基于色差分析的中国淡彩绘画保护性照明光源

为得到博物馆照明光源对中国传统淡彩绘画的色彩影响规律,并确定不同类型中国传统淡彩绘画的最低损害光源,以3种博物馆典型照明光源作为实验光源,分组照射中国传统淡彩绘画模型试件,对模型试件的CIE LAB色度数据进行周期性测量。基于实验数据计算不同周期色差变化值,并绘制色差随曝光量的周期性衰变曲线。进而对色差值变化数据进行回归分析,拟合得到不同光源对4种淡彩绘画颜料的相对影响函数公式,提出不同光源对各类型淡彩绘画的相对影响系数。结果表明：3种照明光源对工笔淡彩绘画的影响系数为K_金卤灯：K_卤钨灯：K_WLED=1.00：0.92：0.84;对小青绿淡彩绘画的影响系数为K_金卤灯：K_卤钨灯：K_WLED=2.05：1.71：1.65;对水墨淡彩绘画的影响系数为K_金卤灯：K_卤钨灯：K_WLED=1.17：0.94：0.91。在淡彩绘画照明保护性照明光源选择时,应选择RYGB型WLED光源。     

Laser welding of aluminium alloys 5083 and 6082 under conduction regime

In this work, samples of aluminium alloys 5083-T0 and 6082-T6 have been welded under conduction regime, using a high power diode laser. The influence of experimental variables, as the laser power and the linear welding rate, on the sizes and properties of the butt weld beads has been studied. In addition to measure the depths and widths of the weld beads, their microstructure, microhardness profile and corrosion resistance have been analysed. The results obtained allow one to define the experimental conditions leading to good quality butt welds with higher penetration than those published in the recent literature under conduction regime. Maximum penetration values of 3 and 2.3 mm were obtained for 5083 and 6082, respectively. Additionally, a simple mathematical expression relating the weld depth (d) with the laser power (P) and the processing rate (v) has been proposed: d=(P−bb^′)/(av)−(ba^′)/a, being a, a′, b and b′ constant values for each alloy and under the employed experimental conditions. The values of these coefficients have been estimated from the fitting to the experimental depth values of 5083 and 6082 butt welds generated under conduction regime.     

Electrodeposition of Al-Mn alloy on AZ31B magnesium alloy in molten salts

The Al-Mn alloy coatings were electrodeposited on AZ31B Mg alloy in AlCl₃-NaCl-KCl-MnCl₂ molten salts at 170 °C aiming to improve the corrosion resistance. However, in order to prevent AZ31B Mg alloy from corrosion during electrodeposition in molten salts and to ensure excellent adhesion of coatings to the substrate, AZ31B Mg alloy should be pre-plated with a thin zinc layer as intermediate layer. Then the microstructure, composition and phase constituents of the coatings were investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDX), and X-ray diffraction (XRD). It was indicated that, by adjusting the MnCl₂ content in the molten salts from 0.5 wt% to 2 wt%, the Mn content in the alloy coating was increased and the phase constituents were changed from f.c.c Al-Mn solid solution to amorphous phase. The corrosion resistance of the coatings was evaluated by potentiodynamic polarization measurements in 3.5% NaCl solution. It was confirmed that the Al-Mn alloy coatings exhibited good corrosion resistance with a chear passive region and significantly reduced corrosion current density at anodic potentiodynamic polarization. The corrosion resistance of the alloy coatings was also related with the microstructure and Mn content of the coatings.     

Influence of treating frequency on microstructure and properties of Al2O3 coating on 304 stainless steel by cathodic plasma electrolytic deposition

Alumina ceramic coatings were fabricated on 304 stainless steel by cathodic plasma electrolytic deposition (CPED). Influence of treating frequency of the power supply on the microstructure and properties of the coatings were studied. The results indicated that coatings obtained at various frequencies on 304 stainless steels were all composed of α-Al₂O₃ and γ-Al₂O₃, and α-Al₂O₃ was the dominant phase. The contents of α-Al₂O₃ decreased gradually in a very small rate with increasing the frequency and γ-Al₂O₃ gradually increased. The surface of alumina ceramic coating was porous. With increasing the frequency, the coating surface gradually became less rough and more compact, resulting in low surface roughness. The bonding strength of Al₂O₃ coating was higher than 22 MPa and was not strongly affected by treating frequency. With increasing the frequency, the alumina coated steels showed better and gradually increasing corrosion resistance than the uncoated one in 3.5% NaCl solution. The coating steel with desirable corrosion resistance was obtained at 800 Hz whose corrosion current potential and corrosion density were −0.237 V and 7.367 × 10⁻⁸ A/cm², respectively.     

