Research

12 pages, 2955 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Oxidation-Induced Changes in the Lattice Structure of YSZ Deposited by EB-PVD in High-Vacuum Conditions

by Gye-Won Lee, In-Hwan Lee and Yoon-Suk Oh

Processes 2023, 11(9), 2743; https://0-doi-org.brum.beds.ac.uk/10.3390/pr11092743 - 14 Sep 2023

Viewed by 604

Yttria-stabilized zirconia (YSZ), a thermal barrier coating material characterized by low thermal conductivity, is typically deposited via electron beam-physical vapor deposition. Notably, oxygen depletion occurs during this process, causing color changes in YSZ. Therefore, YSZ is speculated to undergo phase transformation during this [...] Read more.

Yttria-stabilized zirconia (YSZ), a thermal barrier coating material characterized by low thermal conductivity, is typically deposited via electron beam-physical vapor deposition. Notably, oxygen depletion occurs during this process, causing color changes in YSZ. Therefore, YSZ is speculated to undergo phase transformation during this process, which demands careful consideration owing to its effect on the life of thermal coatings. To study this phenomenon, bulk samples were prepared, subjected to vacuum heat treatment to induce oxygen depletion, and followed by oxidative heat treatment. Experimental results showed that the color of the samples changed to black after the vacuum heat treatment and to a lighter color after the oxidative heat treatment. In addition, X-ray diffraction and Raman analyses were performed. The monoclinic phase formation was confirmed during the vacuum heat treatment; however, it disappeared after the oxidation heat treatment. The coating obtained in a high vacuum atmosphere exhibited a black color and cubic phase, which changed to a bright color and tetragonal phase after the oxidation heat treatment. Full article

(This article belongs to the Special Issue Recent Advances in Ceramic Materials: Processing, Characterization and Applications)

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9 pages, 2223 KiB

Open AccessFeature PaperArticle

Weibull Reliability and Mechanical Properties of Chemical Strengthening Lightweight Glass Containers Using Spray Coating

by Kyung Won Min, Jae Ho Choi, YoonSung Jung, Young Min Byun, Won Bin Im and Hyeong-Jun Kim

Processes 2023, 11(1), 15; https://0-doi-org.brum.beds.ac.uk/10.3390/pr11010015 - 21 Dec 2022

Cited by 1 | Viewed by 1275

Abstract

In this study, the effects of heat-treatment temperature and hot-end coating (HEC) by spray coating on the mechanical properties and reliability of lightweight glass bottles were investigated. When the chemical strengthening occurred at Tg, the hardness and impact strength increased by 163% and [...] Read more.

In this study, the effects of heat-treatment temperature and hot-end coating (HEC) by spray coating on the mechanical properties and reliability of lightweight glass bottles were investigated. When the chemical strengthening occurred at Tg, the hardness and impact strength increased by 163% and 198%, respectively. All specimens exhibited improved mechanical properties with chemical strengthening, regardless of the HEC. The strengthening effect was relatively large in the absence of HEC. However, the distribution of the impact strength was smaller when HEC was applied. Compared to non-HEC bottles, HEC glass bottles had higher Weibull modulus values after chemical strengthening, which increased their reliability. Therefore, it is possible to chemically strengthen a lightweight glass bottle by spray-coating. Chemically strengthened lightweight glass bottles with excellent mechanical properties and high reliability can be produced when both HEC and chemical strengthening are applied. Full article

(This article belongs to the Special Issue Recent Advances in Ceramic Materials: Processing, Characterization and Applications)

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7 pages, 3284 KiB

Open AccessFeature PaperArticle

Reduction of Potential-Induced-Degradation of p-Type PERC Solar Cell Modules by an Ion-Diffusion Barrier Layer Underneath the Front Glass

by Eunjin Jang, Kyoung-suk Oh and Sangwoo Ryu

Processes 2022, 10(2), 334; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10020334 - 10 Feb 2022

Cited by 2 | Viewed by 1448

Abstract

With the maturation of silicon-based technologies, silicon solar cells have achieved a high conversion efficiency that approaches the theoretical limit. Currently, great efforts are being made to enhance the reliability of silicon solar cells. When the silicon solar cells are made into modules, [...] Read more.

