Terephthalic acid decomposition by photocatalytic ozonation with VxOy/ZnO under different UV-A LEDs distributions

Abstract

In this work, the degradation of terephthalic acid (TA) by vanadium oxide (V_xO_y) supported on zinc oxide (ZnO) was evaluated in a photocatalytic ozonation treatment based on two UV-A LEDs distributions. TEM analysis and specific surface area measurement suggest that V_xO_y is not supported on ZnO, while the EDXRF and XPS analysis indicated the presence of V_xO_y. The XPS analysis on V_xO_y/ZnO catalyst showed non-significant surface change between fresh and used catalyst. However, ozone decomposition showed a higher reaction rate constant for catalytic (230%) and photocatalytic ozonation (310%) in comparison with single ozone treatment. Photocatalytic ozonation with central and external irradiation arrays was evaluated in TA elimination by a kinetic study. The irradiation arrays had not statistical differences in the TA decomposition or oxalic acid formation. These results suggest that the construction of central bodies inside the reactor could be not necessary for photocatalytic processes.     

DNA-CTMA/a-Si:H bio-hybrid photodiode: A light-sensitive photosensor

Recently, considerable interest have occurred in the development of an organic-inorganic-based bio-hybrid photodiodes (Bio-HPDs) with metal-free, eco-friendly, and cost-competitive features for light-sensitive devices. This paper reports a bio-inspired optical absorber material for the fabrication of Bio-HPDs using n-type hydrogenated amorphous silicon (a-Si:H) and a natural deoxyribonucleic acid (DNA)-cetyltrimethylammonium chloride (CTMA) biomaterial. a-Si:H is inexpensive and abundant, and DNA-CTMA is metal-free and eco-friendly. A DNA-CTMA coating on n-type a-Si:H leads to a chemically stable material with increased absorption and effective ties of dangling bonds and interface state density. Analysis results showed that the rectification ratio (RR) of the Bio-HPD is found to be 4 times higher than reference PD. This indicates that the effective RR is improved by the DNA-CTMA layer since it creates molecular charge interactions between DNA-CTMA layer and a-Si:H substrate. Moreover, Bio-HPD shows a light photosensitivity (I_photo/I_dark) of 474 with more reliable and has longer life time. In addition, the formation and feasible charge transport mechanisms are discussed. This biomaterial can be used for the development of commercially viable and environmentally safe large-scale Bio-HPDs applications.     

Small-scale portable photovoltaic-battery-LED systems with submersible LED units to replace kerosene-based artisanal fishing lamps for Sub-Saharan African lakes

A technical simulation and economic model was developed for a floating photovoltaic (PV)-battery system powering a submerged light emitting diode (LED) lighting system. The system was designed to provide around the equivalent of 1000 lumens (lm) of light of the existing light fishing technology (a floating pressurised kerosene light) for artisanal light fishers to use for 8 h per night on Lake Victoria and other lakes in the region (Tanganyika, Rukwa, Mweru, Kivu, etc.). The net present cost (NPC) of a technically appropriate PV-battery-LED system was calculated as US$280 over 5 years, five-times less than the existing solar-based technology, a PV-battery-compact fluorescent lamp (CFL) system, and around ten times less than the baseline pressurised kerosene-based technology over the five years. Fishers owning the new PV-battery-LED system outright will likely recoup their initial investment within a year relative to the cost of alternatives, although the upfront capital cost of the new system was higher than the pressurised kerosene and PV-battery-CFL, and found to be practically unaffordable to the subsistence fishers without microcredit. Nonetheless, the technical simulations found that the new system was also able to provide additional lighting services during the day and evening, with little (if any) electrical impact on the system when in use for light fishing during the small hours of moonless nights. This research also demonstrates that the high cost of operating pressurised kerosene lamps precludes them for use in other applications within the community, including in homes. This research suggests that facilitated local development of appropriate new light fishing technology configurations will require training of local individuals to sensitise fishing communities to the new technology, and sustain wider adoption of the more efficient, cost-effective, and safer alternative.     

Impact of extinction coefficient of phosphor on thermal load of color conversion elements of phosphor converted LEDs

Besides their direct impact on the respective correlated color temperature, the extinction coefficient and the quantum effi- ciency of the phosphor also have tremendous impact on the thermal load of the color conversion elements of phosphor converted LEDs under operation. Because of the low thermal conductivity of the silicone matrix in which the phosphor particles are typically embedded, the by far highest temperatures within the LED assembly are reached within the color conversion element. Based on a combined optical and thermal simulation procedure we show that in particular a larger value for the extinction coefficient might have a beneficial impact on the resulting thermal load.     

