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Thaned Pongjanyakul - One of the best experts on this subject based on the ideXlab platform.
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sodium caseinate magnesium Aluminum Silicate nanocomposite films for modified release tablets
Materials Science and Engineering: C, 2018Co-Authors: Wanassnant Kajthunyakarn, Duangkamon Sakloetsakun, Thaned PongjanyakulAbstract:Abstract The aim of this study was to investigate the effect of clay, magnesium Aluminum Silicate (MAS), on the properties of sodium caseinate (SC) dispersions and films. Moreover, the SC-MAS dispersions were evaluated for film coating of modified-release tablets. The results showed that MAS addition led to particle flocculation and viscosity synergism in the SC-MAS dispersions. Exfoliated or intercalated nanocomposites of the SC-MAS films could be formed because of the molecular interaction of both components via hydrogen bonding. The puncture strength and elongation of the dry SC films decreased with increasing MAS ratios. However, MAS added enhanced the puncture strength of the wet films and reduced drug permeability and diffusivity across the films in acidic medium because of lower water uptake and denser matrix structure of the films. The SC-MAS dispersions showed strong potential for use as a film coating material with few defects in the coated acetaminophen (ACT) tablets. The ACT release of the coated tablets in acidic medium was modified by varying the MAS ratios and film coating levels. In addition, the SC-MAS coated tablets possessed sustained-release behavior for the drug under simulated gastrointestinal conditions. This finding indicates that the SC-MAS nanocomposite films can be applied as a tablet coating material to modify drug release.
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nicotine magnesium Aluminum Silicate microparticle surface modified with chitosan for mucosal delivery
Materials Science and Engineering: C, 2013Co-Authors: Watchara Kanjanakawinkul, Satit Puttipipatkhachorn, Thomas Rades, Thaned PongjanyakulAbstract:Abstract Magnesium Aluminum Silicate (MAS), a negatively charged clay, and nicotine (NCT), a basic drug, can interact electrostatically to form microparticles. Chitosan (CS) was used for the surface modification of the microparticles, and a lyophilization method was used to preserve the original particle morphology. The microparticles were characterized in terms of their physicochemical properties, NCT content, mucoadhesive properties, and release and permeation across porcine esophageal mucosa. The results showed that the microparticles formed via electrostatic interaction between MAS and protonated NCT had an irregular shape and that their NCT content increased with increasing NCT ratios in the microparticle preparation solution. High molecular weight CS (800 kDa) adsorbed to the microparticle surface and induced a positive surface charge. CS molecules intercalated into the MAS Silicate layers and decreased the crystallinity of the microparticles, leading to an increase in the release rate and diffusion coefficient of NCT from the microparticles. Moreover, the microparticle surface modified with CS was found to have higher NCT permeation fluxes and mucoadhesive properties, which indicated the significant role of CS for NCT mucosal delivery. However, the enhancement of NCT permeation and of mucoadhesive properties depended on the molecular weight and concentration of CS. These findings suggest that NCT-MAS microparticle surface modified with CS represents a promising mucosal delivery system for NCT.
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preparation and characterization of nicotine magnesium Aluminum Silicate complex loaded sodium alginate matrix tablets for buccal delivery
Aaps Pharmscitech, 2011Co-Authors: Sopaphan Kanjanabat, Thaned PongjanyakulAbstract:Nicotine (NCT) buccal tablets consisting of sodium alginate (SA) and nicotine–magnesium Aluminum Silicate (NCT–MAS) complexes acting as drug carriers were prepared using the direct compression method. The effects of the preparation pH levels of the NCT–MAS complexes and the complex/SA ratios on NCT release, permeation across mucosa, and mucoadhesive properties of the tablets were investigated. The NCT–MAS complex-loaded SA tablets had good physical properties and zero-order release kinetics of NCT, which indicate a swelling/erosion-controlled release mechanism. Measurement of unidirectional NCT release and permeation across porcine esophageal mucosa using a modified USP dissolution apparatus 2 showed that NCT delivery was controlled by the swollen gel matrix of the tablets. This matrix, which controlled drug diffusion, resulted from the molecular interactions of SA and MAS. Tablets containing the NCT–MAS complexes prepared at pH 9 showed remarkably higher NCT permeation rates than those containing the complexes prepared at acidic and neutral pH levels. Larger amounts of SA in the tablets decreased NCT release and permeation rates. Additionally, the presence of SA could enhance the mucoadhesive properties of the tablets. These findings suggest that SA plays the important role not only in controlling release and permeation of NCT but also for enhancing the mucoadhesive properties of the NCT–MAS complex-loaded SA tablets, and these tablets demonstrate a promising buccal delivery system for NCT.
