NOVEL MAGNETIC PROPERTIES IN MULTI-WALLED CARBON NANOTUBE MATS: CONSISTENT WITH THE PARAMAGNETIC MEISSNER EFFECT DUE TO ULTRAHIGH-TEMPERATURE SUPERCONDUCTIVITY

2009 ◽  
Vol 23 (20n21) ◽  
pp. 4285-4296 ◽  
Author(s):  
GUO-MENG ZHAO ◽  
PIEDER BEELI
Keyword(s):  
Carbon Nanotube ◽  
Saturation Magnetization ◽  
Magnetic Measurements ◽  
Meissner Effect ◽  
Magnetic Data ◽  
Ferromagnetic Transition ◽  
Measured Concentration ◽  
Paramagnetic Meissner Effect ◽  
Multi Walled Carbon Nanotube ◽  
Ultrahigh Temperature

We report magnetic measurements up to 1200 K on iron-contaminated multi-walled carbon nanotube mats with a Quantum Design vibrating sample magnetometer. Extensive magnetic data consistently show a ferrromagnetic transition at about 1000 K and a ferromagnetic-like transition at about 1275 K. The ferromagnetic transition at about 1000 K is associated with an Fe impurity phase and its saturation magnetization is in quantitative agreement with the Fe concentration measured by an inductively coupled plasma mass spectrometer. On the other hand, the saturation magnetization for the ferromagnetic-like phase (at 1275 K) is about four orders of magnitude larger than that expected from the measured concentration of Co or CoFe . We show that this ultrahigh-temperature ferromagnetic-like behavior cannot be explained by ferromagnetism of any Fe -carbon phases, carbon-based phases, or magnetic impurities, but is consistent with the paramagnetic Meissner effect (orbital ferromagnetism) due to the existence of π Josephson junctions in a granular superconductor.

Magnetic Properties and Scaling Behavior in Perovskite–like La0.7(Ba1−xPbx)0.3CoO3 System

2001 ◽  
Vol 674 ◽  
Author(s):  
Chiung-Hsiung Chen ◽  
Ting-Sheng Huang ◽  
Ming-Fong Tai
Keyword(s):  
Magnetic Properties ◽  
Magnetic Measurements ◽  
Mean Field Theory ◽  
Mean Field ◽  
Three Dimensional ◽  
Scaling Behavior ◽  
Magnetic Data ◽  
Crystallographic Structure ◽  
Ferromagnetic Transition ◽  
Diffraction Patterns

ABSTRACTIn this study, we used x-ray diffraction patterns and dc magnetic measurements to investigate the crystallographic structure, magnetic properties and scaling behavior of the distorted perovskite La0.7(Ba1−xPbx)0.3CoO3 (0 ≤ x ≤ 0.5) system with a constant ratio of Co4+/Co3+. Samples with x = 0.0 and 0.1 were crystallized in the cubic structure with a ∼ 7.76 Å whereas samples with x ≥ 0.2 were crystallized in an orthorhombic Pbnm space group with a ∼ b ∼ 5.50 Å and c ∼ 7.85 Å. For all our samples the spin-glass-like behavior were observed in low temperature and low field ranges. The Pb2+ substitution on Ba2+ site does not significantly affect the ferromagnetic transition temperature TC, but does introduce large variation in the magnetic strength. In both the ferromagnetic and paramagnetic states the minimum values of the average effective moments provided by every Co ion occur at x = 0.3. We also observed the scaling behaviors of magnetic data in all samples. The derived values of the critical exponents (β, γ, δ) were consistent with those predicted by mean field theory and a three-dimensional Heisenberg model.

scholarly journals Magnetic, Electrical, and Mechanical Behavior of Fe-Al-MWCNT and Fe-Co-Al-MWCNT Magnetic Hybrid Nanocomposites Fabricated by Spark Plasma Sintering

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 436
Author(s):  
Alexandre Tugirumubano ◽  
Sun Ho Go ◽  
Hee Jae Shin ◽  
Lee Ku Kwac ◽  
Hong Gun Kim
Keyword(s):  
Magnetic Properties ◽  
Carbon Nanotube ◽  
Saturation Magnetization ◽  
Volume Content ◽  
Magnetic Particles ◽  
Hybrid Nanocomposites ◽  
Soft Magnetic Properties ◽  
Soft Magnetic ◽  
Continuous Increase ◽  
Multi Walled Carbon Nanotube

This paper aims to investigate different properties of the Fe-Al matrix reinforced with multi-walled carbon nanotube (MWCNT) nanocomposites with the Al volume content up to 65%, according to the Fe-Al combination. In addition, the effect of adding Co content on the improvement of the soft magnetic properties of the nanocomposites was carried out. The nanocomposites were fabricated using the powder metallurgy process. The iron-aluminum metal matrix reinforced multi-walled carbon nanotube (Fe-Al-MWCNT) nanocomposites showed a continuous increase of saturation magnetization from 90.70 A·m2/kg to 167.22 A·m2/kg and microhardness, whereas the electrical resistivity dropped as the Al content increased. The incorporation of Co nanoparticles in Fe-Al-MWCNT up to 35 vol% of Co considerably improved the soft magnetic properties of the nanocomposites by reducing the coercivity and retentivity up to 42% and 47%, respectively. The results showed that Al-based magnetic nanocomposites with a high Al volume content can be tailored using ferromagnetic particles. The composites with a volume content of magnetic particles (Fe+Co) greater than 60 vol% exhibited higher saturation magnetization, higher coercivity, and higher retentivity than the standard Sendust core. Moreover, the produced composites can be used for the lightweight magnetic core in electromagnetic devices due to their low density and good magnetic and mechanical properties.

scholarly journals Photoluminescent Properties of Hydroxyapatite and Hydroxyapatite/Multi-Walled Carbon Nanotube Composites

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 832
Author(s):  
Edna X. Figueroa-Rosales ◽  
Javier Martínez-Juárez ◽  
Esmeralda García-Díaz ◽  
Daniel Hernández-Cruz ◽  
Sergio A. Sabinas-Hernández ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Hexagonal Phase ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Multi Walled Carbon Nanotube ◽  
Nanotube Composites ◽  
Carbon Nanotube Composites ◽  
Co Precipitation ◽  
Functionalized Mwcnts

Hydroxyapatite (HAp) and hydroxyapatite/multi-walled carbon nanotube (MWCNT) composites were obtained by the co-precipitation method, followed by ultrasound-assisted and microwave radiation and thermal treatment at 250 °C. X-ray diffraction (XRD) confirmed the presence of a hexagonal phase in all the samples, while Fourier-transform infrared (FTIR) spectroscopy elucidated the interaction between HAp and MWCNTs. The photoluminescent technique revealed that HAp and the composite with non-functionalized MWCNTs present a blue luminescence, while the composite with functionalized MWCNTs, under UV-vis radiation shows an intense white emission. These findings allowed presentation of a proposal for the use of HAp and HAp with functionalized MWCNTs as potential materials for optoelectronic and medical applications.

Adsorption performance of multi-walled carbon nanotube-SiO2 adsorbent for toluene

2021 ◽  
Vol 49 (6) ◽  
pp. 861-872
Author(s):  
Wei LIU ◽  
Zhuang LI ◽  
Shao-peng ZHANG ◽  
Wei-wei JIAN ◽  
Dan-zhu MA
Keyword(s):  
Carbon Nanotube ◽  
Adsorption Performance ◽  
Multi Walled Carbon Nanotube
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