Simulation on Residual Stress of Shot Peening Based on a Symmetrical Cell Model

The symmetrical cell model is widely used to study the residual stress induced by shot peening. However, the correlation between the predicted residual stresses and the shot peening coverage, which is a big challenge for the researchers of the symmetrical cell model, is still not established. Based on the dynamic stresses and the residual stresses outputted from the symmetrical cell model, the residual stresses corresponding to full coverage are evalu- ated by normal distribution analysis. The predicted nodal dynamic stresses with respect to four corner points indicate that the equi-biaxial stress state exists only for the first shot impact. Along with the increase of shot number, the interactions of multiple shot impacts make the fluctuation of the nodal dynamic stresses about an almost identical value more and more obvious. The mean values and standard deviations of the residual stresses gradually tend to be stable with the increase of the number of shot peening series. The mean values at each corner point are almost the same after the third peening series, which means that an equi-biaxial stress state corresponding to the full coverage of shot peening is achieved. Therefore, the mean values of the nodal residual stresses with respect to a specific transverse cross-section below the peened surface can be used to correlate the measured data by X-ray. The predicted residual stress profile agrees with the experimental results very well under 200% peening coverage. An effective correlation method is proposed for the nodal residual stresses predicted by the symmetrical cell model and the shot peening coverage.

Recent advances and influencing parameters in developing electrode materials for symmetrical solid oxide fuel cells

This article delivers a robust overview of potential electrode materials for use in symmetrical solid oxide fuel cells(S-SOFCs),a relatively new SOFC technology.To this end,this article provides a comprehensive review of recent advances and progress in electrode materials for S-SOFC,discussing both the selection of materials and the challenges that come with making that choice.This article discussed the relevant factors involved in developing electrodes with nano/microstructure.Nanocomposites,e.g.,non-cobalt and lithiated materials,are only a few of the electrode types now being researched.Furthermore,the phase structure and microstructure of the produced materials are heavily influenced by the synthesis procedure.Insights into the possibilities and difficulties of the material are discussed.To achieve the desired microstructural features,this article focuses on a synthesis technique that is either the most recent or a better iteration of an existing process.The portion of this analysis that addresses the risks associated with manufacturing and the challenges posed by materials when fabricating S-SOFCs is the most critical.This article also provides important and useful recommendations for the strategic design of electrode materials researchers.

Radio-frequency magnetron sputtered thin-film La_(0.5)Sr_(0.5)Co_(0.95)Nb_(0.05)O_(3-δ) perovskite electrodes for intermediate temperature symmetric solid oxide fuel cell(IT-SSOFC)

The present work explores the application of La_(0.5)Sr_(0.5)Co_(0.95)Nb_(0.05)O_(3-δ)(LSCNO)perovskite as electrode material for the symmetric solid oxide fuel cell.Symmetric solid oxide fuel cells of thin-film LSCNO electrodes were prepared to study the oxygen reduction reaction at intermediate temperature.The Rietveld refinement of syn-thesized material shows a hexagonal structure with the R-3c space group of the prepared perovskite material.Lattice parameter and fractional coordinates were utilized to calculate the oxygen ion diffusion coefficient for molecular dynamic simulation.At 973 K,the oxygen ion diffusion of LSCNO was 1.407×10^(-8)cm^(2)s^(-1) higher by order of one magnitude than that of the La_(0.5)Sr_(0.5)Co_(0.95)Nb_(0.05)O_(3-δ)(7.751×10^(-9)cm^(2)^(-1)).The results suggest that the Nb doping provide the structural stability which improves oxygen anion diffusion.The enhanced structural stability was analysed by the thermal expansion coefficient calculated experimentally and from molecular dynamics simulations.Furthermore,the density functional theory calculation revealed the role of Nb dopant for oxygen vacancy formation energy at Sr-0 and La-O planes is lower than the undoped structure.To understand the rate-limiting process for sluggish oxygen diffusion kinetics,80 nm and 40 nm thin films were fabricated using radio frequency magnetron sputtering on gadolinium doped ceria electrolyte substrate.The impedance was observed to increase with an increasing thickness,suggesting the bulk diffusion as a rate-limiting step for oxygen ion diffu-sion.The electrochemical performance was analysed for the thin-flm symmetric solid oxide fuel cell,which achieved a peak power density of 390 mW cm^(-2) at 1.02 V in the presence of H_(2) fuel on the anode side and air on the cathode side.

Tungsten doping La_(0.6)Ca_(0.4)Fe_(0.8)Ni_(0.2)O_(3-δ)as electrode for highly efficient and stable symmetric solid oxide cells

Perovskite oxide La_(0.6)Ca_(0.4)Fe_(0.8)Ni_(0.2)O_(3-δ)(LCFN)has been used in symmetric solid oxide cells(SSOCs)to obtain good electrochemical performance in both fuel cells(SOFCs)and electrolysis cells(SOECs)modes.However,its structural stability still faces challenges and the electrocatalytic activity also needs to be further improved.Herein,tungsten-doped La_(0.6)Ca_(0.4)Fe_(0.7)Ni_(0.2)W_(0.1)0_(3-δ)(LCFNW)perovskite oxide material was synthesized which exhibits good structural stability under H_(2)and superior electrochemical performance as an electrode for SSOCs.In SOFCs mode,the cell achieved the maximum power density of 0.58 W·cm^(-2)with wet H_(2)as fuel at 850℃.In SOECs mode,the current density can reach 1.81 A·cm^(-2)for pure CO_(2)electrolysis at 2 V.Moreover,the SSOCs exhibits outstanding long-term stability in both SOFCs and SOECs modes,proving that doping W in perovskite oxide is an effective strategy to enhance the catalytic activity and stability of the electrode.The LCFNW material developed in this work shows promising prospect as an electrode candidate for SSOCs.

Protecting lithium metal anode in all-solid-state batteries with a composite electrolyte

The volume of the metallic lithium anode in allsolid-state Li metal batteries increases significantly due to the lithium dendrite formation during the battery cycling,and the rough surface of lithium metal also reduces Li-ion transport in Li/electrolyte interface.In this work,we developed a solid polymer composite by adding the lowcost Si_(3)N_(4)particles to protect the lithium anode in allsolid-state batteries.The Fourier transform infrared spectroscopy(FTIR)data show that the surface of 10 wt%Si_(3)N_(4)particles interacts with the polyethylene oxide(PEO)and lithium bis(trifluoromethanesulfonyl)imide(LiTFSI)salt;the interaction restricts the anion mobility and improves the ionic conductivity(1×10^(-4)S·cm^(-1))and lithium-ion transference number(0.28)of the composite electrolyte.The lithium metal anode is well protected by the composite electrolyte in all-solid-state cells,including symmetric and Li/LiFePO_(4)cells.The lithium dendrite growth suppression by this composite electrolyte indicates the possible application of these low-cost composite electrolytes for lithium metal protection.

Symmetric is nonidentical:Operation history matters for Zn metal anode

Zn metal electrode is the key to enabling the full vision of next-generation Zn-metal batteries(ZMBs).Thus far,the critical dendrite issue still restricts the Zn anode lifespan,which has even become the Achilles heel to the rejuvenation of ZMBs.This highlight previews the latest advance of Zn anode research,which suggests that Zn electrodes with initial stripping and plating can surprisingly lead to different morphology evolution routes.A proposed pre-deposition strategy is demonstrated to stabilize the Zn anode and homogenize further Zn plating/stripping.