Studies of corrosion in power plant boiler tubes by measurement of oxygen isotopes and trace elements using secondary-ion mass spectrometry

Recent advances in secondary ionization mass spectrometry (SIMS) techniques allow the resolution of differences in the natural abundances of the isotopes of ¹⁸O and ¹⁶O, and their ratio in both conducting and insulating materials. These techniques have been used in this study to measure the oxygen isotope signatures and their spatial distribution in corrosion products formed during high-temperature oxidation of steel boiler tubes from fossil-fuel power plants. The data obtained in this study are interpreted in terms of oxygen isotope fractionation between the available oxygen reservoirs and oxides formed on or within the metal. Results are presented for three different corrosion scenarios: steamside/fireside corrosion, aqueous phosphate corrosion and corrosion due to H₂ damage. Constant, but isotopically depleted values observed in magnetites formed during steamside corrosion and H₂ damage are indicative of interaction with locally derived meteoric water (which constitutes the boiler feed water). In contrast, isotope distributions in maricite (NaFePO₄) suggest equilibrium fractionation between this phase and precursor magnetite. Oxygen isotope patterns in fireside magnetites exhibit a complex zoning that requires at least two isotopically distinct species with significantly different transport rates.     

A study of the interaction of oxide-coated aluminium with chloride solution using secondary ion mass spectrometry

A Cameca Ion Analyser has been used to examine aluminium surfaces, covered by barrier-type anodic films up to 720 Å thick, after natural immersion for 480–1500 min or a brief period of anodic polarization in near-neutral I M potassium chloride solutions at 20°C. After natural immersion, there has apparently been slight film thinning and chloride is abundantly present on the film surface but there is no chloride measurable within the film material, nor is any residual chloride concentration in the tiny incipient pits, likely to be present at this stage, detectable. After anodic polarization, there is again evidence of a chloride peak on the film surface but no chloride within the film material itself. At the clearly detectable major pits, after passing through a surface chloride maximum, the chloride level is reduced until the inner oxide surface is reached, where a further chloride peak provides evidence for the pit undermining the anodic film. The results tend to support the pit initiation theory based on local attack at flaws in the preformed oxide film and provide no evidence for theories involving chloride ion entry into the film material per se.     

A study of the effects of inhibitive and aggressive ions on oxide-coated aluminium using secondary ion mass spectrometry

A Cameca Ion Analyser has been used to examine aluminium surfaces, supporting barrier-type anodic films ca. 720Å thick, after natural immersion for 1–25 h in 1M chloride and chromate/dichromate solutions of varying pH, and neutral 1M phosphate solution. In chloride solutions, chloride is present on the film surface, but not within the film material per se, within the limits of measurement. The degree of film thinning is governed by pH, being more pronounced in alkaline than acid solutions. In chromate/dichromate solutions, chromium uptake occurs by two distinct mechanisms. The first is associated with relatively rapid chromate/dichromate reduction to Cr₂O₃, probably hydrated, within flaws in the anodic film. The second is associated with a more gradual direct chromate/dichromate anion entry into the bulk material probably through the intercrystalline regions in the film, ultimately resulting in film thinning, even in neutral solutions. In phosphate solutions, phosphate anions penetrate and thin bulk anodic alumina in a similar manner to chromate/dichromate anions. The results are interpreted on the basis of the differing surface chemical properties of the various anions in relation to bulk alumina.     

A study of conversion coating development on aluminium in chromate/fluoride solutions using secondary ion mass spectrometry

A Cameca Ion Analyzer has been used to examine aluminium surfaces, covered by 73 nm thick barrier type anodic films, after natural immersion for 1–15 min in a chromate/fluoride conversion coating solution at 293 K. The conversion coating produced is essentially amorphous chromium-containing material, probably largely hydrated chromic oxide, but contains a cellular-type structure with aluminium and fluoride, probably as complex oxyfluoride, concentrated in the inter-cellular regions. The major role of the F^? ion is to remove the initial oxide film, maintain the surface active and permit nucleation and lateral growth of the conversion coating over it. The F^? ion is more aggressive towards anodic and other alumina than CrO₄^2? and PO₄^3? ions, without appearing to enter the anodic film material per se, but is also more aggressive towards the aluminium substrate than C1^? ion, acting initially at flaws and undermining the film.     

