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Ralf Riedel
Technische Universität Darmstadt
470Publications
52H-index
11.6kCitations
Publications 470
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Bernd Mainzer2
Estimated H-index: 2
(German Aerospace Center),
Chaorong Lin (Technische Universität Darmstadt), Raouf Jemmali5
Estimated H-index: 5
(German Aerospace Center)
... more
Four unidirectional fiber reinforced SiCN ceramic matrix composites were manufactured by means of polymer infiltration and pyrolysis. Two carbon fibers (T800H and Granoc XN90) as well as two silicon carbide fibers (Tyranno ZMI and SA3) without fiber coating were chosen. As matrix precursor, a poly(methylvinyl)silazane was investigated and utilized. The composites with the SA3 and the XN90 fiber had the highest tensile strengths of 478 and 288 MPa, respectively. It is considered that these high m...
Ref 33
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Xin’gang Luan3
Estimated H-index: 3
(Northwestern Polytechnical University),
Sen Chang1
Estimated H-index: 1
(Northwestern Polytechnical University),
Rong Yu (Northwestern Polytechnical University)... more
Abstract In the present work, SiBCNO-based ceramic as high temperature adhesives are fabricated by polymer derived ceramic route. The effect of polysiloxane (PSO) and TiB 2 on the microstructure and high temperature strength is studied, and the toughing effect of TiB 2 is discussed. The highest adhesion strength of the joint (S12) reached up to 18.95 MPa at room temperature and 12.3 MPa at 1000 °C in vacuum after pyrolysis at 1000 °C in air for 2 h. It is interesting to find that the crystalliza...
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Daniela Penther1
Estimated H-index: 1
(Technical University of Berlin),
Alireza Ghasemi1
Estimated H-index: 1
(Technical University of Berlin),
Ralf Riedel52
Estimated H-index: 52
(Technische Universität Darmstadt)
... more
The production of fully dense Mg-SiC nanocomposites with a homogeneous distribution of SiC nanoparticles through powder metallurgy techniques is still a challenging issue. We propose to combine sintering and hot extrusion of mechanically milled composite powders to encompass the known difficulties of conventional processing. Here, we report on the effect of SiC nanoparticle content on the compressibility, microstructure and hardness of SiC-Mg nanocomposites during the different consolidation ste...
Ref 28
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Qingbo Wen3
Estimated H-index: 3
(Technische Universität Darmstadt),
Ralf Riedel52
Estimated H-index: 52
(Technische Universität Darmstadt),
Emanuel Ionescu20
Estimated H-index: 20
(Technische Universität Darmstadt)
The short-term oxidation (i.e., exposure time of up to 20 h) of dense monolithic (Hf,Ta)C/SiC-based ceramic nanocomposites at temperatures from 1200 to 1500 °C is presented and discussed. The oxidation behavior of HfC/SiC is similar to that of other UHTCs, indicating that it is mainly determined by the HfC phase. Ta incorporation into HfC leads to a strong decrease of the parabolic oxidation rates (3–4 orders of magnitude). Unlike HfC/SiC, Ta-containing nanocomposites form continuous multiphasic...
Ref 41
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Qingbo Wen3
Estimated H-index: 3
(Technische Universität Darmstadt),
Zhaoju Yu14
Estimated H-index: 14
(Xiamen University),
Yeping Xu14
Estimated H-index: 14
(Technische Universität Darmstadt)
... more
Dense monolithic SiC/HfyTa1−yCxN1−x/C (y = 0, 0.2 and 0.7) ceramic nanocomposites were prepared upon spark plasma sintering of amorphous SiHfTaC(N) ceramic powders which were synthesized from single-source-precursors. The microstructural evolution of the ceramic powders was investigated using elemental analysis, X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). The results reveal that the powdered and dense monoliths of SiC/HfyTa1−yCxN1−x/C ceramic nanocomposites ...
Ref 56Cited 3
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2018 in Materials [IF: 2.65]
Felix Rosenburg1
Estimated H-index: 1
,
Emanuel Ionescu20
Estimated H-index: 20
,
Norbert Nicoloso8
Estimated H-index: 8
... more
The microstructure of segregated carbon in silicon oxycarbide (SiOC), hot-pressed at T = 1600 °C and p = 50 MPa, has been investigated by VIS Raman spectroscopy (λ = 514 nm) within the temperature range 25–1000 °C in air. The occurrence of the G, D’ and D bands at 1590, 1620 and 1350 cm−1, together with a lateral crystal size La < 10 nm and an average distance between lattice defects LD ≈ 8 nm, provides evidence that carbon exists as nano-crystalline phase in SiOC containing 11 and 17 vol % carb...
Ref 44Cited 3
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Xin’gang Luan3
Estimated H-index: 3
(Northwestern Polytechnical University),
Sen Chang1
Estimated H-index: 1
(Northwestern Polytechnical University),
Ralf Riedel52
Estimated H-index: 52
(Northwestern Polytechnical University)
... more
Abstract The high temperature adhesives are required in most critical applications such as nuclear and aerospace technology. To obtain an adhesive with high temperature bond strength and low synthesis temperature, polysilazane (PSNB) was modified by PBSZ, PSO, nano-Al 2 O 3 additives. Effect of the SiO 2 to B 2 O 3 ratio and curing pressure on microstructure and high temperature bond strength has been investigated. After curing and heat-treating at comparatively lower temperatures, the bond stre...
Ref 34Cited 1
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Yao Feng4
Estimated H-index: 4
(Xiamen University),
Shuyi Lai1
Estimated H-index: 1
(Xiamen University),
Le Yang9
Estimated H-index: 9
(Huaqiao University)
... more
Abstract Polymer-derived porous Bi 2 WO 6 /SiC(O) nanocomposites were prepared by a simple mechanical mixing of Bi 2 WO 6 nanopowders with a polyorganocarbosilane, namely allylhydridopolycarbosilane (AHPCS), followed by pyrolysis of the resulting blend at 700 °C for 2 h. The Bi 2 WO 6 nanopowders were synthesized by the reaction between Bi(NO 3 ) 3 ·5H 2 O and Na 2 WO 4 and characterized by means of X-ray diffraction (XRD) and dynamic light scattering (DLS). The cross-linking and polymer-to-cera...
Ref 44
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2018 in Materials [IF: 2.65]
Christina Stabler3
Estimated H-index: 3
,
Andreas Reitz1
Estimated H-index: 1
,
Peter Stein12
Estimated H-index: 12
... more
In the present study, the effect of the chemical and phase composition on the thermal properties of silicon oxide carbides (SiOC) has been investigated. Dense monolithic SiOC materials with various carbon contents were prepared and characterized with respect to their thermal expansion, as well as thermal conductivity. SiOC glass has been shown to exhibit low thermal expansion (e.g., ca. 3.2 × 10−6 K−1 for a SiOC sample free of segregated carbon) and thermal conductivity (ca. 1.5 W/(m∙K)). Furthe...
Ref 52Cited 4
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