Ultrahigh Rate Research Articles

Unveiling the Double‐Edged Behavior of Controlled Selenium Substitution in Cobalt Sulfide for Balanced Na‐Storage Capacity and Rate Capability

AbstractTransition metal sulfide‐based anodes usually suffer from huge volumetric change and sluggish reaction kinetics, hindering their application for long‐term and high‐power/energy sodium‐ion batteries. Herein, a new design of CoS2‐xSex (0≤x≤2) nanocrystals with highly controllable selenium substitution and S, Se‐codoped graphene immobilization (CoS2‐xSex@SG) is proposed to tune the reaction kinetics and structural stability. The nanocrystal‐on‐graphene structure and robust C─S &C─Se bonding rivets between CoS2‐xSex and SG greatly improve the structural stability of the CoS2‐xSex@SG. Electrochemical performance, kinetic analysis, and theoretical calculation reveal that Se substitution plays a double‐edged role in sodium storage: the increase of Se substitution content enhances the Na+ diffusion kinetics but decreases the Na‐storage capacity. When the Se substitution content is 0.4, the CoS1.6Se0.4@SG electrode demonstrates the best performance: high initial Coulombic efficiency (95.5%), ultrahigh rate capability (412.8 mAh g−1 at 30 A g−1), and ultra‐stable cycling performance (97.6% capacity retention after 1000 cycles). In situ/ex situ measurements further unveil that the conversion reaction between Co0 and Na2S/Na2Se generates the micro‐scaled CoSe2–CoS2 heterostructure, synergistically improving the Na‐storage active sites and reaction kinetics. This work provides a controllable anion substitution strategy to balance the Na+ storage active sites and kinetics with potential applications for high‐power/energy sodium‐ion batteries.

Across the stages: a multiscale extension of the generalized stochastic microdosimetric model (MS-GSM2) to include the ultra-high dose rate

Ultra-high dose rate (UHDR) irradiations with different types of radiation have shown a larger sparing of normal tissue and unchanged tumor control with respect to conventional delivery. In recent years, there has been an accumulation of experimental evidence related to the so-called FLASH effect. However, the underpinning mechanism remains, to date, extremely debated and largely unexplained, while the involvement of multiple scales of radiation damage has been suggested. Since it is believed that the chemical environment plays a crucial role in the FLASH effect, this work aims to develop a multi-stage tool, the multiscale generalized stochastic microdosimetric model (MS-GSM2), that can capture several possible effects on DNA damage at the UHDR regime, such as reduction of DNA damage yield due to organic radical recombination, damage fixation due to oxygenation, and spatial and temporal dose deposition effects, allowing us to explore most of the candidate mechanisms for explaining the FLASH effect. The generalized stochastic microdosimetric model (GSM2) is a probabilistic model that describes the time evolution of DNA damage in a cell nucleus using microdosimetric principles, accounting for different levels of spatio-temporal stochasticity. In particular, the GSM2 describes radiation-induced DNA damage formation and kinetic repair in the case of protracted irradiation without considering the Poissonian assumption to treat the number of radiation-induced DNA damage. In this work, we extend the GSM2, coupling the evolution of DNA damage to fast chemical reaction kinetics, described by a system of ordinary differential equations, accounting for an additional level of stochasticity, i.e., in chemistry. We simulate energy deposition by particles in a microscopic volume, which mimics the cell nucleus, in order to examine the combined effects of several chemical species and the time evolution of DNA damage. We assume that UHDR modifies the time evolution of the peroxyl radical concentration, with a consequent reduction in the yield of the indirect DNA damage. This damage reduction emerges only at UHDR and is more pronounced at high doses. Moreover, the indirect damage yield reduction depends on the radiation quality. We show that the MS-GSM2 can describe the empirical trend of dose- and dose rate-dependent cell sensitivity over a broad range, particularly the larger sparing of healthy tissue occurring at the FLASH regime. The complete generality of the MS-GSM2 also allows us to study the impact of different dose delivery time structures and radiation qualities, including high LET beams.

Simulation-guided development of an optical calorimeter for high dose rate dosimetry.

