The Experts below are selected from a list of 204 Experts worldwide ranked by ideXlab platform
Pradip B. Sarawade - One of the best experts on this subject based on the ideXlab platform.
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effect of drying technique on the physicochemical properties of sodium silicate based mesoporous precipitated silica
Applied Surface Science, 2011Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Dang Viet QuangAbstract:Abstract The conventional drying (oven drying) method used for the preparation of precipitated mesoporous silica with low surface area (>300 m 2 /g) and small Pore Volume is often associated with a high production cost and a time consuming process. Therefore, the main goal of this study was to develop a cost-effective and fast drying process for the production of precipitated mesoporous silica using inexpensive industrial grade sodium silicate and spray drying of the precipitated wet-gel silica slurry. The precipitated wet-gel silica slurry was prepared from an aqueous sodium silicate solution through the drop-wise addition of sulfuric acid. Mesoporous precipitated silica powder was prepared by drying the wet-gel slurry with different drying techniques. The effects of the oven drying (OD), microwave drying (MD), and spray drying (SD) techniques on the physical (oil, water absorption, and tapping density), and textural properties (specific BET surface area, Pore Volume, Pore size, and % porosity) of the precipitated mesoporous silica powder were studied. The dried precipitated mesoporous silica powders were characterized with field-emission scanning electron microscopy; Brunauer, Emmett and Teller and BJH nitrogen gas adsorption/desorption methods; Fourier-transform infrared spectroscopy; thermogravimetric and differential analysis; N 2 physisorption isotherm; Pore size distribution and particle size analysis. There was a significant effect of drying technique on the textural properties, such as specific surface area, Pore size distribution and Cumulative Pore Volume of the mesoporous silica powder. Additionally, the effect of the microwave-drying period on the physicochemical properties of the precipitated mesoporous silica powder was investigated and discussed.
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synthesis of sodium silicate based hydrophilic silica aerogel beads with superior properties effect of heat treatment
Journal of Non-crystalline Solids, 2011Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Dang Viet Quang, Sun Jeong JeonAbstract:Abstract This work demonstrates the synthesis of hydrophilic and hydrophobic high surface area silica aerogel beads with a large Pore Volume. Wet gel silica beads were modified and heat-treated under atmospheric pressure after modification of the surface by trimethychlorosilane (TMCS). The effects of heat treatment on the physical (hydrophobicity) and textural properties (specific surface area, Pore Volume, and Pore size) of silica aerogel beads were investigated. The results indicated that hydrophobicity of the silica aerogel beads can be maintained up to 400 °C. The hydrophobicity of the silica aerogel beads decreased with increasing temperature in the range of 200–500 °C, and the beads became completely hydrophilic after heat treatment at 500 °C. The specific surface area, Cumulative Pore Volume, and Pore size of the silica aerogel beads increased with increasing temperature. Heating the TMCS modified bead gel at 400 °C for 1 h resulted in silica aerogel beads with high surface area (769 m2/g), and large Cumulative Pore Volume (3.10 cm3/g). The effects of heat treatment on the physical and textural properties of silica aerogel beads were investigated by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric and differential analysis (TG-DTA), Fourier-transform infrared spectroscopy (FT-IR), and Brunauer, Emmett and Teller (BET) and BJH nitrogen gas adsorption and desorption methods.
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synthesis of hydrophilic and hydrophobic xerogels with superior properties using sodium silicate
Microporous and Mesoporous Materials, 2011Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Dang Viet QuangAbstract:Abstract Highly porous hydrophilic and hydrophobic silica xerogels were synthesized by surface modification of silica hydrogels at ambient pressure drying. The silica hydrogels were prepared by a sol–gel polymerization of an inexpensive silica precursor (sodium silicate) under atmospheric conditions. In order to minimize shrinkage due to drying, the hydrogel surface was modified using trimethylchlorosilane (TMCS) in the presence of ethanol/ n -hexane solution before ambient pressure drying (APD). Properties of the final product were investigated using Field-Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric and Differential Analysis (TG–DTA), and nitrogen physisorption studies. The final product was observed to have an extremely high specific surface area (783 m 2 /g) and a large Cumulative Pore Volume (2.74 cm 3 /g). Highly porous hydrophilic xerogels were obtained after heat-treating the modified xerogels. At temperatures above 450 °C the surface alkyl groups ( CH 3 ) were significantly oxidized and, consequently, the properties of the resulting xerogels were altered. Products obtained via the proposed inexpensive approach have superior properties and the method exploits an inexpensive silica source (sodium silicate). Thus it is feasible for large-scale economic industrial production.
