Controllable self-assembly of ordered and regularly patterned semiconductor nanoarchitectures is of great interest in achieving fantastic functionalities and properties of nanomaterials in nanodevices. Here we demonstrate a symmetric confined growth methodology for fabricating a geometrically patterned and well-oriented two-dimensional nanonet by a solution growth. A uniform orthogonal VO2 nanonet composed of single-crystalline nanowalls is self-assembled in a one-step process and exhibits single-crystal-like crystallographic characteristics. It is revealed that the 4-fold symmetric structure of (001) TiO2 determines the orthogonal geometrical pattern of the nanonet; in addition, the interfacial mismatch energy controls the horizontal growth direction and morphology of one-dimensional nanocrystals competing with the surface energy. The unique VO2 nanonet exhibits excellent thermochromic performances due to its self-generated porosity and sluggish phase transition. The initial optical modulation temperature is near room temperature. The solar modulating ability (ΔTsol) is up to 11.82% with the maximum visible light transmittance (Tvis-max) more than 70%. The proposed growth strategy could be adopted in more systems to perform self-assembly of regularly patterned nanoarchitectures with well interconnectivity and preferred orientation, which offers promising opportunities for exploiting potential nanodevices in various applications.

Taking the advantage of hierarchical nanostructures into consideration, herein a facile and template free approach to achieve hierarchical microspheres assembled from the α-Fe2O3 nanosheet was formulated. The followed freeze-drying treatment is employed to realize the construction of nanostructured Fe2O3/graphene composite. The unique hierarchical structure of α-Fe2O3 combined with the flexible graphene layer not only effectively buffer the volume expansion during the cycling process, but also promote the transport of lithium ion and electron through three-dimensional networks when being assessed for lithium ion battery. The as-obtained composite exhibits significantly enhanced cycling stability (1850 mA h g−1 after 190 cycles at the current of 300 mA g−1) and superior rate performance (around 520 mA h g−1 for the current of 5000 mA g−1). The obtained-results illustrate that the rational designing of the nanostructured composite can result in the fast lithium insertion/de-insertion in lithium ion batteries which mimic merits seen in high-power electrochemical capacitors.

Application products moving from small-sized devices to large-scale energy storage systems have pushed the development of lithium-ion batteries towards high-energy densities, high-power densities, and long cycle life. Germanium-based anode materials with high theoretical capacities are expected as promising anode candidates to fulfill those requirements, but suffer from the huge volume expansion upon lithiation, leading to serious material pulverization and capacity fading. Herein, a convenient and cost-effective strategy was conceived focusing on construction of dually-protected Zn2GeO4/graphene composites. The rationally designed composite was composed of hollowed Zn2GeO4 nanostructures and flexible graphene layers, which acted as two functional nanoframes to synergistically alleviate the volume change during lithiation/delithiation. As a result, the Zn2GeO4/graphene composite exhibited high specific capacities, excellent cycling stability and desirable rate capability. Specifically, the Zn2GeO4/graphene composite electrode delivered specific capacity of 702 mA h g−1 at 300 mA g−1 after 600 cycles with capacity retention of 85%. In addition, a high reversible capacity of 600 mA h g−1 was retained over 1000 cycles at a high current density of 800 mA g−1. Those achieved-results suggested that rational design of electrode nanostructures offers an effective insight for obtaining high-performance batteries.

•Sm0.5Bi4.5Ti3FeO15 ceramics was synthesized for the first time.•A ferroelectric transition was observed at ∼440 °C.•Dielectric and electrical properties were investigated.•Two dielectric relaxation behaviors were clarified.Single-phase Aurivillius Sm0.5Bi4.5Ti3FeO15 ceramics was synthesized by the conventional solid-state reaction technique. Dielectric response and electrical properties of the ceramics were investigated in a wide range of temperature and frequency by dielectric and impedance spectroscopies. Two dielectric relaxation behaviors were distinguished by the combination of impedance and electric modulus analysis which could be attributed to the contributions of grains and grain boundaries, respectively. The resistance of grain boundaries was found to be much larger than that of grains, whereas the capacitances were in the same level. A ferroelectric phase transition was observed to take place at ∼440 °C. The kinetic analysis was performed to study the corresponding relaxation-conduction mechanisms in the material. Above 270 °C the conduction behavior of the compound was ascribed to the motion of ionized oxygen vacancies.

