The rapid progress on MgB 2 superconductor since its discovery  has made this material a strong competitor to low and high temperature superconductors (HTS) for applications with a great potential to catch the niche market such as in magnetic resonant imaging (MRI). Thanks to the lack of weak links and the two-gap superconductivity of MgB 2 [2,3] a number of additives have been successfully used to enhance the critical current density, J c and the upper critical field, H c2 .  Carbon nanotubes (CNTs) have unusually electrical, mechanical and thermal properties  and hence is an ideal component to fabricate composites for improving their performance. To take advantages of the extraordinary properties of CNTs it is important to align CNTs in the composites.Here we report a method of alignment of CNTs in the CNT/MgB 2 superconductor composite wires through a readily scalable drawing technique. The aligned CNT doped MgB 2 wires show an enhancement in magnetic J c (H) by more than an order of magnitude in high magnetic fields, compared to the undoped ones. The CNTs have also significantly enhanced the heat transfer and dissipation. CNTs have been used mainly in structural materials, but here the advantage of their use in functional composites is shown and this has wider ramifications for other functional materials.
We investigated the feasibility of using calcined hydrotalcite (CHT) as the adsorbent of chromate to treat Cr(VI)-contaminated water through column tests under varied conditions. The column tests reveal that CHT can take up 34.3−44.7 mg(Cr)/g when the Cr(VI) concentration in the influent varies over a range of 50−200 mg/L (e.g., 0.96−3.85 mM) with pH 6−7 at 298 K. This uptake capacity is only reduced to 29.1 mg(Cr)/g when HCO3
− (1.0 mM) and Cl− (1.0 mM) coexist in the influent. We note that the treated water is of high quality and is free of Cr(VI), with Mg and Al concentrations of <5−10 mg/L, and a pH of 6.5−7.0. The quick desorption of Cr(VI) from the adsorbent (CHT) has enabled us to recover Cr(VI) from the contaminated water and regenerate the adsorbent. All these findings promise CHT as an effective regenerable adsorbent for the remediation of Cr(VI)-contaminated groundwater.
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  . 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  . 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  . 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 ...
A wireless passive temperature sensor is designed on the basis of a resonant circuit, fabricated on multilayer high temperature cofired ceramic (HTCC) tapes, and measured with an antenna in the wireless coupling way. Alumina ceramic used as the substrate of the sensor is fabricated by lamination and sintering techniques, and the passive resonant circuit composed of a planar spiral inductor and a parallel plate capacitor is printed and formed on the substrate by screen-printing and postfiring processes. Since the permittivity of the ceramic becomes higher as temperature rises, the resonant frequency of the sensor decreases due to the increasing capacitance of the circuit. Measurements on the input impedance versus the resonant frequency of the sensor are achieved based on the principle, and discussions are made according to the exacted relative permittivity of the ceramic and quality factor (Q) of the sensor within the temperature range from 19°C (room temperature) to 900°C. The results show that the sensor demonstrates good high-temperature characteristics and wide temperature range. The average sensitivity of the sensor with good repeatability and reliability is up to 5.22 KHz/°C. It can be applied to detect high temperature in harsh environment.
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