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production of low density sodium silicate based hydrophobic silica aerogel beads by a novel fast gelation process and ambient pressure drying process
Solid State Sciences, 2010Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Jongkil Kim, Hee Taik KimAbstract:We report a method to synthesize low-density transparent mesoporous silica aerogel beads by ambient pressure drying (APD). The beads were prepared by acid–base sol–gel polymerization of sodium silicate in aqueous ammonia solution via the ball dropping method (BDM). To minimize shrinkage during drying, wet silica beads were initially prepared; their surfaces were then modified using trimethylchlorosilane (TMCS) via simultaneous solvent exchange and surface modification. The effects of the Volume percentage (%V) of TMCS on the physical and textural properties of the beads were investigated. The specific surface area and Cumulative Pore Volume of the silica aerogel beads increased with an increase in the %V of TMCS. Silica aerogel beads with low packing bed density (0.081 g/cm 3 ), high surface area (917 m 2 /g), and large Cumulative Pore Volume (2.8 cm 3 /g) was obtained when 10%V TMCS was used. Properties of the final product were examined by FE-SEM, TEM, BET, and TG–DT analyses. Surface chemical modifications were confirmed by FTIR spectroscopy. The hydrophobic silica aerogel beads were thermally stable up to 411 � C.
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production of low density sodium silicate based hydrophobic silica aerogel beads by a novel fast gelation process and ambient pressure drying process
Solid State Sciences, 2010Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Jongkil Kim, Hee Taik KimAbstract:Abstract We report a method to synthesize low-density transparent mesoporous silica aerogel beads by ambient pressure drying (APD). The beads were prepared by acid–base sol–gel polymerization of sodium silicate in aqueous ammonia solution via the ball dropping method (BDM). To minimize shrinkage during drying, wet silica beads were initially prepared; their surfaces were then modified using trimethylchlorosilane (TMCS) via simultaneous solvent exchange and surface modification. The effects of the Volume percentage (%V) of TMCS on the physical and textural properties of the beads were investigated. The specific surface area and Cumulative Pore Volume of the silica aerogel beads increased with an increase in the %V of TMCS. Silica aerogel beads with low packing bed density (0.081 g/cm3), high surface area (917 m2/g), and large Cumulative Pore Volume (2.8 cm3/g) was obtained when 10%V TMCS was used. Properties of the final product were examined by FE-SEM, TEM, BET, and TG–DT analyses. Surface chemical modifications were confirmed by FTIR spectroscopy. The hydrophobic silica aerogel beads were thermally stable up to 411 °C. We discuss our results and compare our findings for modified versus unmodified silica beads.
Askwar Hilonga - One of the best experts on this subject based on the ideXlab platform.
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effect of drying technique on the physicochemical properties of sodium silicate based mesoporous precipitated silica
Applied Surface Science, 2011Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Dang Viet QuangAbstract:Abstract The conventional drying (oven drying) method used for the preparation of precipitated mesoporous silica with low surface area (>300 m 2 /g) and small Pore Volume is often associated with a high production cost and a time consuming process. Therefore, the main goal of this study was to develop a cost-effective and fast drying process for the production of precipitated mesoporous silica using inexpensive industrial grade sodium silicate and spray drying of the precipitated wet-gel silica slurry. The precipitated wet-gel silica slurry was prepared from an aqueous sodium silicate solution through the drop-wise addition of sulfuric acid. Mesoporous precipitated silica powder was prepared by drying the wet-gel slurry with different drying techniques. The effects of the oven drying (OD), microwave drying (MD), and spray drying (SD) techniques on the physical (oil, water absorption, and tapping density), and textural properties (specific BET surface area, Pore Volume, Pore size, and % porosity) of the precipitated mesoporous silica powder were studied. The dried precipitated mesoporous silica powders were characterized with field-emission scanning electron microscopy; Brunauer, Emmett and Teller and BJH nitrogen gas adsorption/desorption methods; Fourier-transform infrared spectroscopy; thermogravimetric and differential analysis; N 2 physisorption isotherm; Pore size distribution and particle size analysis. There was a significant effect of drying technique on the textural properties, such as specific surface area, Pore size distribution and Cumulative Pore Volume of the mesoporous silica powder. Additionally, the effect of the microwave-drying period on the physicochemical properties of the precipitated mesoporous silica powder was investigated and discussed.
