Moessbauer study of Martensitic transformation and collective magnetic excitations in Fe9Ni1 fine particles

The austenite to martensity ransformation in fine Fe90Ni.10 particles prepared by evaporation is studied by Moessbauer technique.Unlike bulk Fe.9Ni.1 which is entirely transformed to martensite.these particles show a remarkable austenite stability upon cooling upto liquid nitrogen temperature.This stability is associated with the oxide surface layer formed on the particles and also with their small size.A hyperfine field approach is employed to analyze the martensitic transformation in the particles.It is also shown that,in contrast with large particles ,the temperature variation of the Moessbauer average hyperfine field of the fine particles can be satisfactorily explained in terms of the collective magnetic excitations model.     

In situ X-ray diffraction study of the δ to α′ isothermal martensitic transformation kinetics in a Pu-Ga alloy

The sequence of phase formation and the isothermal kinetics of the δ to α′ phase transformation in a Pu-1.9 at.% Ga alloy are investigated with in situ X-ray diffraction at the Advanced Photon Source. It has been proposed that the formation of a γ′ intermediate phase may be responsible for the unusual double-C curve kinetics reported for this isothermal martensitic transformation. While a γ′ intermediate phase was not observed at either −120 °C or −155 °C, an unexplained shoulder on the δ (1 1 1) peak was detected at −155 °C. The isothermal kinetics of the δ → α′ transformation appear to fit a Johnson-Mehl-Avrami-Kolmogorov equation, but the exponent is not described by existing JMAK theory. The double-C curve kinetics of the δ to α′ transformation remain unresolved in plutonium science, and understanding this behavior is key to predicting phase stability in aging Pu-Ga alloys.     

Mssbauer study of the orientation of the magnetic moments in Fe-based nanocrystalline alloys

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Moessbauer study of the orientation of the magnetic moments in Fe—based nanocrystalline alloys

Magneto-impedance(MI) effect in Fe-based nanocrystalline Fe73 Cu1Nb1.5Mo2Si13.5B alloys has been observed by Moessbauer spectroscopy.The results show that the field dependence of the MI ratio is strongly influenced by the transverse magnetic structure in samples.     

The effect of a strong magnetic field on the magnetohydrodynamic stability of plasma and the containment of charged particles in the “Tokamak”

Results of an investigation of plasma in the toroidal apparatus TM-2 in a strong longitudinal magnetic field (up to 22 kOe) are described. It is shown that increasing the magnetic field sharply decreases the low frequency oscillations in the oscillograms of the loop voltage and discharge current derivative, and also weakens the interaction between the plasma and the wails of the discharge chamber.For a large enough ratio of the longitudinal field intensity to the intensity of the current selffield, oscillations are not observed. According to radiointerferometric measurements, the mean electron density in this case hardly alters during the course of the operations. The conductivity reaches a value of about 10¹⁶ cgs.Translated from Atomnaya Énergiya, Vol. 15, No. 5, pp. 363–369, November, 1963     

Fe_（73．5）Cu_1Nb_3Si_（13．5）B_9非晶合金化过程的X射线

采用Ｘ射线衍射和正电子湮没多普勒展宽测量相结合，研究了纳米晶态材料Ｆｅ７３．５Ｃｕ１Ｎｂ３Ｓｉ１３．５Ｂ９的结构随退火温度的变化。实验结果表明：急冷非品样品在４８０℃开始明显晶化，基体中析出体心立方结构的α－Ｆｅ（Ｓｉ）固溶体。随着退火温度的升高，非晶漫射峰不断减弱，而晶态相的衍射谱逐渐增强。进一步计算对衍射谱的分离，给出了品化分数和非晶相平均原子间距随退火温度的变化规律。正电子湮没实验证实了约５５０℃退火时样品内出现以Ｎｂ、Ｂ原子为主的晶界非晶相，Ｓ参数随退火温度的变化与非晶相平均原子间距随退火温度的变化规律一致。     

