Pub Date : 2023-11-01DOI: 10.26599/jac.2023.9220824
Qiang Liu, Suwan Ma, Zeshuai Yuan, Yuan Li, Xiaodong Gong, Junping Li, Man Zhu, Tianjian Lu
An insightful understanding of the formation mechanism of process-inherent defects and deformation is increasingly important for the property evaluation and structural design of ceramic matrix composites (CMCs). For this purpose, a coupled thermal–diffusive–mechanical modeling approach was proposed by considering three important phenomena that occurs during the pyrolysis process for manufacturing CMCs: variations of the physical and mechanical properties of the constituents, generation and diffusion of pyrolysis gas, and multiple thermal deformations. The synergistic effects of these three phenomena on the stress, damage development, microstructural morphology, and process deformation of SiC matrix composites were investigated using finite-element simulations. This new approach was validated by comparing the simulation and experimental results. Significant volume shrinkage of the matrix during the polymer-to-ceramic transformation resulted in large tensile stresses and subsequent highly fragmented microstructure in the CMCs. The pyrolysis-gas-induced expansion on the matrix under damage state may yield a positive process deformation of CMCs at the macroscale, overcoming the effects of the volume shrinkage of the bulk matrix at the microscale. The modeling approach is expected to guide high-quality manufacturing of CMCs and comprehensive studies of structure-processing-property relationships.
{"title":"Modeling of the process-induced stress, damage, microstructure, and deformation evolution during the pyrolysis process manufacturing CMCs","authors":"Qiang Liu, Suwan Ma, Zeshuai Yuan, Yuan Li, Xiaodong Gong, Junping Li, Man Zhu, Tianjian Lu","doi":"10.26599/jac.2023.9220824","DOIUrl":"https://doi.org/10.26599/jac.2023.9220824","url":null,"abstract":"An insightful understanding of the formation mechanism of process-inherent defects and deformation is increasingly important for the property evaluation and structural design of ceramic matrix composites (CMCs). For this purpose, a coupled thermal–diffusive–mechanical modeling approach was proposed by considering three important phenomena that occurs during the pyrolysis process for manufacturing CMCs: variations of the physical and mechanical properties of the constituents, generation and diffusion of pyrolysis gas, and multiple thermal deformations. The synergistic effects of these three phenomena on the stress, damage development, microstructural morphology, and process deformation of SiC matrix composites were investigated using finite-element simulations. This new approach was validated by comparing the simulation and experimental results. Significant volume shrinkage of the matrix during the polymer-to-ceramic transformation resulted in large tensile stresses and subsequent highly fragmented microstructure in the CMCs. The pyrolysis-gas-induced expansion on the matrix under damage state may yield a positive process deformation of CMCs at the macroscale, overcoming the effects of the volume shrinkage of the bulk matrix at the microscale. The modeling approach is expected to guide high-quality manufacturing of CMCs and comprehensive studies of structure-processing-property relationships.","PeriodicalId":14862,"journal":{"name":"Journal of Advanced Ceramics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135510340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.26599/jac.2023.9220825
Gwang Min Park, Seunghyeok Lee, Jun-Yun Kang, Seung-Hyub Baek, Heesuk Kim, Jin-Sang Kim, Seong Keun Kim
This study investigated the effects of KCl treatment on the microstructure and thermoelectric properties of n-type Bi2Te2.7Se0.3 (BTS) thermoelectric materials. The innovative KCl treatment was originally intended to introduce nanopores through the selective dissolution of KCl from a mixture of thermoelectric materials and KCl. However, it unexpectedly induced substantial variations in the material composition and microstructure during the subsequent spark plasma sintering (SPS) process. The hydroxyl groups adsorbed on the powder surface during the dissolution resulted in the emergence of a Bi2TeO5 secondary phase within the BTS matrix after the SPS process at 450 °C. The concentration of Bi2TeO5 increased with an increase in the KCl content. Furthermore, a remarkable grain growth occurred at low KCl concentrations, likely due to the liquid-phase formation in a Te-rich composition during SPS. However, excessive Bi2TeO5 at higher KCl concentrations hindered grain growth. These variations in the microstructure had complex effects on the electrical properties: the TeBi antisite defects increased the electron concentration, and Bi2TeO5 reduced the electron mobility. Additionally, the lattice thermal conductivity decreased due to the presence of Bi2TeO5, from 0.8 Wm-1K-1 at 298 K for the pristine BTS to 0.6 Wm-1K-1 at 298 K for the BTS treated with 1 wt% KCl. These insights allowed precise adjustments of the electrical and thermal conductivities, leading to an enhancement in ZTmax from 0.76 to 0.96 through the selective dissolution of KCl approach. We believe that our observations potentially enable advances in thermoelectric materials by engineering microstructures.
