Cold-sintered ceramics typically exhibit inferior mechanical properties compared to high-temperature sintered counterparts.We demonstrate that introducing large internal stress through highly concentrated nanodiamonds...Cold-sintered ceramics typically exhibit inferior mechanical properties compared to high-temperature sintered counterparts.We demonstrate that introducing large internal stress through highly concentrated nanodiamonds(NDs)significantly enhances cold-sintered a-quartz composites to structural ceramic levels.At 500 MPa cold-sintering pressure,uniformly dispersed NDs generate 1.2 GPa local prestress via Young's modulus difference,while pressure-modulated internal stress is evidenced by dielectric property changes.The optimized composite achieves fracture toughness of(3.65±0.21)MPa·m^(1/2)(180%increase)and Vickers hardness of 10.6 GPa(80%increase),matching some hightemperature-sintered ceramics.Toughening arises from prestress-driven crack deflection and crack tip bridging,while hardness enhancement stems from NDs'rigid constraint and high-pressure-induced dislocations in silica matrix.Compressive strength increases by 90%and fatigue life exceeds 1000 cycles,attributed to internal stress-strengthened grain boundaries and improved toughness.This work presents a transformative strategy for developing damage-resistant ceramics,meriting further exploration of scalability and engineering applications.展开更多
With the rapid development of the electronics industry,the demand for dielectric materials with high permittivities,low losses,and excellent electrical breakdown strengths prepared via low-temperature fabrication tech...With the rapid development of the electronics industry,the demand for dielectric materials with high permittivities,low losses,and excellent electrical breakdown strengths prepared via low-temperature fabrication techniques is increasing.Herein,we propose a one-step cold sintering process route to improve the comprehensive performance of BaTiO_(3)−based ceramics by integrating polyetherimide(PEI).Dense BaTiO_(3)–PEI nanocomposites can be prepared via a cold sintering process at 250℃ using Ba(OH)_(2)∙8H_(2)O and H_(2)TiO_(3) as the transient liquid phase.The grain growth of BaTiO_(3) is inhibited,and thin PEI layers less than 10 nm in size are located at the grain boundaries.The dissolution‒precipitation process triggered by the transient liquid phase and viscous flow assisted by PEI dominates the cold sintering mechanism of the(1−x)BaTiO_(3)–xPEI nanocomposites.The dielectric properties are stable over a broad temperature range up to 200℃.Compared with BaTiO_(3),80%BaTiO_(3)–20%PEI has superior performance,with a relative permittivity of 163 and a low dielectric loss of 0.014,and the electrical breakdown strength is increased by 80.65%compared with BaTiO_(3).Overall,the cold sintering process provides a potential way to develop dielectric nanocomposites with excellent comprehensive performance.展开更多
基金supported by the National Natural Science Foundation of China(No.52472066,No.52350443 and No.52302061)“Dawn”Program of Shanghai Education Commission(No.24SG32)the Natural Science Foundation of Shanghai(No.21ZR1400300).
文摘Cold-sintered ceramics typically exhibit inferior mechanical properties compared to high-temperature sintered counterparts.We demonstrate that introducing large internal stress through highly concentrated nanodiamonds(NDs)significantly enhances cold-sintered a-quartz composites to structural ceramic levels.At 500 MPa cold-sintering pressure,uniformly dispersed NDs generate 1.2 GPa local prestress via Young's modulus difference,while pressure-modulated internal stress is evidenced by dielectric property changes.The optimized composite achieves fracture toughness of(3.65±0.21)MPa·m^(1/2)(180%increase)and Vickers hardness of 10.6 GPa(80%increase),matching some hightemperature-sintered ceramics.Toughening arises from prestress-driven crack deflection and crack tip bridging,while hardness enhancement stems from NDs'rigid constraint and high-pressure-induced dislocations in silica matrix.Compressive strength increases by 90%and fatigue life exceeds 1000 cycles,attributed to internal stress-strengthened grain boundaries and improved toughness.This work presents a transformative strategy for developing damage-resistant ceramics,meriting further exploration of scalability and engineering applications.
基金supported by the Natural Science Foundation of Shaanxi Province,China(No.2024JC-YBMS-349)the Guangdong Provincial Key Laboratory Program(No.2021B1212040001)the staff at the Instrument Analysis Centre of Xi’an Jiaotong University for the XRD,FT-IR,and TEM measurements.We also thank Xiaohua Cheng from the School of Materials Science and Engineering,Xi’an Jiaotong University for SEM measurements.
文摘With the rapid development of the electronics industry,the demand for dielectric materials with high permittivities,low losses,and excellent electrical breakdown strengths prepared via low-temperature fabrication techniques is increasing.Herein,we propose a one-step cold sintering process route to improve the comprehensive performance of BaTiO_(3)−based ceramics by integrating polyetherimide(PEI).Dense BaTiO_(3)–PEI nanocomposites can be prepared via a cold sintering process at 250℃ using Ba(OH)_(2)∙8H_(2)O and H_(2)TiO_(3) as the transient liquid phase.The grain growth of BaTiO_(3) is inhibited,and thin PEI layers less than 10 nm in size are located at the grain boundaries.The dissolution‒precipitation process triggered by the transient liquid phase and viscous flow assisted by PEI dominates the cold sintering mechanism of the(1−x)BaTiO_(3)–xPEI nanocomposites.The dielectric properties are stable over a broad temperature range up to 200℃.Compared with BaTiO_(3),80%BaTiO_(3)–20%PEI has superior performance,with a relative permittivity of 163 and a low dielectric loss of 0.014,and the electrical breakdown strength is increased by 80.65%compared with BaTiO_(3).Overall,the cold sintering process provides a potential way to develop dielectric nanocomposites with excellent comprehensive performance.
