Co-reporter:Chunlei Yan, Rongjun Liu, Changrui Zhang, Yingbin Cao, Yanfei Wang
Journal of the European Ceramic Society 2017 Volume 37, Issue 6(Volume 37, Issue 6) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.jeurceramsoc.2017.01.017
Effects of SiC/HfC ratios on the ablation and mechanical properties of 3D Cf/HfC–SiC composites by precursor impregnation and pyrolysis (PIP) process were investigated systematically. Both strength (flexural and compressive strength) and modulus increase as the SiC/HfC ratio are improved. The compact and stiff HfC-SiC matrix in addition to the carbon fiber and PyC interphase with less reaction damage accounts for the improved mechanical properties of Cf/HfC-SiC with higher SiC/HfC ratios. Meanwhile, both weight loss and erosion depth of Cf/HfC-SiC are improved with the increased SiC/HfC ratios. Therefore, in order to balance the ablation and mechanical properties, an appropriate SiC/HfC ratio should be considered.
Co-reporter:Chunlei Yan, Rongjun Liu, Changrui Zhang, Yingbin Cao, Xianhai Long
Powder Technology 2016 Volume 301() pp:596-600
Publication Date(Web):November 2016
DOI:10.1016/j.powtec.2016.06.043
•MB2-Al2O3 in situ composite powders were successfully synthesized at 1500 °C.•Metal (Ti, Zr, Hf, Nb, Ta) oxide, Al, and BN were firstly used as precursors for MB2-Al2O3.•These boride-alumina products formed an interwoven network and were intimately mixed.MB2-Al2O3 in situ composite powders were synthesized at 1500 °C via a novel solid-state precursor route using Group IV–V metal (M, M = Ti, Zr, Hf, Nb, Ta) oxide, Al, and BN as raw materials. As a moderate cost boron source, BN has a well-defined stoichiometry and low impurity. In these precursor powder systems, the TiO2-Al-BN is an exception, which gives rise to the final TiB2-Al2O3-AlN product, whereas the rest produce the diboride-Al2O3 composite powders. As to HfB2–Al2O3 and TaB2–Al2O3 composite powders, the diboride phases have a smaller particle size (submicrometer) while the Al2O3 phase possesses a larger size (several micrometers). Besides, these diboride-alumina products produced by the solid-state precursor route form an interwoven network and are intimately mixed on a microscopic scale.
Co-reporter:Chunlei Yan, Rongjun Liu, Changrui Zhang, Yingbin Cao
Ceramics International 2016 Volume 42(Issue 11) pp:12756-12762
Publication Date(Web):15 August 2016
DOI:10.1016/j.ceramint.2016.04.187
Abstract
Three-dimensional (3D) Cf/ZrC–SiC composites were successfully prepared by the polymer infiltration and pyrolysis (PIP) process using polycarbosilane (PCS) and a novel ZrC precursor. The effects of PyC interphase of different thicknesses on the mechanical and ablation properties were evaluated. The results indicate that the Cf/ZrC–SiC composites without and with a thin PyC interlayer of 0.15 µm possess much poor flexural strength and fracture toughness. The flexural strength grows with the increase of PyC layer thickness from 0.3 to 1.2 µm. However, the strength starts to decrease with the further increase of the PyC coating thickness to 2.2 µm. The highest flexural strength of 272.3±29.0 MPa and fracture toughness of 10.4±0.7 MPa m1/2 were achieved for the composites with a 1.2 µm thick PyC coating. Moreover, the use of thicker PyC layer deteriorates the ablation properties of the Cf/ZrC–SiC composites slightly and the ZrO2 scale acts as an anti-ablation component during the testing.
Co-reporter:Chunlei Yan, Rongjun Liu, Changrui Zhang, Yingbin Cao, Xianhai Long
Advanced Powder Technology 2016 Volume 27(Issue 2) pp:711-716
Publication Date(Web):March 2016
DOI:10.1016/j.apt.2016.02.030
Highlights
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ZrB2–Al2O3 in situ composite powders were successfully synthesized at 1550 °C.
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ZrO2, Al, and BN were firstly used as precursors for ZrB2–Al2O3.
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A novel formation mechanism was put forward for the ZrB2–Al2O3 powders.
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Zr–Al alloy compounds acted as an intermediary phase leading to boride formation.
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These boride–alumina products formed an interwoven network and were intimately mixed.
