). Co3+/POL-salen has a hierarchical porosity and an extraordinary hydrothermal stability. Importantly, catalytic tests in epoxide hydration demonstrate that Co3+/POL-salen affords excellent high activities, which are even better than those of the homogeneous version. This phenomenon is related to the very high concentration of Co3+/salen in the catalyst. In addition, this catalyst can be recycled readily because of its excellent hydrothermal stability. [ABSTRACT FROM AUTHOR]

Oxidation induced phase transformation from γ′ to γ phase can severely degrade creep properties of superalloys and has been studied by in-situ environmental transmission electron microscopy, energy dispersive spectrometer and electron energy loss spectroscopy in detail. The in-situ observation showed that, during oxidization, the ordered γ′ phase (L1 2) gradually transformed to disordered γ phase (face-centered cubic (fcc)) with the appearance of oxidation product consisted of γ-Al 2 O 3 crystallites with a strong crystallographic texture. This directly proves that γ′-γ phase transformation are induced by aluminum oxidation with aluminum depleted in γ′ phase. Furthermore, the oxygen was demonstrated to diffuse preferentially through γ′-γ phase interface which is different from previously thought (γ matrix). [ABSTRACT FROM AUTHOR]

Here, we investigate a new type of kink structure that is found at γ/γ′ interfaces in nickel-based single crystal superalloys. We studied these structures at the atomic and elemental level using aberration corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The core of the dislocation absorbs high-Z elements (i.e., Co and Re) that adopt hexagonal arrangements, and it extrudes elements (i.e., Ni and Al) that adopt face centered cubic (fcc) structures. High-Z elements (i.e., Ta and W) and Cr, which is a low-Z element, are stabilized in body centered cubic (bcc) arrangements; Cr tends to behave like Re. High-Z elements, which migrate and adopt a hexagonal structure, induce kink formation at γ/γ′ interfaces. This process must be analyzed to fully understand the kinetics and dynamics of creep in nickel-based single crystal superalloys. [ABSTRACT FROM AUTHOR]

The oxidation of ZrB2 nanoparticles was observed at high temperature of 1500°C under low oxygen partial pressure of 5 × 10−2 Pa by an environmental transmission electron microscope. The results demonstrate that the oxidation starts on the surface of ZrB2 nanoparticles with decomposition of ZrB2 into ZrO2 and B2 O3. The nucleation and growth of ZrO2 on the surface of ZrB2 proceed with B2 O3 being evaporated. [ABSTRACT FROM AUTHOR]

Highlights: [•] The structure of Al20Cu2Mn3 with a space group of Bbmm is completely determined. [•] The actual formula of Al20Cu2Mn3 is Al31Cu3Mn5. [•] Al20Cu2Mn3 is formed by a parallel tessellation of hexagon subunits. [•] Al20Cu2Mn3 is prone to twinning by an alternate tessellation of hexagon subunits. [•] The Al20Cu2Mn3 is coherent with α-Al along its longitudinal axis. [Copyright &y& Elsevier]

Abstract: A novel flat-peach-like ZnO has been synthesized by hydrothermal method. The obtained ZnO is twined flat-peach-like structure with about 4μm in diameter and 2μm in thickness, which is a new member of the ZnO family. XRD, TEM, SEM, RS, SAED, EDX and Photocurrent spectra are employed to characterize the crystal phase, morphologies, the chemical compositions, and photocurrent properties of the ZnO microstructure. The experimental results show the as-prepared ZnO is single-crystalline structure and the reaction time plays a key role in modulating the morphology of ZnO. And the growth mechanism of ZnO is tentatively investigated. Furthermore, the flat-peach-like ZnO exhibits larger photocurrent intensity than the plate-like one in the 300–450nm region. [Copyright &y& Elsevier]

Abstract: Humidity sensors based on K-doped mesoporous silica SBA-15 were prepared and characterized by XRD, SEM, TEM and N2 adsorption-desorption isotherms. The humidity sensing test results show that KCl doping improves the sensing characteristic of humidity sensors. The optimal result is obtained via sample 50wt% KCl-doped SBA-15, which exhibits an excellent linearity in the whole humidity range of 11%-95%. It also shows satisfactory reversibility and fast responses to the environmental moisture. The investigation of the humidity sensitive characteristics of the K-doped SBA-15 sensor shows that this material could have good prospects of application in humidity sensor. [Copyright &y& Elsevier]

