scholarly journals Influence of the pH Values of the Sol–Gel State on the Properties of SnO2Powders Obtained From a Sol–Gel Route

1995 ◽  
Vol 18 (1) ◽  
pp. 53-60 ◽  
Author(s):  
S. D. Han ◽  
S. Y. Huang ◽  
G. Campet ◽  
M. A. Kennard ◽  
Y. M. Son
Keyword(s):  
Specific Surface ◽  
Crystallite Size ◽  
Surface Area ◽  
Calcination Temperature ◽  
Specific Surface Area ◽  
Ph Value ◽  
Ph Dependence ◽  
Sol Gel ◽  
Ph Values ◽  
Colloidal State

The evolution of the specific surface area and crystallite size of SnO2powders, prepared from a sol-gel process, was studied as a function of the calcination temperature of the stannic hydroxyde colloid, and for two different pH values (7.5 and 12.5) of the colloïdal state. The samples were characterized by TGA, IR spectroscopy, BET, and XRD techniques. The crystallite size and specific surface area were strongly affected not only by the calcination temperature, but unexpectedly, by the initial pH value of the colloïdal state. A framework model, relating the pH dependence to the resulting properties, is presented.

The Preparation and Characterization of the Mesoporous Poly(bisphenol-A carbonate) – Silica Nanocomposites

2014 ◽  
Vol 513-517 ◽  
pp. 82-85
Author(s):  
Rui Rui Li ◽  
Yue Shi ◽  
Lei Zu ◽  
Hui Qin Lian ◽  
Yang Liu ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Pore Diameter ◽  
Ph Value ◽  
Sol Gel ◽  
Synthesis System ◽  
Silica Nanocomposites

The mesoporous polycarbonate-silica nanocomposite materials were synthesized through the modified sol-gel approach under acidic condition. The specific surface area, pore diameter and pore volume of polycarbonate-silica could be controlled by changing the acidity of the synthesis system. The polycarbonate-silica possess an irregular block morphology according to the scanning electron microscopy observations. With decreasing the pH value of the synthesis system, the specific surface area and pore diameter of polycarbonate-silica were raised but the pore volume was reduced. The maximum specific surface area of polycarbonate-silica was 701.71m2/g which presented by the results of Nitrogen adsorptiondesorption isotherms.

scholarly journals Study of the effect of Mg (II) addition and the annealing conditions on the structure of mesoporous aluminum oxide using Plackett-Burman design

2015 ◽  
Vol 80 (12) ◽  
pp. 1529-1540 ◽  
Author(s):  
Tatjana Novakovic ◽  
Ljiljana Rozic ◽  
Srdjan Petrovic ◽  
Zorica Vukovic ◽  
Miodrag Mitric
Keyword(s):  
Specific Surface ◽  
Crystallite Size ◽  
Heating Rate ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Magnesium Nitrate ◽  
Degree Of Crystallinity ◽  
Burman Design ◽  
Plackett Burman Design

A statistical design was used to investigate the effect of various processing conditions on the structure of sol-gel derived Mg(II) doped alumina. Six processing variables were selected based on the Plackett-Burman design: concentration of magnesium nitrate, time and temperature of alcohol evaporation, temperature and time of annealing and heating rate were changed at two levels. For every set of conditions, samples with different specific surface area and degree of crystallinity were obtained. Analysis of the results showed that annealing temperature , heating rate and concentration of magnesium nitrate were the main factors affecting average crystallite size of the predominant phase of alumina. In the case of the specific surface area, two of selected six variables had pronounced effect; however the temperature of annealing was more effective than others. The present results show that the proposed model that uses crystallite size as a response variables is preferable to further research.

scholarly journals Relationship between Synthesis Conditions and Photocatalytic Activity of Nanocrystalline TiO2

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Yosep Han ◽  
Hyung-Seok Kim ◽  
Hyunjung Kim
Keyword(s):  
Methylene Blue ◽  
Photocatalytic Activity ◽  
Specific Surface ◽  
Crystallite Size ◽  
Surface Area ◽  
Calcination Temperature ◽  
Specific Surface Area ◽  
Molar Ratio ◽  
Hydroxyl Groups ◽  
Synthesis Conditions

