Evolution of patinas on copper exposed in a suburban area

Copper plates were exposed under sheltered outdoor conditions for up to one year, starting in September 2001 in Musashino City, Tokyo, a suburban area. Following various periods of exposure, the patinas on the plates were characterized to investigate their evolution by using X-ray fluorescence analysis, X-ray diffraction, field emission scanning electron microscopy, and glow discharge optical emission spectroscopy. The difference in the roles of sulfur and chlorine in the early stages of copper patination were identified by analyzing the depth profiles of these two elements. Sulfur was found on top of the patina as cupric sulfates such as posnjakite (Cu₄SO₄(OH)₆ · H₂O) or brochantite (Cu₄SO₄(OH)₆). Brochantite appeared only after 12 months of exposure. In contrast, chlorine was found on the surface after only one month of exposure. It gradually penetrated the patina as the exposure period lengthened, forming copper chloride complexes. Chloride ions accumulated at the patina/copper interface, forming nantokite (CuCl), which promoted corrosion.     

Improvement in galvannealed coating of IF-HS steel strips by combined GDOES and colour-etching method

Galvannealed coating of high strength interstitial free (IF-HS) steel was characterised by Glow Discharge Optical Emission Spectroscopy (GDOES) and colour-etching techniques. Overalloyed galvannealed coatings with considerably high amount of Γ and Γ1 phases were detected in the first set of experiments. Necessary process modifications in galvannealing furnace were made to maximise the ä phase in the galvannealed coating, which was confirmed through GDOES and colour-etching techniques. As a result, an improvement in galvannealed product quality with a better powdering resistance property during forming has been achieved.     

SiO2 thin film deposition on the inner surface of a poly(tetra-fluoroethylene) narrow tube by atmospheric-pressure glow microplasma

SiO₂ thin films were deposited on the inner surfaces of a commercial poly(tetrafluoroethylene) narrow tube with an inner diameter of 0.5 mm using tetraethoxysilane/O₂ feedstock gases and He carrier gas by atmospheric-pressure microplasma-enhanced chemical vapor deposition. A glow microplasma was generated inside the tube by radio frequency (RF) capacitively coupled discharge. X-ray photoelectron spectroscopy spectra showed that the tube inner surface was covered by a SiO₂ thin film. Transparent SiO₂ thin films were obtained with a deposition rate of 230 nm/min at an RF power of 6 W and substrate temperature of 100 °C. The wettability of the SiO₂-coated tube was about 3 times as large as that of an untreated sample tube.     

Effects of exo-electron emission from MgO thin film on statistical delay of glow discharge of ac-PDP

Relationship between exo-electron emission currents and statistical delay of glow discharges of ac-PDP was investigated by measuring exo-electron currents. The currents were measured as a function of time and doping elements. The measured results indicated that the exo-electron currents decrease exponentially with time, while the statistical delay increases with time. The results demonstrate that the statistical discharge delay is inversely proportional to the currents of exo-electron emission from MgO film in a time interval of 1 to 10 ms.     

RGD3型热释光剂量仪的改进

概述了ＲＧＤ３型热释光剂量仪改进后的主要性能,特点。基本性能实验及其结果分析表明,改进后的ＲＧＤ３型热释光剂量仪,在标准光源稳定性,数据分散性以及发光曲线测读效果等方面都有较明显的改善。在新开发的数据处理软件配合下,该系统的综合性能将会得到更大的提高。     

Study of the effect of process parameters for n-heptylamine plasma polymerization on final layer properties

Plasma polymerization processes are widely used to chemically functionalize surfaces, which properties can be tuned by different operating variables. In this study, thin amine-containing polymer layers were produced on solid substrates in a custom-made cylindrical plasma polymerization reactor by radio frequency glow discharges of n-heptylamine vapours. Carefully planned experiments were conducted to evaluate the importance of four different process parameters on the chemical composition and thickness of the resulting films. The parameters investigated were: 1) deposition time, 2) power of the glow discharge, 3) distance between the electrodes, and 4) monomer pressure. Possible interactions between these variables were investigated through the use of statistical analyses (i.e., factorial design). This study reveals that n-heptylamine plasma polymer (HApp) layer thickness is influenced by the power of the glow discharge and the deposition time, as assessed by surface plasmon resonance and atomic force microscopy step height measurements. Also, the atomic ratio of nitrogen to carbon atoms on the treated surfaces is mainly influenced by the power of the glow discharge, as revealed by X-ray photoelectron spectroscopy. Quartz crystal microbalance analysis also confirmed that HApp layers are stable when immersed in aqueous solution.     

