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14 pages, 8478 KiB

Open AccessArticle

Preparation and Performance of Ferric-Rich Bauxite-Tailing-Based Thermal Storage Ceramics

by Qi Wang, Minghao Fang, Xin Min, Pengpeng Du, Zhaohui Huang, Yangai Liu, Xiaowen Wu, Yulin Liu, Changmiao Liu and Feihui Huang

Materials 2023, 16(21), 6900; https://doi.org/10.3390/ma16216900 - 27 Oct 2023

Viewed by 741

Abstract

In recent years, regenerative thermal oxidizer (RTO) has been widely used in the petroleum industry, chemical industry, etc. The massive storage required by solid waste has become a serious problem. Due to their chemical composition, bauxite tailings as raw materials for high-temperature thermal [...] Read more.

In recent years, regenerative thermal oxidizer (RTO) has been widely used in the petroleum industry, chemical industry, etc. The massive storage required by solid waste has become a serious problem. Due to their chemical composition, bauxite tailings as raw materials for high-temperature thermal storage ceramics show enormous potential in the fields of research and application. In this study, we propose a method for preparing ferric-rich and high specific storage capacity by adding Fe₂O₃ powder to bauxite tailings. Based on a 7:3 mass ratio of bauxite tailings to lepidolite, Fe₂O₃ powder with different mass fractions (7 wt%, 15 wt%, 20 wt%, 30 wt%, and 40 wt%) was added to the ceramic material to improve the physical properties and thermal storage capacity of thermal storage ceramics. The results showed that ferric-rich thermal storage ceramics with optimal performance were obtained by holding them at a sintering temperature of 1000 °C for 2 h. When the Fe₂O₃ content was 15 wt%, the bulk density of the thermal storage ceramic reached 2.53 g/cm³, the compressive strength was 120.81 MPa, and the specific heat capacity was 1.06 J/(g·K). This study has practical guidance significance in the preparation of high thermal storage ceramics at low temperatures and low costs. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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17 pages, 40526 KiB

Open AccessArticle

Investigation of Tribological Characteristics of PEO Coatings Formed on Ti6Al4V Titanium Alloy in Electrolytes with Graphene Oxide Additives

by Sergey Grigoriev, Nikita Peretyagin, Andrey Apelfeld, Anton Smirnov, Alexei Morozov, Elena Torskaya, Marina Volosova, Oleg Yanushevich, Nikolay Yarygin, Natella Krikheli and Pavel Peretyagin

Materials 2023, 16(11), 3928; https://doi.org/10.3390/ma16113928 - 24 May 2023

Cited by 6 | Viewed by 1020

Abstract

Coatings with a thickness from ~40 to ~50 µm on Ti6Al4V titanium alloys were formed by plasma electrolytic oxidation (PEO) in a silicate-hypophosphite electrolyte with the addition of graphene oxide. The PEO treatment was carried out in the anode–cathode mode (50 Hz) at [...] Read more.

Coatings with a thickness from ~40 to ~50 µm on Ti6Al4V titanium alloys were formed by plasma electrolytic oxidation (PEO) in a silicate-hypophosphite electrolyte with the addition of graphene oxide. The PEO treatment was carried out in the anode–cathode mode (50 Hz) at a ratio of anode and cathode currents of 1:1; their sum density was 20 A/dm², and the treatment’s duration was 30 min. The effect of the graphene oxide’s concentration in the electrolyte on the thickness, roughness, hardness, surface morphology, structure, composition, and tribological characteristics of the PEO coatings was studied. Wear experiments, under dry conditions, were carried out in a ball-on-disk tribotester with an applied load of 5 N, a sliding speed of 0.1 m·s⁻¹, and a sliding distance of 1000 m. According to the obtained results, the addition of graphene oxide (GO) into the base silicate-hypophosphite electrolyte leads to a slight decrease in the coefficient of friction (from 0.73 to 0.69) and a reduction in the wear rate by more than 1.5 times (from 8.04 to 5.2 mm³/N·m), with an increase in the GO’s concentration from 0 to 0.5 kg/m³, respectively. This occurs due to the formation of a GO-containing lubricating tribolayer upon contact with the coating of the counter-body in the friction pair. Delamination of the coatings during wear occurs due to contact fatigue; with an increase in the concentration of GO in the electrolyte from 0 to 0.5 kg/m³, this process slows down by more than four times. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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21 pages, 6083 KiB

Open AccessArticle

Numerical Investigation on Protective Mechanism of Metal Cover Plate for Alumina Armor against Impact of Fragment by FE-Converting-SPH Method

by Linlong Dou, Liling He and Yihui Yin

Materials 2023, 16(9), 3405; https://doi.org/10.3390/ma16093405 - 27 Apr 2023

Cited by 2 | Viewed by 1179

Abstract

It is of extreme importance to develop a reliable numerical prediction technique to simulate the ballistic response of ceramic armor subjected to high-velocity impact (HVI) to economize the test cost and shorten the design period. In the present manuscript, a series of experiments [...] Read more.