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synthesis of sodium silicate based hydrophilic silica aerogel beads with superior properties effect of heat treatment
Journal of Non-crystalline Solids, 2011Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Dang Viet Quang, Sun Jeong JeonAbstract:Abstract This work demonstrates the synthesis of hydrophilic and hydrophobic high surface area silica aerogel beads with a large Pore Volume. Wet gel silica beads were modified and heat-treated under atmospheric pressure after modification of the surface by trimethychlorosilane (TMCS). The effects of heat treatment on the physical (hydrophobicity) and textural properties (specific surface area, Pore Volume, and Pore size) of silica aerogel beads were investigated. The results indicated that hydrophobicity of the silica aerogel beads can be maintained up to 400 °C. The hydrophobicity of the silica aerogel beads decreased with increasing temperature in the range of 200–500 °C, and the beads became completely hydrophilic after heat treatment at 500 °C. The specific surface area, Cumulative Pore Volume, and Pore size of the silica aerogel beads increased with increasing temperature. Heating the TMCS modified bead gel at 400 °C for 1 h resulted in silica aerogel beads with high surface area (769 m2/g), and large Cumulative Pore Volume (3.10 cm3/g). The effects of heat treatment on the physical and textural properties of silica aerogel beads were investigated by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric and differential analysis (TG-DTA), Fourier-transform infrared spectroscopy (FT-IR), and Brunauer, Emmett and Teller (BET) and BJH nitrogen gas adsorption and desorption methods.
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synthesis of hydrophilic and hydrophobic xerogels with superior properties using sodium silicate
Microporous and Mesoporous Materials, 2011Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Dang Viet QuangAbstract:Abstract Highly porous hydrophilic and hydrophobic silica xerogels were synthesized by surface modification of silica hydrogels at ambient pressure drying. The silica hydrogels were prepared by a sol–gel polymerization of an inexpensive silica precursor (sodium silicate) under atmospheric conditions. In order to minimize shrinkage due to drying, the hydrogel surface was modified using trimethylchlorosilane (TMCS) in the presence of ethanol/ n -hexane solution before ambient pressure drying (APD). Properties of the final product were investigated using Field-Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric and Differential Analysis (TG–DTA), and nitrogen physisorption studies. The final product was observed to have an extremely high specific surface area (783 m 2 /g) and a large Cumulative Pore Volume (2.74 cm 3 /g). Highly porous hydrophilic xerogels were obtained after heat-treating the modified xerogels. At temperatures above 450 °C the surface alkyl groups ( CH 3 ) were significantly oxidized and, consequently, the properties of the resulting xerogels were altered. Products obtained via the proposed inexpensive approach have superior properties and the method exploits an inexpensive silica source (sodium silicate). Thus it is feasible for large-scale economic industrial production.
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production of low density sodium silicate based hydrophobic silica aerogel beads by a novel fast gelation process and ambient pressure drying process
Solid State Sciences, 2010Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Jongkil Kim, Hee Taik KimAbstract:We report a method to synthesize low-density transparent mesoporous silica aerogel beads by ambient pressure drying (APD). The beads were prepared by acid–base sol–gel polymerization of sodium silicate in aqueous ammonia solution via the ball dropping method (BDM). To minimize shrinkage during drying, wet silica beads were initially prepared; their surfaces were then modified using trimethylchlorosilane (TMCS) via simultaneous solvent exchange and surface modification. The effects of the Volume percentage (%V) of TMCS on the physical and textural properties of the beads were investigated. The specific surface area and Cumulative Pore Volume of the silica aerogel beads increased with an increase in the %V of TMCS. Silica aerogel beads with low packing bed density (0.081 g/cm 3 ), high surface area (917 m 2 /g), and large Cumulative Pore Volume (2.8 cm 3 /g) was obtained when 10%V TMCS was used. Properties of the final product were examined by FE-SEM, TEM, BET, and TG–DT analyses. Surface chemical modifications were confirmed by FTIR spectroscopy. The hydrophobic silica aerogel beads were thermally stable up to 411 � C.