•α-Fe2O3 nanocubes exposed with (012) facets was synthesized via hydrothermal.•Freeze-drying was utilized to construct nanostructured Fe2O3/graphene composite.•Designed hierarchical composite demonstrated excellent performances.•This strategy renders reference scalable production of diverse hybrids.Owing to scientific importance associated with highly reactive surfaces, the research concerning inorganic single crystals with a large percentage of exposed high-index facets has attracted much attention. In current research, α-Fe2O3 nanocubes exposed with (012) active facet was firstly synthesized via a hydrothermal method. And then a freeze-drying approach was utilized to construct nanostructured Fe2O3/graphene composite. The as-obtained composite exhibited s higher BET surface area than that of bare α-Fe2O3 nanocubes. When evaluated for lithium storage properties, the Fe2O3/graphene rendered remarkable electrochemical cycle stability and high rate performance. At the rate of 300 mA g−1, a high reversible discharge capacity of 1136 mAh g−1 was obtained up to 200 cycles. In addition, the excellent rate performance was also achieved. Excellent electrochemical properties are probably ascribed to the synergistic effect of α-Fe2O3 nanocubes and graphene sheets, as a result of smart structure design via a freeze-drying route. This strategy with merits of rational construction and scalable production could establish new perspective for diverse composites towards commercial application.

Constructing hybrids of transition metal oxides with different kinds of carbon based materials has attracted a lot of attention recently. However, scalable synthesis of homogeneous hybrids with active controllable of microstructure remains great challenge. Here, we proposed a convenient and efficient strategy named freeze-drying process for scalable production of 3D NiO/graphene hybrids. With a controllable procedure, NiO microflowers and graphene layers could preserve uniform configuration from fully mixed solvent to final hybrids materials. The mechanical stability and electrical conductivity of NiO microflowers was increased by graphene. NiO microflowers as spacers intercalated into graphene layers and effectively prevented it from aggregation or restacking, leading to a high specific surface area in hybrids. The NiO/graphene exhibited enhanced cycle stability and rate performance when evaluated as an anode for lithium ion batteries. It rendered high specific capacities about 1000 mA h g−1 after 70 cycles, and 770 mA h g−1 after 100 cycles at 300 mA g−1. Excellent electrochemical properties were probably ascribed to the synergistic effect of NiO microflowers and graphene layers, as a result of smart structure design by a freeze-drying route. This strategy with merits of rational construction and scalable production could establish new aspects for diverse hybrid towards industrialization.

•Contributions of grains and grain boundaries to dielectric relaxations were distinguished.•Grain boundaries were determined more resistive than grains.•A ferroelectric transition was observed at ∼440 °C.•The possible defect behaviors were discussed based on the kinetic analysis of relaxation and conduction.Aurivillius single-phase Bi3.5La0.5Ti2Nb0.5Fe0.5O12 ceramics was synthesized by solid state reaction route. The ac data in terms of dielectric and impedance were collected to probe the dielectric relaxation behaviors in the ceramics. Two relaxations were distinguished and determined to originate from grains and grain boundaries, respectively, by the combination of impedance and electric modulus analysis. A phase transition was observed to take place at ∼440 °C. The possible relaxation-conduction mechanisms were discussed on the basis of kinetic analyses of dielectric data. This work elucidated the contributions of microstructures and defects to the relaxations and conduction. It is significant for correct understanding of electrical properties of Bi3.5La0.5Ti2Nb0.5Fe0.5O12 related ceramics and consequent modification of process to improve the performance of ceramics.Download high-res image (436KB)Download full-size image

Single-phase Aurivillius Bi4Nd0.5Gd0.5Ti3FeO15 ceramics was synthesized via the solid-state reaction technique. Rietveld refinement of the full XRD pattern was carried out to obtain the detailed structure of the compound. Dielectric response and electrical properties of the ceramics were investigated in a wide range of frequency and temperature by dielectric/impedance spectroscopies. Two dielectric relaxations were distinguished, which were attributed to grains and grain boundaries respectively, by the combination of impedance and modulus analysis. Resistance of grain boundaries was determined much larger than that of grains. The kinetic analysis of temperature dependent dielectric data was performed to study the corresponding relaxation-conduction behaviors in the material. The thermal magnetization measurement evidenced the paramagnetic characteristic of the material, but localized antiferromagentic coupling would exist below 200 K. In addition, a phase transition was observed at ~240 °C.

•Er2O3 doped KNN ceramic was prepared via solid state reaction.•Owing to donor effect the ceramics exhibited enhanced electrical properties.•The optical behavior was enhanced in the poled sample.Er2O3 doped (K,Na)NbO3 (KNN) ceramics with the composition around the morphotropic phase boundary was synthesized by the conventional solid state reaction. Compared to pure KNN ceramics, KNN doped Er3+ ceramics exhibited enhanced ferroelectric, piezoelectric properties owing to the donor doping effect. And the maximum value of d33=132 pC/N and kp=0.44 were obtained for the ceramics with the addition of 0.5 mol% Er2O3. Meantime, the intensity of absorb spectra and photoluminescence were obviously enhanced in this kind of sample owing to the lattice distortion induced by the polarization reorientation during poling process. The present work indicated the proposed system exhibited potential application in multifunctional integration device.

