Influence of thermodynamic parameters on the synthesis of porous silicate materials and their functional application

Glavni cilj ove doktorske disertacije je sinteza poroznog aluminosilikatnog materijala za potencijalnu primenu u oblasti zaštite životne sredine. Aluminosilikatni materijali ekološki su prihvatljivi u smislu energetske efiksanosti i male potrošnje energije za sintezu. Sinteza ovakvih materijala podrazumeva i smanjenje proizvodnje gasova sa efektom staklene bašte, odnosno CO2. U prvom delu doktorske disertacije ispitivane su termodinamičke karakteristike homogenih rastvora alkalnih aktivatora na osnovu kojih se mogu tumačiti molekulske interakcije unutar rastvora. Ispraćena je promena termodinamičkih parametara (gustine, viskoznosti, indeksa refrakcije i brzine zvuka) u zavisnosti od temperature. Porozni silikatni materijali sintetisani su od polazne komponente (metakaolin-MK), alkalnog aktivatora koji se sastoji od rastvora NaOH različitih koncentracija (2M-16M NaOH) i natrijum silikata. Potencijalna primena usmerena je na ispitivanje adsorpcionih karakteristika ovih materijala za adsorpciju teških metala i ispitane su mehaničke osobine materijala radi potencijalne primene u građevinarstvu. Umrežena je i organska faza (poli(vinil-alkohol)-(PVA)) radi poboljšanja karakteristika sintetisanog materijala. Različitim metodama (rendgenska difrakciona analiza (XRD), Furijeova transformacija infracrvena spektroskopija (FTIR), Raman spektorskopija, Skenirajuća elektronska mikroskopija, (SEM)) analizirane su promene strukture sintetisanog materijala kao i morfologije čestica prahova prekursora i mikrostruktura sintetisanih uzoraka. Rendgenskom flurescentnom analizom (XRF) određen je hemijski sastav polaznih sirovina i sintetisanog materijala. XRD analizom i Raman spektroskopijom izvršena je identifikacija faza i praćenje veličina kristalita i udela amorfne faze u sintetisanom poroznom silikatnom materijalu. SEM metodom je ispitana morfologija čestica prahova prekursora, veličina i oblik pora sintetisanih poroznih materijala, a metodom energetske disperzione spektroskopije (EDS) utvrđen je sastav čestica prahova i faza kako prekursora, tako i sintetisanih materijala. Veličina čestica sintetisanih materijala praćena je laserskom metodom za određivanje veličine čestica. Određena je specifična površina i poroznost sintetisanog materijala pomoću BET metode. Ispraćen je proces polimerizacije alkalno-aktiviranog materijala (AAM) XRD i FTIR analizom. MALDI-TOF metodom potvrđeni su sintetisani polimerni materijali. Ispitana je i prirodna radioaktivnost materijala polazne sirovine, metafaze i polimernog materijala. Urađena je i termička analiza pomoću TGA/DTA metode. Takođe je urađena i karakterizacija termički tretiranih uzoraka kao i rendgenska fotoelektronska spektroskopija (XPS)The main goal of this doctoral dissertation is the synthesis of porous aluminosilicate materials for potential application in the field of environmental protection. Aluminosilicate materials are environmentally friendly in terms of energy efficiency and low energy consumption for synthesis. The synthesis of such materials implies a reduction in the production of greenhouse gases, i.e., CO2. In the first part of the doctoral dissertation, the thermodynamic characteristics of homogeneous solutions of alkaline activators were examined, on the basis of which molecular interactions within the solution can be interpreted. The change of thermodynamic parameters (density, viscosity, refractive index and speed of sound) depending on temperature was monitored. Porous silicate materials were synthesized from the starting component (metakaolin-MK), an alkaline activator consisting of a solution of NaOH of different concentrations (2M-16M NaOH) and sodium silicate. The potential application is aimed at testing the adsorption properties of these materials for adsorption of heavy metals and the mechanical properties of the materials for potential application in construction have been examined. The organic phase (Poly(vinyl alcohol) (PVA)) was also crosslinked to improve the characteristics of the synthesized material. Changes in the structure of the synthesized material as well as the morphology of the precursor powder particles and the microstructure of the synthesized samples were analyzed by various methods (X - ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, Scanning electron microscopy (SEM)). The chemical composition of the starting materials and the synthesized material was performed by X - ray fluorescence analysis (XRF). XRD and Raman spectroscopy identified the phases and monitored the crystallite size and the proportion of the amorphous phase in the synthesized porous silicate material. SEM examined the morphology of precursor powder particles, pore size and shape of synthesized porous materials, and the composition of powder particles and phases of both precursors and synthesized materials was determined by energy dispersion spectroscopy (EDS). The particle size of the synthesized materials was monitored by the laser method for determining the particle size. The specific surface area and porosity of the synthesized material were determined using the BET method. The polymerization process of alkali-activated material (AAM) was monitored by XRD and FTIR method. The synthesized polymeric materials were confirmed by the MALDI-TOF method. The natural radioactivity of the raw material, metaphase and polymeric material was also examined. Thermal analysis was performed using the TGA / DTA method. Characterization of thermally treated samples as well as X-ray photoelectron spectroscopy (XPS) was also performed

