scholarly journals The phase structure and morphology of electrodeposited nickel-cobalt alloy powders

2011 ◽  
Vol 43 (3) ◽  
pp. 313-326 ◽  
Author(s):  
M. Spasojevic ◽  
L. Ribic-Zelenovic ◽  
A. Maricic
Keyword(s):  
Current Density ◽  
Amorphous Powder ◽  
Nanocrystalline Powders ◽  
Content Increase ◽  
Nickel Powders ◽  
Electrodeposited Nickel ◽  
Current Densities ◽  
Two Phases ◽  
A Current ◽  
Deposition Current Density

Cobalt and nickel powders of three different compositions: Ni0.8Co0.2, Ni0.55Co0.45 and Ni0.2Co0.8 were obtained by electrodeposition from an ammonium chloride-sulphate solution. It was shown that the microstructure and morphology of the powders depended on the deposition current density as well as on the bath composition. Amorphous powder of Ni0.8Co0.2 was obtained at the current density higher than 200 mA cm-2, but nanocrystalline powders having the same composition were obtained at current densities lower than 200 mAcm-2. The nanocrystalline powders with lower Ni contents (0.55 and 0.2) obtained at a current density ranging from 40 mA cm-2 to 450 mA cm-2 were solid solutions of two phases, FCC (?-Ni) and HCP (?-Co) ones. The increase of the HCP phase in the powder was a result of both the Co content increase in the powder and decrease of the deposition current density.

Facet Topography and Dislocation Structure as a Possible Source for Electrical Heterogeneity in [001] TILT Bicrystals of YBa2Cu3O7-δ

1996 ◽  
Vol 54 ◽  
pp. 338-339
Author(s):  
I-Fei Tsu ◽  
D.L. Kaiser ◽  
S.E. Babcock
Keyword(s):  
Grain Boundary ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Electromagnetic Properties ◽  
Length Scale ◽  
Density Values ◽  
Current Densities ◽  
Applied Fields ◽  
A Current

A current theme in the study of the critical current density behavior of YBa2Cu3O7-δ (YBCO) grain boundaries is that their electromagnetic properties are heterogeneous on various length scales ranging from 10s of microns to ˜ 1 Å. Recently, combined electromagnetic and TEM studies on four flux-grown bicrystals have demonstrated a direct correlation between the length scale of the boundaries’ saw-tooth facet configurations and the apparent length scale of the electrical heterogeneity. In that work, enhanced critical current densities are observed at applied fields where the facet period is commensurate with the spacing of the Abrikosov flux vortices which must be pinned if higher critical current density values are recorded. To understand the microstructural origin of the flux pinning, the grain boundary topography and grain boundary dislocation (GBD) network structure of [001] tilt YBCO bicrystals were studied by TEM and HRTEM.

scholarly journals Effect of deposition current density and annealing temperature on the microstructure and magnetic properties of nanostructured Ni-Fe-W-Cu alloys

2019 ◽  
Vol 51 (2) ◽  
pp. 209-221 ◽  
Author(s):  
Milica Spasojevic ◽  
Dusan Markovic ◽  
Miroslav Spasojevic ◽  
Zoran Vukovic ◽  
Aleksa Maricic ◽  
...  
Keyword(s):  
Current Density ◽  
Amorphous Matrix ◽  
Ammonium Citrate ◽  
High Current ◽  
Cathodic Polarization Curve ◽  
Cu Alloy ◽  
Powder Particles ◽  
Current Densities ◽  
Deposition Current Density ◽  
Microstructure And Magnetic Properties

Ni-Fe-W-Cu alloy powders were obtained by electrodeposition from an ammonium citrate bath at current densities ranging between 70 and 600 mA cm-2. As the deposition current density increased, the contents of Fe and W in the alloy increased, and those of Ni and Cu decreased. The total cathodic polarization curve was recorded, and partial polarization curves for Ni, Fe and W deposition and hydrogen evolution were determined. The current efficiency of alloy deposition was measured. The powders contained an amorphous matrix and FCC nanocrystals of the solid solution of Fe, W and Cu in Ni. At high current densities, small-sized nanocrystals exhibiting high internal microstrain values were formed. Powder particles were dendrite- and cauliflower-shaped. The dendrites had a large number of secondary branches and higher-order branches containing interconnected globules. The density of branches was higher in particles formed at high current densities. The powders formed at high current densities exhibited higher magnetization. Annealing at temperatures up to 460?C resulted in structural relaxation, accompanied by an increase in magnetization. At temperatures above 460?C, amorphous matrix crystallization and FCC crystal growth took place, accompanied by a decrease in magnetization.

scholarly journals Na channel distribution in vertebrate skeletal muscle.

