Magnetic Susceptibility of Molecular Carbon: Nanotubes and Fullerite

Ramirez, A. P.; Haddon, Robert C.; Zhou, Otto; Fleming, R. M.; Zhang, J.; McClure, S. M.; Smalley, R. E.

doi:10.1126/science.265.5168.84

Cited by 151 publications

(92 citation statements)

References 35 publications

(19 reference statements)

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“…−0.812 × 10 −6 emu/gOe is one order of magnitude lower than the value (−8 × 10 −6 emu/gOe) of straight CNTs. 19 In contrast, the mass magnetization at 5 K keeps increasing with the rise of applied field even when the applied field is high up to 6.5 T, a typical paramagnetic characteristic. Actually, the as-prepared HCNTs show typical Curie-like paramagnetic characteristic, and which can be confirmed by the M-T curve [shown in Fig.…”

Section: Resultsmentioning

confidence: 97%

High-temperature ferromagnetism of helical carbon nanotubes

et al. 2013

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Section: Resultsmentioning

confidence: 97%

High-temperature ferromagnetism of helical carbon nanotubes

et al. 2013

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“…Magnetic fields have been found to have strong effects on the electronic and bulk properties of nanotubes. Ramirez and coworkers [5] found nanotubes have significantly larger orientation-averaged susceptibility, on a per carbon basis, than any other form of elemental carbon. Lu [6] predicted a field-induced metal-insulator transition for all nanotubes.…”

Section: Introductionmentioning

confidence: 99%

“…The most common magnetic material used for the preparation of MR fluids is high purity iron powder derived from decomposition of iron penta-carbonyl (Fe(CO) 5 ). In the absence of an applied magnetic field, (MR) fluids typically behave as nearly ideal Newtonian liquids.…”

Section: Introductionmentioning

confidence: 99%

Magnetorheology of Multiwalled Nanotube Dispersions in Mineral Oil

D’Souza

Yang

2008

JNanoR

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Abstract. The magnetorheological (MR) effect of multi-walled carbon nanotubes (MWNT) was investigated. Three concentrations of MWNT were dispersed in mineral oil (0.5, 1.5 and 2.53 vol% nanotubes). Rheological investigations were conducted on a magnetorheological cell coupled to a controlled stress rheometer. Oscillatory tests and rotational tests were conducted. A sinuisoidal strain between 0 and 1 with a frequency of 1 Hz was applied and the stress amplitude measured for 0, 171 and 343 kA/m magnetic field strengths. Linear viscoelasticity was determined to exist at strains less than 5%. Dynamic frequency sweeps were conducted at a strain of 1% between 0 and 100 radians/s. A crossover from viscous to elastic behavior was observed for some concentrations. The crossover frequency decreased with field strength as well as with concentration of MWNT. Rotational tests were conducted between shear rates of 0 to 100/s. All dispersions had a zero shear yield stress indicative of Bingham behavior. A magnetosweep was conducted by keeping the strain within the linear viscoelastic region at a frequency of 1 Hz and ramping the magnetic field strength from 0 to 343 kA/m. The results indicate that MWNT show MR behavior.

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“…This observation is consistent with the observed anisotropy in J c (H) for field processed CNT doped MgB 2 , which is lacking for pure MgB 2 . Ajiki et al 26 , Lu 27 and Ramirez et al 28 found that the susceptibility, χ, of CNT is large enough to be aligned in certain magnetic field.The advantages of the magnetic field processing include the provision of a unique window of opportunity to control the microstructure and the behavior of various additives that have a response to magnetic field. We can extend the conventional materials processing variables of pressure, composition and temperature, f(P,C.T) to include field (H) and magnetization (M) of the matrix and additives, f(P,C,T,H,M).…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Magnetic field processing to enhance critical current densities of MgB2 superconductors

Dou

Yeoh

Shcherbakova

et al. 2006

Applied Physics Letters

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Magnetic field of up to 12 T was applied during the sintering process of pure MgB 2 and carbon nanotube (CNT) doped MgB 2 wires. We have demonstrated that magnetic field processing results in grain refinement, homogeneity and significant enhancement in J c (H) and H irr . The J c of pure MgB 2 wire increased by up to a factor of 3 to 4 and CNT doped MgB 2 by up to an order of magnitude in high field region respectively, compared to that of the non-field processed samples. H irr for CNT doped sample reached 7.7 T at 20 K. Magnetic field processing reduces the resistivity in CNT doped MgB 2 , straightens the entangled CNT and improves the adherence between CNTs and MgB 2 matrix. No crystalline alignment of MgB 2 was observed. This method can be easily scalable for a continuous production and represents a new milestone in the development of MgB 2 superconductors and related systems.The new superconductor, MgB 2 , has made a significant impact on the research and development of superconductors since its discovery 1 . The special feature of the two-gap superconductivity 2 and lack of week links at the grain boundaries 3 makes MgB 2 highly tolerant for doping which has been successfully used to enhance the critical current density, J c and the upper critical field, H c2 4-8 . Carbon and silicon carbide doping resulted in a significant increase of in-field J c and H c2 , and these records still stand for MgB 2 [5][6][7][8][9][10][11] . To further advance the development of MgB 2 for applications we report a new method of combining the advantages of magnetic field processing and of doping for processing MgB 2 superconductors. Magnetic field processing technology has been proved to be a powerful tool to produce aligned CNT in composites and neat macroscopic membranes 12-14 and control the phase transformation and behavior of the melts during condensation processes, resulting in major improvements in material properties 15,16 . Magnetic field processing has also been used to achieve the desired texture and improved J c performance in HTS [17][18][19][20] . In processing of MgB 2 bulk and wires the reaction in-situ technique in combination with the powder-in-tube (PIT) method has been used to produce the wires with the best field performance [21][22][23] . Other advantages of this process include easy fabrication of coils and the ability to incorporate dopants and additives, which are important for improvement of flux pinning and H c2 . In the in-situ reaction process, Mg melts before the MgB 2 formation by solid state reaction, provided the heating rate is high enough. The presence of a liquid phase provides a window of opportunity for applying a magnetic field processing technique to achieve a crystalline refinement, homogeneous distribution of additives and inclusions and possible alignment of both matrix materials and additives.In this work, a standard powder-in-tube method was used for Fe clad MgB 2 wire 23 . Powders of magnesium (99%) and amorphous boron (99%) were well mixed with 0 and 10 wt% of multi-wall ...

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Magnetic Susceptibility of Molecular Carbon: Nanotubes and Fullerite

Cited by 151 publications

References 35 publications

High-temperature ferromagnetism of helical carbon nanotubes

High-temperature ferromagnetism of helical carbon nanotubes

Magnetorheology of Multiwalled Nanotube Dispersions in Mineral Oil

Magnetic field processing to enhance critical current densities of MgB2 superconductors

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