Kontrola strukturnih i mikrostrukturnih karakteristika binarnih i ternarnih oksida titana za primenu u obnovljivim izvorima energije

Abstract

U disertaciji je dat pregled binarnih i ternarnih oksidi titana, počev od fundamen-talnih principa, preko sinteze, karakterizacije i procesiranja, do konkretne primene. Osnovni cilj istraživanja bilo je uspostavljanje zavisnosti između sinteze, svojstava i primene nestehiometrijskih binarnih oksida: titan-monoksida (TiOx) i Manjelijevih faza (TinO2n-1), kao i ternarnih oksida: Li4Ti5O12 spinela i α-Li2-xTiO3-x (OH)x · yH2O koji sadrže litijum. Dobijeni materijali su ispitivani za primenu kao strujni kolektori u olovnim, ili kao elektrode u Li-jonskim akumulatorima. Materijali su sintetisani mehanohemijskim postupkom, koji je u nekim slučajevima praćen termičkim tretmanom, zatim reakcijama u čvrstom stanju, ili hidrotermalnim tretmanom. Za karakterizaciju su korišćene: rendgenska difrakcija, termogravimetrija i diferencijalno-skenirajuća kalorimetrija, skenirajuća i transmisiona elektronska mikroskopija, spektroskopija kuplovana sa plazmom, metoda tri tačke za određivanje provodnosti i ciklična voltametrija. Mlevenjem smeša Ti i TiO2 sa različitim stehiometrijskim odnosima (1:1, 1,1:1 i 1,25:1) već na sobnoj temperaturi dobijen je TiOx, sa x = 0,92 – 1,19 sa veličinom kristalita oko 6 nm. Podešavanjem odnosa reaktanata moguće je diktirati fazni sastav krajnjih, žarenih proizvoda, čime se ostvaruje kontrola provodnosti ovog materijala. Uzorci Manjelijevih faza, TinO2n-1, sa n = 4 – 6, dobijeni su žarenjem mehanohemijski aktiviranih smeša TiO i TiO2 ili Ti2O3 i TiO2, pri čemu je pokazano da temperatura potrebna za dobijanje ovih faza može da se snizi za čak 30 % u odnosu na uobičajeni postupak. Dobijeni oksidi i smeše oksida, kao i originalni EBONEX® prah, prevedeni su u folije uz korišćenje polietilena. Na osnovu poređenja provodnosti i korozione stabilnosti, pokazano je da sintetisani novi materijali imaju bolje karakteristike od EBONEX®-a. Dobijeni su neporozni i elastični strujni kolektori, a neki od ispitanih uzoraka veoma obećavaju kao mogući strujni kolektori u veoma agresivnim sredinama kakva je H2SO4...

Binary and ternary titanium oxides are studied, starting with the fundamental principles, through synthesis, characterization and processing, to the specific applications of these materials. The main goal of this work was to establish functional relations between synthesis, properties and application of nonstoichiometric binary oxides: titanium monoxide (TiOx) and Magneli phases (TinO2n-1), as well as ternary, Li-containing titanium oxides: Li4Ti5O12 spinel and α-Li2-xTiO3-x (OH)x · yH2O. The prapared materials were tested for application as bipolar plate in bipolar Pb-acid battery or as electrode in Li-ion batteries. The materials were prepared by mechanochemical method, in some cases followed by thermal treatment, as well as by solid state reactions and hydrothermal treatment. The products are characterized by X-ray powder diffraction, thermogravimetry and differential scanning calorimetry, scanning and transmission electronic microscopy, optical emission spectrometry coupled with plasma (ICP-OS), three point probe conductivity measurements and cyclic voltammetry. Nanocrystalline cubic titanium monoxide, TiOx (0.92 < x < 1.19), with the mean crystallite size of about 6 nm, was synthesized by mechanochemical treatment of Ti and TiO2 powder mixtures with molar ratios of 1:1, 1.10:1 and 1.25:1. The phase composition of the products after annealing can be directed by setting of the ratio of reactants, and in this way the conductivity of TiOx can be controlled. Some Magneli phases TinO2n-1, with n = 4 – 6, or their mixtures were prepared using mechanochemical procedure followed by thermal treatment from stoichiometric mixtures of TiO and TiO2 or Ti2O3 and TiO2 powders. The temperature needed for synthesis of Magneli phases is lowered for about 30 % in respect to common methods. The prepared oxides and mixtures identical or similar to the Ebonex® powder, and original Ebonex® powder have proceeded into plastic-bonded, non-porous and flexible foil electrodes using a low density polyethylene. The electrodes were tested for corrosion stability in real lead-acid battery conditions and their conductivities were compared. Some investigated samples iii iv are very promising for application as current collector in extremely aggressive H2SO4 surrounding...