Effect of Interface Form on Creep Failure and Life of Dissimilar Metal Welds Involving Nickel-Based Weld Metal and Ferritic Base Metal

For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature failure.In this study,a new form of WM/BM interface form,namely double Y-type interface was designed for the DMWs.Creep behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests,and creep failure mechanisms were investigated by stress-strain analysis and microstructure characterization.By applying double Y-type interface instead of conventional I-type interface,failure location of DMW could be shifted from the WM/ferritic heat-affected zone(HAZ)interface into the ferritic HAZ or even the ferritic BM,and the failure mode change improved the creep life of DMW.The interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation,stress and strain concentrations,and oxide notch on the WM/HAZ interface.The creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ,which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain boundaries.The double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface,preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure cracking.It is a novel scheme to prolong creep life and enhance reliability of DMW,by means of optimizing the interface form,decoupling the damage factors from WM/HAZ interface,and then changing the failure mechanism and shifting the failure location.

Failure Analysis of Dissimilar Metal Welds between Ferritic Heat Resistant Steels and Austenitic Stainless Steels in Power Plant

This study analysed the failure of dissimilar metal welds(DMWs)between ferritic heat resistant steels and austenitic stainless steels and investigated its influencing factors by means of numerical simulation,microstructure characterization and mechanical property test.Under the long-term high-temperature service condition in practical power plant,the DMW failure mode was along the interface between nickel-based weld metal(WM)and ferritic heat resistant steel,and the failure mechanism was stress/strain concentration,microstructure degradation and oxidation coupling acting on the interface.The numerical simulation results show that interface stress/strain concentration was due to the differences in coefficient of thermal expansion and creep strength,and the degree of stress/strain concentration was related to service time.The ferrite band formed at the WM/ferritic steel interface was prone to cracking,attracting the fracture along the interface.The interface crack allowed oxidation to develop along the WM/ferritic steel interface.During long-term service,the interface stress/strain concentration,microstructure and oxidation all evolved,which synergistically promoted interface failure of DMW.However,only under the long-term service of low stress conditions could trigger the interface failure of DMW.Meanwhile,long-term service would reduce the mechanical strength and plasticity of DMW.

Material basis and pharmacodynamic mechanism of YangshenDingzhi granules in the intervention of viral pneumonia:Based on serum pharmacochemistry and network pharmacology

Background:YangshenDingzhi granules(YSDZ)are clinically effective in preventing and treating COVID-19.The present study elucidates the underlying mechanism of YSDZ intervention in viral pneumonia by employing serum pharmacochemistry and network pharmacology.Methods:The chemical constituents of YSDZ in the blood were examined using ultraperformance liquid chromatography-quadrupole/orbitrap high-resolution mass spectrometry(UPLC-Q-Exactive Orbitrap MS).Potential protein targets were obtained from the SwissTargetPrediction database,and the target genes associated with viral pneumonia were identified using GeneCards,DisGeNET,and Online Mendelian Inheritance in Man(OMIM)databases.The intersection of blood component-related targets and disease-related targets was determined using Venny 2.1.Protein-protein interaction networks were constructed using the STRING database.The Metascape database was employed to perform enrichment analyses of Gene Ontology(GO)functions and Kyoto Encyclopedia of Genes and Genomes(KEGG)signaling pathways for the targets,while the Cytoscape 3.9.1 software was utilized to construct drug-component-disease-target-pathway networks.Further,in vitro and in vivo experiments were performed to establish the therapeutic effectiveness of YSDZ against viral pneumonia.Results:Fifteen compounds and 124 targets linked to viral pneumonia were detected in serum.Among these,MAPK1,MAPK3,AKT1,EGFR,and TNF play significant roles.In vitro tests revealed that the medicated serum suppressed the replication of H1N1,RSV,and SARS-CoV-2 replicon.Further,in vivo testing analysis shows that YSDZ decreases the viral load in the lungs of mice infected with RSV and H1N1.Conclusion:The chemical constituents of YSDZ in the blood may elicit therapeutic effects against viral pneumonia by targeting multiple proteins and pathways.

