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Kinetics of oxidation of MgO-C refractories was investigated by shrinking core modeling of the gas-solid reactions taking place during heating the porous materials to the high temperatures. Samples containing 4.5-17 wt pct graphite were isothermally oxidized at 1000-1350°C. Weight loss data was compared with predictions of the model. A mixed 2-stage mechanism comprised of pore diffusion plus boundary layer gas transfer was shown to generally control the oxidation rate. Pore diffusion was however more effective, especially at graphite contents lower than 10 wt pct under forced convection blowing of the air. Model calculations showed that effective gas diffusion coefficients were in the range... 

The effects of graphite content on the density and oxidation behavior of MgO-C refractory samples were studied. The samples were formulated with various amounts of graphite and their oxidation behavior was investigated (in an isothermal condition); using a Thermo Gravimetric system (TG), in air and at temperatures ranging from 900"C to 1450"C. The preliminary results showed that the porosity and density of tempered samples were decreased when the graphite content was increased. However, after heating the samples at higher temperatures, the decreasing rate of porosity was lowered. At the beginning of the oxidation process, the rate of weight loss was high, but was gradually decreased when the... 

Kinetics of air oxidation of MgO-C-Al refractory at 600°-1300°C were investigated using the software based on the modifled shrinking core model (KDA). Commercial bricks containing 88.5% MgO, 10% residual carbon, and 1.5% aluminum anti-oxidant were oxidized isothermally with air. Combination of experimental data with model calculations indicated gas diffusion through solid material and pores as a major controlling step. Previously observed chemisorption process was eliminated from the rate-controlling mechanism with addition of aluminum antioxidant. Comprehensive rate equations were devised for MgO-C-Al and MgO-C oxidation reactions. Overall activation energies of Q id (internal diffusion) =... 

In this research, the properties of Dolomite Graphite refractories with different additives were evaluated. The samples were prepared with various amounts of Graphite and resin content. After preparation of the samples, the physical, mechanical properties, slag corrosion and thermal shock resistance were evaluated. The properties of the samples were evaluated up to 11% total Carbon (10% Graphite and 1% residual Carbon from resin) in the system. The reduction in MOR of the specimens, before and after heat treatment was measured, as a measure for the thermal shock resistance evaluation. The slag corrosion test was conducted based on the crucible test, at 1600°C for 5 hr. Then, the depth of... 

Dolomite base refractories have advantages such as high refractoriness, potential to produce pure steel molten, high alkaline corrosion resistance, and economical for consumers. However, application of these refractories has been limited due to their high potential to hydration with atmosphere humidity. In this research work, the impact of ZrSiO4 nanoparticles addition on the physical, thermo-mechanical, mechanical, and microstructure of the dolomite base refractories is investigated. Also, XRD and SEM/EDX analyses were used for determining generated ceramic phases and microstructure evaluation, respectively. Up to 3 wt% ZrSiO4 nanoparticles were added to the compositions. Compositions fired... 

Progressive conversion/shrinking core (PC-SC) models of constant-size cylinders were exploited to interpret the decarburization reactions of MgO-C-Si bricks heated up under blown air. Chemical adsorption/solid (or pore) diffusion mechanisms governed the reaction rate. With 5% silicon, chemical adsorption vanished at 1000 and 1100°C. The oxidation rate lowered then with temperature. This was due apparently to the blocking of the pore-end gorges by the voluminous compounds (like Forstrite). Arrhenius plots of the specific rates yielded the activation energies of the prevailing steps. Without Si antioxidant, three steps were appreciated having activation energies of 51.65 (for chemical... 

Influence of two nano-size additives oSubject:A. Suspensions. Subject:C. Electrical conductivity. Subject:Castable. Subject:E. Refractories. Subject:Castables. Subject:Electrical conductivity. Subject:Electrical property. Subject:High alumina. Subject:matrix. Subject:Mechanical strength. Subject:Nano-size. Subject:Polycarboxylate ethers. Subject:Refractory castables. Subject:Working time. Subject:Alumina. Subject:Cement additives. Subject:Electric conductivity. Subject:Ethers. Subject:Suspensions (fluids) Subject:Refractory materials. n electrical properties of suspension matrix of self-flowing low-cement high alumina refractory castable is investigated. For this purpose, castament FS 10 and... 

