LiFePO₄ quantum-dots composite synthesized by a general microreactor strategy for ultra-high-rate lithium ion batteries

Wang, Bo,Xie, Ying,Liu, Tong,Luo, Hao,Wang, Bin,Wang, Chunhui,Wang, Lei,Wang, Dianlong,Dou, Shixue,Zhou, Yu Elsevier 2017 Nano energy Vol.42 No.-

<P><B>Abstract</B></P> <P>Due to the relatively slow, diffusion-controlled faradaic reaction mechanisms of conventional LiFePO<SUB>4</SUB> (LFP) materials, which is hard to deliver satisfied capacity for high rate applications. In this work, ultrafine LFP quantum dots (LFP-QDs) co-modified by two types of carbonaceous materials - amorphous carbon and graphitized conductive carbon (graphene) have been successfully synthesized through a novel microreactor strategy. Because of the very limited area constructed by the dual-carbon microreactor for the growth of LFP crystal, it's demension was furthest suppressed to a very small level (~ 6.5nm). Such a designed nano-composite possesses a large specific surface area for charge adsorption and abundant active sites for faradaic reactions, as well as ideal kinetic features for both electron and ion transport, and thus exhibits ultra-fast, surface-reaction-controlled lithium storage behavior, mimicking the pseudocapacitive mechanisms for supercapacitor materials, in terms of extraordinary rate capability (78mAhg<SUP>−1</SUP> at 200C) and remarkable cycling stability (~ 99% over 1000 cycles at 20C). On the other side, due to the quasi-2D structure of the synthesized LFP-QDs composite, which can be used as the basic unit to further fabricate free-standing film, aerogel and fiber electrode without the addition of binder and conductive agent for different practical applications. In addition, to deeper understand its electrochemical behavior, a combined experimental and density functional theoretical (DFT) calculation study is also introduced.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A general microreactor strategy has been developed for structure-optimized Li-contained electrode materials. </LI> <LI> Ultrafine LiFePO<SUB>4</SUB> quantum dots are first reported through the designed microreactor strategy. </LI> <LI> The synthesized G/LFP-QDs@C exhibits ultra-fast, surface-reaction-controlled Li storage behavior. </LI> <LI> A combined experimental and DFT calculation study is introduced to reveal the energy storage mechanism of G/LFP-QDs@C. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Ultrafine LiFePO<SUB>4</SUB> quantum dots (~ 6.5nm) co-modified by two types of carbonaceous materials - amorphous carbon and graphitized conductive carbon (graphene) have been successfully synthesized through a novel microreactor strategy, which exhibit ultra-fast, surface-reaction-controlled energy storage behavior, mimicking the pseudocapacitive mechanisms for supercapacitor materials, in terms of excellent rate capability and outstanding cycling stability.</P> <P>[DISPLAY OMISSION]</P>

Freeze-Casting Produces a Graphene Oxide Aerogel with a Radial and Centrosymmetric Structure

Wang, Chunhui,Chen, Xiong,Wang, Bin,Huang, Ming,Wang, Bo,Jiang, Yi,Ruoff, Rodney S. American Chemical Society 2018 ACS NANO Vol.12 No.6

<P>We report the assembly of graphene oxide (G-O) building blocks into a vertical and radially aligned structure by a bidirectional freeze-casting approach. The crystallization of water to ice assembles the G-O sheets into a structure, a G-O aerogel whose local structure mimics turbine blades. The centimeter-scale radiating structure in this aerogel has many channels whose width increases with distance from the center. This was achieved by controlling the formation of the ice crystals in the aqueous G-O dispersion that grew radially in the shape of lamellae during freezing. Because the shape and size of ice crystals is influenced by the G-O sheets, different additives (ethanol, cellulose nanofibers, and chitosan) that can form hydrogen bonds with H<SUB>2</SUB>O were tested and found to affect the interaction between the G-O and formation of ice crystals, producing ice crystals with different shapes. A G-O/chitosan aerogel with a spiral pattern was also obtained. After chemical reduction of G-O, our aerogel exhibited elasticity and absorption capacity superior to that of graphene aerogels with “traditional” pore structures made by conventional freeze-casting. This methodology can be expanded to many other configurations and should widen the use of G-O (and reduced G-O and “graphenic”) aerogels.</P> [FIG OMISSION]</BR>

Numerical simulation of ice loads on a ship in broken ice fields using an elastic ice model

