Research

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13 pages, 4166 KiB

Open AccessArticle

Effect of Co-Doping of Al³⁺, In³⁺, and Y³⁺ on the Electrical Properties of Zinc Oxide Varistors under Pre-Synthesizing BiSbO₄

by Bo Xu, Lei Wang, Mengfan Yang, Yu Xiang and Lingyun Liu

Materials 2024, 17(6), 1401; https://doi.org/10.3390/ma17061401 - 19 Mar 2024

Viewed by 444

Abstract

Under the premise of using the solid-phase method to pre-sinter Bi₂O₃ and Sb₂O₃ into BiSbO₄ as a substitute for equal amounts of Bi₂O₃ and Sb₂O₃ in the formula, the effects [...] Read more.

Under the premise of using the solid-phase method to pre-sinter Bi₂O₃ and Sb₂O₃ into BiSbO₄ as a substitute for equal amounts of Bi₂O₃ and Sb₂O₃ in the formula, the effects of co-doping with In(NO₃)₃, Al(NO₃)₃, and Y(NO₃)₃ on the microstructure and electrical properties of ZnO varistors were studied. The experimental results show that with an increase in In³⁺-doped molar concentration, the leakage current of the ZnO varistor shows a rapid decrease and then a slow increase trend. However, the nonlinear coefficient is the opposite of it. With the combined effect of the rare earth element Y³⁺, the average grain size is significantly reduced, which leads to an increase in the voltage gradient. At the same time, a certain amount of doped In³⁺ and Al³⁺ is dissolved into the grains, resulting in a decrease in grain resistance and thus a low level of residual voltage. The varistor with 0.6 mol% In³⁺, 0.1 mol% Al³⁺, and 0.9 mol% Y³⁺ doping ratios exhibits excellent overall performance. The nonlinear coefficient is 62.2, with the leakage current being 1.46 µA/cm² and the voltage gradient being 558 V/mm, and the residual voltage ratio is 1.73. The prepared co-doped ZnO varistors will provide better protection for metal oxide surge arresters. Full article

(This article belongs to the Special Issue Advances in Functional Ceramic Materials: Fabrication, Properties, and High-Temperature Applications)

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24 pages, 9742 KiB

Open AccessArticle

Comparison of Additively Manufactured Polymer-Ceramic Parts Obtained via Different Technologies

by Katarzyna Jasik, Janusz Kluczyński, Danuta Miedzińska, Arkadiusz Popławski, Jakub Łuszczek, Justyna Zygmuntowicz, Paulina Piotrkiewicz, Krzysztof Perkowski, Marcin Wachowski and Krzysztof Grzelak

Materials 2024, 17(1), 240; https://doi.org/10.3390/ma17010240 - 01 Jan 2024

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Abstract

This paper aims to compare two ceramic materials available for additive manufacturing (AM) processes—vat photopolymerization (VPP) and material extrusion (MEX)—that result in fully ceramic parts after proper heat treatment. The analysis points out the most significant differences between the structural and mechanical properties [...] Read more.

This paper aims to compare two ceramic materials available for additive manufacturing (AM) processes—vat photopolymerization (VPP) and material extrusion (MEX)—that result in fully ceramic parts after proper heat treatment. The analysis points out the most significant differences between the structural and mechanical properties and the potential application of each AM technology. The research revealed different behaviors for the specimens obtained via the two mentioned technologies. In the case of MEX, the specimens exhibited similar microstructures before and after heat treatment. The sintering process did not affect the shape of the grains, only their size. For the VPP specimens, directly after the manufacturing process, irregular grain shapes were registered, but after the sintering process, the grains fused, forming a solid structure that made it impossible to outline individual grains and measure their size. The highest compression strength was 168 MPa for the MEX specimens and 81 MPa for the VPP specimens. While the VPP specimens had half the compression strength, the results for the VPP specimens were significantly more repeatable. Full article

