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Special Issue "Ultra-high Temperature Ceramics"

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 March 2013)

Special Issue Editor

Guest Editor
Dr. Angel L. Ortiz

Department of Mechanical, Energy and Materials Engineering, University of Extremadura, Badajoz 06006, Spain
E-Mail
Interests: ceramics; ceramic composites; ceramic thin-films and coatings; processing and sintering; mechanical properties; tribology; X-ray diffraction theory and methods; microstructural characterization; severe plastic deformation.

Special Issue Information

Dear Colleagues,

Borides, carbides, and nitrides of the transition metals comprise a family of ultra-refractory materials known as ultra-high-temperature ceramics (UHTCs), and are a key element without which many applications within the world of the extreme-environment engineering would/will not be possible. Examples of applications for UHTCs include hypersonic flight, scramjet and rocket propulsion, atmospheric re-entry, ultra-refractory crucibles, plasma-arc electrodes, advanced nuclear fuels, and fusion first walls and divertors, to cite just some. In terms of melting point, oxidation, thermal shock, strength, thermal conductivity, thermal expansion, and density the requirements of the world of extreme-environment engineering are so stringent that not surprisingly UHTCs today represent a very active research field in Material Science and Engineering. However, despite the significant progress accumulated to date by the UHTCs community, more research efforts are still required to extend our overall knowledge of UHTCs and to solve the limitations of the current UHTCs.
This special issue of Materials is aimed at presenting the state-of-art and latest research progress in any aspect of UHTCs, that is, powder synthesis and preparation, processing and shaping, sintering, oxidation behaviour, and mechanical and physical properties. In addition to review papers, full-length manuscripts and short communications on any of these UHTCs topics are welcome.

Dr. Angel L. Ortiz
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs).


Keywords

  • ultra-high-temperature ceramics
  • ultra-refractory ceramics
  • transition metal borides, carbides and nitrides
  • extreme-environment materials
  • synthesis of UHTC powders
  • preparation and milling of UHTC powders
  • processing, shaping, and sintering of UHTCs
  • microstructure and microstructural development in UHTCs
  • high-temperature oxidation of UHTCs
  • mechanical and physical properties of UHTCs

Published Papers (6 papers)

