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A novel WO 3 ·H 2 O nanostructure assembled by numerous one-dimensional nanorods as building units were synthesized successfully through a facile hydrothermal process. As a comparison, we also prepared the monodispersed WO 3 ·H 2 O nanorods. The crystal structures and morphologies of two products were characterized by X-ray diffraction and scanning electron microscope. Furthermore, gas sensing experiments indicated that a superior gas-sensing property of aligned WO 3 ·H 2 O nanorods occurs over that of the monodispersed WO 3 ·H 2 O nanorods, which is likely attributed to large effective surface areas and abundant accessible diffusion channels provided by this special structure for sufficient gas reactions. [ABSTRACT FROM AUTHOR]

Sparsely and closely flower-like WO 3 ·H 2 O hierarchical architectures were successfully synthesized via a one-step hydrothermal process. The obtained samples are both WO 3 ·H 2 O nanoflowers assembled by ultrathin nanosheets with the thickness less than electron deletion layer. And the possible formation processed was proposed based on the comparative studies. Furthermore, gas sensing experiments demonstrated that the closely WO 3 ·H 2 O nanoflowers which possess numerous semi-closed spaces have a superior gas-sensing performance compared with the sparsely one. We believe this unique structure will critically enhance the gas sensing properties of WO 3 ·H 2 O nanomaterials. [ABSTRACT FROM AUTHOR]

Nanomaterials with hierarchical architectures consisting of two-dimensional nanostructures have attracted considerable attention for their potential applications in recent years. In current work, flake-flower NiO architectures self-assembled by aggregative nanosheets have been successfully synthesized via the hydrothermal route. It is notable that the NiO sensors exhibit excellent gas sensing performances owing to the open and well-defined structure as well as abundant micro reaction rooms built by two-dimensional ultrathin nanosheets, which are thinner than the thickness of electron depletion layer. Moreover, a possible growth mechanism for the interactions between PVP and Ni 2+ ions in the synthesis of the precursors Ni(OH) 2 and the novel morphology evolution of the NiO nanoflowers are proposed in detail. [ABSTRACT FROM AUTHOR]

Previously, hollow Cu 2 O configurations have been fabricated with the use of template or etchant. However, in this study, simply mixing aqueous sodium dodecyl sulfate (SDS), CuCl 2 , NaOH, and NH 2 OH·HCl in the order listed, Cu 2 O polyhedron with empty interior arise, which is rarely reported. Observations made on the novel particles confirm the hollow polyhedral feature and reveal that the uniform particles exhibit a narrow size distribution at around 300–400 nm in diameter and ca. 50 nm in wall thickness. It was recorded that, upon the addition of reductant (NH 2 OH·HCl), the solution color changed orderly from light blue to green, yellow, and then orange within 1 h, while the basic mixture solution turned to acid immediately. We have reason to attribute the formation of hollow polyhedron to the surfactant role of SDS and the co-etching effect of oxidative etching and acidic etching, acting on dissolving Cu 2 O nanocrystals via oxidation with oxygen and reaction with HCl (from NH 2 OH·HCl). [ABSTRACT FROM AUTHOR]

Self-assembly of one-dimensional nanoscale building blocks into functional three-dimensional super-structures has attracted vast interests. In current work, novel NiO flower-like architectures have been successfully synthesized via a facile hydrothermal method and subsequent calcination. Notably, it has been observed that the sodium oxalate plays a vital role on the aggregation of needles and a novel growth mechanism of needle-flower NiO has been proposed in detail based on the experimental results. More importantly, it is noted that the gas sensing properties of the flower-like architectures are superior to needle-like structures on the basis of the investigation. Such a synthetic way may open up an avenue to tailor the morphologies of some other metal oxides and enhance their gas sensing performance. [ABSTRACT FROM AUTHOR]

Monodisperse hexagonal tungsten oxide (h-WO 3 ) nanowires were novelly prepared on a large scale by the hydrothermal method with the assistance of K 2 SO 4 and Na 2 SO 4 . The morphologies and structures of the nanowires were characterized by X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM) and high-resolution transmission electron microscopy (TEM). These nanowires with a diameter of 80 nm and high crystallinity are especially bundles-like structure, which are growth from primary particles with same growth direction of [001] and the exposure to 〈200〉 facets. These primary nanoparticles are believed to have a crystal structure of hexagonal prism morphology. Based on the TEM characterizations and crystal structure analyses, the morphology evolvement and is given and the growth mechanism is discussed. This research is potentially applied to controlled synthesis 1D semiconductor oxides through hydrothermal route. [ABSTRACT FROM AUTHOR]