High quality self-assembled ZnS mesoporous nanospheres have been successfully synthesized by a facile solvothermal method. The sample was synthesized using ethylene glycol aqueous solution without any surfactant assistance. Size and shape control of the ZnS mesoporous nanospheres is achieved by simple adjustments of the reactants' concentration. Investigation results show that ZnS spheres are made up of small ZnS nanocrystallites and show good photocatalytic activity in the degradation of MB under the irradiation of ultraviolet light because of their mesoporous structures. [ABSTRACT FROM AUTHOR]

Abstract: Nanostructured Gd0.1Ce0.9O1.95 (GDC)-impregnated La0.7Ca0.3CrO3−δ (LCC) composites were investigated as symmetrical electrodes for La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM)-supported solid oxide fuel cells (SOFCs) without using interlayer at anode/electrolyte interface. The impregnation of aqueous Gd0.1Ce0.9(NO3)x solution into the porous LCC electrode backbones was found to form nanosized GDC particles on LCC surfaces after calcining at 850 °C for 30 min. The optimized performance of electrodes for SOFCs had been achieved through the impregnation cycles of 3–7 times. The introduction of the ion conducting phase GDC in nanometer significantly enhanced the symmetrical electrode performance. The symmetrical cell with the impregnation of five times displayed the best performance and the maximum power densities were 521 mW cm−2 and 638 mW cm−2 at 850 °C and 900 °C with dry H2 as fuel, respectively. Using commercial city gas containing H2S as fuel, the maximum power densities of the cell reached 362 mW cm−2 and 491 mW cm−2 at 850 °C and 900 °C, respectively. The microstructure, valence state of Ce element and electrochemical stability of the nanostructured GDC-impregnated LCC composites were also discussed. [Copyright &y& Elsevier]

Abstract: A new route for the synthesis of silicon nanoparticle (Si NP)/carbon nanotube (CNT) composites by a low-temperature magnesiothermic reduction process is presented. The size of the Si NPs can be controlled by varying the silica (SiO2) thickness of SiO2/CNT precursors. The structural and morphological characterizations of the Si NP/CNT composites have been carried out using powder X-ray diffraction and transmission electron microscopy. [Copyright &y& Elsevier]

Abstract: Pt-doped mesoporous indium oxide (In2O3) has been successfully obtained by a simple and effective in situ nanocasting method. The resultant samples were characterized by XRD, FE-SEM, TEM, N2 physisorption, XPS and EDX. The gas sensing properties for hydrogen sulfide (H2S) of the Pt-doped mesoporous In2O3 specimens were also examined. The results exhibit those In2O3 specimens possess much higher response to H2S even at low concentration of 2ppm and a lower optimum working temperature of 150°C. A possible mechanism was also provided to explain the improvement of the sensing properties. [Copyright &y& Elsevier]

Abstract: Dye Coumarin 151 was postgrafted into the rodlike SBA-15 mesoporous materials, which were synthesized by a direct hydrothermal synthesis method and further modified by an organic silane with a terminal amino group. Characterization by powder X-ray diffraction, N2 adsorption–desorption, transmission electron microscopy, photoluminescence and scanning electron microscopy were carried out. Small-angle X-ray diffraction and N2 adsorption–desorption characterizations showed that these dye containing materials remained as ordered mesostructures and the pore size was from 6nm for blank sample to 3.6nm for postgrafting sample. PL characterization of composite samples exhibited optical properties with different dye concentrations. The characterization showed the existence of Coumarin 151 in the channels of SBA-15 and the composite materials with novel optical properties enabled possible applications in optical sensing and electron acceptors. [Copyright &y& Elsevier]

Abstract: Multiwalled carbon nanotubes (MWNTs) have been successfully decorated with magnetic CoO and NiO nanoparticles via the interaction of (M=Co,Ni) ions and the carboxyl groups on the surface of acid-treated MWNTs. The obtained composites were characterized by X-ray diffraction, scanning electron and transmission electron microscopies. The soaking time plays an important role in the preparation of the composites. Magnetic measurements indicate that both the CoO/MWNT and NiO/MWNT composites present superparamagnetic behavior which can be attributed to the small size of CoO and NiO nanoparticles. [Copyright &y& Elsevier]

