排序方式: 共有60条查询结果,搜索用时 46 毫秒
1.
Hydrogenation, structure and magnetic properties of La(Fe0.91Si0.09)13 hydrides and deuterides 下载免费PDF全文
Hydrogenation, crystal structure and magnetic properties of La(Fe0.91Si0.09)13H(D)y have been studied by pressure-composition isotherms (PCI), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and magnetization measurements. The maximum absorption capacity is found to be 1.9 H(D) atoms per formula unit as a solid solution. All hydrides and deuterides crystallize in the NaZn13-type cubic structure with the lattice parameter increasing linearly with H(D) concentration. The H(D) absorption enhances the Curie temperature significantly. The magnetic entropy change of the highly H-absorbed compound La(Fe0.91Si0.09)13H1.81 reaches ~26 J/kg·K under a magnetic field change of 5 T near the Curie temperature TC = 350 K. No observable isotope effect seems to imply that only the magnetovolume effect is responsible for the strong interplay between magnetism and lattice. 相似文献
2.
在不使用模板剂的条件下,以工业硫酸氧钛溶液为原料合成介孔偏钛酸前驱体,再经正硅酸乙酯浸渍焙烧制备了具有良好热稳定性的Si掺杂介孔SO2-4/TiO2.采用X射线衍射、N2吸附-脱附、扫描电镜、X射线能谱和傅里叶变换红外光谱等表征方法对样品的组成和结构进行了分析,并考察了该材料在亚甲基蓝氧化降解反应中的光催化性能.结果表明,在焙烧过程中,被吸附在偏钛酸孔道内的正硅酸乙酯发生水解,并与偏钛酸孔壁上的自由羟基形成 Ti - O - Si 键;Si进入二氧化钛骨架中,对孔结构起到了支撑作用,从而提高了介孔SO2-4/TiO2的热稳定性.700 ℃焙烧 2 h 后,Si掺杂介孔SO2-4/TiO2材料的比表面积仍达到189 m2/g,平均孔径为2.8 nm.400 ℃焙烧的样品在亚甲基蓝降解反应中表现出较好的光催化活性. 相似文献
3.
4.
5.
对稀土金属间Laves相赝二元化合物进行X射线衍射分析。其(440)峰出现劈裂,由(440)峰劈裂的程度可以确定内禀磁致伸缩的大小。本文采用X射线衍射的方法对Pr0.15TbxDy0.85-xFe2系列粉末样品的(440)峰步进扫描,并对扫描结果进行拟合,对拟合得到的两组双线峰之间的间距计算得到内禀磁致伸缩λ111,拟合曲线与实验点符合很好,结果表明Pr0.15TbxDy0.85-xFe2的内禀磁致伸缩随Tb含量的增加而增加,并且用0.15的Pr替代Dy后,在x=0.3时,Pr0.15TbxDy0.85-xFe2的内禀磁致伸缩λ111比Tb0.27Dy0.73Fe2的内禀磁致伸缩λ1ll大。 相似文献
7.
Huifang Kang 《中国物理 B》2022,31(3):34301-034301
The quantitative investigation of parameters in the renegerator is essential for the optimization of thermoacoustic devices, while the majority of the previous research only considered parameters of the working field, working gas and the hydraulic radius. Based on the linear thermoacoustic theory, this paper extracts a normalized parameter for low-amplitude conditions, which is called the regenerator operation factor. By extracting the regenerator operation factor and relative hydraulic radius, the influence of frequency on the efficiency can be controlled and offset. It can be found that thermoacoustic devices with different frequencies can perform the same efficiency by adjusting the radius in proportion to the axial length. Finally, this paper synthetically optimizes the dimension of the thermoacoustic regenerator by taking the regenerator operation factor, relative hydraulic radius and acoustic field parameter as variables. Conclusions in this paper are of great significance for explaining the best working conditions of engines and directing the miniaturization and optimal design of thermoacoustic devices. 相似文献
8.
Monodispersive ZnO nanoparticles each with a hexagonal wurtzite structure are facilely prepared by the hightemperature organic phase method.The UV-visible absorption peak of ZnO nanoparticles presents an obvious blue-shift from 385 nm of bulk ZnO to 369 nm.Both the real part and the image part of the complex permittivity of ZnO nanoparticles from 0.1 GHz to 10 GHz linearly decrease without obvious resonance peak appearing.The real parts of intrinsic permittivity of ZnO nanoparticles are about 5.7 and 5.0 at 0.1 GHz and 10 GHz respectively,and show an obvious size-dependent behavior.The dielectric loss angle tangent(tan 5) of ZnO nanoparticles with a different weight ratio shows a different decreasing law with the increase of frequency. 相似文献
9.
本文借助COMSOL多物理场耦合软件构建了二维、瞬态磁制冷模型。利用该模型模拟了两种不同的算例,算例1中回热器与换热器直接连接,算例2中采用渐变段连接,渐变段为普通绝热管道,包含了死容积的影响,两种算例的回热器结构完全相同。通过对比上述算例研究了流体流入回热器时由于管道截面积突变导致的流动不均匀现象对制冷机性能的影响。模拟结果显示,尽管算例2中增加了死容积,但渐变段使流动更加均匀,磁制冷机无负荷温跨由18.65K增大到26.14 K,提升了40.16%;温跨为5 K时,算例2相对于算例1制冷量提高31.57%,COP提高69.85%。因此,回热器两端的截面积突变对磁制冷机的影响不容忽视,本模拟对磁制冷系统结构设计及改进具有重要的借鉴意义。 相似文献
10.
以Co (NO3)2和Eu (NO3)3为原料,采用草酸盐-热分解法制得了系列不同Co/Eu比例(nCo/nEu)的多孔双金属复合氧化物催化剂,并对其活化过一硫酸盐(PMS)降解亚甲基蓝(MB)的性能进行对比评价。结果表明,按nCo/nEu=9制得的材料(Co9Eu1)具有最为优异的活化PMS降解MB的性能。在温度为25℃、催化剂用量和PMS浓度分别为0.10 g·L-1和0.6 mmol·L-1的反应条件下,Co9Eu1/PMS体系对MB的降解率可达86.66%,而纯Co3O4催化下的MB降解率仅为52.62%。Co9Eu1出色的催化性能是由于Eu3+的缺电子特性增强了对吸附于催化剂表面PMS的极化而使其更易被主催化成分Co3O4活化。体系中阴离子C2O42-和HCO3-的存在对Co9Eu1/PMS氧化降解MB的性能具有明显抑制作用。猝灭实验和电子顺磁共振谱(EPR)证实Co9Eu1/PMS体系中同时存在SO4-·、·OH和·O2-三种自由基型活性物种以及1O2非自由基型活性物种,其中SO4-·对MB的氧化降解起关键作用。Co9Eu1具有良好的稳定性,在连续4次循环使用中其催化性能未见明显变化。 相似文献