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nicotine loaded sodium alginate magnesium Aluminum Silicate sa mas films importance of sa mas ratio
Carbohydrate Polymers, 2010Co-Authors: Thaned Pongjanyakul, Hatairat SuksriAbstract:The objective of this work was to investigate the influence of the sodium alginate–magnesium Aluminum Silicate (SA–MAS) ratio on film properties for nicotine (NCT) mucosal delivery. NCT-loaded SA–MAS films with varying SA–MAS ratios were prepared at acidic and basic pH, which represent the protonated and neutral species of NCT, respectively. The film characteristics, such as NCT content, muco-adhesive properties, NCT release and skin and mucosal membranes NCT permeation were examined. The result showed that increasing the MAS ratio in the films caused an increase in NCT retention and a decrease in the NCT release rate. The NCT release mechanism of the NCT-loaded SA–MAS films prepared at acidic and basic pH was an anomalous transport and a swelling controlled mechanism, respectively, and was primarily impacted by the SA content in the films. The NCT permeation rate across the mucosal membrane decreased with increasing MAS ratio of the films. The mucosal drug permeation kinetics suggested a matrix diffusion controlled mechanism, whereas skin penetration acted as a rate-limiting step of drug permeation. Film preparation pH also affected NCT release and permeation due to the unique charge characteristics of the various NCT species formed. Furthermore, films with a high MAS ratio could adhere to the mucosal membrane. These findings suggest the SA–MAS ratio remarkably influences the characteristics of the NCT-loaded SA–MAS films, and that these films demonstrate a promising mucosal drug delivery system.
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propranolol magnesium Aluminum Silicate complex dispersions and particles characterization and factors influencing drug release
International Journal of Pharmaceutics, 2010Co-Authors: Sarasit Rojtanatanya, Thaned PongjanyakulAbstract:Abstract In this study, complexation of magnesium Aluminum Silicate (MAS) and propranolol HCl (PPN) in the form of dispersions and solid particles was investigated. PPN–MAS dispersions at different pHs were prepared and characterized. The physicochemical properties and in vitro drug release of the complexes were also examined. Incorporation of PPN into MAS dispersions at various pHs caused the formation of PPN–MAS flocculates with a different particle size, zeta potential and amount of PPN adsorbed. The PPN–MAS complexes prepared at various pHs were formed via cation exchange, hydrogen bonding and water bridging mechanisms, which were revealed by FTIR and solid-state 29 Si NMR spectroscopy. This led to the intercalation of PPN molecules into the Silicate layers of MAS. In vitro drug release studies demonstrated that the kinetic release of PPN can be described using the particle diffusion controlled mechanism, suggesting that drug release was controlled by diffusion of the drug in aqueous channels in the particle matrix of the complexes. The PPN–MAS complexes provided a sustained-release of PPN after an initial burst release in acidic medium and pH 6.8 phosphate buffer when compared with the physical mixture and pure PPN powder. This was due to a slow diffusion of drug that was intercalated in the inside of the particle matrix. The preparation pH of the complexes did not influence the release of PPN; the important factors affecting drug release were particle size, percentage of drug loaded in the complexes and the type of release medium. This finding suggests that the PPN–MAS complexes obtained in this study are strong candidates for use as drug carriers in oral modified-release dosage forms.
Tao Zhang - One of the best experts on this subject based on the ideXlab platform.
