Properties of electrospun superconducting and magnetoresistive nanowires

Supraleitende Nanofasern und magnetoresistive Nanodrähte wurden durch Elektrospinnen und entsprechende Temperaturbehandlung hergestellt. Der Mechanismus des Elektrospinnens wird vorgestellt. Die Kernpunkte der Herstellung von Nanobändern und die Idee des Auffangens von parallelen Nanofasern werden demonstriert. Um supraleitende oder magnetoresistive Phasen unter Erhalt der Faserstruktur zu erzeugen, wird die Temperaturbehandlung basierend auf einer thermogravimetrischen Analyse vorgeschlagen. Die Untersuchung der supraleitenden Nanofasern basiert auf den zwei Kuprat- Supraleitern La1.85Sr0.15CuO4 und Bi2Sr2CaCu2O8 (Bi-2212). Ein Vergleich der supraleitenden Eigenschaften zwischen La1.85Sr0.15CuO4 Nanodrähten und Nanobändern wird vorgestellt. Die magnetischen und elektrischen Eigenschaften der Bi-2212 - Netzwerke, mit reiner Bi-2212 Phase, aber auch Pb - und Li - dotierten Phasen, werden präsentiert. Das erweiterte Bean-Modell des kritischen Zustandes wird zur Bestimmung der kritischen Stromdichte angewendet und ein Modell eines Netzwerks bestehend aus Josephson-Kontakten wird vorgeschlagen, um die einzigartigen elektrischen Eigenschaften zu erklären. In einem eigenen Abschnitt werden die Eigenschaften einer einzelnen, dicken Bi-2212 Faser demonstriert. Die Eigenschaften von magnetoresistiven Nanodrahtnetzwerken werden anhand des Perowskits La1−xSrxMnO3 untersucht. Der Einfluss des Dotierungsgrads von Sr auf die magnetischen und magnetoresistiven Eigenschaften wird diskutiert. Zum Schluss werden die Eigenschaften von hybriden La1.85Sr0.15CuO4/La0.7Sr0.3- MnO3 - Nanodrahtnetzwerken präsentiert.Superconducting nanofibers (nanowires and nanoribbons) and magnetoresistive nanowires were fabricated by the electrospinning technique accompanied with appropriate thermal treatment. The mechanism of electrospinning is introduced. The key points of producing nanoribbons and the idea of parallel nanofiber collection are demonstrated. To obtain the superconducting or magnetoresistive phases while maintaining the fiber structure, a thermal treatment based on the thermal gravity analysis is proposed. The investigation of the superconducting nanofibers is based on two cuprate superconducting materials: La1.85Sr0.15CuO4 and Bi2Sr2CaCu2O8 (Bi-2212). A comparison of the superconductivity between La1.85Sr0.15CuO4 nanowires and nanoribbons is presented. The magnetic and electric properties of the Bi-2212 nanowire networks are presented, including a comparison between pure Bi-2212, Pb-doped Bi-2212, and Li-doped Bi-2212 nanowire networks. The extended critical state model is applied for the critical current density estimation, and a Josephson junction network model is proposed to explain the unique features of the electric properties. As a special section, the properties of a single Bi-2212 thick fiber are also demonstrated. The characterization of the magnetoresistive nanowire networks is based on the perovskite materials La1−xSrxMnO3. The influence of the Sr doping level on the magnetic properties and magnetoresistance is discussed. At the end, the properties of La1.85Sr0.15CuO4/La0.7Sr0.3MnO3 hybrid nanowire networks are presented

Conversion of Hard to Soft Magnetic Ferrite Nanowires by Paramagnetic Shielding

In this study, we investigate the magnetization behavior of coaxial nanowires fabricated through the sol-gel electrospinning method. Our analysis uncovers a significant reduction in coercivity for CoFe2O4 nanowires when BaTiO3 is used as the shell material, effectively transforming them from hard to soft magnetic. This intriguing behavior is attributed to the magnetization reversal effect at the interface between ferromagnetic and paramagnetic regions, and it is also observed in NiFe2O4 and Fe2O3 nanowires. Surprisingly, introducing a GdBa2Cu3O7 shell induces a similar effect. Additionally, we employ magnetic impedance measurements on the coaxial nanowires, unveiling their potential for magnetic field sensing applications

An integrated model to select an ERP system for Chinese small- and medium-sized enterprise under uncertainty

Enterprise Resource Planning (ERP) system is a vital investment that can significantly affect future competitiveness and performance of small- and medium-sized enterprises (SMEs). Selecting the best desirable ERP software covering both qualitative and quantitative factors has been the most critical problem for a long time. On the other hand, multiple criteria decision making has been found to be a useful approach to analyze conflicting factors. Qualitative criteria are often accompanied by ambiguities and vagueness. This makes fuzzy and grey logic become more natural approaches to handle this kind of problem. This paper presents a new approach for the selection of SME-specific ERP systems. Firstly, criteria for SMEs in China to evaluate the most suitable ERP system are put forward using group-discussing and anonymous questionnaire methods. An effective and practical algorithm, which is integrated of modified Delphi, analytic hierarchy process, fuzzy comprehensive evaluation and grey relational analysis, is utilized to convert the qualitative description to quantitative data to select the most appropriate alternative in the presence of vagueness and uncertainty. Finally, the potential use of the proposed model is illustrated through a case study. First published online: 02 Nov 201

An efficient ICT-based ratio/colorimetric tripodal azobenzene probe for the recognition/discrimination of F−, AcO− and H2PO4− anions

The tripodal probe L was readily prepared via introducing rhodamine and azobenzene groups in a two-step procedure. Studies of the recognition properties indicated that probe L exhibited high sensitivity and selectivity towards F−, AcO− and H2PO4− through a ratiometric colorimetric response with low detection limits of the order of 10−7 M. The complexation behaviour was fully investigated by spectral titration, 1H NMR spectroscopic titration and mass spectrometry. Probe L not only recognizes F−, AcO− and H2PO4−, but can also distinguish between these three anions via the different ratiometric behaviour in their UV–vis spectra (387/505 nm for L-H2PO4−, 387/530 nm for L-AcO− and 387/575 nm for L-F− complex) or via different colour changes (light coral for L-H2PO4−, light pink for L-AcO− and violet for the L-F− complex). Additionally, given the presence of NH and OH groups in probe L, which can be protonated and deprotonated, probe L further exhibited an excellent pH response over a wide pH range (pH 3 to pH 12)

Magnetoresistance and Structural Characterization of Electrospun La1−xSrxMnO3 Nanowire Networks

Nanowire network fabrics of La1−xSrxMnO3 (LSMO) with different doping levels x = 0.2, 0.3, and 0.4 were fabricated by means of electrospinning. The resulting nanowires are up to 100 μm long with a mean diameter of about 230 nm. The nanowires form a nonwoven fabric-like arrangement, allowing to attach electric contacts for magnetoresistance (MR) measurements. The resistance in applied magnetic fields and the MR effect were measured in the temperature range 2 K < T < 300 K in magnetic fields up to 10 T applied perpendicular to the sample surface. An MR ratio of about 70% is obtained for x = 0.2 at 10 T applied field and T = 20 Kr. The highest low-field MR of 5.2% (0.1 T) is obtained for the sample with x = 0.2. Magnetization measurements reveal the soft magnetic character of the samples. A thorough analysis of the microstructure of these nanowire networks is performed including scanning electron microscopy (SEM) and transmission electron microscopy (TEM)