Crystallization behaviour of multicomponent germanate glasses

Predmet ove doktorske disertacije je ispitivanje kristalizacionog ponašanja germanatnih i germanatnofosfatnih stakala iz sistema K2O-Nb2O5-GeO2 i Li2O-Al2O3- GeO2-P2O5. Na osnovu preliminarnih ispitivanja za proučavanje su izabrana stakla sastava: 30K2O·34Nb2O5·36GeO2 (mol%) i 22,5Li2O·10Al2O3·30GeO2·37,5P2O5 (mol%). Kristalizacione osobine ispitane su pri izotermskim i neizotermskim uslovima kristalizacije. Dobijeni rezultati pokazuju da trokomponentno germanatno staklo kristališe primarnom kristalizacijom, pri čemu fazni sastav kristalisanog uzorka kao i nastajanje pojedinih kristalnih faza zavise od temperature kristalizacije. Na temperaturama kristalizacije < 800 °C kao primarna faza javlja se K3.8Nb5Ge3O20.4, a kao sekundarne faze javljaju se K4Nb6O17 i K6Nb6Ge4O26. Na temperaturama kristalizacije > 800 °C kao primarna faza javlja se K6Nb6Ge4O26, a kao sekundarne faze javljaju se: K3.8Nb5Ge3O20.4, K10Nb22Ge4O68 i KNbO3 faza. Dimenzije kristalita su 20-100 nm. U slučaju četvorokomponentnog germanatnofosfatnog stakla utvrñena je primarna kristalizacija LiGe2[PO4]3 faze sa dimenzijama kristalita 30-500 nm. Odreñen je uticaj granulacije praha stakla na mehanizam kristalizacije i fazni sastav kristalisanih uzoraka. U slučaju kompaktnih uzoraka stakla konstatovan je zapremiski mehanizam kristalizacije sa sferulitskom morfologijom rasta kristala kod oba sastava. Ispitan je proces nukleacije i odreñena je temperaturna i vremenska zavisnost brzine nukleacije. Brzine nukleacije ovih stakala su u oblasti 1,77·1014 - 7,34·1016 m-3s-1 . Odreñena je temperaturna zavisnost brzina rasta kristala i energije aktivacije koje iznose od 294 kJ/mol do 1150 kJ/mol u zavisnosti od faze koja se formira. Odreñene su oblasti nukleacije i rasta kristala, temperature maksimalne brzine nukleacije i procenjene temperature maksimalne brzine rasta kristala. Konstatovano je preklapanje oblasti nukleacije i rasta kristala kod oba sastava. U ispitivanjima su korišćene metode atomske apsorpcione (emisione) spektrometrije (AAS), spektrofotometrije, dilatometrije, diferencijalno-termijske analize (DTA), diferencijalno-skenirajuće kalorimetrije (DSC), infracrvene spektroskopije (FT-IC), rendgenske difrakcione (XRD) i skenirajuće elektronsko mikroskopske (SEM) analize...The subject of this thesis is the study of the crystallization behavior of germanate and germano-phosphate glasses from the systems K2O-Nb2O5-GeO2 and Li2O-Al2O3-GeO2- P2O5. Based on preliminary experiments the glasses of composition 30K2O·34Nb2O5·36GeO2 (mol%) and 22,5Li2O·10Al2O3·30GeO2·37,5P2O5 (mol%) were selected for examination. The crystallization properties were examined under isothermal and non-isothermal crystallization conditions. Three-component germanate glass crystallize by primary crystallization while the phase composition of crystallized sample and formation of the crystalline phases depends on temperature of crystallization. At crystallization temperatures < 800°C as the primary phase K3.8Nb5Ge3O20.4, appeared and as seconday ones are K4Nb6O17 and K6Nb6Ge4O26. For T > 800 °C, the K6Nb6Ge4O26 appeared as primary phase and as secondary ones are K3.8Nb5Ge3O20.4, K10Nb22Ge4O68 and KNbO3. In the case of four-component germano-phosphate glass the primary crystallization of LiGe2[PO4]3 phase with crystallites dimension of 30-500 nm was detected. The effect of the grain size of glass powders on crystallization mechanism and phase composition of the crystallized samples was determined. For both glass compositions the volume crystallization mechanism with a spherulitic growth morphology of crystals was determined on compact glass samples. The nucleation process was studied and the temperature and time dependencies of nucleation rate were defined. The nucleation rate of these glasses are in the range 1,77·1014 - 7,34×1016 m-3s-1 . Also, the temperature dependence of crystal growth rate was determined and the activation energies calculated are 294 - 1150 kJ/mol depending on the phase formed. The temperature ranges of nucleation and crystal growth and the temperature of maximal nucleation rate and the temperatures of maximal crystal growth rates were determined. For both glass compositions, an overlapping of nucleation and crystal growth range was noted. The methods employed for investigation are: atomic absorption spectroscopy (AAS), spectrophotometry, dilatometry, differential thermal analysis (DTA), differential scanning calorimetry (DSC), infra reed spectroscopy (FTIR), X- ray diffraction (XRD) and scanning electron microscopy (SEM)..

