Rotating Copper Disc Research Articles

Optimizacija performansi trenja i električnog otpora u električnim kontaktima grafit-bakar korišćenjem sive relacione analize zasnovane na Tagučiju

This study aims to investigate how the load, the intensity, and the polarity of electric current influence the frictional behavior and electrical resistance between a graphite pin loaded against a rotating copper disc. A pin-on-cylinder tribometer was utilized to achieve this. A gray relational grade obtained from gray relational analysis was employed to assess the performance characteristic in the Taguchi mixed L18 (2 1 x 3 2) method. The Taguchi design method determined the optimal control factors that affect the friction coefficient and electrical resistance. Analysis of variance (ANOVA) was employed to analyze the effects of the control parameters on the friction coefficient and electrical resistance of the contact. The experiment parameters included applied normal load (3, 5.5, and 8.5 N), electrical current (10, 25, and 30 A), and polarity (cathode and anode). The analysis results indicated that the polarity was the primary factor influencing the friction coefficient, while the electrical current was the most effective factor in the electrical resistance of the contact. The optimal control parameters for achieving the lowest friction coefficient values were X1Y3Z1, while for the lowest electrical resistance values were X2Y3Z3. Based on the gray relational analysis results, the optimal parameters for minimizing both the friction coefficient and electrical resistance were X1Y3Z1.

A CFD analysis of the rotating target holder of the 14-MeV neutron generator

An accelerator based 14-MeV neutron generator is installed at Institute for Plasma Research, Gandhinagar to generate high energy neutrons by using a water-cooled rotating tritium target. In this device, neutrons would be generated from the nuclear reaction 3H(D, n)4He by bombarding accelerated deuterium ions on a solid tritium target. The rotating target holder mainly consists of a rotating copper disc water-cooled case mounted on the rotating shaft. The high-energy deuterium ion beam impacted on solid TiT target fitted on the copper case imparting its energy to the case. This energy is taken away from the system through the water passing through the annulus cavity of the shaft. This paper presents details of the engineering CFD (computed fluid dynamics) analysis carried out for optimizing two important parameters of the rotating target. Firstly optimization of the location of flow parameters of the water as mass flow rate and Secondly optimization of speed of the rotating target and the design of fins inside the copper case.

Green Recycle of Copper Ions in Saccharin Sodium Wastewater by Direct Electrodeposition Using Rotating Thin Copper Disc Electrode

Green recycle and reuse of copper ions in saccharin sodium wastewater have been proved to be practically applicable, and the most difficult electrodeposition step of [CuCl4]2– to Cu0, much more difficult than normal Cu2+ to Cu0, has been successfully overcome by the rotating copper disk method. The developed method was precisely targeted at the demand of saccharin sodium wastewater and met the quality standard of reused copper product for original manufacturing process in Kaifeng Xinghua Special Chemical Ltd., the largest saccharin sodium salt manufacturer. Experimental data show that the rotating disk electrode significantly increased the reaction current in both lab scale and pilot scale, indicating that the disadvantages of the slight increase in the reaction current and low reaction rate in conventional copper electrodeposition have been successfully overcome. Impedance analysis revealed a huge reduction of dissociative electron-transfer capacitance and double-layer capacitance simultaneously. The ove...

A Cascade of Phase Transitions in Amorphous FeB Films

Samples of Fe–B alloys have been prepared by quenching a melt using a rotating copper disk and then were certified by XRD analysis. Some of the alloys were found to possess an amorphous structure. Fe–B amorphous ribbons exhibit a sequence of gyromagnetic effects that replace each other as the temperature of the sample changes. These features were interpreted using magnetometry.