Novel urchinlike hexagonal WO 3 microspheres have been fabricated by a facile hydrothermal method in the presence of K 2 SO 4 . Morphology analysis reveals that the as-synthesized WO 3 microstructures are assembled by numerous one-dimensional nanorods. Based on comparative studies, a possible formation mechanism is proposed in detail. What’s more, gas-sensing measurement indicates that the well-defined urchinelike WO 3 microspheres exhibit excellent gas sensing properties. [ABSTRACT FROM AUTHOR]

Abstract: Materials with hierarchical architectures often exhibit novel functional properties. In this paper, the hierarchical SnO2 flower-like architecture, consisting of numerous aggregative nanosheets was successfully synthesized via a facile hydrothermal method and subsequent calcination. The structures and morphologies of this hierarchical architecture were characterized in detail by means of powder X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). Further comparative experiments show that the sodium citrate was benefit to promote the growth of SnO2 nanosheets and accelerate the assembling of nanosheets into flower-like architecture, the PEG provided nucleation sites and made the nanoflowers grow uniformly and separated. Moreover, a possible growth mechanism of the flower-like architectures was proposed. The non-trivial behavior of flower-like SnO2 may be driven by the properties of grain boundaries. [Copyright &y& Elsevier]

Monodisperse WO3·H2O square nanoplates were obtained under hydrothermal conditions with the assistance of malic acid. The morphologies and structures of the plates are characterized by the analyses of XRD, SEM and TEM. In addition, the growth mechanism of the plate-like tungsten oxides has been primarily discussed and the schematic model and crystal structure have been given out. These WO3·H2O nanoplates are revealed as orthorhombic crystal structure with exposure (010) facet. It is proved that malic acid will preferable absorb on the (010) facets during the crystal growth, leading to the growth along the crystal direction [100] and [001], and further determining the formation of plate-like WO3·H2O. This research is of great significance in the preparations, characterizations and applications of various 2D semiconductor metal oxides. [ABSTRACT FROM AUTHOR]

Monodisperse NiO hierarchical nanoflowers fabricated by nanobundles have been successfully synthesized under hydrothermal conditions followed by a calcination treatment. It is amazingly observed that the bundle-like nanoflowers possessed the emanative needle-like ends on the nanoscale, which was different from the previous 3D hierarchical architectures only fabricated by nanosheets, entire solid rod-like and emanative needle-like structures. Furthermore, based on the further experiments, the amount of ethylene glycol (EG, 99.5 wt%) play a key role on the formation of emanative needle-like ends and constructions of the 3D hierarchical flower-like architectures, and the relative formation mechanism was primarily discussed. Such an unexpected morphology may provide a non-trivial behavior driven by the properties of emanative needle-like ends and electron transformation continuity. [ABSTRACT FROM AUTHOR]

Nanomaterials with low-dimensional architectures frequently exhibit novel functional properties. In current work, NiO nanobelts with well-defined morphologies and uniform size have been successfully synthesized via a facile hydrothermal method. Furthermore, a novel growth mechanism of NiO nanobelts has been proposed in detail. Surprisingly, it is worth mentioning that the sodium oxalate is of great benefit to the formation of NiO one-dimensional nanostructures and plays a vital role on tailoring morphologies of nanobelts on the basis of further comparative experiments. Such a synthetic way may open up an avenue to prepare some other oxides. [ABSTRACT FROM AUTHOR]

Molybdenum trioxides (MoO 3 ) with flower-like hierarchical structure and distinct nanobelts have been synthesized via a hydrothermal method. A series of comparative experiments show that cetyltrimethyl ammonium bromide (CTAB) and HNO 3 have evident impact on forming the morphologies of MoO 3 . Interestingly, the add order of CTAB and HNO 3 can be also a determinant factor in the assemble process. This research is of great significance in the preparations, characterizations and applications of various 1D and 3D semiconductor metal oxides. The possible growth mechanism is also proposed. [ABSTRACT FROM AUTHOR]

Abstract: Self-assembly of one-dimensional nanoscale building blocks into functional 2D or 3D complex superstructures has stimulated a great deal of interest. In current work, using the hydrothermal method and reagent of hexamethylenetetramine (HMT), we synthesize the SnO2 3D hierarchical nanostructures with an average diameter of 200–400nm, which exhibit flower-like architectures assembled by numerous one-dimensional tetragonal prism nanorods. Further comparative studies demonstrate that the HMT provides nucleation sites for the assembling of the nanorods, which plays a crucial role in producing such unique flower-like architectures. Meantime, a novel growth mechanism is proposed in detail. In property, the prepared SnO2 nanoflowers show excellent gas-sensing performances to ethanol of 50ppm at an optimal temperature as low as 250°C. Such unique architectures may open up an avenue to further enhance the gas-sensing performances of SnO2 nanostructures for future sensor application. [Copyright &y& Elsevier]

