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This article reports trap-related forward conduction instability of GaN quasi-vertical p-i-n diodes grown on a Si substrate. Three hole traps with activation energies of 0.38, 0.60, and 0.70 eV together with one electron trap with an energy level of 0.26 eV under the conduction band were revealed by deep-level transient spectroscopy (DLTS). Pulsed ${I}$ – ${V}$ measurements were performed on a device whose traps were prefilled. The rest time durations and OFF-state bias levels and periods were varied to investigate the forward ${I}$ – ${V}$ recovery phenomenon, which was highly correlated with the carrier detrapping process inside the device. The detrapping process could be greatly accelerated by a reverse bias or a lifted temperature. An “on-the-fly” resistance characterization was carried out to study the time-dependent carrier release process using short positive voltage pulses. The device was further submitted to switch-on transient assessment to investigate the time-resolved dynamic ${R}_{ \mathrm{\scriptscriptstyle ON}}$ evolution. The initial dynamic ${R}_{ \mathrm{\scriptscriptstyle ON}}$ ratio was proportional to the reverse bias level and duration and was gradually decreased after continuous carrier injection until the trapping effects were overwhelmed. With a forward voltage slightly higher than the threshold voltage, it took dozens of milliseconds for the dynamic ${R}_{ \mathrm{\scriptscriptstyle ON}}$ to be equal to its static counterpart. It was found that at 350 K, the ON-resistance ratio could reach unit more rapidly than the room temperature case, indicating mitigation of current collapse of p-i-n diodes and their great potential for high-temperature switching applications.

This study investigated the relationship of synthesis pressure and corresponding thermoelectric parameters of PbSe. These thermoelectric parameters include the energy gap (Eg), resistivity (R), and the Seebeck coefficient (S). The variation tendency of these parameters with synthesis pressure is similar to the in-situ measurement results of the measurement pressure dependence of Eg, R, and S. Moreover, high-pressure synthesis achieved the best power factor with sample synthesized at 1.5 GPa synthesis pressure. With regard to the high pressure in-situ measurement of PbSe, there is a possible best measurement pressure interval. The 1.5 GPa (synthesis pressure) here is consistent with the “best pressure interval”. These results indicate that high-temperature and high-pressure synthesis is able to capture partial high pressure features of PbSe to the ambient pressure. Despite several innovative properties of PbSe in the high-pressure environment, it does not have direct applied value for the ambient pressure state. However, the high-pressure synthesis, perhaps, could provide an alternative way.

Oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are the rate-controlling and/or energy-intensive reactions of numerous energy conversion and storage devices. It is a great challenge to attain a high catalytic efficiency with a single electrocatalyst towards these reactions simultaneously. Herein, a porous carbon was prepared by pyrolysis of chitin with the assistance of CoCl2 and ZnCl2 and a subsequent sulfurization process, which resulted in uniform loading of Co, N and S elements. The porous and modified carbon exhibited high catalytic performance towards ORR, OER and HER. Furthermore, the catalyst was used as air electrode to construct Zn-air batteries, which showed a power of 142 mW cm−2 and discharging and charging voltages of 1.3 V and 1.74 V at 1 mA cm−2 after 100 cycles, respectively. When used as both the anode and cathode for water splitting, the voltage to achieve a 10 mA cm−2 electrolysis current was 1.58 V which was stable over 75 h of operation. The performance enhancement is attributed to the etching effect which generates defects in both carbonaceous matrix and the Co9S8 crystallites during the sulfurization, as well as the doping of S and N elements which creates multiple active sites.

Dissimilatory iron-reducing microorganisms play an important role in the biogeochemical cycle of iron and influence iron mineral formation and transformation. However, studies on microbial iron-red...

