共查询到20条相似文献,搜索用时 125 毫秒
1.
使用小孔径阳极氧化铝模板制备Fe0.3Co0.7纳米线有序阵列,研究了热处理对其磁性的影响.结果表明,热处理对Fe0.3Co0.7纳米线有序阵列的结晶度和局部形状各向异性有重大的影响,导致纳米阵列的矫顽力和剩磁比发生相应的变化.在适当热处理条件下获得的Fe0.3Co0.7纳米线有序阵列具有较高的矫顽力和剩磁比.在H2保护下550℃处理时获得最高的矫顽力2.63×105 A/m,矫顽力随着热处理时间的增加先是快速增加,然后趋向平缓,最后有一定程度的下降. 相似文献
2.
3.
大规模制备Ni纳米线阵列及其磁学特性研究 总被引:1,自引:0,他引:1
在多孔氧化铝模板的纳米孔洞中,利用直流电化学沉积的方法成功地制备了高度有序的磁性金属Ni纳米线阵列.利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)和物理性质测量系统(PPMS)对样品的形貌、晶体结构和磁学性能进行了表征测试.SEM和TEM观察结果显示,Ni纳米线均匀地生长在氧化铝模板的孔洞中,直径约为300nm,其表面非常光滑.XRD结果显示,生长的Ni纳米线为fcc结构.磁测量结果表明,与体材料相比,Ni纳米线展现出增强的矫顽力和剩磁比,并且表现出较强的磁各向异性,其居里温度约为627K,与块体Ni的居里温度相当,说明在较高温度下,纳米线仍可呈现铁磁特性. 相似文献
4.
采用直流电沉积在多孔有序氧化铝模板中制备了不同结构的有序镍纳米线阵列。采用扫描电子显微镜和透射电子显微镜对所制备的镍纳米线的形貌和结构进行了表征。研究了镍纳米线不同结构对镍纳米线阵列磁性性能的影响规律。当电沉积电压为2.5V时制备的镍纳米线为多晶结构;电沉积电压4V时,镍纳米线为沿[220]择优取向的单晶结构;电沉积电压大于5V时,择优取向由[220]转为[111]方向。磁滞回线结果表明,单晶镍纳米线阵列与多晶纳米线阵列相比具有更高的矩形度,沿[111]择优取向的单晶纳米线相比沿[220]取向的单晶镍纳米线具有更大的矩形度,表现出显著的磁各向异性。 相似文献
5.
采用电化学沉积法,在氧化铝模板中成功制备了直径50nm的Fe纳米线的高度有序阵列。纳米线的结构和磁学特性分别用透射电子显微镜(TEM),扫描电子显微镜(SEM),X射线衍射仪(XRD)和振动样品磁力计(VSM)测试。结果表明,Fe纳米线是以fcc结构存在。当外加磁场与纳米线的线轴平行时,测得的矫顽力为21000e,剩磁比为0.89,而当外加磁场与纳米线线轴垂直时,所测得的矫顽力仅为1600e,剩磁比为0.2。这表明纳米线阵列具有明显的各向异性,纳柴癌的易妯方向为纳粜姥姥妯方向. 相似文献
6.
采用直流电沉积在多孔有序氧化铝模板中制备了不同结构的有序镍纳米线阵列。采用SEM和TEM对所制备的镍纳米线的形貌和结构进行了表征。研究了镍纳米线不同结构对镍纳米线阵列磁性性能的影响规律.当电沉积电压为2.5V时制备的镍纳米线为多晶结构;电沉积电压4V时,镍纳米线为沿[220]择优取向的单晶结构;电沉积电压>5V时,择优取向由[220]转为[111]方向.磁滞回线结果表明,单晶镍纳米线阵列与多晶纳米线阵列相比具有更高的矩形度,沿[111]择优取向的单晶纳米线相比沿[220]取向的单晶镍纳米线具有更大的矩形度,表现出显著的磁各向异性。 相似文献
7.
8.
9.
在氧化铝模板的纳米孔洞中,用电化学的方法沉积钴铁合金纳米线,经过550℃、30h氧化处理,成功制备出钴铁氧体纳米线阵列.分别用透射电子显微镜(TEM)、X射线衍射仪(XRD)和振动样品磁场计(VSM)对样品的形貌、晶体结构和磁学性质进行了表征测试.TEM观察结果显示纳米线粗细均匀,直径约为70nm.XRD显示纳米线的物相结构为CoFe2O4;VSM测试结果表明,CoFe2O4纳米线阵列的磁滞回线矫顽力为1.190×105A/m,比氧化处理前的钴铁合金纳米线阵列有显著提高. 相似文献
10.
