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.

In this study, UiO-66-NH2 was synthesized and incorporated with graphene aerosol (UiO-66-NH2/GA) and ethylenediamine functionalized graphene oxide (UiO-66-NH2/GO-NH2). These composites were characterized using infrared spectroscopy, powder X-ray diffraction, ultraviolet–visible light spectroscopy, scanning electron microscope, and energy-dispersive X-ray spectroscopy. UiO-66-NH2/GO-NH2 exhibited 93% adsorption of quinoline in 5 h, UiO-66-NH2 and UiO-66-NH2/GA presented 80.4% and 86.5%, respectively. The high adsorption observed on UiO-66-NH2/GO-NH2 was attributed to the unique electronic properties, and hydrogen bonding between the nitrogen atom of quinoline and NH2- phenyl fragment of UiO-66-NH2, and N–H of ethylenediamine. GO also offered combined strong π–π interactions on its surface, and the oxygen coverage (~ 50%) on GO within the structure is responsible for the formation of strong hydrogen bonds with quinoline. Theoretical calculation suggested that UiO-66-NH2/GO-NH2 presented a more favourable adsorption energy (− 18.584 kcal/ mol) compared to UiO-66-NH2 (− 16.549 kcal/mol) and UiO-66-NH2/GA (− 13.991 kcal/mol). These results indicate that nanocomposites have a potential application in quinoline capture technologies in the process of adsorptive denitrogenation.

Due to their fascinating properties, there is a rise in the critical consideration of carbon-based nanomaterials in a plethora of applications. Carbon nanomaterials, such as nanotubes, graphene, fullerenes, and nanodiamonds, have broad applicability and potential research prospects. In the past few years, the developments and consumption of still smaller nanomaterials, namely graphene quantum dots and carbon nanodots or carbon dots (CDs) have been explored. Since carbon as a component exhibits insignificant cytotoxicity and remarkable biocompatibility, CDs have found a wide scope of potential applications. Owing to their fascinating aspects, such as small size, biocompatibility, low toxic nature, environment-friendliness, costeffectiveness, ease of chemical functionalization, derivatization and surface modification, and photoluminescence tenability, CDs have been widely acknowledged. CDs have found major prospects in the areas of catalysis, sensors, and optical and bio-related applications. CDs are generally synthesized by employing techniques of pyrolysis, laser ablation, arc discharge, electrochemical method; hydrothermal and solvothermal techniques; and microwave and ultrasonic irradiations. This review article presents a brief account of the major properties of CDs, and applications, with particular emphasis on the green and environment-friendly synthesis methodologies. An overview of the microwave and ultrasound irradiation-induced syntheses for the preparation of CDs is presented in the light of green chemistry principles. In addition, some of the green and environmentally benign precursors for the production of CDs are outlined. The most recent work on CDs is included in this review article.

Recently, research on MAX phase materials has been actively conducted. M of MAX phase is made of early transition metal element, A is A-group (IIIA or IVA) element, and X is Carbon or Nitrogen. It has the chemical formula of MnAXn-1, and is called the 211, 312, and 413 groups according to the indices(n=1,2,3). MXene material is characterized by having a layered structure of 2D structure like graphene by etching the element corresponding to A-gruop in the MAX phase. So far, MXene materials have been reported to be applied in various fields. In particular, research is being actively conducted as anode material for Li secondary batteries, electromagnetic wave shielding material, and hydrogen storage alloy material. In the pulse energization active sintering method, the surface of the powder particles is cleaned and activated more easily than the conventional electrical sintering process and material transfers at both the macro and micro level, so that a high-quality sintered body can be obtained at low temperature and fast time. In this study, the MAX phase was synthesized in a short time by using a pulse current active sintering apparatus, and the MXene material was prepared from the synthesized MAX phase and the structure was analyzed.

Lithium lanthanum titanium oxide (LLTO) is a promising ceramic electrolyte because of its high ionic conductivity at room temperature, low electrical conductivity, and outstanding physical properties. Several routes for the synthesis of bulk LLTO are known, in particular, solid-state synthesis and sol-gel method. However, the extremely low ionic conductivity of LLTO at grain boundaries is one of the major problems for practical applications. To diminish the grain boundary effect, the structure of LLTO is tuned to nanoscale morphology with structures of different dimensionalities (0D spheres, and 1D tubes and wires); this strategy has great potential to enhance the ion conduction by intensifying Li diffusion and minimizing the grain boundary resistance. Therefore, in this work, 0D spherical LLTO is synthesized using ultrasonic spray pyrolysis (USP). The USP method primarily yields spherical particles from the droplets generated by ultrasonic waves passed through several heating zones. LLTO is synthesized using USP, and the effects of each precursor and their mechanisms as well as synthesis parameters are analyzed and discussed to optimize the synthesis. The phase structure of the obtained materials is analyzed using X-ray diffraction, and their morphology and particle size are analyzed using field-emission scanning electron microscopy.

국제 중국어 교재에 초과 한자와 초과 어휘가 존재한다는 것은 객관적인 사실이다. 이는 학생 이 텍스트를 이해하는데 영향을 주며, 교사가 수업을 진행하는데 있어서도 피하기 힘든 문제이 다. 본고는 《국제 중국어 교육 중국어 수준 등급 표준》를 기준으로, 『發展漢語』 고급 종합 교재에 포함되어 있는 초과 한자와 초과 어휘를 연구 대상으로 삼았다. 코퍼스 기술을 바탕으로 빠른 식별과 태깅을 진행하여, 『發展漢語』 고급 종합 단계 교재에 나타난 초과 한자와 초과 어휘 현황을 분석하였다. 또한, 초과 한자를 기준으로 真性과 假性으로 구분하고 글자 단위의 의미와 어휘 단위의 의미의 연관성을 근거로 교육 방법을 제안하였다. 한자와 연결되는 동사를 함께 가르치고, 한자와 어휘를 연결하여 학습시키는 방안은 학생의 중국어 학습 능력을 향상시킬 것이다.