Preparation and characterization of nucleated glass-ceramics based on basaltic rocks

Abstract

Glass-ceramics were prepared from basaltic rocks and by-pass cement dust. The effects of addition of the nucleating agents Cr 2 O 3 , ZrO 2 , and CaF 2 on crystallization, phase assemblages, and microstructure were investigated. The glasses were melted at a temperature of around 1400°C and heat-treated at 1000°C for 2 h; the produced glass was examined by DTA, while glass-ceramics was examined by XRD and SEM. The presence of Cr 2 O 3 , ZrO 2 , and CaF 2 was found to enhance and favor the crystallizability of wollastonite, quartz formation, and retarded the formation of gehlenite. Cr 2 O 3 and ZrO 2 are much better than CaF 2 in promoting homogeneous nucleation as well as in the growth of the extremely fine-grained microstructure of aluminous pyroxene, wollastonite, quartz, and magnetite with uniform crystal size that is below 50 nm in the glass containing Cr 2 O 3. Mechanical and physical properties, such as microhardness, bending strength, density, and thermal expansion coefficient of the glass have been examined. The results demonstrate that the glass-ceramics have a potential for a wide range of application, such as building materials.

A Value-Added Synthetic Process Utilizing Mining Wastes and Industrial Byproducts for Wear-Resistant Glass Ceramics

“…47 The average grain diameter was calculated by dividing the number of intersected grains by the line length. According to previous studies of fused cast basalt, 37,43,48 the average crystal size is approximately within the range of 1 to 10 μm, which is similar to the present result. Therefore, it can be inferred that the fine grain observed in the SEM image is the crystal of diopside or magnetite.…”

“…This is in excellent agreement with the conventional fused cast basalt system showing that the main crystalline phase is monoclinic pyroxene, with a general formula of XY(Si,Al) 2 O 6 . 30 In previous studies, 28,35,37,42 the diopside phase (CaMgSi 2 O 6 ) and augite phase ((Ca, Na)(Mg,Fe,Al,Ti)(Si,Al) 2 O 6 ) were mainly observed in fused cast basalt made from natural basalt rock. The monoclinic pyroxene phase is crystallized in the globular spherulite form at relatively low temperatures between 1073 and 1173 K. 28 On the other hand, magnetite (Fe 3 O 4 ) forms at relatively high temperatures between 1473 and 1573 K as the idiomorphic form.…”

“…35 The microstructure of the present glass ceramic sample was observed through SEM (JSM-6380LA; JEOL, Tokyo, Japan). Following the mirror polishing of the surface of thermally treated sample, the sample was chemically etched by 1% HF and 1% HNO 3 solution for 1 s. 36,37 The sample was dried followed by surface coating with a gold film. The crystalline phase after thermal treatment was determined using XRD (D/Max 2200; Rigaku, Tokyo, Japan).…”

High-Density Ceramics Obtained By Andesite Basalt Sintering

“…Moreover, basalts can be used as raw materials for the obtainment of iron-rich glass and glass-ceramic materials [19][20][21][22][23][24] due to their chemical composition since these volcanic rocks are mainly composed of silica, alumina, iron oxide, calcium, and magnesia with lower content of potassium, titania, manganese, and phosphorus oxide [14]. Classi cation of basalt rocks is conducted according to the SiO 2 content present in their composition and thus basalts can be classi ed as alkaline (up to 42% SiO 2 ), mildly acidic (43-46% SiO 2 ), and acidic (over 46% SiO 2 ) [25].…”

Effect of CaO/SiO2 molar ratio on the electrical and physical properties of basaltic glass materials

“…The major constituents of basalt are some oxides of (Silica, alumina, iron, calcia, magnesia) in addition to some other minor alkali constituents (soda, potassia, titania and manganese) [2]. Low viscosity basaltic rocks produce polycrystalline components at low temperatures with short production cycles [3, 4]. Also, basaltic rocks have a high oxidation resistance, low thermal conductivity, and high softening and melting temperatures.…”