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61.
62.
Pengfei Liang Jie Zhu Di Wu Hui Peng Xiaolian Chao Zupei Yang 《Journal of the American Ceramic Society》2021,104(6):2702-2710
Due to the demand of miniaturization and integration for ceramic capacitors in electronic components market, TiO2-based ceramics with colossal permittivity has become a research hotspot in recent years. In this work, we report that Ag+/Nb5+ co-doped (Ag1/4Nb3/4)xTi1−xO2 (ANTOx) ceramics with colossal permittivity over a wide frequency and temperature range were successfully prepared by a traditional solid–state method. Notably, compositions of ANTO0.005 and ANTO0.01 respectively exhibit both low dielectric loss (0.040 and 0.050 at 1 kHz), high dielectric permittivity (9.2 × 103 and 1.6 × 104 at 1 kHz), and good thermal stability, which satisfy the requirements for the temperature range of application of X9R and X8R ceramic capacitors, respectively. The origin of the dielectric behavior was attributed to five dielectric relaxation phenomena, i.e., localized carriers' hopping, electron–pinned defect–dipoles, interfacial polarization, and oxygen vacancies ionization and diffusion, as suggested by dielectric temperature spectra and valence state analysis via XPS; wherein, electron-pinned defect–dipoles and internal barrier layer capacitance are believed to be the main causes for the giant dielectric permittivity in ANTOx ceramics. 相似文献
63.
Yixuan ZHOU Huajie WANG Yi YU Yihang CHEN Rui KE Min XU Chijie XIAO Zhanhui WANG Jiquan LI Xuru DUAN Minyou YE 《等离子体科学和技术》2021,23(7):75105-52
In this article, we present the optical design of a novel diagnostic on the HL-2 A tokamak, i.e. the20-channel edge Lyman-alpha beam emission spectroscopy, which is a promising solution for edge density turbulence research on tokamaks, as it offers the possibility of density fluctuation measurement with a 3.3 mm spatial resolution while maintains a high temporal resolution of1 μs. The optical path, including the reflective collection optics, the high-dispersion spectrometer, and the linear detector array, is carefully optimized to obtain a good image quality and a high throughput. The maximum root mean square radius of the collection optics is 64 μm.The detected photon flux is estimated to be about 10~(11) photons/s/channel. 相似文献
64.
针对现有的混凝土裂缝检测算法在各种复杂环境中检测精度不够、鲁棒性不强的问题,根据深度学习理论和U-net模型,提出一种全U型网络的裂缝检测算法。首先,依照原U-net模型路线构建网络;然后,在每个池化层后都进行一次上采样,恢复其在池化层之前的特征图规格,并将其与池化之前的卷积层进行融合,将融合之后的特征图作为新的融合层与原U-net网络上采样之后的网络层进行融合;最后,为了验证算法的有效性,在测试集中进行实验。结果表明,所提算法的平均精确率可达到83.48%,召回率为85.08%,F1为84.11%,相较于原U-net分别提升了1.48%,4.68%和3.29%,在复杂环境中也能提取完整裂缝,保证了裂缝检测的鲁棒性。 相似文献
65.
Qi Yafang Chen Yifan Wang Rui Wang Lijing Zhang Fuli Shen Qi Qu Peng Liu Daosheng 《Catalysis Letters》2021,151(6):1546-1555
Catalysis Letters - g-C3N4 has great application prospect in the field of photocatalytic nitrogen fixation owing to the advantages of abundant raw materials, low toxicity, low consumption, high... 相似文献
66.
