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.
XIAN BIN WANG, SONG TANG, LIANG JI WANG
Abstract
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.
Keywords
Piezoelectric ceramic materials; Cr2O3 doping; PMS-PZT material; Finite element analysis; Piezoelectric performance