The reduction of titania-ferrous ore (ironsand) containing 57.2 wt% of iron and 7-8 wt% of TiO 2 was investigated in non-isothermal and isothermal reduction experiments using CO-CO 2 -Ar gas mixtures in a laboratory fixed bed reactor. Samples in the course of reduction were characterised using XRD, EPMA and SEM.Two types of particles were identified in ironsand: 1) homogeneous particles of titano-magnetite with cubic spinel structure (a major type); and 2) non-homogeneous particles, characterised by lamellar structure of rhombohedral titano-hematite, exsoluted from the titano-magnetite.Titano-magnetite, which is a magnetite-ulvospinel solid solution (Fe 3 O 3 ) 1Ϫx (Fe 2 TiO 4 ) x , with xϭ0.27Ϯ0.02, was reduced to metallic iron and titanium sub-oxides. Titanium had a strong effect on the mechanism and rate of reduction of iron oxide in ironsand.KEY WORDS: titano-magnetite (Fe 3Ϫx Ti x O 4 ); magnetite (Fe 3 O 4 ); ulvospinel (Fe 2 TiO 4 ); titano-hematite; reduction; carbon monoxide.and then kept at 1 373 K until the completion of the reduction. CO-CO 2 -Ar gas mixture was prepared from highly purified argon, carbon monoxide and chemically pure carbon dioxide using mass flow controllers. The gases were purified before mixing by passing through traps filled with Drierite and 4A molecular sieve to remove moisture. The inlet gas flow rate was maintained at 800 ml/min. The reducing gas was introduced into the reactor from the top and left the reactor through a porous plug at the bottom. The outlet gas was analysed on-line by mass spectrometer.Samples reduced to different extent were analysed by XRD and microprobe spectrometer (EPMA, Cameca SX-50 Probe). The morphology of samples was observed by Field Emission Scanning Electron Microscope (FESEM, HITACHI S-4500). The extent of reduction was calculated as a mass fraction of oxygen in iron oxides removed in the course of reduction. Results and Discussion Phase Characterisation of IronsandThe XRD patterns of ironsand, hematite iron ore and magnetite obtained by partial reduction of the hematite iron ore are shown in Fig. 2. The XRD pattern of ironsand included peaks for magnetite, hematite and traces of maghemite (g-Fe 2 O 3 ). The peaks of Ti-rich phases such as ulvospinel (Fe 2 TiO 4 ), ilmenite (FeTiO 3 ) and rutile (TiO 2 ) were not detected.The EPMA analysis showed that the main phase of the New Zealand ironsand was homogeneous TTM. A small proportion of ironsand exhibited exsolution caused by partial oxidation (weathering) of TTM to TTH, which has the XRD pattern identical to hematite. Homogeneous Titanomagnetite ParticlesParticles with homogeneous TTM phase constituted the bulk of the ironsand. Quantitative elemental analysis across of such particles with a step of 1 micron is shown in Fig. 3. The analysed elements were Fe, Ti, Al, Mg, Si and O. Iron and titanium in the particle were distributed uniformly along the line of analysis with the average compositions of 32.8 at% Fe and 2.98 at% Ti. However, the concentrations of aluminium and magnesium fluctuated in t...

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Iron carbide was prepared by iron ore reduction and iron cementation using Ar-H 2 -CH 4 gas mixture with and without sulfur. Phases formed in the reduction/cementation process were examined by Xray diffraction (XRD), Mossbauer, and Raman spectroscopy. The sample surface was also analyzed by X-ray photoelectron spectroscopy (XPS). XRD and Mossbauer analyses showed that iron oxide was first reduced to metallic iron, and then, metallic iron was carburized to cementite. Addition of a small amount of H 2 S to the reaction gas retarded the cementite formation but made the cementite more stable. XPS analysis showed that the surface of samples converted to iron carbide using sulfurcontaining gas consisted of mainly Fe 3 C and a small amount of graphitic carbon. Raman spectra of a sample produced in the iron carbide process showed the G and D bands, which are characteristic for carbon-carbon bonds. The intensity ratio of G/D bands depended on the sulfur content in the reducing/carburizing gas.