Optical Calorimetry (OC) is based on interferometry and provides a direct measurement of spatially resolved absorbed dose to water by measuring refractive index changes induced by radiation. The purpose of this work was to optimize and characterize in software an OC system tailored for ultra-high dose rate applications and to build and test a prototype in a clinical environment.A radiation dosimeter using the principles of OC was designed in optical modelling software. Traditional image quality instruments, fencepost and contrast phantoms, were utilized both in software and experimentally in a lab environment to investigate noise reduction techniques and to test the spatial and dose resolution of the system. Absolute dose uncertainty was assessed by measurements in a clinical 6 MV Flattening Filter Free (FFF) photon beam with dose rates in the range 0.2-6Gy/s achieved via changing the distance from the source.Design improvements included: equalizing the pathlengths of the interferometer, isolating the system from external vibrations and controlling the system's internal temperature as well as application of mathematical noise reduction techniques. Simulations showed that these improvements should increase the spatial resolution from 22 to 35 lp/mm and achieve a minimum detectable dose of 0.2Gy, which was confirmed experimentally. In the FFF beam, the absolute dose uncertainty was dose rate dependent and decreased from 2.5 ± 0.8 to 2.5 ± 0.2Gy for dose rates of 0.2 and 6Gy/s, respectively.A radiation dosimeter utilizing the principles of OC was developed and constructed. Optical modelling software and image quality phantoms allowed for iterative testing and refinement. The refined OC system proved capable of measuring absorbed dose to water in a linac generated photon beam. Reduced uncertainty at higher dose rates indicates the potential for OC as a dosimetry system for high dose rate techniques such as microbeam and ultra-high dose-rate radiotherapy.

Making Nanofiber Membrane Stand on End to Construct Vertically Interfacial Evaporators for Efficient Solar Evaporation, Omnidirectional Solar Absorption, and Ultrahigh-Salinity Brine Desalination.

Solar-driven interfacial desalination is widely considered to be a promising technology to address the global water crisis. This study proposes a novel electrospun nanofiber-based all-in-one vertically interfacial solar evaporator endowed with a high steam generation rate, steady omnidirectional evaporation, and enduring ultrahigh-salinity brine desalination. In particular, the electrospun nanofiber is collected into the tubular structure, followed by spraying with a dense crosslinked poly(vinyl alcohol) film, which renders them sufficiently strong for the preparation of a vertically array evaporator. The integrated evaporator made an individual capillary as a unit to form multiple thermal localization interfaces and steam dissipation channels, realizing zone heating of water. Thus a high steam generation rate exceeding 4.0kgm-2h-1 in pure water is demonstrated even under omnidirectional sunlight, and outperforms existing evaporators. Moreover, salt ions in the photothermal layer can be effectively transported to the water in capillaries and subsequently exchanged with the bulk water due to the strong action of capillary force, which ensures an ultrahigh desalination rate (≈12.5kgm-2h-1 under 3 sun) in 25wt% concentration brine over 300min. As such, this work provides a meaningful roadmap for the development of state-of-the-art solar-driven interfacial desalination.

The future service scenarios of 6G telecommunications technology

In the field of mobile communication, 6G technology has enhanced features, such as ultrahigh data rates and sharing, bandwidth connectivity, and low data latency, compared to 5G technology. As new services become possible due to these characteristics, attempts to present promising future services based on 6G technology are occurring in academia and industry. However, because 6G technology has a very wide range of applications as a fundamental technology, 6G service scenario research is also being conducted for each sector. To predict 6G technology use in the future, it is necessary to understand comprehensively the scenarios being studied sporadically by sector. Therefore, we aim to derive major service scenarios by analyzing in-depth public data for 6G service scenarios. We collected research papers, corporate reports, and news articles on 6G service scenarios and performed topic modeling to derive four major domains and 16 application areas. Afterward, the derived service's feasibility and promising scenario were evaluated by utilizing the future-context canvas and business model canvas that analyze the service's value from the user's and supplier's perspectives, respectively. The research results are expected to support technology development and business planning in the field by enhancing understanding of 6G service scenarios.