Technologically controlling nanostructures is essential to tailoring the functionalities and properties of nanomaterials. Various methods free from lithography-based techniques have been employed to fabricate 2D nanostructures; however it is still hard to achieve a well interconnected 2D regular nanostructure. Here, we demonstrate a facile chemical solution method to self-assemble a regular and interconnected VO2 nanonet on the wafer scale. The nanonet shows a well-defined 2D truss network constructed by VO2 nanorods with twinning relationships. The growth direction and crystallographic orientation of nanorods are synchronously controlled, leading to horizontally epitaxial growth of nanorods along three symmetric directions of the (001) single-crystal sapphire substrate. The unique nanonets enable the acquisition of excellent resistance switching properties and dramatic fatigue endurance. A large resistance change of near 5 orders with a 1.7 °C width of the hysteresis loop is characterized comparably to the properties of single crystals without detectable degradation after 500 cycles over the metal-to-insulator transition. It indicates that the nanonet can serve as an exceptional candidate for practical application in switching functional devices. Our findings offer a novel pathway for self-assembly of 2D ordered nanostructures, which would provide new opportunities for the bottom-up integration of nanodevices.

In this study, few-layered MoS2 nanosheets (MoS2-NS) were obtained via the top-down exfoliation method from bulk MoS2 (MoS2-Bulk), and the dielectric properties and microwave absorption performance of MoS2-NS were first reported. The dimension-dependent dielectric properties and microwave absorption performance of MoS2 were investigated by presenting a comparative study between MoS2-NS and MoS2-Bulk. Our results show that the imaginary permittivity (ε′′) of MoS2-NS/wax is twice as large as that of MoS2-Bulk/wax. The minimum reflection loss (RL) value of MoS2-NS/wax with 60 wt% loading is −38.42 dB at a thickness of 2.4 mm, which is almost 4 times higher than that of MoS2-Bulk/wax, and the corresponding bandwidth with effective attenuation (<−10 dB) of MoS2-NS/wax is up to 4.1 GHz (9.6–13.76 GHz). The microwave absorption performance of MoS2-NS is comparable to those reported in carbon-related nanomaterials. The enhanced microwave absorption performance of MoS2-NS is attributed to the defect dipole polarization arising from Mo and S vacancies and its higher specific surface area. These results suggest that MoS2-NS is a promising candidate material not only in fundamental studies but also in practical microwave applications.

Hierarchically nanostructured materials have proven their superiority in high performance lithium ion batteries. Herein, we successfully fabricate hierarchical vanadium pentoxide (V2O5) nanobelts by an economical and facile hydrothermal strategy followed by annealing treatment. A self-template growth of hierarchical V2O5 nanobelts was achieved from precursor VO2 (B) nanobelts, resulting in open structure of hierarchical V2O5 nanobelts composed of plate-like V2O5 nanocrystals and tiny haircuts. The hierarchical nanobelts deliver a high specific surface area of 137.5 m2 g−1. When used as the cathode material for lithium ion battery, the hierarchical V2O5 nanobelts exhibit high discharge capacity of 288 mAh g−1, which maintain 246 mAh g−1 at the end of 50th cycle with capacity retention of 85.4 %.The present electrochemical results demonstrate the high discharge capacity, superior cycling stability and rate capability of the hierarchical V2O5 nanobelts, which could be attributed to the advantages of unique hierarchical nanobelt structure.

China rose-like structured β-Co(OH)2 was fabricated by a facile and surfactant free solvothermal method. The self-assembly process of the 3D flower-like structure was preliminarily explored via time-dependent observation. The chemical transformation achieved by thermal treatment from brucite-like β-Co(OH)2 to spinel Co3O4 was investigated in detail, while the original flower-like framework of the precursor was preserved during the entire process. With increase in the temperature of heat treatment, the specific surface area decreased correspondingly. Meanwhile, propagation of cracks and the following cavitation progress were realized on petal-like flakelets. Topotactic nucleation and crystallization in the [111] direction of spinel-structured Co3O4 inheriting the [0001] direction of hexagonal structured β-Co(OH)2 were analyzed in detail. The catalytic performance of the obtained Co3O4 materials on the thermal decomposition of ammonium perchlorate (AP) was analyzed. It was fortunately found that samples annealed at 280 °C could lower the thermal decomposition temperature of AP from 450 °C to 245 °C, when the obtained Co3O4 made up 4% w/w of the mixture. This excellent performance is of great practical significance in the development of solid rocket fuels.

