THE PRELIMINARY CHARACTERIZATION OF SERPENTINITE FROM LJESKOVAC LOCALITY IN CROATIA

Transcription

1 Acta Metallurgica Slovaca, 14, 2008, 2 ( ) 275 THE PRELIMINARY CHARACTERIZATION OF SERPENTINITE FROM LJESKOVAC LOCALITY IN CROATIA Sučik G. 1, Hršak D. 2, Fedoročková, A 1, Lazić L. 2 1 Faculty of Metallurgy Technical University of Košice, Slovakia, Gabriel.Sucik@tuke.sk 2 Faculty of Metallurgy University of Zagreb, Sisak, Croatia, damirhrsak@yahoo.com ZÁKLADNÁ CHARAKTERIZÁCIA SERPENTINITU Z LOKALITY LJESKOVAC V CHORVÁTSKU Sučik G. 1, Hršak D. 2, Fedoročková, A 1, Lazić L. 2 1 Faculty of Metallurgy Technical University of Košice, Slovakia, Gabriel.Sucik@tuke.sk 2 Faculty of Metallurgy University of Zagreb, Sisak, Croatia, damirhrsak@yahoo.com Abstrakt Článok sa zaoberá stanovením základných fyzikálno-chemických vlastností serpentínu z lokality Ljeskovac na území Chorvátska pomocou vhodných analytických metód. Chemické zloženie bolo stanovené štandardnými analytickými metódami s ohľadom na majoritné zložky MgO, SiO 2, CaO, FeO a Al 2 O 3 [1][2]. Fázová analýza bola práškovou RTG difrakciou žiarenia CuK α. Termochemické vlastnosti boli sledované diferenčnou termickou analýzou. Rozmerové zmeny vplyvom teploty boli sledované dilatometriou. Získané informácie poslúžia ako základ pre ďalšie štúdium možností využitia konkrétneho typu serpentínu serpentínu v priemyselnej oblasti žiaruvzdornými materiálmi počnúc až po čisté oxidy určené pre špeciálne technológie. Abstract In this paper the basic physical and chemical properties of serpentinite from Ljeskovac locality, Croatia, were preliminary studied by suitable analytic methods. Chemical composition was obtained by standard analytical methods with respect of major oxides MgO, SiO 2, CaO, FeO and Al 2 O 3 [1][2]. The powder X-ray diffraction of CuK α radiation was used for determination of phase composition. Thermo-chemical properties of serpentinite were measured by differential thermal analysis. Temperature effect on dimension change followed by chemical and structural changes was observed by dilatometry. The properties knowledge of the examined rock will be used as basic information for next steps in investigation of possibilities to use it in industrial fields from special refractory materials to pure oxides for high technologies. Keywords: serpentinite, lizardite, X-ray powder diffraction, differential thermal analysis, dilatometry Introduction Serpentinite is general name for ultramafic rock containing different minerals called serpentines [3][4][7]. This is analogical to kaoline rock containing kaoline minerals; however, the kaolinite is one of them [5][6][7]. The serpentine-kaoline group include minerals with chemical formula Mg 3 Si 2 O 5 (OH) 4 and they are widespread and occur as alteration products of olivine and other magnesium-rich silicates. Serpentinite minerals are present in metamorphic and igneous rocks [7]. The serpentine-kaoline group includes three closely related minerals:

