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Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications
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Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Physics".

Deadline for manuscript submissions: closed (1 March 2023) | Viewed by 30438

Special Issue Editors

Dr. Zhong Huang

E-Mail Website
Guest Editor
The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science & Technology, Wuhan, China
Interests: functional refractory; refractory castable; powder technology; porous ceramic; nanomaterials
Special Issues, Collections and Topics in MDPI journals
Dr. Bin Li

E-Mail Website
Guest Editor
School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, China
Interests: refractory; structure ceramics; nanomaterials; high-temperature ceramic; powder technology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Refractories, as a class of ceramics with high fusion points, are basic materials in high-temperature industries such as metallurgy, cement/glass production, and thermal power. Today, “new refractory” is being developed to not only meet high-temperature structural support, but also to be designed or tailored to special functional requirements, such as the purification of liquid steel, energy conservation, and pollution reduction. In terms of eco-friendliness, long life, and safety, the overall performance (e.g., mechanical strength, thermal/chemical stability, corrosion/oxidation/thermal shock resistances, workability) of “new refractory” can be greatly improved with the development of new material systems, precise control of microstructures, and use of intelligent manufacturing technology. 

The “new refractory” is extending the frontiers of design and preparation of traditional high-temperature ceramics and allows significant improvements in high-temperature industries on economic and environmental impacts. In addition, the “structure–function” relationship of these ceramics as related to their high-temperature service performance should be known for every application.

This Special Issue focuses on the development of new refractories and novel ceramics. The potential topics concerning their microstructure, properties, and applications include but are not limited to:

  • Functional refractory;
  • Novel ceramics;
  • Non-oxide ceramics;
  • High-temperature heat-insulating materials;
  • Green ecological refractory;
  • Refractory castable;
  • Refractory raw materials;
  • High-temperature behavior.

Dr. Zhong Huang
Dr. Bin Li
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • refractory
  • ceramic
  • non-oxide
  • castable
  • green refractory
  • raw material
  • microstucture
  • high-temperature behavior

Related Special Issue

Published Papers (20 papers)

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Research

11 pages, 3297 KiB  
Article
Effects of Sodium Tripolyphosphate Addition on the Dispersion and Hydration of Pure Calcium Aluminate Cement
by Benjun Cheng, Hao Feng, Erbolat Armia, Hongli Guo, Shaowei Zhang and Haijun Zhang
Materials 2023, 16(8), 3141; https://doi.org/10.3390/ma16083141 - 16 Apr 2023
Cited by 1 | Viewed by 1515
Abstract
In this paper, the effect of a sodium tripolyphosphate (STPP) addition on the dispersion and hydration of pure calcium aluminate cement (PCAC) was investigated, and the corresponding mechanism of effect was studied. The effects of STPP on the dispersion, rheology, and hydration processes [...] Read more.
In this paper, the effect of a sodium tripolyphosphate (STPP) addition on the dispersion and hydration of pure calcium aluminate cement (PCAC) was investigated, and the corresponding mechanism of effect was studied. The effects of STPP on the dispersion, rheology, and hydration processes of PCAC and its adsorption capacity on the surface of cement particles were analysed by measuring the 𝜁-potential on the surface of cement particles, the changes in the concentrations of elemental P and Ca2+ ions in a solution at different STPP additions. The experimental results show that STPP easily complexes with Ca2+ ions to produce the complex [CaP3O10]3− adsorbed on the surface of cement particles, which changes the potential on the surface of cement particles and increases the electrostatic repulsive force between cement particles, thus improving the dispersion and rheology of cement. At the same time, the contact area between cement particles and water is reduced, which hinders the hydration process and makes the time of hydration process longer. A comprehensive analysis shows that the best effect of STPP on pure calcium aluminate cements is achieved when the addition of STPP is 0.2%. This study can provide a reference for the addition of water-reducing agents in refractory castables as well as improving the quality of refractory materials. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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11 pages, 3024 KiB  
Article
First Principles Calculation of Adsorption of Water on MgO (100) Plane
by Bin Li, Hongqiang Chen, Jisheng Feng, Qiao Ma, Junhong Chen, Bo Ren, Shu Yin and Peng Jiang
Materials 2023, 16(5), 2100; https://doi.org/10.3390/ma16052100 - 5 Mar 2023
Cited by 1 | Viewed by 1490
Abstract
The hydration reaction seriously affects the quality and performance of MgO-based products. The final analysis showed that the problem is the surface hydration of MgO. By studying the adsorption and reaction of water molecules on the surface of MgO, we can understand the [...] Read more.