It is of extreme importance to develop a reliable numerical prediction technique to simulate the ballistic response of ceramic armor subjected to high-velocity impact (HVI) to economize the test cost and shorten the design period. In the present manuscript, a series of experiments on tungsten heavy alloy (WHA) fragment’s penetration into 99.5% alumina (AD995) armors are systematically simulated by employing the FE-converting-SPH technique. The numerical results are compared with the experimental counterparts to find that the FE-converting-SPH method is fairly efficient in predicting the depth of penetration, the residual velocity, length and mass of fragment, and reproducing the crack forms of ceramic. The applicability and accuracy of the numerical model in terms of the algorithm, material model parameters and contact definitions are validated. Then, the relevant parameters of the calibrated numerical model are incorporated to explore the influence of cover-layer thickness on the armor performance. A few mechanisms regarding the cover plate have been identified to act on the armor performance, such as the alteration of fracture cone half-angle, proportion of energy absorbed by ceramic, mushrooming deformation of fragment, etc. The result of multi-mechanism superposition is that the best ballistic performance is endued with 1 mm cover-layer armor, which demonstrates a 24.6% improvement over the bi-layer armor with 4.96 g/cm² area density, only at the cost of 15.7% increase in areal density, when back-plate thickness is held as 2 mm; for a constant area density of 4.96 g/cm², a 1 mm cover-layer is also expected to be the best choice, with 10.7% improvement in armor performance. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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25 pages, 23986 KiB

Open AccessArticle

Impact Deposition Behavior of Al/B₄C Cold-Sprayed Composite Coatings: Understanding the Role of Porosity on Particle Retention

by Hannaneh Manafi Farid, André McDonald and James David Hogan

Materials 2023, 16(6), 2525; https://doi.org/10.3390/ma16062525 - 22 Mar 2023

Cited by 1 | Viewed by 1698

Abstract

This study explores the role of porosity in the impact deposition of a ceramic-reinforced metal-matrix (i.e., Al/B

_{4}

C) composite coating fabricated via cold spraying. The Johnson–Holmquist–Beissel constitutive law and the modified Gurson–Tvergaard–Needleman model were used to describe the high strain-rate behavior of [...] Read more.

This study explores the role of porosity in the impact deposition of a ceramic-reinforced metal-matrix (i.e., Al/B

_{4}

C) composite coating fabricated via cold spraying. The Johnson–Holmquist–Beissel constitutive law and the modified Gurson–Tvergaard–Needleman model were used to describe the high strain-rate behavior of the boron carbide and the aluminum metal matrix during impact deposition, respectively. Within a finite element model framework, the Arbitrary Lagrangian–Eulerian technique is implemented to explore the roles of reinforcement particle size and velocity, and pore size and depth in particle retention by examining the post-impact crater morphology, penetration depth, and localized plastic deformation of the aluminum substrate. Results reveal that some degree of matrix porosity may improve particle retention. In particular, porosity near the surface facilitates particle retention at lower impact velocities, while kinetic energy dominates particle retention at higher deposition velocities. Altogether, these results provide insights into the effect of deposition variables (i.e., particle size, impact velocity, pore size, and pore depth) on particle retention that improves coating quality. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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26 pages, 9904 KiB

Open AccessArticle

Research on the Roundness Approximation Search Algorithm of Si₃N₄ Ceramic Balls Based on Least Square and EMD Methods

by Jian Sun, Wei Chen, Jinmei Yao, Zhonghao Tian and Longfei Gao

Materials 2023, 16(6), 2351; https://doi.org/10.3390/ma16062351 - 15 Mar 2023

Cited by 2 | Viewed by 1406

Abstract

This paper aims to obtain the best shape accuracy evaluation algorithm for silicon nitride ceramic balls after lapping, and to extract the initial signal of the ball surface to improve the accuracy and reliability of the algorithm. The research methods of this paper [...] Read more.

This paper aims to obtain the best shape accuracy evaluation algorithm for silicon nitride ceramic balls after lapping, and to extract the initial signal of the ball surface to improve the accuracy and reliability of the algorithm. The research methods of this paper are as follows: Firstly, an analysis of the uniform envelope of the lapping trajectory of ceramic balls is carried out to verify whether the lapping trajectory after processing can achieve a consistent envelope on the balls’ surface. On this basis, it is found through experiments that the standard deviation SD between the roundness deviations of different contour sections is small. The value is maintained at approximately 0.03 μm, and the roundness deviation can approximately replace the spherical deviation. Then the different contour sections of the sphere are sampled by the Taylor roundness instrument. Considering the uncertainty, the sampling points of different contour sections are averaged and used as the original signal of the sphere surface. Then the EMD method is used to process the signal to be detected on the sphere surface. The initial signal of the sphere surface is extracted by judging whether the number of ripples Kc obtained by decomposition is greater than the critical value. Then the initial signal is used as the input value of the approximation algorithm. Through the roundness deviation approximation algorithm based on the least square method, the given minimum approximation domain range is finely processed. The divided fine points are used as the center of the circle to intersect with the initial signal. The maximum, minimum, and range of each circle are calculated to obtain the roundness error based on the minimum circumscribed circle, the maximum inscribed circle, and the minimum region method. Finally, the calculated values are compared with those obtained by the traditional algorithm. The experimental results of this paper show that the algorithm is consistent with the roundness error measured by the instrument, compared with the mainstream evaluation criteria. In summary, the conclusions can be drawn as follows: Through a large number of experimental cases and comparative experiments, the algorithm has high accuracy and reliability. The research results of this paper have essential reference significance for accurately evaluating the shape accuracy of ceramic balls in actual production. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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11 pages, 8318 KiB

Open AccessArticle

Assessment Effect of Nanometer-Sized Al₂O₃ Fillers in Polylactide on Fracture Probability of Filament and 3D Printed Samples by FDM

by Anton Smirnov, Pavel Peretyagin and Nikita Nikitin

Materials 2023, 16(4), 1671; https://doi.org/10.3390/ma16041671 - 16 Feb 2023

Cited by 4 | Viewed by 1409

Abstract

In this paper, a mathematical model for the description of the failure probability of filament and fused deposition modeling (FDM)-printed products is considered. The model is based on the results of tensile tests of filament samples made of polyacrylonitrile butadiene styrene (ABS), polylactide [...] Read more.

