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排序方式: 共有1680条查询结果,搜索用时 31 毫秒
1.
《Ceramics International》2022,48(12):16839-16844
In this work, the effects of starting oxide powders with different-scale particle sizes on the synthesis of gadolinium zirconate pyrochlore (Gd2Zr2O7, GZO) and its physical properties were studied. Micron Gd2O3 (μG), micron ZrO2 (μZ), nano Gd2O3 (nG), and nano ZrO2 (nZ) powders were used. GZO ceramics were prepared by employing solid-state reactive sintering at 1300 °C, 1400 °C, 1500 °C and 1600 °C with mixed powders of different sizes (μGμZ, μGnZ, nGμZ and nGnZ). X-ray diffraction and Raman analyses of the ceramics revealed that nG has a more significant impact on the crystallization process than nZ. All ceramics synthesized with different sized oxide powders crystallized into pyrochlore phases except for those synthesized with μGnZ mixed powders, which resulted in a fluorite phase. The results indicated that decreasing the particle size of only ZrO2 to synthesize pyrochlore-phase Gd2Zr2O7 with high crystallinity may not be effective. Samples obtained at 1500 °C were further analyzed. Scanning electron microscopy results revealed that all four ceramics have a non-homogeneous grain size and that the average grain size ranges from 5.40 to 8.30 μm. In addition, the density and Vickers hardness measurements showed that the use of nanopowders significantly improves the mechanical properties. 相似文献
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《International Journal of Hydrogen Energy》2020,45(11):6425-6436
Graphitic carbon nitride (g-C3N4) is a promising metal-free photocatalyst for solar photocatalytic hydrogen gas (H2) generation from water. In particularly, high-crystalline g-C3N4 (GCN-HC) material with fewer structural defects possesses the fast photoexcited electron-hole pair's separation efficiency as comparison with bulk g-C3N4 (GCN-B) powders, leading to the drastic improvement of photocatalytic activity. However, the fabrication of such GCN-HC photocatalyst by a simple and economical synthesis approach still remains a challenge. Herein, we firstly develop a one-step rapid polymerization strategy for synthesizing the GCN-HC, that is direct calcination of melamine at 550 °C not only without the early heating process, but also without the assistance of any additive or salt intercalation. As a result, the GCN-HC exhibits an obviously boosting visible-light-induced photocatalytic H2-generation performance, which is over 2.06-folds much greater than that of GCN-B. Our work provides an available one-step synthetic strategy for the large-scale preparation of high performance GCN-HC towards sustainable solar-to-chemical energy conversion. 相似文献
4.
《International Journal of Hydrogen Energy》2020,45(24):13290-13299
The exploration of highly efficient non-precious electrocatalysts is essential for water splitting devices. Herein, we synthesized CoS2–MoS2 multi-shelled hollow spheres (MSHSs) as efficient electrocatalysts both for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) using a Schiff base coordination polymer (CP). Co-CP solid spheres were converted to Co3O4 MSHSs by sintering in air. CoS2–MoS2 MSHSs were obtained by a solvothermal reaction of Co3O4 MSHSs and MoS42− anions. CoS2–MoS2 MSHSs have a high specific surface area of 73.5 m2g-1. Due to the synergistic effect between the CoS2 and MoS2, the electrode of CoS2–MoS2 MSHSs shows low overpotential of 109 mV with Tafel slope of 52.0 mV dec−1 for HER, as well as a low overpotential of 288 mV with Tafel slope of 62.1 mV dec−1 for OER at a current density of 10 mA cm−2 in alkaline solution. The corresponding two-electrode system needs a potential of 1.61 V (vs. RHE) to obtain anodic current density of 10 mA cm−2 for OER and maintains excellent stability for 10 h. 相似文献
5.
《Microelectronics Reliability》2015,55(11):2178-2182
A hydrogen plasma treatment on the back-channel region of large-sized amorphous silicon thin film transistor (a-Si TFT) with high RF power and optimal process time of 20 s is proposed in this work to effectively reduce off current (Ioff) and threshold voltage (Vth) shift under high and low electrical-field stresses. The channel width (W) of large-sized a-Si TFT is ranged from 1000 to 10,000 μm, which are comparable to the realistic TFTs used in the gate driver on array (GOA) of display. It is experimentally found that the mechanism of Vth shift (ΔVth) after high electrical stress is dominated by the defect generation in a-Si layer rather than charge trapping in the gate insulator (GI) layer, which is different from the observation in previous literatures. It could be due to the effects of back-channel treatment (BCT). In addition, after low electrical stresses, the mechanism of ΔVth is dominated by defect generation in a-Si layer, which is consistent with previous reports. 相似文献
6.
