A. Shamim

Isochronal crystallization of metglass Fe83B17 using Mössbauer effect and resistivity measurements

Abstract Mossbauer effect and resistivity measurements indicate three stages of crystallization in iron-boron metglass Fe 83 B 17 . During the structural relaxation stage (300–625K), the incipient crystallization produces a boron-rich Feue5f8B phase. In crystallization region (625–660K) α-Fe and t-Fe 3 B phases are produced. In structure coarsening stage (660–925K) the production of o-Fe 3 B and Fe 23 B 6 takes place. o-Fe 3 B phase is found to be a stable while t-Fe 3 B is a metastable phase.

Phase transition in melt-spun Fe88B12 and Fe72B28 alloys by resistivity measurements and Mössbauer spectroscopy

Abstract Resistivity measurements and Mossbauer spectroscopy indicate that the as-quenched Fe 88 B 12 and Fe 72 B 28 melt-spun alloys are not completely crystallized. This is not in agreements with the earlier observations on the same alloys by DTXD measurements. In as-quenched Fe 88 B 12 α-Fe, o-Fe 3 B and amorphous phases are found while in Fe 72 B 28 the phases found are α-Fe and t-Fe 3 B. The phases o-Fe 3 B and t-Fe 3 B are metastable while t-Fe 2 B is stable upto 825K.

Dynamic temperature resistometry analysis of rapidly quenched Fe86B14 alloy and its correlated study by Mössbauer spectroscopy and scanning electron microscopy

Abstract Dynamic temperature resistometry has been used in order to characterize the stability and crystallization behaviour of amorphous Fe 86 B 14 alloy prepared by the single-roll melt spinning technique in a helium atmosphere at constant heating rates (17, 40, 80 K h −1 ) from room temperature to 900 K. The crystallization temperature first increases and then decreases with the increase in heating rate. The data were recorded in forward and reverse directions, indicating different behaviour in the amorphous region. Mossbauer spectroscopy was used to study various steps involved in the resistivity-temperature (RT) curve and corresponding phases formed on samples air quenched after being exhibited subjected to the same heat treatments. The as-received sample exhibited some percentage of γ-Fe phase up to the last temperature; however, its value increases as crystallization proceeds. The first product phase formed from the amorphous matrix was observed to be α-Fe, followed simultaneously by metastable Fe 3 B and Fe 2 B, resulting in a rapid decrease in resistivity. Fe 3 B breaks into α-Fe and Fe 2 B at higher temperatures, which is also highlighted by a steep and sudden fall in the RT curve. The percentages of these final phases almost remain constant up to the final temperature which is in agreement with the linear rise of the RT curve. Scanning electron microscopy analysis revealed the presence of round and ribbon-shaped zones in amorphous areas in the as-received sample which break up into pieces on heating.

Crystallization and other phase-change studies of (Fe0.8Ni0.2)76B24 glassy alloy, using resistivity measurements

Etude comparative avec les resultats obtenus par diffraction RX. La methode de mesure de la resistivite electrique permet de determiner les temperatures de transition de phase, ce qui est impossible par diffraction RX. Cette derniere methode est cependant necessaire pour letude structurale de chaque phase

Study of crystallization process of metglass Fe86B14 by Mössbauer effect and resistivity measurements

Abstract Both isochronal resistivity measurements and phase identification using Mossbauer effect in amorphous alloy Fe86B14, quenched at selected temperatures from 300 to 925K, show three main stages. The slight rise in resistivity in stage I, 300 to 550K, may be because of γ-FeB which is the only phase which crystallizes in this stage. The decrease in resistivity in stage II, 550 to 735K, is due to the formation of α-Fe, Fe2B and Fe3B. The appearance of a step in resistivity curve in this stage, from 640 to 680K, can be attributed to γ-FeB, whose percentage increases appriciably in the same interval of temperature. In stage III, 735 to 925K, where the crystallization seems to be complete, the sharp rise in resistivity may be because of lattice scattering of electrons. In this stage α-Fe, γ-FeB and Fe2B are present. γ-FeB is the first phase to crystallize from the amorphous phase instead of α-Fe as previously reported.

Determination of fibre orientation factor and interfacial strength of filler-matrix bond of hammer-milled glass-fibre reinforced polyurethane networks

The advantages of fibre-reinforced materials are well known, and have been described extensively in the literature [1, 2]. The deformation behaviour of short-fibre reinforced composite is a complicated phenomenon and cannot be described by a simple relationship. Complications arise from a number of material and geometrical variables which can influence the stress-strain behaviour of these materials. Apart from the matrix filler properties, variables such as fibre length, fibre length distribution, interface strength and fibre orientation have significant influence on the stress-strain properties of short-fibre reinforced composites. Bowyer and Bader [3] have developed a model to describe the stress-strain behaviour of glassnylon 6.6 and glass-polypropylene composites. Other workers [4, 5] have successfully applied this model to similar materials. In this work, Bowyer and Baders model has been applied to calculate the interracial strength and fibre orientation factor of composites fabricated by incorporating hammer-milled fibreglass in a reaction injection moulded (RIM) polyurethane network of high Tg ( ~ 130 ° C), from their stress-strain curves and fibre-length distribution. Bowyer and Bader [3] have presented an equation for the composite stress, ao, which takes into account the variation in the fibre lengths a n d c a n be written as

Optical band gap determination in lead silicate glasses

Photoconduction measurements are made on lead silicate glass in the spectral range 2xa0·xa082–6xa0·xa020eV. The values of energy band gap are deduced by extrapolation of the linear portion of photoconduction vs. photon energy curve, obtained at various electric fields. In addition, impurity trap levels are also detected.

Analysis of amorphous (Fe0.7Ni0.3)3B alloy using resistivity measurements

Abstract In this paper results of a study on the crystallization behaviour of the amorphous (Fe0·7 Ni0·3)3B alloy by electrical resistivity measurement at a uniformly increasing temperature are presented. Results are also presented of measurements of phase-transition temperatures after crystallization.