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21 pages, 13391 KiB

Open AccessArticle

Spark Plasma Sintering of Ceramics Based on Solid Solutions of Na_1+2xZr_2−xCo_x(PO₄)₃ Phosphates: Thermal Expansion and Mechanical Properties Research

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Ceramics 2023, 6(1), 278-298; https://doi.org/10.3390/ceramics6010017 - 16 Jan 2023

Viewed by 1653

Abstract

The structure, microstructure, coefficient of thermal expansion (CTE), and mechanical properties of Na_1+2xZr_2−xCo_x(PO₄)₃ ceramics (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were studied. Na_1+2xZr_2−xCo_x(PO₄)₃ [...] Read more.

The structure, microstructure, coefficient of thermal expansion (CTE), and mechanical properties of Na_1+2xZr_2−xCo_x(PO₄)₃ ceramics (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were studied. Na_1+2xZr_2−xCo_x(PO₄)₃ submicron powders with the NaZr₂(PO₄)₃ structure (NZP, kosnarite type) were obtained by the solid-phase method. The starting reagents (NaNO₃, ZrOCl₂·8H₂O, NH₄H₂PO₄, CoCl₂·6H₂O, ethanol) were mixed with the addition of ethyl alcohol. The resulting mixtures were annealed at 600 °C (20 h) and 700 °C (20 h). The obtained phosphates crystallized in the expected structure of the NaZr₂(PO₄)₃ type (trigonal system, space group R

\bar{3}

c). Thermal expansion of the powders was studied with high-temperature X-ray diffraction at temperatures ranging from 25 to 700 °C. CTEs were calculated, and their dependence on the cobalt content was analyzed. Na_1+2xZr_2−xCo_x(PO₄)₃ ceramics with high relative density (93.67–99.70%) were obtained by Spark Plasma Sintering (SPS). Ceramics poor in cobalt (x = 0.1) were found to have a high relative density (98.87%) and a uniform fine-grained microstructure with a grain size of 0.5–1 µm. Bigger cobalt content leads to a smaller relative density of ceramics. During the sintering of ceramics with high cobalt content, anomalous grain growth was observed. The powder compaction rate was shown to be determined by creep and diffusion intensity in the Na_1+2xZr_2−xCo_x(PO₄)₃ crystal lattice. SPS activation energy in ceramics increased as the cobalt content grew. The microhardness and fracture toughness of ceramics did not depend on their cobalt content. Full article

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

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16 pages, 7653 KiB

Open AccessArticle

Structure, Mechanical and Luminescent Properties of Solid Solution (Y_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01)Nb_0.7Ta_0.3O₄

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Ceramics 2023, 6(1), 86-101; https://doi.org/10.3390/ceramics6010007 - 09 Jan 2023

Viewed by 1244

Abstract

Ceramic samples of polycomponent solid solution (Y_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01)Nb_0.7Ta_0.3O₄ have been prepared by sol–gel synthesis from fine powders obtained using nitrate solutions of rare earth elements REE and coprecipitated hydroxides [...] Read more.

Ceramic samples of polycomponent solid solution (Y_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01)Nb_0.7Ta_0.3O₄ have been prepared by sol–gel synthesis from fine powders obtained using nitrate solutions of rare earth elements REE and coprecipitated hydroxides of niobium and tantalum. The structural state of the initial powders’ crystal lattice has been investigated. The morphological features of the microstructure of the ceramics samples have been studied in dependence of temperature regimes of their preparation. The ceramics’ strength characteristics (Young’s modulus) and the critical stress intensity factor of the mode I K_IC have been estimated. Cathode- and photoluminescent properties of ceramic solid solutions (Y_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01)Nb_0.7Ta_0.3O₄ have been studied. Full article

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

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17 pages, 4707 KiB

Open AccessArticle

Microporous Ceramics Based on β-Tricalcium Phosphate

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

Viewed by 1374

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

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Marek Kostecki

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Mateusz Petrus

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Tomasz Płociński

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Andrzej Roman Olszyna

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

Viewed by 1218

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, 1590 KiB

Open AccessArticle

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

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Margarita A. Sadovnikova

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

Cited by 2 | Viewed by 1456

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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10 pages, 3329 KiB

