scholarly journals Spectral and Texture Properties of Hydrophobic Aerogel Powders Obtained from Room Temperature Drying

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1796
Author(s):  
Dimitar Shandurkov ◽  
Petar Ignatov ◽  
Ivanka Spassova ◽  
Stoyan Gutzov
Keyword(s):  
Room Temperature ◽  
Fractal Dimensions ◽  
Nitrogen Adsorption ◽  
Attenuated Total Reflectance ◽  
Ir Absorption ◽  
Solvent Exchange ◽  
Texture Properties ◽  
Surface Fractal ◽  
Desorption Isotherms ◽  
Adsorption Desorption

Attenuated Total Reflectance Infrared (ATR-IR) spectroscopy and texture measurements based on nitrogen adsorption-desorption isotherms are combined to characterize silica aerogel granules with different degrees of hydrophobicity. The aerogels were prepared from tetraethoxysilane via a room temperature hydrolysis-gelation process, solvent exchange, hydrophobization, and drying at subcritical conditions. The dependencies between the texture properties, pore architectures, surface fractal dimensions, and degree of hydrophobicity of the samples are extracted from the ATR-IR spectra and the adsorption-desorption isotherms. The IR absorption in the region of the Si-O-Si and Si-OH vibrations is used for a description of the structural and chemical changes in aerogel powders connected with their surface hydrophobization. The Frenkel–Halsey–Hill (FHH) theory is applied to determine the surface fractal dimension of the powder species.

Synthesis of Nanoporous SiO2 Based Ceramic Materials via Sol-Gel Technology

2018 ◽  
Vol 762 ◽  
pp. 317-321
Author(s):  
Margarita Karpe
Keyword(s):  
Room Temperature ◽  
Sol Gel ◽  
Nitrogen Adsorption ◽  
Ceramic Materials ◽  
X Rays ◽  
Xrd Diffraction ◽  
Ceramic Samples ◽  
Desorption Isotherms ◽  
Adsorption Desorption ◽  
Hydrolysis Of

The aim of research was developed area of nanoporous ceramic matrials of ternary - ZrO2-TiO2-SiO2 system. The ceramic materials of system ZrO2-TiO2-SiO2 was synthesized via sol-gel technology by hydrolysis of tetraethylorthosilicate (TEOS), zirconia propoxide and titanium isporopoxide solutions. The sols were polymerized at room temperature to obtain gels. Then gels were dried at 100 OC 72 hours. Xerogel was milled 1 or 6 hours and the powder was axial pressed for nanoporous ceramic samples. All the samples were sintered at 800 OC or 1000 OC in air. 1M HYPERLINK "res://\\\\ld1062.dll/type=1_word=hydrochloric%20acid" hydrochloric acid (HCl) and destilled water were used as a catalyst to promote the hydrolysis and condensation reactions. All samples were characterized by X-rays (XRD) diffraction, particle size distribution and compressive strength. Apparent density and specific surface area of ceramic samples were determined by a Brunauer, Emmett and Teller (BET) nitrogen adsorption-desorption isotherms.

Variation in Pore Structure Characteristics with Composition in the High Volatile Bituminous Coal of Binchang Area

2014 ◽  
Vol 962-965 ◽  
pp. 890-898
Author(s):  
Jin Ping Li ◽  
Da Zhen Tang ◽  
Ting Xu Yu ◽  
Gang Sun
Keyword(s):  
Low Temperature ◽  
Pore Structure ◽  
Parallel Plate ◽  
Bituminous Coal ◽  
Nitrogen Adsorption ◽  
Bet Surface Area ◽  
Test Results ◽  
Structure Characteristics ◽  
Desorption Isotherms ◽  
Adsorption Desorption

Pore structure characteristics and the effect of lithotype and maceral on pore for three types of high-volatile bituminous coals from Binchang area were investigated by combined low-temperature nitrogen adsorption/desorption, nuclear magnetic resonance (NMR), scanning electron microscope (SEM) and maceral analysis. The low temperature N2 adsorption/desorption test results show that: micropores are more abundant than transitional pores with high BET surface area; two types of pore structures can be identified by adsorption/desorption isotherms; Pore morphology is mainly represented by well-connected, ink-bottled, cylindrical and parallel plate pores. NMR T2 distributions at full saturated condition are apparent or less obvious trimodal and three types of T2 distributions are identified; Seepage pores are better developed when compared with the middle-high rank coal. Further research found that the three coal lithotypes are featured by remarkably different pore structure characteristics and maceral contents of coal are linearly correlated to some of pore structure parameters.

