Ceramics

14 pages, 2252 KiB

Open AccessArticle

Optimization of Aluminum Boride Synthesis in the Self-Propagating High-Temperature Synthesis Mode to Create Waste-Free Technology

by Sestager Khusainovich Aknazarov, Alibek Zhumabekovich Mutushev, Juan Maria Gonzalez-Leal, Olga Stepanovna Bairakova, Olga Yuryevna Golovchenko, Natalia Yuryevna Golovchenko and Elena Alexandrovna Ponomareva

Ceramics 2022, 5(4), 1286-1299; https://doi.org/10.3390/ceramics5040091 - 14 Dec 2022

Cited by 1 | Viewed by 1378

Abstract

This paper is the continuation of our previous paper. In this work, we optimized the synthesis of aluminum borides by the SHS method. The purpose of the research was to develop the foundations of waste-free technology. The initial components were powders of boric [...] Read more.

This paper is the continuation of our previous paper. In this work, we optimized the synthesis of aluminum borides by the SHS method. The purpose of the research was to develop the foundations of waste-free technology. The initial components were powders of boric anhydride (B₂O₃), aluminum (Al), the oxide-heating additive (KNO₃), various fluxing additives, including mixed ones. The optimal ratios of the initial components for increasing the yield of aluminum boride with a high boron content and obtaining slag suitable for the production of high-alumina clinkers were determined. Studies have shown that the development of a waste-free technology for producing aluminum borides by the method of self-propagating high-temperature synthesis (SHS) is possible and yields target (alloy) and by-product (slag) products that meet the requirements for chemical and phase composition. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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17 pages, 4707 KiB

Open AccessArticle

Microporous Ceramics Based on β-Tricalcium Phosphate

by Tatiana Safronova, Grigorii Grigorev, Tatiana Shatalova, Ilya Roslyakov, Vadim Platonov and Dinara Khayrutdinova

Ceramics 2022, 5(4), 1269-1285; https://doi.org/10.3390/ceramics5040090 - 12 Dec 2022

Viewed by 1664

Abstract

Microporous ceramic material, based on β-tricalcium phosphate β-Ca₃(PO₄)₂ with grain size 2–5 μm, pore size smaller than 10 mm, and density 1.22 g/cm³ corresponding to ~40% of the theoretical density (3.07 g/cm³) of β-Ca₃ [...] Read more.

Microporous ceramic material, based on β-tricalcium phosphate β-Ca₃(PO₄)₂ with grain size 2–5 μm, pore size smaller than 10 mm, and density 1.22 g/cm³ corresponding to ~40% of the theoretical density (3.07 g/cm³) of β-Ca₃(PO₄)₂, was obtained from a powder mixture with a given molar ratio Ca/P = 1.5 after firing at 1100 °C. A homogenized powder mixture of synthetic dicalcium hydrogen phosphates with the molar ratio Ca/P = 1 and calcium citrate tetrahydrate Ca₃(C₆H₅O₇)₂·4H₂O with the molar ratio Ca/P = ∞ was used for microporous ceramic preparation. The phase composition of calcium phosphate powder, synthesized from an aqueous solution of phosphoric acid H₃PO₄ and calcium carbonate CaCO₃ powder, included brushite CaHPO₄·2H₂O as the predominant phase. Formation of β-tricalcium phosphate β-Ca₃(PO₄)₂ during firing occurred due to the heterophase interaction of the products of thermal decomposition of the components of the starting powder mixture, namely, calcium pyrophosphate Ca₂P₂O₇ and calcium oxide CaO. The formation of arch-like structures from β-tricalcium phosphate β-Ca₃(PO₄)₂ grains, which were tightly sintered together, hindered the shrinkage of ceramics. The microporous ceramics obtained, based on β-tricalcium phosphate β-Ca₃(PO₄)₂, can be recommended as a biocompatible and biodegradable material for treatment of bone defects and as a substrate for bone-cell cultivation. Full article

(This article belongs to the Special Issue Ceramic Processing and Sintering)

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14 pages, 4810 KiB

Open AccessArticle

Spark Plasma Sintering of Variable SiC α/β Ratio with Boron and Carbon Additions—Microstructure Transformation

by Marek Kostecki, Mateusz Petrus, Tomasz Płociński and Andrzej Roman Olszyna

Ceramics 2022, 5(4), 1255-1268; https://doi.org/10.3390/ceramics5040089 - 10 Dec 2022

Viewed by 1537

Abstract

This study investigated the possibility of obtaining dense silicon carbide sinters with the use of a spark plasma sintering (SPS) process by changing the composition of SiC α/β polymorphs in a starting powder mixture. Amorphous boron was used as the basic additive to [...] Read more.

This study investigated the possibility of obtaining dense silicon carbide sinters with the use of a spark plasma sintering (SPS) process by changing the composition of SiC α/β polymorphs in a starting powder mixture. Amorphous boron was used as the basic additive to activate the sintering processes. Some of the compositions were prepared with additional carbon in two different forms: multilayer graphene flakes and carbon black. The well-described effect of the β–α transition in the form of elongated lamellar grains in the sintered structure was confirmed. The obtained sinters were analyzed qualitatively and quantitatively in terms of the microstructure and density. The hardness and the participation of the polytypes in the sinter structures were examined. During the study, SPS sintering allowed us to obtain a material with a density close to the theoretical (relative density of 99.5% and hardness of 27 MPa) without the addition of carbon. It was found that the role of carbon was not limited to the activation of the sintering process. Additional effects accompanying its presence, depending on the initial α/β composition, included grain size reduction and an influence on the transformation kinetics. Full article

(This article belongs to the Special Issue Ceramic Processing and Sintering)

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13 pages, 5153 KiB

Open AccessArticle

Tensile Adhesion Strength of Atmospheric Plasma Sprayed MgAl₂O₄, Al₂O₃ Coatings

by Andrey Zayatzev, Albina Lukianova, Dmitry Demoretsky and Yulia Alexandrova

Ceramics 2022, 5(4), 1242-1254; https://doi.org/10.3390/ceramics5040088 - 09 Dec 2022

Cited by 5 | Viewed by 1422

Abstract

This study analyses the distribution of stress during the testing of glued cylindrical specimens with thermally sprayed MgAl₂O₄, Al₂O₃ oxide coatings in order to evaluate the tensile adhesion strength. The set of studies that make up [...] Read more.

