Improving electrochemical activity of PtRu/SnO_2/C catalyst by reduction treatment and alkaline etching

PtRu/SnO/C catalyst was prepared in a polyol process, followed by reduction treatment and alkaline etching. X-ray diffraction, transmission electron microscope with energy dispersive spectrometer and Xray photoelectron spectroscopy were used to characterize the morphology, structure and composition of the catalysts. CO and methanol electro-oxidation activities of the catalysts were evaluated by CO stripping voltammetry, cyclic voltammetry and chronoamperometry measurements. Reduction treatment of the prepared PtRuSnO/C catalyst in a polyol process induced the enrichment of Sn on the surface, inhibiting methanol dissolution and CO adsorption on Pt. Alkaline etching removed Sn or SnOand thus exposed PtRu on the surface, resulting in enhanced activities for CO and methanol electro-oxidation due to the synergy effects of PtRu on the surface and Sn species beneath.

Optical Properties of Hexagonal and Cubic ZnS Nanoribbons： Experiment and Theory

Optical properties of hexagonal and cubic ZnS nanoribbons are studied by using valence electron energy loss spectroscopy （VEELS） and ab initio band structure calculations. The peaks in VEELS are assigned to interband transitions by comparing the interband transition strengths with the calculated densities of states. The optical properties are deduced from the experimental VEELS, and the theoretical calculations give consistent results. This combination of experimental and theoretical approaches provides a comprehensive understanding of the optical properties of polytype ZnS.

First-principles study of magnetism of 3d transition metals and nitrogen co-doped monolayer MoS2

The electronic structures and magnetic properties of diverse transition metal (TM=Fe, Co, and Ni) and nitrogen (N) co-doped monolayer MoS2 are investigated by using density functional theory. The results show that the intrinsic MoS2 does not have magnetism initially, but doped with TM (TM=Fe, Co, and Ni) the MoS2 possesses an obvious magnetism distinctly. The magnetic moment mainly comes from unpaired Mo:4d orbitals and the d orbitals of the dopants, as well as the S:3p states. However, the doping system exhibits certain half-metallic properties, so we select N atoms in the V family as a dopant to adjust its half-metal characteristics. The results show that the (Fe, N) co-doped MoS2 can be a satisfactory material for applications in spintronic devices. On this basis, the most stable geometry of the (2Fe-N) co-doped MoS2 system is determined by considering the different configurations of the positions of the two Fe atoms. It is found that the ferromagnetic mechanism of the (2Fe-N) co-doped MoS2 system is caused by the bond spin polarization mechanism of the Fe-Mo-Fe coupling chain. Our results verify that the (Fe, N) co-doped single-layer MoS2 has the conditions required to become a dilute magnetic semiconductor.

Controlled Synthesis of CuO Nanoparticles by TritonX-100-based Microemulsions

CuO nanoparticles were synthesized by using microreactors made of Triton X-100/n-hextnol/cyclohexane/water W/O microemulsion system. Basic synthesis parameters were determined. The results of thermo gravimetric/differential thermal analysis（TG/DTA） of the precursor products indicated that the proper calcination temperature was about 500 ℃. The nanoparticles were characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM） and UV-visible spectra. It was indicated that the grain size was highly dependent on the ratio of water to surfactant（R）. With the R value increasing, the particles size became larger.

Preparation of Ti–Nb–Ta–Zr alloys for load-bearing biomedical applications

Ti–Nb–Ta–Zr alloys for biomedical applications were successfully fabricated by arc melting(AM) and diffusion bonding.The microstructure, mechanical properties and electrochemistry behavior in a simulated body fluid(SBF) were studied.It shows that melted Ti–Nb–Ta–Zr alloy mainly contains β phase although there are a few Ti-rich phases and micropores, the number of which is lower than that in sintered sample with a few Ti-rich and Ta-rich phases.The melted alloys present higher strength(1224 MPa), Young’s modulus(15.3 GPa) and corrosion potential(-0.34 V) in SBF, while total recovery strain ratio(67.5%) and pseudoelastic strain ratio(8.4%) of sintered Ti–Nb–Ta–Zr alloy keep higher value than 35.7%and 5.0% for melted Ti–Nb–Ta–Zr.The reasons were discussed based on the microstructure of the Ti–Nb–Ta–Zr alloys.

