DEVELOPMENT OF GLASS-CERAMICS BY CONTROLLED NUCLEATION AND CRYSTALLIZATION OF GLASS SAMPLES PRODUCED FROM LOCAL RAW MATERIALS

By

Author

Presented To

Department of Environmental Design

ABSTRACT
Glass-ceramic materials were produced by the process of controlled nucleation and crystallization of glass samples. The glass samples were produced using locally available raw materials. (Feldspar, Limestone and Magnesite). The raw materials were sourced from Matari (Kaduna State), Kalambaina (Sokoto State) and Tsakesimptah (Adamawa State). The raw materials and the resultant glass-ceramics were characterized using instrumental analytical techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersion spectroscopy (EDS) to ascertained their chemical compositions, mineral phases present, surface morphologies and elemental distributions respectively to enable the researcher to determined their suitability in glass and glass-ceramics making while differential scanning calorimetry (DSC) was used to determine the glass transition temperatures (Tg) of the produced glasses.Each glass-ceramics was produced using two main steps: In the first step, the produced glass was heated to a temperature 100? above the transition temperature and maintained at that temperature for 1-4 hours to achieve nuclei formation. In the second step, the nucleated material was heated to a higher temperature 300? above transition temperature to allow the growth of crystal onto the nuclei. Mechanical, chemical and physical properties of the resultant glass-ceramics were evaluated using standard procedures. The XRFresult revealed that potash- K2O (11.33wt %) was the major alkali oxide in Matari feldspar. Therefore, the feldspar ore can be classified as potash feldspar while silica(67.32wt %SiO2) and alumina(17.54wt %Al2O3) were also present in the form of aluminosilicate. Other oxide such as Fe2O3 (0.10wt %), Cr2O3 (<0.01 ??%) werewithin the tolerable levels.The XRD pattern of Matari feldspar revealed that the dominant mineral phase was microcline (K2O.Al2O3.6SiO2) (59.6wt %) alongside albite (Na2O.Al2O3.6 SiO2) (34.7wt %) and Quartz (SiO2) (5.71wt %), as lesser phases. SEM image shows that microcline is characterized by lamellar twinning and the EDS confirmed the presence of the following elements: K, Si, Al, C, O and Na in the feldspar.XRF showed that the primary oxide present in Kalambaina limestone was CaO (53.08wt %). The impurities (0.55wt %Fe2O3), (0.33wt %MnO2), (<0.01wt %Cr2O3), (<0.01 wt %NiO2) and (<0.01 wt %Cu2O) among others were present. XRD denotes calcite (99.5 wt %) as major mineral phase in Kalambaina limestone and quartz (0.5 wt %) as minor mineral phase. SEM displays massive agglomeration of dust particles and the EDS revealed the presence of the following elements: Ca,Si, Mg, Ba, O.The chief oxide present in Tsakesimptah magnesite as determined by XRFwas magnesia (63.03wt %MgO) alongside impurities such as: (2.86 wt%Fe2O3),(0.08wt%MnO2), (9.77 wt%CaO)among others. The primary mineral phase present in the sample was calcio-olivine (80.08 wt %) whileolivine Hp(19.2 wt %) was the secondary mineral phase. SEM displays very fine particles and K, Ca, Fe, Si, Al and Mg were the elements distributed on SEM micrograph as determined by EDS.The produced glass samples from the raw materials were undesirably brown, and this was due to the presence of large amounts ofthe Fe2O3, Cr2O3, MnO2, Cu2O and V2O5among others, which are often used as colourants in glass making. It has been observed that the glass transition temperature of each sample decreases decreases on titania (TiO2) addition indicating stability and network homogeneity in the glass systems.The SEM images viii of the produced glass-ceramics were characterized by dense, needle-like, circular-like, and ellipsoidal-like and fewer micro sized bubbles dispersed in the matrix of residual glassy phase while XRD detected the presence of the following crystalline phases: Albite, cordierite, wollastonite, monticellite, titanate, witherite, andradite and calcite, hematite, quartz, calcite and microcline in the glass- ceramic samples.The effect of heat treatment time and titania (TiO2) addition produced a wide variety of microstructural configuration, crystalline phases, physical properties, chemical stability and mechanical properties.However, glass-ceramic sample to which 10wt% TiO2 was incorporated and heat treated for four hours containedthe following crystalline phases:titanate, calcite, microcline, wollastonite, albite, cordierite, monticellite, andradite, hematite and quartz. Also, the same sample possesses the highest hardness value(988 HV) and density of (2.8873 g/cm3) as well as least porosity value (0.1422%), minimum water absorption value (0.0598%), highest resistance(0.2443g/cm3) in 1M HCl and (0.3211g/cm3) in 1M NaOH solutions. Therefore, the glass-ceramic sample can be recommended for use in cladding, tiling and abrasion resistant applications based on crystalline phases, chemical, mechanical and physical properties.