A study of barrier film growth on aluminium in solutions of film-promoting and aggressive ions using secondary ion mass spectrometry

A Cameca Ion Analyser has been used to examine barrier-type anodic films grown on aluminium in neutral phosphate, chromate or phosphate/chromate solutions and in phosphate and chromate solutions containing relatively small amounts of chloride ion. Barrier layers grow at relatively high current efficiencies in phosphate solution, and are characterized by a rather wide phosphorus-containing layer adjacent to the oxide/solution interface. In chromate solutions, barrier layers grow at relatively low current efficiencies and contain little, if any, chromium resulting from the film growth process itself. Barrier layers grown in chromate-phosphate mixtures are generally typical of those grown in pure phosphate solutions, even at quite high chromate/phosphate concentration ratios. The presence of chloride ions in either phosphate or chromate solutions lowers the current efficiency of barrier film growth, and is associated with pitting of the aluminium substrate at the bases of flaws in the growing film, resulting in lateral undermining of the film. The results are explained in terms of a model for film development, involving growth partly by ionic migration and partly by a dissolution/precipitation process.     

A photo-electron and secondary ion mass spectrometric study of the chemical composition of thermal oxide layers on technically pure aluminium

The thickness and chemical composition of oxide films on aluminium of technical purity (Al 99.2–99.5) has been studied by photo-electron spectroscopy and secondary ion mass-spectrometry for differently prepared surfaces. Special emphasis has been placed in understanding quantitatively the oxidative surface enrichment processes of alkali and alkaline earth elements that take place during annealing at higher temperatures (250–340°C). The concentration of these elements (particularly those of lithium and magnesium) in the oxide layers of annealed foil samples is higher by a factor of 10³ to 10⁴ compared to the bulk metal contents. How these surface enrichment processes modify the chemical properties of the oxide film is discussed. An enhanced susceptibility of the surface to corrosion in the presence of humidity is found which can cause interfacial reactions and delamination problems in the case of lacquered foil.     

Effective efficiency coefficients for standard-free analysis of solid substances by the method of mass spectrometry of secondary ions

Mass-spectrometry research of secondary ion emission (MSSI) products is a direct method of analysis of the element and isotope content of conducting and nonconducting solid substances. Similar to other methods of mass-spectrometric analysis, MSSI also has some analytical characteristics that enable one to detect a simple reaction between a concentration of the analyzed element and the registered initial signal.     

HPLC-MS/MS法测定人体血浆中吲哒帕胺的浓度

目的: 建立一种简便、灵敏的测定人体血浆中吲哒帕胺浓度的高效液相色谱-串联质谱 (HPLC-MS/MS) 方法。方法: 以瑞格列奈钙为内标,采用乙腈:0.1%甲酸水溶液=90∶10为流动相,以Agilent-ZORBAX-C₁₈柱(2.1 mm×150 mm,5.0 m)色谱柱为分析柱,通过电喷雾离子源(ESI),以正离子多反应监测(MRM)方式进行进样检测。检测离子为 [M+H]+m/z 364.1 m/z 188.8(吲哒帕胺)和[M+H]+m/z 451.1 m/z 134.8(瑞格列奈钙,内标)。结果: 吲哒帕胺线性范围为 0.5～50 ng/mL,定量下限为 0.5 ng/mL,线性关系良好;高、中、低三个浓度的日内、日间的RSD均<15%,平均回收率为 94.60%～110.33%。结论: 本方法专属性强,操作简便,灵敏度高,适用于吲哒帕胺制剂的临床药动学研究。     

Photo-luminescence from passive oxide films on nickel and chromium by photo-excitation of UV light

Photo-luminescence emission was measured from the thin passive oxide film on nickel and chromium under the in-situ condition in 0.1 kmol m⁻³ (M) sulfuric acid solution at pH 0.9 and neutral buffer solution of borate-boric acid mixture at pH 8.4 in order to obtain the insight of the electronic properties in the passive oxide film as thin as a few nm. The photo-luminescence induced by UV laser beam at 325 nm wavelength from nickel oxidized in both pH 0.9 sulfuric acid and pH 8.4 borate buffer solutions exhibited a broad spectrum feature with a peak at 400-420 nm. The energy of the peak wavelength from 400 to 420 nm is 2.95-3.10 eV which may correspond to the band-gap energy of the semiconduncting NiO. The photo-luminescence spectra from chromium oxidized in the sulfuric acid and neutral borate solutions had a peak at 400 nm and about 440 nm, respectively. These photo-emission from nickel and chromium oxidized is assumed to correspond to luminescence accompanied by recombination between excess electrons produced by UV light illumination in the conduction band and positive holes in the valence band. The broad tailing of the luminescence at longer wavelength side may represent high density of localized states originated in an amorphous nature of the passive oxides.     

