Study on first-order inversion curve of calcined Indian red mud
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https://www.eduzhai.net International Journal of M aterials and Chemistry 2012, 2(4): 123-127 DOI: 10.5923/j.ijmc.20120204.01 Fist-order reversal curve Study on Calcined Indian Redmud D. Govindarajan1, G. Jayalakshmi1, R. Gopalakrishnan2,*, A. Stancu3 1Department of Physics, Annamalai University, Tamilnadu, India 2Department of Physics, SRM University, Kattankulathur, Tamilnadu, India 3Faculty of Physics, A1. I. Cuza ‘University, 11 Bd. Carol I, 6600 Iasi, Romania Abstract The present work deals with red mud were calcined at different temperatures ranging fro m 30℃ and 1000℃ for 1 hour in furnace and characterised by First order reversal curve (FORC). The magnetic hysteresis parameters as a function of temperature were determined fro m the FORC curves. The test results indicate good reactivity was observed till a temperature of 900℃, after which it started declining. Keywords Red mud, Coerciv ity, Different Temperature 1. Introduction Red mud is a solid waste product discharged in Al2O3, smelt ing as well as the largest pollutant fro m Al2O3 production. The name derives fro m its colour, for it is similar in appearance to red-colour med. Large amounts of redmud are p iled up in outside storage yards, causing environmental pollution, soil basification, paludification, surface water and ground water pollution as well as resource pollution. The effective recycling and safe treat ment of redmud has become a serious problem. So me efforts have been made to treat the red mud by producing cement or making bricks by recycling useful materials fro m the redmud. But these methods have in general not been intensively applied. The alkaline nature of red mud makes it a potential acid-neutralizing agent. Redmud has also been found to have strong binding capacity for heavy metal and therefore can be used for remed iation of heavy metal contaminated soils. Bayer p rocess red mud and their environ mental applications have received substantial research. Calcination is one of the best ways for recycling the red mud. FORC diagrams are more convenient because they do not require the magnetization to be measured in a remanent state. FORC diagram also gives information about coercive field d is t rib ut ion and the rat io o f th e revers ib le and irrevers ib le magnet izat ion p rocesses in the samp le. The study of hysteresis loops can produce significant dynamical informat ion, but it reduces the often complex dynamics of magnetization reversal to only a few quantities, usually the hysteresis loop area and the coercive field. The first-order reversal curve (FORC) method was recently developed to extract more information fro m experiments on magnetic systems. It has produced interesting results, mostly in systems with strong disorder in the physics of magnetism. Fist order reversal curves diagram for soft magnetic materials were reported by Fecioru- Morariu and Stancu. Micro magnetic and Preisach analysis of the First order Reversal curves diagram were proposed to Stancu etal., and explain the single – do main ferro magnetic particle systems. FORC analysis of Ni (SiO2) nanogranular film in the blocked regime was reported by Lav in et al., and explained the magnetic measurements as function of temperature. A simp le approach to the first order reversal curves of two phase magnetic systems were reported by Panagiolopoulos and explained the biasing field as well as coercivity of magnetic systems. XRD, FTIR and microstructure studies of calcined sugarcane Bagasse ash was reported by Govindarajan and Jayalakshmi. He was concluded the temperature increases, the sugarcane Bagasse ash colour changes from black to grey and white, which indicates that the carbon content present reasonably reduced, in the sugarcane Bagasse ash. However little has been done to redmud that is derived or partially derived fro m calcinations methods. In this paper, we report on calcinations of red mud investigated for the first time with the FORC method and correlation between coercivity and hysteresis lo o p s . 