废旧锂电池正极材料回收技术研究进展

介绍了当前国内外三种车用锂电池正极材料的回收技术,包括火法冶金技术、湿法冶金技术和生物冶金技术。经过比较,以酸浸出—沉淀/萃取法为工艺流程的湿法技术对设备和能耗要求低、浸出效率高,是工业上方便引入的一种优异技术。     

Piezoelectricity in Monolayer Hexagonal Boron Nitride

2D hexagonal boron nitride (hBN) is a wide-bandgap van der Waals crystal with a unique combination of properties, including exceptional strength, large oxidation resistance at high temperatures, and optical functionalities. Furthermore, in recent years hBN crystals have become the material of choice for encapsulating other 2D crystals in a variety of technological applications, from optoelectronic and tunneling devices to composites. Monolayer hBN, which has no center of symmetry, is predicted to exhibit piezoelectric properties, yet experimental evidence is lacking. Here, by using electrostatic force microscopy, this effect is observed as a strain-induced change in the local electric field around bubbles and creases, in agreement with theoretical calculations. No piezoelectricity is found in bilayer and bulk hBN, where the center of symmetry is restored. These results add piezoelectricity to the known properties of monolayer hBN, which makes it a desirable candidate for novel electromechanical and stretchable optoelectronic devices, and pave a way to control the local electric field and carrier concentration in van der Waals heterostructures via strain. The experimental approach used here also shows a way to investigate the piezoelectric properties of other materials on the nanoscale by using electrostatic scanning probe techniques.     

Dielectric properties and electromagnetic interference shielding studies of nickel oxide and tungsten oxide reinforced polyvinylchloride nanocomposites

ABSTRACT

Polyvinylchloride (PVC)/nickel oxide (NiO)/tungsten oxide (WO₃) nanocomposite films were prepared via solution casting technique. The crystallinity, morphology, and the analysis of dispersion state of PVC/NiO/WO₃ nanocomposite was carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dielectric studies of nanocomposite films were investigated and a maximum dielectric constant of 2.3 with dielectric loss (tan δ) of 2.4 was attained. The EMI shielding studies were carried out in the X and Ku-band frequency range (8 GHz-18 GHz). The maximum SE of 15.78 dB in X-band and 12.05 dB in Ku-band was achieved for 75/20/5 compositions of the PVC/NiO/WO₃ nanocomposite.     

Microwave dielectric properties of SrLa[Ga1−x(Mg0.5Ti0.5)x]O4 and SrLa[Ga1−x(Zn0.5Ti0.5)x]O4 (x = 0.2-0.8) ceramics

SrLa[Ga_1−x(R_0.5Ti_0.5)_x]O₄ (R = Mg, Zn) ceramics were prepared by a standard solid state sintering method. The single-phase ceramics with K₂NiF₄-type layered perovskite structure and I4/mmm space group were obtained, indicating that SrLa(R_0.5Ti_0.5) and SrLaGaO₄ can form the unlimited solid solutions. With increasing x for R = Mg and Zn, ε_r increases monotonously, the Qf value first increases and then decreases, while τ_f increases from a negative to a positive value. The optimized microwave dielectric properties were obtained as following: ε_r = 23.3, Qf = 89 400 GHz, τ_f = −0.8 ppm/°C for SrLa[Ga_0.6(Mg_0.5Ti_0.5)_0.4]O₄ and ε_r = 23.3, Qf = 76 200 GHz, τ_f = 0.2 ppm/°C for SrLa[Ga_0.7(Zn_0.5Ti_0.5)_0.3]O₄, indicating that the present solid solution ceramics are the promising candidates as microwave resonator materials for the telecommunication applications.     

Processing capabilities of micro ultrasonic machining for hard and brittle materials: SPH analysis and experimental verification

Micro ultrasonic machining (micro-USM) is an unconventional micromachining technology that has capability to fabricate high aspect ratio micro-holes, intricate shapes and features on various hard and brittle materials. The material removal in USM is based on brittle fracture of work materials. The mechanical properties and fracture behaviour are different for varied hard and brittle materials, which would make a big difference in the processing capability of micro-USM. To study the processing capability of USM and exploit its potential, the material removal of work materials, wear of abrasive particles and wear of machining tools in USM of three typical hard and brittle materials including float glass, alumina, and silicon carbide were investigated in this work. Both smoothed particle hydrodynamics (SPH) simulations and verification experiments were conducted. The material removal rate is found to decrease in the order of glass, alumina, and silicon carbide, which can be well explained by the simulation results that cracking of glass is faster and larger compared to the other materials. Correspondingly, the tool wear rate also dropped significantly thanks to the faster material removal, and a formation of concavity on the tool tip center due to intensive wear was prevented. The SPH model is proved useful for studying USM of different hard and brittle materials, and capable of predicting the machining performance.     