Abstract: Highly crystallized α′-NaV2O5 needles were prepared by a simple hydrothermal process. X-ray diffraction showed that the material had an orthorhombic structure. Scanning electron microscopy and high-resolution transmission electron microscopy confirmed that the α′-NaV2O5 needles were fabricated along the 〈010〉 axis. The local structure of the material was studied by Raman scattering. X-ray photoelectron spectroscopy confirmed that the oxidation state of vanadium of the material was +4.5. The formation mechanism of α′-NaV2O5 crystals depended on the hydrothermal conditions. Highly crystallized α′-NaV2O5 needles could be obtained with the presence of F−, while α′-NaV2O5 sheets were obtained without F− or in the presence of other haloid anions such as Cl− and Br−. [Copyright &y& Elsevier]

Abstract: Multi-walled carbon nanotubes (MWNTs) have been successfully modified with CuO, Cu2O and Cu nanoparticles via a simple method, and the calcination temperature, the amount of NH3·H2O and soaking time play critical roles in controlling the final products. The modified MWNTs have been characterized by X-ray diffraction, infrared spectrum, scanning electron and transmission electron microscopies. Optical absorption of the obtained products has also been investigated, and the quantum confinement effect was illustrated in the absorption spectra. [Copyright &y& Elsevier]

Abstract: Drastically different catalytic behaviors of nanometer-sized platinum particles which have diverse sizes are observed using in-situ transmission electron microscopy. For small platinum catalyst particles (with diameters less than 5nm), carbon shells form on the surfaces of the platinum catalyst particles. The formation of the carbon shells starts from the nucleation of amorphous carbon on the preferred (111) planes of platinum nanoparticles. For these small platinum catalyst particles encapsulated in graphitic shells, they are passivated by the carbon shells and their coalescence is hindered by the surrounding shells. After the platinum catalyst particles ultimately coalesce, they interact to form a compact platinum particle after breaking the encapsulating shells. For larger platinum nanoparticles (with diameters larger than 5nm), no encapsulation of platinum nanoparticles is observed and there occurs only the coalescence of platinum nanoparticles. [Copyright &y& Elsevier]

Abstract: Multiwalled carbon nanotubes (MWNTs) have been successfully modified with ZnO nanostructures by zinc–ammonitum complex ion covalently attached to the MWNTs through the C–N bonds. Flower-like ZnO on the tips of MWNTs and ZnO nanoparticles on the surface of MWNTs have been obtained, respectively, via adjusting the reaction time. The modified MWNTs have been characterized with X-ray diffraction, scanning electron and transmission electron microscopy. A growth mechanism has been proposed in which the soaking time plays a key role in controlling the size, morphology, and site of ZnO nanostructures. Photoluminescence properties of the as-synthesized products have also been investigated. [Copyright &y& Elsevier]

Perovskite oxides have provided magical structural models for superconducting and colossal magnetoresistance, and the search for nano-scale and/or atomic-scale devices with particular property by specific preparations in the same systems has been extensively conducted. We present here the three oxidation states of manganese (Mn3+, Mn4+, Mn5+) in the perovskite oxide, La0.66Ca0.29K0.05MnO3, which most interestingly shows the rectifying effect as atomic-scale p–n junctions (namely FY-Junctions) of single crystals and films. The family of cubic perovskite oxides were synthesised by the so-called hydrothermal disproportionation reaction of MnO2 under the condition of strong alkali media. The new concept of the atomic-scale p–n junctions, based on the ideal rectification characteristic of the p–n junctions in the single crystal, basically originates from the structural linkages of [Mn3+–O–Mn4+–O–Mn5+], where Mn3+ $$ {\left( {{\text{t}}^{{\text{3}}}_{{{\text{2g}}}} {\text{e}}^{1}_{{\text{g}}} } \right)} $$ and Mn5+ $$ {\left( {{\text{t}}^{{\text{2}}}_{{{\text{2g}}}} {\text{e}}^{{\text{0}}}_{{\text{g}}} } \right)} $$ in octahedral symmetry serve as a donor and an acceptor, respectively, corresponding to the localized Mn4+ $$ {\left( {{\text{t}}^{{\text{3}}}_{{{\text{2g}}}} {\text{e}}^{{\text{0}}}_{{\text{g}}} } \right)} $$ . [ABSTRACT FROM AUTHOR]