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Research

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Open AccessCommunication Co-Dispersion Behavior of ZrB2–SiC–B4C–C Powders with Polyethyleneimine
Materials 2013, 6(9), 4249-4258; doi:10.3390/ma6094249
Received: 8 July 2013 / Revised: 20 August 2013 / Accepted: 20 August 2013 / Published: 23 September 2013
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Abstract
The aqueous dispersion behavior of ZrB2, SiC powders with B4C and C as sintering aids was investigated. Well co-dispersed suspension can be obtained in acidic solutions in presence of polyethyleneimine (PEI). The adsorption of PEI on the powder surface
[...] Read more.
The aqueous dispersion behavior of ZrB2, SiC powders with B4C and C as sintering aids was investigated. Well co-dispersed suspension can be obtained in acidic solutions in presence of polyethyleneimine (PEI). The adsorption of PEI on the powder surface was measured by thermal gravimetric (TG) analysis. Rheological measurements displayed the effect of dispersant on the flow behavior of as-prepared slurries. An optimum condition was obtained with 1 wt % PEI. The viscosity of 40 vol % ZrB2–SiC–B4C–C (ZSBC) suspension at 100 s−1 was as low as 0.74 Pa·s, which was suitable for aqueous processing. Full article
(This article belongs to the Special Issue Ultra-high Temperature Ceramics)
Open AccessArticle Effect of Milling on the Mechanical Properties of Chopped SiC Fiber-Reinforced ZrB2
Materials 2013, 6(5), 1980-1993; doi:10.3390/ma6051980
Received: 22 March 2013 / Revised: 8 May 2013 / Accepted: 8 May 2013 / Published: 15 May 2013
Cited by 5 | PDF Full-text (705 KB) | HTML Full-text | XML Full-text
Abstract
This work aims at studying the effect of the milling conditions on the microstructure and mechanical properties of a ZrB2-5 vol% Si3N4 matrix reinforced with chopped Hi-Nicalon SiC fibers. Several composites were obtained using different milling conditions in
[...] Read more.
This work aims at studying the effect of the milling conditions on the microstructure and mechanical properties of a ZrB2-5 vol% Si3N4 matrix reinforced with chopped Hi-Nicalon SiC fibers. Several composites were obtained using different milling conditions in terms of time, speed and type of milling media. The composites were prepared from commercial powders, ball milled, dried and shaped, and hot pressed at 1720 °C. Their relative bulk densities achieved values as high as 99%. For each material the fiber length distribution, the extent of reacted fiber area and matrix mean grain size were evaluated in order to ascertain the effects of milling time, milling speed and type of milling media. While the fracture toughness and hardness were statistically the same independently of the milling conditions, the flexural strength changed. From the results obtained, the best milling conditions for optimized mechanical properties were determined. Full article
(This article belongs to the Special Issue Ultra-high Temperature Ceramics)
Open AccessArticle TiB2-Based Composites for Ultra-High-Temperature Devices, Fabricated by SHS, Combining Strong and Weak Exothermic Reactions
Materials 2013, 6(5), 1903-1919; doi:10.3390/ma6051903
Received: 8 April 2013 / Revised: 2 May 2013 / Accepted: 2 May 2013 / Published: 10 May 2013
Cited by 12 | PDF Full-text (977 KB) | HTML Full-text | XML Full-text
Abstract
TiB2-based ceramic matrix composites (CMCs) were fabricated using elemental powders of Ti, B and C. The self-propagating high temperature synthesis (SHS) was carried out for the highly exothermic “in situ” reaction of TiB2 formation and the “tailing” synthesis
[...] Read more.
TiB2-based ceramic matrix composites (CMCs) were fabricated using elemental powders of Ti, B and C. The self-propagating high temperature synthesis (SHS) was carried out for the highly exothermic “in situ” reaction of TiB2 formation and the “tailing” synthesis of boron carbide characterized by weak exothermicity. Two series of samples were fabricated, one of them being prepared with additional milling of raw materials. The effects of TiB2 vol fraction as well as grain size of reactant were investigated. The results revealed that combustion was not successful for a TiB2:B4C molar ratio of 0.96, which corresponds to 40 vol% of TiB2 in the composite, however the SHS reaction was initiated and self-propagated for the intended TiB2:B4C molar ratio of 2.16 or above. Finally B13C2 was formed as the matrix phase in each composite. Significant importance of the grain size of the C precursor with regard to the reaction completeness, which affected the microstructure homogeneity and hardness of investigated composites, was proved in this study. The grain size of Ti powder did not influence the microstructure of TiB2 grains. The best properties (HV = 25.5 GPa, average grain size of 9 μm and homogenous microstructure), were obtained for material containing 80 vol% of TiB2, fabricated using a graphite precursor of 2 μm. Full article
(This article belongs to the Special Issue Ultra-high Temperature Ceramics)
Open AccessArticle Effect of SiC Content on the Ablation and Oxidation Behavior of ZrB2-Based Ultra High Temperature Ceramic Composites
Materials 2013, 6(5), 1730-1744; doi:10.3390/ma6051730
Received: 9 February 2013 / Revised: 28 March 2013 / Accepted: 29 March 2013 / Published: 29 April 2013
Cited by 7 | PDF Full-text (2192 KB) | HTML Full-text | XML Full-text
Abstract
The ablation and oxidation of ZrB2-based ultra high temperature ceramic (UHTC) composites containing 10%, 15% and 30% v/v SiC were tested under different heat fluxes in a high frequency plasma wind tunnel. Performance was significantly affected by the surface temperature, which
[...] Read more.
The ablation and oxidation of ZrB2-based ultra high temperature ceramic (UHTC) composites containing 10%, 15% and 30% v/v SiC were tested under different heat fluxes in a high frequency plasma wind tunnel. Performance was significantly affected by the surface temperature, which was strongly dependent on the composition. Composites containing 10% SiC showed the highest surface temperature (>2300 °C) and underwent a marked degradation under both conditions. In contrast, composites with 30% SiC exhibited the lowest surface temperature (<2000 °C) and demonstrated excellent ablation resistance. The surface temperature of UHTCs in aerothermal testing was closely associated with the dynamic evolution of the surface and bulk oxide properties, especially for the change in chemical composition on the exposed surface, which was strongly dependent on the material composition and testing parameters (i.e., heat flux, enthalpy, pressure and test time), and in turn affected its oxidation performance. Full article
(This article belongs to the Special Issue Ultra-high Temperature Ceramics)
Open AccessArticle Theoretical Research on Thermal Shock Resistance of Ultra-High Temperature Ceramics Focusing on the Adjustment of Stress Reduction Factor
Materials 2013, 6(2), 551-564; doi:10.3390/ma6020551
Received: 27 November 2012 / Revised: 30 January 2013 / Accepted: 31 January 2013 / Published: 18 February 2013
Cited by 3 | PDF Full-text (386 KB) | HTML Full-text | XML Full-text
Abstract
The thermal shock resistance of ceramics depends on not only the mechanical and thermal properties of materials, but also the external constraint and thermal condition. So, in order to study the actual situation in its service process, a temperature-dependent thermal shock resistance model
[...] Read more.
The thermal shock resistance of ceramics depends on not only the mechanical and thermal properties of materials, but also the external constraint and thermal condition. So, in order to study the actual situation in its service process, a temperature-dependent thermal shock resistance model for ultra-high temperature ceramics considering the effects of the thermal environment and external constraint was established based on the existing theory. The present work mainly focused on the adjustment of the stress reduction factor according to different thermal shock situations. The influences of external constraint on both critical rupture temperature difference and the second thermal shock resistance parameter in either case of rapid heating or cooling conditions had been studied based on this model. The results show the necessity of adjustment of the stress reduction factor in different thermal shock situations and the limitations of the applicable range of the second thermal shock resistance parameter. Furthermore, the model was validated by the finite element method. Full article
(This article belongs to the Special Issue Ultra-high Temperature Ceramics)

