*Article* **Synthesise and Characterization of Cordierite and Wollastonite Glass—Ceramics Derived from Industrial Wastes and Natural Raw Materials**

**Gamal A. Khater \*, Amany A. El-Kheshen and Mohammad M. Farag**

Glass Research Department, National Research Centre, Cairo 12622, Egypt; aelkheshen1@yahoo.com (A.A.E.-K.); mmfaragnrc@gmail.com (M.M.F.)

**\*** Correspondence: j.khater@yahoo.com

**Abstract:** Industrial waste is one of the primary sources that harm the environment, and this topic has occupied many scientists on how to take advantage of these wastes or dispose of them and create a clean environment. By-pass cement dust is considered one of the most dangerous industrial wastes due to its fine granular size and its volatilization in the air, which causes severe environmental damage to human and animal health, and this is the reason for choosing the current research point. In this article, eight samples of glass–ceramics were prepared using by-pass cement dust and natural raw materials known as silica sand, magnesite, and kaolin. Then melted by using an electric furnace which was adjusted at a range of temperatures from 1550 to 1600 ◦C for 2 to 3 h; the samples were cast and were subjected to heat treatment at 1000 ◦C for 2 h based on the DTA results in order to produce crystalline materials. Various techniques were used to study the synthesized glass–ceramic samples, including differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscope (SEM), and thermal expansion coefficient (CTE). X-ray analysis showed that the phases formed through investigated glass–ceramic samples consisted mainly of β- wollastonite, parawollastonite, diopside, anorthite, and cordierite. It was noticed that β- the wollastonite phase was formed first and then turned into parawollastonite, and also, the anorthite mineral was formed at low temperatures before the formation of the diopside mineral. SEM showed that the formed microstructure turned from a coarse grain texture to a fine-grained texture, by increasing the percentage of cordierite. It also showed that the increase in time at the endothermic temperature significantly affected the crystalline texture by giving a fine-grained crystalline texture. The linear thermal expansion measurements technique used for the studied glass–ceramic samples gives thermal expansion coefficients ranging from 6.2161 <sup>×</sup> <sup>10</sup>−<sup>6</sup> to 2.6181 <sup>×</sup> <sup>10</sup>−<sup>6</sup> <sup>C</sup>−<sup>1</sup> (in the range of 20–700 ◦C), and it decreased by increasing cordierite percent.

**Keywords:** crystallization; glass–ceramics; diopside; β-wollastonite; parawollastonite; anorthite; by-pass cement
