Dissolution amounts of nickel, chromium and iron from SUS 304, 316 and 444 stainless steels in sodium chloride solutions

The release of nickel and chromium from stainless steels by sweat, is often responsible for allergic contact dermatitis. The amounts of metal released from stainless steels were in trace amounts, because corrosion resistance was excellent. However, measurement of dissolution amounts is difficult, and if these amounts are not known, the improvement and development of stainless steels with excellent resistance to NaCl solution is difficult. In this work, trace dissolution amounts from the main components of stainless steels which can cause an allergy were investigated. SUS 304, 316 and 444 stainless steels were used in this test. The test solutions used were 0.9 (isotonic sodium chloride solution), 1, 3, 5 and 10 wt% NaCl solutions. Nickel,chromium and iron ions in the test solutions were rapidly determined by stripping voltammetry. The detection limits of Ni(II), Cr(VI) and Fe(III) ions in 1 wt% NaCl solution were 1.0, 0.1 and 0.5 ng cm^-3, respectively, with standard deviations of five tests at 5 ng cm^-3 Ni(II), Cr(VI) and Fe(III) ions, of 6.4%, 1.8% and 2.2%, respectively. Generally, the amounts of the metals dissolved increased in direct proportion to the immersion, in the range 30–60 days for nickel, 30–90 days for chromium and 30–120 days for iron. The dissolution amounts of nickel from SUS 304 and 316 stainless steels increased rapidly over 60 days, while that of chromium increased rapidly over 90 days, in isotonic sodium chloride solution. The ratio of the three dissolved metal ions was not consistent with the composition of the specimens. The ratio of dissolved nickel in SUS 304 and 316 stainless steels was larger than that in the specimen, and dissolved preferentially. The dissolution ratio of chromium and iron in SUS 444 stainless steel approximately agreed with the composition of the specimen. This revised version was published online in November 2006 with corrections to the Cover Date.     

Synthesis and characterization of Fe(III)-silicate precipitation tubes

Fe(III)-silicate precipitation tubes synthesized through “silica garden” route have been characterized using a number of analytical techniques including X-ray diffraction, infrared spectroscopy, atomic force microscopy, scanning and transmission electron microscopy. These tubes are brittle and amorphous and are hierarchically built from smaller tubes of 5-10 nm diameters. They remain amorphous at least up to 650 °C. Crystobalite and hematite are the major phases present in Fe(III)-silicate tubes heated at 850 °C. Morphology and chemical compositions at the external and internal walls of these tubes are remarkably different. These tubes are porous with high BET surface area of 291.2 m²/g. Fe(III)-silicate tubes contain significant amount of physically and chemically bound moisture. They show promise as an adsorbent for Pb(II), Zn(II), and Cr(III) in aqueous medium.     

Effect of microwave power on the morphology and optical property of zinc oxide nano-structures prepared via a microwave-assisted aqueous solution method

The effect of the microwave power on the morphology and optical properties of zinc oxide nanostructures prepared using a microwave-assisted aqueous solution method has been investigated. The ZnO nanostructures were synthesized from zinc chloride and sodium hydroxide mixed aqueous solutions exposed for 5 min to microwave radiation at four different powers, namely 150, 450, 700 and 1000 W. The morphologies of the samples have been characterized by transmission electron microscope (TEM) and scanning electron microscope (SEM). The results showed that the power of microwave radiation influenced the shape and size of the synthesized nanostructures. It is also found that the average particle size of nanostructures decreased with decreasing microwave power. The results of X-ray diffraction (XRD) showed that all the as-prepared ZnO nanostructures are in crystalline form with high purity. The infrared (IR) spectra indicated that the as-prepared nano ZnO product can be used as infrared gas sensors such as an infrared carbon dioxide (CO₂) and/or CO sensor. Optical properties of the as-prepared ZnO nanostructures were investigated by UV–vis spectroscopy and showed that the optical properties of as-synthesized ZnO samples are sensitive to the variation of the power of microwave radiation.     

