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Publikācija: Modification of Illite Structure by Differential Treatment

Publication Type Conference paper
Funding for basic activity Unknown
Defending: ,
Publication language English (en)
Title in original language Modification of Illite Structure by Differential Treatment
Field of research 2. Engineering and technology
Sub-field of research 2.5 Materials engineering
Authors Gaida Maruta Sedmale
Mārtiņš Randers
Valdis Seglins
Keywords Illīti, struktūra, keramika
Abstract Commonly illite is described as a clay mica with a general composition of [KxAlx(Si4-xAlx)O10 (OH)2 (where 0.75<x<0.9). Structural illite belong to sheet silicates where structural units consist two Si-O tetrahedral sheets always joined with an octahedral Al-O sheet. One of more investigated processes to attain an increased compressive strength of clay minerals containing materials is by proper mix development with highly alkaline solution. Although for this preparation the mainly used is 1:1 layer lattice alumosilicates, i.e., geopolymers, it is also of interest 2:1 minerals such as 2:1 illite. The aim of this study is to show how the chemical, mechanical and thermal treatment condition influenced the structure and some properties of treated illite, as well as impact of its on development of dense high–temperature ceramics. MATERIALS and METHODS In this study Quartenary limno-glacial clays from State importance meaning clay deposit, Apriki, are used. The mean SiO2/Al2O3 wt. ratio for clay is in range 3,20 -3,45. Clay fraction, mainly illite, from Apriki clay were separated using sedimentation and chemical methods. For characteristic not treated and treated illite as well as sintered ceramic samples there was used X-ray diffraction analysis, as well SEM- analysis. Differential thermal analysis was applied to characterize the phases change by thermal treatment of illite. There were used four differentially treated illite samples: ap 0- not treated, ap 1 – milled for 10h, ap 2 –treated with 3M NaOH, ap 3- treated with 6M NaOH and ap 4 – thermally treated at 580°C. Some ceramics properties were established in accordance with EN. RESULTS and DISCUSSIONS The XRD patterns showed that chemical, mechanical and thermal treatment impact on change of intensity of diffraction peaks of illite which could characterize that the breakdown of illite structure is insignificant. The DTA analysis indicate significant changes of illite for the thermally treated sample. For other treated samples the DTA curves seem similar with a little shifted exo-effect to the lowest temperatures, Fig.1. Fig.1.DTA - curves of differential treated illite: : ap 0- not treated, ap-1-milled for 24h, ap-2, 3 treated by 3M and 6M NaOH, ap-4 pre-thermal treated at 580°C for 1h. Scanning electron micrographs of clay fraction powder before and after treatment show that thermal treatment yield homogenous illite powder mixture with particles having almost spherical shape. Significantly differs illite sample treated by 6M NaOH there is observed needle-shaped new crystalline phase formation –sodium aluminosilicate hydrate-Na(AlSiO4)6·H2O, which pervades illite. Thermal treated illite was used for new compositions development with Al(OH)3. After sintering samples with 40 % Al(OH)3 additive there was found that compressive strength of ceramic samples reaches value 168 N/mm2. CONCLUSIONS It is shown that more effective is the thermal and chemical by 6M NaOH treatment. Thermal treatment yield to homogenous illite formation, chemical -by 6M NaOH lead to formation of a new crystalline phase –sodium aluminosilicate hydrate -Na(AlSiO4)6·H2O, which pervades illite. After sintering samples of thermal teated illite sample with 40 % Al(OH)3 there was found that compressive strength of ceramics reaches value 168 N/mm2.
Reference Sedmale, G., Randers, M., Seglins, V. Modification of Illite Structure by Differential Treatment. In: Abstracts of Riga Technical University 56th International Scientific Conference, Latvia, Rīga, 10-16 October, 2015. Riga: RTU Press, 2015, pp.44-44. ISBN 978-9934-10-733-7.
ID 21441