Staklokeramika, 70 godina od otkrića Kurajica, Stanislav
Kemija u industriji; časopis kemičara i tehnologa Jugoslavije,
11/2023, Volume:
72, Issue:
11-12
Journal Article
Peer reviewed
Open access
Ove će se godine navršiti 70 godina od otkrića staklokeramike. Tim povodom u ovom je članku dan sveobuhvatan opis ovog materijala i njegovog napretka od otkrića do danas. Objašnjeno je što je ...staklokeramika te ukazano na rast interesa i komercijalni uspjeh ovog materijala. Opisan je proces priprave staklokeramike, a posebna pozornost posvećena je ulozi nukleatora te procesu nukleacije i rasta. Navedeni su čimbenici koji presudno utječu na svojstva staklokeramike poput kristalne faze, njenog udjela, sastava preostale staklene faze i mikrostrukture. Zahvaljujući utjecaju navedenih čimbenika moguće je pripraviti različite vrste staklokeramike, s različitim kristalnim fazama i morfologijama te posljedično različitim svojstvima, prikladne za različite namjene. Predstavljeni su najvažniji sustavi i vrste staklokeramike, opisana su i objašnjena njihova svojstva i navedene namjene, a spomenuti su i nazivi najvažnijih robnih marki komercijalne staklokeramike. U zaključku je dano viđenje perspektive ovog materijala te vrste staklokeramike i područja primjene u kojima je napredak najizvjesniji.
This year will be the 70th anniversary of the discovery of glass-ceramics. On this occasion, a review paper presenting this material and its progress from discovery to the present day is given. It is explained what glass-ceramic is and pointed out to the growth of interest in this material and its commercial success. The process of preparing glass-ceramics is described, while special attention is paid to the role of nucleating agents and the process of nucleation and growth. Factors that decisively affect the properties of glass-ceramics, such as the crystalline phase, its proportion, the composition of the remaining glass phase and the microstructure, are listed. Owing to the influence of the mentioned factors, it is possible to prepare different types of glass-ceramics, with different crystal phases and morphologies and consequently different properties, suitable for different purposes. The most important systems and types of glass-ceramics are presented, their properties and uses are described and explained. The names of the most important brands of commercial glass-ceramics are also mentioned. In the conclusion, a view of the perspective of this material, glass-ceramic types and areas of application in which the progress is most certain is given.
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, 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 LiGe2PO43 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).
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 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 utvrđena je primarna kristalizacija LiGe2PO43 faze sa dimenzijama kristalita 30-500 nm. Određen 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 određena je temperaturna i vremenska zavisnost brzine nukleacije. Brzine nukleacije ovih stakala su u oblasti 1,77•1014 - 7,34•1016 m-3s-1 . Određena 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. Određene 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.
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