Anti-amyloidogenic effect of ethanol extract from the mixture of leaves and stem of Mallotus japonicus (L. F.) Müll. Arg. on β-amyloid induced memory impairment in Alzheimer’s disease mouse model

Abinash Chandra, Shrestha 우석대학교 대학원 2019 국내석사

Development of Super Acidic Proton Exchange Polymer Membranes for Fuel Cells with improved Thermal and Chemical Stability

Chandra Sutradhar, Sabuj 건국대학교 대학원 2019 국내박사

The growing concerns on energy supply and global warming from greenhouse gas emissions have intensified further the issues from the environmental impact of fuel consumption. The modern industrialized society is heavily dependent on energy which is mostly obtained from coal, petroleum, and natural gas by producing the vast majority of fuel, electricity, and heat used by people across the globe. Globally, about 15 percent of manmade carbon dioxide comes from cars, trucks, airplanes, ships and other vehicles which is the major greenhouse gas for global warming. Reducing transportation emissions is one of the most vital steps in fighting global warming and solutions to the transportation problem are already available. The development of alternative energy technologies is set to play a major role in addressing the ever-growing concerns over fossil fuel carbon emissions, climate change and global warming, and also the future availability and security of a sustainable energy supply. Therefore, compared to conventional thermal machine, fuel cell power generation system is certainly very promising due to reduce substantially the harmful exhaust emissions of carbon monoxide, unburned hydrocarbons, particulate emissions from diesel engines and their long-term sustainability. Among different fuel cell types, proton exchange membrane fuel cell (PEMFC) has the aforementioned advantages because of operating temperature and pressure with higher power density compared to other types of fuel cells. Proton exchange membrane (PEM) is the core component of the Fuel cell. Among the state-of-the-art PEMs, sulfonated perfluoropolymers (e.g., Dupont's Nafion®, 3M, and Aquivion® membranes), have been widely used in PEFCs due to their high proton conductivity and high chemical stability. Nevertheless, excessive manufacturing cost, environmental ineptitude, and the low glass ‒transition temperature of perfluorosulfuric acid (PFSA) cause researchers to prefer on alternative polymer electrolyte membranes. Therefore, Hence, a number of non-fluorinated acid ionomers, especially the sulfonated aromatic hydrocarbon polymers, have been widely studied as a branch of alternatives to develop new alternative materials for PEM. Among the aromatic polymers, sulfonated aromatic polymers are considered as a potential candidate for PEM, for being its high mechanical, chemical stabilities and enhanced conductivity. However, sulfonated PEMs, having higher IEC, show high proton conductivity and lower thermal and chemical stability due to excessive water uptake. Hence, a new approach to structural design can resolve the critical issues of hydrocarbon PEMs. The major challenges experienced by the researchers till now are to synthesis the chemically and mechanically stable proton exchange membranes. To redeem the existing problems, we have developed novel monomers and polymers with super acidity with thermal and chemical stability. In this research Ni/Zn catalyzed completely aromatic carbon-carbon bonded polymer electrolyte membranes have developed as follows (1) synthesis of thermally and chemically stable polymer membranes by developing symmetrical monomers (2) controlling the swelling ratio by synthesizing the membranes from primarily sulfonated monomers (3) developing polymer electrolytes with high molecular weight and flexibility using Ni catalyzed C–C coupling and condensation reactions (4) Improving the micro phase separation and flexibility using grafted pendant acid moiety (5) developing super conductive the polymer electrolyte membranes from strongest gas phase acidic groups. All the synthesized carbon-carbon coupled proton exchange membranes exhibited outstanding thermal, chemical and dimensional stability which are the substantial requirements for the fuel cell operation effectively. keyword: PEMFC, Carbon-Carbon bonding, Nickel catalyst, Proton exchange membrane, Proton conductivity.  