Influence of Annealing at Various Temperatures on the Structure and Hardness of Amorphous Ribbons of the Al85Y8Ni5Co2 Alloy

Aluminum-based metal glasses are a promising new family of materials. However, the influence of thermal treatment on the structure and properties of amorphous alloys of the Al–Y–Ni–Co system is still not studied in detail. In this work, amorphous ribbons of the Al85Y8Ni5Co2 alloy are formed by quenching on a rotating copper disc. The influence of annealing in vacuum at temperatures from 100 to 500°C for 30 min on the structure and hardness of these ribbons is investigated. To investigate the variations occurring in their structure after thermal treatment, scanning electron microscopy, X-ray structural analysis, and differential scanning calorimetry are used. To investigate the influence of annealing on mechanical properties of ribbons, the Vickers microhardness is measured. Conclusions on the variation in hardness depending on the structure of ribbons of the Al85Y8Ni5Co2 alloy are made based on these results. It is established that their microhardness increases with an increase in temperature, reaching the maximal value of 575 ± 7 HV after annealing at 350°C, and then decreases with a further increase in the thermal-treatment temperature. It is shown that ribbons of the Al85Y8Ni5Co2 alloy remain totally amorphous after annealing at t ≤ 250°C for 30 min, and crystalline phases are absent in the structure. An abrupt increase in hardness after annealing at 350°C is associated with the formation of nanocrystals of the aluminum solid solution 10–30 nm in size in an amorphous matrix surrounded by the residual amorphous matrix, while its further decrease is caused by an increase in the size of these crystals and the appearance of Al3Yand Al19Ni5Y3 intermetallic compounds in the structure.

Механические свойства магниевых сплавов, полученных по технологии, включающей быструю кристаллизацию и последующее компактирование

The structure and mechanical properties of magnesium alloys containing aluminum, calcium and rare earth metals (Y, Nd, La, Yb), which were obtained by extruding pellets made from the alloy ribbons bystrozakristallizovannyh. Tapes magnesium alloys obtained by quenching from the liquid state by casting on the outer side surface of a rapidly rotating copper disc in a helium atmosphere that provides a high cooling rate during solidification alloys 106K / s. Briquettes izgotalivalis at room temperature. Most of them have been further subjected to extrusion precipitate at 150-200 ° C for the purpose of sealing. The resulting preform was extruded into rods with a diameter of 4.3 mm at a draw ratio of 16 at a temperature 350-430ºS depending on the alloy composition. Fractometrical study sites obtained rarusheniya tensile bars showed no pores, which could be due to their method of preparation. The microstructure of rods by light and transmission electron microscopy showed that the structure of the extruded alloy is heterogeneous with very fine particles of the second phase. The grain size in bystrozakristallizovannyh tapes and compact materials was in the 1-2 micron. The structure of the belt rods and alloys containing rare earth metals, yttrium and neodymium together with aluminum crystals are present or second phases Mg24Y5 Mg12Nd, the separated magnesium solid solution during extrusion, and the larger crystallized from a liquid phase or Al2Y Al2Nd. The presence of these intermetallic compounds within the structure of the material in a significant amount leads to a reduction in its plasticity. Use the described technology for production and processing of magnesium alloys can increase their level of strength properties up to 500 MPa, which is the result of grinding of structural components while maintaining their size with further technological heating and supersaturation magnesium solid solution with its subsequent decay.

Surface modification of silver microparticles with 4-thioaniline

Abstract Silver microparticles have been prepared by chemical reduction method onto a rotating copper disc. It was found that in the presence of polyvinylpyrrolidone (PVP) in the initial AgNO 3 aqueous solution the radius of the Ag particles decreased from 1.18 to 0.48 μm and the formation of dendritic clusters with the fractal dimension of 1.61 occurred. The two-stage modification of the surface of synthesized silver particles with bifunctional 4-thioaniline (TAn) and further grafting of polyaniline (PAn) chains to the end amino-group of formed self-assembled surface layer were carried out. The modified surfaces were studied by scanning electron microscopy and X-ray diffraction methods, the physico-chemical properties of the formed products have been investigated. The obtained results indicate that the highest thermal stability is displayed by the silver particles produced in the presence of PVP, while the sample with grafted polyaniline exhibits the lowest thermal stability among the investigated samples. The reactivity of TAn has been examined by cyclic voltammetric method. In contrast to aniline, the electrochemical oxidation of TAn did not result in the formation of an electroconductive film on Pt electrode. It was found that oxidative condensation of aniline is suppresses by the TAn: when the molar ratio of aniline/TAn is 2:1 the formation of an electrochemically active product is stopped. The phenomenon of inhibition of the oxidative polymerization of aniline with TAn is related to an impossibility of growing of polymeric chains in the result of the “head-to-tail” type of bonding of the thioaniline links.

