Ceramics: Processes, Microstructures, and Properties

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Polycrystalline Ceramics".

Deadline for manuscript submissions: 1 June 2024 | Viewed by 5019

Special Issue Editors

School of Engineering Science, University of Science and Technology of China, Hefei 230026, China
Interests: 3D/4D additive–subtractive manufacturing; shape memory ceramics; intelligent manufacturing equipment
School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Interests: ceramics; additive manufacturing; 3D printing; application
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Institute of Advanced Structure Technology, Beijing Institute of Technology, Beijing 100081, China
Interests: structural ceramics; ceramic matrix composites
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Relative to polymers and metals, the processing of ceramics is challenging due to their extremely high melting points. The development of polymer-derived ceramics, prepared through the thermolysis of polymeric ceramic precursors, offers potential for manufacturing ceramics with tuneable microstructures and properties. Additive manufacturing (AM), also known as three-dimensional printing, has boomed over the last 30-40 years. AM is a material-oriented manufacturing technology, and printing resolution versus printing scalability/speed trade-off exists among various types of ceramic materials. The AM of ceramic structures is typically achieved with powder/slurry-based ceramic printing feedstocks, coating-film-based ceramic printing feedstocks, and polymeric precursor-based ceramic printing feedstocks. The rapid development of AM and other ceramic processing technologies is expected to broaden the applications of ceramic materials in aerospace, biomedical, electronics, and art fields. This Special Issue is mainly focused on the ceramic processes and microstructure of ceramics, including (but not limited to) the additive manufacturing of ceramics, ceramic matrix composites, polymer-derived ceramics, the microstructure of ceramics, materials characterization, thermal/environment barrier coatings, and bio-ceramics. 

Dr. Guo Liu
Dr. Jiamin Wu
Dr. Rujie He
Guest Editors

Manuscript Submission Information

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Keywords

  • additive manufacturing of ceramics
  • ceramic matrix composites
  • polymer-derived ceramics
  • microstructure of ceramics
  • materials characterization
  • thermal/environment barrier coatings
  • bio-ceramics

Published Papers (5 papers)