Influence of Ti Powder Characteristics on the Mechanical Properties of Porous Ti Using Space Holder Technique

Porous Ti samples were fabricated by powder metallurgy technique using three kinds of Ti powder and the space holder of polymethyl methacrylate. The final morphological features and mechanical properties were described. Results show that there is only α-Ti phase in porous Ti samples. After sintering, the oxygen content of three porous Ti is increased from the range of 0.34-0.63 wt% to 0.95-1.3 wt%. The porous Ti prepared from the uneven powders with an average particle size of （22.75 ±11.09） μm presents the largest micro-pore size, grain size, and oxygen content, which lead to the lowest strength and Young＇s modulus.

A periodic DFT study on adsorption of small molecules(CH4,CO,H2O,H2S,NH3)on the WO3(001) surface-supported Au

Gas molecules(such as CH4,CO,H2O,H2S,NH_3)adsorption on the pure and Au-doped WO3(001)surface have been studied by Density functional theory calculations with generalized gradient approximation.Based on the the calculation of adsorption energy,we found the most stable adsorption site for gas molecules by comparing the adsorption energies of different gas molecules on the WO3(001)surface.We have also compared the adsorption energy of five different gas molecules on the WO3(001)surface,our calculation results show that when the five kinds of gases are adsorbed on the pure WO3(001)surface,the order of the surface adsorption energy is CO>H2S>CH4>H2O>NH3.And the results show that NH3 is the most easily adsorbed gas among the other four gases adsorbed on the surface of pure WO3(001)surface.We also calculated the five different gases on the Au-doped WO3(001)surface.The order of adsorption energy was found to be different from the previous calculation:CO>CH4>H2S>H2O>NH3.These results provide a new route for the potential applications of Au-doped WO3 in gas molecules adsorption.

Microstructure,mechanical property and corrosion behavior of porous Ti-Ta-Nb-Zr

In this paper,biomedical porous Ti-Nb-Ta-Zr with 40%porosity and 166±21μm macro-pore size was successfully fabricated by space holder method.The microstructure,Vickers hardness,compressive and electrochemistry behavior were studied.It results that a few second phases exist inβmatrix of the porous Ti-Nb-Ta-Zr.Its Young's modulus is 0.8 GPa,close to 0.01-3 GPa for trabecular bone.The total recovery strain ratio and pseudoelastic strain ratio are 8.8%and 2.7%,respectively.It fails mainly by brittle cleavage with the fan-shaped and smooth cleaved facets.Although,local ductile fracture by a few dimples and a small amount of transcrystalline fracture with the cleavage of similarly oriented laths in a colony are observed on the fracture surface.The impedance spectrum of porous Ti-Nb-Ta-Zr has the characteristics of half capacitive arc resistance,showing good corrosion resistance in SBF solution.

Mechanism of ferromagnetism in(Fe,Co)-codoped 4H-SiC from density functional theory

First-principles calculations are performed to investigate the electronic structures and magnetic properties of(Fe,Co)-codoped 4H-SiC using the generalized gradient approximation plus Hubbard U method.We find that 4H-SiC doped with an isolated Fe atom and an isolated Co atom produces a total magnetic moment of 5.98μB and 6.00μB respectively.We estimate TC of about 263.1 K for the(Fe,Co)-codoped 4H-SiC system.We study ferromagnetic and antiferromagnetic coupling in(Fe,Co)-codoped 4H-SiC.Ferromagnetic behavior is observed.The strong ferromagnetic couplings between local magnetic moments can be attributed to p–d hybridization between Fe,Co and neighboring C.However,the(Fe,Co,V(Si))-codoped 4H-SiC system shows antiferromagnetic coupling when an Si vacancy is introduced in the same 4H-SiC supercell.The results may be helpful for further study on transition metal-codoped systems.