Papers by Keyword: Energy Density

Abstract: With the continuous advancement of SiC device design and manufacturing processes, devices of the same ratings are achieving higher turn-on speeds and smaller chip areas. These improvements enhance the speed and power density of power electronic systems but also pose greater challenges for thermal management and the parasitic parameters of packaging. To address these issues, this paper proposes a multi-chip SiC power module packaging structure based on a multilayer ceramic substrate. Compared to a conventional single-layer DBC substrate, the multilayer substrate structure incorporates an additional intermediate copper layer, which serves as a current return path. Due to the close proximity between this return path and the upper copper layer, the overall loop area is reduced, thereby lowering the parasitic loop inductance. Simulation results show that the designed 800 V, 50 kW SiC power module achieves a parasitic loop inductance of around 3.22 nH at 10 MHz. In addition, traditional multilayer DBC structures are typically formed by soldering two separate DBC substrates together. Such soldered interfaces are often mechanically unstable, and electrical continuity between the upper and intermediate copper layers is not established. The structure proposed in this work adopts a monolithic substrate, in which a single 300 μm thick copper layer is embedded without the use of additional solder. Compared to conventional multilayer substrates, this configuration offers improved thermal conduction by eliminating solder interfaces and enhancing heat flow.

Abstract: Polymer-metal hybrid nanocomposites have garnered significant attention in recent years due to their exceptional electrical and dielectric properties, which find applications in a wide range of industries, including electronics, energy storage, and advanced materials. This review article provides a comprehensive overview of the current state-of-the-art in the field of polymer-metal hybrid nanocomposites, with a particular focus on their electrical and dielectric properties. The first section of the review delves into the synthesis and fabrication techniques employed to create these nanocomposites, highlighting the importance of controlling the dispersion and distribution of metal nanoparticles within the polymer matrix. Various approaches, such as in-situ polymerization, melt mixing, and electrospinning, are discussed in detail, along with their respective advantages and limitations.The subsequent sections explore the influence of metal nanoparticles on the electrical conductivity and dielectric constant of the nanocomposites. The role of factors such as nanoparticle size, shape, and concentration in determining these properties is thoroughly examined. Moreover, the impact of metal surface modifications and the choice of polymer matrix on enhancing electrical and dielectric performance are also addressed. In addition to discussing fundamental aspects, this review highlights practical applications of polymer-metal hybrid nanocomposites in the development of high-performance capacitors, sensors, electromagnetic shielding materials, and flexible electronics. The potential for these materials to revolutionize various technological sectors is discussed, emphasizing their role in advancing miniaturization, energy efficiency, and durability. Furthermore, the review outlines current challenges and future prospects in the field, including the need for a deeper understanding of the underlying mechanisms governing electrical and dielectric behavior in these nanocomposites. Emerging trends such as the incorporation of 2D materials and the development of multifunctional hybrid systems are also explored, hinting at exciting avenues for further research and innovation. In conclusion, polymer-metal hybrid nanocomposites offer a promising platform for tailoring electrical and dielectric properties to meet the demands of modern technology. This review serves as a valuable resource for researchers, engineers, and scientists seeking to explore the potential of these materials and drive advancements in the field of electrical and dielectric engineering.

Abstract: Rare-earth-based nanocomposites are currently attracting extensive research interest in biology, medicine, physics, chemistry and material science owing to their optical, electrical and electronic properties, their stability and novel applications. Rare-earth based nanomaterials, especially rare earth oxides (Yttrium oxide, Gadolinium oxide, lanthanum oxide, cerium dioxide, etc.) have fascinated people's devotion owing to their good environmentally friendly and redox properties characteristics. Rare-earth based nanomaterials with exceptional electrochemical properties can be attained by simple, low-cost, environmentally friendly approaches such as hydrothermal/solvothermal method, electrodeposition method, atomic layer deposition method, etc. The electrochemical and microstructures properties of the samples were characterized by X-ray diffraction, scanning electron microscopy, galvanostatic charge/discharge cycling, potentiostatic electrochemical impedance spectroscopy and cyclic voltammetry, in this review, we present a wide-ranging explanation of synthesis methods, morphology and electrochemical performance of numerous rare-earth based nanomaterials used in supercapacitors. We present in this review a brief overview of the recent and general progresses in their functionalization and synthesis.