2. Materials and Experimental Methods * Corresponding author: firstname.lastname@example.org (R. Gopalakrishnan) Published online at https://www.eduzhai.net Copyright © 2012 Scientific & Academic Publishing. All Rights Reserved 2.1. Material The original red mud sample was provided by NALCO, Orrissa, India. 124 D. Govindarajan et al.: Fist-order reversal curve Study on Calcined Indian Redmud 2.2. Experi mental Methods The samples in s mall amounts were heated in muffle furnace at different fixed temperatures (for 1 hour) ranging fro m 30℃ to 1000℃ ). The samples were named as RM, RM 500℃ , RM 600℃ , RM 700℃ , RM 800℃ , RM 900℃ and RM 1000℃ . RM means the red mud samp le heated at 30℃ , RM 500 means the red mud samples heated at 500℃ etc., The hysteresis parameters of thermally treated redmud samples were recorded at roo m temperature and the FORC were recorded under a sinusoidal waveform of amp litude E0 = 2.5 Kv/mm and frequency f = 1 Hz, using a modified sawyer – Tower circu it. 2.3. Chemical Anal ysis Chemical analysis of the original red mud yielded weight percentages values were Al2O3 (43.75%), Fe2O3 (28.25%), TiO3 (1.89%), SiO2 (2.08%) and LiO2 (23.1) respectively. 3. Results and Discussion 3.1. Hysteresis Parameter FORC’S were measured in red mud samples at different temperatures upto 1000℃ . The corresponding hysteresis loop and the FORC diagrams were shown in Figs 1-14. The standard hysteresis properties Saturation magnetization (Ms (emu)), Remanent magnetizat ion (Mr (emu)), coerciv ity (Hc (Oe)), Squareness of the hysteresis loop (S), Saturation of the mass unit of the sample (Ms (emu/g)), and Remanent mo ment of the mass unit of the sample (Mr (emu/g)) of redmud at different temperatures were measured and reported in table 1.1. The FORC d iagram provides a detailed characterization of the hysteric response of a system because it evidences dominant magnetic interactions, magnetic effects and the annihilation of memory during the demagnetization process. The hysteresis parameter Ms, Hc, and Mr were directly obtained from the FORC measurements. It must be realized that determining the hysteresis parameters fro m FORC measurements may give slightly different values to those determined fro m standard hysteresis measurements because of differences in field history. Figure 2. Hysteresis loop of calcined redmud at 500℃ Figure 3. Hysteresis loop of calcined redmud at 600℃ Figure 4. Hysteresis loop of calcined redmud at 700℃ Figure 1. Hysteresis loop of calcined redmud at room temperature (30℃) Figure 5. Hysteresis loop of calcined redmud at 800℃ International Journal of M aterials and Chemistry 2012, 2(4): 123-127 125 FORC RM6 Figure 6. Hysteresis loop of calcined redmud at 900℃ Figure 10. FORC diagram of calcined redmud at 600℃ FORC RM7 Figure 7. Hysteresis loop of calcined redmud at 1000℃ FORC RM Figure 11. FORC diagram of calcined redmud at 700℃ FORC RM8 Figure 8. FORC diagram of calcined redmud at room temperature FORC RM5 Figure 12. FORC diagram of calcined redmud at 800℃ FORC RM9 Figure 9. FORC diagram of calcined redmud at 500℃ Figure 13. FORC diagram of calcined redmud at 900℃ 126 D. Govindarajan et al.: Fist-order reversal curve Study on Calcined Indian Redmud Name RM RM5 RM6 RM7 RM8 RM9 RM10 Table 1.1. Hyst eresis loop paramet ers of Redmud samples at different temperat ures mass(g) 4.80E-02 4.35E-02 6.56E-02 8.40E-02 5.58E-02 7.95E-02 8.52E-02 Ms(emu) 1.89E-02 1.60E-02 2.08E-02 3.66E-02 1.98E-02 1.70E-02 1.88E-02 Mr(emu) 1.80E-03 1.93E-03 3.18E-03 7.14E-03 2.29E-03 3.24E-03 4.49E-03 Hc(Oe) S 1.79E+02 0.10 1.97E+02 0.12 3.20E+02 0.15 2.33E+02 0.19 1.97E+02 0.12 8.07E+02 0.19 1.26E+03 0.24 Ms(emu/g) 3.94E-01 3.68E-01 3.17E-01 4.36E-01 3.55E-01 2.14E-01 2.20E-01 Mr(emu/g) 3.76E-02 4.45E-02 4.85E-02 8.50E-02 4.12E-02 4.08E-02 5.27E-02 FORC RM10 14 12 10 8 Hc (10-2 Oe) 6 4 2 0 0 200 400 600 800 1000 1200 Figure 14. FORC diagram of calcined redmud at 1000℃ 3.2. FORC Measurement Fig. 1-7 Shows the study of hysteresis