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production of low density sodium silicate based hydrophobic silica aerogel beads by a novel fast gelation process and ambient pressure drying process
Solid State Sciences, 2010Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Jongkil Kim, Hee Taik KimAbstract:Abstract We report a method to synthesize low-density transparent mesoporous silica aerogel beads by ambient pressure drying (APD). The beads were prepared by acid–base sol–gel polymerization of sodium silicate in aqueous ammonia solution via the ball dropping method (BDM). To minimize shrinkage during drying, wet silica beads were initially prepared; their surfaces were then modified using trimethylchlorosilane (TMCS) via simultaneous solvent exchange and surface modification. The effects of the Volume percentage (%V) of TMCS on the physical and textural properties of the beads were investigated. The specific surface area and Cumulative Pore Volume of the silica aerogel beads increased with an increase in the %V of TMCS. Silica aerogel beads with low packing bed density (0.081 g/cm3), high surface area (917 m2/g), and large Cumulative Pore Volume (2.8 cm3/g) was obtained when 10%V TMCS was used. Properties of the final product were examined by FE-SEM, TEM, BET, and TG–DT analyses. Surface chemical modifications were confirmed by FTIR spectroscopy. The hydrophobic silica aerogel beads were thermally stable up to 411 °C. We discuss our results and compare our findings for modified versus unmodified silica beads.
Hee Taik Kim - One of the best experts on this subject based on the ideXlab platform.
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production of low density sodium silicate based hydrophobic silica aerogel beads by a novel fast gelation process and ambient pressure drying process
Solid State Sciences, 2010Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Jongkil Kim, Hee Taik KimAbstract:We report a method to synthesize low-density transparent mesoporous silica aerogel beads by ambient pressure drying (APD). The beads were prepared by acid–base sol–gel polymerization of sodium silicate in aqueous ammonia solution via the ball dropping method (BDM). To minimize shrinkage during drying, wet silica beads were initially prepared; their surfaces were then modified using trimethylchlorosilane (TMCS) via simultaneous solvent exchange and surface modification. The effects of the Volume percentage (%V) of TMCS on the physical and textural properties of the beads were investigated. The specific surface area and Cumulative Pore Volume of the silica aerogel beads increased with an increase in the %V of TMCS. Silica aerogel beads with low packing bed density (0.081 g/cm 3 ), high surface area (917 m 2 /g), and large Cumulative Pore Volume (2.8 cm 3 /g) was obtained when 10%V TMCS was used. Properties of the final product were examined by FE-SEM, TEM, BET, and TG–DT analyses. Surface chemical modifications were confirmed by FTIR spectroscopy. The hydrophobic silica aerogel beads were thermally stable up to 411 � C.
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production of low density sodium silicate based hydrophobic silica aerogel beads by a novel fast gelation process and ambient pressure drying process
Solid State Sciences, 2010Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Jongkil Kim, Hee Taik KimAbstract:Abstract We report a method to synthesize low-density transparent mesoporous silica aerogel beads by ambient pressure drying (APD). The beads were prepared by acid–base sol–gel polymerization of sodium silicate in aqueous ammonia solution via the ball dropping method (BDM). To minimize shrinkage during drying, wet silica beads were initially prepared; their surfaces were then modified using trimethylchlorosilane (TMCS) via simultaneous solvent exchange and surface modification. The effects of the Volume percentage (%V) of TMCS on the physical and textural properties of the beads were investigated. The specific surface area and Cumulative Pore Volume of the silica aerogel beads increased with an increase in the %V of TMCS. Silica aerogel beads with low packing bed density (0.081 g/cm3), high surface area (917 m2/g), and large Cumulative Pore Volume (2.8 cm3/g) was obtained when 10%V TMCS was used. Properties of the final product were examined by FE-SEM, TEM, BET, and TG–DT analyses. Surface chemical modifications were confirmed by FTIR spectroscopy. The hydrophobic silica aerogel beads were thermally stable up to 411 °C. We discuss our results and compare our findings for modified versus unmodified silica beads.
