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161.
Seoung-Soo Lee Ho-In Park Chung-Hyung Joh Song-Ho Byeon 《Journal of solid state chemistry》2007,180(12):3529-3534
Three different synthetic methods, the liquid phase process in HCl solution, the solvothermal reaction, and the surfactant-assisted solvothermal reaction, were explored to selectively control the particle shape and to enhance the luminescence intensity of the PbFCl-type red-emitting oxychloride phosphors LnOCl:Eu (Ln=La and Gd). The solvothermal pressure facilitated the low-temperature crystallization of the rod-shape particles for both Ln=La and Gd. It is noted that LaOCl:Eu nanorods show highly porous particle surface and quite low photoemission intensity. In contrast, the solvothermal synthesis could highly enhance the red-emission of GdOCl:Eu with no porous surface so as to be comparable to that of commercial Y2O3:Eu phosphor. An addition of surfactant material during solvothermal reaction yielded a rhomboidal-shape phosphor particles with no porous surface for both Ln=La and Gd. Interestingly, the elimination of surface porosity by using a surfactant significantly increased the emission intensity of LaOCl:Eu. It is proposed that the application of solvothermal technique for the synthesis of the PbFCl-type oxychloride phosphors is very effective to selectively control the particle shape and consequently to enhance the photoemission intensity if we use an appropriate surfactant material. 相似文献
162.
After the laser was invented in 1960, a phase conjugation mirror has been respected to be the most fantastic one for the laser
resonator composition because it can compensate any distortions of the laser beams occurred by the many inhomogenuities of
the laser media and optical components. Among the many phase conjugation configurations, the stimulated Brillouin scattering
phase conjugation mirror is the most simple one and many researchers have tried to utilize it to develop high power/energy
laser systems. For realizing a high energy/power laser system the thermal problem is the most difficult to solve, and some
researchers suggested a beam combination technique to reduce the thermal load of the big laser media to many small sized ones.
To accomplish the beam combination using stimulated Brillouin scattering phase conjugation mirrors (SBS-PCMs), it is necessary
to lock/control the phases of the SBS-PCMs. And some researchers have developed several ways for it, but they can lock the
phases of a limited number of beams overlapped at the foci less than 5, or lock the phases by back-seeding technique but it
loses the phase conjugation characteristics. For realization of the laser fusion driver, it is necessary to combine more than
10 or 100 beams. And the authors have developed recently a new phase controlling/locking technique which is isolated and independent
totally from other beams and it can be applied to an unlimited number of beams in principle. 相似文献
163.
164.
Jin Kyu Park Dong Hun Lee Bok Ju Song Jae Buem Oh Hwan Kyu Kim 《Journal of polymer science. Part A, Polymer chemistry》2006,44(3):1326-1342
We have designed and synthesized novel perfluorinated polyimides with 3D controlled structure. At first, we successfully developed the new synthetic routes to diamines with pendant bulky perfluorinated aromatic units in a multi‐step synthetic procedure. Novel perfluorinated polyimides were prepared in a two‐step reaction in N‐methyl‐2‐pyrrolidinone (NMP) solution: The first step was for the synthesis of polyamic acids (PAAs) and the second reaction was for the imidization of PAA. The polymer yield was over 89% and the inherent viscosity of PAAs was in the range of 0.24–0.36 dL/g. The thin films were prepared by spin‐coating the PAA solution in NMP onto various substrates such as a Si wafer or a KBr pellet, dried at 80 °C and further cured at 230 °C. The resultant polyimides are thermally stable over 400 °C. The refractive index and birefringence of the resultant polyimides are 1.5858–1.6452 and 0.01–0.005, respectively. The refractive index of polyimide decreases with increasing the fluorine content. The copolymerization and the ether linkages into the backbone reduce the birefringence of polyimides. Surprisingly, the pendant ether linkage is not a crucial factor in reducing the polyimide birefringence. Their birefringence is comparatively very low, compared with that of previous polyimides. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1326–1342, 2006 相似文献
165.
166.
T.W. Lim S.H. Park D.Y. Yang H.J. Kong K.S. Lee 《Applied Physics A: Materials Science & Processing》2006,84(4):379-383
A nano-surfacing process (NSP) is proposed to directly fabricate three-dimensional (3D) concavo–convex-shaped microstructures such as micro-lens arrays using two-photon polymerization (TPP), a promising technique for fabricating arbitrary 3D highly functional micro-devices. In TPP, commonly utilized methods for fabricating complex 3D microstructures to date are based on a layer-by-layer accumulating technique employing two-dimensional sliced data derived from 3D computer-aided design data. As such, this approach requires much time and effort for precise fabrication. In this work, a novel single-layer exposure method is proposed in order to improve the fabricating efficiency for 3D concavo–convex-shaped microstructures. In the NSP, 3D microstructures are divided into 13 sub-regions horizontally with consideration of the heights. Those sub-regions are then expressed as 13 characteristic colors, after which a multi-voxel matrix (MVM) is composed with the characteristic colors. Voxels with various heights and diameters are generated to construct 3D structures using a MVM scanning method. Some 3D concavo–convex-shaped microstructures were fabricated to estimate the usefulness of the NSP, and the results show that it readily enables the fabrication of single-layered 3D microstructures. PACS 85.40.Hp; 81.16.Nd; 42.82.Cr 相似文献
167.
J.-S. Kang G. Kim S.S. Lee S. Choi S. Cho S.W. Han H.J. Shin B.I. Min 《Journal of magnetism and magnetic materials》2006
The spatial concentration distribution and local electronic structure of ferromagnetic Ge1−xTx (T=Cr, Mn, Fe) DMS single crystals have been investigated by using scanning photoelectron microscopy (SPEM), X-ray absorption spectroscopy (XAS), and photoemission spectroscopy (PES). It is found that doped T ions in Ge1−xTx crystals are chemically phase-separated, suggesting that the observed ferromagnetism arises from the phase-separated T-rich phases in Ge1−xTx. 相似文献
168.
169.
Structure and electrical transport properties of bismuth thin films prepared by RF magnetron sputtering 总被引:1,自引:0,他引:1
Bismuth thin films were prepared on glass substrates with RF magnetron sputtering and the effects of deposition temperature on surface morphology and their electrical transport properties were investigated. Grain growth of bismuth and the coalescence of grains were observed above 393 K with field emission secondary electron microscopy. Continuous thin films could not be obtained above 448 K because of the segregation of grains. Hall effect measurements showed that substrate heating yields the decrease of carrier density and the increase of mobility in exponential ways until 403 K. Resistivity of sputter deposited bismuth films has its minimum (about 0.7 × 10−3 Ω cm) in range of 403-433 K. Annealing of bismuth films deposited at room temperature was carried out in a radiation furnace with flowing hydrogen gas. The change of resistivity was not significant due to the cancellation of the decrease of carrier density and the increase of mobility. However, the abrupt change of electrical properties of film annealed above 523 K was observed, which is caused by the oxidation of bismuth layer. 相似文献
170.