Nalazite se na CroRIS probnoj okolini. Ovdje evidentirani podaci neće biti pohranjeni u Informacijskom sustavu znanosti RH. Ako je ovo greška, CroRIS produkcijskoj okolini moguće je pristupi putem poveznice www.croris.hr
izvor podataka: crosbi !

Micro- and nano-features of kaolin aggregates as a result of weathering processes (CROSBI ID 631131)

Prilog sa skupa u zborniku | sažetak izlaganja sa skupa | domaća recenzija

Bermanec, Vladimir ; Botha, Andre ; Tomašić, Nenad Micro- and nano-features of kaolin aggregates as a result of weathering processes // Proceedings - 3rd Croatian Microscopy Congress with International Participation / Ambriović Ristov, Andreja ; Gajović, Andreja, Weber, Igor ; Vidoš, Ana (ur.). Zadar: Institut Ruđer Bošković, Hrvatsko-mikroskopijsko društvo, 2015. str. 74-75

Podaci o odgovornosti

Bermanec, Vladimir ; Botha, Andre ; Tomašić, Nenad

engleski

Micro- and nano-features of kaolin aggregates as a result of weathering processes

Kaolin is a member of kaolin-serpentine group. It is a sheet silicate, and is found to be a result of hydrothermal alteration, weathering processes or even combination of it. Kaolin is found in different environments such as tropical soils, sedimentary deposits, hydrothermal mineral deposits, and even on the Mars surface. As a clay mineral, kaolin displays various particle sizes, layer stacking defects, and consequently different models of its real crystal structure (1, 2). Kaolin samples from various localities in tropical areas in Brazil and Africa. X-ray diffraction and high-resolution scanning electron microscopy (Zeiss Gemini Ultra microscope with in-lens detectors) were employed. Microscopic examinations revealed existence of defects between the layers in layered crystal structure which are observed as divergent crystals resembling half open books (Fig. 1a). The size of such crystals varies from a few hundred nanometers up to 10 or 15 micrometers. A distinguishable thickness of layers within the crystals can vary from 10 to 150 nm. The book-like texture of kaolin crystals is due to deformation of crystal structure, i.e. because of filling two-thirds of octahedral sites with aluminum (or other trivalent cation), and because of lateral misfit between octahedral and tetrahedral sheets. Accumulation of these misfits in the crystal structure results in defects easily observable on high resolution scanning electron images. The second micro-feature of the kaolin samples was observed at the edges of crystals. The edges are frequently found undefined, and look like lace. It is obvious that such an edge is a result of growing, and it can be easily recrystallized even through a simple process like lyophilization. Low magnification and high electron energy used in conventional scanning microscopy do not allow an observation of real hexagonal shapes of small kaolin crystals or even layers. By applying low voltages and in-lens detectors the hexagonal symmetry of single layers of kaolin becomes clearly visible. The observed stacking is responsible for lowering the symmetry, what is obvious from different elongation for the duration of growing, and three types of crystal growth can be recognized. The first one is more common stacking of layers, layer by layer. The second one is skeletal growth of kaolin like snowflake.The third type of crystal growth is screw-like. Every investigated sample of kaolin has cracks between the blocks or layers within the big crystals. Inside the cracks/defects within the crystals nanowhiskers were found (Fig. 1b). They are randomly distributed, sometimes very often. The size of whiskers varies between 100 and 200 nm in length and about 20 nm in width. Some of whiskers are broken. These nanowhiskers could influence to mechanical properties of clay containing kaolin.

kaolin; stacking; nanowhiskers

nije evidentirano

nije evidentirano

nije evidentirano

nije evidentirano

nije evidentirano

nije evidentirano

Podaci o prilogu

74-75.

2015.

objavljeno

Podaci o matičnoj publikaciji

Proceedings - 3rd Croatian Microscopy Congress with International Participation

Ambriović Ristov, Andreja ; Gajović, Andreja, Weber, Igor ; Vidoš, Ana

Zadar: Institut Ruđer Bošković, Hrvatsko-mikroskopijsko društvo

978-953-7941-05-5

Podaci o skupu

3rd Croatian Microscopy Congress with International Participation

predavanje

26.04.2015-29.04.2015

Zadar, Hrvatska

Povezanost rada

Geologija