Removal of uranium (VI) from aqueous solution by acid modified zeolites

Cilj ovog rada je prikaz mogućnosti primene prirodnog i modifikovanog zeolitskog minerala kao adsorbenta i materijala za sanaciju voda kontaminiranih uranijum jonom. Modifikovani uzorci zeolita dobijeni su tretiranjem prirodnog zeolita - klinoptilolita sa kiselinama: hlorovodoničnom, oksalnom i limunskom. Polazni i modifikovani zeoliti su okarakterisani hemijskom analizom, skenirajućom elektronskom mikroskopijom (SEM), rendgenskom analizom (XRPD), IC spektroskopijom, termičkom (TG/DTA) analizom i određivanjem kapaciteta katjonske izmene, a polazne i neadsorbovane količine uranijum jona su određene fluorimetrijski. Eksperimenti su sprovedeni da se ispita uticaj odnosa čvrsto/tečno, pH i vremena na adsorpciju uranijum jona na zeolitu. Utvrđeno je da tretman sa kiselinama zeolita povećava adsorpciju uranijum jona. Najviši indeks adsorpcije imao je uzorak zeolita modifikovan sa hlorovodoničnom kiselinom. Dobijeni rezultati adsorpcije na H-zeolitu su izračunati prema Langmirovom modelu. Projekat MPNTR, br. 142057 Razvoj stakala sa kontrolisanim otpuštanjem jona za primenu u poljoprivredi i medicini (MPNTR - 34001)The objective of this study was the review of natural zeolite, modified with acid, as a candidate material for the remediation of groundwater contaminated by uranium(VI). The modified zeolite samples were obtained by treatment of natural zeolite - clinoptilolite with acids: hydrochloric, oxalyc and citric. Starting and modified zeolites were characterized by chemical analysis, SEM, XRPD analysis, IR spectroscopy, thermal (TG/DT) analysis and by determination of cation exchange capacity, while starting and nonadsorbed amounts of uranium(VI) ion were determined by fluorometric method. Batch experiments were conducted to investigate the effect of solid/liquid ratio, pH and time on the U(VI) uptake by zeolite. Modification of zeolitic tuff with acids significantly increased adsorption of uranium(VI). The highest adsorption of uranium(VI) ion was achieved on clinoptilolite modified with hydrochloric acid. Uranium(VI) adsorption data for zeolite modified with hydrochloric acid was fitted to the Langmuir model. Projekat MPNTR, br. 142057 The development of glasses with controlled ions release for application in agriculture and medicine (MESTD - 34001

The Analysis of the Nucleation Process of the Lithium Germanium Phosphate Glass

The nucleation process of lithium germanium-phosphate glass was studied to determine the temperature range of nucleation and the temperature of the maximum nucleation rate. The differential thermal analysis (DTA), and scanning electron microscope (SEM) were used to reveal the nonisothermal and isothermal process of nucleation, respectively. The crystallization process occurred at a high homogeneous nucleation rate and the spherulitic crystal growth morphology. Nanostructured samples were obtained

Oxide powder mixture with poly-vinyl alcohol (PVA) and added polyethylene glycol (PEG) as plasticizer

Powder mixture consisted of ZnO, Mn2O3 (MnCO3) and Fe2O3 blended powders, was found laminating during compaction. Polyvinyl alcohol (PVA) and a combination of PVA with polyethylene glycol (PEG) added as a plasticizer, were introduced as polymer binders to improve the compaction of oxide mixtures. It has been done by forming a suspension of oxide mixture and varying the polymer solution concentration and composition. By evaporating the solvent, new materials were obtained, which consist of oxide particles bound via polymer. In such a manner obtained hybrid materials were characterized with attenuated total reflection Fourier transformed infrared (ATR-FTIR) spectroscopy, differential thermal analysis (DTA) and transmission electron microscopy (TEM). The oxide polymer material was compacted at 200 MPa and the expansion of this compact during heating was monitored in temperature range up to 550 ºC with dilatometer. It was found that PVA forms graft polymer with PEG and specific interaction with oxide particles surface was revealed

Sintering and Phase Transition of the ZnTiO3 Nano Powder Dilatometric Data Deconvolution

