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Journal of Advanced Ceramics 2020年第3期9卷 320-328页

作者： Zhaoju YU Yujing YANG Kangwei MAO Yao FENG Qingbo WEN ralf riedel College of Materials Key Laboratory of High Performnance Ceramic Fibers(Xiamen University)Ministry of EducationXiamen 361005China College of Materials Fujian Key Laboratory of Advarced MaterialsXiamen UniversityXiamen 361005China Technische Universitit Darmstad Institut fir MaterialwissenschafDarmstadt 64287Germany

A novel single-source-precursor for SiC-TaC-C nanocomposites was successfully synthesized by the chemical reaction between a polycarbosilane(allylhydridopolycarbosilane,AHPCS)and tantalum(V)chloride(TaCls),which was confirmed by Fourier transform infrared spectra(FTIR)*** pyrolysis of the resultant single-source-precursors at 900"C,amorphous ceramic powders were *** 900 C ceramics were anncaled at different temperatures in the range of 1200-1600℃ to gain SiC-TaC-C *** phase evolution of ceramic nanocomposites was investigated by X-ray diffraction(XRD)and transmission electron microscopy(TEM).The results indicate that the TaC starts to crystallize at lower temperature than theβ-*** is particularly worth pointing out that the unique core-shell structured TaC-C nanoparticles were in-situ formed and homogeneously distributed in the ceramic matrix after annealing at 1400 *** at a high temperature of 1600 C,the grain sizes ofβ-SiC and TaC are smaller than 30 nm,flilling the definition of *** present study related to SiC-TaC C nanocomposites paves a new road for enriching ultra-high temperature ceramic family suitable for structural/functional applications in harsh environment.

关键词： polymer-derived ceramies TaC SiC nanocomposites core-shell structure

Si-based polymer-derived ceramics for energy conversion and storage

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Journal of Advanced Ceramics 2022年第2期11卷 197-246页

作者： Qingbo WEN Fangmu QU Zhaoju YU Magdalena GRACZYK-ZAJAC Xiang XIONG ralf riedel State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China College of Materials Key Laboratory of High-Performance Ceramic Fibers(Xiamen University)Ministry of EducationXiamen 361005China Technische Universität Darmstadt Institut für MaterialwissenschaftOtto-Berndt-Straβe 3D-64287DarmstadtGermany EnBW Energie Baden-Württemberg AG Durlacher Allee 9376131 KarlsruheGermany

Since the 1960s,a new class of Si-based advanced ceramics called polymer-derived ceramics(PDCs)has been widely reported because of their unique capabilities to produce various ceramic materials(e.g.,ceramic fibers,ceramic matrix composites,foams,films,and coatings)and their versatile ***,due to their promising structural and functional properties for energy conversion and storage,the applications of PDCs in these fields have attracted much attention in recent *** review highlights the recent progress in the PDC field with the focus on energy conversion and storage ***,a brief introduction of the Si-based polymer-derived ceramics in terms of synthesis,processing,and microstructure characterization is provided,followed by a summary of PDCs used in energy conversion systems(mainly in gas turbine engines),including fundamentals and material issues,ceramic matrix composites,ceramic fibers,thermal and environmental barrier coatings,as well as high-temperature ***,applications of PDCs in the field of energy storage are reviewed with a strong focus on anode materials for lithium and sodium ion *** possible applications of the PDCs in Li–S batteries,supercapacitors,and fuel cells are discussed as ***,a summary of the reported applications and perspectives for future research with PDCs are presented.

