Sodium cobaltite (NaxCoO2) is one of the most renowned and thermoelectrically promising p‐type cobalt oxide materials, showing exceptional performance in this domain. Nonetheless, its thermal instability in air renders it unsuitable for high‐temperature applications such as energy harvesting from industrial waste heat. To utilize the beneficial properties of NaxCoO2, microscale NaxCoO2 template particles of significantly larger size were effectively embedded within a thermally stable Ca3Co4−yO9+δ–NaxCoO2–Bi2Ca2Co2O9 triple‐phase matrix. This approach additionally aimed to enhance the texture and boost the thermoelectric performance of the ceramic composite. Highly textured p‐type ceramic composites were fabricated via uniaxial cold‐pressing and pressureless sintering in air. The unique hexagonal NaxCoO2 template particles, produced through molten‐flux synthesis, allowed precise control over their shape and dimensions, while the matrix was synthesized via a sol–gel synthesis. The integrated NaxCoO2 particles of the textured composite exhibited increased thermal stability, showing no sign of decomposition at 1173 K in air, whereas the sole template particles decomposed at 1073 K during sintering. A 20 wt% template particle content in the textured composites resulted in a remarkably high and nearly temperature‐independent power factor of 8.8 µW cm−1 K2, corresponding to an improvement of 13% compared to that of the pure matrix material.
钴酸钠（NaxCoO2）是最著名和最有热电前景的 p 型氧化钴材料之一，在这一领域表现出卓越的性能。然而，它在空气中的热不稳定性使其不适合高温应用，如从工业废热中收集能量。为了利用 NaxCoO2 的有利特性，在热稳定的 Ca3Co4-yO9+δ-NaxCoO2-Bi2Ca2Co2O9 三相基质中有效地嵌入了尺寸显著增大的微尺度 NaxCoO2 模板颗粒。这种方法还旨在增强陶瓷复合材料的质地并提高其热电性能。通过单轴冷压和空气中无压烧结，制备出了高纹理 p 型陶瓷复合材料。独特的六角形 NaxCoO2 模板颗粒是通过熔融流动合成法生产的，可以精确控制其形状和尺寸，而基体则是通过溶胶-凝胶合成法合成的。纹理复合材料中的集成 NaxCoO2 颗粒显示出更高的热稳定性，在空气中 1173 K 时没有分解迹象，而唯一的模板颗粒在烧结过程中 1073 K 时分解。纹理复合材料中模板颗粒含量为 20 wt%时，功率因数高达 8.8 µW cm-1 K2，几乎与温度无关，与纯基体材料相比，功率因数提高了 13%。
{"title":"Advanced thermoelectric performance of a textured ceramic composite: Encapsulation of NaxCoO2 into a triple‐phase matrix","authors":"Katharina Kruppa, Tobias Hennig, Giamper Escobar Cano, Jytte Möckelmann, Armin Feldhoff","doi":"10.1111/jace.20110","DOIUrl":"https://doi.org/10.1111/jace.20110","url":null,"abstract":"Sodium cobaltite (Na<jats:italic><jats:sub>x</jats:sub></jats:italic>CoO<jats:sub>2</jats:sub>) is one of the most renowned and thermoelectrically promising <jats:italic>p</jats:italic>‐type cobalt oxide materials, showing exceptional performance in this domain. Nonetheless, its thermal instability in air renders it unsuitable for high‐temperature applications such as energy harvesting from industrial waste heat. To utilize the beneficial properties of Na<jats:italic><jats:sub>x</jats:sub></jats:italic>CoO<jats:sub>2</jats:sub>, microscale Na<jats:italic><jats:sub>x</jats:sub></jats:italic>CoO<jats:sub>2</jats:sub> template particles of significantly larger size were effectively embedded within a thermally stable Ca<jats:sub>3</jats:sub>Co<jats:sub>4−<jats:italic>y</jats:italic></jats:sub>O<jats:sub>9+<jats:italic>δ</jats:italic></jats:sub>–Na<jats:italic><jats:sub>x</jats:sub></jats:italic>CoO<jats:sub>2</jats:sub>–Bi<jats:sub>2</jats:sub>Ca<jats:sub>2</jats:sub>Co<jats:sub>2</jats:sub>O<jats:sub>9</jats:sub> triple‐phase matrix. This approach additionally aimed to enhance the texture and boost the thermoelectric performance of the ceramic composite. Highly textured <jats:italic>p</jats:italic>‐type ceramic composites were fabricated via uniaxial cold‐pressing and pressureless sintering in air. The unique hexagonal Na<jats:italic><jats:sub>x</jats:sub></jats:italic>CoO<jats:sub>2</jats:sub> template particles, produced through molten‐flux synthesis, allowed precise control over their shape and dimensions, while the matrix was synthesized via a sol–gel synthesis. The integrated Na<jats:italic><jats:sub>x</jats:sub></jats:italic>CoO<jats:sub>2</jats:sub> particles of the textured composite exhibited increased thermal stability, showing no sign of decomposition at 1173 K in air, whereas the sole template particles decomposed at 1073 K during sintering. A 20 wt% template particle content in the textured composites resulted in a remarkably high and nearly temperature‐independent power factor of 8.8 µW cm<jats:sup>−1</jats:sup> K<jats:sup>2</jats:sup>, corresponding to an improvement of 13% compared to that of the pure matrix material.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198281","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}
