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Ablation properties of c/c-UHTcs and their preparation by reactive infiltration of K₂MeF₆ (Me = Zr, Ti) molten salt

JOURNAL OF THE EUROPEAN cERAMIc SOcIETY 2021年第11期41卷 5405-5416页

作者： Xu, Yonglong Sun, Wei Miao, chunmao Shen, Yuzhu chen, Haikun Liu, Yufeng Zhang, Hongbo Xiong, Xiang Cent South Univ State Key Lab Powder Met Changsha 410083 Peoples R China Cent South Univ Natl Key Lab Sci & Technol Natl Def High Strength Changsha 410083 Peoples R China Aerosp Res Inst Mat & Proc Technol Sci & Technol Adv Funct Composites Lab Beijing 100089 Peoples R China

Ultra-high temperature ceramic-modified c/c composites (c/c-UHTcs) were prepared by the reactive infiltration of K2MeF6 (Me = Zr, Ti) mixed with Si and Zr-Si powders. Molten salt infiltration can be divided into two stages: salt ion melt and Me-Si alloy melt. In the temperature range below 1400 degrees c, Zr and Si dissolve in the molten salt, are carried by the ion melt, and precipitate at the Pyc interface to form carbides. Above 1400 degrees c, a large amount of molten salt volatilises and thermally decomposes. The Me-Si alloy forms a melt and infiltrates the c/c matrix, and finally forms c/c-Zrc-Sic, c/c-Ti3Sic2-Sic, and c/c-Zrc-Tic-Sic composites. The c/c-ZrcSic composite with the highest Zrc content exhibited the lowest mass rate (2.6 +/- 0.02 mg/s) and linear ablation rate (0.82 +/- 0.04 mu m/s), which were reduced by 43.5 and 50.8 %, respectively, compared to the unmodified c/cZrc-Sic composite.

关键词： K2ZrF6 K2TiF6 Reactive molten salt infiltration c c composites Ultra-high temperature ceramics (UHTcs)

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LiFePO4/c cathode material prepared with a spherical, porous, hollow Fe3(PO4)2/c composite as a precursor for lithium-ion batteries

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IONIcS 2019年第12期25卷 5669-5680页

作者： Ma, Zhiming Xiao, Rengui Liao, Xia Huang, Yu Guizhou Univ Sch Chem & Chem Engn Guiyang Guizhou Peoples R China

Spherical porous hollow Fe-3(PO4)(2)/c composites with graftonite crystals were prepared in a mixed solvent of water and ethylene glycol by the solvothermal method. Then, olivine-structured LiFePO4/c was successfully synthesized by a solid phase reaction using Fe-3(PO4)(2)/c as the precursor mixed with nanospherical Li3PO4. The experimental results show that different proportions of mixed solvents have important effects on the morphology and carbon content of Fe-3(PO4)(2)/c, which further influence the electrochemical properties of LiFePO4/c. compared with LiFePO4/c prepared with FePO4 as the precursor, LiFePO4/c prepared using Fe-3(PO4)(2)/c with a water/ethylene glycol ratio of 1:1 as the precursor shows a better electrochemical performance with a discharge capacity of 165 mAh/g and a capacity retention rate of 96% over 100 cycles at 0.5 c. Using porous hollow Fe-3(PO4)(2)/c as the precursor for preparing LiFePO4/c is beneficial to the lithium-ion escaping and embedding during the process of charging and discharging, enhancing the discharge capacity and cycle stability of the cathode material.

关键词： Porous and hollow Fe-3(PO4)(2) c LiFePO4 c Glucose Electrochemical performance

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Seismic retrofitting of gravity-loads designed r.c. framed buildings combining cFRP and hysteretic damped braces

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BULLETIN OF EARTHQUAKE ENGINEERING 2019年第6期17卷 3423-3445页

作者： Mazza, Fabio Mazza, Mirko Univ Calabria Dipartimento Ingn Civile I-87036 Cosenza Italy

