Multifunctional characteristics of 3D printed polymer nanocomposites under monotonic and cyclic compression

This study presents the multifunctional characteristics of multi-walled carbon nanotube(MWCNT)/polypropylene random copolymer(PPR) composites enabled via fused filament fabrication(FFF) under monotonic and quasi-static cyclic compression. Utilizing in-house MWCNT-engineered PPR filament feedstocks, both bulk and cellular composites were realized. The morphological features of nanocomposites were examined via scanning electron microscopy, which reveals that MWCNTs are uniformly dispersed. The uniformly dispersed MWCNTs forms an electrically conductive network within the PPR matrix, and the resulting nanocomposite shows good electrical conductivity(~10^(-1)S/cm), improved mechanical performance(modulus increases by 125% and compressive strength increases by 25% for 8 wt% MWCNT loading) and pronounced piezoresistive response(gauge factor of 27.9-8.5 for bulk samples)under compression. The influence of strain rate on the piezoresistive response of bulk samples(4 wt% of MWCNT) under compression was also measured. Under repeated cyclic compression(2% constant strain amplitude), the nanocomposite exhibited stable piezoresistive performance up to 100 cycles. The piezoresistive response under repeated cyclic loading with increasing strain amplitude of was also assessed.The gauge factor of BCC and FCC cellular composites(4 wt% of MWCNT) with a relative density of 30%was observed to be 46.4 and 30.2 respectively, under compression. The higher sensitivity of the BCC plate-lattice could be attributed to its higher degree of stretching-dominated deformation behavior than the FCC plate-lattice, which exhibits bending-dominated behavior. The 3D printed cellular PPR/MWCNT composites structures were found to show excellent piezoresistive self-sensing characteristics and open new avenues for in situ structural health monitoring in various applications.

Anticorrosive and antibacterial smart integrated strategy for biomedical magnesium

Biomedical magnesium is an ideal material for hard tissue repair and replacement.However,its rapid degradation and infection after implantation significantly hindersclinical applications.To overcome these two critical drawbacks,we describe an integrated strategybased on the changes in pH and Mg^(2+)triggered by magnesiumdegradation.This system can simultaneously offer anticorrosion and antibacterial activity.First,nanoengineered peptide-grafted hyperbranched polymers(NPGHPs)with excellent antibacterial activity were introduced to sodium alginate(SA)to construct a sensitive NPGHPs/SA hydrogel.The swelling degree,responsiveness,and antibacterial activity were then investigated,indicating that the system can perform dual stimulation of pH and Mg^(2+)with controllable antimicrobial properties.Furthermore,an intelligent platform was constructed by coating hydrogels on magnesium with polydopamine as the transition layer.The alkaline environment generated by the corrosion of magnesium reduces the swelling degree of the coatingso that the liquid is unfavorable for contacting the substrate,thus exhibiting superior corrosion resistance.Antibacterial testing shows that the material can effectively fight against bacteria,while hemolytic and cytotoxicity testing suggest that it is highly biocompatible.Thus,this work realizes the smart integration of anticorrosion and antibacterial properties of biomedical magnesium,thereby providing broader prospects for the use of magnesium.

Tailoring MgH_(2) for hydrogen storage through nanoengineering and catalysis

Hydrogen energy has been recognized as “Ultimate Power Source” in the 21st century, which could be the best solution to the looming energy crisis and climate degeneration in the near future. Due to its high safety, low price, abundant resources and decent hydrogen storage density, magnesium based solid-state hydrogen storage materials are becoming the leading candidate for onboard hydrogen storage. However,the high operation temperature and slow reaction rate of MgH_(2), as a result of the large formation enthalpy and high reaction activation energy,respectively, are the first and most difficult problems we need to face and overcome to realize its industrialization. Herein, a state-of-the-art review on tailoring the stable thermodynamics and sluggish kinetics of hydrogen storage in MgH_(2), particularly through nanoengnieering and catalysis is presented, aiming to provide references and solutions for its promotion and application. Promising methods to overcome the challenges faced by MgH_(2)/Mg, such as bidirectional catalysts and nanoconfinement with in-situ catalysis are compared and the required improvements are discussed to stimulate further discussions and ideas in the rational design of MgH_(2)/Mg systems with ability for hydrogen release/uptake at lower temperatures and cycle stability in the near future.

