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Abstract The prerequisite for bioactive glasses to bond to living bone is the formation of biologically active apatites on their surface in the body. Reactions and bioactivity mechanisms between bioactive glasses and bone depend on the glass composition. We study a glass in the SiO2‐Na2O‐CaO‐P2O5‐K2O‐Al2O3‐MgO system. To characterise physicochemical reactions at the materials periphery, we immersed the glass pastilles into biological fluids for periods of 5, 10, and 20 days. The surface changes were studied at the micrometer scale by a Particle Induced X‐ray Emission (PIXE) method associated with Rutherford Backscattering Spectroscopy (RBS). After 20 days of immersion, elemental maps showed the formation of a calcium‐phosphate layer at the surface of the glass pastilles. The thickness of this layer was around 15 µm. Thanks to the PIXE method, we demonstrated the presence of traces of Mg in this layer. The glass doped with MgO leads to the formation of an apatite which incorporates magnesium. Formation of this Ca‐P‐Mg layer represents the bioactive properties of the studied glass. This biologically active layer improves the properties of the glass and will permit a chemical bond between the ceramic and bone. 相似文献
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N. Iguergaziz A. Boukhiar F.-Z. Djallouli A. Guebrili N.-E. Angar 《Chemical Engineering Communications》2019,206(4):524-534
Release characteristics of paracetamol from date (Phoenix dactylifera L., var. Mech-Degla) fruit tablets enriched and non-enriched with freeze-dried olive leaf extract (OLE) were studied. For this, two types of tablets (T) were obtained by direct compression: (1) T1 from P1-powder blend, containing 60% date powder (DP) and 40% paracetamol, and (2) T2 from P2-powder blend, containing 57% DP, 40% paracetamol, and 3% OLE. The release of paracetamol was studied in phosphate buffer (pH?6.8) and HCl solution (0.1N). Additionally, the oleuropein released was investigated in the case of T2-tablets. Based on obtained results, P1- and P2-powder blends showed acceptable flow properties in terms of Hausner’s ratio (1.30, in the case of P2) and angle of repose for both P1 (31 degrees) and P2 (33 degrees). Dissolution study showed that the released paracetamol achieved 80% after 70?min, whereas the oleuropein release was almost complete after 30?min. On the other hand, the Peppas model described correctly dissolution kinetics of both paracetamol (R2=?0.99) and oleuropein (R2=?0.89) whatever the applied dissolution medium. Furthermore, the presence of OLE in T2-tablets enhanced their microbiological shelf-life. 相似文献
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Yu-cheng Lei Xiao-kai Guo Hong-xia Chang Tian-qing Li Qiang Zhu Gang Chen Long-ren Xiao 《钢铁研究学报(英文版)》2017,24(9)
The cavitation erosion of weld joint and base metal of China low activation martensitic(CLAM)steel in liquid lead-bismuth eutectic alloy(LBE)at 550°C was investigated to simulate the cavitation erosion of the first wall and the nuclear main pump impeller in the accelerator driven sub-critical system(ADS).A suit of ultrasonic cavitation facility was self-designed to study the cavitation erosion.By studying the surface micro topography,roughness and mean pit depth of the tested specimens,it was found that some crater clusters and large scale cracks appeared on the tested specimen surface after the formation of numerous single craters,and the base metal exhibited much better cavitation erosion resistance than the weld bead due to the difference in their mechanical properties and microstructures.In addition,by comparing the results of static corrosion and cavitation erosion,it could be concluded that the cavitation erosion and the dissolution and oxidation corrosion in liquid LBE would accelerate mutually. 相似文献
16.
