Publications
493 results found
Horlait D, Grasso S, Al Nasiri N, et al., 2016, Synthesis and Oxidation Testing of MAX Phase Composites in the Cr-Ti-Al-C Quaternary System, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Vol: 99, Pages: 682-690, ISSN: 0002-7820
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- Citations: 49
Chroneos A, Horlait D, Lee WE, et al., 2016, Synthesis and DFT investigation of new bismuth- containing MAX phases, Scientific Reports, Vol: 6, ISSN: 2045-2322
The Mn + 1AXn phases (M = early transition metal; A = group A element and X = C and N) are materials exhibiting many important metallic and ceramic properties. In the present study powder processing experiments and density functional theory calculations are employed in parallel to examine formation of Zr2(Al1−xBix)C (0 ≤ x ≤ 1). Here we show that Zr2(Al1−xBix)C, and particularly with x ≈ 0.58, can be formed from powders even though the end members Zr2BiC and Zr2AlC seemingly cannot. This represents a significant extension of the MAX phase family, as this is the first report of a bismuth-based MAX phase.
Hsieh Y-H, Horlait D, Humphry-Baker S, et al., 2016, Wasteforms for waste from advanced reprocessing, MRS ADVANCES, Vol: 1, Pages: 4255-4260, ISSN: 2059-8521
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- Citations: 3
Jayaseelan DD, Zapata-Solvas E, Chater RJ, et al., 2015, Structural and compositional analyses of oxidised layers of ZrB<sub>2</sub>-based UHTCs, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, Vol: 35, Pages: 4059-4071, ISSN: 0955-2219
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- Citations: 23
Zapata-Solvas E, Jayaseelan DD, Brown PM, et al., 2015, Effect of oxidation on room temperature strength of ZrB<sub>2</sub>- and HfB<sub>2</sub>-based ultra high temperature ceramics, ADVANCES IN APPLIED CERAMICS, Vol: 114, Pages: 407-417, ISSN: 1743-6753
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- Citations: 7
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
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- Citations: 70
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.
Liao C-Z, Shih K, Lee WE, 2015, Crystal Structures of Al-Nd Codoped Zircon lite Derived from Glass Matrix and Powder Sintering, INORGANIC CHEMISTRY, Vol: 54, Pages: 7353-7361, ISSN: 0020-1669
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- Citations: 18
Jayaseelan DD, Zapata-Solvas E, Carney CM, et al., 2015, Microstructural evolution of HfB<sub>2</sub> based ceramics during oxidation at 1600-2000°C, ADVANCES IN APPLIED CERAMICS, Vol: 114, Pages: 277-295, ISSN: 1743-6753
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- Citations: 11
Harrison R, Rapaud O, Pradeilles N, et al., 2015, On the fabrication of ZrC<i><sub>x</sub></i>N<i><sub>y</sub></i> from ZrO<sub>2</sub> via two-step carbothermic reduction-nitridation, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, Vol: 35, Pages: 1413-1421, ISSN: 0955-2219
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- Citations: 14
Harrison R, 2015, Mechanism and Kinetics of Oxidation of ZrN Ceramics, Journal of the American Ceramic Society, ISSN: 1551-2916
Oxidation of ZrN ceramics from 973–1373 K under static conditions reveals parabolic rate behavior, indicative of a diffusion-controlled process. In-situ high temperature powder XRD found the oxidation mechanism begins with destabilization of ZrN through formation of a ZrN1−x phase with oxide peaks initially detected at around 773 K. The zirconium oxide layer was found to be monoclinic by in-situ XRD with no evidence of tetragonal or cubic polymorphs present to 1023 K. Bulk ceramic samples oxidized at 1173 and 1273 K underwent slower oxidation than those oxidized at 973 and 1073 K. This change in oxidation rate and hence mechanism was due to formation of a denser c-ZrO2 polymorph stabilized by nitrogen defects. This N-doped dense ZrO2 layer acts as a diffusion barrier to oxygen diffusion. However, at an oxidation temperature of 1373 K this layer is no longer protective due to increased diffusion through it resulting in grain boundary oxidation.
Quadling A, Vandeperre L, Parkes M, et al., 2015, Second Phase-Induced Degradation of Fused MgO Partially Stabilized Zirconia Aggregates, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Vol: 98, Pages: 1364-1371, ISSN: 0002-7820
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- Citations: 5
Ojovan MI, Lee WE, 2015, About U(t) form of pH-dependence of glass corrosion rates at zero surface to volume ratio, Pages: 153-161, ISSN: 0272-9172
The pH-dependence of glass corrosion rates has a well-known U-shaped form with minima for near-neutral solutions. This paper analyses the change of U-shaped form with time and reveals that the pH dependence evolves even for solutions that have pH not affected by glass corrosion mathematically corresponding to a zero surface to volume ratio. The U(t) dependence is due to changes of concentration profiles of elements in the near-surface layers of glasses in contact with water and is most evident within the initial stages of glass corrosion at relatively low temperatures. Numerical examples are given for the nuclear waste borosilicate glass K-26 which is experimentally characterised by an effective diffusion coefficient of caesium Dc 4.5 10-12 cm2/day and by a rate of glass hydrolysis in non-saturated groundwater as high as n, = 100 nm/year The changes of U-shaped form need to be accounted when assessing the performance of glasses in contact with water solutions.
