The effect of pre-surface treatment and crystal orientation on microstructural changes in the aluminized 4(th), generation Ni-based single-crystal superalloy TMS-138 was investigated. The substrate superalloy was cut along the {100} and {110} planes on which three kinds of surface finishing, such as grit-blasting, mechanically polishing and electro-polishing were conducted prior to the conventional high-activity aluminizing process. A thermal cycling test at 1373 K revealed that heavy deformation of substrate surface by grit blasting gave rise to the formation of a secondary reaction zone (SRZ) in the vicinity of interdiffusion zone/substrate interfaces. While when the surfaces were finished by electro-polishing, voids were formed in the vicinity of interdiffusion zone/substrate interfaces. It is also found that accelerated formation of SRZ and voids was observed along < 110 > directions rather than < 100 > directions during the thermal cycling test. The difference in morphological changes of substrates can be related to the residual stress introduced by the surface finishing.

Oxidation resistance of electroplated Pt and Pt-Ir alloy coatings followed by simple annealing heat treatments was investigated. The so-called 2nd generation Ni-based single crystal superalloy TMS-82 + and 4th generation TMS-138 were used as substrate materials. The cyclic oxidation tests and corresponding surface observations suggested the comparable oxidation resistance of Pt-coated TMS-82 + and Pt-Ir-coated TMS-138. However, cross-sectional microstructural analysis revealed that Pt-coated TMS-82 + exhibited the accelerated formation of voids, indicating the beneficial effect of Ir addition in terms of suppressed void formation. This study also revealed the importance of cross sectional analysis for thoroughly evaluating specimens subjected to the cyclic oxidation tests, and confirmed that oxidation resistance of the electroplated coatings was dependent on the quality of films deposited, which was drastically affected by the substrate surface finishing and substrate composition.

A novel thiocyanate-free cyclometalleted ruthenium sensitizer for solar cells is designed and developed. Upon anchoring to nanocrystalline TiO(2) films, it exhibits a remarkable incident monochromatic photon-to-current conversion efficiency of 83%. The solar cell employing a liquid-based electrolyte exhibits a short circuit photocurrent density of 17 mA/cm(2), an open circuit voltage of 800 mV, and a fill factor of 0.74, corresponding to an overall conversion efficiency of 10.1% at standard AM 1.5 sunlight. To understand the structural, electronic, and optical properties of the cyclometalleted ruthenium sensitizer, we have investigated using density functional theory (DFT) and time-dependent DFT (TDDFT). Our results show the HOMO is located mostly on ruthenium and cyclometalated ligand, while the LUMO is on 4-carboxylic acid-4'-carboxylate-2,2'-bipyridine. Molecular orbitals analysis confirmed the experimental assignment of redox potentials, and TDDFT calculations allowed assignment of the visible absorption bands. The present findings provide new design criteria for the next generation of ruthenium sensitizers and help foster widespread interest in the engineering of new sensitizers that interact effectively with the I(-)/I(3)(-) redox couple.

Hot-dip zinc-coated steel sheets are used as an outdoor industrial material, but they corrode because of acid rain.In this study, the corrosion process of hot-dip zinc-coated steel sheets in simulated acid rain solution with in-situ Raman spectroscopy has been studied.The current density of specimen decreased with constant potential holding at −0.6V vs. Ag/AgCl in simulated acid rain solution. And, the main peak, ZnSO4·7H2O was detected with in-situ Raman spectroscopy at the time of decreasing current density. Therefore, it is considered to be the case that the following equation describes the reactions that occurred.Zn2++SO42−+7H2O→ZnSO4·7H2O.The current density was decreased by ZnSO4·7H2O because the growth of ZnSO4·7H2O covered surface area of the specimen.Hot-dip zinc-coated steel sheets showed an anticorrosive effect as a result of the hot-dip zinc-coating layer being dissolved by a sacrificial anode function, and ZnSO4·7H2O was formed in the simulated acid rain solution.

