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High entropy alloys (HEAs) are defined as a multi-element alloy including more than 4 elements with near equi-atomic percentage. In general, the configurational entropy of the HEAs is known to be sufficient to stabilize a single solid solution, such as body-centered cubic (BCC), face-centered cubic (FCC) and hexagonal-closed pack (HCP). Compared to BCC single-phase alloys, FCC single-phase alloys draw extensive attention because they are advantageous in manufacturing and processing. FCC-based HEAs show excellent ductility but limited strength, so many research on improving strength has been conducted. Outstanding mechanical properties with a balance of strength and ductility are rarely achieved in single-phase FCC-based HEAs. This is why most alloys for structural applications exhibit a multi-phase microstructure. In this study, we aimed to develop multi-phase FCC-based HEA with superior mechanical properties than single-phase CoCrFeMnNi HEA, via Co substitution in CoCrFeMnNi HEA by Cu, which has a high mixing enthalpy. It was found that the CuCrFeMnNi HEA is composed of two FCC phases and one BCC phase. The CuCrFeMnNi HEA was cold-rolled, and subsequently aged at 500, 700, 900oC for 1 hour. As the annealing temperature increased, the volume fraction of the FCC phase (FCC1 + FCC2) increased and the residual stress was gradually relieved by recrystallization. Furthermore, small amount of sigma phase was formed at 900oC. The effect of the microstructural evolution on the mechanical properties, such as hardness and tensile properties at room temperature, will be discussed.

To evaluate the effects of drought on groundwater system in rural areas, the standardized groundwater level index (SGI) was applied to groundwater monitoring wells over S. Korea. Moreover, accumulation period (AP), representing the month with the highest correlation coefficient between SGI and the standardized precipitation index (SPI), was calculated for monitoring wells. In this case, correlation analysis was performed to investigate differences in the response of precipitation and groundwater level to drought using SPI. Groundwater level data from 68 monitoring wells were used for the analysis. The response time of groundwater level to precipitation appeared to be very short, but the groundwater level did not go with SPI during the long-term drought. Results of correlation analysis between reservoir level and SPI show high correlation on the relatively long AP. The results of analysis between SGI and SPI appeared that the AP values ranged from 1 to 3 months for most of the wells indicating that the total amount of groundwater will not decrease significantly in long-term drought periods unlikely it of reservoirs with the high AP values. The nationwide maximum AP values between SGI and SPI were around 4 in the central part of S. Korea, while the minimum AP values were around 2 in the eastern and western part of S. Korea. Consequently, it could be concluded that the wells with low AP value tend to respond to short-term drought, but it has little effect on groundwater system when the long drought occurs. Acknowledgement: This research was supported by the Institute of Planning and Evaluation for Technology in Food, Agriculture, and Forestry (IPET) [Grant number 320046053HD020].

Interest in wearable electronics has led to extensive studies on woven textiles that are mechanically robust and stretchable, have high electrical conductivities, and exhibit fire resistance properties even at high temperatures. We demonstrate a highly easy and scalable method for fabricating defect-free graphene (

It is generally accepted that while efficient suppression of molecular vibration is inevitable for purely organic phosphors due to their long emission lifetime in the regime of 1 ms or longer, fluorophores having a lifetime in the nanoseconds regime are not sensitive to collisional quenching. Here, however, we demonstrate that a fluorophore, 2,5-bis(hexyloxy)terephthaldehyde (BHTA), capable of having hydrogen bonding (H bonding) via its two aldehyde groups can have a largely enhanced (450%) fluorescence quantum yield (QY) in amorphous poly(acrylic acid) (PAA) matrix compared to its crystalline powder. We ascribe this enhanced QY to the efficient suppression of molecular vibrations via intermolecular H bonding. We confirm this feasibility by conducting temperature-dependent fluorescence emission intensity measurement. As gaseous phenol can intervene with the H bonding between BHTA and PAA, interestingly, BHTA embedded in PAA can selectively detect gaseous phenol by a sharp fluorescence emission intensity drop that is visibly recognizable by the naked eye. The results provide an insightful molecular design strategy for a fluorophore and fluorometric sensory system design for enhanced photoluminescence QY and convenient detection of various volatile organic compounds.

