Performance improvement of MgO-C refractory bricks by the addition of Nano-ZrSiO4

Accepted Manuscript Performance improvement of MgO-C refractory bricks by the addition of Nano-ZrSiO4 Hassan Gheisari Dehsheikh, Salman Ghasemi-Kahrizsangi PII:

S0254-0584(17)30756-3

DOI:

10.1016/j.matchemphys.2017.09.055

Reference:

MAC 20022

To appear in:

Materials Chemistry and Physics

Received Date: 2 March 2017 Revised Date:

1 August 2017

Accepted Date: 19 September 2017

Please cite this article as: H. Gheisari Dehsheikh, S. Ghasemi-Kahrizsangi, Performance improvement of MgO-C refractory bricks by the addition of Nano-ZrSiO4, Materials Chemistry and Physics (2017), doi: 10.1016/j.matchemphys.2017.09.055. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Performance Improvement of MgO-C Refractory Bricks by the Addition of Nano-ZrSiO4 Hassan Gheisari Dehsheikh1, Salman Ghasemi-Kahrizsangi2* 1-Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad

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University, Khomeinishahr/ Isfahan, Iran 2- Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11155-9466, Azadi Ave., Tehran, Iran

*Corresponding author: [email protected]

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Abstract:

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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

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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 8h and 3h, respectively. Results showed that addition of Nano-

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ZrSiO4 led to generation some phases such as zirconia carbide (ZrC), forsterite (2MgO.SiO2), and enstatite (MgO.SiO2). Formation of aforementioned phases results

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in improving properties of MgO-C bricks through the following ways (i) converting free-graphite phase to high oxidation resistance phases such as ZrC phase, (ii) creating a dense matrix by formation low melting phase such as MgO.SiO2 which decreases the voids and porosities (reduce the oxygen penetration ways into the matrix), and (iii) covering free graphite phase and protect it from the oxidation. Keywords: MgO-C Refractory, Nano-ZrSiO4, Oxidation Resistance, Free Graphite.

ACCEPTED MANUSCRIPT 1. Introduction: Magnesia-graphite(MgO-C)refractory brick is a ceramic composite composed of80-93 wt.% magnesia (MgO), 1-2 wt.% metallic or non-metallic powder (as anti-oxidants), and7-20wt.% graphite(C) which these materials are connected together with high carbon containing pitch or resin(2-4wt.%) at a high pressure(>100MPa)[1-4]. These

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refractory bricks have more advantages such as high refractoriness, low thermal expansion, high thermal conductivity, high slag and molten penetration resistance, and excellent ability to absorb stress [1, 5-8]. Because of its unique advantages and very high demand in the steel industry, MgO-C refractory bricks are used extensively in the

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steel making processes especially in basic oxygen furnaces, electric arc furnaces, lining of steel ladles, slag line of ladles, etc. [1, 11-14]. But the application of these

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refractory bricks is restricted due to low mechanical strength and high carbon oxidation susceptibility at high temperatures [1, 14-17]. The first sequel of carbon oxidation is diminishing of mechanical strength, increase porosity, and reduces of slag penetration resistance [1, 2, 6,8,11 and 18]. Carbon can be oxidized to form CO (g) and CO2

(g)

phases resulting in a porous structure with poor strength and corrosion

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resistance [1, 11, 13, and 19]. Another problem is environmental pollution, because carbon oxidation can generate CO (g) and CO2 (g) phases which are released into the atmosphere. Taking into account the world steel industry the oxidation of the carbon in the refractory bricks can produce over two billion tons of CO2(g)[20]. The carbon

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oxidation can be done in two following ways [1, 16, 18, and 21]. The first carbon oxidation way with oxygen (O2)(direct-oxidation) occurs at

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the temperature between 400°C and 1200°C and oxygen partial pressure in the range more than 10−4 mbar (Eq: 1). C(s) + O2 (g)

°

CO2 (g)

Eq :( 1)