This study focuses on designing and calibrating a blade system that allows for modeling downbursts outflows at the Subsonic Wind Tunnel (WT) at Ryerson University (RU). The system is based on flow redirection to generate downburst outflow gust fronts. A system of multiple louvers was suggested and calibrated using (CFD) simulations in 3 stages. In stage 1, flow resulting from the system with stationary inclined blades (do not move with the time) was characterized to understand formation of the outflow-like vortices. Stage 2 focuses on the non-stationary effects resulting from suddenly rotating the blades to a specific angle over a specific time. Stage 3 focuses on developing a superposition code to combine different cases from stage 2 (blades rotate to different angles). This superposition code was coupled with an optimization technique to generate arbitrary downburst outflows at the full scale. Three full scale records were selected, and optimization was carried out to identify blade angles and time simulating the records. Accuracy of the blade system and optimization was confirmed by conducting CFD simulations and experimental wind tunnel testing with comprehensive blade rotation as described from the optimization and achieving a reasonable match to the full scale.

The poor electrical conductivity of titanium oxide is a chief hurdle against the enhancement of its thermoelectric properties and increasing its reduction degree is an effective way for advancing its electrical conductivity. Strongly reduced titanium oxides, however, are rarely investigated for their thermoelectric properties so far. Here they were successfully synthesized by the efficient high-pressure and high-temperature (HPHT) method and the first systematic investigations about their thermoelectric properties were conducted. It was revealed that the samples were composed of phases TiO and Ti2O3. The high-pressure modulated morphologies were complicated and the microstructures were rich in lattice defects and nanoscale grains, the characteristics of pressure-modulated samples. Consequently, the electrical resistivity was greatly suppressed compared with that of other semiconductors and the changes in the conducting types of the samples with measurement-temperature were diverse, p → n or n → p → n or n-type all the time. Besides, the common Lorentz number was no longer applicable. The modulation by high-pressure is responsible for these. This work provides prospective strategies about upgrading the thermoelectric properties of titanium oxides under HPHT.

A retransmission chipless tag with multiple U-shaped slot resonators is proposed to cut down the cost of traditional tags with chips. Multiple side-by-side U-shaped slot structures of different lengths are printed on the microstrip line, and the two terminals of the microstrip line are connected correspondingly with two orthogonal ultra-wideband (UWB) transceiver antennas to form the retransmission chipless tag. The U-shaped slot resonator has high Q values and narrow impedance bandwidth. The bandwidth that each resonator adds to the protection bandwidth is 300 MHz. Several 6-bit coding U-shaped slot resonator chipless tags are designed and fabricated for comparison and measurement. Results show that the simulation and the measurement are in agreement. The slot width of the U-shaped slot resonator and the distance between the resonators are reduced, resulting in deepened spectrum notch depth of the resonator. Decreasing the dielectric constant of the substrate or increasing the thickness of the substrate increases the spectrum notch depth of the resonator.

In this study, we optimized the high-temperature parameter of high-pressure and high-temperature (HPHT) for enhancing the thermoelectric properties of TiO1.76. The phase compositions, morphologies and microstructures were significantly modulated during the optimization process of HPHT. Correspondingly, the electrical properties were improved yet the thermal conductivity reduced compared with other means. As a result, a zT of 0.35 at 700 °C was achieved, outperforming all reported results of nonstoichiometric titanium oxide obtained using ambient pressure. Besides, the mechanical performance was also significantly better than most alloy-based thermoelectric materials. For all these both high-pressure and high-temperature are indispensable and the coordination between them is the key to transforming potential edges into performance advantages.

The present work explores the feasibility of advancing the thermoelectric properties of nonstoichiometric TiO 2−x through introducing more and more oxygen deficiencies. Compared with previous work, it is found that this compositional manipulation induces phase transition; in addition, the scattering mechanisms of both carrier and phonon have changed, resulting in the temperature-independent electrical resistivity, inferior electrical performance and an unexpected high thermal conductivity. As a consequence, a moderate zT value of 0.13 is obtained in TiO 1.72 at 600 ℃. Through this work, we understand deeply about thermoelectric properties of nonstoichiometric titanium oxide by high pressure and high temperature, and further investigations about this system have been directed.

