V. T. Burtsev

Interaction of refractory compound nanoparticles with a surfactant in a nickel melt: I. Heterophase interaction

The interaction of nanoparticles of refractory compounds Al2O3 and TiN with a model nickel melt containing a surfactant (sulfur) is studied. The choice of the type of nanoparticles for their interaction with the metal at 1873 K and possible versions of sulfur removal from the melt in the form of S2, SO2, and H2S are grounded. A technique for the preparation of an Ni-Al2O3 (TiN) compact and its introduction into the melt is developed. The character of the change in the sulfur content in the metal after introducing the compact is determined, and the effect of the isothermal holding time of the melt on sulfur removal is revealed.

Interaction of exogenous refractory nanophases with tin dissolved in liquid iron

The interaction of refractory phase nanoparticles (Al2O3 and TiN as an example) 30–100 nm in size with a surface-active substance in the Fe-Sn melt and the subsequent removal of nanoparticle + Sn ensembles to the M/ceramics and M/gas interfaces is studied. A technique for choosing nanoparticles is developed and grounded, and a technique for the introduction of nanoparticles in the melt in the form of nanoparticles-Fe composite material is developed. The dependences of the degree of tin removal during heterophase interaction on the time of holding of nanoparticles in a liquid metal (5–20 min) and the size and the fraction of nanoparticles in the melt are investigated. The changes of the surface tension and the density of the Fe, Fe-Sn, Fe-Sn-Al2O3, and Fe-Sn-TiN melts are analyzed, and the influence of the nature and size of refractory nanoparticles on these properties when temperature changes is revealed.

Interaction of alumina and alumomagnesium spinel nanoparticles with sulfur in model iron melts

The interaction of exogenous nanoparticles of refractory compounds Al2O3 and MgAl2O4 with model iron melts containing sulfur as a surfactant is studied. The choice of these nanoparticles and possible variants of sulfur removal from the melt in the form of S2, SO2, and H2S are confirmed by thermodynamic calculations. The dependences of the degree of sulfur removal in the course of the heterophase interaction on the size factors (duration of isothermal storage after the addition of nanoparticles), the type of added nanoparticles, and the sulfur concentration in the model melts are studied. The degree of sulfur removal is 17–32 and 16–35 rel. % upon the introduction of Al2O3 and MgAl2O4 nanoparticles, respectively.

Effect of the size factors on the heterophase interaction of exogenous refractory compound nanoparticles with sulfur in a model nickel melt

The dependence of the degree of sulfur removal on the size factors is studied during the heterophase interaction of refractory compound nanoparticles in a nickel melt. These factors are the time of holding of Al2O3 and TiN nanoparticles in a liquid metal (2–10 min), the size and number of Al2O3 and TiN nanoparticles, the time of processing of a nickel powder with nanoparticles in a planetary mill (0−300 min), and the sulfur concentration in a Ni-(0.0775−0.1750 wt %) S melt. It is shown that the degree of sulfur removal increases as the average size of Al2O3 nanoparticles decreases from 150 to 35 nm and that of TiN nanoparticles decreases from 2 × 104 to 30 nm. The effect of the number of Al2O3 nanoparticles in a metal on the degree of sulfur removal is considered. A change in the time of processing of a powder mixture in a planetary mill is found to weakly affect the degree of sulfur removal.

Interaction of refractory compound nanoparticles with a surfactant in a nickel melt: II. Surface tension and density

The surface tension and density of Ni-S melts with Al2O3 or TiN nanoparticles are studied by the sessile drop method using a digital photographic camera and computer processing of images with special-purpose computer programs. The dependences of the surface tension and density of (Ni-S) + (Al2O3, TiN) melts on the temperature and the type of introduced refractory compound nanoparticles are determined, and the inversion of the temperature dependence of the surface tension of the Ni-S-Al2O3 system is detected. Metallographic analysis of polished sections demonstrates the presence of aluminum, nickel, and sulfur in nonmetallic inclusions at grain boundaries in the first series of experiments and the presence of titanium, nickel, and sulfur in globular nonmetallic inclusions in the second series of experiments.

Interaction of exogenous zirconium oxide nanophases with sulfur and tin in nickel melts

The interaction of exogenous refractory compound (ZrO2) nanoparticles with sulfur and tin, which are present as surfactants in model nickel melts, is studied. Thermodynamic calculations are performed to consider the versions of removal of sulfur and tin from a melt in the form of S2, SO2, H2S, Sn, and SnO. It is shown that the probability of their removal under melting conditions is low. Their contents is found to decrease when ZrO2 nanoparticles are introduced: the degree of removal is α = 12–18% S in a model Ni–S alloy and 14–20% Sn in a model Ni–Sn alloy.

Study of the surface properties of nickel-based melts by the constrained drop method: I. Surface tension

The constrained drop method is used to study the surface tension σ of the following melts at 1773–1923 K and pAr = 0.1 MPa: nickel of various grades (with various oxygen contents), binary Ni-Al (Re) alloys, and a complex Ni-Re-(W, Mo, Co) alloy. The value of σ of liquid nickel is shown to decrease with increasing oxygen content in it. The additions of aluminum (6%) and rhenium (3–7%) to nickel in binary alloys weakly change its surface tension. Alloying elements (W, Mo, Co) in Ni-Re-(W, Mo, Co) alloys insignificantly affect σ of their melts.

Interaction of the oxyfluoride melts of Ca, Al, Mg, Si, Ba, and Cr with refractories based on alumina and magnesia

The interaction of slags consisting of the oxides and fluorides of Ca, Al, Mg, Si, Ba, and Cr with refractories based on Al2O3, MgO, and MgO · Al2O3 is experimentally studied at 1600–1700°C and pAr = 0.3 MPa. Laser emission microprobe analysis is used to study the fracture surfaces in the slag-crucible contact zone, to analyze the depth profile of the chromium concentration in the bulk of the refractory material, and to determine the diffusion coefficient of chromium. The values of the diffusion coefficient are related to the slag melt composition. These relations are established using the optical basicity of the slag.

Behavior of tin dissolved in liquid iron in the presence of refractory nanophases

Nanoparticles of the refractory phases Al2O3 and MgO are introduced in model Fe-Sn melt on the basis of thermodynamic analysis. The preparation of the composite consisting of a mixture of iron micropowder and oxide nanopowders is improved by producing a pressed composite, which is subjected to solid-phase refining before introduction in the melt. The reaction of nanoparticles with surfactant Sn is studied, and the heterophase interaction of Al2O3 and MgO with Sn is established. It is shown that, in the Fe-Sn-Al2O3 system, 17.1–22.8% (rel.) of the Sn is removed, depending on the isothermal holding time (5–20 min) and the content of nanoparticles in the melt (0.06–0.18 wt %); the corresponding result for the Fe-Sn-MgO system is 19.8–24.6% (rel.).

Interaction of barium oxyfluorochloride melts with refractories based on aluminum and magnesium oxides

The contact surface of oxyfluorochloride melts containing 20–40 wt % BaO with Al2O3, MgO, or MgO · Al2O3 ceramics is studied by laser emission microspectral analysis in the course of melting of complexly alloyed nickel alloys in vacuo. The distribution profiles of barium in a crucible material are determined at different chemical compositions of a slag and ceramics to a depth of 800 μm. The diffusion coefficient of barium DBa is calculated and ranges from 0.45 × 10−5 to 5.8 × 10−5 cm2/s. A tendency for increasing DBa in experiments with the Al2O3 ceramics and an insignificant decrease of DBa in experiments with ceramics of another composition is observed with an increase in the weight fraction of BaO (to 40 wt %).