The second carbon oxidation way (indirect-oxidation) occurs at temperatures more than 1400°C. In this way carbon reacts with oxides or liquids combined in the system. One of the methods for improvement of carbon oxidation resistance in refractory bodies is covering the carbon grains surface with creating a protective layer by

ACCEPTED MANUSCRIPT application of specific oxides (such as Al2O3, SiO2, TiO2, MgAl2O4, and ZrO2) or carbides (SiC, B4C) [1, 4, 9, 13, 16, 23, and 24]. The second way to improve the oxidation resistance of carbon-containing matrixes is using anti-oxidants. These materials (anti-oxidants) react with carbon phase and thereby contribute to reducing carbon oxidation rate. Some of the products generated

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through the reactions of carbon phase with anti-oxidant show volumetric expansion. The porosity of the carbon-containing matrix is reduced and, the same is true for the permeability and oxygen diffusion in the refractory. The most prevalent anti-oxidants for refractories body are metallic powders (Al, Mg, and Si), carbides (SiC, B4C),

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borates (ZrB2, CaB2) or a combination of those materials [12, 20, 22, 25, and 26]. It is reported that the choice of the anti-oxidant materials relay on the refractory body

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material. For instance, metallic powder of Mg and Al are usually used in MgO-C system, while SiC and B4C are used in the Al2O3-C system [16, 22, and 26]. In recent times several researchers’ investigated the impact of different oxide and non-oxide materials on the oxidation resistance of graphite-content refractory bodies. Also, it has been reported that the presence of Nano-sized particles in graphite content refractory

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bodies improved their properties in the lower content [1, 27-29]. Taking the above into account, in this work, the impact of nano-ZrSiO4 addition as structural bonding on the microstructure and performance of the MgO-C refractory was investigated

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2. Experimental Procedure:

2.1. Materials (Starting Materials, Additive, and Resin):

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In order to prepare MgO-C compositions the sintered magnesite (MgCaCO3) [supplied by Dashiqiao Yutong Refractories Co., Ltd.China, Table 1] and the flake graphite(C) [supplied by Sinopharm Chemical Reagent Co. Ltd., Beijing, China, Table 2] were used as starting materials. Phenolic Novalac resin and hexamethylenetetramine (Hexa) were used as binder and hardener, respectively (Table 3). Also, oxide additive was synthesis Nano-ZrSiO4 (zircon) (supplier: Nanoshel Co. CAS=10101-52-7, Table 4, Fig.1).

ACCEPTED MANUSCRIPT 2.2. Specimens Mixes Preparation: For investigate the impact of the Nano-ZrSiO4 addition on the microstructure and performance of the magnesia-C refractory bricks, micron sized magnesia is substituted by Nano-ZrSiO4 according to the following equation for each composition (Table 5) Eq. (2)

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Micron-sized MgO (8-X) wt. % + (X ZrSiO4) % X=0, 0.5, 1, 1.5, and 2 wt. %

The mixing sequences of the raw materials, resin, additive, and hardener are

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mentioned in Table 6. In order to obtain a suitable and stable suspension of Nanooxides, a dispersion process was carried out using an acrylic copolymer (Zephrym

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PD3315) as a dispersant agent and acetone as a dispersion medium. The ultrasonic agitation method (Aqua Sonic TM 75T model) was carried out for 1h for homogenization. Each batch was mixed inside a twin blade mixer. After composition preparation, all composition was aged for 8 h in the air. The prepared compositions were shaped into 50 mm * 50 mm sized compacted by using a cold isostatic press

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under pressure of 150 MPa. All compositions were then tempered at 250 °C for 8h after it fired at an electrical furnace (under coke bed to create a reducing atmosphere) at 1650°C for 4h at a rate of 5°C/min. In order to exactly investigate the effect of Nano-ZrSiO4 on the performance of magnesia-C refractory bricks, other conventional

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anti-oxidants such as Al, Si, Mg, and etc. didn’t use in the study.

