Effect of magnetic field on reduction of nickel oxide

Rowe, M. W.; Fanick, R.; Jewett, D. N.; Rowe, Joan D

doi:10.1038/263756a0

Cited by 12 publications

(4 citation statements)

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“…Examples are interaction of magnetic fields with electrochemical systems consisting of iron electrodes in copper sulfate solutions, and copper electrodes in copper sulfate solutions. − The electronic interaction mechanism involves electron transfer via radical pair intermediates that are highly sensitive to static magnetic interactions. An example is the photoinduced charge-transfer reaction that occurs in the bacterial photosynthesis. − The magnetomechanical mechanism includes the orientation of magnetically anisotropic macromolecules in strong homogeneous fields and the translation of paramagnetic species in high gradient fields. , Examples are the reduction of paramagnetic metal ions or metal oxides to ferromagnetic metal, which seems to be favorable within magnetic fields. − …”

Section: Introductionmentioning

confidence: 99%

“…1,2 Examples are the reduction of paramagnetic metal ions or metal oxides to ferromagnetic metal, which seems to be favorable within magnetic fields. [14][15][16][17][18][19] In some previous publications carried out by Waskaas, 20-24 O'Brien and Santhanam, 25 and Ragsdale et al, 26 the effects of magnetic fields on electrochemical systems have been explained in terms of a gradient of paramagnetic ions in the vicinity of an electrode surface, i.e., in terms of magnetoconvection, which is a kind of the magnetomechanical mechanism. However, their considerations were concentrated on transport of only paramagnetic ions because of the magnetic field.…”

Section: Introductionmentioning

confidence: 99%

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Magnetoconvection Phenomena: A Mechanism for Influence of Magnetic Fields on Electrochemical Processes

1999

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The objective of this study is to suggest an interaction mechanism for the influence of static magnetic fields on electrochemical processes occurring at a ferromagnetic electrode immersed in a paramagnetic electrolytic solution. The hypothesis is that the magnetic field will cause a transport of all ions due to the difference in the magnetic susceptibility in the solution at the electrode surface. The ion transport induced by the magnetic field is directed from electrode into solution. Experimentally, the effects of static magnetic fields on electrochemical systems were observed only within systems consisting of ferromagnetic electrodes immersed in paramagnetic solutions. The results showed that the magnetic field caused an anodic polarization for the ferric/ferrous system and a cathodic polarization for the nickel/nickel-ion and the cobalt/cobalt-ion system. The results were obtained by the open-circuit potential and the potentiostatic/galvanostatic methods. The suggested interaction mechanism is magnetoconvection, which predicts that to obtain any magnetic field effect, there has to exist a gradient of paramagnetic ion concentration in the solution at the electrode surface. Theoretically, it is shown that the magnetic field tends to cause an additional convective transfer of all components of the solution, which will be generated in the vicinity of the electrode surface. Further, both the experimental results and the suggested mechanism show that the magnetic field effect increases with increasing magnetic flux density and magnetic susceptibility of the solution and decreases with increasing temperature and stirring rate. The evidence presented here show that the proposed hypothesis and the proposed interaction mechanism are verified.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Magnetoconvection Phenomena: A Mechanism for Influence of Magnetic Fields on Electrochemical Processes

1999

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“…Other reports suggest no influence of external magnetic fields on these and related reactions [10][11][12]. The effects of an intrinsic magnetic moment have also been noted by observations of anomalies, at the magnetic transition, in the reaction rates of reduclions [13][14][15][16][17], oxidations [18][19][20][21], and other reactions [22] of these metals and oxides.…”

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confidence: 92%

An evolved gas analysis study of the reduction of nickel oxide by hydrogen

Gallagher¹,

György²,

Jones³

1982

Journal of Thermal Analysis

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The reduction of NiO by H 2 was followed by conventional thermogravimetry and a new evolved gas analysis approach which follows the course of the reaction by measuring the H20 content of the gas stream. Excellent correspondence is observed between the two techniques for simultaneous measurements. Heating rates between 0.5 and 10 ~ min-~ shift the temperature of the reaction as does changing the surface area of the NiO. These shifts are discussed in terms of the Neel temperature (TN) of NiO and the thermal history of the sample. No correlation between reaction rate and T N is observed under dynamic conditions. Preheating the sample in vacuum at 130 ~ has a marked effect on shape of the DTG and EGA curves.The chemical, metallurgical, and magnetic uses of the transition metals, iron, cobalt, nickel, and their alloys are enormous. Recently fabricated powdered metal shapes have been prepared from these materials by the in-situ reduction of the preformed oxides by H2 [1 ]. Catalysts of these finely divided metals supported on an inert refractory material are also prepared by H2 reduction of oxides and salts of these metals [2]. Consequently, methods for controlling the rates, mechanisms, and resulting morphologies of such reductions are of considerable technological importance.In recent years there have been studies that suggest an applied magnetic field will influence the rate of such reductions [3][4][5][6] and even more complicated behavior has been reported for the effects of a magnetic field on the direct formation of Ni(CO)4 [7][8][9]. Other reports suggest no influence of external magnetic fields on these and related reactions [10][11][12]. The effects of an intrinsic magnetic moment have also been noted by observations of anomalies, at the magnetic transition, in the reaction rates of reduclions [13][14][15][16][17], oxidations [18][19][20][21], and other reactions [22] of these metals and oxides.Studies of the reduction of melal oxides by H2 in the presence of an external magnetic field have been performed using gravimetric techniques [4,5]. Such investigations have been hampered by the strong influence of the magnetic field upon the mass of the reactant, product or both. Evaluating the extent of the reac'ion by changes in weight therefore is ten~aqve. Variations of the magnetic influence would

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“…[ 10 ] On the other hand, ZnO is a structurally stable n-type semiconductor whose electronic conductivity can be easily enhanced by many orders of magnitude by employing very low doping levels (up to 3% atomic weight) [ 11 ] of Ni. ZnObased oxides supply either electrons or holes in different conditions.…”

Section: Introductionmentioning

confidence: 99%

An Electrolyte‐Free Fuel Cell Constructed from One Homogenous Layer with Mixed Conductivity

Zhu

Raza

Abbas

et al. 2011

Adv Funct Materials

152

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Rather than using three layers, including an electrolyte, a working fuel cell is created that employs only one homogenous layer with mixed conductivity. The layer is a composite made from a mixture of metal oxide, Li0.15Ni0.45Zn0.4 oxide, and an ionic conductor; ion‐doped ceria. The single‐component layer has a total conductivity of 0.1–1 S cm−1 and exhibits both ionic and semiconducting properties. This homogenous one‐layer device has a power output of more than 600 mW cm−2 at 550 °C operating with H2 and air. Overall conversion is completed in a similar way to a traditional fuel cell, even though the device does not include the electrolyte layer critical for traditional fuel‐cell technologies using the three‐component anode–electrolyte–cathode structure.

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Effect of magnetic field on reduction of nickel oxide

Cited by 12 publications

References 4 publications

Magnetoconvection Phenomena: A Mechanism for Influence of Magnetic Fields on Electrochemical Processes

Magnetoconvection Phenomena: A Mechanism for Influence of Magnetic Fields on Electrochemical Processes

An evolved gas analysis study of the reduction of nickel oxide by hydrogen

An Electrolyte‐Free Fuel Cell Constructed from One Homogenous Layer with Mixed Conductivity

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