A silicon carbide coating was formed on the surface of graphite flakes by reaction of molten Si with carbon at 1100-1300. °C in a 95%KCl-5%NaF molten salt under Ar atmosphere. The effect of temperature and Si/graphite ratio in the initial mixture on the quality and the amount of SiC were investigated by XRD and SEM/EDS analyses. Also, the water wettability, oxidation resistance and zeta potential of un-coated and coated graphite were examined by TGA analysis and sedimentation test. The results show the amount of coating to increase in the coated flakes with increasing temperature and Si/graphite ratio. The SiC coating improves water wettability of graphite and acts as a protective layer to... 

The high hydration potential of CaO and MgO phases restricted the application of Mag-Dol refractory composites. In this study, the impact of nano-silica (SiO2) addition on the physical, mechanical, thermo-mechanical as well as microstructure of Mag-Dol refractory composites is investigated. Mag-Dol compositions were prepared by using calcined dolomite and magnesite particles (micron, 0–1, 1–3, 3–5, and 5–8 mm), liquid resin, and 0, 0.5, 1, 1.5, 2, and 2.5 wt% nano SiO2 as additives. Specimens were heated up to 1650 °C for the 3 h soaking period. Fired specimens were characterized by physical (apparent porosity, bulk density, and hydration resistance), mechanical (cold crushing strength), and... 

Many benefits of the MgO-C refractory bricks such as excellent corrosion resistance, high thermal shock resistance, good mechanical strength at high temperatures, and permeability have attracted attention of consumers in various industries. But on the other hand, the low oxidation resistance of these refractory bricks at high temperatures has restricted their application. For this purpose, in this research study, the impact of Nano-ZrSiO4 addition on microstructure and performance of MgO-C refractory was investigated. 0, 0.5, 1, 1.5, and 2 wt % of Nano-ZrSiO4 was added to compositions. After samples preparation, all specimens tempered and fired (in a coke bed) at the 250 °C and 1600 °C for 8... 

In the present paper, the effect of silicon carbide (SiC) fines was studied on the phase and microstructural properties of bauxite-based low-cement refractory castables (LCC) at different firing temperatures. XRD and SEM techniques were employed to evaluate phase and microstructure analysis, and physical/mechanical properties were measured according to standard methods. The results showed that the oxidation of SiC particles related to the oxygen partial pressure and active/passive oxidation behavior of SiC fines could markedly affect the microstructure and properties of bauxite-based LCC fired at high temperatures. Despite the negative influence of addition of SiC fines on cold mechanical... 

Epitaxial formation of CoSi2 nanolayer by solid state reaction of Co-Si in refractory metal intermediate-layer and cap-layer systems was investigated. Thin films of Ta and W, as the refractory metal intermediate or cap layers of the Co film, were deposited on Si(100) substrate and then heat-treated. The both interlayers resulted in formation of epitaxial CoSi 2 with (100) crystallographic orientation at 900°C. However, in the Ta intermediated system, the grown CoSi2 layer was thermally unstable at 1000°C, unlike the W system with a stable silicide layer. We found that use of W cap-layer cannot yield an epitaxial CoSi2 phase. But, a Ta cap-layer resulted in formation of epitaxial CoSi2(100)... 

Attempts have been made to quantify the amount of contaminants absorbed by liquid metal from commercial ZrO2-, Al2O3-, and SiC-base crucibles used for vacuum melting of Ni-45 wt pet Ti alloy. The molten alloy was held under vacuum for 90 minutes at 1450°C to become homogenized. Reactions between the liquid metal and the crucible were investigated by visual observation, chemical analysis, scanning electron microscopy (SEM) image processing, and X-ray mapping. The relative degree of contamination declined in the following sequence: commercially pure SiC > SiC-5 wt pct Al2O3-5 wt pet SiO2] > slurry cast alumina > recrystallized alumina > zircon type A > oxygen deficient high-purity zirconia.... 