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preparation of hydrophobic mesoporous silica powder with a high specific surface area by surface modification of a wet gel slurry and spray drying
Powder Technology, 2010Co-Authors: Pradip B. Sarawade, Askwar Hilonga, Jongkil Kim, Hee Taik KimAbstract:article i nfo A hydrophobic mesoporous silica powder was prepared by surface modification of a sodium silicate-based wet-gel slurry. The effects of the Volume percentage (%V) of trimethylchlorosilane (TMCS), used as surface- modifying agent, on the physicochemical properties of the silica powder were investigated. We observed that as the %V of TMCS in the simultaneous solvent exchange and surface modification process increased, so did the specific surface area and Cumulative Pore Volume of the resulting silica powder. Hydrophobic silica powder with low tapping density (0.27 g/cm 3 ), high specific surface area (870 m 2 /g), and a large Cumulative Pore Volume (2.2 cm 3 /g) was obtained at 10%V TMCS. Surface silanol groups of the wet-gel slurry were replaced by non-hydrolysable methyl groups (-CH3), resulting in a hydrophobic silica powder as confirmed by FT-IR spectroscopy and contact angle measurements. We also employed FE-SEM, EDS, TG-DTA, and nitrogen physisorption studies to characterize the silica powders produced and to compare the properties of modified and unmodified silica powders. Moreover, we used a spray-dying technique in the present study, which significantly reduced the overall processing time, making our method suitable for economic and large- scale industrial production of silica powder.
Sharad D Bhagat - One of the best experts on this subject based on the ideXlab platform.
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a continuous production process for silica aerogel powders based on sodium silicate by fluidized bed drying of wet gel slurry
Solid State Sciences, 2008Co-Authors: Sharad D Bhagat, Kyungtae Park, Yongha Kim, Jongsoon Kim, Jonghun HanAbstract:Abstract The present study described a continuous process for the production of hydrophobic silica aerogel powders based on an inexpensive precursor such as sodium silicate. Fluidization technique was employed for the drying of wet-gel slurry at an ambient pressure. The fluidization column was fed with the silylated wet-gel slurry in a continuous mode and the fluidization was carried out at 220 °C. The aerogel powder collected in Trap-I was fluidized twice at room temperature in order to separate the lighter aerogel particles from the first trap. The tapping density of the aerogel powder decreased from 0.09 to 0.05 g/cm3 for Trap-II, however, the microstructure did not differ significantly. Using this process, hydrophobic silica aerogel powders exhibiting tapping density as low as 0.05 g/cm3, high specific surface area of 783 m2/g and Cumulative Pore Volume of 1.79 cm3/g have been obtained. The aerogels were characterized by Field-Emission Scanning Electron Microscopy (FE-SEM), BET specific surface area, N2 physisorption isotherms, Pore size distribution and particle size analyses. The results have been compared with aerogel powders obtained by ambient pressure drying of the wet-gel slurry in a furnace.
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methyltrimethoxysilane based monolithic silica aerogels via ambient pressure drying
Microporous and Mesoporous Materials, 2007Co-Authors: Sharad D Bhagat, Changsup OhAbstract:Abstract We have developed a novel route to monolithic silica aerogels via ambient pressure drying by the acid–base sol–gel polymerization of methyltrimethoxysilane (MTMS) precursor. An extent of silica polymerization in the alcogels plays a crucial role in obtaining the monolithic aerogels which could be optimized by a proper control over the MeOH/MTMS molar ratio ( S ) during the sol–gel synthesis. The alcogel undergoes the distinct “spring-back effect” at the critical stage of the drying and thereby preserving the highly porous silica network without collapse. The process yields silica aerogels exhibiting very low bulk density and high specific surface area of 0.062 g/cm 3 and 520 m 2 /g, respectively. The average Pore diameter and the Cumulative Pore Volume varied from 4.5 to 12.1 nm and 0.58 to 1.58 cc/g, respectively. In addition, the aerogels are superhydrophobic with contact angle as high as 152°. We anticipate that the new route of the monolithic silica aerogel production will greatly expand the commercial exploitation of these materials.
