scholarly journals Preparation of Gradient Materials with Molten Salts Electrodeposition

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 590
Author(s):  
Hui Li ◽  
Jinglong Liang ◽  
Hongyan Yan ◽  
Yungang Li ◽  
Le Wang
Keyword(s):  
Diffusion Coefficient ◽  
Current Density ◽  
Molten Salts ◽  
Pulse Electrodeposition ◽  
Composition Gradient ◽  
Gradient Materials ◽  
Functional Gradient ◽  
Gradient Layer ◽  
Gradient Change ◽  
Uniform Composition

A new way of preparing W–Cu functional gradient materials (FGM) with molten salts electrodeposition is studied. The results show that, with the conditions of current density 70 mA·cm−2, electrodeposition temperature 700 °C and bidirectional pulse electrodepositing for 30 minutes (min), the Cu–Ni gradient layer prepared under this condition is widely used dense and smooth. Fundamental to the preparation of Cu–Ni functional gradient layer, Cu–Ni is used as a cathode to deposit W. Under the current density of 50 mA·cm−2, the time of 20 min, with bidirectional pulse electrodeposition, the Cu+Ni+W gradient layer has uniform composition gradient change and larger thickness. The W–Cu gradient materials prepared in this study have good cohesiveness. The addition of Ni would promote the inter-diffusion of Cu and W, and increase the diffusion coefficient significantly.

Activated Prominences; Mechanisms for Activation and Eruption

1979 ◽  
Vol 44 ◽  
pp. 307-313
Author(s):  
D.S. Spicer
Keyword(s):  
Pressure Gradient ◽  
Density Gradient ◽  
Current Density ◽  
Convective Instability ◽  
Tearing Mode ◽  
Magnetic Shear ◽  
Long Wavelength ◽  
Ideal Mhd ◽  
Gradient Change ◽  
Accelerated Particles

A possible relationship between the hot prominence transition sheath, increased internal turbulent and/or helical motion prior to prominence eruption and the prominence eruption (“disparition brusque”) is discussed. The associated darkening of the filament or brightening of the prominence is interpreted as a change in the prominence’s internal pressure gradient which, if of the correct sign, can lead to short wavelength turbulent convection within the prominence. Associated with such a pressure gradient change may be the alteration of the current density gradient within the prominence. Such a change in the current density gradient may also be due to the relative motion of the neighbouring plages thereby increasing the magnetic shear within the prominence, i.e., steepening the current density gradient. Depending on the magnitude of the current density gradient, i.e., magnetic shear, disruption of the prominence can occur by either a long wavelength ideal MHD helical (“kink”) convective instability and/or a long wavelength resistive helical (“kink”) convective instability (tearing mode). The long wavelength ideal MHD helical instability will lead to helical rotation and thus unwinding due to diamagnetic effects and plasma ejections due to convection. The long wavelength resistive helical instability will lead to both unwinding and plasma ejections, but also to accelerated plasma flow, long wavelength magnetic field filamentation, accelerated particles and long wavelength heating internal to the prominence.

scholarly journals On the question of using solid electrodes in the electrolysis of cryolite-alumina melts. Part 3. Electric field distribution on the electrodes

2021 ◽  
Vol 25 (2) ◽  
pp. 235-251
Author(s):  
E. S. Gorlanov ◽  
A. A. Polyakov
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Edge Effect ◽  
Current Density ◽  
Molten Salts ◽  
Functional Relationship ◽  
Electric Field Distribution ◽  
Chemical Inhomogeneity ◽  
Electrolytic Process ◽  
Solid Electrodes