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permittivity regulating strategy enabling superior electromagnetic wave absorption of lithium Aluminum Silicate rgo nanocomposites
ACS Applied Materials & Interfaces, 2019Co-Authors: Siru Lu, Bo Zhong, Tao Zhang, Jiaming Xu, Chuheng Ding, Tiantian Li, Hua Yang, Longnan Huang, Li Xiong, Xiaoxiao HuangAbstract:Lithium Aluminum Silicate (LAS) nanoparticles have been successfully loaded on graphene nanosheets by adding a silane coupling agent KH-550 by sol–gel process, hydrothermal reaction, and heat treatment process. By regulating the complex permittivity of reduced graphene oxide (rGO) by LAS nanoparticles and KH-550, LAS/rGO-KH-550 possesses excellent microwave absorption performance. The maximum reflection loss of LAS/rGO-KH-550 reaches −62.25 dB at 16.48 GHz with thickness of only 2.7 mm, and the widest bandwidth is up to 6.64 GHz below −10 dB. The LAS/rGO-KH-550 has effective absorption (99.9%) below −20 dB at all X and Ku bands (8–18 GHz). Also, the added quantity of composites in the paraffin matrix is only 20 wt %. The results demonstrate that the interfacial polarization, the Debye dipolar relaxation, the well-matched characteristic impedance, and the quarter-wavelength matching all play important roles in improving the microwave absorption properties of LAS/rGO-KH-550 nanocomposites. Consequently, the...
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permittivity regulating strategy enabling superior electromagnetic wave absorption of lithium Aluminum Silicate rgo nanocomposites
ACS Applied Materials & Interfaces, 2019Co-Authors: Long Xia, Bo Zhong, Tao Zhang, Chuheng Ding, Hua Yang, Longnan Huang, Li Xiong, Xiaoxiao Huang, Guangwu WenAbstract:Lithium Aluminum Silicate (LAS) nanoparticles have been successfully loaded on graphene nanosheets by adding a silane coupling agent KH-550 by sol-gel process, hydrothermal reaction, and heat treatment process. By regulating the complex permittivity of reduced graphene oxide (rGO) by LAS nanoparticles and KH-550, LAS/rGO-KH-550 possesses excellent microwave absorption performance. The maximum reflection loss of LAS/rGO-KH-550 reaches -62.25 dB at 16.48 GHz with thickness of only 2.7 mm, and the widest bandwidth is up to 6.64 GHz below -10 dB. The LAS/rGO-KH-550 has effective absorption (99.9%) below -20 dB at all X and Ku bands (8-18 GHz). Also, the added quantity of composites in the paraffin matrix is only 20 wt %. The results demonstrate that the interfacial polarization, the Debye dipolar relaxation, the well-matched characteristic impedance, and the quarter-wavelength matching all play important roles in improving the microwave absorption properties of LAS/rGO-KH-550 nanocomposites. Consequently, the LAS/rGO-KH-550 nanocomposites can be readily applied as an ultra-wide-band, light weight, and ultra-high-performance microwave-absorbing material.