The hydration reaction seriously affects the quality and performance of MgO-based products. The final analysis showed that the problem is the surface hydration of MgO. By studying the adsorption and reaction of water molecules on the surface of MgO, we can understand the nature of the problem from the root cause. In this paper, first-principles calculations are performed on the crystal plane of MgO (100) to study the influence of the different orientation, sites and coverage of water molecules on the surface adsorption. The results show that the adsorption sites and orientations of monomolecular water has no effect on the adsorption energy and adsorption configuration. The adsorption of monomolecular water is unstable, with almost no charge transfer, belonging to the physical adsorption, which implies that the adsorption of monomolecular water on MgO (100) plane will not lead to the dissociation of water molecule. When the coverage of water molecules exceeds 1, water molecules will dissociate, and the population value between Mg and Os-H will increase, leading to the formation of ionic bond. The density of states of O p orbital electrons changes greatly, which plays an important role in surface dissociation and stabilization. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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12 pages, 3542 KiB  
Article
Investigations of Photoluminescence Properties of CaxMg2-xSi2O6:yEu2+ (x = 0.5–1.25, y = 0.015–0.035) Phosphors
by Juan Lu, Chia-Ching Su, Cheng-Shong Hong, Guoxiang Peng and Cheng-Fu Yang
Materials 2023, 16(5), 2032; https://doi.org/10.3390/ma16052032 - 1 Mar 2023
Cited by 1 | Viewed by 1030
Abstract
Previously, there were almost no relevant studies on developing the optimal CaxMg2-xSi2O6:yEu2+ phosphor composition for its finest optical properties. This study employs two steps to determine the optimal composition for CaxMg2-x [...] Read more.
Previously, there were almost no relevant studies on developing the optimal CaxMg2-xSi2O6:yEu2+ phosphor composition for its finest optical properties. This study employs two steps to determine the optimal composition for CaxMg2-xSi2O6:yEu2+ phosphors. First, CaMgSi2O6:yEu2+ (y = 0.015, 0.020, 0.025, 0.030, 0.035) was used as the primary composition of specimens synthesised in a reducing atmosphere of 95% N2 + 5% H2 to investigate the effect of Eu2+ ions on the photoluminescence properties of each variant. The emission intensities of the entire photoluminescence excitation (PLE) and photoluminescence (PL) emission spectra of the CaMgSi2O6:yEu2+ phosphors initially increased as the concentration of the Eu2+ ions increased, peaking at y = 0.025. The cause of the variations across the entire PLE and PL spectra of all five CaMgSi2O6:yEu2+ phosphors was investigated. Because the CaMgSi2O6:0.025Eu2+ phosphor had the highest PLE and PL emission intensities, in the next step, CaxMg2-xSi2O6:0.025Eu2+ (x = 0.5, 0.75, 1.0, 1.25) was used as the primary composition to investigate the effect on the photoluminescence properties when the CaO content varied. We also show that the Ca content has an apparent effect on the photoluminescence properties of CaxMg2-xSi2O6:0.025Eu2+ phosphors, and the optimal phosphor composition is Ca0.75Mg1.25Si2O6:0.025Eu2+ because it has the largest PLE and PL values. X-ray diffraction (XRD) analyses of CaxMg2-xSi2O6:0.025Eu2+ phosphors were performed to identify the factors responsible for this outcome. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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13 pages, 19062 KiB  
Article
Effect of In Situ Mg-Sialon on the Oxidation Behavior of Low-Carbon MgO-C Refractories
by Bo Dong, Chao Yu, Guangchao Xing, Jinghui Di, Jun Ding, Qingyou Zhu, Hongxi Zhu and Chengji Deng
Materials 2023, 16(5), 1892; https://doi.org/10.3390/ma16051892 - 24 Feb 2023
Cited by 4 | Viewed by 1167
Abstract
The in situ Mg-sialon in low-carbon MgO-C refractories was studied with respect to its oxidation behavior and mechanism at 1500 °C. The results indicated that the oxidation index and rate constant of low-carbon MgO-C refractories with Mg-sialon were 26.2% and 0.51 × 10 [...] Read more.
The in situ Mg-sialon in low-carbon MgO-C refractories was studied with respect to its oxidation behavior and mechanism at 1500 °C. The results indicated that the oxidation index and rate constant of low-carbon MgO-C refractories with Mg-sialon were 26.2% and 0.51 × 10−3 cm2/min at 1500 °C for 2 h, respectively. The formation of a dense MgO-Mg2SiO4-MgAl2O4 protective layer contributed to considerable oxidation resistance, and the generation of this thicker layer was due to the combined volume effect of Mg2SiO4 and MgAl2O4. The reduced porosity and more complex pore structure were also found in the refractories with Mg-sialon. Therefore, further oxidation was restricted as the oxygen diffusion path was effectively blocked. This work proves the potential application of Mg-sialon in improving the oxidation resistance of low-carbon MgO-C refractories. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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14 pages, 7464 KiB  
Article
Improved Mechanical Properties of Alumina Ceramics Using Plasma-Assisted Milling Technique
by Shaopeng Tang, Lvping Fu, Huazhi Gu, Ao Huang, Shuang Yang and Renxiang Lv
Materials 2023, 16(3), 1128; https://doi.org/10.3390/ma16031128 - 28 Jan 2023
Cited by 9 | Viewed by 1356
Abstract
In order to improve the mechanical properties of alumina ceramics, dielectric barrier discharge plasma-assisted milling (DBDPM) was employed to activate alumina powder. The effect of the plasma-assisted milling technique on the grinding behavior of alumina powder, as well as the microstructure and properties [...] Read more.
