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IEEE Energy Conversion Congress and Exposition, ECCE

作者： Ryan Brody Paul Ohodnicki Brandon Grainger Department of Electrical and Computer Engineering University of Pittsburgh Pittsburgh PA USA Department of Mechanical Engineering and Materials Science University of Pittsburgh Pittsburgh PA USA

ISBN: (数字)9798350376067

ISBN: (纸本)9798350376074

Permanent magnets (PM) demagnetization occurs when applying external fields opposite the PM’s polarity. To a certain degree, this effect is reversible and useful in high-speed permanent magnet synchronous motors (PMSMs) by enabling flux weakening control and reluctance torque. However, relatively large external fields cause irreversible demagnetization, damaging the magnet and, thus, the motor. In PMSMs, irreversible demagnetization can significantly limit torque density, especially when using rare earth (RE) free PMs with low coercivity. Irreversible demagnetization risk can be controlled in motor designs to increase torque density if the motor drive is designed appropriately, but the impact of this relationship has yet to be quantified statistically. Therefore, this paper does so by designing and comparing PMSMs with varying demagnetization risk and comparing their performance in terms of torque density and short circuit current. The motor designs presented here are based on the specifications for the 2011 Nissan Leaf, and electric vehicles (EVs) contribute significantly to RE PM demand by typically using interior permanent magnet motors (IPMSMs) with RE PMs. Therefore, the authors also assess demagnetization risk during EV drive cycles for the MnBi motor designs presented here. Because demagnetization effects are particularly limiting in permanent magnet assisted synchronous reluctance motors (PMASynRM) that use MnBi PMs, this paper focuses on various MnBi PMASynRM designs and compare them to a MnBi IPMSM design previously published by the authors.

关键词： Temperature dependence Temperature distribution Torque Short-circuit currents Magnetomechanical effects Permanent magnet motors Permanent magnets Topology Demagnetization Reluctance motors

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Soft Magnetic Properties of Amorphous Ring Cores Prepared Via Spark Plasm Sintering Using Fe-Based Amorphous Powders (Fe, Co)68.7(C, Si, B, P)24.5(Mo,Al)6.8

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SSRN 2024年

作者： Yi, Seonghoon Lee, Jae-Won Kim, Jin-Ah Sohn, In-Joon Yun, Kyyoul Department of Materials Science and Engineering Kyungpook National University Daegu Korea Republic of Department of Electrical Electronic and Computer Engineering Gifu University Gifu Japan

In this study, an Fe-based amorphous alloy (Fe, Co)68.7(C, Si, B, P)24.5(Mo,Al)6.8 with a large supercooled liquid region was developed for fabricating soft magnetic composites utilized in applications involving high-frequency conditions. The alloy was prepared as amorphous ribbons (~25 μm thick) and amorphous rods (Ф3 mm), which were crushed and sieved to form powders with different shapes and particles smaller than 53 μm: amorphous flake powders made from crushed ribbons and amorphous irregular powders made from crushed rods. Additionally, the amorphous flake powder was coated with an amorphous SiO2 layer. Both powders were consolidated via spark plasma sintering into dense ring cores with a relative density exceeding 90%;this high density is attributed to the Newtonian flow within the temperature range of the amorphous powder’s supercooled liquid region. The ring cores remained amorphous even after spark plasma sintering. Excellent soft magnetic properties originating from the amorphous nature and high density of the ring cores were confirmed based on measurements using a vibrating sample magnetometer, a direct current B-H loop tracer, and an alternating current B-H analyzer. Additionally, due to electrical isolation between the powder particles, the eddy current loss of the amorphous ring cores made from the SiO2-coated amorphous flake powder was significantly reduced to 4.86 W/kg (at Bm = 100 mT, 100 kHz). The mechanical hardness of the amorphous ring cores (>690 Hv 0.5) was also observed to be considerably higher than that of commercially available ring cores. These findings verify that the ring cores prepared in this study can be reliable for practical applications involving harsh conditions. © 2024, The Authors. All rights reserved.

