Pure Metal Values Research Articles

Delocalization and charge transfer studies of PERMENDUR49, KOVAR and Ti50Co50 alloys from relative K X-ray intensity ratios

Kβ-to-Kα X-ray intensity ratios of Fe, Ni, Co, Ti, V in pure form and PERMENDUR49 (Fe49Co49V2), KOVAR (Fe54Ni29Co17) and Ti50Co50 alloys were calculated in order to determine valence-electron structure of the samples. The obtained experimental Kβ-to-Kα X-ray intensity ratios were found to be 0.1252 ± 0.0025, 0.1256 ± 0.0027, 0.1298 ± 0.0026, 0.1327 ± 0.0028, 0.1346 ± 0.0027 for pure Ti, V, Fe, Co and Ni, respectively. These values of present pure metals have increased with the increment in atomic number of these pure metals. Also, although the obtained these values for metal atoms in PERMENDUR49, Ti50Co50 and for Fe, Ni metal atoms in KOVAR approximately compatible with respect to results same pure metals, the obtained experimental Kβ-to-Kα X-ray intensity ratios for Co in KOVAR are significantly different from the appropriate values for pure Co metal. Then, the valence-electron populations of these alloys were calculated in order to answer as to why the characteristic properties of the studied alloys are distinct from each other. The valence-electron structures of these metals in pure form and alloys were determined by comparison of the calculated Kβ-to-Kα X-ray intensity ratios with the results of multi-configurations Dirac-Fock (MCDF) calculations to understand the charge-transfer and/or delocalization phenomena of these alloys. The experimental n3d values were found to be 3.2694, 4.7905, 7.7941, 7.9618, 8.500 for pure Ti, V, Fe, Co and Ni, respectively. The calculated 3d and 4s, 4p electron population values for Ti, V and Co in pure form have shown very little deviation from the appropriate values of Ti in Ti50Co50 and Co, V in PERMENDUR49. Also, the deviation for these values is greater for Fe, Ni, in KOVAR, Co in Ti50Co50, Fe in PERMENDUR49 with respect to the corresponding values of pure metals and the largest deviation for these values is observed for Co metal atoms in KOVAR alloy. We have also calculated the weighted average numbers of 3d and 4s, 4p electrons per one atom as well as the superposition of 3d and 4s, 4p electrons, as obtained from pure metal values. While the obtained superposition 3d electron numbers of present alloys exhibit a decreasing tendency as S3d(Ti50Co50) < S3d(PERMENDUR49) < S3d(KOVAR), the obtained weighted average 3d electron numbers of present alloys has opposite tendency (A3d(KOVAR) < A3d(PERMENDUR49) < A3d(Ti50Co50)). The analysis show that valance-electron population of elements in these alloys indicated differences with respect to the pure metal and each other. These differences can be related to type of alloy elements, concentration of alloy elements, charge transfer and/or delocalization phenomena between of individual metal atoms in alloys. Also, the obtained results show that there are alloying effect on valence-electron population due to charge transfer and/or delocalization phenomena.

Scatter of Young's Modulus E and of sound velocity values of pure metals

Abstract There exists a large scatter of Young's moduli handbook values. The most important reason for this is the diversity of measurement methods used in various laboratories. The average E-value of these measurements is not the best one. A more accurate value may be obtained by verification of handbook data for four elastic coefficients E, G, B and PR, using two known relations for isotropic materials. In some cases discussed by the author, a correlation exists between the E-moduli and the latent fusion heat magnitude sequences for a certain group of metals, which may be used for verification of some E-values. The E-values obtained in a previous MP-paper by the author published in Materials Testing 11–12/2004, using the relative method of calculation based on a correct E-value for pure aluminum, seem to be superior to those obtained directly by the formula E = V2d.

Kβ-to-Kα X-ray intensity ratio studies on the changes of valence electronic structures of Ti, V, Cr, and Co in their disilicide compounds

Kβ-to-Kα X-ray intensity ratios of Ti, V, Cr, and Co in pure metals and their disilicide compounds have been measured following excitation by 59.54 keV γ-rays from a 200 mCi 241Am point-source. The Kβ-to-Kα intensity ratios of all these metals in the disilicide compounds are found to be less than the corresponding ratios for pure metals. Comparison of the measured Kβ-to-Kα intensity ratios for the disilicides and pure metals with the multiconfiguration Dirac–Fock calculations indicates increase of the 3d electron populations of Ti, V, Cr, and Co in the disilicides from their pure metal values suggesting the rearrangement of electrons between 3d and 4s states of the individual metal atom. This rearrangement is found to be opposite to that observed in our previously reported work on NiSi 2 and CuSi 2.

Influence of chemical effect on the K β-to-K α X-ray intensity ratios of Ti, V, Cr and Fe in TiC, VC, CrB, CrB 2 and FeB

K β-to-K α X-ray intensity ratios of Ti, V, Cr and Fe have been measured in pure metals and in the compounds of TiC, VC, CrB, CrB 2 and FeB following excitation by 59.54 keV γ-rays from a 200 mCi 241Am point-source. Comparison of the measured K β-to-K α X-ray intensity ratios with the multiconfiguration Dirac–Fock calculation indicates significant change in the 3d electron population of Ti in TiC and Cr in CrB and CrB 2 from their pure metal values and almost no change for V in VC and Fe in FeB. In TiC we have found a transfer of 0.65±0.16 electrons from the 3d state of Ti whereas for CrB and CrB 2 the 3d electron population of Cr increases by 0.60±0.30 and 0.75±0.30 electrons, respectively, over the pure metal value. Although our charge transfer result for TiC is closer to the prediction of the APW band structure calculations no firm conclusion can be made from our VC result. Our result for the relative K β-to-K α ratio of VC with respect to pure V does not agree with the previously reported experimental result of Chang et al. (J. Phys. B: At. Mol. Opt. Phys. 27 (1994) 5251). Our results for CrB and CrB 2 predict transfer of electrons from boron to 3d band of Cr in agreement with some of the earlier published results of magnetic and Hall effect measurements.