Towards high-performance anodes:Design and construction of cobalt-based sulfide materials for sodium-ion batteries

Sodium-ion batteries are increasingly becoming important in the energy storage field owing to their low cost and high natural abundance of sodium.Cobalt-based sulfide materials have been extensively studied as anode materials owing to their remarkable Na storage capability.Nevertheless,the application of cobalt-based sulfides is hampered by their serious capacity degradation and unsatisfactory cycling stability due to severe structural changes during cycling.Therefore,it is important to comprehensively summarize advances in the understanding and modification of cobalt-based sulfides from various perspectives.In the present review,recent advances on various cobalt-based sulfides,such as CoS,CoS_(2),Co_(3)S_(4),Co_(9)S_(8),NiCo_(2)S_(4),CUCo_(2)S_(4),and SnCoS_(4),are outlined with particular attention paid to strategies that improve their sodium storage performance.First,the mechanisms of charge storage are introduced.Subsequently,the key barriers to their extensive application and corresponding strategies for designing high-performance cobalt-based sulfide anode materials are discussed.Finally,key developments are summarized and future research directions are proposed based on recent advancements,aiming to offer possible fascinating strategies for the future promotion of cobalt-based sulfides as anode materials applied in sodium-ion batteries.

Preparation and Thermoelectric Properties of SiO_2/β-Zn_4Sb_3 Nanocomposite Materials

A series of SiO2/β-Zn4Sb3 core-shell composite particles with 3, 6, 9, and 12 nm of SiO2 shell in thickness were prepared by coatingβ-Zn4Sb3 microparticles with SiO2 nanoparticles formed by hydrolyzing the tetraethoxysilane in alcohol-alkali-water solution. SiO2/β-Zn4Sb3 nanocomposite thermoelectric materials were fabricated with these core-shell composite particles by spark plasma sintering （SPS） method. Microstructure, phase composition, and thermoelectric properties of SiO2/β-Zn4Sb3 nanocomposite thermoelectric materials were systemically investigated. The results show thatβ-Zn4Sb3 microparticles are uniformly coated by SiO2 nanoparticles, and no any phase transformation reaction takes place during SPS process. The electrical and thermal conductivity gradually decreases, and the Seebeck coefficient increases compared to that ofβ-Zn4Sb3 bulk material, but the increment of Seebeck coefficient in high temperature range remarkably increases. The thermal conductivity of SiO2/β-Zn4Sb3 nanocomposite material with 12 nm of SiO2 shell is the lowest and only 0.56 W·m^-1·K^-1 at 460 K. As a result, the ZT value of the SiO2/β-Zn4Sb3 nanocomposite material reaches 0.87 at 700 K and increases by 30%.

Regulating non-precious transition metal nitrides bifunctional electrocatalysts through surface/interface nanoengineering for air-cathodes of Zn-air batteries

Zn-air batteries(ZABs),especially the secondary batteries,have engrossed a great interest because of its high specific energy,economical and high safety.However,due to the insufficient activity and stability of bifunctional electrocatalysts for air-cathode oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)processes,the practical application of rechargeable ZABs is seriously hindered.In the effort of developing high active,stable and cost-effective electrocatalysts,transition metal nitrides(TMNs)have been regarded as the candidates due to their high conductivity,strong corrosion-resistance,and bifunctional catalytic performance.In this paper,the research progress in TMNs-based material as ORR and OER electrocatalysts for ZABs is discussed with respect to their synthesis,chemical/physical characterization,and performance validation/optimization.The surface/interface nanoengineering strategies such as defect engineering,support binding,heteroatom introduction,crystal plane orientation,interface construction and small size effect,the physical and chemical properties of TMNs-based electrocatalysts are emphasized with respect to their structures/morphologies,composition,electrical conductivity,specific surface area,chemical stability and corrosion resistance.The challenges of TMNs-based materials as bifunctional air-cathode electrocatalysts in practical application are evaluated,and numerous research guidelines to solve these problems are put forward for facilitating further research and development.

