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In order to improve the superhydrophobic and oil-wet properties of raw cotton fibers come from Jiangsu province, China. A novel adsorbent, hydrophobic cotton fibers (HCF) with an excellent superhydrophobic and larger length was synthesized via modified sol–gel method and examined for the removal of nitrobenzene in aqueous solution. Results show that the treated raw cotton fibers exhibited outstanding non-wettability with the WCA of 152° and the larger length of 0.2–0.4 cm, which offers an opportunity to separation in for the removal of nitrobenzene. It was found that adsorption isotherm and kinetics of nitrobenzene onto HCF were well described by the Freundlich and pseudo-second-order kinetic models, respectively. The thermodynamic data showed that the nitrobenzene adsorption onto HCF was a spontaneous, endothermic and physisorption reaction. The monolayer adsorption capacity of nitrobenzene was found to be 16.85 mg/g at 30 °C.

We present a study on the investigation of the proper secondary phases for engineering magnetic flux pinning centers in textured Gd–Ba–Cu–O bulk superconductors. Compared with the joint TiO 2 and BaO 2 doping methods, the addition of BaTiO 3 shows a relevant advantage due to its perovskite structure. Both TiO 2 and BaO 2 doping tends to enter the crystal lattice of the superconducting matrix by ionic substitution, which leads to the variable peak effect in the J c – B diagram. The BaTiO 3 doping method shows a unique pinning behavior, which is attributed to the distinctive precipitations generated by the additions. The composition of the BaTiO 3 doping-related precipitation appears to be controlled under different growth temperatures. The self-field J c improved by nearly double at 77 K in a sample grown with a low growth temperature. In addition, the second peaks caused by various types of additions are located in a narrow field range of 1.25–1.5 T in the J c – B diagram, indicating that the dilute doping follows a unique tendency, which is likely relevant to anisotropic crystal growth. The different observed peak heights suggest the existence of several average pinning potentials provided by various types of additions. BaTiO 3 doping exhibited a stabilization of the unique onset superconducting transition temperature. Therefore, BaTiO 3 can be classified as a useful dopant to control flux pinning behavior in Gd–Ba–Cu–O bulk superconductors.

Since the potential widespread applications of RE–Ba–Cu–O superconducting bulks, it is crucial to enhance their superconducting performances. Binary oxide HfO 2 nanoparticles were added into Gd–Ba–Cu–O superconducting matrix before the melt textured growth process. It was found that the HfO 2 particles reacted with surrounding matrix and consequently formed BaHfO 3 inclusions maintaining nanoscale without significant ripening during the melt growth process. The superconducting transition temperature T C is almost not affected by HfO 2 addition, and interestingly, the T C of 0.8 mol% HfO 2 doped sample increases slightly by about 0.1 K in comparison with the undoped one. Meanwhile, the critical current density J C was improved over the whole magnetic field range. These BaHfO 3 particles discovered near the liquid phase (Ba–Cu–O, Cu–O, etc.) should be the origin for the improvement of flux trapping capability and critical current density in this system.

A series of nanocapsules with carboxymethyl cellulose (CMC)-modified melamine-formaldehyde as the shell material and phase change paraffin as the core material were prepared by in situ polymerization. The modified capsules were examined using Fourier transform infrared spectra, scanning electronic microscope, differential scanning calorimeter, and optical microscopy, and two factors that influence paraffin emulsion preparation (emulsifier type and stirring rate) were investigated. The effects of the synthesis conditions used for the prepolymer on the surface morphology of the capsules were also studied. We found that phase change capsules prepared with both anionic and nonionic emulsifiers were superior to those prepared with a simple emulsifier. The best performance of the paraffin emulsion was obtained when the emulsion was stirred at 8,000 rpm during preparation. The optimal prepolymer reaction conditions to give smooth capsules with good dispersibility and complete morphology were reaction temperature 72.5 °C, reaction time 75 min, and pH 8.5. The CMC-modified nanocapsules have a phase change enthalpy of 83.46 J/g, are fully encased, and are uniform, with an average particle size of 50 nm.

