In this study, we evaluated the effects of acid leaching on the properties of Cr powder synthesized using self-propagating high-temperature synthesis (SHS). Cr powder was synthesized from a mixture of Cr2O3 and magnesium (Mg) powders using the SHS Process, and the byproducts after the reaction were removed using acid leaching. The properties of the recovered Cr powder were analyzed via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), particle size analysis (PSA), and oxygen content analysis. The results show that perfect selective leaching of Cr is challenging because of various factors such as incomplete reaction, reaction kinetics, the presence of impurities, and incompatibility between the acid and metal mixture. Therefore, this study provides essential information on the properties under acidic conditions during the production of high-quality Cr powder using a self-propagating high-temperature synthesis method.

본 연구에서는 현탁중합을 통해 이온교환입자를 합성하였다. 또한 음이온 교환막을 제조하기 위해 brominated poly(phenylene oxide) (Br-PPO)로 교환막 합성을 진행하였으며, 합성한 이온교환입자를 Br-PPO에 첨가하여 음이온 교환막 에 성능을 향상시키고자 하였고, 이를 적용하여 음이온 교환막 연료전지 시스템의 성능 평가를 진행했다. 이온교환입자는 FT-IR, TGA 및 UTM을 통해 구조 분석, 열적 기계적 특성을 평가하였다. Br-PPO는 NMR을 통해 화학적 구조 분석 및 합성 여부를 확인하였고, 음이온 교환막 연료 전지 셀 테스트를 진행하기 전 이온전도도와 이온교환용량, 팽윤도 및 수분함수율을 측정해 연구되고 있는 다른 음이온 교환막들과 비교를 통해 성능을 평가했다. 최종적으로 가장 성능이 우수했던 이온교환입 자를 0.7 wt%를 첨가한 Br-PPO-TMA- SDV 음이온 교환막을 연료전지 시스템에 도입하여 상용 막인 FAA-3-50과 성능을 비 교했다.

Mass production of high-quality carbon nanotubes (CNTs) remains a challenge, requiring the development of new wetimpregnated catalyst suitable for the catalytic chemical vapor deposition (CCVD) of CNTs in a fluidized bed reactor. For the successful development of a new catalyst, a highly robust system to synthesize CNTs must be established. Here, we systematically investigated the robustness of CNT synthesis by CCVD using a wet-impregnated catalyst. We statistically tested four factors that could potentially affect the robustness of CNT synthesis system, focusing on carbon yield and IG/ID. First, we tested the effect of vacuum baking before CNT growth. F test and CV equality test concluded that vacuum baking recipe did not significantly reduce the variability of the CNT synthesis. Second, we tested the batch-to-batch variation of catalysts. The results of t test and one-way analysis of variance indicate that there is significant difference in carbon yield and IG/ID among catalysts from different batches. Third, we confirmed that there is spatial non-uniformity of wet-impregnated catalysts within a batch when they are produced in large scale. Finally, we developed a multi-step heating recipe to mitigate the temperature overshooting during the CNT synthesis. The multi-step recipe increased the mean of carbon yield, but did not influence the variability of CNT synthesis. We believe that our research can contribute to the establishment of a robust CNT synthesis system and development of new wet-impregnated catalysts.

Biomass-derived porous carbon is an excellent scientific and technologically interesting material for supercapacitor applications. In this study, we developed biomass-derived nitrogen-doped porous carbon nanosheets (BDPCNS) from cedar cone biomass using a simple KOH activation and pyrolysis method. The BDPCNS was effectively modified at different temperatures of 600 °C, 700 °C, and 800 ℃ under similar conditions. The as-prepared BDPCNS-700 electrode exhibited a high BET surface area of 2883 m2 g− 1 and a total pore volume of 1.26 cm3 g− 1. Additionally, BDPCNS-700 had the highest electrical conductivity (11.03 cm− 1) and highest N-doped content among the different electrode materials. The BDPCNS-700 electrode attained a specific capacitance of 290 F g− 1 at a current density of 1 A g− 1 in a 3 M KOH electrolyte and an excellent longterm electrochemical cycling stability of 93.4% over 1000 cycles. Moreover, the BDPCNS-700 electrode had an excellent energy density (40.27 Wh kg− 1) vs power density (208.19 W kg− 1). These findings indicate that BDPCNS with large surface areas are promising electrode materials for supercapacitors and energy storage systems.

