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71.
Tian Shi Xuewu Li Chuanwei Zhang Hongxing Wang Zhenyan He Xuegang Zhou Danni Yang Hejie Yang Binbin Zhang Kang Yang 《工业材料与腐蚀》2021,72(5):904-911
Corrosion and wear failures are bottlenecks for restricting applications and developments of Al-based functional materials. As a new lubrication technology, superhydrophobic preparation provides an effective way to settle Al alloy corrosion. The preparation methods of superhydrophobic Al alloys are mainly multistep strategies. In this study, superhydrophobic Al alloy, has been prepared by an efficient one-step electrochemical etching process. Meanwhile, its micromorphology has been observed by a scanning electron microscope. The wettability has been measured by video optical contact angle meter. The corrosion behavior has been tested by electrochemical workstation, and wear performance has been characterized by friction tester. The results show that the micro-nanoterraced concave–convex structure has been fabricated and an as-prepared surface exhibits excellent superhydrophobic behavior. Further electrochemical and tribological tests show that corrosion resistance and wear resistance have also been significantly improved. This study provides a new method to prepare wear-resistant and corrosion-resistant Al alloy for widening applications of multifunctional Al-based engineering materials. 相似文献
72.
Zhencai Li Dacheng Zhou Lars R. Jensen Jianbei Qiu Yanfei Zhang Yuanzheng Yue 《Journal of the American Ceramic Society》2021,104(9):4471-4478
The transparent Er3+-Yb3+-doped fluoro-aluminosilicate glass-ceramic (GC) was prepared by melt-quenching. The crystal phase, morphology, and up-conversion (UC) luminescence of as-produced GC were characterized by X-ray diffraction, scanning electron microscopy, and fluorescence spectrophotometry, respectively. The results show that BaYF5 nanocrystals were uniformly distributed in the glass matrix of the as-produced GC. When the as-produced GC was subjected to heat treatment, the crystallinity was increased, but the crystal identity remains unchanged. Such heat-treatment doubled the intensity of the UC luminescence, and this enhancement was ascribed to the increased incorporation of both Er3+ and Yb3+ ions into the lower phonon energy environment of BaYF5 nanocrystals. Furthermore, the heat-treated GC was stable against further crystallization, and consequently its UC luminescence was stable at the application temperature. The heat-treated GC was found to possess an outstanding temperature-sensing capability. 相似文献
73.
Yuping Ji Kaixin Song Shiyu Zhang Zhilun Lu Ge Wang Linhao Li Di Zhou Dawei Wang Ian M. Reaney 《Journal of the European Ceramic Society》2021,41(1):424-429
Dense (1-x)wt%CaSnSiO5-xwt%K2MoO4 (CSSO-KMO) composite ceramics were fabricated by the cold sintering process at 180 °C under 400 MPa for 60 min. X-ray diffraction, Energy dispersive X-ray and Raman spectroscopy confirmed that CSSO and KMO coexisted without intermediate phases. As KMO weight fraction increased, relative permittivity (εr) and temperature coefficient of resonant frequency (τf) decreased and the microwave quality factor (Q×f, where f is resonant frequency) increased. Near-zero τf (-0.5 ppm/°C) was obtained for 65 wt%CSSO-35 wt%KMO with εr ~ 9.2 and Q×f ~ 6240 GHz. No chemical reaction between ceramic composites and silver was observed, demonstrating potential for cofiring with Ag-paste. A prototype antenna was fabricated from 65 wt%CSSO-35 wt%KMO composite ceramic with a bandwidth of 144 MHz @ -10 dB, a gain of 5.7 dBi and a total efficiency of 88.4 % at 5.2 GHz, suitable for 5 G mobile communication systems. 相似文献
74.
Xiaoyu Ji Hongfei Gao Shuai Zhang Yan Jia Ming-Sheng Ji Xingui Zhou Changwei Shao 《Journal of the European Ceramic Society》2021,41(10):5016-5025
Given the superior thermal stability and electromagnetic features, continuous Si–B–(C)–N ceramic fibers have displayed great potential to fulfill the increasing demand for the high-temperature structural and functional materials. Manufacture of such ceramic fibers depends heavily upon the design of processable polymer precursors. Herein, a class of polyborosilazanes (PBSZs) with high spinnability were created through a facile one-pot synthesis. The trade-off between spinnability and ceramic yield of PBSZs was overcome by using heptamethyldisilazane and hexamethyldisilazane as the co-condensing agents to polymerize silicon and boron chloride monomers. The optimal PBSZs can fabricate continuous Si–B–C–N fibers with homogeneous diameter of 7.9 ± 0.5 μm and high ceramic yield of 80 wt%. Experimental characterization and quantum chemical computation revealed the mechanistic pictures of the impact of pendant groups on the polycondensation, melt spinning, and pyrolyzing process. These insights improve our understanding of spinnable pre-ceramic polymers for exploiting high-performance nitride ceramic fibers. 相似文献
75.
Angel L. Ortiz Camila S. Rodrigues Fernando Guiberteau Yu Zhang 《Journal of the European Ceramic Society》2021,41(11):5728-5739
The microstructural development during crystallization firing of a commercially-available dental-grade nanostructured lithia-zirconia glass-ceramic (Vita Suprinity® PC) was unraveled using a wide battery of ex-situ and in-situ characterization techniques. It was found that the milling blocks are slightly crystallized glass-ceramics, with a complex chemical composition and consisting of partially de-polymerized glass plus lithium silicate (Li2SiO3) nanocrystals. It was also found that during crystallization firing the glassy matrix first reacts with part of the Li2SiO3 to form lithium disilicate (Li2Si2O5) at ~810?820 °C, and then lithium orthophosphate (Li3PO4) precipitates from the glass. This results in glass-ceramics with abundant nanocrystals embedded in a sparse zirconosilicate glass matrix (containing many other cations subsumed) that, due to its high viscosity, inhibited crystal growth. Therefore, these dental glass-ceramics are not reinforced with zirconia (ZrO2) crystals unless over-fired above ~890 °C and at the expense of its singular nanostructure. Finally, this study opens doors for optimizing the clinical performance of these dental glass-ceramics via microstructural tailoring. 相似文献
76.
