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1.
Large-scale VO2 nanowires have been synthesized by two-step method. First, we have been obtained (NH4)0.5V2O5 nanowire precursors by hydrothermal treatment of ammonium metavanadate solution at 170 °C. Secondly, the precursors have been sealed in quartz tube in vacuum and annealed to form VO2 nanowires at 570 °C. Scanning electron microscope and transmission electron microscope analysis show that the nanowires have self-assembling nanostructure with the diameter of about 80-200 nm, length up to125 μm. Electrical transport measurements show that it is semiconductor with conduction activate energy of 0.128 eV. A metal-semiconductor transition can be observed around 341 K. 相似文献
2.
Honeycomb-like graphitic macroporous carbon (HGMC) was synthesized by means of pyrolysis of NH4HCO3 using Mg powder as reductant in an autoclave at 550 °C. The characterization of structure and morphology was carried out by X-ray diffraction (XRD), Raman spectrum, field-emission scanning electron microscopy (FESEM), and (High-resolution) transmission electron microscope [(HR)TEM]. The results of nitrogen adsorption-desorption indicate that the products are macropore materials with the pore size of 1-3 μm, and the Brunauer-Emett-Teller (BET) surface area was 14 m2/g. As a typical morphology, the possible growth process of HGMC was also investigated and discussed. The experimental results show that the in situ formed MgO microparticles play a template role during the HGMC formation. 相似文献
3.
In this paper, the sol-gel synthesis and characteristic properties of kalsilite-type alumosilicates (KAlSiO4 and K0.5Na0.5AlSiO4) are reported. The polycrystalline powders were characterized by thermal analysis (TG/DTA), powder X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Single-phase kalsilite oxides have been obtained after annealing precursor gels for 5 h in the temperature range of 750-850 °C. It was demonstrated that crystallinity of the samples slightly depends on the temperature of annealing. From the results obtained, it could be concluded that the KAlSiO4 solids are composed of the volumetric plate-like grains with no regular size (from 5 μm to 30 μm at 750 °C and around 5-50 μm at 850 °C). Larger crystallites for mixed potassium-sodium kalsilite have formed (from 10 μm to 80 μm at 750 °C and >100 μm at 850 °C) in comparison with potassium kalsilite samples). The erosion of obtained dental porcelain samples stored in saliva, beer and Coca-Cola was compared. 相似文献
4.
Jae-hyun Kim Gyu-bong Cho Yeon-min Im Byong-sun Chun Yeon-wook Kim Tae-hyun Nam 《Materials Research Bulletin》2013
Si was coated on the surface of Ti–49Ni (at%) alloy powders by ball milling in order to improve the electrochemical properties of the Si electrodes of secondary Li ion batteries and then the microstructure and martensitic transformation behavior were investigated by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Ti–Ni powders coated with Si were fabricated successfully by ball milling. As-milled powders consisted of highly deformed Ti–Ni powders with the B2 phase and amorphous Si layers. The thickness of the Si layer coated on the surface of the Ti–Ni powders increased from 3–5 μm to 10–15 μm by extending the milling time from 3 h to 48 h. However, severe contamination from the grinding media, ZrO2 occurred when the ball milling time was as long as 48 h. By heating as-milled powders to various temperatures in the range of 673–873 K, the highly deformed Ti–Ni powders were recovered and Ti4Ni4Si7 was formed. Two-stage B2–R–B19′ transformation occurred when as-milled Si-coated Ti–49Ni alloy powders were heated to temperatures below 873 K, above this temperature one-stage B2–B19′ transformation occurred. 相似文献
5.
Pulse electric field induced electron emission from the Pb(Zr0.65Ti0.35)O3 ferroelectric films has been investigated as a function of the film thickness from 0.2 to 4.0 μm and the upper electrode diameter from 200 to 1100 μm. The electron emission charge from the 3.0 μm film was several nC per pulse, which was comparable to that of the bulk ferroelectrics. However, the local dielectric breakdown occurred in the films below 1.0 μm without the electron emission, which was confirmed by the optical microscopy observation after the emission tests. As the upper electrode size decreased and the film thickness increased, electrons were more easily emitted without breakdown. 相似文献
6.