Bulk materials Ba 8 Ga 16 In x Ge 30-x (x = 0.5, 1.0, 1.5) were prepared by High-Pressure and High-Temperature (HPHT) method and the crystal structure has been confirmed by X-ray diffraction and cell refinement. The actual In composition was much lower than the starting composition, and lattice constants increased with the increase of substitution. As the temperature increased, the Seebeck coefficient and electrical resistivity increased first and then decreased, while the thermal conductivity was the opposite, which leads to significant enhancement on thermoelectric properties of the clathrates. The substitution of indium elements decreased the seebeck coefficient and electrical resistivity, and also changed the microstructure of the compounds. A minimum thermal conductivity of 0.84 Wm −1 K −1 was obtained, and a good ZT value of 0.52 was achieved. The grain boundaries and lattice defects generated by high pressure can effectively scatter phonons of different frequencies, which reduce the lattice thermal conductivity.

In this letter, Ni substitution for Co and Ba filling into the voids were simultaneously applied to the CoSb3 bulks by the high pressure and high temperature (HPHT) method. As the results, the polycrystalline Ba0.3Ni0.15Co3.85Sb12 skutterudite bulks were successfully synthesized and the systematic thermoelectric properties were investigated. In our experiments, the synthesized time was sharply shortened to 30 min, which is markedly an advantage for mass production. The multiple textures and microstructures were revealed, including vortices-like structures, defects, and lattice dislocations. Remarkably, pressure tuning led to the increase of the Seebeck coefficient and electrical resistivity, yielding an optimized power factor of 11.7 × 10−4 Wm−1K−2 in the Ba0.3Ni0.15Co3.85Sb12 sample prepared at 3 GPa at room temperature, which yielded a 10-fold improvement in power factor and showed distinct reduction of thermal conductivity compared with pure CoSb3 sample. The maximum zT value 0.91 was obtained at 700 K for Ba0.3Ni0.15Co3.85Sb12 sample. The experimental results suggest that the effective elements doping combining with HPHT synthesis could optimize electrical and thermal transport properties in skutterudites.

N-type polycrystalline skutterudite compounds Ni0.15Co3.85Sb12 and Fe0.2Ni0.15Co3.65Sb12 with the bcc crystal structure were synthesized by high pressure and high temperature (HPHT) method. The synthesis time was sharply reduced to approximately half an hour. Typical microstructures connected with lattice deformations and dislocations were incorporated in the samples of Ni0.15Co3.85Sb12 and Fe0.2Ni0.15Co3.65Sb12 after HPHT. Electrical and thermal transport properties were meticulously researched in the temperature range of 300 K to 700 K. The Fe0.2Ni0.15Co3.65Sb12 sample shows a lower thermal conductivity than that of Ni0.15Co3.85Sb12. The dimensionless thermoelectric figure-of-merit (zT) reaches the maximal values of 0.52 and 0.35 at 600 K and 700 K respectively, for Ni0.15Co3.85Sb12 and Fe0.2Ni0.15Co3.65Sb12 samples synthesized at 1 GPa.

Surface properties of nanoceria can strongly affect the catalytic performance in oxidation reactions. In this work, a simple but efficient post-treatment, where H2O2 is used as a complexing agent to dissolve Ce3+ from the surface of CeO2 nanorods with the help of ultrasonic treatment, is carried out to tune the surface properties and increase their catalytic performance for catalytic wet air oxidation (CWAO) of phenol. It is found that the dissolution of Ce3+ from the surface of CeO2 nanorods can create more surface defects and result in a much rougher surface. The H2O2–ultrasonic treatment can also increase Ce3+ concentration, create more surface oxygen vacancies, and narrow the band gap of CeO2 nanorods. These properties enable H2O2–ultrasonic-treated CeO2 nanorods (CeO2-H2O2-sf) to possess strong oxidizing ability to effectively oxidize phenol. Additionally, for the sake of comparison, other post-treatments, including calcination, H2O2, and ultrasonic–H2O, are also imposed on CeO2 nanorods.

Herein, an electrocatalyst consisting of iron and nitrogen co-doped porous carbon (Fe–N/C) was prepared by catalytic carbonization of chitin with the assistance of FeCl3 and ZnCl2. The catalytic activity of Fe–N/C towards the oxygen reduction reaction (ORR) in both acidic and alkaline electrolytes was significantly enhanced by air-plasma etching for only 120 s, showing a four-electron ORR process with an onset potential and limiting current comparable to those of Pt catalysts. This performance enhancement originated from the removal of less stable sp3 and amorphous sp2 carbons which would expose more active catalytic FeN4 centers, as well as the transformation of a small fraction of iron-based nanoparticles into FeN4 species.

