Eva Gil‐González, Ahmed Taibi, Antonio Perejón, Pedro E. Sánchez‐Jiménez, Luis A. Pérez‐Maqueda
The first demonstration of plasma‐flash sintering (PFS) is presented in this work. PFS is performed under a low‐pressure atmosphere that consecutively generates plasma and flash events. It is shown, by using several combined characterization techniques, that PFS stabilizes metastable phases on the surface of the material, which may be partially, but not solely, attributed to the generation of oxygen vacancies, and induces the absorption of ionized species, if a reactive atmosphere is employed. Even though additional research is required to understand the fundamentals of PFS, it is evidenced its potential to be used as a material surface engineering tool, which may widen the technological capabilities of flash sintering.
{"title":"Plasma‐flash sintering: Metastable phase stabilization and evidence of ionized species","authors":"Eva Gil‐González, Ahmed Taibi, Antonio Perejón, Pedro E. Sánchez‐Jiménez, Luis A. Pérez‐Maqueda","doi":"10.1111/jace.20105","DOIUrl":"https://doi.org/10.1111/jace.20105","url":null,"abstract":"The first demonstration of plasma‐flash sintering (PFS) is presented in this work. PFS is performed under a low‐pressure atmosphere that consecutively generates plasma and flash events. It is shown, by using several combined characterization techniques, that PFS stabilizes metastable phases on the surface of the material, which may be partially, but not solely, attributed to the generation of oxygen vacancies, and induces the absorption of ionized species, if a reactive atmosphere is employed. Even though additional research is required to understand the fundamentals of PFS, it is evidenced its potential to be used as a material surface engineering tool, which may widen the technological capabilities of flash sintering.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bianlei Hao, Guangchao Sun, Fatang Xu, Lunliang Zhang, Kaiqi Liu
The increase in size and efficiency of gas turbines leads to higher temperature in the combustion chamber, putting greater demands on the performance of the thermal insulation tiles. Corundum–mullite has been used because of its high-temperature resistance, thermal shock resistance, and low thermal conductivity. However, how to inhibit heat transfer through composition regulation while ensuring the safe use of high-temperature insulation tiles is the key to improving the heat conversion efficiency of gas turbines. In this study, thermal insulation tiles were prepared by casting molding. On the basis of determining the optimal corundum/mullite ratio (22:45 wt%) in the aggregate, the thermal conductivity of the sample was reduced by adding MgO (2 wt%). The results show that phonon intrinsic and defect scattering, caused by changes in phase composition, effectively reduce the thermal conductivity of the insulation tile sample to 2.05 W·m−1·K−1, which is 34.71 % lower than the maximum value before regulation. During 30 cycles of thermal shock (air-cooling at 1000°C), the residual strength gradually decreased and tended to be stable, with a minimum of 8.6 MPa, indicating that the thermal insulation tile can provide better thermal insulation without affecting the safety of gas turbines, providing new ideas and methods for improving the thermal insulation performance of high-temperature thermal insulation materials.