Reverse‐Conducting IGBT Using MEMS Technology on the Wafer Back Side

In this paper, we present a 600‐V reverse conducting insulated gate bipolar transistor (RC‐IGBT) for soft and hard switching applications, such as general purpose inverters. The newly developed RC‐IGBT uses the deep reactive‐ion etching trench technology without the thin wafer process technology. Therefore, a freewheeling diode (FWD) is monolithically integrated in an IGBT chip. The proposed RC‐IGBT operates as an IGBT in forward conducting mode and as an FWD in reverse conducting mode. Also, to avoid the destructive failure of the gate oxide under the surge current and abnormal conditions, a protective Zener diode is successfully integrated in the gate electrode without compromising the operation performance of the IGBT.     

Crystal structure,luminescent properties and white light emitting diode application of Ba3GdNa(PO4)3F:Eu2+ single-phase white light-emitting phosphor

A series of single-phase white-light-emitting phosphors, Eu²⁺-activated Ba₃GdNa(PO₄)₃F phosphors were synthesized by solid-state reactions. The crystal structure of Ba₃GdNa(PO₄)₃F was been identified by Rietveld refinement of X-ray diffraction pattern. The Eu²⁺-activated Ba₃GdNa(PO₄)₃F phosphors exhibit broad excitation spectra from 250 to 420 nm, which matched well with the n-UV LED chips. Under the excitation of 365 nm, the emission spectrum almost covered the entire visible region including two emission bands peaked at 472 nm and 640 nm. Three different Eu²⁺ emission centers in Ba₃GdNa(PO₄)₃F:Eu²⁺ phosphor were confirmed by their fluorescence decay lifetimes. The optimal concentration of Eu²⁺ in Ba₃GdNa(PO₄)₃F:xEu²⁺ was 3 mol% and the corresponding concentration quenching mechanism was verified to be exchange coupling interaction. Furthermore, the white light-emitting diode fabricated with Ba₃GdNa(PO₄)₃F:0.05Eu²⁺ phosphor and a 370 nm UV chip has a CIE of (0.3267, 0.2976) with a color-rendering index of 78.4 at the CCT of 5287 K.     

Study of polarization phenomena in Schottky CdTe diodes using infrared light illumination

Schottky CdTe diode detectors suffer from a polarization phenomenon, which is characterized by degradation of the spectral properties over time following exposure to high bias voltage. This is considered attributable to charge accumulation at deep acceptor levels. A Schottky CdTe diode was illuminated with an infrared light for a certain period during a bias operation, and two opposite behaviors emerged. The detector showed a recovery when illuminated after the bias-induced polarization had completely progressed. Conversely, when the detector was illuminated before the emergence of bias-induced polarization, the degradation of the spectral properties was accelerated. Interpretation of these effects and discussion on the energy level of deep acceptors are presented.     

Boron and aluminum diffusion into 4H-SiC substrates

Boron and aluminum doping by diffusion into n-type 4H-SiC Si-face substrates was carried out at the temperatures of 1800-2000 °C. Secondary ion mass spectroscopy (SIMS) was employed to obtain the impurity profiles, which showed that linearly graded boron profile and shallow aluminum profiles have been achieved, which may be a promising application in SiC device fabrication, such as p-n diode or ohmic contact. Characterization of high temperature processing influence on SiC surface morphology has been performed. Elemental boron and aluminum carbide were determined to be the best candidates as an impurity source materials for realizing p-type diffusion.     

垂直阵列DL巴间准直光束指向精度测量方法

简介了大功率二极管激光器垂直阵列巴条(Bar)间准直光束指向精度问题,及其对激光器垂直阵列输出光束的影响.采用单透镜远场探测系统对激光器垂直阵列远场光斑进行采集,搭建了实验测试装置.结合光斑强度质心算法对实验室封装的20巴条连续输出2 kw二极管激光器垂直阵列进行了测量,测试结果为巴间准直光束指向精度±1.7 mrad...     

An advanced VHDL‐AMS PiN diode model: towards simulation‐based design of power converters

This paper focuses on the modeling of a power PiN diode. The focal point basis is the dependence on temperature. The PiN diode remains a difficult device to model mainly during switching transients. An advanced PiN diode temperature‐dependent model is developed and implemented in VHDL‐AMS. Heterogeneous simulation scheme including the circuit wiring parasitic components, the probe effects and the dependent diode models is successfully simulated using SIMPLORER simulator. Experimental data of several commercial PiN diodes are compared to simulation results at different temperature levels. A good rate of consistency is found. Copyright © 2014 John Wiley & Sons, Ltd.