{"title":"Understanding secondary phase inclusion and composition variations in the microstructure design of n-type Bi <sub>2</sub>Te <sub>3</sub> alloys via selective dissolution of KCl","authors":"Gwang Min Park, Seunghyeok Lee, Jun-Yun Kang, Seung-Hyub Baek, Heesuk Kim, Jin-Sang Kim, Seong Keun Kim","doi":"10.26599/jac.2023.9220825","DOIUrl":"https://doi.org/10.26599/jac.2023.9220825","url":null,"abstract":"This study investigated the effects of KCl treatment on the microstructure and thermoelectric properties of n-type Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub> (BTS) thermoelectric materials. The innovative KCl treatment was originally intended to introduce nanopores through the selective dissolution of KCl from a mixture of thermoelectric materials and KCl. However, it unexpectedly induced substantial variations in the material composition and microstructure during the subsequent spark plasma sintering (SPS) process. The hydroxyl groups adsorbed on the powder surface during the dissolution resulted in the emergence of a Bi<sub>2</sub>TeO<sub>5</sub> secondary phase within the BTS matrix after the SPS process at 450 °C. The concentration of Bi<sub>2</sub>TeO<sub>5</sub> increased with an increase in the KCl content. Furthermore, a remarkable grain growth occurred at low KCl concentrations, likely due to the liquid-phase formation in a Te-rich composition during SPS. However, excessive Bi<sub>2</sub>TeO<sub>5</sub> at higher KCl concentrations hindered grain growth. These variations in the microstructure had complex effects on the electrical properties: the Te<sub>Bi</sub> antisite defects increased the electron concentration, and Bi<sub>2</sub>TeO<sub>5</sub> reduced the electron mobility. Additionally, the lattice thermal conductivity decreased due to the presence of Bi<sub>2</sub>TeO<sub>5</sub>, from 0.8 Wm<sup>-1</sup>K<sup>-1</sup> at 298 K for the pristine BTS to 0.6 Wm<sup>-1</sup>K<sup>-1</sup> at 298 K for the BTS treated with 1 wt% KCl. These insights allowed precise adjustments of the electrical and thermal conductivities, leading to an enhancement in ZT<sub>max</sub> from 0.76 to 0.96 through the selective dissolution of KCl approach. We believe that our observations potentially enable advances in thermoelectric materials by engineering microstructures.","PeriodicalId":14862,"journal":{"name":"Journal of Advanced Ceramics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135510342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, the concept of incorporating core–shell structured units as secondary phases to toughen Al2O3 ceramics is proposed. An Al2O3 composite ceramic toughened by B4C@TiB2 core–shell units is successfully synthesized using a combination of molten salt methodology and spark plasma sintering. The synthesis of B4C@TiB2 core–shell toughening units stems from the prior production of core–shell structural B4C@TiB2 powders, and this core–shell structure is effectively preserved within the Al2O3 matrix after sintering. The B4C@TiB2 core–shell toughening unit consists of a micron-sized B4C core enclosed by a shell approximately 500 nm thick, composed of numerous nanosized TiB2 grains. The regions surrounding these core–shell units exhibit distinct geometric structures and encompass multidimensional variations in phase composition, grain dimensions, and thermal expansion coefficients. Consequently, intricate stress distributions emerge, fostering the propagation of cracks in multiple dimensions. This behavior consumes a considerable amount of crack propagation energy, thereby enhancing the fracture toughness of the Al2O3 matrix. The resulting Al2O3 composite ceramics displays a relative density of 99.7±0.2%, a Vickers hardness of 21.5±0.8 GPa, and a fracture toughness 6.92±0.22 MPa·m1/2.