2 Acta Metallurgica Slovaca, 14, 2008, 2 ( ) 276 lizardite Mg 3 [Si 2 O 5 ](OH) 4, antigorite (Mg, Fe) 3 [Si 2 O 5 ](OH) 4 and chrysotile Mg 3 [Si 2 O 5 ](OH) 4, which have the similar crystal structure and chemical composition, but their different curvature of the layers results in antigorite and lizardite being dense or fine-grained and in chrysotile being fibrous [1][2]. Serpentinite is raw material which is again in focus in recent time because possibility of industrial production of forsterite refractory materials and pure oxides from serpentinites origin, as well as use as efficient absorber of green house gases H 2 O, SO 2 a CO 2. It is necessary to have individual approach because of difference in mineral and chemical composition of serpentinite rock from different localities. This article deals with basic characterization of serpentinite from Ljeskovac locality in Croatia. Experimental procedure Original serpentinite was characterized using X-ray diffraction (XRD) with CuKα radiation. The Philips X Pert Pro type diffractrometer from Institute of Material Research, Slovak Academy of Science in Kosice was used. Diffractometer is equipped by high temperature camera to 1600 C, ultrafast detector-x`celerator and diffracted beam monochromator. Raw data were treated by included software to correction of background and intensities. Deconvolution to α1 and α2 was executed. The α1 diffraction was used for data evaluation. The minor components of serpentinite chemical composition were analyzed by the atomic absorption spectrometer Perkin Elmer 3100, while SiO 2 and MgO content were analyzed by wet chemical analysis. The jaw crusher was used for bulk serpentinite crushing to 0 5 mm and Fritsch Pulverisette 502 ball mill with Hatfield steel chamber was used for finally grain size µm. Differential thermal analysis (DTA) and thermal gravimetric analysis (TGA) were conducted by derivatograph MOM Q 1500D at the heat speed of 10 C.min -1 in air atmosphere. The sample initial weight was 100 mg and the maximum temperature was 1000 C. The sample was smeared before analysis in agate cup. For the dilatation analysis Netzsch dilatometer 402 E type was used, at the maximum analysis temperature of 1250 C, heat speed of 5 C.min -1 and measurement range of 5000 µm/scale. The sample length was mm. Mechanical treatments and analysis has done at work places of Faculty of Metallurgy, Technical University of Kosice. Analog output signals from equipments were converted by LabJack U12 measuring terminal with 12 bites A/D converter and stored to personal computer. Obtained data evaluation was done by special software [8]. All graphic outputs were made by MS Excel table processor and prepared for presentation [9]. Results and Discussion The results of the chemical analysis of raw serpentinite indicate Table 1. Difference between ignition loss determination by chemical analysis and by TGA has been caused by different analytical procedures. It follows, that TGA brings more exact results. Table 1 Chemical composition of raw serpentinite in % MgO SiO 2 Al 2O 3 CaO FeO Fe 2O 3 Cr 2O 3 Na 2O K 2O MnO NiO ZnO Wet Ign. loss

3 Acta Metallurgica Slovaca, 14, 2008, 2 ( ) 277 Results of XRD analysis represented in Fig.1show that lizardite-1t is dominant mineral constituents of Ljeskovac serpentinite. The main diffraction lines are on: [001], [002], and [003] hkl positions. This reflection belongs to tetrahedral layer of (SiO 4 ) 4- with 7Å 7.3Å interlayer distance and characterizes of mineral group serpentinite-kaoline. Next smaller reflections are described in table 2. The position of the measured reflections were compared with calculated diffraction data databases of lizardite [10][11], antigorite [12], magnesioferrite [13] and magnetite [14]. 1 5 Intensity theta CuKα [ ] Fig.1 XRD scattering of Ljeskovac serpentinite Table 2 Measured diffraction data of Ljeskovac serpentinite Peak 2Θ [ ] d [Å] RI [%] h k l Mineral Lizardite Lizardite Antigorite Lizardite Lizardite Antigorite Magnesioferrite Lizardite Magnesioferrite Lizardite Lizardite Lizardite Magnesioferrite Lizardite Lizardite Magnesioferrite Magnesioferrite Lizardite Lizardite Magnesioferrite Lizardite Lizardite

4 Acta Metallurgica Slovaca, 14, 2008, 2 ( ) 278 The graphic results of TGA and DTA of the studied serpentinite are shown in Fig.2. The endothermic peaks at 598 C and 694 C indicate the decomposition of crystal structure of serpentinite. The crystal lattice decomposition is connected with 11.2 % weight loss caused by disappearing of the chemical bonded water. Forsterite formation is indicated by exothermic peak at 825 C, with beginning at 804 C [15][16] mg mg (-5.5%) Weight [mg] mg (-11.2%) 825 C C 804 C C Temperature [ C] Fig.2 DTA of the serpentinite Dilatation [%] Temperature [ C] Fig.3 Results of dilatation analysis of serpentinite sample For industrial processing of the raw serpentinite is good to know bulks size changes by thermal treatment, as well as changes of mechanical properties with reference to crushing and

