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  • American Institute of Physics (AIP)  (82)
  • National Academy of Sciences  (39)
  • 2000-2004  (60)
  • 1995-1999  (61)
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1959-1964 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Diamond-like carbon (DLC) films were prepared with mass-selected C+, CH2+, CH3+, and CH4+ ions, and the dependence of film microstructures and properties on ion species was investigated with micro-Raman spectroscopy, optical band gap measurement and atomic force microscopy (AFM). The results indicate that highly sp3 bonded DLC films are achieved using carbon and hydrocarbon ions with ion energy of 100 eV. AFM results exhibit that the surface roughness for these films is very low, which is associated with the formation of a dense diamond-like phase as suggested by the subplantation model. The thermal stability of the films were investigated in the temperature region of 200–800 °C. Raman measurements show that the D peak evolves at much lower temperatures for the film prepared with CH4+ than that for the film prepared with C+ ions during annealing. The results indicate that hydrogen-free carbon films have a much better thermal stability than hydrogenated carbon films. © 2001 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5287-5289 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of a partial substitution of Cu or Nb for Fe on the structure and magnetic properties of mechanically alloyed Nd8Fe84Ti8 alloys were studied. Compared with Nd8Fe84Ti8 alloys prepared under the same conditions, the temperature necessary for the formation of the Nd(Fe, Ti)12 phase decreases from 900 to 750 °C with the addition of 3 at. % Cu. The addition of Cu hinders the nitrogenation of the Nd(Fe, Ti)12 phase. The pretreatment of hydrogenation on the Cu-added alloys at 300 °C facilitates the formation of nitrides. With increasing annealing temperature, the intrinsic coercivity of the nitrides increases until it attains a maximum at 850 °C. The addition of Nb is harmful to the formation of the perfect Nd(Fe, Ti)12 phase. For the 3 at. % Nb-containing alloys, annealing at 960 °C makes a metastable phase Nd(Fe, Ti)7 be formed. The addition of Nb is unfavorable for the intrinsic coercivity and the maximum magnetic energy product of the nitrides. © 2000 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4226-4231 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural transformations from amorphous, metastable-to-equilibrium phases during annealing treatment of rapidly quenched Nd10Fe90−xTix (x=0, 2, 4, 6, 8, and 10) alloys have been studied systematically. By means of ac initial susceptibility and x-ray diffraction, a CaCu5-type metastable phase was observed for 0≤x≤10 as the crystallization of the amorphous alloys occurs below 700 °C. The CaCu5-type structure transforms into a TbCu7-type one with increasing the annealing temperature (above 700 °C). These melt-spun alloys have different structures including Th2Zn17 type for 0≤x≤4 and TbCu7 and ThMn12 types for 6≤x≤10, when annealed at high temperature (above 1000 °C). Nitrogenation was carried out at 400 °C for 10 h. Both Nd(Fe,Ti)5 and its nitride are soft-magnetic phases, like Nd(Fe,Ti)7 and Nd2(Fe,Ti)17. © 2000 American Institute of Physics.