LiBH4 for hydrogen storage-New perspectives

Hydrogen energy has been recognized as“Ultimate Power Source”in the 21st century.It is a boon in these days of energy crunches and concerns about climate change because of the characterized advantages,such as high energy density,large calorific value,abundant resource,zero pollution,zero carbon emission,storable and renewable.State-of-the-art perspectives on tuning the stable thermodynamics and sluggish kinetics of dehydrogenation and re-hydrogenation of LiBH4,which has been regarded as a promising hydrogen storage alternative for onboard energy carrier applications have been discussed.Five major technological approaches are involved,including nanoengineering,catalyst modification,ions substitution,reactant destabilization and a novel process termed as high-energy ball milling with in-situ aerosol spraying(BMAS).It is worth noting that BMAS has the potential to help overcome the kinetic barriers for thermodynamically favorable systems like LiBH4 t MgH2 mixture and provide thermodynamic driving force to enhance hydrogen release at a lower temperature.

Molecular Simulation of Cement-Based Materials and Their Properties

Hydrated cement is one of the complex composite systems due to the presence of multi-scale phases with varying morphologies.Calcium silicate hydrate,which is the principal binder phase in the hydrated cement,is responsible for the stiffness,strength,and durability of Portland cement concrete.To understand the mechanical and durability behavior of concrete,it is important to investigate the interactions of hydrated cement phases with other materials at the nanoscale.In this regard,the molecular simulation of cement-based materials is an effective approach to study the properties and interactions of the cement system at the fundamental scale.Recently,many studies have been published regarding atomistic simulations to investigate the cement phases to define/explain the microscopic physical and chemical properties,thereby improving the macroscopic performance of hardened binders.The research in molecular simulation of cementitious systems involves researchers with multidisciplinary backgrounds,mainly in two areas:(1)cement chemistry,where the hydration reactions govern most of the chemical and physical properties at the atomic scale;and(2)computational materials science and engineering,where the bottom-up approach is required.The latter approach is still in its infancy,and as such,a study of the prevailing knowledge is useful,namely through an exhaustive literature review.This state-of-theart report provides a comprehensive survey on studies that were conducted in this area and cites the important findings.

Enhancement in boiling heat transfer performance using reduced graphene oxide coating with controllable components and porous structures

Enhancement in boiling heat transfer performance is significant for addressing thermal management bottlenecks of advanced electronic systems.Reduced graphene oxides(rGO)are regarded as promising candidates for thermal management due to their excellent thermal properties,chemical stability and adjustable wettability.In this study,rGO coatings with micron pores and controllable oxygen contents are prepared on Al substrate via cathodic electrophoretic deposition and subsequent thermal annealing,leading to enhanced pool boiling performance.The heat transfer coefficient for Al/rGO450is 37.2 kW m-2K-1,which is increased by 112.6%compared with bare Al,also outperformed previously reported Al based substrates.It is assumed that the hydrophilic and aerophobic r GO coatings effectively promote the liquid infiltration and bubble departure during pool boiling process.Importantly,repeatability tests indicate the durable stability of vertically oriented rGO nanosheets.Reverse nonequilibrium molecular dynamics simulation indicates that the interfacial transmission coefficients of Al/rGO increase after thermal annealing,indicative of the enhanced heat transfer performance of heterogeneous interface.Our study opens a new avenue for endowing metal substrates with high pool boiling performance using porous carbon coating nanoengineering strategy with controllable morphology and components.

