A double toroidal analyzer for scanning probe electron energy spectrometer

An ultra-high vacuum （UHV） compatible electron spectrometer employing a double toroidal analyzer has been de- veloped. It is designed to be combined with a custom-made scanning tunneling microscope （STM） to study the spatially localized electron energy spectrum on a surface. A tip-sample system composed of a piezo-driven field-emission tungsten tip and a sample of highly ordered pyrolytic graphite （HOPG） is employed to test the performance of the spectrometer. Two-dimensional images of the energy-resolved and angle-dispersed electrons backscattered from the surface of HOPG are obtained, the performance is optimized and the spectrometer is calibrated. A complete electron energy loss spectrum covering the elastic peak to the secondary electron peaks for the HOPG surface, acquired at a tip voltage of -140 V and a sample current of 0.5 pA, is presented, demonstrating the viability of the spectrometer.

Electron Energy Spectroscopic Mapping of Surface Plasmon by Parallel Scanning Method

In this work,electron energy spectroscopic mapping of surface plasmon of Ag nanostructures on highly oriented pyrolytic graphite is reported.Benefitting from the angular dispersive feature of the present scanning probe electron energy spectrometer,a multi-channel detection mode is developed.By scanning along one direction,the two-dimensional intensity distribution of Ag surface plasmon excitation due to the collision of electron emitted from the tip can be obtained in parallel.The spectroscopic spatial resolution is determined to be around 80 nm.

Influence of PTFE on Electrode Structure for Performance of PEMFC and 10-Cells Stack

Water plays a critical role on the performance, stability and lifetime of proton exchange membrane fuel cells（PEMFCs）. The addition of poly tetrafluoroethylene（PTFE） to the gas diffusion layer, especially, the cathode side, would optimize the transportation of water, electron and gas and thus improve the performance of the fuel cell. But until now, the studies about directly applying the PTFE to the catalyst layer are rarely reported. In this paper, the membrane electrode is fabricated by using directly coating catalyst to the membrane method（CCM） and applying PTFE directly to the cathode electrode catalyst layer. The performance of the single cell is determined by polarization curves and durability tests. Electrochemical impedance spectroscopy（EIS） and scanning electron microscopy（SEM） techniques are used to characterize the electrochemical properties of PEMFC. Also the performance of a 10-cells stack is detected. Combining the performance and the physical-chemistry characterization of PEMFC shows that addition of appropriate content of PTFE to the electrode enhances the performance of the fuel cell, which may be due to the improved water management. Addition of appropriate content of PTFE enhances the interaction between the membrane and the catalyst layer, and bigger pores and highly textured structure form in the MEA, which favors the oxygen mass transfer and protons transfer in the fuel cell. While superfluous addition of PTFE covers the surface of catalysts and hindered the contact of catalyst with Nation, which leads to the reduction of electrochemical active area and the decay of the fuel cell performance. The proposed research would optimize the water management of the fuel cell and thus improve the performance of the fuel cell.

Effects of Different Concentrations and Exposure Time of Sodium Hypochlorite on the Structural,Compositional and Mechanical Properties of Human Dentin

This study evaluated the effects of sodium hypochlorite（NaOCl） with different concentrations and exposure time on the structural, compositional and mechanical properties of human dentin in vitro. Sixty dentin slabs were obtained from freshly extracted premolars, randomly distributed into four groups（n=15）, and treated with 1%, 5%, 10% NaOCl and distilled water（control group）, respectively, for a total of 60 min. Attenuated total reflection infrared（ATR-IR） spectroscopy, Raman spectroscopy and X-ray diffraction（XRD） were carried out before, 10 min and 60 min after the treatment. Scanning electron microscopy（SEM） and flexural strength test were conducted as well. The results showed that dentins experienced morphological alterations in the NaOCl groups, but not in the control group. Two-way repeated-measures analysis of variance revealed that the carbonate：mineral ratio（C：M）, Raman relative intensity（RRI）, a-axis, c-axis length and full width at half maximum（FWHM） with the increase of time and concentration in the NaOCl groups were not significantly different from those in the control group（P〉0.05）. Nevertheless, the mineral：matrix ratio（M：M） increased and the flexural strength declined with the increase of concentration and the extension of time in the NaOCl groups（P〈0.05）. Additionally, it was found that the M：M and the flexural strength remained unchanged after 1% NaOCl treatment（P〉0.05）, and the morphology changes were unnoticeable within 10 min in 1% NaOCl group. These results indicated that NaOCl has no significant effects on the inorganic mineral of human dentin; but it undermines and eliminates the organic content concentration-and time-dependently, which in turn influences the flexural strength and toughness of dentins. In addition, an irrigation of 1% NaOCl within 10 min can minimize the effects of NaOCl on the structural and mechanical properties of dentin during root canal treatment.