This study analyses the distribution of stress during the testing of glued cylindrical specimens with thermally sprayed MgAl₂O₄, Al₂O₃ oxide coatings in order to evaluate the tensile adhesion strength. The set of studies that make up this work were conducted in order to evaluate the influence of the geometric parameters of cylindrical test specimens, 25 mm in diameter by 16–38.1 mm in height, on the measured tensile adhesion strength of the specimens. The stress and strain states inside the coating and at the coating-substrate interface were determined using the finite element modelling method. The debonding mechanisms, failure mode and influence of the coating microstructure on bond strength are also discussed. The finite element stress analysis shows a significant level of non-uniform stress distribution in the test specimens. The analysis of the results of the modelling stresses and strains using the finite element method for six types of cylindrical specimens, as well as the values obtained for the adhesion testing of MgAl₂O₄, Al₂O₃ coatings, show a need to increase the height of the standard cylindrical specimen (according to ASTM C633-13 (2021), GOST 9.304-87). The height should be increased by no less than 1.5–2.0 times to reduce the level of a non-uniform stress distribution in the separation area. Full article

(This article belongs to the Special Issue Ceramic Coatings for High-Temperature Applications)

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17 pages, 11725 KiB

Open AccessArticle

Reducing the Distortion in Particle Filled Material Extrusion (MEX)-Based Additive Manufacturing (AM) by Means of Modifying the Printing Strategy

by Johannes Abel, Siddharth Tiwari, Milán Kardos, Maria Reichel and Uwe Scheithauer

Ceramics 2022, 5(4), 1225-1241; https://doi.org/10.3390/ceramics5040087 - 08 Dec 2022

Cited by 3 | Viewed by 2152

Abstract

This study addresses a ubiquitous challenge in powder metallurgy: sintering distortion. Sintering distortion can have various causes. On one hand, external factors such as friction with the sintering support during sintering or temperature gradients in the furnace, and, on the other hand, internal [...] Read more.

This study addresses a ubiquitous challenge in powder metallurgy: sintering distortion. Sintering distortion can have various causes. On one hand, external factors such as friction with the sintering support during sintering or temperature gradients in the furnace, and, on the other hand, internal factors such as anisotropic shrinkage due to directional layer build-up or residual stresses during production, can cause deformation by relieving mechanical stress. This paper presents an approach to reducing residual stresses in components produced by ceramic Fused Filament Fabrication (CerAM FFF) by changing the printing strategy using thermoplastic porcelain filaments with a solid loading of 57% vol. The starting point of the investigation was the torsion of standard sliced porcelain fragments after solvent debinding, which led to the idea to change the printing direction to prevent the distortion. Therefore, a Python™-based post-processor was developed to control the printing direction. It has been shown that this approach can even prevent warpage both for printed ceramic and also for the metal components for technical applications. This simple observation will help all powder metallurgical manufacturers using Material Extrusion (MEX)-based Additive Manufacturing (AM). Full article

(This article belongs to the Special Issue Advances in Ceramics)

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18 pages, 10048 KiB

Open AccessArticle

Comparative Study on the Scratch and Wear Resistance of Diamond-like Carbon (DLC) Coatings Deposited on X42Cr13 Steel of Different Surface Conditions

by Shiraz Ahmed Siddiqui and Maria Berkes Maros

Ceramics 2022, 5(4), 1207-1224; https://doi.org/10.3390/ceramics5040086 - 08 Dec 2022

Cited by 1 | Viewed by 2223

Abstract

Tribological investigations are of great importance, especially in the case of novel combinations of materials used for the tribosystem. In the current research, multilayer diamond-like carbon coating deposited by plasma enhanced chemical vapour deposition on an X42Cr13 plastic mould tool steel is studied [...] Read more.

Tribological investigations are of great importance, especially in the case of novel combinations of materials used for the tribosystem. In the current research, multilayer diamond-like carbon coating deposited by plasma enhanced chemical vapour deposition on an X42Cr13 plastic mould tool steel is studied with two different surface conditions of the substrate. On the one hand, it is secondary hardened; on the other hand, it is additively plasma nitrided preceding the diamond-like carbon coating. This latter combined treatment, called duplex treatment, has an increasingly wide range of applications today. However, its effectiveness largely depends on applying the appropriate nitriding technology. The tribological behaviour was characterised by an instrumented scratch test and a reciprocating ball-on-plate wear test. The results demonstrate better scratch resistance for the duplex-treated samples, while they show weaker performance in the applied wear type of loading. The current comparative study reveals the reason for the unexpected behaviour and highlights some critical aspects of the heat treatment procedure. The architecture of the tested multilayer DLC coating is unique, and no tribological results have yet been published on tribosystems combined with an X42Cr13 steel substrate. The presented results may particularly interest tribologists and the materials research community. Full article

(This article belongs to the Special Issue Ceramic Coatings for High-Temperature Applications)

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9 pages, 2646 KiB

Open AccessArticle

The Impact of BiF₃ Doping on the Yb³⁺ to Yb²⁺ Reduction during the LiYF₄:Yb³⁺ Crystal-Growth Process

by Amir Khadiev, Niyaz Akhmetov, Stella Korableva, Oleg Morozov, Alexey Nizamutdinov, Vadim Semashko, Maksim Pudovkin and Marat Gafurov

Ceramics 2022, 5(4), 1198-1206; https://doi.org/10.3390/ceramics5040085 - 06 Dec 2022

Viewed by 1493

Abstract

Here, we report on the opportunity to suppress Yb³⁺ to Yb²⁺ dopant-ion reduction in LiYb_xY_1−xF₄ mixed crystals during growth processes, using the Bridgmen–Stocbarger technique in graphite crucibles in vacuum. This was carried out by the additional [...] Read more.

Here, we report on the opportunity to suppress Yb³⁺ to Yb²⁺ dopant-ion reduction in LiYb_xY_1−xF₄ mixed crystals during growth processes, using the Bridgmen–Stocbarger technique in graphite crucibles in vacuum. This was carried out by the additional doping of the LiF-YF₃-YbF₃ powder mixture with 1% of BiF₃ additive. The crystals of LiY_0.8Yb_0.2F₄ and LiY_0.8Yb_0.2F₄ with BiF₃ doping in the charge, were grown. The spatial distribution of the spectral-kinetic properties of Yb³⁺ and Yb²⁺ ions along the grown crystalline-boules were studied. It was established that the Yb²⁺ concentration rises during the LiY_0.8Yb_0.2F₄ crystal-growth processes without the BiF₃ additive: the absorption coefficient of Yb²⁺ (π-polarization) at 340 nm rises from 0 (at the beginning of the boule) to 2.5 cm⁻¹ (at the end of the boule). In contrast, the undetectable absorption of Yb²⁺ along the crystals grown from the BiF₃ doped melt was displayed. The luminescence-decay time of Yb³⁺ decreases from 3.7 to 1.8 ms from the beginning to the end of the LiY_0.8Yb_0.2F₄ boule grown from the BiF₃ undoped melt, and stays constant (~3.7 ms) along the samples grown with BiF₃. Here we demonstrate a positive effect of BiF₃ doping on the optical homogeneity of LiYF₄:Yb³⁺ crystals. Full article

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13 pages, 3027 KiB

Open AccessArticle

Structural and Luminescence Properties of (Gd_1−xY_x)₂O₃ Powders Doped with Nd³⁺ Ions for Temperature Measurements

by Vladimir Aseev, Anastasiia Babkina, Sergey Evstropiev, Natalia Kuzmenko, Irina Sevastianova, Denis Prokuratov and Mikhail Khodasevich

Ceramics 2022, 5(4), 1185-1197; https://doi.org/10.3390/ceramics5040084 - 03 Dec 2022

Cited by 1 | Viewed by 1225

Abstract

Rare earth activated powders are widely regarded as promising candidates for optical thermometry due to their unique photoluminescence characteristics. The paper presents the structural and luminescent properties of crystalline powders of gadolinium and yttrium oxides (Gd_1−xY_x)₂O₃ [...] Read more.