Abstract: Clusters of polyaniline nanorods were synthesized by polymerization of aniline using ammonium persulfate (APS) and potassium dichromate (K2Cr2O7) as oxidant through self-assembly method. Different characterization techniques, such as FT-IR, X-ray diffraction, SEM and TEM, reveal that the PANI nanorods take on cluster morphology and grow on the substrate. The reaction mechanism was discussed in this paper. [Copyright &y& Elsevier]

Abstract: Employing the seeded monocrystalline silicon slice (SMSS) method, we have successfully synthesized the largest zeolite beta crystals (400μm×200μm×200μm) to date. The X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), the atom force microscope (AFM), thermogravimetric (TG) and differential thermal analysis (DTA) and high-resolution transmission electron microscopy (HRTEM) characterizations were completed. The results of X-ray diffraction illustrated that the large zeolite beta presents a sequence of stacking disorder which is different from what is presented by the zeolite beta synthesized in an the alkali system. Through the optic microscopy investigation of the large zeolite beta crystals, we observed the hourglass phenomenon in the zeolite beta crystals for the first time. The FE-SEM and AFM analyses show that the surface of the large zeolite beta is formed in rugged layers. HRTEM characterization reveals the microstructure details of the large zeolite beta. Moreover, the synthesis mechanism has been discussed as a seeded growth with slowly released nutrition via gradually dissolving MSS and the crystals grow by a layer growth manner. [Copyright &y& Elsevier]

Abstract: W/WS2 inorganic fullerene-like (IF) nanoparticles with core–shell structure are synthesized by the reaction of tungsten nanospheres and sulfur at relatively low temperatures (380–600°C) under hydrogen atmosphere, in which tungsten nanospheres were prepared by wire electrical explosion method. Images of transmission electron microscopy and high-resolution transmission electron microscopy show that the composite particles are of core–shell structure with spherical shape and the shell thickness is about 10nm. X-ray powder diffraction results indicate that the interlayer spacing of IF-WS2 shell decreases and approaches that of 2H-WS2 with increasing annealing temperatures, representing an expansion of 3.3–1.6%. A mechanism of IF-WS2 formation via sulfur diffusion into fullerene nanoparticles is discussed. Thermal analysis shows that the nanoparticles obtained at different temperatures exhibit similar thermal stability and the onset temperature of oxidization is about 410°C. Encapsulating hard tungsten core into IF-WS2 and the spherical shape of the core–shell structures may enhance their performance in tribological applications. [Copyright &y& Elsevier]

Metal doping has been demonstrated to be an effective strategy to modulate photocatalytic properties. However, it is very challenging to achieve tunable electronic structures and controllable morphologies with more active sites only via metal doping. Herein, Zr doped CaTiO 3 photocatalysts with enhanced photocatalytic activities toward the hydrogen evolution was prepared by one-step mild hydrothermal reaction. We revealed that zirconium doping would regulate the surface structures of CaTiO 3 from smooth surface to characteristic nanosteps structures. This nanosteps structure with more exposed active sites accompanied by higher exposed surface area, oxygen vacancies and reduction ability, effectively promote the separation of photo-induced carriers, thus resulting in increased photocatalytic properties. This work provides a guideline for surface structures and electronic structures modification simultaneously to design powerful photocatalysts only by metal doping. Unlabelled Image • Zr doping regulated the surface structures of CaTiO 3. • Oxygen vacancies were induced in the reducing solution without calcination. • Z doping and oxygen vacancies induced CaTiO 3 more negative conduction band position than undoped sample, resulting in stronger reduction ability of photogenerated electrons. [ABSTRACT FROM AUTHOR]

