New results on Xi'an-AMS and sample preparation systems at Xi'an-AMS center

IEECAS SKLLQG

ENVIRONMENTAL EVOLUTION OF ORDOS DESERT IN CHINA SINCE 1.1MA B. P. AS INDICATED BY YULIN STRATIGRAPHICAL SECTION AND ITS GRAIN-SIZE ANALYSIS RESULTS

IEECAS SKLLQG

Blue-violet luminescence double peak of In-doped films prepared by radio frequency sputtering

ZnO films doped with different contents of indium were prepared by radio frequency sputtering technique. The structural, optical and emission properties of the films were characterized at room temperature using XRD, XPS, UV-vis-NIR and PL techniques. Results showed that the indium was successfully incorporated into the c-axis preferred orientated ZnO films, and the In-doped ZnO films are of over 80% optical transparency in the visible range. Furthermore, a double peak of blue-violet emission with a constant energy interval (similar to 0.17 eV) was observed in the PL spectra of the samples with area ratio of indium chips to the Zn target larger than 2.0%. The blue peak comes from the electron transition from the Zn-i level to the top of the valence band and the violet peak from the In-Zn donor level to the V-Zn level, respectively.

First results of SECRAL at 18GHz for intense beam production of highly charged ions

A Superconducting ECR ion source with Advanced design in Lanzhou (SECRAL) was successfully built to produce intense beams of highly charged ions for Heavy Ion Research Facility in Lanzhou (HIRFL). The ion source has been optimized to be operated at 28GHz for its maximum performance. The superconducting magnet confinement configuration of the ion source consists of three axial solenoid coils and six sextupole coils with a cold iron structure as field booster and clamping. For 28GHz operation, the magnet assembly can produce peak mirror fields on axis 3.6T at injection, 2.2T at extraction and a radial sextupole field of 2.0T at plasma chamber wall. A unique feature of SECRAL is that the three axial solenoid coils are located inside of the sextupole bore in order to reduce the interaction forces between the sextupole coils and the solenoid coils. During the ongoing commissioning phase at 18GHz with a stainless steel chamber, tests with various gases and some metals have been conducted with microwave power less than 3.2kW and it turned out the performance is very promising. Some record ion beam intensities have been produced, for instance, 810e mu A of O7+, 505e mu A of Xe20+, 306e mu A of Xe27+, 21e mu A of Xe34+, 2.4e mu A of Xe38+ and so on. To reach better results for highly charged ion beams, further modifications such as an aluminium chamber with better cooling, higher microwave power and a movable extraction system will be done, and also emittance measurements are being prepared.

Preliminary results of the updated LECR2 source-LECR2M

The Latest developed LECR2M (Lanzhou ECR No. 2 Modified) source is the updated one of LECR2 (Lanzhou ECR No. 2) source at IMP. It has been assembled on the low energy ion beam experimental platform to produce MCI beams for atomic physics and material physics experimental research. In our updating program, the structure of injection and extraction components has been modified to make the source structure more simple and effective. The hexapole magnet has also been replaced by a new hexapole magnet with higher radial field and larger inner diameter. With this updating, stronger magnetic field confinement of the ECR plasma is possible and better base vacuum condition is also achieved. LECR2M was designed to be operated at 14.5GHz. During the preliminary test, 1.3emA O6+ beam was extracted with the injected rf power of 1.1kW. The source has been used to deliver intense MCI beams for different experiments. After some discussion of the main features of this newly updated source, some of the typical commissioning test results of LECR2M will be presented.

Photon production in a chemically equilibrating quark-gluon plasma at finite Baryon density: Complete leading order results

We investigate hard photon production of the near-collinear bremsstrahlung and a new process called the inelastic pair annihilation, fully including the LPM effect, in a chemically equilibrating quark-gluon plasma at finite baryon density, and find that the effect of the system evolution on the photon production and large contribution of the bremsstrahlung make the total photon yield of the two processes as a strongly increasing function of the initial quark chemical potential.

Field emission from TiO2/Ti nanotube arrays with different morphologies

Well-aligned TiO2/Ti nanotube arrays were electrochemically formed in a HF solution for different anodization times. Field emission scanning electron microscopy (FE-SEM) images reveal that anodization time had a great influence on the morphology of TiO2/Ti nanotube arrays. The composition of resulting nanotubes was analyzed by X-ray photoelectron spectroscopy (XPS). Field emission properties of the prepared samples with different morphologies were investigated by the Fowler-Nordheim (F-N) theory. The results indicate that the morphology can affect field emission behaviors. TiO2/Ti nanotube arrays with clear, uniform, and short nanotubes display moderate field emission properties, and have the better turn-on field of 4.6 V/mu m and good field emission stability. (C) 2010 Elsevier B.V. All rights reserved.

Probing into the catalytic nature of Co/sulfated zirconia for selective reduction of NO with methane

In this work, the structural and surface properties of Co-loaded sulfated zirconia (SZ) catalysts were studied by X-ray diffraction (XRD), N-2 adsorption, NH3-TPD, FT-IR spectroscopy, H-2-TPR, UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and NO-TPD. NH3-TPD and FT-IR spectra results of the catalysts showed that the sulfation process of the support resulted in the generation of strong Bronsted and Lewis acid sites, which is essential for the SCR of NO with methane. On the other hand, the N-2 adsorption, H-2-TPR, UV/vis DRS, and XPS of the catalysts demonstrated that the presence of the SO42- species promoted the dispersion of the Co species and prevented the formation Of Co3O4. Such an increased dispersion of Co species suppressed the combustion reaction of CH4 by O-2 and increased the selectivity toward NO reduction. The NO-TPD proved that the loading of Co increased the adsorption of NO over SZ catalysts, which is another reason for the promoting effect of Co. (C) 2004 Elsevier Inc. All rights reserved.

