Papers by Keyword: Characterization Method

Abstract: With the further deterioration of the oil and gas exploitation environment, the corrosion of tubing becomes an intractable problem. Therefore, choosing suitable anticorrosive coating is of great significance to the safe operation life of tubing and reduce economic cost. Effect addition of appropriate graphene in coatings can significantly improve its corrosion resistance of the coating. However, most of the applied research are focus on marine heavy corrosion condition; the relationship between the corrosion mechanism and performance of graphene coating for tubing is not clear, probably due to difficulty in the characterization of the organizational structure characterization of the graphene modified coating. In the present work, Typical methods of the graphene coating characterization: Scanning Electron Microscope (SEM) with EDS, Transmission Electron Microscope (TEM), Atomic Force Microscope (AFM), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) will be introduced, and the application prospect of the coating will be discussed. It indicated that the single characteristic method cannot analysis the structure and morphology information of graphene anticorrosion coating comprehensively. Flexibly use of a variety of characterization methods to study the anticorrosion mechanism and performance of the graphene modified coating for tubing is a better choice. The graphene modified anticorrosive coating for tubing is with the potential of wide applications.

Abstract: This paper presents a novel and effective characterization method for giant piezoresistive properties of silicon nanowires by using the reference structures. This contrast detection approach investigates the influences of quantum size effect and surface defects effect on piezoresistive coefficients of silicon nanowires by direct comparison of the resistivity change ratio of silicon wires with nanoscale-to-microscale width under the same applied stress conditions. The characterization experiments based on four-point bending tensile test demonstrate that piezoresistive coefficient of small nanowidth silicon nanowire can be significantly increased to about five times higher levels than that of bulk silicon under the same impurity concentration, which indicates that the silicon nanowire can have giant piezoresistive effect. On the other hand, to solve the problem on nanowires pick-up, we proposed a nanowire piezoresistive detection approach, whose validity is confirmed by the dynamic LDV resonance test. Meanwhile, to investigate the influence of undercut arising from the wet chemical release process of the suspended silicon nanowire, a three-dimensional finite element simulation is also carried out for the fundamental resonant frequency using ANSYS software. The numerical and experimental results show that our piezoresistive detection is accurate and effective and the undercut should be carefully considered in the design of the high frequency resonator and mixer. The findings of this paper provide some useful references for the piezoresistive effect measurement and the piezoresistive pick-up in nanoelectromechanical system.

Abstract: Aiming at the radar vertical detection coverage limitation given by manufacturing factories, this paper put forwards a new characterization method of radar’s air surveillance coverage: it is the projection distance of furthest detection point for different RCS targets at different altitudes, which can directly show radar’s quick response to the attack action launched by fighter. Then this paper gives the calculating method of coverage characterization method, and calculates radar detection coverage of typical medium-low altitude search. The result shows that the detection ability to penetration fighter is weak for high altitude and below 300m altitude, especially for the high altitude penetration stealth fighter.

Abstract: Curing rate is one of the most important performance parameters of UV curing system. During the curing process, curing degree is closely related to curing rate. Cross linking and curing degree of the system could be reflected by rheological characteristics. A method based on rheokinetics was used to characterize radical polymerization reaction which initiated by UV light. Changes of G’ (dynamic modulus) in every stage of curing process were real-time monitored by a rheometer equipped with UV curing accessory. The influence of varieties and contents of photo-initiators on curing process of polyester acrylates was studied. Associating conversion rate with dynamic modulus, a nonlinear kinetic equation was set up to describe the cure reaction. The results show that, this paper has put forward a method based on rheokinetics, to study the curing rate of UV curing system, and provided a new approach to study UV cure reaction.

Abstract: The energy characterization method of friction sensitivity about high-burning rate solid propellant, which identified by 50% explosion probability was studied, and it was verified in the practical application. This method solved the problems about the conventional test methods can not be compared with similar formulations friction degree.

Abstract: The hollow-triangle fiber is a novel profiled fiber. Its cross-sectional shape and shape factor index were obtained by a microcomputer image acquisition system, with a polarization capability and image analysis software. The shape factors of the fiber, such as shape factor in radius, shape factor in cross-section, branch factor and volume content were tested. The cross-section shape of cross-hollow fiber was compared with that of the hollow fiber. After that, a novel method about equivalent diameter was proposed to evaluate the characteristic shape coefficient. The method possesses many merits such as rapid, simple, accurate, convenient and thus being of great practical value.

Abstract: Moiré grating is a basic optical component, and can be used in various moiré methods. The conventional grating fabrication technology is based on photolithography and holographic interferometry, however, it requires complex optical components and is very difficult to put into practice. In this study, nanoimprint lithography (NIL), or rather, hot embossing lithography (HEL), is proposed for producing high frequency grating. Compared with silicon mold, holographic moiré grating mold costs less and is not easy to break, thus is chosen to be the mold in HEL. Using this mold and the hot embossing system, the grating structure can be transferred to the polymer after HEL process. Through a number of experiments, the process parameters were optimized and gratings were successfully fabricated. The multi-scale morphology of the fabricated gratings was then characterized by scanning electron microscope (SEM), atomic force microscope (AFM) and moiré interferometry. The microscale images observed by AFM and SEM show the regulate dots with equal spacing and the macroscale moiré patterns illuminate the excellent qualities of fabricated grating in a large area. The successful experimental results demonstrate the feasibility of the grating fabricated by HEL for the moiré measurement.

Abstract: It was recently shown [1] that EMPA-WDS (Electron Probe MicroAnalysis by Wavelength Dispersive X-ray Spectroscopy) can be used to detect and to accurately quantify monolayer surface and grain boundary segregation. This paper presents the last developments of this application. It focuses on the measurement of sulphur grain boundary segregation in nickel on fractured surfaces. A special attention was paid to the quantification of the sulphur coverage, taking into account the non-normal incidence of the electron beam on a fracture surface. Sulphur grain boundary segregation kinetics was measured at 750°C in nickel to document the quantitative possibilities of the technique.