[en] Cu coating is deposited by a micro-plasma spraying system under a low power of 2.8-4.2 kW. The effects of the main processing parameters including plasma arc power, operating gas flow and spray distance on the particle velocity during spraying, and the microstructure and microhardness and the oxygen content in the coating are investigated. The microstructure of the coating are examined using optical and scanning electron microscopy (SEM). The property of the coating is characterized by cross-sectional microhardness. The particle velocity during in-flight is measured using a particle velocity/temperature measurement system based on thermal radiation. The dependency of the microstructure and property of the coating on spray particle conditions is examined through comparing the particle velocity, microstructure, and microhardness of the coating deposited by the micro-plasma spray with that by the conventional plasma spray at a power one order higher. It has been found that a dense copper coating comparable to the conventional plasma-sprayed one can be produced by the micro-plasma spray under a power one order lower. The present results confirm that the coating of comparable microstructure and property can be produced regardless of the plasma power level provided that the comparable particle velocity and molten state are achieved

[en] Titanium dioxide photocatalytic coatings were deposited through high velocity oxy-fuel (HVOF) spraying agglomerate anatase powder. Different spray parameters (e.g. flow of fuel gas) were utilized with the aim to reveal their influence on microstructure and photocatalytic performance of the HVOF titania coatings. The microstructure of the coatings was characterized using X-ray diffraction and scanning electron microscope. The photocatalytic performance of the coatings was evaluated through analyzing photocatalytical degradation of phenol using an ultraviolet spectrometry. Results showed that the phase compositions of the titania coatings were significantly influenced by melting state of the sprayed particles, which was influenced mainly by fuel gas flow. The HVOF TiO₂ coating with up to 70% anatase phase can be obtained through assuring a limited melting state of the titania powder during the coating deposition. A content of 40% of the anatase phase was obtained in the coating deposited from well-melted particles. Furthermore, the present HVOF titania coatings showed promising effect in photocatalytically degrading phenol in the solution. It was found that the complete mineralization of phenol was controlled by the degradation of the intermediates resulting from the decomposition of phenol. It was also noted that the presence of certain rutile phase in the HVOF titania coatings enhanced their photocatalytic performance

[en] Cr₃C₂-25% NiCr coatings were deposited by high velocity oxy-fuel (HVOF) spraying process using two commercial powders. The microstructure of the deposited coating was characterized by scanning electron microscopy. The carbon contents in both the deposited coatings and the collected powders were characterized by chemical analysis to clarify the main mechanism controlling the carbon loss during deposition of Cr₃C₂-NiCr coating by HVOF spraying. The results revealed that the carbon loss in the collected powders was much lower than that in the coatings. A model involved in a solid-liquid two-phase particle deposition behavior and rebound-off of large carbide particles during splatting was proposed to explain the effect of droplet conditions including carbide particle size on the carbon loss during deposition of Cr₃C₂-NiCr. It was suggested that the rebound-off of larger carbide particles when the two-phase droplet impacts on the surface is main mechanism responsible for overall high carbon loss during HVOF spraying of Cr₃C₂-NiCr

[en] The effect of gallium added by blending method on the magnetic properties, thermal stability and microstructure of Nd_16.5Dy_16.0Fe_53.45Co_13.0B_1.05 (wt%) sintered magnets was investigated. The experimental results show that an appropriate Ga addition can markedly increase the coercivity, reduce the irreversible loss and slightly enhance the remanence. For instance, by adding 0.5 wt% Ga, the coercivity is increased from 1232 to 1819 kA/m; the irreversible loss after being exposed at 200 deg. C for 0.5 h is reduced from above 33% to below 5%. Microstructure analyses show that the grain boundaries of the magnets with and without Ga addition are substantially different. The grain boundaries of the Ga-free magnet are meandrous. On the other hand, most of the boundaries of Ga-containing magnets are straight and smooth. These characteristics can be explained by the appearance of new phases during sintering process

[en] We demonstrate an experimental scheme for studying the light shift effect in an optical magnetic double resonance system by using "4He atoms. The dependences of the light shift caused by left- and right-circularly polarized laser light, respectively with laser frequency detuning and laser power are investigated, which show good agreement with theoretical analysis. Based on these, the above parameters are optimized in order to reduce light shift effect for a typical optical magnetic double resonance system. (paper)