Rare earth activated powders are widely regarded as promising candidates for optical thermometry due to their unique photoluminescence characteristics. The paper presents the structural and luminescent properties of crystalline powders of gadolinium and yttrium oxides (Gd_1−xY_x)₂O₃, doped with Nd³⁺ ions, synthesized by the liquid polymer-salt method. The addition of polyvinylpyrrolidone increases the homogeneity of the mixture and ensures high adhesion of the resulting powders. Scanning electron microscopy shows that powders are μm-sized aggregates, which consist of particles with several tens of nanometers in size. A smooth shift of the diffraction peaks of the powders occurs when Gd is replaced by Y without additional peaks. The successive decrease in the lattice constant of the powders from 10.816 to 10.607 Å confirms the existence of continuous solid solutions in the system. The Stark sublevels of the ⁴F_3/2 → ⁴I_9/2 fluorescent band are shifted to 4 nm when Gd is replaced by Y since the strength of the local field has a stronger effect on the inner F-shell of Nd ions in the case of Y. For thermometry, we chose the ratio of the fluorescence intensities between the Stark sublevels ⁴F_3/2(2) → ⁴I_9/2(2) and ⁴F_3/2(1) → ⁴I_9/2(2). The best obtained sensitivity is 0.22% °C⁻¹ for Nd-doped GdYO₃ powder in the range of 10–70 °C. This value of temperature sensitivity, together with radiation and excitation lying in the biological window, opens the possibility of using Nd³⁺-doped (Gd_1−xY_x)₂O₃ powders for real-time thermal probing of under tissue luminescence with sub-degree resolution. Full article

(This article belongs to the Special Issue Composite Nanopowders: Synthesis and Applications)

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11 pages, 3710 KiB

Open AccessArticle

Microwave Plasma Assisted Aerosol Deposition (μ-PAD) for Ceramic Coating Applications

by Soo Ouk Jang, Changhyun Cho, Ji Hun Kim, In Je Kang, Hyonu Chang, Hyunjae Park, Kyungmin Lee, Dae Gun Kim and Hye Won Seok

Ceramics 2022, 5(4), 1174-1184; https://doi.org/10.3390/ceramics5040083 - 02 Dec 2022

Viewed by 1623

Abstract

To improve plasma and chemical resistance on various vacuum components used for semiconductor manufacturing equipment, various ceramic coating techniques have been applied. Among these methods for ceramic coating, the well-known atmospheric plasma spray (APS) is advantageous for providing thick film (100 µm or [...] Read more.

To improve plasma and chemical resistance on various vacuum components used for semiconductor manufacturing equipment, various ceramic coating techniques have been applied. Among these methods for ceramic coating, the well-known atmospheric plasma spray (APS) is advantageous for providing thick film (100 µm or more) deposition. However, there are problems associated with the phase transition of the coating film and poor film quality due to formation of voids. To solve these problems, the aerosol deposition (AD) method has been developed. This method provides nice ceramic film quality. However, the coating rate is quite slow and has difficulty producing thick films (>30 µm). To overcome these limitations, microwave plasma-assisted aerosol deposition (μ-PAD) is applied at low vacuum conditions without the AD nozzle. This method uses a microwave plasma source during the AD process. After enduring a long-term durability test, as a trial run, μ-PAD has been applied on the actual process site. With the Al₂O₃ powder, μ-PAD shows a coating rate that is 12 times higher than the AD method. In addition, the formation of a thicker film (96 µm) deposition has been demonstrated. On the other hand, the coating film hardness, porosity, adhesion, and withstand voltage characteristics were confirmed to be less than the AD method. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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7 pages, 1323 KiB

Open AccessBrief Report

Fabrication of Reaction-Bonded Boron Carbide-Based Composites by Binder Jetting 3D Printing

by Larissa Wahl, Samuel Schmiedeke, Moritz Knorr, Ines Schneider and Nahum Travitzky

Ceramics 2022, 5(4), 1167-1173; https://doi.org/10.3390/ceramics5040082 - 01 Dec 2022

Cited by 2 | Viewed by 1641

Abstract

In this work, the binder jetting 3D printing of boron carbide was combined with a subsequent liquid silicon infiltration procedure to produce reaction-bonded boron carbide (RBBC)-based structures. After printing, the samples were isostatically pressed to obtain more homogeneous and denser microstructures while maintaining [...] Read more.

In this work, the binder jetting 3D printing of boron carbide was combined with a subsequent liquid silicon infiltration procedure to produce reaction-bonded boron carbide (RBBC)-based structures. After printing, the samples were isostatically pressed to obtain more homogeneous and denser microstructures while maintaining their complex shapes. The RBBC bodies were successfully fabricated, and the influence of the binder content on the amount of residual silicon was studied. By increasing the binder content from 10 to 22.5 vol.%, the Si content decreased from ~28 to ~12 vol.%. The mechanical properties dependent on the Si content were additionally investigated. The measured average values for the bending strength (~355 MPa), Young’s modulus (~348 GPa), and hardness (~20 GPa) are comparable to those reported in the literature for RBBC-based materials. Full article

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13 pages, 1590 KiB

Open AccessArticle

Study of Tricalcium Phosphate Ceramics Doped with Gadolinium Ions with Various EPR Techniques

by Margarita A. Sadovnikova, Fadis F. Murzakhanov, Inna V. Fadeeva, Anna A. Forysenkova, Dina V. Deyneko, Georgy V. Mamin and Marat R. Gafurov

Ceramics 2022, 5(4), 1154-1166; https://doi.org/10.3390/ceramics5040081 - 01 Dec 2022

Cited by 3 | Viewed by 1804

Abstract

Tricalcium phosphate (TCP)-based materials, such as β-Ca₃(PO₄)₂ doped with rare earth ions (RE), have shown applications as biomaterials, lighting emitting materials, scintillating materials, in vivo imaging probes, and thermoluminescent dosimeters. Their properties are found to be dependent on [...] Read more.