The relationship between the microstructures and catalytic behaviors of iron–oxygen precursors during direct coal liquefaction

A series of both unsupported and coal‐supported iron–oxygen compounds with gradual changes in microstructure were synthesized by a precipitation‐oxidation process at 20 to 70°C.The relationship between the microstructures and catalytic activities of these precursors during direct coal liquefaction was studied.The results show that the microstructure could be controlled through adjusting the synthesis temperature during the precipitation‐oxidation procedure,and that compounds synthesized at lower temperatures exhibit higher catalytic activity.As a result of their higher proportions ofγ‐FeOOH orα‐FeOOH crystalline phases,the unsupported iron–oxygen compounds synthesized at 20–30°C,which also had high specific surface areas and moisture levels,generate oil yields 4.5%–4.6%higher than those obtained with precursors synthesized at 70°C.It was also determined that higher oil yields were obtained when the catalytically‐active phase formed by the precursors during liquefaction(pyrrhotite,Fe1-xS)had smaller crystallites.Feed coal added as a carrier was found to efficiently disperse the active precursors,which in turn significantly improved the catalytic activity during coal liquefaction.

《走向优质——中国幼儿园教育质量评价标准》的测量学属性分析——基于我国100所幼儿园与1670名儿童的测评数据

幼儿园教育质量评价标准的编制具有重要的理论与实践意义。中国学前教育研究会组建了一个包含了来自国内6所高校的专家的跨学科研究团队,遵循严谨的测量学研制程序,经过两年扎实的研究,编制了《走向优质——中国幼儿园教育质量评价标准》(简称《优质标准》)。为验证该标准的有效性,课题组采用分层抽样的方法,在位于我国不同区域的5个省区抽取了不同性质与等级的城乡幼儿园共计100所,采用《优质标准》进行质量评价,同时从300个样本班级中随机抽取了1670名儿童(男女各半),对其语言、数学认知、情感社会性发展水平进行测评。基于幼儿园教育质量和儿童发展水平测评数据,课题组对《优质标准》进行了信效度分析。结果显示,《优质标准》总体及其各领域内部一致性均达到较高水平;绝大部分项目具有良好的区分度;《优质标准》具有良好的结构效度,包含两个潜在的质量因子,分别是课程教学与学习环境、管理支持与师资保障;幼儿园教育质量评价结果与儿童发展水平测评结果总体上呈显著相关,不同质量领域与儿童不同发展领域之间的相关性存在一定差异。综合以上证据表明,《优质标准》是适用于我国幼儿园教育情境的有效评估工具,其评价结果是可靠、可信的。

Magnetic properties and microstructure of nanocrystalline bulk Nd-Fe-B with Ce-Co addition

The influence of Ce-Co alloy addition and sintering holding time on permanent magnetic properties and micro structure of nanocrystalline Nd-Fe-B bulk alloy were investigated.The coercivity of Nd-Fe-B bulk alloy can be enhanced greatly by more than 100% after adding Ce-Co powders.However,when the concentration of Ce-Co is up to 30 wt%,the density of the magnet can reach the maximum value of 7.58 g/cm^(3),but the coercivity does not increase significantly.On the other hand,with the increase of holding time to 10 min,the density and coercivity of magnets increase gradually,reaching up to 7.55 g/cm^(3) and 1134.3 kA/m,respectively.After the addition of Ce-Co alloy,Ce-Co may easily diffuse into the Nd-Fe-B matrix during hot-pressing and under the high pressure and temperature,thus increasing the content of grain boundary phase and the pinning effect of grain boundary,which leads to the increase of coercivity.The extension of the hot-pressing holding time may be more conducive to the diffusion of CeCo into the Nd-Fe-B matrix.In addition,the effect of Ce-Co addition on the magnetic properties of Nd-FeB with different content of rare earth was also studied.The addition of Ce-Co can effectively increase the coercivity of nanocomposite Nd_(2)Fe_(14)B/α-Fe magnets.The addition of Nb to the parent alloy can further improve the coercivity.For Nd_(11)Fe_(81.5)Nb_(1)Ga_(0.5)B_(6) alloy with 10 wt% Ce-Co addition,the coercivity can increase from 740.28 to 1098.48 kA/m.

