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11.
Mg(Ti1-xNbx)O3 (x = 0–0.09) ceramics were prepared by the conventional solid-state reaction method. The phase composition, sintering characteristics, microstructure and dielectric properties of Ti4+ replacement by Nb5+ in the formed solid solution Mg(Ti1-xNbx)O3 (x = 0–0.09) ceramics were systematically studied. The structural variations and influence of Nb5+ doping in Mg(Ti1-xNbx)O3 were also systematically investigated by X-ray diffraction and Raman spectroscopy, respectively. X-ray diffraction and its Rietveld refinement results confirmed that Mg(Ti1-xNbx)O3 (x = 0–0.09) ceramics crystallised into an ilmenite-type with R-3 (148) space group. The replacement of the low valence Ti4+ by the high valence Nb5+ can improve the dielectric properties of Mg(Ti1-xNbx)O3 (x = 0–0.09). This paper also studied the different sintering temperatures for Mg(Ti1-xNbx)O3 (x = 0–0.09) ceramics. The obtained results proved that 1350 °C is the best sintering temperature. The permittivity and Q × f initially increased and then decreased mainly due to the effects of porosity caused by the sintering temperature and the doping amount of Nb2O5, respectively. Furthermore, the increased Q × f is correlated to the increase in Ti–O bond strength as confirmed by Raman spectroscopy, and the electrons generated by the oxygen vacancies will be compensated by Nb5+ to a certain extent to suppress Ti4+ to Ti3+, which was confirmed by XPS. The increase in τf from ?47 ppm/°C to ?40.1 ppm/°C is due to the increment in cell polarisability. Another reason for the increased τf is the reduction in the distortion degree of the [TiO6] octahedral, which was also confirmed by Raman spectroscopy. Mg(Ti0.95Nb0.05)O3 ceramics sintered at 1350 °C for 2 h possessed excellent microwave dielectric properties of εr = 18.12, Q × f = 163618 GHz and τf = ?40.1 ppm/°C. 相似文献
12.
Yunyan Liu Ning Jiang Yao Liu Dawei Cui Chang-Feng Yu Huiqiang Liu Zhao Li 《Ceramics International》2021,47(16):22416-22423
Pulsed laser deposition (PLD) was used to prepare tungsten trioxide (WO3) films on ITO substrates with a varying laser power density of 4.0–5.5 W/cm2. XPS indicated that when the laser power density decreased, the peak positions of the W 4f and O 1s orbits shifted slightly to low energy due to the difference in oxygen vacancies. As the laser power density decreased, W6+ gradually replaced the lattice position of O2?, increasing oxygen vacancies in the lattice. The transmittance modulated values (ΔT) were over 44% at 830 nm, indicating strong absorption by the WO3 thin films in the near-infrared ray. The switching time of the WO3 thin films between bleached states and coloured states decreased as the laser power density increased due to the amorphous structure, morphology, and lower oxygen deficiency at a high power density. The high ΔT and very fast switching time of tb (1.09 s) and tc (6.01 s) demonstrated the excellent electrochromic (EC) properties of the WO3 films prepared by PLD. 相似文献
13.
为了探讨氮含量及固溶温度对21-6-9不锈钢组织和硬度的影响,分别在950、1000、1050和1100 ℃对3种不同氮含量的热轧态21-6-9不锈钢进行1 h固溶处理,通过光学显微镜观察其组织结构,结合Thermo-Calc热力学计算对试验钢的微观组织进行分析,并对其进行硬度测试。结果表明,0.20%~0.28%N的21-6-9不锈钢热轧后沿轧制方向析出铁素体,且钢中铁素体经950~1100 ℃固溶处理可消除,当N含量达到0.34%时,试验钢中不再出现铁素体。随着固溶处理温度的升高,21-6-9不锈钢的晶粒组织长大,硬度降低。N含量的增加可显著提高固溶态21-6-9不锈钢的硬度,其增加程度随固溶处理温度的升高而减弱。 相似文献
14.