In this study platform, electrocatalytic detection of the antibiotic chloramphenicol (CAP) in phosphate buffer (pH 7) was easily achieved using a carbon paste electrode modified with NiO nanoparticles (note NiO-CPE). The peak reduction potential of chloramphenicol on the modified electrode is at (− 0.60 V/NiO-CPE vs. Ag/AgCl), its electrochemical behavior is completely irreversible, and controlled by adsorption phenomena. An excellent electrocatalytic activity has been demonstrated by the modified elaborated electrode towards the NO2 attracting group on the side chain of chloramphenicol. The structure and chemical composition of the NiO-CPE sensor were analyzed by SEM, and the X-ray diffraction results indicated that nickel oxide microcrystals were formed on the carbon sheets. The electrochemical characteristics of the NiO-CPE sensor were examined by cyclic voltammetry and electrochemical impedance spectroscopy in comparison with the unmodified carbon. Since the DPV technique allows plotting the linearity curve between the electrocatalytic current intensity of the Chloramphenicol peak and their concentration, the proposed sensor showed a remarkable detection limit of 1.08 × 10– 8 mol/L M (S/N = 3) and a wide determination range from 100 to 0.1 μM for Chloramphenicol. The developed sensor was successfully applied in the detection of Chloramphenicol in real samples.

Graphene oxide/Iron III oxide (GO: Fe2O3) nanocomposites (NCs) have been topical in recent times owing to the enhanced properties they exhibit. GO acting as a graphene derivative has demonstrated superior features as obtainable in a graphene sheet. Furthermore, the attachment of oxygen functional groups at its basal and edge planes of graphene has allowed for easy metal/oxide functionalization for improved properties harvesting. Fe2O3 nanoparticles (NPs) on the other hand have polymorphic property enabling the degeneracy of Fe2O3 in different phases, thereby resulting in different physical and crystalline properties when used to functionalize GO. The properties of GO: Fe2O3 have been applied to supercapacitor energy harvesting, Li-ion batteries, and biomedicine. The enhanced properties are attributed to the adsorption and electronic structure properties of Fe atoms. In this review, the various synthesis used in the preparation of reduced/graphene oxide: Fe2O3 is discussed. As indicated in the considered literature, the XPS analysis suggests electronic bond interactions between C–C, C–O, C–Fe and Fe–C. The available report on UPS measurements further suggests the formation of mixed states emanating from  and  bonds. The discussed reports further suggest that the various applications based on the harvesting of electronic, electrical, and magnetic properties are due to the ionic and exchange interactions between the different orbital states of carbon, oxygen and iron. The challenges and future prospects of the synthesis and application of GO/Fe2O3 are examined. Graphical abstract showing the process of exfoliation, reduction and functionalization of graphite to produce reduced graphene oxide (rGO).

Transition metal oxides formed by a single or heterogeneous combination of transition metal ions and oxygen ions have various types of crystal structures, which can be classified as layered structures and non-layered structures. With non-layered structures, it is difficult to realize a two-dimensional structure using conventional synthesis methods. In this study, we report the synthesis of cobalt oxide into wafer-scale nanosheets using a surfactant-assisted method. A monolayer of ionized surfactant at the water-air interface acts as a flexible template for direct cobalt oxide crystallization below. The nanosheets synthesized on the water surface can be easily transferred to an arbitrary substrate. In addition, the synthesizing morphological and crystal structures of the nanosheets were analyzed according to the reaction temperatures. The electrochemical properties of the synthesized nanosheets were also measured at each temperature. The nanosheets synthesized at 70 °C exhibited higher catalytic properties for the oxygen evolution reaction than those synthesized at other temperatures. This work suggests the possibility of changing material performance by adjusting synthesis temperature when synthesizing 2D nanomaterials using a wide range of functional oxides, resulting in improved physical properties.