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2.3. Physical Properties:

2.3.1. Bulk Density (BD) and Apparent Porosity (AP): The bulk density and apparent porosity of the specimens were measured using Archimedes method in a kerosene medium according to the following equations (ASTM C- 0133-97R03). BD (g/cm3) = W1 / (W2-W3)

Eq. (3)

AP (%) = [(W2-W1) / (W2-W3)] × 100

Eq. (4)

Where, W1, W2, and W3 are the weight of dried sample, saturated weight with kerosene, and weight of the sample in water suspended by a thin thread without

ACCEPTED MANUSCRIPT contacting the vessel walls, but fully inside the kerosene, respectively. Three specimens were tested for each composition.

2.4. Mechanical Properties: 2.4.1. Cold Crushing Strength (CCS):

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The cold crushing strength of the specimens was measured by hydraulic testing machine type Amsler model D3010/2E. For this purpose, ASTM C 0020-00R05 was used. The cross-head speed was 1 N/sec. Three specimens were tested for each

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composition.

2.5.1. Oxidation Resistance:

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2.5. Thermo-Chemical Properties:

The oxidation resistance test was done in a special electric furnace with controlled air support. Specimens of all the compositions were placed on a rotating disc and treated at 1250 ◦C for 5 h. Then cylindrical samples (height = 50 mm, diameter = 50 mm) cut horizontally into two pieces and oxidation was measured diametrically by dimensional

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measurement using a vernier caliper. The oxidation depth was measured on the cross section at three different positions (ASTM C-874). Oxidation (%) = [(D1+D2+D3)/3]/D0

D1, D2, and D3 = oxidation depth on the cross section at three different positions.

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D0= initial diameter (50mm).

2.5. 2. Slag Corrosion Resistance:

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In this work, the slag corrosion resistance test was carried out according to ASTM C768. For this purpose, a crucible having a hole of 3cm in diameter and 3cm in depth was drilled in the central part of the fired samples of 5 cm in diameter and 5cm in height. The hole was filled by normal slag micro powder of BOF (Table 7). Then all samples were fired at 1500°C for 3h. Slag penetration depth was measured which it used for comparison the corrosion resistance of the specimen.

ACCEPTED MANUSCRIPT 2.6. Characterization 2.61. Phase analysis (XRD): In order to analyze the change of phase compositions of the specimens fired 1650°C the X-ray diffractometer (XPert Pro MPD, Philips, Netherlands) with Cu target at 40

step was used. 2.6.2. Microstructure analysis (SEM/EDX):

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kV and 30 mA with the 2q range of 10-90°, 0.02° step size and 1 s collecting time per

Microstructural characterization of the fired samples was done by using a scanning electron microscope (SEM, Philips XL30) equipped with an electron dispersive X-ray

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spectroscopy (EDX) detector (EDAX, Apollo XP model, 2930 serial number).

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3.1. Phases Analysis Results:

Figs.2-3 illustrates the X-ray diffraction patterns of the MC, MCZ0.5, and MCZ2 compositions after fired at 1650 for 4h. For MC composition, magnesia (MgO) (JCPDS 45-948) and graphite(C) (JCPDS 75-1621) have been diagnosed as the major constituent phases. Also, for MCZ0.5; magnesia (MgO), graphite(C), zirconia carbide

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(Zr C) (JCPDS 19-1487), forsterite (2MgO.SiO2) (JCPDS 34-189) and enstatite (MgO.SiO2) (JCPDS 84-652) have been identified (Table 8). But for MCZ2 composition; except graphite phase(C), all phases that existence in the MCZ0.5 composition were detected. Of course it is quite visible that the peak intensity of the

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zirconia carbide (Zr C), forsterite (2MgO.SiO2), and enstatite (MgO.SiO2) phases have increased. And magnesia peak intensity has decreased. Generation of the

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aforementioned phases in the MCZ0.5 and MCZ2 compositions occurs according to the following chemical reactions: ZrSiO4(s) → ZrO2(s) +SiO2 (s)

Eq :( 5)