Xiaohui Wu Jingkang Xu Xingyu Huo Junbo Chen Qin Zhang Fangyi Huang Yuanxun Li Hua Su Lezhong Li 《Journal of the European Ceramic Society》2021,41(10):5193-5200
This work investigates the influence of niobium pentoxide (Nb2O5) as dopant, on the structural, magnetic, and dielectric properties of NiZnCo ferrites. The results showed that Nb2O5 was an effective dopant, and the Nb5+ ions entered the B site to replace Fe3+ ions, which altered the electromagnetic properties of the NiZnCo ferrite. In particular, the coercivity (Hc) was 20~24 Oe, and the magnetic quality factor (Q), was more than 200 at x = 0 and x = 0.1 wt%, which is 4~5 times higher than that of NiZn and NiCuZn ferrites. Excellent electromagnetic properties were obtained for 0.1 wt% Nb2O5-doped NiZnCo ferrite, i.e., Ms = 88.3 emu/g, Hc =20.4 Oe, ρ = 2.4 × 105 Ω m and Q = 202 @20 MHz. These excellent electromagnetic properties of Nb2O5-doped NiZnCo ferrites could be potentially applied to resonators and capacitors at high frequency. 相似文献
77.
78.
Yuanyuan Chen Jian Peng Tian Sheng Ruixuan Qin Shuqi Dai Zaifa Shi Zichao Tang Laisen Wang Qinghua Zhang Bin Han Liping Sun Jun Xu Jian Weng 《Advanced functional materials》2021,31(42):2104246
Radicals are closely related to human life and health and have been widely used in biology, chemistry, functional materials, etc. However, the high reactivity, disorder, and short half-lives limit their wide applications. Therefore, it remains a great challenge to prepare stable and ordered radicals. Herein, radicals are prepared with protective umbrellas (diethylmethyleneamine, DEMA) that are integrated on the surface of 2D layered materials to isolate water and oxygen and enhance the stability of radicals. Taking 2D black phosphorus (BP) as an example: triethylamine reacts with dichloromethane to form quaternary ammonium salts with further Hoffmann elimination to produce DEMA radicals that could react with one electron of a lone pair electrons in P on the surface of BP to produce P radicals, which shows a prolonged half-life of 21 days at room temperature. First-principle calculations and electron paramagnetic resonance fitting confirm that the steric hindrance constructed by dense DEMA passivation layer acts as a protective umbrella and the 2D coupling of P radicals and other P atoms in 2D BP plane to enhance the stability and strong superexchange interaction of P radicals. Furthermore, it is a general strategy to produce stable radicals integrated on the 2D plane. 相似文献
79.
Pushing popular contents to the edge of the network can meet the growing demand for data traffic, reduce latency and relieve the pressure of the backhaul. However, considering the limited storage space of the base stations, it is impossible to cache all the contents, especially in ultra-dense network ( UDN). Furthermore, the uneven distribution of mobile users results in load imbalance among small base stations (SBSs) in both time and space, which also affects the caching strategy. To overcome these shortcoming, the impact of the changing load imbalance in UDN was investigated, and then a dynamic hierarchical collaborative caching (DHCC) scheme was proposed to optimize latency and caching hit rate. The storage of the SBS is logically divided into the independent caching layer and the collaborative caching layer. The independent caching layer caches the most popular contents for local users爷interest, and the collaborative caching layer caches contents as much as possible for the benefit of content diversity in the region. Different SBSs have respective storage space layer division ratios, according to their real-time traffic load. For SBSs with heavy load, the independent caching layers are allocated with more space. Otherwise, the collaborative caching layers could store more contents with larger space. The simulation results show that, DHCC improved both transmission latency and hit rate compared with existing caching schemes. 相似文献
80.
Da-Wang Tan Zhen-Yong Lao Zhan Zhang Wei-Ming Guo Shi-Kuan Sun Hua-Tay Lin 《Journal of the American Ceramic Society》2021,104(6):2860-2867
B4C-TiB2 ceramics (TiB2 ranging 5~70 vol%) with Mo-Co-WC as the sintering additive were prepared by spark plasma sintering. In comparison with B4C-TiB2 without additive, the enhanced densification was evident in the sintered specimen with Mo-Co-WC additive. Core-rim structured grain was observed around TiB2 grains. The interface of the rim between TiB2 and B4C phases demonstrated different feature: the inner borderline of the rim exhibited a smooth feature, whereas a sharp curved grain boundary was observed between the rim and the B4C grain. The formation mechanism is discussed: the epitaxial growth of (Ti,Mo,W)B2 rim around the TiB2 core may occur as a result of the solid solution and dissolution-precipitation between TiB2 phase and the sintering additive. It was revealed that the fracture toughness increased as the content of TiB2 content increased, alongside the decreased hardness. B4C-30 vol% TiB2 specimen demonstrated the optimal combination of mechanical properties, reaching Vickers hardness of 24.3 GPa and fracture toughness of 3.33 MPa·m1/2. 相似文献