High Temperature Operation Research Articles

Stacked structure dependence on resistive switching characteristics in sumanene molecular memory

Nonvolatile memories using molecule (molecule memories) are attracting attention. This is because these materials are suitable for miniaturization and higher capacity of memories in terms of their properties and dimensions. We have already demonstrated that the metal–insulator–metal (MIM) devices with sumanene-inserted bilayer graphene show huge resistive switching characteristics. However, the reason why resistive switching occurs in the graphene/sumanene/graphene structure has yet to be clarified. In this work, to investigate the mechanisms of the resistive switching phenomenon in sumanene-inserted bilayer graphene, plural kinds of stacked MIM structures are fabricated and evaluated. As a result, the measurement results clearly show that the graphene/sumanene/graphene structure is indispensable in the resistive switching phenomenon. Furthermore, based on the temperature dependence of the resistive switching, it is confirmed that a significant I ON/I OFF ratio can be obtained at higher operation temperatures.

Target Development towards First Production of High-Molar- Activity 44gSc and 47Sc by Mass Separation at CERN-MEDICIS.

The radionuclides 43Sc, 44g/mSc, and 47Sc can be produced cost-effectively in sufficient yield for medical research and applications by irradiating natTi and natV target materials with protons. Maximizing the production yield of the therapeutic 47Sc in the highest cross section energy range of 24-70 MeV results in the co-production of long-lived, high-γ-ray-energy 46Sc and 48Sc contaminants if one does not use enriched target materials. Mass separation can be used to obtain high molar activity and isotopically pure Sc radionuclides from natural target materials; however, suitable operational conditions to obtain relevant activity released from irradiated natTi and natV have not yet been established at CERN-MEDICIS and ISOLDE. The objective of this work was to develop target units for the production, release, and purification of Sc radionuclides by mass separation as well as to investigate target materials for the mass separation that are compatible with high-yield Sc radionuclide production in the 9-70 MeV proton energy range. In this study, the in-target production yield obtained at MEDICIS with 1.4 GeV protons is compared with the production yield that can be reached with commercially available cyclotrons. The thick-target materials were irradiated at MEDICIS and comprised of metallic natTi, natV metallic foils, and natTiC pellets. The produced radionuclides were subsequently released, ionized, and extracted from various target and ion source units and mass separated. Mono-atomic Sc laser and molecule ionization with forced-electron-beam-induced arc-discharge ion sources were investigated. Sc radionuclide production in thick natTi and natV targets at MEDICIS is equivalent to low- to medium-energy cyclotron-irradiated targets at medically relevant yields, furthermore benefiting from the mass separation possibility. A two-step laser resonance ionization scheme was used to obtain mono-atomic Sc ion beams. Sc radionuclide release from irradiated target units most effectively could be promoted by volatile scandium fluoride formation. Thus, isotopically pure 44g/mSc, 46Sc, and 47Sc were obtained as mono-atomic and molecular ScF 2+ ion beams and collected for the first time at CERN-MEDICIS. Among all the investigated target materials, natTiC is the most suitable target material for Sc mass separation as molecular halide beams, due to high possible operating temperatures and sustained release.

Interfacial self-healing polymer electrolytes for Long-Cycle silicon anodes in High-Performance solid-state lithium batteries

For all-solid-state lithium-ion batteries (ASSLIBs), silicon (Si) stands out as an appealing anodes material due to its high energy density and improved safety compared to lithium metal. However, the substantial volume changes during cycling result in poor solid-state physical contact and electrolyte–electrode interface issues, leading to unsatisfactory electrochemical performance. In this study, we employed in-situ polymerization to construct an integrated Si anodes/self-healing polymer electrolyte for ASSLIBs. The polymer chain reorganization stems from numerous dynamic bonds in the constructed self-healing dynamic supermolecular elastomer electrolyte (SHDSE) molecular structure. Notably, SHDSE also serves as a Si anodes binder with enhanced adhesive capability. As a result, the well-structured Li|SHDSE|Si-SHDSE cell generates subtle electrolyte–electrode interface contacts at the molecular level, which can offer a continuous and stable Li+ transport pathway, reduce Si particle displacement, and mitigate electrode volume expansion. This further enhances cyclic stability (>500 cycles with 68.1 % capacity retention and >99.8 % Coulombic efficiency). More practically, the 2.0 Ah wave-shaped Si||LiCoO2 soft-pack battery with in-situ cured SHDSE exhibits strongly stabilized electrochemical performance (1.68 Ah after 700 cycles, 86.2 % capacity retention) in spite of a high operating temperatures up to 100 °C and in various bending tests. This represents a groundbreaking report in flexible solid-state soft-pack batteries containing Si anodes.