Metastable structures with composition fluctuation in cuprate superconducting films grown by transient liquid-phase assisted ultra-fast heteroepitaxy

Rare earth-barium-copper oxides superconducting tapes are key candidate materials for high-field magnet applications. The synergetic realization of high-speed growth and high field current carrying capacity of superconducting film is gaining prominence in academics and industry. In this paper, a pulsed laser deposition technique with an ultra-high growth rate two orders of magnitude higher than that of conventional methods (up to 100 nm/s) is engaged to grow nanocomposite EuBa2Cu3O7-δ (EuBCO) superconducting films. Dynamic heating and rapid quenching deposition process make intermediate phases to persist in the EuBCO matrix. As an evidence of the vapor-liquid-solid growth mechanism, a dome-like wetting structure composed of Ba–Cu–O and Eu-rich particles, is observed on the top of the EuBCO layer. In addition, high-density column-like copper-rich metastable amorphous structures appear from the EuBCO matrix to the dome-like structure, resulting in a high level of nanostrain and a large number of nano-defects (i.e., oxygen vacancies). The mixture of artificial and natural defects attributes to a pinning behavior dominated by random pinning at which the pinning force exceeds 345 GN/m3 at low temperature (20 K) and high field (14 T).

Toward a Transportable Cell Culture Platform for Evaluating Radiotherapy Dose Modifying Factors

The current tools for validating dose delivery and optimizing new radiotherapy technologies in radiation therapy do not account for important dose modifying factors (DMFs), such as variations in cellular repair capability, tumor oxygenation, ultra-high dose rates and the type of ionizing radiation used. These factors play a crucial role in tumor control and normal tissue complications. To address this need, we explored the feasibility of developing a transportable cell culture platform (TCCP) to assess the relative biological effectiveness (RBE) of ionizing radiation. We measured cell recovery, clonogenic viability and metabolic viability of MDA-MB-231 cells over several days at room temperature in a range of concentrations of fetal bovine serum (FBS) in medium-supplemented gelatin, under both normoxic and hypoxic oxygen environments. Additionally, we measured the clonogenic viability of the cells to characterize how the duration of the TCCP at room temperature affected their radiosensitivity at doses up to 16 Gy. We found that (78±2)% of MDA-MB-231 cells were successfully recovered after being kept at room temperature for three days in 50% FBS in medium-supplemented gelatin at hypoxia (0.4±0.1)% pO2, while metabolic and clonogenic viabilities as measured by ATP luminescence and colony formation were found to be (58±5)% and (57±4)%, respectively. Additionally, irradiating a TCCP under normoxic and hypoxic conditions yielded a clonogenic oxygen enhancement ratio (OER) of 1.4±0.6 and a metabolic OER of 1.9±0.4. Our results demonstrate that the TCCP can be used to assess the RBE of a DMF and provides a feasible platform for assessing DMFs in radiation therapy applications.

FLASH radiotherapy and the associated dosimetric challenges

At Lund University and Skåne University Hospital in Lund, Sweden, we have, as the first clinic, modified a clinical Elekta Precise linear accelerator for convertible delivery of ultra-high dose rate (FLASH) irradiation. Whereas recently published reviews highlighted the need for standardised protocols for ultra-high dose rate beam dosimetry to be able to determine the true potential of FLASH irradiation, several dosimetry studies as well as in-vitro and in-vivo experiments have been carried out at our unit. Dosimetric procedures for verification of accurate dose delivery of FLASH irradiation to cell cultures, zebrafish embryos and small animals have been established using radiochromic films and thermo-luminescent dosimeters. Also, recently the first experience of electron FLASH radiotherapy (FLASH-RT) in canine patients in our clinical setting was published. Our research facilities also include a laboratory for 3D polymer gel manufacturing. Recently, we started investigating the feasibility of a NIPAM polymer gel dosimeter for ultra-high dose rate dosimetry. Furthermore, in the bunker of the modified Elekta linear accelerator, a Surface Guided Radiotherapy (SGRT) system is accessible. The Catalyst™ system (C-Rad Positioning, Uppsala, Sweden) provides optical surface imaging for patient setup, real-time motion monitoring and breathing adapted treatment. Aiming at treating patients using ultra-high dose rates, a real-time validation of the alignment between the beam and the target is crucial as the dose is delivered in a fraction of a second. Our research group has during the last decade investigated and developed SGRT workflows which improved patient setup and breathing adapted treatment for several cancer patient groups. Recently, we also started investigating the feasibility of a real-time motion monitoring system for surface guided FLASH-RT. Both FLASH related studies; 3D polymer gel dosimetry and surface guided FLASH-RT are to our knowledge the first of their kind. Following an introduction to the field of FLASH and the associated dosimetric challenges, we here aim to present the two ongoing studies including some preliminary results.

