Magnesium composites with hybrid nano-reinforcements:3D simulation of dynamic tensile response at elevated temperatures

3D numerical simulations of dynamical tensile response of hybrid carbon nanotube(CNT)and SiC nanoparticle reinforced AZ91D magnesium(Mg)based composites considering interface cohesion over a temperature range from 25 to 300℃ were carried out using a 3D representative volume element(RVE)approach.The simulation predictions were compared with the experimental results.It is clearly shown that the overall dynamic tensile properties of the nanocomposites at different temperatures are improved when the total volume fraction and volume fraction ratio of hybrid CNTs to SiC nanoparticles increase.The overall maximum hybrid effect is achieved when the hybrid volume fraction ratio of CNTs to SiC nanoparticles is in the range from 7:3 to 8:2 under the condition of total volume fraction of 1.0%.The composites present positive strain rate hardening and temperature softening effects under dynamic loading at high temperatures.The simulation results are in good agreement with the experimental data.

Effect of hybrid ratio on friction and wear behavior of AZ91D matrix nanocomposites under oil lubricated conditions

Friction and wear behavior of AZ91D and its nanocomposites reinforced by different contents of hybrid multi-walled CNTs and nano-SiC particulates under oil lubrication was investigated using a MRS-10P four-ball tribometer.Friction coefficients and wear rates were measured within a load range of 200-1000 N at a spindle rotary speed of 380 r/min.Worn surface morphologies,phase and element compositions were studied by scanning electron microscope(SEM),X-ray diffraction(XRD)and energy dispersive spectroscopy(EDS),respectively.The mechanism of synergistic effect of CNTs and SiC nanoparticles was discussed.The results indicate that the AZ91D nanocomposites show better wear resistance properties and different wear mechanisms compared with AZ91D.The AZ91D nanocomposites reinforced with 0.5%CNTs and 0.5%nano-SiC have the best tribological capacity.The wear mechanisms for the Mg-based hybrid nanocomposites appear to be a mix-up of micro-ploughing,micro-cutting,slight adhesive wear and delamination.

Review on the nanoparticle fluidization science and technology

Gas fluidization has an ability to turn static particles to fluid-like dense flow, which allows greatly improved heat transfer among porous powders and highly efficient solid processing to become reality. As the rising star of current scientific research, some nanoparticles can also be fluidized in the form of agglomerates, with sizes ranging from tens to hundreds of microns. Herein, we have reviewed the recent progress on nanomaterial agglomeration and their fluidization behavior, the assisted techniques to enhance the fluidization of nanomaterials,including some mechanical measures, external fields and improved gas injections, as well as their effects on solid fluidization and mixing behaviors. Most of these techniques are effective in breaking large agglomerates and promoting particulate fluidization, meanwhile, the solid mixing is intensified under assisted fluidization. The applications of nanofluidization in nanostructured material production and sustainable chemical industry are further presented. In summary, the fluidization science of multidimensional, multicomponent and multifunctional particles, their multi-phase characterization, and the guideline of fluidized bed coupled process are prerequisites for the sustainable development of fluidized bed based materials, energy and chemical industry.

Molecular dynamics simulations on the relationship between the elastic parameters and the molecular structures of nano-hybrid POSS materials

To research the relationship between the elastic parameters and the molecular structures of nano hybrid polyhedral oligomeric silsesquioxanes （POSS） materials, the mechanical properties at different temperatures for three POSS polymers with different molecular architectures, polymerlized norbornene POSS homopolymer （PNPOSS, pedant architecture）, γ- （2, 3 glycidoxy） propyl diaminoethane POSS polymer （GPDP, catena architecture） and trimethoxysilylcyelopentyl POSS polymer （ TSCP, cage - cage network architecture） were obtained by molecular dynamics simulations based on the Compass force-field. Results indicate that the moleculax architectures of the POSS polymers have great influence on the reinforced effects. The effect of the cage-cage network architecture is best, while that of the catena architecture takes second place and the pedant architecture has the least influence comparatively. The reinforced effects of the POSS monomers were examined. The influences of the temperatures on these effects were analyzed also. It may provide some basis for the reasonable applications of the excellent mechanical properties of the organic-inorganic nano-hybrid materials. It may also provide references for exploitation and design of the POSS materials.