一维纳米材料在光学、电学、磁学等领域有着广阔的应用前景。采用二次阳极氧化法,结合逐级降压法制备了多孔阳极氧化铝(AAO)模板,然后在其上交流电沉积了单晶镍纳米线阵列。利用SEM,XRD,TEM等对镍纳米线阵列的形貌和结构进行了表征,探讨了沉积效果与沉积电流密度一时间曲线和稳定沉积电流密度大小之间的关系。结果表明:沉积电... 相似文献
11.
Deepak Saini R. P. Chauhan Sanjeev Kumar 《Journal of Materials Science: Materials in Electronics》2014,25(1):124-127
Cobalt nanowires of 100 nm diameter were synthesised electrochemically, in the pores of anodic alumina membrane (AAM). Electrochemical impedance spectroscopy was used to study the in situ growth of cobalt nanowires in the AAM. The structural and morphological characterization of template synthesized cobalt nanowires was done through X-ray diffractometer and scanning electron microscope, respectively. Effect of annealing on electrical and magnetic properties of cobalt nanowires was also investigated. 相似文献
12.
S. Talapatra X. Tang M. Padi T. Kim R. Vajtai G. V. S. Sastry M. Shima S. C. Deevi P. M. Ajayan 《Journal of Materials Science》2009,44(9):2271-2275
We report on the synthesis and magnetic characterization of ordered arrays of cobalt–nickel alloy nanowires. These alloy nanowires
were electrodeposited into the pores of anodic alumina templates. The physical properties of the samples were investigated
using scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and vibrating
sample magnetometer. We found that for the alloy nanowires the field at which the magnetization saturates increases with increasing
Co fraction and the saturation field in the normal direction is smaller than the parallel direction, indicating easy magnetization
direction normal to wire axis. Nanowires with different compositional ratio of cobalt and nickel showed a nonlinear dependence
of coercivity as a function of cobalt concentration. These findings will help tailor magnetic nanoalloys with controlled properties
for various applications, such as high density magnetic storage or nanoelectrode arrays. 相似文献
13.
Electrodeposition has been demonstrated to be useful in preparing well defined composite nanowires and as a way to modify their magnetic properties. A sulphamate bath containing barium ferrite nanoparticles has been used to test nanoparticle incorporation during an alloy (NiCo) electrodeposition process. The nanoparticles enter the membrane pores during the electrodeposition, being uniformly distributed into them.Home-made alumina membranes prepared in the laboratory were used as an electrodeposition template. Composite 10–15 μm length nanowires containing 7 wt.% of ferrite with a good particle distribution were obtained. The formation of composite nanowires has been demonstrated both by TEM observation and by magnetic properties analysis. The feasibility of incorporating magnetic nanoparticles to metallic nanowires in order to modify their magnetic properties has thus been confirmed. 相似文献
14.
Naeem Ahmad J. Y. Chen W. P. Zhou D. P. Liu X. F. Han 《Journal of Superconductivity and Novel Magnetism》2011,24(1-2):785-792
Vertically aligned Ni nanowires and nanotubes have been electrodeposited in alumina templates at room temperature. The detailed study of angular dependent coercivity and squareness demonstrates that the magnetic easy axis of Ni nanowires is perpendicular to that of Ni nanotubes axis. The mechanisms of magnetization reversal in Ni nanowires and Ni nanotubes are found to occur through the nucleation mode with the propagation of transverse domain wall and curling mode, respectively. Field dependant magnetization results at different temperatures have depicted that the magnetocrystalline anisotropy might cause a crossover of easy axis at room temperature to that of low temperature in both Ni nanowires and nanotubes. Furthermore, the variation in temperature dependent coercivity illustrates that the magnetoelastic anisotropy induced by the alumina matrix plays a dominant role in the magnetization reversal of the nanowires and nanotubes at low temperature. 相似文献
15.
Prida VM Pirota KR Navas D Asenjo A Hernández-Vélez M Vázquez M 《Journal of nanoscience and nanotechnology》2007,7(1):272-285
Densely packed arrays of magnetic nanowires have been synthesized by electrodeposition filling of nanopores in alumina and titania membranes formed by self-assembling during anodization process. Emphasis is made on the control of the production parameters leading to ordering degree and lattice parameter of the array as well as nanowires diameter and length. Structural, morphological and magnetic properties exhibited by nanowire arrays have been studied for several nanowire compositions, different ordering degree and for different nanowire aspect ratios. The magnetic behaviour of nanowires array is governed by the balance between different energy contributions: shape anisotropy of individual nanowires, the magnetostatic interaction of dipolar origin among nanowires, and magnetocrystalline and magnetoelastic anisotropies induced by the pattern templates. These novel nanocomposites, based on ferromagnetic nanowires embedded in anodic nanoporous templates, are becoming promising candidates for technological applications such as functionalised arrays for magnetic sensing, ultrahigh density magnetic storage media or spin-based electronic devices. 相似文献
16.