[en] Evolution of the surface streamer and the discharge mode transition from the corona discharge to the surface flashover were investigated by pulse sequence resolved electrical and optical measurements under long-term repetitive nanosecond pulses (RNP). The test sample was a cylindrical epoxy resin insulator attached with a needle electrode in 0.1–0.4 MPa nitrogen. Under positive RNP, the inception phase of subsequent streamer discharges decreases with increasing the pulse repetition frequency (PRF), and a periodical streamer stagnation phenomenon appears at high gas pressure. Under negative RNP, the surface streamer does not illustrate symbolic decreasing tendencies in light intensity and corona inception phase in gas gap. The dependence of the evolution of surface streamer velocity on PRF is correlated with the repulsive force from surface charges and the accessibility of seed electrons. Statistical characteristics of back discharges under negative RNP are qualitatively explained by the local electric field around the triple junction. The reversal phenomenon of polarity effect of the allowable repetitive working coefficient is probably resulted from the corona stabilization effect, the surface electron detrapping process, and the assistance of background electric field. Principal results qualitatively support that behaviors of surface streamer and flashover are dominated by the electric field distribution, volume and surface memory effects as well as their interactions and bidirectional transformations, which are different from the monotonically facilitative tendency predicted by the metastable-species-dominated memory effect mechanism. (paper)

[en] Streamer dynamics under repetitive nanosecond pulse (RNP) is of great importance to understand the streamer essence and breakdown phenomenon in non-equilibrium-plasma-based applications. However, the evolution of streamer dynamics, discharge mode transition, and influential mechanisms in high-pressure gas under long-term RNP were not sufficiently clear and required further investigations. We presented the pulse-sequence resolved analysis on streamer dynamics, discharge mode transition, and polarity effect in high-pressure nitrogen under long-term RNP of pulse width from 15 to 800 ns and RNP superimposed by DC sweep voltage. Under positive RNP, the corona discharge probability in a pulse train was affected by the pulse repetition frequency (PRF) and a transformation from the intermittent mode to continuous mode appeared under high PRF. The envelope curve of the number of applied pulses before breakdown followed the shape transformation from capital ‘L’ to ‘U’ with pressure from 0.1 to 0.4 MPa. The streamer channel contraction and the spatial shift of streamer initiation position under high PRF were observed. Under negative RNP, the corona discharge would be in the continuous mode from a low PRF. The average inception voltage and phase of following corona discharges were lower and earlier than those of the first one, respectively. The auxiliary sweep voltage illustrated dramatic and nonlinear effects on discharge characteristics under RNP, which was determined by the sweep voltage amplitude, pulse polarity, and PRF. The inception oscillation stage and steady-state stage were distinct under short-width RNP. An influential mechanism in high-pressure nitrogen was proposed with emphasis on the spatial electric field distortion caused by remaining space charges, which was affected by the pressure-dependent nonlinear diffusion and time-dependent space charge drift under a sweep voltage. The evolution of streamer dynamics and discharge mode transition would help in better understanding of the streamer essence and insulation capability criteria under long-term RNP. (paper)

[en] Material corrosion in lead or Lead-Bismuth Eutectic (LBE) is the important limiting factor to keep integrity of internal components of lead-based reactor. In order to verify engineering feasibility and screen corrosion-resistant material in LBE environment, the compatibility of structural materials with LBE at 500 °C and 550 °C was evaluated. First, T91 and 15-15Ti steels were selected to be tested in stagnant LBE with different oxygen concentrations to investigate the influence of oxygen concentrations on corrosion behaviour of typical martensitic and austenitic steels. For the two types of steels, the formation of protective oxide layer is sensitive to the oxygen concentration. Second, long-term corrosion tests were carried out in large-scaled KYLIN-II material corrosion loop to evaluate the corrosion performance of the candidate structure materials under service condition of CLEAR-I. It is found that the growth kinetics curves of oxide layers for T91, 15-15Ti, CLAM and 316L steels follow a parabolic rule (Δx²=K_pt), and the rate constant for 15-15Ti steel is lowest. Thirdly, new Si-contained stainless steel and ODS-9Cr steel have been developed in INEST and compatibility evaluation revealed that the corrosion resistances of the above steels have attained considerable improvement. (author)

[en] The influence of transverse magnetic field on the liquid-solid interface stability and morphology has been investigated in directionally solidified Al-0.85wt%Cu alloy. Experimental results show that the transverse magnetic field causes the interface to be instable and the interface shape to be depressed on one side along the radius. The interface instability increases with increasing magnetic field. Increasing the solidification velocity reduced extent of interface destabilization by the magnetic field. The depression of the interface with the magnetic field is more dramatic at low solidification velocities. These phenomena are attributed to the thermoelectromagnetic convection (TEMC) on the interface and cellular scale.

[en] Traditional airplane magnetic field models simplify geomagnetic field values as constants, overlooking changes to the model coefficient brought by gradually variational magnetic field which reduces the model accuracy. This paper puts forward an aircraft magnetic field model under geomagnetic gradient change. The geomagnetic gradient change is adopted the truncated singular value decomposition (TSVD) to solve multicollinearity in the model solving. It is proposed to use the coefficient obtained from the truncated singular value as initial conditions and utilize recursive damped least square (RDLS) to conduct adaptive adjustment to model coefficients aiming at the coefficient variation of induction field and Eddy Current Field caused by the geomagnetic field. The simulation outcome indicates that the method boasts a high magnetic compensation effect. (paper)