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Permittivity-Regulating Strategy Enabling Superior Electromagnetic Wave Absorption of Lithium Aluminum Silicate/rGO Nanocomposites
2019Co-Authors: Long Xia, Bo Zhong, Tao Zhang, Chuheng Ding, Hua Yang, Longnan Huang, Li XiongAbstract:Lithium Aluminum Silicate (LAS) nanoparticles have been successfully loaded on graphene nanosheets by adding a silane coupling agent KH-550 by sol–gel process, hydrothermal reaction, and heat treatment process. By regulating the complex permittivity of reduced graphene oxide (rGO) by LAS nanoparticles and KH-550, LAS/rGO-KH-550 possesses excellent microwave absorption performance. The maximum reflection loss of LAS/rGO-KH-550 reaches −62.25 dB at 16.48 GHz with thickness of only 2.7 mm, and the widest bandwidth is up to 6.64 GHz below −10 dB. The LAS/rGO-KH-550 has effective absorption (99.9%) below −20 dB at all X and Ku bands (8–18 GHz). Also, the added quantity of composites in the paraffin matrix is only 20 wt %. The results demonstrate that the interfacial polarization, the Debye dipolar relaxation, the well-matched characteristic impedance, and the quarter-wavelength matching all play important roles in improving the microwave absorption properties of LAS/rGO-KH-550 nanocomposites. Consequently, the LAS/rGO-KH-550 nanocomposites can be readily applied as an ultra-wide-band, light weight, and ultra-high-performance microwave-absorbing material
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crystal structure and wave transparent properties of lithium Aluminum Silicate glass ceramics
Ceramics International, 2018Co-Authors: Long Xia, Yanan Yang, Xinyu Zhang, Jian Zhang, Bo Zhong, Tao Zhang, Huatao Wang, Guangwu WenAbstract:Abstract Lithium Aluminum Silicate (LAS) glass-ceramic exhibits high transmittance to electromagnetic wave and is an ideal radome material. LAS glass-ceramics with different ratios of Li/Al were prepared by sol-gel method. Crystallization behaviors and wave-transparent properties of sintered powders were characterized. β-spodumene was detected as the major phase that precipitated from the sample with 1:1 ratio between Li and Al, which exhibited ultra-low complex permittivity (epsilon, 2.78) and dielectric loss tangent values. The microwave transmittance in 2–18 GHz is higher than 90% when the thickness is within 1.7 mm, suggesting that this kind of LAS glass-ceramic possesses excellent wave-transparent properties.
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enhanced electromagnetic wave absorption properties of laminated sicnw cf lithium Aluminum Silicate las composites
Journal of Alloys and Compounds, 2018Co-Authors: Xinyu Zhang, Yanan Yang, Jian Zhang, Bo Zhong, Tao Zhang, Huatao WangAbstract:Abstract The SiC nanowires have been in situ grown on the carbon fabric by thermal evaporation. Furthermore, to reduce the reflection of electromagnetic (EM) wave on the surface of EM wave absorbents and to improve the impedance matching, the laminated SiC NW -C f /lithium-Aluminum-Silicate (LAS) composites were prepared through slurry impregnation and hot-pressing sintering methods using the fabrics as reinforced body. The as-prepared samples were characterized by X-ray diffraction (XRD), Raman spectra, field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscope (HRTEM). The formation mechanism of SiC nanowires was specified. The SiC NW -C f /LAS composites in this study exhibited superior EM wave absorption abilities and good impedance match in the frequency range of 2–18 GHz compared with SiC NW -C f . A minimum reflection loss (RL) value of −37.8 dB was observed at 7.2 GHz with absorber thickness of only 3 mm. Moreover, the absorption bandwidth for RL less than −10 dB was 4.6 GHz (13.4 GHz - 18 GHz) when the absorber thickness decreased to 1.5 mm. A possible wave absorbing mechanism was discussed. This study proposed a facile method to fabricate a lightweight and broadband material with enhanced EM wave absorption performance.
Bo Zhong - One of the best experts on this subject based on the ideXlab platform.
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permittivity regulating strategy enabling superior electromagnetic wave absorption of lithium Aluminum Silicate rgo nanocomposites
ACS Applied Materials & Interfaces, 2019Co-Authors: Siru Lu, Bo Zhong, Tao Zhang, Jiaming Xu, Chuheng Ding, Tiantian Li, Hua Yang, Longnan Huang, Li Xiong, Xiaoxiao HuangAbstract:Lithium Aluminum Silicate (LAS) nanoparticles have been successfully loaded on graphene nanosheets by adding a silane coupling agent KH-550 by sol–gel process, hydrothermal reaction, and heat treatment process. By regulating the complex permittivity of reduced graphene oxide (rGO) by LAS nanoparticles and KH-550, LAS/rGO-KH-550 possesses excellent microwave absorption performance. The maximum reflection loss of LAS/rGO-KH-550 reaches −62.25 dB at 16.48 GHz with thickness of only 2.7 mm, and the widest bandwidth is up to 6.64 GHz below −10 dB. The LAS/rGO-KH-550 has effective absorption (99.9%) below −20 dB at all X and Ku bands (8–18 GHz). Also, the added quantity of composites in the paraffin matrix is only 20 wt %. The results demonstrate that the interfacial polarization, the Debye dipolar relaxation, the well-matched characteristic impedance, and the quarter-wavelength matching all play important roles in improving the microwave absorption properties of LAS/rGO-KH-550 nanocomposites. Consequently, the...