New understanding on metal recovery of Fe,Ni and Cr during carbon-thermal reduction of stainless steel dust

Stainless steel dust is a typical solid waste from iron and steel smelting. In this study, valuable metal components were recovered from stainless steel dust by carbon-thermal reduction. The effect of reduction conditions on the recovery of Fe, Ni and Cr was studied. The restrictive steps of Fe, Ni and Cr in the reduction process were clarified by XRD and SEM. The results show that the reduction temperature has a great influence on the reduction of metal Fe, Ni and Cr in stainless steel dust, and the increase of reduction temperature, reduction time and appropriate carbon ratio promoted the recovery of metal. The intermediate phase fayalite (Fe,Ni)₂SiO₄ and magnesiochromite Cr₂MgO₄ in the reduction process are the restrictive factors that cause the low recovery of Fe, Ni and Cr metals. In the process of carbon-thermal reduction, with the increase of reduction time, Fe²⁺ and Ni²⁺ in mesophase (Fe, Ni)₂SiO₄ were replaced by Mg²⁺ and Ca²⁺ in MgO and CaO, and finally reduced to MgCaSiO₄; Cr³⁺ in the mesophase Cr₂MgO₄ was replaced by Al³⁺ in Al₂O₃ and finally reduced to Al₂MgO₄, which improves the recovery of metal Fe, Ni and Cr.     

One component metal sintering additive for β-SiC based on thermodynamic calculation and experimental observations

Various types of metals were examined as sintering additives for β-SiC by considering the standard Gibbs formation free energy and vapor pressure under hot pressing conditions (1973-2123 K), particularly for applications in nuclear reactors. Metallic elements having the low long-term activation under neutron irradiation condition, such as Cr, Fe, Ta, Ti, V and W, as well as widely used elements, Al, Mg and B, were considered. The conclusions drawn from thermodynamic considerations were compared with the experimental observations. Al and Mg were found to be effective sintering additives, whereas the others were not due to the formation of metal carbides or silicides from the decomposition of SiC under hot pressing conditions.     

Bioleaching of metal concentrates of waste printed circuit boards by mixed culture of acidophilic bacteria

Metal concentrates of printed circuit boards (PCBs) are the residue valuable metals from which non-metallic components are removed. The non-metallic components show bacterial toxicity in bioleaching process and can be recycled as well. In this study, the effects of initial pH, initial Fe(II) concentration, metal concentrate dosage, particle size, and inoculation quantity on the bioleaching were investigated so as to determine the optimum conditions and evaluate the feasibility of bioleaching of metal concentrates of PCBs by mixed culture of acidophilic bacteria (MCAB). The results showed that the initial pH and Fe(II) concentration played an important role in copper extraction and precipitate formation. Under the optimized conditions of initial pH 2.00, 12 g/L initial Fe(II), 12 g/L metal concentrate dosage, 10% inoculation quantity, and 60-80 mesh particle size, 96.8% the copper leaching efficiency was achieved in 45 h, and aluminum and zinc 88.2% and 91.6% in 98 h, respectively. All findings demonstrated that metals could be efficiently leached from metal concentrates of waste PCBs by using the MCAB, and the leaching period was shorten from about 8 days to 45 h.     

Influence of the filler metal on the mechanical properties of Ti-6Al-4V electron beam weldments

The influence of various filler metals on the mechanical properties of 17 mm thick Ti-6Al-4V electron beam welded joints has been analysed. Autogeneous welded joints exhibit higher toughness when compared to the parent plate but this improvement was less marked than that observed in plasma arc welded joints. To achieve better toughness, without suffering unacceptable losses of strength, different morphologies of commercially pure titanium filler metals have been employed. Using 0.50 mm thick sheet as filler metal leaded to maximum toughness but as counterpart a significant decrease in strength was observed. To obtain high toughness while maintaining a high strength level 0.25 mm sheet and 1 mm diameter filler metals are recommended. Fractographic examination of the failed specimens helped to explain the fracture behaviour of the different welded joints.     

Inhibition and stimulation of enzymatic activities of human fibroblasts by corrosion products and metal salts