With the maturation of silicon-based technologies, silicon solar cells have achieved a high conversion efficiency that approaches the theoretical limit. Currently, great efforts are being made to enhance the reliability of silicon solar cells. When the silicon solar cells are made into modules, potential-induced-degradation (PID) occurs during operation because of the high voltage applied between the frame and the cells, which reduces the efficiency and output power. The diffusion of Na⁺ ions from the front glass and the increased leakage current along the migration path are the major causes of PID. In this work, atomic layer deposition (ALD)-grown amorphous thin Al₂O₃ layers are introduced underneath the front glass to prevent the diffusion of Na⁺ ions and the resulting PID. Accelerated PID tests showed that an ALD-grown Al₂O₃ layer of 30 nm could effectively suppress PID seriously affecting the conversion efficiency or light transmittance. The introduction of an ion-diffusion barrier underneath the front glass is expected to contribute to securing the long-term reliability of silicon-based electricity generation, together with the introduction of barrier layers inside the solar cells. Full article

(This article belongs to the Special Issue Recent Advances in Ceramic Materials: Processing, Characterization and Applications)

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21 pages, 7269 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Thermal Behavior of Ceramic Bodies Based on Estonian Clay from the Arumetsa Deposit with Oil Shale Ash and Clinker Dust Additives

by Tiit Kaljuvee, Igor Štubňa, Tomáš Húlan, Mai Uibu, Marve Einard, Rainer Traksmaa, Mart Viljus, Jekaterina Jefimova and Andres Trikkel

Processes 2022, 10(1), 46; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10010046 - 27 Dec 2021

Cited by 7 | Viewed by 2731

Abstract

The thermal behavior of green clay samples from the Arumetsa and Füzérradvány deposits (Hungary) and the influence of two new types of Estonian oil shale (OS) ashes and cement bypass dust (clinker dust) additives on it were the objectives of this study. Thermal [...] Read more.

The thermal behavior of green clay samples from the Arumetsa and Füzérradvány deposits (Hungary) and the influence of two new types of Estonian oil shale (OS) ashes and cement bypass dust (clinker dust) additives on it were the objectives of this study. Thermal and thermo-dilatometric analysis methods were applied using a Setaram Setsys 1750 thermoanalyzer coupled with a Pfeiffer Omnistar spectrometer and a Setaram Setsys 1750 CS Evolution dilatometer. The kinetic parameters were calculated based on the differential isoconversional method of Friedman. The results of the thermal analysis of clays and blends indicated the emission of physically bound water at 200–250 °C. At temperatures from 200–250 °C to 550–600 °C the release of water is caused by oxidation of organic matter and dehydroxylation of different clay minerals like illite, illite-smectite, mica and kaolin. From blends, in addition, also from the decomposition of portlandite. The emission of CO₂ at these temperatures was a result of the oxidation of organic matter contained in the clays. In the temperature range from 550–600 °C to 800–900 °C, the mass loss was caused by ongoing dehydroxylation processes in clay minerals but was mainly due to the decomposition of the carbonates contained in the OS ashes and clinker dust. These processes were accompanied by contraction and expansion of the ceramic bodies with the corresponding changes in the SSA and porosity values of the samples. Therefore, the decomposition of the clays took place in one step which blends in two steps. At first, dehydroxylation of the clay minerals occurs, followed by decomposition of the carbonates. The value of the conversion-dependent activation energy E along the reaction progress α varied for the Arumetsa and illitic clay between 75–182 and 9–206 kJ mol⁻¹, respectively. For the blends based on Arumetsa and illitic clay, the activation energy of the first step varied between 14–193 and 5–205 kJ mol⁻¹, and for the second step, it was between 15–390 and 135–235 kJ mol⁻¹, respectively, indicating the complex mechanism of the processes. Full article

(This article belongs to the Special Issue Recent Advances in Ceramic Materials: Processing, Characterization and Applications)

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8 pages, 2800 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Effects of the Acid Treatment of ZrB₂ Particles on Their Purity and Aqueous Dispersibility

by Jinuk Choi and Gye Seok An

Processes 2022, 10(1), 18; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10010018 - 23 Dec 2021

Cited by 2 | Viewed by 2050

Abstract

Oxide impurities such as boria (B₂O₃) and zirconia (ZrO₂) on the surfaces of zirconium diboride (ZrB₂) particles are known to limit their sinterability. Among the impurities, B₂O₃ on the surface of ZrB [...] Read more.