{"title":"Heat transfer inhibition of corundum–mullite insulation tiles through composition regulation","authors":"Bianlei Hao, Guangchao Sun, Fatang Xu, Lunliang Zhang, Kaiqi Liu","doi":"10.1111/jace.20100","DOIUrl":"https://doi.org/10.1111/jace.20100","url":null,"abstract":"The increase in size and efficiency of gas turbines leads to higher temperature in the combustion chamber, putting greater demands on the performance of the thermal insulation tiles. Corundum–mullite has been used because of its high-temperature resistance, thermal shock resistance, and low thermal conductivity. However, how to inhibit heat transfer through composition regulation while ensuring the safe use of high-temperature insulation tiles is the key to improving the heat conversion efficiency of gas turbines. In this study, thermal insulation tiles were prepared by casting molding. On the basis of determining the optimal corundum/mullite ratio (22:45 wt%) in the aggregate, the thermal conductivity of the sample was reduced by adding MgO (2 wt%). The results show that phonon intrinsic and defect scattering, caused by changes in phase composition, effectively reduce the thermal conductivity of the insulation tile sample to 2.05 W·m<sup>−1</sup>·K<sup>−1</sup>, which is 34.71 % lower than the maximum value before regulation. During 30 cycles of thermal shock (air-cooling at 1000°C), the residual strength gradually decreased and tended to be stable, with a minimum of 8.6 MPa, indicating that the thermal insulation tile can provide better thermal insulation without affecting the safety of gas turbines, providing new ideas and methods for improving the thermal insulation performance of high-temperature thermal insulation materials.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jesús López-Arenal, Victor Zamora, Fernando Guiberteau, Angel L. Ortiz
Graphene nanoplatelet (GNP)–reinforced TiB2 + SiC composites were fabricated by reactive spark plasma sintering (SPS) from a TiC–B4C–SiC powder mixture with equal-volume percentages, optimizing their SPS temperature and evaluating their unlubricated sliding wear against diamond. First, it is shown that during the heating ramp of the SPS cycle, TiC and B4C react according to the chemical reaction 2TiC + B4C → 2TiB2 + 3C, and that the thus-formed C is graphenized as GNPs, leading to composites with microstructures consisting of a ceramic matrix of fine TiB2 and SiC grains with abundant randomly oriented GNPs at grain boundaries. It is also shown that this reactive SPS is optimal at 2000°C (under 75 MPa pressure and 5 min soaking), resulting in a very hard (∼28.5–29.9 GPa) and very tough (∼6.7(3) MPa m1/2) composite. And second, it is shown that these two properties and its proneness to develop an oxide tribolayer make this composite very resistant to unlubricated sliding wear against diamond (∼2.8(1)·108 (N m)/mm3), undergoing only very mild two-body abrasion. Finally, opportunities for the fabrication of toughened and very hard ceramic composites for contact-mechanical and tribological applications are discussed.
{"title":"Spark plasma sintering of hard wear-resistant graphene nanoplatelet–reinforced TiB2 + SiC composites from TiC–B4C–SiC","authors":"Jesús López-Arenal, Victor Zamora, Fernando Guiberteau, Angel L. Ortiz","doi":"10.1111/jace.20094","DOIUrl":"https://doi.org/10.1111/jace.20094","url":null,"abstract":"Graphene nanoplatelet (GNP)–reinforced TiB<sub>2</sub> + SiC composites were fabricated by reactive spark plasma sintering (SPS) from a TiC–B<sub>4</sub>C–SiC powder mixture with equal-volume percentages, optimizing their SPS temperature and evaluating their unlubricated sliding wear against diamond. First, it is shown that during the heating ramp of the SPS cycle, TiC and B<sub>4</sub>C react according to the chemical reaction 2TiC + B<sub>4</sub>C → 2TiB<sub>2</sub> + 3C, and that the thus-formed C is graphenized as GNPs, leading to composites with microstructures consisting of a ceramic matrix of fine TiB<sub>2</sub> and SiC grains with abundant randomly oriented GNPs at grain boundaries. It is also shown that this reactive SPS is optimal at 2000°C (under 75 MPa pressure and 5 min soaking), resulting in a very hard (∼28.5–29.9 GPa) and very tough (∼6.7(3) MPa m<sup>1/2</sup>) composite. And second, it is shown that these two properties and its proneness to develop an oxide tribolayer make this composite very resistant to unlubricated sliding wear against diamond (∼2.8(1)·10<sup>8</sup> (N m)/mm<sup>3</sup>), undergoing only very mild two-body abrasion. Finally, opportunities for the fabrication of toughened and very hard ceramic composites for contact-mechanical and tribological applications are discussed.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shijia Zhang, Fei Li, Songmo Du, Zhanglin Chen, Shuo Zhao, Dengke Zhao, Binbin Fan, Bohan Wang, Kexin Chen, Guanghua Liu
When a small atom is induced into a larger lattice, new phonon scattering modes are aroused and thermal conductivity is significantly reduced by increased anharmonicity. This effect, called “rattling,” has been reported in pyrochlores and some cage compounds, but not in α-SiAlON. In this study, we reveal that in (Yb+Ca) co-doped α-SiAlON ceramics (YbaCabSi7.5Al4.5O1.5N14.5, x = a/[a+b]), the rattling effect plays a crucial role in reducing thermal conductivity. Samples with different Yb/Ca ratios (x = 0, 0.1, 0.2, 0.3…, 1.0) were sintered by spark plasma sintering (SPS) at 1600°C and their thermal diffusivity/conductivity were measured by the laser-flash method. We found that substituting Ca2+ with smaller Yb3+ cations in Ca-α-SiAlON caused significant reduction in thermal conductivity. On the contrary, substituting Yb3+ with larger Ca2+ cations in Yb-α-SiAlON caused only slight reduction in thermal conductivity. A lowest thermal conductivity of 3.3 W/(m·K) was achieved, when x = 0.3 rather than x = 0.5 or 0.7. Further analysis of phonon scattering intensity confirmed that both intrinsic and extrinsic scatterings are enhanced in the sample of x = 0.3. This study demonstrates that by utilization of the rattling effect, α-SiAlON, well-known for its excellent mechanical properties, can be tuned to exhibit low thermal conductivity comparable to that of La2Zr2O7 and 8YSZ.