Menghan Shi, Daming Sun, Johan F. S. Christensen, Lars R. Jensen, Deyong Wang, Morten M. Smedskjaer
The brittleness of oxide glasses remains a critical problem, limiting their suitability for high‐performance and safety‐critical applications. In this study, we attempt to address this by synthesizing nanostructures in sodium borosilicate glasses through phase separation. While most previous work on the mechanical properties of phase‐separated glasses has focused on phase separation through nucleation and growth, we here create interconnected structures through spinodal decomposition. Interestingly, this leads to improvements in Vickers hardness (from 5.8 to 6.2 GPa), crack initiation resistance (from 4.9 to 8.1 N), and fracture toughness (from 0.85 to 1.09 MPa⋅m1/2). We show that the interconnected glassy phases deflect the propagating cracks, causing the required energy for cracks to cross phase boundaries to increase when subjected to external stress. This study deepens the understanding of how to address the brittleness problem of oxide glasses and provides a promising way to design high‐performance glass materials.
{"title":"Improving the mechanical properties of a sodium borosilicate glass through spinodal decomposition","authors":"Menghan Shi, Daming Sun, Johan F. S. Christensen, Lars R. Jensen, Deyong Wang, Morten M. Smedskjaer","doi":"10.1111/jace.20099","DOIUrl":"https://doi.org/10.1111/jace.20099","url":null,"abstract":"The brittleness of oxide glasses remains a critical problem, limiting their suitability for high‐performance and safety‐critical applications. In this study, we attempt to address this by synthesizing nanostructures in sodium borosilicate glasses through phase separation. While most previous work on the mechanical properties of phase‐separated glasses has focused on phase separation through nucleation and growth, we here create interconnected structures through spinodal decomposition. Interestingly, this leads to improvements in Vickers hardness (from 5.8 to 6.2 GPa), crack initiation resistance (from 4.9 to 8.1 N), and fracture toughness (from 0.85 to 1.09 MPa⋅m<jats:sup>1/2</jats:sup>). We show that the interconnected glassy phases deflect the propagating cracks, causing the required energy for cracks to cross phase boundaries to increase when subjected to external stress. This study deepens the understanding of how to address the brittleness problem of oxide glasses and provides a promising way to design high‐performance glass materials.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198282","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}
This study examines and compares the impact of various interfacial modification strategies in optimizing the contact resistance between the rigid ceramic electrolyte and cathode active material (AM) in solid‐state sodium‐ion batteries (SSBs). All the cells are fabricated using Na3.1V2P2.9Si0.1O12, Na3.456Mg0.128Zr1.872Si2.2P0.8O12, and Na as a cathode AM, solid electrolyte (SE) and anode, respectively. The AM/SE interface is modified by (1) wetting the interface with organic liquid electrolyte (LE), (2) slurry casting and sintering a thin layer of composite cathode, and (3) infiltrating AM precursors inside the porous SE structure followed by drying and sintering. Despite exhibiting a stable cyclability performance, the SSBs prepared using the LE modification and composite cathode approach possess a low AM loading of < 1 mg·cm−2. On the other hand, the SSBs with infiltrated‐cathode exhibit a superior discharge capacity of ∼ 102 mAh·g−1 at 0.2C and less than 5% capacity fading after 50 cycles at room temperature. Notably, these cells contain a high AM loading of 2.12 mg·cm−2. The microstructural analysis reveals the presence of AM particles inside the pores of the porous SE, allowing for the efficient insertion/removal of sodium ions. The porous scaffold of SE not only provides continuous sodium‐ion conduction pathways inside the cathode structure but also renders stability by accommodating stress induced by volume change during repeated cycling. The outcomes of this work demonstrate the effectiveness of the wet‐chemical infiltration technique in improving the AM loading and storage capacity performance of SSBs working at 25°C.
