More Like this

1. A Compact 45 V-to-54 kV Modular DC-DC Converter

   https://doi.org/10.1109/COMPEL.2019.8769612  

   Park, Sanghyeon; Gu, Lei; Rivas-Davila, Juan (June 2019, 2019 20th Workshop on Control and Modeling for Power Electronics (COMPEL))

   This paper presents the design of a compact 45 V-to-54 kV dc-dc converter for high-energy beam applications with the focus on X-ray generation. We describe key design choices for a high power density including a modular structure, high-frequency switching, planar transformers and Dickson topology. High-voltage insulation and thermal management are also described in detail. The experimental data with a 5 kV single module and a 10-module 54 kV converter indicate that the proposed structure can generate high dc voltage while achieving a several times higher power density compared to commercial high-voltage power supplies. 

   more » « less
2. Research Progress in High-Throughput Screening of CO2 Reduction Catalysts

   https://doi.org/10.3390/en15186666  

   Wu, Qinglin; Pan, Meidie; Zhang, Shikai; Sun, Dongpeng; Yang, Yang; Chen, Dong; Weitz, David A.; Gao, Xiang (September 2022, Energies)

   The conversion and utilization of carbon dioxide (CO2) have dual significance for reducing carbon emissions and solving energy demand. Catalytic reduction of CO2 is a promising way to convert and utilize CO2. However, high-performance catalysts with excellent catalytic activity, selectivity and stability are currently lacking. High-throughput methods offer an effective way to screen high-performance CO2 reduction catalysts. Here, recent advances in high-throughput screening of electrocatalysts for CO2 reduction are reviewed. First, the mechanism of CO2 reduction reaction by electrocatalysis and potential catalyst candidates are introduced. Second, high-throughput computational methods developed to accelerate catalyst screening are presented, such as density functional theory and machine learning. Then, high-throughput experimental methods are outlined, including experimental design, high-throughput synthesis, in situ characterization and high-throughput testing. Finally, future directions of high-throughput screening of CO2 reduction electrocatalysts are outlooked. This review will be a valuable reference for future research on high-throughput screening of CO2 electrocatalysts. 

   more » « less
3. Applications of High-Pressure Technology for High-Entropy Alloys: A Review

   https://doi.org/10.3390/met9080867  

   Dong, Wanqing; Zhou, Zheng; Zhang, Mengdi; Ma, Yimo; Yu, Pengfei; Liaw, Peter K.; Li, Gong (August 2019, Metals)

   High-entropy alloys are a new type of material developed in recent years. It breaks the traditional alloy-design conventions and has many excellent properties. High-pressure treatment is an effective means to change the structures and properties of metal materials. The pressure can effectively vary the distance and interaction between molecules or atoms, so as to change the bonding mode, and form high-pressure phases. These new material states often have different structures and characteristics, compared to untreated metal materials. At present, high-pressure technology is an effective method to prepare alloys with unique properties, and there are many techniques that can achieve high pressures. The most commonly used methods include high-pressure torsion, large cavity presses and diamond-anvil-cell presses. The materials show many unique properties under high pressures which do not exist under normal conditions, providing a new approach for the in-depth study of materials. In this paper, high-pressure (HP) technologies applied to high-entropy alloys (HEAs) are reviewed, and some possible ways to develop good properties of HEAs using HP as fabrication are introduced. Moreover, the studies of HEAs under high pressures are summarized, in order to deepen the basic understanding of HEAs under high pressures, which provides the theoretical basis for the application of high-entropy alloys. 

   more » « less
4. Synthesis and Thermal Oxidation Resistance of Boron-Rich Boron–Carbide Material

   https://doi.org/10.3390/ma16196526  

   Iwan, Seth; Sutton, Wesley; Baker, Paul A.; Sereika, Raimundas; Vohra, Yogesh K. (October 2023, Materials)

   A boron-rich boron–carbide material (B4+δC) was synthesized by spark plasma sintering of a ball-milled mixture of high-purity boron powder and graphitic carbon at a pressure of 7 MPa and a temperature of 1930 °C. This high-pressure, high-temperature synthesized material was recovered and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Vickers hardness measurements, and thermal oxidation studies. The X-ray diffraction studies revealed a single-phase rhombohedral structure (space group R-3m) with lattice parameters in hexagonal representation as a = 5.609 ± 0.007 Å and c = 12.082 ± 0.02 Å. The experimental lattice parameters result in a value of δ = 0.55, or the composition of the synthesized compound as B4.55C. The high-resolution scans of boron binding energy reveal the existence of a B-C bond at 188.5 eV. Raman spectroscopy reveals the existence of a 386 cm−1 vibrational mode representative of C-B-B linear chain formation due to excess boron in the lattice. The measured Vickers microhardness at a load of 200 gf shows a high hardness value of 33.8 ± 2.3 GPa. Thermal gravimetric studies on B4.55C were conducted at a temperature of 1300 °C in a compressed dry air environment, and its behavior is compared to other high-temperature ceramic materials such as high-entropy transition metal boride. The high neutron absorption cross section, high melting point, high mechanical strength, and thermal oxidation resistance make this material ideal for applications in extreme environments. 

   more » « less
5. Strength can be controlled by edge dislocations in refractory high-entropy alloys

   https://doi.org/10.1038/s41467-021-25807-w  

   Lee, Chanho; Maresca, Francesco; Feng, Rui; Chou, Yi; Ungar, T.; Widom, Michael; An, Ke; Poplawsky, Jonathan D.; Chou, Yi-Chia; Liaw, Peter K.; et al (December 2021, Nature Communications)

   Abstract Energy efficiency is motivating the search for new high-temperature (high-T) metals. Some new body-centered-cubic (BCC) random multicomponent “high-entropy alloys (HEAs)” based on refractory elements (Cr-Mo-Nb-Ta-V-W-Hf-Ti-Zr) possess exceptional strengths at high temperatures but the physical origins of this outstanding behavior are not known. Here we show, using integrated in-situ neutron-diffraction (ND), high-resolution transmission electron microscopy (HRTEM), and recent theory, that the high strength and strength retention of a NbTaTiV alloy and a high-strength/low-density CrMoNbV alloy are attributable to edge dislocations. This finding is surprising because plastic flows in BCC elemental metals and dilute alloys are generally controlled by screw dislocations. We use the insight and theory to perform a computationally-guided search over 10 7 BCC HEAs and identify over 10 6 possible ultra-strong high-T alloy compositions for future exploration. 

   more » « less