Residual Activity Method Research Articles

Diffusion of 65Zn in the Mg17Al12 intermetallic compound and in the Mg-33.4 wt.% Al eutectic

Abstract The coefficient of 65Zn heterodiffusion in the Mg17Al12 intermetallic compound (β-phase) and the eutectic alloy Mg-33.4 wt.% Al was measured in the temperature region 598 – 698 K using serial sectioning and residual activity methods. The diffusion coefficient of 65Zn in the intermetallic can be written as Δ I = 1.5 × 10– 2 m2 s –1 × exp( – 154.3 kJ mol –1/RT). At temperatures T ≥ 648 K, where the mean diffusion path is greater than the mean interlamellar distance in the eutectic, the effective diffusion coefficient Δ eff = 2.7 × 10– 2 m2 s –1 exp(–155.1 kJ mol– 1/ RT) was evaluated. At two lower temperatures, the diffusion coefficients 65Zn in interphase boundaries were estimated: Δ b (623 K) = 1.6 × 10 –12 m2 τ– 1 and Δ b (598 K) = 4.4 × 10– 13 m2 τ–1. The specific (Mg)/β interfacial energy γ = 140 mJ m– 2 was assessed from measurement of the time dependence of interlamellar distance during isothermal anneal.

Long term Impact of a Disinfectant with Residual Activity on Suppression of Bacteria on Fomites in Hospital Waiting Rooms

Long term Impact of a Disinfectant with Residual Activity on Suppression of Bacteria on Fomites in Hospital Waiting Rooms

Diffusion of Carbon in Niobium and Molybdenum

Diffusion coefficients of carbon in niobium and molybdenum have been determined by the residual activity method with radioactive tracer 14C in the temperature ranges between 1168 and 1567K for niobium and between 1271 and 1669K for molybdenum. The temperature dependences of the diffusion coefficient of carbon in niobium and molybdenum are expressed by D/m2 s11 = 2.2 © 1016 exp(1152 kJmol11/ RT) and D/m2 s11 = 5.2 © 1016 exp(1163 kJmol11/RT), respectively. Since the solubility of carbon in molybdenum is very small, the diffusion of carbon in molybdenum is strongly influenced by carbide precipitation at lower temperatures. [doi:10.2320/matertrans.M2014277]

A simple measurement of the Ni-63 diffusion profiles by residual activity method using a liquid scintillation counter

A simple and sensitive technique based on a solid scintillator in place of the commonly used liquid scintillation (LS) cocktail has been developed to measure the low-energy surface radioactivity with the LS counter. As a test case, the method was applied to the successful determination of the nickel-63 self-diffusion profile in commercial purity nickel by means of the Gruzin′s residual activity method. On the same sample, the additional three methods of diffusion profile determination were used to compare with the proposed new method: (i) proportional counter activity detection, (ii) serial sectioning method and (iii) an integral sample measurement in LS cocktail. In conclusion, the strong and weak points are discussed for each method.

Yields of photonuclear reactions on Sn isotopes at an energy of 29.1 MeV

Yields of photonuclear reaction on natural mixture of Sn isotopes irradiated by bremsstrahlung beam with maximum energy of 29.1 MeV are studied via the residual activity method. Using the TALYS code and a combined model, the cross sections of the photonucleon reaction in stable isotopes of Sn are calculated. Measured yields are compared with the yields calculated using theoretical, experimental, and estimated cross sections.

Photodisintegration of tantalum

The yields of photonucleon reactions on the isotope 181Ta that are induced by bremsstrahlung photons whose endpoint energy is 67.7 MeV are measured by the residual-activity method. The cross sections for photonucleon reactions on the isotope 181Ta are calculated on the basis of the TALYS code and a combined model. The measured reaction yields are compared with their counterparts rescaled from cross sections obtained in experiments that employed beams of quasimonochromatic and bremsstrahlung photons. The spectra of neutrons emitted from 181Ta nuclei after the absorption of photons having various energies are calculated within the TALYS code and the combined model in question.

Grain boundary diffusion of Fe in ultrafine-grained nanocluster-strengthened ferritic steel

Grain boundary diffusion of Fe in nanocluster-strengthened ferritic steel (Fe–14Cr–3W–0.4Ti–0.25Y2O3 in wt.%) has been investigated. The steel was produced by mechanical alloying followed by hot extrusion. The final grain size was ∼200nm. The diffusivity of Fe was measured within the temperature range 423–820K. The grain boundary penetration at lower temperatures revealed a specific time dependence, which indicates a residual interconnected porosity in the ferritic steel. In order to quantify the percolating porosity, conventional radiotracer (59Fe) diffusion measurements were combined with a study of room temperature penetration of liquid 110mAg solution to distinguish between solid-state diffusion along boundaries and penetration along the surface of interconnected cavities. The presence of porosity affected the diffusion process, introducing a hierarchy of internal interfaces. The grain boundary diffusion coefficient and the diffusivity along internal surfaces were determined in the so-called type C–C, C–B and B–B kinetic regimes of interface diffusion in a hierarchical microstructure. Using the residual activity method and a 65Zn tracer, the volume fraction of the percolating porosity was estimated to be 0.6%.

