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Improved Critical Current Density of MgB2–Carbon Nanotubes Composite

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Abstract:

In the present study, we report a systematic study of doping/admixing of carbon nanotubes (CNTs) in different concentrations in MgB2. The composite material corresponding to MgB2−x at.% CNTs (35 at.% ≥ x ≥ 0 at.%) have been prepared by solid-state reaction at ambient pressure. All the samples in the present investigation have been subjected to structural/microstructural characterization employing XRD, Scanning electron microscopic (SEM), and Transmission electron microscopic (TEM) techniques. The magnetization measurements were performed by Physical property measurement system (PPMS) and electrical transport measurements have been done by the four-probe technique. The microstructural investigations reveal the formation of MgB2–carbon nanotube composites. A CNT connecting the MgB2 grains may enhance critical current density due to its size (∼ 5–20 nm diameter) compatible with coherence length of MgB2 (∼5–6 nm) and ballistic transport current carrying capability along the tube axis. The transport critical current density (Jct) of MgB2 samples with varying CNTs concentration have been found to vary significantly e.g., Jct of the MgB2 sample with 10 at.% CNT addition is ∼2.3 × 103 A/cm2 and its value for MgB2 sample without CNT addition is ∼7.2 × 102 A/cm2 at 20 K. In order to study the flux pinning effect of CNTs doping/admixing in MgB2, the evaluation of intragrain critical current density (Jc) has been carried out through magnetic measurements on the fine powdered version of the as synthesized samples. The optimum result on Jc is obtained for 10 at.% CNTs admixed MgB2 sample at 5 K, the Jc reaches ∼5.2 × 106 A/cm2 in self field, ∼1.6 × 106 A/cm2 at 1 T, ∼2.9 × 105 A/cm2 at 2.6 T, and ∼3.9 × 104 A/cm2 at 4 T. The high value of intragrain Jc in 10 at.% CNTs admixed MgB2 superconductor has been attributed to the incorporation of CNTs into the crystal matrix of MgB2, which are capable of providing effective flux pinning centres. A feasible correlation between microstructural features and superconducting properties has been put forward.

Keywords: CARBON NANOTUBES; COMPOSITE; CRITICAL CURRENT DENSITY; SEM; TEM

Document Type: Research Article

DOI: http://dx.doi.org/10.1166/jnn.2007.720

Publication date: June 1, 2007

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  • Journal for Nanoscience and Nanotechnology (JNN) is an international and multidisciplinary peer-reviewed journal with a wide-ranging coverage, consolidating research activities in all areas of nanoscience and nanotechnology into a single and unique reference source. JNN is the first cross-disciplinary journal to publish original full research articles, rapid communications of important new scientific and technological findings, timely state-of-the-art reviews with author's photo and short biography, and current research news encompassing the fundamental and applied research in all disciplines of science, engineering and medicine.
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