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13 pages, 3865 KiB

Open AccessArticle

Microstructure and Mechanical Properties of HfC-SiC Ceramics Influenced by WC Addition

by Yue Cheng, Huaguo Tang, Guangkai Fang, Yuan Yu, Lujie Wang, Yanfei Zhang and Zhuhui Qiao

Materials 2023, 16(9), 3337; https://doi.org/10.3390/ma16093337 - 24 Apr 2023

Cited by 2 | Viewed by 1773

Abstract

The development of HfC-SiC has been challenging due to difficulties in achieving sintering and satisfactory mechanical properties. However, this study aims to overcome these limitations by incorporating WC as an additive. SPS was employed to process HfC-SiC and HfC-SiC doped with 5 vol.% [...] Read more.

The development of HfC-SiC has been challenging due to difficulties in achieving sintering and satisfactory mechanical properties. However, this study aims to overcome these limitations by incorporating WC as an additive. SPS was employed to process HfC-SiC and HfC-SiC doped with 5 vol.% WC. The resulting samples were then evaluated for their oxygen content, relative density, Vickers hardness, bending strength, indentation fracture toughness, and microstructure. The Vickers hardness (20.50 ± 0.20 GPa), flexural strength (600.19 ± 84.00 MPa), and indentation fracture toughness (5.76 ± 0.54 MPa·m^1/2) of HfC-30 vol.% SiC-5 vol.% WC ceramics are higher than HfC-30 vol.% SiC ceramics. Doping 5 vol.% WC in HfC-30 vol.% SiC not only reduces the oxygen content of samples but also produces the (Hf,W)C solid solution and refines the microstructures, which are the main reasons for the higher mechanical properties of HfC-30 vol.% SiC-5 vol.% WC ceramics. In summary, this study successfully addresses the challenges associated with HfC-SiC by incorporating WC as an additive, leading to improved mechanical properties and microstructures. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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15 pages, 4759 KiB

Open AccessArticle

Effect of Two-Step Sintering on the Mechanical and Electrical Properties of 5YSZ and 8YSZ Ceramics

by Yunpeng Li, Hongqian Sun, Jing Song, Zhiyu Zhang, Hao Lan, Liangliang Tian and Keqiang Xie

Materials 2023, 16(5), 2019; https://doi.org/10.3390/ma16052019 - 28 Feb 2023

Cited by 5 | Viewed by 2229

Abstract

Yttria-stabilized zirconia (YSZ) has been widely used in structural and functional ceramics because of its excellent physicochemical properties. In this paper, the density, average gain size, phase structure, and mechanical and electrical properties of conventionally sintered (CS) and two-step sintered (TSS) 5YSZ and [...] Read more.

Yttria-stabilized zirconia (YSZ) has been widely used in structural and functional ceramics because of its excellent physicochemical properties. In this paper, the density, average gain size, phase structure, and mechanical and electrical properties of conventionally sintered (CS) and two-step sintered (TSS) 5YSZ and 8YSZ are investigated in detail. As the grain size of YSZ ceramics became smaller, dense YSZ materials with a submicron grain size and low sintering temperature were optimized in terms of their mechanical and electrical properties. 5YSZ and 8YSZ in the TSS process significantly improved the plasticity, toughness, and electrical conductivity of the samples and significantly suppressed the rapid grain growth. The experimental results showed that the hardness of the samples was mainly affected by the volume density, that the maximum fracture toughness of 5YSZ increased from 3.514 MPa·m^1/2 to 4.034 MPa·m^1/2 in the TSS process, an increase of 14.8%, and that the maximum fracture toughness of 8YSZ increased from 1.491 MPa·m^1/2 to 2.126 MPa·m^1/2, an increase of 42.58%. The maximum total conductivity of the 5YSZ and 8YSZ samples under 680 °C increased from 3.52 × 10⁻³ S/cm and 6.09 × 10⁻³ S/cm to 4.52 × 10⁻³ S/cm and 7.87 × 10⁻³ S/cm, an increase of 28.41% and 29.22%, respectively. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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15 pages, 3909 KiB

Open AccessArticle

Phase Formation, Mechanical Strength, and Bioactive Properties of Lithium Disilicate Glass–Ceramics with Different Al₂O₃ Contents

by Arnon Kraipok, Teerapong Mamanee, Jetsada Ruangsuriya, Poomirat Nawarat and Wilaiwan Leenakul

Materials 2022, 15(23), 8283; https://doi.org/10.3390/ma15238283 - 22 Nov 2022

Cited by 4 | Viewed by 1966

Abstract

Owing to its excellent mechanical properties and aesthetic tooth-like appearance, lithium disilicate glass–ceramic is more attractive as a crown for dental restorations. In this study, lithium disilicate glass–ceramics were prepared from SiO₂–Li₂O–K₂O–P₂O₅–CeO₂ [...] Read more.