Adjustable Contention Window Algorithm for IEEE 802.11 Networks

Chandra Sukanya Nandyala Graduate School of Daegu University 2019 국내석사

분산 엑세스 환경을 지니는 무선 통신 네트워크에서 DCF는 가장 기본적인 채널 엑세스 방법이다. DCF에서의 매체 접근은 다른 대기 시간들에 의해 결정된다. 대기시간이 같거나 가장 짧은 것을 선택하는 station은 각각 충돌과 매체 접근을 경험하는 경향이 있다. 충돌은 네트워크 트래픽을 결정하는 지표로 사용되며 이것은 DCF의 유리한 점이다. 그러나 이것은 또한 충돌이 일어난 후에야 반응하기 때문에 반대로 단점이기도 하다. 사전에 대응하고 미래의 충돌을 피하기 위하여 제안하는 알고리즘은 Back-off counter가 타이머를 freeze 시키는 횟수를 제어하며, 결정된 한계를 넘은 후, Back-off counter는 새로운 윈도우 범위 경합으로부터 값을 선정한다.이 새로운 범위는 최적의 경합 윈도우 크기와 station에서 경험하는 freeze 횟수를 포함하는 제안된 알고리즘에 따라 선택된다. 성능 평가의 결과는 제안하는 알고리즘이 지연, 처리량, 충돌 비율 및 패킷 전송 비율 측면에서 DCF나 freezes 경쟁 스킴를 포함하는 DCF와 비교해서 더 나은 결과를 보인다. In wireless communication networks with distributed access, DCF is the basic channel access method. In DCF, medium access depends on different waiting times. The station that chooses same and shortest waiting time tends to experience collision and medium access respectively. A collision is used as an indication to determine network traffic and it is been a favorable point to DCF. But it is also a drawback, because it responds only after the collision has happened. To respond beforehand and avoid the future collisions, the proposed algorithm controls the number of times that the back-off counter freezes their timer and after crossing the determined limit, the back-off counter chooses its value from the new contention window range. This new range is selected as per proposed algorithm which includes optimal contention window size and the number of freezes experienced by the stations. The performance evaluation results indicate that proposed algorithm provides the better improvement in terms of delay, throughput, collision rate and packet delivery ratio compared to the DCF and DCF with freezes contention schemes.

Perkutane Drainagebehandlung von Fl¨ussigkeitsansammlungen im Abdominalraum

Chandra, Arun Universit¨at Hamburg 1997 국내박사

(A) study on energy storage devices based on binder-free and hierarchical/core-shell-like architectured electrode materials for practical applications

