Computational investigation of calcium aluminosilicate network dissolution
Author
Schade, Anders Mose
Term
4. Term
Education
Publication year
2023
Abstract
The dissolution of stone wool fibers is critical to product durability and health safety, yet the atomic-scale mechanism of network breakdown in the amorphous glass remains unclear. This thesis investigates hydrolysis of network linkages in calcium aluminosilicate (CAS) as a model for stone wool. Using molecular dynamics (MD) with the novel wet-GS force field, stationary water molecules stabilized by hydrogen bonding at the CAS surface are identified. These observations inform density functional theory (DFT) reaction pathway analyses on a small glass model to determine activation energies for hydrolyzing linkages between network formers (Si–O–Si, Si–O–Al, Al–O–Al) and to assess the roles of Qn environments and an additional water molecule. The results indicate that Al–O–Al linkages break most readily with activation energies of 47–85 kJ/mol, whereas Si–O–Si and Si–O–Al show similar likelihoods of hydrolysis with 85–165 kJ/mol. No significant differences are observed across Qn groups, and adding a second water molecule does not reduce activation energies because the mechanism remains unchanged. Overall, the study provides atomistic insight into glass dissolution that can inform the design of stone wool with balanced biosolubility and durability.
Opløseligheden af stenuldsfibre er central for både produkters holdbarhed og sundhed, men de atomare mekanismer bag netværksnedbrydning i det amorfe glas er ikke fuldt klarlagt. Dette projekt undersøger hydrolyse af netværksbindinger i calcium-aluminosilikat (CAS) som modelsystem for stenuld. Ved hjælp af molekylær dynamik (MD) med det nye wet-GS kraftfelt identificeres stationære vandmolekyler stabiliseret af hydrogenbindinger på CAS-overfladen. Disse observationer bruges til at opstille reaktionsforløb i densitetsfunktionalteori (DFT) på en lille glasmodel for at beregne aktiveringsenergier for hydrolyse af bindinger mellem netværksformere (Si–O–Si, Si–O–Al, Al–O–Al) samt vurdere betydningen af Qn-miljøer og et ekstra vandmolekyle. Resultaterne viser, at Al–O–Al-led brydes lettest med aktiveringsenergier på 47–85 kJ/mol, mens Si–O–Si og Si–O–Al har tilsvarende sandsynlighed for brud med 85–165 kJ/mol. Der ses ingen signifikante forskelle mellem Qn-grupper, og inklusion af et ekstra vandmolekyle sænker ikke aktiveringsenergierne, fordi reaktionsmekanismen forbliver den samme. Samlet giver studiet atomistisk indsigt i glasopløsning, som kan understøtte design af stenuld med balanceret biosolubilitet og holdbarhed.
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