english ALEXANDRA GABRIELA PALADE, MIHAELA IVANCIA, DIANA FELICIA LOGHIN, ANCA MIHAELA MOCANU
Rezumat
Lucrarea urmărește obtinerea unor dispozitive protetice confectionate din două ceramici dentare diferite și caracterizate prin spectroscopie de absorbţie în infraroşu (FITR), microscopie electronică cu baleaj (SEM) cuplată cu spectroscopia de raze X prin dispersie de energie (EDX) și analiză termică (TG-DTG-DTA). Cele două tipuri de ceramică dentară (VITA VM 13 şi IPS Style) au fost analizate atât sub formă de pulbere, în forma de dinaintea procesului de ardere, cât şi în cea care rezultată după această etapă, masă sinterizată. Studiul de analiză termică TG, DTG şi DTA a permis identificarea intervalului de temperatură în care ceramicele sunt stabile termic şi pot fi utilizate în tehnica dentară, ceramica IPS Style prezentând astfel un grad mai mic de descompunere.
Cuvinte cheie
kit-uri de masă ceramică, tehnica straturilor, specroscopie de absorbție, SEM, EDX, analiză termică
HIBA A. OLEIWI, TAHA H. ABOOD AL-SAADI, NASRI S. M. NAMER
Rezumat
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.
Cuvinte cheie
geopolimeri, deșeuri de sticlă, activator alcalin, rezistență la compresiune, stabilitate hidrolitică
XIAN BIN WANG, SONG TANG, LIANG JI WANG
Rezumat
The study aims to investigate the effects of Cr2O3 doping on the microstructure and properties of PMS-PZT piezoelectric ceramic materials. The solid-phase reaction method is used to prepare PMS-PZT ceramics. The microstructure is characterized using X-ray diffraction and scanning electron microscope. The research results indicated that doping with Cr2O3 significantly affected the crystal structure and properties of PMS-PZT materials. X-ray diffraction pattern analysis demonstrated that with the increase of Cr2O3 doping, the lattice constant of PMS-PZT samples changed, and the grain size also showed different distributions in scanning electron microscope images. When the doping amount of Cr2O3 was 0.2wt%, the piezoelectric constant d33 reached its maximum value, at 382pC/N, the relative dielectric constant εr was 1,325, and the dielectric loss tanδ decreased to 0.31%. The electromechanical coupling coefficient Kt and mechanical quality factor Qm were 0.68 and 461, respectively. The finite element analysis results indicated that the PMS-PZT material with the optimal doping amount exhibited excellent static and dynamic properties under high-energy density conditions. Therefore, appropriate Cr2O3 doping can optimize the microstructure and piezoelectric properties of PMS-PZT materials, making them promising for high-energy density applications
Cuvinte cheie
Materiale ceramice piezoelectrice, dopare Cr2O3, material PMS-PZT, analiza elementelor finite, performanță piezoelectrică