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Karen Scrivener - One of the best experts on this subject based on the ideXlab platform.
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influence of calcium to Silica Ratio on aluminium uptake in calcium Silicate hydrate
Cement and Concrete Research, 2016Co-Authors: E Lhopital, Barbara Lothenbach, Dmitrii A Kulik, Karen ScrivenerAbstract:Aluminium uptake in calcium Silicate hydrate (C-S-H) was studied at different Ca/Si Ratios from 0.6 to 1.6 at 20 degrees C. Aluminium incorpoRation in C-S-H depends on the total amount of aluminium present in the sample. At low Al/Si Ratio (<= 0.05), the major part of the aluminium is taken up in C-S-H while at higher Al/Si Ratio, the precipitation of stratlingite and/or katoite limits the Al/Si Ratio in C-S-H to approximate to 0.15, regardless of the Ca/Si Ratio. A strong correlation between the aqueous aluminium concentRation and the aluminium uptake in the solid phase is observed. At high Ca/Si Ratios, aluminium in C-S-H is observed mainly as octahedrally coordinated Al(VI) in TAH and the aluminium uptake increases with the aqueous aluminium concentRation. At low Ca/Si Ratio (<= 0.8), aluminium is observed mainly as tetrahedrally coordinated Al(IV) and low aqueous aluminium concentRations (below detection limit) indicate a high affinity of aluminium towards C-S-H. (C) 2016 Elsevier Ltd. All rights reserved.
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influence of calcium to Silica Ratio on aluminium uptake in calcium Silicate hydrate
Cement and Concrete Research, 2016Co-Authors: E Lhopital, Barbara Lothenbach, Dmitrii A Kulik, Karen ScrivenerAbstract:Abstract Aluminium uptake in calcium Silicate hydrate (C–S–H) was studied at different Ca/Si Ratios from 0.6 to 1.6 at 20 °C. Aluminium incorpoRation in C–S–H depends on the total amount of aluminium present in the sample. At low Al/Si Ratio (≤ 0.05), the major part of the aluminium is taken up in C–S–H while at higher Al/Si Ratio, the precipitation of stratlingite and/or katoite limits the Al/Si Ratio in C–S–H to ≈ 0.15, regardless of the Ca/Si Ratio. A strong correlation between the aqueous aluminium concentRation and the aluminium uptake in the solid phase is observed. At high Ca/Si Ratios, aluminium in C–S–H is observed mainly as octahedrally coordinated Al(VI) in TAH and the aluminium uptake increases with the aqueous aluminium concentRation. At low Ca/Si Ratio (≤ 0.8), aluminium is observed mainly as tetrahedrally coordinated Al(IV) and low aqueous aluminium concentRations (below detection limit) indicate a high affinity of aluminium towards C–S–H.
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early age strength enhancement of blended cement systems by cacl2 and diethanol isopropanolamine
Cement and Concrete Research, 2010Co-Authors: Kyle A Riding, Denise A Silva, Karen ScrivenerAbstract:The enhancement of the 1 day strength of cementinous systems by a combination of calcium chlonde (CaCl2) and diethanol-isopropanolamine (DEIPA) was studied, particularly in blended cement systems A combination of quantitative X-ray diffraction with Rietvelcl refinement (QXRD). scanning electron microscopy (SEM)/backscattered electron image analysis. thermogravimetnc analysis (TGA), and isothermal calonmetry were used to investigate the mechanism of strength enhancement by the additives The additives were found to increase the early age mortar strength by enhancing the cement hydRation, with the DEIPA enhancing primarily the aluminate hydRation DEIPA also affected the morphology of portlandite which was formed as thin plates In parallel, the calcium-to-Silica Ratio of the C-S-H was found to increase with the use of DEIPA. possibly because of the inclusion of microcrystalline portlandite After 48 h DEIPA was found to directly enhance the rate of reaction of granulated blast-furnace slag and fly ash (C) 2010 Elsevier Ltd All rights reserved
Siling Wang - One of the best experts on this subject based on the ideXlab platform.