A second-generation Co-free Ni base single crystal superalloy, TMS-82C (Ni-0Co-4.9Cr-1.0Mo-8.7W-5.3Al-6.0Ta-2.4Re-0.1Hf, in mass%) was derived from its base alloy, TMS-82+ (Ni-7.8Co-4.9Cr-1.9Mo-8.7W-5.3Al-6.0Ta-2.4Re-0.1Hf, in mass%), which had been successfully engine tested. The absent of Co can eliminate the product of isotope Co-60 from radioactive decay, and it can improve the maintainability of the gas turbine engine. However, the removal of Co had decreased the creep strength of TMS-82C. To further improve its creep strength, five additional alloys were designed with the addition of 0.5 mass% Mo, W, Ti, Ta and Re to TMS-82C, respectively. Results indicated that creep properties of all five alloys performed better than that of TMS-82C under 900 degrees C/392 MPa and 1000 degrees C/245 MPa conditions. W-bearing alloy exhibits similar creep property comparing to that of TMS-82+ under the 900 degrees C/392 MPa condition.

The isoelectric points (IEPs) of two zwitterions, glycine and both-terminals-terminated poly(ethylene glycol) (NH(2)-PEG-COOH), were determined from the titration curves, and the thicknesses of zwitterion layers immobilized on titanium (Ti) with immersion and electrodeposition at various pH based on IEPs were evaluated with ellipsometry to investigate the effect of pH and the immobilization technique on the interactions between the zwitterions and the Ti surface. From the titration curves, pK(1), pK(2), and the IEP of glycine were determined as 2.8, 8.9, and 5.9, respectively, and pK(1), pK(2), and the IEP of NH(2)-PEG-COOH were determined as 2.1, 11.7, and 6.9, respectively. At a certain specific pH, (+)H(3)N-CH(2)-COO(-) or (+)H(3)N-PEG-COO(-) was formed by hydrolysis of glycine or NH(2)-PEG-COOH. In addition, the Ti surface was negatively charged at this pH. As a result, for immersion, the electrostatic reactivity between terminal groups of zwitterions and hydroxyl groups on the Ti surface was the highest and the thickness of the immobilized layer was significantly the largest at pH 12. For electrodeposition, glycine, with its lower molecular weight, was more easily attracted to the Ti surface than NH(2)-PEG-COOH, which has a higher molecular weight, while the thickness of the immobilized layer was the greatest at pH 12 in both zwitterions.

The concentrations of hydroxyl groups located inside and on the surface oxide films of a commercially pure titanium, cp-Ti, a type 316L austenitic stainless steel, SS, and a cobalt-chromium-molybdenum alloy, Co-Cr-Mo, were evaluated using X-ray photoelectron spectroscopy, XPS, and a zinc-complex substitution technique. As a result, the concentrations of the hydroxyl groups detected by the zinc-complex substitution technique, defined as active hydroxyl groups, were much larger than those detected by other conventional techniques. The concentration of the active hydroxyl groups on Co-Cr-Mo was significantly larger than those on cp-Ti and SS. Poly(ethylene glycol), PEG, is a biofunctional molecule that inhibits the adsorption of proteins. The immobilization of PEG to metal surfaces by electrodeposition or immersion is an important technique to biofunctionalize the metals. The amounts of the PEG layer immobilized on the metals were governed by the concentrations of the active hydroxyl groups on each surface oxide in the case of electrodeposition; it was governed by the relative permittivity of the surface oxide in the case of immersion. The estimation of active hydroxyl groups on the surface oxide film with the zinc-complex substitution technique is useful for the elucidation of reactions between metal substrates and immobilized molecules.

In many biomedical devices such as catheters and diagnostic sensors, blood compatibility is required. The best way to control this property is to prevent or drastically reduce the adsorption of proteins. Poly(ethylene glycol) terminated amine at both terminals, NH2-PEG-NH2, is immobilized on a commercially pure titanium, a 316L austenitic stainless steel, and a cobalt-chromium-molybdenum alloy with immersion or electrodeposition. Chemical bonding states at the interface and orientation of PEG molecules were characterized using X-ray photoelectron spectroscopy, glow discharge optical emission spectroscopy, and Fourie-transformed infrared spectrometer with a reflection absorption spectrometer. As a result, NH2-PEG-NH2 was immobilized onto metal surface as a U-shape mainly with stable NHO bonding in electrodeposition. In the case of electrodepostion, the concentration of active surface hydroxyl groups on surface oxide film played an important role in the immobilization.

