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531.
532.
Xin-Cen Lin Shu-Liang Li Wen-Xiong Li Zi-Hao Wang Jia-Yan Zhang Bo-Wen Liu Teng Fu Hai-Bo Zhao Yu-Zhong Wang 《Advanced functional materials》2023,33(27):2214913
High-performance thermal insulating aerogels are attractive candidates for thermal protection in extreme environments. However, inorganic aerogels’ brittleness and poor machinability limit their applications, while organic aerogels suffer from severe strength degradation and structural collapse at high temperatures. Herein, for the first time, a thermo-responsive self-ceramifiable aerogel is demonstrated with exceptional strengthening and thermal insulation at high temperatures. This aerogel exhibits excellent toughness and processability like polymers under normal conditions but spontaneously transforms into high-strength semi-crystalline hard ceramics upon exposure to high temperatures. After prolonged thermal attack at 800 °C, the strength of the aerogels does not decrease but significantly increases several-fold (from 0.739 to 2.726 MPa). The self-ceramization behavior and mechanism of the aerogel are illustrated in detail. The unique self-ceramifiable capacity enables aerogels to provide fire resistance, high-strength support, and excellent thermal insulation at ultrahigh temperatures. Even with continuous burning at 1300 °C for 60 min, the 15 mm thick aerogel shows low backside temperature below 300 °C, crack-free overall structure, and invariant porous morphology. This self-ceramifiable aerogel opens up a new avenue for developing thermal-protection materials with toughness, machinability, high strength, and thermal insulation in extreme environments. 相似文献
533.
Raimund Ziegler Dr. Markus Seibald Dr. Christiane Stoll Prof. Dr. Hubert Huppertz 《欧洲无机化学杂志》2023,26(20):e202300174
The new zinc borate Zn3B4O9 was synthesized at high-pressure/high-temperature conditions of 10 GPa and 1173 K in a Walker-type multianvil pressure device. It crystallizes in the space group P (no. 2) with a=5.5028(2) Å, b=6.7150(3) Å, c=7.8887(3) Å, α=83.99(1)°, β=73.38(1)°, γ=74.75(1)°, V=269.35(2) Å3, and two formula units (Z=2) per unit cell. The structure was confirmed via single-crystal X-ray diffraction. Zn3B4O9 can be synthesized phase pure, which is shown with a Rietveld refinement. IR-spectroscopic data of a powder sample were collected. 相似文献
534.
Hamzeh Kashani Won June Choi Chunghwan Kim Rohit Berlia Jagannathan Rajagopalan Wonmo Kang 《Advanced functional materials》2023,33(35):2214220
Demands for effective high-temperature electrical conductors continue to increase with the rapid adoption of electric vehicles. However, the use of conventional copper-based conductors is limited to relatively low temperatures due to their poor oxidation resistance and microstructural instability. Here, a highly conductive and thermally stable nickel-graphene-copper (NiGCu) wire that combines the advantages of graphene and its metallic components is developed. The NiGCu wire consists of a conductive copper core, an oxidation-resistant nickel shell, and axially continuous graphene embedded between them. The experiments on 10–80 µm diameter NiGCu wires demonstrate substantial enhancements in electrical properties and thermal stability across a variety of metrics. For instance, the smallest NiGCu wires have a 61.2% higher current density limit, 307.6% higher conductivity, and an order of magnitude smaller change in resistivity compared to conventional Ni-coated Cu counterparts after annealing at 650 °C. By performing both innovative experiments and simulations using different sizes of NiGCu wires, the diffusion coefficients of metals are quantified, for the first time to the best knowledge, through continuous graphene. These results indicate that the dramatic improvement in thermo-electrical properties is enabled by the embedded graphene layer which reduces Ni Cu interdiffusion by ≈104 times at 550 °C and 650 °C. 相似文献