{"title":"Rattling effect in YbaCabSi7.5Al4.5O1.5N14.5 α-SiAlON ceramics","authors":"Shijia Zhang, Fei Li, Songmo Du, Zhanglin Chen, Shuo Zhao, Dengke Zhao, Binbin Fan, Bohan Wang, Kexin Chen, Guanghua Liu","doi":"10.1111/jace.20085","DOIUrl":"https://doi.org/10.1111/jace.20085","url":null,"abstract":"When a small atom is induced into a larger lattice, new phonon scattering modes are aroused and thermal conductivity is significantly reduced by increased anharmonicity. This effect, called “rattling,” has been reported in pyrochlores and some cage compounds, but not in α-SiAlON. In this study, we reveal that in (Yb+Ca) co-doped α-SiAlON ceramics (Yb<sub>a</sub>Ca<sub>b</sub>Si<sub>7.5</sub>Al<sub>4.5</sub>O<sub>1.5</sub>N<sub>14.5</sub>, <i>x</i> = a/[a+b]), the rattling effect plays a crucial role in reducing thermal conductivity. Samples with different Yb/Ca ratios (<i>x</i> = 0, 0.1, 0.2, 0.3…, 1.0) were sintered by spark plasma sintering (SPS) at 1600°C and their thermal diffusivity/conductivity were measured by the laser-flash method. We found that substituting Ca<sup>2+</sup> with smaller Yb<sup>3+</sup> cations in Ca-α-SiAlON caused significant reduction in thermal conductivity. On the contrary, substituting Yb<sup>3+</sup> with larger Ca<sup>2+</sup> cations in Yb-α-SiAlON caused only slight reduction in thermal conductivity. A lowest thermal conductivity of 3.3 W/(m·K) was achieved, when <i>x</i> = 0.3 rather than <i>x</i> = 0.5 or 0.7. Further analysis of phonon scattering intensity confirmed that both intrinsic and extrinsic scatterings are enhanced in the sample of <i>x</i> = 0.3. This study demonstrates that by utilization of the rattling effect, α-SiAlON, well-known for its excellent mechanical properties, can be tuned to exhibit low thermal conductivity comparable to that of La<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> and 8YSZ.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The recent realization of ferroelectricity in scandium‐ and boron‐substituted AlN thin films has spurred tremendous research interests. Here we established a molecular dynamics simulation framework to model the ferroelectricity of AlN thin films. Through reparameterization of Vashishta potential for AlN, the coercive field strength and the AlN polarization were found to be close to experimental values. Furthermore, we examined the effects of film thickness, temperature, in‐plane strain on polarization‐electric field hysteresis loop, and the thickness‐dependent Curie temperature. Lastly, we incorporated electrodes towards atomic‐level modeling of ferroelectric device, by considering the induced charge at the interface between electrodes and ferroelectric film. We found that low dielectric contrast significantly lowers the coercive field for switching AlN.