Abstract: Dielectric elastomer generators (DEGs) are based on the electromechanical response of the dielectric elastomer film sandwiched between the compliant electrodes on each side, which are capable of converting mechanical energy from diverse sources (e.g, ocean wave) into electrical energy. In essence, DEG is a voltage up-converter using mechanical energy to increase the electrical energy of the charge on a soft capacitor. We evaluated the effect of input voltage and the pre-stretch ratios on energy conversion efficiency of DEG. With a power supply of 2.2kV and pre-stretch ratio of 2, the maximum net electrical energy density and energy conversion efficiency in a single harvesting cycle were measured to be 413 J/kg and 15.8%, respectively. The experimental results showed that, with the higher input voltage and the larger stretch ratio range, higher the energy conversion performance of DEG can be achieved.

Abstract: Selective laser melting (SLM) is an additive manufacturing technology that allows to produce functional parts with extremely complex shape from metal powder feedstock. 240 single tracks with the length of 10 mm were fabricated using different SLM process parameters: laser power output, powder layer thickness, point distance and exposure time. Obtained single tracks were measured using optical microscopy. An influence of SLM process parameters on geometrical characteristics of obtained single tracks was investigated.

Abstract: Various "energy density" parameters are used very often for comparison of fabrication modes for Selective Laser Melting (SLM) technology. Each SLM mode is determined by a number of process parameters. In this paper the energy density was considered critically as a reliable parameter for characterization of Selective Laser Melting of four various alloys on one SLM machine, on the example of fabrication of cubic specimen. The results obtained show that the energy density can be used for approximate comparison of SLM modes.

Abstract: Charge transport is one of the most important phenomena, which directly influences the performance of the energy storage and conversation devices. In this work, the authors provide an overview of various rechargeable energy storage battery chemistries and designs, and discuss the charge transport processes related to power capability of the lithium-ion technology. The load distribution by parallel connection of high power batteries or supercapacitor and high-energy cells is discussed and general conclusions are provided. Thus, the reduced peak power load on the high-energy cells are approved by simulation and experiment in passive parallel circuitry of high power and a high energy lithium-ion cells. The definition and advantages of the earlier deduced electrical loss time are explained. It is shown, that at a constant C-rate, defined as the ratio of the applied current and the rated cell capacity in Ah, the electrical loss time has a direct linear correlation to efficiency, and that the electrical loss time allows a direct power capability comparison of various battery cell chemistries and systems. The power capability, specific energy, and energy density of the industry relevant Li-ion battery cells based on electrical loss time approach are summarized and the following conclusions made. Today prismatic cells reach the maximum specific energy of small cylindrical cells, at the same time showing a little bit better power capability, than the investigated high energy cylindrical cells.

Abstract: In this paper, the ablated microstructures on copper film affected by ultraviolet nanosecond pulse laser are presented. The experimental system was consisted of two lasers, optics and controlling electronics. A 3000mW, 355nm Q-switched ultraviolet lasers was used to the micro-polishing experiments in the work. The repetition rate of the ultraviolet pulse laser is from single-shot to 100kHz, and the pulse width is less than 40ns. The sample used in experiment is copper film (200 nm) sputtered on glass. A series of experiments at different laser parameters and speed of work platform are done. The ablating experiments are also carried out on focusing and defocusing application in the laser direct writer. The results were analyzed.

Abstract: In laser processing of surfaces, typically to impart some texture or to drill shallow holes, it is necessary to correlate pulse properties (wavelength, power, beam radius and quality, duration) and material properties (reflectivity, melting temperature, conductivity, diffusivity) mainly with the depth of the formed crater. Crater shape is assumed to be paraboloidal and its maximum diameter is assumed to be uniquely related to its depth. An empirical and an analytical model are suggested to this end. The former entails construction of Artificial Neural Networks from experimental measurements, whilst the latter entails modification of established models from literature. Both types of models are exemplified in this paper drawing on data from available literature.

Abstract: PZT-based ultrasonic guided wave has played an important role in health monitoring of pipeline structures. By using the PZT-based ultrasonic guided wave energy method and finite element software ABAQUS, the numerical simulation is performed to analyze various corrosion damaged pipeline structures, emphasizing on the damage identification, sensitivity analysis and longitudinal energy attenuation of the guided wave along various corrosion damaged pipelines. The preliminary analysis of the echo signals shows that the grass-like clutter wave belongs to echoes of the corrosion damage of the pipeline, and the wave energy spreads faster here. At the same time, by frequency spectrum analysis of the echo signal, the relationship between the reflection coefficient and the radial depth of defection is made which can be used to approximately evaluate geometrical dimension of the damage.