A Nickel Coating Removal Process for ITER Superconducting Cables

A new method is developed for removing the nickel coating on ITER superconducting cables by mechanical polishing.The obvious advantage of the mechanical method,which uses a nylon brush,is that there is no chemical residual left in the cable,which would otherwise result in passive effects on the joint resistance.The coating resistance test results of this newly developed method are compared with those of the two other methods that can meet the requirements of ITER.An automatic polishing machine is designed and manufactured for the procedure to provide quality under precise control.This new technique can replace the conventional manual method due to its improved efficiency.

Constant current electrodeposition preparation of nickel layer and its mechanical properties in ionic liquid

Smooth and compact nickel layers were successfully prepared in the ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate(BMIMBF4)by constant current electrodeposition method.The effects of temperature,additive content,current density,and deposition time on the performance of the nickel layers were systematically analyzed.Scanning electron microscopy(SEM)and X-ray diffraction(XRD)were used to analyze the surface morphology and composition of the nickel layers.Meanwhile,the tensile strengths of the nickel layers were tested by universal tensile testing machine.The results show that different process conditions have a great effect on morphology and performance of the electrodeposited nickel layer.The optimization of process parameters is as follows:BMIMBF4 to ethylene glycol(EG)volume ratio of 2:1,deposition temperature of 120℃,and current density of 1.2 mA·cm^(-2).Current density has a greater influence on the tensile strength of the nickel layer,and the maximum value of tensile strength is 1275 MPa.

Construction of lightweight NiCo-LDH/carbon fiber nanocomposites for broad-band microwave absorption

The rapidly increasing usage of electric technology during the last decades has facilitated the fabrication of high-efficiency microwave absorption(MA)materials(MAMs).In this study,hierarchical NiCo layered double hydroxide(LDH)/carbon fiber(CF)nanocomposites were constructed via simple hydrothermal production,and their MA properties were evaluated.Benefiting from interfacial polarization,defect-induced polarization,and multiple reflections induced by the hierarchical sheets,the LDH/CF composites delivered a better MA perfor-mance than that by pure CF and LDH.The addition ratio of the LDH also played a vital role in determining the impedance matching and microwave absorption performance.Specifically,the optimized LDH/CF composites demonstrated an exceptional reflection loss(RL)of-62.47 dB with a thickness of 2.22 mm,and an effective absorption bandwidth(EAB)covering 6.4 GHz(11.6-18.0 GHz)at a 20 wt.%filling ratio,which outperformed the reported CF-based microwave absorbers.Owing to this superior MA,the as-prepared LDH/CF composites demonstrated to be significantly promising for advancing the usage of CF-based MAMs.

Continuous Surface Metallization of Polyimide Fibers for Textile‑Substrate Electromagnetic Shielding Applications

Despite tremendous effort,continuous fabrication of high-performance conductive polymer fibers for electromagnetic interference(EMI)shielding applications remains a daunting technical challenge.In the current study,we report an efficient strategy for continuous surface metallization of polyimide fibers used in textile-substrate electromagnetic shielding applications.Polyimide fibers with pendent carboxyl groups(PIC)were first fabricated,and a conductive nickel layer was continuously coated on the PIC surface by electroless metal deposition(ELD).The carboxyl groups introduced onto the fiber surface acted as binding sites for the Ni^(2+)ions,and the complexation reactions greatly increased the Ni^(2+)adsorption capacity and efficiency of the PIC fibers during the ELD process and ensured continuous fabrication.Through judicious control of the plating time,a series of nickel-layer-coated PIC fibers(Ni-PIC)were constructed with Ni loadings ranging from 20 to 230 wt%.The resultant Ni-PIC fiber containing 65 wt%Ni exhibited conductivity of 223 S cm^(−1),and the corresponding fabric exhibited an EMI shielding effectiveness(EMI SE)of 44 dB in the X-band.The corresponding EMI SE was further improved to 83 dB after the fiber was treated at 300℃ for 1 h because of the crystallization of the Ni layer.The prepared Ni-PIC fibers and fabrics were also used in pressure sensors and electrothermal conversion,which demonstrated outstanding adaptabilities to various temperatures and mechanical properties.Overall,this work provides an efficient route for developing high-performance conductive polyimide fibers for EMI shielding applications,especially for use in military and aerospace equipment and in other harsh environments.

Green synthesis of NiFe LDH/Ni foam at room temperature for highly efficient electrocatalytic oxygen evolution reaction

Clean energy technologies such as water splitting and fuel cells have been intensively pursued in the last decade for their free pollution. However, there is plenty of fossil energy consumed in the preparation of the catalysts,which results in a heavy pollution. Therefore, it is much desired but challenging to fabricate high-efficiency catalysts without extra energy input. Herein, we used a facile one-pot room-temperature method to synthesize a highly efficient electrocatalyst of nickel iron layered double hydroxide grown on Ni foam(NiFe LDH/NF) for oxygen evolution reaction(OER). The formation of the NiFe LDH follows a dissolutionprecipitation process, in which the acid conditions by hydrolysis of Fe^3+ combined with NO3^- could etch the NF to form Ni^2+. Then, the obtained Ni^2+ was co-precipitated with the hydrolysed Fe^3+ to in situ generate NiFe LDH on the NF. The NiFe LDH/NF exhibits excellent OER performance with a low potential of about 1.411 V vs. reversible hydrogen electrode(RHE) at a current density of 10 m A cm^-2, a small Tafel slope of 42.3 mV dec^-1 and a significantly low potential of ~1.452 V vs. RHE at 100 mA cm^-2 in 1 mol L^-1 KOH. Moreover, the material also keeps its original morphology and structure over 20 h. This energy-efficient strategy to synthesize NiFe LDH is highly promising for widespread application in OER catalyst industry.

Analysis of Non-uniform Mechanical Behavior for a Continuous Casting Mold Based on Heat Flux from Inverse Problem

The distortion of mold plates plays an important role in the formation of surface cracks on continuously cast steel products. To investigate the non-uniform distortion of a mold, a full-scale stress model of the mold was de veloped. An inverse algorithm was applied to calculate the heat flux using the temperatures measured by the thermo- couples buried inside the mold plates. Based on this, a full-scale, finite-element stress model, including four copper plates, a nickel layer and water slots in different depths, was built to determine the complex mechanical behavior of the continuous casting mold used to produce steel slabs. The heat flux calculated by the inverse algorithm was applied to the stress model to analyze the non-uniform mechanical behavior. The results showed that the stress and distortion distributions of the four copper plates were not symmetrical, which reflected the non-uniform distortion behaviors of copper plates, water slots, nickel layer and the corner region of the mold. The gap between the mold and the slab was increased because of the corner distortion, which was very important for the heat transfer of initial solidifying shell, and it may be a major reason for the slow cooling of the slab corner.