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  • 1
    Electronic Resource
    Electronic Resource
    Room-temperature coercivity enhancement in mechanically alloyed antiferromagnetic-ferromagnetic powders (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3177-3179 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The coercivity, HC, and squareness of Co powders have been enhanced at room temperature by mechanically alloying them with antiferromagnetic powders with Néel temperature, TN, above room temperature. The enhancement is maximum after field annealing above TN. The existence of loop shifts and the dependence of HC on the annealing and measuring temperatures indicate that exchange bias effects are responsible for this behavior. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125269
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  • 2
    Electronic Resource
    Electronic Resource
    Coercivity and squareness enhancement in ball-milled hard magnetic–antiferromagnetic composites (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1142-1144 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The room-temperature coercivity, HC, and squareness, MR/MS (remanence/saturation magnetizations), of permanent magnet, SmCo5 powders have been enhanced by ball milling with antiferromagnetic NiO (with Néel temperature, TN=590 K). This enhancement is observed in the as-milled state. However, when the milling of SmCo5 is carried out with an antiferromagnet with TN below room temperature (e.g., for CoO, TN=290 K), the coercivity enhancement is only observed at low temperatures after field cooling through TN. The ferromagnetic–antiferromagnetic exchange coupling induced either by local heating during milling (SmCo5+NiO) or field cooling (SmCo5+CoO) is shown to be the origin of the HC increase. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1392308
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  • 3
    Electronic Resource
    Electronic Resource
    Glass formation and crystallization in the GeSe2-Sb2Te3 system (1984)
    Springer
    Journal of materials science 19 (1984), S. 3005-3012 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The glass formation and crystallization of liquid-quenched (GeSe2)100-y /(Sb2Te3) y alloys was investigated by means of differential scanning calorimetry, X-ray diffraction and optical and scanning electron microscopy. By water quenching glasses are obtained from compositions in the range 5≲y≲30. Qualitative parametrization of glass-forming tendency gives, as best glass formers, alloys with y≅20. Crystallization on heating proceeds in one stage for glasses withy≲20 and in two stages for those with greater Sb2Te3 content. For compositions lying in the GeSe2 primary crystallization region crystals appear preferentially at the surface of the sample, but for the other compositions (24≲y≲30) the crystals emerge in the bulk and often develop in spherulitic or axialitic form.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01026979
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  • 4
    Electronic Resource
    Electronic Resource
    Crystallization kinetic studies: A means to evaluate time-temperature-transformation curves. Application to metallic glasses (1991)
    Springer
    Journal of thermal analysis and calorimetry 37 (1991), S. 1261-1268 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird gezeigt, daß die Untersuchung der Kristallisationskinetik von amorphen Legierungen genutzt werden kann, die korrekte Form des Niedertemperaturbereiches der Zeit-Temperatur-Transformation (T-T-T) Kurven zu erhalten. Es wird ein einheitlicher Überblick über die jüngsten Untersuchungen von Kristallisationskinetiken gegeben und an der allgemeinen Gleichung der Reaktionsgeschwindigkeit als eine Funktion von Temperatur und Kristallanteil wird gezeigt, daß sie Informationen bezüglich der T-T-T-Kurven beinhaltet. Letztlich wird eine Anwendung an zwei, durch schnelles Erstarren gewonnenen metallischen Gläsern Nd3Fe77B20 und Fe67.5Co15Nb1.5B16 dargelegt. Zwischen Theorie und Praxis konnte eine ausreichende Übereinstimmung festgestellt werden.
    Notes: Abstract It is shown that the study of the kinetics of crystallization of an amorphous alloy may be used to obtain the correct form of the low temperature part of the time-temperature-transformation (T-T-T) curves. A unified review of the current kinetics of crystallization studies is presented and the general kinetic equation which gives the reaction rate as a function of temperature and crystalline fraction is shown to contain information related to theT-T-T-curves. Finally examples of application to two metallic glasses, Nd3Fe77B20 and Fe67.5Co15Nb1.5B16, obtained by rapid solidification techniques are presented. The comparison between theory and experiment is satisfactory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01913859
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  • 5
    Electronic Resource
    Electronic Resource
    Evaluation of crystallization kinetics by means of DTA (1977)
    Springer
    Journal of thermal analysis and calorimetry 11 (1977), S. 271-276 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Résumé Etude de la cinétique de la cristallisation dans la masse de verres Se61.5Ge15.4Sb23.1 à partir de leur comportement thermique. La température de recristallisation dépend fortement tant de la vitesse de chauffage que de l'histoire thermique du verre. Des échantillons vitreux ont été préparés par refroidissement rapide. La recristallisation obéit à une cinétique du premier ordre, avec une enthalpie d'activation apparente de 48±5 kcal·mol−1. Une analyse ultérieure permet de déterminer l'enthalpie d'activationH=90±4 kcal-mol−1 ainis que l'exposant cinétiquen=1.9±0.3 de l'équation d'Avrami.