Sintering and phase transition are often superimposed at dimensional change diagram recorded during heating. Phase transition kinetic is thus hard to deconvolute due to the superposition of the sintering and phase transition dimensional change phenomena. Metastabile perovskite phase ZnTiO3has transition to stabile spinel Zn2TiO4which occurs at 945oC with high kinetic rate. Nano powder with 40 nm particle diameter was pressed uniaxially at 200 MPa pressure without binder to form compact that will be consequently sintered. Dimensional change during heating was monitored using dilatometric thermo-mechanical analyzer TMA model SETSYS Evolution. Lever`s rule was used to calculate amount of the emerging phase during phase transition. The compacted specimens were treated on the nonisothermal schedule up to 1050oC.Sintering phenomenon of the ZnTiO3 nanopowder compact was also recorded up to 900oCwith isothermal holding of 25 minutes where phase transition was avoided due to lower temperature and isothermal holding. Second run heating of the obtained sintered specimens were recorded with the heating schedule of non-isothermal heating up to 1050oC. Kinetic of the phase transition was obtained from dilatograms recorded during sintering and from bulk on the second run heating. Furthermore, phase transition kinetics was obtained by subsequent data subtraction of the sintering curves without phase transition from the dilatation sintering curves containing phase transition. In such a manner complex kinetics of phenomena such as sintering, linear expansion and phase transition recorded as dimensional change during heating brings the recognition of their mutual interconnected relations. Also application of these mathematical operations on dilatometric data leads to the established procedure for the sintering and phase transition data treatment

Sintering and Phase Transition of the ZnTiO3 Nano Powder Dilatometric Data Deconvolution

Sintering and phase transition are often superimposed at dimensional change diagram recorded during heating. Phase transition kinetic is thus hard to deconvolute due to the superposition of the sintering and phase transition dimensional change phenomena. Metastabile perovskite phase ZnTiO3has transition to stabile spinel Zn2TiO4which occurs at 945oC with high kinetic rate. Nano powder with 40 nm particle diameter was pressed uniaxially at 200 MPa pressure without binder to form compact that will be consequently sintered. Dimensional change during heating was monitored using dilatometric thermo-mechanical analyzer TMA model SETSYS Evolution. Lever`s rule was used to calculate amount of the emerging phase during phase transition. The compacted specimens were treated on the nonisothermal schedule up to 1050oC.Sintering phenomenon of the ZnTiO3 nanopowder compact was also recorded up to 900oCwith isothermal holding of 25 minutes where phase transition was avoided due to lower temperature and isothermal holding. Second run heating of the obtained sintered specimens were recorded with the heating schedule of non-isothermal heating up to 1050oC. Kinetic of the phase transition was obtained from dilatograms recorded during sintering and from bulk on the second run heating. Furthermore, phase transition kinetics was obtained by subsequent data subtraction of the sintering curves without phase transition from the dilatation sintering curves containing phase transition. In such a manner complex kinetics of phenomena such as sintering, linear expansion and phase transition recorded as dimensional change during heating brings the recognition of their mutual interconnected relations. Also application of these mathematical operations on dilatometric data leads to the established procedure for the sintering and phase transition data treatment

The analysis of the crystal growth process of the lithium germanium phosphate glass : [invited presentation]

The crystal growth rate of lithium germanium-phosphate glass was studied. The glasses have been homogenized using the previously established temperature-time conditions, which make it possible to remove a volatile substances from the glass melt. The AAS was used to determine the chemical content of obtained glass, the differential thermal analysis (DTA), and scanning electron microscope (SEM) were used to reveal the isothermal process of crystal growth, respectively. It has been found that the experimental determined crystal growth rate has a tendency toward of exponentially increase with an increase the temperature

The crystal growth of NASICON phase from the lithium germanium phosphate glass

The crystal growth rate of LiGe2(PO4)3 phase from lithium germanium-phosphate glass was studied. The glass have been homogenized using the previously established temperature-time conditions, which make it possible to remove volatile substances from the glass melt. The atomic absorption spectrophotometry (AAS) was used to determine the chemical content of the obtained glass and scanning electron microscope (SEM) were used to reveal the isothermal process of crystal growth. The crystal growth rates were determined experimentally and theoretically

Psihoanaliza i njezine sudbine: Radovi šestog Okruglog stola Odsjeka za filozofiju