Despite the effectiveness of carbon fibre reinforced polymers (cFRPs) and steel braces equipped with hysteretic dissipative devices (HYDBs) to improve the seismic performance of r.c. framed structures, the only use of cFRPs may be unsatisfactory for the retrofitting of buildings designed for gravity loads only while HDYBs may be unsuitable without a preliminary upgrading. The use of cFRP and HYDB as a combined technique for the seismic retrofitting of reinforced concrete (r.c.) buildings is investigated herein. To this end, two-, four- and eight-storey r.c. framed structures are designed with reference to the structural codes for r.c. buildings in force in Italy before and after 1971. A computer code for the nonlinear static and dynamic analysis of r.c. framed structures is modified to include cFRPs and HYDBs. Firstly, the nonlinear static analysis of the original test structures is carried with the aim of improving preliminarily strength and displacement capacities by applying cFRPs laminates, at the top and bottom sides of r.c. frame members, and cFRPs wraps, at the critical end zones of columns, respectively. Then, a displacement-based design procedure of HYDBs is adopted to complete the seismic retrofitting, starting from capacity curves of the upgraded test structures. To check the reliability of the combined cFRP-HYDB technique, nonlinear dynamic analysis of the original and retrofitted structures is performed considering two sets of seven near- and far-fault ground motions scaled to the seismic design level. Results highlight that the insertion of the HYDBs is effective in reducing the seismic demand of previously upgraded cFRP structures, with Post71 types generally performing better than Ante71 ones.

关键词： R c framed structures carbon fibre reinforced polymers Hysteretic damped braces Seismic upgrading Seismic retrofitting

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Development and application of the chArduino toolkit for teaching how to program Arduino boards through the c/c plus plus interpreter ch

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cOMPUTER APPLIcATIONS IN ENGINEERING EDUcATION 2017年第6期25卷 1053-1065页

作者： Montironi, Maria Alessandra Qian, Binsen cheng, Harry H. Univ Calif Davis Dept Mech & Aerosp Engn Integrat Engn Lab Davis CA 95616 USA

The growing popularity of microcontroller-based prototyping boards in many engineering and science applications has greatly increased the demand of mechatronic skills in the technical job market. The need to keep up with this new tend, combined with the proven effectiveness of integrating theoretical learning with hands-on, project-based activities has driven the development of new educational standards and curricula pivoting on the use of microcontroller-based prototyping boards. However, the most common Integrated Development Environments (IDE) used to simplify program development lack the intuitiveness and post-processing capabilities needed in an instructional environment. This paper presents an approach aimed at overcoming these obstacles. It provides a unique and comprehensive framework for programming Arduino boards through the c/c++ interpreter ch. It extends the authors' previous work on the topic by integrating a Graphical User Interface (GUI) and a library of functions, and by improving the serial communication protocol. The paper also shows how the toolkit can be easily integrated with other features and toolkits available in ch such as plotting and line-by-line debugging to create comprehensive projects tailored for K-14 students at different levels. The concepts presented in this work are applied to programming Arduino boards but provide a general basis upon which similar frameworks can be implemented for other boards or in other programming languages.

关键词： Arduino c c plus interpreter K-14

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Value of cystatin c in predicting atrial fibrillation recurrence after radiofrequency catheter ablation

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Journal of Geriatric cardiology 2018年第12期15卷 725-731页

作者： Li-Li JIN Ling YOU Rui-Qin XIE Department of Cardiology the Second Hospital of Hebei Medical UniversityShijiazhuangChina

Backgroud Recent studies have demonstrated that cystatin c is a valuable risk marker for cardiovascular disease morbidity and ***,we hypothesized that the pre-ablation cystatin c level was associated with post-ablation atrial fibrillation(AF)*** 207 patients were enrolled and completed in this prospective observational *** with AF scheduled for receive radiofrequency catheter ablation(RFcA)therapy were screened for the *** ablation therapy,electrocardiogram,24 h holter monitor,transesophageal echocardiography,serum cystatin c,high-sensitivity c-reactive protein,creatinine levels,and routine blood examinations were *** ablation,patients were followed up every week for the first month,and then at 2,3,6,9,and 12 ***,patients came back to out-patient clinic every six months *** or 24 h holter monitor were repeated if the patient experienced palpitations or every six *** recurrence was defined as atrial flbrillation/atrial flutter or atrial tachycardia lasting≥30 seconds within three months after *** compared to patients with no AF recurrence,patients with recurrence had longer AF history(P=0.007),more early recurrence(P=0.000),a larger left atrium(P=0.004),and higher pre-ablation cystatin c levels(P=0.000).Multivariate regression analysis revealed that cystatin c and left atria(LA)diameter were risk factors for AF *** adjusting for LA diameter,the risk of AF recurrence increased 30%with every milligram cystatin c elevation(95%cI:1.117-1.523).conclusions Pre-ablation cystatin c levels were associated with AF recurrence after RFcA therapy,an optimal cut-off value of 1.190 mg/L(sensitivity=0.576;specificity=0.851).