Quantitative analysis of the size distributions and elements of the precipitates in Fe-3%Si alloy during secondary recrystallization annealing using HAADF imaging and XEDS

The distribution of precipitates on grain boundaries and their role in abnormal grain growth during secondary recrystallization annealing in Fe-3 %Si alloy is studied. The precipitates and grain boundaries were observed simultaneously using high angle annular dark field scanning transmission electron microscopy. The chemical composition of the precipitates was also analyzed by X-ray energy dispersive spectroscopy. During secondary recrystallization annealing, the number of small precipitates (<9000 nm²) increased in the samples heated up to 900°C and decreased in the samples heated up to 1000°C. The increase (of the small precipitates) was strongly correlated with the onset temperature of abnormal grain growth above 900°C. In all samples, 50 % to 80 % of the precipitates consisted of complexes containing both Al and Mn.     

硅渣中金属离子的分离和利用

本实验研究了硅渣用盐酸处理后，加入动物胶，分离出硅，然后通过调节pH值，让溶液中的钙、钠、铝分离开。钙、铝的化合物，过滤后回到氧化铝流程，进行再利用，溶液通过浓缩结晶，回到生产硅产品的流程中去，氧化钠回收利用。本试验为探索出硅渣处理，促进氧化铝生产的发展，搞好环境保护和提高经济效益，提供重要方法。     

Application of auger electron spectroscopy and inert metal marker techniques to determine metal and oxygen transport in oxide films on metals

Auger electron spectroscopy in combination with depth profiling by Ar ion sputtering was employed as a surface analytical technique to determine the positions of thin (3–5 nm) inert Pd markers during growth of oxide films on Al, Ni, and -NiAl. Alumina films 35 and 120 nm thick formed on Al and -NiAl, respectively, grew by inward diffusion of oxygen. Metal migration accounted predominantly for the growth of a NiO film 150 nm thick on the (111) crystal face of Ni. However, an assessment could not be made with respect to oxygen diffusion, if any, in this film due to the limitations imposed on precise depth profiling of the marker position caused by uneven sputtering of the oxide and metal phases.     

Influence of dissolved oxygen on oxide films of Alloy 690TT with different surface status in simulated primary water

Oxidation of Alloy 690 with different surface conditions were performed in oxygenated primary water containing B and Li at 325 °C and 15.6 MPa for 2 months. Oxide scales were analyzed using various methods. Results showed triple-layer oxide films were formed: the outmost layer with dispersed big oxide particles; the intermediated layer with loose sheet-like or needle-like oxides and the inner layer with incompact cellular oxides, which were lack of protectiveness. Oxide morphologies were affected by the surface status of samples. Dissolved oxygen increased the intergranular attack (IGA) sensitivity of Alloy 690TT. Growth mechanism of the oxide film was discussed.     

Applications of porous silicon thin films in solar cells and biosensors

An overview of the applications of porous silicon (PS) thin films, as antireflection coatings (ARC) in silicon solar cells and transducers in biosensors, is presented. The reflectance spectra of PS films have been compared with other conventional ARCs (such as SiN_x TiO₂/MgF₂ and ZnS), and optimal PS ARC with minimum reflectance has been obtained. The implementation of PS into an industrially compatible screen-printed (SP) solar cell by both the electrochemical etching (ECE) and chemical etching (CE) methods are reviewed. Porous silicon films, formed via ECE for short anodization times, on textured n⁺ emitter ofc-Si solar cell having SP front and back contacts, lead to improvements in the performance of solar cells and demonstrate their viability in industrial applications.     

