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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2027-2029 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the Fe–Mo system, amorphous alloys are thermodynamically unstable and are hard to form in the bulk state. In multilayered films, however, amorphous alloys were produced by room temperature 200 keV xenon ion mixing. It was found, when keeping the total thickness of the multilayered film constant at 40 nm, that the composition range favoring amorphization extended from the equiatomic stoichiometry towards the two metal sides with increasing number of metal layers. This alloying behavior is discussed in terms of a simple thermodynamic calculation. © 1997 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 149-154 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphous alloys were formed by room-temperature 200 keV xenon ion mixing of multilayered films in the Zr-Nb system that has a positive heat of formation (+6 kJ mol−1) and the ion-induced amorphization was found to be discontinuous in the composition range. Thermodynamic calculation was conducted and a free-energy diagram, which concerns free-energy curves of the amorphous phase and the initial state of the multilayered films with excess interfacial energy, was constructed. An interpretation to the observed discontinuity of amorphization range was presented based on the calculated free-energy diagram. In addition, two new metastable crystalline phases both of fcc structure with different lattice parameters were formed in the composition range close to pure zirconium and niobium, respectively. © 1995 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3351-3356 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the Ni-Mo system, amorphous alloys and three metastable crystalline (MX) phases, i.e., an hcp (hcp-I), an enlarged hcp (hcp-II), and a fcc phase, were synthesized by solid-state reaction in the Ni-rich multilayers. An interesting point is that with increasing the annealing temperature, the hcp-I phase was formed first in the Ni67Mo33 film and then turned amorphous, while in the Ni75Mo25 film, the amorphous phase was formed first and then changed into the hcp-I phase. The compositions of three MX phases were determined experimentally. A free-energy diagram of the Ni-Mo system was established by calculating the free energies of the amorphous phase and the three MX phases, as well as those of the solid solutions and the related compounds on the basis of the model of Niessen et al. [CALPHAD 7, 51 (1981)] and Alonso's method [Solid State Commun. 46, 765 (1983)]. The calculated free-energy diagram can give relevant interpretation to the observed phase formation behaviors.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4948-4952 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two metastable crystalline phases, i.e., hcp and fcc, were formed in Nb-rich Nb-Fe, Nb-Co, and Nb-Ni multilayered films by room temperature 200 keV xenon ion mixing. The experimental results revealed that the formation sequence was first hcp and then fcc through an abnormal two-step phase transition of bcc→hcp→fcc. To give insight into the phase formation, Gibbs free-energy diagrams of the systems were constructed by the calculation method proposed by Alonso, Gallego, and Somozar [Nuovo Cimento, 12, 587 (1990)]. Besides, steady-state thermal annealing experiments of the corresponding as-deposited multilayers were conducted and the results confirmed the existence as well as the energetic sequence of the hcp and fcc phases predicted by the calculated free-energy diagram. Concerning the growth kinetics of the two metastable crystalline phases, the two-step phase transition was determined to be a shearing plus sliding mechanism.
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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1524-1526 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A free energy diagram of the Ag–Mo system with a very positive heat of formation of +57 kJ/mol was constructed, with special consideration to the interfacial free energy in the multilayered films for ion mixing. It was found that amorphization was possible to achieve within two separate composition ranges toward Ag and Mo ends, respectively, if 12 layers, or about 13% of the interfacial atoms were included in the films. Accordingly, ion mixing of the Ag–Mo multilayered films was conducted at liquid nitrogen temperature by 190 keV xenon ions and the formation of amorphous phases was in good agreement with the calculation. Besides, a new metastable fcc phase was formed and, more interestingly, it transformed into an amorphous state upon aging, which can also be interpreted by a related free energy calculation. © 1995 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 1702-1710 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The amorphization of Ni-Nb multilayered alloy films by xenon ion irradiation at room temperature and by high-temperature solid-state reaction was studied. The composition range favoring amorphization was carefully determined to be 20–85 at. % Ni by energy-dispersive spectroscopy attached to the transmission electron microscope. A new metastable crystalline phase (MX) of hexagonal structure was formed in Ni75Nb25 and Ni70Nb30 multilayered films. Interestingly, in the Ni75Nb25 multilayered films, with increasing mixing dose an amorphous phase was first formed and then the MX-phase was observed, while in the Ni70Nb30 multilayered films the MX phase was formed at relatively low doses and turned amorphous upon further mixing or 400 °C annealing for 2 h. Besides, annealing of the as-deposited Ni70Nb30 multilayered films at 300 °C for half an hour also resulted in the formation of the MX phase. The thermal stability of the ion-mixed amorphous alloys was also studied by subsequent annealing. To give semiquantitative interpretation to all the above observations, the Gibbs free-energy diagram of the system, in which especially the free-energy curve of the MX phase is added, was constructed on the basis of the model of Nissen et al. [CALPHAD 7, 51 (1981)] and the method proposed by Alonso and Simozar [Solid State Commun. 46, 765 (1983)]. The explanation based on this diagram is in good agreement with our experimental results.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3794-3796 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the synthesis of carbon-reinforced silica fibers by methane exposure of metallocene-treated oxidized-Si(001) substrates at 1100 °C. The SiO2 cap layer transforms into silica fibers reinforced by glassy carbon in the core during methane exposure. High-resolution electron microscopy and spatially resolved spectroscopy measurements of the fibers reveal an amorphous structure without a hollow, and domains of glassy carbon embedded at the fiber core. The carbon-reinforced fibers are optically transparent and have an optical band gap of (similar, equals)3.1 eV. These fibers are organized in radial patterns that vary for different metallocene species. On nickelocene-treated substrates, the fibers originate from the circumference of the circular templates and grow outwards, forming radial patterns. On ferrocene-treated substrates, randomly oriented fibers grow within as well as slightly outside the perimeter of the templates, forming wreath-like patterns. Aligned growth of such fibers could be useful for fabricating optoelectronics devices and reinforced composites. © 2001 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2934-2936 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogenated carbon films with a crystalline structure have been synthesized by radio-frequency plasma-enhanced chemical vapor deposition. The mass density of the films is dependent on the plasma power applied. By switching alternatively two different plasma powers during deposition, mass-density-modulated structures of the crystalline hydrogenated carbon films can be produced. The structure and properties of these mass-density-modulated structures have also been investigated. © 2001 American Institute of Physics.
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