High-temperature (1200-1350°C) corrosion of fused-cast ZrO2-Al2O3-SiO2 (ZAS) refractory contacting lead silicate glass melt (LSG) containing 68.5wt% PbO was investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential scanning calorimetry (DSC), x-ray diffraction (XRD), thickness measurement and Archimedes density measurement. ZAS durability was improved by baddeliyete content and deteriorated with open porosity proportion, corundum percentage and eutectic mixture presence. Diffusion of lead resulted in fusion-temperature lowering of the glassy layers embedded within the ZAS particles. Heating caused viscosity drop across the interface, loosening the... 

In this work the effect of nano- and microZrO2 addition on the densification and hydration resistance of MgO–CaO refractories was investigated. 0, 2, 4, 6 and 8 wt% ZrO2 was added to MgO–CaO refractories that contain 35 wt% CaO. The crystalline phases and microstructure characteristics of specimens sintered at 1650 °C for 5 h in an electric furnace were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The physical properties are reported in terms of bulk density, apparent porosity and hydration resistance. Results show that with addition of ZrO2 the bulk density and hydration resistance of the samples increased while apparent porosity decreased. Also... 

Up to 8wt. % of Nano-iron oxide was added to CaO refractory matrix. The crystalline phases and microstructure characteristics of specimens sintered at 1650°C for 5h in an electric furnace were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The physical properties are reported in terms of bulk density, apparent porosity and hydration resistance. The mechanical behavior was studied by a cold crushing strength (CCS) and flexural strength at 1200°C test. As a result, it was found that the presence of Nano-iron oxide in the CaO refractory matrix induced 2CaO.Fe2O3 (C2F), CaO.Fe2O3 (CF) and 3CaO.Al2O3 (C3A) phase's formation, which improved the sintering... 

Magnesia-dolomite refractories have advantages such as stability in the basic environments, clean steel production, high corrosion resistance, proper covering in the cement furnace, and low production costs. However, their application is restricted due to low hydration resistance. In this research, the effects of nano and micro alumina particles on the microstructure, sintering behavior, and properties of magnesia-dolomite refractories were studied. For this purpose, MgO-CaO refractories were formulated using dolomite and magnetite and 0, 2, 4, 6 and 8 wt percentage nano and micro alumina were added to the formulation. Phase and microstructure analysis of the samples were performed using... 

In the present paper, phase and microstructural characterization of low carbon MgO-C refractories with addition of Fe-catalyzed phenolic resins as binder were investigated. Initially, phenolic resin was modified using various amounts of Fe particles as catalyst originated from iron nitrate ([Fe(NO3)3·9H2O]). The MgO-C matrix compositions were prepared by using 7% of modified phenolic resin, shaped and cured at 200 °C for 24 h. The cured samples were coked in the temperature range from 800 to 1400 °C and then characterized by XRD and FE-SEM techniques. Based on attained results, in-situ graphitic carbons, particularly in carbon nanotubes (CNTs) network were gradually formed from Fe-catalyzed... 

In this research study, a comparative evaluation of the additional impact of nanometer-sized tetravalent oxides [Zirconia (ZrO2), Titania (TiO2), and Silica (SiO2)] on the properties and performance of Doloma-Magnesia (MgO-CaO) ceramic refractories, with an emphasis on their hydration resistance improvement, has been done. For this purpose, from 0 to 2.5 wt% ZrO2, TiO2, and SiO2 nanometer-sized particles have been added to the Doloma-Magnesia compositions. After formulation and mixing of the starting materials, the pressed samples (at 150 MPa) were tempered (at 250 °C for 12 h) and fired in a shuttle furnace (at 1650 °C for 3 h). The physical, mechanical, and thermo-mechanical properties of... 

In the present paper, phase and microstructural characterization of low carbon MgO-C refractories with addition of Fe-catalyzed phenolic resins as binder were investigated. Initially, phenolic resin was modified using various amounts of Fe particles as catalyst originated from iron nitrate ([Fe(NO3)3·9H2O]). The MgO-C matrix compositions were prepared by using 7% of modified phenolic resin, shaped and cured at 200 °C for 24 h. The cured samples were coked in the temperature range from 800 to 1400 °C and then characterized by XRD and FE-SEM techniques. Based on attained results, in-situ graphitic carbons, particularly in carbon nanotubes (CNTs) network were gradually formed from Fe-catalyzed...