氧化皮和脱碳层对锅炉部件表面金相检测结果的影响分析及优化

表面金相组织分析是监测锅炉高温部件材质状况的最直接、有效的方法和手段。为了优化金相检测准确性和检测精度,通过梳理表面金相检测的劣化类型、判定依据、检测部位要求和结论评判等理论体系,结合多年积累的现场检测经验,并通过对锅炉部件进行取样,开展实验室试验来验证金属部件表面对金相检测结果的影响程度。结果显示,氧化皮和脱碳层是影响表面金相结果的主要因素。实际工作中对部件的表面打磨深度一般应控制在0.5 mm以上;部件较厚或表面氧化皮较厚时,应采用阶梯式递进开展检测,同时结合强度要求渐进式开展表面金相检测。

Microstructural evolution and mechanical properties of duplex-phase Ti6242 alloy treated by laser shock peening

The effects of laser shock peening(LSP)on the microstructural evolution and mechanical properties of the Ti6242 alloy,including the residual stress,surface roughness,Vickers microhardness,tensile mechanical response,and high-cycle fatigue properties,were studied.The results showed that the LSP induced residual compressive stresses on the surface and near surface of the material.The maximum surface residual compressive stress was−661 MPa,and the compressive-stress-affected depth was greater than 1000μm.The roughness and Vickers micro-hardness increased with the number of shocks,and the maximum hardness-affected depth was about 700μm after three LSP treatments.LSP enhanced the fraction of low-angle grain boundaries,changed the grain preferred orientations,and notably increased the pole density ofαphase on the near surface from 2.41 to 3.46.The surface hardness values of the LSP samples increased with the increase of the number of shocks due to work hardening,while the LSP had a limited effect on the tensile properties.The high-cycle fatigue life of the LSP-treated sample was significantly enhanced by more than 20%compared with that of the untreated sample,which was caused by the suppression of the initiation and propagation of fatigue cracks.

SiCp/Al复合材料端磨磨削力模型构建与试验研究

针对SiCp/Al逐层磨削两相三维重构需要精密高效端磨的问题,基于单颗磨粒磨削SiCp/Al的磨削力,在考虑切屑变形力、摩擦力、SiC颗粒断裂破碎力的基础上,建立SiCp/Al的端磨磨削力解析模型,结合试验研究切削速度、工件进给速度和轴向磨削深度等参数对加工表面粗糙度的影响规律,并探讨SiCp/Al金相表面快速磨削的加工工艺。结果表明:构建的端磨磨削力解析模型与试验的法向磨削力Fn的总体平均误差为12.98%,切向磨削力Ft的总体平均误差为3.49%;表面粗糙度随切削速度增大而减小,随进给速度和轴向磨削深度的增大而增大;用磨料颗粒基本尺寸为13.0μm的磨具,经过6次磨抛获得良好金相表面,所需磨削加工时间为600 s,可实现SiCp/Al金相表面的快速磨削。

Haemocompatibility of Ti-3Zr-2Sn-3Mo-25Nb biomedical alloy with surface heparinization using electrostatic self assembly technology

The haemocompatibility of Ti-3Zr-2Sn-3Mo-25Nb biomedical alloy was studied after surface heparinization. A layer of sol-gel TiO2 films was applied on the alloy samples followed by active treatment in the bio-functionalized solution for introducing the OH- and groups, and then the heparin was immobilized on the active TiO2 films through the electrostatic self assembly technology. It is shown that the heparinized films are mainly composed of anatase and rutile with smooth and dense surface. In vitro blood compatibility was evaluated by haemolysis test, clotting time and platelet adhesion behavior tests. The results show that the haemocompatibility of the alloy could be significantly improved by surface heparinization.