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permittivity regulating strategy enabling superior electromagnetic wave absorption of lithium Aluminum Silicate rgo nanocomposites
ACS Applied Materials & Interfaces, 2019Co-Authors: Long Xia, Bo Zhong, Tao Zhang, Chuheng Ding, Hua Yang, Longnan Huang, Li Xiong, Xiaoxiao Huang, Guangwu WenAbstract:Lithium Aluminum Silicate (LAS) nanoparticles have been successfully loaded on graphene nanosheets by adding a silane coupling agent KH-550 by sol-gel process, hydrothermal reaction, and heat treatment process. By regulating the complex permittivity of reduced graphene oxide (rGO) by LAS nanoparticles and KH-550, LAS/rGO-KH-550 possesses excellent microwave absorption performance. The maximum reflection loss of LAS/rGO-KH-550 reaches -62.25 dB at 16.48 GHz with thickness of only 2.7 mm, and the widest bandwidth is up to 6.64 GHz below -10 dB. The LAS/rGO-KH-550 has effective absorption (99.9%) below -20 dB at all X and Ku bands (8-18 GHz). Also, the added quantity of composites in the paraffin matrix is only 20 wt %. The results demonstrate that the interfacial polarization, the Debye dipolar relaxation, the well-matched characteristic impedance, and the quarter-wavelength matching all play important roles in improving the microwave absorption properties of LAS/rGO-KH-550 nanocomposites. Consequently, the LAS/rGO-KH-550 nanocomposites can be readily applied as an ultra-wide-band, light weight, and ultra-high-performance microwave-absorbing material.
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Permittivity-Regulating Strategy Enabling Superior Electromagnetic Wave Absorption of Lithium Aluminum Silicate/rGO Nanocomposites
2019Co-Authors: Long Xia, Bo Zhong, Tao Zhang, Chuheng Ding, Hua Yang, Longnan Huang, Li XiongAbstract:Lithium Aluminum Silicate (LAS) nanoparticles have been successfully loaded on graphene nanosheets by adding a silane coupling agent KH-550 by sol–gel process, hydrothermal reaction, and heat treatment process. By regulating the complex permittivity of reduced graphene oxide (rGO) by LAS nanoparticles and KH-550, LAS/rGO-KH-550 possesses excellent microwave absorption performance. The maximum reflection loss of LAS/rGO-KH-550 reaches −62.25 dB at 16.48 GHz with thickness of only 2.7 mm, and the widest bandwidth is up to 6.64 GHz below −10 dB. The LAS/rGO-KH-550 has effective absorption (99.9%) below −20 dB at all X and Ku bands (8–18 GHz). Also, the added quantity of composites in the paraffin matrix is only 20 wt %. The results demonstrate that the interfacial polarization, the Debye dipolar relaxation, the well-matched characteristic impedance, and the quarter-wavelength matching all play important roles in improving the microwave absorption properties of LAS/rGO-KH-550 nanocomposites. Consequently, the LAS/rGO-KH-550 nanocomposites can be readily applied as an ultra-wide-band, light weight, and ultra-high-performance microwave-absorbing material
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crystal structure and wave transparent properties of lithium Aluminum Silicate glass ceramics
Ceramics International, 2018Co-Authors: Long Xia, Yanan Yang, Xinyu Zhang, Jian Zhang, Bo Zhong, Tao Zhang, Huatao Wang, Guangwu WenAbstract:Abstract Lithium Aluminum Silicate (LAS) glass-ceramic exhibits high transmittance to electromagnetic wave and is an ideal radome material. LAS glass-ceramics with different ratios of Li/Al were prepared by sol-gel method. Crystallization behaviors and wave-transparent properties of sintered powders were characterized. β-spodumene was detected as the major phase that precipitated from the sample with 1:1 ratio between Li and Al, which exhibited ultra-low complex permittivity (epsilon, 2.78) and dielectric loss tangent values. The microwave transmittance in 2–18 GHz is higher than 90% when the thickness is within 1.7 mm, suggesting that this kind of LAS glass-ceramic possesses excellent wave-transparent properties.
