137 results found
Al Nasiri N, Patra N, Horlait D, et al., 2016, Thermal properties of rare-earth monosilicates for EBC on Si-based ceramic composites, Journal of the American Ceramic Society, Vol: 99, Pages: 589-596, ISSN: 0002-7820
Rare-earth (RE) monosilicates are promising candidates as environmental barrier coating (EBC) materials for ceramic matrix composites for aerospace applications. Five rare-earth monosilicate materials have been investigated: Y2SiO5, Gd2SiO5, Er2SiO5, Yb2SiO5, and Lu2SiO5 produced from RE oxides and silica starting materials pressed and sintered at 1580°C under flowing air. Relative densities above 94% were obtained for all samples and ceramics were made containing 85–100 wt% of the RE monosilicate according to X-ray diffraction (XRD) with RE disilicates as the second phase in the Gd, Yb, and Lu silicate systems. Microstructures were characterized using scanning electron microscopy and XRD, and thermal properties measured including specific heat, thermal expansion, and thermal diffusivity. For the first time, specific heat capacity values are reported for the monosilicates [0.45–0.69 J·(g·K)−1]. Thermal expansion coefficients (TECs) of the dense samples ranged between 5.9 and 10.3 × 10−6 K−1 measured for 473 to 1473 K. All EBCs have low thermal conductivities [1.8 W·(m·K)−1 or less] making them excellent EBC insulators.
Jayaseelan DD, Zapata-Solvas E, Chater RJ, et al., 2015, Structural and compositional analyses of oxidised layers of ZrB2-based UHTCs, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, Vol: 35, Pages: 4059-4071, ISSN: 0955-2219
Zapata-Solvas E, Jayaseelan DD, Brown PM, et al., 2015, Effect of oxidation on room temperature strength of ZrB2- and HfB2-based ultra high temperature ceramics, ADVANCES IN APPLIED CERAMICS, Vol: 114, Pages: 407-417, ISSN: 1743-6753
Patra N, Al Nasiri N, Jayaseelan DD, et al., 2015, Low-temperature solution synthesis of nanosized hafnium carbide using pectin, Ceramics International, Vol: 42, Pages: 1959-1963, ISSN: 0272-8842
Nano-sized hafnium carbide was synthesized from organic–inorganic hybrid polymer based on polycondensation and carbothermal reduction reaction from pectin and hafnium tetrachloride followed by thermal treatment. Orthorhombic and monoclinic hafnia formed on pyrolysis which above 1300 °C transformed to hafnium carbide. Conversion of amorphous to crystalline hafnia was initiated at ~800 °C while the endothermic carbothermal reduction reaction started at ~1275 °C. Total yield of hafnium carbide was ~62%. The resulting carbide powders were equiaxed with narrow size distribution of crystallite size ~50 nm. SEM and EDX mapping confirm the uniform distribution of Hf and C. The high ceramic yield, uniform size particles, and simplicity of the process make it a promising route for polymer infiltration pyrolysis of carbon fiber/ultra high temperature composites.
Jayaseelan DD, Xin Y, Vandeperre L, et al., 2015, Development of multi-layered thermal protection system (TPS) for aerospace applications, COMPOSITES PART B-ENGINEERING, Vol: 79, Pages: 392-405, ISSN: 1359-8368
Patra N, Jayaseelan DD, Lee WE, 2015, Synthesis of ZrB2/SiC composite powders by single-step solution process from organic-inorganic hybrid precursor, Advances in Applied Ceramics, Vol: 115, Pages: 36-42, ISSN: 1743-6761
A precursor of a zirconium diboride/silicon carbide (ZrB2/SiC) composite was synthesised via an organic–inorganic hybrid derived from gum karaya, tetraethyl orthosilicate, boric acid and zirconyl chloride starting materials. Fourier transform infrared spectroscopy of the as-synthesised dried hybrid revealed the formation of Si–O, Zr–O–C and B–O–B. X-ray diffraction revealed that the powder consists of only ZrB2 and β-SiC. Scanning electron microscopy and TEM of the composite powders showed that SiC and ZrB2 occurred in intimately mixed aggregates of spheroidal submicron sized particles for low (3M) boric acid concentration, while at high (5M) boric acid concentration, the two phases are larger with the ZrB2 adopting a blocky, angular morphology (∼10–30 μm long by 5 μm wide and thick), while the SiC remains spheroidal with ∼1 μm diameter particles in 10–20 μm diameter aggregates. Thermogravimetry–differential thermal analysis with the help of X-ray diffraction analysis revealed that the formation temperature was low at 1275°C for ZrB2 and 1350°C for the SiC with 40 wt-% yield.