Structural diagnostics of amorphous, nanocrystalline, and submicrocrystalline magnetically soft materials

The magnetic properties of magnetically soft materials depend on the structural state, the domain structure, and the stabilization of the domain boundaries. By changing the structure of ferromagnetic materials, their magnetic properties may be controlled. Alloy structure may be changed by heat treatment, thermomagnetic treatment, and mechanical thermomagnetic treatment. The structure of amorphous and nanocrystalline alloys (for example, after thermomagnetic treatment) may be characterized by the presence of internal elastic distortion, the appearance of precursors to precipitation (concentration stratification of the amorphous matrix), the size of the nanograins, and the chemical composition of the nanophases. Transmission electron microscopy is widely used in investigating the structure of amorphous and nanocrystalline alloys. Additional information regarding the structure of polycrystalline alloys may be obtained by means of the Barkhausen effect [1, 2]. In the present work, we study the influence of the structure formed in thermal and thermomagnetic treatment in amorphous and nanocrystalline alloys of iron and cobalt on the Barkhausen-effect parameters. Amorphous strip (thickness 20‐25 μ m; width 5 mm) is obtained by quenching melt on a rotating copper disk. The amorphous alloy samples with different magnetostriction λ s take the form of strips and toroids. We investigate the following samples Fe 60 Co 20 Si 5 B 15 ( λ s ≈ 30 × 10 ‐6 ), Fe 5 Co 70 Si 15 B 10 ( λ s ≈ 0.5 × 10 ‐6 ), Fe 73.5 ‐ x Co x Cu 1 Nb 3 Si 13.5 B 9 ( x = 0, 10, 20, 30 at %), Fe 73.5 Cu 1 Nb 1.5 Mo 1.5 Si 13.5 B 9 , Fe 69 Cu 1 Nb 1.5 Mo 1.5 Si 13.5 B 9 Co 4.5 ( λ s ≈ 0.2 × 10 ‐6 ), and Co 81.5 Mn 9.5 Zr 9 ( λ s ∼ 0). The samples are annealed in vacuum at 300‐350 ° C to remove the quenching stress. After annealing, the samples undergo thermomagnetic treatment in a longitudinal magnetic field at various frequencies f : a constant field ( f = 0), an alternating field ( f = 50 Hz), and a highfrequency field ( f = 80 Hz) [3, 4]. Some samples undergo complex thermomagnetic treatment: annealing in a specified temperature range with the simultaneous application of constant and high-frequency magnetic fields. Some of the samples are quenched in water from the Curie temperature, in an alternating magnetic field (at 5000 ° C/min). The structure of the amorphous strip is investigated by transmission electron microscopy on a JEM-200KX microscope. Foil is prepared from alloy strip by electrolytic polishing, for electron-microscopic inspection; the thickness of the thinnest regions of the foil is 200‐300 nm. The Barkhausen-effect parameter considered is the emf e of the flux of Barkhausen discontinuities, which is averaged over the remagnetization period. The flux of Barkhausen discontinuities is observed visually on the oscillograph screen. The emf is measured on the strip samples by means of an applied sensor; the static hysteresis loops are determined. On toroidal samples, the static hysteresis loop, initial magnetic permeability μ 0 , and magnetic losses P 0.2/20000 are determined. The magnetic losses are calculated at frequency 20 kHz and induction 0.2 T, from the area of the dynamic hysteresis loops recorded stroboscopically. The initial magnetic permeability is determined at 80 Hz in a 0.05-A/m field. The basic characteristics (Curie point T C and solidification temperature T so ) of amorphous alloys, nanocrystals, and nanocrystalline structures (denoted by one, two, and three asterisks, respectively) are as follows:

Demonstrating Lenz's Law with Recycled Materials

A number of interesting demonstrations of induced electric currents and of Lenz's law have been described in this journal.1–5 In this paper, a simple version of an experiment that was described6 by Léon Foucault in 1855 is presented. Foucault placed a rotating copper disk between the poles of an electromagnet. When the electromagnet was off, the disk rotated almost without friction, but when the electromagnet was turned on, the disk stopped almost immediately. Nice discussions of this sort of magnetic braking may be found in a number of textbooks.7 Here I describe how to do the demonstration quite simply using recycled materials.