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exploitation of 3d face centered cubic mesoporous Silica as a carrier for a poorly water soluble drug influence of pore size on release rate
Materials Science and Engineering: C, 2014Co-Authors: Wenquan Zhu, Tongying Jiang, Long Wan, Chen Zhang, Yikun Gao, Xin Zheng, Siling WangAbstract:The purposes of the present work were to explore the potential application of 3D face-centered cubic mesoporous Silica (FMS) with pore size of 16.0nm as a delivery system for poorly soluble drugs and investigate the effect of pore size on the dissolution rate. FMS with different pore sizes (16.0, 6.9 and 3.7nm) was successfully synthesized by using Pluronic block co-polymer F127 as a template and adjusting the reaction temperatures. Celecoxib (CEL), which is a BCS class II drug, was used as a model drug and loaded into FMS with different pore sizes by the solvent deposition method at a drug-Silica Ratio of 1:4. Characterization using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformation infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nitrogen adsorption, X-ray diffraction (XRD), and differential scanning calorimetry (DSC) was used to systematically investigate the drug loading process. The results obtained showed that CEL was in a non-crystalline state after incorpoRation of CEL into the pores of FMS-15 with pore size of 16.0nm. In vitro dissolution was carried out to demonstrate the effects of FMS with different pore sizes on the release of CEL. The results obtained indicated that the dissolution rate of CEL from FMS-15 was significantly enhanced compared with pure CEL. This could be explained by supposing that CEL encountered less diffusion resistance and its crystallinity decreased due to the large pore size of 16.0nm and the nanopore channels of FMS-15. Moreover, drug loading and pore size both play an important role in enhancing the dissolution properties for the poorly water-soluble drugs. As the pore size between 3.7 and 16.0nm increased, the dissolution rate of CEL from FMS gradually increased.
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3d cubic mesoporous Silica microsphere as a carrier for poorly soluble drug carvedilol
Microporous and Mesoporous Materials, 2012Co-Authors: Yanchen Hu, Zhuangzhi Zhi, Qinfu Zhao, Chao Wu, Peng Zhao, Haitao Jiang, Tongying Jiang, Siling WangAbstract:Abstract The present work was proposed not only to exploit the potential of 3D cage-like mesoporous Silica SBA-16 with a well-defined spherical morphology as a carrier for poorly soluble drugs, but also to compare the drug loading and release properties of 3D cubic SBA-16 with that of classic 2D hexagonal MCM-41. SBA-16 microsphere with highly ordered mesostructures was synthesized by a facile method using block co-polymer F127 as template, cetyltrimethylammonium bromide (CTAB) as co-template and tetraethyl orthoSilicate (TEOS) as Silica source. Carvedilol (CAR), an antihypertensive agent, was used as a model drug and loaded into mesoporous Silica via solvent deposition method at drug–Silica Ratio of 1:3. In vitro dissolution was performed in both simulated intestinal fluid (SIF, pH 6.8) and simulated gastric fluid (SGF, pH 1.2). Of particular interest was that in SIF both MCM-41 and SBA-16 samples exhibited promoted dissolution profile for CAR as compared to its corresponding crystalline form which exhibited poor dissolution behavior. This dissolution-enhancing effect might be due to the non-crystalline state and increased surface area of confined CAR as well as the hydrophilic nature of Silica. In comparison with MCM-41, SBA-16 displayed a more rapid release profile in both SIF and SGF, which may be ascribed to the 3D interconnected pore networks and the highly accessible surface areas. The suitability of the utilization of SBA-16 microsphere as carriers will open new avenues for the formulation of poorly soluble drugs.
Gholamreza Rashed - One of the best experts on this subject based on the ideXlab platform.
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Effect of Silica Ratio on the Corrosion Behavior of Nano-Silica Potassium Silicate Coatings on Aluminum Alloy 2024
Journal of Materials Engineering and Performance, 2014Co-Authors: H. Bahri, Iman Danaee, Gholamreza Rashed, Davood ZaareiAbstract:Nano-Silica modified potassium Silicate conversion coating was deposited in different nano-Silica/potassium Silicate Ratios on the surface of 2024 aluminum alloy. The corrosion behavior of coatings was studied by electrochemical impedance spectroscopy, current transient, potentiodynamic polarization, and surface techniques. The Ratio of nano-Silica/potassium Silicate was optimized in order to obtain higher corrosion protection. The experimental results indicated that with increasing nano-Silica/potassium Silicate Ratio, the corrosion resistance of aluminum increases. Furthermore, the pitting corrosion probability of potassium Silicate conversion coating decreased with increasing Silica Ratio. This can be related to the size of nano-Silica particles and the ability to fill the pores in potassium Silicate coating and reinforce the created siloxane bridges.
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the effect of curing time and curing temperature on the corrosion behavior of nanoSilica modified potassium Silicate coatings on aa2024
Surface & Coatings Technology, 2014Co-Authors: H. Bahri, Iman Danaee, Gholamreza RashedAbstract:Abstract NanoSilica modified potassium Silicate conversion coatings were deposited on the surface of 2024 aluminum alloy. The corrosion behavior of coatings was studied by electrochemical impedance spectroscopy, potentiodynamic polarization and the surface analyzing techniques. The effect of curing time and the curing temperature was studied on anti-corrosion behavior of coatings. Curing temperature showed a significant effect in Silicate conversion coating and higher corrosion resistance was obtained with 150 °C curing temperature. Also the experimental results indicated that the corrosion resistance was increased with increasing the curing time. This behavior can be related to the increase of the Silicate coating continuity and reinforcement of the siloxane chains which formed on the surface. Surface analysis results indicated that the coating obtained from 2.33 Silica Ratio was more uniform and continuous.
