排序方式: 共有132条查询结果,搜索用时 0 毫秒
61.
Thirty nanometer diameter Co-Pt nanowires of different composition were fabricated by electrodepositing the Co and Pt atoms to nanoporous anodized aluminium oxide (AAO) templates. The structure and magnetic properties are studied by transmission electron microscopy (TEM), induction-coupled plasma spectrometer (ICP), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The as deposited nanowires with Pt content about 50 at.% present a single ferromagnetic phase of fcc CoPt. When the Pt content of the nanowires varies from about 55 to about 75 at.%, the nanowires include a soft phase of fcc CoPt3 and a relatively hard phase of fcc CoPt and the two phases are separate as seen from the hysteresis loops. After annealing to 600 °C, the two phases coupled completely and the coupled phase has the same coercivity as the original hard one. 相似文献
62.
Electrodeposition and magnetic properties of Ni nanowire arrays on anodic aluminum oxide/Ti/Si substrate 总被引:1,自引:0,他引:1
Cai-Ling Xu 《Applied Surface Science》2006,253(3):1399-1403
Ni nanowire arrays with different diameters have now been extended to directly fabricate in porous anodic alumina oxide (AAO) templates on Ti/Si substrate by direct current (DC) electrodeposition. An aluminum film is firstly sputter-deposited on a silicon substrate coated with a 300 nm Ti film. AAO/Ti/Si substrate is synthesized by a two-step electrochemical anodization of the aluminum film on the Ti/Si substrate and then used as template to grow Ni nanowire arrays with different diameters. The coercivity and the squareness in parallel direction of Ni nanowires with about 10 nm diameters are 664 Oe and 0.90, respectively. The Ni nanowire arrays fabricated on AAO/Ti/Si substrates should lead to practical applications in ultrahigh-density magnetic storage devices because of the excellent properties. 相似文献
63.
Gil Jae Park 《Journal of luminescence》2004,106(2):103-108
The femtosecond laser was used to irradiate sol-gel derived Sm3+-doped Al2O3-SiO2 glasses, in which the Sm3+ was reduced into Sm2+ ions. The fluorescence line narrowing was applied to investigate the coordination sphere of the Sm2+ ion. The spectral hole burning was performed on 7F0→5D0 transition of the Sm2+. The depth and width of the burnt holes were ∼27% and ∼4 cm−1 FWHM at 7 K, respectively. Hole spectra were stable up to room temperature. The hole-burning efficiency was superior to that of Sm2+ in H2 treated glasses and comparable to that in X-ray in terms of hole-burning dynamics. 相似文献
64.
X. Liu S. Ye Y. Qiao G. Dong B. Zhu D. Chen G. Lakshminarayana J. Qiu 《Applied physics. B, Lasers and optics》2009,96(1):51-55
In the present paper, we investigate the near-infrared (NIR) luminescence of Tb3+–Yb3+ codoped lanthanum borogermanate (LBG) glasses under visible and ultraviolet light excitation. The results indicate that NIR
quantum cutting occurs through cooperative energy transfer from Tb3+ to Yb3+ ions when only 4f
8 levels of Tb3+ ions are excited in the wavelength region of 300–490 nm. The highest quantum efficiency under the excitation 5
D
4 level of Tb3+ at 484 nm is 146%. Ultraviolet excitation that populates the charge transfer band (CTB) of Yb3+ near 270 nm does not result in quantum cutting as the fast nonradiative decay from CTB to 2
F
5/2 level dominates. These materials are expected to be used as a converting layer for silicon solar cells to enhance their efficiency
by splitting each high-energy photon into two NIR photons. 相似文献
65.
Ordered CoxPb1−x nanowire arrays embedded in the porous anodic aluminum oxide (AAO) template have been fabricated by electrodeposition. XRD experiments prove that neither hexagonal-close-packed (hcp) nor face-centered-cubic (fcc) Co peaks are detected when the Co component (x) is below 0.91. The coercivity (Hc) and squareness (Mr/Ms) are found to increase with ferromagnetic Co component and the maximum value is at the position x=1 (pure Co nanowires). Annealing effects cause Hc and Mr/Ms increase, which surpasses the pure Co nanowires in the 0.2<x<0.6 at the annealing temperature of 700 °C. Microstructure change during annealing process is proposed to explain the magnetic properties change of samples. 相似文献
66.