Owing to its excellent mechanical properties and aesthetic tooth-like appearance, lithium disilicate glass–ceramic is more attractive as a crown for dental restorations. In this study, lithium disilicate glass–ceramics were prepared from SiO₂–Li₂O–K₂O–P₂O₅–CeO₂ glass systems with various Al₂O₃ contents. The mixed glass was then heat-treated at 600 °C and 800 °C for 2 h to form glass–ceramic samples. Phase formation, microstructure, mechanical properties and bioactivity were investigated. The phase formation analysis confirmed the presence of Li₂Si₂O₅ in all the samples. The glass–ceramic sample with an Al₂O₃ content of 1 wt% showed rod-like Li₂Si₂O₅ crystals that could contribute to the delay in crack propagation and demonstrated the highest mechanical properties. Surface treatment with hydrofluoric acid followed by a silane-coupling agent provided the highest micro-shear bond strength for all ceramic conditions, with no significant difference between ceramic samples. The biocompatibility tests of the material showed that Al₂O₃-added lithium disilicate glass–ceramic sample was bioactive, thus activating protein production and stimulating the alkaline phosphatase (ALP) activity of osteoblast-like cells. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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14 pages, 3565 KiB

Open AccessEditor’s ChoiceArticle

Effect of Two-Step Sintering on Properties of Alumina Ceramics Containing Waste Alumina Powder

by Milan Vukšić, Irena Žmak, Lidija Ćurković and Andraž Kocjan

Materials 2022, 15(21), 7840; https://doi.org/10.3390/ma15217840 - 7 Nov 2022

Cited by 1 | Viewed by 2182

Abstract

This study aims to evaluate the recycling potential of solid waste alumina powder (WAP) by utilization of the two-step sintering (TSS) process. For the study, WAP was collected as an industrial scrap after the machining process for the formation of green alumina compacts. [...] Read more.

This study aims to evaluate the recycling potential of solid waste alumina powder (WAP) by utilization of the two-step sintering (TSS) process. For the study, WAP was collected as an industrial scrap after the machining process for the formation of green alumina compacts. The alumina samples were prepared according to the slip casting method by preparing suspensions containing commercial alumina with 0.8 μm average particle size and by adding up to 20 dwb. % (i.e., expressed on a dry weight basis) of WAP with 3.4 μm average particle size. The samples were sintered at optimized TSS conditions and compared with conventional one-step sintering (OSS) by conducting morphological analyses. The average grain size (AGS) was determined from the obtained field emission scanning electron microscopy (FESEM) images, while the sample porosity was calculated based on apparent densities. The obtained micrographs after TSS implementation revealed a partially textured microstructure. Furthermore, a comparison of the mechanical properties of alumina samples lacking or containing 20 dwb. % of WAP obtained after sintering is presented. The indentation fracture toughness (~3.2 MPa m^1/2) and Vickers hardness data (~14.5 GPa) showed a positive effect of adding WAP to alumina samples. The slightly improved mechanical properties of ceramic samples containing waste alumina are a consequence of lower porosity, which is due to the remaining sintering additives in WAP. The collected results demonstrate the possibility of using TSS for sintering ceramic materials that contain WAP. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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8 pages, 1220 KiB

Open AccessCommunication

Flash Sintered Potassium Sodium Niobate: High-Performance Piezoelectric Ceramics at Low Thermal Budget Processing

by Ricardo Serrazina, Alexander Tkach, Luis Pereira, Ana M. O. R. Senos and Paula M. Vilarinho

Materials 2022, 15(19), 6603; https://doi.org/10.3390/ma15196603 - 23 Sep 2022

Cited by 8 | Viewed by 1618

Abstract

Alternative sintering technologies promise to overcome issues associated with conventional ceramic sintering such as high thermal budgets and CO₂ footprint. The sintering process becomes even more relevant for alkali-based piezoelectric ceramics such as K_0.5Na_0.5NbO₃ (KNN) typically fired [...] Read more.