关键词： polymer-derived ceramics(PDCs) high-temperature resistance structural properties electrochemical properties microstructure

Two birds with one stone: Simultaneous fabrication of HfC nanowires and CNTs through efficient utilization of polymer-derived ceramics

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Journal of Materials Science & Technology 2022年第34期129卷 163-172页

作者： Yanqin Fu Yulei Zhang Xuemin Yin Liyuan Han Qiangang Fu Hejun Li ralf riedel Shaanxi Province Key Laboratory of Fiber Reinforced Light Composite Materials Northwestern Polytechnical UniversityXi’an 710072China Technische Universität Darmstadt Institut für MaterialwissenschaftOtto-Berndt-Straβe 3Darmstadt D-64287Germany

Carbon nanotubes(CNTs) are fabricated in carbon cloth by ultilizing the waste gasses when fabricating hafnium carbide nanowires(HfC_(NWS)) through thermal pyrolysis of Hf-containing polymer *** formed HfC_(NWS) are distributed uniformly on the surface of the carbon fibers in carbon/carbon(C/C) composites and display perfect single crystal *** pyrolysis of the Hf-containing organic precursor provides hafnium and carbon source for the growth of HfC_(NWS).The released waste gasses containing CO,CH4and CO_(2)are the main carbon source for the growth of ***,the flexural strength of HfC_(NWS) reinforced carbon/carbon(HfC_(NWS)-C/C) composites is enhanced by ~105% compared with pure C/C,and the CNTs/carbon cloth also displays improved electrochemical performance with respect to capacitor *** present study introduces a novel sustainable and eco-friendly process related to polymer-derived ceramics to form advanced ceramic nanocomposites and proposes a deep understanding of the growth mechanism of CNTs.

关键词： HfC nanowires Carbon nanotubes Waste gasses Effective utilization Polymer-derived ceramics

ZrC-ZrB_2-SiC ceramic nanocomposites derived from a novel single-source precursor with high ceramic yield

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Journal of Advanced Ceramics 2019年第1期8卷 112-120页

作者： Zhaoju YU Xuan LV Shuyi LAI Le YANG Wenjing LEI Xingang LUAN ralf riedel College of Materials Key Laboratory of High Performance Ceramic Fibers (Xiamen University) Ministry of Education College of Materials Fujian Key Laboratory of Advanced Materials (Xiamen University) College of Materials Science and Engineering Huaqiao University Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical University Technische Universit?t Darmstadt Institut für Materialwissenschaft

For the first time, ZrC-ZrB_2-SiC ceramic nanocomposites were successfully prepared by a single-source-precursor route, with allylhydridopolycarbosilane(AHPCS),triethylamine borane(TEAB),and bis(cyclopentadienyl) zirconium dichloride(Cp_2 ZrCl_2) as starting materials. The polymer-to-ceramic transformation and thermal behavior of obtained single-source precursor were characterized by means of Fourier transform infrared spectroscopy(FT-IR) and thermal gravimetric analysis(TGA). The results show that the precursor possesses a high ceramic yield about 85% at 1000 ℃.The phase composition and microstructure of formed ZrC-ZrB_2-SiC ceramics were investigated by means of X-ray diffraction(XRD) and high resolution transmission electron microscopy(HRTEM).Meanwhile, the weight loss and chemical composition of the resultant ZrC-ZrB_2-SiC nanocomposites were investigated after annealing at high temperature up to 1800 ℃. High temperature behavior with respect to decomposition as well as crystallization shows a promising high temperature stability of the formed ZrC-ZrB_2-SiC nanocomposites.

关键词： polymer derived ceramics single-source precursor ceramic nanocomposite

Microstructure and evolution of hafnium carbide whiskers via polymer-derived ceramics:A novel formation mechanism

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Journal of Advanced Ceramics 2023年第3期12卷 578-586页

作者： Yanqin Fu Yulei Zhang Hao Yan Jinhua Li Xuemin Yin Jia Sun Qiangang Fu ralf riedel Shaanxi Key Laboratory of Fiber Reinforced Light Composite Materials Northwestern Polytechnical UniversityXi’an 710072China School of Materials and Chemical Engineering Xi’an Technological UniversityXi’an 710021China Institut für Materialwissenschaft Technische Universität DarmstadtDarmstadt D-64287Germany