Venugopal S, Jayaseelan DD, Paul A, et al., 2015, Screw Dislocation Assisted Spontaneous Growth of HfB2 Tubes and Rods, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Vol: 98, Pages: 2060-2064, ISSN: 0002-7820
Jayaseelan DD, Zapata-Solvas E, Carney CM, et al., 2015, Microstructural evolution of HfB2 based ceramics during oxidation at 1600-2000 degrees C, ADVANCES IN APPLIED CERAMICS, Vol: 114, Pages: 277-295, ISSN: 1743-6753
Zapata-Solvas E, Jayaseelan DD, Brown PM, et al., 2014, Effect of La2O3 addition on long-term oxidation kinetics of ZrB2-SiC and HfB2-SiC ultra-high temperature ceramics, Journal of the European Ceramic Society, Vol: 34, Pages: 3535-3548, ISSN: 0955-2219
Long-term oxidation kinetics of SiC-reinforced UHTCs and La2O3-doped UHTCs over an intermediate temperature range (1400–1600 °C) reveal partially protective behavior for the former characterized by an oxidation kinetic exponent 1 < n < 2. In addition, unstable oxidation behavior was observed in HfB2-based UHTCs due to the presence of SiC agglomerates. On the other hand, La2O3-doped UHTCs were found to be protective over the whole temperature range studied (n = 2), in particular at 1600 °C, where oxidation kinetic exponents as high as 8 were observed as a consequence of formation of new oxidation protective particles, MeOxCy, where Me is Zr, Hf or Si. Adsorption of oxygen-containing species formed protective MeOxCy phases, which enhanced the thermal stability of the oxide scale as well as providing protection against oxidation for long exposure times at 1600 °C.
Patra N, Jayaseelan DD, Lee WE, 2014, Synthesis of Biopolymer-Derived Zirconium Carbide Powder by Facile One-Pot Reaction, Journal of the American Ceramic Society, Vol: 98, Pages: 71-77, ISSN: 1551-2916
Zirconium carbide (ZrC) was synthesized by polycondensation and carbothermal reduction reactions from an organic–inorganic hybrid complex. A natural biopolymer Gum Karaya (GK) and zirconyl oxychloride octahydrate (ZOO) were used as the sources of carbon and zirconium, respectively. FTIR of as-synthesized dried complexes revealed formation of Zr–O. Pyrolysis of the complexes at 1200°C/1 h under argon resulted in tetragonal and monoclinic zirconia which after heat treatment at 1400°C–1550°C transformed to zirconium carbide. Thermal analysis shows that the GK–ZOO complexes lost less mass than the pristine GK to 600°C. The intensity of exothermic decomposition decreases and shifted to higher temperature for the hybrid complexes indicating that zirconia induced thermal stability. A maximum ZrC yield of ~60 wt% is obtained for the intermediate GK–ZOO ratio of 1:2. Particles pyrolyzed for 1 h at 1550°C were coarser (5–10 μm) with flakes for lower GK–ZOO weight ratio, but were spheroidal with narrow size distribution (~1 μm) with increasing GK–ZOO weight ratio.
Harrison R, Ridd O, Jayaseelan DD, et al., 2014, Thermophysical characterisation of ZrCxNy ceramics fabricated via carbothermic reduction-nitridation, JOURNAL OF NUCLEAR MATERIALS, Vol: 454, Pages: 46-53, ISSN: 0022-3115
Zapata-Solvas E, Jayaseelan DD, Lin HT, et al., 2013, Mechanical properties of ZrB2- and HfB2-based ultra-high temperature ceramics fabricated by spark plasma sintering, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, Vol: 33, Pages: 1373-1386, ISSN: 0955-2219
Zapata-Solvasa E, Jayaseelan DD, Brown PM, et al., 2013, Thermal properties of La2O3-doped ZrB2- and HfB2-based ultra-high temperature ceramics
Thermal properties of La2O3-doped ZrB2- and HfB2-based ultra high temperature ceramics (UHTCs) have been measured at temperatures from room temperature to 2000 °C and compared with SiC-doped ZrB2- and HfB2-based UHTCs and monolithic ZrB2 and HfB2. Thermal conductivities of La2O3-doped UHTCs remain constant around 55–60 W/mK from 1500 °C to 1900 °C while SiC-doped UHTCs showed a trend to decreasing values over this range.