Li1.3Al0.3Ti1.7(PO4)3(LATP) is considered a promising material for all-solid-state lithium batteries owing to its high moisture stability, wide potential window (~6 V), and relatively high ion conductivity (10-3–10-4 S/cm). Solid electrolytes based on LATP are manufactured via sintering, using LATP powder as the starting material. The properties of the starting materials depend on the synthesis conditions, which affect the microstructure and ionic conductivity of the solid electrolytes. In this study, we synthesize the LATP powder using sol-gel and co-precipitation methods and characterize the physical properties of powder, such as size, shape, and crystallinity. In addition, we have prepared a disc-shaped LATP solid electrolyte using LATP powder as the starting material. In addition, X-ray diffraction, scanning electron microscopy, and electrochemical impedance spectroscopic measurements are conducted to analyze the grain size, microstructures, and ion conduction properties. These results indicate that the synthesis conditions of the powder are a crucial factor in creating microstructures and affecting the conduction properties of lithium ions in solid electrolytes.

In this study, graphene oxide (GO) was synthesized by the improved Hummers’ method. The degree of oxidation from graphite (Gi) to GO was determined through interlayer spacing calculated from X–ray diffraction. Besides, the effect of KMnO4: Gi ratios (X1), H2SO4 volume (X2), oxidation temperature (X3), oxidation time of stage 1 (X4), and oxidation time of stage 2 (X5) was screened by the Plackett–Burman model. The simultaneous impact of three factors that influenced the degree of oxidation (X1, X2, and X3) was studied by the Box–Behnken experimental model of response surface methodology to achieve suitable conditions for the GO synthesis process. The characterization of GO product was investigated via the modern analytical methods: X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, UV–Vis spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Inaddition, the study was also carried out on a pilot scale for orientation in industrial application with the yield of 14 g/batch.

Recently, hollow carbon spheres (HCS) have aroused great interests in the field of energy storage and conversion owing to their unique morphology, structure and other charming properties. Nevertheless, unsatisfactory electrical conductivity and relatively poor volumetric energy density caused by inevitable gaps between discrete carbon spheres greatly impede the practical application of HCS. In this work, for the first time we propose a novel dual-template strategy and successfully fabricate interconnected 3D hollow N-doped carbon network (HNCN) by a facile and scalable pyrolysis process. By systematical characterization and analysis, it can be found that HNCN is assembled by HCS and lots of mesoporous carbon. Compared to the counterparts, the obtained HNCN exhibits unique 3D interconnected architecture, larger specific surface area, hierarchical meso/macropore structure, higher structure defects, higher N doping amount and more optimized N configurations (especially for pyridinic-N and graphitic-N). As a result, these advantageous features endow HNCN with remarkably promoted electrochemical performance for supercapacitor and oxygen reduction reaction. Clearly, our proposed dual-template strategy provides a good guidance on overcoming the intrinsic shortcomings of HCS, which undoubtedly broadens their application in energy storage and conversion.

Targeting Microcystin (MC), which is most abundantly detected in the North-Han River water area, we analyzed the relationship between the MC biosynthesis gene (mcyA gene), cyanobacteria cell density, and MC concentration, derived an RNA-MC conversion formula, and derived the cyanobacteria. The concentration of MC present in cells was predicted. In the North-Han River waters, the mcyA gene was found mainly at downstream sites of the North-Han River after Muk-Hyeon Stream junction, and higher copy numbers were found on average than other sites. In the Uiam Lake waters upstream of the North-Han River, the mcyA gene copy number increased at the Kong-Ji Stream point, and after September, the mcyA gene copy number decreased throughout the North-Han River waters. The expression of the mcyA gene was concentrated in the short period of summer due to the spatio-temporal difference between upstream and downstream water bodies. The mcyA gene expression level was not only highly correlated with MC concentration, but also correlated with the cell density of Microcystis aeruginosa and Dolichospermum circinale, which are known to biosynthesize MC. Six conversion formulas derived based on the RNA-MC relationship showed statistical significance (p<0.05) and exhibited high correlation coefficients (r) of 0.9 or higher. The expression level of MC biosynthesis gene present in eRNA determines the synthesis of cyanotoxin substances in water, quickly quantifies gene activity, and can be fully utilized for early warning of MC development.