Oxide impurities such as boria (B₂O₃) and zirconia (ZrO₂) on the surfaces of zirconium diboride (ZrB₂) particles are known to limit their sinterability. Among the impurities, B₂O₃ on the surface of ZrB₂ particles could be easily removed by methanol or hydrofluoric acid. However, the remaining ZrO₂ still gave negative influences on the sinterability. In this study, ZrB₂ particles were treated with various acids to remove oxide impurities on their surfaces. The acid treatments were found to vary in efficacy, according to acid type, and affect the crystallinity and morphology of ZrB₂ particles to varying degrees, in some cases forming additional impurities. In particular, the change in the oxygen content of the ZrB₂ particles induced by acid treatment was found to depend on the type of acid. The results of the acid treatments were compared which revealed that HNO₃ treatment optimizes the purity of ZrB₂ particles. In addition, the effects of acid treatment on the surface properties of ZrB₂ particles were considered. In particular, the correlation between the surface properties of the acid-treated ZrB₂ particles and their dispersibility in aqueous solution was investigated. Full article

(This article belongs to the Special Issue Recent Advances in Ceramic Materials: Processing, Characterization and Applications)

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13 pages, 3365 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Microwave Dielectric Properties of β-CaSiO₃ Glass–Ceramics Prepared Using Two-Step Heat Treatment

by Jin-Seok Baek, Nak-Beom Jo and Eung-Soo Kim

Processes 2021, 9(12), 2180; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9122180 - 03 Dec 2021

Cited by 5 | Viewed by 2077

Abstract

The microwave dielectric properties of β-CaSiO₃ glass–ceramics are compared with those of α-CaSiO₃ ceramics. β-CaSiO₃ is prepared using glass–ceramics method with two-step heat treatment at 730 °C for 1–7 h and at 900 °C for 3 h, and α-CaSiO₃ [...] Read more.

The microwave dielectric properties of β-CaSiO₃ glass–ceramics are compared with those of α-CaSiO₃ ceramics. β-CaSiO₃ is prepared using glass–ceramics method with two-step heat treatment at 730 °C for 1–7 h and at 900 °C for 3 h, and α-CaSiO₃ is prepared using conventional solid-state reaction and sintered at 1460–1500 °C for 3 h. With increasing holding time at 730 °C, the degree of crystallisation and Qf of the β-CaSiO₃ glass–ceramics increased. The β-CaSiO₃ specimens heat-treated at 730 °C for 3 h and 900 °C for 3 h exhibit the following dielectric properties: K = 6.57, TCF = −36.22 ppm/°C, and Qf = 52,400 GHz (highest) for the entire range of heat treatment conditions. The Qf difference between β-CaSiO₃ and α-CaSiO₃ could be explained by the bond characteristics using Rietveld refinement. FT-IR analysis shows that the Ca–O bond is the dominant factor for the Qf of CaSiO₃ ceramics compared to the Si–O bond. The higher Qf of β-CaSiO₃ than that of α-CaSiO₃ can be attributed to the higher bond strength of Ca–O for β-CaSiO₃ than that for α-CaSiO₃. Full article

(This article belongs to the Special Issue Recent Advances in Ceramic Materials: Processing, Characterization and Applications)

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11 pages, 340 KiB

Open AccessArticle

Clinical Evaluation of Reduced-Thickness Monolithic Lithium-Disilicate Crowns: One-Year Follow-Up Results

by Davor Špehar and Marko Jakovac

Processes 2021, 9(12), 2119; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9122119 - 25 Nov 2021

Cited by 1 | Viewed by 1625

Abstract

Purpose: The purpose of this in vivo study was to investigate whether the less invasive approach (reduced thickness of the restoration) will result in a comparable risk of failure and similar aesthetic results, compared to conventional layered full porcelain crowns, and can, therefore, [...] Read more.

Purpose: The purpose of this in vivo study was to investigate whether the less invasive approach (reduced thickness of the restoration) will result in a comparable risk of failure and similar aesthetic results, compared to conventional layered full porcelain crowns, and can, therefore, be used as a good alternative. Material and Methods: The tested ceramic was lithium-disilicate ceramic (IPS e.max). Forty-four patients with endodontically treated premolars or molars were randomized into two groups and provided with single crowns. One group received conventional all-ceramic crowns made from a lithium-disilicate core and hand-veneered aesthetic ceramic, while another group received full-contoured lithium-disilicate ceramic crowns with reduced wall thickness than manufactures recommendations. The teeth for conventional crowns were prepared with 1 mm rounded shoulder and 2 mm occlusal reduction, while teeth for monolithic crowns were prepared with 0.6 mm wide rounded shoulder and 1 mm occlusal reduction. All crowns were prepared by the same clinician and manufactured in the same laboratory by the same technician. The survival and aesthetics of the crowns were assessed by the independent clinician. Apart from this, patients’ aesthetic satisfaction was evaluated. The assessment was double blind as both the examiner and the patients did not know which type of crown was provided. The observation period was 36 months. Survival of the crowns was assessed using the modified United States Public Health Service (USPHS) criteria and aesthetics and participants’ aesthetic satisfaction with the crowns was evaluated using a visual analogue scale. Results: The one-year survival rate for layered crowns was 100% and for monolithic crowns 95.5%. The median patients’ aesthetic satisfaction with both crowns was 100%. Conclusions: The results indicate similar one-year survival rate of reduced-thickness monolithic lithium-disilicate crowns and conventional veneered crowns. Differences with patients’ satisfaction with the aesthetics of both crowns were not statistically significant and it can be said that the patients’ aesthetic satisfaction was the same for both crowns. Full article