{"title":"Preparation and toughening mechanism of Al <sub>2</sub>O <sub>3</sub> composite ceramic toughened by B <sub>4</sub>C@TiB <sub>2</sub> core&ndash;shell units","authors":"Yingjie Shi, Weixing Li, Xiaorong Zhang, Jiachao Jin, Jilin Wang, Yu Dong, Jingbo Mu, Guangsuo Wang, Xiaoliang Zhang, Zhixiao Zhang","doi":"10.26599/jac.2023.9220826","DOIUrl":"https://doi.org/10.26599/jac.2023.9220826","url":null,"abstract":"In this paper, the concept of incorporating core–shell structured units as secondary phases to toughen Al<sub>2</sub>O<sub>3</sub> ceramics is proposed. An Al<sub>2</sub>O<sub>3</sub> composite ceramic toughened by B<sub>4</sub>C@TiB<sub>2</sub> core–shell units is successfully synthesized using a combination of molten salt methodology and spark plasma sintering. The synthesis of B<sub>4</sub>C@TiB<sub>2</sub> core–shell toughening units stems from the prior production of core–shell structural B<sub>4</sub>C@TiB<sub>2</sub> powders, and this core–shell structure is effectively preserved within the Al<sub>2</sub>O<sub>3</sub> matrix after sintering. The B<sub>4</sub>C@TiB<sub>2</sub> core–shell toughening unit consists of a micron-sized B<sub>4</sub>C core enclosed by a shell approximately 500 nm thick, composed of numerous nanosized TiB<sub>2</sub> grains. The regions surrounding these core–shell units exhibit distinct geometric structures and encompass multidimensional variations in phase composition, grain dimensions, and thermal expansion coefficients. Consequently, intricate stress distributions emerge, fostering the propagation of cracks in multiple dimensions. This behavior consumes a considerable amount of crack propagation energy, thereby enhancing the fracture toughness of the Al<sub>2</sub>O<sub>3</sub> matrix. The resulting Al<sub>2</sub>O<sub>3</sub> composite ceramics displays a relative density of 99.7±0.2%, a Vickers hardness of 21.5±0.8 GPa, and a fracture toughness 6.92±0.22 MPa·m<sup>1/2</sup>.","PeriodicalId":14862,"journal":{"name":"Journal of Advanced Ceramics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135510198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-01DOI: 10.26599/jac.2023.9220813
Wei Zhang, Lei Su, De Lu, Kang Peng, Min Niu, Lei Zhuang, Jian Feng, Hongjie Wang
With the development of aerospace technology, the Mach number of aircraft continues to increase, which puts forward higher performance requirements for high-temperature wave-transparent materials. Silicon nitride has excellent mechanical properties, high-temperature stability, and oxidation resistance, but its brittleness and high dielectric constant impede its practical applications. Herein, by employing a template-assisted precursor pyrolysis method, we prepared a class of Si3N4@SiO2 nanowires aerogels (Si3N4@SiO2 NWAGs) that are assembled by Si3N4@SiO2 nanowires with diameters ranging from 386 nm to 631 nm. The Si3N4@SiO2 NWAGs have low densities (12-31 mg·cm-3), a specific surface aerogel of 4.13 m2g-1, and an average pore size of 68.9 μm. Mechanical properties characterization shows that the aerogels exhibit reversible compressibility from 60% compressive strain and good fatigue resistance even when being compressed for 100 times at a set strain of 20%. The aerogels also show good thermal insulation performance (0.032 W·m-1K-1 at room temperature), ablation resistance (butane blow torch), and high-temperature stability (maximum service temperature in the air over 1200 °C). The dielectric constant and loss of the aerogels are 1.02-1.06 and 4.3× 10-5-1.4×10-3 at room temperature, respectively. The combination of the good mechanical, thermal, and dielectric properties makes Si3N4@SiO2 NWAG a promising ultralight wave-transparent and thermally insulating material for application at high temperatures.
{"title":"Resilient Si <sub>3</sub>N <sub>4</sub>@SiO <sub>2</sub> nanowire aerogel for high-temperature electromagnetic wave transparency and thermal insulation","authors":"Wei Zhang, Lei Su, De Lu, Kang Peng, Min Niu, Lei Zhuang, Jian Feng, Hongjie Wang","doi":"10.26599/jac.2023.9220813","DOIUrl":"https://doi.org/10.26599/jac.2023.9220813","url":null,"abstract":" With the development of aerospace technology, the Mach number of aircraft continues to increase, which puts forward higher performance requirements for high-temperature wave-transparent materials. Silicon nitride has excellent mechanical properties, high-temperature stability, and oxidation resistance, but its brittleness and high dielectric constant impede its practical applications. Herein, by employing a template-assisted precursor pyrolysis method, we prepared a class of