The degradation efficiency of methylene blue by TiO2nanoparticles, which were synthesized under different synthesis conditions (i.e., molar ratio of water and titanium tetraisopropoxide (TTIP), pH, and calcination temperature) in a sol-gel process, was systematically investigated. The results showed that increasing the molar ratio of water and TTIP led to the enhanced photocatalytic activity of TiO2nanoparticles, which were likely attributed to the increased specific surface area of TiO2nanoparticles synthesized with high molar ratio. The results were supported by the relative increase in the size of interaggregated pores of the aggregated TiO2nanoparticles. The best photocatalytic activity of TiO2nanoparticles was observed at acidic synthesis conditions; however, the results were not consistent with physical properties for the crystallinity and the crystallite size of TiO2nanoparticles but rather explained by the presence of abundant hydroxyl groups and water molecules existing on the surface of TiO2under acidic synthesis environments. Furthermore, methylene blue degradation experiments revealed that the photocatalytic activity of TiO2nanoparticles was maximized at the calcination temperature of 700°C. The trend was likely due to the combined effect of the anatase crystallinity which showed the highest value at 700°C and the crystallite size/specific surface area which did not excessively increase up to 700°C.

scholarly journals Preparation and characterization of alumina-zirconia composite material with different acid ratios by the sol-gel method

2008 ◽  
Vol 6 (3) ◽  
pp. 482-487 ◽  
Author(s):  
Ozgecan Ergu ◽  
Metin Gürü ◽  
Canan Cabbar
Keyword(s):  
Composite Materials ◽  
Specific Surface ◽  
Surface Area ◽  
Calcination Temperature ◽  
Specific Surface Area ◽  
Pore Diameter ◽  
Sol Gel ◽  
Nitrogen Adsorption ◽  
Gel Method ◽  
Sol Gel Method

AbstractAlumina-zirconia composite materials were produced with different acid ratios by the sol-gel method using aluminum isopropoxide and zirconium chloride. The composites were produced by changing acid/alkoxside ratio in alumina. The composite materials were calcinated at 600°C, 900°C and 1300°C. The effects of acid concentration and calcination temperature on the surface area and pore radius were determined from the nitrogen adsorption isotherm at 77 K. The density of the composites was also measured. The minimum density of produced material was recorded as 1.35 g cm−3 at an acid/alkoxside ratio of 0.2. The highest specific surface area and pore diameter of the lightest material are 191.86 m2 g−1 and 18.4 Ǻ, respectively. Although pore diameter and specific surface area are not changed at any of the experimental temperatures which were tested by decreasing acid/alkoxside ratio, the density is slightly increased. However, it was observed that the calcination temperature significantly affects the surface area and density of the material.

Preparation of Sands Modified by Aluminous Salt and its Adsorption Capability of CD2+

2011 ◽  
Vol 130-134 ◽  
pp. 856-859
Author(s):  
Chun Sheng Ding ◽  
Yang Ping Fu ◽  
Qian Fen Zhu ◽  
Jing Fu
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Influencing Factors ◽  
Removal Efficiency ◽  
Specific Surface Area ◽  
Quartz Sand ◽  
Ph Value ◽  
Alkaline Condition ◽  
Initial Concentration ◽  
Adsorption Capability

In this experiment quartz sand was chosen as a carrier to be coated by aluminous salt under alkaline condition, and then the specific surface area was tested, and the adsorption capability and Cd2+ removal influencing factors of modified sand were studied. The investigation results showed that the specific surface area of modified sand was 75.244m2/g which was 9.38 times of that of original sand; the removal efficiency of Cd2+ by aluminous salt modified sand reached 59% contrast to 39% of original sand with pH 7.00. It was also found that the removal efficiency of Cd2+ by the aluminous salt modified sand was reduced with the increase of initial concentration of Cd2+ solution, and was enhanced with the increase of pH value, the Cd2+ removal efficiency was almost 71% with pH 9.0.