CNLS fits and Kramers–Kronig validation of resonant EIS data

Often, unusual electrochemical immittance spectroscopy (EIS) data are reported, characterized by scattered data points in complex impedance coordinates (−Im( Z) vs. Re( Z)) and corresponding sharp resonance-like peaks on Bode amplitude characteristics (log(∣ Z∣/ Ω) vs. log( f/Hz)) represent the state of the electrode close to Hopf bifurcation under current control (galvanostatic, gc) which is stable under voltage control (potentiostatic, pc). An example of such data reported here was obtained for anodic dissolution/passivation of a rotating copper disk electrode in a solution of copper sulphate and sulphuric acid. These data are especially cumbersome when complex nonlinear least squares (CNLS) fits of suitable models including electrical equivalent circuits (eqc) are attempted and this may in some cases even raise doubts as to data validity. It was therefore of importance to validate data with Kramers–Kronig (KK) transformation and this procedure was always successful for our data in their admittance representation while KK transformation in impedance representation failed for data presenting differential negative resistance (nr) i.e. non-minimum phase (nmp) characteristics. CNLS fits were done using 2nd, 3rd and 4th order rational functions of the frequency as the most suitable models, while the electrical equivalent (R, C) circuits and immittance in zero-pole representation were subsequently derived from these functions. It resulted that some forms of the (R, C) eqcs were unsuitable because their calculated parameters were complex numbers. In the case of the 4th order function it was possible to extrapolate data to a very low, experimentally inaccessible frequency, to reveal an additional low time constant.

Electrocontact-discharge sawing of metals

In this paper are presented the results of a study concerned with the application of electrocontact-discharge machining in the sawing of metals. Electrocontact-discharge sawing (ECDS) was performed with a rotating copper disc as the tool, with a flow of ordinary water as the work fluid and with a d.c. source as the power unit. By sawing steel workpieces, ECDS was characterized technologically from the point of view of the material removal rate, the feed velocity, the tool wear, and the workpieces surface integrity.

The cementation of Ag(I) ions from sodium chloride solutions onto a rotating copper disc

The kinetics of cementation of silver chloro-complexes from sodium chloride solutions onto copper was studied using rotating disc electrode systems. Activation energies were found to be I0.8 and 8.0 kJ/mol for 3 M and 4 M NaCl solutions, respectively, confirming that the rate of reaction is controlled by the mass transfer of the precipitating ions onto the precipitant surface. The effect of temperature, concentration of NaCl, Ag(I), and Cu(I) were studied. Scanning electron microscope studies were conducted to evaluate the deposit morphology and its effect on reaction kinetics. Evans diagrams were constructed from current potential data for the dissolution of copper from a copper disc and for the deposition of silver onto a glassy carbon electrode to show the effect of NaCl and dissolved copper concentrations.

Mixed-mode oscillations in the electrodissolution of copper in acetic acid/acetate buffer

A sequence of alternating periodic and chaotic current oscillations was found during the electrodissolution of a rotating copper disc in an acetic acid/sodium acetate buffer. The mixed-mode oscillations consist of combinations of large and small amplitude oscillations in peak current that were generated by incrementing the rotation rate of the copper electrode under potentiostatic control at 770 mV versus the saturated calomel electrode. Return maps of the chaotic intermediates were obtained and chaotic attractors were reconstructed in a three dimensional phase space using the method of time delays. The largest Lyapunov exponent was calculated to confirm the existence of deterministic chaos.

Stabilization of unstable steady states in an electrochemical system using derivative control.

We report the stabilization of an unstable fixed point in both an electrochemical experiment and a model for electrochemical corrosion using a small control signal proportional to the derivative of a measurable function of system variables. Spontaneous periodic oscillations observed during the potentio- static electrodissolution of a rotating copper disk in a sodium acetate--acetic acid buffer were suppressed to steady state behavior by adding to the anodic potential a feedback term proportional to the derivative of the electrical current passing through the cell. A general discussion of derivative control strategies shows that the steady state fixed points are left unchanged while, at the same time, the stability of the fixed points can be altered. We also show that, in general, the dimension of the state space of the system is increased when a derivative control strategy is applied.