Si<sub>3</sub>N<sub>4</sub>@SiO<sub>2</sub> nanowires aerogels (Si<sub>3</sub>N<sub>4</sub>@SiO<sub>2</sub> NWAGs) that are assembled by Si<sub>3</sub>N<sub>4</sub>@SiO<sub>2</sub> nanowires with diameters ranging from 386 nm to 631 nm. The Si<sub>3</sub>N<sub>4</sub>@SiO<sub>2</sub> NWAGs have low densities (12-31 mg·cm<sup>-3</sup>), a specific surface aerogel of 4.13 m<sup>2</sup>g<sup>-1</sup>, and an average pore size of 68.9 μm. Mechanical properties characterization shows that the aerogels exhibit reversible compressibility from 60% compressive strain and good fatigue resistance even when being compressed for 100 times at a set strain of 20%. The aerogels also show good thermal insulation performance (0.032 W·m<sup>-1</sup>K<sup>-1</sup> at room temperature), ablation resistance (butane blow torch), and high-temperature stability (maximum service temperature in the air over 1200 °C). The dielectric constant and loss of the aerogels are 1.02-1.06 and 4.3× 10<sup>-5</sup>-1.4×10<sup>-3</sup> at room temperature, respectively. The combination of the good mechanical, thermal, and dielectric properties makes Si<sub>3</sub>N<sub>4</sub>@SiO<sub>2</sub> NWAG a promising ultralight wave-transparent and thermally insulating material for application at high temperatures.","PeriodicalId":14862,"journal":{"name":"Journal of Advanced Ceramics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135568725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-01DOI: 10.26599/jac.2023.9220822
Zhilin Tian, Keyu Ming, Liya Zheng, Zhilin Chen, Fan Zhou, Peng Liu, Zihao Qiu, Donghui Wei, Bin Li, Jingyang Wang
Rare earth (RE) silicate is one of the most promising environmental barrier coatings for silicon-based ceramics in gas turbine engines. However, CMAS corrosion becomes much more serious and is the critical challenge for RE silicate with the increasing operating temperature. Therefore, it is quite urgent to clarify the mechanism of high-temperature CMAS-induced degradation of RE silicate at relatively high temperatures. Herein, the interaction between RE2SiO5 and CMAS up to 1500oC was investigated by a novel high-temperature in-situ observation method. High temperature promotes the growth of the main reaction product (Ca2RE8(SiO4)6O2) fast along [0 0 1] direction, and the precipitation of short and horizontally distributed Ca2RE8(SiO4)6O2 grains was accelerated during the cooling process. The increased temperature increases the solubility of RE elements, decreases the viscosity of CMAS, and thus elevates the corrosion reaction rate, making RE2SiO5 fast interaction with CMAS and less affected by RE element species.
{"title":"In-situ observation and mechanism of calcium&ndash;magnesium&ndash;alumina&ndash;silicates (CMAS) melts-induced degradation of RE <sub>2</sub>SiO <sub>5</sub> (RE = Tb, Dy, Ho, Y, Er, Tm, and Yb) ceramics at 1500 &deg;C","authors":"Zhilin Tian, Keyu Ming, Liya Zheng, Zhilin Chen, Fan Zhou, Peng Liu, Zihao Qiu, Donghui Wei, Bin Li, Jingyang Wang","doi":"10.26599/jac.2023.9220822","DOIUrl":"https://doi.org/10.26599/jac.2023.9220822","url":null,"abstract":"Rare earth (RE) silicate is one of the most promising environmental barrier coatings for silicon-based ceramics in gas turbine engines. However, CMAS corrosion becomes much more serious and is the critical challenge for RE silicate with the increasing operating temperature. Therefore, it is quite urgent to clarify the mechanism of high-temperature CMAS-induced degradation of RE silicate at relatively high temperatures. Herein, the interaction between RE<sub>2</sub>SiO<sub>5</sub> and CMAS up to 1500<sup>o</sup>C was investigated by a novel high-temperature in-situ observation method. High temperature promotes the growth of the main reaction product (Ca<sub>2</sub>RE<sub>8</sub>(SiO<sub>4</sub>)<sub>6</sub>O<sub>2</sub>) fast along [0 0 1] direction, and the precipitation of short and horizontally distributed Ca<sub>2</sub>RE<sub>8</sub>(SiO<sub>4</sub>)<sub>6</sub>O<sub>2</sub> grains was accelerated during the cooling process. The increased temperature increases the solubility of RE elements, decreases the viscosity of CMAS, and thus elevates the corrosion reaction rate, making RE<sub>2</sub>SiO<sub>5</sub> fast interaction with CMAS and less affected by RE element species.","PeriodicalId":14862,"journal":{"name":"Journal of Advanced Ceramics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136094179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ce dopped Lu3Al5O12 (Ce:LuAG) transparent ceramics are considered as promising color converters for solid-state lighting because of their excellent