Corrosion and tribological behaviors of chromium oxide coatings prepared by the glow-discharge plasma technique

In order to improve the corrosion and tribological properties of steel, chromium oxide coatings were prepared by a new combined process, namely, chromizing and plasma oxidizing treatments using double glow plasma technology under various oxygen flow rates. The composition and microstructure of the coatings were analyzed respectively by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results indicated that the oxygen flow rates had a great effect on the surface structure of the prepared Cr₂O₃ coatings, and dense and smooth Cr₂O₃ coatings were prepared at the oxygen flow rate of 10 sccm. The Cr₂O₃ coatings exhibited the better corrosion resistance which was in good agreement with the results obtained by the microstructure studied. Further mechanical properties test showed that the Cr₂O₃ coatings with high hardness and elastic modulus adhered well to the steel substrates and displayed excellent wear resistance and low coefficient of friction under dry sliding wear test conditions. The wear mechanism was mostly dominated by the “soft abrasion”.     

Characterisation of corrosion products formed on copper exposed at indoor and outdoor sites with high H2S concentrations

Abstract

Corrosion products formed on copper exposed indoors and outdoors at sites with high hydrogen sulphide (H₂S) concentrations were characterised using several analytical techniques. The crystalline corrosion products that formed on the copper exposed indoors were chalcocite (Cu₂S) and cuprite (Cu₂O), while those that formed on the copper exposed outdoors were chalcocite, cuprite and basic copper sulphates. Surface analysis by X-ray photoelectron spectroscopy revealed differences between the copper exposed indoors and outdoors that are explained by the composition, localisation and oxidation of the corrosion products. The surface morphologies of the corrosion products also differed. Elemental depth profiling by glow discharge optical emission spectroscopy revealed that the corrosion products that formed indoors were mainly chalcocite with cuprite only at and near the surface. In contrast, the corrosion products that formed outdoors were a mixture of chalcocite and cuprite. These differences in corrosion products are attributed to the differences in relative humidity during exposure.     

Study of rotational temperature of oxygen molecules in H and T forms of DC glow discharge sustained in pure oxygen

The active DC glow discharge sustained in pure oxygen has been studied in a Silica discharge tube by means of optical emission spectroscopy and double-probe diagnostics for pressures 600, 750 and 1000 Pa and for discharge currents up to 40 mA. Two different forms of positive column of the discharge (high-gradient H form and low-gradient T form) were observed. Our investigation was focused on the variations of the rotational temperature T_rot determined from emission spectra of molecular oxygen (atmospheric A-band at 760 nm) in the dependence on the discharge current and on the pressure with respect to the existence of the two forms of the discharge. An increase of the rotational temperature with increasing discharge current has been observed. Moreover, higher values of T_rot were found in the H form compared with the T form.     

Degradation of 2,4-dichlorophenol by using glow discharge electrolysis

Degradation of 2,4-dichlorophenol (2,4-DCP) in aqueous by glow discharge electrolysis (GDE) has been investigated. Ultraviolet (UV) absorption spectra, atomic force microscopy (AFM), high performance liquid chromatography (HPLC) and gas chromatogram-mass spectrum (GC/MS) are used to monitor the degradation process and to identify the major oxidation intermediate products. It has been found that 2,4-DCP undergoes a series of intermediate step, which leads to form a number of intermediate products, mainly isomeric chlorophenols and aliphatic acids. These products are further oxidized, eventually, mineralized into CO(2) and Cl(-). A degradation pathway for 2,4-DCP is proposed on the basis of detection of intermediate compounds.