Fibroblasts from normal human skin were cultured for a period of 21 days in the absence or in the presence of metal ions. The effects of stainless steel (SS) corrosion products were compared to the effects of iron, chromium and nickel ions used either separately (Fe, Cr, or Ni solutions) or combined (Fe+Cr+Ni solution). At several periods of time (4, 7, 14 and 21 days) the cell cultures were analysed for the following parameters: (a) metal ion accumulation by atomic absorption spectrometry; (b) cell morphology and viability by the neutral red assay; (c) cell proliferation by DNA assessment, and enzyme activity by both (d) MTT reduction and (e) acid phosphatase activity. Results showed that SS-corrosion products and the corresponding metal ions combined at the same concentrations, Fe+Cr+Ni solution, had opposite effects on fibroblast cultures. In fact, SS-corrosion products caused no apparent effects on cell morphology nor on cell proliferation whereas Fe+Cr+Ni solution stimulated both neutral red uptake and cell proliferation. The enzymatic assays showed that SS-corrosion products caused inhibition of both MTT reduction and acid phosphatase activity in contrast to Fe+Cr+Ni solution which stimulated their activity. Furthermore, in all biological parameters studied, a strong association was observed between the effects of Fe+Cr+Ni solution and Cr alone, suggesting that Cr was the metal ion mostly involved in the stimulatory effects of the combined solution.     

Chemical fractionation and translocation of heavy metals in Canna indica L. grown on industrial waste amended soil

A pot experiment was carried out to assess the effect of different amendments of industrial sludge on the growth of Canna indica L. as well as the translocation potential of heavy metals of this plant. The accumulation of metals (Cr, Fe, Cd, Cu, Ni, Zn, Mn and Pb) in different parts of C. indica L. grown on industrial sludge-amended soil increased with time and increasing doses of sludge amendments. Sequential extraction method was followed to estimate the different fractions of heavy metals in sludge-amended soils collected from different periods of this study. The results showed that Mn, Zn, Cd, Cr and Pb were mostly associated with Fe–Mn oxide fraction in all amendments, whereas, Ni was mostly found in residual (RES) fraction. Cu and Fe were found to be higher in organically bounded form (OM) and RES fraction. The metal concentration in C. indica L. after 90 days of experiment started, was in the order of Fe > Cr > Mn > Zn > Ni > Cu > Cd > Pb and the metal translocation was found lesser in shoot. With the increasing percentage of sludge amendments in soil the metal concentrations increased in different parts of plants. Overall, the plant C. indica L. was found to be well adapted in industrial sludge amendments and it may be recommended that this plant was found suitable for phytoremediation of most of the studied metals.     

Distribution, correlation and risk assessment of selected metals in urban soils from Islamabad, Pakistan

Urban soil samples were analyzed for Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Pb, Sr and Zn by atomic absorption spectrophotometric method. Multivariate statistical approach was used to study the apportionment of selected metals in the soil samples during summer and winter. The degree of contamination along with the geoaccumulation index, enrichment factor and contamination factor was also evaluated. In water-extract of the soil samples, relatively higher levels were noted for Na, Ca, K, Fe, Mg, and Pb with average concentrations of 56.38, 33.82, 12.53, 7.127, 5.994, and 1.045 mg/kg during summer, while the mean metal levels during winter were 76.45, 38.05, 3.928, 0.627, 8.726, and 0.878 mg/kg, respectively. In case of acid-extract of the soils, Ca, Fe, Mg, Na, K, Mn and Sr were found at 27,531, 12,784, 2769, 999.9, 737.9, 393.5, and 115.1 mg/kg, during summer and 23,386, 3958, 3206, 254.6, 1511, 453.6, and 53.30 mg/kg, during winter, respectively. Most of the metals showed random distribution with diverse correlations in both seasons. Principal component analysis and cluster analysis revealed significant anthropogenic intrusions of Cd, Pb, Co, Cr, Cu, Li, Zn and Na in the soils. Geoaccumulation indices and contamination factors indicated moderate to heavy contamination for Pb and Cd in the soils, while enrichment factor exhibited significant enrichment (EF > 5) of Cd, Pb, Ca, Co, Li, Mn and Zn by anthropogenic activities. Overall, on the average basis, considerable degree of contamination (C_deg > 16) was observed in both seasons, although it was higher in winter. Present metal levels were also compared with those reported from other areas around the world.     

Mass transfer of metal ion implantation into metal targets at elevated temperatures

A mass transfer model for metal ion implantation into a metal target at elevated temperatures has been built up based on transport of ions in matter and radiation enhanced diffusion. It is used to calculate concentration-depth profiles and compositional changes of the implanted species. The ion implantation at elevated temperatures was simulated by a dynamic Monte Carlo (MC) method, which takes into account a local saturation in the crystalline target by using a maximum atomic fraction allowed in the matrix. For the diffusion process, the transport of the implanted species was obtained from the diffusion equations for the implanted species and nonequilibrium vacancies. The radiation enhanced diffusion coefficient was obtained by taking into account linear annealing of the defects. A nonequilibrium vacancy source function and surface sputtering were introduced into the diffusion equations. Concentration-depth profiles of Cr, Fe and Ni ions implanted into Al at a temperature range from 200 to 510 °C were calculated. The calculated results principally were consistent with measured concentration-depth profiles obtained by Rutherford backscattering spectroscopy (RBS). In some cases deviations occur, which are discussed.     