Structural Characteristics and Adsorption Properties of Alkali Activated Blends Ashes/Metakaolin

The aim of this paper is to show the possibility of using waste materials, blends of (wood ash, fly ash, from thermal power plant, and metakaolin) for the production of alkali activated materials that can be used to purify wastewater from different kinds of pollutants such as heavy metals. Heavy metals are toxic, especially cadmium, so they must be removed from wastewater to prevent or minimize contact with the environment and humans. The synthesis of the alkali activated materials was performed by mixing solid precursors with a liquid alkali activator. Two- and three-component systems of wood ash, fly ash and metakaolin (wood ash/fly ash, wood ash/metakaolin, fly ash/metakaolin and wood ash/fly ash/metakaolin) were used as precursor materials. The alkali activator solution was a mixture of sodium silicate solution and sodium hydroxide solution of concentrations (6M and 12M). The characterization of alkali activated materials was studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS). XRD measurements of investigated samples showed a characteristic halo between 18 and 35º 2 with a dominant crystal phase of quartz. FTIR spectroscopy showed that the main vibration band of all investigated samples appeared between 1037-996 cm-1, and corresponds to Si-O-Si/Si-O-Al bands. SEM/EDS analysis was used to determine the microstructure of the samples. The adsorption efficiency of the investigated alkali activated materials for removing cadmium ions from aqueous solution was tested under different conditions: initial concentration of cadmium ions in the range of 20-100 mg/l, pH values from 3 to 7 and mass of adsorbents from 0.02-0.05 g

Effect of Alkaline Activator Properties on Structure of Metakaolin-Based Geopolymer Samples

Considering geopolymers as inorganic polymers, they are actually amorphous network of interlinked silicate and aluminate groups, so they could be prospective ceramic precursors for materials with defined dimensions obtained by casting and firing, but not from powder processing. In this research, the starting material is metakaolin, which was obtained by calcining domes tic kaolinite clay. Initially, four series of alkaline activators of NaOH and sodium silicate have been used. Activators present the mixtures of Na2SiO3 and solutions of NaOH, of different molarities 2M, 4M, 6M and 8M. The prepared geopolymer slurries were cast into the designated near shape at room temperature and after that at 60oC. In fact, the post-synthesis curing process (28 days) has an important role in the obtaining good characteristics of geopolymers. Densities, viscosities and refractive index of alkaline activators were determined over the temperature range 15-60oC of process of geopolymerizations. Based on the obtained results of investigated parameters have been selected to predict the properties of materials. All geopolymer samples were characterized by XRD, FTIR, SEM/EDS analysis and Raman spectroscopy providing complementary and valuable information of the investigated materials. This route of ceramics production has advantages associated with producing an environmental friendly, energy saving, clean new technology of geopolymer materials

Creating a new academic governance in Poland : assumptions to Law HEI 2.0 (Ustawa 2.0)

W Polsce trwają zaawansowane prace nad przebudową systemu nauki i szkolnictwa wyższego. Powszechne jest przekonanie środowiska akademickiego, ale również opinii społecznej, że istniejące rozwiązania nie wykorzystują w pełni możliwości kadry naukowo-dydaktycznej, studentów i potencjału polskich uczelni. Powszechnie znane są miary słabości, związane chociażby z pozycją uczelni polskich w rankingach międzynarodowych [Wróblewski 2013]. Również efekty edukacyjne, umasowienie kształcenia i niekorzystne zmiany w etosie akademickim napawają niepokojem [Sułkowski 2016]. Naprawy wymaga zatem zarówno poziom ładu systemowego szkolnictwa i nauki (governance), jak i zarządzanie uczelniami wyższymi w Polsce (management) [Antonowicz, Brdulak, Hulicka i in. 2016]. Strategicznym elementem tej zmiany ma być przyjęcie nowej ustawy regulującej system nauki i szkolnictwa wyższego. Na początku 2017 roku odbyły się prezentacje projektów "Założeń do ustawy 2.0", przygotowanych przez zespoły wyłonione w trybie konkursowym w 2016 roku. Rezultaty pracy to trzy koncepcje zmiany ładu legislacyjnego w polskiej nauce i szkolnictwie wyższym. Każdy z trzech projektów ma swoją dominującą logikę, jednak wszystkie próbują odpowiadać na podobne problemy polskiego systemu nauki i kształcenia wyższego, trafnie zidentyfikowane przez zespoły konkursowe na etapie diagnozy. Posługując się metodą porównawczą, pozwolę sobie poddać analizie propozycje Kolegów, zwracając uwagę przede wszystkim na rozwiązania mające poprawić sytuację polskich uczelni i całego systemu szkolnictwa.In Poland we are working on a modification of higher education system because the current solutions are not satisfactory for Polish education potential, as well as for people engaged in this field and, last but not least, students. Law HEI 2.0 (Ustawa 2.0) is supposed to be the strategic element of change. Polish academics prepared projects to the new regulation and three of them have been chosen. The article is a critical analysis of these proposals and it brings attention to solutions that might improve a situation of Polish higher education and the whole system of education

