Analiza modelirne mase in plastelina z rentgensko praškovno difrakcijo

Turk, Maruša (author), Golobič, Amalija (mentor)

Metode rentgenske praškovne difrakcije so osnovne metode za karakterizacijo trdnih, predvsem polikristaliničnih snovi. Z uporabo teh metod sem analizirala štiri vzorce modelirne mase in 17 vzorcev plastelina različnih proizvajalcev. Osredotočila sem se na materiale namenjene likovnemu ustvarjanju otrok. Najprej sem pripravila vzorce, da so bili primerni za merjenje rentgenskih praškovnih difrakrogramov. Kvalitativno rentgensko praškovno analizo sem izvedla s programom Crystallographica Search-Match (CSM) in zbirko praškovnih difraktogramov standardov PDF-2 in postopoma identificirala faze, ki so bile prisotne v posameznem vzorcu. Sledila je še kvantitativna analiza s programom TOPAS z Rietveldovo metodo, kjer sem določila masne deleže predhodno identificiranim fazam v vzorcu. S prilagajanjem skalnih faktorjev ter nekaterih strukturnih in profilnih parametrov sem skušala pridobiti čim boljše ujemanje izračunanega difraktograma z izmerjenim. Plastelini so bili nekako treh tipov. Eno skupino med sabo sorodnih plastelinov tvorijo tisti, ki imajo na difraktogramu visoko ozadje, kot glavno kristalinično snov pa kuhinjsko sol. V teh sem poleg halita razen v enem primeru identificirala tudi sadro. Zelo verjetno amorfno snov predstavlja škrob, saj sem v literaturi zasledila, da obstajajo plastelini, ki sestojijo iz soli, moke in vode. V drugi skupini plastelinov je glavna komponenta kalcit, gnetljivost pa očitno omogoča majhna količina parafina. Kalcit v literaturi sicer omenjajo kot sestavino plastelinov poleg parafina, vendar v manjši količini, kot sem jo ugotovila jaz. Plastelina v tretji skupini vsebujeta večje število snovi, kot ostali. Največ je v njih kalcita, vsebujeta pa tudi nekaj kremena in več plastovitih silikatov oz. alumosilikatov. Plastelini različnih barv istega proizvajalca imajo podobno sestavo, pri čemer pigmentov v plastelinih žal nisem uspela identificirati. Ugotovila sem, da vse štiri modelirne mase vsebujejo zelo veliko sadre in veliko talka ter različno količino klinoklora. Modelirne mase Lumpi in Kreable so vsebovale še malo kremena, obe Kreable masi še malo anhidrita in kalcita. Rdečo barvo ene modelirne mase sem razložila s prisotnostjo hematita. Rezultati analiz so bili kemijsko smiselni in tudi v skladu s tem, kar sem prebrala o možni sestavi teh materialov v literaturi.

• Language: Slovenian
• Keywords: rentgenska praškovna difrakcija, kvalitativna in kvantitaivna analiza, modelirne mase in plastelini
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2023
• PID: 20.500.12556/RUL-150985
• COBISS.SI-ID: 173387779
• Publication date in RUL: 26.09.2023

Secondary language

• Language: English
• Title: Analysis of modelling clay and plasticine by X-ray powder diffraction

Abstract

X-ray powder diffraction methods are the basic methods for the characterization of solids, especially polycrystalline substances. Using these methods, I analyzed four samples of modelling clay and 17 samples of plasticine from different manufacturers. I focused on materials intended for artistic creation by children. First, I prepared the samples so that they were suitable for measuring X-ray powder patterns. I performed a qualitative X-ray powder analysis using the Crystallographica Search-Match (CSM) program and a database of powder diffractograms - PDF-2 standards and identified the phases that were present in each sample. This was followed by a quantitative analysis with the TOPAS program using the Rietveld method, where I determined mass fractions of the identified phases in the sample. By the refinement of the scale factors and several structural and profile parameters, I tried to obtain the best possible fit of the calculated powder pattern with the measured one. I found that all four modelling clays contain a lot of gypsum and a lot of talc and varying amounts of clinochlor. Lumpi and Kreable modelling clays still contained a little quartz, both Kreable clays still contained a little anhydrite and calcite. I explained the red colour of one modelling mass by the presence of hematite. There were three types of plasticine. One group of related plasticine consists of those that have a high background on the powder pattern, and table salt as the main crystalline substance. Apart from halite, I also identified gypsum in these, except in one case. The amorphous substance is most likely represented by starch, as I saw in the literature that there are plasticine consisting of salt, flour and water. In the second group of plasticine, the main component is calcite, and the knead-ability is apparently made possible by a small amount of paraffin. Calcite is mentioned in the literature as a component of plasticine in addition to paraffin, but in a smaller amount than I found. Plasticine in the third group contains a greater number of substances than the others. Most of them contain calcite, but they also contain some quartz and several layered silicates or aluminosilicates. Plasticine of different colours from the same manufacturer have a similar composition, and unfortunately I was unable to identify the pigments in the plasticines. The results of the analyses are chemically reasonable and were also consistent with the information about the possible composition of these materials found in the literature.

• Keywords: X-ray powder diffraction, qualitative nad quantitative analysis, clay and plasticine