Well-aligned ZnO nanorod arrays were synthesized by a wet chemical method on the glass substrate with ZnO thin film as seed layer prepared by pulsed laser deposition. The effect of annealing ...temperature on the luminescence characteristics was investigated. As the annealing temperature increased, the photoluminescence properties show a general enhancing tendency. The nanorod array with high ultraviolet emission and negligible visible light emission (designated by the photoluminescence intensity ratio of ultraviolet to visible emission of 66.4) is obtained by annealing the sample at 700
°C for 1
h. Based on the results of X-ray photoelectron spectroscopy and photoluminescence spectra, the mechanisms of visible emission were discussed.
► ZnO nanorod array with good crystallography, low defects concentration and good optical property was obtained after annealed at 700 °C for 1 h. ► The transition from the conduction band to the
O
i
level may be responsible for the yellow-green emission. ► The yellow emission may originate from the presence of Zn(OH)
2 on the surface or the band transition from conduction band to
V
oZn
i
level. ► The transition from the
Zn
i
level to the level should produce an orange emission or an orange-red emission.
Supported Fe doped ZnO nanorod arrays with different doping concentrations were synthesized by a facile wet chemical method. The structures, surface morphologies and optical properties were ...characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectrometer (PL) and ultraviolet–visible (UV–Vis) spectrophotometer. The results demonstrated that the nanorod arrays uniformly grew aligned along with the 002 direction, densely overspreading the whole substrates. Both PL and UV–Vis spectra presented an extension to visible wavelength range. The photocatalytic activity was evaluated by photodegradation of methyl orange (MO) under UV light irradiation. Supported Fe doped ZnO nanorod arrays exhibited enhanced photocatalytic activity, and the supported 1.0 % Fe doped ZnO nanorod arrays reached to the maximum. After 2 h irradiation, almost 97 % MO solution was decomposed. Supported Fe doped ZnO nanorod arrays could be practical used in environment applications.
Graphical Abstract
Supported Fe doped ZnO nanorod arrays were synthesized by wet chemical method. Supported nanorod arrays exhibited better photocatalytic activity than that of nanocrystalline. Fe doping enhanced the photocatalytic activity furthermore, and it reached to an optimum for 1.0 % Fe. More marked defects introduced by doping should take responsibility.
Hierarchical Cu(OH)
2
/Co
2
(OH)
2
CO
3
nanohybrid arrays grown on copper foam were realized by a simple two-step solution route for the first time, Cu(OH)
2
nanowires were utilized as a scaffold to ...form Cu(OH)
2
nanowire/Co
2
(OH)
2
CO
3
nanoneedle core–shell structures and upper dispersed Co
2
(OH)
2
CO
3
ball-flowers structures. And time gradient experiments were also considered to understand the growth mechanism for the Cu(OH)
2
/Co
2
(OH)
2
CO
3
nanohybrid arrays, the optimized hierarchical architecture electrode of Cu(OH)
2
/Co
2
(OH)
2
CO
3
yields a high areal capacitance of 1.31 F cm
−2
at 2 mA cm
−2
, which is more than three times higher than that of single Cu(OH)
2
electrode (0.37 F cm
−2
) and also superior than that of Co
2
(OH)
2
CO
3
, an excellent rate property (0.74 F cm
−2
at 50 mA cm
−2
), and good cycling stability (91.5% capacity retention after 5000 cycles). Also, the hierarchical Cu(OH)
2
/Co
2
(OH)
2
CO
3
nanohybrid arrays//active carbon asymmetric supercapacitors (ASCs) were fabricated, exhibiting a high energy density of 656 mWh cm
−2
with a power density of 28.8 W cm
−2
. And three different colors (two red, two yellow, two green) of LED indicators can be lighted up by two ASC devices in series, which demonstrate that the hierarchical Cu(OH)
2
/Co
2
(OH)
2
CO
3
nanohybrid arrays on copper foam are promising candidate electrode materials for supercapacitors.
Nitrogen-doped titanium dioxide (TiO2-xNx) thin films have been prepared by pulse laser deposition on quartz glass substrates by ablated titanium dioxide (rutile) target in nitrogen atmosphere. The x ...value (nitrogen concentration) is 0.567 as determined by X-ray photoelectron spectroscopy measurements. UV-vis spectroscopy measurements revealed two characteristic deep levels located at 1.0 and 2.5 eV below the conduction band. The 1.0 eV level is attributable to the O vacancy state and the 2.5 eV level is introduced by N doping, which contributes to narrowing the band-gap by mixing with the O2p valence band. The enhanced degradation efficiency in a broad visible-light range was observed from the degradation of methylene blue and methylene orange by the TiO2-xNx film.