H. Bahri - One of the best experts on this subject based on the ideXlab platform.
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Effect of Silica Ratio on the Corrosion Behavior of Nano-Silica Potassium Silicate Coatings on Aluminum Alloy 2024
Journal of Materials Engineering and Performance, 2014Co-Authors: H. Bahri, Iman Danaee, Gholamreza Rashed, Davood ZaareiAbstract:Nano-Silica modified potassium Silicate conversion coating was deposited in different nano-Silica/potassium Silicate Ratios on the surface of 2024 aluminum alloy. The corrosion behavior of coatings was studied by electrochemical impedance spectroscopy, current transient, potentiodynamic polarization, and surface techniques. The Ratio of nano-Silica/potassium Silicate was optimized in order to obtain higher corrosion protection. The experimental results indicated that with increasing nano-Silica/potassium Silicate Ratio, the corrosion resistance of aluminum increases. Furthermore, the pitting corrosion probability of potassium Silicate conversion coating decreased with increasing Silica Ratio. This can be related to the size of nano-Silica particles and the ability to fill the pores in potassium Silicate coating and reinforce the created siloxane bridges.
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the effect of curing time and curing temperature on the corrosion behavior of nanoSilica modified potassium Silicate coatings on aa2024
Surface & Coatings Technology, 2014Co-Authors: H. Bahri, Iman Danaee, Gholamreza RashedAbstract:Abstract NanoSilica modified potassium Silicate conversion coatings were deposited on the surface of 2024 aluminum alloy. The corrosion behavior of coatings was studied by electrochemical impedance spectroscopy, potentiodynamic polarization and the surface analyzing techniques. The effect of curing time and the curing temperature was studied on anti-corrosion behavior of coatings. Curing temperature showed a significant effect in Silicate conversion coating and higher corrosion resistance was obtained with 150 °C curing temperature. Also the experimental results indicated that the corrosion resistance was increased with increasing the curing time. This behavior can be related to the increase of the Silicate coating continuity and reinforcement of the siloxane chains which formed on the surface. Surface analysis results indicated that the coating obtained from 2.33 Silica Ratio was more uniform and continuous.
E Lhopital - One of the best experts on this subject based on the ideXlab platform.
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influence of calcium to Silica Ratio on aluminium uptake in calcium Silicate hydrate
Cement and Concrete Research, 2016Co-Authors: E Lhopital, Barbara Lothenbach, Dmitrii A Kulik, Karen ScrivenerAbstract:Aluminium uptake in calcium Silicate hydrate (C-S-H) was studied at different Ca/Si Ratios from 0.6 to 1.6 at 20 degrees C. Aluminium incorpoRation in C-S-H depends on the total amount of aluminium present in the sample. At low Al/Si Ratio (<= 0.05), the major part of the aluminium is taken up in C-S-H while at higher Al/Si Ratio, the precipitation of stratlingite and/or katoite limits the Al/Si Ratio in C-S-H to approximate to 0.15, regardless of the Ca/Si Ratio. A strong correlation between the aqueous aluminium concentRation and the aluminium uptake in the solid phase is observed. At high Ca/Si Ratios, aluminium in C-S-H is observed mainly as octahedrally coordinated Al(VI) in TAH and the aluminium uptake increases with the aqueous aluminium concentRation. At low Ca/Si Ratio (<= 0.8), aluminium is observed mainly as tetrahedrally coordinated Al(IV) and low aqueous aluminium concentRations (below detection limit) indicate a high affinity of aluminium towards C-S-H. (C) 2016 Elsevier Ltd. All rights reserved.
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influence of calcium to Silica Ratio on aluminium uptake in calcium Silicate hydrate
Cement and Concrete Research, 2016Co-Authors: E Lhopital, Barbara Lothenbach, Dmitrii A Kulik, Karen ScrivenerAbstract:Abstract Aluminium uptake in calcium Silicate hydrate (C–S–H) was studied at different Ca/Si Ratios from 0.6 to 1.6 at 20 °C. Aluminium incorpoRation in C–S–H depends on the total amount of aluminium present in the sample. At low Al/Si Ratio (≤ 0.05), the major part of the aluminium is taken up in C–S–H while at higher Al/Si Ratio, the precipitation of stratlingite and/or katoite limits the Al/Si Ratio in C–S–H to ≈ 0.15, regardless of the Ca/Si Ratio. A strong correlation between the aqueous aluminium concentRation and the aluminium uptake in the solid phase is observed. At high Ca/Si Ratios, aluminium in C–S–H is observed mainly as octahedrally coordinated Al(VI) in TAH and the aluminium uptake increases with the aqueous aluminium concentRation. At low Ca/Si Ratio (≤ 0.8), aluminium is observed mainly as tetrahedrally coordinated Al(IV) and low aqueous aluminium concentRations (below detection limit) indicate a high affinity of aluminium towards C–S–H.