Liquid phase combustion of iron in an oxygen atmosphere

Abstract

In this article, we report an investigation of laser-initiated ignition of pure iron rods, using optical pyrometry, video observations, and analysis of metallographic cross section of quenched burning liquid on copper plates. When ignition occurs, caused by the melting of metal, the combustion takes place in the liquid. Two distinct superposed phases (L1 and L2) are identified in the liquid, according to the known phase diagram of the iron oxide system. Our observations show that the L1 and L2 phases can be either distinct and immiscible or mixing together. The temperature of the transition at which the mixing occurs is around 2350 K. Two mechanisms are proposed to explain the mixing occurring at high temperature: the spontaneous emulsification resulting from a strong decrease of the interfacial tension between L1 and L2 and the reduction of the miscibility gap between them at high temperature. Based on the experimental data of the evolution of the temperature and the video observation of the melt for different ignition conditions, we provide a complete description of the combustion process of iron induced by laser. Eventually, an extrapolation of the ironoxygen phase diagram, to temperatures higher than 2000 K, is proposed.

Combustion Mechanism of Alloying Elements Cr in Ti-Cr-V Alloys

“…The titanium alloy burns violently with a dazzling white light when the titanium alloy sample heated by a resistance wire reaches the ignition temperature. The titanium alloy is melted by the combustion heat and forms the L1 phase [20,21]. Because the solid solubility of the melting alloy is much higher than that of the solid alloy, a large amount of oxygen atom solutes is present in the melting alloy and reacts with it.…”

Experimental and theoretical study of iron and mild steel combustion in oxygen flows

“…With η = 3.5 · 10 −2 g cm −1 s 1 , ρ 0 = 1.2·10 −3 g cm 3 , we then find ω = −ρ 0 v 2 * /η ≈ −500 s 1 . Inserting this together with θ = 1.12 and the value u = 1 cm s 1 measured on the interval 500 ms to 700 ms into formula (27), one finds tan ϕ = 0.57 or ϕ = 30 o .…”

“…(27); on the other hand, as defined, u is also the speed of the upper rod end with respect to its lower end, that is, the cold metal. Therefore, θ = ρ/ρ l is to be calculated with ρ at T = T 0 .…”

“…IV C 1, derivation of Eq. (27) assumes that the flow near the solid-liquid interface is steady. While the steadiness-on-average of the bulk liquid flow is a natural consequence of its comparatively fast (turbulent) dynamics, so that it is readily established at any given ϕ 0, the flow near the interface may or may not be truly steady.…”

The pulsed laser ablation synthesis of colloidal iron oxide nanoparticles for the enhancement of TiO2 nanotubes photo-activity

“…Although iron oxide NPs prepared using chemical precipitation [58], flame pyrolysis [52], thermal decomposition [59] of precursors are mostly obtained as Fe 2 O 3 , during the laser ablation local physical conditions like oxygen partial pressure and heating/cooling rate strongly differ from the equilibrium conditions and non-stoichiometric phases are expected [36]. Studies regarding the iron ablation in air and water [60][61][62] have shown that during the laser illumination of the target, the dispersed nanosized droplets of melted Fe leaves the target and undergo rapid oxidation in contact with the dissociated solvent. Due to the limited oxygen diffusion across the iron droplet, the final iron oxidation state inside the forming NPs decreases with the increasing cooling rate.…”