Fe Sb System Research Articles

The control of grain boundary structure by ion implantation of solute

The dislocation structures of small and large angle (001) twist boundaries in Fe-S alloys are influenced by the segregation of S to the vicinity of the interface. Since changes in the dislocation structures of (001) twist boundaries due to solute segregation have now been observed in the Fe-Au, Fe-Sb and Fe-S systems, this behavior is believed to represent a widely occurring phenomenon in Fe alloys. This work has also demonstrated that ion implantation can be used to deposit solute in the vicinity of the interface in a bicrystal specimen where the boundary is both parallel, and close to the external surface. The ion implantation technique may be useful for changing boundary structure in order to control boundary properties. The main role of the point defects introduced during ion implantation, in the process that are occurring in the bicrystal, appears to be to help the attainment of the equilibrium distribution of the solute at the interface.

The role of excess antimony as a promoter of activity and selectivity in selective oxidation in the FeSb system

The modifications of two iron-antimony oxides with SbFe ratios of 1 and 2 during calcination up 1000 °C and after catalytic tests (1-butene oxidation to butadiene) were studied by X-ray diffraction, infrared, and Mössbauer analyses. The results show that a nonstoichiometric (NS) rutile structure with excess antimony held within the structure itself is formed on both catalysts calcined up to 900 °C. The strong increase both in selectivity and activity in allylic oxidation showed by the catalyst with an Sb:Fe ratio of 2 is attributed to the formation of a NS-rutile that is stable during catalytic tests. It is suggested that the excess antimony held within the structure creates SbO double bonds which are responsible for the increase of selectivity and activity. The fundamental role of the method of preparation by coprecipitation in a basic medium is also suggested.

Kalorimetrische untersuchungen an festen legierungen der systeme eisen—antimon, kobalt—antimon und nickel-antimon

In order to obtain the formation enthalpies of solid alloys in the FeSb, CoSb and NiSb systems a high-temperature calorimeter has been constructed. With this device, the solution enthalpies of the alloys and their components have been determined. The absolute values of the negative formation enthalpies which were calculated from the solution enthalpies increase within the series FeSb → CoSb → NiSb. The maximum values of the enthalpies of formation are: Δ H B = − 0.044 kJ g-at. −1 (at 57 at.−% Fe); Δ H B = − 27 kJ g-at. −1 (at 52 at.−% Co) and Δ H B = − 33 kJ g-at. −1 (at 51 at.−% Ni). These, for the most part highly negative, values are indicating that considerable non-metallic contributions to the bonding energies are existing in these systems. This leads to the formation of NiAs-phases in the central parts of the concentration ranges.

Fe-Sb系合金の相互拡散

Iron test pieces were diffusion-annealed in an evacuated silica capsule containing the powdered (100∼200 mesh) 50 wt%Sb-Fe alloy consisting of α and ε phases as an Sb vapor source for 9∼440 hr at 700∼950°C. The test pieces were then analysed with an EPMA and the penetration curves of them were obtained.Each penetration curve was analysed by means of the Matano-Boltzmann method to obtain the chemical diffusion coefficients (\ ildeD). From these values the activation energies for diffusion (\ ildeQ) were calculated.Surface concentration of the test pieces (αmax) at each annealing temperature coincided approximately with the solubility observed in the phase diagram of an Fe-Sb system at lower temperatures, while a significant deviation was found in solubility at higher temperatures. Fine alumina makers placed on the test pieces prior to diffusion were found always on the surfaces after annealing so that it is considered that Sb atoms diffuse predominantly in the α-phase of this system. Each penetration curve was similar to an error function curve and \ ildeD at each temperature showed a relatively small dependence upon Sb concentration. There was a gap in the Arrhenius plot owing to magnetic transformation. The activation energies for diffusion (\ ildeQ) obtained from the data at higher temperatures varied from 59.5 kcal/mol for 1 at%Sb to 52.5 kcal/mol for 4 at%Sb and that for impurity diffusion of Sb in iron (QSb*) was evaluated to be about 63 kcal/mol.

Magnetic Properties of the Systems (Cr, Fe) Sb and (Cr, Co) Sb

Magnetic measurements were made of the systems (Cr 1.01 Sb) 1- x (Fe 1.22 Sb) x and (Cr 1.01 Sb) 1- x (Co 1.13 Sb) x . In both systems, ferromagnetism appeared in the intermediate range of x . In the (Cr, Fe)Sb system maximum of the spontaneous magnetization and the Curie temperature was found at x =0.6. However, the temperature variation of the magnetization near the Curie temperature was not so sharp as in the usual ferromagnet, and also the high field susceptibility at low temperatures was anomalously high. X-ray and neutron diffraction measurements revealed that there was no miscibility gap between ferromagnetic and antiferromagnetic phases. Mossbauer effect showed that, for x =0.8 the internal field on Fe 57 nuclei was about 90 kOe, and the isomer shift (against stainless steel) was 0.54 mm/sec. The anomalous behavior of magnetization was even more pronounced in the (Cr, Co)Sb system. Ferromagnetic interactions Cr-Sb-Fe and Cr-Sb-Co can well be interpreted on the basis of the Goodenough-Kanamori theory.