luminous efficiency, high thermal quenching temperature and good thermal stability. However, Ce:LuAG ceramics mainly emit green light. The shortage of red light as well as the expensive price of Lu compounds are hindering their application for white lighting. In this work, transparent (Lu,Gd)3Al5O12-Al2O3 (LuGAG-Al2O3) nanoceramics with different replacing contents of Gd3+ (10%-50%) were successfully elaborated via a glass-crystallization method. The obtained ceramics with full nanoscale grains are composed of main LuGAG crystalline phase and secondary Al2O3 phase, exhibiting eminent transparency of 81.0%@780 nm. After doping by Ce3+, the Ce:LuGAG-Al2O3 nanoceramics show a significant red shift (510 nm→550 nm) and makes up for the deficiency of red light component in the emission spectrum. The Ce:LuAG-Al2O3 nanoceramics with 20% Gd3+ show high internal quantum efficiency (81.5% in IQE, 96.7% of Ce:LuAG-Al2O3 nanoceramics) and good thermal stability (only 9% loss in IQE at 150 ℃). When combined with blue LED chips (10 W), 0.3%Ce:LuGAG-Al2O3 nanoceramics with 20% Gd3+ successfully realize the high quality warm white LED lighting with a color coordinates of (0.3566, 0.435), a color temperature of 4347 K, a CRI of 67.7 and a luminous efficiency of 175.8 lm·W-1. When the transparent 0.3%Ce:LuGAG-Al2O3 nanoceramics are excited by blue laser (5 W·mm-2), the emission peak position red shifts from 517 nm to 570 nm, the emitted light exhibits a continuous change from green to yellow light green light to orange-yellow light and the maximum luminous efficiency is up to 234.49 lm·W-1 (20% Gd3+). Taking into account the high quantum efficiency, good thermal stability, excellent and adjustable luminous properties, the transparent Ce:LuGAG-Al2O3 nanoceramics with different Gd3+ substitution contents in this paper are believed to be promising candidates for high-power white LED/LD lighting.
{"title":"Transparent Ce:(Lu,Gd) <sub>3</sub>Al <sub>5</sub>O <sub>12</sub>&ndash;Al <sub>2</sub>O <sub>3</sub> nanoceramic color converters elaborated via full glass crystallization for high-power white LED/LD lighting","authors":"Jie Fu, Ying Zhang, Shaowei Feng, Mathieu Allix, Cécile Genevois, Emmanuel Veron, Zhibiao Ma, Wenlong Xu, Linghan Bai, Ruyu Fan, Yafeng Yang, Hui Wang, Jianqiang Li","doi":"10.26599/jac.2023.9220823","DOIUrl":"https://doi.org/10.26599/jac.2023.9220823","url":null,"abstract":"Ce dopped Lu<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> (Ce:LuAG) transparent ceramics are considered as promising color converters for solid-state lighting because of their excellent luminous efficiency, high thermal quenching temperature and good thermal stability. However, Ce:LuAG ceramics mainly emit green light. The shortage of red light as well as the expensive price of Lu compounds are hindering their application for white lighting. In this work, transparent (Lu,Gd)<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>-Al<sub>2</sub>O<sub>3</sub> (LuGAG-Al<sub>2</sub>O<sub>3</sub>) nanoceramics with different replacing contents of Gd<sup>3+</sup> (10%-50%) were successfully elaborated via a glass-crystallization method. The obtained ceramics with full nanoscale grains are composed of main LuGAG crystalline phase and secondary Al<sub>2</sub>O<sub>3</sub> phase, exhibiting eminent transparency of 81.0%@780 nm. After doping by Ce<sup>3+</sup>, the Ce:LuGAG-Al<sub>2</sub>O<sub>3</sub> nanoceramics show a significant red shift (510 nm→550 nm) and makes up for the deficiency of red light component in the emission spectrum. The Ce:LuAG-Al<sub>2</sub>O<sub>3</sub> nanoceramics with 20% Gd<sup>3+</sup> show high internal quantum efficiency (81.5% in IQE, 96.7% of Ce:LuAG-Al<sub>2</sub>O<sub>3</sub> nanoceramics) and good thermal stability (only 9% loss in IQE at 150 ℃). When combined with blue LED chips (10 W), 0.3%Ce:LuGAG-Al<sub>2</sub>O<sub>3</sub> nanoceramics with 20% Gd<sup>3+</sup> successfully realize the high quality warm white LED lighting with a color coordinates of (0.3566, 0.435), a color temperature of 4347 K, a CRI of 67.7 and a luminous efficiency of 175.8 lm·W<sup>-1</sup>. When the transparent 0.3%Ce:LuGAG-Al<sub>2</sub>O<sub>3</sub> nanoceramics are excited by blue laser (5 W·mm<sup>-2</sup>), the emission peak position red shifts from 517 nm to 570 nm, the emitted light exhibits a continuous change from green to yellow light green light to orange-yellow light and the maximum luminous efficiency is up to 234.49 lm·W<sup>-1</sup> (20% Gd<sup>3+</sup>). Taking into account the high quantum efficiency, good thermal stability, excellent and adjustable luminous properties, the transparent Ce:LuGAG-Al<sub>2</sub>O<sub>3</sub> nanoceramics with different Gd<sup>3+</sup> substitution contents in this paper are believed to be promising candidates for high-power white LED/LD lighting.","PeriodicalId":14862,"journal":{"name":"Journal of Advanced Ceramics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136094358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-01DOI: 10.26599/jac.2023.9220812