Quantitative TEM analysis of 3-D grain structure in CVD-grown SiC films using double-wedge geometry

We have characterized the structure of chemical vapor deposition-grown polycrystalline cubic SiC films by quantitative transmission electron microscopy. A new double-wedge sample geometry allowed accurate statistical measurements of the grain size as a function of distance from the substrate. The data are well described by the van der Drift model of faceted film growth with a 〈1 1 1〉 texture that narrows with distance h from the substrate. It was found that the distribution of grain sizes d(h) is self-similar and the mean grain size follows a power law of the type 〈d〉 ∝ h^ν. However, the measured exponent ν = 0.68 ± 0.1 is significantly larger than that previously predicted from mean field models and computer simulations of three-dimensional film growth (ν = 0.4). This difference may be due to the polarity of SiC, its low stacking fault energy and abundant defects, or impurities. The accuracy of the experimental observations due to the new sample geometry reported here is sufficient to enable statistical tomography or provide guidelines for improved computer modeling.     

Influence of oxygen ion irradiation on the corrosion aspects of Ti-5%Ta-2%Nb alloy and oxide coated titanium

The corrosion resistance of Ti-5%Ta-2%Nb alloy and DOCTOR (double oxide coating on titanium for reconditioning) coated titanium by O⁵⁺ ion irradiation were compared and investigated for their corrosion behaviour. O⁵⁺ ion irradiations were carried out at a dose rate of 1 × 10¹⁷, 1 × 10¹⁸ and 1 × 10¹⁹ ions/m² at 116 MeV. The surface properties and corrosion resistance were evaluated by using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray (EDX), glancing-angle X-ray diffraction (GXRD) and electrochemical testing methods. The results of electrochemical investigations in 11.5 N HNO₃ indicated that the open circuit potential (OCP) of DOCTOR coated titanium is nobler than Ti-5%Ta-2%Nb alloy. The potentiodynamic polarization study of Ti-5%Ta-2%Nb alloy and DOCTOR coated specimen indicated decrease in passive current density with increase in ion doses (1 × 10¹⁷ to 1 × 10¹⁹ ions/m²) indicating decrease in anodic dissolution. Nyquist arc behaviour in the electrochemical impedance study substantiated the enhancement in oxide layer stability by O⁵⁺ ion irradiation. AFM results revealed that the DOCTOR coated Ti surface was dense without gross voids, and the surface roughness decreased by O⁵⁺ ion irradiation, but increased after corrosion test. EDX and GXRD patterns of DOCTOR coated Ti sample indicated that the coating was mainly composed of rutile TiO₂. Based on the above results, the O⁵⁺ ion irradiation effect on corrosion behavior of Ti-5%Ta-2%Nb alloy and DOCTOR coated titanium are discussed in this paper.     

X-ray study of tin oxide films obtained by reactive DC sputtering from a metallic tin target in pure oxygen plasma

Tin oxide films deposited on glass substrates were prepared using a metallic tin target in a DC-magnetron sputtering system. Pure oxygen (99.9%) was used as oxidant and plasma gas. The experiments were carried out at a fixed current mode of the power supply and the cathode voltage was measured during 15 min, the first 5 min of pre-sputtering and the last 10 were used for film growth. The deposition was carried out under different conditions of current, oxygen pressure and substrate temperature. The crystalline phases present in the films were identified with an X-ray diffractometer, equipped with a grazing incidence attachment. The angle of incidence was 3°. The preferred orientation degree in the tin oxide films and the relative cassiterite (SnO₂) proportion for each reflection were calculated from the deconvoluted X-ray peaks. It was found that the synthesis conditions have a strong influence over the growth texture and the relative cassiterite proportion over romarchite formation (SnO). To obtain tin oxide films with a high SnO₂ proportion and a high texture in reactive oxygen sputtering, were necessary, relatively high values of substrate temperature, current and oxygen pressure.     

次氧化锌中砷的物相及砷的浸出(英文)

研究烟化炉次氧化锌中砷的物相类型。结果表明:按砷的物相可将次氧化锌分为3种类型。在一型次氧化锌中砷以As2O3形态存在,而在二型和三型次氧化锌中砷分别以亚砷酸锌(Zn(AsO2)2)和砷酸铅(Pb(As2O6),Pb4As2O9)形态存在。在热力学分析基础上,对二型次氧化锌进行浸出脱砷。结果表明:采用30g/LNaOH溶液,在液固比3、温度20°C的条件下,砷的浸出率在1h内可达到65%～70%,而铅、锌的损失均小于1%。