Kristalizaciono ponašanje višekomponentnih germanatnih stakala
Crystallization behaviour of multicomponent germanate glasses
Author
Matijašević, Srđan D.Mentor
Grujić, SnežanaCommittee members
Tošić, MihajloPetrović, Rada
![](/themes/MirageNardus/images/orcid.png)
Miladinović, Jelena
![](/themes/MirageNardus/images/orcid.png)
Stojanović, Jovica
Metadata
Show full item recordAbstract
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 četvorokomp...onentnog 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)...
Faculty:
Универзитет у Београду, Технолошко-металуршки факултетDate:
14-12-2012Projects:
- The development of glasses with controlled ions release for application in agriculture and medicine (RS-MESTD-Technological Development (TD or TR)-34001)
- Phenomena and processes of the synthesis of new glassy and nano-structured glass-ceramics materials (RS-MESTD-Basic Research (BR or ON)-172004)