本研究探讨并比较了各种界面改性策略对优化固态钠离子电池（SSB）中刚性陶瓷电解质与阴极活性材料（AM）之间接触电阻的影响。所有电池均采用 Na3.1V2P2.9Si0.1O12、Na3.456Mg0.128Zr1.872Si2.2P0.8O12 和 Na 分别作为阴极 AM、固体电解质 (SE) 和阳极。AM/SE 界面的改性方法是：(1) 用有机液态电解质（LE）润湿界面；(2) 浆料浇铸并烧结一薄层复合阴极；(3) 将 AM 前体渗入多孔 SE 结构内部，然后干燥并烧结。尽管采用 LE 改性和复合阴极方法制备的 SSB 具有稳定的循环性能，但 AM 负载较低，仅为 1 mg-cm-2。另一方面，采用浸润阴极的固态电池在 0.2C 下的放电容量高达 102 mAh-g-1，在室温下循环 50 次后容量衰减小于 5%。值得注意的是，这些电池的 AM 含量高达 2.12 mg-cm-2。微观结构分析表明，多孔 SE 的孔隙内存在 AM 颗粒，可有效地插入/移除钠离子。多孔 SE 支架不仅为阴极结构内部提供了连续的钠离子传导通道，而且还能在反复循环过程中通过容纳体积变化引起的应力而实现稳定性。这项工作的成果证明了湿化学渗透技术在改善 25°C 下工作的 SSB 的 AM 负载和存储容量性能方面的有效性。
{"title":"Tuning the cathode/solid electrolyte interface for high‐performance solid‐state Na‐ion batteries","authors":"Raghunayakula Thirupathi, Saurabh Sharma, Sandipan Bhattacharyya, Shobit Omar","doi":"10.1111/jace.20095","DOIUrl":"https://doi.org/10.1111/jace.20095","url":null,"abstract":"This study examines and compares the impact of various interfacial modification strategies in optimizing the contact resistance between the rigid ceramic electrolyte and cathode active material (AM) in solid‐state sodium‐ion batteries (SSBs). All the cells are fabricated using Na<jats:sub>3.1</jats:sub>V<jats:sub>2</jats:sub>P<jats:sub>2.9</jats:sub>Si<jats:sub>0.1</jats:sub>O<jats:sub>12,</jats:sub> Na<jats:sub>3.456</jats:sub>Mg<jats:sub>0.128</jats:sub>Zr<jats:sub>1.872</jats:sub>Si<jats:sub>2.2</jats:sub>P<jats:sub>0.8</jats:sub>O<jats:sub>12</jats:sub>, and Na as a cathode AM, solid electrolyte (SE) and anode, respectively. The AM/SE interface is modified by (1) wetting the interface with organic liquid electrolyte (LE), (2) slurry casting and sintering a thin layer of composite cathode, and (3) infiltrating AM precursors inside the porous SE structure followed by drying and sintering. Despite exhibiting a stable cyclability performance, the SSBs prepared using the LE modification and composite cathode approach possess a low AM loading of < 1 mg·cm<jats:sup>−2</jats:sup>. On the other hand, the SSBs with infiltrated‐cathode exhibit a superior discharge capacity of ∼ 102 mAh·g<jats:sup>−1</jats:sup> at 0.2C and less than 5% capacity fading after 50 cycles at room temperature. Notably, these cells contain a high AM loading of 2.12 mg·cm<jats:sup>−2</jats:sup>. The microstructural analysis reveals the presence of AM particles inside the pores of the porous SE, allowing for the efficient insertion/removal of sodium ions. The porous scaffold of SE not only provides continuous sodium‐ion conduction pathways inside the cathode structure but also renders stability by accommodating stress induced by volume change during repeated cycling. The outcomes of this work demonstrate the effectiveness of the wet‐chemical infiltration technique in improving the AM loading and storage capacity performance of SSBs working at 25°C.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198283","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}
Mohamed A. Ali, Moushira A. Mohamed, Xiaofeng Liu, Xu Beibei, Jianrong Qiu
Borosilicate glasses possess excellent melting properties and high stability against chemical attack by aqueous solutions, enabling this glass family to be used in various fields. In this article, we design a novel glass network in order to achieve a chemically robust glass with a low melting temperature. Therefore, the substitution effect of Na2O by MgO, Al2O3, Li2O, and K2O on the chemical durability and melting properties of sodium aluminosilicate glass (i.e., 80SiO2‒5Al2O3‒15Na2O [mol%]) was examined using a standard hydrolytic resistance test and viscosity measurement. Interestingly, we found that the partial replacement of Na2O by Al2O3, Li2O, and K2O (i.e., 80SiO2‒5Al2O3‒15Na2O → 80SiO2‒6.5Al2O3‒9Li2O‒2.25Na2O‒2.25K2O) makes the glass network with chemical durability and melting properties comparable to those of the commercial borosilicate network, resulting in a low HCl consumption of 0.04 mL/g and working temperature of 1238°C (i.e., temperature at viscosity 104 dPa s). The structural characterizations indicate that the high chemical stability of this glass composition originates from the abundance of SiO4 tetrahedrons with three and four bridging oxygen in the glass network as well as the increase in cationic field strength of mixed alkali ions. These excellent melting properties and superior chemical durability of glass imply the possibility of using the mixed alkali metal oxides aluminosilicate glass together with the commercial borosilicate glass in the markets for numerous practical applications.