Open AccessArticle

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

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Logan Joyce

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Yi Xie

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

Cited by 1 | Viewed by 1655

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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16 pages, 2955 KiB

Open AccessArticle

Microstructural Characteristics of 3Y-TZP Ceramics and Their Effects on the Flexural Strength

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Manuel Fellipe Rodrigues Pais Alves

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Leonardo Queiroz Bueno de Campos

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Bruno Galvão Simba

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Cosme Roberto Moreira da Silva

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Kurt Strecker

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Claudinei dos Santos

Ceramics 2022, 5(4), 798-813; https://doi.org/10.3390/ceramics5040058 - 17 Oct 2022

Cited by 6 | Viewed by 1729

Abstract

This work evaluates the effects of grain growth and tetragonality of the t-ZrO₂ phase on the mechanical properties of 3Y-TZP ceramics. Samples were sintered at 1475 °C for 2 h, and at 1600 °C for 2, 12, or 24 h. After sintering, [...] Read more.

This work evaluates the effects of grain growth and tetragonality of the t-ZrO₂ phase on the mechanical properties of 3Y-TZP ceramics. Samples were sintered at 1475 °C for 2 h, and at 1600 °C for 2, 12, or 24 h. After sintering, the tetragonal ZrO₂ polytypes t and t′ were observed under all sintering conditions, while a residual content of monoclinic ZrO₂ was detected in samples sintered at 1600 °C for 24 h. The average grain size was found to vary from 0.65 ± 0.10 to 2.20 ± 0.35 μm. Moreover, zirconia ceramics sintered at 1475 °C for 2 h exhibit higher flexural strength (1210 ± 85 MPa), while samples sintered at 1600 °C for 24 h exhibit the lowest flexural strength (910 ± 90 MPa). These results were related to the progressive formation of Y³⁺-rich grains (t′-ZrO₂) due to the grain boundary segregation-induced phase (GBSIPT) mechanism. Due to the high stabilizer concentration in the solid solution, these grains present lower tetragonality, being highly stable at room temperature. Consequently, the observed strength reduction of samples sintered at 1600 °C for 24 h is related to the presence of the t′-ZrO₂ phase, which is less prompt to the phase transformation toughening process, limiting shielding zones’ effectiveness at the crack tip. Full article

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

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12 pages, 2873 KiB

Open AccessArticle

Composite Ceramics in the Na₂O–CaO–SiO₂–P₂O₅ System Obtained from Pastes including Hydroxyapatite and an Aqueous Solution of Sodium Silicate

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Ceramics 2022, 5(3), 550-561; https://doi.org/10.3390/ceramics5030041 - 05 Sep 2022

Cited by 6 | Viewed by 1818

Abstract

The new approach to obtaining ceramic materials in the Na₂O–CaO–SiO₂–P₂O₅ system based on the binder—an aqueous solution of sodium silicate and filler—hydroxyapatite was shown in current research. After heat treatment at 500 °C and 700 °C, [...] Read more.

The new approach to obtaining ceramic materials in the Na₂O–CaO–SiO₂–P₂O₅ system based on the binder—an aqueous solution of sodium silicate and filler—hydroxyapatite was shown in current research. After heat treatment at 500 °C and 700 °C, the ceramic samples included non-reacted hydroxyapatite Ca₁₀(PO₄)₆(OH)₂, β-rhenanite β-NaCaPO₄ and sodium calcium silicophosphate Na₂Ca₄(PO₄)₂SiO₄. An increase in temperature to 900 °C and 1100 °C allowed to obtain ceramic materials with the following phases: devitrite Na₂Ca₃Si₆O₁₆, β-rhenanite β-NaCaPO₄, β-wollastonite β-CaSiO₃, and silicon dioxide SiO₂. The strength of ceramic samples rose with increasing temperature from ≈7.0 MPa (bending) and ≈7.2 MPa (compression) at 500 °C to ≈9.5 MPa (bending) and ≈31.6 MPa (compression) at 1100 °C. At the same time, the apparent density decreased from 1.71 g/cm³ to 1.15 g/cm³. The top of the compressive strength equal to 31.6 MPa was observed when the apparent density was 1.15 g/cm³. Obtained ceramics consisted of biocompatible phases, widely studied in the literature; thus, it confirms the possibility of using an aqueous solution of sodium silicate in medical materials science. Full article