ZrO2(s) + 3C(s) → Zr C(s) + 2CO (g)

Eq :( 6)

SiO2(s) +MgO(s) → MgO.SiO2(s)

Eq :( 7)

SiO2(s) + MgO(s) → 2MgO.SiO2(s)

Eq :( 8)

ACCEPTED MANUSCRIPT According to Figs.3a-b it indicates that after adding Nano-ZrSiO4 in the refractory matrixes free-graphite will not exist. 3.2. Microstructure analysis: Due to more exactly identified and analyze the properties of the samples the

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microstructure studies is extremely important. Specimen's microstructural images analysis led to give an overall image of the microstructure properties such as the following parameters:

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Grading Type, amount, size, and distribution of the phases

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Amount, size, and distribution of the porosities and voids Existence of various defects such as cracks and gaps

Homogeneous or heterogeneous of the microstructure Fig.4a-c shows the microstructure of the different samples (MC, MCZ0.5, and MCZ2) after firing at 1650 for 4 h. For MC composition two main phases of magnesia (MgO) and graphite(C) (which presence of them was confirmed by X-ray diffraction, Fig.2)

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with porosity in the matrix were observed. But for specimens containing Nano-ZrSiO4, it can be seen that have a nearly similar structure to each other. The microstructure of these specimens is composed of magnesia (MgO), zirconium carbide (ZrC), forsterite

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(2MgO.SiO2), and enstatite (MgO.SiO2) phases. For these samples, the amount of porosities and voids is greatly reduced due to the generation of enstatite (MgO.SiO2)

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phase (which is in the glassy state at the firing temperature). And almost uniform and dense microstructures are created. Base on aforementioned generated phases, the formation of Zr C with the desirable and unique properties such as high strength and hardness, resistance to oxidation at high temperatures, excellent toughness, and thermal conductivity. It also exhibits optical properties such as infrared reflectance, high visible light absorption and ability to store large amounts of energy [30, 31]. Formation of Zr C phases leads to a higher oxidation resistance in the samples containing additive compared to the sample without the additive. Although, according to previous studies and reports the Zr C phase can be oxidized [30, 31] but in this case due to the change of free-graphite (which have a low oxidation resistance) to high

ACCEPTED MANUSCRIPT oxidation resistance phase(i.e. Zr C) the generation of the Zr C phase can lead to enhancement the samples oxidation resistance. Also the use of ZrSiO4 Nano-particles (due to being small and high specific surface area)which are widely distributed in the matrix can lead to enstatite (MgO.SiO2) phase formation at the lower temperatures and also generation strong ionic bonds between silica(SiO2) and magnesia (MgO)

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particles (forsterite phase formation) in matrixes. Generation of enstatite (MgO.SiO2) and forsterite (2MgO.SiO2) phases in MCZ0.5, MCZ1, MCZ1.5, and MCZ2 compositions can lead to improvement of oxidation resistance of the samples due to creating liquid phase(at sintering temperature) and strong ionic bonds in the matrixes,

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respectively.

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3.3. Bulk density (BD) and apparent porosity (AP) Results:

Bulk density and apparent porosity as two most important physical parameters for all refractory bricks and always be considered by the consumers in various industries. According to the Fig. 6-7, it is observed that the bulk density (BD) and apparent porosity (AP) of the samples (after sintering at 1650°C for 4 h) have an ascending and

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descending trend, respectively. And the specimen includes further percentage of Nano-ZrSiO4 (MCZ2) has the highest and lowest values of the bulk density (3.29g/cm3) and apparent porosity (5.42%), respectively. This trend is due to the

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following reasons:

Filling and reducing the porosities and voids contents due to the improvement

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the firing process due to the formation and development of some low melting point such as MgO.SiO2 (enhancement the firing process through the liquid

phase sintering mechanism). The presence of fine particles (Nano-ZrSiO4) and better coverage of voids and porosities.

Generation of phases with higher density [such as ZrC (6.7g/cm3)] in the matrix after the firing process.