Tricalcium phosphate (TCP)-based materials, such as β-Ca₃(PO₄)₂ doped with rare earth ions (RE), have shown applications as biomaterials, lighting emitting materials, scintillating materials, in vivo imaging probes, and thermoluminescent dosimeters. Their properties are found to be dependent on the distribution of RE³⁺ on Ca²⁺ sites that can be controlled by pulsed electron paramagnetic resonance (EPR) and electron spin echo envelop modulation (ESEEM) experiments. The main spectroscopic parameters (spin Hamiltonian values) of Gd³⁺ and nitrogen impurity centers are quantitatively determined (g-factor, the fine structure parameters D and E, the hyperfine constants A) as well as dynamic characteristics: spin–lattice T₁ and spin–spin T₂ relaxation times. Based on the analysis of the EPR datasets, the interatomic distance between Gd³⁺ and ³¹P was estimated in the dipole–dipole approximation. Two structurally nonequivalent Gd³⁺ positions in the β-TCP structure have been identified. The obtained valuable results demonstrate applicability of modern EPR techniques to characterize Gd-TCP systems despite the powder structure of the material and high electron spin S = 7/2 of Gd³⁺ ions. Full article

(This article belongs to the Special Issue Ceramic Processing and Sintering)

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26 pages, 7825 KiB

Open AccessArticle

Structural, Optical, Magnetic and Electrical Properties of Sputtered ZnO and ZnO:Fe Thin Films: The Role of Deposition Power

by Ahmed Faramawy, Hamada Elsayed, Carlo Scian and Giovanni Mattei

Ceramics 2022, 5(4), 1128-1153; https://doi.org/10.3390/ceramics5040080 - 01 Dec 2022

Cited by 11 | Viewed by 1916

Abstract

Structural, optical, magnetic, and electrical properties of zinc oxide (henceforth, ZO) and iron doped zinc oxide (henceforth, ZOFe) films deposited by sputtering technique are described by means of Rutherford backscattering spectrometry, grazing incidence X-ray diffraction, scanning electron microscope (SEM), UV–Vis spectrometer, vibrating sample [...] Read more.

Structural, optical, magnetic, and electrical properties of zinc oxide (henceforth, ZO) and iron doped zinc oxide (henceforth, ZOFe) films deposited by sputtering technique are described by means of Rutherford backscattering spectrometry, grazing incidence X-ray diffraction, scanning electron microscope (SEM), UV–Vis spectrometer, vibrating sample magnetometer, and room temperature electrical conductivity, respectively. GIXRD analysis revealed that the films were polycrystalline with a hexagonal phase, and all films had a preferred (002) c-axis orientation. The lattice parameters

a

and c of the wurtzite structure were calculated for all films. The

a

parameter remains almost the same (around 3 Å), while c parameter varies slightly with increasing Fe content from 5.18 to 5.31 Å throughout the co-deposition process. The optical gap for undoped and doped ZO was obtained from different numerical methods based on the experimental data and it was increased with the increment of the concentration of Fe dopant from 3.26 eV to 3.35 eV. The highest magnetization (4.26 × 10⁻⁴ emu/g) and lowest resistivity (4.6 × 10⁷ Ω·cm) values of the ZO films were found to be at an Fe content of 5% at. %. An explanation for the dependence of the optical, magnetic, and electrical properties of the samples on the Fe concentrations is also given. The enhanced magnetic properties such as saturated magnetization and coercivity with optical properties reveal that Fe doped ZO thin films are suitable for magneto-optoelectronic (optoelectronic and spintronics) device applications. Full article

(This article belongs to the Special Issue Ceramic Coatings for High-Temperature Applications)

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13 pages, 4599 KiB

Open AccessArticle

Fabrication of NiO/YSZ-Based Anodes for Solid Oxide Fuel Cells by Hybrid 3D Inkjet Printing and Laser Treatment

by Inna Malbakhova, Artem Bagishev, Alexander Vorobyev, Tatiana Borisenko, Olga Logutenko and Alexander Titkov

Ceramics 2022, 5(4), 1115-1127; https://doi.org/10.3390/ceramics5040079 - 01 Dec 2022

Cited by 4 | Viewed by 2231

Abstract

An anode for solid oxide fuel cells (SOFCs) was fabricated using 3D inkjet printing and layer-by-layer laser treatment of compositions based on the NiO/YSZ system followed by thermal sintering. The samples were characterized by scanning electron microscopy and X-ray phase analysis. The study [...] Read more.

An anode for solid oxide fuel cells (SOFCs) was fabricated using 3D inkjet printing and layer-by-layer laser treatment of compositions based on the NiO/YSZ system followed by thermal sintering. The samples were characterized by scanning electron microscopy and X-ray phase analysis. The study of the morphology of the as-prepared samples revealed the presence of both interlayer macroporosity and intralayer microporosity, which depends on the laser exposure during laser treatment. The use of graphite directly added to the printing composition as the pore former increased the intralayer porosity. The morphology and size of the pores were shown to be similar to those of the pore former. The microstructure and porosity of the anode support can be controlled by varying the laser exposure values and the graphite content of the ceramic composite, which in turn opens up great prospects for using these paste compositions and printing techniques for the manufacture of SOFC anode supports. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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13 pages, 2018 KiB

Open AccessArticle

Synthesis and Characterization of Ceria- and Samaria-Based Powders and Solid Electrolytes as Promising Components of Solid Oxide Fuel Cells

by Marina V. Kalinina, Daria A. Dyuskina, Maxim Y. Arsent’ev, Sergey V. Mjakin and Olga A. Shilova

Ceramics 2022, 5(4), 1102-1114; https://doi.org/10.3390/ceramics5040078 - 24 Nov 2022

Viewed by 1509

Abstract

Finely dispersed (CeO₂)_0.95(Sm₂O₃)_0.05, (CeO₂)_0.90(Sm₂O₃)_0.10 and (CeO₂)_0.80(Sm₂O₃)_0.20 mesoporous powders with a specific pore volume of 0.080–0.092 [...] Read more.

Finely dispersed (CeO₂)_0.95(Sm₂O₃)_0.05, (CeO₂)_0.90(Sm₂O₃)_0.10 and (CeO₂)_0.80(Sm₂O₃)_0.20 mesoporous powders with a specific pore volume of 0.080–0.092 cm³/g and a specific surface of 50–83 m²/g are synthesized by the co-precipitation of cerium and samarium hydroxides from the corresponding nitrate solutions. The prepared powders are used to obtain ceramic nanomaterials with a fluorite-like cubic crystal lattice with a coherent scattering region (CSR) of about 65–69 nm (1300 °C). The study of physicochemical and electrophysical properties of the prepared ceramics revealed the obtained materials featuring an open porosity of 2–6% and a predominantly ionic type of electric conductivity (ion transport numbers t_i = 0.85–0.73 in the temperature range 300–700 °C). The conductivity in solid solutions proceeds via a vacancy mechanism with σ_{700 °C}= 3.3·10⁻² S/cm. The synthesized ceramic materials are shown to be promising as solid oxide electrolytes in medium temperature fuel cells. Full article

(This article belongs to the Special Issue Ceramics for Decarbonization of the Global Industry)

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18 pages, 7516 KiB

Open AccessArticle

Tribological Study of Simply and Duplex-Coated CrN-X42Cr13 Tribosystems under Dry Sliding Wear and Progressive Loading Scratching

by Maria Berkes Maros and Shiraz Ahmed Siddiqui

Ceramics 2022, 5(4), 1084-1101; https://doi.org/10.3390/ceramics5040077 - 24 Nov 2022

Viewed by 1610

Abstract

CrN coatings are widely used in the industry due to their excellent mechanical features and outstanding wear and corrosion resistance. Using scratch and ball-on-disk wear tests, the current study deals with the tribological characterisation of CrN coatings deposited onto an X42Cr13 plastic mould [...] Read more.