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textural properties of ambient pressure dried water glass based silica aerogel beads one day synthesis
Microporous and Mesoporous Materials, 2006Co-Authors: Sharad D BhagatAbstract:Abstract The tedious surface modification and solvent exchange steps (∼six days) involved in the conventional ambient pressure drying of silica hydrogels (bead or bulk type) prohibit the commercial production of silica aerogels despite the low cost of water-glass precursor. The present studies were intended to reduce the processing time of the ambient pressure dried silica aerogel beads using the co-precursor method for the surface modification in the hydrogels. The textural properties of such aerogel beads have been reported and discussed. The experimental results revealed that the aerogel beads (1–2 mm in diameter) are mesoporous solids with average Pore diameter ranging from 32 to 49 A. The specific surface area and Pore size distribution of the aerogel beads could be tailored over a wide range by varying the content of surface modifying agents such as trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDS) in the sol. The aerogel beads with specific surface area as high as 591 m 2 /g and the corresponding Cumulative Pore Volume of 0.5 cc/g have been synthesized in one day using the new route for the rapid surface modification in hydrogels. The aerogel beads retain their hydrophobic property up to a temperature of 773 K.
Elie Kamseu - One of the best experts on this subject based on the ideXlab platform.
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Microstructure and physico-chemical transformation of some common woods from Cameroon during drying
Journal of Thermal Analysis and Calorimetry, 2020Co-Authors: Epiphanie Nouemsi Soubgui, Elie Kamseu, Rufin Theophile Tene Fongang, Rene Oum Lissouck, Fernanda Andreola, Likiby Boubakar, Sylvie Rossignol, Cristina LeonelliAbstract:The influence of drying on the microstructure, physical and chemical properties of some tropical wood species has been investigated using thermogravimetric analysis, differential scanning calorimetric (DSC), FTIR-ATR spectroscopy, mercury intrusion porosimetry (MIP) and environmental scanning electron microscopy (ESEM) analysis. Eleven tropical species were used in this study. Results showed that the common Cameroonian wood species can be grouped into three classes: Ga (lightwood) with cross-linking fibers having high Volume of macroPores, density in the range 0.2–0.4 g cm^−3 and high lignin content; Gb (medium dense) with unidirectional fibers packing, density around 0.6 g cm^−3 and Gc group showing high densification of unidirectional fibers and low porosity justifying the density > 0.8 g cm^−3. Both the Gb an Gc groups have less significant lignin content. A relatively high rate of drying for Ga with respect to low drying rate for Gc was observed in direct relation with their porosity of ~ 72 Vol% and ~ 36 Vol%, respectively. LTF and WG showed similar Cumulative Pore Volume (0.44 mL g^−1) with different Pore size distribution: 28% and 22% of macroPores, 39% and 60% of mesoPores and 33% and 18% microPores, respectively. Thermal analysis revealed that lightwoods have the highest amounts of residues and lower thermal stability of chemical components than dense woods. It has been found that the degradation process of hemicellulose, cellulose and lignin occurs mainly at about 200–300 °C, 300–350 °C and 350–500 °C, respectively. The group Ga with low drying rate, a low cycle of reproduction, a high Volume of porosity together with large Pore sizes appeared promising candidates for the design of ecological, environmental and sustainable management policy of wood transformation in developing countries and even worldwide.
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Cumulative Pore Volume, Pore size distribution and phases percolation in porous inorganic polymer composites: Relation microstructure and effective thermal conductivity
Energy and Buildings, 2015Co-Authors: Elie Kamseu, U.c. Melo, Sylvie Rossignol, Zénabou N.m. Ngouloure, Benoît Nait-ali, S. Zekeng, C. LeonelliAbstract:Rice hush (R) and volcanic (P) ashes, two recycled natural wastes were used for their high amorphous silica to improve the homogeneity and structure composition of inorganic polymer pastes before the expansion with aluminum powder. The fine powders were found to be appropriate in enhancing the geopolymerization and expansion conducting to lightweight structure with Pore size and Pore distribution linked to the viscosity, the concentration of blowing agent, and the crystalline nature of the waste. From the Stereo optical microscope, environmental scanning microscope and the mercury intrusion porosimetry used for the characterization, it appeared that in the interval of complete percolation of the skeleton, there exists correlation between the viscosity, expansion, roundness of Pores, Pores size distribution. The interpretation of the microstructure of porous geopolymer in this interval allows the description of their effective thermal conductivity with the Maxwell–Eucken model and the novel effective medium theory proposed recently.