1986 ◽  
Vol 87 (6) ◽  
pp. 907-932 ◽  
Author(s):  
J H Caldwell ◽  
D T Campbell ◽  
K G Beam
Keyword(s):  
Skeletal Muscle ◽  
Current Density ◽  
Sharp Decrease ◽  
Na Channel ◽  
Na Current ◽  
Na Currents ◽  
Current Densities ◽  
Kinetics Of ◽  
A Current ◽  
Vertebrate Skeletal Muscle

The loose patch voltage clamp has been used to map Na current density along the length of snake and rat skeletal muscle fibers. Na currents have been recorded from (a) endplate membrane exposed by removal of the nerve terminal, (b) membrane near the endplate, (c) extrajunctional membrane far from both the endplate and the tendon, and (d) membrane near the tendon. Na current densities recorded directly on the endplate were extremely high, exceeding 400 mA/cm2 in some patches. The membrane adjacent to the endplate has a current density about fivefold lower than that of the endplate, but about fivefold higher than the membrane 100-200 micron from the endplate. Small local variations in Na current density are recorded in extrajunctional membrane. A sharp decrease in Na current density occurs over the last few hundred micrometers from the tendon. We tested the ability of tetrodotoxin to block Na current in regions close to and far from the endplate and found no evidence for toxin-resistant channels in either region. There was also no obvious difference in the kinetics of Na current in the two regions. On the basis of the Na current densities measured with the loose patch clamp, we conclude that Na channels are abundant in the endplate and near-endplate membrane and are sparse close to the tendon. The current density at the endplate is two to three orders of magnitude higher than at the tendon.

scholarly journals The effect of temperature on structural changes of NI55CO45 amorphous powder

2004 ◽  
Vol 36 (2) ◽  
pp. 105-112 ◽  
Author(s):  
M. Spasojevic ◽  
Aleksa Maricic ◽  
Lidija Rafailovic
Keyword(s):  
Current Density ◽  
Electrical Resistance ◽  
Structural Changes ◽  
Crystallization Process ◽  
Amorphous Powder ◽  
Solution Temperature ◽  
Specific Chemical ◽  
A Current ◽  
Shape And Size ◽  
Cobalt And Nickel

Cobalt and nickel alloy powders were obtained by electrochemical deposition on a titanium cathode from an ammonium solution of cobalt and nickel sulfate. Powders of a specific chemical structure and composition, particle shape and size were obtained by an appropriate choice of electrolysis parameters, current density, deposit growth rate and solution temperature and composition. Within the current density range of 5 - 450 mAcm-2, the current density did not significantly affect the chemical composition of the powders, but had a significant effect on the particle structure, shape and size. Crystal particles formed at a current density lower than 30 mAcm-2. Amorphous powders were obtained at a current density higher than 50 mAcm-2. Structural changes of the obtained amorphous powder of 55mol.% Ni, 45 mol.% Co, pressed under the pressure of 100 MPa, were investigated by measuring the temperature dependence of electrical resistance in isothermal and non-isothermal conditions varying from room temperature to 750?C. The process of thermal stabilization of defects that appeared during pressing occurred within the temperature range of 200-390?C. The DSC method was used to determine that the powder crystallization process occurred in two stages with peak temperatures of the exothermal maximum in the first and second stage of T1 = 438?C and T2 = 573?C, respectively. A distinct correlation between the change of electrical resistance and the crystallization process was established. The reduction of electrical resistively occurs during each crystallization stage.