Microstructural Analysis of Thermally Treated Geopolymer Incorporated with Neodymium

The following investigation presents the thermal treatment of geopolymer at 300 °C, 600 °C and 900 °C. We investigated what happens to the geopolymer base when incorporated with 1% and 5% of neodymium in the form Nd2O3. A total of six samples were synthesized. Geopolymer 1 contained 1% and geopolymer 2 contained 5% Nd2O3, and these samples were treated at 300 °C; then, samples geopolymer 3 and geopolymer 4 also had the same percentage composition of Nd2O3 and were treated at 600 °C, while samples geopolymer 5 and geopolymer 6were treated at 900 °C. Physical and chemical changes in the aluminosilicate geopolymer matrix were monitored. The incorporation of rare earths into the polymer network of aluminosilicates has been proven to disrupt the basic structure of geopolymers; however, with increased temperatures, these materials show even more unusual properties. Diffuse reflectance infrared Fourier transform (DRIFT) analysis showed that the intensity of the vibrational band decreases with the increase in temperature during thermal treatment, suggesting alterations in the chemical structure of the geopolymers. Transmission electron microscopy (TEM) analysis showed that the diameter of the nanoparticles containing Al2O3 is in the range 5–10 nm, while larger crystallites range from 30 to 80 nm. Scanning electron microscopy (SEM) analysis revealed that the temperature of the thermal treatment increases to 300 °C and 600 °C; the porosity of geopolymer increases in the form of the appearance of large pores and cracks in material. X-ray photoelectron spectroscopy (XPS) analysis was used to investigate the surface chemistry of geopolymers, including the chemical composition of the surface, the oxidation state of the elements, and the presence of functional groups. The UV/Vis spectra of the synthesized geopolymers doped with Nd3+ show interesting optical properties at 900 °C; the geopolymer matrix completely disintegrates and an amorphous phase with a rare-earth precipitate appears

Crosslinking of rare earth ions into aluminosilicate inorganic polymer

Rare earth oxides have been broadly utilised in different research areas due to their unique properties. This research aims to examine the effect of Nd and Sm in the form of oxide addition in the metakaolin-based geopolymer matrix. Metakaolin-based geopolymers with the addition of different percentages of Sm2O3 and Nd2O3 (S1-S6) were synthesised. Samples contained 0.1% Sm; 1% Sm; 5% Sm, and 0.1% Nd, 1% Nd, and 5% Nd. The focus was on monitoring the polymerisation process using the DRIFT method for 7, 14, 21 and 28 days. The phase composition of the samples was confirmed by the XRD method, while the morphology of the samples was analysed by SEM analysis. After 28 days, due to the polymerisation process, the binding of Neodymium and Samarium ions were incorporated into the structure.X Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 26-27, 2022; Belgrad

Preparation and Characterization of Geopolymers Based on Metakaolin with the Addition of Organic Phase PVA

Geopolymers have excellent physical and mechanical properties, so they can be used as a substitute for ordinary polymers. Geopolymers are ceramic materials, which exhibit the property of brittleness, which can be a limitation in some structural applications. To overcome this shortcoming, a new group of materials (organic geopolymers) was developed. The aim of this work is the synthesis of organic (hybrid) geopolymers. A geopolymer based on metakaolin was synthesized as a reference sample, while polyvinyl alcohol was added as an organic phase for synthesizing a hybrid geopolymer. It was concluded that the systems follow the rule of behavior in liquid systems. The chemical composition of the samples was determined by X-ray fluorescence analysis (XRF). Structural and phase characterization of hybrid and reference materials were analyzed using X-ray diffraction (XRD)and Fourier-transform infrared spectroscopy (FTIR), which revealed new phases in the PVA-added samples. The results show that the content of added PVA in the reaction mixture affects the phase composition of the synthesized materials. To examine the possibility of adsorption of the samples, Ultraviolet-visible spectroscopy (UV/VIS) was used. The morphology was analyzed using a scanning electron microscope with energy dispersive spectroscopy (SEM/EDS), where efflorescence was observed and identified. After characterizing the geopolymer with the addition of PVA, we obtained a material that was far more porous than the basic sample, and we can conclude that we have synthesized a material that shows good mechanical properties