Waheed S. Khan Zahid Usman Ghulam Nabi Zulfiqar Ali Niaz Ahmad Niaz 《Materials Research Bulletin》2011,46(12):2261-2265
Metallic zinc layered polyhedral microparticles have been fabricated by thermal evaporation and condensation technique using zinc as precursor at 750 °C for 120 min and NH3 as a carrier gas. The zinc polyhedral microparticles with oblate spherical shape are observed to be 2-9 μm in diameter along major axes and 1-7 μm in thickness along minor axes. The structural, compositional and morphological characterizations were performed by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). A vapour-solid (VS) mechanism based growth model has been proposed for the formation of Zn microparticles. Room temperature photoluminescence (PL) emission spectrum of the product exhibited a strong emission band at 369 nm attributed to the radiative recombination of electrons in the s, p conduction band near Fermi surface and the holes in the d bands generated by the optical excitation. 相似文献
7.
Potassium tantalate (KTa5O13) microcones with a maximum diameter of about 47-85 μm were prepared by anodic oxidation of tantalum in (15-20 M) KOH solutions at the temperature of 70 °C and applied voltage of 20 V for 3 h. Different factors affecting on the morphology of tantalum surface were discussed. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry (XRD) were used to characterize the structure of the microcones. The photoelectrochemical properties were studied through electrochemical workstation. The experimental results indicate KTa5O13 microcones have a good performance in photoelectricity. The possible formation mechanism of as-prepared KTa5O13 microcones was also presented. 相似文献
8.
A two layer Ti–6Al–4V(wt.%)/Ti–43Al–9V–Y(at.%) laminate composite sheet with a uniform interfacial microstructure and no discernible defects at the interfaces has been prepared by hot-pack rolling, and its interfacial microstructure and shear strength were characterized. Characterization of the interfacial microstructure shows that there was an interfacial region of uniform thickness of about 250 μm which consisted of two layers: Layer I on the TiAl side which was 80 μm thick and Layer II on the Ti–6Al–4V side which was 170 μm thick. The microstructure of Layer I consisted of massive γ phases, needlelike γ phases and B2 phase matrix, while the microstructure of Layer II consisted of α2 phase. The microstructure of the interfacial region is the result of the interdiffusion of Ti element from Ti–6Al–4V alloy layer into the TiAl alloy layer and Al element from the TiAl alloy layer into the Ti–6Al–4V alloy layer. The shear strength measurement demonstrated that the bonding strength between the TiAl alloy and Ti–6Al–4V alloy layers in the laminate composite sheet was very high. This means that the quality of the interfacial bonding between the two layers achieved by the multi-path rolling is high, and the interface between the layers is very effective in transferring loading, causing significantly improved toughness and plasticity of the TiAl/Ti–6Al–4V laminate composite sheet. 相似文献
9.
This paper describes an ethylene glycol (EG)-assisted approach to the large-scale ultralong Sb2S3 sub-microwires, formed by a simple hydrothermal reaction between SbCl3 and Na2S in the presence of distilled water. Transmission electron microscopy and scanning electron microscopy studies indicate that these Sb2S3 sub-microwires possess a diameter around 200 nm and length up to 100 μm. High-resolution transmission electron microscopy and selected area electron diffraction studies reveal that each Sb2S3 sub-microwire is a single-crystal along the [0 0 1] direction. The possible formation mechanism of the sub-microwires was discussed. The effects of volume ratio of EG/water, reaction temperature and the concentration of CO(NH2)2 on the morphology of Sb2S3 sub-microwires were also investigated. 相似文献
10.
Yuting Wang Shiro Shimada Yasunori Yamamoto Norio Miyaura 《Materials Research Bulletin》2008,43(2):251-256
h-BN nano-tubes, -bamboos, and -fibers were prepared separately from borazine oligomers using an alumina porous template at different wetting times of 20 h, 40 h and 2 weeks at room temperature, respectively. The borazine oligomer in the template was transformed to the h-BN nano-materials by two-step heat-treatment at 600 and 1200 °C in flowing N2. The FT-IR result confirmed the formation of BN. TEM and SEM images showed the formation of the nano-tubes in diameters 200-300 nm with thin walls about 10-20 nm thick, nano-bamboos 200-300 nm wide with knots at the separations of 0.5-1 μm, and the nano-fibers 15-20 μm long with fine crystallized BN particles. The mechanism for the formation of h-BN nano-tubes, -bamboos and -fibers is proposed. 相似文献
11.