Chengwen Wu, Fan Zhang, Qin Zhi, Bo Song, Yongqiang Chen, Hailong Wang, Rui Zhang, Hongxia Li, Bingbing Fan
Due to the chemical inertness of nickel and boron, the preparation of nickel borides and corresponding layered ternary transition metal borides Ni3ZnB2 (MAB phase) has always required high-temperature and/or high-pressure conditions. Yet, an innovative and efficient approach to prepare Ni3ZnB2 at only 600 °C and without applied pressure is presented in this study. It is discovered that by simply adjusting the temperature, a phase transition from Ni3ZnB2 to Ni4B3 with a layered structure could be induced. This transition between binary-component and ternary-component brings about significant variation of electromagnetic wave (EMW) shielding/absorption performance of prepared borides. For instance, Ni2B is of good EMW shielding performance (42.54 dB in X band) and Ni3ZnB2 is of weak EMW shielding (13.43 dB in X band); Ni3ZnB2 has poor EMW absorption performance (-5 dB) while Ni4B3 has excellent EMW absorption performance (-45.19 dB) at a thickness of 2.7 mm with effective absorption bandwidth (10.4 GHz).
{"title":"From binary to ternary and back to binary: Transition of electromagnetic wave shielding to absorption among MAB phase Ni <sub>3</sub>ZnB <sub>2</sub> and corresponding binary borides Ni <em> <sub>n</sub> </em> <sub>+1</sub>B <em> <sub>n</sub> </em>( <em>n</em>= 1, 3)","authors":"Chengwen Wu, Fan Zhang, Qin Zhi, Bo Song, Yongqiang Chen, Hailong Wang, Rui Zhang, Hongxia Li, Bingbing Fan","doi":"10.26599/jac.2023.9220812","DOIUrl":"https://doi.org/10.26599/jac.2023.9220812","url":null,"abstract":"Due to the chemical inertness of nickel and boron, the preparation of nickel borides and corresponding layered ternary transition metal borides Ni<sub>3</sub>ZnB<sub>2</sub> (MAB phase) has always required high-temperature and/or high-pressure conditions. Yet, an innovative and efficient approach to prepare Ni<sub>3</sub>ZnB<sub>2</sub> at only 600 °C and without applied pressure is presented in this study. It is discovered that by simply adjusting the temperature, a phase transition from Ni<sub>3</sub>ZnB<sub>2</sub> to Ni<sub>4</sub>B<sub>3</sub> with a layered structure could be induced. This transition between binary-component and ternary-component brings about significant variation of electromagnetic wave (EMW) shielding/absorption performance of prepared borides. For instance, Ni<sub>2</sub>B is of good EMW shielding performance (42.54 dB in X band) and Ni<sub>3</sub>ZnB<sub>2</sub> is of weak EMW shielding (13.43 dB in X band); Ni<sub>3</sub>ZnB<sub>2</sub> has poor EMW absorption performance (-5 dB) while Ni<sub>4</sub>B<sub>3</sub> has excellent EMW absorption performance (-45.19 dB) at a thickness of 2.7 mm with effective absorption bandwidth (10.4 GHz).","PeriodicalId":14862,"journal":{"name":"Journal of Advanced Ceramics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135605966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-01DOI: 10.26599/jac.2023.9220820
Min Liu, Qiqi Li, Jun Hui, Yongfeng Yan, Renduo Liu, Biao Wang
In this study, the effects of Mg on the formation of He bubbles and diffusion behavior of He atoms in 3C-SiC were investigated by irradiation and annealing experiment as well as the first-principles calculations. TEM results indicated that two damage bands were formed in the He&Mg irradiated SiC. During annealing, Mg could prevent He atoms from diffusing to the surface, resulting in the formation of He bubbles in the deeper areas far from the Mg-implanted regions, which is helpful to avoid the surface blisters. First-principles calculations were then performed to explore the effects of Mg on the He behavior in SiC. The solution energy, binding energy charge density, bond length, and crystal orbital Hamiltonian population of these elements were calculated to identify their states. The results suggested that the binding capacity between He and Mg was weak, and Mg could increase the diffusion energy barrier of He. AIMD simulation showed that Mg could make He in a high-energy unstable state, and force He atom to move toward the vacancy away from Mg, which explains the experimental results.