Uzimajući za povod obljetnice dvaju najpoznatijih Freudovih djela, u napetosti između znanstveno-teorijskog optimizma Tumačenja snova i kulturno-povijesnog pesimizma Nelagode u kulturi, željeli bismo iznova ispitati istraživačke potencijale i/ili granice Freudova djela u njegovim različitim aspektima i primjenama na kritičko promišljanje suvremenih fenomena 21. stoljeća. Iako su ta Freudova djela već davno prerasla okvire i doseg pojedinačnih teorema psihoanalize i postala ishodištem kako mnogih znanstvenih doprinosa tokom 20. stoljeća tako i društvenih i kulturnih formi života, poput terapijskih praksâ i primjenâ psihoanalize u akademskim studijima, polazimo od pretpostavke da ta djela i dalje predstavljaju neiscrpljeno teorijsko uporište i metodološki pokretač bazičnih istraživanja od metapsiholoških i analitičko-praktičkih preko filozofskih i znanstveno-teorijskih do njihovih različitih interdisciplinarnih primjenâ na društvene fenomene, uključujući i preoblikovanja psihoanalitičkih teorema u bliskim izvanznanstvenim područjima psihoterapije te prikazivačkih i izvedbenih umjetnosti. (Iz Uvodne riječi.)Uzimajući za povod obljetnice dvaju najpoznatijih Freudovih djela, u napetosti između znanstveno-teorijskog optimizma Tumačenja snova i kulturno-povijesnog pesimizma Nelagode u kulturi, željeli bismo iznova ispitati istraživačke potencijale i/ili granice Freudova djela u njegovim različitim aspektima i primjenama na kritičko promišljanje suvremenih fenomena 21. stoljeća. Iako su ta Freudova djela već davno prerasla okvire i doseg pojedinačnih teorema psihoanalize i postala ishodištem kako mnogih znanstvenih doprinosa tokom 20. stoljeća tako i društvenih i kulturnih formi života, poput terapijskih praksâ i primjenâ psihoanalize u akademskim studijima, polazimo od pretpostavke da ta djela i dalje predstavljaju neiscrpljeno teorijsko uporište i metodološki pokretač bazičnih istraživanja od metapsiholoških i analitičko-praktičkih preko filozofskih i znanstveno-teorijskih do njihovih različitih interdisciplinarnih primjenâ na društvene fenomene, uključujući i preoblikovanja psihoanalitičkih teorema u bliskim izvanznanstvenim područjima psihoterapije te prikazivačkih i izvedbenih umjetnosti. (Iz Uvodne riječi.

Psihoanaliza i njezine sudbine: Radovi šestog Okruglog stola Odsjeka za filozofiju

Uzimajući za povod obljetnice dvaju najpoznatijih Freudovih djela, u napetosti između znanstveno-teorijskog optimizma Tumačenja snova i kulturno-povijesnog pesimizma Nelagode u kulturi, željeli bismo iznova ispitati istraživačke potencijale i/ili granice Freudova djela u njegovim različitim aspektima i primjenama na kritičko promišljanje suvremenih fenomena 21. stoljeća. Iako su ta Freudova djela već davno prerasla okvire i doseg pojedinačnih teorema psihoanalize i postala ishodištem kako mnogih znanstvenih doprinosa tokom 20. stoljeća tako i društvenih i kulturnih formi života, poput terapijskih praksâ i primjenâ psihoanalize u akademskim studijima, polazimo od pretpostavke da ta djela i dalje predstavljaju neiscrpljeno teorijsko uporište i metodološki pokretač bazičnih istraživanja od metapsiholoških i analitičko-praktičkih preko filozofskih i znanstveno-teorijskih do njihovih različitih interdisciplinarnih primjenâ na društvene fenomene, uključujući i preoblikovanja psihoanalitičkih teorema u bliskim izvanznanstvenim područjima psihoterapije te prikazivačkih i izvedbenih umjetnosti. (Iz Uvodne riječi.)Uzimajući za povod obljetnice dvaju najpoznatijih Freudovih djela, u napetosti između znanstveno-teorijskog optimizma Tumačenja snova i kulturno-povijesnog pesimizma Nelagode u kulturi, željeli bismo iznova ispitati istraživačke potencijale i/ili granice Freudova djela u njegovim različitim aspektima i primjenama na kritičko promišljanje suvremenih fenomena 21. stoljeća. Iako su ta Freudova djela već davno prerasla okvire i doseg pojedinačnih teorema psihoanalize i postala ishodištem kako mnogih znanstvenih doprinosa tokom 20. stoljeća tako i društvenih i kulturnih formi života, poput terapijskih praksâ i primjenâ psihoanalize u akademskim studijima, polazimo od pretpostavke da ta djela i dalje predstavljaju neiscrpljeno teorijsko uporište i metodološki pokretač bazičnih istraživanja od metapsiholoških i analitičko-praktičkih preko filozofskih i znanstveno-teorijskih do njihovih različitih interdisciplinarnih primjenâ na društvene fenomene, uključujući i preoblikovanja psihoanalitičkih teorema u bliskim izvanznanstvenim područjima psihoterapije te prikazivačkih i izvedbenih umjetnosti. (Iz Uvodne riječi.