In order to improve the mechanical properties of alumina ceramics, dielectric barrier discharge plasma-assisted milling (DBDPM) was employed to activate alumina powder. The effect of the plasma-assisted milling technique on the grinding behavior of alumina powder, as well as the microstructure and properties of fabricated alumina ceramic, was investigated in detail. Attributed to the great thermal stress induced via plasma heating, DBDPM showed significantly higher grinding efficiency than the common vibratory milling technique. Moreover, the lattice distortion of alumina grains occurred with the application of plasma, leading to an improved sintering activity of the produced alumina powders. Therefore, compared with the common vibratory milling technique, the fabricated alumina ceramics exhibited smaller grain sizes and improved mechanical properties when using alumina powder produced via the DBDPM method as the starting material. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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10 pages, 13274 KiB  
Article
Improvement of Mechanical Properties of Composites with Surface Modified B4C for Precision Machining
by Jun Ding, Jintao Wang, Hao Yang, Zhenglong Liu, Chao Yu, Xiangcheng Li, Chengji Deng and Hongxi Zhu
Materials 2023, 16(2), 882; https://doi.org/10.3390/ma16020882 - 16 Jan 2023
Cited by 2 | Viewed by 1440
Abstract
In order to solve the problem of difficult sintering and high brittleness of B4C-based ceramics, B4C@ZrB2-TiB2 composite powder was synthesized by molten salt method, and B4C–(Zr, Ti)B2 composite ceramics were successfully prepared by [...] Read more.
In order to solve the problem of difficult sintering and high brittleness of B4C-based ceramics, B4C@ZrB2-TiB2 composite powder was synthesized by molten salt method, and B4C–(Zr, Ti)B2 composite ceramics were successfully prepared by spark plasma sintering. The effects of different raw material ratios on the composition, microstructure, and mechanical properties of the prepared composite ceramics were characterized by XRD, XPS, SEM, and TEM. The results show that ZrB2 and TiB2 were grown on the surface of B4C by template mechanism to form a dense nanocrystalline coating, and the original surface of B4C was exposed gradually with the decrease of the ratio of metal powder. When the composite powders were sintered at 1700 °C, ZrB2 and TiB2 formed a solid solution, which can refine grains and improve strength. When the raw material ratio is n(B4C): n(Zr): n(Ti) = 12:1:1, the composite ceramics have excellent comprehensive properties, the Vickers hardness reaches 41.2 GPa. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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14 pages, 7549 KiB  
Article
Corrosion Behavior of Cobalt Oxide and Lithium Carbonate on Mullite–Cordierite Saggar Used for Lithium Battery Cathode Material Sintering
by Zhenhua Sun, Shaopeng Li, Huiquan Li, Mingkun Liu, Zhanbing Li, Xianjie Liu, Mingyong Liu, Qiyun Liu and Zhaohui Huang
Materials 2023, 16(2), 653; https://doi.org/10.3390/ma16020653 - 9 Jan 2023
Cited by 2 | Viewed by 1898
Abstract
Mullite–cordierite ceramic saggar is a necessary consumable material used in the synthesis process of LiCoO2 that is easily eroded during application. In our study, we systematically investigated the characteristics and surface corrosion behavior of waste saggar samples. We divided the cross sections [...] Read more.
Mullite–cordierite ceramic saggar is a necessary consumable material used in the synthesis process of LiCoO2 that is easily eroded during application. In our study, we systematically investigated the characteristics and surface corrosion behavior of waste saggar samples. We divided the cross sections of waste saggar into the attached layer, hardened layer, permeability layer, and matrix layer. Then, we examined the high-temperature solid-state reactions between saggar powder and lithium carbonate or cobalt oxide to identify erosion reactants correlating with an increase in the number of recycled saggars. The results of time-of-flight secondary ion mass spectrometric analysis (TOF-SIMS) prove that the maximum erosion penetration of lithium can reach 2 mm. However, our morphology and elemental distribution analysis results show that the erosion penetration of cobalt was only 200 μm. When enough lithium carbonate reacted, lithium aluminate and lithium silicate were the main phases. Our X-ray computed tomography (X-ray CT) analysis results show that the change in phase volume before and after the reaction, including the generation of oxygen and carbon dioxide gas, led to the internal crack expansion of the material–saggar interface. Our results can contribute to improving saggar and upgrading waste saggar utilization technology. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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12 pages, 2333 KiB  
Article
Study of Radiation-Induced Damage Processes in CeZrO4–YZrO3 Ceramics Caused by Helium Irradiation
by Artem Kozlovskiy, Daryn B. Borgekov, Maxim V. Zdorovets, Kayrat K. Kadyrzhanov and Dmitriy I. Shlimas
Materials 2023, 16(1), 198; https://doi.org/10.3390/ma16010198 - 26 Dec 2022
Cited by 1 | Viewed by 1354
Abstract
Composite oxide ceramics CeZrO4–YZrO3 obtained by mechanochemical synthesis were chosen as objects of study. The most dangerous type of radiation defect in structural materials is associated with helium accumulation in the structure of the near-surface layer. This can lead to [...] Read more.