关键词： Spark plasma sintering

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Heterogeneous Cathode Work Function Measurement and Interpretation: A case Study with SrVO3 23

Heterogeneous Cathode Work Function Measurement and Interpre...

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23rd International Vacuum Electronics Conference, IVEC 2022

作者： Lin, Lin Jacobs, Ryan Morgan, Dane Booske, John University of Wisconsin-Madison Department of Materials Science and Engineering MadisonWI53706 United States University of Wisconsin-Madison Department of Electrical and Computer Engineering MadisonWI53706 United States

ISBN: (纸本)9781665443258

Work function is a key electron emission property. However, questions remain on how to unambiguously measure and interpret the work function. In this proceeding, using polycrystalline SrVO3 perovskite as an example, we clarify a few key issues in work function characterization. We show that the vacuum level, which is significantly affected by the patch and external electric fields, needs to be carefully selected to obtain a clear work function interpretation. © 2022 IEEE.

关键词： Work function

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MOCVD Epitaxy of α-(AlxGa1-x)2O3(x =0-100%) on m-Plane Sapphire Substrate

MOCVD Epitaxy of α-(AlxGa1-x)2O3(x =0-100%) on m-Plane Sapp...

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2022 Compound Semiconductor Week, CSW 2022

作者： Bhuiyan, A F M Anhar Uddin Feng, Zixuan Huang, Hsien-Lien Meng, Lingyu Hwang, Jinwoo Zhao, Hongping Ohio State University Department of Electrical and Computer Engineering ColumbusOH43210 United States Ohio State University Department of Materials Science and Engineering ColumbusOH43210 United States

ISBN: (数字)9781665453400

ISBN: (纸本)9781665453400

Phase pure single crystal α-(AlxGa1-x)2O3 thin films are successfully grown on m-plane sapphire substrate via MOCVD. Comprehensive characterization by XRD, RSM mapping, atomic resolution STEM, Raman spectroscopy, SEM, AFM and XPS measurements reveal high quality epitaxial growth of α-(AlxGa1-x)2O3 thin films over the entire Al composition range (x=0-100%) and α-GaO/AlGaO superlattice structures with smooth surface morphology, sharp interfaces, and homogenous Al distribution. The bandgap energies of 5.41 eV (x=0) to 8.81 eV (x=1) are extracted from XPS measurements. The determined band offsets reveal a type-I band alignment at the α-AlGaO/GaOinterfaces with valance and conduction band offsets of 0.27 eV and 3.13 eV between α-Ga2O3 and α-Al2O3, respectively. © 2022 IEEE.

关键词： Thin films

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Breakdown Voltage Enhancement of GaN diodes with High-k Dielectric

Breakdown Voltage Enhancement of GaN diodes with High-k Diel...

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2022 Device Research Conference, DRC 2022

作者： Talesara, Vishank Zhang, Yuxuan Cheng, Junao Zhao, Hongping Lu, Wu The Ohio State University Department of Electrical and Computer Engineering ColumbusOH43210 United States The Ohio State University Department of Materials Science and Engineering ColumbusOH43210 United States

ISBN: (数字)9781665498838

ISBN: (纸本)9781665498838

Gallium nitride (GaN) has the great potential for high-power devices due to its wide bandgap and high breakdown field. In particular for high-power GaN pn diodes, critical field is noticed at the p-n interface and electrode edges at a high reverse bias. Therefore, to achieve high breakdown voltage, electric field at the edges need to be decreased. Edge termination techniques such as guard rings and field plate help with field management, the critical electric field is still located at the edge of the electrode. To decrease the effects of high electric field and also to reduce the surface leakage current, addition of passivation layer is generally used. In such device structures, the electric field in the passivation layer decreases abruptly. To mitigate the field crowding effect, in this work, we implemented a thin high-k dielectric layer for breakdown voltage enhancement. We show significant breakdown voltage improvement on GaN p-n diodes with high-k dielectric (Barium titanate, BTO, ϵ 180)/spin-on-glass (SOG) passivation layers in comparison with devices with only low-k (3.9) SOG passivation layer. © 2022 IEEE.