Surgical Diathermy

2011 ◽  
Author(s):  
Patrick Magee ◽  
Mark Tooley
Keyword(s):  
Current Density ◽  
The Body ◽  
Heating Power ◽  
Driving Voltage ◽  
Physiological Effects ◽  
Heating Effect ◽  
Surgical Tool ◽  
Average Current ◽  
Current Densities ◽  
A Current

As discussed in Chapter 4, when a voltage is applied across a conductor, a current will flow. If the voltage is applied across the body via suitable electrodes the body becomes part of the circuit and a current will also flow, the magnitude depending on the properties of the tissues in its path, particularly the resistance. This current can cause heating or other physiological effects, depending on the frequency of the driving voltage. The effects of the domestic mains current flowing through the body was discussed in Chapter 6, but different effects occur as the frequency of the voltage is increased. As the frequency goes up, the heating increases but the tissue stimulation decreases and, at frequencies above 100 kHz (i.e. radio frequencies), the effect is entirely heating. This heating effect in the body by electric current is called diathermy, but the location, concentration and how this heat is used is dependant on the electrode design and the current concentration or current density at any point in the circuit. For a certain applied voltage, the average current throughout the circuit will be the same. The current density is the current per unit area, and so if the material in which the current passes is smaller, the heating effect increases. The resistance of the material is proportional to its size, so as the material becomes smaller then its resistance gets larger. The heating power is the product of the current squared and the resistance (power = I2 × R). Surgical diathermy (or electrosurgery) is where either one or both of the electrodes are very small, and it is used to cut and coagulate tissue. The smaller electrode can be made into a pointed surgical tool and localised heating will occur at the tip of the instrument. The smaller and more pointed the instrument is, the greater the current density will be at the tip. This electrode is classified as the active or live one. The current densities around this electrode can be as much as 10 A cm−2, and the total heating power typically around 200 W.

AN INVESTIGATION ON THE EFFECT OF ELECTROCHEMICAL ADSORBATES ON PROPERTIES OF ELECTRODEPOSITED NANOCRYSTALLINE Fe–Ni ALLOYS

2013 ◽  
Vol 12 (01) ◽  
pp. 1350002 ◽  
Author(s):  
A. SANATY-ZADEH ◽  
K. RAEISSI ◽  
A. SAIDI
Keyword(s):  
Grain Size ◽  
Current Density ◽  
Cathode Surface ◽  
Iron Hydroxide ◽  
Ni Alloys ◽  
Fe Content ◽  
Iron Nickel ◽  
Current Densities ◽  
Eis Measurements ◽  
Deposition Current Density

Iron–Nickel nanocrystalline alloys were electrodeposited from a simple chloride bath using different current densities. The composition and grain size of deposited alloys were in the range of 29–42% Ni and 8–11 nm, respectively. The alloy deposited at lower current density showed higher microhardness, which is most probably due to its higher Fe content and lower grain size. EIS measurements showed that the iron hydroxide species can be formed and adsorbed onto the cathode surface during the deposition. Such species showed an inhibitive effect not only on Ni ion reduction but also on grain growth. By increasing the deposition current density, the adsorption tendency of iron hydroxide was reduced which caused an increase in grain size and Ni percentage of the alloy produced.

Temperature dependence of the soft magnetic character of Fe73.5Cu1Nb3Si13.5B9 amorphous and nanocrystalline alloys

2003 ◽  
Vol 18 (5) ◽  
pp. 1035-1038 ◽  
Author(s):  
J. Gonzáz
Keyword(s):  
Amorphous Alloy ◽  
Current Density ◽  
Curie Point ◽  
Amorphous Matrix ◽  
Body Centered Cubic ◽  
Soft Magnetic ◽  
Current Densities ◽  
Two Phases ◽  
Residual Amorphous Matrix ◽  
Magnetic Hardness

Results on microstructure and coercivity of current-annealed Fe73.5Cu1Nb3Si13.5B9 amorphous alloy treated at different current densities (12–56 A/mm2) and duration (0.5–720 min) are presented. Saturation magnetization and coercivity dependencies with the current density of the nanocrystalline samples is explained by considering the presence of two phases: nanocrystals of Fe(Si) body-centered cubic (bcc) grains and the residual amorphous matrix. An increase in the magnetic hardness observed when the sample was heated by current densities, giving rise to an increase in the sample temperature above the Curie point of the residual amorphous matrix, could be ascribed to exchange and dipolar decoupling of the Fe(Si)-bcc grains.

