Structural and chemical properties of thermally treated geopolymer samples

Kljajević, Ljiljana; Nenadović, Snežana; Nenadović, Miloš; Bundaleski, Nenad; Todorović, Bratislav Ž.; Pavlović, Vladimir B.; Rakočević, Zlatko Lj.

doi:10.1016/j.ceramint.2017.02.066

Cited by 129 publications

(52 citation statements)

References 46 publications

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“…This material is also used as the initial material for CeO 2 -based geopolymers. It is evident that the phase composition corresponds to geopolymers synthesized from metakaoline as the primary raw material, as described in previous papers [40,41]. In addition, from a diffractogram of pure GP, it is observed that the mineral phases SS-Na 4 SiO 4 (ICDD 00-032-1154) was formed during the synthesis of sodium silicate by using a high concentration of NaOH (14 M) and silicon glass.…”

Section: Xrpd Analysissupporting

confidence: 65%

Geopolymer/CeO2 as Solid Electrolyte for IT-SOFC

et al. 2020

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As a material for application in the life sciences, a new composite material, geopolymer/CeO2 (GP_CeO2), was synthesized as a potential low-cost solid electrolyte for application in solid oxide fuel cells operating in intermediate temperature (IT-SOFC). The new materials were obtained from alkali-activated metakaolin (calcined clay) in the presence of CeO2 powders (x = 10%). Besides the commercial CeO2 powder, as a source of ceria, two differently synthesized CeO2 powders also were used: CeO2 synthesized by modified glycine nitrate procedure (MGNP) and self-propagating reaction at room temperature (SPRT). The structural, morphological, and electrical properties of pure and GP_CeO2-type samples were investigated by X-ray powder diffraction (XRPD), Fourier transform infrared (FTIR), BET, differential thermal and thermogravimetric analysis (DTA/TGA), scanning electron microscopy (FE-SEM), energy dispersive spectrometer (EDS), and method complex impedance (EIS). XRPD and matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) analysis confirmed the formation of solid phase CeO2. The BET, DTA/TGA, FE-SEM, and EDS results indicated that particles of CeO2 were stabile interconnected and form a continuous conductive path, which was confirmed by the EIS method. The highest conductivity of 1.86 × 10−2 Ω−1 cm−1 was obtained for the sample GP_CeO2_MGNP at 700 °C. The corresponding value of activation energy for conductivity was 0.26 eV in the temperature range 500–700 °C.

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Section: Xrpd Analysissupporting

confidence: 65%

Geopolymer/CeO2 as Solid Electrolyte for IT-SOFC

et al. 2020

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“…When heated to 1000°C, the main phases in the geopolymers are nepheline [93]. Similarly, Kljajević et al [94] reported that at room temperature, there are amorphous structures for MK geopolymers and the amorphous phase disappears and nepheline appears at 900°C. It is reported that the main phase of MK geopolymers is completely transformed into nepheline at 1000°C, and the strength of nepheline phase decreases after annealing [33,34].…”

Section: Mineralogical Characteristics Of Geopolymersmentioning

confidence: 91%

Thermal and Mechanical Properties of Geopolymers Exposed to High Temperature: A Literature Review

Dai

Wang

2020

Advances in Civil Engineering

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Geopolymers are prepared by alkali solution-activated natural minerals or industrial waste materials, which have been widely used as new sustainable building and construction materials for their excellent thermal and mechanical properties. The thermal and mechanical properties of geopolymers at high temperature have attracted great attention from many researchers. However, there are few systematic works concerning these two issues. Therefore, this work reviewed the thermal and mechanical behaviors of geopolymers at high temperature. Firstly, the thermal properties of geopolymers in terms of mass loss, thermal expansion, and thermal conductivity after high temperature were explained. Secondly, the mechanical properties of residual compressive strength and stress-strain relationship of fly ash geopolymers and metakaolin geopolymers after high temperature were analyzed. Finally, the microstructure and mineralogical characteristics of geopolymers upon heating were interpreted according to the changes of microstructures and compositions. The results show that the thermal properties of geopolymers are superior to cement concrete. The geopolymers possess few mass loss and a low expansion ratio and thermal conductivity at high temperature. The thermal and mechanical properties of the geopolymers are usually closely related to the raw materials and the constituents of the geopolymers. Preparation and testing conditions can affect the mechanical properties of the geopolymers. The stress-strain curves of geopolymer are changed by the composition of geopolymers and the high temperature. The silicon-type fillers not only improve the thermal expansion of the geopolymers but also enhance mechanical properties of the geopolymers. But, they do not contribute to reducing the thermal conductivity. the different raw materials, aluminosilicate precursor and reinforcement materials, result in different geopolymer damage during the heating. However, phase transitions can occur during the process of heating regardless of the raw materials. The additional performance enhancements can be achieved by optimizing the paste formulation, adjusting the inner structure, changing the alkali type, and incorporating reinforcements.

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“…They successfully produced leucite glass-ceramics from geopolymer powder based on potassium precursors. For sodiumbased geopolymers, nepheline-predominated crystallites formed when sintered at elevated temperatures [23,24]. Nepheline ceramics have hitherto been produced through sintering-crystallization, controlled devitrification and vitrification process of zeolites [25,26], fly ash and slag [27] in the temperature range of 600 -1200°C.…”

Section: Introductionmentioning

confidence: 99%

Formation of one-part-mixing geopolymers and geopolymer ceramics from geopolymer powder

Yun-Ming

Cheng-Yong

et al. 2017

Construction and Building Materials

124

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Geopolymer powder prepared through pre-curing and pulverization showed great potential to produce one-part-mixing geopolymers as well as high flexural strength geopolymer ceramics. The one-part-mixing geopolymers were prepared by mixing geopolymer powder with water while the geopolymer ceramics were prepared by powder metallurgy and sintering. The one-part-mixing geopolymers achieved a compressive strength of 10 MPa after 28 days with formation of geopolymer precipitates in conjunction with zeolite phases. Despite the lower strength, they remained stable and did 2 not disintegrate when immersed in water. Besides, the geopolymer ceramics exhibited high flexural strength (90 MPa) after sintering at 1200°C as result of nepheline formation.

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Structural and chemical properties of thermally treated geopolymer samples

Cited by 129 publications

References 46 publications

Geopolymer/CeO2 as Solid Electrolyte for IT-SOFC

Geopolymer/CeO2 as Solid Electrolyte for IT-SOFC

Thermal and Mechanical Properties of Geopolymers Exposed to High Temperature: A Literature Review

Formation of one-part-mixing geopolymers and geopolymer ceramics from geopolymer powder

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