Corrosion of Fe9Cr1Mo steel in stagnant liquid lead–lithium eutectic

The corrosion behaviour of Fe9Cr1Mo steel samples in a static Pb₈₃Li₁₇ eutectic melt at 823 K in a specially designed necked quartz capsule is investigated. The samples are kept isothermally for 500, 1000, 1500 and 2000 h. The changes in microstructure and depletion of alloying components of the sample kept for 2000 h have been studied using scanning electron microscope (SEM), energy disperses X-rays (EDS) and electron probe beam microanalysis (EPMA). Weight loss and thinning of the walls has been calculated by gravimetric analysis method for all the samples. Using this data the change in thickness per year is calculated. Preferential dissolution of major constituent elements namely iron and chromium from the samples with the formation of a ferritic–martenstic layer is observed. Percentage mass loss with respect to time follows a parabolic curve which indicates non linear mechanism of corrosion.     

Interplay of strengthening mechanisms in the interaction of a ½〈1 1 1〉 screw dislocation with Cr precipitates in bcc Fe: An atomistic study

The interaction of Cr precipitates with a ½〈1 1 1〉 screw dislocation in bcc Fe is studied using molecular static calculations to evaluate the contributions from different strengthening mechanisms. The total interaction energy of the precipitate and the dislocation, the surface energy created due to the precipitate shearing and the shear modulus misfit interaction energy were estimated separately. Based on these data the shear modulus misfit was concluded to be the main mechanism determining the precipitate resisting force for the passage of a ½〈1 1 1〉 screw dislocation.     

Analysis of cesium isotope compositions in environmental samples by thermal ionization mass spectrometry – 1. A preliminary study for source analysis of radioactive contamination in Fukushima prefecture

Cesium was recovered from plant samples obtained from Fukushima prefecture. The isotopic ratios of ¹³⁴Cs/¹³⁷Cs and ¹³⁵Cs/¹³⁷Cs were analyzed by thermal ionization mass spectrometry with a single filament method using a TaO activator. Samples containing 5 Bq of ¹³⁷Cs were analyzed with typical analytical errors of approximately 0.5% for ¹³⁴Cs/¹³⁷Cs and approximately 0.1% for ¹³⁵Cs/¹³⁷Cs. Measurements of both ratios showed profiles that were characteristic of the measurements of among other environmental samples reported in the literature. The results showed the isotopic ratios of ¹³⁴Cs/¹³⁷Cs and ¹³⁵Cs/¹³⁷Cs were applicable for the source analysis of radioactive Cs in Fukushima prefecture.     

Analysis of the SPERT-III E-Core experiment using CASMO5/TRACE/PARCS based on JENDL-4.0 and ENDF/B-VII.1

An analysis of the Special Power Excursion Test III E-Core experiment was performed in order to confirm the calculation accuracy of the light-water-reactor core analysis code system, constructed by the authors, of the CASMO5 and the TRACE/PARCS for the reactivity-initiated accident (RIA) analysis. The influence of the resonance up-scatter model (RUM) and the effective Doppler temperature model (EDTM) in the CASMO5 on the Doppler reactivity feedback effect was also discussed through the comparison with the conventional calculation without those models and the perturbation calculation of the Doppler reactivity coefficient. The calculation results by the CASMO5/TRACE/PARCS mostly showed good agreement with the experimental data within the range of experimental uncertainty, which confirmed the calculation accuracy of the analysis code system for the RIA analysis. In the calculation, the JENDL-4.0 and the ENDF/B-VII.1 were used, however, obvious difference was not seen in the calculation results between the two nuclear data libraries. The influence of the RUM on the core parameters was less than that of the 10% increment of Doppler reactivity coefficient on the conventional calculation. The influence of the EDTM became large on the cold condition, which was the same tendency on the Doppler reactivity coefficient discussed in the previous studies.