TiO2 dilute doping in melt-processed GdBa2Cu3O7−δ bulk superconductors was studied. TiO2 fine particles are effective additive for the enhancement of flux pinning. TiO2 doping results in the enhanced δl pinning and the improved Tc. Nevertheless, the pinning force characterizations show that δTc pinning still acts as the main role, which can be attributed to the clustered strong superconducting phases and the high Birr values. The trapped field profiles clearly show that the enhanced flux pinning is realized in the doping range from 0.0 mol.% to 0.3 mol.%. Possible reasons behind them are discussed. The main reason is that Ti occupies the Cu site in the CuO chain and thus Ti substituted region forms the high Tc superconducting phase. On the other hand, owing to the enhanced strains or dislocations caused by ion substitution, this region also contributes to the enhanced δl pinning.

This paper reviews recent advances in the melt process of (RE)–Ba–Cu–O [(RE)BCO, where RE represents a rare earth element] single grain high-temperature superconductors (HTSs), bulks and its applications. The efforts on the improvement of the magnetic flux pinning with employing the top-seeded melt-growth process technique and using a seeded infiltration and growth process are discussed. Which including various chemical doping strategies and controlled pushing effect based on the peritectic reaction of (RE)BCO. The typical experiment results, such as the largest single domain bulk, the clear TEM observations and the significant critical current density, are summarized together with the magnetization techniques. Finally, we highlight the recent prominent progress of HTS bulk applications, including Maglev, flywheel, power device, magnetic drug delivery system and magnetic resonance devices.

Introducing additives into the superconducting matrix is an effective way to enhance the flux pinning performance of superconductors. In this article, we introduce a typical ferroelectric material, namely BaTiO3, into the GdBa2Cu3O7−δ (Gd123)/Ag matrix to increase the inhomogeneous state with stronger pinning effect via polarities or ion substitutions. The top-seeded melt growth processed Gd123/Ag bulk superconductors with different doping amount of BaTiO3 ranging from 0.0 mol.% to 0.4 mol.% were fabricated with a cold seeding method. The effect of BaTiO3 addition on microstructure and superconducting properties was investigated systematically. Critical current density, Jc, shows that there are two optimized doping levels. One is 0.1 mol.% with BaTiO3, in the bulk, Jc was enhanced both around zero field and middle field of 1.5 T. The enhanced peak effect (δTc pinning) is rising from the Gd3+/Ba2+ solid solutions, which was further strengthened by a little amount of entrant of Ba2+ and caused a reduction of Tc. While the enhanced Jc around zero field (δl pinning) is coming from the atomic scale pinning centers formed in the CuO plane due to part of Cu2+/3+ ions were substituted by Ti4+. The other optimized doping level is 0.3 mol.%, in this doping amount, Jc value is close to that in 0.1 mol.% doped bulk at self field, but has a lower peak. Two reasons are involved here. The first is that the Gd3+/Ba2+ solid solutions were suppressed by the increased amount of Ba2+ and lead to a suppression of peak effect. The second is the non-superconducting phases (including the survived BaTiO3) formed in the melting process, which act as core pinning centers and contribute to the enhanced δl pinning. The novel doping effect of BaTiO3 is that it may enter as an interstitial among the crystal lattice of Gd-123. The properties of the final products depend on the doping amount. Microstructure analysis shows that Gd-211 particles are fined by proper doping amounts ranging from 0.1 mol.% to 0.3 mol.%.

Multiferroic ErCrO 3 was synthesized and the detailed magnetic as well as ferroelectric properties were investigated. The dc magnetization shows that ErCrO 3 undergoes a antiferromagnetic ordering at T N = 133 K due to the Cr 3+ –Cr 3+ followed by weak ferromagnetic ordering. Around T SR ≈ 22 K, ErCrO 3 exhibits a spin reorientation from Γ 4 to Γ 1 . And the stability of the ferromagnetic Γ 4 phase increases with the applied magnetic field increasing. Furthermore, at lower temperature, it shows weak antiferromagnetic ordering of Er 3+ . We also present the low temperature polarization data for ErCrO 3 and find a remarkable decreasing of polarization around T N = 133 K on increasing temperature, this effect might be due to the coupling between magnetic and ferroelectric order parameters, and the magnetic field suppresses the polarization which demonstrates convincingly the strong magnetoelectric (ME) coupling in ErCrO 3 .