{"title":"Molecular dynamics simulations on ferroelectricity of AlN thin films","authors":"Binghui Deng, Jian Shi, Yunfeng Shi","doi":"10.1111/jace.20063","DOIUrl":"https://doi.org/10.1111/jace.20063","url":null,"abstract":"The recent realization of ferroelectricity in scandium‐ and boron‐substituted AlN thin films has spurred tremendous research interests. Here we established a molecular dynamics simulation framework to model the ferroelectricity of AlN thin films. Through reparameterization of Vashishta potential for AlN, the coercive field strength and the AlN polarization were found to be close to experimental values. Furthermore, we examined the effects of film thickness, temperature, in‐plane strain on polarization‐electric field hysteresis loop, and the thickness‐dependent Curie temperature. Lastly, we incorporated electrodes towards atomic‐level modeling of ferroelectric device, by considering the induced charge at the interface between electrodes and ferroelectric film. We found that low dielectric contrast significantly lowers the coercive field for switching AlN.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thermally robust and highly stable bulk luminescent materials are essential for advancing high‐power laser‐driven lighting. In this study, we report a yellow–green LuAG:Ce–Al2O3 eutectic, synthesized using the laser‐heated pedestal growth (LHPG) technique. The emission intensity of the eutectics reaches a maximum at an Al2O3 content of 20% due to the enhanced light scattering. Additionally, owing to the high thermal conductivity of Al2O3, the prepared LuAG:Ce–Al2O3 eutectic exhibits low thermal quenching, with only a 5% loss in luminescence observed at 150°C, along with a high luminance saturation threshold of approximately 15.8 W·mm−2. When irradiated under blue laser excitation at 7.9 W, the prepared LuAG:Ce–Al2O3 eutectic demonstrates a luminous flux of 1917 lm and a luminous efficacy of 242.4 lm·W−1. These results highlight that the potential of LuAG:Ce–Al2O3 eutectics as luminescent materials for high‐power laser‐driven lighting applications.
{"title":"Fabrication of LuAG:Ce–Al2O3 eutectics via laser‐heated pedestal growth technique for high‐power laser‐driven lighting","authors":"Wen Hao, Xiao‐Jun Wang, Jun Guo, Jian Liu, Shuxing Li, Xiaodong Xu","doi":"10.1111/jace.20076","DOIUrl":"https://doi.org/10.1111/jace.20076","url":null,"abstract":"Thermally robust and highly stable bulk luminescent materials are essential for advancing high‐power laser‐driven lighting. In this study, we report a yellow–green LuAG:Ce–Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> eutectic, synthesized using the laser‐heated pedestal growth (LHPG) technique. The emission intensity of the eutectics reaches a maximum at an Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> content of 20% due to the enhanced light scattering. Additionally, owing to the high thermal conductivity of Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>, the prepared LuAG:Ce–Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> eutectic exhibits low thermal quenching, with only a 5% loss in luminescence observed at 150°C, along with a high luminance saturation threshold of approximately 15.8 W·mm<jats:sup>−2</jats:sup>. When irradiated under blue laser excitation at 7.9 W, the prepared LuAG:Ce–Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> eutectic demonstrates a luminous flux of 1917 lm and a luminous efficacy of 242.4 lm·W<jats:sup>−1</jats:sup>. These results highlight that the potential of LuAG:Ce–Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> eutectics as luminescent materials for high‐power laser‐driven lighting applications.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ruidong Jia, Chenchen Niu, Xuelian Liu, Kai Xu, Shengheng Tan
Borosilicate glasses are the primary waste forms for the industrial immobilization of high‐level liquid waste. Yet, the compositional variation of waste glasses can form the diopside phase, which can be detrimental to the melting process and the properties of the final glass products. This study prepared simulated waste glasses with variable contents of alkaline earth metals, boron, transition metals, and rare earth metal oxide and subjected them to heat treatments. The effect of the compositional variation on the diopside crystallization behavior was explored using differential scanning calorimetry, X‐ray diffraction, optical microscopy, and scanning electron microscopy‐energy dispersive spectroscopy. The results revealed that the average size of diopside crystals was proportional to the square root of the heat treatment durations. Increased contents of alkaline earth and transition metal oxides could contribute to the growth of diopside crystals, while boron oxide tended to inhibit it. Finally, a prediction model correlating the average crystal size, compositional variation, and heat treatment durations was discussed.