Dramatic increases in fossil fuel consumption inevitably led to the emission of huge amounts of CO2 gas, causing abnormalities in the climate system. Despite continuous efforts to resolve global atmospheric problems through CO2 capture and separation, success has been limited by poor CO2 selectivity in the CO2/N2 mixture. Herein, we demonstrate the fabrication of a three-dimensional (3D) nanostructure from two-dimensional transition metal carbides (Ti3C2Tx, MXene), and assess its utility as an adsorbent in a CO2 capture system. Through structural and textural analysis, we confirm that the as-prepared MXene possesses high size uniformity with a thickness of ~2.5 nm, and that an MXene aerogel interconnected by MXene nanosheets has a 3D porous architecture with micro/nano porosity (Barrett-Joyner-Halenda (BJH) pore size = 11.4 nm). Moreover, the MXene aerogel exhibits favorable adsorption behavior for CO2, due to the high-quality MXene nanosheets even with a low specific surface area. Our approach could lead to significant advances in CO2 capture by adsorbents and open up new opportunities for mass production.

Realizing Li-metal batteries requires overcoming several hurdles, such as volume changes, a thickening solid electrolyte interphase, and safety issues associated with uncontrollable Li growth. Introducing a 3D conductive framework that improves Li reversibility by decreasing the local current density and alleviating volume changes can mitigate these issues, but inevitable Li growth on the top surface remains problematic. To address this, herein, we report an electrical conductivity-controlled 3D host consisting of a glass fiber (GF) framework, size-/conductivity-controlled partially reduced graphene oxide (PrGO), and a Cu substrate (PrGO–GF/Cu). Due to the synergistic interplay between the 3D GF alleviating volume fluctuation and PrGO with desirable conductivity, the PrGO–GF/Cu host mitigates the Li top plating and guides preferential Li deposition/dissolution at the bottom of the structure. As a result, the PrGO–GF/Cu exhibits substantially improved electrochemical performance in coulombic efficiency, symmetric cell, and LiFePO4 full cell tests. Experimental and theoretical studies reveal that modulating the electrical conductivity of the framework within an optimal range is an easy and effective way of suppressing Li top plating and facilitating Li bottom plating/stripping. This work demonstrates the importance of controlling the electrical conductivity to enable reversible behavior of Li in the Li-metal host anode, and a facile method to fabricate a 3D host that prevents Li top plating.

Carbon black has been replaced with silica as a reinforcing filler in tire tread compounds. This change has led to lower rolling resistance and improved hysteretic losses of so-called “green tires.” However, the dispersion of silica in the rubber matrix is an important issue due to the poor compatibility of hydrophilic silica with a hydrophobic rubber matrix. Recently, some rubbers with polar functional groups that can interact with silica have been studied to improve the interaction in silica-filled rubber composites. In this work, we fabricated the silica-filled rubber composites with solution styrene butadiene rubber (SSBR) and epoxidized natural rubber (ENR) and evaluated their properties in a silica-containing rubber formulation compared to conventional SBR and NR. The silica-embedded polar rubber matrix exhibits remarkable enhancement in the modulus, tensile strength, and abrasion properties due to an efficient dispersion of the silica and improvement of interfacial interactions with the rubber matrix. The polar rubber composite exhibits an enhanced dry and wet braking and improved rolling resistance due to the improved dispersion of the silica in the rubber matrix. These results show that rubber composites prepared with polar rubbers have great potential for tire engineering applications.

Photocatalytic water splitting is the most environmentally friendly method to generate energy. Despite intense research in this area, rapid charge-carrier recombination and limited light absorption...

Biomorphic C/SiC composites were prepared by infiltrating liquid Si into a carbon preform made from medium-density fiberboard. The effects of residual Si on the ablation properties of the composite...

With the development of environmentally friendly “green tires” in the tire industry, silica has been used as a reinforcing filler material in tread compounds. With regard to this rubber compounding process, non-toxic, and renewable processing aids are required. We fabricated such processing aids with multi-alcohol components of hydrophobic and hydrophilic groups (M-A-S) to make the hydrophilic silica compatible with the hydrophobic rubber matrix. The rubber composites with M-A-S showed remarkable enhancements in the mechanical properties, specifically the tensile strength, elongation and fatigue properties due to the improved dispersion of silica in the rubber matrix. They also exhibited outstanding heat build-up, good rebound resilience, and abrasion levels at low loadings. Furthermore, M-A-S were added directly to tread compounds to make a pneumatic tire with enhanced high-speed durability and enhanced dry and wet braking due to the strong interfacial interaction between the silica and the rubber matrix. These results demonstrate the advantages of the proposed potential replacement for metal-ion processing aids for tire engineering.

A waste plaster landfill site, established as a high-density polyethylene (HDPE) sheet pile surrounded by a slurry wall to isolate possible contaminants within the landfill, was investigated using ...

