Reduction of Cobalt Oxide (Co3O4) by Low Temperature Hydrogen Plasma

Sabat, Kali Charan; Paramguru, R. K.; Pradhan, S. K.; Mishra, B.K.

doi:10.1007/s11090-014-9602-9

Cited by 48 publications

(29 citation statements)

References 10 publications

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“…In this work we argue that a reasonable explanation for the gas permeation redox effect was related to the silica pore connectivity around the metal oxide particle, which changed from Co 3 O 4 to CoO as reported in literature [19,[41][42][43]. The particles embedded in the porous silica matrix are schematically represented in Fig.…”

Section: Fig 1 the Volumetric Adsorption Systemsupporting

confidence: 67%

“…8, where several pores terminate at the particle surface. The redox effect confers structural changes in the lattice parameters of the particles from 0.8084nm (Co 3 O 4 ) to 0.426nm (CoO) [39][40][41][42][43][44]. However, cobalt oxide particles embedded in silica films using similar methods as in this work are very small to be detected by XRD (X-ray diffraction).…”

Section: Fig 1 the Volumetric Adsorption Systemmentioning

confidence: 68%

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Improved pore connectivity by the reduction of cobalt oxide silica membranes

Ji¹,

Smart²,

Bhatia³

et al. 2015

Separation and Purification Technology

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This work investigated the permeation of binary gas mixtures in non-reducing (He/CO 2 ) and reducing (H 2 /Ar) conditions at temperatures ranging from 200 to 500 ºC. A common performance aspect under both non-reducing and reducing conditions was that the He and H 2 purity in the permeate stream was independent of temperature for the tested binary gas mixtures, except at very high He/CO 2 or H 2 /Ar concentrations (≥90/10) in the retentate stream. Under non-reducing conditions, the transport of gases was consistent with molecular sieving properties of silica derived membranes, and He permeance was constant irrespective of the He/CO 2 binary concentration tested.An anomalous H 2 transport was observed under reduced conditions, as unexpectedly the H 2 permeance was higher for gas mixtures instead of single gas. Further tests showed that H 2 permeance increased 170% as the gas mixture changed from single H 2 gas to H 2 /Ar gas mixtures.This was attributed to the experimental procedure, as the membranes were partially reduced each day and tested for gas permeation from pure H 2 to lower H 2 concentration in gas mixtures. Under these partial reducing conditions, H 2 slowly reacts with the surface of the dense Co 3 O 4 particle, thus 2 forming a porous CoO region. The increase in H 2 permeance was therefore attributed to improved pore connectivity between the silica structure and the porous CoO region.

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Section: Fig 1 the Volumetric Adsorption Systemsupporting

confidence: 67%

Section: Fig 1 the Volumetric Adsorption Systemmentioning

confidence: 68%

Improved pore connectivity by the reduction of cobalt oxide silica membranes

Ji¹,

Smart²,

Bhatia³

et al. 2015

Separation and Purification Technology

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“…Recently, some studies were made using low-temperature hydrogen plasma for reduction of iron oxide [9][10][11] and cobalt oxide [12]. In both the cases, successful reduction took place with a decrease in activation energy due to the presence of activated species in hydrogen plasma.…”

Section: Introductionmentioning

confidence: 99%

Reduction of Copper Oxide by Low-Temperature Hydrogen Plasma

Sabat

Paramguru

Mishra

2016

Plasma Chem Plasma Process

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The paper presents experimental results of reduction of cupric oxide (CuO) by low-temperature hydrogen plasma in a microwave-assisted plasma set-up. The experiments were carried out at low microwave powers in the range of 600-750 W and low hydrogen flow rates in the range of 0.833 9 10 -6 to 2.5 9 10 -6 m 3 s -1 . In all the experiments for reduction of CuO with hydrogen plasma, an initial induction period was observed in the kinetic plots. The induction period decreases with increase in pressure or temperature. The induction period leads to the formation of active sites for adsorption of H 2 . After the induction period, fast autocatalytic reduction takes place followed by a sluggish period towards the end. The reduction process proceeds in sequential steps through the formation of sub-oxides. The kinetic data fits the Avrami-Erofeev equation with 'n' value close to 3. The resultant activation energy measured during hydrogen plasma processing is around 75.64 kJ mol -1 . This is lower compared to activation energies measured by other methods of reduction indicating a clear advantage.

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“…The effect of different process parameters like hydrogen gas flow, microwave power, chamber pressure, microwave power density and temperature on the reduction of hematite are studied in details [2,3]. The same research group used low temperature hydrogen plasma for reduction of cobalt oxide (Co 3 O 4 ) and optimized different process parameters [4]. They also studied the associated chemical reaction involved in the reduction process and estimated the activation energy required for the reduction of the metal oxide.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, the microwave plasma system as reported in [3,4] is used for the reduction of Fe 2 O 3 (99.99 % pure) sample. In the plasma system, an optical emission spectroscope (OES) for in situ monitoring of plasma based reduction process is introduced.…”

Section: Introductionmentioning

confidence: 99%

Monitoring Hydrogen Plasma Reduction of Oxides by Na D Lines

Das

Rajput

et al. 2016

Plasma Chem Plasma Process

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Out of many applications of hydrogen plasma, reduction of metal oxides is an important one. The reduction can be carried out using carbon or hydrogen. While carrying out the reduction of hematite (Fe 2 O 3 ) in hydrogen plasma, an attempt was made to characterize the hydrogen plasma by optical emission spectroscopy. The spectroscopic results provide some new and useful information. In addition to the hydrogen emission lines, two prominent lines at 589 and 589.6 nm were observed. These two lines are confirmed to be sodium D1 and D2 (Na D lines) by comparing with a low pressure sodium vapour lamp (LPSVL). The source of the trace amount of sodium is also confirmed to be from the metal oxide sample as an impurity. These lines are found to be very sensitive to various process parameters such as gas flow rate, microwave power, and reduction chamber pressure. The temporal variation of these two Na D lines also shows a characteristic trend during metal oxide reduction in hydrogen plasma. The weight loss and the X-ray diffraction analyses of reduced Fe 2 O 3 sample for different time duration provides the evidence of correlation with Na D lines' intensity trend. This trend can be used to monitor the state and completion of hydrogen plasma based reduction reaction. In processes where Na is not associated with metal oxide, trace amount of Na in its molecular form such as NaOH can be introduced for monitoring the plasma process parameters as well as the plasma based reduction process.

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Reduction of Cobalt Oxide (Co3O4) by Low Temperature Hydrogen Plasma

Cited by 48 publications

References 10 publications

Improved pore connectivity by the reduction of cobalt oxide silica membranes

Improved pore connectivity by the reduction of cobalt oxide silica membranes

Reduction of Copper Oxide by Low-Temperature Hydrogen Plasma

Monitoring Hydrogen Plasma Reduction of Oxides by Na D Lines

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