SALE, CHANDRA SEKHAR 경희대학교 대학원 2020 국내박사

Emerging new trends in modern consumer electronics have stimulated the researchers to develop alternative, sustainable, economically-viable, and high-performance energy storage systems to mitigate the reliance on conventional energy resources. Particularly, rechargeable batteries and supercapacitors (SCs) have been garnered a substantial attraction among the developed energy storage technologies. The rechargeable batteries demonstrate high capacity and energy density properties owing to the Faradaic charge storage mechanism. Whereas, the SCs exhibit high power density, prolonged lifetime, and rapid charge-discharge ability due to the surface-controlled reaction mechanism. Though the charge storage mechanism is different in these two energy technologies, some common factors such as electrode material and its contact with the current collector, chemical composition, morphology, and preparation methods play a vital role in their energy storage performance. Especially, electrode materials are the main and common factors in attaining the high energy storage performance. Accordingly, the research community has been focusing on the development of versatile electrode materials with enriched redox activity, high electrochemical conductivity, multi-valence states, and good structural stability. Besides the electrode materials, their preparation methods affect the large-scale production and cost of the device fabrication. Therefore, a simple and cost-effective preparation methods need to be developed to ease the abovementioned issues. Employing such simple and economically-viable methods, designing the nanoarchitectures with benefit-enriched characteristics of high surface area, porosity, hierarchical connection, and core-shell-like configuration would be a promising approach. In this thesis, we prepared highly redox-active electrode materials with beneficial morphologies using facile synthesis routes in the absence of non-conductive polymer binders and employed them as electrode materials in rechargeable batteries and SCs. As is well known that the usage of non-conductive binders affects the electrochemical performance and it causes a “dead-mass” in the total mass of active material. Therefore, preparing the electrode materials directly on the surface of current collectors would be a promising strategy in achieving the enhanced performance. Accordingly, we employed simple and cost-effective solution-processing methods to fabricate the binder-free electrode materials. As a result, the production cost of wearable/portable electronics that incorporated with energy storage devices could greatly be reduced. On the other hand, the beneficial features of morphologies such as hierarchical connection and/or core-shell-like configuration have garnered significant interest. Because, the hierarchical connection of nanostructures empowers the rapid charge transportation, which leads to low charge transfer resistance. Whereas, the core-shell-like configuration endows the improved active sites and electrochemical conductivity to an entire composite material. Considering all the above factors, chapter 3 describes the fabrication of nickel-cobalt layered double hydroxide material on the high conductive silver nanowires decorated carbon cloth (NC LDH@Ag@CC) using a facile electrodeposition technique at room temperature (RT). The Ag NWs that are decorated on the CC (Ag@CC) by a facile dip-coating method substantially improved the hydrophilic nature of bare CC. As a result, the loaded mass of NC LDH@Ag@CC was relatively higher than that of NC LDHs on bare CC (NC LDH@CC). The obtained morphology of NC LDH@Ag@CC is similar to core-shell-like architecture, in which, the core-like Ag NWs are served as conductive skeletons to transfer the charge from active material to the load. Whereas, the shell-like NC LDH nanosheets with hierarchical connection and high surface area perform numerous redox reactions with electrolyte ions. Owing to the core-shell-like architecture and improved active material mass, the NC LDH@Ag@CC electrode demonstrated higher electrochemical properties to the NC LDH@CC and Ag@CC electrodes. To demonstrate the practical applicability, the hybrid SC (HSC) was assembled with NC LDH@Ag@CC as positive and activated carbon coated CC (AC@CC) as negative electrodes, respectively. The fabricated HSC device also exhibited superior energy storage performance along with good cycling stability. Besides, the stable performance of HSC was investigated even under different flexed conditions. Chapter 4 introduces a novel hot-water therapy (HWT) method for the growth of ternary LDH nanosheets on the surface of conductive fabric (CF). The proposed HWT method provides the selective growth of nanostructures with hierarchical connection and open-porous properties. Moreover, no chemicals are used in the growth of electrode material, which specifies the eco-friendly and cost-effective features. In addition, the HWT method is a simple and scalable process in the fabrication of large-scale electrodes and exploring the novel active materials. In the HWT method, de-ionized water (DIW) exhibits a significant role in the synthesis of Ni-Cu-Co LDH NSs from the CF substrate without employing any raw chemicals. The impact of DIW on the growth of LDH NSs is extensively elaborated in this chapter. The prepared Ni-Cu-Co LDH NSs/CF sample is directly employed as the cathode in the fabrication of flexible HSC. The fabricated HSC demonstrated a decent energy storage performance by exploiting the structural and morphological properties of the Ni-Cu-Co LDH NSs. Furthermore, practical applications are also demonstrated by harvesting solar energy, thereby switching the electronic components Inspiring from the constructive features of metal-organic frameworks (MOFs) and good electrochemical activity of metal vanadates, Chapter 5 introduces simplistic wet-chemical methods to prepare metal vanadate-based core-shell-like nanoarchitecture. Utilizing Cu(OH)2 nanorod arrays (CH NRAs), which are in-situ grown on copper foam as conductive skeletons, the MOF particles are decorated over their surface. To further improve the electrochemical activity, the vanadium ions are incorporated with these CH NRAs as well as MOF particles by performing the vanadium exchange reactions. All the above procedures are implemented at RT. To improve the crystallinity, the entire composite is carried out to thermal treatment in the inert medium. The resulted metal vanadate composite, i.e., CuV2O6 and Co3V2O8 (CuV-CoV) in the form of core-shell-like architecture demonstrated superior electrochemical performance in lithium (Li)-ion battery (LIB)- as well as SC-study. The metal vanadates in the LIB-study exhibited superior capacity and cycling performance to the metal oxides due to the incorporation of metal ions in host vanadium oxide. In SC-study, the CuV-CoV composite material also demonstrated a fine electrochemical property. Furthermore, the porous carbon is derived from the MOF particles, which can be employed as a negative electrode material in SCs. The HSC is constructed with CuV-CoV as a positive electrode and the porous carbon derived from the MOF particles as negative electrode materials. The fabricated HSC delivered superior energy storage performance. Besides, the real-time applicability of HSC is also explored by successfully harvesting the dynamic energy of a bicycle in the form of an electric energy with the aid of a DC generator. The practical viability of HSC is also investigated by switching/powering the various electronic components.

