Uticaj parametara procesiranja na tok mehanohemijske sinteze i sprečavanje pojave aglomeracije sintetisanih nanostrukturnih prahova

Abstract

Keramički nanomaterijali kao što su cink oksid (ZnO) i cirkonijum dioksid (ZrO2), poseduju veliki potencijal za primenu u najrazličitijim oblastima industrijske proizvodnje pre svega zahvaljujući nanodimenzijama čestica. Konvencionalnim metodama sinteze kao što su sol-gel metoda, metoda precipitacije, hidrotermalna sinteza, sprej piroliza i druge, veoma često nije moguće prevazići problem aglomeracije čestica praha. Mehanohemijska sinteza dala je izuzetne rezultate u dobijanju najrazličitijih materijala izgrađenih od fino dispergovanih čestica nanometarskih dimenzija. U eksperimentima predstavljenim u ovom magistarskom radu korišćena je mehanohemijska metoda u cilju dobijanja nanostrukturnih prahova ZnO i ZrO2. Ispitivan je uticaj parametara (vremena mlevenja, temperature kalcinacije) na tok sinteze. Posebna pažnja posvećena je ispitivanju uticaja različitih vrsta neogranskih i organskih jedinjenja koja predstavljaju reagense za kontrolu procesa, PCA (prosess controling agens), na morfologiju i dimenzije čestica sintetisanih keramičkih prahova. U svim eksperimentima korišćen je planetarni mlin proizvođača Retsch PM4, ahatne posude i kuglice od alumine. Vremena mehaničkog tretiranja varirana su od 30 min do 8 h. Kao neorganski PCA reagensi korišćeni su: natrijum hlorid (NaCl) u sintezi praha ZrO2; kalcijum hlorid (CaCl2) u sintezi praha ZnO; dok je kao organski PCA reagens u sintezi praha ZnO korišćena oksalna kiselina (C2H2O4•2H2O). Temperature kalcinacije kretale su se u intervalu od 300 do 800 °C. Uzorak praha ZnO mehanohemijski je tretiran 4 h u vodenom rastvoru oksalne kiseline kao PCA, potom je kalcinisan 1 h na temperaturi 450 °C. Utvrđeno je da se sastoji od čestica najmanjih dimenzija u odnosu na ostale ispitivane materijale, da ima najveću uniformnost pri čemu su čestice dimenzija 50-90 nm i da je gotovo potpuno sprečena njihova aglomeracija. Uzorci prahova karakterisani su pomoću difrakcije X-zračenja na kristalnom prahu, skanirajuće elektronske mikroskopije (SEM), visokorezolucione skanirajuće elektronske mikroskopije (FE SEM), diferencijalne termijske analize (DTA) i termogravimetrijske analize (TG).

Ceramic nanostructured materials, such as zinc oxide, ZnO, and zirconium dioxide, ZrO2, have a great potential for the application in various areas of industrial production primarily due to their nanosized particles. In conventional methods of synthesis such as solgel processing, precipitation from the solution, hydrothermal synthesis, spray pyrolysis, etc., very often, it is not possible to overcome problems posed by powder particle agglomeration. Mechanochemical synthesis gives excellent results in obtaining nanostructured materials. It has been widely applied for preparation of large variety of materials composed of highly dispersed nanosized particles. In the experiments presented in this thesis, mechanochemical synthesis was used to obtain nanostructured ZnO and ZrO2 powders. We examined the influence of different processing parameters (milling time, calcination temperature) on the course of the synthesis. Special attention was paid to the study of the impact of different types of inorganic and organic compounds used as PCA (process controlling agent) on the morphology and dimensions of synthesized ceramic particles. In all experiments, we used planetary ball-mill, Retsch PM4, agate jars and alumina balls. Mechanical treatment time varied from 30 min to 8 h. NaCl was used in the synthesis of ZrO2 powder as an inorganic PCA, whereas in the synthesis of ZnO powder we used CaCl2. Oxalic acid (C2H2O4•2H2O) was used as an organic PCA in the synthesis of ZnO powder. Calcination temperature ranged in the interval of 300-800 °C. The smallest particle sizes, varying between 50 and 90 nm, and the best particle size uniformity were obtained in the ZnO powder sample mechanochemically treated for 4 h, in water solution of oxalic acid (C2H2O4•2H2O)aq as PCA, calcinated for 1 h at 450 °C. Particle agglomeration was almost completely prevented. Powder samples were characterized using X-ray powder diffraction (XRPD), Scanning electron microscopy (SEM), Field emission microscopy (FE SEM), Differential thermal analysis (DTA) and Thermogravimetric analysis (TG).