Reece N. Oosterbeek Kalliope I. Margaronis Xiang C. Zhang Serena M. Best Ruth E. Cameron 《Journal of the European Ceramic Society》2021,41(1):901-911
Phosphate glasses for bioresorbable implants display dissolution rates that vary significantly with composition, however currently their mechanisms of dissolution are not well understood. Based on this systematic study we present new insights into these mechanisms. Two-stage dissolution was observed, with time dependence initially parabolic and later linear, and a two-stage model was developed to describe this behaviour. Dissolution was accelerated by lower Ca concentration in the glass, and lower pH in the dissolution medium. A new dissolution mechanism is proposed, involving an initial stage where diffusion-controlled formation of a conversion layer occurs. Once the conversion layer is stabilised, layer dissolution reactions become rate-limiting. Under this mechanism the transition time is sensitive to the nature of the conversion layer and solution conditions. These results reveal the dependence of P2O5–CaO–Na2O glass dissolution on solution pH, and provide new insight into the dissolution mechanisms, particularly regarding the transition between the two dissolution stages. 相似文献
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《Ceramics International》2022,48(11):15017-15025
The dissolution behavior of MgO in CaO–SiO2–Al2O3 ternary slag at the interface of single-crystal, dense poly-crystal, and porous poly-crystal MgO was investigated to evaluate the effect of the surface properties of the MgO. The experimental results revealed that a detached spinel layer formed at the MgO interface due to the change in thermodynamic condition of the slag, which was independent of the surface properties. On the other hand, it was also confirmed that the growth rate and morphology of the detached spinel layer strongly depended on the surface properties, such as porosity and curvature of MgO. During the formation of the spinel layer at the interface during MgO dissolution, a kinetic approach adopting parabolic relation theory was employed to determine the correlation between the surface properties and the spinel growth mechanism. 相似文献
18.
Azithromycin is a poorly water-soluble drug with a lower dissolution rate which resulted in poor bioavailability after oral administration. The aim of this study was to enhance Azithromycin dissolution by a solid dispersion (SD) using solvent evaporation and supercritical fluid based on solvent-anti-solvent technique. Solid dispersions of Azithromycin were prepared with various concentrations of PEG 6000, Sorbitol and Poloxamer 188, SLS (in ternary systems). All samples were studied for the drug solubility. The formulations were also characterized by IR, DSC, XRD and SEM. The solubility and dissolution rate were remarkably improved in case of most SDs prepared with of PEG 6000 (in binary systems, 1:6 ratio) and both surfactants (ternary systems) compared to the related PMs and pure Azithromycin. But the best result was obtained in the dispersion (Azithromycin:PEG 6000:SLS) with a weight ratio of (1:4:2). SAS–SCF processes were signs of less crystallinity of the drug due to the transformation of its crystalline stat into amorphous state. The analysis of dissolution data indicated that enhanced drug dissolution can be achieved where the SDs obtained in the supercritical fluid process was consisted of PEG 6000 and SLS. The dissolution rate and solubility of Azithromycin improved significantly with PEG 6000 and SLS utilizing SAS-supercritical fluid. 相似文献
19.
Elnazeer I. HamedelnielJános Bajdik Tamás SoványKlára Pintye-Hódi 《Chemical Engineering Research and Design》2011,89(7):1006-1010
The aim of this study was to develop a delayed-release matrix pellet containing atenolol as active pharmaceutical ingredient. The matrix additionally contained trisodium phosphate dodecahydrate as alkalizing pore-former agent to enhance the dissolution of the atenolol at pH 6.8. The delayed release was ensured by coating with a gastro-resistant polymer. For this purpose, an acryl EZE MP aqueous dispersion was used, which is suggested in the literature for pellet coating. Before this functional film coating, a protective polymer layer was developed, to prevent direct contact between the alkalizing layer and the acryl EZE. The results of in vitro dissolution tests demonstrated that the double-coated pellet preparation is a delayed-release solid dosage form. 相似文献
20.
介绍了涡轮空心叶片用铝基陶瓷型芯的应用背景,探讨了铝基陶瓷型芯强化及溶失性能的重要意义。阐述了造型材料、成孔剂、脱芯方法对氧化铝基陶瓷型芯溶失性能增强的研究现状,并展望了铝基陶瓷型芯未来发展面临的挑战。 相似文献