In this paper, a mathematical model for the description of the failure probability of filament and fused deposition modeling (FDM)-printed products is considered. The model is based on the results of tensile tests of filament samples made of polyacrylonitrile butadiene styrene (ABS), polylactide (PLA), and composite PLA filled with alumina (Al₂O₃) as well after FDM-printed products of “spatula” type. The application of probabilistic methods of fracture analysis revealed that the main contribution to the reduction of fracture probability is made by the elastic and plastic stages of the fracture curve under static loading. Particle distribution analysis of Al₂O₃ combined with fracture probability analysis shows that particle size distributions on the order of 10⁻⁵ and 10⁻⁶ mm decrease the fracture probability of the sample, whereas uniform particle size distributions on the order of 10⁻¹ and 10⁻² mm do not change the distribution probability. The paper shows that uneven distribution of Al₂O₃ fillers in composite samples made using FDM printing technology leads to brittle fracture of the samples. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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8 pages, 3445 KiB

Open AccessEditor’s ChoiceArticle

Effect of Surface Dispersion of Fe Nanoparticles on the Room-Temperature Flash Sintering Behavior of 3YSZ

by Angxuan Wu, Yuchen Zhu, Chen Xu, Nianping Yan, Xuetong Zhao, Xilin Wang and Zhidong Jia

Materials 2023, 16(4), 1544; https://doi.org/10.3390/ma16041544 - 13 Feb 2023

Cited by 2 | Viewed by 1315

Abstract

Arc floating in surface flashover can be controlled by reducing the interfacial charge-transfer resistance of ceramics. However, thus far, only a few studies have been conducted on methods of treating ceramic surfaces directly to reduce the interfacial charge-transfer resistance. Herein, we explore the [...] Read more.

Arc floating in surface flashover can be controlled by reducing the interfacial charge-transfer resistance of ceramics. However, thus far, only a few studies have been conducted on methods of treating ceramic surfaces directly to reduce the interfacial charge-transfer resistance. Herein, we explore the flash sintering behavior of a ceramic surface (3 mol% yttria-stabilized zirconia (3YSZ)) onto which loose metal (iron) powder was spread prior to flash sintering at room temperature (25 °C). The iron powder acts as a conductive phase that accelerates the start of flash sintering while also doping the ceramic phase during the sintering process. Notably, the iron powder substantially reduces the transition time from the arc stage to the flash stage from 13.50 to 8.22 s. The surface temperature (~1600 °C) of the ceramic substrate is sufficiently high to melt the iron powder. The molten metal then reacts with the ceramic surface, causing iron ions to substitute Zr⁴⁺ ions and promoting rapid densification. The YSZ grains in the metal-infiltrated area grow exceptionally fast. The results demonstrate that spreading metal powder onto a ceramic surface prior to flash sintering can enable the metal to enter the ceramic pores, which will be of significance in developing and enhancing ceramic–metal powder processing techniques. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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15 pages, 5026 KiB

Open AccessArticle

Evaluation of the Role of the Activating Application Method in the Cold Sintering Process of ZnO Ceramics Using Ammonium Chloride

by Andrey V. Smirnov, Maxim V. Kornyushin, Anastasia A. Kholodkova, Sergey A. Melnikov, Artem D. Stepanov, Elena V. Fesik, Vilen V. Mnatsakanyan, Anton Smirnov and Yurii D. Ivakin

Materials 2023, 16(1), 408; https://doi.org/10.3390/ma16010408 - 01 Jan 2023

Cited by 2 | Viewed by 1538

Abstract

The influence of the method of applying the activating additive ammonium chloride and its concentration on the density and microstructure of zinc oxide ceramic obtained by cold sintering at 244 °C was investigated. The activating agent was applied by two methods: impregnation and [...] Read more.

The influence of the method of applying the activating additive ammonium chloride and its concentration on the density and microstructure of zinc oxide ceramic obtained by cold sintering at 244 °C was investigated. The activating agent was applied by two methods: impregnation and subsequent autoclave treatment. When the powder was activated by the impregnation method, the crystal sizes remained at the initial level of 0.17–0.19 μm. After the autoclave treatment, the crystal sizes increased to 0.31–0.53 μm. Samples of cold sintering ZnO with relative density up to 0.96 and average grain sizes 0.29–0.86 μm were obtained. ZnO powders and ceramic samples were analyzed using SEM, TGA/DSC, and XRD to reveal the effect of the powder activation method and cold sintering conditions on the material microstructure. The effect of ammonium chloride concentration on grain growth and microstructure of ceramic samples is shown. It was found that the average grain size of ceramic samples with an increase in additive concentration passes through a minimum. In cold sintering of the autoclave activated powder, the effect of reducing the average grain size was observed. The results of this work are discussed on the basis of the idea of the solid-phase mobility of the crystal structure arising when interacting with an aqueous medium. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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11 pages, 2251 KiB

Open AccessFeature PaperArticle

Low Temperature Magnetic Transition of BiFeO₃ Ceramics Sintered by Electric Field-Assisted Methods: Flash and Spark Plasma Sintering

by Alejandro Fernando Manchón-Gordón, Antonio Perejón, Eva Gil-González, Maciej Kowalczyk, Pedro E. Sánchez-Jiménez and Luis A. Pérez-Maqueda

Materials 2023, 16(1), 189; https://doi.org/10.3390/ma16010189 - 25 Dec 2022

Cited by 3 | Viewed by 1560

Abstract

Low temperature magnetic properties of BiFeO₃ powders sintered by flash and spark plasma sintering were studied. An anomaly observed in the magnetic measurements at 250 K proves the clear existence of a phase transition. This transformation, which becomes less well-defined as the [...] Read more.