关键词： Gallium nitride

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13 GHz Acoustic Resonator with Q of 600 in High-Quality Thin-Film Aluminum Nitride

13 GHz Acoustic Resonator with Q of 600 in High-Quality Thin...

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IEEE International Symposium on Applications of Ferroelectrics (ISAF)

作者： Sinwoo Cho Omar A. Barrera Hrithik Agrawal Michael Liao Ellie Y. Wang Vakhtang Chulukhadze Jack Kramer Joshua Campbell Tzu-Hsuan Hsu Ian Anderson Mark S. Goorsky Ruochen Lu Department of Electrical and Computer Engineering The University of Texas Austin TX US Department of Materials Science & Engineering University of California Los Angeles CA US

ISBN: (数字)9798350371901

ISBN: (纸本)9798350371918

This study reports a high-quality thin-film aluminum nitride (AlN) acoustic Lamb wave resonator (LWR) with a compact size and low-loss operation. The device is composed of 60 nm thick Al electrodes on the top of 200 nm thick plasma vapor deposition (PVD) AlN film. The design and stack of the resonator are selected for leveraging of Ku-band operation (12-18 GHz) with top electrodes of wavelengths (λ, 0.5-0.8 µm). Specifically, λ of 0.8 µm implements a 13.0 GHz resonator with a record-breaking Q p_3dB of 600, enabled by fundamental symmetric (S0) mode surpassing prior works. The results highlight the potential for the effectiveness of the new stack and optimized resonator design in Ku-band. Further study will be focused on identifying and minimizing the dominant loss.

关键词： Electrodes Performance evaluation Electric potential Resonant frequency Ku-band Acoustics Plasmas III-V semiconductor materials Frequency control Aluminum nitride

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A Study on the Performance Improvement of Axial Flux Permanent Magnet Machines Based on Stator Slot Design with Semi-Closed Slots or Magnetic Wedges

A Study on the Performance Improvement of Axial Flux Permane...

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IEEE Transportation Electrification Conference and Expo (ITEC)

作者： Jangho Yun Brandon Grainger Paul Ohodnicki Department of Mechanical Engineering and Materials Science University of Pittsburgh Pittsburgh PA USA Department of Electrical and Computer Engineering University of Pittsburgh Pittsburgh PA USA

ISBN: (数字)9798350317664

ISBN: (纸本)9798350317671

The most important specifications for electric propulsion systems are torque, efficiency, and constant power speed range (CPSR). Axial flux permanent magnet (AFPM) machines suitable for applications that require compact design and high-power density are difficult to manufacture and assemble compared to radial flux permanent magnet (RFPM) machines. In this paper, the effects of stator semi-closed slots and magnetic wedges on performance are analyzed. The inner stator dual sided rotor and inner rotor dual sided stator geometries, which are mainly utilized in electric vehicle systems, were created based on the 3-D finite element analysis (FEA) model. FEA results show that the stator slot design increases output power by 8% in the inner rotor dual sided stator motor and increases efficiency by 8.3% in the inner stator dual sided rotor motor compared to open slots. The results show that semi-closed slots and magnetic wedges have a significant impact on the performance of AFPM machines and must be considered for design optimization.

关键词： Geometry Magnetic flux Torque Rotors Stators Motors Permanent magnets

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Supersymmetric Microring Laser Arrays in Higher-Dimensional Space

Supersymmetric Microring Laser Arrays in Higher-Dimensional ...

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CLEO: science and Innovations, S and I 2022

作者： Qiao, Xingdu Midya, Bikashkali Gao, Zihe Zhang, Zhifeng Zhao, Haoqi Wu, Tianwei Yim, Jieun Agarwal, Ritesh Litchinitser, Natalia M. Feng, Liang Department of Electrical and Systems Engineering University of Pennsylvania PhiladelphiaPA19104 United States Department of Materials Science and Engineering University of Pennsylvania PhiladelphiaPA19104 United States Department of Electrical and Computer Engineering Duke University DurhamNC27708 United States

To achieve single fundamental supermode operation in coupled arrays, a two-dimensional supersymmetry formalism for mode control is developed and experimentally demonstrated with microring laser arrays. © Optica P...

