The electrochemical reduction of oxygen was studied on vertically aligned N-doped carbon nanotube (NCNT) modified glassy carbon (GC) electrodes in 0.5
M H
2SO
4 and in 0.1
M KOH solutions using the ...rotating disk electrode (RDE) method. For comparison purposes, the oxygen reduction behaviour of undoped carbon nanotube material has been also investigated. Both catalysts were prepared by chemical vapour deposition (CVD). Acetonitrile was used as the precursor in the synthesis of the NCNT material. The surface morphology and chemical composition of the NCNT catalysts were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The NCNT/GC electrodes showed a significant enhancement of the kinetics of oxygen reduction in both solutions. In acid media the half-wave potential of O
2 reduction on NCNT-modified electrodes shifted by 250
mV to more positive potentials as compared to that of vertically aligned undoped CNT materials. The factors that determine the high electrocatalytic activity of nitrogen-doped carbon nanotubes towards oxygen reduction are discussed.
Abstract
Time Projection Chambers (TPC)s are excellent tracking detectors for high multiplicity
events and can intrinsically be high-rate, but are limited by the ions created in their avalanche
...stage. GEMs and Micromegas can reduce IBF through their geometry and
E͐
-field ratios, but
these can lead to gain fluctuations and still leave IBF as the dominant source of space charge. An
active BPG can block all IBF ions, but their slow drift speed creates too much dead time. A
passive BPG will overcome this limitation by using an external
B͐
-field to allow the
electrons to pass through while still blocking all ions. Since the grid changes the electron's
trajectory, a loss of resolution will occur. The trajectory is shifted symmetrically along the
wires so the wire alignment with respect to the detection pads is a specific question not studied
before. We present completed IBF analysis from data collected at Weizmann Institute of Science
(WIS), along with an intro to our test on wire resolution.
X-ray transition radiation detectors (TRDs) are used for particle identification in both high energy physics and astroparticle physics. In most of the detectors, emission of the X-ray transition ...radiation (TR) starts at Lorentz factors above γ∼500 and reaches saturation at γ∼2÷3⋅103. However, many experiments require particle identification up to γ∼105, which is very difficult to achieve with conventional detectors. Semiconductor pixel detectors offer a unique opportunity for precise simultaneous measurements of spectral and angular parameters of TR photons. Test beam studies of the energy and the angular distributions of TR photons emitted by electrons and muons of different momenta crossing several types of radiators were performed at the CERN SPS with a 480 μm thick silicon detector bonded to a Timepix3 chip. High resolution images of the energy−angle phase space of the TR produced by different radiators were obtained and compared with MC simulations. The characteristic interference patterns are in agreement with the theoretical models with an unprecedented level of details. The studies presented in this paper also show that simultaneous measurements of both the energy and the emission angles of the TR X-rays could be used to enhance the particle identification performances of TRDs.
Formation of the microstructure and properties of pipe steel grade K60 (X70) are studied using physical modeling of thermomechanical processing in a DUO 300 laboratory mill and industrial experiment. ...Steel microstructure is investigated and temperature ranges for formation of various phases and structural components (ferrite, bainite, martensite, M/A-component) with accelerated cooling are determined. It is found that formation of martensitic regions and M/A-component as secondary structural constituents in a ferrite matrix instead of cementite-containing secondary structures facilitates an increase in steel strength and improvement of the σ
y
/σ
f
ratio without a significant reduction in cold resistance. The chemical composition of steel grade K60 (X70) is developed on the basis of laboratory and industrial experiments, as well as a new industrial process for producing rolled product for pipes for the Sila Sibiri gas pipeline sections crossing active tectonic disturbance zones. Sheet and pipes have a low σ
y
/σ
f
ratio, high values of relative and uniform elongation, impact strength and proportion of ductile component in a fracture after DWTT testing at – 20°C.
The methods of convective heating of thin-walled monolithic structures constructed in winter conditions in tunnel formwork are considered. The classification of convection heating methods, based on ...the principle of heat flow to the heated structure, is made: traditional chamber heating, chamber heating with air ducts, convection heating with pre-form curtains, developed at the Department of Construction and the theory of structures of the South Ural State University. The efficiency of capital investments for the methods under consideration is determined on the basis of the determination of the area under the investment curve. The unit costs in rubles per cubic meter of heated concrete for the considered methods are calculated. The results on capital investments and specific costs for heat treatment of concrete by convective methods are compared. The authors draw the conclusions about the effectiveness of using the method of convection heating with pre-form curtains for heat treatment of monolithic thin-walled structures, constructed in tunnel formwork due to a more efficient use of energy from heat generators, which allows shortening the duration of concrete keeping.
The results of studying the influence of the chemical composition and processing technology on the structural-phase state and fire resistance of experimental samples of construction rolled products ...(construction longs) of low-alloyed low-carbon steels microalloyed with carbonitride-forming elements are presented. The mechanical properties were studied and the fire resistance of experimental specimens subjected to controlled rolling and heat treatment (quenching + tempering) was assessed. The microstructure was studied using optical and electron microscopy methods, and the types of dispersed carbonitride particles were identified. The influence of the structural state of the samples on the characteristics of fire resistance was carried out.
Studying of hadron production in forward direction at the LHC energy has a great interest both for understanding of the fundamental QCD processes and also in applied areas such as the description of ...ultra-high energy cosmic particle interactions. The energies of secondary hadrons in such studies almost reach the maximum energy available at the LHC of ~6 TeV, which corresponds to a Lorentz γ-factor up to 104 and above. The only effective technique able to identify particles in this range is based on the transition radiation detectors (TRD). Prototypes of such kind of detector were built and tested at the CERN SPS accelerator. Some experimental results obtained in these tests are briefly presented here and compared with Monte Carlo (MC) simulations. MC model demonstrates a good agreement with the experiment. On this basis a concept of a full-scale TRD optimized for the hadron identification in the TeV energy region is proposed. Different particle identification techniques were considered and examined. The expected detector performance to reconstruct secondary hadrons produced in forward direction at the LHC is presented.
Many modern and future accelerator and cosmic ray experiments require identification of particles with Lorentz γ-factor up to 104 and above. The only technique which reaches this range of Lorentz ...factors is based on the transition radiation detectors (TRD). This paper describes the development of a TRD based on straw proportional tubes. A prototype of such kind of detector was built and tested at the CERN SPS accelerator. Monte Carlo simulation model of the detector which matches well the experimental data was developed. This program was used for the simulation of a full-scale TRD for hadron identification at TeV energy scale.
The propagation of relativistic electrons and muons within multilayer structures is considered. The Geant4 model of X-ray transition radiation (the yield of photons, their angular and spectral ...distributions, and the spectrum absorbed by a gas detector) is compared to experimental and RADIATOR data. It is demonstrated that the Geant4 spectral and, even more so, angular distributions differ from the experimental ones.
•Coatings prepared by Cu microparticle electrodeposition.•Structural and phase transformation in Cu coatings annealed at 400°C.•Annealing is accompanied by intensive growth of CuO whiskers.•Layered ...oxide phases (Cu2O and CuO) in the coating are characterized.•Formation of volumetric defects in the coating is demonstrated.
We describe structural and phase transformation in copper coatings made of microparticles during heating and annealing in air in the temperature range up to 400°C. Such thermal treatment is accompanied by intensive CuO nanowhisker growth on the coating surface and the formation of the layered oxide phases (Cu2O and CuO) in the coating interior. X-ray diffraction and focused ion beam (FIB) are employed to characterize the multilayer structure of annealed copper coatings. Formation of volumetric defects such as voids and cracks in the coating is demonstrated.
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