| 1. |
- Kapilashrami, E., et al.
(författare)
-
Studies of the wetting characteristics of liquid iron on dense alumina by the X-ray sessile drop technique
- 2003
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 34:2, s. 193-199
-
Tidskriftsartikel (refereegranskat)abstract
- In the present work, the reaction between a molten iron drop and dense alumina was studied using the X-ray sessile-drop method under different oxygen partial pressures in the gas atmosphere. The changes in contact angles between the iron drop and the alumina substrate were followed as functions of temperature and varying partial pressures of oxygen in the temperature range 1823 to 1873 K both in static and dynamic modes. The results of the contact angle measurements with pure iron in contact with dense alumina in extremely well-purified argon as well as under different oxygen partial pressures in the gas atmosphere showed good agreement with earlier measurements reported in the literature. In the dynamic mode, when argon was replaced by a CO-CO2-Ar mixture with a well-defined PO, in the gas, the contact angle showed an initial decrease followed by a period of nearly constant contact angle. At the end of this period, the length of which was a function of the P-O2 imposed, a further steep decrease in the contact angle was noticed. An intermediate layer of FeAl2O4 was detected in the scanning electron microscope (SEM) analysis of the reacted substrates. An interesting observation in the present experiments is that the iron drop moved away from the site of the reaction once the product layer covered the interface. The results are analyzed on the basis of the various forces acting on the drop.
|
|
| 2. |
- Kapilashrami, F., et al.
(författare)
-
Investigation of the reactions between oxygen-containing iron and SiO2 substrate by X-ray sessile-drop technique
- 2003
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - 1073-5615 .- 1543-1916. ; 34:5, s. 647-652
-
Tidskriftsartikel (refereegranskat)abstract
- The X-ray sessile-drop method was employed in the present investigation to measure the contact angle between liquid iron and a silica substrate under argon as well as CO-CO2-Ar atmospheres in the temperature range of 1823 to 1833 K. In the latter case, the measurements were carried out in the dynamic mode, and the contact-angle changes were followed as a function of time as oxygen in the gas dissolved in the metal. The static measurements in argon showed that the contact angles in the experimental temperature range are of the order of 135 deg, similar to those observed in the case of the alumina substrate. In the dynamic mode, oxygen partial pressures varying between 9.9.10(-4) and 1.5.10(-2) Pa were imposed on the system. In these experiments, the contact angle decreased in two stages, with an intermediate steady-state region. Fayalite slag, formed due to the reaction between the metallic phase and the substrate, was found to accumulate around the drop. The results are of relevance in understanding the mechanism of corrosion of silica-containing refractories by molten iron.
|
|
| 3. |
- Arvanitidis, I., et al.
(författare)
-
Intrinsic reduction kinetics of cobalt- and nickel-titanates by hydrogen
- 2000
-
Ingår i: Journal of Materials Research. - 0884-2914 .- 2044-5326. ; 15:2, s. 338-346
-
Tidskriftsartikel (refereegranskat)abstract
- The isothermal reduction of synthetic CoTiO3 and NiTiO3 in hydrogen (1 atm) was investigated using thermogravimetric analysis technique in the temperature range, 928-1287 K (CoTiO3) and 884-1387 K (NiTiO3). Shallow beds of fine titanate powders were reduced by hydrogen at a high flow rate. Quenched samples were analyzed by scanning electron microscopy. The rates of the reaction of the titanates with H-2 were very fast during the reduction of Co2+, Ni2+, or Fe2+ ions into metals. The reduction of the remaining titanium oxide was very slow. The activation energy for the reduction of CoTiO3 by hydrogen to Co and TiO2 was evaluated to be 151 +/- 1 kJ/mol, and the activation energy for the reduction of NiTiO3 by hydrogen to Ni and TiO2 was evaluated to be 153 +/- 1 kJ/mol. The study was complemented by hydrogen reduction of synthetic TiO2 (rutile). The results were also compared with the hydrogen reduction of FeTiO3.
|
|
| 4. |
- Kapilashrami, A, et al.
(författare)
-
Drying of oil-in-water emulsions on hydrophobic and hydrophilic substrates
- 2004
-
Ingår i: Colloids and Surfaces A. - 0927-7757 .- 1873-4359. ; 233, s. 155-161
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the effect of the hydrophobic/hydrophilic character of the substrates on the drying behaviour of dilute silicone oil-in-water (o/w) emulsions by light microscopy and ellipsometry. The poly(dimethylsiloxane) (PDMS) emulsion droplets, which are stabilised by a triblock PEO/PPO/PEO copolymer, form a close-packed structure containing domains of hexagonally packed droplets on the hydrophilic substrate. We find that the hydrophilic substrate does not destabilise the emulsion droplets; the close-packed structures are very stable and coalesce very slowly only when most of the water has evaporated. This is supported by ellipsometry measurements, which showed that the emulsion droplets do not adsorb to the hydrophilic substrate. The hydrophobic substrate, on the other hand, destabilises the emulsion and we observed a significant increase in the coalescence rate. Ellipsometry measurements suggest that destabilisation is promoted by the strong interaction between the emulsion droplets and the hydrophobic substrate. We also find that the emulsion undergoes dewetting followed by a release of oil and rewetting of the substrate when the o/w emulsion film reaches a critical thickness on the hydrophobic substrate
|
|
| 5. |
|
|
| 6. |
- Kapilashrami, A, et al.
