Fabrication of NixCo3-xS4 hollow nanosphere as wideband electromagnetic absorber at thin matched thickness

Nowadays, transition metal sulfide (TMS), especially for spinel crystal structure (A_xB_3-xS₄), have been proved to be a promising electromagnetic (EM) absorber if been used to deal with the severe electromagnetic pollution. However, EM performance degradation and absorption layer thickness-decreasing at present remains a big challenge, owning to the poor EM attenuation ability. To overcome this barrier, herein we reported a Ni_xCo_3-xS₄ (x = 0, 0.3, 0.6, 1.0) absorber with hollow sphere structure to realize a good EM performance with a thinner matched thickness (<1.5 mm). The average sizes of these Ni_xCo_3-xS₄ distributed in 450–550 nm. The dielectric loss ability (ε'') can be boosted by tuning the molar ratio of Ni/Co, which attributes to EM performance. Additionally, hollow structure would lead to the electromagnetic multi-reflection, also benefited to EM performance. The results demonstrated that the maximum qualified absorption bandwidth (f_E) of 3.8 GHz can be achieved for the Ni_0·3Co_2·7S₄ sample when specimen thickness only equals to 1.3 mm.     

Simplification and applicability studies of a hydrogen-air detailed reaction mechanism

The research of hydrogen fuel internal combustion engine (HICE) had great significance facing the challenges of energy and environmental problems. Based on the detailed hydrogen-air reaction mechanism, the pre-mix model of CHEMKIN-Pro software was selected to simplify the detailed mechanism GRI-3.0. The most important elements and reactions was chose to construct framework mechanism firstly based on the sensitivity coefficient for H₂O and NO formation, and additional elements and reactions were added to framework mechanism for complementing the oxidation path of N2 and H₂. A simplified mechanism including 24-step elementary reaction was obtained and the laminar burning velocity calculated by this simplified mechanism matches well with the detailed mechanism in a wide range. This simplified mechanism was also applied in a CFD model which predicted the cylinder instantaneous pressure and NOx emission accurately within a large range of fuel air equivalent ratio. Showing that this mechanism has good applicability.     

Decomposition process of bastnaesite concentrate in NaOH-CaO-H_2O system

A novel process of calcification-leaching for bastnaesite concentrate(REFCO_3) was proposed. The prior calcification was carried out in the system of NaOH-CaO-H_2O and the lgC-pH pattern for Ce-F-Ca-C-H_2O system was drawn. The thermodynamics result indicates that decomposition for bastnaesite requires certain alkaline condition, but excessive alkalinity also causes decomposition of CaF_2. XRD and SEM-EDS analyses on the calcification-leaching process reveal that bastnaesite first decomposes into RE(OH)_3 and CaF_2. Then, by HCl leaching rare earths were extracted,while CaF_2 was left in the leaching residue. In addition, effects of temperature, time, NaOH and CaO on the calcification were investigated. The results show that the leaching rate of rare earths(REs)reaches 72.5 wt%, at the same time 99.2 wt% of F is left in leaching residue with 20 wt% NaOH and 38 wt% CaO at 493 K for 180 min.     

Hydrogen storage property of as-milled La7RE3Mg80Ni10 (RE = Sm,Ce) alloys

Element replacement and mechanical milling are considered as the most effective ways to improve Mg-based alloys in their hydrogen storage performance. The as-milled La₇RE₃Mg₈₀Ni₁₀ (RE = Sm, Ce) alloys were prepared in this experiment by introducing both element replacement (replacing La by Ce or Sm partially) and mechanical milling technologies. The influence made by different replacing elements on the structure and hydrogen storage property of La₇RE₃Mg₈₀Ni₁₀ (RE = Sm, Ce) alloys was investigated in detail. X-ray diffraction, transmission electron microscope, automatic Sievert apparatus, thermogravimetry and differential scanning calorimetry were used to investigate the experimental alloys. The experiment reveals that a nanocrystalline and amorphous structure appears after mechanical milling. Moreover, comparing with the RE = Sm alloy, the RE = Ce alloy has a superior hydrogen desorption property, including larger hydrogen absorption capacity, faster hydriding/dehydriding rate, lower onset hydrogen desorption temperature, and lower dehydrogenation activation energy.     

