Simulation Analysis of Stress Field of Walnut Shell Composite Powder in Laser Additive Manufacturing Forming

A calculation model of stress field in laser additive manufacturing of walnut shell composite powder(walnut shell/Co-PES powder)was established.The DFLUX subroutine was used to implement the moveable application of a double ellipsoid heat source by considering the mechanical properties varying with temperature.The stress field was simulated by the sequential coupling method,and the experimental results were in good accordance with the simulation results.In addition,the distribution and variation of stress and strain field were obtained in the process of laser additive manufacturing of walnut shell composite powder.The displacement of laser additive manufacturing walnut shell composite parts gradually decreased with increasing preheating temperature,decreasing laser power and increasing scanning speed.During the cooling process,the displacement of laser additive manufacturing of walnut shell composite parts gradually increased with the increasing preheating temperature,decreasing scanning speed and increasing laser power.

Prediction and Analysis of Post-Treatment of Sustainable Walnut Shell/Co-PES Parts by Laser Sintering

In order to enhance the strength of sustainable walnut shell/Co-PES(WSPC)sintered parts,wax-filtrated posttreatment was carried out.The effects of treating fluid temperature,preheating time and immersion time on the bending strength of WSPC wax-filtrated parts were analyzed by single factor analysis method.To obtain an accurate model for predicting the bending strength of the WSPC wax-filtrated part,the experiments were involved by using Box-Behnken design(BBD).Main parameters,such as treating fluid temperature,preheating time and immersion time,and their interactive effects were analyzed through analysis of variance(ANOVA)and graphical contours.The results demonstrated that all parameters’direct effects were significant to bending strength of the WSPC wax-filtrated part.Its optimum value was 5.0 MPa when the treating fluid temperature of 70°C,preheating time of 50 min,and immersion time of 20 s.The predicted models effectively validated had good predicting accuracy.The WSPC wax-filtrated part using optimal processing parameters was processed by investment casting,and then the metal casting of dimensional stability and smooth surface was obtained.Investment casting was done using WSPC wax-filtrated parts under optimal process parameters and then metal parts with stable structure size and smooth surface can be obtained,which indicates that WSPC material can be used for investment casting.

Surface Engineered Ru_(2)Ni Multilayer Nanosheets for Hydrogen Oxidation Catalysis

The hydrogen oxidation reaction(HOR)in alkaline conditions is of great importance for the application of anion exchange membrane fuel cells(AEMFCs).However,the electrocatalysts for alkaline HOR generally suffer from the disadvantage of sluggish kinetics.Herein,we have fabricated Ru2Ni multilayered nanosheets(Ru2Ni MLNSs)in the layer-by-layer manner and engineered the surface properties via postannealing for efficient alkaline HOR.Detailed investigations reveal that such annealing at different temperatures can alter the surface properties of Ru2Ni MLNSs and thus regulate their adsorption abilities toward*H and*OH.In particular,the optimal catalyst exhibits a mass activity of 4.34 A mgRu−1 at an overpotential of 50 mV,which is 18.1 and 13.2 times higher than those of Ru/C(0.24 A mgRu−1)and Pt/C(0.33 A mgPt−1),respectively.Theoretical calculations indicate that the presence of surface O atoms can facilitate the HOR activity while the excessive coverage of O atoms on Ru2Ni surface leads to the strengthened H binding and the decay of HOR activity.This work not only provides an efficient catalyst for alkaline HOR,but it also may shed new light on the design of high-performance catalysts for electrocatalysis and beyond.We have fabricated Ru2Ni multilayer nanosheets(Ru2Ni MLNSs)and realized the surface engineering via an annealing process.Detailed investigations show that such surface engineering can regulate the surface properties and thus promote the alkaline HOR activity.Consequently,the optimal catalyst exhibits a much higher activity than those of commercial Ru/C and Pt/C and is a promising catalyst for alkaline HOR.

界面工程促进雪花状Ru/RuO_(2)纳米片氢气氧化性能

近年来,贵金属钌(Ru)因其具备与铂(Pt)媲美的氢吸附能以及比铂更低的价格被认为是很有前景的氢氧化反应(HOR)和析氢反应(HER)催化剂.然而,目前钌基催化剂在HOR和HER上的大规模应用依然受限于其活性低、稳定性不高等缺点.本文采用湿化学和热处理结合策略制备了具有Ru/RuO_(2)界面的二维雪花纳米片(Ru/RuO_(2) SNSs).表征和理论计算结果表明, Ru/RuO_(2) SNSs的界面结构与热处理温度密切相关.因此,可通过改变热处理温度调控界Ru/RuO_(2)界面相互作用,并进一步调控催化剂表面的氢结合能(HBE)和氢氧根结合能(OHBE),从而提高HOR和HER的催化性能.当Ru/RuO-12 SNSs用于催化碱性HOR时,在50 mV的过电位为下,其质量活性达到了9.13 A mgRu,分别是Ru SNSs(0.14 A mg^(-1)_(Ru))、RuO_(2) SNSs(0.03 A mg^(-1)_(Ru))和商用Pt/C(0.43 A mg^(-1)_(Ru))的65倍、304倍和21倍.此外, Ru/RuO_(2) SNSs还表现出优异的碱性HER性能.在1 mol L^(-1) KOH中,当电流密度达到10 mA cm^(-2)时,过电位低至20.2 mV.这项工作不仅开发了一种高效的HOR和HER催化剂,而且对开发新型高效催化剂也起到了重要的推动作用.