Ceramics

11 pages, 2252 KiB

Open AccessArticle

Overview of Spark Plasma Texturing of Functional Ceramics

by Jacques G. NOUDEM and Yiteng XING

Ceramics 2021, 4(1), 97-107; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics4010009 - 15 Mar 2021

Cited by 3 | Viewed by 2621

This work reports the progress in the preparation of superconducting and thermoelectric lamellar compounds processed by the unconventional Spark Plasma Sintering (SPS). The SPS equipment was modified with the aim of obtaining the textured and dense superconductor Bi₂Sr₂Ca₂ [...] Read more.

This work reports the progress in the preparation of superconducting and thermoelectric lamellar compounds processed by the unconventional Spark Plasma Sintering (SPS). The SPS equipment was modified with the aim of obtaining the textured and dense superconductor Bi₂Sr₂Ca₂Cu₃O_10,p-type oxide thermoelectric bulk as Ca₃Co₄O₉ and Ca_3-xAg_xCo₄O₉/Ag composites respectively. The new process is referred to as Spark Plasma Texturing (SPT). During SPT, the bulk material can freely deform. As a result, inter-grain preferential crystallographic orientation is created. The series of sintered and textured samples using the same Ag content were processed respectively. From the results, we can evidence: (i) the magnetic and/or structural transition around 350 °C, for both series of samples. (ii) The electrical resistivity (ρ) decreases with increasing Ag-substituted or Ag-added. (iii) The Seebeck coefficient (S) of the textured series is higher than that of the sintered series. In the case of the Ag-substituted, S, decreases with Ag content. The optimized composite is found to be Ca_2.6Ag_0.4Co₄O₉/8wt% Ag. We can note the remarkable reduction of ρ, and the improvement of power factor values up to 360 μW.m⁻¹.K⁻².The superconducting properties of single phased Bi₂Sr₂Ca₂Cu₃O₁₀ (Bi2223) consolidated using SPS and SPT will also be discussed. Full article

(This article belongs to the Special Issue Spark Plasma Sintering Technology)

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14 pages, 3984 KiB

Open AccessArticle

New Interpretation of X-ray Diffraction Pattern of Vitreous Silica

by Shangcong Cheng

Ceramics 2021, 4(1), 83-96; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics4010008 - 13 Mar 2021

Cited by 6 | Viewed by 3522

Abstract

The striking feature of X-ray diffraction pattern of vitreous silica is that the center of its intense but broad ring is located at nearly the same position as the strongest diffraction ring of β-cristobalite. Two fundamentally different explanations to the diffraction patterns were [...] Read more.

The striking feature of X-ray diffraction pattern of vitreous silica is that the center of its intense but broad ring is located at nearly the same position as the strongest diffraction ring of β-cristobalite. Two fundamentally different explanations to the diffraction patterns were appeared about 90 years ago, one based on the smallest crystals of β-cristobalite and the other based on the non-crystalline continuous random network. This work briefly outlines the facts supporting and objecting these two hypotheses, and aims to present a new interpretation based on a medium-range ordering structure on the facets of clusters formed in the glass transition process. It will be shown that the new interpretation provides a more satisfactory explanation of the diffraction pattern and physical properties of silica glass, and offers considerable valuable information regarding the nature of glass and glass transition. Full article

(This article belongs to the Special Issue What Do We Still Want to Know 90 Years After the Continuous Random Network (CRN) Theory?)

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13 pages, 1881 KiB

Open AccessArticle

Electrode Material Effect on the Flash Ignition in Soda-Lime Silicate Glass

by Mattia Cipriani, Vincenzo M. Sglavo, Gian Domenico Sorarù and Mattia Biesuz

Ceramics 2021, 4(1), 70-82; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics4010007 - 25 Feb 2021

Viewed by 2333

Abstract

The need for sustainable solutions to reduce the carbon footprint of the ceramics and glass industry leads towards the development of new electric current-assisted technologies. Flash sintering-like processes in glasses allow a reduction of the softening temperature and could pave the way for [...] Read more.

