Iron Concentration Profiles Research Articles

Radiation damage in ion-irradiated MgO

The microstructures found in specimens of single crystal MgO after irradiation with 2 MeV oxygen or 4 MeV iron ions were examined by transmission electron microscopy of cross-sectional specimens. The observed damage consisted primarily of dislocations. The end of the damage occurred at a depth of 2.4 μm for the oxygen irradiation and 2.8 μm for the iron irradiation. For both irradiations, the damage appeared to have two bands where the density peaked. Between these bands, the dislocation density was suppressed as compared to the balance of the profile. Measurements of the implanted iron concentration profile by energy dispersive X-ray spectroscopy demonstrated that the peak in the iron concentration was located at 2.2 μm, approximately the center of the low dislocation region. Surprisingly, electron energy loss spectroscopy of the damaged region from the oxygen irradiation demonstrated no measurable variations in the nominal 50 at.% oxygen concentration. With simultaneous implantation of helium ions, an additional region with low dislocation density was observed at 0.9 to 1.1 μm, the calculated location of the implanted helium. The observations suggest that the charge associated with the deposited ions may have an influence on the resulting damage. In addition, the experimental profiles indicate damage and ion ranges well beyond the calculated values.

The effect of colchicine on the pigmentation of the enamel surface in rat incisors.

The effect of colchicine and lumicolchicine on the secretion of an iron-containing pigment vesicle onto the enamel surface in the rat maxillary incisors has been studied histologically and by line scan analysis of the iron with an X-ray microanalyzer. Rats were killed at intervals of 12 and 24 hours and 3, 6 and 10 days after the subcutaneous injection of colchicine or lumicolchicine at a dose of 1.3 mg/kg. At 10 days after the colchicine injection, two pigmentation-free bands were observed on the enamel surface in each pair of incisors. By the line scan analysis of the iron with an X-ray microanalyzer, the pigmentation-free bands corresponded to the decrease of the iron concentration profile. By the histological observation at 12 and 24 hours after the injection, no remarkable changes were observed from the late pigmentation stage to the regression stage. However, at 3 and 6 days after the injection, the pigmentation-free bands appeared on the enamel surface. A large number of pigment vesicles was observed in the ameloblasts and in the papillary cells facing the pigmentation-free bands. These phenomena were not observed in the rats injected with lumicolchicine. The present study suggests that the secretion of an iron-containing pigment vesicle in the ameloblasts onto the enamel surface is mediated by the microtubules.

The decomposition of wustite under mixed chemical reaction/mass transport limitations

Numerical solutions have been obtained for the mixed chemical reaction/diffusion limited planar decomposition of a wustite slab prior to iron metal nucleation. The results of the analysis are presented in dimensionless parameters and predict the iron concentration profile within the slab during decomposition, the total loss of oxygen from the sample, and the concentration of iron at the gas/wustite interface, as a function of time. The formulation of the problem allows solutions to be obtained for reduction in H2/H2O or CO/CO2 gas mixtures at reaction temperatures between 873 K and 1573 K.

Ion beam analyses of surface films formed on amorphous Fe12Mo18C alloy in 1 N HCl

The Rutherford backscattering with 2 MeV He + and the 16O(d,p) 17O ∗ nuclear reaction with 1.8 MeV D 2 + were utilized to determine the concentration profiles of iron, molybdenum and oxygen in the surfaces of an amorphous Fe12Mo18C alloy polarized in 1 N HCl at potentials from − 0.17 to 1.6 V(SCE). The thickness of the surface film was estimated as 20–200 nm. In the primary active region, selective dissolution of iron and carbon causes enrichment of molybdenum ions in the corrosion product film and of metallic molybdenum in the topmost part of the underlying alloy. A further potential increase led to a decrease in the molybdenum content in the film by transpassive dissolution. Molybdenum ions were not concentrated in the film formed in the stable passive region of 0.5–1.5 V(SCE). The high passivating ability of the amorphous alloy even in the aggressive HCl was ascribed to the homogeneity of the alloy structure as well as to the effect of molybdenum.

Study of silicon layer implanted with iron

The effects of compressive stress that accompanies an implanted layer due to lattice damage and inclusion of additional atoms have been observed to be predominant for 30 keV room temperature iron implants in 〈111〉 silicon crystals, as investigated by transmission electron microscopy. A slip pattern has been observed for a dose of 5 × 10 14 ions cm −2, which is sufficient to form large damaged regions. This corresponds to maximum stress in the implanted layer. The stress distribution in the implanted layer has been explained by constructing the damage density profile and the iron concentration profile. The latter has been obtained by Auger electron spectroscopy (AES).

Influence des conditions de fusion en zone flottante sur le partage du fer entre titane liquide et titane solide: Application à létude des écoulements au sein de la zone liquide

A new technique of floating zone melting was applied to titanium bars containing up to 800 –1500 ppm Fe. It utilizes the variations in the viscous factional torque induced within the liquid by the fast rotation of the upper part of the ingot to monitor the heating power. This technique requires the use of gas bearings and of an argon atmosphere within the melting chamber, thus reducing the iron volatilization. The partition coefficient of iron between liquid and solid titanium was calculated from the iron concentration profiles along the ingots; it was found to be k = 0.34 ± 0.02. The effect of the ingot rotation speed on the thickness of the concentration boundary layer and on fluid flows within the liquid zone was studied. Rotation speeds of the order of 150 rev min −1 for titanium appear to be optimal for maximum stability of a floating zone 0.3 cm thick.

The Diffusion of Iron in Impurity Controlled Single Crystalline Nickel Oxide Between 1061° and 1241°C

The capability of an x‐ray dispersive microanalyzer attachment on a scanning electron microscope to determine concentration profiles of iron in single crystalline was studied. The technique is less precise but much less time consuming than radiotracer methods. The data support a model involving diffusion of iron via vacant nickel sites. The activation energies varied between 18 and 26 kcal/mole for diffusion under constant oxygen pressures between 0.011 and 1 atm. The diffusion was impurity controlled.