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enhanced electromagnetic wave absorption properties of laminated sicnw cf lithium Aluminum Silicate las composites
Journal of Alloys and Compounds, 2018Co-Authors: Xinyu Zhang, Yanan Yang, Jian Zhang, Bo Zhong, Tao Zhang, Huatao WangAbstract:Abstract The SiC nanowires have been in situ grown on the carbon fabric by thermal evaporation. Furthermore, to reduce the reflection of electromagnetic (EM) wave on the surface of EM wave absorbents and to improve the impedance matching, the laminated SiC NW -C f /lithium-Aluminum-Silicate (LAS) composites were prepared through slurry impregnation and hot-pressing sintering methods using the fabrics as reinforced body. The as-prepared samples were characterized by X-ray diffraction (XRD), Raman spectra, field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscope (HRTEM). The formation mechanism of SiC nanowires was specified. The SiC NW -C f /LAS composites in this study exhibited superior EM wave absorption abilities and good impedance match in the frequency range of 2–18 GHz compared with SiC NW -C f . A minimum reflection loss (RL) value of −37.8 dB was observed at 7.2 GHz with absorber thickness of only 3 mm. Moreover, the absorption bandwidth for RL less than −10 dB was 4.6 GHz (13.4 GHz - 18 GHz) when the absorber thickness decreased to 1.5 mm. A possible wave absorbing mechanism was discussed. This study proposed a facile method to fabricate a lightweight and broadband material with enhanced EM wave absorption performance.
Guangwu Wen - One of the best experts on this subject based on the ideXlab platform.
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permittivity regulating strategy enabling superior electromagnetic wave absorption of lithium Aluminum Silicate rgo nanocomposites
ACS Applied Materials & Interfaces, 2019Co-Authors: Long Xia, Bo Zhong, Tao Zhang, Chuheng Ding, Hua Yang, Longnan Huang, Li Xiong, Xiaoxiao Huang, Guangwu WenAbstract:Lithium Aluminum Silicate (LAS) nanoparticles have been successfully loaded on graphene nanosheets by adding a silane coupling agent KH-550 by sol-gel process, hydrothermal reaction, and heat treatment process. By regulating the complex permittivity of reduced graphene oxide (rGO) by LAS nanoparticles and KH-550, LAS/rGO-KH-550 possesses excellent microwave absorption performance. The maximum reflection loss of LAS/rGO-KH-550 reaches -62.25 dB at 16.48 GHz with thickness of only 2.7 mm, and the widest bandwidth is up to 6.64 GHz below -10 dB. The LAS/rGO-KH-550 has effective absorption (99.9%) below -20 dB at all X and Ku bands (8-18 GHz). Also, the added quantity of composites in the paraffin matrix is only 20 wt %. The results demonstrate that the interfacial polarization, the Debye dipolar relaxation, the well-matched characteristic impedance, and the quarter-wavelength matching all play important roles in improving the microwave absorption properties of LAS/rGO-KH-550 nanocomposites. Consequently, the LAS/rGO-KH-550 nanocomposites can be readily applied as an ultra-wide-band, light weight, and ultra-high-performance microwave-absorbing material.
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crystal structure and wave transparent properties of lithium Aluminum Silicate glass ceramics
Ceramics International, 2018Co-Authors: Long Xia, Yanan Yang, Xinyu Zhang, Jian Zhang, Bo Zhong, Tao Zhang, Huatao Wang, Guangwu WenAbstract:Abstract Lithium Aluminum Silicate (LAS) glass-ceramic exhibits high transmittance to electromagnetic wave and is an ideal radome material. LAS glass-ceramics with different ratios of Li/Al were prepared by sol-gel method. Crystallization behaviors and wave-transparent properties of sintered powders were characterized. β-spodumene was detected as the major phase that precipitated from the sample with 1:1 ratio between Li and Al, which exhibited ultra-low complex permittivity (epsilon, 2.78) and dielectric loss tangent values. The microwave transmittance in 2–18 GHz is higher than 90% when the thickness is within 1.7 mm, suggesting that this kind of LAS glass-ceramic possesses excellent wave-transparent properties.
