Improving room-temperature electrochemical performance of solid-state lithium battery by using electrospun La2Zr2O7 fibers-filled composite solid electrolyte

Low ionic conductivity at room temperature and poor interfacial compatibility are the main obstacles to restrain the practical application of polymer solid electrolytes. In this work, lanthanum zirconate (LZO) fibers were prepared by electrospinning method and used for the first time as fillers in sandwich polypropylene carbonate (PPC)-based solid electrolyte. Meanwhile, a graphite coating was applied on one surface of the composite solid electrolyte (CSE) membrane. The results show that the LZO fibers significantly increases the room-temperature electrochemical performance of the CSE, and the graphite coating enhances the interfacial compatibility between electrolyte and lithium anode. Furthermore, an ultra-thin PPC-LZO CSE with a total thickness of 22 μm was prepared and used in NCM622/CSE/Li solid-state cell, which shows an initial discharge capacity of 165.6 mAh/g at the current density of 0.5C and a remaining capacity of 113.0 mAh/g after 250 cycles at room temperature. Rise to 1C, the cell shows an initial discharge capacity of 154.2 mAh/g with a remaining capacity of 95.6 mAh/g after 250 cycles. This ultra-thin CSE is expected to be widely applied in high energy-density solid-state battery with excellent room-temperature electrochemical performances.     

MOF-derived PPy/carbon-coated copper sulfide ceramic nanocomposite as high-performance electrode for supercapacitor

To obtain a battery-type ceramic electrode material for supercapacitors, we used a metal-organic framework (HKUST-1) as a template to prepare ceramic material Cu₉S₈@C. Firstly, we adopted the calcination–vulcanization method to synthesize Cu₉S₈@C. Then we deposited it onto a carbon fiber cloth and employed it. Moreover, polypyrrole PPy/Cu₉S₈@C-CC nanocomposite electrodes were prepared via electrochemical deposition. By means of high-temperature calcination and vulcanization, the copper atoms of HKUST-1 were successfully transformed into Cu₉S₈ nanoparticles, and the organic ligand was carbonized into amorphous carbon in Cu₉S₈@C. The results showed that the PPy/Cu₉S₈@C-CC electrode presented a specific capacitance of 270.72F/g at a scan speed of 10 mV/s in a 1 M KCL aqueous solution. This value was much higher than that of Cu₉S₈@C-CC and Cu₉S₈-CC electrodes, as confirmed by the results of electrochemical test. At a scan rate of 10 mV/s, the capacitance retention rate for PPy/Cu₉S₈@C-CC after 3000 cycles was 80.36%, indicating its superior cycle characteristics. Moreover, PPy/Cu₉S₈@C-CC exhibited good frequency response. These results indicate that PPy/Cu₉S₈@C is an ideal electrode material for energy storage and conversion applications.     

Calculation of phase diagrams for the metastable Al-Fe phases forming in direct-chill (DC)-cast aluminum alloy ingots

In direct-chill (DC)-cast 1xxx-and 5xxx-series Al sheet-ingots, the presence of mainly Fe and some Si, and cooling rates increasing from ≤1 °C/s in the ingot center to ~20 °C/s near the surface cause the formation of metastable intermetallic Al₆Fe and Al_mFe compounds in addition to the stable Al₃Fe, and hence the fir-tree defect. Since the Al-Fe and Al-Fe-Si phase diagrams are not useful in predicting the metastable phase formation, a binary phase diagram study was conducted to calculate the Al-Al₆Fe and Al-Al_mFe metastable phase equilibria using a thermodynamic software and an Al-alloy database. The Al-Al₃Fe phase diagram was calculated using the existing Gibbs energy data which gives the eutectic point at 1.85wt% Fe and the eutectic temperature as 654 °C. The missing Gibbs energy data for the metastable phases were estimated using substitutional and graphical methods and the phase diagrams were calculated. In the Al-Al₆Fe phase diagram, the eutectic temperature is depressed from 654 °C (equilibrium) to 648 °C and the eutectic point is shifted from 1.85wt% Fe to 3.4wt% Fe. In the Al-Al_mFe phase diagram, the eutectic temperature is 643 °C and the eutectic point is at 4.6wt% Fe. The verification of the calculated eutectic temperatures was carried out by DSC measurements which were conducted on samples removed from Al-Fe alloy rods directionally grown in a Bridgman-type solidification furnace. A good agreement is observed between the calculated and measured values.     