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Research

15 pages, 20842 KiB  
Article
High-Temperature Tribological Behavior of Fast-Hot-Pressed NiCr/Cr3C2-LaF3 Self-Lubrication Composite
by Hao Yang, Chuanbing Huang, Haozhong Lv, Yongjun Liu, Yonghui Sun, Huifeng Zhang, Hao Lan, Yang Wu and Weigang Zhang
Crystals 2024, 14(4), 365; https://doi.org/10.3390/cryst14040365 - 12 Apr 2024
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Abstract
This article details a method for preparing cermet matrix composites via Fast hot pressing (FHP) sintering technology and emphasizes their potential use in extremely high-temperature settings. The material primarily consists of NiCr alloy, Cr3C2, and LaF3. An [...] Read more.
This article details a method for preparing cermet matrix composites via Fast hot pressing (FHP) sintering technology and emphasizes their potential use in extremely high-temperature settings. The material primarily consists of NiCr alloy, Cr3C2, and LaF3. An in-depth investigation was conducted on the tribological properties of the specimen by conducting sliding tests against a Si3N4 ball at varying temperatures, including room temperature (RT), 400 °C, 600 °C, and 800 °C. Advanced techniques such as scanning electron microscopy, micro-XRD, and micro-Raman spectroscopy were employed to examine the friction surfaces formed under different frictional temperatures. The findings reveal a uniform composition and high density within the composites. It is noteworthy that as the LaF3 content increases, the hardness of the ceramic phase diminishes. Conversely, the hardness of the alloy phase augments with the addition of LaF3, provided that its content remains below 15 wt%. The composite material containing 15 wt% LaF3 demonstrates superior hardness values, with the ceramic phase reaching HV1412 and the alloy phase achieving HV384. Furthermore, the coefficient of friction of the composite material was evaluated. The coefficient of friction of the composite is between 0.74 and 0.4 and the wear rate is 4.46 × 10−6–5.72 × 10−5 mm3N−1m−1 from room temperature to 800 °C. The lubrication behavior at low temperature is mainly attributed to the lubricating effect of LaF3, and at high temperature it is due to the tribochemical reaction to form LaCrO3 with good lubricating properties, which plays a synergistic lubricating role with Cr2O3. Full article
(This article belongs to the Special Issue Ceramics: Processes, Microstructures, and Properties)
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13 pages, 5885 KiB  
Article
Structural Evolution and Mechanical Behavior of Ytterbia Doped Hafnia Biphasic Ceramics under Annealing at 1500 °C
by Yang Wu, Hao Lan, Xiaoming Sun, Zihao Hu, Yonghui Sun, Huifeng Zhang, Chuanbing Huang and Weigang Zhang
Crystals 2024, 14(3), 279; https://doi.org/10.3390/cryst14030279 - 15 Mar 2024
Viewed by 687
Abstract
HfO2 has become a promising thermal barrier coating material due to its similarity in structure and chemical properties with ZrO2 and its higher phase structure transition temperature. However, the fracture toughness of HfO2 is not ideal, greatly limiting its application. [...] Read more.
HfO2 has become a promising thermal barrier coating material due to its similarity in structure and chemical properties with ZrO2 and its higher phase structure transition temperature. However, the fracture toughness of HfO2 is not ideal, greatly limiting its application. In this report, we find a special sandwich structure of ceramics, comprising a cubic (C) phase /monoclinic (M) phase/cubic (C) phase. The microstructural evolution and mechanical properties of these ceramics were investigated under annealing at 1500 °C. The results indicate that, with an increase in annealing duration, there was a gradual augmentation in the proportion of the monoclinic (M) phase and the fracture toughness increased from 2.18 MPa·m0.5 to 2.83 MPa·m0.5 after 48 h of annealing, which is higher than many potential TBC materials. The residual compressive stress present in the M phases during the progression of crack propagation served to facilitate the bridging and deflection of cracks. As such, this process led to the alleviation of stress concentration at the crack tip, ultimately enhancing the toughening effect. Full article
(This article belongs to the Special Issue Ceramics: Processes, Microstructures, and Properties)
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12 pages, 10232 KiB  
Article
Rapid Growth of Niobium Oxide Nanowires by Joule Resistive Heating
by Aarón Calvo-Villoslada, Paloma Fernández and Belén Sotillo
Crystals 2024, 14(3), 245; https://doi.org/10.3390/cryst14030245 - 1 Mar 2024
Viewed by 989
Abstract
Joule heating of niobium (Nb) metal wires by running a high electric current density through them has been used to grow Nb2O5 nanowires. The formation of a micrometric oxide layer on the Nb wires has also been observed. The size [...] Read more.
Joule heating of niobium (Nb) metal wires by running a high electric current density through them has been used to grow Nb2O5 nanowires. The formation of a micrometric oxide layer on the Nb wires has also been observed. The size and density of the nanowires are related to the current values applied, as well as the thickness of the oxide layer formed. Characterization of both nanowires and oxide layer has been performed using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, and micro-Raman spectroscopy. It has been observed that this method allows the growth of Nb2O5 nanowires in times as short as tens of seconds. Full article
(This article belongs to the Special Issue Ceramics: Processes, Microstructures, and Properties)
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19 pages, 4398 KiB  
Article
Effect of TiO2 on the Microstructure and Flexural Strength of Lunar Regolith Simulant
by Junhao Chen, Haoming Chen, Zhe Zhao and Xiao Zong
Crystals 2024, 14(2), 110; https://doi.org/10.3390/cryst14020110 - 23 Jan 2024
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Abstract
Lunar regolith is the preferred material for lunar base construction using in situ resource utilization technology. The TiO2 variations in lunar regolith collected from different locations significantly impact its suitability as a construction material. Therefore, it is crucial to investigate the effects [...] Read more.
Lunar regolith is the preferred material for lunar base construction using in situ resource utilization technology. The TiO2 variations in lunar regolith collected from different locations significantly impact its suitability as a construction material. Therefore, it is crucial to investigate the effects of TiO2 on the properties of lunar regolith. This study aims to evaluate the influence of TiO2 content and sintering temperature on phase transformation, microstructure, and macroscopic properties (e.g., the shrinkage rate, mechanical properties, and relative density) of lunar regolith simulant samples (CUG-1A). The flexural strength and relative density of the sample with a TiO2 content of 6 wt% sintered at 1100 °C reached 136.66 ± 4.92 MPa and 91.06%, which were 65% and 12.28% higher than those of the sample not doped with TiO2, respectively. The experiment demonstrated that the doped TiO2 not only reacted with Fe to form pseudobrookite (Fe2TiO5) but also effectively reduced the viscosity of the glass phase during heat treatment. As the sintering temperature increased, the particles underwent a gradual melting process, leading to a higher proportion of the liquid phase. The higher liquid-phase content had a positive impact on the diffusion of mass transfer, causing the voids and gaps between particles to shrink. This shrinkage resulted in greater density and, ultimately, improved the mechanical properties of the material. Full article
(This article belongs to the Special Issue Ceramics: Processes, Microstructures, and Properties)
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11 pages, 2875 KiB  
Article
Unveiling the Transporting Mechanism of (Ti0.2Zr0.2Nb0.2Hf0.2Ta0.2)C at Room Temperature
by Tao Liu, Liwen Lei, Jinyong Zhang and Neng Li
Crystals 2023, 13(4), 708; https://doi.org/10.3390/cryst13040708 - 21 Apr 2023
Viewed by 1380
Abstract
High-entropy materials have been widely researched in recent years, and more work on their thermal and electrical properties is still needed. Herein, we fabricate a high-entropy carbide (Ti0.2Zr0.2Nb0.2Hf0.2Ta0.2)C ceramic and report the thermal [...] Read more.
High-entropy materials have been widely researched in recent years, and more work on their thermal and electrical properties is still needed. Herein, we fabricate a high-entropy carbide (Ti0.2Zr0.2Nb0.2Hf0.2Ta0.2)C ceramic and report the thermal and electrical conductivity at room temperature using first-principles calculations and experiments. The movement of phonons is suppressed in high-entropy carbides when analyzing the thermal and electrical conductivity at room temperature, but the movement of electrons is not. After the first-principles calculations on the electronic structure and lattice vibration and experiments, we give the reasons why the rule of mixture can predict electrical conductivity but not thermal conductivity at room temperature. Finally, we outline the cause of the similar lattice patterns between TaC and (Ti0.2Zr0.2Nb0.2Hf0.2Ta0.2)C. Full article
(This article belongs to the Special Issue Ceramics: Processes, Microstructures, and Properties)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

The sintering mechanism of Si3N4 ceramics with SmF3 as sintering additives using gas pressure sintering

Shengwu Huang, Yanhui Li, Xingchen Yan

Abstract: Silicon nitride (Si3N4) ceramics are widely used in electronic devices due to their outstanding mechanical properties and high thermal conductivity. The thermal conductivity of Si3N4 ceramics is mainly affected by the density and microstructure, as porosity, grain size, grain orientation, grain boundary phase, and lattice oxygen. In this paper, the results revealed that the inclusion of an appropriate amount of SmF3 can effectively enhance the densification process and purity oxygen in Si3N4 grain boundary through the reaction between SmF3 and SiO2 on the surface of Si3N4 particles.

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