Xenotime rare-earth(RE)phosphates are emerging as promising materials for environmental barrier coatings(EBCs)for SiC-based ceramic-matrix composites(CMCs)because of their close coefficients of thermal expansion(CTEs)...
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Xenotime rare-earth(RE)phosphates are emerging as promising materials for environmental barrier coatings(EBCs)for SiC-based ceramic-matrix composites(CMCs)because of their close coefficients of thermal expansion(CTEs)and resistance to calcium-magnesium-alumina-silicate(CMAS)*** this work,high-entropy(HE)(Sc_(0.2)Lu_(0.2)Yb_(0.2)Er_(0.2)Y_(0.2))PO_(4) and five single-component REPO4(RE=Sc,Lu,Yb,Er,and Y)compounds were synthesized,and their stability,thermal properties,and CMAS corrosion resistance were *** CTE values of four REPO_(4) compounds(RE=Lu,Yb,Er,and Y;~(5.6-6)×10^(−6)℃^(−1))are close to those of SiC-CMC((4.5-5.5)×10^(−6)℃^(−1)),whereas ScPO_(4)(6.98×10^(−6)℃^(−1))and HE(5RE_(0.2))PO_(4)(6.39×10^(−6)℃^(−1))have slightly higher values in the temperature range of 200-1300℃.HE phosphate has the lowest thermal conductivity due to its size and mass *** CMAS corrosion tests at 1300℃ for 5,45,and 96 h revealed that all RE phosphates formed a continuous and dense reaction layer predominantly composed of Ca_(8)MgRE(PO_(4))_(7),effectively impeding CMAS ***,REPO_(4) with smaller RE³−cations displays a slower reaction rate and reduced corrosion kinetics,as evidenced by the smaller thickness of the reaction layer.A larger negative difference in the optical basicity(OB)value between REPO_(4) and CMAS signifies greater corrosion resistance.A mechanistic understanding of CMAS corrosion and elucidation of the effects of critical parameters such as the ionic mass and ionic radius of RE elements on their thermal properties and CMAS corrosion kinetics are useful for the development of novel xenotime-type phosphates as EBCs for SiC-CMCs.
Hydrodynamics of surfactant monolayers are governed by surface tension, surface shear viscosity, surface dilatational viscosity, and surface diffusivity. While the first two have been studied comprehensively with cons...
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Hydrodynamics of surfactant monolayers are governed by surface tension, surface shear viscosity, surface dilatational viscosity, and surface diffusivity. While the first two have been studied comprehensively with consistent results, surface dilatational viscosity is plagued with anomalies, including apparent negative values. Here, full-field interfacial velocity measurements together with the Navier-Stokes equations reveal that a source of these anomalies is the use of equilibrium surface diffusivity for systems far from equilibrium. Specifically, surface diffisivity was found to be more than seven orders of magnitude (ten million times) larger in a nonsolenoidal interfacial flow field. Micron-sized phase domains in the monolayer are the likely culprit for the enhanced diffusivity.
Multicomponent rare earth phosphates hold immense potential as next-generation environmental barrier coatings(EBCs),offering enormous possibilities and flexibility by controlling and varying their components and fract...
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Multicomponent rare earth phosphates hold immense potential as next-generation environmental barrier coatings(EBCs),offering enormous possibilities and flexibility by controlling and varying their components and fractions to tailor their *** this work,the key material parameters(e.g.,ionic size and ionic size disorder)and the elements governing their thermal‒mechanical properties and resistance against calcium‒magnesium‒aluminosilicate(CMAS)corrosion were *** thermal conductivities of multicomponent rare-earth phosphates correlate well with cation size disorder,but no clear trend is identified for the coefficient of thermal expansion(CTE).Er-containing compositions display low CTEs and high fracture *** formation of a dense interfacial layer occurs for most CAMS corrosion-resistant compositions when tested at 1300°C,e.g.,(Lu_(0.2)Yb_(0.2)Er_(0.2)Y_(0.2)Gd_(0.2))PO_(4) and(Lu_(0.2)Yb_(0.2)Er_(0.2)Dy_(0.2)Gd_(0.2))PO_(4).These multicomponent phosphates also display the least recession upon molten CMAS attack at 1400°C without significant volumetric swelling,which is superior to their single-component counterparts and state-of-the-art EBCs based on rare-earth *** contrast,Sc-containing multicomponent phosphates display inferior performance against CMAS corrosion and penetration.A mechanistic understanding and understanding of the kinetics of the interfacial interaction at higher temperatures,as well as the key parameters governing their thermomechanical properties and CMAS corrosion,are valuable for designing data-driven materials of multicomponent phosphates for EBC applications.
Challenge 3 of the 2022 NIST additive manufacturing benchmark(AM Bench)experiments asked modelers to submit predictions for solid cooling rate,liquid cooling rate,time above melt,and melt pool geometry for single and ...
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Challenge 3 of the 2022 NIST additive manufacturing benchmark(AM Bench)experiments asked modelers to submit predictions for solid cooling rate,liquid cooling rate,time above melt,and melt pool geometry for single and multiple track laser powder bed fusion process using moving *** in-house developed Additive Manufacturing Computational Fluid Dynamics code(AM-CFD)combined with a cylindrical heat source is implemented to accurately predict these *** heat source calibration is proposed relating volumetric energy density(ψ)based on experiments available in the *** parameters of the heat source of the computational model are initially calibrated based on a Higher Order Proper Generalized Decomposition-(HOPGD)based surrogate *** prediction using the calibrated heat source agrees quantitatively with NIST measurements for different process conditions(laser spot diameter,laser power,and scan speed).A scaling law based on keyhole formation is also utilized in calibrating the parameters of the cylindrical heat source and predicting the challenge *** addition,an improvement on the heat source model is proposed to relate the Volumetric Energy Density(VED_(σ))to the melt pool aspect *** model shows further improvement in the prediction of the experimental measurements for the melt pool,including cases at higher VED_(σ).Overall,it is concluded that the appropriate selection of laser heat source parameterization scheme along with the heat source model is crucial in the accurate prediction of melt pool geometry and thermal measurements while bypassing the expensive computational simulations that consider increased physics equations.
The Unites States commercial unmanned aerial system (UAS) market was valued at $99.6 million in 2020 and is projected to reach $3.7 billion by 2030. Applications for these commercial UAS range from risk mitigation and...
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This study presents a statistical framework for detecting and quantifying damage in multicopter propeller blades through functionally pooled (FP) time series models. The methodology integrates model-based analysis wit...
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