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

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17 pages, 6632 KiB

Open AccessArticle

Biocompatibility of Ceramic Materials in Ca₂P₂O_7–Ca(PO₃)₂ System Obtained via Heat Treatment of Cement-Salt Stone

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Ceramics 2022, 5(3), 516-532; https://doi.org/10.3390/ceramics5030039 - 27 Aug 2022

Cited by 5 | Viewed by 1899

Abstract

Biocompatibility of ceramic materials in Ca₂P₂O₇-Ca(PO₃)₂ system was investigated using different methods, including in vitro and in vivo tests. Ceramic materials in the Ca₂P₂O₇-Ca(PO₃)₂ system [...] Read more.

Biocompatibility of ceramic materials in Ca₂P₂O₇-Ca(PO₃)₂ system was investigated using different methods, including in vitro and in vivo tests. Ceramic materials in the Ca₂P₂O₇-Ca(PO₃)₂ system were obtained by annealing cement-salt stone based on powder mixtures of calcium citrate tet-rahydrate Ca₃(C₆H₅O₇)₂·4H₂O and monocalcium phosphate monohydrate (MCPM) Ca(H₂PO₄)₂·H₂O. The phase composition of cement-salt stone included brushite, monetite as a result of chemical reaction of starting components after adding of water. The presence of citric acid as by-product of chemical reaction, leads to increase the setting time of the cement-salt stone. Highly concentrated aqueous suspensions based on calcium citrate and MCPM powders providing content of calcium polyphosphate Ca(PO₃)₂ up to 20 wt % in ceramics were used for designing bioresorbable materials. The presence of an excess of monocalcium phosphate monohydrate makes it possible to reduce the annealing temperature of ceramics, which is associated with the formation of a lower melting phase of Ca(PO₃)₂. In vivo tests shown that obtained ceramic materials can be recommended for regenerative treatments for bone defects. Full article

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

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15 pages, 8608 KiB

Open AccessArticle

Inorganic Powders Prepared from Fish Scales

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Ceramics 2022, 5(3), 484-498; https://doi.org/10.3390/ceramics5030037 - 26 Aug 2022

Cited by 1 | Viewed by 4130

Abstract

A mixture of abramis brama (freshwater bream), carassius carassius (crucian carp), and sander lucioperca (pike perch) scales was used for the preparation of fish scale powder containing constituents of organic and inorganic nature. The mixture of the mentioned fish scales was washed, dried, [...] Read more.

A mixture of abramis brama (freshwater bream), carassius carassius (crucian carp), and sander lucioperca (pike perch) scales was used for the preparation of fish scale powder containing constituents of organic and inorganic nature. The mixture of the mentioned fish scales was washed, dried, and ground for the preparation of fish scale powder. Vibration sieving was used to prepare fish scale powder enriched with inorganic components. According to thermal analysis data, this fish scale powder enriched with inorganic components included about 36.5 wt.% components removed when heating, primarily those of organic nature, and 63.5 wt.% mineral components. Inorganic powders consisting of hydroxyapatite and magnesium whitlockite were obtained via heat treatment of this fish scale powder at 800–1000 °C. Particles of these inorganic powders consisted of sintered grains with dimensions less than 100 nm after heat treatment at 800 °C, less than 200 nm after heat treatment at 900 °C, and 100–1000 nm after heat treatment at 1000 °C. Fish scale powder enriched with inorganic components as well as heat-treated inorganic powders consisting of hydroxyapatite and magnesium whitlockite can be recommended for the production of different materials, such as ceramics or composites. Full article

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

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12 pages, 3103 KiB

Open AccessArticle

Powders Based on Ca₂P₂O₇-CaCO₃-H₂O System as Model Objects for the Development of Bioceramics

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Ceramics 2022, 5(3), 423-434; https://doi.org/10.3390/ceramics5030032 - 13 Aug 2022

Cited by 3 | Viewed by 1735

Abstract

Nanoscale powders of hydrated Ca₂P₂O₇, CaCO₃, and a product of mixed-anionic composition containing P₂O₇⁴⁻ and CO₃²⁻ anions were synthesized from aqueous solutions of Ca(CH₃COO)₂, pyrophosphoric [...] Read more.

