The oxidation behaviour of the uncoated ferritic Fe-22Cr steel Sanergy HT is compared with an 640 nm Co coated version of the same material. The materials have been subject to corrosion and Cr ...volatilization measurements in air for up to 3000 h at 850 °C. Oxidation tests have been carried out both isothermal and discontinuously. The volatilization measurements were carried out using a recently developed denuder technique, which allows to quantify Cr evaporation in a time resolved manner. The oxidation process is studied from very initial phases (>15 s) to long term behaviour (3000 h). The formed oxide scales are analysed by XRD, SEM/EDX as well as TEM/EDX.
The results show that both materials form an oxide scale with an inner layer of Cr2O3 and a spinel layer on top. In the case of the uncoated material, the spinel layer is of (Cr,Mn)3O4 type while in the presence of a Co coating a (Co,Mn,Fe)3O4 is formed. The Cr evaporation measurements show that despite the fact that the Co coating is very thin (640 nm) it effectively blocks Cr evaporation for at least 3000 h. This is in line with TEM analysis showing that after 3000 h there is only a low Cr content in the outer oxide scale. This long term stability indicates the suitability of the coated material as solid oxide fuel cell (SOFC) interconnect.
▸ Continuous Cr evaporation measurement for 3000 h. ▸ 640 nm Co coating showing no sign of degradation over 3000 h. ▸ Detailed TEM analysis of oxide scale/coating development from 15 s to 3000 h.
The effect of novel Co and Ce nanocoatings on oxidation behaviour and chromium volatilization from a commercial Fe–22Cr steel (Sanergy HT) developed for solid oxide fuel cell interconnect ...applications is investigated. Three different coatings (10nm Ce, 640nm Co and 10nm Ce+640nm Co) are studied. Uncoated and nanocoated samples are exposed isothermally at 850°C in the air with 3% H2O for 168h. The detailed microstructure of the different coatings is investigated. The surface morphology and microstructure of the oxide scales are characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray analysis (EDX). Cross-section TEM thin foils are prepared by using a combined FIB/SEM (focused ion beam/scanning electron microscope) instrument. A 640nm cobalt coating strongly inhibits Cr volatilization but has only minor effects on oxidation rate. In contrast, a 10nm Ce coating decreases the oxidation rate but has no significant effects on chromium volatilization. Combining the two coatings, i.e., applying a 640nm Co coating on top of the 10nm Ce, effectively reduces Cr evaporation and slows down the rate of alloy oxidation.
► 640nm Co coating strongly inhibits Cr volatilization. ► 640nm Co coating has only minor effects on oxidation rate. ► 10nm Ce coating decreases the oxidation rate. ► 10nm Ce coating has no significant effects on chromium volatilization. ► 10nm Ce + 640nm Co reduces Cr evaporation and the rate of alloy oxidation.
The oxidation of a Mo(Si,Al)
2
-based composite is investigated in the temperature range 900–1600 °C in dry air. Exposure time was 72 h. Comparisons are made with the oxidation behavior of a ...conventional MoSi
2
-based material. Cross-sections are examined with scanning electron microscopy and transmission electron microscopy; the phase composition is analyzed by X-ray diffraction and convergent beam electron diffraction. The material forms a continuous external α-alumina scale throughout the temperature range. Below the scale, there is a continuous Mo
5
(Si,Al)
3
layer that overlies Mo(Si,Al)
2
in the bulk. The Mo(Si,Al)
2
phase immediately beneath the Mo
5
(Si,Al)
3
layer is depleted in Al. No indications of MoO
3
volatilization could be found for the Mo(Si,Al)
2
material.