Recent advances and prospects for highly cobalt nanoparticles embedded in polymer improved strategies for high-rate and durable cobalt-ion batteries storage

Cobalt ion batteries are considered as a promising battery chemistry for renewable energy storage. However, there are indeed challenges associated with Co ions batteries that demonstrates undesirable side reactions due to hydrogen gas production. This study demonstrates the use of a nanocomposite electrolyte that provides stable performance cycling and high Co2+ approximately better conductivity (24 mS cm−1). The desirable properties of the nanocomposite material can be attributed to its mechanical strength, which remains better, nearly 68 MPa, and its ability to form bonds with H2O. These findings offer potential solutions to address the challenges of Co dendrite, contributing to the advancement of Co ion batteries as a promising battery chemistry. The exceptional cycling stability of the Co-metal anode, even at ultra-high rates, is a significant achievement demonstrated in the study using the nanocomposite electrolyte. The Co-metal anode a 3500 cycles current density at 80 mA cm−2, which indicates excellent stability and durability. Moreover, the cumulative capacity of 15.6 Ah cm−2 at a current density of 40 mA cm−2 highlights the better energy storage capability. This performance is particularly noteworthy for energy storage applications where high capacity and long cycle life are crucial. The H2O bonding capacity of the component in the nanocomposite electrolyte plays a vital role in reducing surface passivation and hydrogen evolution reactions. By forming strong bonds with H2O molecules, the polyethyne helps and prevents the unwanted reactions that can deteriorate battery performance and efficiency. This mitigates issues typically associated with excess H2O and ion presence in aqueous Co ion batteries. Furthermore, the high-rate performance with excellent stability and cycling stability performance (>500 cycles at 8 C) of full Co||MnO2 batteries fabricated with this electrolyte further validates its effectiveness in practical battery configurations. These results indicate the potential of the nano nanocomposite electrolyte as a valuable and sustainable option and simplifying the development of reliable and performance for the energy storage systems and renewable energy applications.

Research on Optimal Control Method of Load Side Virtual Power Plant Based on Cloud Edge Collaboration

With the advancement of new power system construction, the large-scale layout of new energy power generation has gradually become a new format, and the overall new energy presents the characteristics of “rapid development of installed capacity, an increased proportion of low-voltage grid connection, and ultra-high penetration rate in some areas”. Under the new situation of power generation, power transmission, power distribution, and power consumption, to solve the problem of efficient and friendly interaction of “source, network, load and storage” in the power system and the consumption of renewable energy, “virtual power plant” came into being. However, there are limitations in aggregating resources in virtual power plants. To improve the effective participation of users, such as medium and low loads in power grid interaction, this article designs and implements a load-side virtual power plant control software system based on cloud-side collaboration. We use the virtual power plant operation control system to realize resource bidding and flexible participation in the response. The system can flexibly aggregate multiple types of resources through deployment verification, effectively realize precise tracking of instructions, and guarantee effective grid interaction.

Fabrication of Ni-Cr-FeOx ceramic supercapacitor electrodes and devices by one-step electric discharge ablation

This investigation addresses the need in the development of a facile, low-cost and computer-aided design method to fabricate ceramic supercapacitors, based on patterned metal oxide films. It is motivated by the promising advantages of planar electrode arrangement for the fabrication of ceramic supercapacitors operating at extremely high charge-discharge rates. Herein, one-step electric discharge ablation (EDA) technique is developed for fabricating Ni-Cr-FeOx electrodes using commercial 304 stainless steel current collectors for the first time. The binder-free, noble materials-free, toxic chemical-free and conductive additives-free Ni-Cr-FeOx based in-plane microsupercapacitors (IMSC) are fabricated by the EDA technique. The obtained IMSC delivers a high areal capacitance of 38.3 mF cm−2 at 1 mV s−1 and shows superior capacitive behavior at an ultrahigh scan rate of 152,000 mV s−1, which is >760 times higher than the reported values for ceramic metal oxide based electrodes in the literature. This one-step, low-cost, environmental friendly, and automatic fabrication method is promising for the scale-up synthesis of various ceramic metal oxides and fabrication of supercapacitor devices.