Nanoscale powders of hydrated Ca₂P₂O₇, CaCO₃, and a product of mixed-anionic composition containing P₂O₇⁴⁻ and CO₃²⁻ anions were synthesized from aqueous solutions of Ca(CH₃COO)₂, pyrophosphoric acid (H₄P₂O₇), and/or (NH₄)₂CO₃. Pyrophosphoric acid was previously obtained on the basis of the ion exchange process from Na₄P₂O₇ solution and H⁺-cationite resin for further introduction into the reactions as an anionic precursor. The phase composition of powders after the syntheses was represented by bioresorbable phases of X-ray amorphous hydrated Ca₂P₂O₇ phase, calcite and vaterite polymorphs of CaCO₃. Based on synthesized powders, simple cylindrical constructions were prepared via mechanical pressing and fired in the temperature range of 600–800 °C. Surface morphology observation showed the presence of bimodal porosity with pore sizes up to 200 nm and 2 μm, which is likely to ensure tight particle packing and roughness of the sample surface required for the differentiation of osteogenic cells. Thus, the prepared ceramic samples can be further examined as model objects for bone tissue repair. Full article

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

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15 pages, 5949 KiB

Open AccessArticle

Oxidation Resistance of γ-TiAl Based Alloys Modified by C, Si and Y₂O₃ Microdopants

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Pavel A. Loginov

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Georgy M. Markov

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Nataliya V. Shvyndina

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Gleb V. Smirnov

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Evgeny A. Levashov

Ceramics 2022, 5(3), 389-403; https://doi.org/10.3390/ceramics5030030 - 02 Aug 2022

Cited by 1 | Viewed by 1498

Abstract

This work aimed to study the oxidation resistance of γ-TiAl based alloy, doped with small concentrations of carbon, silicon, and yttrium oxide in air at 800 and 1100 °C for 30 h. The TNM-B1 alloy samples were produced via high-energy ball milling, self-propagating [...] Read more.

This work aimed to study the oxidation resistance of γ-TiAl based alloy, doped with small concentrations of carbon, silicon, and yttrium oxide in air at 800 and 1100 °C for 30 h. The TNM-B1 alloy samples were produced via high-energy ball milling, self-propagating high-temperature synthesis, and hot isostatic pressing techniques. The microstructure, oxidation kinetics at 800–1100 °C, scale structure, and oxidation mechanism were studied. The oxidation of alloys modified with carbon and silicon at 1100 °C was characterized by the formation of a three-layer coating. The Y₂O₃ modified alloy performed the greatest oxidation resistance at 1100 °C and promoted the formation of a dense Al₂O₃ interlayer. Full article

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

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17 pages, 8195 KiB

Open AccessArticle

Ti/Cu/Kovar Multilayer Interlayer PTLP Diffusion Bonding Si₃N₄/Ht250

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Ceramics 2022, 5(3), 372-388; https://doi.org/10.3390/ceramics5030029 - 31 Jul 2022

Viewed by 1624

Abstract

In this paper, partial transient liquid phase (PTLP) diffusion bonding between Si₃N₄ ceramics and Ht250 cast iron was carried out by using an Ti/Cu/Kovar/Cu/Ti interlayer. The effects of the heating temperature and holding time on the microstructure, formation mechanism, and [...] Read more.

In this paper, partial transient liquid phase (PTLP) diffusion bonding between Si₃N₄ ceramics and Ht250 cast iron was carried out by using an Ti/Cu/Kovar/Cu/Ti interlayer. The effects of the heating temperature and holding time on the microstructure, formation mechanism, and mechanical properties of Si₃N₄/Ht250 cast iron joints were studied. The results show that the maximum shear strength of the joint is 112 MPa when the welding temperature is 1000 °C and the holding time is 1 h. In addition, the problems of Ti/Cu/Ti intermetallic compound formation and Cu/Si₃N₄ ceramic residual thermal stress in the joint can be effectively alleviated. Full article

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

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10 pages, 4174 KiB

Open AccessArticle

Synthesis and Thermal Behaviour of Calcium Alkyl Phosphates as Bioceramic Precursors

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Andrey Tikhonov

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Valery Putlayev

Ceramics 2022, 5(3), 362-371; https://doi.org/10.3390/ceramics5030028 - 29 Jul 2022

Cited by 1 | Viewed by 1288

Abstract

Powders of alkyl phosphoric acids and calcium alkyl phosphates with various alkyl chains (butyl, octyl, and dodecyl) have been synthesized. The resulting powders were characterized by X-ray phase analysis, electron microscopy, and thermal analysis. It was shown that the calcium alkyl phosphates correspond [...] Read more.