Nontoxic lead-free multiferroic magnetoelectric composites were successfully prepared by incorporating the dispersed 0.15Ni 0.98 Co 0.02 Fe 2 O 4 (NCF) ferromagnetic nanoparticles into 0.85(K 0.5 Na 0.5 )NbO 3 –LiSbO 3 (KNN–LS) ferroelectric micromatrix. The composites show ferroelectric behaviors and magnetic characteristics. The converse magnetoelectric effect (CME) characteristics with the driving electric field, frequency and bias magnetic field ( H Bias ) were investigated in detail by using double coils at room temperature. The CME behaviors are strongly dependent on the driving electric field, frequency and H Bias . Large CME coefficient (2.21 × 10 −10 s/m) was obtained at low frequency and low magnetic bias field (800 Oe). The induced saturation magnetization ( δM ) has an excellent linear relationship with the applied ac electric field with amplitude varying from 7 to 73 V/cm. The CME coefficient increases initially with the increase in H Bias and then decreases with the further increase in the field.

A new kind of nano/microscale lead-free multiferroic composite with a formal of 0.4CoFe2O4–0.6[0.948(K0.5Na0.5)NbO3–0.052LiSbO3] was prepared. The electric-field-induced dielectric (EID) and magnetization (EIM) behaviors were systemically investigated for this 0–3-type structured multiferroic ME composite. Significant electric-field-induced effects were obtained with a high tunability and a large EIM coefficient, which the former has a value of K = 3.35% under the low dc electric-field of 2 kV/cm and the later is in excess of 2.15 × 10−10 s/m at a low frequency of 1.0 kHz with a low magnetic bias field of 2000 Oe for this composite. It is also proved that its EIM behavior is strongly dependent on the bias magnetic field HBias and the frequency of driving electric-field. The measured EIM has an excellent linear relationship with the applied ac electric-field with amplitude varying from 7.1 to 73.6 V/cm. The electric-field-induced effects indicate that the 0–3-type particulate ME composites not only have physical interest but also have potential practical use.

The BiFeO3 single crystals were grown in air in a Bi2O3/Fe2O3 flux. X-ray microanalysis, high resolution synchrotron radiation powder X-ray diffraction, and selected area electron diffraction pattern showed that these single crystals are high quality and exhibit a rhombohedral R3c structure. The dipole stripes and the complex domains of spontaneous ferroelectric polarization had been observed for the first time using HRTEM technique. This work will facilitate intuitive understanding of the atomic scale spontaneous ferroelectric polarization domain structure and of the impact of defects and oxygen vacancies on magnetic and dielectric properties.

Single-phase HoCrO3 samples were prepared using the conventional solid-state reaction. The temperature dependence of dc magnetic properties show that the ZFC and FC magnetization curves are irreversible strongly and nearly symmetrical below 141.0 K under 100 Oe. Moreover, there appears a novel magnetization behavior with negative magnetization (diamagnetism-like) characteristics. This behavior exhibits the coexistence of canted antiferromagnetic and weak ferromagnetic phase and the existence of competition mechanism below Tc1 = 141.0 K. In addition, it is also proved that Ho ion ordered weak CAFM below 7.5 K. The current novel magnetization can be interpreted from the interaction between paramagnetic Ho3+ moments and canted Cr3+ moments.

In this paper, the temperature dependence of magnetic properties and specific heat are systematically investigated for perovskite ErCrO3 chromites. The results show that there exists a strong temperature dependence of magnetic ordering and phase coexistence in the region of low temperature. Specifically, ErCrO3 possesses the long-range antiferromagnetic ordering and the appearance of weak ferromagnetism, occurring at T N =133 K. In the range of higher temperature, above 133.0 K, the reciprocal of magnetic susceptibility χ −1 behaves linearly, indicating a typical Curie–Weiss behavior fitted. The effective magnetic moment μ eff=10.57μ B and asymptotic paramagnetic Curie temperature T cw=−30 K, which suggests the predominance of antiferromagnetic interactions in ErCrO3 chromites. Around T SR≈22 K, ErCrO3 undergoes a spin reorientation from $\varGamma _{4}(G_{x},A_{y},F_{z};F^{R}_{z})$ to $\varGamma _{1}(A_{x},G_{y},C_{z};C^{R}_{z})$ or Γ 1(0). Also, the stability of the ferromagnetic Γ 4 phase increases with increasing applied field. Furthermore, the ac susceptibilities exhibit frequency-independent anomalies near 133 K and the coexistence of the magnetic configuration $\varGamma _{2}(F_{x},G_{y},C_{z};F^{R}_{x},C^{R}_{y})$ and Γ 4. Combining the magnetic properties and the specific-heat measurements, this current magnetization can be interpreted from the interaction between Cr3+–Cr3+, Cr3+–Er3+ and Er3+–Er3+.