Experimental Investigation of the Matrix Pore Size Distribution and Inner Surface Fractal Dimension of Different-Structure High Rank Coals

2021 ◽  
Vol 21 (1) ◽  
pp. 529-537
Author(s):  
Rui Wang ◽  
Guoqing Li ◽  
Shanshan Liu
Keyword(s):  
Size Distribution ◽  
Fractal Dimensions ◽  
Nitrogen Adsorption ◽  
Full Scale ◽  
High Rank ◽  
Shanxi Province ◽  
Coal Matrix ◽  
Surface Fractal ◽  
Inner Surface ◽  
Scale Matrix

To investigate the nanopore characteristics of different-structure high-rank coal matrices, four samples were collected from the Zhaozhuang Mine, a typical mine highly prone to coal and gas outbursts in Shanxi Province, China, and the nanopore size distribution was measured using a lowtemperature nitrogen adsorption method for these four samples. Based on the nitrogen adsorption isotherms, the inner surface fractal dimensions of micropores, meso- and macropores, and full-scale matrix pores were estimated using a Frenkel–Halsey–Hill (FFH) fractal model, and the relationships between the fractal dimensions and pore parameters were discussed. The inner surface of the high-rank coal matrix is heterogeneous. The inner surface fractal dimensions of micropores (D1) and full-scale matrix pores (DT) can be arranged in a descending sequence for the differentstructure coals: mylonitized coal > granulated coal > cataclastic coal > intact coal, while the inner surface fractal dimensions of meso- and macropores (D2) are in an ascending sequence. With the increasing deformation degree of coals, some macropores and mesopores are transformed into smaller pores, such as micropores; the total pore volume (PV) and total specific surface area (SSA) increase; the SSA percentage and PV percentage of meso- and micropores increase; and those of macropores decrease. The average pore width (APW) is positively correlated with D2 and negatively correlated with D1 and DT. The tectonic deformation enhances the irregularity of micropores and the heterogeneity of the whole coal matrix pores and decreases the inner surface roughness of meso- and macropores.

scholarly journals Structural Study of Microporous Xerogels Prepared by Polycondensation of Pyrogallol with Formaldehyde

2010 ◽  
Vol 6 (1) ◽  
pp. 878-883 ◽  
Author(s):  
Rebeh Moussaoui ◽  
Mongi Ben Mosbah ◽  
Younes Moussaoui ◽  
Elimame Elaloui
Keyword(s):  
Specific Surface ◽  
Aqueous Medium ◽  
Surface Area ◽  
Absorption Spectra ◽  
Structural Study ◽  
Perchloric Acid ◽  
Nitrogen Adsorption ◽  
Desorption Isotherms ◽  
Adsorption Desorption ◽  
Ftir Absorption Spectra

Microporous xerogels were prepared by polycondensation of pyrogallol with formaldehyde catalyzed by perchloric acid in aqueous medium. The samples were characterized by FTIR absorption spectra. The micro-porosity and the specific surface area are characterized by nitrogen adsorption - desorption isotherms. The obtained characteristics depend on the conditions of polycondensation.

scholarly journals Ultrasound-Assisted Rapid ZIF-8 Synthesis, Porous ZnO Preparation by Heating ZIF-8, and Their Photocatalytic Activity

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Pham Dinh Du ◽  
Nguyen Trung Hieu ◽  
Tran Vinh Thien
Keyword(s):  
Photocatalytic Activity ◽  
Room Temperature ◽  
Diffuse Reflectance ◽  
Nitrogen Adsorption ◽  
X Ray Diffraction ◽  
Zeolitic Imidazolate Framework ◽  
X Ray ◽  
Photocatalytic Activities ◽  
Ft Ir ◽  
Adsorption Desorption

Zeolitic imidazolate framework-8 (ZIF-8) is synthesized quickly at room temperature in methanol with the support of ultrasound. Porous ZnO is also prepared via the thermal treatment of ZIF-8. The photocatalytic activities of the obtained materials are demonstrated via methylene blue (MB) decomposition under UV radiation. The obtained materials are characterized by means of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherms, UV-Vis diffuse reflectance spectra (DR-UV-Vis), and photoluminescence spectra. The results indicate that ZIF-8 and the materials obtained from ZIF-8 by heating in the air have photocatalytic activity under UV irradiation. The ZnO sample obtained by ZIF-8 calcination at 660°C for 5 h has the highest photocatalytic activity. However, the MB degradation photocatalytic efficiency of the ZnO samples is even lower than that of the ZIF-8 samples, indicating that ZIF-8 is an effective photocatalyst in the treatment of environmental pollution.

Interpretation of mercury porosimetry applied to aerogels

1995 ◽  
Vol 10 (8) ◽  
pp. 2114-2119 ◽  
Author(s):  
R. Pirard ◽  
S. Blacher ◽  
F. Brouers ◽  
J.P. Pirard
Keyword(s):  
High Pressure ◽  
Porous Material ◽  
Mechanical Model ◽  
Mercury Porosimetry ◽  
Nitrogen Adsorption ◽  
Desorption Isotherms ◽  
Adsorption Desorption

The observation of aerogels submitted to a pressure of mercury indicates that this porous material is compacted and not intruded by the mercury. Consequently, the classical Washburn equation cannot be applied. A relation is established between the pressure P of compaction and the size L of the largest pores. The size of pores is estimated by using the nitrogen adsorption-desorption isotherms analysis and SEM measurements. A relation is found in which P is proportional to L−4 The new relation is applied to mercury porosimetry. Finally, a mechanical model is proposed that reproduces successfully the behavior of aerogels under high pressure of mercury.

