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Low-temperature synthesis of Nb3Sn thin-film cavity is of great significance in the field of superconducting radio frequency (SRF). The bronze process can grow only stable Nb3Sn phase at 700 °C, so it is considered to be the most promising process for low-temperature synthesis of Nb3Sn thin-film cavity. We successfully fabricated the worldwide first Nb3Sn thin-film cavity by bronze process. We technically solved the key problems of precursor preparation, characterized and analyzed the uniformity of the Nb3Sn film, and tested the performance of the cut-out samples and the whole cavity of the Nb3Sn film. It is obtained that the Q 0 value of the cavity at 4.2 K is about 1.2 × 109, which is greater than the performance of the bulk-niobium cavity under the same conditions. This result means that the preparation of Nb3Sn by bronze process has the great potential to more practical copper-based Nb3Sn thin-film cavity, which is expected to achieve a substantial improvement in the performance of SRF cavity and comprehensive engineering applications.

The Li-rich layered oxides show a higher discharge capacity over 250 mAh/g and have been developed into a promising positive material for lithium ion batteries. A rare earth metal oxyfluoride YOF-coated Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 composites have been synthesized by a simple wet chemical method. Crystal structure, micro-morphology and element valence of the pristine and YOF-coated Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 materials are characterized by XRD, SEM, TEM, and XPS. The results indicate that all materials exhibit a typical layered structure, and are made up of small and homogenous particles ranging from 100 nm to 200 nm. In addition, YOF layer with a thickness of approximately 3–8 nm is precisely coated on the surface of the Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 . Constant current charge/discharge tests at various current densities show that the electrochemical performance of 2 wt% YOF-coated Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 has been improved significantly. 2 wt% YOF-coated Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 delivers the highest discharge capacity of 250.4 mAh/g at 20 mA/g among all the samples, and capacity retention of 87% after 100 charge/discharge cycles at 200 mA/g while that of the pristine one is only 81.6%. The superior electrochemical performance of 2wt% YOF - coated sample is ascribed to YOF coating layer, which could not only reduce side reactions between the electrode and liquid electrolyte, but also promote lithium ion migration.

Plasma processing is a fast-emerging surface treatment technology for superconducting radio frequency (SRF) cavities: plasma interacts with the impurity contamination and tiny burrs, resulting in an etched clean-and-smooth RF surface. Among all the variations of plasma processing method, the physical sputtering process might be applied to SRF cavities but has no clear etching profile (including distribution uniformity, ion flux, energy, and etching rate). To investigate that, this paper utilizes a two-dimensional self-consistent model combining the fluid equations and the Monte Carlo collision method. With the model, we introduced the sputtering-yield probability distribution to evaluate the physical sputtering process quantitatively; optimized the plasma distribution characteristics with three electrode structures to attain uniformly distributed plasma; built the correlation between ion flux and ion-energy distribution function (IEDF) under varied power and frequency; and studied the physical sputtering process at different positions. In the end, we performed the plasma physical sputtering experiment on small niobium samples, seeing an etching and smoothing effect. This research successfully evaluated the physical sputtering process for SRF cavities, and indicated the feasibility of pure physical sputtering etching.

This work describes a synthesizing method for Mo-doped SnO2 nanotubes (NTs) with uniform morphology by combining electrostatic spinning and air sintering. The method uses Mo ions to do substitutional doping of Sn ions in SnO2 to construct new lattice defects (such as oxygen vacancies), which provides more active sites for gas adsorption. Ethanol was taken as an example to study gas sensitivity characteristics of synthesized products. The analysis showed that 5 mol% of Mo-doped SnO2 nanotubes sensor exhibited the highest response (46.8) to 100 ppm ethanol at a lower optimum temperature (220 °C) and reduced the response/recovery time to 7/103 s. Also, it manifested excellent selectivity and long-term stability. The functionalized nanotubes structure and optimized parameters (oxygen vacancies concentration, metal vacancies defects, carrier concentration, catalytic sites, and base resistance increased) are the reasons for enhancing gas-sensing performance. This work provides direction that the optimal doping concentration of transition metal elements for metal-oxide NTs gas sensors can achieve the best sensing response.

The Nb3Sn thin film cavity, having the potential to be operated at a higher temperature and higher gradient compared to the cavity made from bulk niobium, is one of the most promising key technologies for the next-generation radio-frequency superconducting accelerators. In our work, several 1.3 GHz single-cell TESLA-shaped Nb3Sn thin film cavities, coated by the vapor diffusion method, were tested at Peking University and Institute of Modern Physics, Chinese Academy of Sciences. It was observed that the performance of the Nb3Sn thin film cavities in the tests without the slow cooling down procedure and the effective magnetic field shielding was significantly improved by using a low temperature baking at 100 °C for 48 hours. Although the peak electric field of the cavity remained unchanged, the rapid drop of the unloaded Q value (Q 0) with the increasing accelerating field (Q-slope) was effectively eliminated, resulting in an improvement of the Q 0 in the intermediate field region by ∼ 8 times. Furthermore, under better test conditions with the shielded magnetic field less than 5 mG and the slow cooling down procedure in the temperature range of 25–15 K, the Q 0 was still improved by about 20%. Our study shows that the low temperature baking can be an effective supplement to the effective post-treatment for the Nb3Sn thin film cavity.

Herein, a simple one-step immersion plating method is firstly used to prepare Cu6Sn5/Sn composite film electrode for lithium ion battery and thiourea (TU) is used as potential adjustment agent in the deposition process. The films with different morphologies are obtained by changing the content of tin(II) chloride (SnCl2). After a series of physical and electrochemical characterizations, the results demonstrate that the content of SnCl2 in the plating solution plays an important role in determining the morphology and component of film electrode. In the condition of SnCl2 6.5 g L−1, film electrode obtains both void space to accommodate volume expansion and stable structure which could inhibit abscission of active material from current collector. Therefore, the film electrode has an excellent areal capacity of 0.84 mA h cm−2 after 70 cycles. In comparison with reported Sn–Cu alloy planar film electrodes for lithium ion battery in recent decade, the film electrode in this work exhibits a higher areal capacity.

A novel sulfur immobilizer named RANEY® nickel is introduced for lithium–sulfur batteries for the first time. The sulfur/RANEY® nickel (S/RN) composite is prepared via an accessible solvent method. The key feature of RANEY® nickel is that it contains poriferous channels, which act as barriers against the loss of active materials due to physical and chemical adsorption during discharge/charge cycling. The chemical adsorption of RANEY® nickel for sulfur, verified using X-ray photoelectron spectroscopy (XPS), leads to the generation of Ni–S chemical bonds. In addition, RANEY® nickel, possessing excellent conductivity, can improve the reaction kinetics of an electrode with a high rate capability. As a result, the S/RN cathode presents an initial discharge capacity of 1469 mA h g−1, achieving a minimal capacity fade of 0.12% per cycle after 500 cycles at the rate of 0.5C with an excellent coulombic efficiency of around 99%. Furthermore, the S/RN cathode is promising for use in compact batteries due to its high volumetric specific capacity.