Glass-Ceramic Materials Obtained by Sintering of Vitreous Powders from Industrial Waste: Production and Properties

Abstract

Glass-ceramics are advanced inorganic silicate materials that can be obtained by sintering glass powders using a careful temperature control to result in the densification, nucleation, and crystallization of the material. In the current work, three different samples were obtained starting from amorphous silicate materials derived from mixtures of metallurgical slag, coal fly ash, and glass cullet, mixed in different proportions. The as-received waste samples were heat-treated to high temperatures to achieve complete melting at 1200, 1300, and 1400 °C for two hours, performing a rapid cooling in order to yield an amorphous material (glass). The obtained frit was ball-milled to a powder, which was then cold pressed to obtain compact pellets. The thermal treatment of pellets was carried out at 800–1100 °C for 2 h followed by a cooling rate of 10 °C/min to obtain the final glass-ceramics. The microstructure of samples was evaluated with scanning electron microscopy (SEM), which showed heterogeneous conglomerates and clusters of ~20 microns. The formation of crystalline phases was corroborated by means of X-ray diffraction (XRD) analysis, showing the presence of anorthite in all samples. Depending on the sample composition, other crystalline phases such as augite, enstatite, and diopside were detected. Using the Debye–Scherrer equation, it was possible to find the average size of the nano-crystalline domains. The quantification of the non-crystalline or amorphous fraction was also performed. Additionally, the density and porosity of the materials were calculated using the procedures defined in the ASTM C373 and ASTM C20 standards, measuring density values in the range 2.2–3.1 g·cm−3. The apparent porosity was approx. 33% in the three materials. Raman spectroscopy analysis showed characteristic signals associated with crystalline phases containing alumina, silica, iron, and calcium. Overall, the study confirmed the possibility of obtaining glass-ceramics with fine (nanometric) crystal sizes from a combination of silicate waste and the capability of modifying the crystalline composition by changing the proportions of the different wastes in the initial formulations.

Influence Mechanism of Water-Soluble Sodium on Zhundong Coal Pyrolysis

“…The lateral size of the crystallite, L a , and the stacking height of the crystallite, L c , were obtained from the 100 and 002 diffraction peaks, respectively, using the Scherrer equation: 15 − 17 …”

Analysis of Experience in the Use of Micro- and Nanoadditives from Silicon Production Waste in Concrete Technologies

“…Microsilica, a by-product of silicon or ferrosilicon production, presents as amorphous silica (SiO 2 ) in spherical particle form [1][2][3][4][5][6][7][8][9][10]. Widely utilized within the construction industry, microsilica serves as a modifying component in concrete production, leveraging its chemical composition and physical attributes as a highly active pozzolan [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The extensive introduction of various highly effective chemical and mineral additives has led to significant advancements in modern concrete technology.…”

“…Cement usage surpasses 4000 million tons annually and is projected to reach approximately 6000 million tons by 2060 [12,13], greatly contributing to climate change through greenhouse gas emissions [13][14][15]. To address this, agricultural and industrial wastes, such as rice husk ash (RHA), sugarcane bagasse ash, and olive oil ash, are utilized to partially substitute OPC in the production of green concrete [16][17][18][19][20][21].…”