Development of a monitor to simultaneously measure dissolved ozone and organic matter in ozonated water

A method for measuring both dissolved ozone (DO₃) concentration and UV absorbance was developed adopting ultraviolet (UV) absorption method (Japan Water Works Association (JWWA), 1993a, Japan Water Works Association (JWWA), 1993b) using sodium thiosulfate (Na₂S₂O₃) solution for removing residual ozone in ozonated water. A DO₃ monitor based on this method was tested. This method was proven to be effective from experimental results. The performance of the monitor was examined with continuous ozonated water. As a result, the monitor performed stably during about 2 months, so that both DO₃ concentration and UV absorbance in the ozonated water could be accurately measured. Therefore, the authors have proposed the new aquatic control system with this monitor for ozonation.     

Improving the electrochemical properties of carbon anodes in lithium secondary batteries

The electrochemical properties of carbon anodes in lithium secondary batteries are improved by the addition of vanadium as V₂O₅. The action of the added V₂O₅ is different from that obtained by incorporating a nonmetallic element such as nitrogen, boron, phosphorous or silicon. Because it can increase the distance between the 002 planes of the carbon and act as nucleating agent that promotes the formation of a layer-like carbon structure, V₂O₅, not only enlarges the carbon anode's reversible capacity of lithium storage but also improves the cycling behavior.     

A one-pot sealed ammonia self-etching strategy to synthesis of N-defective g-C3N4 for enhanced visible-light photocatalytic hydrogen

Photocatalytic hydrogen (H₂) evolution from water is considered as a prospective approach, which can convert inexhaustible solar energy into chemical energy to alleviate energy crisis and environmental problems. Herein, the N-defective g-C₃N₄ with porous structure was firstly synthesized in a sealed crucible by one-step thermal polymerization method. The experimental data showed that the yield of the catalyst was obviously increased under sealing condition. Moreover, the N-defective g-C₃N₄ prepared from urea precursor under sealed condition reached an optimum photocatalytic H₂ production rate of 597.4 μmol/h and an apparent quantum efficiency of 15.6% at wavelength of 420 nm. This enhanced photocatalytic H₂ production performance is mainly ascribed to the introduction of N-defects, which not only extended of the visible light absorption, but also acted as the electron trap centers to suppress the recombination of the photogenerated electron and hole pairs. This work offers one-step facile strategy for the introduction of N-defects to prepare N-defective g-C₃N₄ with superior photocatalytic activity, which is also a great substitute for the high-energy consuming and complicated synthetic routes.     

Characterization of local texture in a moderately deformed polycrystalline AlSi-alloy

Polycrystalline material of various grain sizes of AlSi-alloy containing second-phase particles have been deformed at room temperature in axisymmetric compression. The variation in crystallographic orientation in the as-deformed material was obtained by the Electron Back Scattered Pattern (EBSP) technique in SEM. “Random” and cumulative long range misorientation gradients have been quantified within the matrix (M) and at heterogeneities such as the grain boundary (GB), the triple line region (TL) and in the vicinity of large second phase particles (P) in material compressed to equivalent plastic strains of 0.2 and 0.4. It is shown that the misorientation gradient increases differently in different regions with increasing strain. Maximum values were found in regions expected to be more strained than average in order to accomodate imposed constraint from neighbouring grains or from the presence of large second phase particles. An important feature of the deformed structure seems to be the cumulative rotation of the lattice about an axis close to the 〈111〉-axis in regions with large misorientations.     

Solidification paths of TiTaAl alloys

Microstructure evolution during solidification and high temperature phase equilibria were investigated for TiTaAl alloys in the vicinity of the 50 at.%Al isoconcentrate. Examination of dendrite morphologies and segregation profiles were used to deduce the phase sequencing during solidification and the boundaries of the relevant liquidi surfaces. In situ high-temperature X-ray diffraction and isothermal annealing experiments were conducted to determine the phases present at elevated temperatures and coupled with extensive characterization by transmission electron microscopy to elucidate the solid state transformations during cooling of the solidification microstructure. For approximately equiatomic TiAl, the primary phase selected from the liquid was α for the leaner Ta concentrations (< 7% Ta), as in the binary alloys of equivalent Al content, but changed to β with increasing Ta levels (> 10 %). With increasing Al and Ta the α liquidus penetrates deeply into the ternary. The interdendritic segregate was always γ. Dendrites of the β-forming alloys were heavily segregated leading to different microconstituents in the core and bulk dendrite regions during post-solidification cooling. In alloys with < 15 % Ta, (α₂ + γ_t) lath formed in the dendrite bulk due to the decomposition of α, with σ precipitating in the core (> 10% Ta). With increasing Ta levels the lath is gradually replaced by polycrystalline γ which grows into the dendrite bulk, and the core decomposes into a lamellar (γ + σ) microstructure from the decomposition of σ. The γ segregate does not transform further.