G P Kothiyal - One of the best experts on this subject based on the ideXlab platform.
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mas nmr investigations of the crystallization behaviour of lithium Aluminum Silicate las glasses containing p2o5 and tio2 nucleants
Journal of Solid State Chemistry, 2010Co-Authors: A Ananthanarayanan, G P Kothiyal, Lionel Montagne, Bertrand RevelAbstract:Lithium Aluminum Silicate (LAS) glass of composition (mol%) 20.4Li{sub 2}O-4.0Al{sub 2}O{sub 3}-68.6SiO{sub 2}-3.0K{sub 2}O-2.6B{sub 2}O{sub 3}-0.5P{sub 2}O{sub 5}-0.9TiO{sub 2} was prepared by melt quenching. The glass was then nucleated and crystallized based on differential thermal analysis (DTA) data and was characterized by {sup 29}Si, {sup 31}P, {sup 11}B and {sup 27}Al MAS-NMR. XRD and {sup 29}Si NMR showed that lithium metaSilicate (Li{sub 2}SiO{sub 3}) is the first phase to c form followed by cristobalite (SiO{sub 2}) and lithium diSilicate (Li{sub 2}Si{sub 2}O{sub 5}). {sup 29}Si MAS-NMR revealed a change in the network structure already for the glasses nucleated at 550 {sup o}C. Since crystalline Li{sub 3}PO{sub 4}, as observed by {sup 31}P MAS-NMR, forms concurrently with the Silicate phases, we conclude that crystalline Li{sub 3}PO{sub 4} does not act as a nucleating agent for lithium Silicate phases. Moreover, {sup 31}P NMR indicates the formation of M-PO{sub 4} (M=B, Al or Ti) complexes. The presence of BO{sub 3} and BO{sub 4} structural units in all the glass/glass-ceramic samples is revealed through {sup 11}B MAS-NMR. B remains in the residual glass and the crystallization of Silicate phases causes a reduction in the number of alkali ions available for charge compensation. As amore » result, the number of trigonally coordinated B (BO{sub 3}) increases at the expense of tetrahedrally coordinated B (BO{sub 4}). The {sup 27}Al MAS-NMR spectra indicate the presence of tetrahedrally coordinated Al species, which are only slightly perturbed by the crystallization. - Graphical abstract: {sup 11}B MAS-NMR spectra of LAS glass heat treated at different temperatures, showing the evolution of the residual glass matrix during the crystallization treatment. High-field (18.8 T) NMR enables us to record high resolution spectra, from which the glass network modifications could be related to the formation of intermediate lithium Silicate crystalline phases.« less
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mas nmr studies of lithium Aluminum Silicate las glasses and glass ceramics having different li2o al2o3 ratio
Journal of Solid State Chemistry, 2010Co-Authors: A Ananthanarayanan, G P Kothiyal, Lionel Montagne, Bertrand RevelAbstract:Emergence of phases in lithium Aluminum Silicate (LAS) glasses of composition (wt%) xLi{sub 2}O-71.7SiO{sub 2}-(17.7-x)Al{sub 2}O{sub 3}-4.9K{sub 2}O-3.2B{sub 2}O{sub 3}-2.5P{sub 2}O{sub 5} (5.1<=x<=12.6) upon heat treatment were studied. {sup 29}Si, {sup 27}Al, {sup 31}P and {sup 11}B MAS-NMR were employed for structural characterization of both LAS glasses and glass-ceramics. In glass samples, Al is found in tetrahedral coordination, while P exists mainly in the form of orthophosphate units. B exists as BO{sub 3} and BO{sub 4} units. {sup 27}Al NMR spectra show no change with crystallization, ruling out the presence of any Al containing phase. Contrary to X-ray diffraction studies carried out, {sup 11}B (high field 18.8 T) and {sup 29}Si NMR spectra clearly indicate the unexpected crystallization of a boroSilicate phase (Li,K)BSi{sub 