• A CaTiO 3 /Ca(OH) 2 composite photocatalyst was synthesized by hydrothermal route. • CaTiO 3 /Ca(OH) 2 composite photocatalyst showed excellent photocatalytic performance. • The photocatalytic mechanism of CaTiO 3 /Ca(OH) 2 composite photocatalyst was studied. A calcium titanate/calcium hydroxide (CaTiO 3 /Ca(OH) 2) composite photocatalyst with enhanced activity towards the degradation of organic dyes was synthesized by a simple and direct hydrothermal route through controlling the Ca/Ti molar ratio within the reaction slurry. The photocatalytic performances indicated that the sample generated by Ca/Ti = 4 exhibited the highest photocatalytic activity, which was even higher than that of commercial P25. The enhanced performance of this composite photocatalyst was attributed to the hierarchical concave cuboid structure with high crystallization and high specific surface area, which inhibits the recombination of photogenerated electron and hole pairs, as well as to the combination of CaTiO 3 and Ca(OH) 2 which provides OH− to form OH with strong oxidizing properties to promote the separation of photogenerated electron and hole pairs. [ABSTRACT FROM AUTHOR]

• A novel polyimide with 1.36 mmol g−1 dibenzo-14-crown-4 was synthesized. • The PI membrane prepared by NIPS showed a Li+ adsorption capacity of 34.05 mg g−1. • Adsorption of Li+ on PI followed a monolayer chemical adsorption mechanism. • The selectivity separation factor (α Mg Li) of the membrane reached 23.5. • High performance was provided by the crown ether and porous membrane structure. Crown ethers containing polymer membranes are considered as one of the most promising candidates for selective separation of Li+. Herein, a novel dibenzo- 14-crown-4 ether-based polyimide (Poly(DAB14C4-6FDA)) was synthesized by condensation polymerization between di(aminobenzo)-14-crown-4 (DAB14C4) and 4,4′-(hexafluoro-isopropylidene) diphthalic anhydride (6FDA). The resultant polyimide with a high molecular weight (63 kDa) was employed to fabricate microporous membranes by non-solvent induced phase separation using N,N -Dimethylformamide (DMF) as a solvent and water as coagulation bath. The pure-water permeance of the PI membrane (porosity of 80.5%) reached 580 L/m2 h (LMH) bar−1. Simultaneously, this membrane displayed excellent Li+ adsorption capacity (34.05 mg g−1) owing to the high crown ether content of 1.36 mmol g−1. The Li+ adsorption kinetics followed a pseudo-second-order adsorption equation and the adsorption isotherm data fitted a Langmuir model, indicating monolayer chemical adsorption. The selective separation factors of Li+ to Na+, K+, Mg2+, and Ca2+ were 45.6, 48.3, 23.5, and 41.2, respectively. Adsorption energy results obtained from density functional theory (DFT) calculations were consistent with the experimental results. The membrane also exhibited good adsorption repeatability and stability. The high performance of this novel membrane is ascribed to the sieving and chelating effects of the unique crown ether, and its porous structure. [ABSTRACT FROM AUTHOR]

Silver nanoparticles deposited on TiO2 nanoporous films exhibited unique photochromic property under the irradiation of visible light. Here we investigated the application of photochromic Ag/TiO2 nanocomposite film in holographic data storage. Stable holographic fringes were formed on the Ag/TiO2 film using two coherent green lasers as writing beams, and these fringes could be erased with ultraviolet irradiation. These observations are consistent with the photochromism of Ag/TiO2 nanocomposite film and can be well explained by the visible light-stimulated dissolution and ultraviolet light-stimulated regeneration of silver nanoparticles in TiO2 matrix. [ABSTRACT FROM AUTHOR]

L1 2 structured γ′ phase is the main strengthening phase of Ni-base superalloys, which contain multiple alloying elements. Locations of these elements in the lattice are crucial for understanding the mechanical/physical properties of γ′ phases. Here, we reveal the site occupancy of various elements in γ′ phases of two multi-component Ni-base single crystal superalloys by using advanced scanning transmission electron microscopy and energy disperse spectroscopy. Cr, Mo, Re, Ta, W and Ti atoms preferentially locate at Al sublattices, and Co and Ru atoms prefer Ni sublattices. Moreover, the addition of Ru does not affect the site occupancy of other alloying elements. Image 1 • EDS mapping directly shows atomic distribution of all elements in the γ′ phases. • Cr, Mo, Re, Ta, W and Ti atoms preferentially occupy Al sublattices. • Co and Ru atoms prefer Ni sublattices. • Ru has limited effect on site occupancy of other alloying elements in γ′ phase. [ABSTRACT FROM AUTHOR]