Electrophilic fluorination of α-Fe 2 O 3 nanostructures and influence on magnetic properties

Bahuguna, Gaurav; Janu, Vikash Chandra; Uniyal, Vinay; Kambhala, Nagaiah; Angappane, S.; Sharma, Rakesh K.; Gupta, Ritu

doi:10.1016/j.matdes.2017.09.012

“…4 a, the magnetizations of ZFC and FC curves exhibit a more increment above 260 K, deviating from a linear behavior as noted by the dashed lines. This behavior is also shown in the Ni -beam-irradiated sample, however, deviating greater at a lower temperature of 200 K. This deviation in magnetization implies a transition in magnetic interaction, as is the case in -Fe O known as undergoing a Morin transition at 260 K 14 , 29 . The spin reorientation (Morin) transition implies that a system undergoes from a canted antiferromagnet, i.e., weak ferromagnet above to no canting state, i.e., pure antiferromagnet below , arising from a change in an anisotropic exchange interaction between the in-plane and out-of-plane states 16 – 18 .…”

Section: Resultsmentioning

confidence: 59%

“…1 b,c, Fe O phase on the CI particles was obviously observed, from which the canting of the surface spins or weak ferromagnetism can be introduced upon increasing temperature. -Fe O is a typical weak ferromagnet, exhibiting stronger ferromagnetic behavior at higher temperature 14 , 15 . Previously, in CI and soft composites, ferromagnetic properties are observed 7 , 12 .…”

Section: Resultsmentioning

confidence: 99%

“…Unlike in CI exhibiting typical ferromagnetic hysteresis loops 5 , 7 , 12 , 13 , hematite undergoes an anomalous magnetic transition, so-called Morin (spin reorientation) transition due to its antiferromagnetic properties 11 , 14 – 19 . It is a well known antiferromagnetic insulator with antiparallel sublattice that above the Morin temperature ( = 260 K) a small sublattice canting takes place due to its internal antisymmetric superexchange, Dzyaloshinskii–Moriya (DM), interaction.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced anomalous magnetization in carbonyl iron by Ni+ ion beam irradiation

Park

¹

,

Jang

²

,

Cho

³

et al. 2021

Sci Rep

1

0

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We investigate the magnetic properties in carbonyl iron (CI) particles before and after Ni$$^{+}$$ + and H$$^{+}$$ + ion beam irradiation. Upon increasing temperatures, the saturation magnetization ($$M_{\text {s}}$$ M s ) in hysteresis loops exhibits an anomalous increase at a high temperature for the unirradiated and the Ni$$^{+}$$ + -beam-irradiated samples, unlike in H$$^{+}$$ + -beam-irradiated sample. Moreover, the magnetization values at low and high temperatures are more intense after Ni$$^{+}$$ + beam irradiation, whereas after H$$^{+}$$ + beam irradiation those are remarkably suppressed. Hematite ($$\alpha $$ α -Fe$$_{2}$$ 2 O$$_{3}$$ 3 ) phase introduced on the surface of our CI particles undergoes the Morin transition that was observed in our magnetization-temperature curves. The Morin transition causing canted antiferromagnetism above the Morin temperature was found in the unirradiated and Ni$$^{+}$$ + -beam-irradiated samples, but not in H$$^{+}$$ + -beam-irradiated sample. It is thus revealed that the CI particles undergoing the Morin transition cause the anomalous increase in $$M_{\text {s}}$$ M s . We may suggest that Ni$$^{+}$$ + ion beam increases uncompensated surface spins on the CI particles resulting in a more steep Morin transition and the intensified $$M_{\text {s}}$$ M s . Ion-beam irradiation may thus be a good tool for controlling the magnetic properties of CI particles, tailoring our work for future applications.

