<p>Predmet ovog istraživanja je razvoj nove generacije<br />mineralnih dodataka, dobijenih termičkom i<br />mehanohemijskom aktivacijom kaolinske gline i ispitivanje<br />svojstava kompozita, u kojima je deo portland cementa<br />zamenjen dobijenim pucolanskim materijalima,<br />metakaolinom i amorfnim kaolinom, za različite režime<br />nege. Rezultati su pokazali da su termička i mehanohemijska<br />aktivacija kaolinske gline jednako pogodne metode za<br />dobijanje pucolanskih materijala. Pozitivni efekti na<br />čvrstoće pri pritisku postižu se primenom do 30 %<br />metakaolina u kompozitima pri normalnom režimu nege, a uz<br />dodatno mlevenje, sadržaj metakaolina se može povećati do<br />40 %, uz dodatak CH. Amorfni kaolin se može primeniti u<br />kompozitima, sa stepenom zamene portland cementa do 10 %,<br />pri normalnom i autoklaviranom režimu nege.</p> / <p>The subject of this research is development of a new generation<br />of mineral admixtures, obtained by thermal and<br />mechanochemical activation of kaolin clay, and testing of the<br />properties of the cement based composites, where a part of the<br />portland cement is replaced by pozzolanic materials, metakaolin<br />and amorphous kaolin, for different curing conditions. The<br />results showed that thermal and mechanochemical activation of<br />kaolin clay were equally suitable for obtaining pozzolanic<br />materials. Positive effects on the compressive strength could be<br />achieved by using up to 30 % of MK, and with additional grinding<br />after thermal activation, content of MK could be increased up to<br />40 %, with the addition of CH, under the normal curing<br />conditions. Amorphous kaolin could be used in composites with<br />a cement replacement level of 10 %, under the normal and<br />autoclave curing conditions.</p>