Powders of alkyl phosphoric acids and calcium alkyl phosphates with various alkyl chains (butyl, octyl, and dodecyl) have been synthesized. The resulting powders were characterized by X-ray phase analysis, electron microscopy, and thermal analysis. It was shown that the calcium alkyl phosphates correspond to the composition of acid salts of calcium alkyl phosphates Ca(RPO₄H)₂, data on which are not presented in the literature. The thermal behaviour of calcium alkyl phosphates can be described as a complex phase transformation into biphasic calcium phosphate mixture (of Ca₂P₂O₇ and Ca₃(PO₄)₂) with the increase of the Ca to P ratio in comparison to initial materials. The powders thermally treated in the range of 400–600 °C could be recommended as single precursors of biphasic bioceramics. Full article

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

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11 pages, 2425 KiB

Open AccessArticle

Photonic Sintering of Oxide Ceramic Films: Effect of Colored Fe_xO_y Nanoparticle Pigments

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Ceramics 2022, 5(3), 351-361; https://doi.org/10.3390/ceramics5030027 - 28 Jul 2022

Cited by 2 | Viewed by 2412

Abstract

Alumina and zirconia thin films modified with colored nano-Fe_xO_y pigments were sintered by the flash-lamp-annealing method. We selected a nano α-Al₂O₃ and micron α-Al₂O₃ bimodal mixture as the base precursor material, and we doped [...] Read more.

Alumina and zirconia thin films modified with colored nano-Fe_xO_y pigments were sintered by the flash-lamp-annealing method. We selected a nano α-Al₂O₃ and micron α-Al₂O₃ bimodal mixture as the base precursor material, and we doped it with 5 vol% of Fe_xO_y red/brown/black/yellow pigments. The coatings were deposited from nanoparticle dispersions both on glass and on flexible metal foil. The characteristics of the thin films obtained with the use of various additives were compared, including the surface morphologies, optical properties, crystallinities, and structures. Flash lamp annealing was applied with the maximum total energy density of 130 J/cm² and an overall annealing time of 7 s. Based on the simulated temperature profiles and electron-microscopy results, a maximum annealing temperature of 1850 °C was reached for the red Al₂O₃: Fe₂O₃ ceramic film. The results show that red α-Fe₂O₃ pigments allow for the achievement of maximum layer absorption, which is effective for flash lamp sintering. It was also possible to use the selected red α-Fe₂O₃ particles for the flash-lamp-assisted sintering of ZrO₂ on a 30 µm-thin flexible stainless-steel substrate. Full article

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

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21 pages, 8693 KiB

Open AccessArticle

Chemically Bound Resorbable Ceramics as an Antibiotic Delivery System in the Treatment of Purulent–Septic Inflammation of Bone Tissue

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Ceramics 2022, 5(3), 330-350; https://doi.org/10.3390/ceramics5030026 - 27 Jul 2022

Cited by 2 | Viewed by 1530

Abstract

Local drug delivery systems are an effective approach in the treatment of purulent–septic inflammation of bone tissue. Chemically bonded multiphase ceramics based on calcium-deficient carbonate-substituted hydroxyapatite combine resorbability, osteoconductivity, and the possibility of volumetric incorporation of antibiotics. Macroporosity is regulated by the concentration [...] Read more.