ISBN: (纸本)9781557528209

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Thermo-Mechanical Analysis of a 650 V/150 A e-GaN HEMT Sandwiched between a PCB and DBC Substrate 10

Thermo-Mechanical Analysis of a 650 V/150 A e-GaN HEMT Sandw...

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10th IEEE Workshop on Wide Bandgap Power Devices and Applications, WiPDA 2023

作者： Nicholas, Carl Boshkovski, Filip Arriola, Emmanuel Zhang, Zichen Lu, Guo-Quan Virginia Tech Bradley Department of Electrical and Computer Engineering BlacksburgVA24061 United States Virginia Tech Center for Power Electronics Systems BlacksburgVA24061 United States Virginia Tech Department of Materials Science and Engineering BlacksburgVA24061 United States

ISBN: (纸本)9798350337136

Following successful packaging of a 650 V/150 A e-GaN HEMT between a printed-circuit board and a direct-bond-copper substrate, this study evaluates the thermo-mechanical reliability of the sandwich-style package. Thermo-mechanical fatigue of both soldered and silver-sintered bonds in the package under temperature cycling was studied using ANSYS Mechanical. Deformation properties of eutectic lead-Tin solder and sintered silver were modeled after Anand viscoplastic behavior. The inelastic volume-Averaged strain energy density accumulated per thermal cycle at each bond was used as a metric of bond fatigue. Simulation results showed that the silver-sintered bond at the gate pad and the solder bond closest to the package center have the highest per-cycle strain energy density. Simulations also evaluated the effect of encapsulation materials on bond fatigue. It was found that using rigid encapsulants, such as one with a coefficient of thermal expansion of 14.9 ppm/°C and an elastic modulus of 17.5 GPa, instead of a commonly used silicone gel reduced the per-cycle bond fatigue by 97%. Findings of this study would help guide the development of high performing and high reliability packaging technology for the 650V/150A GaN HEMT. © 2023 IEEE.

关键词： Finite element method

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Characterizing and Mitigating Chemomechanical Degradation in High-Energy Lithium-Ion Battery Cathode materials

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Accounts of materials Research 2022年第5期3卷 511-524页

作者： Norman S.Luu Kyu-Young Park Mark C.Hersam Department of Materials Science and Engineering Northwestern UniversityEvanstonIllinois 60208United States Graduate Institute of Ferrous and Energy Materials Technology Pohang University of Science and TechnologyPohangKyungbuk 37673Republic of Korea Department of Chemistry and Department of Electrical and Computer Engineering Northwestern UniversityEvanstonIllinois 60208United

Lithium-ion batteries(LIBs)are nearly ubiquitous energy storage solutions,powering devices ranging from consumer electronics to electric *** advance these applications,current LIB research efforts are directed toward improving energy and power densities,cyclic lifetimes,charging speeds,and *** parameters are intrinsically tied to properties of the active electrode materials,such as the redox mechanism,chemical composition,and crystal *** particularly challenging issue is that the active electrode materials that possess higher theoretical energy densities are generally more susceptible to degradation during cycling.A notable example is the family of layered multicomponent transition metal oxides,which is the incumbent class of active LIB cathode materials for electric *** increase their theoretical capacities,the transition metal fraction in these materials is trending toward higher Ni ***,Ni-rich chemistries suffer from electrochemical,crystallographic,and mechanical degradation that increase in severity with increasing Ni ***,alternative high-energy cathode materials,including overlithiated layered oxides and disordered rock salt materials,present additional stability challenges that must be overcome before they can be realistically incorporated into LIB *** chemomechanical degradation in high-energy LIB cathode materials occurs at multiple length *** defects,such as antisite defects or vacancies,are commonly generated during electrochemical cycling and can contribute to the loss of cyclable active *** both the primary and secondary particle level,electrochemical cycling also induces significant volumetric changes and state-of-charge heterogeneity,generating regions of high stress and strain that are precursors to mechanical ***,at the electrode level,nonuniform charge transfer reactions throughout the electrode can lead to locally overcharged regions that become

关键词： Battery electrode cycling

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