Proof-of-Principle of Absolute Dosimetry Using an Absorbed Dose Portable Calorimeter with Laser-Driven Proton Beams

Charged particle beams driven to ultra-high dose rates (UHDRs) have been shown to offer potential benefits for future clinical applications, particularly in the reduction of normal-tissue toxicity. Studies of the so-called FLASH effect have shown promise, generating huge interest in high dose rate radiation studies. With laser-driven proton beams, where the duration of the proton burst delivered to a sample can be as short as hundreds of picoseconds, the instantaneous dose rates are several orders of magnitude higher than those used for conventional radiotherapy. The dosimetry of these beam modalities is not trivial, with conventional active detectors, such as ionisation chambers, experiencing saturation effects making them unusable at the extremely high dose rates. Calorimeters, measuring the radiation-induced temperature rise in an absorber, offer an ideal candidate for the dosimetry of UHDR beams. However, their application in the measurement of laser-driven UHDR beams has so far not been trialled, and their effective suitability to work with the quasi-instantaneous and inhomogeneous dose deposition patterns and the harsh environment of a laser-plasma experiment has not been tested. The measurement of the absorbed dose of laser-driven proton beams was conducted in a first-of-its-kind investigation, employing the VULCAN-PW laser system of the Central Laser Facility (CLF) at the Rutherford Appleton Laboratory (RAL), using a small-body portable graphite calorimeter (SPGC) developed at the National Physical Laboratory (NPL) and radiochromic films. A small number of shots were recorded, with the corresponding absorbed dose measurements resulting from the induced temperature rise. The effect of the electromagnetic pulse (EMP) generated during laser–target interaction was assessed on the system, showing no significant effects on the derived signal-to-noise ratio. These proof-of-principle tests highlight the ability of calorimetry techniques to measure the absorbed dose for laser-driven proton beams.

FLASH radiotherapy using high-energy X-rays: Current status of PARTER platform in FLASH research

PurposeRecent studies indicated that ultrahigh dose rate (FLASH) radiation can reduce damage to normal tissue while maintaining anti-tumour activity compared to conventional dose rate (CONV) radiation. This paper provides a comprehensive description of the current status of the Platform for Advanced Radiotherapy Research (PARTER), which serves as the first experimental FLASH platform utilizing megavoltage X-rays and has facilitated numerous experiments. Methods and MaterialsPARTER was established in 2019 based on a superconducting linac to support experimental FLASH studies using megavoltage X-rays. Continuous upgrades have been made to the accelerator, collimators, flattening filters, monitors, other auxiliary devices, and irradiation process in order to achieve optimal results. Passive and active dosimeters are employed for measuring dose distribution and to ensure traceability of radiation doses. ResultsThe dose monitors and dosimeters demonstrate reliable performance with acceptable stability. At PARTER, the maximum mean dose rate is approximately 400 Gy/s at a surface-source distance of 20 cm (over 1000 Gy/s at smaller distances), with an instantaneous dose rate of approximately 8E5 Gy/s. Both passive and active dosimeters exhibit good linearity and agreement during FLASH X-ray irradiation. The monitors show good linearity to dose rate, with short-term fluctuations within 1.5 % for the diamond monitor. The discrepancy between measured absorbed dose and dose protocol is typically less than 4 %. The X-ray energy spectra on PARTER are comparable to those for megavoltage CONV linacs operating in flattening filter-free mode. The maximum field size of the FLASH beam is 4.5 cm × 4.5 cm. The FLASH dose profile demonstrates satisfactory flatness (1.04) and similar penumbra compared to clinical CONV linac, while the percentage depth dose curve of FLASH X-rays is steeper than that of the clinical megavoltage CONV X-ray. ConclusionsPARTER represents a pioneering platform for conducting megavolts FLASH X-ray irradiation in biological experiments. It effectively fulfills the requirements of preclinical research on megavoltage X-ray FLASH and undergoes continuous upgrades to meet increasingly demanding performance criteria.

Development of a velocity measurement method for a microparticle projectile and high-speed impact testing of metallic materials for grain refinement

