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排序方式： 共有1332条查询结果，搜索用时 15 毫秒
131.
《能源学会志》2020,93(3):1064-1073
This study aims to investigate the effect of pyrolysis pressure on the physical and chemical structure characteristics and reactivity of subbituminous demineralized coal char. The pyrolysis experiments were studied under different pressures using a pressurized drop tube reactor (PDTR). Structural properties of coal chars were investigated by the application of scanning electron microscopy (SEM), nitrogen adsorption analyzer, automatic mercury porosimeter, and Raman spectroscopy, respectively. The Random Pore Model was used to determine kinetic parameters and intrinsic reactivity of chars. The specific pore volume of chars pyrolyzed at 900–1000 °C increased first and then decreased with pyrolysis pressure increasing, and the maximum value of the specific pore volume of chars occurred at 1.0 MPa. The degree of graphitization of chars deepened with the increase of temperature or pressure. Intrinsic activation energy of char-O2 was within the range of 126–134 kJ/mol. The intrinsic reactivity of char-O2 reaction showed strong correlation the Raman parameters with the change of pyrolysis conditions, and it suggested that the intrinsic reactivity of char-O2 reaction was mainly affected by aromatic ring structures rather than pore structures. 相似文献
132.
《能源学会志》2020,93(6):2511-2525
Oxy-fuel combustion of heavy oil can be applied to oil field steam injection boilers, allowing the utilization of both heavy oil and CO2 resources. This paper studied the local distribution characteristics of OH on oxy-fuel combustion of heavy oil during the ignition and stable combustion processes. During the ignition process, we observed the generation and evolution of fire kernel, and got the flame propagation velocity. During the stable combustion process, the results showed that the OH distribution and its relative signal intensity were influenced by the oxygen concentration, excess air coefficient, gas flow, reaction atmosphere, oil mist scattering, incident laser energy and laser sheet position. In the same reaction atmosphere, the ranges of OH dense distribution and the high temperature area increased as O2 concentration increased. In the same O2 concentration, both the ranges of OH dense distribution and the high temperature area in O2/N2 were larger than that in O2/CO2. In 29% O2/71% CO2, the flame shape was similar to combust in air, while the OH relative signal intensity and its volatility were much larger than that in air. In the same combustion condition, the location of high concentration of OH relative concentration field lagged behind the high temperature area. The results further reveal the differences between the conventional and oxy-fuel combustion. 相似文献
133.
Yuanming Wang Xue Wang Xifei Li Xiaolong Li Yang Liu Yang Bai Huanhao Xiao Guohui Yuan 《Advanced functional materials》2021,31(7):2008185
The challenges of solid-state supercapacitors (SCs) for flexible and wearable electronics still remain in well balancing the electrochemical performance, mechanical stability, and processing technologies. Herein, a high-performance, tailorable and foldable solid-state asymmetric supercapacitor is developed via one-step scalable chemical oxidization and MXene ink painting of N-doped carbon fiber textile (NCFT) substrate. The employed O/N-functionalized NCFT (ONCFT) and MXene materials under opposite potentials both incorporate excellent electrochemical behaviors of carbon-like materials and pseudocapacitive materials, namely high rate capability and pseudocapacitance. By regulating oxidization time and MXene loading, the active layer of MXene decorated NCFT (MNCFT) and ONCFT electrodes analogously present tight skin structure, fundamentally avoiding the risk of active materials detaching from the support during mechanical deformation. As a result, the assembled MNCFT//ONCFT device not only achieves an extended voltage window of 1.6 V, high areal energy density of 277.3 μWh cm−2 and 90% capacitance retention after 30 000 cycles, but also experiences repeated folding tests. Additionally, the design makes it possible to tailor the textile-based energy storage device (TEESD) into a designed size or shape without impairing its performance for device integration or shape conformable integration. Owing to the whole component fabrication being simple and scalable, the TEESD shows potential practical application. 相似文献
134.
Xinru Li Yue Tian Li Shen Zhibin Qu Tianqiong Ma Fei Sun Xiaoyan Liu Chen Zhang Jianqiang Shen Xianyang Li Lina Gao Shengxiong Xiao Taifeng Liu Yi Liu Yunfeng Lu 《Advanced functional materials》2021,31(22):2009718
Lithium (Li) metal batteries hold considerable promise for numerous energy-dense applications. However, the dendritic Li anode produced during Li+/Li deposition-stripping endangers battery safety and shortens cycle lifespan. Herein, an electrolyte interphase built from 2D anionic covalent organic frameworks (ACOF) is coated on Li for dendrite suppression. The ACOF with Li+-affinity facilitates rapid and exclusive passage of Li-ions from the electrolyte, yielding near-unity Li+ transference number (0.82) and ionic conductivity beyond 3.7 mS cm-1 at the interphase. Such high transport efficiency of Li-ions can fundamentally circumvent the Li+ deficiency that results in dendrite formation. Pairing the ACOF-coated Li against a high-voltage LiCoO2 cathode (4.5 V) achieves exceptional cycle stability, mitigated polarization, as well as improved rate capability. Accordingly, this strategy vastly expands the pool of electrolyte interphases that can be used for coating and protecting Li anode. 相似文献
135.