Characterization of Compositionally Complex Hydrides in a Metastable Refractory High-Entropy Alloy

Here,we study the hydride formation in a metastable Ti-33Zr-22Hf-11Ta(at.%)refractory high entropy alloy(RHEA).Deviating to non-equiatomic compositions of RHEAs promotes the formation of transformation-induced plasticity where the body-centered cubic phase transforms to hexagonal close-packed(HCP)phase.It is found that the phase transformation capability assists the hydride formation due to the low solubility of hydrogen within the HCP phase.In this study,hydrogen is charged via electrochemical polishing and the corresponding phase transformation is activated in the metastable RHEAs.The newly formed HCP phase interacts with hydrogen to form a face-centered cubic hydride verified by electron energy loss spectroscopy.This work provides a primary exploration of the formation of compositionally complex metal hydrides in the metastable RHEAs,which are potential candidates for future hydrogen storage material design.

Microbiologically Induced Corrosion of X80 Pipeline Steel in a Near-Neutral pH Soil Solution

MIC of X80 pipeline steel in a near-neutral pH soil solution in the presence and absence of sulfate-reducing bacteria（SRB） was monitored by electrochemical techniques and microbiological tests. The results show that soil solution is more close to the complex soil environment around pipeline. The activity of SRB leads to the shift of the phase response to low frequency, the decrease of electrolyte resistance and the alteration of dielectric constant of the film. Both the activity and metabolite of SRB influence the corrosion behavior of the steel. The steel surface undergoes localized attack in the SRB-inoculated soil solution, whereas only slight uniform corrosion occurs in the sterile soil solution.

Effect of aluminum stress on the quality of Enteromorpha prolifera based on SEM-EDX and FT-IR

To clarify the effect of aluminum stress on the quality of Enteromorpha prolifera(E.prolifera)and to explore the mechanism of the combination of aluminum and E.prolifera,we analyzed changes in the nutrients,micromorphology,element distribution,and spectrum of E.prolifera treated with different concentrations of aluminum(0,0.2,2.0,and 20.0μmol· L^(-1))using scanning electron microscopy-energy dispersive spectroscopy(SEM-EDX)and Fourier-transform infrared spectroscopy(FT-IR).The biomass,protein,dietary fiber,and ash contents of E.prolifera initially increased and then subsequently decreased with an increasing concentration of aluminum.Meanwhile,the total amount of amino acids decreased.Scanning the surface of E.prolifera by SEM-EDX revealed that a high concentration of aluminum damaged the cells of E.prolifera.Additionally,the content of aluminum on the surface of E.prolifera cells increased and the absorption of other elements was also affected.The FT-IR analysis showed that aluminum might combine with the functional groups at the 3408 cm^(-)1,2928 cm1,and 1072 cm^(-)1 peaks in E.prolifera and alter the characteristic of the different absorption peaks.

Characterization of Intracellular Gold Nanoparticles Synthesized by Biomass of Aspergillus terreus

Greener synthesis of nanoparticle is a revolutionizing area in research field.Biological method of reduction of metal ions is often preferred because they are clean,safe,biocompatible,and environmentally acceptable than physical,chemical,and mechanical methods.The wet biomass of Aspergillus terreus（A.terreus） was utilized for the intracellular synthesis of gold nanoparticles.Gold nanoparticles were produced when an aqueous solution of chloroauric acid was reduced by A.terreus biomass as the reducing agent.Production of gold nanoparticles was confirmed by the color change of biomass from yellow to pinkish violet.The produced nanoparticles were then characterized by FT-IR,SEM,EDS,and XRD.The SEM images revealed that the nanoparticles were spherical,irregularly shaped with no definite morphology.Average size of the biosynthesized gold nanoparticles was 186 nm.The presence of the gold nanoparticle was confirmed by EDS analysis.Crystalline nature of synthesized gold nanoparticle was confirmed by XRD pattern.

Utilization of nano/micro-size iron recovered from the fine fraction of automobile shredder residue for phenol degradation in water

The study investigates the magnetic separation of Fe from automobile shredder residue （ASR） （ 〈 0.25 mm） and its application for phenol degradation in water. The magnetically separated Fe was subjected to an ultrasonically assisted acid treatment, and the degradation of phenol in an aqueous solution using nano/micro-size Fe （n/m Fe） was investigated in an effort to evaluate the possibility of utilizing n/m Fe to remove phenol from wastewater. The prepared n/m Fe was analyzed by scanning electron microscopy （SEM） and Fourier transform infrared spectroscopy （FTIR）. The eflects of the dosages ot n/mFe, pH, concentration of phenol and amount of H2O2 on phenol removal were evaluated. The results confirm that the phenol degradation rate was improved with an increase in the dosages of n/mFe and H2O2; however, the rate is reduced when the phenol concentration is higher. The degradation of phenol by n/mFe followed the pseudo-first-order kinetics. The value of the reaction rate constant （k）was increased as the amounts of n/m Fe and H2O2 increased. Conversely, the value of k was reduced when the concentration of phenol was increased. The probable mechanism behind the degradation of phenol by n/m Fe is the oxidation of phenol through hydroxyl radicals which are produced during the reaction between H2O2 and n/m Fe.