Influence of solid-state effects on theKβ-to-Kαx-ray intensity ratios of Ni and Cu in various silicide compounds

$K\ensuremath{\beta}$-to-$K\ensuremath{\alpha}$ x-ray intensity ratios of Ni and Cu in various silicide compounds ${\mathrm{Ni}}_{2}\mathrm{Si},$ NiSi, ${\mathrm{Ni}}_{2}{\mathrm{Si}}_{3},{\mathrm{NiSi}}_{2},{\mathrm{Cu}}_{2}\mathrm{Si},$ CuSi, and ${\mathrm{CuSi}}_{2}$ have been measured following excitation by 59.54 keV \ensuremath{\gamma} rays from a 200 mCi ${}^{241}\mathrm{Am}$ point source. Comparison of the intensity ratios for Ni with the multiconfiguration Dirac-Fock calculations indicates decreasing $3d$ electron population with the increase of silicon concentration, a trend similar to the one predicted by the previous theoretical calculations [O. Bisi and C. Calandra, J. Phys. C 14, 5479 (1982)]. However, quantitatively our results for the Ni $3d$ electron population are different from the results reported there. The intensity ratios for Ni and Cu in disilicide compounds indicate enhancement of the $K\ensuremath{\beta}$-to-$K\ensuremath{\alpha}$ ratio over the pure metal values, but for the other silicide compounds the Ni intensity ratios show opposite behavior than Cu, suggesting a difference in the nature of electron delocalization.

Alloying effect on K beta -to-K alpha intensity ratios in TixNi1-x and CrxNi1-x alloys studied by gamma -ray fluorescence and fast proton ionization.

K x-ray intensity ratios in Ti x Ni 1-x and Cr x Ni 1-x alloys have been measured for different compositions x, using 59.54-keV γ-ray fluorescence (γRF) and 4.07-MeV-proton ionization. The intensity ratios were found to be higher than those of pure metal values for Ti in Ti x Ni 1-x alloys for x=0. 35 and for Cr in Cr x Ni 1-x alloys for x=0.20. The γRF results are supported by the proton-induced x-ray emission (PIXE) results for all the constituent metals of both the alloys. The results are discussed on the basis of 3d-electron transfer or rearrangement in the individual metals of corresponding alloys

TUNABLE-SAMPLING-DEPTH ELECTRON ENERGY LOSS SPECTROSCOPY AND AUGER ELECTRON SPECTROSC-OPY STUDIES OF Pb/Ni(001) INTERFACE

We have studied the interface formation process of Pb/Ni (001) system by means of tunable-sampling-depth electron energy loss spectroscopy (TELS) and Auger electron spectroscopy (AES). During the deposition of Pb, the AES peak height ratio of Pb to Ni versus time of deposition consists of three segments with the two turning points corresponding to 1 mono-layer (ML) and 2 ML respectively, indicating the Franck-Van der Merwe, i.e. layer by layer growth mode. Also during the Pb deposition, the Pb 6s band ELS peak appears as the Pb coverage is beyond 1 ML, while the Pb bulk plasmon peak appears at about 2 ML of Pb coverage. During the whole process of deposition and annealing, the ELS peak position and width of the Pb bulk plasmon peak, the 6s band peak as well as the Ni 3p band peak maintain their own pure metal values, and there was no new bulk plasmon peak. In view of all these facts, we have reached the conclusion that there is no intermixing of Pb with Ni and the interface of this system is abrupt.

The effect of pressure and temperature on the electric field gradient at111Cd on In sites in intermetallic In-Bi

The time-dependent perturbed angular correlation (TDPAC) technique was used to measure the electric field gradient (EFG) as a function of pressure for the compounds InBi, In2Bi and In5Bi3 and as a function of temperature for In5Bi3 111Cd as probe on the indium sites. It was possible to identify the phase transition induced by pressure in the compound In2Bi as a transformation to the structure of the compound In5Bi3 with defects. Estimates were made of the volume and the explicit temperature dependences of the EFG for the compounds In2Bi and In5Bi3. The high values of the volume dependence of the EFG obtained for In2Bi is comparable to the known values for pure metals. The importance of anharmonic effects in the EFG shows up for In5Bi3.

Note on Some Properties of Gamma Brass

Electrical resistance and magneto-resistance of gamma brass were measured at liquid helium, liquid nitrogen and room temperature. Moreover, Hall coefficient and thermoelectric power of gamma brass were measured at room temperature. Data of the electrical resistance are presented for several samples having various concentrations. In the relation between specific resistivity and concentration, a minimum occurs at about 34 wt.% copper in the curve of resistivity v s . concentration. The value of the Hall coefficient and of the thermoelectric power are comparable to the values of pure metals. The magneto-resistance is small at room temperature but becomes large at liquid helium temperature. Differences of the physical properties between gamma brass and bismuth are discussed.

Self-diffusion of gold in gold-nickel alloys

The self-diffusion rate of gold in gold-nickel alloys was measured as a function of composition and temperature in the region of complete solid solubility, using an autoradiographic method to trace the diffusion of Au 198. The diffusion data reveal no anomalies that correlate with the miscibility gap. However, the D Au ∗ , D o,Au ∗ and Q Au ∗ values show maximum deviations from the linear averages of the pure metal values in the composition range corresponding to the minimum in the solidus curve.