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排序方式: 共有2080条查询结果,搜索用时 15 毫秒
1.
Yumin An Yi Yang Yongna Jia Wenbo Han Yehong Cheng 《Journal of the American Ceramic Society》2022,105(4):2385-2391
Biomimetic Bouligand architecture is constructed in the ceramic to improve its toughness. Firstly, unidirectional carbon fiber-reinforced ZrB2-SiC ceramic films are achieved through a vacuum-assisted filtration method using graphene oxide. Then, ceramic films are helically assembled at a fixed angle of 30° in the graphite die based on the fiber orientation. Finally, the spark plasma sintering method was utilized to densify helical assembly carbon fiber/ceramic films. By constructing Bouligand structure, high fracture toughness (7.4 MPa·m0.5) and work of fracture (∼1055 J/m2) are achieved in ZrB2-based ceramic. The toughening mechanisms mainly are crack deflection, twisting and branching, carbon fiber pulling out, and bridging. 相似文献
2.
The independent influence of microstructural features on fracture toughness of TC21 alloy with lamellar microstructure was investigated. Triple heat treatments were designed to obtain lamellar microstructures with different parameters, which were characterized by OM and SEM. The size and content of α plates were mainly determined by cooling rate from single β phase field and solution temperature in two-phase field; while the precipitation behavior of secondary α platelets was dominantly controlled by aging temperature in two-phase field. The content and thickness of α plates and the thickness of secondary α platelets were important microstructural features influencing the fracture toughness. Both increasing the content of α plates and thickening α plates (or secondary α platelets) could enhance the fracture toughness of TC21 alloy. Based on energy consumption by the plastic zone of crack tip in α plates, a toughening mechanism for titanium alloys was proposed. 相似文献
3.
Jayven Chee Chuan Yeo Joseph Kinyanjui Muiruri Justin Junqiang Koh Warintorn Thitsartarn Xikui Zhang Junhua Kong Ting Ting Lin Zibiao Li Chaobin He 《Advanced functional materials》2020,30(30)
The future of green electronics possessing great strength and toughness proves to be a promising area of research in this technologically advanced society. This work develops the first fully bendable and malleable toughened polylactic acid (PLA) green composite by incorporating a multifunctional polyhydroxybutyrate rubber copolymer filler that acts as an effective nucleating agent to accelerate PLA crystallization and performs as a dynamic plasticizer to generate massive polymer chain movement. The resultant biocomposite exhibits a 24‐fold and 15‐fold increment in both elongation and toughness, respectively, while retaining its elastic modulus at >3 GPa. Mechanism studies show the toughening effect is due to an amalgamation of massive shear yielding, crazing, and nanocavitation in the highly dense PLA matrix. Uniquely distinguished from the typical flexible polymer that stretches and recovers, this biocomposite is the first report of PLA that can be “bend, twist, turn, and fold” at room temperature and exhibit excellent mechanical robustness even after a 180° bend, attributes to the highly interconnected polymer network of innumerable nanocavitation complemented with an extensively unified fibrillar bridge. This unique trait certainly opens up a new horizon to future sustainable green electronics development. 相似文献
4.
Jun Wang Fushuo Wu Ruoan Zou Yueshu Wu Mengdi Gan Jing Feng Xiaoyu Chong 《Journal of the American Ceramic Society》2021,104(11):5873-5882
In this study, high-entropy rare-earth tantalate ceramics (Y0.2Ce0.2Sm0.2Gd0.2Dy0.2)TaO4 ((5RE0.2)TaO4) have been successfully fabricated. The possibility of formation of (5RE0.2)TaO4 was verified via first-principles calculations. In addition, the phase structure, ferroelastic toughening mechanism, thermophysical, and mechanical properties were systematically investigated. The (5RE0.2)TaO4 ceramics have lower phonon thermal conductivity (1.2–2.6 W·m–1·K–1) in the entire temperature range than that of RETaO4 and YSZ. (5RE0.2)TaO4 has a higher fracture toughness and lower brittleness index than YSZ. The thermal expansion coefficients of (5RE0.2)TaO4 are as high as 10.3 × 10-6 K–1 at 1200°C and Young's modulus is 66–189 GPa, and thus, (5RE0.2)TaO4 possesses great potential for application in thermal barrier coatings (TBCs). 相似文献
5.
《Ceramics International》2019,45(16):19610-19616
In this work, a novel way was developed to facilitate the sintering of a binderless cemented carbide with Al2O3 contain while improving its toughness. WC- 1.87 wt % Al2O3- 4.13 wt %ZrO2 cemented carbides with 1 wt % B2O3 as additives were consolidated by high energy ball-milling and spark plasma sintering the as-milled composite powders. The effects of 1 wt % B2O3 content on the sintering behaviour, microstructure and mechanical properties of the obtained cemented carbides were investigated. The presence of B2O3 significantly lowers the sintering temperature by forming liquid phase and react with Al2O3 which contributed to obtaining fully dense specimens at 1350 °C and maintains fine grain sizes of WC until the temperature exceeding 1450 °C. The sintering temperature of the specimens with optimum mechanical properties has been also reduced comparing that of the original WC- 1.87 wt % Al2O3- 4.13 wt %ZrO2 cemented carbides. Furthermore, the addition of B2O3 triggered the reaction between B2O3 and Al2O3 resulting in forming in-situ elongated aluminium borate grains (A4B2O9 and A18B4O33 whiskers), which promoted the toughness. The specimens sintered at 1450 °C exhibited optimal mechanical properties: the Vickers hardness and fracture toughness were 19.26 GPa and 11.49 MPa m1/2, respectively. 相似文献
6.
