Structure and tribological properties of Si/a-C:H(Ag)multilayer film in stimulated body fluid

Si/a-C:H(Ag)multilayer films with different modulation periods are prepared to test their potential applications in human body.The composition,microstructure,mechanical and tribological properties in the simulated body fluid are investigated.The results show the concentration of Ag first decreases and then increases with the modulation period decreasing from 984 nm to 250 nm.Whereas the C content has an opposite variation trend.Notably,the concentration of Ag plays a more important role than the modulation period in the properties of the multilayer film.The a-C:H sublayer of the film with an appropriate Ag concentration(8.97 at.%)(modulation period of 512 nm)maintains the highest sp3/sp2 ratio,surface roughness and hardness,and excellent tribological property in the stimulated body fluid.An appropriate number of Ag atoms and size of Ag atom allow the Ag atoms to easily enter into the contact interface for load bearing and lubricating.This work proves that the Ag nanoparticles in the a-C:H sublayer plays a more important role in the tribological properties of the composite-multilayer film in stimulated body fluid condition.

Tensile properties of phase interfaces in Mg Li alloy: A first principles study

Employing density functional theory, we study the tensile and fracture processes of the phase interfaces in Mg–Li binary alloy. The simulation presents the strain–stress relationships, the ideal tensile strengths, and the fracture processes of three phase interfaces. The results show that the α/α and α/β interfaces have larger tensile strength than that of β/β interface. The fractures of both α/α and β/β interfaces are ductile fractures, while the α/β fractures abruptly._Further analyses show that the fracture of the α/β occurs at the interface.

A novel high-efficient P/N/Si-containing APP-based flame retardant with a silane coupling agent in its molecular structure for epoxy resin

A flame retardant containing multiple antiflaming elements usually exhibits high-efficient flame retardancy. Here, a novel P/N/Si-containing ammonium polyphosphate derivative(APTES-APP) is synthesized from ammonium polyphosphate(APP) and silane coupling agent(3-aminopropyl)triethoxysilane(APTES)via cation exchange, which is quite different in the chemical structure from APTES-modified APP for retaining silicon hydroxyls. APTES-APP is highly efficient for the epoxy resin. 8%(mass) APTES-APP imparts excellent flame retardancy to the epoxy resin, with a V-0 rating at the UL-94 test(1.6 mm)and an LOI value of 26%(vol). The peak heat release rate and total smoke production of the flameretardant epoxy resin are decreased by 68.1% and 31.3%, respectively. The synergy of P/N/Si contributes to the well-expanded char residue with a strong and dense surface layer, which is a very good barrier against heat and mass transfer. Besides, there is no significant deterioration in the mechanical properties of flame-retardant epoxy resin thanks to silicon hydroxyls forming hydrogen bonds with epoxy molecules. Meanwhile, other molecules can be grafted onto APTES-APP via these silicon hydroxyls, if needed.Briefly, this work has developed a new strategy for amino silane as flame retardants. In conjunction with a low-cost and simple preparation method, APTES-APP has a promising prospect in the high-performance flame-retardant epoxy.

Construction of multi-homojunction TiO_(2)nanotubes for boosting photocatalytic hydrogen evolution by steering photogenerated charge transfer

As an effective means to improve charge carrier separation efficiency and directional transport,the gradient doping of foreign elements to build multi-homojunction structures inside catalysts has received wide attentions.Herein,we reported a simple and robust method to construct multi-homojunctions in black TiO_(2) nanotubes by the gradient doping of Ni species through the diffusion of deposited Ni element on the top of black TiO2 nanotubes driven by a high temperature annealing process.The gradient Ni distribution created parts of different Fermi energy levels and energy band structures within the same black TiO_(2) nanotube,which subsequently formed two series of multi-homojunctions within it.This special multi-homojunction structure largely enhanced the charge carrier separation and transportation,while the low concentration of defect states near the surface layer further inhibited carrier recombination and facilitated the surface reaction.Thus,the B-TNT-2Ni sample with the optimized Ni doping concentration exhibited an enhanced hydrogen evolution rate of~1.84 mmol·g^(−1)·h^(−1)under visible light irradiation without the assistance of noble-metal cocatalysts,~four times higher than that of the pristine black TiO_(2)nanotube array.With the capability to create multi-homojunction structures,this approach could be readily applied to various dopant systems and catalyst materials for a broad range of technical applications.