Hiezl Z, Hambley DI, Padovani C, et al., 2015, Processing and microstructural characterisation of a UO<sub>2</sub>-based ceramic for disposal studies on spent AGR fuel, JOURNAL OF NUCLEAR MATERIALS, Vol: 456, Pages: 74-84, ISSN: 0022-3115
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- Citations: 11
Ahmad NE, Fearn S, Lee WE, et al., 2014, Preliminary surface study of short term dissolution of UK high level waste glass, 2nd International Summer School on Nuclear Glass Wasteform: Structure, Properties and Long-Term Behavior, SumGLASS 2013, Pages: 230-236
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.
Gonzalez-Julian J, Cedillos-Barraza O, Doring S, et al., 2014, Enhanced oxidation resistance of ZrB<sub>2</sub>/SiC composite through in situ reaction of gadolinium oxide in patterned surface cavities, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, Vol: 34, Pages: 4157-4166, ISSN: 0955-2219
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- Citations: 16
Hiezl Z, Hambley D, Lee WE, 2014, Preparation and characterization of UO<inf>2</inf>-based AGR SIMFuel, Journal of Fluid Mechanics, Vol: 1665, Pages: 245-251, ISSN: 0022-1120
Preparation and characterization of a Simulated Spent Nuclear Fuel (SIMFuel), which replicates the chemical state and microstructure of Spent Nuclear Fuel (SNF) discharged from UK Advanced Gas-cooled Reactor (AGR) after a cooling time of 100 years is described. Thirteen stable elements were added to depleted UO2 and sintered to simulate the composition of fuel pellets after burn-ups of 25 and 43 GWd/tU and, as a reference, pure UO2 pellets were also investigated. The fission product distribution was calculated using the Fispin code provided by NNL. SIMFuel pellets exhibit a microstructure up to 92% TD. During the sintering process in H2 atmosphere Mo-Ru-Rh-Pd metallic precipitates and grey-phase ((Ba, Sr)(Zr, RE)O3 oxide precipitates) formed within the UO2 matrix. These secondary phases are present in real PWR and AGR SNF, although they are smaller in size than those examined in this study. The grain size of the produced SIMFuel is in good agreement with literature references.
Lee WE, Giorgi E, Harrison R, et al., 2014, Nuclear Applications for Ultra-High Temperature Ceramics and MAX Phases, Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications, Pages: 391-415, ISBN: 9781118700785
Future nuclear reactor systems and the severe conditions under which they will operate are reviewed. Current nuclear applications of ceramics are predominantly as oxide fuels as well as ceramic/glassy waste forms, although non-oxides do find niche uses such as graphite moderators and B4C control rods. UHTCs properties of interest to the nuclear industry include that they may be fissile, and that they have high thermal conductivity, refractoriness, and phase stability. Using such properties, future nuclear ceramics will potentially include UHTCs, for example, as non-oxide fuels (U/Pu carbides and nitrides) and fuel cladding (TaC, ZrC, HfC). MAX phases may also find application as fuel cladding. Oxide and non-oxide composite (e.g., SiC/SiC) and inert matrix fuel systems are under development for future fission reactors while uses of ceramics in fusion reactor systems will be both functional (such as the ceramic superconductors in the magnet systems for controlling the plasma) and structural in various locations outside of the first wall in magnetic confinement fusion. Finally, the importance of thermodynamics in severe conditions and the need for accurate thermodynamics databases are highlighted.