Synthesis of shape-programmable elastomer for a bioresorbable, wireless nerve stimulator

Materials that have the ability to manipulate shapes in response to stimuli such as heat, light, humidity and magnetism offer a means for versatile, sophisticated functions in soft robotics or biomedical implants, while such a reactive transformation has certain drawbacks including high operating temperatures, inherent rigidity and biological hazard. Herein, we introduce biodegradable, self-adhesive, shape-transformable poly (L-lactide-co-ε-caprolactone) (BSS-PLCL) that can be triggered via thermal stimulation near physiological temperature (∼38 °C). Chemical inspections confirm the fundamental properties of the synthetic materials in diverse aspects, and study on mechanical and biochemical characteristics validates exceptional stretchability up to 800 % and tunable dissolution behaviors under biological conditions. The integration of the functional polymer with a bioresorbable electronic system highlights potential for a wide range of biomedical applications.

Cost-based optimization, feasibility study, and sensitivity analysis of forward osmosis/crystallization/reverse osmosis with high-temperature operation for high-salinity seawater desalination

Seawater desalination plants using reverse osmosis (RO) in high temperature and high-salinity conditions, such as in the Middle East, face challenges such as limited achievable recoveries and high energy costs. This study evaluated the economic feasibility under seawater and high-salinity conditions by introducing a forward osmosis/crystallization/reverse osmosis (FO/Cry/RO) hybrid process. The optimization results were then used to compare the specific water cost (SWC), specific energy consumption (SEC), recovery, and permeate quality of the hybrid process with two different draw solutes and a conventional seawater RO process. In addition, a sensitivity analysis was conducted to determine how individual process parameters and operating conditions affect the economic feasibility of the proposed process under seawater and high-salinity conditions. The FO/Cry/RO hybrid process achieved a higher recovery with a lower SWC and SEC as the feed concentration increased compared to the conventional RO process. Utilizing waste heat further increased the economic advantages of the proposed process. In addition, much higher permeate quality can be obtained depending on the type of draw solute. The results of this study revealed that the proposed hybrid system outperformed the conventional RO process in terms of both energy efficiency and cost-effectiveness for seawater desalination under high-temperature and high-salinity conditions.

Mg activation anneal of the p-GaN body in trench gate MOSFETs and its effect on channel mobility and threshold voltage stability

This work addresses the impact of the Mg activation anneal step and the resulting acceptor concentration on the channel mobility and VT stability of vertical MOSFETs. Increasing the annealing time with N2 only ambient and the annealing temperature with O2 in the ambient is shown to be effective in increasing the channel acceptor concentration. When the effective acceptor concentration is increased, the mobility is degraded due to a transition in the main scattering mechanism from Coulomb to surface roughness scattering. Degradation of the on-state current and maximum transconductance at high operating temperatures was linked to bulk mobility degradation of the drift layer due to lattice scattering. The two Mg activation annealing conditions considered here show different trends with regard to the threshold voltage stability, while N2 only ambient did not impact this parameter, including O2 increased threshold voltage instability. It is shown that increasing the Mg chemical concentration in the p-GaN layer degrades channel mobility and threshold voltage stability, irrespectively of the effective acceptor concentration, providing evidence for degradation of the channel/dielectric interface characteristics with higher Mg chemical concentration. This study shows that it is possible to achieve very low threshold voltage hysteresis and high channel mobility by reducing the Mg chemical concentration while maintaining high effective acceptor concentration. These results provide key insights for the development of vertical GaN FETs.