International audience; The seeded infiltration and growth of Gd–Ba–Cu–O single grains using a YBa2Cu3Oy pressed pellet as the liquid source has successfully solved the liquid source leakage problem even at Tmax ~ 1100 °C. As a development of this process, a simple but essential modification to insert a liquid source pellet at the bottom of the pre-form was made to the top-seeded melt growth process. The present method resulted in a significant enhancement of the trapped flux density of the Gd–Ba–Cu–O grains. In the growth kinetics, we interpreted that the enriched liquid source surrounding the growth front leads to a more uniform distribution of Gd2BaCuO5 in the matrix and an enlarged c-orientation growth area, which help suppress the formation of high angle grain boundaries. Furthermore, we demonstrated that the present method is of great advantage in multi-seeded processes.

This paper presents a measurement and analysis system of surface defects on sphere parts. The purpose of the system is a requirement to assure high quality of parts. In the system, the developed surface defect detection (SDD) system using laser and CCD camera with improved accuracy, flexibility and advanced measuring efficiency advantages, and the surface defect analysis are used to identify defects. The proposed surface defect analysis approach first uses an empirical mode decomposition (EMD)-based extracting algorithm to perform initial locating of surface defects and extract the possible defects. Then, the approach applies Canny edge algorithm to narrow down the search space of these defects, and backpropagation (BP) neural network to classify five defects with complex shapes, specifically, bulge, dent, abrasion, oxidation, and exfoliation defects. Once these defects are classified, 3D surface morphology of the extracted bulge and dent defects can be obtained and evaluated. Therefore, the system can work well for surface defects on sphere parts mentioned. Experimental results on measurement and analysis of a variety of the surface defects on sphere parts are reported to show the performance of the system.

The stability and durability of trapped flux is a focus in investigations of melt-growth (RE)Ba2Cu3O7−δ (RE=rare earth, e.g., Y, Gd, Sm) bulk high-temperature superconductors. In magnetic flux engineering applications, two important issues affect the expected performance of bulk superconductors: flux trapping and flux stability or durability. The introduction of effective pinning with homogeneous spatial distribution is inevitable. The materials process and durability studies have been pursued in the last decade with either a stationary or a momentary applied external field. In machine applications, the magnetic flux stability is influenced by external perturbations. We topically summarize our progress and current status in relation to past and ongoing work.

International audience; We report a modified top-seeded melt-growth technology for processing high performance Gd–Ba–Cu–O trapped field magnets (TFMs) by providing an additional liquid source during the melt-textured growth. The enriched liquid source allows sufficient growth in the a−b plane with an increased growth rate, and depresses the accumulation of Gd2BaCuO5 (Gd211) particles, which largely suppresses the formation of sub-grain boundaries in the a-growth sectors. An average trapped magnet field of 1.2 T is achieved for the 32 mm Gd–Ba–Cu–O TFMs at 77 K. These Gd–Bd–Cu–O TFMs exhibit superior in-field flux trapping performance, thanks to the significant second peak effect of the critical current density (Jc). The additional liquid source intensifies the Gd–Ba substitution, and therefore increases the in-field Jc, especially at the temperature range of 30–70 K, which is meaningful for practical applications.

A series of REBa2Cu3Oy (RE123)/Ag bulk superconductors with multi-RE elements at the RE site, were prepared by top-seeded melt growth. By employing the differential thermal analysis, we carefully adjusted the peritectic decomposition temperature (Tp) by changing the ratio of the two RE123 compositions to meet the requirements of the cold-seeding process. The superconducting properties, Tc, Jc and the flux trapping performance were evaluated after achieving the growth of the single grains. The microstructure was also observed. A relatively low growth temperature range depressed the LRE-Ba substitution, which was effective to suppress the probable RE211 coarsening. By employing ZrO2 chemical doping, the flux pinning property was further improved under both zero-field and in-field, and the Jc was enhanced without reducing Tc.

