Yefeng Feng,Peiyao Chen,Bingshuang Mao,Maolin Bo,Qihuang Deng
Ultrahigh dielectric constant is obtained in polymer/MXene composites due to percolation . However, huge dielectric loss is triggered owing to high leakage current . In this work, hybrid filler consisting of Ti 2 C MXene and ZrO 2 was prepared for coordinating high dielectric constant and low dielectric loss in composites. Instead of Ti 2 C percolation, Ti 2 C/ZrO 2 interface effect mildly increased dielectric constant. Ultrahigh insulation and large aspect ratio of ZrO 2 fibers significantly reduced dielectric loss. Binary polymer/Ti 2 C and ternary polymer/Ti 2 C-ZrO 2 composites were fabricated, and better overall electric traits in ternary system were found. Ti 2 C/ZrO 2 interface effect was studied using density functional theory (DFT) calculations. Ternary composite with 12 wt% filler exhibited high dielectric constant of ~40, low dielectric loss of ~0.09 at 100 Hz and high breakdown strength of ~155 MV m −1 . This work might impulse fabrication of MXene-based hybrid fillers for dielectrics.
Bin Tian,Xinzhu Gan,Zhigang Wang,Yong Xu,Lin Wang,Conghe Xu,Ling Li
In this study, TiO 2 nanosheets were directly grown on ZrO 2 fibers by employing a solvothermal technique without requiring a TiO 2 seed layer, targeting thermal radiation shielding applications. The crystalline form and microstructure of the TiO 2 nanosheets were characterized using SEM, Raman, XRD, XPS, and TEM. The infrared thermal radiation extinction properties of the TiO 2 nanosheets were evaluated using DRS and effective specific extinction coefficient ( e *), and their thermal endurance at high temperatures was also assessed. The results showed that, within the infrared band of 2.5 to 8.5 μm, the TiO 2 nanosheet arrays with a thickness of 423 nm enhanced the e* of ZrO 2 fibers by 58.59 %. At similar coating thicknesses, nanosheet coatings exhibited superior thermal radiation shielding performance compared to nanoparticle coatings. These findings suggest that ZrO 2 fibers loaded with TiO 2 nanosheets are promising candidates for thermal radiation shielding in aerogels or extreme environmental conditions.
Yunzhu Ma,Haotian Liu,Chaozhong Wu,Wensheng Liu,Juan Wang,Shuwei Yao
The preparation of high-performance Al 2 O 3 -ZrO 2 fibers is a significant and challenging task. In this study, continuous Al 2 O 3 -ZrO 2 fibers were synthesized via the sol-gel method using aluminum powder and zirconium acetate as raw materials. It was observed that the amorphous state of Al 2 O 3 transformed into γ-Al 2 O 3 and then to α-Al 2 O 3 , while the amorphous ZrO 2 directly transformed into t-ZrO 2 . The formation temperatures of t-ZrO 2 and α-Al 2 O 3 were both approximately 1100 °C. The optimal sintering temperature during the single-step sintering process for Al 2 O 3 -ZrO 2 fibers was 1400 °C. Based on the experiment results, fully dense Al 2 O 3 -ZrO 2 fibers with fine grains were successfully synthesized via a two-step sintering process. The average sizes of Al 2 O 3 and ZrO 2 grains were 153 nm and 62 nm, respectively. The Weibull strength of the Al 2 O 3 -ZrO 2 fibers reached 2.2 GPa with a peak value of 2.6 GPa, which exhibited an increase of approximately 30% compared to that formed by the single-step sintering process. Furthermore, the nucleation, growth, and densification behaviors of Al 2 O 3 -ZrO 2 fibers during the two-step sintering process were discussed.
Abstract ZrO 2 ceramic fibers have gained widespread study for the high temperature stability, low thermal conductivity and high mechanical properties. While for oxide fibers, grain growth is one of the limiting factors for long-term high temperature applications. In the present study, polycrystalline ZrO 2 –6 mol % Y 2 O 3 ceramic fibers with the addition of ~0–5 mol % La 2 O 3 to refine the grain size were fabricated by the dry-spinning method. The XRD and Raman spectral results showed that the pyrochlore La 2 Zr 2 O 7 phase was formed as a second phase in the tetragonal zirconia fiber matrix. The formation of a second phase was an effective way to hinder grain growth for the competition phase effect and solid solution mechanism. With the addition of La 2 O 3 , the grain size decreased and concentrated in a smaller range of 50–250 nm compared with the ZrO 2 –6 mol % Y 2 O 3 matrix at 1400°C. Furthermore, the thermal conductivity of the fibers decreased with the additive of La 2 O 3 less than 3 mol %. The present system is a promising candidate for high temperature applications.
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