Enhancing the performance of thermoelectric generators using novel segmental arrangement of multi-functional gradient materials

Enhancing the performance of thermoelectric generators at wide range of operating temperatures is of great importance to maximize the output power. Thus, different updated semiconductor materials with different values of figure of merit are used. Accordingly, a modified design of the TEG system based on the multi-functional gradient (MFG) technique is developed. A comprehensive three-dimensional modeling and optimization analysis was developed and numerically simulated. The numerical predicted results were validated using the available measurements and numerical data. The results showed that when compared to low operating temperature semiconductor material of traditional (Bi2Te3) at a hot side temperature equals 227 °C, the updated material improved the output power and efficiency by 18.8% and 58%, respectively. At high operating temperature at Th = 620 °C, the upgraded material outperformed the Silicon–germanium (SiGeT) traditional semiconductor material by about 71% in the output power and 100% in the efficiency. Using the MFG-TEG, the performance improvement over the conventional design at Tc = 27 °C, and Th of 477 °C was around 315% for output power and 503% for efficiency. The current findings introduce a brand-new, innovative technique that allows scientists to create thermoelectric generators that are incredibly efficient.

Liquid lithium corrosion of SiC/SiC composites

Silicon carbide fibre reinforced silicon carbide matrix composite (SiC/SiC) is a key structural material for fusion reactors to allow high temperature operation of liquid lithium breeder blankets. This research investigated the corrosion behaviour of two SiC/SiC composites (using Tyranno SA3 and SA4 fibres) immersed in static liquid lithium at 600 °C for 100 h. Utilizing immersion tests and advanced microstructural analysis, the study reveals considerable corrosion in SiC/SiC composites, particularly in local areas enriched with residual carbon or oxygen. The interface carbon layer, while enhancing mechanical properties, induces preferential sites for corrosion cracking, diminishing the material's corrosion resistance. This study offers critical insights into the corrosive interaction between SiC/SiC composites and liquid lithium, highlighting the need for manufacturing process optimization and exploration of alternative interface layers, protective coatings, or avoiding contact between SiC/SiC and molten lithium in breeder blanket system.

Dynamically Reversible Gelation of Electrolyte for Efficient Wide‐Temperature Adaptable Energy Storage

AbstractQuasi‐solid‐state electrolytes (QSEs) via gelation of liquid electrolytes (LEs) are perspective protocols for constructing ingenious potassium‐ion batteries (PIBs) due to the combined advantages of both liquid and solid state. However, most of QSEs yet researched face a trade‐off among low temperature adaptability and safely high temperature operation. Herein, in situ reversible gelation of Ni‐crosslinked pentaerythritol tetrakis (3‐mercaptopropionate) (PETMP‐Ni) co‐polymerized with tyramine‐modified hyaluronic acid (HA‐Tyr) (PHA) modified B, N modified carbon spheres (BNC) enclosing by red P (RP) is backed with compatible electrode‐electrolyte interface with laponite filler (L). Such high reversible in situ gelation displays high low temperature adaptability by LEs, and extraordinary safety in high temperature steered by QSEs, benefiting from topologic space crowding effect (TSCE) and reverse trap of Ni single atoms (Ni SAs). This work enlightens the missing prospects in constructing reversible in situ sol–gel strategy coupled by topologic space crowding effect and reverse SAs trapping stimulate toward revival hybrid electrode for wide‐temperature adaptive batteries.

A Robust Anti-Thermal-Quenching Phosphor Based on Zero-Dimensional Metal Halide Rb3InCl6:xSb3.

High-power phosphor-converted white light-emitting diodes (hp-WLEDs) have been widely involved in modern society as outdoor lighting sources. In these devices, due to the Joule effect, the high applied currents cause high operation temperatures (>500 K). Under these conditions, most phosphors lose their emission, an effect known as thermal quenching (TQ). Here, we introduce a zero-dimensional (0D) metal halide, Rb3InCl6:xSb3+, as a suitable anti-TQ phosphor offering robust anti-TQ behavior up to 500 K. We ascribe this behavior of the metal halide to two factors: (1) a compensation process via thermally activated energy transfer from structural defects to emissive centers and (2) an intrinsic structural rigidity of the isolated octahedra in the 0D structure. The anti-TQ phosphor-based WLEDs can stably work at a current of 2000 mA. The low synthesis cost and nontoxic composition reported here can herald a new generation of anti-TQ phosphors for hp-WLED.