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“…F‐TEDA is also used as an additive in electrolytes for improvement in the electrochemical performance of energy storage devices . Furthermore, fluorination of Fe 2 O 3 nanostructures using F‐TEDA is demonstrated to result in enhanced magnetic and photoelectrochemical properties . Herein, fluorination of commercially available, VC was performed using F‐TEDA, and its electrochemical supercapacitive behavior is investigated by assembling symmetric Swagelok‐type cells in two‐electrode geometry.…”

Section: Introductionmentioning

confidence: 99%

Electrophilic Fluorination of Graphitic Carbon for Enhancement in Electric Double‐Layer Capacitance

Bahuguna

¹

,

Chaudhary

²

,

Sharma

³

et al. 2019

Self Cite

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Graphitic carbon is the ultimate source of carbon electrodes for practical application in energy storage devices as it is commercially available at a much lower cost in contrast to other forms of nanostructured carbon. Recently, fluorinated carbon with improved electrical conductivity and wettability has been found to possess better and efficient electrochemical storage properties. However, the development of a simple fluorination process is still a challenge. Herein, Selectfluor (F‐TEDA) is explored as a fluorinating agent for Vulcan carbon. Fluorination of carbon material results in the formation of semi‐ionic C—F (F = 8.02 at%) and ionic C—F (F = 2.71 at%) bonds as observed in X‐ray photoelectron spectroscopy analysis along with an increase in defect density (ID/IG) by 33.4%. Symmetric two‐electrode supercapacitor cells are assembled in Swagelok‐type geometry, and the specific capacitance of fluorinated carbon is found to increase by ≈15 times in contrast to pristine carbon due to induced surface polarization despite the decrease in specific surface area by ≈34%, which is remarkable. The fabricated device is stable with ≈96% capacitance retention over 10 000 cycles, resulting in enhanced supercapacitive performance.

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“…F‐TEDA does not require any special handling conditions and is highly stable bench‐top reagent unlike the conventional toxic and explosive sources of fluorine. In the previous study, we used F‐TEDA for fluorination of Fe 2 O 3 nanostructures for surface fluorination resulting in band gap modification and ferromagnetic properties ,. In this study, unprecedented fluorine active compound, Selectfluor TM is added to tetrabutyl ammonium tetrafluoroborate salt in acetonitrile to form a mixed electrolyte system resulting in a highly stable electric double layer supercapacitors.…”

Section: Introductionmentioning

confidence: 99%

An Organo‐Fluorine Compound Mixed Electrolyte for Ultrafast Electric Double Layer Supercapacitors

Bahuguna

¹

,

Ram

²

,

Sharma

³

et al. 2018

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Fluorine chemistry has gained tremendous attention in the area of electrochemical energy devices such as lithium ion batteries, fuel cells and solar cells. With the advent of novel fluorinating systems, it is interesting to study the effect of fluorine on the electrochemical characteristics of such energy devices. In this study, an organo‐fluorine compound, SelectfluorTM (F‐TEDA) is used as a co‐electrolyte with organic electrolyte, tetrabutyl ammonium tetrafluoroborate (TBABF4) to facilitate the formation of electrostatic double layer. F‐TEDA is a commercially available N−F fluorinating agent existing as ion‐pair resembling conventional electrolytes. The ionic conductivity of 0.5 M F‐TEDA/TBABF4 is found to be 5.10 mS/cm that increases on introduction of ppm level of water indicating its sensitivity towards water. Symmetric Swagelok‐type cells in two electrode geometry are fabricated using carbon cloth as electrodes and F‐TEDA/TBABF4 as electrolyte. F‐TEDA/TBABF4 in inert condition (Device C) exhibits superior supercapacitive behaviour in terms of high rate capability and capacitance retention. The devices are assembled in ambient and inert conditions to examine the influence of moisture on supercapacitor performance. Interestingly, device based on F‐TEDA assembled in ambient condition despite of decrease in voltage window exhibits a remarkable increase in specific capacitance by 102 % with respect to control electrolyte.

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Electrophilic fluorination of α-Fe 2 O 3 nanostructures and influence on magnetic properties

Cited by 10 publications

References 43 publications

Enhanced anomalous magnetization in carbonyl iron by Ni+ ion beam irradiation

Enhanced anomalous magnetization in carbonyl iron by Ni+ ion beam irradiation

Electrophilic Fluorination of Graphitic Carbon for Enhancement in Electric Double‐Layer Capacitance

An Organo‐Fluorine Compound Mixed Electrolyte for Ultrafast Electric Double Layer Supercapacitors

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