The design of photoactive materials and interface engineering between organic/inorganic layers play a critical role in achieving enhanced performance in energy-harvesting devices. Two-dimensional transitional dichalcogenides (TMDs) with excellent optical and electronic properties are promising candidates in this regard. In this study, we demonstrate the fabrication of size-controlled MoS2 quantum dots (QDs) and present fundamental studies of their optical properties and their application as a hole-transport layer (HTL) in organic solar cells (OSCs). Optical and structural analyses reveal that the as-prepared MoS2 QDs show a fluorescence mechanism with respect to the quantum confinement effect and intrinsic/extrinsic states. Moreover, when incorporated into a photovoltaic device, the MoS2 QDs exhibit a significantly enhanced performance (5/10-nanometer QDs: 8.30%/7.80% for PTB7 and 10.40%/10.17% for PTB7-Th, respectively) compared to those of the reference device (7.24% for PTB7 and 9.49% for PTB7-Th). We confirm that the MoS2 QDs clearly offer enhanced transport characteristics ascribed to higher hole-mobility and smoother root mean square (Rq) as a hole-extraction material. This approach can enable significant advances and facilitate a new avenue for realizing high-performance optoelectronic devices.

The conventional carbon black filler, used in tread formulations, is being replaced with silica with the development of “green tires” in the tire industry. For this, the addition of a processing aid containing zinc ion was required as a dispersing agent and lubricant However, zink being a heavy metal, zinc-free processing aids (ZFAs) are needed to satisfy global environmental issues. Therefore, this study pre sented a series of catalytically synthesized ZFAs and studied the effects of replacing “Y” zinc-containing processing aids (ZCAs) in a silica tread compounds. Interestingly, the rubber composite replacing ZCAs with ZFAs in 2 phr (parts per hundred rubber) improved both its tensile strength and elongation by as much as 31% and 20%, respectively. In addition, the rubber compounds with ZFAs exhibited a two-fold i enhancement in fatigue properties over those with ZCAs. Furthermore, pneumatic tires were fabricated from the rubber compounds containing ZFAs and compared against tires with ZCAs. The tires containing ZFAs rubber composite showed enhanced dry and wet braking and rolling resistance due to enhanced dispersion of silica in the rubber matrix. These results show that rubber composites prepared with ZFAs maybe promising in tire engineering applications.

This study was conducted to delineate agricultural drought-prone zones with respect to each agricultural watershed in South Korea, considering irrigation capacity of agricultural facilities under the representative concentration pathways (RCPs) as the latest generation of climate change scenario. Simulated temporal and spatial data (2011–2100) on precipitation and temperature for two RCPs, high-level greenhouse gases emission scenario (RCP 8.5) and intermediate-level one (RCP 4.5) were applied to the standardized precipitation index (SPI) in order to project meteorological drought periods in the twenty-first century. With consideration of irrigation capacity of agricultural facilities on the each watershed, non-beneficial areas on irrigation were designated to be agricultural drought-prone zones during the projected drought periods. One representative watershed was selected to identify the applicability of the delineating method. Results of the SPI simulation exhibited five separate drought periods (2020s, mid-2030s, mid-2040s, 2050s, and 2080s) during the twenty-first century on this watershed. During the projected drought periods, 22 administrative towns (73%) among 30 towns in this watershed would turn out to be continuously irrigated by 61 agricultural facilities enduring 10-year cycle meteorological drought. Remaining 8 towns (27%) would be vulnerable to droughts due to lack of irrigation water. The standardized groundwater level index exhibited groundwater aquifer has an irrigation capacity on the farm fields during long-term drought periods.

The effect of precipitate structures of a B2-NiAl/L21-Ni2TiAl hierarchical precipitate-strengthened ferritic alloy on the precipitate/matrix interface, elastic strain, and creep resistance has been investigated by systematic heat-treatments and creep experiments. The experimental results reveal that the highest creep strength was achieved in a heat-treated sample containing the largest coherent precipitate with fine internal networks, whereas the semi-coherent precipitate results in a sharp drop of the creep strength. It was found that the strong elastic strain field, affected by the internal structure within the precipitate, plays a crucial role in improving the creep resistance.

Tungsten composites reinforced with 20 vol% of different particle sizes of ZrN and W powders were prepared by ball milling and spark plasma sintering. Correlations between the W and ZrN grain sizes, and the mechanical and ablation properties of the composites, were investigated. The improved mechanical properties of the ZrN/W composite containing fine ZrN and fine W grains is attributed to a W grain refinement effect and a ZrN particle strengthening effect. The mass ablation rate of the composites containing fine ZrN and coarse W grains significantly decreased, i.e., 36% lower that of the composite containing fine ZrN grains and fine W grains. The improved ablation resistance is attributed to better surface coverage of the ZrO2 oxide layer because of uniformly dispersed fine ZrN particles, and to less oxidation and sweeping away of the W matrix during ablation through grain boundary diffusion suppression caused by the large W grain size.