Predictive Landslide Susceptibility Mapping in the Eastern Nepalese Himalaya

Chandra Prakash Poudyal 충남대학교 대학원 2010 국내박사

The objective of the present study is to construct landslide susceptibility maps in a landslide-prone area, Panchthar district, eastern Nepal, by means of bivariate and multivariate analyses using geographic information system (GIS) techniques as a basic analysis tool. GIS is used for the data management and manipulation. The DEM data are collected from the survey department of Nepal government, and aerial photo interpretation is used for the depiction of lineaments. The locations of 111 landslides that occurred in the study area are identified from field survey. Six pre-existing methods (frequency ratio, class variable analysis and area density methods as bivariate analyses, and logistic regression, artificial neural networks and decision tree as multivariate analyses) are utilized to produce the respective susceptibility maps. The three bivariate-derived methods are relatively simple and similar to each other in their applications, whereas the multivariate-derived methods are somewhat complicated in their utilization since each has to use different software for analysis. A total of ten landslide-controlling factors (slope, aspect, curvature, distance from drainage, distance from lineament, stream power index, topographic wetness index, slope-length, geology and landuse) are implemented to produce final landslide susceptibility maps using individual methods, which are compared for their ability to predict landslide probability based on actual landslide events. The accuracies of the landslide susceptibility maps produced by individual methods are 81.9% for frequency ratio, 83.4% for class variable analysis, 79.0% for area density method, 81.6% for logistic regression, 78.3% for artificial neural networks, and 95.9% for decision tree method, indicating that the decision tree method is an incomparably better tool than the others. 본 연구의 목적은 기존에 개발되어 있는 다양한 단변량 분석(bivariate analysis)와 다변량 분석(multivariate analysis)을 네팔 동부의 Panchthar지역에 적용하여 산사태 취약성도를 구축하는데 있다. GIS는 자료 관리 및 처리 하는데 이용하였다. 네팔 정부의 survey department로부터 얻은 DEM 자료를 사용하였으며 항공사진 분석을 통해 선구조를 추출하였다. 연구지역에서 발생한 100개의 산사태 위치는 필드조사에 의해 획득다. 본 연구에서 이용된 단변량 분석방법은 frequency ratio, class variable analysis, area density methods 등이며 다변량 분석은 logistic regression, artificial neural networks and decision tree등이다. . 단변량 분석방법들은 그 활용법이 비교적 용이하고 각각의 분석방법이 서로 유사한데 비해 다변량 분석 방법은 각각의 분석 방법에 활용되는 소프트웨어가 다르기 때문에 그 활용 방법이 다소 복잡하다. 산사태발생과 관련이 있는 10개의 인자(slope, aspect, curvature, distance from drainage, distance from lineament, stream power index, topographic wetness index, slope-length, geology and landuse )를 이용하여 각 방법을 이용해 최종 산사태 취약성도를 작성하였으며 그 결과를 비교하였다. 빈도비(frequency ratio), 통계적 분석(class variable analysis), 지역밀도 방법(area density method), 로지스틱 회귀분석(logistic regression), 인공신경망(neural network), 의사결정나무(decision tree) 분석 방법에 의해 작성한 산사태 취약성도의 정확도는 81.9%, 83.4%, 79.0%, 81.6%, 78.3%, 95.9%로 각각 나타났다. 의사결정나무가 분석방법 중 가장 높은 예측결과를 나타냈다.

Development of electrochemical biosensors for cancer diagnosis based on conducting polymers and nanomaterials