Low temperature magnetic properties of BiFeO₃ powders sintered by flash and spark plasma sintering were studied. An anomaly observed in the magnetic measurements at 250 K proves the clear existence of a phase transition. This transformation, which becomes less well-defined as the grain sizes are reduced to nanometer scale, was described with regard to a magneto-elastic coupling. Furthermore, the samples exhibited enhanced ferromagnetic properties as compared with those of a pellet prepared by the conventional solid-state technique, with both a higher coercivity field and remnant magnetization, reaching a maximum value of 1.17 kOe and 8.5 10⁻³ emu/g, respectively, for the specimen sintered by flash sintering, which possesses the smallest grains. The specimens also show more significant exchange bias, from 22 to 177 Oe for the specimen prepared by the solid-state method and flash sintering technique, respectively. The observed increase in this parameter is explained in terms of a stronger exchange interaction between ferromagnetic and antiferromagnetic grains in the case of the pellet sintered by flash sintering. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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10 pages, 11909 KiB

Open AccessArticle

High-Temperature Oxidation Behavior of TiB₂-HfB₂-Ni Cermet Material

by Zhuo Wang, Jiaojiao Gao and Jinpeng Song

Materials 2022, 15(24), 8860; https://doi.org/10.3390/ma15248860 - 12 Dec 2022

Cited by 1 | Viewed by 1096

Abstract

To analyze the high-temperature oxidation behavior of TiB₂-HfB₂-Ni cermet material, TiB₂-HfB₂-Ni cermets were fabricated by hot-pressing sintering technology. The oxidation resistance and the thermal fracture of TiB₂-HfB₂-Ni cermet were investigated at [...] Read more.

To analyze the high-temperature oxidation behavior of TiB₂-HfB₂-Ni cermet material, TiB₂-HfB₂-Ni cermets were fabricated by hot-pressing sintering technology. The oxidation resistance and the thermal fracture of TiB₂-HfB₂-Ni cermet were investigated at 1100 °C for 1, 4, 7, and 10 h, respectively. Before oxidation, TiB₂-HfB₂-Ni cermet, consisting of TiB₂, HfB₂, and Ni, had the core-rim structure. The core was TiB₂ grain and the rim was composed of Ni and solid solution (Ti, Hf)B₂. After oxidation at 1100 °C, the oxides of the TiB₂-HfB₂-Ni cermet were mainly TiO₂, HfO₂, B₂O₃, and NiO, which the oxidation process abided by the parabolic law. With the oxidation time increasing from 1 h to 10 h, the oxidation degree of the TiB₂-HfB₂-Ni cermet increased, and the oxide layer became thicker. The oxide layer was thin and dense after oxidation at 1100 °C for 1 h. An obvious boundary was discovered between the transition layer and the substrate layer after oxidation at 1100 °C for 7 h. The thermal fracture occurred in the contact regions of different layers at 1100 °C for 10 h. TiB₂-HfB₂-Ni took place in oxidation at different levels from the outer to the inner, and the components of different oxide layers were certainly distinct. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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15 pages, 5498 KiB

Open AccessArticle

Rheological Characterization and Printability of Polylactide (PLA)-Alumina (Al₂O₃) Filaments for Fused Deposition Modeling (FDM)

by Anton Smirnov, Anton Seleznev, Pavel Peretyagin, Ekaterina Bentseva, Yuri Pristinskiy, Ekaterina Kuznetsova and Sergey Grigoriev

Materials 2022, 15(23), 8399; https://doi.org/10.3390/ma15238399 - 25 Nov 2022

Cited by 7 | Viewed by 1502

Abstract

This article presents the study of the rheological properties and the printability of produced ceramic-polymer filaments using fused deposition method (FDM) 3D printing technology. Powder mixtures with an alumina content of 50 to 70 vol.% were fabricated by a wet processing route. A [...] Read more.

This article presents the study of the rheological properties and the printability of produced ceramic-polymer filaments using fused deposition method (FDM) 3D printing technology. Powder mixtures with an alumina content of 50 to 70 vol.% were fabricated by a wet processing route. A series of rheological experiments of the obtained mixtures were conducted in the temperature range from 200 to 220 °C for the commercial polylactide (PLA) powder and from 200 to 240 °C for ceramic-polymer, which corresponds to the recommended temperatures for 3D printing of commercial PLA filaments. The composition with the maximum content of alumina leads to a powdery material in which the molten polymer is insufficient to measure the rheological properties. In spite of this, the filaments were prepared from all the obtained mixtures with a tabletop single-screw extruder, the diameter and surface profile of which were analyzed. As the ceramic content increased, the diameter and surface roughness of the filaments increased. Therefore, it was only possible to print an object from a filament with the lowest ceramic content. However, the print quality of the 3D printed objects from the fabricated ceramic-polymer filament is worse (imperfect form, defects between layers) compared to the commercial PLA filament. To eliminate such defects in the future, it is necessary to conduct additional research on the development of printing modes and possibly modify the software and components of the 3D printer. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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8 pages, 2423 KiB

Open AccessCommunication

Peculiarities of γ-Al₂O₃ Crystallization on the Surface of h-BN Particles

by Sergey N. Grigoriev, Elena A. Trusova, Asya M. Afzal, Thet Naing Soe, Alexandra Yu. Kurmysheva, Ekaterina Kuznetsova, Anton Smirnov and Nestor Washington Solís Pinargote

Materials 2022, 15(22), 8054; https://doi.org/10.3390/ma15228054 - 15 Nov 2022

Cited by 1 | Viewed by 1174

Abstract

The main goal of the present work was to synthesize a composite consisting of h-BN particles coated with a γ-Al₂O₃ nanolayer. A method was proposed for applying nanocrystalline γ-Al₂O₃ to h-BN particles using a sol–gel technique, which [...] Read more.

