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Patrick N. Lemougna Kenneth J.D. MacKenzie U.F. Chinje Melo 《Ceramics International》2011,37(8):3011-3018
The volcanic ash occurring as an abundant and readily accessible natural resource in the Central African country of Cameroon was used to synthesize aluminosilicate geopolymers using sodium hydroxide as the sole alkaline activator. Both the curing conditions and the Na2O/SiO2 molar ratio were found to influence the development of compressive strength of the geopolymer cement paste, which achieved a maximum strength of 55 MPa at Na2O/SiO2 = 0.3. The formation of a mortar by the addition of 40 wt% sand to the optimized geopolymer cement composition reduced the compressive strength to 30 MPa, still within the useful range for construction applications. The geopolymers consist largely of X-ray amorphous material with a small content of crystalline phases. Scanning electron microscopy showed a homogenously distributed mixture of lath-shaped and agglomerated morphologies, with a homogeneous distribution of Si, Al and O in the geopolymer matrix. The geopolymers are relatively stable to heat, shrinking only slowly and retaining about 60% of their as synthesized compressive strength on heating to 900 °C. The FTIR spectra of both the as synthesized and heated geopolymers show two broad absorbance bands, between 820-1250 cm−1 and 450-730 cm−1 assigned to the internal vibrations of Si-O-Si, and Si-O-Al respectively. The compressive strengths and the thermal stability of these materials suggest their suitability for building applications and low-grade refractories. 相似文献
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Patrick N. Lemougna Kenneth J. D. MacKenzie Guy N. L. Jameson H. Rahier U. F. Chinje Melo 《Journal of Materials Science》2013,48(15):5280-5286
The behavior of the iron present in two volcanic ashes was investigated during geopolymer synthesis using sodium hydroxide as the sole alkali activator. XRD, SEM, and room-temperature 57Fe Mössbauer spectroscopy were used to monitor the behavior of the iron during the synthesis reaction. Geopolymers with very good compressive strengths were formed, especially with the finer ash, in which the iron is present in the crystalline minerals ferroan forsterite and augite. Mössbauer spectroscopy identified the ferrous sites in these minerals, plus a ferric site, probably located in an X-ray amorphous phase. The ferroan forsterite in the original ashes did not react with NaOH, but a substantial proportion of the augite reacted to form new ferric sites with parameters similar to distorted tetrahedral or 5-coordinated environments, suggesting the possible incorporation of ferric iron in the tetrahedral network of the geopolymer product. These results indicate that iron is not necessarily deleterious to geopolymer formation, as has sometimes been suggested. 相似文献
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Metekong Jordan Valdès Sontia Kaze Cyriaque Rodrigue Adesina Adeyemi Nemaleu Juvenal Giogetti Deutou Djobo Jean Noel Yankwa Lemougna Patrick Ninla Alomayri Thamer Kamseu Elie Melo Uphie Chinje Tatietse Thomas Tamo 《SILICON》2022,14(13):7399-7416
Silicon - In this study, a laterite soil which is a locally available material in many parts of the world was used as the aluminosilicate precursor. The main objective of this study is to... 相似文献
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Beleuk à Moungam Lynn Myllyam Lemougna Patrick Ninla Kaze Rodrigue Cyriaque Mohamed Hawa Deutou Nemaleu Juvenal Giogetti Billong Ndigui Kamseu Elie Mvondo-Ze Antoine David Tonle Kenfack Ignas 《SILICON》2022,14(6):2595-2608
Silicon - In the present study, multi-scale sized porous inorganic polymers were produced by alkaline activation of volcanic ash. Rice husk ash, an agricultural biomass, was used both in the... 相似文献
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