CrN coatings are widely used in the industry due to their excellent mechanical features and outstanding wear and corrosion resistance. Using scratch and ball-on-disk wear tests, the current study deals with the tribological characterisation of CrN coatings deposited onto an X42Cr13 plastic mould tool steel. Two surface conditions of the secondary-hardened substrate are compared—the plasma nitrided (duplex treated) and the un-nitrided (simply coated) states. The appropriate combination of secondary hardening providing the maximum toughness and the high-temperature nitriding of this high Cr steel is a great challenge due to the nitrogen-diffusion-inhibiting effect of Cr. The beneficial effect of the applied duplex treatment is proven by the 34% improvement of the adhesion strength and the 43% lower wear rate of the investigated duplex coatings. Detailed morphological analyses give insight into the characteristic damage mechanisms controlling the coating failure processes during scratching and wearing. For the simply CrN-coated sample, a new type of scratch damage mechanism, named “SAS-wings”, is identified, providing useful information in predicting the final failure of the coating. The tribological results obtained on tribosystems with the investigated high Cr steel/CrN constituents represent a novelty in the given field. Full article

(This article belongs to the Special Issue Ceramic Coatings for High-Temperature Applications)

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18 pages, 5678 KiB

Open AccessArticle

Silicon Carbide Precursor: Structure Analysis and Thermal Behavior from Polymer Cross-Linking to Pyrolyzed Ceramics

by Sébastien Vry, Marilyne Roumanie, Pierre-Alain Bayle, Sébastien Rolère and Guillaume Bernard-Granger

Ceramics 2022, 5(4), 1066-1083; https://doi.org/10.3390/ceramics5040076 - 23 Nov 2022

Cited by 1 | Viewed by 1975

Abstract

The Silres H62C methyl-phenyl-vinyl-hydrogen polysiloxane is a promising candidate as a SiC precursor for 3D printing based on photopolymerization reaction. An in-depth nuclear magnetic resonance spectroscopy analysis allowed us to determine its structure and quantify its functional groups. The polysiloxane was found to [...] Read more.

The Silres H62C methyl-phenyl-vinyl-hydrogen polysiloxane is a promising candidate as a SiC precursor for 3D printing based on photopolymerization reaction. An in-depth nuclear magnetic resonance spectroscopy analysis allowed us to determine its structure and quantify its functional groups. The polysiloxane was found to have a highly branched ladder-like structure, with 21.9, 31.4 and 46.7% of mono-, di- and tri-functional silicon atoms. The polysiloxane cross-links from 180 °C using hydrosilylation between silyl groups (8.4% of the total functional groups) and vinyl groups (12.0%) and contains a non-negligible ethoxy content (2.4%), allowing cross-linking through a hydrolyze/condensation mechanism. After converting the polymer into ceramic and thus releasing mainly hydrogen and methane, the ceramic yield was 72.5%. An X-ray diffraction analysis on the cross-linked and pyrolyzed polysiloxane showed that the ceramic is amorphous at temperatures up to 1200 °C and starts to crystallize from 1200 °C, leading into 3C-SiC carbon-rich ceramic at 1700 °C in an argon atmosphere. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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15 pages, 4275 KiB

Open AccessArticle

Analysis of the Formed Protective Layer Inhibiting Alkali Corrosion in Aluminosilicate Refractory Castables

by Valentin Antonovič, Rimvydas Stonys, Povilas Zdanevičius, Romualdas Mačiulaitis, Renata Boris and Jurgita Malaiškienė

Ceramics 2022, 5(4), 1051-1065; https://doi.org/10.3390/ceramics5040075 - 19 Nov 2022

Cited by 1 | Viewed by 1664

Abstract

This article analyzes the mechanism of the protective layer formation under the action of alkali in a refractory castable when ground quartz sand (GQS) is used as an admixture to produce refractory conventional castables (CC) and medium cement castables (MCC). It was found [...] Read more.

This article analyzes the mechanism of the protective layer formation under the action of alkali in a refractory castable when ground quartz sand (GQS) is used as an admixture to produce refractory conventional castables (CC) and medium cement castables (MCC). It was found that, independently of the castable composition, the addition of GQS (2.5%) reduces the degree of K₂CO₃ dissolution at high temperature, and the released potassium reacts with the silica and forms a viscous potassium silicate glass, which reduces the mobility of alkali. The liquid phase formed filled some of the open pores and hindered the penetration of potassium into the deeper layers of the refractory castable. The thickness of the formed protective layer, after three cycles of the alkaline corrosion test, varies from 700 µm up to 1300 µm, depending on the castable composition. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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16 pages, 4827 KiB

Open AccessArticle

Characterisation of a Complex CaZr_0.9Ce_0.1Ti₂O₇ Glass–Ceramic Produced by Hot Isostatic Pressing

by Malin C. J. Dixon Wilkins, Clémence Gausse, Luke T. Townsend, Laura J. Gardner and Claire L. Corkhill

Ceramics 2022, 5(4), 1035-1050; https://doi.org/10.3390/ceramics5040074 - 19 Nov 2022

Cited by 2 | Viewed by 1903

Abstract

The behaviour of Ce-containing zirconolites in hot isostatically pressed (HIPed) materials is complex, characterised by redox interactions between the metallic HIP canister that result in reduction of Ce⁴⁺ to Ce³⁺. In this work, a glass–ceramic of composition 70 wt.% CaZr [...] Read more.

The behaviour of Ce-containing zirconolites in hot isostatically pressed (HIPed) materials is complex, characterised by redox interactions between the metallic HIP canister that result in reduction of Ce⁴⁺ to Ce³⁺. In this work, a glass–ceramic of composition 70 wt.% CaZr_0.9Ce_0.1Ti₂O₇ ceramic in 30 wt.% Na₂Al₂Si₆O₁₆ glass was produced by HIP (approx. 170 cm³ canister) to examine the extent of the material–canister interaction. A complex material with six distinct regions was produced, with the extent of Ce reduction varying depending on the distance from the canister. Notably, the innermost bulk regions (those approximately 7 mm from the canister) contained only Ce⁴⁺, demonstrating that a production-scale HIPed glass–ceramic would indeed have a bulk region unaffected by the reducing environment induced by a ferrous HIP canister despite the flow of glass at the HIP temperature. Each of the six regions was characterised by XRD (including Rietveld method refinements), SEM/EDX and linear combination fitting of Ce L₃-edge XANES spectra. Regions in the lower part of the canister were found to contain a significantly higher fraction of Ce⁴⁺ compared to the upper regions. Though zirconolite-2M was the major crystalline phase observed in all regions, the relative abundances of minor phases (including sphene, baddeleyite, rutile and perovskite) were higher in the outermost regions, which comprised a significantly reduced Ce inventory. Full article

(This article belongs to the Special Issue Zirconolite Ceramic and Glass-Ceramic Wasteforms)

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16 pages, 5129 KiB

Open AccessArticle

Complex Oxide Nanoparticle Synthesis: Where to Begin to Do It Right?

by Elizabeth Gager, William Halbert and Juan C. Nino

Ceramics 2022, 5(4), 1019-1034; https://doi.org/10.3390/ceramics5040073 - 19 Nov 2022

Cited by 3 | Viewed by 1949

Abstract

Synthesis of advanced ceramics requires a high degree of control over the particle size and stoichiometry of the material. When choosing a synthesis method for complex oxides it is important to begin with the correct precursors and solvents to achieve high purity nanoparticles. [...] Read more.