The need for sustainable solutions to reduce the carbon footprint of the ceramics and glass industry leads towards the development of new electric current-assisted technologies. Flash sintering-like processes in glasses allow a reduction of the softening temperature and could pave the way for new shaping technologies. Herein, we investigated the flash transition in soda-lime silicate glass using two different electrode materials, silver, and platinum. The high dielectric strength registered on samples tested with platinum electrodes undergoes a significant reduction when silver is used. In other words, in the case of silver electrodes, the flash ignition takes place at a lower onset field. Moreover, the Joule heating developed during the process can be turned from being highly inhomogeneous with Pt electrodes to homogeneous when Ag electrodes are used. Full article

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14 pages, 3682 KiB

Open AccessArticle

Effect of the Heating Rate on the Spark-Plasma-Sintering (SPS) of Transparent Y₂O₃ Ceramics: Microstructural Evolution, Mechanical and Optical Properties

by Lihong Liu, Koji Morita, Tohru S. Suzuki and Byung-Nam Kim

Ceramics 2021, 4(1), 56-69; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics4010006 - 17 Feb 2021

Cited by 6 | Viewed by 3089

Abstract

High strength transparent Y₂O₃ ceramics were fabricated from commercial powders using spark plasma sintering (SPS) technique by optimizing the heating rate. The heating rate significantly influenced the microstructures and the optical/mechanical properties of the Y₂O₃ ceramics. Grain [...] Read more.

High strength transparent Y₂O₃ ceramics were fabricated from commercial powders using spark plasma sintering (SPS) technique by optimizing the heating rate. The heating rate significantly influenced the microstructures and the optical/mechanical properties of the Y₂O₃ ceramics. Grain growth was limited accordingly with increasing the heating rate. The ball milling process of the commercial Y₂O₃ powders is likely to further enhance the sinterability during the SPS processing. The dense Y₂O₃ ceramics, which were sintered by SPS with 100 °C/min, showed good transmittance range from visible to near infrared (IR). For a high heating rate of 100 °C/min, the in-line transmittance at a visible wavelength of 700 nm was 66%, whereas for a slow heating rate of 10 °C/min, it reduced to 46%. The hardness H_v tends to increase with increasing the heating rate and rigorously followed the Hall–Petch relationship; that is, it is enhanced with a reduction of the grain size. The toughness K_IC, on the other hand, is less sensitive to both the heating rate and the grain size, and takes a similar value. This research highlighted that the high heating rate SPS processing can fabricate fully dense fine-grained Y₂O₃ ceramics with the excellent optical and mechanical properties. Full article

(This article belongs to the Special Issue Spark Plasma Sintering Technology)

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2 pages, 165 KiB

Open AccessEditorial

Acknowledgment to Reviewers of Ceramics in 2020

by Ceramics Editorial Office

Ceramics 2021, 4(1), 54-55; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics4010005 - 29 Jan 2021

Viewed by 1537

Abstract

Peer review is the driving force of journal development, and reviewers are gatekeepers who ensure that Ceramics maintains its standards for the high quality of its published papers [...] Full article

14 pages, 1190 KiB

Open AccessArticle

Micro/Nano Indentation Testing of Spark Plasma Sintered Al₂O₃ + ZrO₂ + cBN Ceramics

by Richard Sedlák, Michal Ivor, Piotr Klimczyk, Piotr Wyzga, Marcin Podsiadlo, Marek Vojtko and Ján Dusza

Ceramics 2021, 4(1), 40-53; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics4010004 - 22 Jan 2021

Cited by 4 | Viewed by 2717

Abstract

Al₂O₃ + 30 vol% ZrO₂ matrix composites with 20 and 30 vol% cBN have been prepared with the optimized processing route, using spark plasma sintering (SPS) at temperatures of 1400 °C and 1250 °C. The influence of cBN addition [...] Read more.

Al₂O₃ + 30 vol% ZrO₂ matrix composites with 20 and 30 vol% cBN have been prepared with the optimized processing route, using spark plasma sintering (SPS) at temperatures of 1400 °C and 1250 °C. The influence of cBN addition on the microstructure characteristics, micro/nanohardness, elastic modulus, and crack-extension resistance of the composites and their constitutions have been investigated using scanning electron microscopy (SEM), statistical analyses of the individual grain size and micro/nanoindentation methods. The matrix consists of alumina and zirconia grains with grain sizes/diameter of approximately 220 and 160 nm with approximately 1.9 μm cBN grains in the Al₂O₃ + ZrO₂ + cBN composites. The microhardness is slightly increasing with cBN addition from 16.2 to 17.1 GPa and the crack-extension resistance from 3.72 to 4.29 MPa.m^1/2. The toughening mechanisms are in the form of crack deflection, crack branching, and crack bridging. The nanohardness and indentation modulus of the matrix are approximately 30 and 420 GPa, and the cBN grains 70 and 777 GPa, respectively. Full article

(This article belongs to the Special Issue Spark Plasma Sintering Technology)

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20 pages, 5426 KiB

Open AccessReview

Unconventional Materials Processing Using Spark Plasma Sintering

by Ambreen Nisar, Cheng Zhang, Benjamin Boesl and Arvind Agarwal

Ceramics 2021, 4(1), 20-39; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics4010003 - 08 Jan 2021

Cited by 21 | Viewed by 7050

Abstract

Spark plasma sintering (SPS) has gained recognition in the last 20 years for its rapid densification of hard-to-sinter conventional and advanced materials, including metals, ceramics, polymers, and composites. Herein, we describe the unconventional usages of the SPS technique developed in the field. The [...] Read more.