ACCEPTED MANUSCRIPT 3.4. Cold Crushing Strength (CCS) Results: Usually, cold Crushing strength (CCS) is considered as a criterion for samples sintering process. It means that a high cold crushing strength for samples represents a better and completely firing process and also created more and stronger connections

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and the link between grains in the microstructure of the specimens. Also, the cold Crushing strength is directly related to the grain size distribution. It means that with selection a proper distribution of fine, medium, and coarse grains and placement of the fine grains between medium and coarse grains, the raw density of the specimen's

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increases as its apparent porosity decreases. With the decrease in the apparent porosity of the refractory structure, the cold crush strength increases. Therefore, Fig.7 shows

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the cold crushing strength of the samples as a function of the amount of Nano-ZrSiO4 addition. It can be seen that by increasing the nano-ZrSiO4 content the cold crushing strength has increased. This strength increasing can be caused by the following factors:

Reduce porosity and pore (due to reversed relation between strength and

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porosities).

High compact and dense structure formed by formation forsterite and enstatite phases (Filling porosities and voids and also generation strong ionic bonds in the microstructure).

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Formation of needle-shaped crystals of ZrC (zirconium carbide) (interlock and

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engaging these phases together in the microstructure). 3.5. Oxidation Resistance Results: The oxidation of graphite-contain matrixes is an interesting reaction due to its technological importance. Volatile reaction products of carbon mono-oxide (CO) and carbon dioxide (CO2) are created at all temperatures above 250°C (Eq: 9, 10, and 11). Lower 800°C a small amount of surface oxide is also formed. The rate of oxidation below 800°C is limited by a chemical process having energy of activation of the 39 kcal/mole. Above 800°C the reaction is limited, by either a chemical process or by gaseous diffusion of oxygen through the products of the reaction. The transition

ACCEPTED MANUSCRIPT between the two processes depends on the pressure, sample size, and the nature of the reaction system [1]. C(s) + 1/2 O2 (g)

C(s) + CO2 (g)

Eq :( 9)

CO2 (g) (-394 kJ/mole)

Eq :( 10)

2CO (g) (172 kJ/mole)

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C(s) + O2 (g)

CO (g) (-111 kJ/mole)

Eq :( 11)

following parameters:

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Also, the total carbon removed from a graphite surface is highly dependent on the

Degree of graphitization, surface area/volume ratio, and open porosity. Catalyzing metallic impurity levels.

Temperature of reaction.

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Oxygen supply and turbulence of surface layer.

In this research, the results of the oxidation resistance of the specimens are shown in Fig.8. It can be seen that the samples contain more nano-ZrSiO4 have higher oxidation resistance. And the Diameter-wise oxidation has been decreased from 18.25 % to

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12.15 % (for the MC and MCZ2specimens; respectively). The use of ZrSiO4 Nano particles (due to special and unique properties such as high specific surface area and high reactivity) [32-34] leading to faster and greater extent of different phases such as

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ZrC, MgSiO2, and 2MgOSiO2. Formation of the aforementioned phases improved the oxidation resistance of the specimens through the following way:

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Higher oxidation resistance of the formed carbide phase (Zr C) compared to initial free-graphite. Covering free-graphite by MgSiO2 and 2MgOSiO2 phases.

Filling the porosities and voids by MgSiO2 and 2MgOSiO2 phases which these phases block the oxygen accesses ways to the free graphite (on the other hand. The generation of these phases act as oxygen (O2) barrier in the specimens and

prevention of oxidation reaction).

ACCEPTED MANUSCRIPT 3.6. Static Slag Corrosion Resistance Results: Usually, oxidation of graphite-containing matrix leads to a porous structure which results in a low corrosion resistance. For this purpose, after adding nano-ZrSiO4 the corrosion resistance behavior of the samples is evaluated. Fig.9 shows the slag

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penetration depth as a function of the ZrSiO4 Nano-particles addition. It can be seen that by increasing the ZrSiO4 Nano-particles the slag penetration depth is reduced. This corrosion resistance improvement trend can be caused by the following reasons: Diminish of graphite oxidation (graphite oxidation creates a porous and weak

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structure).