First-principles thermodynamics of metal-oxide surfaces andinterfaces:A case study review

An important step for achieving the knowledge-based design freedom on nano-and interfacial materials is attained by elucidating the related surface and interface thermodynamics from the first principles so as to allow engineering the microstructures for desired properties through smartly designing fabrication processing parameters.This is demonstrated for SnO2 nano-particle surfaces and also a technologically important Ag-SnO2 interface fabricated by in-situ internal oxidation.Based on defect thermodynamics,we first modeled and calculated the equilibrium surface and interface structures,and as well corresponding properties,as a function of the ambient temperature and oxygen partial pressure.A series of first principles energetics calculations were then performed to construct the equilibrium surface and interface phase diagrams,to describe the environment dependence of the microstructures and properties of the surfaces and interfaces during fabrication and service conditions.The use and potential application of these phase diagrams as a process design tool were suggested and discussed.

Surface quality, microstructure and mechanical properties of Cu-Sn alloy plate prepared by two-phase zone continuous casting

Cu-4.7%Sn （mass fraction） alloy plate was prepared by the self-developed two-phase zone continuous casting （TZCC） process. The relationship between process parameters of TZCC and surface quality of the alloy plate was investigated. The microstructure and mechanical properties of the TZCC alloy plate were analyzed. The results show that Cu-4.7%Sn alloy plate with smooth surface can be obtained by means of reasonable matching the entrance temperature of two-phase zone mold and the continuous casting speed. The microstructure of the TZCC alloy is composed of grains-covered grains, small grains with self-closed grain boundaries, columnar grains and equiaxed grains. Compared with cold mold continuous casting Cu-4.7%Sn alloy plate, the room temperature tensile strength and ductility of the TZCC alloy plate are greatly improved.

Nitrate-group-grafting-induced assembly of rutile TiO2 nanobundles for enhanced photocatalytic hydrogen evolution

In this study,an acid-induced assembly strategy for a rutile TiO2 photocatalyst was proposed on the basis of the treatment of lamellar protonated titanate with a concentrated HNO3 solution.Nitrate groups were successfully grafted onto a TiO2 surface and induced the assembly of rutile TiO2 nanorods into uniform spindle-like nanobundles.The resulting TiO2 product achieved a photocatalytic hydrogen evolution rate of 402.4μmol h^?1,which is 3.1 times higher than that of Degussa P25-TiO2.It was demonstrated that nitrate group grafting caused the rutile TiO2 surface to become negatively charged,which is favorable for trapping positive protons and improving charge carrier separation,thereby enhancing photocatalytic hydrogen production.Additionally,surface charges were crucial to structural stability based on electrostatic repulsion.This study not only developed a facile surface modification strategy for fabricating efficient H2 production photocatalysts but also identified an influence mechanism of inorganic acids different from that reported in the literature.

The effect of the support on the surface composition of PtCu alloy nanocatalysts: In situ XPS and HS-LEIS studies

Supported PtCu alloys have been broadly applied in heterogeneous catalysis and electrocatalysis owing to their excellent catalytic performance and high CO tolerance. It is important to analyze the outermost surface composition of the supported alloy nanoparticles to understand the nature of the catalytically active sites. In this paper, homogeneous face-centered cubic PtCu nanoparticles with a narrow particle size distribution were successfully fabricated and dispersed on a high-surface-area Ti〇2 powder support. The samples were oxidized and reduced in situ and then introduced into the ultrahigh vacuum chamber to measure the topmost surface composition by high-sensitivity low-energy ion scattering spectroscopy, and to determine the oxidation states of the elements by X-ray photoelectron spectroscopy. The surface composition and morphology, elemental distribu-tion, and oxidation states of the components were found to be significantly affected by the support and treatment conditions. The PtCu is de-alloyed upon oxidation with CuO wetting on the TiO2 sur-face and re-alloyed upon reduction. Phase diagrams of the surface composition and the bulk com-position were plotted and compared for the supported and unsupported materials.