{"title":"Structure, chemical durability, and melting properties of aluminosilicate glass","authors":"Mohamed A. Ali, Moushira A. Mohamed, Xiaofeng Liu, Xu Beibei, Jianrong Qiu","doi":"10.1111/jace.20034","DOIUrl":"https://doi.org/10.1111/jace.20034","url":null,"abstract":"Borosilicate glasses possess excellent melting properties and high stability against chemical attack by aqueous solutions, enabling this glass family to be used in various fields. In this article, we design a novel glass network in order to achieve a chemically robust glass with a low melting temperature. Therefore, the substitution effect of Na<jats:sub>2</jats:sub>O by MgO, Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>, Li<jats:sub>2</jats:sub>O, and K<jats:sub>2</jats:sub>O on the chemical durability and melting properties of sodium aluminosilicate glass (i.e., 80SiO<jats:sub>2</jats:sub>‒5Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>‒15Na<jats:sub>2</jats:sub>O [mol%]) was examined using a standard hydrolytic resistance test and viscosity measurement. Interestingly, we found that the partial replacement of Na<jats:sub>2</jats:sub>O by Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>, Li<jats:sub>2</jats:sub>O, and K<jats:sub>2</jats:sub>O (i.e., 80SiO<jats:sub>2</jats:sub>‒5Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>‒15Na<jats:sub>2</jats:sub>O → 80SiO<jats:sub>2</jats:sub>‒6.5Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>‒9Li<jats:sub>2</jats:sub>O‒2.25Na<jats:sub>2</jats:sub>O‒2.25K<jats:sub>2</jats:sub>O) makes the glass network with chemical durability and melting properties comparable to those of the commercial borosilicate network, resulting in a low HCl consumption of 0.04 mL/g and working temperature of 1238°C (i.e., temperature at viscosity 10<jats:sup>4</jats:sup> dPa s). The structural characterizations indicate that the high chemical stability of this glass composition originates from the abundance of SiO<jats:sub>4</jats:sub> tetrahedrons with three and four bridging oxygen in the glass network as well as the increase in cationic field strength of mixed alkali ions. These excellent melting properties and superior chemical durability of glass imply the possibility of using the mixed alkali metal oxides aluminosilicate glass together with the commercial borosilicate glass in the markets for numerous practical applications.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198329","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}
Yang Hu, Dewei Ni, Bowen Chen, Feiyan Cai, Xuegang Zou, Fan Zhang, Yusheng Ding, Xiangyu Zhang, Shaoming Dong
The oxide layer formed by ultra‐high melt point oxides (ZrO2, HfO2) and SiO2 glassy melt is the key to the application of traditional thermal structural materials in extremely high‐temperature environment. However, the negative effect of ZrO2 and HfO2 phase transitions on the stability of oxide layer and rapid volatilization of low viscosity SiO2 melt limit its application in aerospace. In this study, the ablation behavior of Cf/(CrZrHfNbTa)C‒SiC high‐entropy composite was explored systematically via an air plasma ablation test, under a heat flux of 5 MW/m2 at temperatures up to 2450°C. The composite presents an outstanding ablation resistance, with linear and mass ablation rates of 0.9 µm/s and 1.82 mg/s, respectively. This impressive ablation resistance is attributed to the highly stable oxide protective layer formed in situ on the ablation surface, which comprises a solid skeleton of (Zr, Hf)6(Nb, Ta)2O17 combined with spherical particles and SiO2 glassy melt. The irregular particles provide a solid skeleton in the oxides protective layer, which increased stability of the oxide layer. Moreover, the spherical particles have a crystal structure similar to that of Ta2O5 and are uniformly distributed in SiO2 glassy melt, which hinder the flow of SiO2 glassy melt and enhance its viscosity to a certain degree. And it reduces the volatilization of SiO2. In summary, the stable oxide layer was formed by irregular particles oxide and the SiO2 glassy melt with certain viscosity, thereby resulting in the impressive ablation resistance of the composite. This study fills a gap in ablation research on the (CrZrHfNbTa)C system.
