Search

The clay mineral/g-C3N4 composites were prepared through a simple one-pot synthesis with acid-treated clay minerals and melamine as precursors. Three typical clay minerals, e.g., kaolinite, sepiolite, and talc, were adopted as photocatalyst carriers. Notably, the acid-treated clay minerals coupled with g-C3N4 in three different ways. The kaolinite/g-C3N4 composite, in particular, proceeded with an intercalation reaction due to the in situ growth of g-C3N4 within the layers of acid-treated kaolinite, leading to the expansion of kaolinite layers and a prominently large specific surface area of 61.9 m2 g−1. The resultant composites were used in photocatalytic H2 generation by water splitting and CO2 reduction, exhibiting superior photocatalytic performance to the g-C3N4. Among the obtained composites, the optimized kaolinite/g-C3N4 showed the best photocatalytic activities, e.g. 3.03 μmol g−1 h−1 of CO evolution and 385 μmol g−1 h−1 of H2 evolution, compared with merely 0.91 μmol g−1 h−1 of CO evolution and 96.4 μmol g−1 h−1 of H2 evolution for bare g-C3N4. The superior performance of kaolinite/g-C3N4 can be ascribed to the large specific surface area and better distribution of g-C3N4, which can enhance the light absorption, increase the number of active sites and favor the charge separation.

We report on erbium (Er) related electroluminescence (EL) in the visible and near infrared (NIR) regions from the light-emitting device (LED) based on the Er-doped ZnO (ZnO:Er)/n-Si isotype heterostructure formed by sputtering ZnO:Er film on n-Si/n+-Si epitaxial wafer. Herein, the ZnO:Er film exhibits n-type in electrical conduction. The aforementioned LED is electroluminescent only under sufficiently high forward bias with the negative voltage connecting to n+-Si substrate. Such forward bias enables the electrons from n-Si to enter into the ultra-thin SiOx (x ≤ 2) layer inherently existing between the ZnO:Er film and n-Si via Poole-Frenkel conduction mechanism and, subsequently, to drift into the ZnO:Er film thus becoming hot electrons, which impact-excite the Er3+ ions to emit characteristic visible and NIR light. Furthermore, the Er-related EL from the aforementioned LED can be significantly enhanced through adopting the strategy of co-doping F− ions into the ZnO host, which brings about twofold primary effects. Firstly, due to the atomic size compensation between F− and Er3+ ions, the ZnO crystal grains become larger to accommodate much more optically active Er3+ ions. Secondly, the partial substitution of F− ions for O2- ions around the Er3+ ion reduces the symmetry of pseudo-octahedral crystal field of Er3+ ion, thus increasing the probabilities of intra-4f transitions of Er3+ ions. We believe that this work sheds light on developing efficient silicon-based LEDs using the Er-doped oxide semiconductors.

Nanostructures have been widely employed to reduce optical refkection for various optoelectronic devices. In this work, the aligned nanostructure arrays of with desirable diameter and density were obtained. We demonstrated the potential applications of nanosphere lithography in fabrication of Si nanoholes (SiNHs) and Si nanowires (SiNWs) with excellent broadband light antirefkectance properties. Both nanostructures drastically suppress the refkection across the whole measured spectrum with wavelength above Si band gap (1.12 eV) as compared to that of planar Si wafer. The refkectance intensity of SiNHs and SiNWs is less than 6% over broad range of 400 to 1000 nm. The nanosphere lithography technique is expected to have potential applications in fabrication of nanostructures with various properties.

A type of metal–insulator–semiconductor (MIS) structured light-emitting device (LED), where a semitransparent gold (Au) film, a polymethyl methacrylate film, and an erbium (Er)-doped ZnO (ZnO:Er) film on a silicon substrate act as the “M”, “I”, and “S” components, respectively, has been prepared. With increasing forward bias with the positive voltage connected to the semitransparent “M” (Au) electrode, such LED first exhibits random lasing (RL) from the ZnO host itself and is then electroluminescent with the characteristic emissions from the Er3+ ions incorporated into the ZnO host. Based on the energy band diagram and the analysis of carrier transportation for the ZnO:Er-based LED applied with different forward bias voltages, the evolution from the RL to the Er-related electroluminescence as mentioned above has been tentatively explained.

We demonstrate the synthesis of Co–Ge three-dimensional nanowire arrays directly anchored on the current collector via the growth of Co nanowire arrays and subsequent RF-deposition of Ge. When used as anode materials for lithium-ion batteries, the Co–Ge nanowire arrays show a reversible capacity of 1535 mAh g−1 after 100 cycles at a current density of 320 mA g−1 and a capacity of 1239 mAh g−1 even at 8000 mA g−1. With respect to sodium-ion batteries, cycling capacity of ∼350mAh g−1 after 100 cycles is obtained. The excellent electrochemical properties may be attributed to the unique three-dimensional array nanostructures that can provide robust mechanical support, fast electron transport, and good strain accommodation.