Fahrenholtz WG, Wuchina EJ, Lee WE, et al., 2014, Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications, ISBN: 9781118700785
The first comprehensive book to focus on ultra-high temperature ceramic materials in more than 20 years Ultra-High Temperature Ceramics are a family of compounds that display an unusual combination of properties, including extremely high melting temperatures (>3000°C), high hardness, and good chemical stability and strength at high temperatures. Typical UHTC materials are the carbides, nitrides, and borides of transition metals, but the Group IV compounds (Ti, Zr, Hf) plus TaC are generally considered to be the main focus of research due to the superior melting temperatures and stable high-melting temperature oxide that forms in situ. Rather than focusing on the latest scientific results, Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications broadly and critically combines the historical aspects and the state-of-the-art on the processing, densification, properties, and performance of boride and carbide ceramics. In reviewing the historic studies and recent progress in the field, Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications provides: • Original reviews of research conducted in the 1960s and 70s • Content on electronic structure, synthesis, powder processing, densification, property measurement, and characterization of boride and carbide ceramics. • Emphasis on materials for hypersonic aerospace applications such as wing leading edges and propulsion components for vehicles traveling faster than Mach 5 • Information on materials used in the extreme environments associated with high speed cutting tools and nuclear power generation Contributions are based on presentations by leading research groups at the conference "Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications II" held May 13-19, 2012 in Hernstein, Austria. Bringing together disparate researchers from academia, government, and industry in a singular forum, the meeting cultivated didactic d
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 ZrC<i><sub>x</sub></i>N<i><sub>y</sub></i> ceramics fabricated via carbothermic reduction-nitridation, JOURNAL OF NUCLEAR MATERIALS, Vol: 454, Pages: 46-53, ISSN: 0022-3115
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- Citations: 22
Grasso S, Saunders T, Porwal H, et al., 2014, Flash Spark Plasma Sintering (FSPS) of Pure ZrB<sub>2</sub>, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Vol: 97, Pages: 2405-2408, ISSN: 0002-7820
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- Citations: 105
Hiezl Z, Hambley D, Lee WE, 2014, Preparation and characterization of UO<inf>2</inf>-based AGR SIMFuel, Pages: 245-251, ISSN: 0272-9172
Preparation and characterization of a Simulated Spent Nuclear Fuel (SIMFuel), which replicates the chemical state and microstructure of Spent Nuclear Fuel (SNF) discharged from UK Advanced Gas-cooled Reactor (AGR) after a cooling time of 100 years is described. Thirteen stable elements were added to depleted UO2 and sintered to simulate the composition of fuel pellets after burn-ups of 25 and 43 GWd/tU and, as a reference, pure UO2 pellets were also investigated. The fission product distribution was calculated using the Fispin code provided by NNL. SIMFuel pellets exhibit a microstructure up to 92% TD. During the sintering process in H2 atmosphere Mo-Ru-Rh-Pd metallic precipitates and grey-phase ((Ba, Sr)(Zr, RE)O3 oxide precipitates) formed within the UO2 matrix. These secondary phases are present in real PWR and AGR SNF, although they are smaller in size than those examined in this study. The grain size of the produced SIMFuel is in good agreement with literature references.
Lee WE, Ojovan MI, Thomas GA, 2014, The uk's radioactive waste and waste management programme, Pages: 157-175, ISSN: 1042-1122
Sources of the UKs radioactive wastes including from power production, military programmes, medical uses and research reactors are described along with options for managing controlled wastes from pretreatment, treatment, conditioning and storage stages through to transportation to final disposal. Immobilisation (wasteform), temporary storage and permanent disposal options including near surface, deep and very deep geological disposal are covered.
Ahmad NE, Jones JR, Lee WE, 2014, Durability studies of simulated UK high level waste glass, Pages: 291-296, ISSN: 0272-9172
A simulated Magnox glass which is Mg- and Al- rich was subjected to aqueous corrosion in static mode with deionised water at 90 °C for 7-28 days and assessed using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) with Energy X-Ray Dispersive Spectroscopy (EDS) and Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP-OES). XRD revealed both amorphous phase and crystals in the glass structure. The crystals were Ni and Cr rich spinels and ruthenium oxide. After two weeks of incubation in deionised water, the glass surface was covered by a ∼ 11 μm thick Si-rich layer whilst mobile elements and transition metals like Na, B, and Fe were strongly depleted. The likely corrosion mechanism and in particular the role of Mg and Al in the glass structure are discussed. Keywords: high level waste glass, durability, corrosion mechanism.
Kubal SK, Pleydell-Pearce C, Powson JR, et al., 2014, Postmortem analysis of BOF tuyeres, Pages: 471-476
In a Basic Oxygen Furnace with bottom agitation, wear around the bottom-blowing elements is one of the main factors limiting lining service life. Therefore, worn tuyeres from a Basic Oxygen Steelmaking converter have been retrieved and characterized after a completed campaign. Chemical and microscopic analysis revealed modifications in MgO monolithic material. These changes involved sintering of the working surface to a depth of ≤ 55 mm, and both intergranular and grain boundary cracking, perpendicular to the ramming direction. The tuyere wear mechanism was defined to occur due to cracking and spalling resulting from a combination of thermo-mechanical stresses enhanced by molten metal and slag penetration, and possibly manufacturing method.
Quadling A, Vandeperre L, Lee WE, et al., 2014, HIGH TEMPERATURE CHARACTERISTICS OF REFRACTORY ZIRCONIA CRUCIBLES USED FOR VACUUM INDUCTION MELTING, 13th Unified International Technical Conference on Refractories (UNITECR), Publisher: AMER CERAMIC SOC, Pages: 107-+
Alex J, Vandeperre L, Touzo B, et al., 2014, EFFECT OF SODIUM IMPURITIES ON PHASE AND MICROSTRUCTURE EVOLUTION IN CALCIUM ALUMINATE CEMENT BONDED CASTABLES AT HIGH TEMPERATURES, 13th Unified International Technical Conference on Refractories (UNITECR), Publisher: AMER CERAMIC SOC, Pages: 911-+
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