The main goal of the present work was to synthesize a composite consisting of h-BN particles coated with a γ-Al₂O₃ nanolayer. A method was proposed for applying nanocrystalline γ-Al₂O₃ to h-BN particles using a sol–gel technique, which ensures the chemical homogeneity of the composite at the nano level. It has been determined that during crystallization on the h-BN surface, the proportion of spinel in alumina decreases from 40 wt.% in pure γ-Al₂O₃ to 30 wt.% as a result of the involvement of the B³⁺ ions from the surface nitride monolayers into the transition complex. For comparison, nano-alumina was synthesized from the same sol under the same conditions as the composite. The characterization of the obtained nanostructured powders was carried out using TEM and XRD. A mechanism is proposed for the formation of a nanostructured γ-Al₂O₃@h-BN composite during the interaction of Al-containing sol and h-BN suspension in aqueous organic media. The resulting composite is a promising model of powdered raw materials for the development of fine-grained ceramic materials for a wide range of applications. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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9 pages, 2439 KiB

Open AccessArticle

Phosphate Ceramics with Silver Nanoparticles for Electromagnetic Shielding Applications

by Edita Palaimiene, Jan Macutkevič, Jūras Banys, Algirdas Selskis, Natalia Apanasevich, Alexander Kudlash, Aliaksei Sokal and Konstantin Lapko

Materials 2022, 15(20), 7100; https://doi.org/10.3390/ma15207100 - 13 Oct 2022

Cited by 3 | Viewed by 1386

Abstract

Ceramic composites with nanoparticles are intensively investigated due to their unique thermal, mechanic and electromagnetic properties. In this work, dielectric properties of phosphate ceramics with round silver nanoparticles of various sizes were studied in the wide frequency range of 20 Hz–40 GHz for [...] Read more.

Ceramic composites with nanoparticles are intensively investigated due to their unique thermal, mechanic and electromagnetic properties. In this work, dielectric properties of phosphate ceramics with round silver nanoparticles of various sizes were studied in the wide frequency range of 20 Hz–40 GHz for microwave shielding applications. The percolation threshold in ceramics is close to 30 wt.% of Ag nanoparticles content and it is higher for bigger-sized nanoparticles. The microwave complex dielectric permittivity of ceramics above the percolation threshold is rather high (ε′ = 10 and ε″ = 10 at 30 GHz for ceramics with 50 wt.% inclusions of 30–50 nm size, it corresponds to almost 61% absorption of 2 mm-thickness plate) therefore these ceramics are suitable for microwave shielding applications. Moreover, the microwave absorption is bigger for ceramics with a larger concentration of fillers. In addition, it was demonstrated that the electrical transport in ceramics is thermally activated above room temperature and the potential barrier is almost independent of the concentration of nanoparticles. At very low temperature, the electrical transport in ceramics can be related to electron tunneling. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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11 pages, 2977 KiB

Open AccessArticle

Controlling the Oxygen Defects Concentration in a Pure BiFeO₃ Bulk Ceramic

by Anton Tuluk, Hans Brouwer and Sybrand van der Zwaag

Materials 2022, 15(19), 6509; https://doi.org/10.3390/ma15196509 - 20 Sep 2022

Cited by 2 | Viewed by 1274

Abstract

BiFeO₃ is a multiferroic material with a perovskite structure that has a lot of potential for use in sensors and transducers. However, obtaining pure single-phase BiFeO₃ ceramic with a low electrical conductivity via solid-state reactions remains a problem that limits its [...] Read more.

BiFeO₃ is a multiferroic material with a perovskite structure that has a lot of potential for use in sensors and transducers. However, obtaining pure single-phase BiFeO₃ ceramic with a low electrical conductivity via solid-state reactions remains a problem that limits its application. In this work, the suppression of secondary phases in BiFeO₃ was studied by varying the compositional parameters and the sintering temperature. The addition of 1% Bi₂O₃ to the stoichiometric precursor mixture prevented the formation of secondary phases observed when sintering stoichiometric precursors. The pure phase ceramic had a p-type conductivity and a three-decade lower electrical conductivity as measured by impedance spectroscopy. Annealing of optimally synthesized material at different partial pressures of oxygen in an oxygen–nitrogen gas atmosphere showed that the reason for this type of conductivity lies in the high concentration of defects associated with oxygen. By annealing in various mixtures of nitrogen and oxygen, it is possible to control the concentration of these defects and hence the conductivity, which can go down another two decades. At a pO₂

\leq 10 %,

the conductivity is determined by intrinsic charge carriers in the material itself. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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13 pages, 2702 KiB

Open AccessArticle

Impact of the Atomic Packing Density on the Properties of Nitrogen-Rich Calcium Silicate Oxynitride Glasses

by Sharafat Ali

Materials 2022, 15(17), 6054; https://doi.org/10.3390/ma15176054 - 01 Sep 2022

Cited by 4 | Viewed by 1330

Abstract

In this work, the impact of the atomic packing density/fractional glass compactness of Ca–Si–O–N glasses on glass transition and crystallization temperatures, glass density, microhardness, molar volume, and refractive index were examined. It was found that the atomic packing density increased with increasing the [...] Read more.

