ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    The early stages of solid-state reactions in Ni/Al multilayer films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6689-6698 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ni/Al multilayer films with pair thicknesses of 10 and 20 nm and with overall compositions in the range 48–88 at. % Al were prepared by sputtering. For comparison, Ni-Al alloy films in the same concentration range were prepared by co-deposition of the elements. The films were studied by x-ray diffraction, electron diffraction, and differential scanning calorimetry. It was found that the B2 NiAl phase with a metastable concentration of approximately 63 at. % Al was the first phase to grow upon annealing of the multilayer films. The growth of this phase could be described by Johnson–Mehl–Avrami kinetics with an activation energy of 0.8 eV and an Avrami exponent of 0.5. This low activation energy was consistent with the observation that the phase had formed during deposition and continued to grow upon annealing at low temperatures to thicknesses of a few nanometers. If the reactant phases were not fully consumed by the B2 phase growth, the subsequent reaction was the formation of NiAl3, previously thought to be the first product phase in the Ni-Al system. The reduction of driving force by the preceding B2 phase growth explains why the formation of NiAl3 takes place by a nucleation-and-growth process, an observation that has been discussed controversially in the recent literature. The nucleation and growth of NiAl3 had an activation energy of 1.5 eV in agreement with previous studies. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363794
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Inverse melting of metastable Nb–Cr solid solutions (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2156-2168 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Metastable body-centered-cubic (bcc) Nb–Cr solid solutions were produced by mechanical alloying over a wide concentration range, and investigated by x-ray diffraction, differential thermal analysis, and transmission electron microscopy. For comparison, metastable bcc and amorphous Nb–Cr alloys were fabricated by sputtering. Upon annealing, the solid solutions prepared by mechanical alloying undergo a transformation to an amorphous phase. The vitrification is polymorphous for a composition Nb45Cr55 whereas two-phase mixtures of amorphous and bcc phases are formed for other concentrations, indicating that metastable equilibria between these two phases develop upon heat treatment. These results, combined with a detailed analysis of the thermodynamic functions of the system, reveal that the amorphous phase has a lower enthalpy and entropy than the bcc phase near equiatomic composition. In consequence, the Gibbs-energy curves of bcc and liquid/amorphous Nb45Cr55 phases versus temperature exhibit two points of intersection, i.e., two melting points, with the amorphous phase being thermodynamically more stable than the bcc phase at low temperatures. Inverse melting is thus thermodynamically possible in the Nb–Cr system, so that the metastable crystalline phase would melt upon cooling. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363048
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Concentration-depth profiling using total-reflection x-ray fluorescence spectrometry in combination with ion-beam microsectioning techniques (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 20-23 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new method for the determination of vertical concentration profiles and its application to bilayer diffusion couples are presented. The method combines sputter sectioning techniques with ex situ total-reflection x-ray fluorescence (TXRF) analysis. It allows quantitative depth-resolved analysis of alloys consisting of elements with atomic numbers ≥13, quantitatively and depth resolved. In contrast to other surface sensitive techniques like Auger electron spectrometry or secondary ion mass spectrometry, TXRF offers the advantage of determining the sampling depth with the same instrument, so that no assumptions about sputtering rates or auxiliary measurements are necessary. With this method a depth resolution of 2.5 nm is obtained, which is comparable with the best achievable results from other depth profiling methods. Moreover, an additional TXRF scan in a nondestructive mode of operation makes a mutual comparison with the results of the sectioning technique possible. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145260
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Structure of the Fe-doped high-temperature superconductors Y1Ba2Cu3Oy and Bi2Sr2Ca1Cu2Oy (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1018-1022 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The high-temperature superconductors YBa2(Cu1−xFex)3Oy and Bi2Sr2Ca1(Cu1−xFex)2Oy have been examined by resistivity measurements, x-ray diffraction, and Mössbauer experiments in order to understand the influence of Fe on the structure of the perovskites. The concentration dependence of the Fe substitution and the results of the annealing experiments are consistent with the following model which explains the observed structural changes with Fe composition in YBa2Cu3Oy. For low Fe content, the Fe atoms mainly substitute on the Cu(I) sites leading only to a slight decrease of Tc, but to an attraction of more oxygen ions, which are introduced into the (001) plane. The Fe ions with five- or sixfold coordination act like local symmetry points inducing the formation of short orthogonal chains crossing at the Fe ions. This leads to the orthorhombic-to-tetragonal transition at an Fe concentration of 2.3%. For higher Fe content, Tc more rapidly decreases, probably due to a partial substitution of Fe also on the Cu(II) sites of the perovskite until the superconductivity vanishes near 16% Fe. The three occuring Mössbauer doublets are assigned to different (four-, five-, and sixfold) oxygen environments of the Fe ions. Similar environments occur in Bi2Sr2Ca1Cu2Oy with 20% Fe, although it is known that no Cu-O chains exist in this structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343058