Polymer-derived ultra-high-temperature ceramic(UHTC)nanocomposites have attracted growing attention due to the increasing demands for advanced thermal structure components in ***,hafnium carbide(HfC)whiskers are successfully fabricated in carbon fiber preforms via the polymer-derived ceramic(PDC)method.A novel carbon nanotube(CNT)template growth mechanism combined with the PDC method is proposed in this work,which is different from the conventional vapor–liquid–solid(VLS)mechanism that is commonly used for polymer-derived nanostructured *** CNTs are synthesized and proved to be the templates for fabricating the HfC whiskers,which are generated by the released low-molecular-weight gas such as CO,CO_(2),and CH4 during the pyrolysis of a Hf-containing *** formed products are composed of inner single crystal HfC whiskers that are measured to be several tens of micrometers in length and 100–200 nm in diameter and outer HfC/HfO_(2)*** work not only proposes a new strategy to prepare the HfC whiskers,but also puts forward a new thinking of the efficient utilization of a UHTC polymer precursor.

关键词： HfC whiskers carbon nanotubes(CNTs) CNT template Hf-containing precursor thermal pyrolysis

Ultra-light, high flexible and efficient CNTs/Ti3C2-sodium alginate foam for electromagnetic absorption application

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Journal of Materials Science & Technology 2019年第12期35卷 2859-2867页

作者： Xingmin Liu Nan Chai Zhaoju Yu Hailong Xu Xinliang Li Jiquan Liu Xiaowei Yin ralf riedel College of Materials Key Laboratory of High Performance Ceramic Fibers(Xiamen University)Ministry of EducationXiamen361005China Institutfiir Materialwissenschaft Technische Universitdt DarmstadtD-64287DarmstadtGermany College of Materials Fujian Key Laboratory of Advanced MaterialsXiamen UniversityXiamen361005China Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical UniversityXi'an710072China Technische Universitat Darmstadt Eduard-Zintl-lnstitutfur Anorganische und Physikalische ChemieAlarich-Weiss-Straβe 4.D-64287DarmstadtGermany

Ultra-light carboxylic functionalized multi-walled carbon nanotubes(CNTs-COOH) and Ti3C2 MXene hybrids modified sodium alginate(CNTs/Ti3C2-SA) based composite foams were prepared through ice-templated freeze-drying method. The microstructure of the synthesized CNTs/Ti3C2 hybrids and CNTs/Ti3C2-SA foams is characterized by the presence of CNTs inserted between MXene layers which prevents their restacking. The resultant CNTs/Ti3C2 hybrids exhibit a unique sandwich-like hierarchical structure. Scanning electron microscopy(SEM) images show that the CNTs/Ti3C2-SA foam exhibits a heterogeneous anisotropic microstructure and CNTs/Ti3C2 hybrids are homogeneously dispersed in the skeleton of the porous foam. In case that the content of the hybrids amounts 40 mg/cm^3, the CNTs/Ti3C2-SA foam possesses excellent electromagnetic(EM) absorption performance with a minimum reflection coefficient(RCmin) as low as-40.0 dB. In case of a sample thickness of 3.95 mm, the RCminreaches-24.4 dB and the effective absorption bandwidth covers the whole X band from 8.2 to 12.4 GHz. A control test shows that, with the same absorbent content, the CNTs/Ti3C2-SA foam exhibits a far better EM performance than that of CNT-free Ti3C2-SA foam.

关键词： Carbon nanotubes MXene Sodium alginate Electromagnetic absorption properties

Novel C_(sf)/SiBCN composites prepared by densifying C_(sf)/MA-SiBCN with the PIP process:Oxidation behavior and damage mechanism

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Journal of Advanced Ceramics 2024年第5期13卷 666-678页

作者： Wenhao Dou Daxin Li Bingzhu Wang Zhihua Yang Jun Chen Dechang Jia ralf riedel Yu Zhou Institute for Advanced Ceramics School of Materials Science and EngineeringHarbin Institute of TechnologyHarbin 150001China Key Laboratory of Advanced Structural-Functional Integration Materials and Green Manufacturing Technology Harbin Institute of TechnologyHarbin 150001China Chongqing Research Institute of HIT Chongqing 401135China Beijing Institute of Control Engineering Beijing 100094China Institut für Materialwissenschaft Technische Universität DarmstadtDarmstadt D-64287Germany School of Materials Science and Engineering Harbin Institute of Technology(Shenzhen)Shenzhen 518055China