(This article belongs to the Special Issue Advances in Functional Ceramic Materials: Fabrication, Properties, and High-Temperature Applications)

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18 pages, 4700 KiB

Open AccessEditor’s ChoiceArticle

Ultra-High-Temperature Ceramic-Doped Inorganic Polymers for Thermo-Structural Fiber-Reinforced Composites

by Valentina Medri, Annalisa Natali Murri, Elettra Papa, Claudio Mingazzini, Matteo Scafè and Elena Landi

Materials 2023, 16(20), 6649; https://doi.org/10.3390/ma16206649 - 11 Oct 2023

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Abstract

New inorganic nanostructured matrices for fiber-reinforced composites with enhanced high-temperature stability were developed from alkali aluminosilicate polymers doped with different ultra-high-temperature ceramic (UHTC) particles. The alkali aluminosilicate matrices were synthesized at room temperature with a high SiO₂:Al₂O₃ ratio [...] Read more.

New inorganic nanostructured matrices for fiber-reinforced composites with enhanced high-temperature stability were developed from alkali aluminosilicate polymers doped with different ultra-high-temperature ceramic (UHTC) particles. The alkali aluminosilicate matrices were synthesized at room temperature with a high SiO₂:Al₂O₃ ratio and then further functionalized by doping with 4–5 wt % of micrometric SiC, ZrB₂, ZrC, and HfC powders and finally thermally stabilized as glass–ceramics at 750 °C. The different UHTC-doped matrices were characterized according to their dimensional and microstructural changes after thermal cycling in air flux at 1000 °C. The first results showed that carbide-based UHTC powders improved the thermal stability of the matrices, preventing the excessive swelling of the material and the formation of detrimental voids that might result in the lack of adhesion with reinforcing fibers. Contrarily, the addition of ZrB₂ resulted in an excessive matrix swelling at high temperature, thus proving no efficacy compared to the undoped matrix. Impregnation tests carried out on C-fiber fabrics showed good processability, adhesion to the fibers, and fracture pull-out, especially for carbide-based matrices. Full article

(This article belongs to the Special Issue Advances in Functional Ceramic Materials: Fabrication, Properties, and High-Temperature Applications)

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10 pages, 5466 KiB

Open AccessArticle

Ni-Infiltrated Spherical Porcelain Support as Potential Steam Reforming Microchannel Reactor

by Sandrine Ricote and William Grover Coors

Materials 2023, 16(4), 1519; https://doi.org/10.3390/ma16041519 - 11 Feb 2023

Viewed by 794

Abstract

This paper describes the fabrication of kaolinite (Al₂O₃-2SiO₂-2H₂O) spherical bulbs by slip casting. The bisque-fired parts present a porosity of about 30% with submicron porosity confirmed by scanning electron microscopy. In addition, plate-like grains with [...] Read more.

This paper describes the fabrication of kaolinite (Al₂O₃-2SiO₂-2H₂O) spherical bulbs by slip casting. The bisque-fired parts present a porosity of about 30% with submicron porosity confirmed by scanning electron microscopy. In addition, plate-like grains with channels were observed. After nickel infiltration of the specimens, nanosized Ni particles covered the surfaces of the channels of these grains. Permeation tests in 5% H₂ at 400 and 600 °C resulted in fluxes between 0.05 and 0.06 mol·m⁻²·s⁻¹ at a pressure gradient of 200 MPa·m⁻¹. Potential applications of these specimens include supports for hydrocarbon (namely ethanol) steam reforming. Full article

(This article belongs to the Special Issue Advances in Functional Ceramic Materials: Fabrication, Properties, and High-Temperature Applications)

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11 pages, 4842 KiB

Open AccessArticle

Fabrication of MgO-Y₂O₃ Composite Nanopowders by Combining Hydrothermal and Seeding Methods

by Shangyu Yang, Hao Lan, Xiaoming Sun, Shaowei Feng and Weigang Zhang

Materials 2023, 16(1), 126; https://doi.org/10.3390/ma16010126 - 23 Dec 2022

Cited by 2 | Viewed by 1445

Abstract

In this study, the combination of hydrothermal technique and seed-doping method was conducted to coordinately control the formation of fine MgO-Y₂O₃ powders, which are promising mid-infrared materials applied to hypersonic aircraft windows due to their excellent infrared transmissions over wide [...] Read more.