Sunlight responsive photocatalysts:AgBr/ZnO hybridna nomaterial

A novel high-effective sunlight-induced AgBr/ZnO hybrid nanophotocatalyst has been synthesized and it was characterized by different techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and ultraviolet-visible spectrophotometry (UV-vis). The AgBr/ZnO hybrid nanophotocatalyst has excellent photocatalytic activity for photodegradation of methyl orange (MO) under sunlight irradiation. The MO degradation efficiency for AgBr/ZnO is about 98% after 1 hour under sunlight irradiation. These results suggested that AgBr/ZnO is a promising candidate for the development of highly efficient sunlight photocatalysts. In addition, the photocatalytic mechanism of AgBr/ZnO under sunlight irradiation is illustrated and discussed.

An ultrahigh-sensitivity and selective sensing material for ethanol： α-/γ-Fe2O3 mixed-phase mesoporous nanofibers

A process for synthesizing Fe2O3 based on electrospinning and the hard-template method was proposed such that the crystal phase of Fe2O3 could be tailored with precision. Mesoporous γ-Fe2O3, α-/γ-Fe2O3, and α-Fe2O3 nanofibers could be fabricated successfully by changing the synthesis parameters. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction analyses, Raman spectroscopy, and nitrogen adsorption-desorption analyses were used to characterize the structures of the synthesized products. The optimal calcination conditions for preparing α-/γ-FeaO3 nanofibers with the highest ethanol response were determined through ethanol-sensing measurements. The mixed-phase material exhibited a significantly higher sensitivity than the corresponding purephase ones. The superior ethanol-sensing performance of the α-/γ-Fe2O3 nanofibers suggested that they may be suitable for use in alcohol sensing. Hence, a novel strategy for improving the sensing performance of metal oxide semiconductors is to assemble the different crystalline forms of the same metal oxide in one structure. Finally, the mechanism responsible for the sensing performance of α-/γ-Fe2O3 being higher than those of γ-Fe2O3 and α-Fe2O3 was elucidated on the basis of data from X-ray photoelectron spectroscopy and resistance measurements.

Stable ZnO/ionic liquid hybrid materials: novel dual-responsive superhydrophobic layers to light and anions

Novel dual-responsive superhydrophobic hybrid materials, ZnO/SAMs （self-assembled monolayers） of ionic liquids （ILs） with different counter-anions （I^-, BF4^-, PF6^- and Tf2N^-）, were synthesized and characterized. ZnO nanoparticles were first deposited on glass surfaces to produce roughness. Next, SAMs of fluorinated-alkyl-3-（3-triethoxysilylpropyl）-4,5-dihydro-imidazoliumiodide （abb. [C8Ftespim]I） were grafted onto these surfaces via -Si-O- covalent bonds using self-assembly technique. The I- ion could be subsequently exchanged with BF4, PF6-or Tf2N- through a simple aqueous anion-exchange reaction. The ZnO/ILs hybrid layers were characterized by atomic-force microscopy （AFM）, scanning-electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS）. Their wettability was estimated through the measurements of static and dynamic contact angles （CAs）. Compared to corresponding films of ZnO/[CsFtespim]I with CAs 140.7° ±2.0°, films of ZnO/[CsFtespim]PF6 and ZnO/[CsFtespim]Tf2N showed CAs with 154.0° ± 2.0° and 152.0° ± 2.0°, respectively that remained for a long time. This result suggests that anion-exchange can afford superhydrophobic materials. In addition, the wettability of ZnO/[CsFtespim]X hybrid layers can be reversibly switched by altering ultraviolet （UV） irradiation and dark storage, which shows a photo-induced reversible switch of wettability. The synergistic action of ZnO nanoparticles and SAMs of ILs produced light-anion dual-responsive superhydrophobic materials with ideal stability.