{"title":"Compositional effects on the growth of diopside crystals in the simulated high‐level waste glass","authors":"Ruidong Jia, Chenchen Niu, Xuelian Liu, Kai Xu, Shengheng Tan","doi":"10.1111/jace.20071","DOIUrl":"https://doi.org/10.1111/jace.20071","url":null,"abstract":"Borosilicate glasses are the primary waste forms for the industrial immobilization of high‐level liquid waste. Yet, the compositional variation of waste glasses can form the diopside phase, which can be detrimental to the melting process and the properties of the final glass products. This study prepared simulated waste glasses with variable contents of alkaline earth metals, boron, transition metals, and rare earth metal oxide and subjected them to heat treatments. The effect of the compositional variation on the diopside crystallization behavior was explored using differential scanning calorimetry, X‐ray diffraction, optical microscopy, and scanning electron microscopy‐energy dispersive spectroscopy. The results revealed that the average size of diopside crystals was proportional to the square root of the heat treatment durations. Increased contents of alkaline earth and transition metal oxides could contribute to the growth of diopside crystals, while boron oxide tended to inhibit it. Finally, a prediction model correlating the average crystal size, compositional variation, and heat treatment durations was discussed.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Suruj Protim Neog, Namit Pai, Deepesh Yadav, Nicholas Curry, Shrikant Joshi, B. Nagamani Jaya, Indradev Samajdar
This study explored the impact of microstructure and residual stresses on the fracture behavior of as‐deposited thermal barrier coatings (TBCs). Two distinct air plasma sprayed TBCs, Coating A (conventional lamellar porous) and Coating B (dense vertically cracked), were investigated. Coating A involved coarser but less dense powders as feedstock and a lower substrate temperature during deposition. Further, Coating A had times higher randomly oriented porosities, finer grains, lower hardness, and elastic stiffness. Strikingly, however, the fracture strength was higher for the porous as‐deposited Coating A. The answer to this apparent contradiction emerged from the intergranular residual stresses. These were measured using both X‐ray diffraction and high‐resolution‐electron backscattered diffraction. Coating B, deposited at a higher substrate temperature, had clear growth selection of oriented grains. These also had more out‐of‐plane normal and shear residual stresses. The growth selection induced residual stresses appeared responsible for the decohesion of Coating B from the substrate and, correspondingly, lower fracture strength.
本研究探讨了微观结构和残余应力对沉积热障涂层（TBC）断裂行为的影响。研究了两种不同的空气等离子喷涂热障涂层，即涂层 A（传统片状多孔）和涂层 B（致密垂直裂纹）。涂层 A 采用较粗但密度较低的粉末作为原料，沉积过程中的基底温度较低。此外，涂层 A 的随机定向孔隙率更高，颗粒更细，硬度和弹性刚度更低。这一明显矛盾的答案来自晶间残余应力。这些残余应力是通过 X 射线衍射和高分辨率电子反向散射衍射测量的。涂层 B 在较高的基底温度下沉积，具有明显的取向晶粒生长选择。这些晶粒还具有更多的平面外法向和剪切残余应力。生长选择引起的残余应力似乎是涂层 B 从基底脱粘并相应降低断裂强度的原因。
{"title":"Growth selection induced residual stresses and fracture behavior of as‐deposited thermal barrier coatings","authors":"Suruj Protim Neog, Namit Pai, Deepesh Yadav, Nicholas Curry, Shrikant Joshi, B. Nagamani Jaya, Indradev Samajdar","doi":"10.1111/jace.20070","DOIUrl":"https://doi.org/10.1111/jace.20070","url":null,"abstract":"This study explored the impact of microstructure and residual stresses on the fracture behavior of as‐deposited thermal barrier coatings (TBCs). Two distinct air plasma sprayed TBCs, Coating A (conventional lamellar porous) and Coating B (dense vertically cracked), were investigated. Coating A involved coarser but less dense powders as feedstock and a lower substrate temperature during deposition. Further, Coating A had times higher randomly oriented porosities, finer grains, lower hardness, and elastic stiffness. Strikingly, however, the fracture strength was higher for the porous as‐deposited Coating A. The answer to this apparent contradiction emerged from the intergranular residual stresses. These were measured using both X‐ray diffraction and high‐resolution‐electron backscattered diffraction. Coating B, deposited at a higher substrate temperature, had clear growth selection of oriented grains. These also had more out‐of‐plane normal and shear residual stresses. The growth selection induced residual stresses appeared responsible for the decohesion of Coating B from the substrate and, correspondingly, lower fracture strength.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Roberto Cestaro, Bastian Rheingans, Peter Schweizer, Arnold Müller, Christof Vockenhuber, Claudia Cancellieri, Lars P. H. Jeurgens, Patrik Schmutz
