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Ceramics, Volume 3, Issue 3 (September 2020) – 11 articles

Cover Story (view full-size image): Spark plasma sintering (SPS) is employed for the first time to produce continuously fiber-reinforced metal matrix composites made of aluminum alloys. For this purpose, prepregs with aluminum alloys as a surface coating on carbon fiber textile structures were manufactured by robot-controlled, twin-arc wire spraying, and subsequently consolidated by SPS in the semi-solid temperature range of the alloys in graphite dies. Fully densified samples were achieved, which demonstrate improved mechanical properties and thereby the potential of the technology. View this paper
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Open AccessReview
Advances in Methods for Recovery of Ferrous, Alumina, and Silica Nanoparticles from Fly Ash Waste
Ceramics 2020, 3(3), 384-420; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics3030034 - 22 Sep 2020
Cited by 2 | Viewed by 868
Abstract
Fly ash or coal fly ash causes major global pollution in the form of solid waste and is classified as a “hazardous waste”, which is a by-product of thermal power plants produced during electricity production. Si, Al, Fe Ca, and Mg alone form [...] Read more.
Fly ash or coal fly ash causes major global pollution in the form of solid waste and is classified as a “hazardous waste”, which is a by-product of thermal power plants produced during electricity production. Si, Al, Fe Ca, and Mg alone form more than 85% of the chemical compounds and glasses of most fly ashes. Fly ash has a chemical composition of 70–90%, as well as glasses of ferrous, alumina, silica, and CaO. Therefore, fly ash could act as a reliable and alternative source for ferrous, alumina, and silica. The ferrous fractions can be recovered by a simple magnetic separation method, while alumina and silica can be extracted by chemical or biological approaches. Alumina extraction is possible using both alkali- and acid-based methods, while silica is extracted by strong alkali, such as NaOH. Chemical extraction has a higher yield than the biological approaches, but the bio-based approaches are more environmentally friendly. Fly ash can also be used for the synthesis of zeolites by NaOH treatment of variable types, as fly ash is rich in alumino-silicates. The present review work deals with the recent advances in the field of the recovery and synthesis of ferrous, alumina, and silica micro and nanoparticles from fly ash. Full article
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Open AccessArticle
Experimental Investigation of the Tension and Compression Creep Behavior of Alumina-Spinel Refractories at High Temperatures
Ceramics 2020, 3(3), 372-383; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics3030033 - 22 Sep 2020
Viewed by 1004
Abstract
Refractory materials are subjected to thermomechanical loads during their working life, and consequent creep strain and stress relaxation are often observed. In this work, the asymmetric high temperature primary and secondary creep behavior of a material used in the working lining of steel [...] Read more.
Refractory materials are subjected to thermomechanical loads during their working life, and consequent creep strain and stress relaxation are often observed. In this work, the asymmetric high temperature primary and secondary creep behavior of a material used in the working lining of steel ladles is characterized, using uniaxial tension and compression creep tests and an inverse identification procedure to calculate the parameters of a Norton-Bailey based law. The experimental creep curves are presented, as well as the curves resulting from the identified parameters, and a statistical analysis is made to evaluate the confidence of the results. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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Open AccessArticle
Effect of SiC on Microstructure, Phase Evolution, and Mechanical Properties of Spark-Plasma-Sintered High-Entropy Ceramic Composite
Ceramics 2020, 3(3), 359-371; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics3030032 - 18 Sep 2020
Viewed by 886
Abstract
Ultra-high temperature ceramic composites have been widely investigated due to their improved sinterability and superior mechanical properties compared to monolithic ceramics. In this work, high-entropy boron-carbide ceramic/SiC composites with different SiC content were synthesized from multicomponent carbides HfC, Mo2C, TaC, TiC, [...] Read more.
Ultra-high temperature ceramic composites have been widely investigated due to their improved sinterability and superior mechanical properties compared to monolithic ceramics. In this work, high-entropy boron-carbide ceramic/SiC composites with different SiC content were synthesized from multicomponent carbides HfC, Mo2C, TaC, TiC, B4C, and SiC in spark plasma sintering (SPS) from 1600 °C to 2000 °C. It was found that the SiC addition tailors the phase formation and mechanical properties of the high-entropy ceramic (HEC) composites. The microhardness and fracture toughness of the HEC composites sintered at 2000 °C were improved from 20.3 GPa and 3.14 MPa·m1/2 to 26.9 GPa and 5.95 MPa·m1/2, with increasing SiC content from HEC-(SiC)0 (0 vol. %) to HEC-(SiC)3.0 (37 vol. %). The addition of SiC (37 vol. %) to the carbide precursors resulted in the formation of two high-entropy ceramic phases with two different crystal structures, face-centered cubic (FCC) structure, and hexagonal structure. The volume fraction ratio between the hexagonal and FCC high-entropy phases increased from 0.36 to 0.76 when SiC volume fraction was increased in the composites from HEC-(SiC)0 to HEC-(SiC)3.0, suggesting the stabilization of the hexagonal high-entropy phase over the FCC phase with SiC addition. Full article
(This article belongs to the Special Issue Spark Plasma Sintering Technology)
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Open AccessArticle
Structural Design of 5 mol.% Yttria Partially Stabilized Zirconia (5Y-PSZ) by Addition of Manganese Oxide and Direct Firing
Ceramics 2020, 3(3), 345-358; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics3030031 - 09 Sep 2020
Cited by 1 | Viewed by 916
Abstract
In this study, 5Y-PSZ-based ceramics with 15 mol.% of manganese oxide were obtained from PSZ + MnO2 powders mixtures by pressing and direct firing. The resulting materials show a stable cubic fluorite structure with only minor traces of segregated manganese oxides and [...] Read more.