Stem cell therapy is one of the novel and prospective fields. The ability of stem cells to differentiate into different lineages makes them attractive candidates for several therapies. It is essential to understand the cell fate, distribution, and function of transplanted cells in the local microenvironment before their applications. Therefore, it is necessary to develop an accurate and reliable labeling method of stem cells for imaging techniques to track their translocation after transplantation. The graphitic quantum dots (GQDs) are selected among various stem cell labeling and tracking strategies which have high photoluminescence ability, photostability, relatively low cytotoxicity, tunable surface functional groups, and delivering capacity. Since GQDs interact easily with the cell and interfere with cell behavior through surface functional groups, an appropriate surface modification needs to be considered to get close to the ideal labeling nanoprobes. In this study, polyethylene glycol (PEG) is used to improve biocompatibility while simultaneously maintaining the photoluminescent potentials of GQDs. The biochemically inert PEG successfully covered the surface of GQDs. The PEG-GQDs composites show adequate bioimaging capabilities when internalized into neural stem/progenitor cells (NSPCs). Furthermore, the bio-inertness of the PEG-GQDs is confirmed. Herein, we introduce the PEG-GQDs as a valuable tool for stem cell labeling and tracking for biomedical therapies in the field of neural regeneration.

The charge excitation and decay pathways of two-dimensional heteroatomic quantum dots (QDs) are affected by the quantum confinement effect, bandgap structure and strong exciton binding energy. Recently, semiconducting transition metal dichalcogenides (TMDs) have been intensively studied; however, the charge dynamics of metallic phase QDs (mQDs) of TMDs remain relatively unknown. Herein, we investigate the photophysical properties of TMD-mQDs of two sizes, where the TMD-mQDs show different charge excitation and decay pathways that are mainly ascribed to the defect states and valence band splitting, resulting in a large Stokes shift and two excitation bands for maximum photoluminescence (PL). Interestingly, the dominant excitation band redshifts as the size increases, and the time-resolved PL peak redshifts at an excitation wavelength of 266 nm in the smaller QDs. Additionally, the lifetime is shortened in the larger QDs. From the structural and theoretical analysis, we discuss that the charge decay pathway in the smaller QDs is predominantly affected by edge oxidation, whereas the vacancies play an important role in the larger QDs. Metallic phase transition metal dichalcogenides quantum dots show different pathways of optical charge excitation and decay according to the size and sort of defects, resulting into the large Stoke shift, two bands for charge excitation, and TRPL peak shift. This result is mainly ascribed to the valance band splitting and the emerging defect states originated from atomic vacancy of basal plane and edge oxidation.

Dramatic increases in fossil fuel consumption inevitably led to the emission of huge amounts of CO₂ gas, causing abnormalities in the climate system. Despite continuous efforts to resolve global atmospheric problems through CO₂ capture and separation, success has been limited by poor CO₂ selectivity in the CO₂/N₂ mixture. Herein, we demonstrate the fabrication of a three-dimensional (3D) nanostructure from two-dimensional transition metal carbides (Ti₃C₂T

A nanohybrid filler of functionalized graphene created with eco-friendly coupling agents (ECAs) and silica was fabricated by decorating silica onto graphene through a sol-gel process. To do this, relatively large high-quality graphene flakes with an extremely low oxygen content were fabricated using a ternary graphite intercalation compound method. The ECAs with hydrophobic and the hydrophilic groups mitigate graphene aggregation while also acting as an interfacial or bridging material. Furthermore, graphene-silica nanohybrids (GSNs) were incorporated by compounding to solution-styrene-butadiene rubber (SSBR) through mechanical mixing. The GSN-embedded SSBR matrix shows remarkable enhancements in the mechanical properties, thermal and electrical conductivities, and the gas barrier properties, even at a low loading rate, due to the efficient dispersion of GSNs, which enhances the interaction with the rubber matrix. The incorporation of GSNs improved the storage modulus considerably upon evolution of the filler network and with the creation of a crosslinking network of the composites.

Highly dispersive molybdenum disulfide nanoflakes (MoS2 NFs), without any phase transition during the exfoliation process, are desirable for full utilization of their semiconductor properties in practical applications. Here, we demonstrate an innovate approach for fabricating MoS2 NFs by using hydrazine-assisted ball milling via the synergetic effect of chemical intercalation and mechanical exfoliation. The NFs obtained have a lateral size of 600&ndash, 800 nm, a thickness less than 3 nm, and high crystallinity in the 2H semiconducting phase. They form a stable dispersion in various solvents, which will be helpful for many applications, due to the oxygen functional group. To investigate production of a two-dimensional (2D) photodetector, 2D semiconducting MoS2, MoS2&ndash, p-Si vertical devices were fabricated, and their optical properties were characterized. The photodiode exhibited consistent responses with excellent photo-switching characteristics with wavelengths of 850, 530, and 400 nm.