Tailoring of the stoichiometry, crystallinity, and microstructure of manganese oxides (MnOx) is of utmost importance for technological applications in the field of catalysis, energy storage, and water splitting. In this work, α‐Mn2O3, α‐Mn3O4, and MnO thin films with defined stoichiometric compositions and crystal structures were prepared by calcination of an anodically electrodeposited Mn‐oxyhydroxide precursor film in different gas atmospheres (air, inert, or reducing gas). The crystal structure and composition of the precursor and product films were determined by combining X‐ray diffraction, transmission electron microscopy, Raman spectroscopy, Rutherford backscattering spectrometry, and elastic recoil detection analysis. The anodically electrodeposited precursor film consists of nanocrystals of α‐Mn3O4 dispersed in an amorphous MnOOH matrix phase, and can be fully transformed into either crystalline α‐Mn2O3, α‐Mn3O4, or MnO upon calcination in an oxidizing, inert or reducing atmosphere, respectively. In situ high‐temperature X‐ray diffraction was applied to derive the phase transformation kinetics, resulting in a corresponding activation energy which decreases in the order α‐Mn2O3 (268 kJ/mole) > MnO (102 kJ/mole) > α‐Mn3O4 (60 kJ/mole). The disclosed synthesis routes for the preparation of single‐phase MnOx films with a defined crystal structure and stoichiometry can be exploited for a wealth of applications.
调整锰氧化物（MnOx）的化学计量、结晶度和微观结构对于催化、储能和水分离领域的技术应用至关重要。在这项研究中，通过在不同的气体环境（空气、惰性气体或还原性气体）中煅烧阳极电沉积的氢氧化锰前驱体薄膜，制备了具有确定化学成分和晶体结构的 α-Mn2O3、α-Mn3O4 和 MnO 薄膜。通过结合 X 射线衍射、透射电子显微镜、拉曼光谱、卢瑟福反向散射光谱和弹性反冲探测分析，确定了前驱体薄膜和产物薄膜的晶体结构和成分。阳极电沉积的前驱体薄膜由分散在无定形 MnOOH 基相中的 α-Mn3O4 纳米晶体组成，在氧化、惰性或还原气氛中煅烧后可分别完全转化为结晶 α-Mn2O3、α-Mn3O4 或 MnO。应用原位高温 X 射线衍射法推导了相变动力学，得出了相应的活化能，其递减顺序为：α-Mn2O3（268 kJ/mole）>；MnO（102 kJ/mole）>；α-Mn3O4（60 kJ/mole）。所揭示的制备具有确定晶体结构和化学计量的单相氧化锰薄膜的合成路线可用于多种应用。
{"title":"Well‐defined synthesis of crystalline MnO, Mn2O3, and Mn3O4 phases by anodic electrodeposition and calcination","authors":"Roberto Cestaro, Bastian Rheingans, Peter Schweizer, Arnold Müller, Christof Vockenhuber, Claudia Cancellieri, Lars P. H. Jeurgens, Patrik Schmutz","doi":"10.1111/jace.20081","DOIUrl":"https://doi.org/10.1111/jace.20081","url":null,"abstract":"Tailoring of the stoichiometry, crystallinity, and microstructure of manganese oxides (MnO<jats:italic><jats:sub>x</jats:sub></jats:italic>) is of utmost importance for technological applications in the field of catalysis, energy storage, and water splitting. In this work, α‐Mn<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>, α‐Mn<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub>, and MnO thin films with defined stoichiometric compositions and crystal structures were prepared by calcination of an anodically electrodeposited Mn‐oxyhydroxide precursor film in different gas atmospheres (air, inert, or reducing gas). The crystal structure and composition of the precursor and product films were determined by combining X‐ray diffraction, transmission electron microscopy, Raman spectroscopy, Rutherford backscattering spectrometry, and elastic recoil detection analysis. The anodically electrodeposited precursor film consists of nanocrystals of α‐Mn<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> dispersed in an amorphous MnOOH matrix phase, and can be fully transformed into either crystalline α‐Mn<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>, α‐Mn<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub>, or MnO upon calcination in an oxidizing, inert or reducing atmosphere, respectively. In situ high‐temperature X‐ray diffraction was applied to derive the phase transformation kinetics, resulting in a corresponding activation energy which decreases in the order α‐Mn<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> (268 kJ/mole) > MnO (102 kJ/mole) > α‐Mn<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> (60 kJ/mole). The disclosed synthesis routes for the preparation of single‐phase MnO<jats:italic><jats:sub>x</jats:sub></jats:italic> films with a defined crystal structure and stoichiometry can be exploited for a wealth of applications.