Comparative Analysis on Chemical Composition and Charcoal Characterization of Two Miscanthus Species

2011 ◽  
Vol 415-417 ◽  
pp. 1265-1272
Author(s):  
Wen Biao Zhang ◽  
Wen Zhu Li ◽  
Bing Song Zheng
Keyword(s):  
Chemical Composition ◽  
Specific Surface ◽  
Water Content ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ph Value ◽  
Perennial Grass ◽  
Water Extract ◽  
Carbonization Temperature ◽  
Hot Water

Miscanthus is a highly productive, rhizomatous, C4 perennial grass that should be considered as an excellent active carbon precursor. This paper compares the charcoal characterization and chemical composition between M. sinensis and M. floridulus. Species differed in water content, hot water extract, 1% NaOH extract, organic solvent extract, cellulose, lignin and ash. Carbonization temperatures have effects on charcoal yields of Miscanthus, which ranged from 23.5% to 48.0% for M. sinensis and 11.3% to 37.2% for M. floridulus. Water content, charcoal density, pH value, and specific surface area of charcoal characterization varied between two species of Miscanthus. The specific surface area increased with the increase of carbonization temperature. The highest specific surface area of M. sinensis and M. floridulus was 351.74 m2g−1and 352.74 m2g−1, respectively, when the carbonization temperature was 800°C.

Preparing of Silica Aerogel and Adsorption Performance on Nitrobenzene

2012 ◽  
Vol 512-515 ◽  
pp. 1980-1985
Author(s):  
Ya Jun Luo ◽  
Xue Li ◽  
Xiao Li Hu ◽  
Deng Liang He ◽  
Peng Lin
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ph Value ◽  
Adsorption Property ◽  
Infrared Absorption Spectrum ◽  
Nitrobenzene Solution ◽  
Silica Source ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes

SiO2aerogel is prepared under normal conditions by taking tetraethyl orthosilicate (TEOS) as the silica source, N-hexane as the displacer, trimethylchlorosilane hexane as the modifier and hydrolysis environment provided by hydrochloric acid and ammonia water. The effect of pH value, time, temperature, initial concentration on the adsorption of nitrobenzene by aerogel has been studied. The results show that the best range of the pH value for adsorption is 10.72. When adsorption time is 100 min, adsorption equilibrium can be reached. The best temperature for adsorption is 40 °C. The adsorption capacity becomes larger with the concentration increasing of the nitrobenzene solution. When the concentration reaches 500 mg/L, the adsorption reaches 32.402 mg/g. The adsorption equation matches Langmuir model. Scanning Electron Microscopes (SEM), infrared absorption spectrum and specific surface area measurements have shown that the adsorption property of SiO2aerogel for the nitrobenzene is related to cellular structure of the aerogel and large specific surface area.

scholarly journals Tuning the Morphological Properties of Cellulose Aerogels: An Investigation of Salt-Mediated Preparation

2021 ◽  
Author(s):  
Prakash Parajuli ◽  
Sanjit Acharya ◽  
Julia Shamshina ◽  
Noureddine Abidi
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Earth Metal ◽  
Morphological Properties ◽  
Cellulose Solution ◽  
Bet Analysis ◽  
Sol Gel Transition ◽  
Gel Transition