BaTiO3 nanoparticle/poly(2-hydroxyethyl methacrylate) (PHEMA) hybrid nanofibers were fabricated from an in situ synthesized BaTiO3 nanoparticle/polymer hybrid by electrospinning. The bulk hybrid for nanofibers was synthesized through the in situ hydrolysis of Ba–Ti alkoxide modified with 2-vinyloxyethanol and subsequent copolymerization with HEMA monomer. IR and 13C NMR spectra showed the formation of polymer matrix. The molecular weights of BaTiO3 nanoparticle/PHEMA hybrid for spinning were 1.3 × 105 for 20 equiv. PHEMA and 5.7 × 105 for 30 equiv. PHEMA. The crystallite size of BaTiO3 particles in the hybrid was 4.5 nm according to the Scherrer equation. The diameter of BaTiO3 nanoparticle/PHEMA hybrid nanofibers ranged from 500 nm to 1 μm. A field stress–strain curve was observed for the BaTiO3 nanoparticle/PHEMA hybrid nanofiber. 相似文献
12.
In this study, we report the growth of ZnO nanowire on quartz glass substrates with Au-catalyst assistance by electric current heating of ZnO ceramic bar. The effect of substrate temperature on the properties of ZnO nanostructures has been investigated systematically. Structural analysis indicates that the grown ZnO crystals belong to hexagonal phase with preferential growth along (0 0 2) orientation. Scanning electron microscopic studies reveal the aligned ZnO nanowires were grown at 800 °C. The typical length and diameter of nanowires are in the uniform ranges of 4–20 μm and 20–100 nm, respectively, showing their high aspect ratio of about 1000. We have made an attempt to discuss about the change in ZnO nanostructures with different substrate temperatures and the possible mechanism for the growth of nanowires. Optical reflectance studies show the infrared reflectivity was controlled through the substrate temperature. 相似文献
13.
Composite coatings were prepared using hypophosphite reduced electroless nickel bath containing 7 g/L SiO2 nano-particles at pH 4.6 ± 0.2 and temperature 90 ± 2 °C. Deposition rate for SiO2 nano-composite coatings was 10–12 μm/h. The amount of SiO2 nano-particles co-deposited in the Ni–P matrix was around 2 wt.%. The analyzes of coating compositions, carried out by Energy Dispersive Analysis of X-ray (EDAX), showed that plain Ni–P and Ni–P/nano-SiO2 deposits contained around 8 wt.% phosphorus. The X-ray diffraction (XRD) pattern of Ni–P/nano-SiO2 coating was very similar to that of plain electroless Ni–P coating, whose structure was also amorphous. 相似文献
14.
A vanadium oxide-carbon nanotube composite was prepared by solution-based hydrolysis of NH4VO3 in the presence of carbon nanotubes. The carbon nanotubes induce the nucleation of the 1D vanadium oxide nanostructures, with the nuclei growing into long freestanding nanorods. The vanadium oxide nanorods with the lengths up to 20 μm and the widths of 5-15 nm exhibit a well-ordered crystalline structure. Catalytic tests show that the composite with nanostructured vanadium oxide is active for the partial oxidation of n-butane to maleic anhydride at 300 °C. 相似文献
15.
Anuja Datta 《Materials Research Bulletin》2008,43(4):983-989
Thin films of indium sulfide (In2S3) micro- and nanorods were successfully prepared by sulfurization of electrodeposited metal indium layers. The films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and UV-vis spectroscopy. From XRD and TEM observations it was concluded that the In2S3 nanorods and microrods have ∼50 nm and ∼0.5 μm diameter, respectively. A plausible top-growth mechanism was proposed for the formation of the nanorods in which the hydroxide layer was found to play an important role. The micro- and nanorods showed optical bandgap of ∼2.2 and ∼2.54 eV, respectively. This facile and cost effective method may be extended to fabricate other metal chalcogenide nanostructures on solid substrates. 相似文献
16.