Yingbin Hu Fuda Ning Weilong Cong Yuanchen Li Xinlin Wang Hui Wang 《Ceramics International》2018,44(3):2752-2760
Laser additive manufactured zirconia-alumina ceramic (ZrO2-Al2O3) parts demonstrate severe problems resulting from cracking and inhomogeneous material dispersion. To reduce these problems, we propose a novel ultrasonic vibration-assisted laser engineered net shaping (LENS) process for fabrication of bulk ZrO2-Al2O3 parts. Results showed that the initiation of cracks and the crack propagation were suppressed in the parts fabricated by LENS process with ultrasonic vibration. For the parts fabricated without ultrasonic vibration, the sizes of cracks decreased with the increase of laser power. Scanning electron microscope analyses proved that the introduction of ultrasonic vibration was beneficial for grain refinement and uniform material dispersion. Due to the suppressed cracking, refined grains, and homogenized material dispersion, the parts fabricated with ultrasonic vibration demonstrated better mechanical properties (including higher microhardness, higher wear resistance, and better compressive properties), compared with the parts fabricated without ultrasonic vibration. 相似文献
7.
Intercalation structure and toughening mechanism of graphene/urea‐formaldehyde nanocomposites prepared via in situ polymerization 下载免费PDF全文
Based on the industrialized graphene (GN) product, a series of graphene/urea‐formaldehyde nanocomposites were synthesized via in situ polymerization by incorporation of silicon coupling agent with terminal amino groups (SA) as the compatibilizer. The results showed that addition of SA coupling agent led to much more efficient grafting of UF molecules on the GN surface with high layer thickness by formation of hydrogen bonding, and thus complete exfoliation and uniform dispersion of GN were achieved for the composites. Compared with neat UF, the addition of 1.0 wt% GN resulted in a roughly 25% increase in tensile strength and 12% increase in impact strength; meanwhile the impact fracture surfaces of the composite showed obvious ductile fracture characteristics, indicating the reinforcing and toughening effect of GN on the UF matrix. With increasing GN content, the storage modulus, glass transition temperature and crosslinking density of UF increased, while the tan δmax decreased, suggesting that a double crosslinking network structure with GN centered crosslinking point and chemical crosslinking point of UF molecular chains formed, leading to improvement in the stiffness of the composites. The present work showed promising potential for developing high performance UF resin on an industrial scale. © 2017 Society of Chemical Industry 相似文献
8.
Effect of the composition and degree of crosslinking on the properties of poly(l‐lactic acid)/crosslinked polyurethane blends 下载免费PDF全文
Meng Ma Kai Liu Haiming Zheng Si Chen Bozhen Wu Yanqin Shi Xu Wang 《Polymer International》2018,67(9):1221-1228
Poly(l ‐lactic acid)/crosslinked polyurethane (PLLA/CPU) blends which were prepared via reactive blending of PLLA with poly(?‐caprolactone) (PCL), glycerol and 4,4′‐methylenediphenyl diisocyanate showed excellent toughness. The effects of the composition of the mixture and degree of crosslinking of CPU on the toughness of the PLLA/CPU blends (80/20 w/w) were studied in detail. Dynamic mechanical analysis and rheological measurements were used to characterize the structure of the in situ formed CPU in the PLLA matrix. A novel netlike phase structure was observed when the average molecular weight of PCL and degree of crosslinking were 1 kDa and 10%, respectively. The impact strength of the blend was enhanced from 2.2 kJ m?2 for pure PLLA to 62.4 kJ m?2; meanwhile, the elongation at break was increased to 489.8%. Therefore, the mechanical properties of PLLA/CPU blends can be easily tailored by tuning the composition of the mixture and the degree of crosslinking of CPU. © 2018 Society of Chemical Industry 相似文献
9.
Yu Chen Jiageng Xu Qian Xu Shaoxiong Xie Qingyuan Wang Jianguo Zhu 《Journal of the American Ceramic Society》2020,103(2):1067-1078
In this work, ferroelastic domain switching and R-curve behavior in lead zirconate titanate (Nb/Ce co-doped Pb(Zr0.52Ti0.48)O3, ab. PZT-NC)-based ferroelectric ceramics were investigated, using the indentation-strength-in-bending (ISB) method. Firstly, Vickers indentation test examined the notable fracture anisotropy of PZT-NC ceramics between the poling direction and its perpendicular direction, and the crack open displacement (COD) profiles in the two directions were also theoretically calculated from the indentation fracture mechanics. And then two kinds of ferroelastic domain switching modes (in-plane and out-of-plane) were used for explaining such anisotropic propagation behavior of indentation cracks. The subsequent three-point bending test illustrated the dependence of fracture strength on indentation load and the rising crack growth resistance curves (R-curves) in two directions. The resulted R-curves were fitted by the Hill's type Growth Function successfully, giving the reasonable values of crack extension exponential (n), plateau fracture toughness (Kmax), and initial fracture toughness (Kini). The in-plane ferroelastic domain switching was identified as a more significant toughening mechanism for PZT-NC ceramics than the out-of-plane switching due to more switchable domains. 相似文献
10.
采用拉力试验机、差示扫描量热仪及扫描电子显微镜等仪器,对比分析了不同种类聚烯烃弹性体(POE)产品对共聚聚丙烯(PP)的增韧效果。结果表明:POE的添加对PP具有明显的增韧效果,且随着其添加量的增加,增韧效果越加显著;自制的中试产品的增韧效果达到进口产品Engage 8540水平。 相似文献