Magnetic properties of carbon nanodisk and nanocone powders

Abstract

We have investigated the magnetic properties of carbon powders which consist of nanodisks, nanocones, and a small fraction of carbon-black particles. Magnetization measurements were carried out using a superconducting quantum interference device in magnetic fields −5 < µ 0 H < 5 T for temperatures in the range 2 ≤ T < 350 K. Measurements of the magnetization M versus temperature T and magnetic field µ 0 H for these carbon samples show diamagnetism and paramagetism with an additional ferromagnetic contribution. The ferromagnetic magnetization is in agreement with the calculated magnetization from Fe impurities as determined by the particle-induced x-ray emission method (< 75 µg/g). Magnetization measurements in weak magnetic fields show thermal hysteresis, and for strong fields the magnetization M decreases as M ∼ aT −α with α < 1, which is slower than the Curie law (α = 1), when the temperature increases. The magnetization M versus magnetic field µ 0 H shows paramagnetic free-spin S = 1 2 and 3 2 behaviors for temperatures T = 2 K and 15 ≤ T ≤ 50K, respectively. A tendency for localization of electrons was found by electron spin resonance when the temperature T decreases (2 < T < 40 K). The magnetic properties in these carbon cone and disk powder samples are more complex than a free-spin model predicts, which is apparently valid only for the temperature T = 2 K.2

Impact of carbon-fluorine doped titanium dioxide in the performance of an electrochemical sensing of dopamine and rosebengal sensitized solar cells

“…47 It states that the F doped Ti 4+ and the observed O − 2 contact with Ti 3+ produce EPR signals for F-TiO 2 material as previously reported. 44 The appeared EPR signals are due to the reduced Ti 3+ where titanium ions are in the octahedral co-ordination mode.…”

Synthesis, characterization and assessment of hydrophilic oxidized carbon nanodiscs in bio-related applications

“…27 However, their disc shaped structure differentiates signicantly certain of CNDs' properties, enabling their applicability in new elds. Within this context CNDs, which are more close to graphene, differ from fullerenes' curved structure in both shape and wall thickness, 28 which in the case of CNDs may range from a few up to several tens of graphene layers. Additionally, the CNDs, due to their stacking properties possess a well-dened structure, which is associated with improved heterogeneous electron transfer rate at the graphene edges, 29 and are thus expected to exhibit improved electrochemical properties, compared to other graphitic materials.…”

“…26,34 Similarly, oxidized CNDs are expected to be superior to 1D oxidized carbon nanotubes and exible graphene oxides when used as llers to improve for instance barrier properties since they provide a rigid, at, functional yet nonpermeable surface. 35 Up to day, and due to their unique combination of morphological and structural characteristics, CNDs have been proposed as very attractive candidate nanomaterials for applications relative to electrochemistry, 26 improvement of friction properties, 36 magnetic properties 28 and llers for composite materials. 37 The particular size of these disc-like carbon nanoakes is crucial for maintaining important properties, such as electrical conductivity and on the other hand, small enough or even ideal in some cases, for application in bionanotechnology, nanomedicine and drug delivery, micromanipulation, nanochemistry etc.…”

Magnetoresistance of composites based on graphitic disks and cones

“…In the HT-1600 powder, the content of Fe is < 75 µg/g. In HT-2700 powder, the content of Fe is lower than the method can detect (< 3 µg/g) [36].…”

“…In a previous study of magnetic properties of raw nanocarbon powder [36], we have determined a residual amount of Fe using the particle-induced x-ray emission method. In the HT-1600 powder, the content of Fe is < 75 µg/g.…”