Enhancement of the critical current density (JC) and trapped flux density (BT) of bulk high-temperature superconductor are essential for large-scale applications. Introducing artificial pinning centers into the superconducting matrix has been proved to be an effective way to enhance JC and BT. It has been suggested that the ferromagnetic particles doping may provide higher pinning potential. The doping effects of Fe-B soft magnetic particles for GdBa2Cu3O7 - σ (Gd123) bulk were reported previously. In the present work, we reported the improvements in both JC and BT of Gd123 bulk doped by Fe-Ni alloy particles. To make sure a uniform distribution of the dopant, Fe-Ni alloy particles, with amount varied from 0 to 20 mol%, were initially added to prepare Gd123 precursor powders for the bulk processing. X-ray diffraction showed a tetragonal-orthorhombic transition of Gd123 crystal structure with increasing doping amount. The in-field JC was greatly enhanced by the Fe-Ni particles doping and the optimal doping amount was found to be 0.5 mol%. The microstructure of the bulk samples were also investigated by scanning electron microscopy. The great improvement of trapped flux by Fe-Ni doping was considered to be benefit for practical applications.

In the application of a miniature serial-link coordinate measuring machine, it is necessary to calibrate the structural parameters and improve the positioning accuracy for accurate task performance. In this study, using a designed compound calibration artefact, a new calibration method which includes kinematic calibration and laser tool centre point (TCP) calibration is proposed. In the kinematic calibration, geometric parameters included in the kinematic model can be identified by using the constraint that the cone angle or cylinder diameter for several different positions is invariable. For the laser TCP calibration, the relative positions between the laser sensor and the end effector are calibrated by means of the cone surface part of the calibration artefact, using the constraint that the conic node positions for several different measurements are invariable. During the calibration process, the identification of all structural parameters from measuring data can be separated furthest, so the calibration errors brought by strong correlations between all the parameters can be decreased. Moreover, the differences of different positions of end effector in calculations can be used; thus, the calibration error which is due to the positioning error of the end effector can be decreased. Experimental results on real data have demonstrated the effectiveness of our method.

A novel cold-seeding approach of top-seeded melt growth of RE–Ba–Cu–O bulk was studied by employing a MgO crystal seed and a buffer pellet. The growth process is divided into two steps. The MgO seed is used to texture-grow the small RE–Ba–Cu–O pellet with high melting point (Tp) and the textured pellet induces the texture growth of the bulk at lower temperature. Undercooling and RE211 content of the pellet are adjusted to avoid the misorientation caused by lattice mismatch between MgO and the RE–Ba–Cu–O matrix. Bulk samples prepared with this method show good growth sections and superconducting performance. One of the promising advantages of this method is to process high Tp RE–Ba–Cu–O bulks with a cold-seeding method, for example Nd–Ba–Cu–O bulk.

The temperature dependence of the dc magnetization and the specific heat capacity are systematically investigated for the perovskite YbCrO3 chromites. The results show that there exist two complex sequences of magnetic transitions with the characteristics of magnetization reversal and Yb3+/Cr3+ spin ordering at different temperature, respectively. The antiferromagneticlike transition around TN=118 K is attributed to the antiferromagnetic ordering of the Cr3+ spins and a negative magnetization, accompanied with a tendency to the plateau below 10 K caused by the Yb3+ ordering. We obtain the Weiss constant of −197.0 K and an effective moment of 5.99μB for the sum of the free ion values of 4.53μB for Yb3+ and 3.87μB for high-spin Cr3+ from the experiments, which shows an antiferromagnetic interaction and the existence of weak canted antiferromagnetic (CAFM) characteristics. Corresponding to the magnetic phase transition in the Cr sublattice, the specific heat capacity under zero fields exhibits a sharp λ-shap...

Fe–B magnetic particles doped GdBa2Cu3O7-δ superconducting bulks were fabricated by using the top-seeded melt growth method. 10 wt% Ag2O or equivalent 9.31 wt% nano–Ag particles (50 nm in diameter) were added into the precursors before the sample preparation. The Fe–B doped GdBa2Cu3O7-δ/nano–Ag showed poorer mechanical properties with an obviously porous/cracked structure than the GdBa2Cu3O7-δ/Ag2O one especially at the bottom part of the bulk. In the GdBa2Cu3O7-δ/Ag2O bulk, doped Fe element is mainly wrapped or attached by Ag particles. In contrast, the Fe element prefers to substitute on the Cu sites in the GdBa2Cu3O7-δ/nano–Ag bulk due to less protection from Ag particle. The microstructure and superconducting properties were investigated in these two series samples.