关键词： Atrial fibrillation catheter ablation cystatin c Recurrence

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A new multi-scale modeling method for needled c/c composites

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MEcHANIcS OF ADVANcED MATERIALS AND STRUcTURES 2024年第15期31卷 3309-3323页

作者： Shi, Haolin Guo, Zhangxin Zhang, Yifan Liang, Jianguo Li, Yongcun Guo, Meiqing Taiyuan Univ Technol Inst Appl Mech Coll Mech & Vehicle Engn Taiyuan Peoples R China Tiangong Univ Key Lab Adv Text Composite Mat Minist Educ Tianjin Peoples R China Tiangong Univ Sch Text Sci & Engn Tianjin Peoples R China Taiyuan Univ Technol Inst Appl Mech Shanxi Key Lab Mat Strength & Struct Impact Taiyuan Peoples R China Taiyuan Univ Technol Natl Demonstrat Ctr Expt Mech Educ Taiyuan Peoples R China Taiyuan Univ Technol Inst Appl Mech Coll Mech & Vehicle Engn Taiyuan 030024 Peoples R China Tiangong Univ Key Lab Adv Text Composite Mat Minist Educ Tianjin 300387 Peoples R China

Needled composites have stronger interlaminar properties compared to two-dimensional fiber composite structures due to the introduction of z-directional fibers in the fiber composite layup. An effective multi-scale finite element model is developed in this paper for the complex structure of needle-punched composites. Three scales, namely fRVE, pRVE, and lRVE, are modeled from the fiber scale, the delamination scale, and the laminate scale. using ABAQUS, periodic boundary conditions are applied to the RVEs at different scales to obtain the effective mechanical properties of various RVEs. Meanwhile, the effect of needling density on the needled composites is predicted by applying the above multi-scale model. The increase of needling density can enhance the out-of-plane effective mechanical properties of the composites, but it also weakens the in-plane effective mechanical properties. The maximum error of the elastic modulus calculation is 17.68% with that of the reference, thus verifying the rationality of the multi-scale model.

关键词： c c needled composites finite element model multi-scale mechanical properties

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Using Peanut Shells to construct a Porous MnO/c composite Material with Highly Improved Lithium Storage Performance

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cHEMELEcTROcHEM 2020年第1期7卷 347-354页

作者： Zhan, Dan Wen, Tao Li, Yuqi Zhu, Yuqing Liu, Ke cui, Ping Jia, Zhiyong Liu, Huajun Lei, Kelin Xiao, Zuoan Hubei Univ Arts & Sci Hubei Key Lab Low Dimens Optoelect Mat & Devices 296 Longzhong Rd Xiangyang 441053 Peoples R China Hubei Univ Arts & Sci Hubei Key Lab Power Syst Design & Test Elect Vehi 296 Longzhong Rd Xiangyang 441053 Peoples R China Hubei Univ Arts & Sci Dept Food Sci & Chem Engn 296 Longzhong Rd Xiangyang 441053 Peoples R China

Rational utilization of biomass waste in creating new clean energy such as lithium-ion batteries is conducive to alleviating the energy crisis and boosting environmental protection. Herein, using peanut shells as the carbon source, a MnO/c composite material was successfully prepared through an eco-environmental and facile approach based on hydrothermal treatment and pyrolysis. The resultant MnO/c composite material demonstrated a hierarchical porous structure and MnO particles with irregular morphology were embedded in the pores. When used in a lithium-ion battery, the material exhibited much better lithium storage properties than those for pristine MnO and peanut shell-derived carbon. In 0.0-3.0 V, the composite material can supply an initial specific capacity of 1169.5 mA h g(-1), with a capacity retention ratio of 84.9 % after 200 electrochemical cycles. Even at 2400 mA g(-1), the material can still offer a discharge capacity of 532.3 mA h g(-1), manifesting an outstanding rate performance. The enhanced lithium storage properties of the composite material are attributed to the support of the porous carbon matrix derived from peanut shells, which are not only conducive to improving conductivity but also capable of buffering the volume expansion/shrinkage caused by lithiation/delithiation during charge/discharge processes.