Co-reporter:Chunlei Yan, Rongjun Liu, Changrui Zhang, Yingbin Cao and Xianhai Long
RSC Advances 2015 vol. 5(Issue 96) pp:78606-78613
Publication Date(Web):11 Sep 2015
DOI:10.1039/C5RA13010G
ZrB2 powders were synthesized by a polymerizable complex method based on the Pechini-type reaction route, wherein a precursor solution of citric acid, glycerol, boric acid, and zirconium ions was prepared, and polymerized to form a semitransparent resin without any precipitation at 150 °C. The precursor solutions and the resulting resins were characterized by FT-IR and 13C NMR spectroscopy. The results show the formation of a hybrid polymer with zirconium and boron arrested within the polymeric chain by complexation. The submicrometer ZrB2 powders (200–600 nm) are formed after pyrolysis of the polymeric precursor with 4 B/metal molar ratios at 1400 °C. Investigation of the formation mechanism of ZrB2 powders indicates that ZrC is the intermediary phase and two reduction reactions determine the specific pathway leading to ZrB2 formation: (1) ZrC formation, (2) the formed ZrC directly reacts with B2O3 to form ZrO2 and ZrB2. In the whole conversion process, ZrC formation by carbothermal reduction is a fast reaction, while the direct reaction of ZrC with B2O3 to form ZrO2 and ZrB2 is the rate-limiting step.
Co-reporter:Chunlei Yan, Rongjun Liu, Changrui Zhang and Yingbin Cao
RSC Advances 2015 vol. 5(Issue 46) pp:36520-36529
Publication Date(Web):02 Apr 2015
DOI:10.1039/C4RA14996C
An in situ polymerizable complex method to produce zirconium carbide, hafnium carbide and their ternary carbides at a relatively low temperature (1300 °C) using simple and mainly nontoxic starting reagents is presented. In this aqueous process, citric acid (CA) was used to chelate the metal ion and ethylene glycol (EG) to form a polymerized complex resin. We suggest that, based on the results of FT-IR and 13C NMR spectroscopies, a very stable metal–CA chelate complex formed in the starting solution, which was thermally stable upon gelation even up to 350 °C. Immobilization of the metal ion in a rigid polymer can largely guarantee the in situ charring, resulting in carbon adjacent to the metal oxide in the pyrolysed product. The contiguous carbon and metal oxide led to in situ reaction (1100 °C) with a minimum of diffusion, which involved the formation of large numbers of metastable phases. Afterwards, well-defined binary and ternary carbide nanoparticles (∼100 nm) were formed through localized particle coarsening by Ostwald ripening.
Co-reporter:Chunlei Yan, Rongjun Liu, Yingbin Cao, Changrui Zhang
Materials Science and Engineering: A 2014 Volume 591() pp:105-110
Publication Date(Web):3 January 2014
DOI:10.1016/j.msea.2013.10.102
Three-dimensional (3D) Cf/ZrC–SiC composites were successfully prepared by the polymer infiltration and pyrolysis (PIP) process using polycarbosilane (PCS) and a novel ZrC precursor. The Cf/ZrC–SiC composite with relatively more PIP cycles of PCS has a higher density and a lower porosity, which account for the improved mechanical property of the composite. The composite with 6 PIP cycles of PCS has a flexural strength of 136.0±13.1 MPa, and a fracture toughness of 7.3±0.3 MPa m1/2, which is superior to the monolithic ultrahigh temperature ceramics. The relatively low flexural strength and elastic modulus of the Cf/ZrC–SiC composites are attributed to the small stiffness of the matrix because of the debonding feature of the ZrC matrix. The high temperature oxidation testing of the S6-Cf/ZrC-SiC composite reveals that the surface molten ZrO2 layer contributes mainly to the improved anti-ablation property.
Co-reporter:R. J. Liu;Y. B. Cao;C. L. Yan;C. R. Zhang;P. B. He
Journal of Superhard Materials 2014 Volume 36( Issue 6) pp:410-414
Publication Date(Web):2014 November
DOI:10.3103/S1063457614060069
Diamond-SiC-Si composites have been prepared using gaseous silicon vacuum infiltration. The evolution of the phases and microstructures of the composites have been analyzed using X-ray diffraction technique and scanning electron microscopy. It has been found that the diamond-SiC-Si composite is composed of β-SiC, diamond, and residual Si. The diamond particles were distributed homogeneously in the dense matrix of the composites. Besides, the effects of particle size and content of diamond on the properties of diamond-SiC-Si composites have been analyzed. The thermal conductivity of the composites increases with particle size and content of diamond. When the particle size and content of diamond are 300 μm and 80 wt %, respectively, the thermal conductivity of the composites approaches the value of 280 W·m−1·K−1.
Co-reporter:MARY E. MARSH;RONALD L. SASS
Science 1980 Volume 208(Issue 4449) pp:1262-1263
Publication Date(Web):13 Jun 1980
DOI:10.1126/science.208.4449.1262
Abstract
Molluscan bivalve hinge ligaments are composed of long needle-shaped aragonite crystals embedded in a protein matrix. These crystals are twinned and, in general, the twin forms a thin lamella through the center of the crystal.