Local drug delivery systems are an effective approach in the treatment of purulent–septic inflammation of bone tissue. Chemically bonded multiphase ceramics based on calcium-deficient carbonate-substituted hydroxyapatite combine resorbability, osteoconductivity, and the possibility of volumetric incorporation of antibiotics. Macroporosity is regulated by the concentration of polyethylene glycol granules introduced into the initial powder composition, followed by their extraction. The selected conditions for the consolidation of the ceramic matrix and the extraction of PEG granules retain the activity of vancomycin, which is confirmed by the results of microbiological studies. The concentration of vancomycin and the porosity affect the local concentration and release of the antibiotic. The incorporation method provides a prolonged release of the antibiotic for up to 31 days. In vivo experiments with bone implantation have shown that chemically bound macroporous ceramics with incorporated vancomycin are a therapeutically effective carrier of the substance during the healing of bone defects in conditions of surrounding purulent–septic inflammation, and can be considered as a carrier for local antibacterial therapy, at the site of implantation. Full article

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

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12 pages, 2777 KiB

Open AccessArticle

Incorporation of Manganese (II) in Beta-Tricalcium Phosphate from EPR and ENDOR Measurements for Powders

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,

and

Ceramics 2022, 5(3), 318-329; https://doi.org/10.3390/ceramics5030025 - 26 Jul 2022

Cited by 1 | Viewed by 1572

Abstract

Powders of β-tricalcium phosphate (β-TCP, Ca₃PO₄) doped with manganese (Mn²⁺) are comprehensively analyzed with electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) techniques. The modeling of the spectra permitted to calculate the values of zero-field splitting [...] Read more.

Powders of β-tricalcium phosphate (β-TCP, Ca₃PO₄) doped with manganese (Mn²⁺) are comprehensively analyzed with electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) techniques. The modeling of the spectra permitted to calculate the values of zero-field splitting (

B_{2}^{0}

= −904 MHz;

B_{4}^{0}

= −1.41 MHz and

B_{4}^{3}

= 195.2 MHz) and explain the origin of the low-field hyperfine structures as the allowed spin transitions of fine structure. Three structurally inequivalent positions for Mn²⁺ in the β-TCP crystal lattice are identified and their g-factors and hyperfine constants are quantified. The obtained results can serve as fundamental background to the study of structurally disordered matrices with high spin (S ≥ 1) impurities which are important for catalytic systems. Full article

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

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13 pages, 5626 KiB

Open AccessArticle

FIB and Wedge Polishing Sample Preparation for TEM Analysis of Sol-Gel Derived Perovskite Thin Films

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and

Ceramics 2022, 5(3), 288-300; https://doi.org/10.3390/ceramics5030023 - 20 Jul 2022

Viewed by 2629

Abstract

In ceramic thin films, choosing an appropriate sample preparation method for transmission electron microscopy (TEM) analyses is of paramount importance to avoid preparation-induced damage and retain nanoscale features that require investigation. Here we compare two methods of TEM thin film sample preparation, namely [...] Read more.

In ceramic thin films, choosing an appropriate sample preparation method for transmission electron microscopy (TEM) analyses is of paramount importance to avoid preparation-induced damage and retain nanoscale features that require investigation. Here we compare two methods of TEM thin film sample preparation, namely conventional wedge polishing and focused ion beam (FIB) based lift out preparation applied to ferroelectric barium titanate (BaTiO₃, BT) thin films made by chemical solution deposition (CSD). The aim of the work is to determine the pros and cons of each method considering not only the quality of the TEM specimen, but also aspects such as availability, ease of use, and affordability. Besides some limitations on the selection of visualized area due to thickness constraints on the FIB-made sample, both methods offer the capability to prepare samples with very comparable quality, as indicated by achieving the same thickness, a largely agreeing microstructure, no secondary phases on the diffraction pattern, and good atomic resolution. This last observation is especially important in the current context of material science, where more nanoscale phenomena are becoming the subject of study. The wedge polishing method, however, is deemed more affordable in terms of instrumentation, as it only requires a tripod polisher, a polishing wheel, and a precision ion polishing system, whereas the lift out method requires a scanning electron microscope (SEM) equipped with an FIB system. We believe that this work serves groups working on ferroelectric thin films in preparing TEM samples in a more effective and uncomplicated manner, facilitating progress in understanding this fascinating class of materials. Full article

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

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12 pages, 5951 KiB

Open AccessArticle

Investigation of Targeted Process Control for Adjusting the Macrostructure of Freeze Foams Using In Situ Computed Tomography

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and

Ceramics 2022, 5(3), 269-280; https://doi.org/10.3390/ceramics5030021 - 07 Jul 2022

Cited by 2 | Viewed by 1546

Abstract

Freeze foams are novel and innovative cellular structures that are based on a direct foaming process and that can be manufactured using any material that can be processed by powder technology. The foam formation process is characterized by the highly complex interaction of [...] Read more.