Ag/AgX nanostructures serving as antibacterial agents:achievements and challenges

Bacterial infections,especially the frequently emerging "superbugs",seriously affect the quality of human life and even threaten human health.As the emerging antimicrobial agents that effectively eradicate pathogens,nanomaterials have been widely explored due to their effectiveness against wide-spectrum bacteria and“superbugs”.Of them,Ag/AgX nanostructures(X representing Cl,Br or I)have emerged as an excellent antibacterial agent because of their excellent photocatalytic performance in inactivating pathogens under light irradiation,which provides a new opportunity for the development of high-efficient visible-light driven photocatalytic sterilization.To date,Ag/AgX nanostructures have been widely employed in antibacterial associated fields because they are efficient in producing reactive oxygen species(ROS)and reactive chlorine species(RCS)under visible light irradiation.In this review,we summarized the recent progress of Ag/AgX nanostructures as plasmonic photocatalysts in the antibacterial field,focusing on the antibacterial effects and mechanisms of Ag/AgX nanostructures,as well as their potent applications.Finally,the challenges and prospects of Ag/AgX nanostructures acting as active antibacterial agents were discussed.

Accurate construction of cell membrane biomimetic graphene nanodecoys via purposeful surface engineering to improve screening efficiency of active components of traditional Chinese medicine

Biomimetic nanoengineering presents great potential in biomedical research by integrating cell membrane(CM) with functional nanoparticles. However, preparation of CM biomimetic nanomaterials for custom applications that can avoid the aggregation of nanocarriers while maintaining the biological activity of CM remains a challenge. Herein, a high-performance CM biomimetic graphene nanodecoy was fabricated via purposeful surface engineering, where polyethylene glycol(PEG) was used to modifying magnetic graphene oxide(MGO) to improve its stability in physiological solution, so as to improve the screening efficiency to active components of traditional Chinese medicine(TCM). With this strategy, the constructed PEGylated MGO(PMGO) could keep stable at least 10 days, thus improving the CM coating efficiency. Meanwhile, by taking advantage of the inherent ability of He La cell membrane(HM) to interact with specific ligands, HM-camouflaged PMGO showed satisfied adsorption capacity(116.2 mg/g) and selectivity. Finally, three potential active components, byakangelicol, imperatorin,and isoimperatorin, were screened from Angelica dahurica, whose potential antiproliferative activity were further validated by pharmacological studies. These results demonstrated that the purposeful surfaceengineering is a promising strategy for the design of efficient CM biomimetic nanomaterials, which will promote the development of active components screening in TCM.

Nanoengineering of Flux Pinning Sites in High-T_c Superconductors

Volume pinning forces were determined for a variety of bulk high-Tc superconductors of the 123-type from magnetization measurements. By means of scaling of the pinning forces, the acting pinning mechanisms in various temperature ranges were identified. The Nd-based superconductors and some YBCO crystals exhibited a dominating pinning of the δTc-type (i.e. , small, superconducting pinning sites). In contrast to this, the addition of insulating 211 particles provided pinning of the δ/-type; providing effective pinning in the entire temperature range acting as a 'background' pinning mechanism for the peak effect. Due to the small coherence lengths of the high-Tc compounds, effective pinning sites are defects or particles of nanometer size relative to ζ3. Integral magnetic measurements of the magnetization as a function of temperature in large applied magnetic fields (up to 7 T) revealed that practically all high-Tc compounds were spatially inhomogeneous, which could be caused by oxygen deficiency (YBCO), solid solutions of Nd/Ba (NdBCO and other light rare earth compounds), intergrowths (Bi-based superconductors), and doping by pair-breaking dopants like Zn, Pr. This implies that the superconducting sample consists of stronger and weaker superconducting areas, coupled together. In large applied fields, this coupling gets broken and the magnetization versus temperature curves revealed more than one superconducting transition. In contrast, irradiation experiments by neutrons, protons, and heavy-ions enabled the artificial introduction of very effective pinning sites into the high-Tc superconductors, thus creating a large variety of different observations using magnetic data. From all these observations, we construct a pinning diagram for bulk high-Tc superconductors explaining many features observed in high-Tc samples.