186,203 research outputs found
Martensitic transformation in TiPd shape memory alloys studied by PAC method with Cd-111 probes
No full textPerturbed angular correlation (PAC) method was applied to study the martensitic phase transition of the TiPd shape memory alloy doped with In-111/In-111 Cd probe atoms. The hyperfine interaction parameters and their concentration and temperature dependences for probes with cubic and noncubic surroundings of the lattice sites, consistent with the respective crystal structures in martensite and austenite phase, were determined. A strong dependence of the martensite start temperature (M-S) and shape of the hysteresis loop (T-H) on the small admixture of the In impurities in TiPd compound was evidenced. The observed decrease in the M-S depends not only on the amount of the third element, but also on the element itself. The data were compared with those obtained with Hf-181/Ta-181 probes in TiPd alloy with hafnium admixture. (C) 2010 Elsevier B.V. All rights reserved
Hyperfine interactions of Ta-181 and Cd-111 in Zr(2)RhC16 compound
No full textThe hyperfine quadrupole interaction parameters and the character of the EFG temperature dependence for Hf-181/Ta-181 and In-111/(111) Cd probes in Zr2Rh compound were determined by means of the perturbed angular correlation (PAC) technique. The site location of In-111/Cd-111 probes in both 8(h)-Zr and 4(a)-Rh positions was determined. (c) 2007 Elsevier B.V. All rights reserved
Hf2Ni and Zr2Ni compounds studied by PAC with Cd-111 probes
No full textThe perturbed angular correlation method (PAC) was applied to investigate the lattice location of implanted In-111 probe ions in Hf2Ni and Zr2Ni intermetallic compounds. It is Concluded that the In-111/Cd-111 probe nuclei experiencing the highly asymmetric electric field gradient (EFG) Occupy the unique hafnium or zirconium 8(h) sites in the investigated phases. Above room temperature, the EFGs decrease linearly with temperature. The results are compared with that of previous PAC measurements with Ta-181 probes
The Zr2Al and Zr3Al compounds studied by PAC with Ta-181 and Cd-111 probes
No full textThe perturbed angular correlation technique was applied to study the electric field gradients of In-111/Cd-111 and Hf-181/Ta-181 radioactive probe atoms in the compounds Zr2Al and Zr3Al. In both matrices Hf-181/Ta-181 was found to substitute into the Zr sites. The In-111/Cd-111 probes were assigned to the unique Al site in the Zr2Al compound, while in the Zr3Al compound they were distributed between the unique Zr and Al positions of this lattice, with a clear preference for the Al site. The temperature dependences of the various quadrupole frequencies were measured in the temperature range from 20 to 1100 K. (C) 2003 Elsevier B.V. All rights reserved
The hafnium aluminides HfAl3 and Hf2Al3 studied by perturbed angular correlations with 181Ta and 111Cd probes
No full textThe electric quadrupole hyperfine interactions for Hf-181/Ta-181 and In-111/Cd-111 probes in the polycrystalline hafnium aluminides HfAl3 and Hf,AI, were measured in the temperature range 30-1100 K. On the basis of the similarities of the numbers, sizes and asymmetries of electric field gradients, lattice site allocations were made. In all matrices, Hf-181/Ta-181 was found to substitute into the Hf site. The In-111/Cd-111 impurities were also assigned to the Hf lattice site in the low-temperature phase of HfAl3, which has DO23 structure, but appear to substitute into the two non-equivalent Al sites in the Hf2Al3 phase, which has Fdd7 crystallographic structure. (C) 2000 Elsevier Science BN. All rights reserved
Switching of In-111 impurity sites in the HfAl2 lattice
No full textPerturbed angular correlation measurements in the HfAl2 C14-type Laves phase exhibit a very surprising temperature behavior of the ion-implanted In-111 probe atoms. Below 370 K the In-111 impurities are located at the unique hafnium site. Above 400 K they occupy the two aluminum sites, however with a clear preference of the 2(a) site. This process, which is fully reversible when heating and cooling the sample, is attributed to atomic size effects. (C) 2001 Elsevier Science B.V. All rights reserved
The HfAl2 and ZrAl2 Laves phases studied by Ta-181 and Cd-111 perturbed angular correlation spectroscopy
No full textUsing perturbed angular correlation (PAC) spectroscopy and Hf-181/Ta-181 and In-111/Cd-111 radioactive probes, the electric field gradients (EFGs) in the ZrAl2 and HfAl2 Laves phases were measured in the temperature range 20-1100 K. In both matrices, Hf-181 was found to substitute at the unique Hf/Zr site. In the ZrAl2 compound, the In-111 probes were assigned to the two Al sites. The relative fractions of the corresponding EFGs indicate a strong preference of these impurities in favor of the 2(a) Al site over the 6(h) Al site. In the HfAl2 compound, the In-111 impurities substitute for Hf up to 370 K and reach the Al sites only above 420 K. In both compounds and for both radioactive probes, the temperature dependence of the quadrupole interaction frequencies was measured. It is interesting to note that, for Ta-181 in both compounds, they increase with temperature. (C) 2002 Elsevier Science B.V. All rights reserved
Solution of (111)In impurities in the Hf(Zr)(3)Al(2) minority phases of Hf(Zr)(4)Al(3) samples
No full textThe hyperfine quadrupole interactions of (111)In/(111)Cd probes in the polycrystalline isostructural Zr(4)Al(3) and Hf(4)Al(3) compounds were studied. Strong preference of (111)In solute for the Zr(3)Al(2) and Hf(3)Al(2) phases occurring as contaminant fractions in the measured samples was observed
Solid state amorphisation reaction in evaporated Hf/Ag multilayer films
No full textThe perturbed angular correlation technique (PAC) was applied to observe the interdiffusion in Hf/Ag multilayers. Sample with 10 Ag layers of 40 Angstrom intercalated with Hf layers of 100 Angstrom was implanted with In-113 probes or irradiated with thermal neutrons in order to achieve the presence of the radioactive PARC probes In-111 or Hf-181, respectively. A solid slate reaction caused by thermal diffusion led to the formation of an amorphous structure in the investigated samples
Lattice location of Ta-181 and Cd-111 probes in hafnium and zirconium aluminides studied by perturbed angular correlation
No full textThe perturbed angular correlation technique was applied to study the lattice location of the In-111/Cd-111 and Hf-181/Ta-181 probe atoms in hafnium and zirconium aluminides. Compounds of different stoichiometrics and crystallographic structures were the subject of investigation. According to the expectation, in all investigated compounds Hf-181/Ta-181 probes occupy the Hf(Zr) crystallographic sites. The In-111/Cd-111 probes are placed at the sites of all constituent Metals-aluminum, hafnium and zirconium, depending on the crystallographic structure of compound, concentration Of the constituent metals and temperature of the sample
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