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排序方式: 共有367条查询结果,搜索用时 15 毫秒
41.
本论文发展了一种简单、低成本的一步"同步还原-自组装(SRSA)"水热法并制备了自组装Fe3O4分级结构的微球(Fe3O4HMSs).在合成过程中,仅使用甘油、水和铁氰化钾作为反应物,而无需任何其他还原剂、表面活性剂或添加剂即可获得自组装Fe3O4HMSs.其中,K3[Fe(CN)6]和甘油是合成自组装Fe3O4HMSs的两个重要因素.自组装Fe3O4HMSs可以作为高性能的锂离子存储材料,在0.5Ag-1的电流密度下,经过270次循环后比容量大于1000 mA hg-1.进一步充电和放电结果表明自组装Fe3O4HMSs表现出良好的可逆性能(放电比容量维持在1000mA h g-1以上)和循环稳定性(700次循环).此外,作为多功能材料,自组装Fe3O4HMSs的饱和磁化强度达到99.5 emu g-1,其可以进一步作为高效、磁性可回收的催化剂用于高效的硝基化合物加氢反应. 相似文献
42.
43.
《Ceramics International》2017,43(3):3405-3413
The specific magnetic structure and magnetic relaxation phenomena in magnetite nanoentities grown in a glassy matrix by controlled crystallization of Fe-containing borosilicate and boroaluminosilicate glasses in the presence of two types of nucleating agents, Cr2O3 and P2O5, were investigated. The structure, morphology and magnetic properties are strongly influenced by the nucleating agents. Cr2O3 generates magnetite-based glass ceramics with magnetite configurations showing an upward relaxation of magnetization at low and high temperatures but downward at intermediate temperatures. The magnetite grown with P2O5 displays only downward relaxation but with different signs of the temperature derivative of the relaxation rate S in different temperature ranges. The observed effects are discussed with respect to the following factors: i) the existence of a multimodal size distribution of the magnetite (nano)particles as revealed by high resolution electron microscopy; ii) the degree of occupation of different sublattices of the magnetite structure with Fe3+ and Fe2+ ions; and iii) the interplay between the relaxation mechanisms in different temperature ranges. 相似文献
44.
The spheroidizing heat treatment is normally required prior to the cold forming in GCr15 steel in order to improve its machinability.
In the conventional spheroidizing process, very long annealing time, generally more than 10 h, is needed to assure proper
spheroidizing. It results in low productivity, high cost, and especially high energy consumption. Therefore, the possibility
of directly spheroidizing during hot deformation in GCr15 steel is preliminarily explored. The effect of hot deformation parameters
on the final microstructure and hardness is investigated systematically in order to develop a directly spheroidizing technology.
Experimental results illustrate that low deformation temperature and slow cooling rate is the favorite in directly softening
and/or spheroidizing during hot deformation, which allows the properties of asrolled GCr15 to be applicable for post-machining
without requirement of prior annealing. 相似文献
45.
Hydriding combustion synthesis (HCS) has been regarded as an innovative process for the preparation of high active magnesium-based
hydrogen storage alloys. For the purpose of understanding the interrelation of the unique hydrogen storage properties and
the surface characteristics of the HCS product, the samples of Mg2Ni alloy/hydride with and without exposure to air were prepared from the HCS product of Mg2NiH4. The hydriding and dehydriding properties were compared and the surface compositions were analyzed by means of X-ray photoelectron
spectroscopy (XPS) and auger electron spectroscopy (AES). It was shown that the air exposure considerably decreases the hydriding
activity of Mg2Ni. Absorbing of 3.0 wt.% of hydrogen under the conditions of 603 K and 3.0 MPa after the air exposure takes 1500 s, which
is six times longer than for the unexposed alloy. The hydrogen desorption of the hydride are also impeded by the air-exposure,
which results in the increase of dehydriding temperature from 450 K to 540 K. XPS and AES analyses indicated that Mg segregates
and exists in the form of hydroxide on the surface of the air-exposed sample, which is responsible for the degradation of
the hydriding and dehydriding properties. It was confirmed that the fresh surfaces generated during the dehydriding process
of the as-synthesized hydride product contributes to the high activity of the HCS product in the first cycle of the hydriding
determination. 相似文献
46.