{"title":"Ablation behavior and mechanisms of Cf/(CrZrHfNbTa)C‒SiC high‐entropy composite at temperatures up to 2450°C","authors":"Yang Hu, Dewei Ni, Bowen Chen, Feiyan Cai, Xuegang Zou, Fan Zhang, Yusheng Ding, Xiangyu Zhang, Shaoming Dong","doi":"10.1111/jace.20079","DOIUrl":"https://doi.org/10.1111/jace.20079","url":null,"abstract":"The oxide layer formed by ultra‐high melt point oxides (ZrO<jats:sub>2</jats:sub>, HfO<jats:sub>2</jats:sub>) and SiO<jats:sub>2</jats:sub> glassy melt is the key to the application of traditional thermal structural materials in extremely high‐temperature environment. However, the negative effect of ZrO<jats:sub>2</jats:sub> and HfO<jats:sub>2</jats:sub> phase transitions on the stability of oxide layer and rapid volatilization of low viscosity SiO<jats:sub>2</jats:sub> melt limit its application in aerospace. In this study, the ablation behavior of C<jats:sub>f</jats:sub>/(CrZrHfNbTa)C‒SiC high‐entropy composite was explored systematically via an air plasma ablation test, under a heat flux of 5 MW/m<jats:sup>2</jats:sup> at temperatures up to 2450°C. The composite presents an outstanding ablation resistance, with linear and mass ablation rates of 0.9 µm/s and 1.82 mg/s, respectively. This impressive ablation resistance is attributed to the highly stable oxide protective layer formed in situ on the ablation surface, which comprises a solid skeleton of (Zr, Hf)<jats:sub>6</jats:sub>(Nb, Ta)<jats:sub>2</jats:sub>O<jats:sub>17</jats:sub> combined with spherical particles and SiO<jats:sub>2</jats:sub> glassy melt. The irregular particles provide a solid skeleton in the oxides protective layer, which increased stability of the oxide layer. Moreover, the spherical particles have a crystal structure similar to that of Ta<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub> and are uniformly distributed in SiO<jats:sub>2</jats:sub> glassy melt, which hinder the flow of SiO<jats:sub>2</jats:sub> glassy melt and enhance its viscosity to a certain degree. And it reduces the volatilization of SiO<jats:sub>2</jats:sub>. In summary, the stable oxide layer was formed by irregular particles oxide and the SiO<jats:sub>2</jats:sub> glassy melt with certain viscosity, thereby resulting in the impressive ablation resistance of the composite. This study fills a gap in ablation research on the (CrZrHfNbTa)C system.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198287","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}
Zi‐Yang Liu, Wei Wang, Di‐Ming Xu, Chao Du, Xin Wang, Guo‐Qiang He, Fayaz Hussain, Tao Zhou, Biao‐Bing Jin, Ke‐Hong Zhou, Jun Li, Chao Liang, Di Zhou
Low‐εr (the low dielectric constant) microwave dielectric ceramics play an important role in sub‐6 GHz band communication by virtue of their small signal delay. In this paper, Ba2CoSi2O7 ceramics were synthesized by the solid‐phase reaction method, and X‐ray diffraction (XRD) confirms that they belong to a new melilite structure, with C2/c (No.15) space group, and the ceramics have good microwave dielectric properties with an εr ∼ 7.37, a Q×f (Q = 1/dielectric loss, f = resonant frequency) ∼ 26,320 GHz and a TCF (the temperature coefficient of resonant frequency) ∼ −55 ppm/°C after being sintered at 1150°C, and the theoretical dielectric constants derived from the Clausius–Mosotti as well as the porosity equation, respectively, are also used to further demonstrate the low‐εr properties. Based on the group theory, the one‐dimensional integrable representations of Γacoustic (the phonon modes) and Γoptical (optical modes) of Ba2CoSi2O7 are obtained, and the internal vibrational modes of Ba2CoSi2O7 are deconstructed and the main modes of influence of the electronic polarization are analyzed in conjunction with the results of the validly fitted peaks of the 17 Raman and 25 IR tests. A microstrip Yagi antenna is also designed based on the ceramic properties, which can achieve a gain of 9.65 dBi at the center tuning frequency of 5.47 GHz, with a S11 (return loss) close to −60 dBi. Based on the above results, the Ba2CoSi2O7 ceramic is a low‐εr microwave dielectric ceramic with significant potential for communication application.