Composite oxide ceramics CeZrO4–YZrO3 obtained by mechanochemical synthesis were chosen as objects of study. The most dangerous type of radiation defect in structural materials is associated with helium accumulation in the structure of the near-surface layer. This can lead to the destruction and swelling of the material, resulting in a decrease in its strength and thermal characteristics. During the studies, it was found that the most significant structural changes (deformation of the crystal lattice, the magnitude of microdistortions of the crystal lattice) are observed with irradiation fluence above 5×1016 ion/cm2, while the nature of the changes is exponential. X-ray diffraction analysis found that the nature of the crystal structure deformation has a pronounced type of stretching due to the accumulation of implanted helium and its subsequent agglomeration. A comparative analysis with data on microdistortions of the crystal lattice and the values of microhardness and softening of ZrO2 and CeO2 showed that two-phase ceramics of the cubic type CeZrO4-YZrO3 are more resistant to radiation-induced degradation than single-phase ZrO2 and CeO2. Results of strength and thermophysical characteristics showed that the presence of two phases increases resistance to destruction and disorder, leading to a decrease in strength and thermal conductivity. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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9 pages, 2428 KiB  
Article
Effective Method for the Determination of the Unit Cell Parameters of New MXenes
by Alexander Syuy, Dmitry Shtarev, Alexey Lembikov, Mikhail Gurin, Ruslan Kevorkyants, Gleb Tselikov, Aleksey Arsenin and Valentyn Volkov
Materials 2022, 15(24), 8798; https://doi.org/10.3390/ma15248798 - 9 Dec 2022
Cited by 4 | Viewed by 1780
Abstract
MXenes are of great practical interest. While the physical properties of such a well-known MAX phase as Ti3AlC2 and the Ti3C2 MXene that is based on it have been widely studied, it is extremely important to study [...] Read more.
MXenes are of great practical interest. While the physical properties of such a well-known MAX phase as Ti3AlC2 and the Ti3C2 MXene that is based on it have been widely studied, it is extremely important to study the properties of new four-component MAX-phases and the MXenes based on them. To do this, first, it is necessary to characterize the obtained materials. In this work, the Ti3−xNbxC2 MXene was characterized. Since the material is fairly new, there are no crystallographic data for such systems in the international databases. We proposed a method for the determination of the main unit cell parameters of the new Ti3−xNbxC2 MXene, which was based on a combination of the DFT method, TEM studies, and an X-ray diffraction analysis. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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21 pages, 6659 KiB  
Article
Use of Municipal Solid Waste Incineration Fly Ash in Geopolymer Masonry Mortar Manufacturing
by Ning Lu, Xin Ran, Zhu Pan and Asghar Habibnejad Korayem
Materials 2022, 15(23), 8689; https://doi.org/10.3390/ma15238689 - 6 Dec 2022
Cited by 9 | Viewed by 1719
Abstract
The feasibility of partially replacing pulverized fly ash (PFA) with municipal solid waste incineration fly ash (MSWIFA) to produce ambient-cured geopolymers was investigated. The influence of mixture design parameters on the compressive strength of geopolymer paste was studied. The investigated parameters included MSWIFA [...] Read more.