{"title":"Repelling effects of Mg on the diffusion of He atoms towards surface in SiC: Irradiation and annealing experiments combined with the first-principles calculations","authors":"Min Liu, Qiqi Li, Jun Hui, Yongfeng Yan, Renduo Liu, Biao Wang","doi":"10.26599/jac.2023.9220820","DOIUrl":"https://doi.org/10.26599/jac.2023.9220820","url":null,"abstract":"In this study, the effects of Mg on the formation of He bubbles and diffusion behavior of He atoms in 3C-SiC were investigated by irradiation and annealing experiment as well as the first-principles calculations. TEM results indicated that two damage bands were formed in the He&Mg irradiated SiC. During annealing, Mg could prevent He atoms from diffusing to the surface, resulting in the formation of He bubbles in the deeper areas far from the Mg-implanted regions, which is helpful to avoid the surface blisters. First-principles calculations were then performed to explore the effects of Mg on the He behavior in SiC. The solution energy, binding energy charge density, bond length, and crystal orbital Hamiltonian population of these elements were calculated to identify their states. The results suggested that the binding capacity between He and Mg was weak, and Mg could increase the diffusion energy barrier of He. AIMD simulation showed that Mg could make He in a high-energy unstable state, and force He atom to move toward the vacancy away from Mg, which explains the experimental results.","PeriodicalId":14862,"journal":{"name":"Journal of Advanced Ceramics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135849581","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-01DOI: 10.26599/jac.2023.9220811
Jun Wang, Qianqian Jin, Jianbo Song, Di Zhang, Bin Xu, Zhiyi Ren, Meng Wang, Shixiao Yan, Xiaoliang Sun, Chi Liu, Xiaoyu Chong, Jing Feng
Thermal barrier coatings (TBCs) materials can improve energy conversion efficiency and reduce fossil fuel use. Herein, the novel rare earth tantalates RETaO4, as promising candidates for TBCs, were reassembled into multi-component solid solutions with a monoclinic structure to further depress the thermal conductivity via an entropy strategy. The formation mechanisms of oxygen vacancy defects, dislocations and ferroelastic domains associated with thermal conductivity are demonstrated by aberration-corrected scanning transmission electron microscopy. Compared to single-RE RETaO4 and 8YSZ, the intrinsic thermal conductivity of (5RE1/5)TaO4 was decreased by 35% ~ 47% and 57% ~ 69% at 1200°C, respectively, which is likely attributed to the multi-scale phonon scattering from Umklapp phonon–phonon, point defects, domain structures and dislocations. and low-temperature thermal conductivity are negatively correlated, as are E/κ and high-temperature thermal conductivity. Meanwhile, the high defects' concentration and lattice distortion in high-entropy ceramics enhances the scattering of transverse-wave phonons and reduces the transverse-wave sound velocity, leading to a decrease in the thermal conductivity and Young's modulus. In addition, 5HEC-1 has ultra-low thermal conductivity, moderate thermal expansion coefficients and high hardness among the three five-component high-entropy samples. Thus, 5HEC-1 with superior thermal barrier and mechanical properties can be used as a promising thermal insulating material.