Synthesis of advanced ceramics requires a high degree of control over the particle size and stoichiometry of the material. When choosing a synthesis method for complex oxides it is important to begin with the correct precursors and solvents to achieve high purity nanoparticles. Here, we detail the selection process for precursors and solvents for liquid-phase precipitation synthesis. Data for metal nitrate, chloride, acetate, and oxalate precursors has been compiled to assist future synthesis. The role of hydration within the precursors is discussed as it affects the final stoichiometry of the material. Melting temperatures are also compiled for these compounds to assist in material selection. The solubility of the precursors in different solvents is examined to determine the correct solvent during synthesis. As an example, using the methodology presented here, two different materials are synthesized based on commonly available precursors. A catalyst based on a quaternary perovskite and an advanced ionic conductor based on a high entropy fluorite oxide are synthesized using precipitation methods and their characterization is detailed. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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10 pages, 3329 KiB

Open AccessArticle

A Rapid Sintering Method for Cerium Nitride Pellet: A Uranium Mononitride Surrogate

by Logan Joyce and Yi Xie

Ceramics 2022, 5(4), 1009-1018; https://doi.org/10.3390/ceramics5040072 - 18 Nov 2022

Cited by 1 | Viewed by 2003

Abstract

Uranium mononitride (UN) is a candidate fuel material for light water reactors with higher uranium (U) loading and thermal conductivity than uranium dioxide (UO₂). However, the sintering of UN pellets is challenging as the UN powder particles oxidize rapidly at high [...] Read more.

Uranium mononitride (UN) is a candidate fuel material for light water reactors with higher uranium (U) loading and thermal conductivity than uranium dioxide (UO₂). However, the sintering of UN pellets is challenging as the UN powder particles oxidize rapidly at high temperatures unless the oxygen concentration is extremely low. Oxidation during sintering either reduces the relative density of the sintered UN pellet or disintegrates the sintered UN pellet to powder. To address this problem, the present work developed a rapid sintering method for producing highly densified UN surrogate pellets with minimal oxidation. Cerium nitride (CeN) is used as a surrogate for UN to reduce radiation hazards. With the custom-developed fast-heating system, the sintering process was completed within 150 s. The sintering atmosphere was flowing nitrogen (N₂). The sintered CeN pellet density was 95% of the theoretical density (TD) or higher. The microstructure was uniform with a 10–25 µm grain size as demonstrated by scanning electron microscopy (SEM) and contained trivial levels of oxides as demonstrated by X-ray diffraction (XRD). The resultant pellets indicate that the rapid sintering method is a promising method to make UN fuel pellets with equivalent or higher density to pellets made by conventional sintering methods, while also being more efficient in time and costs. Full article

(This article belongs to the Special Issue Ceramic Processing and Sintering)

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18 pages, 4779 KiB

Open AccessArticle

Deterioration of Mortar Bars Using Binary and Ternary Mixtures Immersed in Sodium Sulfate Solutions

by Federico Aguayo and Mehrab Nodehi

Ceramics 2022, 5(4), 991-1008; https://doi.org/10.3390/ceramics5040071 - 17 Nov 2022

Cited by 4 | Viewed by 1758

Abstract

In this study, the performance of several binary and ternary mixtures containing high-calcium fly ash and other pozzolans, such as Class F fly ash and silica fume, were investigated for their sulfate resistance using different sodium sulfate solutions. The mortar bars were placed [...] Read more.

In this study, the performance of several binary and ternary mixtures containing high-calcium fly ash and other pozzolans, such as Class F fly ash and silica fume, were investigated for their sulfate resistance using different sodium sulfate solutions. The mortar bars were placed in a similar sulfate solution as per modified ASTM C 1012/1012M (33,800 ppm SO₄²⁻) with a less severe sulfate solution (6000 ppm SO₄²⁻) has been tested to resemble actual field performance for a duration of 18 months. The phase composition of the mortar samples was investigated using X-ray diffraction and scanning electron microscope coupled with energy dispersive spectroscopy (SEM/EDS). Results show that the mortar bars placed in the moderate sulfate concentration experience less expansion and deterioration than the same bars placed in the higher sulfate concentration. Storage in sodium sulfate solutions resulted in the formation of ettringite and gypsum in both sulfate concentrations. Replacement of cement by high-calcium fly ash showed significantly higher amounts of ettringite formation, especially for the mortar bars stored in the higher sulfate concentration. SEM analysis revealed ettringite to be the primary cause of disruption and deterioration observed in the mortar bars. Full article

(This article belongs to the Special Issue Ceramics for Decarbonization of the Global Industry)

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10 pages, 964 KiB

Open AccessReview

Tooth-Derived Matrix Granules for Enhanced Bone Healing: Chemical Composition, Morphological Aspects, and Clinical Outcomes

by Júlio C. M. Souza, Mario Escobar, Inês Sofia Pimentel, João Caramês, Wim Teughels, Filipe Silva and Bruno Henriques

Ceramics 2022, 5(4), 981-990; https://doi.org/10.3390/ceramics5040070 - 11 Nov 2022

Cited by 2 | Viewed by 1505

Abstract

Bone grafting has increasingly been used in surgical procedures for enhanced bone augmentation. Tooth-derived graft material has received considerable attention due to its chemical composition and autogenous source that can improve bone tissue healing. The main aim of this study was to provide [...] Read more.