In this work, the impact of the atomic packing density/fractional glass compactness of Ca–Si–O–N glasses on glass transition and crystallization temperatures, glass density, microhardness, molar volume, and refractive index were examined. It was found that the atomic packing density increased with increasing the nitrogen content and decreased with increasing the Ca content in the glass network. Furthermore, density, glass transition and crystallization temperatures, and refractive index, increased with an increasing atomic packing density of the glass, while molar volume increased with decreasing atomic packing density values. The change in hardness with atomic packing density is less clear and suggests that the atomic packing density does not solely control the underlying deformation mechanism. There is indeed competition between densification (favored at low packing density values) and isochoric shear (at larger packing density). Despite that, the effects of nitrogen as a network former and Ca as a modifier are significantly independent. The obtained results indicate that the atomic packing density of the prepared samples linearly depends on many mechanical and optical properties, suggesting that the glass network and cross-linking are proportional to the ionic radius of the Ca and the nitrogen content, respectively. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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13 pages, 7248 KiB

Open AccessArticle

Study of Morphological, Structural, and Strength Properties of Model Prototypes of New Generation TRISO Fuels

by Inesh Kenzhina, Petr Blynskiy, Artem Kozlovskiy, Meiram Begentayev, Saulet Askerbekov, Zhanna Zaurbekova and Aktolkyn Tolenova

Materials 2022, 15(14), 4741; https://doi.org/10.3390/ma15144741 - 06 Jul 2022

Viewed by 1315

Abstract

The purpose of this work is to characterize the morphological, structural, and strength properties of model prototypes of new-generation TRi-structural ISOtropic particle fuel (TRISO) designed for Generation IV high-temperature gas reactors (HTGR-type). The choice of model structures consisting of inner pyrolytic carbon (I-PyC), [...] Read more.

The purpose of this work is to characterize the morphological, structural, and strength properties of model prototypes of new-generation TRi-structural ISOtropic particle fuel (TRISO) designed for Generation IV high-temperature gas reactors (HTGR-type). The choice of model structures consisting of inner pyrolytic carbon (I-PyC), silicon carbide (SiC), and outer pyrolytic carbon (O-PyC) as objects of research is motivated by their potential use in creating a new generation of fuel for high-temperature nuclear reactors. To fully assess their full functional value, it is necessary to understand the mechanisms of resistance to external influences, including mechanical, as in the process of operation there may be external factors associated with deformation and leading to the destruction of the surface of fuel structures, which will critically affect the service life. The objective of these studies is to obtain new data on the fuel properties, as well as their resistance to external influences arising from mechanical friction. Such studies are necessary for further tests of this fuel on corrosion and irradiation resistance, as closely as possible to real conditions in the reactor. The research revealed that the study samples have a high degree of resistance to external mechanical influences, due to the high strength of the upper layer consisting of pyrolytic carbon. The presented results of the radiation resistance of TRISO fuel testify to the high resistance of the near-surface layer to high-dose irradiation. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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11 pages, 2377 KiB

Open AccessArticle

Investigation of MAO Coatings Characteristics on Titanium Products Obtained by EBM Method Using Additive Manufacturing

by Sergey Grigoriev, Nikita Peretyagin, Andrey Apelfeld, Anton Smirnov, Oleg Yanushevich, Natella Krikheli, Olga Kramar, Sergey Kramar and Pavel Peretyagin

Materials 2022, 15(13), 4535; https://doi.org/10.3390/ma15134535 - 28 Jun 2022

Cited by 10 | Viewed by 1519

Abstract

Coatings with a thickness from 27 to 62 µm on electron beam melted Ti-6Al-4V have been formed by micro-arc oxidation (MAO) in a silicate-hypophosphite electrolyte. MAO tests in the anode-cathode mode (50 Hz) with an anode-to-cathode current ratio of 1:1 and sum current [...] Read more.

Coatings with a thickness from 27 to 62 µm on electron beam melted Ti-6Al-4V have been formed by micro-arc oxidation (MAO) in a silicate-hypophosphite electrolyte. MAO tests in the anode-cathode mode (50 Hz) with an anode-to-cathode current ratio of 1:1 and sum current densities 10 and 20 A/dm² were carried out. The duration of the MAO treatment was 30 and 60 min. The effect of the processing parameters on the structural properties of the MAO treated coatings was studied. The current density and treatment time significantly affect the coating thickness and surface roughness. The values of these characteristics increase as the current density increases. The effect of thermal cycling tests on surface morphology, thickness and roughness, and elemental and phase composition of MAO coatings was analyzed. After 50 cycles of thermal cycling from +200 °C to −50 °C, no cracking or delamination of coatings was observed. Coatings formed in 30 min at a current density of 20 A/dm² turned out to be the best in terms of such indicators as surface morphology, thickness, and roughness. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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13 pages, 5837 KiB

Open AccessArticle

The Effects of Sn Doping MnNiFeO₄ NTC Ceramic: Preparation, Microstructure and Electrical Properties

by Dongcai Li, Cangbao He, Ranran Wu, Haiyan Xu and Fengjun Zhang

Materials 2022, 15(12), 4274; https://doi.org/10.3390/ma15124274 - 16 Jun 2022

Cited by 2 | Viewed by 1566

Abstract

Sn-doped MnNiFeO₄ ceramic with negative temperature coefficient (NTC) was prepared through the low-temperature solid-phase reaction route (LTSPR), aiming at improving the sintering behavior and modulating the electrical properties. The experimental results of the ceramic powder precursor indicate that the calcination of the [...] Read more.