新型工艺制备Fe/Cr/Si复合薄膜的结构研究

采用改进的水热法和新型工艺在SUS304不锈钢表面制备了Fe/Cr掺杂SiO2薄膜,并通过扫描电镜(SEM)、X射线衍射(XRD)、电子探针(EPMA)和X射线光电子能谱深度分析(XPS)等检测手段对薄膜结构进行了分析.结果表明膜层主要分为两层:表层为共溶氧化物层;底层为Cr、Fe的氧化物,主要为尖晶石结构和Si网状结构.通过XPS检测结果得知,Si元素的加入不是简单的物理混合,而是与金属元素生成了Si-Fe键,进一步提高了膜层的结合力和耐酸性.     

Chemical states of oxygen implanted in SUS 304 stainless steel and pure metals studied by in situ XPS using synchrotron radiation

The chemical states of oxygen implanted in SUS304 stainless steel and pure metals (Fe,Ni,Cr) by O₂ ⁺ ion bombardment have been investigated by means of X-ray photoelectron spectroscopy (XPS) using synchrotron soft X-ray. For SUS304, all of implanted oxygen is chemically combined with the constituent metals, forming metallic oxides. For pure metals, on the other hand, only a part of implanted oxygen react with the target metals. The other part of the implanted oxygen in pure metals does not react with the target, and they are inserted into the crystal lattice (we call them as dissolved oxygen). The ratio of dissolved oxygen to the reacted oxygen depends on the chemical reactivity of target metals.     

Nickel/carbon hybrid nanostructures as microwave absorbers

Magnetic metal/carbon hybrid nanostructures are novel materials having multifunctional properties. Here we report the microwave absorbing properties of nickel/carbon nanostructures synthesized by a controlled pyrolysis method. Their complex dielectric permittivity and magnetic permeability were measured at different microwave frequencies using the technique of cavity perturbation. Reflection losses were evaluated and found to be less than −10 dB over the entire X-band (8-12 GHz) for a thickness of 2.2-2.8 mm. A minimum reflection loss of −45 dB was attained for an absorber thickness of 6.6 mm at 3.13 GHz.     

Magnetic and transport properties of La0.3Ca0.7Mn0.9T0.1O3 (T = Cr, Fe, and W)

We have carried out structural, magnetic and magneto transport measurements of the electron-doped manganite La_0.3Ca_0.7MnO₃ substituted with 10% of Cr, Fe and W on the Mn site. The substitution by Cr, Fe and W suppresses the charge order transition present at 260 K in the parent compound. All the samples show a semiconducting behavior. Whereas the parent compound does not show any magneto resistance (MR) even in a field of 14 T, a maximum MR of 6% in 5 T at 25 K is observed for the Cr substituted sample that is attributed to a spin-cluster glass like states induced by Cr. The Fe and W substituted samples showed a MR of 1.5 and 3%, respectively which may be attributed to a smaller number of FM domains/spin-clusters and to an increase in anti-ferromagnetic interaction.     

Formation and characterization of thin films from phthalocyanine complexes: An electrosynthesis study using the atomic-force microscope

(μ-Cyano)(phthalocyaninato)metal(III) [PcMCN]_n species with a central transition metal ion, such as Fe(III) and Co(III), were used to prepare molecular films on a highly oriented pyrolytic graphite electrode substrate by using the cyclic voltammetry technique. In order to investigate the influence of the ligand on the film properties, 1,8-dihydroxyanthraquinone and 2,6-dihydroxyanthraquinone as bivalent ligands were employed. The structure of the molecular materials was analyzed by infrared spectroscopy. The in situ film formation, texture, composition and conductivity of each film were further investigated using atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and the four-probe technique, respectively. The [PcMCN]_n complexes provided conductive films with an electrical conductivity of 1 × 10^− 6 Ω^− 1 cm^− 1 at 298 K.     