Synthesis and Characterization of the Catalysts 5 wt.% and 10 wt.% Co/SBA-15

2010 ◽  
Vol 660-661 ◽  
pp. 561-566
Author(s):  
L.A. Lima ◽  
B.V. Sousa ◽  
Meiry Glaúcia Freire Rodrigues
Keyword(s):  
Ethylene Oxide ◽  
Molecular Sieve ◽  
Nitrogen Adsorption ◽  
X Ray Diffraction ◽  
X Ray ◽  
Poly Ethylene Oxide ◽  
Desorption Isotherms ◽  
Poly Ethylene ◽  
Adsorption Desorption

Catalysts supported on SBA-15 were obtained by wet impregnation using aqueous solution of cobalt nitrate, where different contents of cobalt (5 wt% and 10 wt%) were prepared. The molecular sieve SBA-15 was synthesized using tetra ethyl ortho silicate (TEOS) as silicate source, and triblock copolymer, poly-(ethylene oxide)-poly (propylene oxide)-poly-(ethylene oxide) PEO-PPO-PEO as the organic structure directing agent. These materials were characterized by X-ray diffraction (XRD), X-ray energy dispersion spectrophotometer (EDX) and Nitrogen adsorption–desorption isotherms (BET). The results from the XRD showed that the molecular sieve mesoporous (SBA-15) was identified by X-ray diffraction, especially from the (210) and (300) peaks, which represent a typical spectrum for the SBA-15. Characterization of catalysts by Nitrogen adsorption–desorption isotherms (BET) made it possible to verify the the samples had been of type IV with hysteresis of corresponding the H2 type the porous materials.

scholarly journals Preparation, Properties and Applications of the Hybrid Organic/Inorganic Nanocomposite Based on Nanoporous Carbon Matrix

2021 ◽  
Author(s):  
NABIL BEN MANSOUR ◽  
Wahid Djeridi ◽  
Lassaad El Mir
Keyword(s):  
Glucose Sensor ◽  
Picric Acid ◽  
Sol Gel ◽  
Carbon Matrix ◽  
Nitrogen Adsorption ◽  
Xrd Analysis ◽  
Nanoporous Carbon ◽  
Ir Absorption ◽  
Nickel Oxide Nanoparticles ◽  
Adsorption Desorption

Abstract Nanoporous carbon matrix was prepared by the sol-gel process from pyrogallol-formaldehyde (PF) mixtures in water using picric acid as catalyst. For the second sample, nickel oxide nanoparticles were added in the PF matrix to get a PF/NiO hybrid nanocomposite. The samples were heat treated at the pyrolysis temperature of 650°C for two hours. The obtained materials have been characterized by different techniques such as: X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), differential thermalanalysis (DTA),nitrogen adsorption-desorption isotherms, voltage-current characteristics, electrochemical measurementsand UV-Vis-IR absorption. The XRD analysis shows that PF matrix is amorphous while PF/NiO nanocomposite exhibited a metallic phase of nickel. The SEM and TEM images indicated the presence of nickel particles in the PF/NiO nanocomposite which are dispersed randomly in the carbon matrix. The adsorption-desorption of nitrogen revealed that the PF matrix is microporous and the PF/NiO nanocomposite is mesoporous. The adsorption capacities of carbon dioxide (CO2) and methane (CH4) show that the PF matrix has the highest adsorption at low pressures and the PF/NiO nanocomposite tends to adsorb gases better at high pressure. The V(I) characteristics showed that the PF/NiO nanocomposite can be considered as a smart material. Indeed, the characteristic behavior can be adjusted according to the maximum applied current. Electrochemical measurements have shown that the PF/NiO nanocomposite is very promising for the detection of non-enzymatic glucose. The absorption spectra showed that the addition of the NiO nanoparticles increased the disorder. The obtained materials are promoters for various applications such as gas storage, negatronic devices and glucose sensor.

Properties of active carbon with various particle shapes obtained in char-steam reaction Properties of active carbon with various particle shapes obtained in char-steam reaction

2012 ◽  
Vol 33 (3) ◽  
pp. 335-344 ◽  
Author(s):  
Bronisław Buczek
Keyword(s):  
Mechanical Properties ◽  
Porous Structure ◽  
Active Carbon ◽  
Nitrogen Adsorption ◽  
Steam Gasification ◽  
Active Carbons ◽  
Desorption Isotherms ◽  
Adsorption Desorption ◽  
Particle Shapes ◽  
Micropore Size

Abstract The porous structure of cylindrical and ring-shaped char material was developed by partial steam gasification. Micropore and mesopore structures of active carbons with various forms of burn-off were evaluated by nitrogen adsorption/desorption isotherms. Parameters of the Dubinin- Radushkevich equation were calculated as well as the micropore size distribution by the Horvath- Kawazoe method. The results of textural investigations showed that more uniform micropore structure and better mechanical properties were found for ring-shaped active carbons.

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