Since grain refinement, such as the nano-twinning and nano-crystallization of metallic materials, can improve mechanical properties, surface modification to generate nano-structures is an in-demand technology. This study aims to conduct ultrahigh velocity impact testing using microparticle projectiles to generate indentation craters via impact. Due to the resulting extreme plastic deformation with high strain rate, grain refinement is expected to occur. This study conducts the laser-induced particle impact test (LIPIT), in which laser ablation induces supersonic ejection of a microparticle, resulting in the generation of an impact crater. We first propose a method for measuring particle projectile velocity using a mechanoluminescent (ML) material. A particle collision against the ML material emits light as a result of the mechanical stimulus. The light is detected to determine the timing of particle arrival, thus, the particle projectile velocity is obtained. This measurement method is verified using a high-speed video camera. Next, LIPIT is applied to pure copper (Cu) and pure iron (Fe), thus producing nano-structures including twinning around the impact indentation craters. To clarify this mechanism, a molecular dynamics (MD) simulation is conducted to reveal the formation of nano-twinning around the impact craters. In addition, nano-indentation testing is conducted, indicating plastic hardening around the impact craters unlike the craters obtained using quasi-static indentation. This indicates that plastic deformation due to LIPIT improves mechanical properties, owing to the extreme plastic strain and strain rates involved. Therefore, our LIPIT has potential as a new surface modification technique to induce extreme plastic deformation with ultrahigh strain rates, resulting in grain refinement.

Shape-Memory Three-Dimensional Evaporators with High Portability for Efficient Solar-Driven Freshwater Production.

Solar-driven water evaporation can alleviate the severe water scarcity situation in a nonpolluting and sustainable manner. Although the design of integrated three-dimensional (3D) solar evaporators has been proven to be effective in achieving ultrahigh evaporation rates and energy efficiency, their scalable application is still hindered by complex manufacturing processes and poor portability. Herein, we report a highly portable shape-memory 3D solar evaporator by depositing MXene on low-cost lignin-cellulosic sponges for freshwater production. When not in use, the 3D evaporator can be compressed into a thin film with up to 89.3% volume reduction, ensuring minimal space occupation and high portability. When needed, due to the shape-memory effect, the 3D structure can be rapidly restored by swelling the compressed film in water, resulting in an efficient 3D solar evaporator. This 3D evaporator exhibits not only a high evaporation rate of 2.48 kg m-2 h-1 under 1 sun illumination but also excellent long-term stability and recyclability. In addition, the 3D evaporator itself can serve as a water reservoir without requiring a continuous water supply during evaporation, showing remarkable application flexibility. This work opens a new perspective for manufacturing highly portable and efficient 3D solar evaporators and may facilitate their progress from the laboratory to commercial applications.

High modulation laser systems integrated with hybrid pulse generators for high speed fiber transmission systems

Abstract This study has simulated the high modulation laser systems integrated with hybrid pulse generators for high speed fiber transmission systems. The directly modulated laser with raised cosine/Gaussian pulse generators are employed for ultra-high data rates for modified multi band range applications. The total estimated light power after fiber cable system is demonstrated based on electro-absorption, phase, and single drive MZM measured modulators. The light base band signal and noise signal configuration is clarified after fiber cable system based on various proposed modulators. The degree of signal polarization configuration is studied after fiber cable system based on various modulators. Signal power level with Q, BER, signal eye height, and the total estimated electrical modulated signal power are evaluated after receiver system after receiver side based on proposed modulators.

Key changes in the future clinical application of ultra-high dose rate radiotherapy.

Ultra-high dose rate radiotherapy (FLASH-RT) is an external beam radiotherapy strategy that uses an extremely high dose rate (≥40 Gy/s). Compared with conventional dose rate radiotherapy (≤0.1 Gy/s), the main advantage of FLASH-RT is that it can reduce damage of organs at risk surrounding the cancer and retain the anti-tumor effect. An important feature of FLASH-RT is that an extremely high dose rate leads to an extremely short treatment time; therefore, in clinical applications, the steps of radiotherapy may need to be adjusted. In this review, we discuss the selection of indications, simulations, target delineation, selection of radiotherapy technologies, and treatment plan evaluation for FLASH-RT to provide a theoretical basis for future research.

Ultra-high growth rate of boron-doped diamond films with optimized growth parameters using in-liquid microwave plasma CVD