Chandra, Pranjal 부산대학교 2013 국내박사

As a sensitive, rapid, simple, and cost-effective analytical technique, electrochemical biosensor has been used in many fields. The combination of conducting polymers and nanomaterials promises an excellent platform for biomolecule immobilization and diagnosis of various clinical targets and cancers. A highly sensitive and selective sensor for daunomycin was developed using phosphatidylserine (PS) and aptamer as bioreceptors. The PS and aptamer were co-immobilized onto gold nanoparticles modified/functionalized [2,2′:5′,2″-terthiophene-3′-(p-benzoic acid)] (polyTTBA) conducting polymer. Direct electrochemistry of daunomycin was used to fabricate a label free sensor that monitors current at −0.61 V. The formation of each layer was confirmed with XPS, SEM, and QCM. Response of the sensor was compared with and without PS in terms of sensitivity and selectivity. Interaction between the sensor probe and daunomycin was determined with DPV. The experimental parameters affecting sensor performance were optimized in terms of concentration of immobilized aptamer, PS:aptamer ratio, temperature, pH, and reaction times. The dynamic range for daunomycin analysis ranged between 0.1 and 60.0 nM with a detection limit of 52.3 ± 2.1 pM. Sensor was also examined for interference effect of other drugs. The present sensor exhibited long term stability and successfully detected daunomycin in a real human urine spiked with daunomycin. A simple and highly sensitive method for simultaneous detection of anticancer drugs is developed by integrating the preconcentration and separation steps in a microfluidic device with an amperometric biosensor. An amperometric detection with dsDNA and cardiolipin modified screen printed electrodes are used for the detection of anticancer drugs at the end of separation channel. The preconcentration capacity is enhanced thoroughly using field amplified sample stacking and field amplified sample injection techniques. The experimental parameters affecting the analytical performances, such as pH, temperature, buffer concentration, water plug length, and detection potential are optimized. A reproducible response is observed during multiple injections of samples with a RSD <5%. The calibration plots are linear with the correlation coefficient between 0.9913 and 0.9982 over the range of 2–60 pM. The detection limits of four drugs are determined to be between 1.2 (±0.05) and 5.5 (±0.3) fM. The applicability of the device to the direct analysis of anticancer drugs is successfully demonstrated in a real spiked urine sample. Device was also examined for interference effect of common chemicals present in real samples. The amperometric immunosensor has demonstrated the toxicity of endocrine disrupters (EDs) through monitoring the in vitro i-NOS concentration change, where the antibody of inducible nitric oxide synthase (i-NOS) was immobilized on the conducting polymer–gold nanoparticles composite. The performance of the sensor and the experimental parameters affecting the immunoreaction were optimized. Neuronal cells treated by EDs decreased in the in vitro i-NOS concentration. The effect of bisphenol A (BPA) on the i-NOS concentration released in the cells was investigated with different incubation times, and the interfering by nonspecific binding species present in a neuronal cell lysate was also examined. Of all the tested EDs, BPA showed the inhibitoriest effect and the minimum inhibitory concentration of BPA affecting the i-NOS concentration was 0.09 ± 0.005 μM. The result shows that monitoring of i-NOS in the neuronal cells treated by EDs will be a useful method to evaluate the toxic behavior of EDs. Based on the stable binding of anticancer drugs to cancer cell membrane, the interaction between daunomycin (anticancer drug) and cancer cell membrane was utilized to develop a new method for the detection of cancer cells. The sensing probe was assembled by immobilizing daunomycin selective aptamer onto conducting polymer-gold nanoparticles composite to selectively capture the daunomycin treated cancer cells (CCD). The formation of each layer of the sensor probe was confirmed with XPS and SEM. Cytotoxicity of the probe material, pTTBA was also studied to ensure its application for biosensor fabrication. Capturing of CCD on the sensor probe was evaluated using electrochemical impedance spectroscopy, scanning electron microscopy, and fluorescent microscopy. The dynamic range using the impedometric method for CCD detection was between 80 and 10000 cells with a detection limit of 43 ± 3 cells/mL. HeLa, MCF-7, HT 29, and SKBr-3 cells were successfully detected in 15 min. An amperometric sensor for the diagnosis of MDR cancer cells was developed for the first time through the detection of cell membrane P-gp. This study is also the first report of an immunosensor for the direct detection of cancer cell detection where 3-APBA has been used with Hyd-AuNPs conjugate. The immunosensor probe was fabricated by forming covalent bonds between P-gp monoclonal antibodies (MAb) and carboxylic acid group-functionalized conducting polymer (polyTTBA) layer on the GC/AuNPs electrode surface. The immobilization of MAb on the nanocomposite surface was confirmed using X-ray photon spectroscopy (XPS) and quartz crystal microbalance (QCM). The sandwich immunosensing method was adopted, where 3-APBA was reacted with the sensor probe captured MDR cancer cells. The Hyd-AuNPs conjugate was applied to monitor the immunoreaction in term of the catalytic reduction of hydrogen peroxide. The experimental parameters such as; antibody dilution ratio, incubation time, pH, concentration of 3-APBA, applied potential, and temperature were optimized and the detection limit of the MDR cancer cells was determined. Interference studies and direct detection of MDR cancer cells in blood samples was performed to evaluate the performance of sensor in real sample.