《Ceramics International》2019,45(10):12757-12763
Dense silicon nitride (Si3N4) ceramics were prepared using Y2O3 and MgF2 as sintering aids by spark plasma sintering (SPS) at 1650 °C for 5 min and post-sintering annealing at 1900 °C for 4 h. Effects of MgF2 contents on densification, phase transformation, microstructure, mechanical properties, and thermal conductivity of the Si3N4 ceramics before and after heat treatment were investigated. Results indicated that the initial temperature of liquid phase was effectively decreased, whereas phase transformation was improved as increasing the content of MgF2. For optimized mechanical properties and thermal conductivity of Si3N4, optimum value for MgF2 content existed. Sample with 3 mol.% Y2O3 and 2 mol.% MgF2 obtained optimum flexural strength, fracture toughness and thermal conductivity (857 MPa, 7.4 MPa m1/2 and 76 W m−1 K−1, respectively). It was observed that excessive MgF2 reduced the performance of the ceramic, which was caused by the presence of excessive volatiles. 相似文献
136.
《Journal of the European Ceramic Society》2019,39(11):3315-3319
Multilayer ceramic capacitors (MLCCs) of lead-free NBT-based ceramics are produced and their electrocaloric effect (ECE) is characterised for the first time. Dense MLCCs with 97μm-thick active layers are successfully produced by tape casting. Dielectric permittivity measurements reveal the MLCCs to have properties similar with that reported for the corresponding bulk ceramics, including Td∼50°C and TS∼100°C. Direct ECE measurements also reveal agreement and confirm the previously reported tendency of the high-field ECE peak to shift towards TS. The highest value of ECE, ΔTmax∼1.7K is measured at 90°C under 90kV/cm. A low breakdown strength of 93kV/cm needs to be solved to realise stronger electric fields and achieve commercially viable ECE values. 相似文献
137.
138.
《材料科学技术学报》2019,35(10):2345-2356
The corrosion kinetics and patina (corrosion products) layer evolution of galvanized steel submitted to wet/dry cyclic corrosion test in a simulated coastal-industrial atmosphere was investigated. The results show that zinc coating has a greater corrosion rate during the initial period and a lower corrosion rate during the subsequent period, and the patina composition and structure can greatly affect the corrosion kinetics evolution of zinc coating. Moreover, Zn5(OH)6(CO3)2 and Zn4(OH)6SO4 are identified as the main stable composition and exhibit an increasing relative amount; while Zn12(OH)15Cl3(SO4)3 cannot stably exist and diminish in the patina layer as the corrosion develops. 相似文献
139.
《材料科学技术学报》2019,35(10):2144-2155
Ni-Cu nano-coatings were prepared by pulsed electroplating technique in the baths containing various amount of boric acid. Their microstructure, morphologies and corrosion resistance were characterized in detail. The addition of boric acid strongly influences on the microstructure of the Ni-Cu coatings. The coating with a grain size of 130 nm, obtained from the bath containing 35 g L−1 boric acid, shows the highest corrosion resistance. This is attributed to the low-valence Cu ion (Cu+) additions in nickel oxide, which could significantly decrease the oxygen ion vacancy density in the passive film to form a more compact passive film. The higher Cu+ additions and the lower diffusivity of point defects (D0) are responsible for the formation of more compact passive film on the coating obtained from the bath with 35 g L−1 boric acid. 相似文献
140.
A.M. Al-Saie M. Bououdina A. Jaffar S. Arekat John M. Melnyczuk Ynhi T. Thai Christopher S. Brazel 《Journal of Alloys and Compounds》2011
Single and nanosized spinel CoFe2O4 phase has been prepared successfully by a simple combination of mechanical milling from a mixture of Fe2O3 and Co3O4 powder precursors followed by a subsequent annealing. X-ray diffraction analysis reveals that the estimated crystallite size of CoFe2O4 increases with increasing temperature but remains at the nanoscale, i.e. 85 nm at 900 °C. Moreover, magnetic measurements show that a great enhancement in the saturation magnetization was achieved whereas a large hysteresis loop was observed (i.e.72 emu/g at 900 °C). Evaluation and applicability of CoFe2O4 nanoparticles under high frequency AC magnetic field for heating in biomedical applications were examined. It was found that under fixed amplitude (516 Oe) and frequency (229 kHz), the prepared nanoparticles generate significant heat: after 5 s the temperature was around 97 °C for the as-milled powder and reached almost 178 °C for the powder annealed at 900 °C. 相似文献