To improve the oxidation resistance of short carbon fiber(C_(sf))-reinforced mechanically alloyed SiBCN(MA-SiBCN)(C_(sf)/MA-SiBCN)composites,dense amorphous C_(sf)/SiBCN composites containing both MA-SiBCN and polymer-derived ceramics SiBCN(PDCs-SiBCN)were prepared by repeated polymer infiltration and pyrolysis(PIP)of layered C_(sf)/MA-SiBCN composites at 1100℃,and the oxidation behavior and damage mechanism of the as-prepared C_(sf)/SiBCN at 1300–1600℃ were compared and discussed with those of C_(sf)/*** C_(sf)/MA-SiBCN composites resist oxidation attack up to 1400℃ but fail at 1500℃ due to the collapse of the porous framework,while the PIP-densified C_(sf)/SiBCN composites are resistant to static air up to 1600℃.During oxidation,oxygen diffuses through preexisting pores and the pores left by oxidation of carbon fibers and pyrolytic carbon(PyC)to the interior of the *** to the oxidative coupling effect of the MA-SiBCN and PDCs-SiBCN matrices,a relatively continuous and dense oxide layer is formed on the sample surface,and the interfacial region between the oxide layer and the matrix of the as-prepared composite contains an amorphous glassy structure mainly consisting of Si and O and an incompletely oxidized but partially crystallized matrix,which is primarily responsible for improving the oxidation resistance.

关键词： mechanically alloyed SiBCN(MA-SiBCN) polymer-derived ceramics SiBCN(PDCs-SiBCN) short carbon fiber-reinforced SiBCN(C_(sf)/SiBCN)composites polymer infiltration and pyrolysis(PIP) oxidation damage mechanism

Micro/nano multiscale reinforcing strategies toward extreme high-temperature applications:Take carbon/carbon composites and their coatings as the examples

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Journal of Materials Science & Technology 2022年第1期96卷 31-68页

作者： Qiangang Fu Pei Zhang Lei Zhuang Lei Zhou Jiaping Zhang Jie Wang Xianghui Hou ralf riedel Hejun Li State Key Laboratory of Solidification Processing Shaanxi Key Laboratory of Fiber Reinforced Light Composite MaterialsCarbon/Carbon Composites Research CenterNorthwestern Polytechnical UniversityXi’an 710072China School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Faculty of Engineering University of NottinghamUniversity ParkNottingham NG72RDUnited Kingdom Institut für Materialwissenschaft Technische Universität DarmstadtOtto-Berndt-Straße 3Darmstadt D-64287Germany

Carbon fiber reinforced carbon composites(C/Cs),are the most promising high-temperature materials and could be widely applied in aerospace and nucleation fields,owing to their superior ***,C/Cs are very susceptible to destructive oxidation and thus fail at elevated *** matrix modification and coating technologies with Si-based and ultra-high temperature ceramics(UHTCs)are valid to enhance the oxidation/ablation resistance of C/Cs,it’s not sufficient to satisfy the increasing practical applications,due to the inherent brittleness of ceramics,mismatch issues between coatings and C/C substrates,and the fact that carbonaceous matrices are easily prone to high-temperature *** effectively solve the aforementioned problems,micro/nano multiscale reinforcing strategies have been developed for C/Cs and/or the coatings over the past two decades,to fabricate C/Cs with high strength and excellent high-temperature *** review is to systematically summarize the most recent major and important advancements in some micro/nano multiscale strategies,including nanoparticles,nanowires,carbon nanotubes/fibers,whiskers,graphene,ceramic fibers and hybrid micro/nano structures,for C/Cs and/or the coatings,to achieve high-temperature oxidation/ablation-resistant C/***,this review is concluded with an outlook of major unsolved problems,challenges to be met and future research advice for C/Cs with excellent comprehensive mechanical-thermal ***’s hoped that a better understanding of this review will be of high scientific and industrial interest,since it provides unusual and feasible new ideas to develop potential and practical C/Cs with improved high-temperature mechanical and oxidation/ablation-resistant properties.