{"title":"Revealing the low thermal conductivity of high-entropy rare-earth tantalates via multiscale defects analysis","authors":"Jun Wang, Qianqian Jin, Jianbo Song, Di Zhang, Bin Xu, Zhiyi Ren, Meng Wang, Shixiao Yan, Xiaoliang Sun, Chi Liu, Xiaoyu Chong, Jing Feng","doi":"10.26599/jac.2023.9220811","DOIUrl":"https://doi.org/10.26599/jac.2023.9220811","url":null,"abstract":"Thermal barrier coatings (TBCs) materials can improve energy conversion efficiency and reduce fossil fuel use. Herein, the novel rare earth tantalates RETaO<sub>4</sub>, as promising candidates for TBCs, were reassembled into multi-component solid solutions with a monoclinic structure to further depress the thermal conductivity via an entropy strategy. The formation mechanisms of oxygen vacancy defects, dislocations and ferroelastic domains associated with thermal conductivity are demonstrated by aberration-corrected scanning transmission electron microscopy. Compared to single-RE RETaO<sub>4</sub> and 8YSZ, the intrinsic thermal conductivity of (5RE<sub>1/5</sub>)TaO<sub>4</sub> was decreased by 35% ~ 47% and 57% ~ 69% at 1200°C, respectively, which is likely attributed to the multi-scale phonon scattering from Umklapp phonon–phonon, point defects, domain structures and dislocations. and low-temperature thermal conductivity are negatively correlated, as are <em>E/κ</em> and high-temperature thermal conductivity. Meanwhile, the high defects' concentration and lattice distortion in high-entropy ceramics enhances the scattering of transverse-wave phonons and reduces the transverse-wave sound velocity, leading to a decrease in the thermal conductivity and Young's modulus. In addition, 5HEC-1 has ultra-low thermal conductivity, moderate thermal expansion coefficients and high hardness among the three five-component high-entropy samples. Thus, 5HEC-1 with superior thermal barrier and mechanical properties can be used as a promising thermal insulating material.","PeriodicalId":14862,"journal":{"name":"Journal of Advanced Ceramics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135568225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The rapid miniaturization and high integration of modern electronic devices have brought an increasing demand for polymer-based thermal management materials with higher thermal conductivity. Boron nitride nanosheets (BNNS) have been widely used as thermally conductive fillers benefiting from the extremely high intrinsic thermal conductivity. However, the small lateral size and weak interface bonding of BNNS enabled them to only form thermally conductive networks through physical overlap, resulting in high interfacial thermal resistance. To address this issue, an innovative strategy based on interface engineering was proposed in this study. High-aspect-ratio boron nitride belts (BNb) were successfully synthesized by carbon thermal reduction nitridation method through the in-situ generation and sintering of BNNS. The surface of BNb showed the sintering of numerous smaller-sized BNNS, which precisely addresses the issue of weak interfacial bonding between BNNS. On this basis, the as-synthesized BNb were combined with nano-fibrillated cellulose (NFC) to prepare NFC/BNb composite films through a facile vacuum filtration process. Due to the thermally conductive network formed by the horizontal oriented arrangement of BNb and their particular morphological advantages, the NFC/BNb films demonstrated significantly higher in-plane thermal conductivity than that of NFC/BNNS films, achieving a highest value of 19.119 W·m-1·K-1 at a 20 wt% filling fraction. In addition, the NFC/BNb films also exhibited superior thermal stability, mechanical strength, flexibility and electrical insulation performance, suggesting the significant application potential of the designed BNb fillers in the thermal management field.
{"title":"Enhancing the thermal conductivity of nanofibrillated cellulose films with 1D BN belts formed by in-situ generation and sintering of BN nanosheets","authors":"Baokai Wang, Zheng Zhao, Mengyi Li, Mengyang Niu, Jialu Tian, Chang Yu, Shiqin Wan, Ming Yue, Weiwei Xuan, Wenbin Cao, Zhaobo Tian, Kexin Chen, Qi Wang","doi":"10.26599/jac.2023.9220817","DOIUrl":"https://doi.org/10.26599/jac.2023.9220817","url":null,"abstract":"The rapid miniaturization and high integration of modern electronic devices have brought an increasing demand for polymer-based thermal management materials with higher thermal conductivity. Boron nitride nanosheets (BNNS) have been widely used as thermally conductive fillers benefiting from the extremely high intrinsic thermal conductivity. However, the small lateral size and weak interface bonding of BNNS enabled them to only form thermally conductive networks through physical overlap, resulting in high interfacial thermal resistance. To address this issue, an innovative strategy based on interface engineering was proposed in this study. High-aspect-ratio boron nitride belts (BNb) were successfully synthesized by carbon thermal reduction nitridation method through the in-situ generation and sintering of BNNS. The surface of BNb showed the sintering of numerous smaller-sized BNNS, which precisely addresses the issue of weak interfacial bonding between BNNS. On this basis, the as-synthesized BNb were combined with nano-fibrillated cellulose (NFC) to prepare NFC/BNb composite films through a facile vacuum filtration process. Due to the thermally conductive network formed by the horizontal oriented arrangement of BNb and their particular morphological advantages, the NFC/BNb films demonstrated significantly higher in-plane thermal conductivity than that of NFC/BNNS films, achieving a highest value of 19.119 W·m<sup>-1</sup>·K<sup>-1</sup> at a 20 wt% filling fraction. In addition, the NFC/BNb films also exhibited superior thermal stability, mechanical strength, flexibility and electrical insulation performance, suggesting the significant application potential of the designed BNb fillers in the thermal management field.","PeriodicalId":14862,"journal":{"name":"Journal of Advanced Ceramics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135606031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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