Enhanced dielectric reliability in the X9R‐type Bi1/2Na1/2TiO3‐CaZrO3 relaxor ferroelectric ceramics

AbstractHigh‐performance dielectric ceramic capacitors for automotive applications require high operation temperature, thermal stability, and reliability for dielectric ceramics. A broad composition search has been carried out to replace the existing BaTiO3‐based dielectrics having limited upper operating temperature due to the relatively low Curie temperature at around 120°C. However, most of the developed compositions are too complicated and compositionally sensitive, making them difficult to commercialize. This study introduces a dielectrically reliable ceramic system based on Bi1/2Na1/2TiO3 (BNT) with a wide operation temperature range simply by adding paraelectric CaZrO3 (CZ). At 15 mol% addition of CZ to BNT, the permittivity variation within ±15% from −55 to 280°C was achieved, which surpasses the EIA‐X9R standard. Moreover, the dielectric reliability was shown with low dielectric loss (tanδ < 0.02) for the aforementioned temperature range and remarkable dielectric breakdown strength (∼260 kV/cm) at room temperature. Along with the proposal of a promising high‐performance dielectric material, structural analysis and dielectric behavior investigation as a function of CZ contents were presented.

Ionic liquid electrolyte selection for high voltage supercapacitors in high-temperature applications.

Systematic analyses of electrolyte physicochemical properties are important to screen ionic liquids (ILs) and understand the electrochemical performance of supercapacitor electrolytes. This study harmonizes the evaluation of electrochemical performance and transport properties of eight shortlisted ILs from 22 commercially available hydrophobic ILs toward achieving a 5V supercapacitor capable of high-temperature operation (up to 353.15K). The eight ILs are N-Propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([Pyr 1, 3] [TFSI], N-Pentyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([Pyr 1, 5] [TFSI]), N-Propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide ([Pyr 1, 3] [FSI]), 1-Methyl-1-(2-methoxyethyl)pyrrolidinium Bis(trifluoromethanesulfonyl)imide ([Pyr 1, 102] [TFSI]), 1-Methyl-1-propylpiperidinium bis(trifluoromethanesulfonyl)imide ([Pip 1, 3] [TFSI]), 1-Methyl-1-propylpiperidinium bis(fluorosulfonyl)imide ([Pip 1, 3] [FSI]), N-Trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide ([N 111, 3] [TFSI]), N-Trimethyl-N-hexylammonium bis(trifluoromethanesulfonyl)imide ([N 111, 6] [TFSI]). The density, viscosity, and ionic conductivity of the eight ILs were measured between 278.15 and 373.15K to confirm the effects of temperature and ion structure before electrochemical characterization. The [FSI]-based ILs ([Pip 1, 3] [FSI] and [Pyr 1, 3] [FSI]) showed lower densities and viscosities compared to other ILs among the eight based on [TFSI]. Consequently, the highest conductivity was obtained for [Pyr 1, 3] [FSI]. Cyclic voltammetry and impedance spectroscopy was performed on supercapacitors assembled with the eight ILs as electrolytes between 298.15-353.15K. Conclusion from the two-electrode supercapacitors using multi-walled carbon nanotubes showed the 6 most-applicable ILs towards the targeted ≥ 5V SC at high temperature are [Pip 1, 3] [TFSI] (5.4V), [Pip 1, 3] [FSI] (5V), [N 111, 3] [TFSI] (5.1V), [N 111, 6] [TFSI] (5.2V), [Pyr 1, 102] [TFSI] (5.2V), and [Pyr 1, 5] [TFSI] (5.2V).

Organic-Inorganic Hybrid Synaptic Transistors: Methyl-Silsesquioxanes-Based Electric Double Layer for Enhanced Synaptic Functionality and CMOS Compatibility.