Zn Diffusion in Binary Base of Light Mg-Al Alloys

Heterodiffusion of 65Zn in Mg, Mg – x Al (x = 1.77, 3.9 and 9 wt.% Al) and in the commercial AZ91 alloy was studied in the temperature interval 498 – 848 K by serial sectioning and residual activity methods. The concentration and temperature dependence of Zn bulk diffusion coefficient D is described by the relation D = exp (0.1 × cAl – 9.16) × exp (-125.8 kJ mol-1/RT) m2 s-1 (cAl – concentration of Al in wt.%). Zn grain boundary diffusivity P = s δ Db (s – segregation factor, δ - grain boundary width and Db – diffusion coefficient in grain boundary) was also determined and it was found that it obeys the Arrhenius law P = 7.2 × 10-15 × exp (-46 kJ mol-1/RT) m3 s-1.

Diffusion of 65Zn in the Mg17Al12 intermetallic compound and in the Mg-33.4wt.% Al eutectic

Abstract The coefficient of 65Zn heterodiffusion in the Mg17Al12 intermetallic compound (-phase) and the eutectic alloy Mg-33.4wt.% Al was measured in the temperature region 598–698K using serial sectioning and residual activity methods. The diffusion coefficient of65Zn in the intermetallic can be written as DI=1.5×10−2m2s−1× exp(–154.3kJmol−1/RT). At temperatures T648K, where the mean diffusion path is greater than the mean interlamellar distance in the eutectic, the effective diffusion coefficient Deff=2.710−2m2s−1exp(–155.1kJmol−1/RT) was evaluated. At two lower temperatures, the diffusion coefficients 65Zn in interphase boundaries were estimated: Db (623K)=1.610−12m2s−1 and Db (598K)=4.4 10−13m2s−1. The specific (Mg)/ interfacial energy =140mJm−2 was assessed from measurement of the time dependence of interlamellar distance during isothermal anneal.

Diffusion of 65Zn in Mg and in Mg–x Al solid solutions

AbstractHeterodiffusion of 65Zn in Mg, Mg–x Al (x = 1.77, 3.9 and 9 wt% Al) and the commercial AZ91 alloy was studied in the temperature interval 498–848 K by serial sectioning and residual activity methods. The concentration and temperature dependence of the Zn bulk diffusion coefficient D is described by the relation D = exp (0.1c Al – 9.16) exp (–125.8 kJ mol–1/RT ) m2 s–1 (c Al – concentration of Al in wt%). The Zn grain boundary diffusivity P = sδD b (s – segregation factor, δ – grain boundary width and D b – diffusion coefficient in the grain boundary) was also determined and obeyed the Arrhenius law P = 7.2 × 10–15 exp (–46 kJ mol–1/RT ) m3 s–1. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Zinc Self-Diffusion in ZnO

This work deals with the study of zinc self-diffusion in ZnO polycrystal of high density and of high purity. The diffusion experiments were performed using the 65Zn radioactive isotope as zinc tracer. A thin film of the tracer was deposited on the polished surface of the samples, and then the diffusion annealings were performed from 1006 to 1377oC, in oxygen atmosphere. After the diffusion treatment, the 65Zn diffusion profiles were established by means of the Residual Activity Method. From the zinc diffusion profiles were deduced the volume diffusion coefficient and the product dDgb for the grain-boundary diffusion, where d is the grain-boundary width and Dgb is the grain-boundary diffusion coefficient. The results obtained for the volume diffusion coefficient show good agreement with the most recent results obtained in ZnO single crystals using stable tracer and depth profiling by secondary ion mass spectrometry, while for the grain-boundary diffusion there is no data published by other authors for comparison with our results. The zinc grain-boundary diffusion coefficients are ca. 4 orders of magnitude greater than the volume diffusion coefficients, in the same experimental conditions, which means that grain-boundary is a fast path for zinc diffusion in polycrystalline ZnO.

Grain boundary diffusion of 67Ga in polycrystalline magnesium

Grain boundary (GB) diffusion of 67Ga in polycrystalline Mg was measured by the residual activity method in temperature range 639–872 K. An approximate evaluation procedure was proposed to calculate both volume diffusion coefficient D v and GB diffusivity P= sδD b ( s––segregation factor, δ––GB width, D b––GB diffusion coefficient).

Diffusion of the 65Zn radiotracer in ZnO polycrystalline ceramics

Zinc self-diffusion coefficients were measured in polycrystalline ZnO of high density (>99% of the theoretical density) and of high purity (> 99.999%). The diffusion experiments were performed from 1006 to 1377 °C, in oxygen atmosphere, for times between 16 and 574 h. The diffusion profiles were established by means of Residual Activity Method using the 65Zn radioactive isotope as zinc tracer. In our experimental conditions, the zinc volume diffusion coefficients can be described by the following Arrhenius relationship: D(cm²/s) = 1.57×10-3 exp[(-2.66 ± 0.26) eV/kT]. In the same experimental conditions, the grain-boundary diffusion coefficients are approximately 4 orders of magnitude greater than the volume diffusion coefficients, and can be described by the Arrhenius relation: D'delta (cm³/s) = 1.59×10-6 exp[(-2.44 ± 0.45) eV/kT], where D' is the grain-boundary diffusion coefficient and delta is the grain boundary width.