The antimicrobial and antioxidant activities, as well as the DNA-binding of four square-planar Pd(II) complexes, Pd(terpy)Cl+ (C1), Pd(en)Cl2 (C2), Pd(DMEAImiPr)Cl2 (C3) and Pd(dach)Cl2 (C4) (terpy = ...2,2?:6?,2??- -terpyridine, en = ethylenediamine, dach = trans-1,2-diaminocyclohexane and DMEAImiPr = N2-((1,3-dihydro-1,3-diisopropyl-4,5-dimethyl)-2H-imidazol-2- ylidene)-N1,N1-dimethyl-1,2-ethanediamine are reported. The antimicrobial activities of the Pd(II) complexes with the appropriate ligands were tested using the microdilution method against 18 strains of microorganisms, whereby the minimal inhibitory concentration (MIC) and the minimal microbicidal concentration (MMC) were determined. The antibiofilm activity of Pd(terpy)Cl+ and the corresponding ligand were determined on a formed biofilm. The intensity of antimicrobial activity varied depending on the type of microorganism and the tested compound. The C1 complex with the corresponding ligand demonstrated significantly greater overall antimicrobial activity than C2, C3 and C4. The antibacterial activity of the C1 complex was better than its antifungal activity that was overall greater than that of the positive control, fluconazole. The greatest sensitivity for C1 and L1 was with Penicillium italicum (MIC < 0.49 ?g mL-1) among the fungi, and with Proteus mirabilis ATCC 12453 (MIC = 0.98 ?g mL-1) among the tested bacteria. The tested compounds show low and moderate antibiofilm activity. The complexes showed weak antioxidant properties when tested using the DPPH (1,1-diphenyl-2- -picrylhydrazyl) method. The interaction of the metal complexes C1?C4 with calf thymus DNA (CT-DNA) was further examined by absorption (UV?Vis) and emission spectral studies (EthBr displacement studies). Overall, the investigated complexes exhibited good DNA interaction ability.
► The general microstructure of the alumina layers depends on the underlying surface. ► The TiC and alumina layers grow epitaxially on the c- and a-surface substrates. ► On the r-surface, epitaxy is ...present only at some rare locations. ► On the c- and a-surfaces the TiC layer was oxidized to an fcc TiCO phase. ► On the r-surface the initially deposited fcc TiC transformed to a monoclinic TiCO phase.
Multilayers of TiC/α-Al
2O
3 consisting of three (1
μm thick) alumina layers separated by thin (∼10
nm) oxidized TiC layers have been deposited onto c-, a- and r-surfaces of single crystals of α-Al
2O
3 by chemical vapour deposition (CVD). The aim of this paper is to describe and compare the detailed microstructure of the different multilayer coatings by using transmission electron microscopy (TEM).
The general microstructure of the alumina layers is very different when deposited onto different surfaces of α-Al
2O
3 single crystal substrates. On the c- and a-surfaces the alumina layers grow evenly resulting in growth of single crystal layers of TiC and alumina throughout the coating. However, when deposited on the r-surface the alumina layers generally grow unevenly. No pores are observed within the alumina layers, while a small number of pores are found at the interfaces below the TiC layers. The TiC and alumina layers grow epitaxially on the c- and a-surface substrates. On the r-surface, epitaxy is present only at some rare locations. The TiC layers were oxidized in situ for 2
min in CO
2/H
2 prior to the alumina layer deposition. For all three samples chemical analyses show that the whole TiC layer is oxidized. On the c- and a-surfaces the TiC layer was oxidized to an fcc TiCO phase. On the r-surface the oxidation stage resulted in a transformation of the initially deposited fcc TiC to a monoclinic TiCO phase, which appears to be a modified TiO structure with a high carbon content.
Grain contrast imaging in FIB and SEM Canovic, S; Jonsson, T; Halvarsson, M
Journal of physics. Conference series,
08/2008, Letnik:
126, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Grain contrast imaging can be performed with several techniques. In order to be able to choose the most suitable one it is important to know which techniques are available and also to be aware of the ...strengths and weaknesses of each technique. In this work, the grain contrast imaging is performed with secondary electrons, backscattered electrons, forward scattered electrons, transmitted electrons in the scanning electron microscope, and with secondary electrons in the focused ion beam instrument. The advantages and disadvantages of each method are discussed in order to make it easier to choose the most appropriate technique for grain contrast imaging.