loop of FORC diagram measured on calcined red mud samples. The figures clearly indicate the superior and pro minent minerals of hematite are existing in the red mud samples. The ability of FORC d iagrams to give a better description of grain size distribution and magnetic mineralogy. On heating the redmud samples at temperature 600℃ (Fig. 10), the FORC d istributions contract toward the origin, but do not change significantly in shape or appearance until 500℃ (Fig.9). If the contraction is primarily related to the decrease in Hc, then this imp lies that the dominant domain structure does not change significantly with te mperature. The room temperature calcined redmud FORC d iagram (Fig. 8) is asymmetrical, although the Asymmetry decreases with temperature. The FORC d istributions change marked ly with increasing the temperature (Fig 11-14). In addition all FORC distribution strong asymmetry. 3.3. Coerci vity Vs Temperatures A FORC diagram is a contour plot that contains informat ion regarding magnetostatic particle interaction and domain state. The domain state of a particle depends on the particle size. The rat io of Mr/Ms yield information of magnetic do main . The table (1.1) indicates a single domain value of 0.1-0.2. This region clearly indicates the magnetic state of red mud samples are pseudo – single domain and the particle size is 0.1-20 microns. Fig. 15 shows coercivity Vs different temperatures derived FROM fo rc diagra ms . Tem perature Figure 15. Hc Vs temperat ure of redmud sample The coercivity i.e., the width of the thermal hysteresis loop, reflects the strength of intradomain interactions. Low coercivity values can appear upto 500℃ calcined redmud. The temperature at 600℃ of redmud has optimu m Hc compared to other calcined red mud samples. Sudden decrease of Hc is appeared at 800℃ . The rate of decrease is not constant, suggesting thermofluctuation effects are not significant at most temperature. Higher values of Hc are present at 900 and 1000℃ calcined redmud samples. Higher values of coercivity indicate the particles interactions are high. 3.4. Squareness Vs Temperature The squareness of the hysteresis loop (Mr/Ms) Vs diffe rent temperature of red mud samples are shown in Fig . 16. 0.3 0.25 0.2 S 0.15 0.1 0.05 0 0 200 400 600 800 1000 1200 Temperature Figure 16. SVs temperature of redmud sample International Journal of M aterials and Chemistry 2012, 2(4): 123-127 127 The squareness of the hysteresis loop (Mr/Ms) values are  K. E. Snars, R.J. Gilkes and M .T.F. Wong, Aust. J. Soil. Res., increases up to 700℃ calcinations of redmud. calcination 42 (3), (2004), 321-328. of 1000℃ redmud sample having a higher value of Mr/Ms.  O. Lin, M .W. Clark, D. M cConchie, G. Lancaster and N. For the calcinations of 800℃ , Mr/Ms display a sharp Ward, Aust. J. Soil. Res., 40 (2002) 556-563. decrease compared to other red mud samp les. The most likely cause of this is chemical alterat ion during heating. It is  H.S.Altundogan, S. Altundogan, F. Tumen and M . Blldik, Wast. M ang., 22(3), 92002) 357-363. known that the ratio between the remanent and saturation magnetization in a red mud sample is an indicator of the  T.R.F. Peixoto, D.R. Cornejo, J. M ag. M agnetic M at., 320 importance of the reversible processes. The hysteresis (2008) e279-e282. loops of each calcinations red mud samples were rectangular  P.G. Bercoff, M .I. Oliva, E. Broclone and H.R.Bertorello., and completely characterized by the values of saturation Physica B., 320 (2002) 291. magnetic mo ment Ms.  M . F. Morariu, A. Stancu., J.Opto electronics and Adv. M at., 5(4) (2003) 939-944 4. Conclusions The calcination of red mud was studied in th is work by FORC Technique. Fo rce d iagrams appear to be a p ro mising tool for developing an understanding of the magnetic grain size distribution of bulk natural red mud samp les at elevated temperatures. The FORC diagram results showed that calcined red mud have been good reactivity upto 900℃ and the single domain value is 0.1-0.2. 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