Abstract In this study, alkali and alkaline earth metal chlorides with different cationic radii (LiCl, NaCl, and KCl, MgCl2, and CaCl2) were used to gain insight into the behavior of cellulose solutions in the presence of salts. The specific focus of the study was evaluation of the effect of salts’ addition on the sol-gel transition of the cellulose solutions and on their ability to form monoliths, as well as evaluation of the morphology (e.g., specific surface area, pore characteristics, and microstructure) of aerocelluloses prepared from these solutions. The effect of the salt addition on the sol-gel transition of cellulose solutions was studied using rheology, and morphology of resultant aerogels was evaluated by Scanning Electron Microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis, while the salt influence on the aerocelluloses’ crystalline structure and thermal stability was evaluated using powder X-Ray Diffraction (pXRD) and Thermogravimetric Analysis (TGA), respectively. The study revealed that the effect of salts’ addition was dependent on the component ions and their concentration. The addition of salts in the amount below certain concentration limit significantly improved the ability of the cellulose solutions to form monoliths and reduced the sol-gel transition time. Salts of lower cationic radii had a greater effect on gelation. However, excessive amount of salts resulted in the formation of fragile monoliths or no formation of gels at all. Analysis of surface morphology demonstrated that the addition of salts resulted in a significant increase in porosity and specific surface area, with salts of lower cationic radii leading to aerogels with much larger (~1.5 and 1.6-fold for LiCl and MgCl2, respectively) specific surface area compared to aerocelluloses prepared with no added salt. Thus, by adding the appropriate salt into the cellulose solution prior to gelation, the properties of aerocelluloses that control material’s performance (specific surface area, density, and porosity) could be tailored for a specific application.

scholarly journals Synthesis of Spherical Silica by Sol-Gel Method and Its Application as Catalyst Support

2011 ◽  
Vol 10 (2) ◽  
pp. 25
Author(s):  
Anirut Leksomboon ◽  
Bunjerd Jongsomjit
Keyword(s):  
Particle Size ◽  
Ethylene Glycol ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Weight Ratio ◽  
Gel Method ◽  
Sol Gel Method ◽  
Spherical Silica

In this present study, the spherical silica support was synthesized from tetraethyloxysilane (TEOS), water, sodium hydroxide, ethylene glycol and n-dodecyltrimethyl ammonium bromide (C12TMABr). The particle size was controlled by variation of the ethylene glycol co-solvent weight ratio of a sol-gel method preparation in the range of 0.10 to 0.50. In addition, the particle size apparently increases with high weight ratio of co-solvent, but the particle size distribution was broader. The standard deviation of particle diameter is large when the co-solvent weight ratio is more than 0.35 and less than 0.15. However, the specific surface area was similar for all weight ratios ranging from 1000 to 1300 m2/g. The synthesized silica was spherical and has high specific surface area. The cobalt was impregnated onto the obtained silica to produce the cobalt catalyst used for CO2 hydrogenation.</

scholarly journals Obtaining of transition phases of alumina starting from sodium aluminate in Bayer process

2011 ◽  
Vol 65 (3) ◽  
pp. 271-277
Author(s):  
Zoran Obrenovic ◽  
Radislav Filipovic ◽  
Marija Milanovic ◽  
Ivan Stijepovic ◽  
Ljubica Nikolic
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ph Value ◽  
Sodium Aluminate ◽  
High Specific Surface Area ◽  
Heterogeneous Structure ◽  
Aluminate Solution ◽  
Bayer Liquor ◽  
Sodium Aluminate Solution

Transition (active) phases of alumina were synthesized starting from sodium aluminate solution prepared out of Bayer liquor. The neutralisation of sodium aluminate solution was performed by sulphuric acid. Powder X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and low-temperature nitrogen absorption studies were employed to trace the formation of the transition phases of alumina. The results show that the properties of the powders (phase composition, morphology and specific surface area) are strongly influenced by the initial pH value of the system, as well as by the duration of neutralisation step. It is possible to obtain powders with heterogeneous structure with dominant phase of bayerite, gibbsite or boehmit by tuning the pH and concentration of the starting sodium aluminate solution. The transition (active) phases of alumina (?- and ?-alumina) with high specific surface area (264-373 m2/g) are formed through the thermal dehydratation of aluminium hydroxide (bayerite and gibbsite) and aluminium oxyhydroxide (boehmite or pseudoboehmite) at the temperature of 500?C. Namely, bayerite and pseudoboehmite transforms to ?-phase of alumina upon heating, while gibbsite transforms to ?-phase, maintaining the parent morphology.

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