低εr（低介电常数）微波介质陶瓷因其信号延迟小，在 6 GHz 以下频段通信中发挥着重要作用。本文采用固相反应法合成了 Ba2CoSi2O7 陶瓷，X 射线衍射（XRD）证实其属于一种新的美利来石结构，具有 C2/c （No.15陶瓷具有良好的微波介电性能，εr ∼ 7.37, Q×f (Q = 1/dielectric loss, f = resonant frequency) ∼ 26,320 GHz and TCF (the temperature coefficient of resonant frequency) ∼ -55 ppm/°C, and the theoretical dielectric constants derived from the Clausius-Mosotti as well as the porosity equation, are also used, respectively, to further demonstrate the lowεr properties.基于群论，得到了 Ba2CoSi2O7 的Γ声（声子模式）和Γ光（光学模式）的一维可积分表示，并结合 17 拉曼和 25 红外测试的有效拟合峰结果，解构了 Ba2CoSi2O7 的内部振动模式，分析了电子极化的主要影响模式。此外，还根据陶瓷特性设计了一种微带八木天线，在 5.47 GHz 中心调谐频率下可获得 9.65 dBi 的增益，S11（回波损耗）接近 -60dBi。基于上述结果，Ba2CoSi2O7 陶瓷是一种低εr 微波介电陶瓷，在通信应用方面具有巨大潜力。
{"title":"Microwave dielectric properties, vibrational spectrum, and antenna design of a novel melilite‐type Ba2CoSi2O7 ceramic","authors":"Zi‐Yang Liu, Wei Wang, Di‐Ming Xu, Chao Du, Xin Wang, Guo‐Qiang He, Fayaz Hussain, Tao Zhou, Biao‐Bing Jin, Ke‐Hong Zhou, Jun Li, Chao Liang, Di Zhou","doi":"10.1111/jace.20097","DOIUrl":"https://doi.org/10.1111/jace.20097","url":null,"abstract":"Low‐ε<jats:sub>r</jats:sub> (the low dielectric constant) microwave dielectric ceramics play an important role in sub‐6 GHz band communication by virtue of their small signal delay. In this paper, Ba<jats:sub>2</jats:sub>CoSi<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> ceramics were synthesized by the solid‐phase reaction method, and X‐ray diffraction (XRD) confirms that they belong to a new melilite structure, with <jats:italic>C</jats:italic>2/<jats:italic>c</jats:italic> (No.15) space group, and the ceramics have good microwave dielectric properties with an ε<jats:sub>r</jats:sub> ∼ 7.37, a <jats:italic>Q</jats:italic>×<jats:italic>f</jats:italic> (<jats:italic>Q</jats:italic> = 1/dielectric loss, <jats:italic>f</jats:italic> = resonant frequency) ∼ 26,320 GHz and a TCF (the temperature coefficient of resonant frequency) ∼ −55 ppm/°C after being sintered at 1150°C, and the theoretical dielectric constants derived from the Clausius–Mosotti as well as the porosity equation, respectively, are also used to further demonstrate the low‐ε<jats:sub>r</jats:sub> properties. Based on the group theory, the one‐dimensional integrable representations of Γ<jats:sub>acoustic</jats:sub> (the phonon modes) and Γ<jats:sub>optical</jats:sub> (optical modes) of Ba<jats:sub>2</jats:sub>CoSi<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> are obtained, and the internal vibrational modes of Ba<jats:sub>2</jats:sub>CoSi<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> are deconstructed and the main modes of influence of the electronic polarization are analyzed in conjunction with the results of the validly fitted peaks of the 17 Raman and 25 IR tests. A microstrip Yagi antenna is also designed based on the ceramic properties, which can achieve a gain of 9.65 dBi at the center tuning frequency of 5.47 GHz, with a S<jats:sub>11</jats:sub> (return loss) close to −60 dBi. Based on the above results, the Ba<jats:sub>2</jats:sub>CoSi<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> ceramic is a low‐ε<jats:sub>r</jats:sub> microwave dielectric ceramic with significant potential for communication application.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198284","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}
Ji Zou, Guanlin Zhao, Huayue Liang, Jingjing Liu, Wei Ji, Weimin Wang, Zhengyi Fu
This study selected ZrB2–hBN ceramics as the matrix for low‐cost second‐generation SiC fibers, due to their low modulus and ability to be sintered at relatively low temperatures. The resulting composites, which contained up to 30 wt.% short‐chopped SiCf, were consolidated using reactive spark plasma sintering at 1550 and 1700°C under 50 MPa for 5 min. Without needing to prepare interfaces on the SiCf surfaces, fiber pullout, strengthening, and toughening during the fracture process were realized. By constructing the volatility phase diagram for the fiber, the microstructural changes that occurred on the fiber surfaces during sintering were successfully illustrated. Mechanical properties of ZrB2–hBN ceramics with 10 wt.% SiCf sintered at 1550°C still showed considerable improvements, including an elastic modulus of 187 GPa, a flexural strength of 337 ± 16 MPa, and a fracture toughness of 4.12 ± 0.25 MPa m1/2, increases of 12.6%, 61.2%, and 118%, respectively, compared to the counterparts without adding chopped fibers. Variations in these properties were linked to the matrix porosity and SiCf pullout behaviors, which were subsequently analyzed using the He–Hutchinson model.
