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81.
Teng Zheng Laihui Luo Peng Du Anmeng Deng Weiping Li 《Journal of the European Ceramic Society》2018,38(2):575-583
The (0.98-x)(0.6Pb(Mg1/3Nb1/3)O3-0.4PbTiO3)-xPb(Yb1/3Nb1/3)O3-0.02Pb(Er1/2Nb1/2)O3 ((0.98-x)(PMN-PT)-xPYN:Er3+) ceramics were prepared through a solid-state reaction method. The phase structure, piezoelectric response, ferroelectric performance and upconversion emission of the ceramics were systematically investigated. The phase structure, the electrical and optical properties are strongly related to the content of PYN. The optimized piezoelectric response and upconversion emissions of the ceramics were achieved near x = 0.12, which locates in the morphotropic phase boundary (MPB) composition. Furthermore, the temperature sensing behaviors of the resultant compounds based on the thermally coupled levels of 2H11/2 and 4S3/2 of Er3+ ions in the temperature range of 133–573 K were studied by utilizing the fluorescence intensity ratio technique. Additionally, the thermal effect, which is induced by the laser pump power, of the studied ceramics is also investigated and the produced temperature is enhanced from 268 to 348 K with the pump power rising from 109 to 607 mW. 相似文献
82.
Bingcheng Luo Xiaohui Wang Enke Tian Hongzhou Song Qiancheng Zhao Ziming Cai Wei Feng Longtu Li 《Journal of the European Ceramic Society》2018,38(4):1562-1568
Fe doped BaTiO3 ceramics with giant permittivity and low dielectric loss were synthesized in N2/H2 atmosphere started with BaTiO3 powders and iron powders. XRD analysis exhibited the tetragonal-pseudocubic phase transition when the Fe content is 3 mol%. XPS spectra confirmed the iron oxides with mixed-valence structure of Fe2+/Fe3+, while Ti-ions maintain Ti4+3d0 states without any oxidization-reduction. For the case of ceramics with 5 mol% Fe, the dielectric constant was 66,650 at 1000 Hz at room temperature, 19 times higher than that of pure BaTiO3 ceramics, while the dielectric loss tangent was 0.13. Comparison with other giant-permittivity materials demonstrated the superior potential of present ceramics. First-principles calculations investigated the interfacial interaction of Fe-[TiO2] interface and Fe-[BaO] interface. Giant dielectric constant was induced by the interfacial polarization between insulating ferroelectrics and semiconducting iron oxides with mixed-valence states, as well as the contribution from the generated electron hopping conduction. 相似文献
83.
Yang Luo Shi-li Zheng Shu-hua Ma Chun-li Liu Xiao-hui Wang 《Journal of the European Ceramic Society》2018,38(16):5282-5293
A novel mullite-bonded SiC-whisker-reinforced SiC matrix composite (SiCw/SiC, SiC whisker-to-SiC powder mass ratio of 1:9) was designed and successfully prepared. Before preparing the composite, the inexpensive lab-made SiCw was first modified by an oxidation/leaching process and then coated with Al2O3. The kinetics results indicate that the oxidation process can be described by improved shrinking-cylinder models. The aspect ratio of SiCw improved after modification. Subsequently, raw materials with a SiC–SiO2–Al2O3 triple-layered structure were obtained after the Al2O3-coating process and used as feedstocks during the subsequent hot-pressing sintering. Finally, the characterization of the composites indicates that the mullite-bonded sample performs better (relative density of 93.8?±?1.4%, flexural strength of 533.3?±?18.2?MPa, fracture toughness of 13.6?±?2.1?MPa?m1/2, and Vickers hardness of 20.6?±?2.5?GPa) than the reference sample without the mullite interface. The improved toughness could essentially be attributed to the moderately strong interface bonding and effective load transfer effects of the mullite interface. 相似文献
84.
Core–shell type multi‐arm azide polymers based on hyperbranched copolyether as potential energetic materials in solid propellants 下载免费PDF全文
A series of novel multi‐arm azide copolymers (POGs) with the same hyperbranched poly[3‐ethyl‐3‐(hydroxymethyl)oxetane] core (PEHO‐c) and different content of linear glycidyl azide polymer shell (GAP‐s) have been synthesized by sequential cationic ring‐opening polymerization and azidation. Detailed structural information of these copolyethers was deduced from Fourier transform infrared, 1H NMR and inverse gated decoupled 13C NMR spectroscopies, matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry, gel permeation chromatography and elemental analysis. The molecular weight of POG having GAP‐s and PEHO‐c with a molar ratio 14.95:1 (Rs/c) was around 31 000 g mol?1, far above that of linear GAP (around 4000 g mol?1). The apparent viscosity and glass transition temperature (?51 to ?23 °C) decreased first and then slightly increased with increasing molecular weight. Thermal analysis revealed that all the obtained POGs exhibited excellent resistance to thermal decomposition up to 220 °C. Moreover, the energetic properties, investigated using oxygen bomb calorimetric measurements, indicated that the enthalpy of formation of the POGs was higher than that of general linear GAP, but similar to that of branched GAP under reasonable Rs/c. The compatibilities of the POGs with common materials used in solid propellants were studied using differential scanning calorimetry and the results indicated that the POGs had good compatibility with these materials. © 2017 Society of Chemical Industry 相似文献
86.