2 MJ超导储能磁体失超保护的研究

本文介绍了一种用于2 MJ超导储能磁体的失超保护系统.该失超保护系统采用数字失超检测方法,依托高性能的数字采集卡NI-6224,能快速可靠地检测到磁体失超;采用卸能电阻可变的失超卸能同路极大地提高了移能效率,减少了冷却介质的挥发.     

A novel process for electroless nickel plating on anodized magnesium alloy

In this paper, a novel palladium-free activation electroless nickel (EN) plating process, by which a TiB₂ powders contained intermediate film was used as catalyst, was introduced for anodized magnesium alloy AZ91D. The corrosion behavior of AZ91D without and with coating was compared and the bonding strength of the EN plating to the substrate was also measured. The results showed that the EN plating could easily take place on the intermediate catalytic layer, directly on which a smooth and compact Ni–P alloy layer without obvious flaws, about 20 μm thickness, was successfully deposited. The catalytic function was principally from TiB₂ powder. The adhesive tensile test indicated a good bonding strength of about 11 MPa between the substrate and the catalytic layer. An obvious passivation range and higher E_corr (−0.323 V) for the EN plating during anodic polarization in 3.5 wt.% NaCl solution, implied a typical character of a compact Ni–P alloy layer, with an effective protection for the substrate.     

Influence of embedded particles on microstructure, corrosion resistance and thermal conductivity of CuO/SiO2 and NiO/SiO2 nanocomposite coatings

Homogeneous CuO/SiO₂ and NiO/SiO₂ nanocomposite coatings containing CuO and NiO nanoparticles in silica matrix were successfully synthesized by sol–gel process on an aluminum alloy substrate, respectively. The evolution of phase and morphology of both nanocomposites was characterized by XRD, SEM, TEM and FTIR. The effect of incorporating various nanoparticles on the corrosion behavior and the thermal conductivity of nanocomposite coatings was investigated by potentiodynamic polarization curve and comparative exponential method. The thermal conductivity as well as the corrosion resistance of nanocomposite coatings was significantly improved by the introduction of metal oxide particles. In comparison with NiO/SiO₂ nanocomposite coatings, CuO/SiO₂ composite coatings displayed lower protective behavior as well as higher thermal conductivity. Experimental results revealed that those improvements can directly be related to the nanocomposite effect and the nature of added nanoparticles.     

Composition and corrosion resistance of cerium conversion films on the AZ31 magnesium alloy and its relation to the salt anion

Pre-treatments based on different cerium salts were applied to the AZ31 Mg alloy. The pre-treatments were performed by immersion in solutions of various Ce(III) salts: cerium chloride, cerium nitrate, cerium sulphate and cerium phosphate. The chemical composition of the treated surfaces was investigated by X-ray photoelectron spectroscopy and Auger electron spectroscopy, whereas the corrosion behaviour of the pre-treated AZ31 substrates was investigated in 0.005 M NaCl solutions using potentiodynamic polarisation and open circuit potential monitoring. The surface film contained a mixture of Ce(IV) and Ce(III) salts. The film thickness depends upon the cerium salt used. The electrochemical results show that all the conversion pre-treatments reduced the corrosion activity of the AZ31 Mg alloy substrates in the presence of chloride ions. The corrosion protection efficiency is related with the anion present in the cerium salt.     

Microstructural modification by laser surface remelting and its effect on the corrosion resistance of an Al-9 wt%Si casting alloy

Aluminum alloys with silicon as a major alloying element constitute a class of materials, which provides the most significant part of all shaped castings manufactured. Such alloys have a wide range of applications in the automotive and aerospace industries. The literature presents contradictory results and no satisfactory explanations concerning to resulting microstructures provided by laser surface remelting (LSR) and its effect on the electrochemical behavior of Al-Si alloys. The aim of this study was to investigate the effect of microstructural refinement by LSR on corrosion resistance of an Al-9 wt%Si casting alloy. As-cast samples were subjected to a continuous 1 kW CO₂ laser. Corrosion resistance has been analyzed by an electrochemical impedance spectroscopy (EIS) technique and polarization curves carried out in both 0.5 M NaCl and 0.5 M H₂SO₄ solutions at 25 °C. An equivalent circuit has also been proposed and impedance parameters were simulated by the ZView^® software. It was found that the structural modification provided by the LSR process induces a decreasing effect on the corrosion resistance when compared to that of the untreated sample.