Bone grafting has increasingly been used in surgical procedures for enhanced bone augmentation. Tooth-derived graft material has received considerable attention due to its chemical composition and autogenous source that can improve bone tissue healing. The main aim of this study was to provide a short and comprehensive review on the chemical composition, morphological aspects, and clinical outcomes of bone grafting using tooth-derived matrix granules. Dentin tissue has a chemical composition similar to that on bone tissues regarding the presence of hydroxyapatite, type I collagen, and different growth factors. Dentin-matrix granules are often processed at well-controlled size ranging from approximately 300 up to 1300 µm, while maintaining porosity and organic content. In addition, a dense collagen fiber network is still present after the milling and chemical treatment of dentin granules. Thus, dentin-matrix granules can improve the bone healing process considering their chemical composition, porous structure, and adequate size. However, further in vivo and in vitro studies should be performed taking into consideration different demineralization procedures, remnant organic content, porosity, and granule size. Full article

(This article belongs to the Special Issue Ceramic Materials in Oral Applications)

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20 pages, 1468 KiB

Open AccessArticle

Optical Properties of Five Esthetic Ceramic Materials Used for Monolithic Restorations: A Comparative In Vitro Study

by Saleh N. Almohammed, Belal Alshorman and Layla A. Abu-Naba’a

Ceramics 2022, 5(4), 961-980; https://doi.org/10.3390/ceramics5040069 - 10 Nov 2022

Cited by 2 | Viewed by 2298

Abstract

Zirconia has generated tremendous interest in the esthetic materials used for dental restorations. However, using conventional zirconia has some limitations especially in highly esthetically demanding situations, as it lacks the translucency that other ceramic materials possess. This study aimed to evaluate and compare [...] Read more.

Zirconia has generated tremendous interest in the esthetic materials used for dental restorations. However, using conventional zirconia has some limitations especially in highly esthetically demanding situations, as it lacks the translucency that other ceramic materials possess. This study aimed to evaluate and compare the optical properties (shade, translucency, and opalescence) of three CAD-CAM monolithic multilayer zirconia ceramics (GNX; Ceramill Zolid^® Gen-X, ZCP; IPS e.max^® ZirCAD, and UPC; Upcera^® Esthetic Explore Prime) and one CAD-CAM monolithic multilayer polymer-infiltrated hybrid ceramic (ENM; Vita^® Enamic) with a CAD-CAM monolithic lithium disilicate ceramic as control (EMX; IPS e.max^® CAD). 200 discs (GNX = 40, ZCP = 40, UPC = 40, ENM = 40, and EMX = 40) were cut, polished, and fully crystallized. Half of the samples for each group were subjected to hydrothermal aging. Descriptive analysis and ANOVA tests were used to compare the groups. Zirconia GNX, ZCP, and UPC groups showed significantly lower optical properties than ENM and EMX groups for both the non-aged and aged samples (p < 0.05). UPC and ENM groups showed a significant decrease in translucency and opalescence after aging (p < 0.05). The optical properties of monolithic multilayer zirconia ceramics were lower than monolithic multilayer polymer-infiltrated hybrid ceramic and lithium disilicate ceramic. Polymer-infiltrated hybrid ceramic was significantly affected by aging. Full article

(This article belongs to the Special Issue Ceramic Materials in Oral Applications)

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14 pages, 7927 KiB

Open AccessArticle

Forming of Additively Manufactured Ceramics by Magnetic Fields

by Christina Klug, Simone Herzog, Anke Kaletsch, Christoph Broeckmann and Thomas H. Schmitz

Ceramics 2022, 5(4), 947-960; https://doi.org/10.3390/ceramics5040068 - 03 Nov 2022

Cited by 1 | Viewed by 1602

Abstract

The application of additive manufacturing using liquid material extrusion is inherently linked to material-related deformations and limitations in the choice of component geometry. This empirical study addresses the question of how the plasticity of a ceramic composite material can be utilized for a [...] Read more.

The application of additive manufacturing using liquid material extrusion is inherently linked to material-related deformations and limitations in the choice of component geometry. This empirical study addresses the question of how the plasticity of a ceramic composite material can be utilized for a new integrated design and manufacturing process. In the exploratory approach, the liquid material is not limited in its soft plastic state, but its malleability is harnessed for a design-oriented approach. For this purpose, soft magnetic particles are added to a liquid clay mass. The developed composite material can be controlled, stabilized, and shaped by magnetic fields directly in the additive manufacturing process using modified equipment. In this study a permanent magnet and an electromagnet were compared while the distance between the printed part and the magnet was controlled by an optical sensor. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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19 pages, 16805 KiB

Open AccessArticle

The Solution Combustion Synthesis of ZnO Powder for the Photodegradation of Phenol

by Aleksandr P. Amosov, Vladislav A. Novikov, Egor M. Kachkin, Nikita A. Kryukov, Alexander A. Titov, Ilya M. Sosnin and Dmitry L. Merson

Ceramics 2022, 5(4), 928-946; https://doi.org/10.3390/ceramics5040067 - 03 Nov 2022

Cited by 5 | Viewed by 1942

Abstract

Nanoscale and submicron powder of zinc oxide (ZnO) is known as a highly efficient photocatalyst that is promising for solving the problem of wastewater treatment from toxic organic pollutants including phenol and its derivatives. The results of laboratory studies of ZnO preparation by [...] Read more.

Nanoscale and submicron powder of zinc oxide (ZnO) is known as a highly efficient photocatalyst that is promising for solving the problem of wastewater treatment from toxic organic pollutants including phenol and its derivatives. The results of laboratory studies of ZnO preparation by a simple, energy-saving, and highly productive method of solution–combustion synthesis from a mixture of solutions of zinc nitrate and glycine, as well as the use of the ZnO powder synthesized by combustion for the photocatalytic decomposition of phenol, are presented. The modes and characteristics of combustion, phase composition, chemical composition, and structure of the combustion product at different ratios of glycine with zinc nitrate were determined. It is shown that calcination at 650 °C reduces the content of carbon impurity in the combustion product to ~1 wt.% and leads to obtaining ZnO powder in the form of porous agglomerates up to 100 μm in size sintered from crystalline nanoscale and submicron ZnO particles with an average crystallite size of 44 nm. The ZnO powder exhibits high photocatalytic activity, leading to the almost complete degradation of phenol in an aqueous solution under the action of ultraviolet irradiation in less than 4 h. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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20 pages, 2358 KiB

Open AccessArticle

Micro-Analytical Study of a Zeolites/Geo-Polymers/Quartz Composite, Dielectric Behaviour and Contribution to Brønsted Sites Affinity

by Abdel Boughriet, Oscar Allahdin, Nicole Poumaye, Gregory Tricot, Bertrand Revel, Ludovic Lesven and Michel Wartel

Ceramics 2022, 5(4), 908-927; https://doi.org/10.3390/ceramics5040066 - 02 Nov 2022

Cited by 2 | Viewed by 1649

Abstract

The chemical and mineralogical surface properties of a brick-derived composite were examined by using an environmental scanning electron microscopy (ESEM) equipped with an energy dispersive X-ray spectrometer (EDS). Investigations revealed that the material could be assimilated to an adsorptive membrane having zeolites deposited [...] Read more.