Zinc oxide nanoparticles (ZnO NPs) have shown adverse health impact on the human male reproductive system, with evidence of inducing apoptosis. However, whether or not ZnO NPs could promote autophagy, and the possible role of autophagy in the progress of apoptosis, remain unclear. In the current study, in vitro and in vivo toxicological responses of ZnO NPs were explored by using a mouse model and mouse Leydig cell line. It was found that intragastrical exposure of ZnO NPs to mice for 28 days at the concentrations of 100, 200, and 400 mg/kg/day disrupted the seminiferous epithelium of the testis and decreased the sperm density in the epididymis. Furthermore, serum testosterone levels were markedly reduced. The induction of apoptosis and autophagy in the testis tissues was disclosed by up-regulating the protein levels of cleaved Caspase-8, cleaved Caspase-3, Bax, LC3-II, Atg 5, and Beclin 1, accompanied by down-regulation of Bcl 2. In vitro tests showed that ZnO NPs could induce apoptosis and autophagy with the generation of oxidative stress. Specific inhibition of autophagy pathway significantly decreased the cell viability and up-regulated the apoptosis level in mouse Leydig TM3 cells. In summary, ZnO NPs can induce apoptosis and autophagy via oxidative stress, and autophagy might play a protective role in ZnO NPs-induced apoptosis of mouse Leydig cells.

In this report, electrical characteristics of the Ni/GaN Schottky barrier diode grown on sapphire have been investigated in the range of 20 K–300 K, using current–voltage, capacitance–voltage, and deep level transient spectroscopy (DLTS). A unified forward current model, namely a modified thermionic emission diffusion model, has been developed to explain the forward characteristics, especially in the regime with a large ideality factor. Three leakage current mechanisms and their applicability boundaries have been identified for various bias conditions and temperature ranges: Frenkel–Poole emission for temperatures above 110 K; variable range hopping (VRH) for 20 K–110 K, but with a reverse bias less than 20 V; high-field VRH, in a similar form of Fowler–Nordheim tunneling, for cryogenic temperatures below 110 K, and relatively large bias (>25 V). Four trap levels with their energy separations from the conduction band edge of 0.100 ± 0.030 eV, 0.300 eV, 0.311 eV, and 0.362 eV have been tagged together with their capture cross sections and trap concentrations. The significantly reduced DLTS signal at 100 K suggested that traps practically became inactive at cryogenic temperatures, thus greatly suppressing the trap-assisted carrier hopping effects.

Di-2-ethylhexyl phthalate (DEHP) is extensively used as a plasticizer in many products, especially medical devices, furniture materials, cosmetics, and personal care products. DEHP is noncovalently bound to plastics, and therefore, it will leach out of these products after repeated use, heating, and/or cleaning of the products. Due to the overuse of DEHP in many products, it enters and pollutes the environment through release from industrial settings and plastic waste disposal sites. DEHP can enter the body through inhalation, ingestion, and dermal contact on a daily basis, which has raised some concerns about its safety and its potential effects on human health. The main aim of this review is to give an overview of the endocrine, testicular, ovarian, neural, hepatotoxic, and cardiotoxic effects of DEHP on animal models and humansin vitroandin vivo.

The polycrystalline skutterudite [Formula: see text] were successfully synthesized from 1.5 GPa to 3.5 GPa by the high pressure and high temperature (HPHT) method. Negative Seebeck coefficient confirmed the n-type conductivity of all samples. The phase compositions of samples were investigated by X-ray diffraction (XRD) and the microstructures were observed by scanning electron microscopy (SEM). It was found that the grains appeared smaller and the grain boundaries became more abundant when pressures were higher. We measured the electrical properties from room temperature to 723 K. Both the electrical resistivity and absolute value of Seebeck coefficient increase with the increasing synthetic pressure. At 723 K, the maximum power factor of [Formula: see text] was obtained for the sample synthesized under 3 GPa. The maximum ZT value of 0.61 was reached by [Formula: see text] synthesized under 3 GPa and measured at 723 K.