Periodic and Chaotic Current Oscillations at a Copper Electrode in an Acetate Electrolyte

Periodic and chaotic current oscillations are observed during electrodissolution of copper in a pH 3.5 sodium acetate/ acetic acid buffer under potentiostatic conditions using a rotating copper disk electrode. Periodic or chaotic oscillations are observed depending on the applied potential and electrode rotation rate. The oscillations arise after the formation and dissolution of an acetate salt film precursor to oxide passivation. The nature and composition of the surface films were examined using scanning electron microscopy and x‐ray powder diffraction data. Nonlinear dynamic analysis methods have been used to show the existence of deterministic chaos. Time series data of the chaotic oscillations were used to generate a return map that appears to be one‐dimensional. The chaotic attractor was reconstructed in a three‐dimensional state space using the method of time delays and the largest Lyapunov exponent was calculated and was positive for the chaotic oscillations indicating a sensitive dependence on initial conditions characteristic of deterministic chaos.

Control of chaos in an electrochemical cell.

We report control of chemical chaos observed during the electrodissolution of a rotating copper disk in a sodium acetate-acetic acid buffer. An adaptation of a simple recursive proportional-feedback control strategy, generally applicable to systems well described by one-dimensional maps, was used to stabilise the chaotic response of the system on an unstable period-1 orbit. The successive minima in the measured anodic current generated a return map that was used to characterise the dynamics and the control algorithm prescribed small changes in the anodic potential to affect the control

Reduction of carbon dioxide by nickel macrocyclic catalysts adsorbed on a mercury electrode or a copper rotating disc electrode

A new method for evaluating the efficiency of nickel macrocyclic electrocatalysts for reduction of CO2 to CO using a rotating copper disc electrode has led to the discovery of a new highly active complex, [NiL2]2+[L2= 3,10-dimethyl-1,3,5,8,10,12-hexaazacyclotetradecane (diazacyclam)].

The modeling of mixed-mode and chaotic oscillations in electrochemical systems

We develop a simple but general three-variable model skeleton to describe complex nonlinear behaviors in electrochemical processes taking place at either a hanging mercury drop electrode (HMDE) or a rotating-disk electrode (RDE). We apply our formalism to the reduction of indium(III) at a HMDE in the presence of thiocyanate, a reaction known to exhibit complex mixed-mode and chaotic oscillations. Besides the role of the negative Faradaic impedance in destabilizing the electrochemical system, mass transport appears to be crucial as the model explicitly takes into account, in a truncated fashion, the time-dependent relaxation of the concentration profile. We study in detail the nonlinear dynamic behavior of our model of the indium/thiocyanate system and a RDE model. The models support mixed-mode sequences that appear either as incomplete Farey sequences or as periodic-chaotic sequences, which we discuss in terms of an incomplete homoclinic scenario whose definition and properties are worked out here. Our results compare very well to the experimental observations in the indium/thiocyanate system and the electrodissolution of a rotating copper disk in phosphoric acid. This satisfactory agreement strongly suggests that diffusion relaxation is an important phenomenon in electrochemical oscillations and could be the essential third variable in many dynamical electrochemical processes.

Periodic current oscillations in the anodic dissolution of copper in acetate buffer

In this note we describe the oscillations which were observed during the anodic dissolution of copper in an acetate buffer (pH<4) under potentiostatic conditions using a rotating copper disc as the working electrode. The basis of this work is to apply nonlinear dynamics with the techniques of electrochemistry for the purpose of obtaining information on mechanisms related to chemical corrosion

A mass transfer model for the autocatalytic dissolution of a rotating copper disc in oxygen saturated ammonia solutions

A mathematical model of mass transfer processes during autocatalytic dissolution of metallic copper in oxygen-containing ammonia solutions using the rotating disc technique is presented. The model is based on the equations of steady state convective diffusion with volumetric mass generation terms and boundary conditions of the third kind, in more generalized form, at the disc surface and of the first kind in the bulk solution. The boundary value problem was solved numerically using the finite difference method with variable mesh spacing. Comparison of calculated and experimental results indicates that the model quantitatively represents the measurements. The rate of the reaction Cu(II)+Cu→2Cu(I) determines the overall rate of the process.