A cross-linked sheet structured poly(3,4-ethylenedioxythiophene) grown on Ni foam: Morphology control and application for long-life cyclic asymmetric supercapacitor

In this work, a cross-linked sheet structured conducting polymer ploy(3,4-ethylenedioxythiophene) (PEDOT) decorated on Ni foam is synthesized via one-step electrodeposition using the sodium p-toluenesulfonate (STSA) as surfactant and applied for supercapacitor electrode. The surfactants play a vital role in controlling the morphologies of PEDOT leading to the electrochemical performance difference. The optimized PEDOT electrode exhibits the highest capacitance of 711.6 mF cm⁻² at 3.0 mA cm⁻² in the three-electrode system. An asymmetric device (PEDOT/STSA//AC) is constructed by PEDOT/STSA (the positive electrode), activated carbon (AC) (the negative electrode) as well as 1 M Na₂SO₄ (the electrolyte). The device has been worked in a high-voltage range of 0–1.5 V, which displays the satisfied energy density of 14.0 Wh·kg⁻¹ at 535.5 W kg⁻¹. Furthermore, the PEDOT/STSA//AC device presents excellent rate capability and long-time cyclic stability.     

Fe–N–Si tri-doped carbon nanofibers for efficient oxygen reduction reaction in alkaline and acidic media

The most ideal substitute for Pt/C to catalyze the oxygen reduction reaction (ORR) is the transition metal and nitrogen co-doped carbon-based material (TM-N-C). However, large particles with low catalytic activity are formed easily for the transition metals during high-temperature carbonization. Herein, PAN nanofibers uniformly distributed with FeCl₃ were coated with SiO₂ and then carbonized to obtain Fe–N–Si tri-doped carbon nanofibers catalyst (Fe–N–Si-CNFs). The SiO₂ can further anchor the Fe atoms, thus preventing agglomeration during the carbonization process. Meanwhile, Si atoms have been doped in CNFs during this process, which is conducive to the further improvement of catalytic performance. The Fe–N–Si-CNFs catalyst has a 3D network structure and a large specific surface area (809.3 m² g⁻¹), which contributes to catalyzing the ORR. In alkaline media, Fe–N–Si-CNFs exhibits superior catalytic performance (E_1/2 = 0.86 V vs. RHE) and higher stability (9.6% activity attenuation after 20000s) than Pt/C catalyst (20 wt%).     

Psychrophilic hydrogen production from petrochemical wastewater via anaerobic sequencing batch reactor: techno-economic assessment and kinetic modelling

Independent hydrogen production from petrochemical wastewater containing mono-ethylene glycol (MEG) via anaerobic sequencing batch reactor (ASBR) was extensively assessed under psychrophilic conditions (15–25 °C). A lab-scale ASBR was operated at pH of 5.50, and different organic loading rates (OLR) of 1.00, 1.67, 2.67, and 4.00 gCOD/L/d. The hydrogen yield (HY) progressed from 134.32 ± 10.79 to 189.09 ± 22.35 mL/gMEG_initial at increasing OLR from 1.00 to 4.00 gCOD/L/d. The maximum hydrogen content of 47.44 ± 3.60% was achieved at OLR of 4.0 gCOD/L/d, while methane content remained low (17.76 ± 1.27% at OLR of 1.0 gCOD/L/d). Kinetic studies using four different mathematical models were conducted to describe the ASBR performance. Furthermore, two batch-mode experiments were performed to optimize the nitrogen supplementation as a nutrient (C/N ratio), and assess the impact of salinity (as gNaCl/L) on hydrogen production. HY substantially dropped from 62.77 ± 4.09 to 6.02 ± 0.39 mL/gMEG_initial when C/N ratio was increased from 28.5 to 114.0. Besides, the results revealed that salinity up to 10.0 gNaCl/L has a relatively low inhibitory impact on hydrogen production. Eventually, the cost/benefit analysis showed that environmental and energy recovery revenues from ASBR were optimized at OLR of 4.0 gCOD/L/d (payback period of 7.13 yrs).     

