Search

In the process of minimizing stress in sputtered molybdenum (Mo) films for fabricating transition-edge sensor devices, we have investigated correlations between the stress and film deposition parameters. At a fixed sputtering power, the tensile stress of our film samples decreases toward both low and high ends of Ar pressure, suggestive of two physical mechanisms at work: an ‘atomic peening’ effect at low Ar pressure and the development of voids at high Ar pressure. We have also carried out correlative studies of the stress and electrical properties (including superconducting critical temperature and residual resistivity) of the film samples, and found that the results are complex. We have made extensive comparisons with the published results, and attempted to explain the discrepancies in terms of film deposition techniques, sample preparation and treatment, and dynamical ranges of measurements. It is fairly clear that the microscopic properties, including porosity and disorder, of Mo films may have significant impact on the correlations. [ABSTRACT FROM AUTHOR]

The residual resistivity, Hall effect, and magnetization of Co2YSi (Y = Ti, V, Cr, Mn, Fe, Co, Ni) Heusler alloys were considered at T = 4.2 K and in fields up to 100 kOe. It is shown that as the number of valence electrons z ranges from 26 to 32, significant changes in the residual resistivity ρ0, magnetization Ms, sign and magnitude of the normal R0 and anomalous RS Hall effect coefficients are observed during the transition from Co2TiSi to Co2NiSi. It is established that there is a clear correlation between the values ρ0, R0, RS and Ms, depending on the number z, which can be associated with the appearance of a half-metal ferromagnetic state and/or spin gapless semiconductor. As z changes, the anomalous Hall effect coefficient has a power-law dependence on the residual electrical resistivity with an exponent of k = 3.1, which diverges with existing theories but agrees well with the experimental data obtained earlier for similar half-metallic ferromagnetic Heusler alloys. [ABSTRACT FROM AUTHOR]

Soil discharge occurs when it is subjected to high impulse current, and it is closely associated with the impulse performance of grounding systems. In this paper, a new method is put forward to visualize the inner impulse discharge region of simulate soil (fine sand) directly, using X-ray imaging technology. According to the three views of the discharge region, the boundary surface of the discharge region can be obtained based on image filtering and edge extraction by 3-D reconstruction. On this basis, the ionization parameters (i.e., the residual resistivity of soil discharge region \rhores and the critical breakdown electric-field strength E_c ) are calculated by a finite-element method. The results show that discharge region volume enlarges with water content increasing, and \rho_{0} . E_c$ increases from 100 to 150 kV/m, as soil water content decreases from 5% to 2%. [ABSTRACT FROM AUTHOR]

Methods of X-ray diffraction analysis and measurements of residual resistivity have been used to study effects of electron irradiation in the temperature range of 250–330 K on the structural and phase state of the Cu-15 at % Al solid solution. The results obtained are explained by the presence in the Cu-Al alloys of an inhomogeneous short-range order of two types, i.e., low-temperature, α 2 type; and high-temperature, γ 2 type. [ABSTRACT FROM AUTHOR]

X-ray diffraction analysis and residual resistivity measurements are used to study the short-range order and fine crystal structure of the Pd-25 at % Ni solid solution deformed at room temperature and their changes during isochronous annealings. A short-range order was shown to exist in the deformed alloy; the structure of the order does not correspond to the L12 superstructure. During the annealing, the character of the order remains unchanged. Possible physical processes that cause the nonmonotonic changes in the short-range order, fine crystal structure parameters, and residual resistivity are considered. [ABSTRACT FROM AUTHOR]

The residual resistivity for 156 dilute alloys of 19 hosts of different groups of the periodic table has been studied on the basis of the single parametric model potential formalism. Ashcroft's empty core model (EMC) potential is explored for the first time with five different local field correction functions, viz, Hartree (H), Taylor (T), Ichimaru–Utsumi (IU), Farid et al. (F), and Sarkar et al. (S) to investigate the effect of the exchange and correlation on the aforesaid properties. The comparison of the presently computed outcomes with the available theoretical and experimental data is highly encouraging. The investigation of residual resistivity is found to be quite sensitive to the selection of local field correction function, showing a significant variation with the change in the function. [ABSTRACT FROM AUTHOR]

Partial discharge of soil occurs when a lightning current enters the ground, and the strength of partial discharge is closely related to the magnitude of its critical breakdown field strength. Therefore, how to accurately obtain the variation law of the typical soil critical breakdown field strength and residual resistivity is the key to realizing the safe operation of the grounding devices and cables in the ground. This paper first selects a variety of typical soils to study the influence of various factors on the morphology of the discharge channel, and then studies the calculation methods of the soil critical breakdown field strength and residual resistivity under the introduction of different discharge channel morphologies and structures, and further discusses the reason why typical soil media factors have a small impact on the critical breakdown field. The experimental results show that under the same conditions, the critical breakdown field strengths of different soils from small to large are sand soil, loam soil and Yellow cinnamon soil. The largest ratio of residual resistivity to initial resistivity of the three soils is sand soil. [ABSTRACT FROM AUTHOR]

Measurements of the residual resistivity of Nb are usually carried out in longitudinal magnetic fields > H ≈4.7 kOe. After annealing of Nb wires in helium or vacuum of 5·10 Torr a shift of the transition to normal conductivity towards higher fields (up to 9.3 kOe) was observed. This increase of the critical field is most likely caused by changes in the surface of the samples due to the annealing treatments. [ABSTRACT FROM AUTHOR]

The residual resistivity of copper stabilizer (/spl rho/), is deteriorated by the diffusion of chromium plated on the strand surface during heating of Nb/sub 3/Al strands. To improve this degradation, the copper stabilizer has been located on the center of the cross-section of the strand rather than near the strand surface. As a result, /spl rho/ is improved to one-sixth of previous value achieving 1.6/spl times/10/sup -10/ /spl Omega/m in a laboratory scale strand. The critical current density (J/sub c/) of this strand was 715 A/mm/sup 2/ at 12 T. This technique was applied to prototype strands to be used in a Nb/sub 3/Al Insert Coil developed in ITER R&D programme resulting in a /spl rho/ of 1.5/spl times/10/sup -10/ /spl Omega/m, which meets ITER specification. In addition, the improvement of J/sub c/ was also studied by two-stage reaction including a continuous heating procedure, which resulted in a J/sub c/ of 1130 A/mm/sup 2/ at 12 T and good longitudinal uniformity. [ABSTRACT FROM PUBLISHER]