Ni and Ga diffusion in polycrystalline Ni 3Ga

The volume and grain boundary (GB) diffusion of 63Ni and 67Ga radiotracers in polycrystals of Ni 3Ga intermetallic was studied in the vicinity of the stoichiometric composition A 3B (23.5–28.3 at.% Ga). Both volume and GB diffusivity was investigated in the temperature interval 773–1373 K by the residual activity method. The obtained Ga volume diffusivity increases with increasing Ga concentration x Ga; the increasing tendency of Ni volume diffusivity with increasing x Ga is pronounced at lower temperatures. GB diffusivity of both Ga and Ni in Ni 3Ga are close one to another and—contrary to the diffusion behavior of components in Ni 3Al—they do not show any significant dependence on x Ga.

Grain-boundary diffusion of nickel in Cr-, Fe-, and Zr-modified Ni 3Al intermetallic

Tracer grain-boundary diffusion of 63Ni in slightly hypostoichiometric ( x Al < 25 at.%) Ni 3Al alloys containing several percents of Cr, Fe and Zr was studied using both serial sectioning and residual activity methods. Measurements of grain-boundary diffusivity P were carried out in the temperature interval 873–1273 K. It was found that the additions of Cr, Fe and Zr decrease the P and increase the activation enthalpy of 63Ni grain-boundary diffusion.

Short-circuit diffusion in NiAl alloys

Abstract The tracer grain boundary diffusivity, P, of nickel in polycrystalline NiB, Ni-9 at%AlB and in NiAlB intermetallic has been measured with boron concentrations xB up to 0.3 at% B. The measurements were done by the residual activity method in the temperature interval from 773 to 1073 K. It was observed that P decreases with growing concentration of boron in NiB and Ni-9 at% AlB. This behaviour is similar to the dependence of P on xB in Ni3Al, reported in our previous paper. In boron-doped NiAl intermetallic, on the other hand, P does not depend on xB.

Grain-boundary diffusion of chromium in Ni3Al intermetallic modified by Fe, Cr and Zr

Tracer grain-boundary diffusion (GBD) of chromium Cr-51 in slightly hypostoichiometric (xAl < 25 at%) Ni3Al alloys containing several at. pct of Fe, Cr and Zr was studied using both serial sectioning and residual activity methods. Measurements of the product of the diffusion coefficient in grain boundary and the width of grain boundary, P, were carried out in the temperature interval from 773 to 1273 K. It was found that the addition of Fe and Cr up to about 6 at% does not alter the diffusion characteristics of Cr grain-boundary diffusion. The addition of a small amount of Zr, on the other hand, tends to increase the activation enthalpy and pre-exponential factor of Cr grain-boundary diffusion.

Influence of boron doping and stoichiometry upon the Ni grain boundary diffusion in Ni 3Al intermetallic

63Ni GB diffusion in polycrystalline Ni 3Al intermetallic was studied using the residual activity method in the temperature interval 773 – 1173 K. Experimental alloys, which compositions varied around the stoichiometry (24.0 – 26.8 at.% Al), were prepared without boron and with two different concentrations of boron (0.106 and 0.268 at.% B). Expressive differences were observed between the nickel GB diffusivity in pure stoichiometric alloy on one hand and in off-stoichiometric and boronized alloys on the other hand. Proposed interpretation of observed results is based ( i) on the influence of boron additions and deviations from stoichiometry on degree of order of GB's, ( ii) on accelerating effect of extended defects (columnar cavities) in GB's upon GB diffusion, and ( iii) on strong interaction between nickel and boron atoms that, most likely, causes an increase in activation energy of GB diffusion.

Influence of Boron on Nickel Grain Boundary Self-Diffusion in Ni3Al Intermetallic

Grain boundary diffusion of 63Ni in pure and boron-doped Ni3Al intermetallic was studied at temperatures 833 and 893 K using the residual activity method. The decrease of the triple product P with increasing boron concentration was observed.

Grain boundary self-diffusion of 63Ni in austenitic Ni–Cr alloys

The tracer diffusion of the isotope 63 Ni in Ni and three austenitic Ni–Cr alloys containing 9.8, 20.1 and 29.1 wt.% Cr have been studied from 853 to 1203 K using a residual activity method. It appears that, within the frames of experimental error, the activation enthalpy and pre-exponential factor do not depend on the composition of the alloys. The differences between the Arrhenius parameters obtained in this work for Ni diffusion and the analogous parameters published earlier for the diffusion of Fe and Cr in Ni–Ce–Cr alloys were discussed in terms of Ni, Fe and Cr interaction with C impurities.