In this study, the combination of hydrothermal technique and seed-doping method was conducted to coordinately control the formation of fine MgO-Y₂O₃ powders, which are promising mid-infrared materials applied to hypersonic aircraft windows due to their excellent infrared transmissions over wide regions. Y(NO₃)₃·6H₂O, Mg(NO₃)₂·6H₂O, Y₂O₃ seeds and MgO seeds were used as raw materials to prepare the MgO-Y₂O₃ composite powders (50:50 vol.%), and the influences of the seed contents and hydrothermal treatment temperatures on the final powders and hot-pressed ceramics were investigated by XRD, SEM and TEM techniques. The results show that powders with a seed content of 5% that are hydrothermally synthesized at 190 °C can present a better uniformity and dispersion with a particle size of ~125 nm. Furthermore, the ceramics prepared with the above powders displayed a homogenous two-phase microstructure, fewer pores and a fine grain size with Y₂O₃ of ~1 µm and MgO of ~620 nm. The present study may open an avenue for developing transparent ceramics based on MgO-Y₂O₃ nanopowders prepared by hydrothermal technique. Full article

(This article belongs to the Special Issue Advances in Functional Ceramic Materials: Fabrication, Properties, and High-Temperature Applications)

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13 pages, 6963 KiB

Open AccessArticle

Influence of Sb³⁺ Cations on the Structural, Magnetic and Electrical Properties of AlFeO₃ Multiferroic Perovskite with Humidity Sensors Applicative Characteristics

by Iulian Petrila and Florin Tudorache

Materials 2022, 15(23), 8369; https://doi.org/10.3390/ma15238369 - 24 Nov 2022

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Abstract

The effects of Sb³⁺ cations substitution on the structural, magnetic and electrical properties of Al_1−xSb_xFeO₃ multiferroic perovskite are investigated. The partial or total substitution of Al³⁺ cations with Sb³⁺ cations, in stoichiometric composition Al_1−x [...] Read more.

The effects of Sb³⁺ cations substitution on the structural, magnetic and electrical properties of Al_1−xSb_xFeO₃ multiferroic perovskite are investigated. The partial or total substitution of Al³⁺ cations with Sb³⁺ cations, in stoichiometric composition Al_1−xSb_xFeO₃ (x = 0.00, 0.25, 0.50, 0.75 and 1.00) were made in order to identify composite materials with sensors applicative properties. Multiferroic perovskite samples were prepared following technology of the ceramic solid-state method, and the thermal treatments were performed in air atmosphere at 1100 °C temperature. The X-ray diffraction studies have confirmed the phase composition of samples and scanning electron microscopy the shape of the crystallites has been evidenced. The perovskite material was subjected to representative magnetic investigations in order to highlight substitutions characteristics. Investigations on electrical properties have evidenced the substitution dependence of relative permittivity and electrical resistivity under humidity influence and the characteristics of humidity sensors based on this material. The results are discussed in term of microstructural changes induced by the substitutions degree and its sensor applicative effects. Full article

(This article belongs to the Special Issue Advances in Functional Ceramic Materials: Fabrication, Properties, and High-Temperature Applications)

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Review

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29 pages, 9500 KiB

Open AccessEditor’s ChoiceReview

Zirconium Carbide for Hypersonic Applications, Opportunities and Challenges

by Glenn R. Peterson, Ryan E. Carr and Ernesto E. Marinero

Materials 2023, 16(18), 6158; https://doi.org/10.3390/ma16186158 - 11 Sep 2023

Viewed by 1140

Abstract

At ultra-high temperatures, resilient, durable, stable material choices are limited. While Carbon/Carbon (C/C) composites (carbon fibers and carbon matrix phases) are currently the materials of choice, zirconium carbide (ZrC) provides an option in hypersonic environments and specifically in wing leading edge (WLE) applications. [...] Read more.