Alternative sintering technologies promise to overcome issues associated with conventional ceramic sintering such as high thermal budgets and CO₂ footprint. The sintering process becomes even more relevant for alkali-based piezoelectric ceramics such as K_0.5Na_0.5NbO₃ (KNN) typically fired above 1100 °C for several hours that induces secondary phase formation and, thereby, degrades their electrical characteristics. Here, an ability of KNN ceramics to be of high performance is successfully demonstrated, using an electric field- and current-assisted Flash sintering technique at 900 °C only. Reported for the first time, Flash sintered KNN ceramics have room-temperature remnant polarization P_r = 21 μC/cm² and longitudinal piezoelectric coefficient d₃₃ = 117 pC/N, slightly superior to that of conventional ones due to the reduced content of secondary phases. High-performance KNN ceramics Flash sintered at a low-thermal budget have implications for the development of innovative low carbon technologies, electroceramics stakeholders, and piezoelectric energy harvesters. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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19 pages, 9251 KiB

Open AccessArticle

Addition of Nano CaF₂@SiO₂ and SiC Whiskers in Ceramic Tools for Wear Reduction and Improved Machinability

by Wenhao Zhang, Zhaoqiang Chen, Congfeng Tian, Jun Wu, Guangchun Xiao, Niansheng Guo, Mingdong Yi, Jingjie Zhang and Chonghai Xu

Materials 2022, 15(15), 5430; https://doi.org/10.3390/ma15155430 - 7 Aug 2022

Cited by 2 | Viewed by 1496

Abstract

The addition of CaF₂@SiO₂ and SiC whiskers to ceramic tools can improve their flexural strength and fracture toughness, reduce surface damage, and improve their cutting performance. The cutting experiments showed that under the same cutting conditions, the surface roughness of [...] Read more.

The addition of CaF₂@SiO₂ and SiC whiskers to ceramic tools can improve their flexural strength and fracture toughness, reduce surface damage, and improve their cutting performance. The cutting experiments showed that under the same cutting conditions, the surface roughness of the workpiece processed with the Al₂O₃/TiC/SiC/CaF₂@SiO₂ (ATSC10) tool was significantly lower than that of the workpiece processed with the Al₂O₃/TiC/ SiC (ATS) tool. Additionally, the main cutting force and cutting temperature when cutting with the ATSC10 tool were lower by 30 and 31.7%, respectively. These results were attributed to the precipitation of CaF₂ from the nanocoated particles during cutting and the formation of a uniform and continuous lubricating film on the surface of the tool. The wear on the front surface of the ATS tool was mainly adhesive, and that on the back tool surface was mainly abrasive. For ATSC10, the main forms of wear on the tool front surface were adhesive and abrasive, whereas the main form of wear on the tool back surface was abrasive with slight adhesive wear. The addition of nano-coated particles and whiskers improved the mechanical properties of the cutting tool while maintaining good cutting performance. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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16 pages, 4030 KiB

Open AccessArticle

Powder 3D Printing of Bone Scaffolds with Uniform and Gradient Pore Sizes Using Cuttlebone-Derived Calcium Phosphate and Glass-Ceramic

by Francesca Cestari, Yuejiao Yang, Janka Wilbig, Jens Günster, Antonella Motta and Vincenzo M. Sglavo

Materials 2022, 15(15), 5139; https://doi.org/10.3390/ma15155139 - 24 Jul 2022

Cited by 8 | Viewed by 2410

Abstract

The pore geometry of bone scaffolds has a major impact on their cellular response; for this reason, 3D printing is an attractive technology for bone tissue engineering, as it allows for the full control and design of the porosity. Calcium phosphate materials synthesized [...] Read more.

The pore geometry of bone scaffolds has a major impact on their cellular response; for this reason, 3D printing is an attractive technology for bone tissue engineering, as it allows for the full control and design of the porosity. Calcium phosphate materials synthesized from natural sources have recently attracted a certain interest because of their similarity to natural bone, and they were found to show better bioactivity than synthetic compounds. Nevertheless, these materials are very challenging to be processed by 3D printing due to technological issues related to their nanometric size. In this work, bone scaffolds with different pore geometries, with a uniform size or with a size gradient, were fabricated by binder jetting 3D printing using a biphasic calcium phosphate (BCP) nanopowder derived from cuttlebones. To do so, the nanopowder was mixed with a glass-ceramic powder with a larger particle size (45–100 µm) in 1:10 weight proportions. Pure AP40mod scaffolds were also printed. The sintered scaffolds were shown to be composed mainly by hydroxyapatite (HA) and wollastonite, with the amount of HA being larger when the nanopowder was added because BCP transforms into HA during sintering at 1150 °C. The addition of bio-derived powder increases the porosity from 60% to 70%, with this indicating that the nanoparticles slow down the glass-ceramic densification. Human mesenchymal stem cells were seeded on the scaffolds to test the bioactivity in vitro. The cells’ number and metabolic activity were analyzed after 3, 5 and 10 days of culturing. The cellular behavior was found to be very similar for samples with different pore geometries and compositions. However, while the cell number was constantly increasing, the metabolic activity on the scaffolds with gradient pores and cuttlebone-derived powder decreased over time, which might be a sign of cell differentiation. Generally, all scaffolds promoted fast cell adhesion and proliferation, which were found to penetrate and colonize the 3D porous structure. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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14 pages, 4920 KiB