The aim of this work is to identify the theoretical limitations of molten salts electrolysis using solid electrodes to overcome these limitations in practice. We applied the theory of electric field distribution on the electrodes in aqueous solutions to predict the distribution of current density and potential on the polycrystalline surface of electrodes in molten salts. By combining the theoretical background of the current density distribution with the basic laws of potential formation on the surface of the electrodes, we determined and validated the sequence of numerical studies of electrolytic processes in the pole gap. The application of the method allowed the characteristics of the current concentration edge effect at the periphery of smooth electrodes and the distribution of current density and potential on the heterogeneous electrode surface to be determined. The functional relationship and development of the electrolysis parameters on the smooth and rough surfaces of electrodes were established by the different scenario simulations of their interaction. It was shown that it is possible to reduce the nonuniformity of the current and potential distribution on the initially rough surface of electrodes with an increase in the cathode polarisation, alumina concentration optimisation and melt circulation. It is, nonetheless, evident that with prolonged electrolysis, physical and chemical inhomogeneity can develop, nullifying all attempts to stabilise the process. We theoretically established a relationship between the edge effect and roughness and the distribution of the current density and potential on solid electrodes, which can act as a primary and generalising reason for their increased consumption, passivation and electrolytic process destabilisation in standard and low-melting electrolytes. This functional relationship can form a basis for developing the methods of flattening the electric field distribution over the anodes and cathodes area and, therefore, stabilising the electrolytic process. Literature overview, laboratory tests and theoretical calculations allowed the organising principle of a stable electrolytic process to be formulated -the combined application of elliptical electrodes and the electrochemical micro-borating of the cathodes. Practical verification of this assumption is one direction for further theoretical and laboratory research.

scholarly journals Nano-Grain Ni/ZrO2 Functional Gradient Coating Fabricated by Double Pulses Electrodeposition with Enhanced High Temperature Corrosion Performance

Coatings ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 332 ◽  
Author(s):  
Wen Ge ◽  
Taisong He ◽  
Meijiao Wang ◽  
Jiamei Li
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Surface Morphology ◽  
Vertical Direction ◽  
Double Pulse ◽  
Pulse Electrodeposition ◽  
Face Centered Cubic ◽  
X Ray ◽  
Functional Gradient ◽  
Gradient Coating

Functional gradient materials (FGM) have many excellent properties, and high-performance gradient coating exhibits good prospective application. In this paper, the nano-grain Ni/ZrO2 gradient coating was prepared by double pulse electrodeposition (BP). The surface morphology, crystal structure and electrochemical corrosion resistance of the nano-grain Ni/ZrO2 coating and Ni coating, annealed at different temperatures (400–800 °C), have been compared. In the vertical direction to the substrate surface, the content of ZrO2 increases from 0% to 34.99%. X-ray diffraction (XRD) revealed that the average crystal size of Ni/ZrO2 gradient coating gradually increases from 13.75 to 27.75 nm, and the crystal structure is a face-centered cubic (FCC). The main crystal orientation faces are (111) and (200), while the (200) face exhibited a stronger preferred orientation. Compared with the Ni coating by scanning electron microscopy, the surface morphology of double pulse fabricated Ni/ZrO2 gradient coating was revealed as being smoother, denser, and having fewer pores, and the crystal particle size distribution became narrow. X-ray photoelectron spectroscopy (XPS) shows that the chemical binding states of elements Ni and Zr have been altered. The binding energies of 2p3/2 and 2p1/2 for Ni have been increased, resulting in a higher electron donor state of Ni. The binding energy of 3d5/2 and 3d3/2 of Zr4+ in ZrO2 is decreased, thus becoming better electron acceptors. Chemical bonding has been formed at the Ni/ZrO2 interface. This study demonstrated that double pulse electrodeposition is a promising fabrication method for functional gradient coatings for high temperature applications.

Preparation of Pulse Electrodeposited Mo-Ni Coating

2014 ◽  
Vol 971-973 ◽  
pp. 161-164
Author(s):  
Xiao Zhen Liu ◽  
Le Tian Xia ◽  
Jian Qiang Gen ◽  
Xiao Zhou Liu ◽  
Jie Chen ◽  
...  
Keyword(s):  
Current Density ◽  
Duty Cycle ◽  
Deposition Temperature ◽  
Deposition Time ◽  
Pulse Electrodeposition ◽  
Electro Deposition ◽  
Electrodeposition Method ◽  
Electrodeposition Time ◽  
Ni Alloy