{"title":"Processing, microstructure, and mechanical properties of chopped SiC fibers reinforced ZrB2–hBN–based composites","authors":"Ji Zou, Guanlin Zhao, Huayue Liang, Jingjing Liu, Wei Ji, Weimin Wang, Zhengyi Fu","doi":"10.1111/jace.20107","DOIUrl":"https://doi.org/10.1111/jace.20107","url":null,"abstract":"This study selected ZrB<jats:sub>2</jats:sub>–<jats:italic>h</jats:italic>BN ceramics as the matrix for low‐cost second‐generation SiC fibers, due to their low modulus and ability to be sintered at relatively low temperatures. The resulting composites, which contained up to 30 wt.% short‐chopped SiC<jats:sub>f</jats:sub>, were consolidated using reactive spark plasma sintering at 1550 and 1700°C under 50 MPa for 5 min. Without needing to prepare interfaces on the SiC<jats:sub>f</jats:sub> surfaces, fiber pullout, strengthening, and toughening during the fracture process were realized. By constructing the volatility phase diagram for the fiber, the microstructural changes that occurred on the fiber surfaces during sintering were successfully illustrated. Mechanical properties of ZrB<jats:sub>2</jats:sub>–<jats:italic>h</jats:italic>BN ceramics with 10 wt.% SiC<jats:sub>f</jats:sub> sintered at 1550°C still showed considerable improvements, including an elastic modulus of 187 GPa, a flexural strength of 337 ± 16 MPa, and a fracture toughness of 4.12 ± 0.25 MPa m<jats:sup>1/2</jats:sup>, increases of 12.6%, 61.2%, and 118%, respectively, compared to the counterparts without adding chopped fibers. Variations in these properties were linked to the matrix porosity and SiC<jats:sub>f</jats:sub> pullout behaviors, which were subsequently analyzed using the He–Hutchinson model.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198285","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}
Gregory N. Morscher, Christopher Ferguson, Sarah Pratt, Jonathan B. Clawson, Seyed Mostafa Razavi, Suresh Subramanian
Ceramic matrix composites (CMCs) on one level are excellent materials for acoustic emission (AE) analysis. They are excellent waveguides for AE waveform transmission due to the high modulus to density ratio. CMC inelastic behavior is due to micro‐ and macrocrack formation from matrix crack interaction with the fibers via a relatively weak fiber/matrix interface which create ideal stress waves. Because of this, AE is an excellent detector of microcracks in general, and most importantly in the case of CMCs, the initial or lowest stress crack formation. This property can be related to long time stressed‐oxidation degradation of nonoxide composites, in particular. In addition, AE has been used to effectively determine the stress distribution for matrix cracks which cause the nonlinear stress–strain behavior. However, a key to quantitatively correlating AE with sources is first and foremost to locate where the AE originated. For a tensile test, most AE comes from the near‐grip region and the radius region outside the gage area of interest. Outside the gage region AE would not be considered useful data pertaining to stress/strain behavior and must be sorted out from the AE dataset. Location is determined by the difference in time of arrivals (TOAs) of waveforms received on each sensor from a given AE source. Automated TOA techniques such as threshold voltage crossing or Akaike information criteria (AIC) have limitations in overall accuracy of differences in TOA (Δt) of two different sensors required for location analysis. This study has incorporated several signal filter and enhancement techniques and an approach toward increasing the accuracy of the classic TOA techniques. First TOA was determined for the two sensors of the AE tests “manually” based on first extensional peak of the waveform, this served as the “exact” difference in TOA. Δt’s were then determined for the various filter/TOA techniques and compared to those from the manual determined Δt. The best filter/TOA techniques resulted in more than two times better accuracy (defined as percentage of events within 0.1 µs of the exact Δt) than the conventional threshold crossing or AIC technique.