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Mössbauer effect on mechanically alloyed Fe-Zr glasses (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 117-119 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphous Fe-Zr powders have been prepared by mechanical alloying in a powder mill and studied by means of Mössbauer spectroscopy. It is shown, that, within the glass-forming range from about 30 to 78 at. % Fe, the local structure of the mechanically alloyed samples, detected by the Mössbauer effect, is the same as in the corresponding melt-spun or sputtered samples. The existence of a two-phase region above 78 at. % Fe between an amorphous phase and crystalline Fe confirms that amorphization by mechanical alloying is a metastable equilibrium process. There is evidence that mechanical alloying enhances the Zr solubility in Fe up to 5 at. %.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339168
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Amorphization of Ti/Cr multilayer films by solid-state reaction (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2249-2253 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The solid-state reaction in Ti/Cr multilayered diffusion couples at temperatures between 450 and 650 °C was investigated by x-ray diffraction. It was found that an amorphous phase is formed at a concentration around 55 at. % Cr. The results are in excellent agreement with those obtained from mechanically alloyed powders, and with the corresponding metastable phase diagram calculated by the calculation of phase diagrams method. The observations strongly suggest that inverse melting is possible in the Ti-Cr system at around 55 at. % Cr.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353129
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Mössbauer study of Fe-substituted Co-Zr and Cu-Zr metallic glasses (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 269-274 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure of pseudobinary Co-Zr and Cu-Zr metallic glasses, where Co and Cu were substituted by Fe, was studied by means of 57Fe-Mössbauer spectroscopy. The resulting spectra can be divided into two different classes: (1) For Zr concentrations larger than 67 at. %, the structure of the glass, as derived from Mössbauer spectroscopy, is nearly independent from a substitution, leading to only small changes of the average isomer shifts and quadrupole splittings. These small variations of hyperfine parameters can be ascribed to charge transfer effects. (2) For lower Zr contents, pronounced systematic changes of hyperfine parameters occur upon Co or Cu substitution. Beyond changes of the average hyperfine values, the corresponding quadrupole-splitting distributions become dependent on the degree of substitution, i.e., there is a concentration dependent splitting into two peaks. For the amorphous binary Zr-Fe system, these two peaks have been connected to two amorphous phases with concentrations near Zr2Fe and ZrFe2. At least for the Fe-doped Cu-Zr metallic glasses it could be demonstrated that Fe does not substitute the Cu sites but rather creates preferred environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347127
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    The thermodynamics of amorphous phases in immiscible systems: The example of sputter-deposited Nb–Cu alloys (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 6024-6030 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphous metallic alloys, frequently observed to occur in systems with large negative heats of mixing, are much less common in systems which are immiscible in the equilibrium solid state, such as Nb–Cu. However, amorphous Nb–Cu alloys can be produced over a wide composition range by sputtering. Using isothermal and nonisothermal differential scanning calorimetry, both the kinetics and the thermodynamics of these amorphous Nb–Cu alloys were characterized quantitatively. It was found that the formation enthalpies of the amorphous alloys amounted to only 4.5–7.6 kJ/g atom. These data were combined with a modeling of the thermodynamic functions of the system. The unexpected low enthalpies and Gibbs energies of the amorphous phase demonstrate the thermodynamic stabilization of the liquid phase which develops with undercooling. This is connected with a change of sign in the heat of mixing of the liquid phase, which is positive at high temperatures and negative at low temperatures. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364451
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Inverse melting of a metastable Nb45Cr55 solid solution (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 318-320 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An Nb45Cr55 solid solution was prepared by mechanical alloying in a planetary ball mill and investigated by x-ray diffraction and calorimetry. It was found that the structure evolution upon heating exhibited three distinct stages, the first resulting in complete amorphization, whereas the second and third are related to the subsequent crystallization of the amorphous phase. These results are in agreement with the free-energy functions calculated from the thermochemical data of the system. They show that for a composition of Nb45Cr55 a second melting point (often termed "inverse melting point'') exists at about 900 °C, below which the undercooled liquid has a lower free energy than the crystalline body-centered-cubic phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112358
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    (Fe"1"-"xMn"x)"7"5P"1"5C"1"0 - an ideally mixed amorphous metallic glass?
    Amsterdam : Elsevier
    Journal of Magnetism and Magnetic Materials 82 (1989), S. 204-212 
    Details
    ISSN: 0304-8853
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0304-8853(89)90155-8
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...