Open AccessArticle

Experimental Evaluations on Seismic Performances of Porcelain and GFRP Composite UHV GIS Bushings

by Chang He, Ziwei He and Qiang Xie

Materials 2022, 15(11), 4035; https://doi.org/10.3390/ma15114035 - 6 Jun 2022

Cited by 6 | Viewed by 2073

Abstract

To evaluate the seismic performances of the ultra-high voltage (UHV) gas-insulated switchgear (GIS) bushings made by porcelain and glass fiber reinforced polymer (GFRP) composite materials, shaking table tests were conducted on the two full-scale GIS bushings. The dynamic characteristics and seismic responses of [...] Read more.

To evaluate the seismic performances of the ultra-high voltage (UHV) gas-insulated switchgear (GIS) bushings made by porcelain and glass fiber reinforced polymer (GFRP) composite materials, shaking table tests were conducted on the two full-scale GIS bushings. The dynamic characteristics and seismic responses of the two UHV GIS bushings were obtained. The experimental results indicated that the two UHV GIS bushings meet the seismic requirements in the corresponding standards. The supporting frame and bus canister amplify the seismic responses of the UHV GIS bushings. Under earthquakes, the GFRP composite UHV GIS bushing is safer than the porcelain bushing. In the seismic design of the electrical substation, the large seismic displacement of the GFRP composite UHV GIS bushings should be considered. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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9 pages, 2184 KiB

Open AccessArticle

Reactive Flash Sintering of High-Entropy Oxide (Mg, Co, Ni, Cu, Zn)_1−xLi_xO at Room Temperature

by Nianping Yan, Yuchen Zhu, Muliang Cai, Bojiang Li, Bichuan Xu, Yueji Li, Xilin Wang and Zhidong Jia

Materials 2022, 15(11), 3836; https://doi.org/10.3390/ma15113836 - 27 May 2022

Cited by 5 | Viewed by 2065

Abstract

(Mg, Co, Ni, Cu, Zn)_1−xLi_xO is a type of high-entropy oxide that has high ionic conductivity at room temperature and is used as a solid electrolyte. (Mg, Co, Ni, Cu, Zn)_1−xLi_xO was successfully synthesized from [...] Read more.

(Mg, Co, Ni, Cu, Zn)_1−xLi_xO is a type of high-entropy oxide that has high ionic conductivity at room temperature and is used as a solid electrolyte. (Mg, Co, Ni, Cu, Zn)_1−xLi_xO was successfully synthesized from precursor powder by applying reactive flash sintering for less than 4 min at room temperature (25 °C). AC and DC electric fields were independently applied to sinter ceramic samples; consequently, AC and DC electric field application resulted in relative densities that exceeded 90% and 80%, respectively. X-ray diffraction spectra of samples revealed the existence of a clear halite structure with an insignificant impurity phase, proving that (Mg, Co, Ni, Cu, Zn)_1−xLi_xO crystals were successfully produced. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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14 pages, 2487 KiB

Open AccessArticle

Effect of Cooling Rate during Glazing on the Mechanical and Optical Properties of Monolithic Zirconia with 3 mol% Yttria Content

by Mi-Hyang Cho and Hyo-Joung Seol

Materials 2021, 14(23), 7474; https://doi.org/10.3390/ma14237474 - 6 Dec 2021

Cited by 6 | Viewed by 1988

Abstract

Glazing is the final heat treatment process in the manufacturing of a monolithic zirconia prosthesis. Herein, the effect of cooling rate during zirconia glazing was investigated. A 3 mol% yttria-stabilized tetragonal zirconia polycrystal was glazed at the general cooling rate suggested by the [...] Read more.