Nanomaterials with three-dimensional architectures, frequently exhibiting novel functional properties, have attracted considerable attention of the researchers. In current work, we have successfully synthesized the NiO flower-like microspheres with abundant nanoparticles adhering to the petals via a facile hydrothermal method. Interestingly, it is found that the excellent gas sensing properties of the samples towards ethanol are likely attributed to the well-aligned porous architectures as well as great amounts of nanoparticles adhering to the petals, considered as active sites. Meanwhile, we also elaborated a distinctive growth mechanism of such a unique architecture and a plausible gas sensing mechanism, respectively. [ABSTRACT FROM AUTHOR]

We report the successful synthesis of novel Sn 2 O 3 with hierarchical 3D nanostructures via a facile hydrothermal method for the first time. The as-prepared Sn 2 O 3 products transform into SnO 2 after calcinations (800 °C) and a simultaneous TGA and DSC analysis of the as-prepared Sn 2 O 3 sample determines that the main increment of mass takes place in the temperature range 534–800 °C. The well-defined nanostructures are composed of thin nanosheets. The growth mechanisms are also discussed by observing the morphology revolution at various reaction times. Furthermore, the oxidation states of the Sn 2 O 3 hierarchical nanostructures are confirmed by the shape analysis of corresponding XPS O 1 s and Sn 3 d peaks using the decomposition procedure. [ABSTRACT FROM AUTHOR]

The thorn-like surface can avert the compact stacking of nanoparticles through the mutual supporting of thorns, while the hollow structure can provide more active sites by the utilization of the inner surface. On account of these, we reported the facile synthesis of self-supporting MnCo 2 O 4 hollow structures using a hydrothermal way and subsequent calcination. Fluorine-coordinated metal ions (Mn 2+ and Co 2+ ) react with OH − and CO 3 2− , generating the initial nanoparticles. Nanoparticles then go through a two-step assembly and a gas-driven deformation, ultimately forming the aforementioned morphology. In this process, the fluorine ion and the urea are regarded to play significant roles. [ABSTRACT FROM AUTHOR]

Abstract: New morphologies often play a critical role in governing properties of nano-materials. Here, using hydrothermal method and reagents of sodium citrate and polyethylene glycol (PEG), we synthesize the ZnO nano-crystals and find that they exhibit hierarchical flower-like architectures assembled by nanosheets. Further comparative studies demonstrate that the sodium citrate assists a uniform growth of the nanosheets, and the PEG provides nucleation sites for the assembling of the nanosheets, both of which play a critical role in producing such unique flower-like architectures. Consequently, this sample is found to show excellent sensing performances to the target ethanol owing to its largest amount of petals, intervals, and pores. Such an unexpected morphology holds substantial promise for rendering ZnO as a potential gas-sensing material for a broad range of future sensor applications. [Copyright &y& Elsevier]

Novel urchin-like SnO 2 nanostructures were prepared by a facile hydrothermal process. The well-defined nanostructures were composed of numerous one-dimensional nanowires with a diameter of ∼8–10 nm. Based on comparative studies, a possible formation mechanism was proposed in detail. It was believed that the nucleation was initiated by formation of ZnSn(OH) 6 . Furthermore, gas-sensing measurement indicated that the urchin-like SnO 2 nanoflowers showed excellent gas-sensing properties. [ABSTRACT FROM AUTHOR]

Multi-layered ZnO circular nanodisks were efficiently fabricated using sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP) polymer by a controlled hydrothermal method. As-prepared ZnO nanostructures were characterized by X-ray powder diffraction, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. The effect of SDS and PVP polymer on the formation of ZnO multi-layer nanostructures was described in detail. Based on experimental results, a possible mechanism of circular disk formation was proposed. The gas-sensing properties of multi-layered nanodisks were reported for formaldehyde under different concentrations from 5 to 1200 ppm at 300 °C. A higher response toward formaldehyde was observed, rendering the multi-layered nanostructures a promising gas-sensing material for the on-site detection of formaldehyde. [ABSTRACT FROM AUTHOR]