关键词： Carbon/carbon composites Micro/nano multiscale reinforcing strategies Oxidation Ablation Erosion Hybrid structures

Trends of Abundance of Salton Sea Fish: A Reversible Collapse or a Permanent Condition?

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Natural Resources 2016年第10期7卷 535-543页

作者： ralf riedel Gulf Coast Research Laboratory College of Marine Sciences University of Southern Mississippi Ocean Springs MS USA S&R Consultancy Ocean Springs MS USA

The Salton Sea is a closed-basin, 980 km2 salt lake in the Sonoran Desert of southern California. Three marine species, bairdiella (Bairdiella icistia), orangemouth corvina (Cynoscion xanthulus), and sargo (Anisotremus davidsoni), established from introductions of over 34 species beginning in 1929. During the late 1960s and early 1970s, a hybrid tilapia (Oreochromis mossambicus × O. urolepis hornorum) invaded the Salton Sea and became dominant by number and weight. Recent surveys show a precipitous decline of all four species above starting sometime between 2001 and 2002. Declines were more evident in nearshore than in estuarine habitats. Corvina has probably declined the soonest, followed by Gulf croaker. Tilapia declines were followed by more recent increases in population numbers. The tilapia rebound observed are probably only sustainable if a curb in Salton Sea salinity levels is realized. The marine species will likely need restocking to reach historic levels, if the salinity of the lake is managed at 40 g•L–1 or below. Restoration alternatives for the Salton Sea must take into consideration estuarine areas as essential fish habitats and fish refuge against high salinities.

关键词： Tilapia Sciaenidae Salt Lakes Fisheries Collapse Restoration Salinity

Composition-dependent structural characteristics and mechanical properties of amorphous SiBCN ceramics by ab-initio calculations

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Journal of Advanced Ceramics 2023年第5期12卷 984-1000页

作者： Yuchen Liu Yu Zhou Dechang Jia Zhihua Yang Wenjiu Duan Daxin Li Shuzhou Li ralf riedel Bin Liu Institute for Advanced Ceramics School of Materials Science and EngineeringHarbin Institute of TechnologyHarbin 150001China School of Materials Science and Engineering Shanghai UniversityShanghai 200444China Tsinghua Shenzhen International Graduate School Tsinghua UniversityShenzhen 518055China School of Materials Science and Engineering Nanyang Technological UniversitySingapore 639798Singapore Institut für Materialwissenschaft Technische Universität DarmstadtDarmstadt D-64287Germany

The atomic structural features and the mechanical properties of amorphous silicoboron carbonitride ceramics with 13 different compositions in the Si–BN–C phase diagram are investigated employing ab-initio *** chemical bonds and local structures within the amorphous network relate to the elemental *** distribution of nine types of chemical bonds is composition-dependent,where the B–C,Si–N,Si–C,and B–N bonds hold a large proportion for all *** prefers to be tetrahedrally coordinated,while B and N prefer sp^(2)-like trigonal *** the case of C,the tetrahedral coordination is predominant at relatively low C contents,while the trigonal coordination is found to be the main feature with the increasing C *** local structural characteristics greatly influence the mechanical properties of SiBCN *** the studied amorphous ceramics,SiB_(2)C_(3)N_(2) and SiB_(3)C_(2)N_(3) with low Si contents and moderate C and/or BN contents have high elastic moduli,high tensile/shear strengths,and good debonding *** increment of Si,C,and BN contents on this basis results in the decrease of mechanical *** increasing Si content leads to the increment of Si-contained bonds that reduce the bond strength of SiBCN ceramics,while the latter two cases are attributed to the raise of sp^(2)-like trigonal configuration of C and *** discoveries are expected to guide the composition-tailored optimization of SiBCN ceramics.

关键词： ultra-high-temperature ceramics density functional theory(DFT) amorphous structure mechanical properties