Cui B, Jayaseelan DD, Lee WE, 2012, TEM study of the early stages of Ti2AlC oxidation at 900 degrees C, SCRIPTA MATERIALIA, Vol: 67, Pages: 830-833, ISSN: 1359-6462
Zhang S, Jayaseelan DD, Li ZS, et al., 2012, Molten salt synthesis of ceramic materials, EUCHEM conference on Molten Salts and Ionic Liquids
Jayaseelan DD, Zapata-Solvas E, Brown P, et al., 2012, In situ Formation of Oxidation Resistant Refractory Coatings on SiC-Reinforced ZrB2 Ultra High Temperature Ceramics, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Vol: 95, Pages: 1247-1254, ISSN: 0002-7820
Cui B, Sa R, Jayaseelan DD, et al., 2012, Microstructural evolution during high-temperature oxidation of spark plasma sintered Ti2AlN ceramics, ACTA MATERIALIA, Vol: 60, Pages: 1079-1092, ISSN: 1359-6454
Desimone D, Jayaseelan DD, Lee WE, et al., 2012, Development of ZrO2 interfaces for all-oxide composites, COMPOSITES SCIENCE AND TECHNOLOGY, Vol: 72, Pages: 197-203, ISSN: 0266-3538
Paul A, Jayaseelan DD, Venugopal S, et al., 2012, UHTC composites for hypersonic applications, AMERICAN CERAMIC SOCIETY BULLETIN, Vol: 91, Pages: 22-28, ISSN: 0002-7812
Cui B, Jayaseelan DD, Lee WE, 2011, Reply to comment on "Microstructural evolution during high-temperature oxidation of Ti2AlC ceramics", SCRIPTA MATERIALIA, Vol: 65, Pages: 933-934, ISSN: 1359-6462
Jackson HF, Jayaseelan DD, Manara D, et al., 2011, Laser Melting of Zirconium Carbide: Determination of Phase Transitions in Refractory Ceramic Systems, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Vol: 94, Pages: 3561-3569, ISSN: 0002-7820
Cui B, Jayaseelan DD, Lee WE, 2011, Microstructural evolution during high-temperature oxidation of Ti2AlC ceramics, ACTA MATERIALIA, Vol: 59, Pages: 4116-4125, ISSN: 1359-6454
Eakins E, Jayaseelan DD, Lee WE, 2011, Toward Oxidation-Resistant ZrB2-SiC Ultra High Temperature Ceramics, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, Vol: 42A, Pages: 878-887, ISSN: 1073-5623
Jayaseelan DD, de Sa RG, Brown P, et al., 2011, Reactive infiltration processing (RIP) of ultra high temperature ceramics (UHTC) into porous C/C composite tubes, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, Vol: 31, Pages: 361-368, ISSN: 0955-2219
Jayaseelan DD, Wang Y, Hilmas GE, et al., 2011, TEM investigation of hot pressed-10 vol.% SiC-ZrB2 composite, ADVANCES IN APPLIED CERAMICS, Vol: 110, Pages: 1-7, ISSN: 1743-6753
Jayaseelan DD, Jackson H, Eakins E, et al., 2010, Laser modified microstructures in ZrB2, ZrB2/SiC and ZrC, Workshop on Aerospace Materials for Extreme Environments, Publisher: ELSEVIER SCI LTD, Pages: 2279-2288, ISSN: 0955-2219
Jackson HF, Jayaseelan DD, Clegg WJ, et al., 2010, MICROSTRUCTURE OF LASER-MELTED ZIRCONIUM CARBIDE CERAMICS, Materials Science and Technology 2009 Conference and Exhibition, Publisher: AMER CERAMIC SOC, Pages: 113-+, ISSN: 1042-1122
Inam F, Yan H, Jayaseelan DD, et al., 2010, Electrically conductive alumina-carbon nanocomposites prepared by Spark Plasma Sintering, 11th Electroceramics Conference 2008, Publisher: ELSEVIER SCI LTD, Pages: 153-157, ISSN: 0955-2219
Jackson HF, Jayaseelan D, Lee WE, et al., 2009, Laser Melting of Spark Plasma-Sintered ZirconiumCarbide: Thermophysical Properties of a Generation IVVery High-Temperature Reactor Material, International Journal of Applied Ceramic Technology, Pages: 1-11
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