(författare)
-
Ellipsometric studies of nonionic block copolymers adsorbed at the solid/water and oil/water interfaces
- 2003
-
Ingår i: Colloids ad Surfaces a-Physicochemical and Engineering Aspects. ; 225:1-3, s. 181-192
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the interfacial behaviour of a series of nonionic diblock copolymers at solid hydrophobic and hydrophilic surfaces/water and silicone oil/water interfaces, studied by ellipsometry. The polymers consist of a hydrophobic C-18 chain linked to a hydrophilic poly(ethylene oxide) (PEO), block varying from 50 to 250 U. The adsorption of these copolymers at low bulk concentrations was found to be dominated by the PEO block at all interfaces. At higher concentration the copolymer forms surface aggregates at the silica surface whereas we observe a gradual increase in the adsorbed layer thickness with increased surface excess at the solid hydrophobic surface, indicating a transition from a flat conformation to brush-like layer structure. The results indicate a similar evolution in adsorbed amount with concentration at the silicone oil/water interface as at the hydrophobic silica surface. The influence of the rheological proper ies of the interface on the adsorption of the diblock copolymer was investigated by comparing results from two silicon oils with different viscosities. The copolymers were found to have stronger affinity to a low viscosity (990 mPa s) silicone oil than to a higher viscosity (12 800 mPa s) silicone oil and the hydrophobised silica surface. At the silicone oil/water interface the adsorption of a commercial nonionic triblock copolymer was furthermore investigated and compared with the diblock copolymers. (C) 2003 Elsevier B.V. All rights reserved.
|
|
| 7. |
|
|
| 8. |
- Kapilashrami, A., et al.
(författare)
-
Ellipsometric studies of nonionic copolymers adsorbed at the solid/water and oil/water interfaces
- 2003
-
Ingår i: Colloids and Surfaces A. - 0927-7757 .- 1873-4359. ; 225, s. 181-192
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the interfacial behaviour of a series of nonionic diblock copolymers at solid hydrophobic and hydrophilic surfaces/water and silicone oil/water interfaces, studied by ellipsometry. The polymers consist of a hydrophobic C18 chain linked to a hydrophilic poly(ethylene oxide) (PEO), block varying from 50 to 250 U. The adsorption of these copolymers at low bulk concentrations was found to be dominated by the PEO block at all interfaces. At higher concentration the copolymer forms surface aggregates at the silica surface whereas we observe a gradual increase in the adsorbed layer thickness with increased surface excess at the solid hydrophobic surface, indicating a transition from a flat conformation to brush-like layer structure. The results indicate a similar evolution in adsorbed amount with concentration at the silicone oil/water interface as at the hydrophobic silica surface. The influence of the rheological properties of the interface on the adsorption of the diblock copolymer was investigated by comparing results from two silicon oils with different viscosities. The copolymers were found to have stronger affinity to a low viscosity (990 mPa s) silicone oil than to a higher viscosity (12800 mPa s) silicone oil and the hydrophobised silica surface. At the silicone oil/water interface the adsorption of a commercial nonionic triblock copolymer was furthermore investigated and compared with the diblock copolymers
|
|
| 9. |
- Kapilashrami, E., et al.
(författare)
-
Reactions Between Refractories and Molten Iron in Steelmaking Processes
- 2001
-
Ingår i: 59th Electric Furnace Conference and 19th Process Technology Conference Proceedings. - : Iron and Steel Society. ; , s. 287-298
-
Konferensbidrag (refereegranskat)abstract
- The reactions between dense refractories and molten iron containing oxygen were examined by finger experiments as well as by X-ray sessile-drop method. The finger experiments with alumina revealed the formation of a FeA12O4 layer, beyond which, non-wetting conditions prevailed. The corrosion was more significant when dispersed oxide layer was present. In the case of silica rod, the rod was deformed. In the experiments with mullite, the rods became extremely brittle. In contact angle measurements with alumina substrate, the time taken to reach the equilibrium value was a function of the oxygen partial pressure of the gas phase. After the attainment of the equilibrium, the drop was found to move due to imbalance in the forces acting on the drop. The magnitude of the force was roughly estimated. Contact angle measurements with silica substrate revealed the formation of a circular track along the periphery of the drop. This is attributed to the loss of SiO along this boundary and consequent increase in the corrosion of silica. Preliminary experiments with mullite substrates indicate that the behaviour is somewhat similar to that of alumina.
|
|
