A physically-based representative stress methodology for predicting stress rupture life of Ni-based DS superalloy

Smooth and three types of U-shape single-edge notched plate specimens adopted to experimentally investigate stress rupture behavior of Ni-based Directionally Solidified(DS)superalloy at 850℃ exhibit notch weakening effect and multi-source cracking initiation near the notch root.However,stress rupture behavior of smooth and V-shape notched round bars at 1040℃ revealed by Li et al indicates notch strengthening effect and creep micro-holes originating mostly from the central portion.A combined creep-viscoplastic constitutive model is employed to analyze the distribution of stress,strain and stress Triaxial Factor(TF)near the notch root.The different stress distribution and creep restraint between asymmetric notched plate specimens and symmetric notched round bars are the main reasons for the corresponding failure mechanism.Meanwhile,a good qualitative relationship exists between TF value and stress rupture life of notched specimen.Especially,the area with maximum TF value(TF_(max))is highly consistent with creep damage initiation region.Hence,based on the distribution characteristics of the initial tensile loading,a representative stress method independent of time-changing creep load at the location of TF_(max) is conducted for life prediction.The predicted results of both smooth and notched plate specimens and round bars agrees well with the experimental results.

Large-scale blow spinning of heat-resistant nanofibrous air filters

Particulate matter(PM)pollution has become a serious problem worldwide and various kinds of nanofibrous filters aiming to solve the problem have been developed.It is urgent to remove PM from high-temperature pollution sources,such as industrial emissions,coal furnaces,and automobile exhaust gases.However,filtration at pollution sources remains challenging because most existing air filters are not resistant to high temperature.Herein,heat-resistant polyimide(PI)nanofibrous air filters are fabricated via a simple and scalable solution blow-spinning method.These air filters show excellent thermal stability at high temperature up to 420℃.They exhibit a filtration efficiency as high as 99.73%at ambient temperature and over 97%at 300℃.In addition,a field test shows that the filters remove>97%of PM from the car exhaust fumes.Hence,the blow-spun PI nanofibrous membranes combined with the facile preparation strategy have great potential in high temperature air filtration fields and other similar applications such as water purification and protein separation.

Room-temperature production of silver-nanofiber film for large-area, transparent and flexible surface electromagnetic interference shielding

A kind of pollution known as electromagnetic interference(EMI),which results from ubiquitous usage of various electronic communication and military radar equipment,has been receiving increasing attention recently.However,large-area EMI shielding on transparent and/or curved surfaces,including building windows,curved glass wall,and special requirements spaces(SRSs),remains hard to achieve.In this paper,a silver nanofiber(AgNF)based flexible and transparent EMI shielding film was successfully assembled via a room-temperature roll-to-roll production method.For transparent application scenario,AgNF with 89%transmittance in visible range and 1μm thickness shows~20 dB shielding efficiency(EMI SE).On the other hand,total shielding(>50 dB)is obtained when the thickness of AgNF increases to 10μm,while its transmittance in visible range remains higher than 75%.Considering the facile and scale-free production technology,this material can be readily applied in large-scale,transparent,and/or SRSs EMI shielding.

A large-area AgNW-modified textile with high-performance electromagnetic interference shielding

Manufacturing a flexible,light,large-area,and high-efficiency electromagnetic shielding materials in a straightforward and cost-effective manner presently remains a significant challenge.In this work,we propose a conductive network design and verify its electromagnetic interference(EMI)shielding effectiveness(SE)by simulation.Using the structure and parameters obtained by simulation,we prepare a flexible EMI shielding material using silver nanowires(AgNWs)/polyvinyl butyral(PVB)ethanol solution and textile substructure via a facile immersing method.In the frequency range of 5-18 GHz,the AgNWs/PVB textile with 1.4 mm thickness achieves an EMI SE of 59 dB,which exceeds the requirements for commercial applications.Due to the low density of 56 mg/cm^(3),specific shielding effectiveness(SSE)of this material reaches 1053 dB m^(3)/g.It is found that the AgNWs/PVB textile is more resistant to washing with water and oxidation than AgNWs textile without a PVB protector.As a result,the conductivity of AgNWs/PVB textile exhibits no change after washing with water and varies slightly after being kept in hot air.We find that a signal monitor is unable to detect a signal emitted by a mobile phone from a jacket lined with AgNWs/PVB textile.AgNWs/PVB textile with these properties can be mass-produced as high-efficiency EMI shielding material for commercial applications.