关键词： peanut shells biomass MnO c anodes lithium storage

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Preparation of Li4Ti5O12/c composite by one-step solid state method

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FERROELEcTRIcS 2019年第1期548卷 34-41页

作者： Ma, Guangqiang cheng, Min Panzhihua Univ Panzhihua Peoples R China

The Li4Ti5O12/c composites were synthesized by one-step solid-phase reaction using metatitanic acid, lithium carbonate and sucrose as raw materials. The effects of the molar ratio of lithium to titanium, calcining temperature, calcination time, and sucrose content on the structure of Li4Ti5O12/c composites were studied. XRD, SEM, TEM and electrochemical performance tests were used to characterize the results. The results showed that n(Li):n(Ti) = 0.85, calcination temperature was 750 degrees c, calcination time was 6 h, and the sucrose addition amount was 30% of the total mass of raw materials. Under the conditions, the pure Li4Ti5O12/c composites can be synthesized. The particles are uniform, the particle size is 0.1-1 mu m, and the carbon envelopment is better. The specific capacity is up to 163.94 mAh/g at 0.1 c rate, and the theoretical specific capacity is 175 mAh/g very close.

关键词： Li4Ti5O12 c solid-phase method carbon package

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Ablation behavior of mullite modified c/c-Sic-Hfc composites under oxyacetylene torch for single and cyclic ablations with two heat fluxes

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JOURNAL OF THE EUROPEAN cERAMIc SOcIETY 2023年第14期43卷 5851-5862页

作者： Jiao, Xiaoyang He, Qinchuan Tan, Qing Yin, Xuemin Chengdu Univ Technol Coll Mat & Chem & Chem Engn Chengdu 610059 Peoples R China Northwestern Polytech Univ Sch Mat Sci & Engn Xian Peoples R China

To investigate the ablation mechanism of the mullite modified c/c-Sic-Hfc composites prepared by precursor infiltration pyrolysis, a 60 s single ablation and 30 s x 3 cyclic ablations were carried out at heat fluxes of 2.38 and 4.18 MW/m2, respectively. Results showed that the ablation temperatures played a vital role in the ablation process. Under the lower heat flux condition, the single ablation behavior was mainly influenced by the escape of gaseous oxidation products and slight airflow erosion, while cyclic ablation was influenced primarily by the stresses induced by crystallization transformation during the heating-cooling process. Under the higher heat flux condition, HfSiO4 was gradually generated at the interface between HfO2 and SiO2, which stabilized the crystallization of HfO2. The ablation behavior under higher heat flux was mainly influenced by thermal-induced stresses and mechanical forces of high-velocity airflow.

关键词： c c-Sic-Hfc composites Mullite Precursor infiltration and pyrolysis Microstructure Ablation

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Facile synthesis and electrochemical properties of high tap density LiFePO4/c

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IONIcS 2019年第10期25卷 4589-4596页

作者： Wang, Xiaoyan Wen, Lizhi Zheng, Yi Liu, Hao Liang, Guangchuan Hebei Univ Technol Inst Power Source & Ecomat Sci Tianjin 300130 Peoples R China North China Univ Sci & Technol Qinggong Coll Tangshan 063000 Peoples R China Tianjin Sino German Univ Appl Sci Automobile & Rail Transportat Sch Tianjin 300350 Peoples R China Hebei Univ Technol Key Lab Special Funct Mat Ecol Environm & Informa Minist Educ Tianjin 300130 Peoples R China Hebei Univ Technol Key Lab New Type Funct Mat Hebei Prov Tianjin 300130 Peoples R China

A facile way of synthesizing LiFePO4/c with high tap density was introduced. LiFePO4/c composites were synthesized by a combination of wet ball milling, spray drying, and carbothermal reduction technology using inexpensive FePO4. The effect of sphericity of secondary microsphere on electrochemical properties and tap density of LiFePO4/c composite was systematically investigated. The sphericity of the secondary microsphere is controlled by particle size of primary particle with varying the ball grinding time. The composites were characterized in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), and tap density testing. The particle size of primary particle can effectively influence the sphericity of the secondary microsphere, and consequently change the electrochemical properties and tap density of LiFePO4/c. The optimum LiFePO4/c with high tap density of 1.68 g cm(-3) contains 2.1 wt% carbon and shows an excellent rate capability and cycle performance, with the initial discharge capacities of 164.0, 159.6, 154.9, 148.3, and 138.3 mAh g(-1) at 0.2 c, 0.5 c, 1 c, 2 c, and 5 c. The good electrochemical properties are attributed to the smaller particle, uniform primary particle size distribution, and the uniform carbon coating. The high tap density of LiFePO4/c composite is attributed to the better sphericity of secondary microsphere. With the primary particle size decreasing, the secondary microsphere sphericity is better.

关键词： LiFePO4 c Sphericity High tap density Electrochemical properties Particle size

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