Effects of Ni Content and Ball Milling Time on the Hydrogen Storage Thermodynamics and Kinetics Performances of La–Mg–Ni Ternary Alloys

The effects of Ni content and ball milling time on the hydrogen storage thermodynamics and kinetics performances of asmilled La_5Mg_(95-x)Ni_x(x = 5, 10, 15) ternary alloys have been investigated.The evolution of microstructure and phase of experimental alloys in the absorption/desorption process has been characterized by XRD, SEM and HRTEM.The hydrogen storage kinetics and thermodynamics performances and PCI curves have been tested using the Sievert apparatus.It is found that the rising of Ni content remarkably improves the hydrogen storage kinetic performance, but reduces hydrogen storage capacity.And with the increase in milling time, hydrogen desorption activation( E_a) value decreases firstly and then increases; the minimum value is 47.6 kJ/mol, and the corresponding milling time is 10 h for La_5Mg_(85)Ni_(10) alloy.As for the thermodynamics properties, the hydrogenation enthalpy(Δ H) and hydrogenation entropy(Δ S) both decrease firstly and then increase with the rising of Ni content and milling time.The composite La_5Mg_(85)Ni_(10)alloy milled for 10 h exhibits the best thermodynamics and kinetics performances, the lowest E_a of 47.6 kJ/mol, absorption of 5.4 wt.% within 5 min and desorption of 5.2 wt.% within 3 min at 360 ℃ and the lowest Δ H and Δ S of 72.1 kJ/mol and 123.2 J/mol/K.     

Enable high reversibility of Fe/Cu based fluoride conversion batteries via interfacial gas release and detergency of garnet electrolytes

Garnet-type Ta-doped Li₇La₃Zr₂O₁₂ (LLZTO) electrolyte suffers from unstable chemical passivation under air exposure, responsible for the poor interfacial wettability and conductivity with Li metal. Instead of conventional methods to remove surface contaminants by mechanical polishing, acid etching and high temperature reduction, herein we propose a simple strategy of interfacial gas release and detergency to smartly convert Li₂CO₃ passivation layer into ion-conductive Li₃PO₄ domains at mild temperature (∼200 ℃). The in-situ formation of PH₃ vapor and its phosphorization enables a dramatic decrease of Li/garnet interfacial resistance down to 2 Ω cm² at room temperature (RT). The improved interfacial wettability and conductivity endow the symmetric cells with ultra-stable galvanostatic cycling over 1500 h and high critical current density of 2.6 mA/cm². The high coulombic efficiency of Li plating enables a high reversibility of solid-state NCM811/Li cells even under a low N/P ratio (∼4) and high cut-off voltage of 4.5 V at RT. The prototype of fluoride-garnet solid-state batteries are successfully driven as rechargeable system (rather than widely known primary battery) with high conversion capacity (400 ∼ 500 mAh/g) and high-rate performance (251.2 mAh/g at 3 C). This interface infiltration-detergency approach provides a practical solution to the achievement of high-energy solid-state Li metal batteries.     

The quasi ternary system TiB2-CrB2-WB2 between 1900 and 2300°C

The quasi-ternary TiB₂-CrB₂-WB₂ system has been studied up to 2300 °C by means of hot-pressing, SPS and pressureless dilatometry. Liquid phase is generated by two binary eutectics at the TiB₂-WB₂ edge at 2230 ± 30 °C (e₁) and at the CrB₂-WB₂ edge at 1965 °C (e₂). A large homogeneity range of a (Ti,W,Cr)B₂ solid solution has been noticed. A new ternary γ-phase emerges from a critical tie line between (W,Cr,Ti)₂B₄ and α-(Ti,W,Cr)B₂ solid solution at 1950 °C, spreads slightly into both the WB₂ and CrB₂ direction and decomposes by the peritectic reaction P: γ ⇆ α-(Ti,Cr,W)B₂ + (W,Cr,Ti)₂B₄ + Liquid at 2170 ± 30 °C. γ reacts with the CrB₂-WB₂-rich liquid according to the transition equilibrium T: δ-(Ti,Cr,W)B₂ + (W,Cr,Ti)₂B₄ ⇆ γ + Liquid at 2050 °C. The γ-phase is characterized by broad 00 l x-ray reflections which implies a layerwise accumulation and differentiation of Cr and W atoms in the basal plane of the AlB₂-type structure.