Oxide scale cross-sections of CeO
2
coated FeCr based solid oxide fuel cell interconnect materials were examined using secondary ion mass spectrometry (SIMS) depth profiling. A duplex spinel∶chromia ...scale was formed after 1 h at 850°C. Ti and ceria were observed between these layers. Additionally, minor concentrations of Mn, Si and Nb were observed at the oxide/metal interface. Furthermore, Al and Ti were concentrated primarily in the metal surface close to the oxide/metal interface. Secondary ion mass spectrometry sputter depth profiles using different ion sources;
69
Ga
+
, Bi
3
+
/Cs
+
and C
60
+
/C
60
2+
were compared with TEM oxide scale cross-section and field emission gun-Auger electron spectroscopy depth profiling. Secondary ion mass spectrometry depth profiling with
69
Ga
+
, Bi
3
+
/Cs
+
showed decreased secondary ion yields in the metallic matrix. This decrease could be avoided using oxygen flooding. The C
60
cluster ion depth profiles were less sensitive to type of matrix and gave the best correspondence to the TEM cross-section. However, the impact energy has to be high enough to avoid carbon deposition.
Thin films of alumina were deposited by alternate-current inverted magnetron sputtering at 350 °C on stainless steel substrates. Chromium oxide was used as a template layer because it can be ...deposited at low temperatures and has a low lattice mismatch with alpha alumina. X-ray diffraction and selected area electron diffraction results showed that pure alpha alumina coatings could be grown at 6 kW and 0.5 % partial pressure of oxygen. Cross-sectional transmission electron microscopy analysis showed a crystalline layer of alumina on top of the chromium oxide layer. Pure alpha alumina could be grown if deposited for 2 h. Layers with mixed phases of alpha and gamma alumina were obtained with other deposition parameters.
Alpha-phase aluminum oxide thin films were deposited at 480 °C by AC inverted cylindrical magnetron sputtering on nickel coated transmission electron microscopy (TEM) grids and stainless steel ...substrates. Several previous studies have demonstrated that an alpha phase was possible at low temperature if a chromium template layer was present. However, here we show that alpha phase is possible without the chromium oxide layer. The presence of alpha phase alumina has been confirmed by TEM. Cross-sectional TEM observations have indicated deposition rates as high as 270 nm/h. This intriguing result is attributed to the unique characteristics of the sputtering system which provides more energetic species at the substrate.
This paper investigates the interfacial structure in hot-wall CVD TiN/kappa-Al2O3 multilayer coatings using both HREM and DFT modeling. Two multilayers with different thicknesses of the TiN layers ...(50 and 600nm) separating the kappa-Al2O3 layers are analyzed. The general microstructure of the two multilayers is relatively similar. The TiN layer in the thicker TiN/kappa-Al2O3 coating is thick enough to be several TiN grains high. This means that epitaxial columns, which are often found in the thinner TiN/kappa-Al2O3 coatings, are not present. However, the orientation relationships at the TiN/kappa-Al2O3 interfaces are the same in both multilayers. The HREM investigations show that kappa-Al2O3 (001) planes can grow directly on flat (111) TiN faces, without any other phases or detectable amounts of impurities, such as sulphur, present. Where the TiN layers are more curved, gamma-Al2O3 can be grown, at least partly stabilized by the cube-on-cube orientation relationship between gamma-Al2O3 and the underlying TiN. The DFT calculations show very similar adsorption strengths for an O monolayer positioned on Ti-terminated TiC(111) and TiN(111) surfaces, with preferred adsorption in the fcc site. O adsorption on N-terminated TiN(111) is much weaker, with preferred adsorption in the top site. Calculated elastic-energy contributions yield a higher stability for kappa-Al2O3 on TiN(111) than on TiC(111) and a higher stability for kappa-Al2O3 than for alpha-Al2O3 on both TiC and TiN. This indicates that the observed higher stability of kappa-Al2O3 on TiC(111) than on TiN(111) is not due to the lattice mismatch, while the preferred epitaxial growth of kappa-Al2O3 over alpha-Al2O3 can be partly attributed to the mismatch.
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