Studies on state and structure of noble metals in electrocatalyst made by coprecipitation method

The electrocatalysts of Pt/C, PtRu/C and Ru/C were prepared by the impregnation method. The facet characterization, the dispersion and the particle size for the catalysts were determined by means of X-ray diffraction and transmission electron microscopy. X-ray photoelectron spectroscopy was also used to analyze the state and the valency of the noble metals. The results show that the particle size was in nanometer range and the binary metals have come into being an alloy. The platinum in the catalysts existed in zero valency. The valency of the ruthenium on the surface is different from that in the body, while the ruthenium on the surface existed in oxide-form. PtRu/C and Pt/C are of good activity to the electrooxidation of hydrogen except Ru/C. PtRu/C is more tolerant of CO than Pt/C, and CO is only adsorbed on Pt.

A facile and effective method for the distribution of Mo/HZSM-5 catalyst active centers

Post-steaming treatment of Mo/HZSM-5 catalysts results in more molybdenum species migrating into and residing in the HZSM-5 zeolite channels. This is confirmed by XRF and XPS measurements. H-1 MAS NMR and Si-29 MAS NMR also demonstrate that the number of free Bronsted acid sites decreases in the Mo/HZSM-5 catalysts that underwent post-steaming treatment, compared to untreated Mo/HZSM-5 catalysts. As a result, the deactivation rate constant (kd) on the Mo/HZSM-5 catalyst after post-steaming treatment for 0.5 h is much smaller, and the catalyst therefore shows remarkable stability in the probe reaction of methane dehydro-aromatization. The results suggest that a more beneficial bi-functional balance between active Mo species for methane activation and acid sites for the following aromatization is developed over those Mo/HZSM-5 catalysts that have experienced post-steaming treatment for 0.5 h, in comparison with the untreated Mo/HZSM-5 catalysts.

Analytical intercomparison results from the 1990 Intergovernmental Oceanographic Commission open-ocean baseline survey for trace metals: Atlantic Ocean

“Dissolved” (< 0.4 μm filtered) and “total dissolvable” (unfiltered) trace element samples were collected using “clean” sampling techniques from four vertical profiles in the eastern Atlantic Ocean on the first IOC Trace Metals Baseline expedition. The analytical results obtained by 9 participating laboratories for Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, and Se on samples from station 4 in the northeast Atlantic have been evaluated with respect to accuracy and precision (intercomparability). The data variability among the reporting laboratories was expressed as 2 × SD for a given element and depth, and was comparable to the 95% confidence interval reported for the NASS seawater reference standards (representing analytical variability only). The discrepancies between reporting laboratories appear to be due to inaccuracies in standardization (analytical calibration), blank correction, and/or extraction efficiency corrections.Several of the sampling bottles used at this station were not adequately pre-cleaned (anomalous Pb results). The sample filtration process did not appear to have been a source of contamination for either dissolved or particulate trace elements. The trace metal profiles agree in general with previously reported profiles from the Atlantic Ocean. We conclude that the sampling and analytical methods we have employed for this effort, while still in need of improvement, are sufficient for obtaining accurate concentration data on most trace metals in the major water masses of the oceans, and to enable some evaluation of the biogeochemical cycling of the metals.

Investigation of Degradation Behavior of Polymer on Surface of Film Due to the Existence of Monochromatic X-ray

Degradation and its temperature dependence of poly(methyl methacrylate) (PMMA) in the blend film of PMMA/SAN were investigated via ire-situ X-ray photoelectron spectroscopy(XPS). The results show that thermal degradation of PMMA takes place at 185, 130, 80 degrees C and even room temperature due to the existence of monochromatic X-ray. Furthermore, the degradation rate depends crucially on the experiment temperature.

Carbon-supported Pd nanocatalyst modified by non-metal phosphorus for the oxygen reduction reaction

A carbon-supported palladium catalyst modified by non-metal phosphorus(PdP/C) has been developed as an oxygen reduction catalyst for direct methanol fuel cells.The PdP/C catalyst was prepared by the sodium hypophosphite reduction method. The as-prepared Pd nanoparticles have a narrow size distribution with an average diameter of 2 nm. Energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) results indicate that P enters into the crystal lattice of Pd and forms an alloy.

Novel Hybrid Electrocatalyst with Enhanced Performance in Alkaline Media: Hollow Au/Pd Core/Shell Nanostructures with a Raspberry Surface

In this paper, a hollow Au/Pd core/shell nanostructure with a raspberry surface was developed for methanol, ethanol, and formic acid oxidation in alkaline media. The results showed that it possessed better electrocatalyst performance than hollow Au nanospheres or Pd nanoparticles. The nanostructure was fabricated via a two-step method. Hollow Au nanospheres were first synthesized by a galvanic replacement reaction, and then they were coated with a layer of Pd grains. Several characterizations such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were used to investigate the prepared nanostructures.