Structural Characterization of Geopolymers with the Addition of Eggshell Ash

It is well known that geopolymers are a new group of binder materials of alumosilicate origin. Geopolymers are made by the reaction of precursor aluminosilicate materials with alkaline activator solutions. The current research relates to a low-cost and eco-friendly procedure, suitable of being implemented in two easy steps. The first step is the production of a solid phase based on fly ash (Obrenovac, Serbia) and eggshell ash as waste materials rich in calcium. The second step is alkali activating the solid phase using an alkaline activator (a mixture of NaOH and Na2SiO3) and procedures in proper laboratory conditions. Four samples with different eggshell ash content were synthesized. The concentration of used NaOH was 12 mol dm−3. The structural properties of all investigated samples were analyzed by XRD (X-ray diffraction), DRIFT (diffuse reflectance infrared Fourier transform), SEM (scanning electron microscopy) and UV/Vis spectroscopy analysis. XRD determined the amorphous halo with the presence of quartz as the crystal phase in all of the investigated samples. These results were confirmed by DRIFT analysis. The morphology of the samples was determined by SEM analysis. UV/Vis showed that the material could be a potential adsorbent

Lead Free Polymer Composites for Radiation Shielding

Radiation shielding is a crucial precautionary measure in decreasing the dose of exposure medical personnel experience. The physical dimensions of these shields, specifically thickness and shape, are dependent on the type of radiation, energy and specific radioactivity. Currently, the most common radiation shielding equipment is made of lead, tungsten or uranium. Although these heavy metals have favorable shielding properties against ionizing radiation, protective garments such as lead aprons are heavy to wear and can pose significant health risks. Taking this into account, the primary goal of this study is to understand the radiation shielding properties of lead-free polymer geopolymer-polyurethane based composites. The geopolymer was synthesized using an 80%-20% mixture of fly ash and a bio-polyol substrate which was subsequently homogenized using MDI44. As a result, 6 samples of the geopolymer-polyurethane based composites were fabricated of which 5 were 90%-10% compositions between the mixture and varying concentrations of BaSO4 and Bi2O3 respectively. The last sample consisted of the pure fly ash/bio-polyol mixture. XRF and ICP analysis was used to chemically characterize the fly ash. The composite structures were analyzed using XRD, while the microstructural morphology was investigated using SEM techniques. Utilizing an energy-dispersive x-ray spectrometer (EDS), elemental abundance and agglomerating behavior was analyzed for each composite variant. The X-ray attenuation measurements pointed out that the obtained composites have the potential for a design of lead-free protective clothing against X-ray shielding in medical applications

Heat Treatment of Geopolymer Samples Obtained by Varying Concentration of Sodium Hydroxide as Constituent of Alkali Activator

In this paper, raw natural metakaolin (MK, Serbia) clay was used as a starting material for the synthesis of geopolymers for thermal treatment. Metakaolin was obtained by calcination of kaolin at 750 °C for 1 h while geopolymer samples were calcined at 900 °C, which is the key transition temperature. Metakaolin was activated by a solution of NaOH of various concentrations and sodium silicate. During the controlled heat treatment, the geopolymer samples began to melt slightly and coagulate locally. The high-temperature exposure of geopolymer samples (900 °C) caused a significant reduction in oxygen, and even more sodium, which led to the formation of a complex porous structure. As the concentration of NaOH (6 mol dm−3 and 8 mol dm−3) increased, new semi-crystalline phases of nepheline and sanidine were formed. Thermal properties were increasingly used to better understand and improve the properties of geopolymers at high temperatures. Temperature changes were monitored by simultaneous use of thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The loss of mass of the investigated samples at 900 °C was in the range of 8–16%. Thermal treatment of geopolymers at 900 °C did not have much effect on the change in compressive strength of investigated samples. The results of thermal treatment of geopolymers at 900 °C showed that this is approximately the temperature at which the structure of the geopolymer turns into a ceramic-like structure. All investigated properties of the geopolymers are closely connected to the precursors and the constituents of the geopolymers