The chemical and mineralogical surface properties of a brick-derived composite were examined by using an environmental scanning electron microscopy (ESEM) equipped with an energy dispersive X-ray spectrometer (EDS). Investigations revealed that the material could be assimilated to an adsorptive membrane having zeolites deposited onto quartz matrix. In our calculation, the membrane was considered as a diphase composite and its dielectric constant was evaluated from theoretical models developed in the literature. Electro-kinetic analysis showed that composite surfaces were hydroxylated with the formation of hydroxyl groups which behaved amphoterically. A theory-based approach was used for calculating thermodynamic constants relative to surface-protonation equilibriums. In the H-form of the composite, the occurrence of bridging Si–(OH)–Al sites were evidenced by mathematical calculations utilizing equations in direct relation to mineralogical, crystallographic and dielectric surface characteristics. ¹H MAS NMR spectroscopy confirmed the existence of bridging Brønsted acid sites at acidified composite surfaces interacting with ammonium (as probe ions). Owing to advancements in brick-based composites research, this should lead more to the development of “ceramic” adsorptive membranes with natural clay materials. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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7 pages, 736 KiB

Open AccessArticle

In Vitro Antibacterial Activity of Different Bioceramic Root Canal Sealers

by Alberto Dagna, Marco Colombo, Claudio Poggio, Gianluigi Russo, Matteo Pellegrini, Giampiero Pietrocola and Riccardo Beltrami

Ceramics 2022, 5(4), 901-907; https://doi.org/10.3390/ceramics5040065 - 01 Nov 2022

Cited by 2 | Viewed by 1860

Abstract

Bioceramic root canal sealers have been introduced in clinical dental use, but less is known about the antibacterial activity against Streptococcus mutans, Streptococcus salivarius, and Streptococcus sanguis. The purpose of the study is to compare new bioceramic sealers with a [...] Read more.

Bioceramic root canal sealers have been introduced in clinical dental use, but less is known about the antibacterial activity against Streptococcus mutans, Streptococcus salivarius, and Streptococcus sanguis. The purpose of the study is to compare new bioceramic sealers with a traditional zinc-oxide eugenol material considered as a control. The different bioceramic root canal sealants tested were FillRoot ST, BioRoot™RCS, Well-Root™ PT, and CeraSeal. In vitro antibacterial activity against Streptococci was assessed using the agar disc diffusion test at two different intervals, 24 h and 48 h. A non-parametric statistical analysis was performed to compare the inhibition zones for each of the different materials. Bioceramic root canal sealers showed mild antibacterial activity, while zinc-oxide eugenol-based material showed a stronger inhibition of Streptococci diffusion. No differences were detected for the measurements of inhibition zones between 24 h and 48 h except for FillRoot ST and BioRoot™RCS. Full article

(This article belongs to the Special Issue Ceramic Materials in Oral Applications)

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18 pages, 6304 KiB

Open AccessArticle

Deliberate Surface Treatment of Zirconium Dioxide with Abrasive Brushing Tools

by Anton Hoyer and Eckart Uhlmann

Ceramics 2022, 5(4), 883-900; https://doi.org/10.3390/ceramics5040064 - 01 Nov 2022

Cited by 1 | Viewed by 1338

Abstract

Brushing with bonded abrasives is a flexible finishing process used to reduce the roughness of technical surfaces. Although industrially widespread, especially for the finishing of metallic surfaces, insufficient knowledge of the motion, the material removal, and the wear behavior of the abrasive filaments [...] Read more.

Brushing with bonded abrasives is a flexible finishing process used to reduce the roughness of technical surfaces. Although industrially widespread, especially for the finishing of metallic surfaces, insufficient knowledge of the motion, the material removal, and the wear behavior of the abrasive filaments complicates predictions of the work result. In particular, the reliable finishing of ceramics with bonded diamond grains proves difficult due to increased material removal rates, quickly leading to undesirable changes in the workpiece geometry. Based on technological investigations with abrasive brushing tools, this article provides insights into the surface finishing of zirconium dioxide with a focus on finding compromises between reduction in the surface roughness and alteration of the workpiece shape. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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21 pages, 3564 KiB

Open AccessReview

The Role of Clay Mineral-Derived Photocatalysts in Insights of Remediation

by Walber Freitas, Pollyana Trigueiro, Thiago Marinho, Luzia M. Honorio, Edson C. Silva-Filho, Marcelo B. Furtini, Juan A. Cecília, Maria G. Fonseca and Josy Osajima

Ceramics 2022, 5(4), 862-882; https://doi.org/10.3390/ceramics5040063 - 26 Oct 2022

Cited by 6 | Viewed by 1788

Abstract

Clay minerals have advantages to be used as supports for obtaining new catalysts, in which colloidal and surface characteristics play a significant role. In addition to their favorable physicochemical properties, clay minerals allow different modifications to form structures with broad photochemical capabilities. This [...] Read more.

Clay minerals have advantages to be used as supports for obtaining new catalysts, in which colloidal and surface characteristics play a significant role. In addition to their favorable physicochemical properties, clay minerals allow different modifications to form structures with broad photochemical capabilities. This review collects pertinent works of semiconductor nanoparticles loaded onto clay minerals and their potential application in hazardous contaminant photodegradation. Web of Science, Scopus, and Science Direct were used for bibliographic research databases. The sol–gel method is the most frequent technique used to obtain semiconductors immobilized onto clay minerals, but other methods have also proven helpful in forming these structures. Thence, the types of synthesis and different parameters that influence their photocatalytic efficiency will be discussed. Pillared clay minerals have been applied to photo-oxidation reactions involving photodecomposition of environmental contaminants. The homogeneous dispersion of nanoparticles on the surface of clay minerals, reduction of fine particles, its non-toxicity, and the generation of a suitable suspension for photocatalytic reactions may be the main characteristics of these inorganic supports to obtain successful photoactive materials. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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14 pages, 6100 KiB

Open AccessArticle

Characterization of Thermal Barrier Coatings Using an Active Thermography Approach

by Francesca Curà, Raffaella Sesana, Luca Corsaro and Riccardo Mantoan

Ceramics 2022, 5(4), 848-861; https://doi.org/10.3390/ceramics5040062 - 25 Oct 2022

Cited by 1 | Viewed by 1501

Abstract

The aim of this paper is to define and set up an experimental procedure, based on active thermography, for the characterization of coatings for industrial applications. This procedure is intended to be a fast and reliable method, alternative to the consolidated one described [...] Read more.

The aim of this paper is to define and set up an experimental procedure, based on active thermography, for the characterization of coatings for industrial applications. This procedure is intended to be a fast and reliable method, alternative to the consolidated one described in International Standards. In more detail, a classical active thermographic set up, and not a dedicated apparatus, was used for that aim, and data processing techniques referred to the analytical approach described in Standards. The active thermography procedure provided the measurement of the surface temperature of specimens undergoing a thermal excitation, applied by means of a laser pulse (Pulsed Technique). Temperature data processing, according to and adapting the Standard procedures, allowed to obtain thermal conductivity and diffusivity information. In particular, two coating processes (Atmospheric and Suspension Plasma Spray) applied to the same base material, Inconel 601, and the same coating material were investigated. These results were compared in terms of thermal properties variation with respect to base and coated materials, and in terms of different coating processes (APS and SPS). Obtained results were also compared to those available in literature. Full article

(This article belongs to the Special Issue Ceramic Coatings for High-Temperature Applications)

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