The feasibility of partially replacing pulverized fly ash (PFA) with municipal solid waste incineration fly ash (MSWIFA) to produce ambient-cured geopolymers was investigated. The influence of mixture design parameters on the compressive strength of geopolymer paste was studied. The investigated parameters included MSWIFA dosage, the ratio of sodium silicate to sodium hydroxide (SS/SH), the ratio of liquid to solid (L/S) alkaline activator, and the ratio of SH molar. A water immersion method was selected as a pretreatment process for MSWIFA, leading to effectively maintaining the volume stability of the MSWIFA/PFA geopolymer. The mixture of 30% treated MSWIFA and 70% PFA with 12 M SS, 0.5 L/S ratio, and 3.0 SS/SH ratio produced the highest three-day compressive strength (4.9 MPa). Based on the optimal paste mixture, category four masonry mortars (according to JGJT98-2011) were prepared to replace various ratios of natural sand with fine recycling glasses. Up to a 30% replacement ratio, the properties of the mortars complied with the limits established by JGJT98-2011. The twenty-eight-day leaching rate of mortars containing 30% MSWIFA was lower than the limits proposed by GB5085.3-2007. Microstructural analysis indicated that the main reaction product was a combination of calcium silicate hydrate gel and aluminosilicate gel. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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17 pages, 5265 KiB  
Article
Influence of the Sintering Method on the Properties of a Multiferroic Ceramic Composite Based on PZT-Type Ferroelectric Material and Ni-Zn Ferrite
by Dariusz Bochenek, Artur Chrobak and Grzegorz Dercz
Materials 2022, 15(23), 8461; https://doi.org/10.3390/ma15238461 - 28 Nov 2022
Cited by 3 | Viewed by 1404
Abstract
This paper presents the research results of multiferroic ceramic composites obtained with three sintering methods, i.e., free sintering FS (pressureless), hot pressing HP, and spark plasma sintering SPS. The multiferroic composite was obtained by combining a ferroelectric material of the PZT-type (90%) and [...] Read more.
This paper presents the research results of multiferroic ceramic composites obtained with three sintering methods, i.e., free sintering FS (pressureless), hot pressing HP, and spark plasma sintering SPS. The multiferroic composite was obtained by combining a ferroelectric material of the PZT-type (90%) and zinc-nickel ferrite (10%). Research has shown that the combination of a magnetic material and ferroelectric materials maintains the multiferroic good ferroelectric and magnetic properties of the composites for all sintering methods. A sample sintered with the HP hot pressing method exhibits the best parameters. In the HP method, the composite sample has high permittivity, equal to 910 (at room temperature) and 7850 (at the phase transition temperature), residual polarization 2.80 µC/cm2, a coercive field of 0.95 kV/mm, and the magnetization of 5.3 and 4.95 Am2/kg at −268 °C and RT, respectively. Optimal technological process conditions are ensured by the HP method, improving the sinterability of the ceramic sinter which obtains high density and proper material compaction. In the case of the SPS method, the sintering conditions do not allow for homogeneous growth of the ferroelectric and magnetic component grains, increasing the formation of internal pores. On the other hand, in the FS method, high temperatures favor excessive grain growth and an increase in the heterogeneity of their size. In obtaining optimal performance parameters of multiferroic composites and maintaining their stability, hot pressing is the most effective of the presented sintering methods. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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14 pages, 6011 KiB  
Article
Preparation of B4Cp/Al Composites via Selective Laser Melting and Their Tribological Properties
by Guodong Yang, Jialian Zhang, Houbo Xie, Faliang Li, Zhong Huang, Gaoqian Yuan, Jingzhe Zhang, Quanli Jia, Haijun Zhang, Hasibe Aygul Yeprem and Shaowei Zhang
Materials 2022, 15(23), 8340; https://doi.org/10.3390/ma15238340 - 23 Nov 2022
Cited by 1 | Viewed by 1284
Abstract
B4C-particle-reinforced Al (B4Cp/Al) composites are widely used in various areas, e.g., armors, electronic packaging and fuel storage, owing to their several outstanding properties including high specific rigidity, excellent wear resistance and light weight. Selective laser melting (SLM) [...] Read more.
B4C-particle-reinforced Al (B4Cp/Al) composites are widely used in various areas, e.g., armors, electronic packaging and fuel storage, owing to their several outstanding properties including high specific rigidity, excellent wear resistance and light weight. Selective laser melting (SLM) is favored in manufacturing complex components because of its high raw material utilization rate and high efficiency. In this work, a B4Cp/Al composite was successfully synthesized by SLM, and the effects of one of the most important parameters, scanning speed (100–700 mm/s), on the phase composition, density, microhardness and tribological properties of the samples were investigated. The microhardness, relative density and dry-sliding wear resistance of as-prepared B4Cp/Al composites were improved with the decrease in scanning speed, and the sample fabricated at a scanning speed of 100 mm/s exhibited a relative density as high as about 97.1%, and a maximum microhardness of ~180 HV0.1 (approximately six times more than that of the SLM-formed pure Al sample, 31 HV0.1), a minimum wear rate of 4.2 × 10−5 mm3·N−1·m−1 and a corresponding friction coefficient of 0.41. In addition, abrasive wear, adhesive wear and oxidation wear were found to be behind the overall wear behavior of as-prepared B4Cp/Al composites. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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19 pages, 5130 KiB  
Article
Tailoring the Stability of Ti-Doped Sr2Fe1.4TixMo0.6−xO6−δ Electrode Materials for Solid Oxide Fuel Cells
by Kun Zheng, Maciej Albrycht, Min Chen, Kezhen Qi and Paweł Czaja
Materials 2022, 15(22), 8268; https://doi.org/10.3390/ma15228268 - 21 Nov 2022
Viewed by 1421
Abstract
In this work, the stability of Sr2(FeMo)O6−δ-type perovskites was tailored by the substitution of Mo with Ti. Redox stable Sr2Fe1.4TixMo0.6−xO6−δ (x = 0.1, 0.2 and 0.3) perovskites were successfully obtained [...] Read more.
