română ALEXANDRA GABRIELA PALADE, MIHAELA IVANCIA, DIANA FELICIA LOGHIN, ANCA MIHAELA MOCANU
Abstract
The paper aims to obtain prosthetic devices made of two different dental ceramics and characterized by infrared absorption spectroscopy (FITR), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) and thermal analysis (TG- DTG-DTA). The two types of dental ceramics (VITA VM13 and IPS Style) were analyzed both in powder form, in the form before the firing process, and in the one resulting after this stage, sintered mass. The TG, DTG and DTA thermal analysis study identified the temperature range in which the ceramics are thermally stable and can be used in dental technique, with IPS Style ceramics showing a lower degree of decomposition.
Keywords
ceramic mass kits, layering technique, absorption spectroscopy, scanning electron microscopy, X-ray spectroscopy, thermal analysis.
HIBA A. OLEIWI, TAHA H. ABOOD AL-SAADI, NASRI S. M. NAMER
Abstract
The composition, hydrolytic stability, and mechanical properties, as well as the microstructure of produced geopolymers (as paste and as mortar), were investigated. The manufacturing processes investigated in this study involved green glass powder as raw materials and two types of alkali activators (i.e., NaOH and KOH) solutions. For pastes, different molarity concentrations of alkali activator solutions (N3, N6, N9, K3, K6, and K9) were employed to assess the mechanical properties (compressive strength). N6 and K9 alkali activators were used for mortar preparation, and for comparison, they were considered ordinary Portland cement paste and mortar. Generally, the compressive strength values of paste specimens increase with NaOH and KOH concentrations increasing. It is worth mentioning that N6 and K9-based geopolymer formulas are the best mixtures due to their highest compressive strength as compared with cement paste at the same curing conditions of 7 and 28 days. In addition, for mortar specimens, the compressive strength of N6 mortar is higher than that of K9 specimens for curing times 7 and 28 days. The hydrolytic stability of pastes and mortars was assessed by measuring the compressive strength and weight changes for the specimens before and after immersion in distilled water. It is to be mentioned that for all studied pastes, the compressive strength losses are 30-70%, and for studied mortars, the compressive strength losses are 1-20% compared with cement under the same conditions. Moreover, weight loss is recorded for all geopolymer compositions.
Keywords
Geopolymers, glass waste, alkali activator, compressive strength, hydrolytic stability.