Freeze foams are novel and innovative cellular structures that are based on a direct foaming process and that can be manufactured using any material that can be processed by powder technology. The foam formation process is characterized by the highly complex interaction of various process and material parameters that were chosen empirically and that have so far been difficult to reproduce. To allow properties to be specifically tailored towards certain applications, it is necessary to examine the phenomena observed during foam formation as well as the impact of the process and material parameters on the structural constitution to deduce guidelines for manufacturing and quality assessment (e.g., mechanical strength, cell and pore sizes, pore size distribution). The variety of possible applications are a result of the wide spectrum of initial suspensions and especially the foam structure properties derived from process parameters such as the cell geometry, pore size distribution, fraction of open and closed porosity, and the textures of the cell struts. Due to earlier findings, the focus of this paper focuses on adjusting and tailoring the macrostructure (homogenization of the pore sizes and their distribution inside foam cells) to create load- and application-adapted ceramic foams. To this end, an experiment was designed using previously identified pore and characteristic influencers (air and water content, temperature of the suspension, pressure reduction rate) as influencing parameters. Their interconnected impacts on selected target values were examined during the freeze foaming process using an in situ freeze foaming device inside an X-ray. Full article

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

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12 pages, 2853 KiB

Open AccessArticle

Powder Mixture for the Production of Microporous Ceramics Based on Hydroxyapatite

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Ceramics 2022, 5(1), 108-119; https://doi.org/10.3390/ceramics5010010 - 18 Feb 2022

Cited by 2 | Viewed by 3068

Abstract

Powder mixtures with a given molar ratio of Ca/P = 1.67 were prepared under mechanical activation conditions from hydroxyapatite powder Ca₁₀(PO₄)₆(OH)₂ and a 1M aqueous solution of oxalic acid H₂C₂O₄ at [...] Read more.

Powder mixtures with a given molar ratio of Ca/P = 1.67 were prepared under mechanical activation conditions from hydroxyapatite powder Ca₁₀(PO₄)₆(OH)₂ and a 1M aqueous solution of oxalic acid H₂C₂O₄ at a molar ratio of Ca₁₀(PO₄)₆(OH)₂/H₂C₂O₄ = 1:4. The phase composition of obtained powder mixture included brushite (calcium hydrophosphate dihydrate) CaHPO₄·2H₂O, calcium oxalate monohydrate CaC₂O₄·H₂O in form of whewellite and weddellite, and some quantity of quasi-amorphous phase. This powder mixture was used to produce microporous monophase ceramics based on hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ with apparent density of 1.25 g/cm³ after firing at 1200 °C. Microporosity of sintered ceramics was formed due to the presence of particles with plate-like morphology, restraining shrinkage during sintering. Microporous ceramics based on hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ with the roughness of the surface as a consequence of the created microporosity can be recommended as a biocompatible material for bone defects treatment 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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20 pages, 8554 KiB

Open AccessArticle

Sinterability, Mechanical Properties and Wear Behavior of Ti₃SiC₂ and Cr₂AlC MAX Phases

by

Eduardo Tabares

,

Michael Kitzmantel

,

Erich Neubauer

,

Antonia Jimenez-Morales

and

Sophia A. Tsipas

Ceramics 2022, 5(1), 55-74; https://doi.org/10.3390/ceramics5010006 - 31 Jan 2022

Cited by 6 | Viewed by 2638

Abstract

MAX phases are a promising family of materials for several demanding, high-temperature applications and severe conditions. Their combination of metallic and ceramic properties makes MAX phases great candidates to be applied in energy production processes, such as high temperature heat exchangers for catalytic [...] Read more.