Sn-doped MnNiFeO₄ ceramic with negative temperature coefficient (NTC) was prepared through the low-temperature solid-phase reaction route (LTSPR), aiming at improving the sintering behavior and modulating the electrical properties. The experimental results of the ceramic powder precursor indicate that the calcination of the ceramic precursors at above ~300 °C is an exothermic process, which contributes to the transition of the ceramic powder from the amorphous phase into the crystal spinel phase; the spinel phase of ceramic powders can be formed initially at ~450 °C and well-formed at ~750 °C. A high densification of ~98% relative densities and evenly distributed grains within an average size of 2~12 μm for the sintered Sn-doped specimen were obtained. The specific resistance and B-value were notably increased from 12.63 KΩ·cm to ~24.65 KΩ·cm, and from 3438 K to ~3779 K, respectively, with the Sn-doping amount. In contrast, the aging rates of the Sn-doped specimen have not changed markedly larger, waving around ~2.7%. The as-designed Sn-doped MnNiFeO₄ can be presented as a candidate for some defined NTC requirements. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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12 pages, 6368 KiB

Open AccessArticle

Mechanical Properties and Microstructure of Hot-Pressed Silica Matrix Composites

by Weili Wang, Jianqi Chen, Xiaoning Sun, Guoxun Sun, Yanjie Liang and Jianqiang Bi

Materials 2022, 15(10), 3666; https://doi.org/10.3390/ma15103666 - 20 May 2022

Cited by 1 | Viewed by 1320

Abstract

Silica is one of the most widely used ceramics due to its excellent chemical stability and dielectric property. However, its destructive brittle nature inhabits it from wider application as a functional ceramic. An improvement in toughness is a challenging topic for silica ceramic, [...] Read more.

Silica is one of the most widely used ceramics due to its excellent chemical stability and dielectric property. However, its destructive brittle nature inhabits it from wider application as a functional ceramic. An improvement in toughness is a challenging topic for silica ceramic, as well as other ceramics. In the paper, silica ceramic with different types of boron nitride powders and alumina platelets was fabricated by hot-pressing. Introduction of the additives had great influence on the composites’ mechanical properties and microstructure. The silica matrix composite containing micro-sized boron nitride powders possessed the best mechanical properties, including the bending strength (134.5 MPa) and the fracture toughness (1.85 Mpa·m^1/2). Meanwhile, the introduction of alumina platelets combined with boron nitride nanosheets achieved an effective enhancement of fracture toughness while maintaining the bending strength. Compared with the monolithic silica, the composite with simultaneous addition of alumina platelets and boron nitride nanosheets had a fracture toughness of 2.23 Mpa·m^1/2, increased by approximately 27% (1.75 Mpa·m^1/2). The crack deflection and platelet pullout were contributing to enhancement of the fracture toughness. The improved mechanical properties, combined with the intrinsic excellent dielectric and chemical properties, make the silica matrix composites promising wave transparent and thermal protection materials. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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13 pages, 4755 KiB

Open AccessArticle

Preparation and Properties of Highly Elastic, Lightweight, and Thermally Insulating SiO₂ Fibrous Porous Materials

by Yitian Li, Anran Guo, Xiaojing Xu, Yunjia Xue, Liwen Yan, Feng Hou and Jiachen Liu

Materials 2022, 15(9), 3069; https://doi.org/10.3390/ma15093069 - 23 Apr 2022

Cited by 4 | Viewed by 1841

Abstract

Fibrous porous materials are one of the most commonly used high-temperature insulation materials because of their high porosity and low thermal conductivity. Due to their wide applications in the aerospace and energy industries, the investigation of high-elastic thermally insulating porous materials has attracted [...] Read more.

Fibrous porous materials are one of the most commonly used high-temperature insulation materials because of their high porosity and low thermal conductivity. Due to their wide applications in the aerospace and energy industries, the investigation of high-elastic thermally insulating porous materials has attracted increasing attention. In order to improve the elasticity of fibrous porous materials, quartz fibers with high aspect ratio were used as matrix, sodium hexametaphosphate (SHMP) was selected as dispersant. We innovatively reported that a unique three-dimensional skeleton structure was constructed by adjusting the dispersion of fibers in the slurry, and the lightweight, thermal insulating and elastic SiO₂ fibrous porous material was then prepared by the compression molding method. The characterization results of zeta potential and absorbance showed that the addition of SHMP was an effective method to enhance the dispersibility of quartz fibers in the slurry. SiO₂ fibrous porous materials with 0.4 wt% SHMP content exhibited an ideal three-dimensional skeleton structure, which endowed the porous material with high porosity (89.39%), low density (0.04751 g/cm³), and low thermal conductivity (0.0356 W·m⁻¹·K⁻¹). The three-dimensional skeleton structure formed by overlapping fibers with high aspect ratios endowed the porous material with excellent elasticity. SiO₂ fibrous porous materials with 0.4 wt% SHMP content could undergo large strains of 30% and achieved a resilience ratio of 81.69% under the 30th compression cycle. Moreover, after heat treatment at 800 °C, SiO₂ fibrous porous materials also maintained good elasticity with a resilience ratio of more than 80%. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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11 pages, 1345 KiB

Open AccessArticle

Calculation of Thermal Expansion Coefficient of Rare Earth Zirconate System at High Temperature by First Principles

by Xingqi Wang, Xue Bai, Wei Xiao, Yuyang Liu, Xiaoning Li, Jianwei Wang, Cheng Peng, Lijun Wang and Xingming Wang

Materials 2022, 15(6), 2264; https://doi.org/10.3390/ma15062264 - 18 Mar 2022

Cited by 6 | Viewed by 2287

Abstract

Compounds of rare earth zirconates with pyrochlore structure are candidates for the application of thermal barrier coatings of next generation. In order to modify the mechanic properties and maintain the low thermal conductivity, other trivalent rare-earth element substitution is commonly used. Presently, investigation [...] Read more.