The ultrasonic method is an alternative to the conventional route to produce structured carbon materials, offering the advantages of synthesis in a short period of time under room temperature. The main objective of this work is to synthesize a sulfonated mesoporous carbon catalyst from a phenolic resin composed of phloroglucinol and formaldehyde. The synthesis was performed by the soft-template method in an ultrasonic processor and the product was subsequently carbonized and sulfonated for application in the esterification model reaction. Functionalization with sulfuric acid of MCS5-6 h sample brought about a decrease in porosity but simultaneously resulted in the generation of functional groups of an acidic nature. The MCS5-6 h catalyst with a sulfonic density of 1.6 mmol g− 1, surface area of 402 m2 g− 1 and pore diameter of 10.6 nm maintained in mesoporous even after acid treatment. MCS5-6 h showed excellent activity in the esterification reaction with 95% oleic acid conversion. The recyclability of MCS5-6 h was satisfactory during five reaction cycles. The present work addressed a promising alternative for the synthesis of carbon catalysts using ultrasound irradiation, thus providing an alternative with a lower cost of time and energy for large-scale production.

This work describes the synthesis and characterization of a heterogeneous catalyst consisting of piperazine-functionalized reduced graphene oxide decorated with Fe3O4 nanoparticles ( Fe3O4@rGO-NH), and the study of its catalytic activity as a magnetic heterogeneous catalyst for the Pechmann synthesis of coumarins. Catalyst Fe3O4@ rGO-NH was fully characterized by various techniques, including IR, XRD, TEM, VSM, TGA, and elemental analysis. Then, the catalyst was used as an efficient and easy-separable heterogeneous catalyst for the solvent-free synthesis of some coumarins by Pechmann reaction. The reaction was optimized in terms of reaction time and temperature, catalyst dosage, and the presence/absence of the solvent. Finally, the reusability of the catalyst was studied.

Gas turbine engines are widely used as prime movers of generator and propulsion system in warships. This study addresses the problem of designing a DS-based PID controller for speed control of the LM-2500 gas turbine engine used for propulsion in warships. To this end, we first derive a dynamic model of the LM-2500 using actual sea trail data. Next, the PRC (process reaction curve) method is used to approximate the first-order plus time delay (FOPTD) model, and the DS-based PID controller design technique is proposed according to approximation of the time delay term. The proposed controller conducts set-point tracking simulation using MATLAB (2016b), and evaluates and compares the performance index with the existing control methods. As a result of simulation at each operating point, the proposed controller showed the smallest in , which means that the rpm does not change rapidly. In addition, IAE and IAC were also the smallest, showing the best result in error performance and controller effort.

In this study, an Al82Ni7Co3Y8 (at%) bulk metallic glass is fabricated using gas-atomized Al82Ni7Co3Y8 metallic glass powder and subsequent spark plasma sintering (SPS). The effect of powder size on the consolidation of bulk metallic glass is considered by dividing it into 5 m or less and 20–45 m. The sintered Al82Ni7Co3Y8 bulk metallic glasses exhibit crystallization behavior and crystallization enthalpy similar to those of the Al82Ni7Co3Y8 powder with 5 m or less and it is confirmed that no crystallization occurred during the sintering process. From these results, we conclude that the Z-position-controlled spark plasma sintering process, using superplastic deformation by viscous flow in the supercooled liquid-phase region of amorphous powder, is an effective process for manufacturing bulk metallic glass.

In this paper, we describe the first multi-frequency synthesis observations of blazar 0059+581 made with the Radioastron spaceground interferometer in conjunction with the Korean VLBI Network (KVN), Medicina and Torun ground telescopes. We conducted these observations to assess the spaceground interferometer multi-frequency mode capability for the first time.