Geopolymerization of halloysite via alkali-activation: Dependence of microstructures on precalcination

The additive manufacturing technologies are fast-developing industrial sector and, potentially, a ground-breaking technology. They have many advantages such as the saving of resources and energy efficiency. However, the full exploitation of 3D printing technology for ceramic materials is currently limited; a lot of research is being conducted in this area. A promising solution seems to be geopolymers, but its application requires a better understanding of the behaviour this group of materials. This article analyses the influence of microstructure on mechanical properties whilst taking the production method into consideration. The paper is based on comparative analysis – the investigation is focused on the influence of material structure on the mechanical properties and fracture mechanism of these kinds of composites, including those reinforced with different kind of fibres. As a raw material for the matrix, fly ash from the Skawina coal power plant (located in: Skawina, Lesser Poland, Poland) was used. The investigation was made by SEM analysis. The results show that the microstructural analysis did not sufficiently explain the underlying reasons for the observed differences in the mechanical properties of the composites.

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“…3-6 have a structure characteristic of the geopolymers after the curing process (min. 28 days) [26][27][28]. In Fig.…”

Section: Resultsmentioning

confidence: 92%

“…8. The charts are typical for geopolymers [27][28][29] The main element is silica due to the composition of raw materials -sand and fly ash. EDS analysis also shows a high content of oxygen, which is composed of oxides of various elements.…”

Section: Resultsmentioning

confidence: 99%

The influence of microstructure on mechanical properties of 3D printable geopolymer composites

et al. 2020

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“…Kaze et al [24] showed that calcined halloysite at 600 °C is suitable for geopolymers with good mechanical properties and long-term durability. Zhang et al [25] in their investigation claimed that 700 °C appeared as optimal calcination temperature of halloysite-clay that insured high strength. Recently, Tchakounté et al [26] produced geopolymer binder from calcined halloysite and kaolinite clays at 700 °C, consolidated with sodium alkaline solution.…”

Section: Introductionmentioning

confidence: 99%

Mechanical and microstructural properties of geopolymer mortars from meta-halloysite: effect of titanium dioxide TiO2 (anatase and rutile) content

et al. 2020

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This study aimed to investigate the effect of Titanium Dioxide TiO 2 (anatase and rutile) on mechanical and microstructural properties of meta-halloysite based geopolymer mortars namely GMHA and GMHR series. Meta-halloysite received 2.5, 5.0, 7.5 and 10 wt% of anatase or rutile as addition before calcination and geopolymerization. The raw materials and the end products were characterized using XRD, FTIR, ESEM and MIP analyses. The flexural strength increases from 6.90 to 9.13 MPa and from 6.90 to 12.33 MPa for GMHA and GMHR series respectively. The cumulative pore volume decreases from 102.2 to 84.2 mm 3 g −1 and from 102.2 to 51.3 mm 3 g −1 for GMHA and GMHR products respectively. Both matrices present micrographs with very low capillaries pores and fractured surfaces that confirmed the enhancement of the mechanical properties. It was concluded that TiO 2 in both forms is beneficial for the reduction of porosity and densification of geopolymer matrices. Rutile enabled more compact and denser geopolymer structure compared to anatase. The aforementioned results showed the efficiency of both fine TiO 2 particles to improve the geopolymer network significant for its durability.

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“…A broad band at range of 900-1,000 cm −1 (986 cm −1 ) was attributed to the Si-O-Si stretching vibration mode 53 . Besides, due to the formation of geopolymer structure, the Si-O-Si stretching vibration mode has shifted to the lower wavenumbers 53 . A broad band Fig.…”

Section: Resultsmentioning

confidence: 99%

“…According to this spectrum, the band amplification and high transmittance percentage of OH groups have been increased; also, an observed strong absorbance band around 1,430 cm −1 51 , 52 was confirmed the existence of C–O–C asymmetric vibration mode of CO 3 2– ion which has been determined in all spectra of geopolymer samples. A broad band at range of 900–1,000 cm −1 (986 cm −1 ) was attributed to the Si–O–Si stretching vibration mode 53 . Besides, due to the formation of geopolymer structure, the Si–O–Si stretching vibration mode has shifted to the lower wavenumbers 53 .…”

Section: Resultsmentioning

confidence: 99%

Development of novel and green NiFe2O4/geopolymer nanocatalyst based on bentonite for synthesis of imidazole heterocycles by ultrasonic irradiations

Hajizadeh

Radinekiyan

Eivazzadeh‐Keihan

et al. 2020

Sci Rep

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Geopolymers as aluminosilicate inorganic polymers and eco-friendly building materials which can be used as substrate for different kinds of composite. In this research, according to the fabrication of geopolymer based on bentonite as a substrate and embedment of nife 2 o 4 nanoparticles in the construction of this polymer, the synthesis of a new magnetic nanocomposite (nife 2 o 4 /geopolymer) was investigated for the first time. In order to describe its chemistry and morphology features, different analyses such as Fourier transform infrared spectroscopy, field-emission scanning electron microscopy and transmission electron microscopy images, Brunauer-emmet-teller adsorptiondesorption isotherm, X-ray diffraction pattern, energy-dispersive X-ray analysis, thermogravimetric analysis, and vibrating-sample magnetometer analysis were used. The application of this novel nanocatalyst was studied for one-pot three-component condensation reaction of substituted imidazole derivatives by accelerated ultrasonic irradiations. Compared to the other conventional catalysts which were used for the synthesis of imidazole derivatives, the green synthesis method for fabrication of this heterogeneous and magnetic nanocatalyst, its high thermal stability, being ecofriendly, noticeable efficiency and easy reusability have become privileges to be superior. Geopolymeric compounds as amorphous, three-dimensional alkali aluminosilicate binder materials were first introduced by Davidovits in 1978. In recent years, the perusal of geopolymeric materials has been increased due to their specific properties such as compliance with green chemistry, high mechanical performance as building materials, having micro or nano-porosity, thermal stability, high surface hardness, and acid and fire resistance 1. These kind of materials can be fabricated by alkaline activation of various aluminosilicate materials including natural minerals such as kaolin 2 and montmorillonite 3 , mineral resources like bentonite 4 , and also, industrial wastes such as fly ash 1,5. Among them, natural bentonite is one of the most multifunctional mineral clays with low cost, abundant accessibility, superb swelling capability, viscoelastic property at low concentration, superb absorption capacity and eco-friendly properties 1. This phyllosilicate clay primarily consists of montmorillonite. Two main contributions to the surface charges of montmorillonite are the constant negative charges on the basal planes; which are related to the isomorphic substitutions and the pH-dependent charges developed on the hydroxyl groups at broken edges 6. A localized charge distribution can be generated by a negative charge associated with a cation replacement (e.g., Al +3 for Si +4) in the tetrahedral sheet; while, a diffused negative charge can be achieved by the cation replacement (e.g., Mg +2 for Al +3) in the octahedral sheet 6. This natural clay can be utilized as superb absorbent in various fields such as water purification and absorption of heavy metals 7 due to its specific structure. The ...

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Geopolymerization of halloysite via alkali-activation: Dependence of microstructures on precalcination

Cited by 92 publications

References 70 publications

The influence of microstructure on mechanical properties of 3D printable geopolymer composites

The influence of microstructure on mechanical properties of 3D printable geopolymer composites

Mechanical and microstructural properties of geopolymer mortars from meta-halloysite: effect of titanium dioxide TiO2 (anatase and rutile) content

Development of novel and green NiFe2O4/geopolymer nanocatalyst based on bentonite for synthesis of imidazole heterocycles by ultrasonic irradiations

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