At ultra-high temperatures, resilient, durable, stable material choices are limited. While Carbon/Carbon (C/C) composites (carbon fibers and carbon matrix phases) are currently the materials of choice, zirconium carbide (ZrC) provides an option in hypersonic environments and specifically in wing leading edge (WLE) applications. ZrC also offers an ultra-high melting point (3825 K), robust mechanical properties, better thermal conductivity, and potentially better chemical stability and oxidation resistance than C/C composites. In this review, we discuss the mechanisms behind ZrC mechanical, thermal, and chemical properties and evaluate: (a) mechanical properties: flexure strength, fracture toughness, and elastic modulus; (b) thermal properties: coefficient of thermal expansion (CTE), thermal conductivity, and melting temperature; (c) chemical properties: thermodynamic stability and reaction kinetics of oxidation. For WLE applications, ZrC physical properties require further improvements. We note that materials or processing solutions to increase its relative density through sintering aids can have deleterious effects on oxidation resistance. Therefore, improvements of key ZrC properties for WLE applications must not compromise other functional properties. We suggest that C/C-ZrC composites offer an engineering solution to reduce density (weight) for aerospace applications, improve fracture toughness and the mechanical response, while addressing chemical stability and stoichiometric concerns. Recommendations for future work are also given. Full article

(This article belongs to the Special Issue Advances in Functional Ceramic Materials: Fabrication, Properties, and High-Temperature Applications)

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34 pages, 5241 KiB

Open AccessEditor’s ChoiceReview

Radiopaque Crystalline, Non-Crystalline and Nanostructured Bioceramics

by Maziar Montazerian, Geovanna V. S. Gonçalves, Maria E. V. Barreto, Eunice P. N. Lima, Glauber R. C. Cerqueira, Julyana A. Sousa, Adrine Malek Khachatourian, Mairly K. S. Souza, Suédina M. L. Silva, Marcus V. L. Fook and Francesco Baino

Materials 2022, 15(21), 7477; https://doi.org/10.3390/ma15217477 - 25 Oct 2022

Cited by 10 | Viewed by 3327

Abstract

Radiopacity is sometimes an essential characteristic of biomaterials that can help clinicians perform follow-ups during pre- and post-interventional radiological imaging. Due to their chemical composition and structure, most bioceramics are inherently radiopaque but can still be doped/mixed with radiopacifiers to increase their visualization [...] Read more.

Radiopacity is sometimes an essential characteristic of biomaterials that can help clinicians perform follow-ups during pre- and post-interventional radiological imaging. Due to their chemical composition and structure, most bioceramics are inherently radiopaque but can still be doped/mixed with radiopacifiers to increase their visualization during or after medical procedures. The radiopacifiers are frequently heavy elements of the periodic table, such as Bi, Zr, Sr, Ba, Ta, Zn, Y, etc., or their relevant compounds that can confer enhanced radiopacity. Radiopaque bioceramics are also intriguing additives for biopolymers and hybrids, which are extensively researched and developed nowadays for various biomedical setups. The present work aims to provide an overview of radiopaque bioceramics, specifically crystalline, non-crystalline (glassy), and nanostructured bioceramics designed for applications in orthopedics, dentistry, and cancer therapy. Furthermore, the modification of the chemical, physical, and biological properties of parent ceramics/biopolymers due to the addition of radiopacifiers is critically discussed. We also point out future research lacunas in this exciting field that bioceramists can explore further. Full article

(This article belongs to the Special Issue Advances in Functional Ceramic Materials: Fabrication, Properties, and High-Temperature Applications)

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