engleski

Influence of the additives on geopolymer thin-films and their electrical performance

In the course of investigating alternatives for cement in terms of building materials, various materials were proposed. Among them, geopolymers stand out, commonly referred to as the third generation of concrete. Geopolymers have mechanical properties in the range of other building materials, but more important can be prepared sustainably. Therefore, with respect to their market ratio, their impact in lowering the environmental carbonaceous gasses footprint is considerable. An even greater contribution would arise from ability to manufacture geopolymers in thin film configurations, which would be highly utilisable in the vertically-mounted solar cells, as in absorbing layers or as transparent conductive layers (TCL). For this purpose, the precursors used for the preparing of geopolymers via activation by alkali solutions, need to be studied in detail. Those are normally aluminosilicate materials. Also, gelation and curing steps in the geopolymer preparation should be optimized. When it comes to vertically mounted solar cells, and in this case TCO, it is important that the layer is transparent and conductive. Aluminosilicate geopolymers without additives are known to be non-conductive, or at least insufficient for the desired application. In this context, different additives should improve the properties of geopolymers, which has not been investigated yet. Here we focus on the preparation of geopolymers in thin-film configuration and their modification by various additives. For activation, we studied the influence of potassium and sodium ions (from the alkali solutions) on the prepared geopolymers. Each combination of samples studied was prepared in bulk, followed by the tape-casting method in a thin-film configuration. The premullite precursors were activated with alkaline solutions previously mixed with polyethylene glycol (PEG) and gold nanoparticles, added to improve the conductivity and transparency properties. The morphology of treated and untreated thin-films was examined by using a scanning electron microscope (SEM) and an atomic force microscope (AFM). Regarding structural behaviour, grazing incidence X-ray diffraction (GIXRD), and Fourier-transformed infrared spectroscopy (FTIR) were employed. Targeted improvement of electrical properties was investigated using solid-state impedance spectroscopy (SS-IS).

geopolymer ; thin-film ; electrical properties ; impedance spectroscopy

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