A comparative study of bismuth-based photocatalysts with titanium dioxide for perfluorooctanoic acid degradation

Bismuth-based material has been broadly studied due to their potential applications in various areas,especially used as promising photocatalysts for the removal of persistent organic pollutants(POPs) and several approaches have been adopted to tailor their features.Herein,the bismuth-based photocatalysts(BiOCl,BiPO4,BiOPO4/BiOCl) were synthesized by hydrothermal method and advanced characterization techniques(XRD,SEM,EDS elemental mapping,Raman and UV-vis DRS) were employed to analyze their morphology,crystal structure,and purity of the prepared photocatalysts.These synthesized photocatalysts offered a praiseworthy activity as compared to commercial TiO2(P25) for the degradation of model pollutant perfluorooctanoic acid(PFOA) under 254 nm UV light.It was interesting to observe that all synthesized photocatalysts show significant degradation of PFOA and their photocatalytic activity follows the order:bismuth-based catalysts> TiO2(P25)> without catalyst.Bismuth-based catalysts degraded the PFOA by almost 99.99% within 45 min while this degradation efficiency was 66.05% with TiO2 under the same reaction condition.Our work shows that the bismuth-based photocatalysts are promising in PFOA treatment.

Microstructure and high temperature fracture toughness of NG-TIG welded Inconel 617B superalloy

In the present study,the microstructure,fracture toughness,and fracture behavior of Inconel 617 B narrow gap tungsten inert gas(NG-TIG)welded joint were investigated systematically at the designed service temperature of 700℃.Fracture toughness(J0.2)of base metal(BM)and heat affected zone(HAZ)was higher than that of weld metal(WM).In HAZ and BM,strain mainly loc alised at grain boundaries with large misorientation and there were lots of coincidence site lattice(CSL)∑3 boundaries related to twins inside grains,which led to the much higher fracture toughness of BM and HAZ than WM.The high numbers of twins as well as the less serious strain localization at grain boundaries resulted in the most outstanding fracture toughness of BM.

Oxidation Behaviors of Different Grades of Ferritic Heat Resistant Steels in High-Temperature Steam and Flue Gas Environments

For steam tubes used in thermal power plant,the inner and outer walls were operated in high-temperature steam and flue gas environments respectively.In this study,structure,microstructure and chemical composition of oxide films on inner and outer walls of exservice low Cr ferritic steel G102 tube and exservice high Cr ferritic steel T91 tube were analyzed.The oxide film was composed of outer oxide layer,inner oxide layer and internal oxidation zone.The outer oxide layer on the original surface of tube had a porous structure containing Fe oxides formed by diffusion and oxidation of Fe.More specially,the outer oxide layer formed in flue gas environment would mix with coal combustion products during the growth process.The inner oxide layer below the original surface of tube was made of Fe–Cr spinel.The internal oxidation zone was believed to be the precursor stage of inner oxide layer.The formation of internal oxidation zone was due to O diffusing along grain boundaries to form oxide.There were Fe–Cr–Si oxides discontinuously distributed along grain boundaries in the internal oxidation zone of G102,while there were Fe–Cr oxides continuously distributed along grain boundaries in that of T91.

V-shaped substrate for surface and volume enhanced Raman spectroscopic analysis of microplastics

Research on the microplastics(MPs)is developing towards smaller size,but corresponding methods for the rapid and accurate detection of microplastics,especially nanoplastics still present challenge.In this work,a novel surface and volume enhanced Raman spectroscopy substrate was developed for the rapid detection of microplastic particles below 5μm.The gold nanoparticles(NPs)were deposited onto the surface and into the V-shaped nanopores of anodized aluminum oxide(AAO)through magnetron sputtering or ion sputtering,and then AuNPs@V-shaped AAO SERS substrate was obtained and studied for microplastic detection.SERS performance of AuNPs@V-shaped AAO SERS substrate was evaluated through the detection of polystyrene and polymethyl methacrylate microspheres.Results indicated that individual polystyrene sphere with a diameter of 1μm can be well detected on AuNPs@V-shaped AAO SERS substrate,and the maximum enhancement factor(EF)can reach 20.In addition,microplastics in ambient atmospheric samples were collected and tested to verify the effectiveness of the AuNPs@V-shaped AAO SERS substrate in the real environment.This study provides a rapid,economic and simple method for detecting and identifying microplastics with small size.