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metakaolin based inorganic polymer composite effects of fine aggregate composition and structure on porosity evolution microstructure and mechanical properties
Cement & Concrete Composites, 2014Co-Authors: Elie Kamseu, Maria Cannio, Esther Adhiambo Obonyo, Fey Tobias, Maria Chiara Bignozzi, Vincenzo M Sglavo, Cristina LeonelliAbstract:Abstract This paper examines the phase transformation, Pore evolution, microstructural and mechanical changes that occur in inorganic polymer cement (IPC) in the presence of three different grade of fine aggregates (ф M A S phases in relation to the dissolution and interaction of amorphous/disordered fraction of aggregates. H C S and H C A S with H M A S phases were identified in the ladle slag based specimens. The formation of these new phases reduced both the Cumulative Pore Volume and Pores size. The apparent increase in Volume of capillary Pores in ladle slag based specimens was explained by the residual bubbles from the carbonates included in raw slag. The flexural strength of the inorganic polymer cement increases from 4 MPa to 4.2, 4.8 and 6.8 MPa with the addition of 20 wt% of quartz sand, nepheline syenite and ladle slag respectively. These values increase significantly between 28 and 180 days of curing (9.1 MPa for ladle slag and 10.0 MPa for nepheline syenite). It was concluded that fines can be used to remove the HM and poorly bounded alumina oligomers in metakaolin based inorganic polymer matrices and improve the interfacial zone for the design of an optimum grade and high-performance composites.
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Metakaolin-based inorganic polymer composite: Effects of fine aggregate composition and structure on porosity evolution, microstructure and mechanical properties
'Elsevier BV', 2014Co-Authors: Elie Kamseu, Maria Cannio, Esther Adhiambo Obonyo, Fey Tobias, Maria Chiara Bignozzi, Vincenzo M Sglavo, Cristina LeonelliAbstract:This paper examines the phase transformation, Pore evolution, microstructural and mechanical changes that occur in inorganic polymer cement (IPC) in the presence of three different grade of fine aggregates (a < 100 lm) of ladle slag, nepheline syenite and quartz sand. Experimental results indicate that polycondensation was enhanced in nepheline syenite based specimens, compared to quartz sand, due to the increase in H-M-A-S phases in relation to the dissolution and interaction of amorphous/disordered fraction of aggregates. H-C-S and H-C-A-S with H-M-A-S phases were identified in the ladle slag based specimens. The formation of these new phases reduced both the Cumulative Pore Volume and Pores size. The apparent increase in Volume of capillary Pores in ladle slag based specimens was explained by the residual bubbles from the carbonates included in raw slag. The flexural strength of the inorganic polymer cement increases from 4 MPa to 4.2, 4.8 and 6.8 MPa with the addition of 20 wt% of quartz sand, nepheline syenite and ladle slag respectively. These values increase significantly between 28 and 180 days of curing (9.1 MPa for ladle slag and 10.0 MPa for nepheline syenite). It was concluded that fines can be used to remove the HM and poorly bounded alumina oligomers in metakaolin based inorganic polymer matrices and improve the interfacial zone for the design of an optimum grade and highperformance composites
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Porcelain stoneware with pegmatite and nepheline syenite solid solutions: Pore size distribution and descriptive microstructure
Journal of The European Ceramic Society, 2013Co-Authors: Elie Kamseu, T. Bakop, C. Djangang, U.c. Melo, Miriam Hanuskova, Cristina LeonelliAbstract:Abstract Investigations correlating the Pore size distribution-Cumulative Pore Volume to the microstructure are used to compare the efficiency of two solid solutions of pegmatite and nepheline syenite as fluxing agents for the design of porcelainized stoneware. Particularly the fusibility of the two solid solutions was modified by adjusting the CaO content of the bodies. As results, the pegmatite based flux produced an extended viscous phase capable on embedding the crystalline phases and close open porosity as from 1175 °C. Conversely, the bodies with nepheline syenite remained relatively porous up to 1225 °C although the similar results of the mechanical strength at this temperature. The investigations on microstructure, Pores size distribution and Cumulative Pore Volume indicated almost complete reduction of the open Pores in the pegmatite based bodies and the development of a band of closed Pores ranged between 0.080 and 0.9 μm showing P series as a more compact structure. For the nepheline syenite based bodies, the incomplete reduction of the open Pores and the relative absence of the band of Pores between 0.080 and 0.9 μm were ascribed to the difference in fusibility and the viscosity of the glassy phases. These differences were interpreted in term of the differential action of CaO in Na 2 O–Al 2 O 3 –SiO 2 and K 2 O–Al 2 O 3 –SiO 2 on the amount and viscosity of the liquid phase formed already described in the literature.