In this study, 5Y-PSZ-based ceramics with 15 mol.% of manganese oxide were obtained from PSZ + MnO2 powders mixtures by pressing and direct firing. The resulting materials show a stable cubic fluorite structure with only minor traces of segregated manganese oxides and relative density from 90% to 98%. The linear thermal expansion coefficient is in the order of 10−5 K−1 at 500 K and increases gradually with temperature, due to the onset of a contribution of chemical expansion, reaching about 13 × 10−6 K−1 at 1100 K. These results are suitable for prospective applicability as buffer layers to minimize degradation and delamination of electrolyte/oxygen electrode interfaces in solid electrolyte cells. The electrical conductivity remains close to 1 S/m at 973 K and close to 7 S/m at 1273 K, suggesting mixed conductivity with a prospective contribution to electrode processes occurring at electrode/electrolyte interfaces. Guidelines for further improvement were also established by a detailed analysis of the impact of heating/cooling rate, firing temperature, and time on those properties, based on Taguchi planning. Full article
(This article belongs to the Special Issue High-Temperature Ceramics)
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Open AccessEditorial
100th Paper Milestone
Ceramics 2020, 3(3), 340-344; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics3030030 - 01 Sep 2020
Viewed by 827
Abstract
The Ceramics journal has reached its first milestone with the publication of the 100th paper since its creation in 2018 [...] Full article
Open AccessReview
Chemical Preparation Routes and Lowering the Sintering Temperature of Ceramics
Ceramics 2020, 3(3), 312-339; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics3030029 - 18 Aug 2020
Cited by 1 | Viewed by 1025
Abstract
Chemically and thermally stable ceramics are required for many applications. Many characteristics (electrochemical stability, high thermomechanical properties, etc.) directly or indirectly imply the use of refractory materials. Many devices require the association of different materials with variable melting/decomposition temperatures, which requires their co-firing [...] Read more.
Chemically and thermally stable ceramics are required for many applications. Many characteristics (electrochemical stability, high thermomechanical properties, etc.) directly or indirectly imply the use of refractory materials. Many devices require the association of different materials with variable melting/decomposition temperatures, which requires their co-firing at a common temperature, far from being the most efficient for materials prepared by conventional routes (materials having the stability lowest temperature determines the maximal firing temperature). We review here the different strategies that can be implemented to lower the sintering temperature by means of chemical preparation routes of oxides, (oxy)carbides, and (oxy)nitrides: wet chemical and sol–gel process, metal-organic precursors, control of heterogeneity and composition, transient liquid phase at the grain boundaries, microwave sintering, etc. Examples are chosen from fibers and ceramic matrix composites (CMCs), (opto-)ferroelectric, electrolytes and electrode materials for energy storage and production devices (beta alumina, ferrites, zirconia, ceria, zirconates, phosphates, and Na superionic conductor (NASICON)) which have specific requirements due to multivalent composition and non-stoichiometry. Full article
(This article belongs to the Special Issue High-Temperature Ceramics)
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Open AccessArticle
Synthesis of Titanium Carbide by Means of Pressureless Sintering
Ceramics 2020, 3(3), 306-311; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics3030028 - 18 Aug 2020
Cited by 1 | Viewed by 752
Abstract
In this study, titanium carbide was obtained by low-temperature pressureless (at pressure less than 1 MPa) sintering of a mixture of elementary titanium and graphite powders in a hot-pressing plant with a preliminary mechanical treatment of the initial mixture. The sintering was carried [...] Read more.
In this study, titanium carbide was obtained by low-temperature pressureless (at pressure less than 1 MPa) sintering of a mixture of elementary titanium and graphite powders in a hot-pressing plant with a preliminary mechanical treatment of the initial mixture. The sintering was carried out at temperatures of 900 and 1000 °C in argon media. As a result, cubic modification (Fm3m) of titanium carbide was obtained. The content of impurities was about 12–13 wt.% Full article
(This article belongs to the Special Issue High-Temperature Ceramics)
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Open AccessCommunication
Amorphization Mitigation in Boron-Rich Boron Carbides Quantified by Raman Spectroscopy
Ceramics 2020, 3(3), 297-305; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics3030027 - 23 Jul 2020
Cited by 1 | Viewed by 900
Abstract
Boron carbide is an extremely hard and lightweight material used in armor systems. Upon impact above the Hugoniot elastic limit (HEL), boron carbide loses strength and suddenly fails. Atomistic models suggest that boron-rich boron carbides could mitigate amorphization. Such samples were processed, and [...] Read more.