Bin Feng Xin Jiang Guisheng Zou Wengan Wang Tianming Sun Heng Yang Guanlei Zhao Mingye Dong Yu Xiao Hongwei Zhu Lei Liu 《Advanced functional materials》2021,31(29):2102359
The realization of liquid metal-based wearable systems will be a milestone toward high-performance, integrated electronic skin. However, despite the revolutionary progress achieved in many other components of electronic skin, liquid metal-based flexible sensors still suffer from poor sensitivity due to the insufficient resistance change of liquid metal to deformation. Herein, a nacre-inspired architecture composed of a biphasic pattern (liquid metal with Cr/Cu underlayer) as “bricks” and strain-sensitive Ag film as “mortar” is developed, which breaks the long-standing sensitivity bottleneck of liquid metal-based electronic skin. With 2 orders of magnitude of sensitivity amplification while maintaining wide (>85%) working range, for the first time, liquid metal-based strain sensors rival the state-of-art counterparts. This liquid metal composite features spatially regulated cracking behavior. On the one hand, hard Cr cells locally modulate the strain distribution, which avoids premature cut-through cracks and prolongs the defect propagation in the adjacent Ag film. On the other hand, the separated liquid metal cells prevent unfavorable continuous liquid-metal paths and create crack-free regions during strain. Demonstrated in diverse scenarios, the proposed design concept may spark more applications of ultrasensitive liquid metal-based electronic skins, and reveals a pathway for sensor development via crack engineering. 相似文献
15.
Weiwen Wang Hui Zhao Peng Pan Kang Xue Zisheng Zhang Jihai Duan 《Ceramics International》2021,47(5):6094-6104
In order to enhance the photocatalytic activity of TiO2 under visible light, Ag nanoparticles were introduced into tridoped B–C–N–TiO2 (TT) catalyst by photoreduction deposition. Ag/B–C–N–TiO2 (ATT) catalysts with the functions of reducing band gap and carrier recombination were prepared. At the same time, the effect of the amount of Ag on the photocatalytic performance of ATT catalyst was investigated. Through XRD, XPS, PL and other characterization methods, the (211)/(101)/Ag interface heterojunction mechanism similar to the traditional Z-scheme heterojunction was proposed. The intervention of Ag nanoparticles changed the P–N interface heterojunction between (211)/(101) to the (211)/(101)/Ag Z-scheme interface heterojunction. The results show that ATT catalyst exhibits the highest photocatalytic activity when the molar amount of Ag is 0.005% with the MB degradation rate of the ATT catalyst (0.01707 min?1), which is 14.59 times of TiO2 (0.00117 min?1) and 2.02 times of TT (0.00847 min?1). In addition, the four cycles efficiencies of ATT for MB degradation were all above 94.00%.This study reveals the possibility of construction of Z-scheme heterojunctions between precious metal nanoparticles and different interfaces of TiO2, and provides a reference for the construction of Z-scheme interface heterojunctions. 相似文献
16.
Developing non-platinum group metal (non-PGM) electrocatalysts for the hydrogen oxidation reaction (HOR) represents the efforts towards the more economical use of hydrogen fuel cells and hydrogen energy, which has attracted tremendous attention recently. However, non-PGM electrocatalysts for the HOR are still in their early development stages as compared with the significant advances in those for the oxygen reduction reaction and hydrogen evolution reaction. Herein, this paper summarizes the recent progresses and highlights the key challenges for the rational design of non-PGM electrocatalysts, aiming to promote the development of non-PGM HOR electrocatalysts. Fundamental understandings of the HOR mechanism are firstly reviewed, where theoretical interpretations on the low HOR kinetics in alkaline media, including the hydrogen binding energy theory, the bifunctional mechanism, and the water molecule reorganization, are particularly discussed. Subsequently, progresses of typical non-PGM HOR electrocatalysts in acid and alkaline media are summarized separately. For the HOR under alkaline conditions, the superiorities and challenges of Ni-based catalysts are discussed with a particular focus as they are the most promising non-PGM electrocatalysts. Finally, this paper highlights the challenges and provide perspectives on the future development directions of non-PGM HOR electrocatalysts. 相似文献
17.
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19.
High purity AlN fiber is a promising thermal conductive material. In this work, AlN fibers were prepared using solution blow spinning followed by nitridation under N2 or NH3 atmosphere. Soluble polymer, such as polyaluminoxane, and allyl-functional novolac resin were adopted as raw materials to form homogeneous distribution of Al2O3 and C nanoparticles within the fibers, which could inhibit the growth of alumina crystal and promote their nitridation process. The effect of nitriding atmosphere on the fiber morphology was investigated. XRD results showed that complete nitridation was achieved at 1300 °C in the NH3 or at 1500 °C in the N2 atmosphere. Hollowed fiber structure was observed when fiber was nitrided in N2 at high temperature, which was caused by gaseous Al gas diffusion, and this phenomenon was eliminated in NH3 atmosphere. The nitridation mechanisms in different atmosphere were analyzed in detail. It was demonstrated that the nitridation of Al2O3 fibers in the NH3 atmosphere offered the favored AlN morphology and chemical quality. Flexible AlN fiber with O content of 0.7 wt% was achieved after nitriding in NH3 at 1400 °C. The high quality AlN can be used in thermal conductive composite materials. 相似文献
20.