In this work, the stability of Sr2(FeMo)O6−δ-type perovskites was tailored by the substitution of Mo with Ti. Redox stable Sr2Fe1.4TixMo0.6−xO6−δ (x = 0.1, 0.2 and 0.3) perovskites were successfully obtained and evaluated as potential electrode materials for SOFCs. The crystal structure as a function of temperature, microstructure, redox stability, and thermal expansion properties in reducing and oxidizing atmospheres, oxygen content change, and transport properties in air and reducing conditions, as well as chemical stability and compatibility towards typical electrolytes have been systematically studied. All Sr2Fe1.4TixMo0.6−xO6−δ compounds exhibit a regular crystal structure with Pm-3m space group, showing excellent stability in oxidizing and reducing conditions. The increase of Ti-doping content in materials increases the thermal expansion coefficient (TEC), oxygen content change, and electrical conductivity in air, while it decreases the conductivity in reducing condition. All three materials are stable and compatible with studied electrolytes. Interestingly, redox stable Sr2Fe1.4Ti0.1Mo0.5O6−δ, possessing 1 μm grain size, low TEC (15.3 × 10−6 K−1), large oxygen content change of 0.72 mol·mol−1 between 30 and 900 °C, satisfactory conductivity of 4.1–7.3 S·cm−1 in 5% H2 at 600–800 °C, and good transport coefficients D and k, could be considered as a potential anode material for SOFCs, and are thus of great interest for further studies. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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14 pages, 5483 KiB  
Article
Microstructure and Properties of Densified Gd2O3 Bulk
by Pei-Hu Gao, Can Jin, Sheng-Cong Zeng, Rui-Guang Xie, Bo Zhang, Bai-Yang Chen, Zhong Yang, Yong-Chun Guo, Min-Xian Liang, Jian-Ping Li, Li-Na Zhang, Zhi-Yi Yan, Lu Jia and Dan Zhao
Materials 2022, 15(21), 7793; https://doi.org/10.3390/ma15217793 - 4 Nov 2022
Cited by 1 | Viewed by 1351
Abstract
In this work, Gd2O3 bulks were sintered at temperatures ranging from 1400 °C to 1600 °C for times from 6 h to 24 h, and their microstructure and properties were studied for a wider application of materials in thermal barrier [...] Read more.
In this work, Gd2O3 bulks were sintered at temperatures ranging from 1400 °C to 1600 °C for times from 6 h to 24 h, and their microstructure and properties were studied for a wider application of materials in thermal barrier coatings. The densification of the Gd2O3 bulk reached 96.16% when it was sintered at 1600 °C for 24 h. The elastic modulus, hardness, fracture toughness and thermal conductivity of the bulks all increased with the rise in sintering temperature and extension of sintering time, while the coefficient of thermal expansion decreased. When the Gd2O3 bulk was sintered at 1600 °C for 24 h, it had the greatest elastic modulus, hardness, fracture toughness and thermal conductivity of 201.15 GPa, 9.13 GPa, 15.03 MPa·m0.5 and 2.75 W/(m·k) (at 1100 °C), respectively, as well as the smallest thermal expansion coefficients of 6.69 × 10−6/°C (at 1100 °C). Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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12 pages, 5521 KiB  
Article
Reaction Mechanism of CA6, Al2O3 and CA6-Al2O3 Refractories with Refining Slag
by Jie Liu, Zheng Liu, Jisheng Feng, Bin Li, Junhong Chen, Bo Ren, Yuanping Jia and Shu Yin
Materials 2022, 15(19), 6779; https://doi.org/10.3390/ma15196779 - 30 Sep 2022
Cited by 6 | Viewed by 1414
Abstract
In this study, to clarify the corrosion mechanism of CA6 based refractory by refining slag, the static crucible tests for CA6, CA6-Al2O3, and Al2O3 refractory, were carried out and the detail [...] Read more.