{"title":"Acoustic emission accuracy from a tensile test of a ceramic matrix composite","authors":"Gregory N. Morscher, Christopher Ferguson, Sarah Pratt, Jonathan B. Clawson, Seyed Mostafa Razavi, Suresh Subramanian","doi":"10.1111/jace.20104","DOIUrl":"https://doi.org/10.1111/jace.20104","url":null,"abstract":"Ceramic matrix composites (CMCs) on one level are excellent materials for acoustic emission (AE) analysis. They are excellent waveguides for AE waveform transmission due to the high modulus to density ratio. CMC inelastic behavior is due to micro‐ and macrocrack formation from matrix crack interaction with the fibers via a relatively weak fiber/matrix interface which create ideal stress waves. Because of this, AE is an excellent detector of microcracks in general, and most importantly in the case of CMCs, the initial or lowest stress crack formation. This property can be related to long time stressed‐oxidation degradation of nonoxide composites, in particular. In addition, AE has been used to effectively determine the stress distribution for matrix cracks which cause the nonlinear stress–strain behavior. However, a key to quantitatively correlating AE with sources is first and foremost to locate where the AE originated. For a tensile test, most AE comes from the near‐grip region and the radius region outside the gage area of interest. Outside the gage region AE would not be considered useful data pertaining to stress/strain behavior and must be sorted out from the AE dataset. Location is determined by the difference in time of arrivals (TOAs) of waveforms received on each sensor from a given AE source. Automated TOA techniques such as threshold voltage crossing or Akaike information criteria (AIC) have limitations in overall accuracy of differences in TOA (Δ<jats:italic>t</jats:italic>) of two different sensors required for location analysis. This study has incorporated several signal filter and enhancement techniques and an approach toward increasing the accuracy of the classic TOA techniques. First TOA was determined for the two sensors of the AE tests “manually” based on first extensional peak of the waveform, this served as the “exact” difference in TOA. Δ<jats:italic>t</jats:italic>’s were then determined for the various filter/TOA techniques and compared to those from the manual determined Δ<jats:italic>t</jats:italic>. The best filter/TOA techniques resulted in more than two times better accuracy (defined as percentage of events within 0.1 µs of the exact Δ<jats:italic>t</jats:italic>) than the conventional threshold crossing or AIC technique.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198289","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 mechanical properties at microlevels are of important meaning for refractories while determining these values is of great challenges. In this contribution, a tailored grid nanoindentation test was employed to determine the micromechanical properties of low‐carbon Al2O3–C refractories featuring reduced brittleness with in situ magnesium aluminate spinel/carbon nanotubes (MgAl2O4/CNTs) compound interfacial layer between the aggregate and matrix. The micromechanical properties, especially Young's modulus (E) and specific fracture energy (Gc) of the aggregate, matrix, and aggregate/matrix interface area of the refractories, were determined and compared. Statistical analysis on the nanoindentation results of the aggregate and matrix in the reference sample and the sample with interfacial layer shows high consistency, which reveals the high feasibility of the method. The median microspecific fracture energy of the aggregate/matrix interface increases from 63.67 J m−2 of the reference group to 132.90 J m−2 of the sample with the compound interfacial layer, which means that higher energy is needed for the initiation and propagation of microcracks within the interfacial layer, accounting for the brittleness reduction of the refractories. Consistent conclusions were drawn from the nanoindentation test at microlevels along with the macrolevel thermal shock test and wedge splitting test.
{"title":"Micromechanical properties of Al2O3–C refractories with aggregate/matrix interfacial layer by nanoindentation","authors":"Jiyuan Luo, Donghai Ding, Guoqing Xiao","doi":"10.1111/jace.20078","DOIUrl":"https://doi.org/10.1111/jace.20078","url":null,"abstract":"The mechanical properties at microlevels are of important meaning for refractories while determining these values is of great challenges. In this contribution, a tailored grid nanoindentation test was employed to determine the micromechanical properties of low‐carbon Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>–C refractories featuring reduced brittleness with in situ magnesium aluminate spinel/carbon nanotubes (MgAl<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub>/CNTs) compound interfacial layer between the aggregate and matrix. The micromechanical properties, especially Young's modulus (<jats:italic>E</jats:italic>) and specific fracture energy (<jats:italic>G</jats:italic><jats:sub>c</jats:sub>) of the aggregate, matrix, and aggregate/matrix interface area of the refractories, were determined and compared. Statistical analysis on the nanoindentation results of the aggregate and matrix in the reference sample and the sample with interfacial layer shows high consistency, which reveals the high feasibility of the method. The median microspecific fracture energy of the aggregate/matrix interface increases from 63.67 J m<jats:sup>−2</jats:sup> of the reference group to 132.90 J m<jats:sup>−2</jats:sup> of the sample with the compound interfacial layer, which means that higher energy is needed for the initiation and propagation of microcracks within the interfacial layer, accounting for the brittleness reduction of the refractories. Consistent conclusions were drawn from the nanoindentation test at microlevels along with the macrolevel thermal shock test and wedge splitting test.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198286","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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