This review highlights the synthesis, physical properties, and emerging technologies of state-of-the-art segmented copolymers containing amide hydrogen bonding sites. Amide hydrogen bonding plays a crucial role in the physical properties associated with amide-containing segmented copolymers. Amide hard segments are accessible in many different forms from amorphous alkyl amides to crystalline aramids and greatly influence copolymer morphology and mechanical properties. Variations in copolymer structure allow for the fine tuning of physical properties and the ability to predict mechanical performance based upon structural modifications. This review includes various synthetic methods for producing well-defined amide-containing segmented copolymers as well as common applications. Also, the morphological and mechanical properties associated with modifications in copolymer structure are discussed. 相似文献
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Three dimensional integrated microstrip antenna (3DIMA) can carry the designed load while functioning as an antenna. In this study, the cylindrical conformal single-patch 3DIMAs with various curvatures were designed, simulated, fabricated and tested experimentally using a 3D orthogonal woven glass preform/epoxy resin composite system. The electromagnetic performances of the cylindrical microstrip antennas were analyzed. The simulated and tested results matched well and the return losses of the cylindrical conformal 3DIMAs with radii of curvatures of 60, 45 and 25 mm were less than −10 dB while resonant frequencies and their gain values were significantly influenced by the radius of curvature and the feeding direction. The 3DIMAs with the curvature perpendicular to the feeding directions showed more stable resonant frequencies and larger gain values than those of 3DIMAs with the curvature along their feeding directions. 相似文献
9.
《Ceramics International》2020,46(7):8928-8934
Multifunctional nanomaterials composed of magnetic and fluorescent nanoparticles have been one of the most extensive pursuits because of the potential application in bio-research. In this paper, we demonstrated an efficient method by coupling CdSe/CdS/ZnS quantum dots (QDs) with Fe3O4 magnetic nanoparticles(MNPs) while functionalized multiwall carbon nanotubes (f-MWCNTs) were used as matrix to synthesize a kind of magnetic fluorescent nanocomposite. Compared with other matrix materials, carbon nanotubes have the advantages of high surface areas and good biocompatibility. The incorporation of f-MWCNTs supplies plenty of nucleation sites for the preferential growth of Fe3O4 nanoparticles, avoiding the agglomeration phenomenon of Fe3O4 MNPs in traditional co-precipitation method. Moreover, the un-reacted functional groups of f-MCNTs can further adsorb biological species and drugs, averting the decline of fluorescent intensity caused by the modification of biological species and drugs. The synthetic product maintains the unique properties of rapid magnetic response and efficient fluorescence, which shows a broad application prospect in fluorescent labeling, biological imaging, cell tracking and drug delivery. 相似文献
10.
Preparation and characterization of novel addition cured polydimethylsiloxane nanocomposites using nano‐silica sol as reinforcing filler 下载免费PDF全文
Dongzhi Chen Fengxiang Chen Hongwei Zhang Xianze Yin Xin Liu Yingshan Zhou 《Polymer International》2015,64(12):1741-1746
A series of novel addition cured polydimethylsiloxane (PDMS) nanocomposites with various amounts of nano‐silica sol were prepared via hydrosilylation for the first time. The influence of various amounts of nano‐silica sol on the morphology, thermal behavior, mechanical and optical properties of these PDMS nanocomposites was studied in detail. It was found that with an increment in the amount of nano‐silica sol the reinforcing effect of the nano‐silica sol on the thermal and mechanical properties of the PDMS nanocomposites was very noticeable compared with the reference material. The prominent improvements in resistance to thermal degradation and mechanical properties can probably be attributed to the strong interaction of PDMS chains and uniformly dispersed particles resulting from the nano‐silica sol. However, the transparency of the PDMS nanocomposites slightly decreased with an increment in weight fraction of nano‐silica, compared with that of PDMS composite without nano‐silica (Sol‐0), which can probably be ascribed to an increasing size of the aggregated particles in the PDMS nanocomposites. The optimum amount of nano‐silica sol for preparing novel addition curing PDMS nanocomposites was about 15 wt%. © 2015 Society of Chemical Industry 相似文献