Compounds of rare earth zirconates with pyrochlore structure are candidates for the application of thermal barrier coatings of next generation. In order to modify the mechanic properties and maintain the low thermal conductivity, other trivalent rare-earth element substitution is commonly used. Presently, investigation on the evaluation of the property of thermal expansion is attracting more attention. In this paper, a feature parameter of thermal expansion coefficient at high temperature (α_∞) was proposed by combining Grüneisen’s equation and the Debye heat capacity model. Using α_∞ model, the thermal expansion property of different compounds can be easily figured out by first principles. Firstly, α_∞ of ZrO₂, HfO₂, were calculated, and results are in good agreement with the experimental data from the literature. Moreover, α_∞ of La₂Zr₂O₇, Pr₂Zr₂O₇, Gd₂Zr₂O₇, and Dy₂Zr₂O₇ were calculated, and results demonstrated that the model of α_∞ is a useful tool to predict the thermal expansion coefficient at high temperature. Finally, Gd₂Zr₂O₇ with 4 different Yb dopant concentrations (Gd₁_-xYb_x)₂Zr₂O₇ (x = 0, 0.125, 0.3125, 0.5) were calculated. Comparing with the experimental data from the literature, the calculation results showed the same tendency with the increasing of Yb concentration. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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Review

Jump to: Research

60 pages, 33352 KiB

Open AccessEditor’s ChoiceReview

The Influence of Surface Texturing of Ceramic and Superhard Cutting Tools on the Machining Process—A Review

by Sergey N. Grigoriev, Thet Naing Soe, Khaled Hamdy, Yuri Pristinskiy, Alexander Malakhinsky, Islamutdin Makhadilov, Vadim Romanov, Ekaterina Kuznetsova, Pavel Podrabinnik, Alexandra Yu. Kurmysheva, Anton Smirnov and Nestor Washington Solís Pinargote

Materials 2022, 15(19), 6945; https://doi.org/10.3390/ma15196945 - 06 Oct 2022

Cited by 2 | Viewed by 2345

Abstract

Machining is an indispensable manufacturing process for a wide range of engineering materials, such as metals, ceramics, and composite materials, in which the tool wear is a serious problem, which affects not only the costs and productivity but also the quality of the [...] Read more.

Machining is an indispensable manufacturing process for a wide range of engineering materials, such as metals, ceramics, and composite materials, in which the tool wear is a serious problem, which affects not only the costs and productivity but also the quality of the machined components. Thus, the modification of the cutting tool surface by application of textures on their surfaces is proposed as a very promising method for improving tool life. Surface texturing is a relatively new surface engineering technology, where microscale or nanoscale surface textures are generated on the cutting tool through a variety of techniques in order to improve tribological properties of cutting tool surfaces by reducing the coefficient of friction and increasing wear resistance. In this paper, the studies carried out to date on the texturing of ceramic and superhard cutting tools have been reviewed. Furthermore, the most common methods for creating textures on the surfaces of different materials have been summarized. Moreover, the parameters that are generally used in surface texturing, which should be indicated in all future studies of textured cutting tools in order to have a better understanding of its effects in the cutting process, are described. In addition, this paper proposes a way in which to classify the texture surfaces used in the cutting tools according to their geometric parameters. This paper highlights the effect of ceramic and superhard textured cutting tools in improving the machining performance of difficult-to-cut materials, such as coefficient of friction, tool wear, cutting forces, cutting temperature, and machined workpiece roughness. Finally, a conclusion of the analyzed papers is given. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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23 pages, 7111 KiB

Open AccessReview

Granulation of Silicon Nitride Powders by Spray Drying: A Review

by Sergey N. Grigoriev, Thet Naing Soe, Alexander Malakhinsky, Islamutdin Makhadilov, Vadim Romanov, Ekaterina Kuznetsova, Anton Smirnov, Pavel Podrabinnik, Roman Khmyrov, Nestor Washington Solís Pinargote and Alexandra Yu. Kurmysheva

Materials 2022, 15(14), 4999; https://doi.org/10.3390/ma15144999 - 18 Jul 2022

Cited by 6 | Viewed by 3656

Abstract

Spray drying is a widely used method of converting liquid material (aqueous or organic solutions, emulsions and suspensions) into a dry powder. Good flowability, narrow size distribution, and controllable morphology are inherent in powders produced by spray drying. This review considers the granulation [...] Read more.

Spray drying is a widely used method of converting liquid material (aqueous or organic solutions, emulsions and suspensions) into a dry powder. Good flowability, narrow size distribution, and controllable morphology are inherent in powders produced by spray drying. This review considers the granulation factors that influence the final properties of the silicon nitride dried powders. The first group includes the types of atomizers, manifolds, and drying chamber configurations. The process parameters fall into the second group and include the following: inlet temperature, atomizing air flow, feed flow rate, drying gas flow rate, outlet temperature, and drying time. Finally, the last group, feedstock parameters, includes many factors such as feed surface tension, feed viscosity, solvent type, solid particle concentration, and additives. Given the large number of factors affecting morphology, particle size and moisture, optimizing the spray drying process is usually achieved by the “trial and error” approach. Nevertheless, some factors such as the effect of a solvent, dispersant, binder, and sintering additives considered in the literature that affect the Si₃N₄ granulation process were reviewed in the work. By summarizing the data available on silicon nitride powder production, the authors attempt to tackle the problem of its emerging demand in science and industry. Full article

(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)

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