Electrochemical treatments are expected to be effective for the coating of calcium phosphate ceramics to a titanium substrate. In the present study, two types of chronoamperometry with a step potential and a cyclic wave potential at low voltage (up to 2.0 V) and low current density were performed in Hanks' solution to modify the surface characteristics of titanium. Titanium oxide film formed by self-passivation, that formed as reconstructed film during electrochemical treatments, and a calcium phosphate layer precipitated through treatments were characterised by X-ray photoelectron spectroscopy. The thickness and compositions of the surface films and layers were quantified from the XPS results. Calcium phosphate formation during immersion in Hanks' solution for 1.0 Ms was evaluated by scanning electron microscopy with energy-dispersive X-ray spectrometry. The results confirmed that the electrolytic treatments in this study were effective to accelerate calcium phosphate formation on titanium in Hanks' solution in spite of their lower voltage than conventional methods. The results also suggested that the hydroxyl group in the surface oxide film might contribute to the formation of calcium phosphate. This technique is a promising process for the treatment of thin titanium materials.

A high molar extinction coefficient charge transfer sensitizer tetrabutylammonium [Ru(4,-carboxylic acid-4'-carboxylate-2,2'-bipyridine)(4,4'di-(2-(3,6-dimethoxyphenyl)ethenyl)-2,2'-bipyridine)(NCS)(2)], is developed which upon anchoring onto nanocrystalline TiO2 films exhibit superior power conversion efficiency compared to the standard sensitizer bistetrabutylammonium cis-dithiocyanatobis(4,4'-dicarboxylic acid-2,2'bipyridine)ruthenium(II) (N719). The new sensitizer anchored TiO2 films harvest visible light very efficiently over a large spectral range and produce a short-circuit photocurrent density of 18.84 mA/cm(2), open-circuit voltage 783 mV and fill factor 0.73, resulting remarkable solar-to-electric energy conversion efficiency (eta) 10.82, under Air Mass (AM) 1.5 sunlight. The Time Dependent Density Functional Theory (TDDFT) excited state calculations of the new sensitizer show that the first three HOMOs have ruthenium t(2g) character with sizable contribution coming from the NCS ligands and the pi-bonding orbitals of the 4,4'-di-(2-(3,6-dimethoxyphenyl)ethenyl)-2,2'-bipyridine. The LUMO is a pi* orbital localized on the 4,4'-dicarboxylic acid-2,2'-bipyridine ligand. (c) 2006 Elsevier B.V. All rights reserved.

In the present study, the effect of Hf addition on oxidation kinetics of Pt-Ir modified aluminide coatings was investigated. Pt-15 at%Ir and Pt- 15 at%Ir with trace amount of Hf films with 7 similar to 8 mu m thick were deposited on a Ni-based single crystal superalloy TMS-82+ using magnetron sputtering, followed by a diffusion treatment and conventional Al pack cementation. While there were no significant microstructual differences observed in as aluminized specimens, cyclic oxidation test at 1423 K revealed clear advantages of Hf addition. Hf containing coatings showed smaller mass change with retarded surface rumpling during cyclic oxidation test. These results confirmed the beneficial effects of Hf addition reported for other alloy systems such as Pt modified gamma-gamma' coatings and Pt modified aluminide coatings.

The immobilization of poly(ethylene glycol), PEG, to a solid surface is useful to functionalize the surface, e.g., to prevent the adsorption of proteins. No successful one-stage technique for the immobilization of PEG to base metals has ever been developed. In this study, PEG in which both terminals or one terminal had been modified with amine bases was immobilized onto a titanium surface using electrodeposition. PEG was dissolved in a NaCl solution, and electrodeposition was carried out at 3 10 K with -5 V for 300 min. The thickness of the deposited PEG layer was evaluated using ellipsometry, and the bonding manner of PEG to the titanium surface was characterized using X-ray photoelectron spectroscopy after electrodeposition. The results indicated that a certain amount of PEG was adsorbed on titanium through both electrodeposition and immersion when PEG was terminated by amine. However, terminated amines existed at the surface of titanium and were combined with titanium oxide as N-HO by clectrodeposition, while amines randomly existed in the molecule and showed an ionic bond with titanium oxide by immersion. The electrodeposition of PEG was effective for the inhibition of albumin adsorption. This process is useful for materials that have electroconductivity and a complex morphology. (c) 2006 Elsevier B.V. All rights reserved.