    Abstract: Zusammenfassung Die Kinetik der Massenkristallisation von Glas-Arten der Zusammensetzung Se61.5Ge15.4Sb23.1 wurde an Hand ihres thermischen Verhaltens studiert. Bei der thermischen Charakterisireung von Glas hängt die Rekristallisationstemperatur stark sowohl von der Aufheizgeschwindigkeit als auch von der Wärmevorgeschichte des Glases ab. Glasige Proben wurden durch rasches Abkühlen hergestellt. Aus den geschwindigkeitsabhängigen Thermogrammen geht hervor, dass der Rekristallisierungsprozess der Kinetik erster Ordnung gehorcht, mit einer scheinbaren Aktivierungsenthalpie von 48±5 kcal/mol. Die weitere Analyse ermöglicht die Bestimmung sowohl der AktivierungsenthalpieH=90±4 kcal/mol als auch des kinetischen Exponentenn=1.9±0.3 der Avrami-Gleichung.
    Notes: Abstract The kinetics of bulk crystallization of Se61.5Ge15 4Sb23.1 glasses was investigated from their thermal behaviour. In the thermal characterization of a glass the recrystallization temperature is highly dependent on both the rate of heating and the thermal history of the glass. Vitreous samples were prepared by quenching. From ratedependent curves it was found that the recrystallization process obeys first-order kinetics with an apparent activation enthalpy of 48±5 kcal/mole. Further analysis allows determination of both the activation enthalpy,H=90±4 kcal/mole, and the kinetic exponent of the Avrami equation,n=1.9±0.3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01909965
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  • 6
    Electronic Resource
    Electronic Resource
    DSC study of some Ge-Sb-S glasses (1991)
    Springer
    Journal of materials science 26 (1991), S. 3680-3684 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Differential scanning calorimetric analysis was made on three glasses of the Ge-Sb-S system in order to obtain insight into the kinetics of glass transition and of the inherent relaxation processes occurring in the glass transition region. The heat capacity of the supercooled liquid referred to as the glass was measured. The value of the heat capacity jump at the glass transition, ΔCp, has been obtained for each glass. These values are in good agreement with those found for similar chalcogenide glasses. The relaxation process in the glassy alloy Ge30Sb10S60 was investigated by measuring the excess heat capacity of the annealed glass in the glass transition region. A relaxation enthalpy of 2.7 meV for annealing at 595 K for 17 h was determined. A kinetic study of the glass transition in the Ge20Sb10S70 glass was done. From the change in the glass transition temperature with scanning rate, an apparent activation energy of 3.9 eV was obtained. This value agrees with those measured for the apparent activation energy of the shear viscosity in similar glasses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00557163
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  • 7
    Electronic Resource
    Electronic Resource
    A crystallization study of the Ge25Sb20S55 glassy alloy (1991)
    Springer
    Journal of materials science 26 (1991), S. 678-682 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Differential scanning calorimetry analysis was used to gain insight on the thermal stability and calorimetric behaviour on heating of the Ge25Sb20S55 glassy alloy. The as-quenched glass shows a glass transition atT g=570 K. From the variation ofT g with the heating rate a value of Δh=240 kJ mol−1 was obtained for the activation enthalpy of the mean relaxation time. On further heating an exothermic process appears ranging from 725 to 800 K giving rise to glassy GeS2 and needle-like crystals of antimony. The microstructure of the crystallization product was obtained from X-ray diffraction and scanning electron microscopy. The resulting material shows two glass transitions. The crystallization process is explained correctly by the Johnson-Mehl-Avrami-Erofe'ev equation with a kinetic exponent ofn=1.6. The apparent activation energy of crystallization is evaluated asE=286 kJ mol−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588303
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  • 8
    Electronic Resource
    Electronic Resource
    Reordering, recrystallization and recovery behaviour of (Co0.78Fe0.22)3V as a function of the initial state of order (1993)
    Springer
    Journal of materials science 28 (1993), S. 538-546 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The ordering kinetics of the L12 alloy (Co0.78Fe0.22)3V have been studied on annealing below the order-disorder transition temperature and starting from different initial conditions induced by different thermo-mechanical treatments. The results obtained are reported in two parts. In Part I, we have determined by means of dilatometric, resistometric and calorimetric analysis, the relevant temperatures and energies dissipated in the transformations, and how the rates are affected by the initial conditions and annealing temperatures. The variation of hardness and the long-range order parameter have also been measured. The results obtained suggest that the overall kinetics are dependent on the way in which ordering, recrystallization and recovery phenomena occur at different temperatures and on how they affect each other.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00357835
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal investigation of GeSb2Se4 chalcogenide alloy glass (1975)
    Springer
    Journal of thermal analysis and calorimetry 8 (1975), S. 589-591 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Differential thermal analysis measurements were performed between 115 and 550° on glass samples of GeSb2Se4 chalcogenide alloy, and the latent heats of structural transformations were obtained. Heat treatment was found to result in the appearance of an endothermic peak associated with the glass transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01910138
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  • 10
    Electronic Resource
    Electronic Resource
    Thermally activated crystallization of (GeSe2)70 (Sb2Te3 20(GeTe)10 alloy glass: morphological and calorimetric study (1983)
    Springer
    Journal of materials science 18 (1983), S. 1381-1388 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The rate of crystallization of (GeSe2)70(Sb2Te3)20(GeTe)10 vitreous samples was investigated by means of differential scanning calorimetry. Crystallization proceeds in two stages. The activation energy of each stage of crystallization was determined. The evolution of the microstructure during crystallization was investigated by X-ray analysis and optical and scanning electron microscopy. Crystalline nuclei emerge in the bulk and develop in a spherulitic form. A lamellar structure is clearly observed when crystallization is completed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01111958
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