Spark plasma sintering (SPS) has gained recognition in the last 20 years for its rapid densification of hard-to-sinter conventional and advanced materials, including metals, ceramics, polymers, and composites. Herein, we describe the unconventional usages of the SPS technique developed in the field. The potential of various new modifications in the SPS technique, from pressureless to the integration of a novel gas quenching system to extrusion, has led to SPS’ evolution into a completely new manufacturing tool. The SPS technique’s modifications have broadened its usability from merely a densification tool to the fabrication of complex-shaped components, advanced functional materials, functionally gradient materials, interconnected materials, and porous filter materials for real-life applications. The broader application achieved by modification of the SPS technique can provide an alternative to conventional powder metallurgy methods as a scalable manufacturing process. The future challenges and opportunities in this emerging research field have also been identified and presented. Full article

(This article belongs to the Special Issue Spark Plasma Sintering Technology)

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8 pages, 5139 KiB

Open AccessArticle

In Situ Graded Ceramic/Reduced Graphene Oxide Composites Manufactured by Spark Plasma Sintering

by Cristina Ramírez, Pilar Miranzo, Maria Isabel Osendi and Manuel Belmonte

Ceramics 2021, 4(1), 12-19; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics4010002 - 29 Dec 2020

Cited by 2 | Viewed by 2580

Abstract

The present work merges two key strategies for the manufacturing of advanced ceramics, in particular, the development of functionally graded materials (FGMs) and the addition of graphene-based fillers into a ceramic matrix. A silicon nitride/reduced graphene oxide FGM composite is produced, in one [...] Read more.

The present work merges two key strategies for the manufacturing of advanced ceramics, in particular, the development of functionally graded materials (FGMs) and the addition of graphene-based fillers into a ceramic matrix. A silicon nitride/reduced graphene oxide FGM composite is produced, in one step, from a single powder composition using the spark plasma sintering (SPS) technique with an asymmetric setting of the punches and die to create a continuous temperature gradient along the cross section of the powder compact. A deep microstructural and mechanical characterization has been done across the specimen thickness. The FGM composite exhibits bottom-top gradients in both the matrix grain size (150% increase) and α-phase content (89→1%). The FGM bottom surface is 10% harder than the top one and, on the other hand, the latter is 15% tougher. The presence of reduced graphene oxide sheets homogeneously distributed within the ceramic composite reduces the mechanical gradients compared to the monolithic silicon nitride FGM, although allows reaching a maximum long-crack toughness value of 9.4 MPa·m^1/2. In addition, these graphene-based fillers turn the insulating ceramics into an electrical conductor material. Full article

(This article belongs to the Special Issue Spark Plasma Sintering Technology)

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11 pages, 5619 KiB

Open AccessArticle

Recyclable Porous Glass-Ceramics from the Smelting of MSWI Bottom Ash

by Patricia Rabelo Monich, Hugo Lucas, Bernd Friedrich and Enrico Bernardo

Ceramics 2021, 4(1), 1-11; https://0-doi-org.brum.beds.ac.uk/10.3390/ceramics4010001 - 29 Dec 2020

Cited by 2 | Viewed by 3038

Abstract

Material from the electric arc furnace smelting of municipal solid waste incineration (MSWI) bottom ash was easily converted into highly porous glass-ceramics by a combination of inorganic gel casting and sinter-crystallization at 1000 °C. In particular, the gelation of aqueous suspensions of fine [...] Read more.

Material from the electric arc furnace smelting of municipal solid waste incineration (MSWI) bottom ash was easily converted into highly porous glass-ceramics by a combination of inorganic gel casting and sinter-crystallization at 1000 °C. In particular, the gelation of aqueous suspensions of fine glass powders, transformed into “green” foams by intensive mechanical stirring, occurred with a limited addition of alkali activator (1 M NaOH). The products coupled the stabilization of pollutants with good mechanical properties (e.g., compressive strength approaching 4 MPa). Interestingly, they could be used also as raw material for new glass-ceramic foams, obtained by the same gel casting and sintering method, with no degradation of chemical stability. Limitations in the crushing strength, derived from the limited viscous flow densification of semi-crystalline powders, were overcome by mixing powders from recycled foams with 30 wt% soda-lime glass. The new products finally featured an even higher strength-to-density ratio than the foams from the first cycle. Full article

(This article belongs to the Special Issue Waste-Derived Functional Ceramic and Glass-Based Products)

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Ceramics, Volume 4, Issue 1 (March 2021) – 9 articles

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