The alloying effect of Cobalt (Co) to microstructural parameters and mechanical properties, such as partitioning ratios of alloying elements and creep strength, of Re-bearing Ni-base single crystal superalloys have been investigated. The second generation single crystal superalloys, TMS-82 +, Ni-7.8Co-4.9Cr-1.9Mo-8.7W-5.3AI-6.0Ta-2.4Re-0.1Hf, in mass% (8Co) was compared to a Co-free (0Co) and 15 mass% Co (15Co) alloy which had the same chemical composition as TMS-82 + except that Co was changed.It was shown that the partitioning ratios of alloying elements tend to k(= X-y/K-y') = 1, as the content of Co was increased.Furthermore, it was found that there was suitable content of Co for the creep strength under various temperature-stress conditions.

A post service examination of a turbine blade from a civil aeroengine has been carried out to ascertain the degree of microstructural coarsening and the distribution of crack damage induced during service. This was with the purpose to elucidate their correlation with the actual operating conditions. Samples were sectioned from different parts of the turbine blade for detailed examination by optical microscope and scanning electron microscope. The average length of cracks was used as one of the parameters to quantitatively illustrate the distribution of cracks on the turbine blade. Experimental results suggested that cracks were mainly concentrated on certain area of the pressure side. Leading edge of the suction side of the turbine blade consisted of mostly coarsened microstructure due to higher temperature exposure. In conclusions, there was no clear correlation between the crack damage distribution and the degree of microstructure evolution.

The alloying effect of Cobalt (Co) to microstructural parameters and mechanical properties, such as partitioning ratios of alloying elements and creep strength, of Re-bearing Ni-base single crystal superalloys have been investigated. The second generation single crystal superalloys, TMS-82+, Ni-7.8Co-4.9Cr-1.9Mo-8.7W-5.3Al-6.0Ta-2.4Re-0.1Hf, in mass% (8Co) was compared to a Co-free (0Co) and 15 mass% Co (15Co) alloy which had the same chemical composition as TMS-82+ except that Co was changed. It was shown that the partitioning ratios of alloying elements tend to k(=Xγ/Xγ′)=1, as the content of Co was increased. Furthermore, it was found that there was suitable content of Co for the creep strength under various temperature-stress conditions.

The change in the chemical composition of the corrosion product on steel can be identified with in-situ Raman spectroscopy while the steel is polarized in a solution. In this paper, we tried to clarify the corrosion process of the steel for gas pipelines.γ-FeOOH and Fe3O4 were detected with the Raman spectra measured in the 100mg/dm3Cl− solution holding at −0.3V vs.Ag/AgCl. The coexistence of γ-FeOOH and Fe3O4 was confirmed from the Raman spectrum measured in the corrosion test. It is considered that Fe3O4 was formed via the reduction as follows:Fe2+ + 8FeOOH + 2e− → 3Fe3O4 + 4H2OIn the early stage of corrosion, γ-FeOOH was detected from Raman spectra measured in the 1000mg/dm3HCO3− solution holding at 0.5V vs. Ag/AgCl. However, the peak of γ-FeOOH disappeared from the Raman spectra measured in the corrosion test after the middle stage of corrosion. It is conceivable that the γ-FeOOH disappeared or that the surface was covered with corrosion products inert to Raman measurement.We were able to investigate the corrosion process of the steel for gas pipelines with in-situ Raman spectroscopy while it was polarized in a solution.

Effect of Cobalt on micro-structural parameters, such as the lattice misfit and partitioning behaviors of alloying elements, of Re-bearing Ni-base single crystal superalloys have been investigated. The second-generation single crystal superalloys, TMS-82 + (Ni-7.8Co-4.9Cr-1.9Mo-8.7W-5.3Al-6.0Ta-2.4Re-0.1Hf, in mass%), was compared to a Co-free (0Co) alloy which had the same chemical composition as TMS-82+ except that Co was removed.The lattice misfit of 0Co alloy was found to be more negative value than that of TMS-82 + at any temperature. Additionally, when 0Co alloy was equilibrated at 1100 degrees C, Cr, Mo and W partitioned more into the gamma matrix; in contrast, Al and Ti partitioned into the gamma' precipitates. Increase in partitioning of Cr, Mo and W to the gamma phase resulted in an increase in the lattice parameter of gamma phase. Thus, lattice misfit of 0Co tend to more negative value than that of TMS-82 +.