Characteristic of synthesis and transformations of hardystonite in willemite glass-crystalline glaze based on thermal analysis

Abstract

A new crystalline phase hardystonite (Ca 2 ZnSi 2 O 7 ) has been obtained in willemite glass-ceramic glaze containing more than 20 % by mass ZnO. To our knowledge, there was no report about the presence of this calcium zinc silicate in glazes. The aim of this study was to investigate the synthesis and thermal behavior of Ca 2 ZnSi 2 O 7 in ceramic glaze. A hardystonite formed in glaze at 750°C and exist to 850°C, as confirmed by X-ray phase powder diffraction findings and scanning electron microscope image (SEM) with chemical elemental analysis. The second formed of zinc calcium silicate is corresponding with liquid phase presence in glaze observed at 1150°C and also decompose below 1200°C. Because glaze is complicated multi-component system with different crystalline phases, it is developed for research transformations in stoichiometric hardystonite. On this basis, an oxide system was prepared from SiO2, ZnO and CaCO 3 to designated precise chemical synthesis temperature of pure hardystonite powders. Thermal analysis method such as differential scanning calorimetry has confirmed that in 1175°C formed hardystonite according to X-ray phase powder diffraction of a reaction mixture. Hot-stage microscope is useful to detailed description of the processes and transformations which occur when mixture and glaze were heated. SEMs of the new phase in mixture and in glaze are presented. Phenomena related with the influence of heating cycle and liquid phase on the transformation of hardystonite are examined and analytically discussed.

Effects of polyvinylpyrrolidone on structural and optical properties of willemite semiconductor nanoparticles by polymer thermal treatment method

“…For example, in photonic devices [19,20], laser crystals [21,22], optoelectronics [23,24], as well as adsorbents [25,26]. Several investigations regarding the synthesis techniques of willemite have been reported by numerous researchers, including the sol-gel technique [27,28], solid-state route [18,[29][30][31], co-precipitation method [32], spray pyrolysis method [33] spray drying method [34], hydrothermal method [35,36], supercritical methods [37,38], solvothermal method [39] and sonochemical method [40]. Conventional sol-gel and solid-state technique are often used methods for producing willemite NPs for phosphor application.…”

“…Similarly, Babu and Buddhudu [42] produced willemite NPs with a mean particle size of 100 nm. However, this involves a very long reaction period by allowing the precursor to be evaporated naturally in the air for 2 or 3 months and later calcined at 950°C for 2 h. On the other hand, solid-state technique often involves higher calcination temperature as compared to sol-gel, usually ranging between 1000 and 1500°C [18,30,31]. For instance, Diao et al [43] fabricated willemite NPs with average size larger than 200 nm using solid-state technique at a temperature between 900 and 1300°C.…”

Preparation, microstructure studies and mechanical properties of glazes ceramic sanitary ware based on kaolin

“…At temperature around 570 o C, the α-quartz is transformed into β-quartz without weight loss [32]. A mass decrease of about 5 % was observed during the decomposition of calcium carbonate [33] to CO 2 and CaO between 600 and 750 o C. The decomposition of dolomite (CaMg (CO 3 ) 2 ) [34] into CaO and MgO with a new mass loss of 2 % and the recrystallization of kaolinite into mullite and cristoballite occur at temperatures comprising between 750 and 1050 o C. Overall, the mixture of the starting powders undergoes a total mass loss estimated to be around 9 to 11 % after heating at 1050 o C. With increasing of temperature, the sodium feldspar begins to melt congruently and decompose at about 1100 o C [35], favored by the presence of sodium oxide. At temperatures above 1200 o C, the mixture melts to form the glaze, the zircon remains stable in this temperature range and dispersed in the glassy matrix (see Fig.…”

Influence of SrO content on microstructure and crystallization of glazes in the SiO2–Al2O3–CaO–MgO–K2O system

“…The literature provides the results of research on various glass systems, such as MgO-Al 2 O 3 -SiO 2 [11][12][13][14], CaO-MgO-Al 2 O 3 -SiO 2 [7,11,[15][16][17][18][19] [17,20,21] [11,15,17,[23][24][25][26][27], which can form the basis for the development of frit compositions, and consequently glazes.…”