Peixin Gao Peng Dong Zeyun Zhou Qian Li Honghui Li Zhi Zhou Mao Xia Peihua Zhang 《Ceramics International》2021,47(12):16588-16596
Deep-red light emitting phosphors are widely used in LEDs for indoor plant growth because of the critical role played by red light in plant growth. The luminescence properties of deep-red phosphors are still not well understood at present. An energy transfer strategy is a common and effective method to improve luminescence properties. In principle, the energy transfer process may occur when the sensitizer's emission spectra overlap with the activator's excitation spectra. In this work, Bi3+ and Mn4+ were incorporated into the matrix of Gd2MgTiO6 as sensitisers and activators, respectively. Mn4+ ions tend to occupy the [TiO6] octahedral site and the Bi3+ ions are expected to substituted in the site of Gd3+. The energy transfer process from Bi3+ to Mn4+ was realised and the photoluminescence (PL) intensity of Mn4+ increased with the doping content of Bi3+. Upon excitation at 375 nm, the PL intensity of Mn4+ increased to 116.4% when the doping concentration of Bi3+ reached 0.3%. Finally, the pc-LED devices were prepared by a Gd2MgTiO6:Bi3+, Mn4+ phosphor. The high red luminescence indicated that this phosphor has potential applications in indoor LED lighting. 相似文献
67.
Huimin Tang Zhiwei Peng Foquan Gu Lei Yang Weiguang Tian Qiang Zhong Mingjun Rao Guanghui Li Tao Jiang 《Ceramics International》2021,47(8):10809-10818
The chromium-promoted preparation of forsterite refractory materials from ferronickel slag was investigated by microwave sintering of the slag with the additions of sintered magnesia and 0–10 wt% chromium oxide (Cr2O3). The thermodynamic calculations revealed that the addition of Cr2O3 can promote the formations of spinel and liquid phase and maintain high content of forsterite below 1500 °C. The experimental results showed that there existed a stronger promoting effect of Cr2O3 additive on the properties of refractory materials in the microwave field than that in conventional sintering. It was attributed to the preferential formation and growth of spinel with stronger microwave absorption than other phases (e.g., enstatite), the existence of more forsterite, and the enhanced densification in association with the presence of more liquid phase at the same temperature. By microwave sintering of the mixture of ferronickel slag, 25 wt% sintered magnesia, and 4 wt% Cr2O3 at 1350 °C for 20 min, a superior refractory material with refractoriness of 1801 °C, thermal shock resistance of 6 times, bulk density of 2.97 g/cm3, apparent porosity of 1.4%, and compressive strength of 197 MPa was obtained. Compared with that prepared by conventional sintering at 1350 °C for 2 h, the refractoriness and thermal shock resistance were increased by 175 °C and 100%, respectively. The present study provided a novel method for preparing high-quality refractory materials from ferronickel slag and relevant industrial wastes. 相似文献
68.
69.
高能量密度燃料是为新型高性能飞行器提供动力保障的关键,其合成及应用研究具有重要的前瞻性和重大战略意义。煤炭是我国的主体能源和重要原料,通过煤直接转化获取的煤基油,充分保留了煤中特有的环状分子化学结构,具有良好的热安定性和较高的能量密度,被认为是高超音速飞行器的优选燃料。以煤直接液化工艺生产的煤液化石脑油馏分为起始原料,通过富集轻质芳烃、化学合成、催化加氢稳定和产物分离提纯等方法制备煤基高能量密度燃料,并对其产物进行分子结构表征和性能评价。结果表明,煤直接液化生产的石脑油馏分是一种优异的催化重整原料,经催化重整富集轻质芳烃后,其轻质芳烃质量分数高达71.05%。Diels-Alder化学合成主产物是由多个封闭环平面组成且具有空间立体构型的二环或三环烃类物质,质量分数为46.18%,因分子内存在较大的张力能,结构紧凑,其拥有更大的密度和体积热值。煤基高能量密度燃料的密度和体积热值分别为0.8990 g/cm3与38.06 MJ/L,均大大超过现行的国内石油基喷气燃料(RP-3和RP-6)、煤基大比重喷气燃料、美国和俄罗斯军用标准。与单一纯物质合成高能量密度燃料(JP-10和T-10)比较,其密度与体积热值偏小。究其原因主要是轻质芳烃的富集度仅为71.05%,需进一步提高其轻质芳烃质量分数。另外,制备的煤基高能量密度燃料种类复杂,其主产物质量分数仅46.18%,下一步可重点调控合成产物的分子构型和纯化分离。 相似文献
70.
Wireless Networks - In this paper, a grouping-based uplink orthogonal frequency division multiple access (OFDMA) random access method is studied which can improve users’ satisfaction in the... 相似文献