Wang, Chao,Hu, Xiaohan,Tian, Taiping,Guo, Chunyu,Wang, Chunhui The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.-

The finite element method is used to simulate the navigation of an ice-area bulk carrier in broken ice fields. The ice material is defined as elastic, and the simulations are accomplished at four model speeds and three ice concentrations. The movements of ice floes in the simulation are consistent with those in the model test, and the percentage deviation of the numerical ice resistance from the ice resistance in the model test can be controlled to be less than 15 %. The key characteristics of ice loads, including the average ice loads, extreme ice loads, and characteristic frequency, are analyzed thoroughly in a comprehensive manner. Moreover, the effects of sailing speed and ice concentration on the ice loads are analyzed. In particular, the stress distribution of ice floes is presented to help understand how model speed and concentration affect the ice loads. The "ice pressure" phenomenon is observed at 90 % ice concentration, and it is realistically reflected both in the time―and frequency―domain ice force curves.

Chemical constituents from Inula wissmanniana and their anti-inflammatory activities

Chunhui Wang,Xufeng Zhang,Panlei Wei,Xiangrong Cheng,Jie Ren,Shi Kai Yan,Wei Dong Zhang,Hui Zi Jin 대한약학회 2013 Archives of Pharmacal Research Vol.36 No.12

Two new inositol derivatives, 4-acetate-1,2,3,5-tetrakis(2-methyl-2-butenoate) inositol (1) and 3-acetate-1,2,4,5-tetrakis(2-methyl-2-butenoate) inositol (2), onenew flavonolignan 23-o-acetylsilychristin A (3), and onenew thymol derivative 3-hydroxy-4-(2-hydroxy-1-methylethyl)benzoic acid (4), along with 13 known compounds,including ten flavonolignans (5–14) and three thymolderivatives (15–17) were isolated from the aerial part ofInula wissmanniana. The structures of new compoundswere elucidated by detailed spectroscopic analysis,including HRESIMS and 2D-NMR spectroscopic data. Allthe compounds were isolated from this plant for the firsttime. The anti-inflammatory activities of the compoundswere tested against LPS-induced NO production in RAW264.7 macrophages.

Numerical simulation of ice loads on a ship in broken ice fields using an elastic ice model

Wang, Chao,Hu, Xiaohan,Tian, Taiping,Guo, Chunyu,Wang, Chunhui The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.1

The finite element method is used to simulate the navigation of an ice-area bulk carrier in broken ice fields. The ice material is defined as elastic, and the simulations are accomplished at four model speeds and three ice concentrations. The movements of ice floes in the simulation are consistent with those in the model test, and the percentage deviation of the numerical ice resistance from the ice resistance in the model test can be controlled to be less than 15 %. The key characteristics of ice loads, including the average ice loads, extreme ice loads, and characteristic frequency, are analyzed thoroughly in a comprehensive manner. Moreover, the effects of sailing speed and ice concentration on the ice loads are analyzed. In particular, the stress distribution of ice floes is presented to help understand how model speed and concentration affect the ice loads. The "ice pressure" phenomenon is observed at 90 % ice concentration, and it is realistically reflected both in the time―and frequency―domain ice force curves.

Preventing and Detecting Plagiarism in Programming Course

Wang Chunhui,Liu Zhiguo,Liu Dongsheng 보안공학연구지원센터 2013 International Journal of Security and Its Applicat Vol.7 No.5

Bimetallic PtRu Nanoparticles Supported on Functionalized Multiwall Carbon Nanotubes as High Performance Electrocatalyst for Direct Methanol Fuel Cells

Chunhui Tan,Juhui Sa,Feipeng Cai,Bo Jiang,Gai Yang,Bo Wang,Jinhua Gao,Hua Chen,Xianzhong Qin 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.2

PtRu nanoparticles (NPs) supported on acid treated multiwall carbon nanotubes (Pt1Ru1/ MWCNTs) were prepared by a modified polyol method without adding any other surfactant or protective agent. The structural and compositional properties of the as-obtained samples were characterized by transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and X-ray photoelectron (XPS) spectroscopy. The electrocatalytic performance of the catalyst was evaluated by cyclic voltammetry (CV), CO stripping voltammetry and chronoamperometry, indicating a high catalytic activity, excellent CO tolerance and stability for methanol oxidation. Interestingly, a series of accurate controllable experiments have been designed to explore the enhancement mechanism of Pt1Ru1/MWCNTs for methanol oxidation reaction. Most importantly, Pt1Ru1/MWCNTs composites were used as an anode catalyst in the direct methanol fuel cells (DMFCs) exhibiting outstanding power density (126.1 mW/cm2) 1.7 times higher than that of the commercial catalyst of Pt1Ru1/C (74.1 mW/cm2Þ)(E-TEK).