Longquan Hou Jinyun Ju Wenzong Yin Xu Tang Renjie Chen Ailin Xia Yeyuan Du Ruihua Du Aru Yan 《中国稀土学报(英文版)》2022,40(3):457-461
To investigate the influence of the addition of Pr-Ga alloys on magnetic properties and morphology of materials,the hot-deformed PrNd-Fe-B magnets were prepared... 相似文献
47.
48.
《International Journal of Hydrogen Energy》2020,45(56):32089-32097
Liquid organic hydrogen carriers (LOHCs) represent a promising approach for hydrogen storage due to their favorable properties including stability and compatibility with the existing infrastructure. However, fossil-based LOHC molecules are not green or sustainable. Here we examined the possibility of using norbelladine and trisphaeridine, two representative structures of Amaryllidaceae alkaloids, as the LOHCs from the sustainable and renewable sources of natural products. Our first principles thermodynamics calculations reveal low reversibility for the reaction of norbelladine to/from perhydro-norbelladine because of the existence of stabler isomers of perhydro-norbelladine. On the other hand, trisphaeridine is found promising due to its high hydrogen storage capacity (~5.9 wt%) and favorable energetics. Dehydrogenation of perhydro-trisphaeridine has an average standard enthalpy change of ~54 kJ/mol-H2, similar to that of perhydro-N-ethylcarbazole, a typical LOHC known for its low dehydrogenation enthalpy. This work is a first exploration of Amaryllidaceae alkaloids for hydrogen storage and the results demonstrate, more generally, the potential of bio-based molecules as a new sustainable resource for future large-scale hydrogen storage. 相似文献
49.
根据Gleeble-3500热模拟试验机测量30CrNi3MoV钢的真应力-真应变曲线,系统研究了应变速率为0.01、0.1 s-1时钢材的动态再结晶行为,并构建了其动态再结晶模型。结果表明:30CrNi3MoV钢在高温小应变速率下更容易发生动态再结晶,其热变形激活能为328.2 kJ/mol;通过加工硬化率随流变应力变化曲线(θ-σ)的拐点确定临界应变,可得动态再结晶临界应变方程为εc=0.001 22Z0.175;构建的动态再结晶体积分数及其平均晶粒尺寸模型能够较好地预测试验钢的动态再结晶体积分数及其晶粒尺寸;当应变速率为0.1 s-1、变形温度为1050 ℃时,试验钢的晶粒最细小、均匀,平均晶粒尺寸约为19.9 μm。 相似文献
50.
《International Journal of Hydrogen Energy》2020,45(43):22629-22637
Developing low-cost and high efficient electrocatalysts for both oxygen and hydrogen evolution reaction in an alkaline electrolyte toward overall water splitting is still a significant challenge. Here, a novel hierarchically heterostructured catalyst composed of ultrasmall Mo2C and metallic Co nanoparticles confined within a carbon layer is produced by a facile phase separation strategy. During thermal reduction of CoMoO4 nanosheets in CO ambient, in-situ generated nanoscale Co and ultrafine Mo2C conformally encapsulated in a conductive carbon layer. In addition, some carbon nanotubes catalyzed by Co nanoparticles vertically grew on its surface, creating 3D interconnected electron channels. More importantly, the integrated C@Mo2C/Co nanosheets assembled into the hierarchical architecture, providing abundant active surface and retaining the structural integrity. Benefiting from such unique structure, the constructed hierarchical heterostructure shows low overpotentials of 280 mV and 145 mV to reach a current density of 10 mA cm−2 for OER and HER in an alkaline electrolyte. Furthermore, the symmetrical electrolyzer assembled with catalyst exhibits a small cell voltage of 1.67 V at 10 mA cm−2 in addition to outstanding durability, demonstrating the great potential as a high efficient bifunctional electrocatalyst for overall water splitting. 相似文献