Progress in ceramic materials and structure design toward advanced thermal barrier coatings

Thermal barrier coatings(TBCs)can effectively protect the alloy substrate of hot components in aeroengines or land-based gas turbines by the thermal insulation and corrosion/erosion resistance of the ceramic top coat.However,the continuous pursuit of a higher operating temperature leads to degradation,delamination,and premature failure of the top coat.Both new ceramic materials and new coating structures must be developed to meet the demand for future advanced TBC systems.In this paper,the latest progress of some new ceramic materials is first reviewed.Then,a comprehensive spalling mechanism of the ceramic top coat is summarized to understand the dependence of lifetime on various factors such as oxidation scale growth,ceramic sintering,erosion,and calcium–magnesium–aluminium–silicate(CMAS)molten salt corrosion.Finally,new structural design methods for high-performance TBCs are discussed from the perspectives of lamellar,columnar,and nanostructure inclusions.The latest developments of ceramic top coat will be presented in terms of material selection,structural design,and failure mechanism,and the comprehensive guidance will be provided for the development of next-generation advanced TBCs with higher temperature resistance,better thermal insulation,and longer lifetime.

Low-thermal-conductivity thermal barrier coatings with a multi-scale pore design and sintering resistance following thermal exposure

High-insulation,long-life thermal barrier coatings(TBCs)decrease the service temperature of superalloys and improve the service life of gas turbines.Improvement in the thermal insulation properties of the coating mainly depends on the optimization of the TBC structure.An important challenge for TBCs is maintaining a high performance during thermal exposure without degradation,as the pore-rich structure of the topcoat would inevitably be transformed by sintering.A low-thermalconductivity anti-sintering coating can overcome the tradeoff between thermal insulation and sinter degradation.In this review,the design,preparation,and serviceability evaluation of a low-thermal-conductivity anti-sintering coating will be discussed.Furthermore,directions for potential development are introduced.This paper provides a comprehensive understanding of the structured tailoring of TBCs for better thermal insulation and anti-sintering performance.

Characterization of Changes and Driver Microbes in Gut Microbiota During Healthy Aging Using A Captive Monkey Model

Recent population studies have significantly advanced our understanding of how age shapes the gut microbiota.However,the actual role of age could be inevitably confounded due to the complex and variable environmental factors in human populations.A well-controlled environment is thus necessary to reduce undesirable confounding effects,and recapitulate age-dependent changes in the gut microbiota of healthy primates.Herein we performed 16S rRNA gene sequencing,characterized the age-associated gut microbial profiles from infant to elderly crab-eating macaques reared in captivity,and systemically revealed the lifelong dynamic changes of the primate gut microbiota.While the most significant age-associated taxa were mainly found as commensals such as Faecalibacterium,the abundance of a group of suspicious pathogens such as Helicobacter was exclusively increased in infants,underlining their potential role in host development.Importantly,topology analysis indicated that the network connectivity of gut microbiota was even more agedependent than taxonomic diversity,and its tremendous decline with age could probably be linked to healthy aging.Moreover,we identified key driver microbes responsible for such age-dependent network changes,which were further linked to altered metabolic functions of lipids,carbohydrates,and amino acids,as well as phenotypes in the microbial community.The current study thus demonstrates the lifelong age-dependent changes and their driver microbes in the primate gut microbiota,and provides new insights into their roles in the development and healthy aging of their hosts.

Numerical investigation on the effects of current headings on vortex induced motions of a semi-submersible

In this paper,numerical simulations on vortex-induced motions(VIM)of a semi-submersible at two different current headings are conducted over a wide range of current velocities.The simulations are performed with the computational fluid dynamics(CFD)solver VIM-FOAM-SJTU which is an in-house solver developed based on the OpenFOAM framework.The turbulent flows are resolved with a shear stress transport-delayed detached eddy simulation(SST-DDES)model.Free decay tests for transverse and yaw motion are performed in calm still water to make sure the equivalent stiffness is setup correctly.Then the results of VIM,including motion response,forces and moments,and flow patterns are presented and analyzed carefully.Motions including transverse,in-line and yaw motion at different current headings and velocities are compared.Instantaneous vorticity in the wake regions at different time stamps are also illustrated for different current headings and velocities.