Formation of high corrosion resistance phases such as Zr C and 2MgO.SiO2.

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Filling the porosities and voids by the formation MgO.SiO2 phase which is prevented of slag penetration into the matrix.

And, the existence of some oxide such as SiO2, CaO, and Al2O3 as an impurity in the slag composition leads to the generation of some low melting phase such as CaO.Al2O3.2SiO2 (Tm=1553°C), SiO2.CaO

(Tm=1544°C),

MgO.SiO2

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(Tm=1558°C), and 3CaO.Al2O3 (Tm=1535°C), which form of these phase depth.

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Conclusion:

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increases the viscosity of liquid slag and led to reducing the slag penetration

1- Up to2 wt. % Addition of the Nano-ZrSiO4 increased and decreased the bulk density and apparent porosity values from 2.94 to 3.29 g/cm3 and from 7.82 to

5.42%, respectively.

2- The cold crushing strength of the MgO-C samples is increased by the addition of nano-ZrSiO4 due to the formation of forsterite, enstatite, and also needleshaped crystals of Zr C phases. 3- Converting free graphite phase to high oxidation resistance phases such as ZrC phase, creating a dense matrix by formation low melting phase such as MgO.SiO2 and covering free graphite phase and protect it from the oxidation

ACCEPTED MANUSCRIPT are the reasons for oxidation resistance improvement of MgO-C refractories by the addition of nano-ZrSiO4. 4- For the purpose of improving the performance of the magnesia-C refractories the addition of nano-ZrSiO4 could be effected by nanotechnology. The nano-

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surface effect, size effect, and higher activity.

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ZrSiO4 was more effective due to its intrinsic properties such as a significant

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[26] T. Suruga, Effect of Mg–B material addition to MgO–C bricks, Taikabutsu Overseas 15 (1995) 25–31. [27]. S. Behera, R. Sarkar, and Low-Carbon Magnesia-Carbon Refractory: Use of N220 Nanocarbon Black, int . j . appli .ceram . tech. 11 (2014)968–976. [28]R. R.Das, B. B. Nayak, S. Adak, A. K. Chattopadhyay, Influence of Nanocrystalline MgAl2O4 Spinel Addition on the Properties of MgO-C Refractories, Mater Manuf Proc, 27(2012) 213-217 [29]M. Bag, S. Adak b, R. Sarkar, Study on low carbon containing MgO-C refractory: Use of nano carbon, Ceram Int 38 (2012) 2339–2346.

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[30] M. Jalaly, M. Tamizifar, M.Sh. Bafghi, F.J. Gotor, Mechanochemical synthesis of ZrB2–SiC– ZrC nanocomposite powder by metallothermic reduction of zircon, J Alloy. Comp 581 (2013) 782– 787

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[31] L. Kljajević1, B.Matović1, S. Nenadović1, Z. Baščarević, N. Cvetićanin, A. Devečerski, Fabrication of ZrC/SiC, ZrO2/SiC and ZrO2 powders by carbothermal reduction of ZrSiO4, Proc Appl Ceram , 5 [2] (2011) 103––112

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[32] S. Ghasemi–Kahrizsangi, A.Nemati, A. Shahraki, M. Farooghi, Densification and Properties of Fe2O3 Nanoparticles added CaO Refractories, Ceram. Int journal 42(2016) 12270-12275 [33] S. Ghsemi-Kahrizsangi, M .Barati, H. Gheisari, A. Shahraki, and M. Farooghi, Densification and properties of ZrO2 nanoparticles added magnesia–doloma refractories, Ceram Int, 29(2016) 15658–15663 [34] S. Ghsemi-kahrizsangi, A. Nemati, A. Shahraki. M. Farooghi, Effect of Nano-Sized Fe2 O3 on Microstructure and Hydration Resistance of MgO-CaO Refractories, Int. J. Nanosci. Nanotech 12(2016) 19-26