The self-induced unsteadiness in tip leakage flow (TLF) of a micro-axial fan rotor is numerically studied by solving Reynolds-averaged Navier-Stokes equations. The micro-axial fan, which is widely used in cooling systems of electronic devices, has a tip clearance of 6% of the axial chord length of the blade. At the design rotation speed, four cases near the peak efficiency point (PEP) with self-induced unsteadiness and four steady cases which have much weaker pressure fluctuations are investigated.

We have previously developed silicon-based light-emitting devices (LEDs) with luminescent erbium (Er)-doped TiO2 (TiO2:Er) films [Yang et al., Appl. Phys. Lett. 100, 031103 (2012)]. In an LED therein, the TiO2:Er film is sandwiched between the ITO film and heavily boron-doped p-type silicon (p+-Si). In this work, we have investigated the electroluminescence (EL) from two LEDs with the TiO2:Er films annealed at 650 and 850 °C, respectively. It is revealed that between the TiO2:Er film and p+-Si, there is an intermediate silicon oxide (SiOx, x ≤ 2) layer and its thickness increases from ∼4 to 8 nm with the increase of annealing temperature from 650 to 850 °C. Interestingly, the thickness of the intermediate SiOx layer is found to exhibit a profound impact on the EL from the LED with the TiO2:Er film on p+-Si. The EL from the LED with the 650 °C-annealed TiO2:Er film is activated only under the forward bias with the positive voltage connecting to the p+-Si substrate. Such EL consists of the oxygen-vacancy-related emissions from TiO2 host and the characteristic visible and ∼1540 nm emissions from the Er3+ ions, while the EL from the LED with the 850 °C-annealed TiO2:Er film can only be enabled by the reverse bias with the negative voltage applied on the p+-Si substrate. Such EL features only the visible and ∼1540 nm emissions from the Er3+ ions. The difference in the EL behaviors of the two LEDs as mentioned above is found to be ascribed to the different electrical conduction mechanisms.We have previously developed silicon-based light-emitting devices (LEDs) with luminescent erbium (Er)-doped TiO2 (TiO2:Er) films [Yang et al., Appl. Phys. Lett. 100, 031103 (2012)]. In an LED therein, the TiO2:Er film is sandwiched between the ITO film and heavily boron-doped p-type silicon (p+-Si). In this work, we have investigated the electroluminescence (EL) from two LEDs with the TiO2:Er films annealed at 650 and 850 °C, respectively. It is revealed that between the TiO2:Er film and p+-Si, there is an intermediate silicon oxide (SiOx, x ≤ 2) layer and its thickness increases from ∼4 to 8 nm with the increase of annealing temperature from 650 to 850 °C. Interestingly, the thickness of the intermediate SiOx layer is found to exhibit a profound impact on the EL from the LED with the TiO2:Er film on p+-Si. The EL from the LED with the 650 °C-annealed TiO2:Er film is activated only under the forward bias with the positive voltage connecting to the p+-Si substrate. Such EL consists of the oxygen-vacancy-re...

We have recently reported erbium (Er)-related visible and near-infrared (∼1540 nm) electroluminescence (EL) from the light-emitting device (LED) with a structure of ITO/TiO2:Er/SiO2/Si in which TiO2:Er refers to the Er-doped TiO2 film [Zhu et al., Appl. Phys. Lett. 107, 131103 (2015)]. In this work, we codope yttrium (Y) into the TiO2:Er film in the aforementioned LED to achieve the significantly enhanced Er-related visible and ∼1540 nm EL. It is suggested that the Y-codoping leads to a less symmetric and distorted crystal field around the Er3+ ions incorporated into the TiO2 host, thus increasing the probabilities of intra-4f transitions of Er3+ ions. Moreover, the Y-codoping facilitates the dispersion of Er3+ ions into the TiO2 host, which is favorable for reducing the concentration quenching effect on the Er-related EL. For the aforementioned two reasons, the EL from the LED based on the TiO2:Er film can be enhanced by means of codoping Y into the TiO2 host.

The transportation of bulk materials is of importance in many industrial applications, ranging from minerals, agriculture, pharmaceuticals, chemicals, pigments, plastics, cement, sand, salt and food processing. Screw conveyors are widely used for transportation of particulates at controlled and steady rates. In this paper, we use the Discrete Element Method (DEM) to analyze the performance of a screw conveyor including visualization of the motion of particles, angular and axial velocity of particles, overall torque and total force, kinetic energy and total energy dissipation. The DEM model was established by applying periodic boundary conditions to a single pitch of the screw and the particles are modeled as spheres. DEM simulation shows that the nature of the particle flow in a horizontal screw conveyor is surprisingly complex and is reasonably sensitive to the operating conditions. The dependence of the performance of a screw conveyor on the operating conditions is analyzed..