Showing papers on "Chemical state published in 1980"

Chemical state of ion‐implanted nitrogen in Fe18Cr8Ni steel

Abstract: Auger electron spectroscopy (AES) and x‐ray photoelectron spectroscopy (XPS), in conjunction with ion milling, were used to determine the chemical state of nitrogen implanted at relatively high doses (1016–1018/cm2) into type‐304 steel. Nitrogen atoms were bonded in the nitrided state, at all doses, according to both AES and XPS. As the nitrogen concentration increased, the lineshape of the Cr MVV Auger spectra evolved from that of metallic Cr to Cr nitride; at highest doses, the Fe MVV lineshape could be identified as Fe nitride. Auger and XPS spectra of implanted 304 and thermally nitrided 304 were virtually identical at comparable nitrogen concentrations. The Cr(2p3/2) binding energies of both, however, were about 1 eV lower than found in Cr nitride but 0.5 eV higher than in metallic Cr.

Electrochemical process and apparatus to control the chemical state of a material

Abstract: Electrochemical process and apparatus to control the chemical state of a material, that is, to cause said material to retain desired characteristics in an environment that normally would cause a change in those characteristics or to cause a material that has deteriorated from a desired chemical state to revert to the desired state.

Molecular units in ionic crystals via abstraction of matrix atoms by implanted metal ions

Abstract: Heavy metal ions (*M = *Re, *Os, *Ir, *Pt) were implanted into halogen containing ionic crystals KX and K2MX6 (X = CI, Br; M = Sn, Re, Os, Ir, Pt) with energies ranging from 40 to 400 keV. They were generated via ion acceleration or recoil processes as a consequence of fast neutron capture. Optical spectroscopy and radiochemical methods were applied to analyse the chemical state of the projectiles after thermalization. Depending on the geometrical arrangement of the halogens in the different target materials up to 84% of the implanted ions were recovered in form of octahedral complexes *MX2− 6. In K2MX6 the amount of halogen ligand abstraction by *M showed a linear dependence on the relative strength of the broken M–X to that of the new *M–X bond. The beam experiments combined with low temperature optical spectroscopy proved a complex formation even for implantations at 5 K. The experiments demonstrated that implanted ions may undergo chemical reactions which are both spontaneous and selective.

Application of secondary ion mass spectrometry to the study of carburization of superalloy

Abstract: Secondary ion analysis was applied to the study of the carburization behavior of a superalloy by using the ion microprobe mass analyzer (IMMA). The corrosion test of Inconel 617 was carried out for 1000 h under an environment of methane-doped impure helium gas at 1000 °C. 20 KeV O 2 + and N 2 + were used as primary ions. IMMA showed that C, O, Al, Si, Ti and Mo were enriched near the surface. The chemical states of the scale and the precipitates were determined from chemical shifts of X-ray emission spectra. It was confirmed that silicon carbide and molybdenum carbide were coprecipitated in the same areas: in the scale, in the matrix at a depth of 10 μm to about 40 μm below the scale, and at grain boundaries. Aluminum and titanium were found to exist as oxides near the surface. It was shown that carburization was limited near the surface, and the grain boundary precipitation of carbides in the bulk was due to aging at high temperatures. The concentration profiles of silicon and molybdenum in (Si,Mo)-carbide were obtained by using standard carbide samples assuming that the concentration of implanted oxygen atoms of the specimen was equal to that of the standard sample. The ratio, (Si)/(Mo), was increased from about 0.1 in bulk to 2.4 ∼ 3.8 near the surface. This result indicates that silicon is carburized much more preferentially than molybdenum.

The Role of Chemical and Structural Changes on the Surface in Deactivation of Chromia-Alumina Catalysts in Dehydrogenation of Paraffinic Hydrocarbons

Abstract: The chemical and structural changes on the surface of chromia-alumina catalysts, operated for long time in dehydrogenation of paraffins hydrocarbons have been investigated. In reduced media at 500°C a gradual decrease of the number of active site associated with Cr 2+ ions was established. A loss of surface area of chromia may be considered as the main reason of this phenomenon. The process was especially pronounced at 700°C. In oxidizing media at 500°C no change in the surface area and chemical state of the chromia surface were observed, whereas at 700°C the improvement in the dispersity of chromium compounds were found. The processes of reversible, partially reversible and complete deactivation of chromia-alumina catalyst were considered.

Adhesive-Adherend Bond Joint Characterization by Auger Electron Spectroscopy and Photoelectron Spectroscopy

Abstract: Chemical and physical information about intact adhesive bond joints is usually inferred from data obtained from each isolated component (adhesive and adherend) prior to bonding or after bond failure. A technique is presented in which the chemical state as well as the elemental distribution can be obtained from intact bond joints using conventional surface characterization techniques such as Auger electron and photoelectron spectroscopies. The technique involves the use of thin film adherend adhesively bonded structures. The thin film adherends (5×10-7m) are prepared by vacuum deposition, which, after various treatments and subsequent bonding, can be ion beam etched away until the adherend-adhesive interface is reached for characterization. A number of bonding parameters have been investigated using this technique, including effects of adherend surface treatments (i.e. anodization, protection primers, corrosion inhibitors) and cure conditions (i.e. time, temperature and pressure).

Surface Characterization of Chemically Treated Titanium and Titanium Alloys.

Abstract: : A thorough knowledge of adherend surfaces is necessary to adequately evaluate adhesive bond joint performance. Auger Electron Spectroscopy (AES), Secondary Ion Mass Spectroscopy (SIMS), SCanning Electron Microscopy (SEM), and X-Ray Photoelectron Spectroscopy (XPS) were used to characterize the surface topography (roughness, selective etching) composition (relative concentration of alloyed element on surface, contaminated overlayer...) chemical state (titanium or alloy surface oxide, oxy-fluoride...) and oxide thickness of different chemically treated titanium alloys. Seven alloys and the metal were conditioned with seven different chemical treatments. Data from each treated alloy has been compiled to show physical and chemical effects of each treatment on each alloy. (Author)

Utility of the MÖssbauer Effect in the Assessment of Chemical Transformations in Unsupported Catalyst Systems as a Function of the Metal Salt

Abstract: This paper is presented to illustrate the utility of Fe-57 Mossbauer spectroscopy in the physical and chemical characterization of metallic catalysts as a function of preparation and subsequent treatment. The particular example chosen for investigation is the Ru-Fe bimetallic salt system which has significant potential as an active Fischer-Tropsch catalyst. The interpretation of the resulting Mossbauer parameters provides information on the chemical state of the metals as a function of treatment and initial salt properties and allows certain deductions to be made about particle size and solid state properties.

Electronic Densities in Molecules, Chemical Bonds and Chemical Reactions

Abstract: This paper is mainly devoted to the discussion of a central problem in molecular physics and chemistry: the relations between electronic distribution, chemical bonds and chemical reactions.