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of a partial substitution of Ga for Fe on the structure and magnetic properties of mechanically alloyed Nd8.4Fe87.1B4.5 were studied. With increasing Ga content, the magnetic properties of the nanocomposite magnets first improve, reach maxima at 1.1 at. % Ga, and then degrade. The addition of Ga helps to control the morphology, especially the grain sizes of both α-Fe and Nd2Fe14B. © 2000 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1317-1321 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A hydrogenated carbon film in a crystalline form has been prepared on Si (001) using a radio frequency plasma enhanced chemical vapor deposition process. The crystalline film is metastable and has polymer-like features with a mass density of about 1.20 g/cm3 and an optical band gap of about 2.75 eV. The stability of the structure and properties of the film was studied by thermal annealing at successively higher temperatures in the air. Upon heating, the film showed a two-step structure change which resulted in a two-step change in the film properties. The relationship between the properties and the bonded hydrogen in the film was also discussed. © 1999 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1062-1064 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Monoclinic Ga2O3 nanobelts and nanosheets are obtained by a simple chemical route involved with H2O at 950 °C in Ar atmosphere. Electron microscopy observations reveal that the as-synthesized Ga2O3 nanobelts and nanosheets are structurally uniform, single crystalline, and most of them are free of defects and dislocations. The nanobelts are growing along with [001] facets, and the nanosheets are stacked up by (011) facets. The Raman scattering spectrum of Ga2O3 nanostructures shows a 30 cm−1 redshift at high wave numbers in comparison with that of bulk Ga2O3 powder. The photoluminescence spectrum reveals that there exists a stable blue emission band centered at 460 nm, which is mainly attributed to the oxygen vacancies in the Ga2O3 nanostructures. © 2002 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 2835-2839 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used electron microscopy to investigate the microstructure of Ni80Fe20/Cu magnetic multilayers which were synthesized by dc magnetron sputtering. Columnar structure was found in the specimen with and without giant magnetoresistance (GMR). All the columnar crystallites (CCs) originate from the Fe buffer layer on silicon wafer or glass substrate and penetrate though all the multilayers up to the surface of the film. The lateral size of the CCs ranges from 10 to 30 nm. Cross-sectional high-resolution electron microscopy study shows that the CCs are single-crystal-like with fcc structure resulting from the epitaxial growth of NiFe and Cu sublayers. Electron diffraction contrast imaging and electron energy filtered elemental mapping confirmed that multilayer nature is maintained throughout the entire NiFe/Cu film. Grain boundaries between CCs can be the most likely place where NiFe or Cu bridging will occur. Columnar structure was also found in a Ta/NiFe/Cu/NiFe/FeMn/Ta spin valve film. The possible influence of the columnar crystalline structure on the GMR related problems is discussed. The microstructure results revealed in this article provide useful information for the GMR property investigation of NiFe/Cu based metallic multilayers. © 2000 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 4017-4022 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Erbium/ytterbium co-doped fibers have been investigated in this work for the first time to determine their potential in thermometry applications based on the use of fluorescence decay. Several samples have been used and their performance characteristics determined. These have included studies of fiber annealing as well as thermal cycling tests and it was found that unlike other rare-earth ion doped fibers previously studied, such as Nd3+, Er3+, or Tm3+ doped fibers, the Er/Yb co-doped samples used here have shown a much smaller degree of thermal annealing when their thermal characteristics have been evaluated and compared. The response of the thermometer and the error in the measurement was found to be, at 〈±5 °C, within the stability of the oven used in the tests over a wide temperature range from 0 to 850 °C. © 2000 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 139-145 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A detailed investigation of the practical spectroscopic features and the effect of prolonged exposure to elevated temperatures of an intrinsic Nd:doped fiber optic thermometer probe using the fluorescence decay time technique has been carried out. Results have shown the optimum length for the doped fiber and a maximum operating temperature of 750 °C, beyond which a range of high-temperature "annealing" effects are seen. These are discussed in light of the operation of the thermometers over the range from −196 to 750 °C and potentially above. © 1998 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 146-151 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The use of multiple material fluorescence-based sensors, where each is optimized to a particular temperature range yet is pumped by the same light source, emitting over the same spectral region, makes for a very simple, convenient and promising optical arrangement which can be applied in real-time, quasidistributed temperature sensor systems. The fluorescence lifetime approach, which is an important technique to enable fluorescence emission to be exploited for thermometry, is adopted in the system discussed. An analysis scheme using Prony's method has been reported which enables exponential decays from either single-material or two material and quasidistributed sensors to be deconvolved and thus data and associated measurand information encoded in each individual signal to be recovered. In this work, in the development of quasidistributed temperature sensor algorithms based on Prony's method are used for the estimation of exponential time constants of a convolved triple exponential fluorescence decay, each corresponding to a different-point temperature. Experimental results obtained are presented to justify their use in practical multiexponential fluorescence decay analysis and show a comparison of the Prony method to the Marquardt nonlinear least-squares approximation algorithm to achieve the deconvolution. The computational time for Prony's approach is approximately one-thousandth that of the Marquardt technique while the accuracy achieved using Prony's method is still high enough for practical use. © 1998 American Institute of Physics.
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