Preparation of In-doped Y2O3 ceramics through a sol-gel process: Effects on the structural and electronic properties

The Pechini-type sol-gel (PSG) process has been used for the preparation of doped oxides due to its capability to overcome most of the difficulties that frequently occur by using other producing methods. In this work we analyze the case of samples of pure and In-doped yttria (Y₂O₃) prepared by the PSG process. We experimentally characterize the synthesized samples by x-ray diffraction, micro-Raman spectroscopy, electrochemical impedance spectroscopy (EIS), and time-differential perturbed γ-γ angular correlation (PAC) spectroscopy, and we compare these results with those obtained starting from commercial oxide powders. We found that the PSG process can be used to successfully produce doped yttria in the cubic phase, with the impurities substitutionally located at the cationic sites of the structure. By the proposed PSG route, the inclusion of impurities does not affect the particle size nor the resistivity. However, when we compare the PSG samples with other samples produced from commercial powder, we found that the first have lower resistivities at grain interiors. On the other hand, PAC spectroscopy in ¹¹¹In(→¹¹¹Cd)-doped yttria allows the study of the dynamic hyperfine interactions observed by the radioactive ¹¹¹Cd impurity-probe, which can be used to “sense” the host electron availability near the impurities after the electron-capture decay of ¹¹¹In. Differences between PAC spectra for PSG samples and the commercial powder suggest that the PSG process introduces additional donor defects into the yttria electronic structure, which is consistent with the lower resistivity observed in the PSG samples by EIS spectroscopy.     

Facile synthesis of cauliflower-like cobalt-doped Ni3Se2 nanostructures as high-performance cathode materials for aqueous zinc-ion batteries

Ni₃Se₂ and Co-doped Ni₃Se₂ cauliflower-like nanostructures are synthesized using a simple and feasible electrochemical deposition technique. Electrochemical measurements of the resultant nanostructures in 1 M KOH electrolyte solution revealed that the energy storage performance of the cauliflower-like Ni₃Se₂ nanostructures was considerably improved by cobalt doping. Particularly, 6 wt% Co-doped Ni₃Se₂ electrodes exhibited remarkable high specific capacity (179.34 mAh g⁻¹) and excellent stability with capacity retention of 85.9% over 1000 cycles because of their high electrical conductivity. Furthermore, to verify the feasibility of the optimized Co-doped Ni₃Se₂ electrodes for practical applications, Zn ion batteries were constructed by using a Zn plate as the anode and the Co-doped Ni₃Se₂ nanostructures as the cathode. The constructed Zn ion battery achieved high energy and power densities of 199.34 W h kg⁻¹ and 24,510 W kg⁻¹ at the current densities of 1 and 20 A g⁻¹, respectively. In addition, up to 2.2 electrons per formula unit of Ni₃Se₂ were successfully utilized, indicating considerably higher utilization of Ni²⁺/Ni³⁺ redox sites by Co doping the selenite. This work demonstrated an effectual strategy for rational design of highly robust, low-cost flexible electrodes for energy storage devices.     

太赫兹可调谐滤波器设计

为了实现太赫兹信号的可调谐滤波，设计了一种基于柔性材料的太赫兹可调谐滤波器。通过扭曲特氟龙（Teflon）波导形成环型谐振器，实现了160～200 GHz频段的带阻滤波功能。改变谐振腔长可实现自由频谱范围（FSR）和滤波频点的调谐，实验测试了自由频谱范围在1.9 GHz和2.8 GHz间切换以及相应的滤波特性。研究表明，谐振腔长一定时，改变弯曲半径可实现滤波阻带抑制度的调节，柔性材料太赫兹环型谐振器可用于可调谐滤波，且具有较高的自由度。     

Thermoplastic and low dielectric constants polyimides based on BPADA-BAPP

ABSTRACT

The thermoplastic and low dielectric constants polyimides were introduced. The polyimides were prepared by pyromellitic dianhydride (PMDA) or 4,4?-(4,4?-Isopropylidenediphenoxy)diphthalic anhydride (BPADA) as anhydride monomer and 4,4?-oxydianiline (ODA) or 2,2-bis(4-(4-aminephenoxy)phenyl)propane (BAPP) as amine monomer. The polyimides were well characterized by FT-IR, thermogravimetric analysis, dynamic thermomechanical analysis, dielectric measurement, and tensile test. The dielectric constants were 2.32–2.95 compared with 3.10 of ODA-PMDA polyimide, while partly polyimides were thermoplastic. The results indicated anhydride monomers, containing lateral methyl groups, made polyimides become thermoplastic. The results of molecular simulations via Materials Studio also proved this conclusion.     

Investigation of improved dielectric and thermal properties of ternary nanocomposite PMMA/MXene/ZnO fabricated by in-situ bulk polymerization

Electric power system applications demand for high-temperature dielectric materials. The improved performance of polymer nanocomposites requires improvement in their thermal conductivity & stability, dielectric stability and processing technique. However, they often lose their dielectric properties with a rise in temperature. Here, we offer a solution by incorporating electrically conducting material (MXene) and semiconducting inorganic nanoparticles (ZnO NPs) into an insulating PMMA polymer matrix to maintain high dielectric constant, both at the room and high temperature. Therefore, to achieve desirable thermal and dielectric properties is the main objective of the present study based on the homogeneous distribution of the nanofillers by in-situ bulk polymerization assisted by strong sonication in the corresponding polymer. The introduction of MXene and ZnO NPs into the PMMA not only acquires a substantial increment in the dielectric constant, to attain a value 437, with minimum energy loss of 0.36 at 25 Hz, but also improves the thermal conductivity of PMMA up to 14 times by causing the reduction of thermal resistance, which is actually responsible for the poor thermal conductivity of amorphous pure PMMA polymer. More importantly, hybrid PMMA/4:2 wt% MXene:ZnO nanocomposite leads to an excellent thermal stability. Moreover, further characterization of the synthesized nanocomposites by FTIR, SEM and XRD leads to the evaluation of strong interaction of ternary components with PMMA matrix.