The multi-purpose forensics is an important tool for forge image detection. In
this paper, we propose a universal feature set for the multi-purpose forensics which is
capable of simultaneously identifying several typical image manipulations, including
spatial low-pass Gaussian blurring, median filtering, re-sampling, and JPEG
compression. To eliminate the influences caused by diverse image contents on the
effectiveness and robustness of the feature, a residual group which contains several highpass filtered residuals is introduced. The partial correlation coefficient is exploited from
the residual group to purely measure neighborhood correlations in a linear way. Besides
that, we also combine autoregressive coefficient and transition probability to form the
proposed composite feature which is used to measure how manipulations change the
neighborhood relationships in both linear and non-linear way. After a series of dimension
reductions, the proposed feature set can accelerate the training and testing for the multipurpose forensics. The proposed feature set is then fed into a multi-classifier to train a
multi-purpose detector. Experimental results show that the proposed detector can identify several typical image manipulations, and is superior to the complicated deep CNN-based
methods in terms of detection accuracy and time efficiency for JPEG compressed image
with low resolution. 相似文献
87.
Guihua Liu Dan Luo Rui Gao Yongfeng Hu Aiping Yu Zhongwei Chen 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(37)
The practical application of lithium–sulfur (Li–S) batteries is hindered by the “shuttle” of lithium polysulfides (LiPS) and sluggish Li–S kinetics issues. Herein, a synergistic strategy combining mesoporous architecture design and defect engineering is proposed to synthesize multifunctional defective 3D ordered mesoporous cobalt sulfide (3DOM N‐Co9S8?x) to address the shuttling and sluggish reaction kinetics of polysulfide in Li–S batteries. The unique 3DOM design provides abundant voids for sulfur storage and enlarged active interfaces that reduce electron/ion diffusion pathways. Meanwhile, X‐ray absorption spectroscopy shows that the surface defect engineering tunes the CoS4 tetrahedra to CoS6 octahedra on Co9S8, endowing abundance of S vacancies on the Co9S8 octahedral sites. The ever‐increasing S vacancies over the course of electrochemical process further promotes the chemical trapping of LiPS and its conversion kinetics, rendering fast and durable Li–S chemistry. Benefiting from these features, the as‐developed 3DOM N‐Co9S8?x/S cathode delivers high areal capacity, superb rate capability, and excellent cyclic stability with ultralow capacity fading rate under raised sulfur loading and low electrolyte content. This design strategy promotes the development of practically viable Li–S batteries and sheds lights on the material engineering in related energy storage application. 相似文献
88.
Zhen Luo Zhuoqing Li Zhe Xie Inna M. Sokolova Lan Song Willie J. G. M. Peijnenburg Menghong Hu Youji Wang 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(36)
Titanium dioxide nanoparticles (nano‐TiO2) are widely used in consumer products, raising environmental and health concerns. An overview of the toxic effects of nano‐TiO2 on human and environmental health is provided. A meta‐analysis is conducted to analyze the toxicity of nano‐TiO2 to the liver, circulatory system, and DNA in humans. To assess the environmental impacts of nano‐TiO2, aquatic environments that receive high nano‐TiO2 inputs are focused on, and the toxicity of nano‐TiO2 to aquatic organisms is discussed with regard to the present and predicted environmental concentrations. Genotoxicity, damage to membranes, inflammation and oxidative stress emerge as the main mechanisms of nano‐TiO2 toxicity. Furthermore, nano‐TiO2 can bind with free radicals and signal molecules, and interfere with the biochemical reactions on plasmalemma. At the higher organizational level, nano‐TiO2 toxicity is manifested as the negative effects on fitness‐related organismal traits including feeding, reproduction and immunity in aquatic organisms. Bibliometric analysis reveals two major research hot spots including the molecular mechanisms of toxicity of nano‐TiO2 and the combined effects of nano‐TiO2 and other environmental factors such as light and pH. The possible measures to reduce the harmful effects of nano‐TiO2 on humans and non‐target organisms has emerged as an underexplored topic requiring further investigation. 相似文献
89.
Owing to lack of proper recycling methods, plastic flexible film wastes are usually directly discarded or incinerated, which brings about severe environmental pollution. Therefore, converting plastic wastes into value‐added products has received more and more attention in recent years. In this work, paper‐like composites derived from plastic flexible film wastes were prepared via the thermally induced phase separation method by adding polyethylene‐graft‐maleic anhydride (PE‐g‐MAH) as a compatibilizer and fumed silica as an additive. The resulting paper‐like composites were characterized by SEM and infrared spectroscopy. Other properties such as mechanical properties, thermal properties, whiteness, printability and adsorption performance were also tested in detail. It was found that remarkable enhancements in mechanical, thermal and printable properties of the paper‐like composites were obtained when nano‐SiO2 loading was 2.5–3 wt%. Uniformly distributed holes that can endow good printability by providing space for ink or other functional molecules were observed by using SEM. Furthermore, the CIE whiteness value of the resulting composites can reach 91.6%–96.7% on adding nano‐SiO2. Additionally, the paper‐like composites integrating nano‐SiO2 and PE‐g‐MAH exhibited good solid ink affinity and high water or oil adsorption capacity. Thus, according to this research, high‐performance printable paper‐like composites used as major components of multifunctional papers can be prepared based on plastic flexible film wastes. © 2019 Society of Chemical Industry 相似文献
90.