Glazing is the final heat treatment process in the manufacturing of a monolithic zirconia prosthesis. Herein, the effect of cooling rate during zirconia glazing was investigated. A 3 mol% yttria-stabilized tetragonal zirconia polycrystal was glazed at the general cooling rate suggested by the manufacturer, as well as at higher and lower cooling rates, and the differences in flexural strength, hardness, optical properties, and crystal structure were evaluated. A higher cooling rate did not affect the flexural strength, hardness, grain size, optical properties, or crystal structure; however, the Weibull modulus decreased by 1.3. A lower cooling rate did not affect the flexural strength, optical properties, or crystal structure; however, the Weibull characteristic strength increased by 26.7 MPa and the Weibull modulus increased by 0.9. The decrease in hardness and the increase in grain size were statistically significant; however, the numerical differences were negligible. This study revealed that a lower cooling rate provides more reliable flexural strength. Therefore, glazing can proceed at a general cooling rate, which takes 3–4 min; however, glazing at a lower cooling rate will provide a more consistent flexural strength if desired, despite being time-consuming. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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9 pages, 2660 KiB

Open AccessArticle

An Engineering Zirconia Ceramic Made of Baddeleyite

by Vyacheslav V. Rodaev, Andrey O. Zhigachev, Alexander I. Tyurin, Svetlana S. Razlivalova, Viktor V. Korenkov and Yuri I. Golovin

Materials 2021, 14(16), 4676; https://doi.org/10.3390/ma14164676 - 19 Aug 2021

Cited by 11 | Viewed by 2302

Abstract

Wet high-energy milling and uniaxial pressing are used to fabricate CaO-stabilized tetragonal zirconia polycrystalline ceramic (Ca-TZP) with decent mechanical characteristics, i.e., a hardness of 11.5 GPa, Young’s modulus of 230 GPa, and fracture toughness of 13 MPa·m^0.5. The effect of CaO [...] Read more.

Wet high-energy milling and uniaxial pressing are used to fabricate CaO-stabilized tetragonal zirconia polycrystalline ceramic (Ca-TZP) with decent mechanical characteristics, i.e., a hardness of 11.5 GPa, Young’s modulus of 230 GPa, and fracture toughness of 13 MPa·m^0.5. The effect of CaO concentration and the sintering temperature on phase composition and mechanical characteristics of CaO-stabilized zirconia ceramic made of baddeleyite is investigated. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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9 pages, 10718 KiB

Open AccessCommunication

Flash Sintering of YSZ/Al₂O₃ Composites: Effect of Processing and Testing Conditions

by Mattia Biesuz, Andrea Ometto and Vincenzo Maria Sglavo

Materials 2021, 14(4), 1031; https://doi.org/10.3390/ma14041031 - 22 Feb 2021

Cited by 11 | Viewed by 2890

Abstract

The flash sintering behavior of yttria-stabilized zirconia/alumina composites was investigated to understand the role of the fundamental processing and testing parameters (electric field intensity, electric current limit, thermal insulation, homogeneity and dispersion of the two phases) on densification. A strong relation between the [...] Read more.

The flash sintering behavior of yttria-stabilized zirconia/alumina composites was investigated to understand the role of the fundamental processing and testing parameters (electric field intensity, electric current limit, thermal insulation, homogeneity and dispersion of the two phases) on densification. A strong relation between the composite compositions and the electric parameters needed to promote flash sintering is revealed. Interestingly, the composite preparation method, which affects the two-phases dispersion homogeneity, was shown to have a relevant effect on the flash onset conditions, where the more homogeneous material is more difficult to be flashed. Moreover, the use of a simple thermal insulation system around the green body allowed to improve the final density of the composites under constant electric current. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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Review

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10 pages, 1299 KiB

Open AccessReview

Extraction of Alkalis from Silicate Materials Part 1—Amorphous Silicate Materials

by Wiktor Szewczenko

Materials 2022, 15(12), 4056; https://doi.org/10.3390/ma15124056 - 7 Jun 2022

Cited by 1 | Viewed by 1517

Abstract

The main building materials widely used worldwide are those based on cement, glass, and ceramics. Taking into account the fact that the raw material base for the production of these materials is narrowing, and the quality of raw materials is declining, methods are [...] Read more.

The main building materials widely used worldwide are those based on cement, glass, and ceramics. Taking into account the fact that the raw material base for the production of these materials is narrowing, and the quality of raw materials is declining, methods are being used to modify the structure of silicate materials in order to improve their properties when using cheaper raw materials and industrial waste, which should help reduce the energy intensity of their production. One of the ways to reduce energy consumption is the use of alkaline components in the chemical composition of silicate materials, which makes it possible to reduce the temperature of their synthesis. However, the presence of alkalis in the material at the stage of the operation is undesirable since it contributes, for example, to a decrease in the chemical resistance of silicate glasses or leads to the phenomenon of alkaline corrosion in cement products. In this regard, in order to reduce the negative impact of alkalis, it is necessary to extract them from the surface layers of the silicate material. There are various methods for extracting alkalis from silicate materials, some of which are presented in this article. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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