Mo-Ni coatings were prepared on Ni alloy by pulse electrodeposition method. The effects of current density, electrodeposition temperature, frequency, duty cycle and electrodeposition time on microhardness of Mo-Ni coating were researched, respectively. Microhardness of Mo-Ni coating increases with the increase of current density, electrodeposition temperature, frequency and electro-deposition time in 17.75 A/dm2 ~ 19.25 A/dm2. 21 °C~ 25 °C, 1000 Hz ~ 5000 Hz and 10 min ~ 20 min, respectively. Microhardness of Mo-Ni coating decreases with the increase of electrodeposition temperature, electrodeposition time and duty cycle in 25 °C ~ 37 °C, 20 min ~ 30 min and 0.5 ~ 0.9, respectively. In the range of current density from 19.25A/dm2 to 20.75 A/dm2, microhardness of Mo-Ni coating is neariy constant with the increase of current density. When electrodeposition parameters: current density 19.25 A/dm2, electro-deposition temperature 25 °C, frequency 5000 Hz, duty cycle 0.5 and electrodeposition time 20 min, microhardness of Mo-Ni coatin is as high as 707.9 HV.

Bending Actuators Based on Monolithic Barium Titanate-Stannate Ceramics as Functional Gradient Materials

2005 ◽  
Vol 494 ◽  
pp. 167-174 ◽  
Author(s):  
R. Steinhausen ◽  
H.Th. Langhammer ◽  
A.Z. Kouvatov ◽  
C. Pientschke ◽  
Horst Beige ◽  
...  
Keyword(s):  
Piezoelectric Materials ◽  
Tape Casting ◽  
Calculated Data ◽  
Production Costs ◽  
Layered System ◽  
Gradient Materials ◽  
Poling Process ◽  
Functional Gradient ◽  
Powder Pressing

In the field of applications of piezoelectric materials properties, functional gradient materials (FGM) are suitable for bending devices due to reduced internal mechanical stresses and lower production costs as well as for ultrasonic transducers because of their increased band width. This paper reports both on preparation, poling, characterization of FGM actuators, and on the description of suitable models of the poling and the bending processes. The calculations of the bending behavior show that the deflection at the end of the cantilever with a continuous gradient still reaches 2/3 of the deflection of a bimorph, whereas the maximum stress goes to zero, which is the main advantage of FGM compared to the commonly used bimorph devices. As a model system with well-defined electromechanical and dielectric properties of the homogeneous components the solid solution of BaTi1-xSnxO3 (BTS) with 0.075 £ x £ 0.15 was chosen. The FGMs approximated by a layered system with a one-dimensional gradient of the Sn-content were prepared both by successive uniaxial powder pressing and by tape casting with the doctor blade method. The chemical gradient was transformed into a gradient of the piezoelectric properties by a poling process. Several models were developed for the description of the non-trivial problem of the poling process in layered systems. The calculated data were compared with experimental results. It was shown that the very small electrical conductivity of the single layers generally cannot be neglected during the poling process and must be incorporated into more sophisticated models. The bending properties of several poled BTS structures with up to 4 layers were measured and discussed.

Preparation of Ni-ZrO2-CeO2 Nanocomposite Coatings by Pulse Electrodeposition

2013 ◽  
Vol 395-396 ◽  
pp. 174-178 ◽  
Author(s):  
Yang Yang Xu ◽  
Yu Jun Xue ◽  
Fang Yang ◽  
Chun Yang Liu ◽  
Ji Shun Li
Keyword(s):  
Current Density ◽  
Smooth Surface ◽  
Pulse Current ◽  
Nanocomposite Coating ◽  
Pulse Electrodeposition ◽  
Nanocomposite Coatings ◽  
Duty Ratio ◽  
Average Current Density ◽  
Average Current ◽  
Surface Morphologies

Ni-ZrO2-CeO2nanocomposite coatings were prepared by pulse electrodeposition. The effect additions of ZrO2and CeO2nanoparticles, average current density, duty ratio and frequency of pulse current on nanoparticle contents of Ni-ZrO2-CeO2nanocomposites were studied. The surface morphologies and microhardness of different nanocomposite coatings (Ni-ZrO2, Ni-CeO2, Ni-ZrO2-CeO2) were analyzed. The results show that, with the average current density, duty ratio and frequency increased, the nanoparticle contents increased at first and then decreased. Compared with Ni-ZrO2and Ni-CeO2, the surface morphology of Ni-ZrO2-CeO2nanocomposite coating showed better smooth surface and more compact microstructure, the microhardness was also higher.

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