An ultralight,flexible,and biocompatible all-fiber motion sensor for artificial intelligence wearable electronics

New-generation human body motion sensors for wearable electronics and intelligent medicine are required to comply with stringent requirements in terms of ultralight weight,flexibility,stability,biocompatibility,and extreme precision.However,conventional sensors are hard to fulfill all these criteria due to their rigid structure,high-density sensing materials used as the constituents,as well as hermetical and compact assembly strategy.Here,we report an ultralight sensing material based on radial anisotropic porous silver fiber(RAPSF),which has been manufactured by phase separation and temperature-controlled grain growth strategy on a modified blow-spinning system.The resistance of RAPSF could be dynamically adjusted depending on the deflected shape.Furthermore,an all-fiber motion sensor(AFMS)with an ultra-low density of 68.70 mg cm^(−3) and an overall weigh of 7.95 mg was fabricated via layer-by-layer assembly.The sensor exhibited outstanding flexibility,breathability,biocompatibility,and remarkable body motion recognition ability.Moreover,the AFMS was shown to have great potential as an artificial intelligence throat sensor for throat state identification at the accuracy above 85%,allowing one to spot the early onset of the viral throat illness.

Mass Production of Ultrafine Fibers by a Versatile Solution Blow Spinning Method

CONSPECTUS:Ultrafine fiber materials have shown great application prospects in many fields due to their superior properties,including large specific surface area,high porosity,low density,and good mechanical flexibility.Various spinning methods have been developed to prepare ultrafine fiber materials,including electrospinning,solution blow spinning(SBS),centrifugal spinning,melt-blowing,etc.Among them,SBS combines the merits of electrospinning and melt-blowing.Unlike electrospinning,SBS uses a high-speed airflow as the driving force to stretch the spinning solution,and solvent evaporates rapidly in the process of liquid flow movement,thus obtaining ultrafine fibers.Compared with other spinning methods,SBS has many advantages,including simple and safe process,high efficiency,suitability for a wider range of solution systems,controllability of fiber structure and diameter,etc.Since its development in 2009,SBS has received widespread attention and has become an efficient and versatile tool for fabricating various ultrafine fiber materials with controlled microstructures and morphologies.Solution blow spun fibers can be assembled into a variety of configurations,including sponges,mats,papers,and films.The thickness of the fiber materials also can be easily regulated,which is an important advantage of SBS over electrospinning.The various forms of the blow spun fibers enable them to have a wide range of applications in environmental remediation,flexible electronic devices,energy storage and conversion,and biomedicine,among others.In this Account,we review the recent progress of SBS and mainly focus on our group’s contributions to this technology.We begin with an introduction to the principles and setup of SBS,including(1)the mechanism of fiber formation from spinning solution under the action of airflow;(2)the effects of spinning solution parameters(concentration and viscosity),processing parameters(gas pressure,feeding rate and working distance),and ambient conditions on the fiber morphology;and(3)the operation modes and development progress of SBS equipment.Then,we review the latest developments of fiber materials prepared by SBS,including polymer fibers,ceramic fibers,carbon fibers,metal fibers,and polymer-based composite fibers.After that,we discuss the application progress of blow spun fibers in the fields of air filtration,water treatment,sound absorption,electromagnetic interference shielding,flexible electronic devices,high temperature thermal insulation,and uranium extraction.In the final section,we offer some remarks on the challenges,opportunities,and future development directions of SBS technology,especially pointing out the problems and research directions for the engineering of SBS.We envision that this Account will attract more researchers’attention to SBS technology,thus greatly promoting the development of this technology.