Clinical and Genetic Features of Brainstem Glioma in Adults: A Report of 50 Cases in a Single Center

Chunhui Zhou,Hao Zhao,Fan Yang,Luokai Huangfu,Chao Dong,Shuwei Wang,Jianning Zhang 대한신경과학회 2021 Journal of Clinical Neurology Vol.17 No.2

Background and Purpose Brainstem gliomas (BSGs) in adults are rare brain tumors with dismal outcomes. The aim of this study was to determine the clinical and genetic features in a series of BSGs and their association with the prognosis. Methods Fifty patients who underwent a stereotactic biopsy between January 2016 and April 2018 at a single institution were collected. Data on clinicopathological characteristics were analyzed and factors associated with patient survival were identified using a Cox regression model. Results The median age at diagnosis was 55.5 years, and 62% of the patients were male. Glioblastoma (44%) accounted for the largest proportion of BSGs, and oligodendroglioma (2 of 50) was rarely encountered. The IDH mutation (6 of 44) occurred infrequently in astrocytomas, and IDH-mutant tumors harbored both ATRX loss and MGMT promoter methylation at a relatively low level. Wild-type IDH astrocytomas were identified as having high rates of 1p/19q codeletion (5 of 38) and loss of heterozygosity 1p (8 of 38) or 19q (8 of 38) only. In diffuse midline glioma H3K27M mutant, MGMT promoter methylation occurred in three of four cases. Patients were offered radiotherapy and/or concurrent/adjuvant temozolomide chemotherapy, and their median survival time was 13 months. Multivariate analysis revealed that a low tumor grade, absence of tumor enhancement, duration of symptoms ≥3 months, Karnofsky performance status ≥70, and ATRX loss conferred a survival advantage. Conclusions Adult BSGs showed different molecular genetic characteristics, but also resembled supratentorial gliomas in their clinical features associated with oncological outcomes.

Numerical Simulations on Warm Forming of Stainless Steel with TRIP-Effect

Xiumei Wang,Chunhui Yang,Bernard Rolfe 한국소성가공학회 2010 기타자료 Vol.2010 No.6

In steels with TRIP-effect, a phase transformation from the retained-austenite to martensite occurs during forming, and it significantly affects hardening behaviours. Such an effect is sensitive to the amount of strain as well as the temperature variation. For materials with a strong TRIP-effect, new forming techniques are needed to develop that can lead to lighter and stronger components in automotive industry. This paper presents a coupled thermo-mechanical finite element modelling and simulation of a warm deep drawing of austenitic stainless steel (including a TRIP-effect) using LS-DYNA and temperature effect on forming process of such materials is investigated.

Simultaneous Optimization of Passive Transit Priority Signals and Lane Allocation

Weiguo Shi,Chunhui Yu,Wanjing Ma,Ling Wang,Lei Nie 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.2

This paper presents an integrated optimization model for the concurrent design of passive bus priority signal settings and lane allocation including lane markings for general traffic and exclusive bus lanes at isolated intersections. Traditional passive transit signal priority (TSP) strategies considered both lane markings for general traffic and exclusive bus lane settings as exogenous inputs. However, in our method, two modes of transportation (passenger cars and buses) have been considered in a centralized framework while exclusive bus lane settings, lane markings, and the optimal passive transit priority signal settings can be optimized concurrently. Minimization of the weighted delay of buses and cars is adopted as the aim of the integrated optimization model. Based on traditional National Electrical Manufacturers Association (NEMA) phase constructure, a precedence graph was employed, by which the mathematical optimization model is formulated. A set of restrictions have been set up to verify efficiency and safety for the resulting optimal lane markings and signal settings. A simulated annealing (SA) algorithm is designed to resolve the mix-integer-nonlinear-programming (MINLP) problem. In order to demonstrate the efficacy of the method proposed, numerical examples have been provided. The results from sensitivity analysis show that the proposed method can generate sub-optimal solutions for the intersection of different combinations of car demand, bus demand, and left turn ratios.