A Pharmaceutical Cold Chain System using Wireless Sensor Network and Sensor Cloud infrastructure : 무선 센서네트워크와 센서 클라우드 시스템을 사용한 의약품 Cold Chain 시스템

Chandra, Abel Avitesh 목포대학교 대학원 2014 국내석사

There is a new evolution in technological advancement taking place called the Internet of Things (IoT). This IoT paradigm is a new research field which connects the physical field objects to the Internet and allowing easy access to these objects in order to monitor and manage them. The objects are associated with unique identifiers and the capability to transfer data over the network to the Internet without the intervention of humans and traditional computers. For this idea to come to life, two infrastructures are required: the Sensing Entity in the environment which collects data and connects to the cloud and the cloud service (sensor cloud) that host the data. Wireless sensor networks play a major role in this paradigm in relating the physical world object data to the Internet. These wireless sensor networks are put together using low cost computing devices and embedded systems such as the Arduino, Raspberry Pi and other RF technologies. The sensor cloud is a secondary form of cloud computing which enables the management of objects on cloud with features to store, process, visualize and share data from these objects. The sensor cloud is therefore becoming popular in providing an open, flexible and a reconfigurable platform for many monitoring and controlling applications. This thesis proposes a method to monitor the storage conditions of pharmaceutical products within the cold chain. The pharmaceutical cold chain deals with transporting and storage of harmaceutical products at various stages along the distribution from manufacturing to consumption. The pharmaceutical cold chain requires controlled environmental conditions for the sensitive products in order for them to maintain their potency and quality. In this work, the environmental conditions monitored are humidity and temperature in transport and storage facilities which are the critical parameters in pharmaceutical storage applications. The monitoring is achieved by introducing two subsystems, one for transport facility and the other for storage facility, which are integrated to the cloud to provide an improved and enhanced method for monitoring. 사물을 인터넷에 연결시키는 기술인 Internet of Things(IoT)는 새로운 연구분야가 되어 기술적으로 많은 발전이 이루어져왔다. 이러한 IoT 기술은 사물을 관찰하거나 다루는데 있어 쉽게 접근하도록 하여 네트워크 상에서 인터넷으로 데이터의 전달을 가능하게 한다. 이는 두가지의 인프라를 필요로 하는데 하나는 데이터를 수집하는 Sensing Entity이고 다른 하나는 데이터를 점유하는 Sensor Cloud이다. 여기서 무선 센서 네트워크는 사물로부터 측정되는 데이터를 인터넷에 연결시키는데 매우 중요한 역할을 하는데 간단한 컴퓨팅 디바이스나 Arduino, Raspberry Pi와 같은 임베디드시스템으로 구성될 수 있다. Sensor Cloud는 사물로부터 측정되어 나오는 데이터의 공유나 처리를 하도록 하는 클라우드 컴퓨팅으로 모니 링 혹은 컨트롤 시스템에 대한 플랫폼을 제공한다. 본 논문에서는 의약품의 저장 조건들을 모니터링 하는 Cold Chain을 제안한다. 제안된 Cold Chain은 생산에서 소비단계까지 이르는 이동이나 저장상태에 대한 여러 환경적 조건인 습도, 온도, 저장 장소 등을 모니터링 하는 시스템이다. 시스템은 두개의 부시스템으로 구성되는데 하나는 이동에 관련된 것을 다루고 다른 하나는 저장에 관련된 것을 다룬다. 이 두 개의 시스템은 보다 향상된 모니터링 방법을 제공하기 위해 Sensor Cloud 시스템으로 통합된다.

Pulsed Eddy Current Nondestructive Testing to Detect Wall Thinning in Pipelines of Nuclear Power Plants

Chandra Sekhar Angani 충남대학교 대학원 2011 국내박사

Unravelling the storage mechanism of silicon oxycarbide in rechargeable sodium ion batteries

