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61.
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
62.
In the field of industry, it is very important that boron compounds are produced from boron ores. The aim of this study was to investigate the dissolution kinetics with carbon dioxide of colemanite in methanol medium in a pressure reactor and to derive an alternative process for producing boron compounds. Reaction temperature, stirring speed, solid/liquid ratio, pressure, and particle size were selected as parameters for the dissolution rate of colemanite. It was found that the dissolution rate increased with increase in pressure and reaction temperature, and with decrease in particle size and solid/liquid ratio. No effect of stirring speed was observed on conversion. The dissolution kinetics of colemanite were examined using both heterogeneous and homogeneous reaction models, and it was determined that the reaction rate can be described by a second-order pseudo-homogeneous reaction model. The activation energy was found to be 51.4 kJ/mol. 相似文献
63.
《Journal of Industrial and Engineering Chemistry》2014,20(2):372-378
A series of new bis (imidazolium) cation-based ionic liquids, wherein two imidazole rings are tethered by alkyl ether chains (oxygen numbers) of different lengths, were prepared, and their coal dissolution and dispersion properties were studied. It was found these ionic liquids can be used to fragment, disperse, and partially dissolve micrometer-size coal particles by simply mixing ionic liquid/coal dispersions. Dissolution performances and light hydrocarbon production were found to be sensitively increased by increasing the lengths of alkyl ether chains between imidazolium rings. 相似文献
64.
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
65.
The selection of pharmaceutical polymorphisms in the final production step is very important in terms of product recovery, properties, and storage. The amorphous, dihydrated crystalline, and anhydrous crystalline forms of paclitaxel were prepared using precipitation, spray drying, and colloid formation methods. These methods were found to be highly efficient and convenient, giving high recovery, short processing time, and good stability, as compared with conventional methods such as freeze drying, evaporation, recrystallization, and melting. The polymorphic natures of the resulting paclitaxel samples were confirmed by XRPD, IR, TGA, DSC, and SEM. The dissolution rates of the paclitaxel samples were studied in pharmaceutical solvents, which included cotton seed oil, corn oil, tricaprylin, and tributyrin. For each solvent, all of the amorphous paclitaxel samples showed much higher dissolution rates than the dihydrated crystalline, anhydrous crystalline, and commercial forms, and can be used for clinical applications that demand improvements in drug delivery. 相似文献
66.
The early deformation of the cathode material has been confirmed to be a significant factor in shortening the cell life. Thus, a new kind of cathode with both lower solubility and lighter deformation is highly desirable. In this work, a novel composite material, LiCoO2‐Ni, was prepared by the electrophoretic deposition (EPD) technique, which, remarkably, is able to reduce the deformation and dissolution of cathode materials simultaneously. It was demonstrated to be very promising for the MCFC industry. 相似文献
67.
Yi Liu Lingling Xiao Dawei Song Yaping Wang Lifang Jiao Huatang Yuan 《Electrochimica acta》2008,53(5):2265-2271
A series of CoxB (x = 1, 2, 3) alloys were prepared by arc melting, the phase structure of the alloys were characterized by X-ray diffraction (XRD). The electrochemical experimental results demonstrated that the CoxB (x = 1, 2, 3) series alloys showed excellent cycling stability, the capacity retention was 94.2%, 93.6% and 93.8% in the 100th cycle, respectively, as the cobalt content decreased. The CoB alloy electrode showed very good electrochemical reversibility in cyclic voltammetry (CV) curves, the oxidation and reduction peaks resembled the pure cobalt element powder electrode. The electrode mechanism was discussed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), using pure CoB alloy cast electrode. From the SEM, after first and second cycle, the surface became porous and pulverous; also, the oxidation state of Co changed through XPS, after second cycle, the Co of 0 oxidation state could not be found on the surface. Based on the experiment, a proper mechanism was proposed: on this condition, the discharge capacity may due to the Co(OH)2/Co reaction, which happened on the porous surface as the boron dissolved when the cycle increased. 相似文献
68.
69.
在高钛焊丝钢的连铸过程中,钢液中生成的TiN夹杂物容易诱发“结鱼”物的形成,从而引发连铸坯表面缺陷,甚至漏钢。针对以上问题,本文采用热力学计算、旋转柱法和高温共聚焦法实验对高钛焊丝钢连铸保护渣对TiN夹杂物的吸收进行了研究。热力学计算结果表明：CaO-SiO2保护渣中的SiO2和Al2O3均能与TiN发生反应,且SiO2与其反应的能力更强;旋转柱实验表明：保护渣对柱状TiN的溶解能力有限,TiN和保护渣的界面处有反应发生;高温共聚焦实验表明：TiN很容易被空气所氧化,从反应前后试样总量的变化来看,TiN能够被保护渣所氧化。因此,采用保护渣氧化组分氧化TiN来减小结鱼有一定的可行性。 相似文献
70.
Dissolution of barium ion and its effect on dispersion behavior of aqueous barium titanate suspensions at various pH values have been investigated. The amount of leached barium ion decreases with increasing pH value. The dissolution of barium ion also causes an increase in pH value of suspension, but the change decreases with increasing initial pH value. The iso-electric point (IEP) of leached barium titanate powder increases with increasing leaching pH value and solid loading as well. The dissolution of barium ion enhances the colloidal stability of aqueous barium titanate suspension, in agreement with zeta potential measurement. 相似文献