Boron carbide is an extremely hard and lightweight material used in armor systems. Upon impact above the Hugoniot elastic limit (HEL), boron carbide loses strength and suddenly fails. Atomistic models suggest that boron-rich boron carbides could mitigate amorphization. Such samples were processed, and indentation-induced amorphous zones were created throughout the boron-rich samples of varying degrees and were mapped with Raman spectroscopy to assess changes in the amorphization intensity. Boron-rich samples with a B/C ratio of 6.3 showed a large reduction in amorphization intensity compared to commonly used stoichiometric B4 C, in agreement with recent TEM results. Additionally, hardness trends were also noted as boron content is varied. This offers another pathway in which doping boron carbide can reduce amorphization. Full article
(This article belongs to the Special Issue High-Temperature Ceramics)
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Open AccessArticle
Microfabrication of High-Aspect Ratio KNN Lead-Free Piezoceramic Pillar Arrays by Aqueous Gelcasting
Ceramics 2020, 3(3), 287-296; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics3030026 - 10 Jul 2020
Viewed by 882
Abstract
The present paper reported a novel approach for the fabrication of a high-aspect ratio (K, Na)NbO3 (KNN) piezoelectric micropillar array via epoxy gelcasting, which involves the in situ consolidation of aqueous KNN suspensions with added hydantoin epoxy resin on a polydimethylsiloxane (PDMS) [...] Read more.
The present paper reported a novel approach for the fabrication of a high-aspect ratio (K, Na)NbO3 (KNN) piezoelectric micropillar array via epoxy gelcasting, which involves the in situ consolidation of aqueous KNN suspensions with added hydantoin epoxy resin on a polydimethylsiloxane (PDMS) soft micromold. KNN suspensions with solid loadings of up to 45.0 vol.% have rheological behavior, which was suitable for the gelcasting process. The uniform green KNN bodies derived from the optimized suspension of 42.0 vol.% solid loading and 15.0 wt.% resin had exceptionally high mechanical strength (9.14 MPa), which was responsible for the integrity of the piezoceramic micropattern structure. The square-shaped KNN piezoelectric pillar array with lateral dimensions of up to 5 μm and an aspect ratio of up to five was successfully fabricated. Full article
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Open AccessArticle
Tunable Magneto-Dielectric Material for Electrically Small and Reconfigurable Antenna Systems at Vhf Band
Ceramics 2020, 3(3), 276-286; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics3030025 - 06 Jul 2020
Viewed by 942
Abstract
The main issue to tune controlled devices by the application of a DC magnetic field comes up against the high value of the field’s intensity required for their implementation. This work presents an implementation of magneto-dielectric materials (MDM) specifically manufactured for their integration [...] Read more.
The main issue to tune controlled devices by the application of a DC magnetic field comes up against the high value of the field’s intensity required for their implementation. This work presents an implementation of magneto-dielectric materials (MDM) specifically manufactured for their integration in antenna devices operating in VHF band. The twofold objective is: (i) reduction in antenna size, (ii) frequency tuning of the antenna using a low intensity magnetic control. A notable permeability variation of MDM samples is observed when the symmetry of the lines of the control field, with an intensity less than 10 Oe, is consistent with the one of the structures in the magnetic domains. The MDM allows a miniaturization of 20% of an inverted-F antenna (IFA) antenna structure, and an agility of about 2.5% for a control field of 1.5 Oe. Full article
(This article belongs to the Special Issue Innovative Processing Routes for Electroactive Materials)
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Open AccessArticle
Manufacturing of Continuous Carbon Fiber Reinforced Aluminum by Spark Plasma Sintering
Ceramics 2020, 3(3), 265-275; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics3030024 - 30 Jun 2020
Viewed by 1035
Abstract
In the field of metal matrix composites (MMC), spark plasma sintering (SPS) technique has been used so far for the manufacture of particle, whisker and short-fiber reinforced alloys. In this work, SPS technique is employed for the first time to produce continuous fiber [...] Read more.
In the field of metal matrix composites (MMC), spark plasma sintering (SPS) technique has been used so far for the manufacture of particle, whisker and short-fiber reinforced alloys. In this work, SPS technique is employed for the first time to produce continuous fiber reinforced light metals. For this purpose, metal matrix composite prepregs with aluminum as a surface coating on carbon fiber textiles are manufactured by twin arc wire spraying and subsequently consolidated by SPS in the semi-solid temperature range of the alloy. Shear thinning rheological behavior of the metal alloy at temperatures between solidus and liquidus enables the infiltration of fiber rovings under reduced forming loads. SPS offered a better controlled and more efficient heat transfer in the green body and faster consolidation cycles in comparison with alternative densification methods. Fully densified samples with no porosity proved the suitability of SPS for densification of MMC with a remarkable stiffness increase in comparison with samples densified by thixoforging, an alternative consolidation method. However, the pulse activated sintering process leads to a quite strong fiber/matrix adhesion with evidence of aluminum carbide formation. Full article
(This article belongs to the Special Issue Spark Plasma Sintering Technology)
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