Chandra, Christian Sungkyunkwan university 2021 국내박사

실리콘 옥시 카바이드 (SiOC)는 나트륨 이온 배터리의 양극 재료로 사용되었습니다. 저비용 실리콘 오일은 H2/Ar 흐름 조건에서 900 °C에서 간단히 열분해되어 25 mA g–1 전류 밀도에서 200 사이클 후 160 mAh g–1의 우수한 가역 용량을 가진 SiOC를 형성했습니다. 온도가 1400 °C로 증가하면 SiOC에서 산소가 풍부한 SiOxCy 상과 탄소가 풍부한 SiOxCy 상 분리가 유도되고 미세 기공, 흑연 층 및 탄화 규소 상이 진화했습니다. 고온 합성 SiOC는 0.1 V (총 용량의 45%-63%) 미만의 큰 전압 안정 용량을 나타 냈습니다. SiOC의 Na 저장 메커니즘은 현장 외 측정 및 밀도 함수 이론 (DFT) 시뮬레이션을 사용하여 조사되었습니다. 경 사진 전압 영역에서 Na+ 이온 흡수는 주로 미세 기공/고체 전해질 인터 페이즈 층, C가 풍부한 SiOxCy 상 및 일부 O가 풍부한 SiOxCy상에서 발생합니다. 대조적으로, O가 풍부한 SiOxCy 상으로의 삽입과 Na가 풍부한 Si 화합물의 형성은 0.1 V 미만의 전압 안정기에서 주요 Na+ 이온 흡수 메커니즘입니다. DFT 시뮬레이션을 기반으로 SiOC에서 Na 및 Li의 저장 메커니즘은 다음과 같습니다. 비슷한. 그러나 이온 크기가 작기 때문에 SiOC는 더 많은 Li를 저장할 수 있습니다. 더욱이, 리튬이 풍부한 Si 화합물의 형성이 더 유리하다. SiOC의 Na 저장 메커니즘을 고려하여 SiOC의 조성을 제어했습니다. N2 유동 조건에서 탄소가 풍부한 SiOC 전구체를 열분해함으로써 C가 풍부한 SiOxCy 및 O가 풍부한 SiOxCy상의 양은 증가하고 비활성 SiO2, SiC 및 Cfree상의 양을 줄였습니다. 25 mA g-1 전류 밀도에서 234 mAh g-1 가역 용량을 제공하는 고용량 SiOC가 합성되었습니다. 정전류/정전압 테스트를 수행하여 용량을 299mAh g-1로 더 늘 렸습니다. Diglyme에서 1M NaOTf를 사용하여 전기 화학적 성능이 더욱 향상되었습니다. 에테르 기반 전해질의 장점은 낮은 SEI 층 형성 및 분극화로, 특히 높은 전류 밀도에서 더 높은 저장 용량을 제공합니다. 결과적으로 SiOC는 25 mA g-1 전류 밀도에서 287 mAh g-1, 정전류/정전압 모드에서 322 mAh g-1의 훨씬 더 높은 용량을 달성 할 수 있습니다. 이 연구는 SiOC의 저장 메커니즘에 대한 정보와이를 나트륨 이온 배터리의 활성 물질로 활용하려는 다른 연구자들을 위해 전기 화학적 성능을 향상시키기위한 전략을 제공합니다. Silicon oxycarbide (SiOC) was utilized as anode materials for sodium ion batteries. Low-cost silicone oil was simply pyrolyzed at 900 °C in H2/Ar flow condition to form SiOC with an excellent reversible capacity of 160 mAh g–1 after 200 cycles at 25 mA g–1 current density. The increase of temperature to 1400 °C induced phase separation of oxygen-rich and carbon-rich SiOxCy phases in SiOC, as well as evolution of micropores, graphitic layers, and silicon carbide phase. The high-temperature-synthesized SiOC exhibited a large voltage plateau capacity below 0.1 V (45–63% of the total capacity). Na storage mechanism in SiOC was investigated using ex situ measurements and DFT simulations. In the sloping voltage region, Na+ ion uptake occurs mainly in micropores/SEI layers, C-rich SiOxCy phase, and some O-rich SiOxCy phase. In contrast, the insertion into the O-rich SiOxCy phase and formation of Na-rich Si compounds are the main Na+ ion uptake mechanisms in the voltage plateau below 0.1 V. Based on DFT simulations, the storage mechanism of Na and Li in SiOC are similar. However, due to smaller ionic size, SiOC can store more Li. Moreover, the formation of Li-rich Si compounds is more favorable. Considering the Na storage mechanism in SiOC, the compositions of SiOC were controlled. By pyrolyzing carbon-rich SiOC precursor in N2 flow condition, the amount of C-rich SiOxCy and O-rich SiOxCy phases were increased, while reducing the amount of inactive SiO2, SiC, and Cfree phases. The high-capacity iOC was synthesized, which deliver 234 mAh g–1 reversible capacity at 25 mAg–1 current density. The capacity was further increased to 299 mAh g−1 by conducting constant-current/constant-voltage test. The electrochemical performance was further enhanced using 1 M NaOTf in diglyme. The advantages of ether-based electrolytes are lower SEI layers formation and polarization, providing higher storage capacity, especially at high current density. As a result, SiOC can achieve much higher capacity of 287 mAh g−1 at 25 mAg−1 current density and 322 mAh g−1 in constant-current/constant-voltage mode. This study gives information about storage mechanism in SiOC and strategies to enhance its electrochemical performance for other researchers who wants to utilize it as active material in sodium ion batteries.