The possibility of obtaining relatively high dielectric constant polymer–ceramic composite by incorporating the giant dielectric constant material, CaCu3Ti4O12 (CCTO) in a Poly(vinylidene fluoride) (PVDF) polymer matrix by melt mixing and hot pressing process was demonstrated. The structure, morphology and dielectric properties of the composites were characterized using X-ray diffraction, Thermal analysis, scanning electron microscope, and impedance analyzer. The effective dielectric constant (εeff) of the composite increased with increase in the volume fraction of CCTO at all the frequencies (100 Hz–1 MHz) under study. The dielectric loss did not show any variation up to 40% loading of CCTO, but showed an increasing trend beyond 40%. The room temperature dielectric constant as high as 95 at 100 Hz has been realized for the composite with 55 vol.% of CCTO, which has increased to about 190 at 150 °C. Theoretical models like Maxwell’s, Clausius–Mossotti, Effective medium theory, logarithmic law and Yamada were employed to rationalize the dielectric behaviour of the composite and discussed. 相似文献
17.
Clara Casado José R. García José M. González-Calbet Joaquín Coronas 《Materials Research Bulletin》2009,44(6):1225-1231
Titanosilicate ETS-10 crystals were prepared by hydrothermal synthesis varying Ti source (TiCl3 and commercial TiO2-anatase), time in autoclave and seeding with previously prepared ETS-10 crystals. The crystalline powders were characterized by X-ray diffraction, N2 adsorption, thermogravimetric analysis, and scanning and transmission electron microscopies. Control of the particle size of ETS-10 crystals ranging from 0.32 μm × 0.41 μm to 16.4 μm × 32.5 μm was successfully achieved varying the seeding and synthesis conditions. In particular, it was found that the use of TiO2-anatase alone or together with TiCl3 promotes heterogeneous primary nucleation. Transmission electron microscopy demonstrated that the largest crystals obtained here were twinned. 相似文献
18.
Ba–Ti–O films were prepared on Pt-coated Si substrate by laser chemical vapor deposition, and their orientations and microstructures were compared. Ba2TiO4, BaTiO3, BaTi2O5, Ba4Ti13O30 and BaTi4O9 single-phase films were prepared at Ti to Ba molar ratio from 0.41 to 3.49. The α′-Ba2TiO4 film showed (0 1 0) and (0 9 1) co-orientation with elongated, truncated columnar grains. The BaTiO3 film was composed of triangular and hexagonal grains with slight (1 1 1) orientation. The BaTi2O5 film had (0 1 0) orientation and faceted columnar grains. The Ba4Ti13O40 film showed (1 0 0) and (0 1 2) co-orientation with shellfish-like grains. The BaTi4O9 film showed (0 1 0) orientation with slightly rounded faceted columnar grains. The deposition rates of Ba–Ti–O films ranged from 30 to 144 μm h−1. 相似文献
19.
A unique solution-phase route was devised to synthesize crystal Ag nanowires with high aspect-ratio (8-10 nm in diameter and length up to 10 μm) by the reduction of AgNO3 with Vitamin C in SDS/ethanol solution. The resultant nanoproducts were characterized by transmission electron microscope (TEM), X-ray diffraction (XRD) and electron diffraction (ED). A soft template mechanism was put forward to interpret the formation of metal Ag nanowires. 相似文献
20.
The pure single phase of multiferroic material TbMnO3 powders were successfully synthesized by one-step molten salt synthesis (MSS) method in the NaCl–Na2SO4 eutectic salts at the temperature as low as 800 °C for 1 h. The temperature of synthesized high purity TbMnO3 is limited in a very narrow range. Prolonging the sintering time will not have an effect on the purity of samples, and either lower or higher salt concentration is not conducive to form pure TbMnO3. The obtained TbMnO3 was indexed to an orthorhombically distorted perovskite phase. The as-prepared crystals exhibit uniform and regular rhombic-like morphology with an average size of about 2 μm in edge length and 1–2 μm in thickness. The elements Mn and Tb in TbMnO3 exist dominantly as Mn3+ and Tb3+, respectively. The magnetic measurements of the TbMnO3 powders exhibit antiferromagnetism. Because of the simplicity and generalizability of the MSS method, it is reasonable to expect that the MSS method could also be exploited in future works which involves the nanoscale investigation of ferroelectric, ferromagnetic and multiferroic materials. 相似文献