Review

Jump to: Research

Open AccessReview Comparison of Reactive and Non-Reactive Spark Plasma Sintering Routes for the Fabrication of Monolithic and Composite Ultra High Temperature Ceramics (UHTC) Materials
Materials 2013, 6(5), 1566-1583; doi:10.3390/ma6051566
Received: 18 March 2013 / Revised: 17 April 2013 / Accepted: 18 April 2013 / Published: 29 April 2013
Cited by 7 | PDF Full-text (610 KB) | HTML Full-text | XML Full-text
Abstract
A wider utilization of ultra high temperature ceramics (UHTC) materials strongly depends on the availability of efficient techniques for their fabrication as dense bodies. Based on recent results reported in the literature, it is possible to state that Spark Plasma Sintering (SPS) technology
[...] Read more.
A wider utilization of ultra high temperature ceramics (UHTC) materials strongly depends on the availability of efficient techniques for their fabrication as dense bodies. Based on recent results reported in the literature, it is possible to state that Spark Plasma Sintering (SPS) technology offers a useful contribution in this direction. Along these lines, the use of two different SPS-based processing routes for the preparation of massive UHTCs is examined in this work. One method, the so-called reactive SPS (R-SPS), consists of the synthesis and densification of the material in a single step. Alternatively, the ceramic powders are first synthesized by Self-propagating High-temperature Synthesis (SHS) and then sintered by SPS. The obtained results evidenced that R-SPS method is preferable for the preparation of dense monolithic products, while the sintering of SHS powders requires relatively milder conditions when considering binary composites. The different kinetic mechanisms involved during R-SPS of the monolithic and composite systems, i.e., combustion-like or gradual solid-diffusion, respectively, provides a possible explanation. An important role is also played by the SHS process, particularly for the preparation of composite powders, since stronger interfaces are established between the ceramic constituents formed in situ, thus favoring diffusion processes during the subsequent SPS step. Full article
(This article belongs to the Special Issue Ultra-high Temperature Ceramics)

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