The effects of TiO_(2)crystal-plane-dependent Ir-TiO_(x)interactions on the selective hydrogenation of crotonaldehyde over Ir/TiO_(2)catalysts

Three supported Ir/TiO_(2)catalysts,containing anatase TiO_(2)nanocrystals with predominantly exposed{101},{100},and{001}planes,were subjected to various pre-treatments(H2 reduction at different temperatures and O_(2)re-oxidation)and then tested in the vapor phase selective hydrogenation of crotonaldehyde.The pre-treatments significantly altered the Ir-TiO_(x)interactions,including the morphologies and electronic properties of the Ir species and their surface acidity.These interactions were also closely related to the crystal planes of TiO_(2),which further supported the observed reaction behaviors of the various Ir/TiO_(2)catalysts.The best performance was obtained using the Ir/TiO_(2)-{101}catalyst pre-reduced at 300℃,owing to its higher Ir^(0)surface concentration and moderate surface acidity compared to the other catalysts.Moreover,these findings indicated the synergistic role of the Ir-TiO_(x)interface in the reaction,as the interfacial sites were responsible for the adsorption/activation of H_(2)and the C=O bond in the crotonaldehyde molecule.However,pre-reduction at 400℃resulted in partial encapsulation of the Ir particles by TiO_(x)via strong metal-support interactions,which is unfavorable for the catalytic reaction owing to the loss of Ir-TiO_(x)interfacial sites.

Directional migration behavior of cerium during sintering process of mischmetal doped cemented carbide

Three observation methods were used to investigate the existing form and the behavior of rare earth during the sintering process of high activity mischmetal （RE, with lanthanum and cerium） doped WC-8%Co-0.048%RE（mass fraction） alloy with low carbon-containing level by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDXS）, considering the fact that the addition amount of rare earth in the alloy is very minute. The directional migration process and mechanism of cerium were discussed. First, the sinter skin （surface） is observed. oxide on the sinter skin, and lanthanum in these cerium observed, and lanthanum containing phase/micro-zone in It is shown that there exists a dispersedly distributed cerium containing enrichment positions is very minute. Secondly, the polished section is the alloy is identified. Finally, based on the fact that the fracture of cemented carbide is resulted from the heterogeneous phase or other defects within the microstructure, the fracture surface is observed and cerium containing phase/micro-zone in the fracture source approximately 260 μm from the surface is identified. These combined observations reveal adequately the fact that lanthanum and cerium get separated and cerium predominantly migrates towards the surface during the sintering process.

Formation of Rutile Nanoparticles from the Condensed Disperse Phase at a Surface of High-Temperature Particles

The photos, which are done by electron microscope, of the condensed disperse phase, surrounding high-temperature metal particles are presented. The dependence of concentration of condensed dispersive phase which surrounds a high-temperature metal particle upon the temperature of the particle was obtained. The dependence of concentration of electrons in condensed dispersive phase upon the temperature of the particle was studied. The dependence of an equilibrium charge of a metal particle surrounded with condensed disperse phase on the temperature of a particle in a positive and negative region is presented. The dependence of a charge of a metal particle on time at the fixed temperature is obtained.

Anisotropic gapping of topological Weyl rings in the charge-density-wave superconductor In_(x)TaSe_(2)

Topological materials and topological phases have recently become a hot topic in condensed matter physics.In this work,we report an In-intercalated transition-metal dichalcogenide In_(x)TaSe_(2)(named 112 system),a topological nodal-line semimetal in the prep seffiffinffi ce of both charge density wave(CDW)and superconductivity.In the x=0.58 sample,the 2×√3 commensurate CDW(CCDW)and the 2×2 CCDW are observed below 116 and 77 K,respectively.Consistent with theoretical calculations,the spin–orbital coupling gives rise to two twofold-degenerate nodal rings(Weyl rings)connected by drumhead surface states,confirmed by angle-resolved photoemission spectroscopy.Our results suggest that the 2×2 CCDW ordering gaps out one Weyl ring in accordance with the CDW band folding,while the other Weyl ring remains gapless with intact surface states.In addition,superconductivity emerges at 0.91 K,with the upper critical field deviating from the s-wave behavior at low temperature,implying possibly unconventional superconductivity.Therefore,we think this type of the 112 system may possess abundant physical states and offer a platform to investigate the interplay between CDW,nontrivial band topology and superconductivity.