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Table1; Physic-chemical of sintered Magnesite Magnesite

SiO2

0.95

Al2O3

1.6

Fe2O3

0.6

TiO2

0.2

CaO

2.7

MgO

93.2

Alkalis

0.3

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Oxide

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Physical properties Bulk Density(g/cm3) Apparent porosity (%)

3.28-3.3 3.75-3.80

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Table 2; Properties of the flak graphite

(%)

(%)

95.15

3.85

Volatile Matter

SSA(m2/g)

Color

0.63

5.80

Black

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Ash

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Carbon

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Table 3; Physic -chemical of phenolic novalac resin Value

Viscosity (CPS) at 250C

8500-9000 1.85

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Specific gravity at 25 0C

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Properties

Fixed carbon (%)

>55

80.18

Moisture (%)

<2.5

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Non-volatile matter (%)

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Purity (%)

Size(nm)

SSA(m2/g)

ZrSiO4

>99

50-6-

>50

density(g/cm3)

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Powder

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Table 4; Properties of the high-purity Nano-ZrSiO4

6.7

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Table 5; Batches composition and chemical properties of the specimens

Graphite content

Liquid resin

(wt. %)

(wt.%)

(wt.%)

MC

0

12

3

MCZ0.5

0.5

12

3

MCZ1

1

12

MCZ1.5

1.5

12

MCZ2

2

12

SC

(wt. %)

8

7.5

3

7

3

6.5

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Micro Sized Magnesia

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Nano-ZrSiO4

Sample code

3

6

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Table 6; Mixing sequence of MgO-C compositions Mixing steps

Mixing time(min)

1

Coarse and medium magnesite

3

2

Addition of liquid resin

3

Addition of nano-ZrSiO4, hardener, graphite, and

7

12

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fine magnesite

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Steps

Table; 7 Chemical properties of steel converter slag

Oxide CaO MgO (wt.%) 40.66 6.04

SiO2 Fe2O3 Al2O3 TiO2 12.17 30.54 7.26 2.13

MnO 1.20

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Table; 8 EDX analyses of 1) MgO, 2) Graphite, 3) ZrC, 4) 2MgO.SiO2, and 5) MgO.SiO2 points. Element

Graphite

Zr C

2MgO.SiO2

MgO.SiO2

(wt.%)

(wt.%)

( wt.%)

( wt.%)

(wt.%)

O

30.20

3.33

1.70

20.28

Mg

69.63

-

-

40.50

Si

-

-

-

39.0

C

-

97.17

30.10

Zr

-

-

68.0

Au

0.27

0.50

SC

26.53

38.65

34.76

-

-

-

-

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MgO

0.22

0.54

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Fig.1 TEM image of the Nano-ZrSiO4 particles.

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Fig.2 X-ray diffraction patterns of the MC composition.

Fig.3 X-ray diffraction patterns of the a) MCZ0.5 and b) MCZ2 compositions.

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Fig.4 Scanning Electron Microscopy (SEM) images of the a) MC, b) MC0.5, and C) MCZ2 compositions.

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Fig.5 Bulk density variation trends of the compositions by nano-ZrSiO4 addition.

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Fig.6 Apparent porosity variation trends of the compositions by nano-ZrSiO4 addition.

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Fig.7 Cold Crushing Strength (CCS) variation trends of the compositions by nano-ZrSiO4 addition.

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Fig. 8 Impact of the ZrSiO4 addition on the oxidation resistance of the compositions.

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Fig. 8 Impact of the ZrSiO4 addition on the corrosion resistance of the compositions.

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Highlights: Nano-ZrSiO4 addition improved MgO-C samples properties compared to without additive samples.

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Densification and cold crushing strength properties enhanced up to2 wt. % nano-ZrSiO4. Diameter wise oxidation reduced from 18.25 to 12.15 % for MC and MCZ2 compositions, respectively.