《Journal of Experimental Nanoscience》2013,8(4):287-295
Nickel nanotubes and nanowires are grown by galvanostatic electrodeposition in the pores of 1000, 100, and 15 nm polycarbonate as well as in anodised alumina membranes at a current density of 10 mA cm?2. The effects of pore size, porosity, electrodeposition time, effective current density, and pore aspect ratio are investigated. Nickel nanotube structures are obtained with 1000 nm pore size polycarbonate membrane without any prior treatment method. At the early stages of electrodeposition hollow nickel nanotubes are produced and nanotubes turn into nanowires at longer depositon times. As effective current density accounting for the membrane porosity decreases, the axial growth direction is favoured yielding nanowires rather than nanotubes. However, for smaller pore size polycarbonate membranes, nanowires are obtained even though effective current densities were higher. We believe that when the pore diameter is below a critical size, nanowires grow regardless of current density since narrow pores promote layer by layer growth of nanorods due to smaller surface area of the pore bottom compared to pore walls. Pore size has a dominant effect over effective current density in determining the structure of the fibres produced for small pores. Nickel nanowires are also obtained in the small pores of anodised alumina, which has higher aspect ratios. High aspect ratio membranes favour the fabrication of nanowires regardless of current density. 相似文献
17.
Fe nanowire array with strong shape anisotropy was employed as the soft phase in Nd–Fe–B based nanocomposites. The effects of the Fe nanowire distribution on magnetic properties of the nanocomposites were investigated by micromagnetic simulation. The results indicate that the shape anisotropy of Fe wires added in the same direction as the uniaxial magnetocrystalline anisotropy of the hard phase cannot increase the coercivity of the nanocomposite. When the nanowires are distributed perpendicular to the easy axis of the hard phase, the shape anisotropy of soft phase can retard the moments from rotating to the full reversed direction, leading to enhanced coercivity. In addition, with increasing the nanowire diameter, the coercivity of the nanocomposite decreases, but the dipolar interaction shows different roles in magnetic reversal of nanocomposite for different distributions of nanowires. The current results suggest that the coercivity of the Nd2Fe14B/α-Fe nanocomposite can be enhanced by introducing the soft magnetic nanowire array with the diameter less than the exchange length and with the long axis along the direction other than the easy axis of hard phase. 相似文献
18.
Fe nanowire array with strong shape anisotropy was employed as the soft phase in Nd-Fe-B based nanocomposites. The effects of the Fe nanowire distribution on magnetic properties of the nanocomposites were investigated by micromagnetic simulation. The results indicate that the shape anisotropy of Fe wires added in the same direction as the uniaxial magnetocrystalline anisotropy of the hard phase cannot increase the coercivity of the nanocomposite. When the nanowires are distributed perpendicular to the easy axis of the hard phase, the shape anisotropy of soft phase can retard the moments from rotating to the full reversed direction, leading to enhanced coercivity. In addition, with increasing the nanowire diameter, the coercivity of the nanocomposite decreases, but the dipolar interaction shows different roles in magnetic reversal of nanocomposite for different distributions of nanowires. The current results suggest that the coercivity of the Nd2Fe14B/α-Fe nanocomposite can be enhanced by introducing the soft magnetic nanowire array with the diameter less than the exchange length and with the long axis along the direction other than the easy axis of hard phase. 相似文献
19.
《Journal of Experimental Nanoscience》2013,8(4):341-346
Selenium (Se) nanowires were grown in the pores of anodic alumina membrane as template. Facile electrodeposition technique was used for the synthesis of Se nanowires. Scanning electron microscopy was used for the morphological study of the nanowires. X-ray diffraction and Energy dispersive X-ray fluorescence were utilised for the structural characterisation. The optical properties of Se nanowires were investigated using optical absorption spectroscopy. 相似文献
20.
To reduce the cost of the catalyst for direct ethanol fuel cells and improve its catalytic activity, highly ordered Ni-Cu alloy nanowire arrays have been fabricated successfully by differential pulse current electro-deposition into the pores of a porous anodic alumina membrane (AAMs). The energy dispersion spectrum, scanning and transmission electron microscopy were utilized to characterize the composition and morphology of the Ni-Cu alloy nanowire arrays. The results reveal that the nanowires in the array are uniform, well isolated and parallel to each other. The catalytic activity of the nanowire electrode arrays for ethanol oxidation was tested and the binary alloy nanowire array possesses good catalytic activity for the electro-oxidation of ethanol. The performance of ethanol electro-oxidation was controlled by varying the Cu content in the Ni-Cu alloy and the Ni-Cu alloy nanowire electrode shows much better stability than the pure Ni one. 相似文献