Structural Characterization of Electrodeposited Nickel-Iron Alloy Films

2010 ◽  
Vol 654-656 ◽  
pp. 2430-2433 ◽  
Author(s):  
Yusrini Marita ◽  
Iskandar Idris Yaacob
Keyword(s):  
Dislocation Density ◽  
Crystallite Size ◽  
Current Density ◽  
Iron Alloy ◽  
Face Centered Cubic ◽  
Alloy Films ◽  
Nickel Iron ◽  
Current Densities ◽  
Nickel Iron Alloy ◽  
Deposition Current Density

Nickel-iron nanocrystalline alloy films were prepared on copper substrates by electrochemical deposition at various current densities of 6, 9.7, 11.5 and 15.2 A dm-2. X-ray diffraction measurements confirmed that all nickel-iron alloy films formed have face-centered cubic structure. The structural parameters such as the lattice constant, crystallite size, microstrain and dislocation density were determined for the nickel-iron alloy films. The crystallite size of the films reduced from 17 to 12.9 nm when the current densities were decreased. The reduction in crystallite size increased the dislocation density. Magnetic property measurements using alternating gradient magnetometer indicated that these alloys were ferromagnetic. The saturation magnetization Ms of nickel-iron alloy films increased with decreasing deposition current density, which was attributed to the increase of iron content. Nickel-iron alloy film prepared at deposition current density of 6 A dm-2 showed the maximum value of Ms. The coercivity of nickel-iron alloy films increased with decreasing current density, which was likely caused by reduction in crystallite size.

Electromigration Reliability of Electroplated Gold Interconnects

2014 ◽  
Vol 1692 ◽  
Author(s):  
Steve H. Kilgore ◽  
Dieter K. Schroder
Keyword(s):  
Current Density ◽  
Open Circuit ◽  
Constant Current ◽  
Measured Temperature ◽  
Lifetime Distributions ◽  
Current Densities ◽  
Log Normal ◽  
Equipment Application ◽  
A Current

ABSTRACTThe electromigration lifetimes of a very large quantity of passivated electroplated Au interconnects were measured utilizing high-resolution in-situ resistance monitoring equipment. Application of moderate accelerated stress conditions with current density limited to 2 MA/cm2 and oven temperatures in the range of 300°C to 375°C prevented large Joule-heated temperature gradients and electrical overstress failures. A Joule-heated Au film temperature increase of 10°C on average was determined from measured temperature coefficients of resistance (TCRs). A failure criterion of 50% resistance degradation was selected to avoid thermal runaway and catastrophic open circuit failures. All Au lifetime distributions followed log-normal statistics. An activation energy of 0.80 ± 0.05 eV was measured from constant-current electromigration tests at multiple temperatures. A current density exponent of 1.91 ± 0.03 was extracted from multiple current densities at a single constant temperature.

Electrically Assisted Compression of Tungsten Carbide and its Implications for Electrically Assisted Machining

2016 ◽  
Author(s):  
Brandt J. Ruszkiewicz ◽  
Laine Mears
Keyword(s):  
Tungsten Carbide ◽  
Current Density ◽  
Cutting Tools ◽  
Compression Tests ◽  
Machining Processes ◽  
Electrically Assisted ◽  
Maximum Current ◽  
Current Densities ◽  
Improve Surface Finish ◽  
A Current

It has been shown that electrically assisted machining has the ability to reduce cutting force, change chip type, and improve surface finish. However, the effect of electricity on tungsten carbide has not been examined, a material often used to create cutting tools used in electrically assisted machining. During machining processes, depending on the type of cut, a small amount of the tool may be in contact with the workpiece. This will lead to an increased current density at that point on the tool which could lead to undesired effects with respect to tool wear and life. This paper conducts electrically assisted compression tests on uncoated tungsten carbide rod to examine the effect of electricity on the material and determine if there are any current densities that cause large magnitude weakening of the tungsten carbide. It is concluded that there is a maximum current density that can be passed through tungsten carbide before thermal softening becomes a problem. At a current density lower than this threshold, electricity has little effect on the strength of the carbide. This work is related to past electrically assisted turning experimentation.

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