In this study, to clarify the corrosion mechanism of CA6 based refractory by refining slag, the static crucible tests for CA6, CA6-Al2O3, and Al2O3 refractory, were carried out and the detail reaction processes were analyzed from the perspective of thermodynamic simulation and structural evolution. From the results, CaAl4O7 plays a vital role in the slag corrosion resistance of the three refractories. Regarding CA6 refractory, the double pyramid module in CA6 crystal structure was destroyed very quickly, leading to the rapid collapse of its structure to form the denser CaAl4O7 in high amounts. As a result, a reaction layer mainly composed of CaAl4O7 formed, which effectively inhibited the slag corrosion, so CA6 refractory exhibits the most excellent slag corrosion. Meanwhile, the formation of CaAl4O7 can also avoid CA6 particles entering the molten steel to introduce exogenous inclusions. For Al2O3 refractory, the generation of CaAl4O7 is much slower than that of CA6 and CA6-Al2O3 refractory, and the amount generated is also quite small, resulting in its worst slag corrosion among the three crucibles. Therefore, CA6 based refractory has excellent application potential in ladle refining and clean steel smelting. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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13 pages, 1564 KiB  
Article
Construction Products between Testing Laboratory and Market Surveillance: Case study of Cementitious Ceramic Tile Adhesives
by Cristina Stancu, Dawid Dębski and Jacek Michalak
Materials 2022, 15(17), 6167; https://doi.org/10.3390/ma15176167 - 5 Sep 2022
Cited by 5 | Viewed by 1934
Abstract
This article presents the results of the interlaboratory comparison (ILC) study of the following four characteristics of ceramic tile adhesives (CTAs): initial tensile adhesion strength, tensile adhesion strength after heat ageing, tensile adhesion strength after immersion in water, and tensile adhesion strength after [...] Read more.
This article presents the results of the interlaboratory comparison (ILC) study of the following four characteristics of ceramic tile adhesives (CTAs): initial tensile adhesion strength, tensile adhesion strength after heat ageing, tensile adhesion strength after immersion in water, and tensile adhesion strength after freeze–thaw cycles. The results showed that the objective of the ILC was achieved—the z-score analysis carried out following ISO 13528 allowed for classifying all results obtained by 23 laboratories out of 27 as satisfactory. The results of the remaining four laboratories were rated worse. Despite the achieved goal, the ILC notes high heterogeneity of the results in terms of failure patterns, as well as significant differences between the lowest and the highest values of tensile adhesion strength for various measurement conditions. The results of the ILC were discussed in terms of the possibility of including them in the risk analysis conducted by the manufacturer. The results of the ILC are also valuable information for market surveillance authorities, who, in the authors’ opinion, should be more cautious about results on samples taken from the market. The ILC results for CTAs are also a valuable recommendation for a possible revision of EN 12004. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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9 pages, 2538 KiB  
Article
Liquid-Phase-Assisted Catalytic Nitridation of Silicon and In Situ Growth of α-Si3N4
by Zhenglong Liu, Zhinan Chai, Chao Yu, Jun Ding, Chengji Deng, Xiangcheng Li and Hongxi Zhu
Materials 2022, 15(17), 6074; https://doi.org/10.3390/ma15176074 - 1 Sep 2022
Cited by 4 | Viewed by 1073
Abstract
Si3N4 powders were synthesized with Fe, Co, or Ni as catalysts using Si powder at 1250 °C in a nitrogen atmosphere by liquid-phase-assisted catalytic nitridation synthesis (LPA–CNS). The catalytic effects of the metals on the nitridation of silicon powder were [...] Read more.
Si3N4 powders were synthesized with Fe, Co, or Ni as catalysts using Si powder at 1250 °C in a nitrogen atmosphere by liquid-phase-assisted catalytic nitridation synthesis (LPA–CNS). The catalytic effects of the metals on the nitridation of silicon powder were investigated by mixing the powder with 2 wt% by mass of Fe, Co, or Ni in a high-temperature liquid phase in flowing nitrogen. The α-Si3N4 micro-morphology could be effectively changed by adjusting the type of catalyst in the initial reaction mixtures. Fe, Co, and Ni promoted the formation of α-Si3N4 at 1250 °C and controlled the morphology of the α-Si3N4 particles. The hexagonal flakes of α-Si3N4 with a better defined morphology were obtained using Ni as the catalyst, compared to that obtained from the other two catalysts. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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12 pages, 4731 KiB  
Article
Investigation of the Gamma-ray Shielding Performance of CuO-CdO-Bi2O3 Bentonite Ceramics
by Hanan Al-Ghamdi, Mohamed Elsafi, Aljawhara H. Almuqrin, Sabina Yasmin and M. I. Sayyed
Materials 2022, 15(15), 5310; https://doi.org/10.3390/ma15155310 - 2 Aug 2022
Cited by 14 | Viewed by 1283
Abstract
The purpose of this research is to identify the radiation shielding capability of ceramics adding CuO, CdO, and Bi2O3 with diverse wt (%). The chemical compositions of the raw ceramics were documented through Energy Dispersive X-ray “EDX” techniques. For aesthetic [...] Read more.