Assisting Bi_(2)MoO_(6) microspheres with phenolic resin-based ACSs as attractive tailor-made supporter for highly-efficient photocatalytic CO_(2) reduction

It is rather essential to design glorious system with high CO_(2) adsorption capacity and electron migration efficiency for improving selective and effective CO_(2) reduction into solar fuels.Here,as-synthesized phenolic resin spheres via suspension polymerization were carbonized and activated by water vapor to obtain activated carbon spheres(ACSs).Subsequently,Bi_(2)MoO_(6)/ACSs were prepared via hydrothermal-impregnated method.The systematical characterizations of samples,including XRD,XPS,SEM,EDX,DRS,BET,PL,CO_(2) adsorption isotherm,EIS and transient photocurrent,were analyzed.The results clearly demonstrated that Bi_(2)MoO_(6) with suitable oxidation reduction potentials and bandgap and ACSs with admirable CO_(2) adsorption and electrical conductivity not only enhanced separation efficiency of photoindued electron-hole pair,but also displayed as 1.8 times CO_(2) reduction activity to CO as single Bi_(2)MoO_(6) sample under Xe-lamp irradiation.Finally,a concerned photocatalytic CO_(2) reduction mechanism was proposed and investigated.Our findings should provide innovative guidance for designing a series of photocatalytic CO_(2) reduction materials with highly efficient and selective ability.

Laser Cladding Al-Si/Al_2O_3-TiO_2 Composite Coatings on AZ31B Magnesium Alloy

To improve the wear resistance and corrosion resistance of magnesium alloys, a 5 kW continuous wave CO2 laser was used to investigate the laser surface cladding on AZ31 B magnesium alloys with Al-Si/Al2O3-TiO2 composite powders. A detailed microstructure, chemical composition, and phase analysis of the composite coatings were studied by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and X-ray diffraction （XRD）. The laser cladding shows good metallurgical bonding with the substrate. The composite coatings are composed of Mgl7Al12, Al3Mg2, Mg2Si, Al2O3, and TiO2 phases. Compared to the average microhardness （50HV0.05） of the AZ3 1 B substrate, that of the composite coatings （230HV0.05） is improved significantly. The wear resistances of the surface layers were evaluated in detail. The results demonstrate that the wear resistances of the laser surface-modified samples are considerably improved compared to the substrate. It also show that the composite coatings exhibit better corrosion resistance than that of the substrate in 3.5wt% NaCI solution.

Surface adsorption and diffusion of N on γ-Fe-Al (111) using first principles calculations

The adsorption and diffusion of N on γ-Fe-Al (111) surface have been investigated using the first principle calculations combined with density functional theory to explore the formation mechanism of AlN in the oxidation process of austenitic stainless steel. The results indicate that the most preferential adsorption site of N on the surface of γ-Fe (111) is fcc-hollow site. In addition, the stable positions are located at fcc adsorption site on clean and Al-doped γ-Fe (111) surface adsorbed 4.76 at.% N. Compared with the pure Fe system,γ-Fe-Al (111) system reduces the energy difference of N from the surface to the bulk. The system is most stable for 9.09 at.% N adsorbed on the octahedral interstice of the 2nd and 3rd atom interlamination of γ-Fe-Al (111) surface. Thus, the doping of Al makes it easier to spread N on the surface of γ-Fe (111). The increase in N in the atmosphere also accelerates the diffusion. Moreover, according to the density of states analysis, the interaction between Al and N was enhanced when 9.09 at.% N was adsorbed on the surface of γ-Fe-Al (111).