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Based on the Matusita–Sakka equation and the exothermic peaks in the differential thermal analysis (DTA) curves, in silicate glasses with complex crystallization processes containing the precipitation of two or more crystal phases, the effects of particle sizes on the calculations of crystal growth dimensionality and activation energy of crystal growth have been studied in depth. In crystallization processes with two or more crystal phases but one exothermic peak, 0.3 mm is considered as the boundary between the fine and the coarse particles in this type of glass. For glass samples with a particle size less than 0.3 mm, the crystal growth dimensionality is a three‐dimensional mechanism, and EG increases slightly with decreasing particle size. For glass samples with a particle size greater than 0.3 mm, the crystal growth dimensionality is a two‐dimensional mechanism, and EG increases with decreasing particle size. The EG for the fine‐particle starting material is much lower than that of the coarse‐particle starting material. In crystallization processes with two or more crystal phases and two exothermic peaks, 0.104 mm is considered as the boundary between the fine and the coarse particles in this type of glass raw material. For the first peak, in glass samples with a particle size less than 0.104 mm, the crystal growth mechanism is mainly one‐dimensional growth, and EG increases slightly with decreasing particle size. And for glass samples with particle size greater than 0.104 mm, the crystal growth mechanism is mainly two‐dimensional growth, and EG decreases with decreasing particle size. For the second peak, the crystal growth mechanism is mainly a three‐dimensional growth, and EG increases with decreasing particle size.
{"title":"Effects of particle size on the crystallization kinetics characterization in CaO–SiO2‐based glass, Part 2: In complex crystallization processes with two or more crystal phases","authors":"Zhen Wang, Renze Xu","doi":"10.1111/jace.20073","DOIUrl":"https://doi.org/10.1111/jace.20073","url":null,"abstract":"Based on the Matusita–Sakka equation and the exothermic peaks in the differential thermal analysis (DTA) curves, in silicate glasses with complex crystallization processes containing the precipitation of two or more crystal phases, the effects of particle sizes on the calculations of crystal growth dimensionality and activation energy of crystal growth have been studied in depth. In crystallization processes with two or more crystal phases but one exothermic peak, 0.3 mm is considered as the boundary between the fine and the coarse particles in this type of glass. For glass samples with a particle size less than 0.3 mm, the crystal growth dimensionality is a three‐dimensional mechanism, and <jats:italic>E</jats:italic><jats:sub>G</jats:sub> increases slightly with decreasing particle size. For glass samples with a particle size greater than 0.3 mm, the crystal growth dimensionality is a two‐dimensional mechanism, and <jats:italic>E</jats:italic><jats:sub>G</jats:sub> increases with decreasing particle size. The <jats:italic>E</jats:italic><jats:sub>G</jats:sub> for the fine‐particle starting material is much lower than that of the coarse‐particle starting material. In crystallization processes with two or more crystal phases and two exothermic peaks, 0.104 mm is considered as the boundary between the fine and the coarse particles in this type of glass raw material. For the first peak, in glass samples with a particle size less than 0.104 mm, the crystal growth mechanism is mainly one‐dimensional growth, and <jats:italic>E</jats:italic><jats:sub>G</jats:sub> increases slightly with decreasing particle size. And for glass samples with particle size greater than 0.104 mm, the crystal growth mechanism is mainly two‐dimensional growth, and <jats:italic>E</jats:italic><jats:sub>G</jats:sub> decreases with decreasing particle size. For the second peak, the crystal growth mechanism is mainly a three‐dimensional growth, and <jats:italic>E</jats:italic><jats:sub>G</jats:sub> increases with decreasing particle size.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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