Sommer JU 《The European physical journal. E, Soft matter》2006,19(4):413-422
The equilibrium state of polymer single crystals is considered by explicitly taking into account the amorphous fraction formed
by loops and tails of the chains using a statistical model introduced by Muthukumar (Philos. Trans. R. Soc. London, Ser. A
361, 539 (2003)). We show that under realistic conditions below the equilibrium melting temperature, tight loops and close re-entries
are favored, and that the amorphous fraction can be mapped into an excess surface free energy. The model is extended to many-chain
crystals where it is shown that the lamellar thickness increases with the number of chains in the crystal and extended-chain
conformations are thermodynamically favored if the number of chains in the crystal is sufficiently large. The number of chains
necessary to form an extended-chain crystal in thermodynamic equilibrium scales with the square of the degree of polymerization
of the chains. We discuss the temperature behavior of the equilibrium crystal thickness in the under-cooled state. 相似文献
67.
Jun Xu Ling Yang Jiaxin Mei Wei Li Ling Xu Kunji Chen 《Solid State Communications》2005,133(9):565-568
Hydrogenated amorphous SiC thin films deposited at low substrate temperature (100 °C) show the different bonding configurations and microstructures which depend on the carbon concentrations in the films controlled by the gas ratio R of methane to silane during the deposition. Photoluminescence characteristics are investigated for these samples with different structures. A strong luminescence in red light region can be observed for samples deposited with low gas ratio R which is significantly reduced its intensity with increasing the carbon concentrations in the films. On the other hand, the luminescence bands located at blue-green light region are detected under UV light excitation for samples deposited with high gas ratio R, which can be associated with the existence of amorphous SiC clusters in the films. 相似文献
68.
69.
The stilbene-3 doped lead-tin-fluorophosphate glasses were successfully prepared and the luminescence spectra obtained from VUV-UV synchrotron radiation were investigated. The emission peaked about 440 nm from the undoped glass is observed at low temperature but quenches at room temperature. The doped glass exhibits strong characteristic emission of stilbenen-3 with 467 and 436 nm Gaussian bands under ultraviolet 250-330 nm excitation (characteristic excitation of stilbene-3) but weak emission under vacuum ultraviolet 190 nm excitation (host excitation). It is suggested that the energy transfer from host to the stilbene-3 dye can occur but the efficiency is still fairly low. 相似文献
70.
We studied viscoelastic properties and scaling behavior of multilamellar vesicles (MLVs) confined between two parallel plates
as a function of the shear rate and sample thickness (gap size between parallel plates). The rheological properties are classified
into two regimes; the shear-thinning regime at high shear rates and the shear-thickening regime at low shear rates. In the
former, the MLV radius results from the mechanical balance between the effective surface tension σeff and viscous stress force. The MLV radius is independent of the gap size. σeff estimated by van der Linden model is 2.1 ±0.15 ×10-4 Nm-1 corresponding to the same value obtained by SANS measurement. Power law exponents for the steady state viscosity and yield
stress against pre-shear rate (
,
) well agree with prediction based on the layering of membranes. Therefore, viscoelastic properties in this regime could be
modeled by assuming that the dynamics of MLVs are driven by layering of MLV polydomains, which could be accompanied by the
viscous dissipation, i.e., the stress relaxation on the MLV, induced by continuous sequence of yields of MLVs. The flow curve is empirically explained
by the assumption of a relaxation time for the MLV shape. In the latter, however, scaling laws observed in the shear-thinning
regime break down. The MLV radius increases when the gap size is reduced below the threshold value and MLV is no longer formed
at very small gap sizes. Different dynamics from the shear-thinning regime seem to dominate the viscoelasticity. 相似文献