In this paper, we report the possible transient behavior for 20 nm partially depleted silicon-on-insulator (PD SOI) n-channel MOSFET studied using Synopsys TCAD program. Tunnelling model is set at Si/SiO2 interface by varying front gate oxide. Parasitic floating body effects also have been observed in the device behavior for both linear and saturation regions, the magnitude of these effects depends on the front gate oxide thickness. For 4 nm gate oxide thickness, the parasitic floating body effect is dominant at low drain voltage.

In this work, reduced graphene oxide (r-GO) and graphite nanosheet (GN) were obtained via the chemical approach. Furthermore, r-GO composites and GN composites were prepared with a paraffin wax host. r-GO composites show high dielectric properties and electromagnetic interference shielding efficiency (EMI SE). Compared with the GN composites, the loss tangent and EMI SE of the r-GO composites with the same mass ratio are enhanced ∼5 to 10 times and ∼3 to 10 times, respectively. The enhanced attenuation capacity arises from higher specific surface area, clustered defects and residual bonds of the r-GOs, which increase the polarization loss, scattering and conductivity of the composite. Moreover, the higher conductivity of r-GO composites leads to higher EMI SE compared with that of GN composites. These results suggest that r-GOs are highly promising fillers for microwave attenuation in the carbon family and that r-GO composites are high-performance EMI shielding materials with application anticipated to many fields.

Structural stability along with the electronic and the optical properties of intrinsic 3C–SiC and Ni-doped 3C–SiC were studied by the first principles calculation. For the Ni-doped 3C–SiC, substitution of Ni in Si sub-lattice is energetically more favorable than that in C sub-lattice. Some new impurity energy levels appear in the band gap of Ni-doped 3C–SiC, which can improve the conductivity of 3C–SiC. The imaginary part of the dielectric function of Ni-doped 3C–SiC has three remarkable peaks at 0.69 eV, 2.35 eV, and 4.16 eV. This reveals that doping with Ni can improve the photo-absorption efficiency of 3C–SiC. In the absorption spectrum of Ni-doped 3C–SiC, the absorption edge red-shifts towards the far-infrared region. Furthermore, three new absorbing peaks emerge in the near-infrared region, visible region, and middle-ultraviolet region. These features confer Ni-doped 3C–SiC qualifications of a promising optical material.Research highlights► The structural stability, electronic and optical properties of Ni-doped 3C–SiC are, for the first time to our knowledge, presented using the first-principles calculation, which implying that Ni-doped 3C–SiC is a promising optical material. ► The preferential substituting position of Ni in 3C–SiC supercell is determined by comparing the formation energy calculation. ► Compared with intrinsic 3C–SiC, Ni doping can improve the electric conductivity and photo-absorption efficiency of 3C–SiC significantly. The related results are explained with band theory in detail.

The influence of mechanical activation of powder mixtures of Si and C, via high energy attrition milling (up to 12 h), on combustion synthesis of SiC was experimentally investigated. β-SiC fine powder was successfully fabricated in 1.0 MPa N2 atmosphere without other additional treatments, such as preheating, electric action, or chemical activation. Relatively weak peaks of α-SiC, α-Si3N4 and Si2ON2 were also found in the final products. The experimental results and their theoretical treatment showed that mechanical activation via high energy ball-milling provides to the initial Si/C powder mixture extra energy, which is needed to increase the reactivity of powder mixture and to make possible the ignition and the sustaining of combustion reaction to form SiC.Fine sized powders of β-SiC was fabricated by combustion reaction of mechanical activation Si and C powder successfully. The average particle size of the formed SiC powders is about 400 nm. The influence mechanism of high energy attrition ball-milling on combustion synthesis of SiC powder including particle size, amorphization, and inner strain in the crystallites was studied comprehensively.X-ray diffractograms of the powder mixture, benignly mixed and after ball-milling in Ar and N2 atmospheres (atmospheric pressure) for different times.

The surface engineering strategy has exhibited unique advantages in photocatalysis, electrocatalysis, sensing, etc. Here in this work, NiO nano octahedron aggregates with exposure of active {111} facets are synthesized through a facile and scalable way. When evaluated as anode materials for Li ion batteries (LIBs), the NiO nano octahedron aggregates exhibit excellent rate performance and long-life cycling performance with high reversible capability. A reversible capability of as high as 793 mA h g−1 is retained after 200 cycles at 0.2C. Moreover, the excellent rate performance is achieved. The exceeding lithium storage performance is attributed to the synergy effect of nano size and exposed (111) surface of the NiO octahedra improving kinetics of charge transportation and Li ion diffusion. The NiO octahedron aggregates can be used as prospective host materials for investigation of surface effect on catalysis, sensing, switching, supercapacitors and electrodes for sodium batteries, fuel cells, etc.