Removal of metals from landfill leachate by sorption to activated carbon, bone meal and iron fines

Sorption filters based on granular activated carbon, bone meal and iron fines were tested for their efficiency of removing metals from landfill leachate. Removal of Al, As, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sr and Zn were studied in a laboratory scale setup. Activated carbon removed more than 90% of Co, Cr, Cu, Fe, Mn and Ni. Ca, Pb, Sr and Zn were removed but less efficiently. Bone meal removed over 80% of Cr, Fe, Hg, Mn and Sr and 20-80% of Al, Ca, Cu, Mo, Ni, Pb and Zn. Iron fines removed most metals (As, Ca, Co, Cr, Cu, Fe, Mg, Mn, Pb, Sr and Zn) to some extent but less efficiently. All materials released unwanted substances (metals, TOC or nutrients), highlighting the need to study the uptake and release of a large number of compounds, not only the target metals. To remove a wide range of metals using these materials two or more filter materials may need to be combined. Sorption mechanisms for all materials include ion exchange, sorption and precipitation. For iron fines oxidation of Fe(0) seems to be important for metal immobilisation.     

Interaction of highly dissociated low pressure hydrogen plasma with W-C thin film deposits

Thin film deposits of carbon and tungsten on stainless steel substrate were prepared by RF sputtering of a tungsten target in acetylene atmosphere. At the target bias of − 1700 V and the target current of 30 mA cm^− 2, a rather uniform film containing 50 at.% of C and 50 at.% of W was deposited. The thickness of the deposited film was about 1 μm. Samples were exposed to highly dissociated hydrogen plasma created by a microwave discharge at the power of 1000 W. Some samples were heated additionally by concentrated solar radiation. After plasma treatment, the samples were characterized by X-Ray Diffraction and Auger Electron Spectroscopy. The results showed that aggressive hydrogen plasma allows for the removal of carbon from the deposits at moderated temperatures. Prolonged treatment showed formation of highly crystalline pure tungsten, and finally the tungsten film interacted with the substrate forming a thin film rich of Fe₇W₆ compound. The range of temperature and/or treatment time for the removal of carbon from the W-C film was found very narrow.     

Metal catalyst adsorption effects in the growth of carbon nanostructures on mesoporous material

Mesoporous silica films were used as host for metal-based (Me = Fe, Co, Ni) nanoparticles via wet impregnation at pH = 5. A hydrogen ion beam was used to reduce the metallic oxide and hydroxides, previously detected by X-ray photoelectron spectroscopy, in metals. Chemical vapor deposition processes at three different conditions varying the acetylene-nitrogen proportion were performed on the mesoporous films decorated by different metal-based nanoparticles. The grown carbon nanostructures were characterized by high-resolution transmission electron microscopy and scanning electron microscopy. The ability to grow carbon nanostructures decreases in the following order: Fe > Co > Ni. When pure acetylene is used, iron allows to form graphene sheets around the metal catalyst like carbon nanocapsules, whereas cobalt allows to form structures that seem to be carbon nanotubes. Nitrogen leads to control the size and shape of carbon nanocapsules for iron catalyst and avoid the growth of such carbon nanotube-like structures for cobalt catalyst.     

First-principles models for phase stability and radiation defects in structural materials for future fusion power-plant applications

Generic materials-related problems foreseen in connection with the operation of a fusion power plant present a major challenge for the development of magnetically confined fusion as a commercial power generation option. In this review, we focus on the predictive capabilities of first-principles-based atomistic models for radiation defects and phase stability of body-centred cubic Fe–Cr-based ferritic-martensitic and ferritic steels and tungsten alloys, which are presently under consideration as candidate structural materials for the first wall and diverter applications. Density-functional calculations predict that low-Cr iron alloys are stabilized by intra-atomic exchange, giving rise to magnetism and changes in interatomic chemical bonding. Magnetic effects are also responsible for the fact that the atomic structure of radiation defects in iron and steels is different from the structure of defects formed under irradiation in non-magnetic body-centred cubic metals, for example vanadium or tungsten. Ab initio-based magnetic cluster expansion-based Monte–Carlo simulations showed unusual non-collinear magnetic configurations forming at interfaces and around Cr precipitates in FeCr alloys. In W–Ta and W–V alloys, ab initio calculations helped to identify several low temperature ordered inter-metallic phases that are not included in the existing phase diagrams based on high-temperature experimental data. Ab initio calculations have also made it possible to predict atomic structures of point defects formed in these alloys under irradiation.