In this work, boron doped diamond (BDD) films were deposited onto a silicon substrate using the in-liquid microwave plasma chemical vapor deposition (IL-MPCVD) method. During the synthesis of BDD films, the effect of solvent, pressure, power and distance between the substrate and the microwave antenna on the growth rate of BDD films was studied. Pressure varied from 20 to 80 kPa at the interval of 20 kPa, power from 500 to 600 W at the interval of 50 W and distance from 1 to 1.5 mm. These different conditions resulted in the formation of both nanocrystalline and microcrystalline BDD films. Synthesized BDD films were characterized by Raman spectroscopy, laser microscopy, and optical emission spectroscopy. The highest growth rate of 410 μm/h is obtained as compared to the previous literature. Good synthesis parameters were used to deposit large area BDD films and the surface area expanded from 7 to 35 mm2. Along with this, the electrochemical properties of BDD films were studied in two different electrolytes. Concerning the growth rate, larger redox potential difference, IL-MPCVD is an effective method than the conventional microwave plasma chemical vapor deposition (MPCVD) method for the fabrication of high growth BDD films. Prime novelty statementIn this research, we synthesized BDD films with a B/C ratio of 1000 ppm by adjusting pressure, microwave power, and the substrate-to-electrode distance to determine the optimal synthesis conditions. This enabled us to determine the optimal synthesis conditions while examining variables like boron concentration and growth rate. By employing these optimized synthesis conditions, we successfully expanded the surface area of the BDD film from 7 to 35 mm2, which represents a fivefold increase. Most importantly, this is the first time reported the highest growth rate of 410 μm/h is achieved using this technique with to obtain highly crystalline BDD films. Additionally, we conducted an investigation into the electrochemical properties of BDD films in various electrolytes.

Facile Synthesis and the Thermal Properties of Al/Si Composites Prepared via Fast Hot-Pressing Sintering

In this paper, a novel power sintering technique, named fast hot-pressing sintering (FHP), which is able to achieve an ultrahigh heating rate similar to the spark plasma sintering (SPS) technique, but at a much lower cost, was applied to prepare a series of Al/Si composites with different Si volume ratios (12 vol.% to 70 vol.%) to meet the requirements of advanced packaging materials for electronic devices. In contrast to SPS, the FHP oven possesses a safe and budget-friendly current power supply, rather than a complex and expensive pulse power supply, for its heating power. The optimized sintering parameters (temperature, pressure and holding time) of FHP for preparing Al/Si composites were investigated and determined as 470 °C, 300 MPa and 5 min, respectively. In order to characterize the potential of Al/Si composites as packaging materials, thermal conductivities and coefficients of thermal expansion were studied. The thermal conductivity of the Al-40Si composite sintered by the FHP method is higher than that of the conventional SPS method (139 to 107 W m−1 K−1). With the increase in Si, the thermal conductivities and coefficients of thermal expansion on both decreases. Furthermore, the thermal conductivities obey the Agari model, whereas the coefficient of thermal expansion and Si volume ratios obey additivity. The numeric modeling would help develop required packaging materials based on the thermal performances of the substrate materials, like Si or GaAs semiconductor devices.

Hydrothermal Synthesis of Highly Crystalline Zwitterionic Vinylene-Linked Covalent Organic Frameworks with Exceptional Photocatalytic Properties.

Ionic covalent organic frameworks (COFs) featuring both crystallinity and ionic characteristics have attracted tremendous attention in recent years. Compared with single anion- or cation-containing ionic COFs, zwitterionic COFs possess unique functionalities beyond single ionic COFs such as tunable charge density and superhydrophilic and highly ion-conductive characteristics, endowing them with huge potential in various applications. However, it remains a considerable challenge to directly synthesize robust, highly crystalline zwitterionic COFs from the original building blocks. Herein, we report a green hydrothermal synthesis strategy to prepare highly crystalline zwitterionic vinylene-linked COFs (ZVCOFs) from the predesigned zwitterionic building block by utilizing 4-dimethylaminopyridine (DMAP) as the high-efficiency catalyst for the first time. Detailed theoretical calculations and experiments revealed that both the high catalytic activity of DMAP and the unique role of water contributed to the formation of highly crystalline ZVCOFs. It was found that the participation of water could not only remarkably reduce the activation energy barrier and thus enhance the reaction reversibility but also enable the hydration of zwitterionic sites and facilitate ordered layered arrangement, which are favorable for the ZVCOF crystallization. Benefiting from the highly π-conjugated structure and hydrophilic characteristic, the obtained ZVCOFs achieved an ultrahigh sacrificial photocatalytic hydrogen evolution rate of 2052 μmol h-1 under visible light irradiation with an apparent quantum yield up to 47.1% at 420 nm, superior to nearly all COF-based photocatalysts ever reported. Moreover, the ZVCOFs could be deposited on a support as a photocatalytic film device, which demonstrated a remarkable photocatalytic performance of 402.1 mmol h-1 m-2 for hydrogen evolution.