The purpose of this research is to identify the radiation shielding capability of ceramics adding CuO, CdO, and Bi2O3 with diverse wt (%). The chemical compositions of the raw ceramics were documented through Energy Dispersive X-ray “EDX” techniques. For aesthetic appeal and solidification, CuO has been chosen to be added to ceramic. Moreover, in the interest of increasing the radiation shielding ability, the high atomic number and density of both CdO and Bi2O3 were suggested for the raw ceramics. To obtain the morphological features of the prepared ceramic samples, a Scanning Electron Microscope, or SEM, was utilized. To verify the experimental results, the MCA value obtained from the Phy-X software was compared to the experimental value collected from the HPGe detector. At energies 0.06 MeV, 0.662 MeV, 1.173 MeV, and 1.333 MeV the linear and mass attenuation coefficients of the prepared ceramics have been measured using a high purity germanium “HPGe” detector as well as three different point sources. Moreover, the relationship between ln(I) and the thickness of the ceramics has been presented here, and the comparison between the LAC of the prepared ceramics with other materials has also been displayed. Bentonite ceramic containing CuO (15 mol %)-CdO (15 mol %)-Bi2O3 (20 mol %) with density 3.6 showed the lowest HVL, MFP, and TVL at all studied energies, yet pure Bentonite ceramic containing only CuO (50 mol %), having density 3.4, presented the greatest values. Hence, it can be concluded that the addition of CdO and Bi2O3 enhances the radiation shielding ability. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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11 pages, 5418 KiB  
Article
A First-Principles Study on the Hydration Behavior of (MgO)n Clusters and the Effect Mechanism of Anti-Hydration Agents
by Yu Gao, Long Dong, Liang Huang, Zhong Huang, Faliang Li, Haijun Zhang and Shaowei Zhang
Materials 2022, 15(10), 3521; https://doi.org/10.3390/ma15103521 - 13 May 2022
Cited by 1 | Viewed by 1633
Abstract
Magnesia-based refractory is widely used in high-temperature industries; its easy hydration is, however, a key concern in refractory processing. Understanding the hydration mechanism of MgO will help in solving its hydration problem. Herein, the hydration behavior of (MgO)n (n = 1–6) at [...] Read more.
Magnesia-based refractory is widely used in high-temperature industries; its easy hydration is, however, a key concern in refractory processing. Understanding the hydration mechanism of MgO will help in solving its hydration problem. Herein, the hydration behavior of (MgO)n (n = 1–6) at the molecular level and the effect mechanisms of several anti-hydration agents on the hydration of (MgO)4 were investigated with first-principles calculations. The results indicated that the following: (1) The smaller the (MgO)n cluster size, the more favorable the hydration of MgO and the tendency to convert into Mg(OH)2 crystal; (2) Anti-hydration agents can coordinate with the unsaturated Mg atom of (MgO)4 to form a bond, increasing the coordination number of Mg, thus reducing its activity when reacting with H2O; (3) The greater the number of −COOH groups and the longer the chain length in the anti-hydration agents, the better its effect of inhibiting the hydration of MgO. These findings could enhance the understanding of the mechanism of hydration of MgO and provide theoretical guidance for the design of novel anti-hydration agents. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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9 pages, 1605 KiB  
Article
Low-Temperature, Efficient Synthesis of Highly Crystalline Urchin-like Tantalum Diboride Nanoflowers
by Delei Liu, Jianghao Liu, Peikan Ye, Haijun Zhang and Shaowei Zhang
Materials 2022, 15(8), 2799; https://doi.org/10.3390/ma15082799 - 11 Apr 2022
Cited by 2 | Viewed by 1276
Abstract
Urchin-like tantalum diboride (TaB2) nanoflowers were successfully synthesized via a high-efficiency and energy-saving methodology, molten-salt and microwave co-modified boro/carbothermal reduction, using less expensive B4C as a reducing agent. By taking advantage of the synergistic effects of the molten-salt medium [...] Read more.
Urchin-like tantalum diboride (TaB2) nanoflowers were successfully synthesized via a high-efficiency and energy-saving methodology, molten-salt and microwave co-modified boro/carbothermal reduction, using less expensive B4C as a reducing agent. By taking advantage of the synergistic effects of the molten-salt medium and microwave heating conditions, the onset formation temperature of TaB2 was drastically reduced to below 1000 °C, and phase-pure powders of TaB2 nanoflowers were obtained at temperatures as low as 1200 °C within only 20 min. Notably, the present temperature conditions were remarkably milder than those (>1500 °C for several hours) required by conventional reduction methods, which use the strong, but expensive, reducing agent, elemental boron. The resulting urchin-like TaB2 nanoflowers consisted of numerous uniform single-crystalline nanowires with lengths up to 4.16 μm, and high aspect ratios >10. This result indicated that the as-synthesized urchin-like TaB2 nanoflowers possessed high specific surface area and anisotropic morphology, which were favorable not only for sintering, but also for toughening their bulk counterparts. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications)
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