Ces travaux de thèse ont porté sur le développement de nouveaux engrais à relargage contrôlé grâce à la mise en œuvre d’un procédé de mechanosynthèse à partir de mélanges contenant des composés lamellaires soit naturels (montmorillonite, talc et chrysotile) soit synthétiques (les Hydroxydes Doubles Lamellaires (HDL) à base de Mg, d’Al et de Fe) et de monohydrogénophosphate de potassium. Ce sel est déjà utilisé en agriculture en tant que fertilisant conventionnel. Toutefois sa forte solubilité en solution aqueuse induit des pertes importantes lors de l’épandage via des procédés de lixiviation, de volatilisation ou encore de fixation dans les sols, limitant ainsi l’efficacité des nutriments pour les plantes. Il est alors nécessaire d’en utiliser des quantités excessives pour observer une efficacité en agriculture. Aussi la principale alternative est de contrôler l’apport en éléments venant d’une part du sel soluble mais également des constituants chimiques des matrices lamellaires impliquées. Une telle approche pourrait réduire les coûts en permettant une fertilisation accrue tout en en diminuant la solubilité des ions impliqués. La méthode utilisée consiste à broyer les réactifs ensemble en modifiant les conditions de broyage utilisées. Afin d’évaluer les modifications structurales induites par le broyage, les échantillons obtenus sont caractérisés à l’aide de différentes techniques de caractérisation du solide, en fonction des éléments chimiques impliqués. La diffraction des rayons X (PXRD), la microscopie électronique à balayage couplé avec un analyseur (SEM-EDX) et les méthodes spectroscopiques SSNMR, FTIR, RAMAN, RPE…) se sont avérées pertinentes pour réaliser le suivi des réactions de mechanosynthèse et mettre en évidence une amorphisation des matrices précruseurs et éventuellement la formation de nouvelles phases cristallisées. La microscopie montre sytématiquement une modification importante de la taille des particules avec perte de la morphologie des matériaux précurseurs et parfois apparition de nouveaux cristaux de forme bien définie ayant une composition chimique différente. Grâce à la spectroscopie RMN à l’état solide il est possible de mettre en évidence de fortes modifications de l’environnement chimique après mechanosynthèse, suggérant la formation de composés métastables impliquant des cations métalliques issus des phases lamellaires, du phosphore et de l’oxygène. Les composés obtenus ont ensuité été étudiés dans des conditions de relargage mettant en évidence des propriétés de realargage contrôlé quelle que soit la matrice lamellaire précurseur impliquée dans le procédé. La vitesse de relargage des nutriments est influencée par la nature et la composition chimique de la matrices de départ, sachant qu’en fonction de leur composition chimique des produits différents peuvent être formés. / The present work describes the development of slow release fertilizers from the mechanochemical activation of of natural (montmorillonite, talc, chrysotile) and synthetic (Layered Double Hydroxides (LDH) MgAl and MgFe) lamellar matrix mixtures with potassium monohydrogen phosphate. This salt is used in agriculture as a conventional fertilizer and is highly soluble in aqueous solution, which implies large losses due to leaching processes, volatilization or even fixation in the soil, limiting the efficiency of the nutrients for the plants. Due to these characteristics, there is a need to apply large quantities of these products in agriculture. Therefore, the main idea is to control the supply of both the elements coming from the soluble salt as well as the constituting elements of the lamellar matrices. Such approach could reduce costs with exacerbated fertilization, potentiating the use of the products and decreasing the solubility of the ions involved. The methodology used basically consists of the milling of the reagents varying the processing conditions. For the characterization of the samples, several techniques were used according to the nature of the compounds involved. Particularly, PXRD, SEM / EDX and spectroscopic (SSNMR, FTIR, RAMAN, EPR…) techniques proved to be highly efficient for the monitoring of the mechano-chemical reaction, and to highlight the amorphization of the precursors and/or the formation of a distinct crystalline phase. SEM/EDX showed after the mechanochemical activation the changes in particle size, the disappearance of precursor morphologies, and the formation of particles with distinct morphologies and different chemical composition. Using solid state NMR measurements significant changes in the chemical environments involved were evidenced, suggesting the formation of metastable compounds between metal cations from the lamellar matrices, phosphorus and oxygen, as well as other possible compounds as products. After the mechanochemical reaction, in the nutrient release assays, the slow release behavior was observed for all the matrices analyzed. The release rate can be influenced by the chemical composition of the starting matrices, since each matrix can produce similar and distinct products, for example, SiO2 from natural clays which is not possible in the LDH products.

This doctoral thesis is focused on the study of reactions in the CaO–SiO2–H2O complex system, primarily to the synthesis of crystalline tobermorite. Hydrothermal conditions are necessary for the formation of crystalline tobermorite, whereas the course of the reaction is influenced by several factors. The main studied factor was the choice of the silica sources differing in means of solubility, crystallinity, particle size distribution, specific surface area, and purity. The water-to-solid ratio turned to be also an important factor as the length of the hydrothermal reaction. The influence of the mechanochemical pretreatment of starting materials to the final phase composition of samples was studied as well. The obtained results show that the crystallinity of the silica source is the main factor influencing the reaction rate and the purity of the synthesized tobermorite. While using the crystalline silica source the shorter silicate chains are formed and the formation of tobermorite structure is easier. Using the amorphous silica sources and the mechanochemical pretreatement of starting materials prolong the hydrothermal reaction. The prepared samples are always the mixture of crystalline or semicrystalline calcium hydrosilicates instead of the phase pure tobermorite.

The thesis deals with study of mechnochemical activation of chemical reactions at interphase of MDF composites. MDF composites are high-perspective composite materials on polymer-cement base. They excel especially in terms of flexural strengths. High flexural stregth is caused by binding interactions between the polymer and the cement. This interactions arise due to mechanochemical activation of raw material mixture at the stage of production. This work focuses on the creation of artificial cement-polymer interphase by contacting the surfaces of two molded tablets (polyvinyl alcohol and monocalcium aluminate), activation of chemical reactions at interphase by means of specially designed appartus, which achieves good plane-parallelism of activation surfaces and good definability of activation conditions (shear rate, pressure). After experiments under different conditions, the activated surfaces are analyzed by SEM, EDS, XPS and FT-IR.