A nanocrystalline nickel with a broad grain size distribution was prepared by direct current electrodeposition, which exhibited high ultimate strength of 1440–1916
MPa and good ductility of 5.6–11.3% ...under tensile test at a wide strain rate range (1.35E−6 to 1.35
s
−1) and room temperature. The good ductility of nc Ni can be attributed to the increased strain hardening ability induced by the inhomogeneous microstrucutre. Two distinguished strain rate sensitivity (0.016 and 0.045) and flow stress activation volume (26
b
3 and 11
b
3) were obtained at normal and high strain rate and low strain rate, respectively. The intrinsic microstructure and extrinsic deformation conditions (low strain rate) lead to the transition in the deformation mechanism from the dislocation mediated deformation to both grain boundary and dislocation deformation with decreasing strain rate. The high near-uniform elongation at low strain rate can be explained by its corresponding high
m value. The variation of fracture surface morphology with strain rates also implies the underlying deformation mechanism transition.
Ultrathin dual phase nanosheets consisting of alternating spinel Li4Ti5O12 (LTO) and rutile TiO2 (RT) lamellas are synthesized through a facile and scalable hydrothermal method, and the formation ...mechanism is explored. The thickness of constituent lamellas can be controlled exactly by adjusting the mole ratio of Li:Ti in the original reactants. Alternating insertion of the RT lamellas significantly improves the electrochemical performance of LTO nanosheets, especially at high charge/discharge rates. As anodes in lithium-ion batteries (LIBs), the dual phase nanosheet electrode with the optimized phase ratio can deliver stable discharge capacities of 178.5, 154.9, 148.4, 142.3, 138.2, and 131.4 mA h g–1 at current densities of 1, 10, 20, 30, 40, and 50 C, respectively. Meanwhile, they inherit the excellent cyclic stability of pure spinel LTO and exhibit a capacity retention of 93.1% even after 500 cycles at 50 C. Our results indicate that the alternating nanoscaled lamella structure is a good alternative to facilitate the transfer of both the Li ions and electrons into the spinel LTO, giving rise to an excellent cyclability and fast rate performance. Therefore, the newly prepared carbon-free LTO-RT nanosheets with high safety provide a new opportunity to develop high-power anodes for LIBs.
ZnO thin films with typical
c-axis (0
0
2) orientation were successfully deposited on quartz glass substrates by pulse laser ablation of Zn target in oxygen atmosphere at a relatively low temperature ...range of 100–250
°C. The structural and optical properties of the films were studied. In photoluminescence (PL) spectra at room temperature, single ultraviolet emission (without deep-level emission) was obtained from ZnO film deposited at the temperature of 200
°C. This was attributed to its low intrinsic defects.
Traditional conversion coatings on magnesium alloys are usually immersed in a solution containing hexavalent chromium compounds. However, the replacement treatments have been proposed by the present ...environmental driving to eliminate hexavalent chromium. In this work, a tannic acid based conversion coating on AZ91D magnesium alloy was obtained by treatment in a solution containing tannic acid and ammonium metavanadate. SEM, XPS and IR were used to determine the morphology and structure of the conversion coatings. Continuous and uniform conversion coating was deposited on AZ91D alloy and the main components of the coatings were Al
2O
3, MgF
2 and penta-hydroxy benzamide–magnesium complex. The formation mechanism of the coating was discussed. Polarization measurement and salt spray test showed that the corrosion resistance of the conversion coating was much higher than that of traditional chromate conversion coating.
A tannic acid based conversion coating was formed on AZ91D magnesium alloy through a solution containing C
76H
52O
46 (tannic acid), NH
4VO
3, K
2ZrF
6 and H
3PO
4. The growth process and corrosion ...resistance of the conversion coating were investigated by SEM, FESEM, XPS, IR, potentiodynamic polarization and EIS test. The results showed that the main components of the coatings were penta-hydroxy benzamide–magnesium complex, Al
2O
3 and MgF
2. Zr(HPO
4)
2·H
2O(α-ZrP) was first formed in the time interval of 70
s–120
s, which acted as catalyst to activate the main reaction of gallic acid being oxidized into the penta-hydroxy benzamide–magnesium complex, as well as the formation of MgF
2 and Al
2O
3, which took place in the time interval of 120
s to 600
s. The thickness of coating treated for 300
s and 600
s was 1.1
μm and 1.6
μm, respectively. Polarization measurement and EIS test in 3
wt.% NaCl solution indicated that the conversion coating treated for about 300–600
s shows good corrosion resistance while an excess time treatment (720
s) induces the coating surface coarse and uneven, leading to the reduction of corrosion resistance of the conversion coating.