(This article belongs to the Special Issue Recent Advances in Ceramic Materials: Processing, Characterization and Applications)

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10 pages, 25858 KiB

Open AccessArticle

The Effect of PVA Binder Solvent Composition on the Microstructure and Electrical Properties of 0.98BaTiO₃-0.02(Ba_0.5Ca_0.5)SiO₃ Doped with Dy₂O₃

by Nak-Beom Jo, Jin-Seok Baek and Eung-Soo Kim

Processes 2021, 9(11), 2067; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9112067 - 18 Nov 2021

Cited by 4 | Viewed by 2418

Abstract

In this study, the effect of the polyvinyl alcohol (PVA) binder solvent composition on the electrical properties of sintered 0.98BaTiO₃-0.02(Ba_0.5Ca_0.5)SiO₃ ceramics doped with x wt.% Dy₂O₃ (0.0 ≤ x ≤ 0.3) was investigated. [...] Read more.

In this study, the effect of the polyvinyl alcohol (PVA) binder solvent composition on the electrical properties of sintered 0.98BaTiO₃-0.02(Ba_0.5Ca_0.5)SiO₃ ceramics doped with x wt.% Dy₂O₃ (0.0 ≤ x ≤ 0.3) was investigated. In the absence of the PVA binder, the specimens sintered at 1260 and 1320 °C for 1 h in a reducing atmosphere showed a single BaTiO₃ phase with the perovskite structure. The relative densities of the specimens were higher than 90%, and the grain morphologies were uniform for all the solvent compositions. At 1 kHz, the dielectric constant of the specimens depended not only on their crystal structural characteristics, but also on their microstructural characteristics. The microstructural characteristics of the specimens with the PVA binder were affected by the ethyl alcohol:water ratio of the 10 wt.% PVA-111 solution. A homogeneous microstructure was observed for the 0.1 wt.% Dy₂O₃-doped specimens sintered at 1320 °C for 1 h when the ethyl alcohol/water ratio of the binder solution was 40/60. These specimens showed the maximum dielectric constant (ε_r = 2723.3) and an insulation resistance of 270 GΩ. The relationships between the microstructural characteristics and dissipation factor (tanδ) of the specimens were also investigated. Full article

(This article belongs to the Special Issue Recent Advances in Ceramic Materials: Processing, Characterization and Applications)

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12 pages, 5257 KiB

Open AccessArticle

Influence of Carboxylic Modification Using Polyacrylic Acid on Characteristics of Fe₃O₄ Nanoparticles with Cluster Structure

by Jae Rok Shin, Gye Seok An and Sung-Churl Choi

Processes 2021, 9(10), 1795; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9101795 - 10 Oct 2021

Cited by 10 | Viewed by 2103

Abstract

Fe₃O₄ nanoparticles with cluster structure are superparamagnetic particles with applicability in various high-tech fields. In this study, the influence of surface modification with polyacrylic acid (PAA), a polymeric precursor, on the characteristics of Fe₃O₄ nanoparticles was investigated. [...] Read more.

Fe₃O₄ nanoparticles with cluster structure are superparamagnetic particles with applicability in various high-tech fields. In this study, the influence of surface modification with polyacrylic acid (PAA), a polymeric precursor, on the characteristics of Fe₃O₄ nanoparticles was investigated. The particles were synthesized by the polyol method and surface modified with various amounts of PAA. The surficial, structural, optical, and magnetic properties of the PAA-modified Fe₃O₄ nanoparticles were analyzed, confirming that negatively charged carboxyl groups were formed on the particle surface, and the particle dispersibility was enhanced by surface modification. This arises from an increase in the electrostatic repulsive force due to the surface functional groups. Functionalization promoted dissociation of the cluster particles, which became more pronounced as the PAA content increased. The optical parameters changed with the PAA content. Analysis of the magnetic properties showed that the saturation magnetization decreased as the PAA content increased. Overall, PAA modification induces structural changes of the Fe₃O₄ nanoparticles that enhance the dispersibility and influence the characteristics of the particles. Full article

(This article belongs to the Special Issue Recent Advances in Ceramic Materials: Processing, Characterization and Applications)

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