Kiyoshi Kusabiraki

Infrared and raman spectra of vitreous silica and sodium silicates containing titanium

Infrared and Raman spectra of vitreous silica and sodium silicates containing various concentrations of Ti were studied. Vibrational bands associated with the titanium groups, TiO4 tetrahedra and TiO6 octahedra, were identified. From structural symmetry and selection rule arguments, the TiO2 tetrahedra were found to exist in vitreous silica and the TiO2 tetrahedra and TiO6 octahedra to coexist in vitreous sodium silicates as a titanium group. With increasing titanium content in TiO2-SiO2 glasses, the concentration of TiO4 tetrahedra increased. With increasing sodium content in TiO2-Na2O-SiO2 glasses, the concentration of the TiO4 tetrahedra decreased and that of the TiO6 octahedra increased.

Infrared spectra of vitreous silica and sodium silicates containing titanium

Abstract Infrared spectra of vitreous silica and sodium silicates containing various concentrations of Ti were studied. Vibrational bands associated with the titanium groups, TiO4 tetrahedra and TiO6 octahedra, were identified. From structural symmetry and selection rule arguments, the TiO4 tetrahedra were found to exist in vitreous silica and the TiO4 tetrahedra and TiO6 octahedra to coexist in vitreous sodium silicates as a titanium group. With increasing titanium content in TiO2SiO2 glasses, the concentration of TiO4 tetrahedra increased. With increasing sodium content in TiO2Na2OSiO2 glasses, the concentration of the TiO4 tetrahedra decreased and that of the TiO6 octahedra increased.

High-temperature oxidation of pure titanium in CO2 and Ar-10%CO2 atmospheres

The oxidation behavior of pure titanium has been investigated in the temperature range of 1000 K to 1300 K in CO2 or Ar-10%CO2. Optical microscopy, electron probe microanalyses, and X-ray measurements on the oxide scales formed during oxidation indicate that their structures are nearly independent of temperature and the corrosion atmosphere. The scales consisted of two layers, an external one and an internal one, having a rutile (TiO2) structure. The parabolic rate law was confirmed for growth of the external scale and the permeation depth of oxygen in titanium with apparent activation energies of 266 and 226 kJ/mol, respectively. The rate-determining diffusion species in the oxidation processes are discussed.

High-Temperature Scale Formation of Fe–36% Ni Bicrystals in Air

Fe–36% Ni bicrystals were oxidized at temperatures from 1100 to 1250 K in air, both under and without tensile stress. The scales were divided into three categories: external scales, intragranular subscales, and intergranular subscales. A linear relationship exists beween the thickness of scales and subscales and the square root of oxidation time. Tensile stress significantly accelerates intergranular oxidation, but has essentially no influence on either the formation of intragranular subscales or that of external scales. The external scales are composed of α-Fe2O3 and Fe3O4 after a longer oxidation time. The intergranular and intragranular subscales consist of Fe3O4 and FeO particles and an Ni-enriched matrix. Cellular or dendritic oxide nodules sometimes exist in the intragranular subscales, causing their frontier interfaces to significantly undulate.

Oxidation behavior of an Fe-38Ni-13Co-4.7Nb-1.5Ti-0.4Si superalloy at high temperature in Ar-H2O atmospheres

The oxidation of an Fe-38Ni-13Co-4.7Nb-1.5Ti-0.4Si superalloy (Incoloy 909 type alloy), was investigated at temperatures between 1000 K and 1400 K in Ar-(1, 10%)H20 atmosphere using metallographic, electron probe microanalysis, and X-ray diffraction techniques. The oxide scales consist of an external scale and an internal scale which has an intergranular scale (above 1200 K) and an intergranular scale. The oxide phases in each scale are identified asα-Fe2,O3 (below 1200 K) or FeO (above 1300 K) and CoO · Fe2O3 and FeO · Nb2O5, respectively. The morphologies, the oxide phases and the oxidation rates do not depend on the partial pressure of H2O in the range between one and ten percent in Ar gas. The rate constants for the intergranular-scale formation in this alloy are about one-tenth as large as those in Fe-36%Ni alloy reported previously. At all the temperatures the scales grow according to a parabolic rate law and the apparent activation energies for the processes are estimated.