Electrical double-layer (EDL) synaptic transistors based on organic materials exhibit low thermal and chemical stability and are thus incompatible with complementary metal oxide semiconductor (CMOS) processes involving high-temperature operations. This paper proposes organic-inorganic hybrid synaptic transistors using methyl silsesquioxane (MSQ) as the electrolyte. MSQ, derived from the combination of inorganic silsesquioxanes and the organic methyl (-CH3) group, exhibits exceptional thermal and chemical stability, thus ensuring compatibility with CMOS processes. We fabricated Al/MSQ electrolyte/Pt capacitors, exhibiting a substantial capacitance of 1.89 µF/cm2 at 10 Hz. MSQ-based EDL synaptic transistors demonstrated various synaptic behaviors, such as excitatory post-synaptic current, paired-pulse facilitation, signal pass filtering, and spike-number-dependent plasticity. Additionally, we validated synaptic functions such as information storage and synapse weight adjustment, simulating brain synaptic operations through potentiation and depression. Notably, these synaptic operations demonstrated stability over five continuous operation cycles. Lastly, we trained a multi-layer artificial deep neural network (DNN) using a handwritten Modified National Institute of Standards and Technology image dataset. The DNN achieved an impressive recognition rate of 92.28%. The prepared MSQ-based EDL synaptic transistors, with excellent thermal/chemical stability, synaptic functionality, and compatibility with CMOS processes, harbor tremendous potential as materials for next-generation artificial synapse components.

AlN Thin-Film Vacuum Ultraviolet Photodetector With High Operating Temperature and High Rejection Ratio

AlN Thin-Film Vacuum Ultraviolet Photodetector With High Operating Temperature and High Rejection Ratio

An Investigation of the Thermal Properties of LM13- Quartz- Fly-Ash Hybrid Composites

In the present work, a metal–matrix composite was casted using the LM13 aluminum alloy, which is most widely used for casting automotive components. Such applications require materials to withstand high operating temperatures and perform reliably without compromising their properties. In this regard, particulate-reinforced composites have gained widespread adaptability. The particulate reinforcements used comprise of one of the widely available industrial by-products. which is fly ash, along with the abundantly available quartz. Hybrid composites are fabricated through the economical liquid route that is widely used in mass production. Though there are numerous published research articles investigating the mechanical properties of metal–matrix composites, very few investigated the thermal properties of the composites. In the present work, thermal properties such as thermal conductivity and thermal diffusivity of cast hybrid composites were evaluated. The particulate reinforcements were added in varied weight percentages to the molten LM13 alloy and were dispersed uniformly using a power-driven stirrer. The melt with the dispersed particulate reinforcements was then poured into a thoroughly dried sand mold, and the melt was allowed to solidify. The quality of the castings was ascertained through density evaluation followed by a microstructural examination. It was found that the composites with only the fly ash particles as a reinforcement were less dense in comparison to the composites cast with the quartz particulate reinforcement. However, the hybrid composite, with both particulate reinforcements were dense. The microstructure revealed a refined grain structure. The thermal diffusivity and thermal conductivity values were lower for the composites cast with only the fly ash reinforcement. On the other hand, the composites cast with only quartz as the particulate reinforcement exhibited higher thermal diffusivity and thermal conductivity. The specific heat capacity was found to be lower for the fly ash-reinforced composites and higher for the quartz-reinforced composites in comparison to the LM13 base matrix alloy. However, the highest value of thermal diffusivity and thermal conductivity were reported for the hybrid composites with a 10 wt.% inclusion of both fly ash and quartz particulate reinforcements.