Regular hexagonal embedded ZnO nanorods were successfully prepared by a simple hydrothermal method. The addition of urea as a homogeneous precursor was found to play a vital role in the embedding of secondary nanorods. The nanostructures were characterized by XRD, SEM, and EDS. The gas-sensing properties of secondary grown embedded nanorods were reported for formaldehyde, ethanol, methanol, acetone, and ammonia at different concentrations and temperatures. A higher response and greater selectivity toward formaldehyde than other gases was observed. A sharp response with the best recovery time was achieved at an optimum temperature of 200 °C. [ABSTRACT FROM AUTHOR]

In this article, a sealed nanotube of ZnO was successfully obtained by a simple hydrothermal technique, which employed Hexamethylene tetramine (HMT) and Fluorinion (F−) as the active agents. The rod-like nanotubes structures were observed through field-emission scanning electron microscopy. The high-resolution transmission electron microscope exhibited a shell-enclosed nanotube structures. On the basis of experimental observations, including temperature, pH of the solution and acting agents, a growth mechanism was proposed. The as-prepared nanostructures showed excellent gas sensitivities to different gases (ethanol, ammonia gas, formaldehyde gas) with a quite low concentration respectively. [ABSTRACT FROM AUTHOR]

Abstract: We report a successful fabrication of tungsten disulfide (WS2) nanostructures with different morphologies including rod-like, sheet-like and fiber-like ones via a simple yet facile hydrothermal process by adding surfactants cetyltrimethyl ammonium bromide (CTAB) and polyethylene glycol (PEG). The structural features of the as-prepared WS2 are characterized systematically by the X-ray powder diffraction and scanning electron microscopy. We find that the surfactants play a critical role in producing low dimensional WS2 structures with different morphologies. We also propose growth mechanisms for the various WS2 morphologies. The simple fabrication of WS2 nanostructures can also be applied for the synthesis of other transition metal sulfides with novel nanostructures. [Copyright &y& Elsevier]

Abstract: Hexagonal ZnO nanocones were successfully prepared using a controlled hydrothermal method with the assistance of double anionic surfactants. The products were characterized using X-ray powder diffraction. The morphologies of ZnO nanostructures were characterized using field-emission scanning electron microscopy and high-resolution transmission electron microscopy. The effects of the addition of one anionic to another anionic reagent in the crystal structure formation were discussed in detail. The gas sensing properties were measured for formaldehyde. [Copyright &y& Elsevier]

Abstract: Regular hexagonal twinned ZnO nanodisks were successfully prepared from nanodisks using a controlled hydrothermal method with the assistance of double surfactants. The products were characterized using X-ray powder diffraction. The morphologies of ZnO nanostructures were characterized in detail using field-emission scanning electron microscopy and high-resolution transmission electron microscopy. Based on the experimental results, a growth mechanism for hexagonal structure was proposed. [Copyright &y& Elsevier]

Highlights: [•] Three different kinds of flower-like NiO nanostructure were synthesized. [•] Effects of PVP, reaction time and temperature were investigated in detail. [•] Growth mechanism of the camellia-like NiO was discussed. [•] Sensor with camellia-like NiO showed the good performance toward the alcohol. [ABSTRACT FROM AUTHOR]

Abstract: Nanomaterials with unusual architectures or morphologies often exhibit novel functional properties. Here, we apply a simple two-step solution method to synthesize the ZnO/SnO2 microspheres with an average size of 1–2μm, which exhibit a unique core–shell architecture with a uniform dispersion of SnO2 nanoparticles on surfaces of spherical ZnO cores. We further investigate in detail the morphology evolution with reaction time, based upon which a likely growth mechanism is proposed. In property, the prepared core–shell structural ZnO/SnO2 microspheres show excellent gas-sensing functions to ethanol gas of 50ppm at an optimal temperature as low as 250°C, rendering the hybrid microspheres a promising gas-sensing material for the on-site detection of ethanol. [Copyright &y& Elsevier]

Abstract: In this paper, a combined cold-rolling and welding technique was applied to magnesium alloy AZ31 in order to investigate the effect of cold rolling and static recrystallization on microstructures evolution and mechanical properties of the welded joints. The results showed that the 7% rolled-weld sample obtained the highest tensile strength (252MPa) and strength coefficient (87.6%). With the increase of rolling strain, the average grain size decreased in heat affected zone due to the effect of static recrystallization. The recovery, recrystallization nuclei, and grain growth processes in heat affected zone during welding were analyzed by thermodynamic theories and models, respectively. However, abnormal voids and intergranular fracture behavior were found in the 10% rolled-weld joints after tensile test, which was mainly attributed to the gas inclusions, initial micro-voids and high residual stress in base metal. [Copyright &y& Elsevier]