2}O{sub 6}, whose structure is similar to the aluminoSilicate virgilite. Also, lithium diSilicate (Li{sub 2}Si{sub 2}O{sub 5}), lithium metaSilicate (Li{sub 2}SiO{sub 3}) and quartz (SiO{sub 2}) were identified in the {sup 29}Si NMR spectra of the glass-ceramics. {sup 31}P NMR spectra of the glass-ceramics revealed the presence of Li{sub 3}PO{sub 4} and a mixed phase (Li,K){sub 3}PO{sub 4} at low alkali concentrations. - Graphical Abstract: The {sup 11}B MAS-NMR spectra of lithium Aluminum Silicate (LAS) glass-ceramics indicatingmore » the formation of Li/KBSiO{sub 6} phase. This phase is isostructural with virgilite and cannot be distinguished in X-ray diffractograms.« less
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preparation structural and thermo mechanical properties of lithium Aluminum Silicate glass ceramics
Ceramics International, 2009Co-Authors: A Arvind, Rakesh Kumar, V K Shrikhande, G P KothiyalAbstract:Abstract Lithium Aluminum Silicate glasses of composition (wt%) 12.6Li 2 O–71.7SiO 2 –5.1Al 2 O 3 –4.9K 2 O–3.2B 2 O 3 –2.5P 2 O 5 were prepared by the melt quench technique. These glasses were converted to glass–ceramics based on DTA data. X-ray diffraction (XRD) and Fourier transform infra-red spectroscopy (FTIR) were used to discern the phases evolved in the glass–ceramics. Phase morphology was studied using scanning electron microscopy (SEM). Thermal expansion coefficient (TEC) and glass transition temperature ( T g ) of all samples were measured using thermo-mechanical analyzer (TMA). It was found that 3 h dwell time at crystallization temperature yielded samples with good crystallinity with a TEC of 9.461 × 10 −6 °C −1 . Glass–ceramic-to-metal compressive seal with SS-304 was fabricated using LAS glass–ceramic. The presence of metal housing and compressive stresses at the glass–ceramic-to-metal interface reduced average grain size and changed the overall microstructure.
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the effect of tio2 addition on the crystallization and phase formation in lithium Aluminum Silicate las glasses nucleated by p2o5
Journal of Physics and Chemistry of Solids, 2008Co-Authors: A Arvind, V K Shrikhande, A Sarkar, A K Tyagi, G P KothiyalAbstract:Abstract We have prepared lithium Aluminum Silicate (LAS) glasses of compositions (wt%) 10.6Li 2 O–71.7SiO 2 –7.1Al 2 O 3 –4.9K 2 O–3.2B 2 O 3 –2.5P 2 O 5 (LAS-P) and 10.6Li 2 O–71.7SiO 2 –7.1Al 2 O 3 –4.9K 2 O–3.2B 2 O 3 –1.25P 2 O 5 –1.25TiO 2 (LAS-PT) by the conventional melt quench technique. P 2 O 5 and TiO 2 are added as nucleating agents to transform them into glass ceramics. We have studied the interdependence of different phases formed, microstructure, thermal expansion coefficient (TEC), and microhardness (MH) using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-mechanical analysis (TMA), and MH (μ-hardness) measurements. The incorporation of TiO 2 , in addition to P 2 O 5 , greatly affects phase evolution and morphology, thereby affecting the thermo-physical properties. Its presence resulted in the formation of only lithium diSilicate phase in LAS-PT samples as compared to lithium diSilicate and quartz in LAS-P samples on heat treatment at 820 °C. This produced low-aspect-ratio plate-like crystallites in LAS-PT vis-a-vis granular microstructure in LAS-P. Consequently due to the combined effect of both phase formation and morphology a single-phase glass ceramic with overall higher MH, TEC, and glass transition temperature ( T g ) is produced.