MAX phases are a promising family of materials for several demanding, high-temperature applications and severe conditions. Their combination of metallic and ceramic properties makes MAX phases great candidates to be applied in energy production processes, such as high temperature heat exchangers for catalytic devices. For their successful application, however, the effect of the processing method on properties such as wear and mechanical behavior needs to be further established. In this work, the mechanical and wear properties of self-synthesized Ti₃SiC₂ and Cr₂AlC MAX phase powders consolidated by different powder metallurgy routes are evaluated. Uniaxial pressing and sintering, cold isostatic pressing and sintering and hot pressing were explored as processing routes, and samples were characterized by analyzing microstructure, phase constitution and porosity. Wear behavior was studied by reciprocating-sliding tests, evaluating the wear rate by the loss of material and the wear mechanism. Full article

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

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24 pages, 6750 KiB

Open AccessArticle

Synthesis and Characterization of Novel Calcium-Silicate Nanobioceramics with Magnesium: Effect of Heat Treatment on Biological, Physical and Chemical Properties

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Georgia K. Pouroutzidou

,

Eleni Likotrafiti

,

Konstantinos Chrissafis

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Theodoros Lialiaris

,

Lambrini Papadopoulou

,

Eleana Kontonasaki

and

Evgenia Lymperaki

Ceramics 2021, 4(4), 628-651; https://doi.org/10.3390/ceramics4040045 - 27 Nov 2021

Cited by 5 | Viewed by 3425

Abstract

Glass-ceramic nanopowder with a composition of 55SiO₂-35CaO-10MgO (mol %) was synthesized by the sol–gel method and was heat treated at three temperatures (T1 = 835 °C, T2 = 1000 °C, T3 = 1100 °C) in order to obtain different materials (C1, [...] Read more.

Glass-ceramic nanopowder with a composition of 55SiO₂-35CaO-10MgO (mol %) was synthesized by the sol–gel method and was heat treated at three temperatures (T1 = 835 °C, T2 = 1000 °C, T3 = 1100 °C) in order to obtain different materials (C1, C2, C3, respectively) varying in crystal structure. Bioactivity and oxidative stress were evaluated in simulated body fluid (SBF) for various time periods (up to 10 days). The structure of the synthesized materials and their apatite-forming ability were investigated by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy and Energy Dispersive Spectroscopy (SEM/EDS). The antibacterial properties of the synthesized materials were evaluated against three Gram-positive and four Gram-negative bacterial strains and their biocompatibility was verified on a primary cell line of human gingival fibroblasts (HGFs) by the MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyl tetrazolium bromide) assay. The crystallization of the materials was increased by sintering temperature. Heat treatment did not inhibit the bioactive behavior of the materials as apatite formation started after 3 days in SBF. C2, C3 showed some indications of apatite forming even from the first day. Regarding cell viability, a variety of biological behaviors, concerning both dose and time points, was observed between the positive control and the tested materials by both the MTT assay and oxidative stress analysis. In conclusion, the nanobioceramic materials of this study possess a multitude of attractive physicochemical and biological properties that make them suitable candidates for bone regeneration applications, fillers in nanocomposite scaffolds, or as grafts in bone cavities and periodontal lesions. Full article

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

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8 pages, 2135 KiB

Open AccessPerspective

Synthesis of Ceramic Reinforcements in Metallic Matrices during Spark Plasma Sintering: Consideration of Reactant/Matrix Mutual Chemistry

by

Dina V. Dudina

,

Tomila M. Vidyuk

and

Michail A. Korchagin

Ceramics 2021, 4(4), 592-599; https://doi.org/10.3390/ceramics4040042 - 22 Oct 2021

Cited by 3 | Viewed by 2149

Abstract

Metal–ceramic composites are obtained via ex-situ or in-situ routes. The in-situ route implies the synthesis of reinforcement in the presence of a matrix and is often regarded as providing more flexibility to the microstructure design of composites than the ex-situ route. Spark plasma [...] Read more.

Metal–ceramic composites are obtained via ex-situ or in-situ routes. The in-situ route implies the synthesis of reinforcement in the presence of a matrix and is often regarded as providing more flexibility to the microstructure design of composites than the ex-situ route. Spark plasma sintering (SPS) is an advanced sintering method that allows fast consolidation of various powder materials up to full or nearly full density. In reactive SPS, the synthesis and consolidation are combined in a single processing step, which corresponds to the in-situ route. In this article, we discuss the peculiarities of synthesis of ceramic reinforcements in metallic matrices during SPS with a particular consideration of reactant/matrix mutual chemistry. The formation of carbide reinforcements in Cu, Al, and Ni matrices is given attention with examples elaborated in the authors’ own research. Factors determining the suitability of reactive SPS for manufacturing of composites from a matrix/reactants system and features of the structural evolution of the reaction mixture during sintering are discussed. Full article

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

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