Stable High Temperature Operation of p-GaN Gate HEMT With Etch-Stop Layer

Stable High Temperature Operation of p-GaN Gate HEMT With Etch-Stop Layer

Design of Half-Bridge Switching Power Module Based on Parallel-Connected SiC MOSFETs for LLC Resonant Converter with Symmetrical Structure and Low Parasitic Inductance

SiC MOSFETs are used in many power conversion applications because of their superior characteristics, such as fast switching speed, low on-resistance, and high operating temperature. In certain high-power systems, SiC MOSFETs are connected in parallel to enhance their current capacity and power efficiency. However, compared with Si-based devices, the current imbalance caused by the parasitic inductance difference becomes more severe when driving SiC MOSFETs in parallel, owing to the fast switching speed. Furthermore, the power loop inductance imbalance that occurs when constructing a half-bridge with parallel SiC MOSFETs has rarely been addressed in previous studies. In this study, a half-bridge switching power module based on parallel-connected SiC MOSFETs is proposed to solve the current imbalance through a symmetric structure of the gate and power loops. The effects of the magnitude and imbalance of the gate and power loop inductances in the half-bridge structure based on parallel-connected devices are also explained. A detailed printed circuit board layout of the proposed switching power module is provided, and the inductance symmetry is verified through simulations. A double-pulse test is conducted to verify the current-balancing capability of the proposed switching power module. In addition, an LLC resonant converter is designed using the proposed switching power module, and the power loss between parallel SiC MOSFETs is compared. The experimental results indicate the total power loss error between the parallel-connected SiC MOSFETs of the proposed power module is only 1.94%.

Effects of Visible Light on Gas Sensors: From Inorganic Resistors to Molecular Material-Based Heterojunctions.

In the last two decades, many research works have been focused on enhancing the properties of gas sensors by utilising external triggers like temperature and light. Most interestingly, the light-activated gas sensors show promising results, particularly using visible light as an external trigger that lowers the power consumption as well as improves the stability, sensitivity and safety of the sensors. It effectively eliminates the possible damage to sensing material caused by high operating temperature or high energy light. This review summarises the effect of visible light illumination on both chemoresistors and heterostructure gas sensors based on inorganic and organic materials and provides a clear understanding of the involved phenomena. Finally, the fascinating concept of ambipolar gas sensors is presented, which utilised visible light as an external trigger for inversion in the nature of majority charge carriers in devices. This review should offer insight into the current technologies and offer a new perspective towards future development utilising visible light in light-assisted gas sensors.

Schottky infrared detectors with optically tunable barriers beyond the internal photoemission limit

Internal photoemission is a prominent branch of the photoelectric effect and has emerged as a viable method for detecting photons with energies below the semiconductor bandgap. This breakthrough has played a significant role in accelerating the development of infrared imaging in one chip with state-of-the-art silicon techniques. However, the performance of these Schottky infrared detectors is currently hindered by the limit of internal photoemission; specifically, a low Schottky barrier height is inevitable for the detection of low-energy infrared photons. Herein, a distinct paradigm of Schottky infrared detectors is proposed to overcome the internal photoemission limit by introducing an optically tunable barrier. This device uses an infrared absorbing material-sensitized Schottky diode, assisted by the highly adjustable Fermi level of graphene, which subtly decouples the photon energy from the Schottky barrier height. Correspondingly, a broadband photoresponse spanning from ultraviolet to mid-wave infrared is achieved, with a high specific detectivity of 9.83×1010 cm Hz1/2 W-1 at 2,700nm and an excellent specific detectivity of 7.2×109 cm Hz1/2 W-1 at room temperature under blackbody radiation. These results address a key challenge in internal photoemission and hold great promise for the development of the Schottky infrared detector with high sensitivity and room temperature operation.

Ultra-reliable quantum dot colliding pulse mode-locked laser as multi-wavelength source for integrated optical interconnects.

For optical interconnect applications, multi-wavelength comb sources require uniform comb spacings and high reliability at high operating temperature. Here, the high-temperature reliability measurements of a InAs quantum dot colliding pulse mode-locked (QD-CPML) laser with 100 GHz comb spacing are systematically investigated. Laser lifetime measurements are performed for over 1600 hours at 80 °C under constant stress current of 150 mA. The mean time to failure (MTTF) of the laser is approximately 38 years (336,203 hours), extracted from the threshold currents extrapolation method. The optical spectral revolutions are also monitored during the aging process, while the grids of comb laser are remarkably stable. The outstanding reliability and spectrum stability make this 100 GHz QD-CPML a promising candidate as a multi-wavelength laser source for datacom and optical I/O applications.