Synergistic effect of MXene on the flame retardancy and thermal degradation of intumescent flame retardant biodegradable poly(lactic acid)composites

The effect of Ti3C2 MXene nanosheets on the intumescent flame retardant(IFR)poly(lactic acid)(PLA)composites was investigated among a series of PLA/IFR/MXene,which were prepared by melt blending 0-2.0 wt%MXene,10.0 wt%-12.0 wt%IFR and PLA together.The results of limiting oxygen index(LOI)and vertical burning(UL-94)discover that the combination of 0.5 wt%MXene and 11.5 wt%IFR synergistically improves the fire safety of PLA to reach UL-94 V-0 rating with LOI value of 33.0%.The PLA/IFR/MXene composites perform an obvious reduction in peak of heat release rate(HRR)in cone calorimeter tests(CCTs).Furthermore,the carbon residues after CCTs were characterized by scanning electron microscope(SEM),laser Raman spectroscopy(LRS),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).It is demonstrated that both the titanium composition of the MXene structure and the characteristics of the two-dimensional material enhance the PLA/IFR/MXene composite materials’ability to produce a dense barrier layer to resist burnout during thermal degradation.

S-scheme CoTiO_(3)/Cd_(9.51)Zn_(0.49)S_(10)heterostructures for visible-light driven photocatalytic CO_(2) reduction

CdZnS solid solutions with strong light absorption are promising materials for solar-driven COreduction;however,their relatively weak redox ability and intrinsic photo-corrosion limit their further development as a photocatalyst.The addition of a second photocatalyst with a suitable band structure to construct a S-scheme photocatalytic system can solve both problems simultaneously.Here,we report a S-scheme photocatalyst based on the heterostructure of CoTiO_(3)/CdZnS(abbreviated as CoTiO_(3)/Cd_(9.51)Zn_(0.49)S_(10))that enables the efficient photocatalytic reduction of CO.Detailed physicochemical characterization resolves the S-scheme charge transfer mechanism in this composite photocatalyst.With the well-designed structure of particles and desirable band offsets,this hybrid system offers visible light absorption in a broad spectral region,large surface area,strong redox ability,and fast carrier separation and transportation.Under visible-light illumination,the CoTiO_(3)/Cd Zn S hybrid system displays a CO formation rate of about 11 mmol hgcombined with a long-term operational stability.Besides,a high apparent quantum efficiency(AQE)of 7.27%is realized for the CO_(2)-to-CO reduction reaction by the optimized Co TiO/Cd Zn S hybrid under 420 nm monochromatic light irradiation.

Modeling and boundary control of a flexible marine riser coupled with internal fluid dynamics

In this paper, vibration reduction of a flexible marine riser with time-varying internal fluid is studied by using boundary control method and Lyapunov＇s direct method. To achieve more accurate and practical riser＇s dynamic behavior, the model of marine riser with time-varying internal fluid is modeled by a distributed parameter system （DPS） with partial differential equations （PDEs） and ordinary differential equations （ODEs） involving functions of space and time. The dynamic responses of riser are completely different if the time-varying internal fluid is considered. Boundary control is designed at the top boundary of the riser based on original infinite dimensionality PDEs model and Lyapunov＇s direct method to reduce the riser＇s vibrations. The uniform boundedness and closed-loop stability are proved based on the proposed boundary control. Simulation results verify the effectiveness of the proposed boundary control.

Superior anti-corrosion and self-healing bi-functional polymer composite coatings with polydopamine modified mesoporous silica/graphene oxide

In this article,graphene oxide(GO)and benzotriazole-loaded mesoporous silica nanoparticles(BTA/MSNs)are combined on micro scale through the in situ polymerization of polydopamine(PDA),preparing a selfhealing bi-functional GO(fGO)used as nano-fillers for anti-corrosion enhancement of waterborne epoxy(WEP)coatings.Scanning electronic microscopy(SEM)images show that the BTA/MSNs are uniformly distributed on the surface of high aspect ratio GO nanosheets to endow GO nanocontainer characteristics.UV-vis profiles demonstrate that fGO has p H-controlled release function.Modulus at lowest frequency is generally used for comparing the corrosion resistance of organic coatings.Modulus at lowest frequency(1.42×10^(5)Ωcm^(2))after 30 days immersion in 3.5 wt.%Na Cl solution revealed 2 orders of magnitude higher that of blank WEP(1.17×10^(7)Ωcm^(2)).With artificial cracks on its coatings,fGO/WEP had no obvious rust compared with blank WEP after 240 h of immersion.We anticipate that self-healing and physical barrier bi-functional nanocontainers improve the traditional anticorrosion coating efficiency with better,longer-lasting performance for shipping,oil drilling or bridge maintenance.

Visualizing light-induced dynamic structural transformations of Au clusters-based photocatalyst via in situ TEM

Ultrasmall gold(Au)clusters have been regarded as one of the prototypes materials for solar energy conversion due to their unique strong molecular-like light absorption properties.However,the light-induced aggregation of Au clusters into nanoparticles is one of the most important factors that restricts its application in photocatalysis.Although Au clusters aggregation has been widely demonstrated,the underlying mechanism for cluster fusion is still unclear due to the lack of experimental evidence.Herein,we report the direct observation of Au clusters on TiO_(2) nanosheets aggregating when used as visible light photocatalysts for the reduction of nitroaromatics.Through in situ high-resolution transmission electron microscopy(TEM),the coexistence of two fusion mechanisms of Au clusters on TiO_(2) under ultraviolet-visible(UV-Vis)light irradiation in air is identified,i.e.,the migration and coalescence(MC)and Ostwald ripening(OR).Additionally,the correlation between the photostability of Au clusters and reaction atmospheres has been investigated,among which Au clusters have higher stability in an inert N_(2) atmosphere or vacuum than the oxidizing atmospheres(i.e.,air and O_(2)).These results indicate the inherent stability of Au cluster during photocatalysis,and instability comes from the consuming of ligand layer.This work not only discloses the underlying mechanism of Au cluster sintering but also provides guidelines for enhancing metal clusters-based photocatalysts stability.