5 Acta Metallurgica Slovaca, 14, 2008, 2 ( ) 279 grinding. In Fig.3 is shown the dilatation of serpentinite raw material engraved from serpentinite compact sample is shown in Fig.4. Its shape was limited by construction of dilatometer sample holder. The sample dimensions were mm. The curve corresponding with DTA investigations shows that the first contraction of sample is caused by dehydration of lizardite near 700 C accompanied by forsterite phase formation, which begins above 800 C. The second contraction of sample, which begins at 1000 C, is induced by sintering of fine grains. The first contraction is 0.45 % and the second 9.17 %. The sample after dilatometry process was damaged and lot of disruptions appears. Initial strength of measured sample was lost. Fig.4 Cut profile from the Ljeskovac serpentinite for the dilatation measurement Conclusion Serpentinite from Ljeskovac locality, Banovina, Croatia, was studied. The lizardite is the dominant constituents of this serpentinite and magnesioferrite is the second determined phase. For successful decomposition of original crystal lattice of serpentinite by thermal treatment 3 hours, dwell at 660 C is need. The beginning of forsterite phase formation is at 804 C. Presence of the forsterite stable lattice in treated powder increases its thermal and chemical stability. The dilatation curve is in accord with the dehydration of serpentinites at 650 C and the forsterite phase formation is accompanied with contraction of 0.45 %. The contraction of sintering after 1000 C is 9.17 %. Literature [1] Deer W. A., Howie R. A., Zussman J.: An Introduction to the Rock - Forming Minerals, Longman Scientific & Technical, Hong Kong, [2] Hall A.: Igneous Petrology, Longman Scientific & Technical, Malaysia, [3] Blatt H., Tracy R. J.: Petrology: Igneous, Sedimentary, and Metamorphic, W. H. Freeman and Company, New York, [4] Hyndman D. W.: Petrology of Igneous and Metamorphic Rocks, McGraw-Hill, New York, [5] Bailey S.W. et. al: Summary of recommendaions of AIPEA nomenclature committee on clay minerals. Amer. Mineral., 65, p.1-7, [6] Bailey S.W. et. al: Nomenclature for regular interstratifications. Clay minerals, 17, p , 1982, [7] Weiss Z., Kužvart M.: Jílové minerály: Jejich nanostruktura a využití. Univerzita Karlova v Praze, Karolinum, Praha 2005, ISBN

6 Acta Metallurgica Slovaca, 14, 2008, 2 ( ) 280 [8] Sučik G., Ďurišin J., Kuffa T.: Pripojenie derivatografu Q1500D na PC AT/XT. In: TERMANAL '94 : Zborník z 13. konferencie o termickej analýze s medzinárodnou účasťou : Stará Lesná, Bratislava : CHTF STU, s [9] Šimoňák S., Tomášek M., Vokorokos L.: Programové prostriedky pre tvorbu dokumentov, tabuľkové výpočty a sieťové služby. Elfa Košice 2000, ISBN [10] Guggenheim S, Zhan W.: Effect of temperatureon the structures of lizardite - 1T and lizardite - 2H1. The Canadian Mineralogist 36 (1998) [11] Mellini M: The Crystal Structure of Lizardite - 1T: hydrogen bonds and polytypism. American Mineralogist, 68 (1982) [12] Uehara S.: TEM and XRD study of antigorite superstructures. The Canadian Mineralogist 36 (1998) [13] Michejev V., I.: Rentgenometričeskij opredeliteľ mineralov. Kartfabrika Gosgeoltechizdata, [14] Fjellvag H., Gronvold V., Stolen S., Hauback B.C.: On the crystallographic and magnetic structures of nearly stoichiometric iron monoxide. Journal of solid state chemistry, 124 (1996) [15] Hršak D., Malina J., Hadžipašić A.B.: The Decomposition of Serpentinite by Thermal Treatment. Materiali in Tehnologije, vol. 39(6) (2005), p , Slovenia. [16] Sučik G., Hršak D.: DTA a rafinácia serpentinitu. Zborník prednášok, Medzinárodná konferencia o termickej analýze a kalorimetrii TERMANAL 2003, Vysoké Tatry.