Mesoporous crystalline SnO2 of large surface area

2003 ◽  
Vol 18 (12) ◽  
pp. 2890-2894 ◽  
Author(s):  
Chien-Yueh Tung ◽  
Nae-Lih Wu ◽  
I.A. Rusakova
Keyword(s):  
Heat Treatment ◽  
Surface Area ◽  
Pore Volume ◽  
Cetyltrimethylammonium Bromide ◽  
Sol Gel ◽  
Large Surface Area ◽  
Combined Process ◽  
Thermal Crystallization ◽  
Surface Areas ◽  
Sol Gel Process

Mesoporous crystalline SnO2 was synthesized by using templating process with cetyltrimethylammonium bromide as the template, combined with a pretreatment process of hexamethyldisilazane vapor prior to thermal crystallization. The combined process resulted in crystalline SnO2 exhibiting large pore volumes and surface areas that cannot be achieved by either of the processes alone, or by the conventional sol-gel process. Fully crystallized SnO2 powder with a pore volume of approximately 0.2 cc/g, a surface area of 220 m2/g, and mesopores mainly of 5 nm in diameter were obtained after heat treatment at 500°C.

Preparation of Nanoporous MgAl2O4 by Combined Utilization of Sol-Gel Process and Combustion of Biorenewable Oil

2011 ◽  
Vol 1306 ◽  
Author(s):  
Christian Hörtz ◽  
Danielle M. Ladd ◽  
Dong-Kyun Seo
Keyword(s):  
Surface Area ◽  
Pore Volume ◽  
Sol Gel ◽  
Average Particle Size ◽  
Average Particle ◽  
Solvent Exchange ◽  
Drastic Reduction ◽  
Average Pore ◽  
Surface Areas ◽  
Sol Gel Process

ABSTRACTNanoporous MgAl2O4 particulates with high porosities were successfully prepared from sol-gel reactions, solvent exchange with castor oil and subsequent combustion and calcination at 700 °C. The products were crystalline and semitransparent. Changes in the metal precursor concentrations allowed control of pore volumes from 0.7 to 1.1 cm3/g and average pore sizes from 14 to 19 nm. The specific surface areas are about 200 m2/g regardless of the precursor concentrations. After heating at 1000 °C for 10 hours, the products kept about 70% of their original pore volume and about 60% of the original surface area. Heating at 1100 °C caused a drastic reduction of pore volume and surface area to 40 and 36%, respectively, as the average particle size increased to 23 nm.

Preparation And Characterization Of Ultra-Small Sized Metal And Semiconductor Particles In Sol-Gel Materials

1994 ◽  
Vol 346 ◽  
Author(s):  
Kyung Moon Choi ◽  
Kenneth J. Shea
Keyword(s):  
Pore Size ◽  
Surface Area ◽  
Sol Gel ◽  
High Vacuum ◽  
Particle Sizes ◽  
Transition Metal Clusters ◽  
Surface Areas ◽  
Sol Gel Process ◽  
Bridged Silsesquioxanes

ABSTRACTPoly(l,4-phenylene)-bridged and poly(1,6-hexylene)-bridged silsesquioxanes (PPS and HPS) were prepared by the sol-gel process. The surface areas and pore diameters of these porous xerogels were obtained by BET and BJH methods, respectively. These porous materials were used as a confinement matrix for the growth of small-sized semiconductor and transition metal clusters. Quantum-sized CdS particles in PPS (approximately 58+12 Â) and HPS (91+16 Â) matrices were prepared by first soaking the xerogel in a CdCl2 solution. Following a washing with water, a Na2S solution was then added. EDAX and electron diffraction techniques were used to identify the CdS particles. The particle sizes of CdS in PPS and HPS were determined by both UV measurements and from TEM images. Small-sized Cr clusters were prepared in dried xerogels by an internal doping method. Mixed Cr/CdS phases were also prepared by internal loading of a chromium metal precursor. Following deposition of CdS the xerogel was heated at 120 °C under high vacuum, resulting in formation of intimately mixed phases of Cr metal and CdS. Changes in morphology, in particular the surface area and pore size distribution were noted. A decrease in surface area and an increase in pore size were observed as a result of Cr metal deposition.

scholarly journals Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1787
Author(s):  
Simon Carstens ◽  
Ralf Meyer ◽  
Dirk Enke
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Surface Areas ◽  
Alumina Membranes ◽  
Sol Gel Process ◽  
Specific Surface Areas ◽  
Α Al2o3 ◽  
Sol Gel Synthesis

This article combines a systematic literature review on the fabrication of macroporous α-Al2O3 with increased specific surface area with recent results from our group. Publications claiming the fabrication of α-Al2O3 with high specific surface areas (HSSA) are comprehensively assessed and critically reviewed. An account of all major routes towards HSSA α-Al2O3 is given, including hydrothermal methods, pore protection approaches, dopants, anodically oxidized alumina membranes, and sol-gel syntheses. Furthermore, limitations of these routes are disclosed, as thermodynamic calculations suggest that γ-Al2O3 may be the more stable alumina modification for ABET > 175 m2/g. In fact, the highest specific surface area unobjectionably reported to date for α-Al2O3 amounts to 16–24 m2/g and was attained via a sol-gel process. In a second part, we report on some of our own results, including a novel sol-gel synthesis, designated as mutual cross-hydrolysis. Besides, the Mn-assisted α-transition appears to be a promising approach for some alumina materials, whereas pore protection by carbon filling kinetically inhibits the formation of α-Al2O3 seeds. These experimental results are substantiated by attempts to theoretically calculate and predict the specific surface areas of both porous materials and nanopowders.

scholarly journals Kinetic of sintering of polyethilene glycol and lanthanum dopped aluminum oxide obtained by the sol-gel method

2011 ◽  
Vol 65 (4) ◽  
pp. 355-362
Author(s):  
Tatjana Novakovic ◽  
Ljiljana Rozic ◽  
Zorica Vukovic ◽  
Srdjan Petrovic
Keyword(s):  
Heat Treatment ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Initial Period ◽  
Sol Gel ◽  
Textural Properties ◽  
Sintering Behavior ◽  
Isothermal Heat Treatment ◽  
Surface Areas

Sintering and crystallization of low-density polyethylene glycol (PEG) and lanthanum, La(III)-doped Al2O3 aerogels prepared from aluminum isopropoxide were investigated. The sintering behavior of non-doped and doped aerogels was examined by following the change of specific surface area with isothermal heat-treatment. The specific surface area and crystalline phases of non-doped and PEG+La(III)-doped aerogels were determined, and the effects of dopants on the sintering and crystallization of Al2O3 aerogels are discussed. Isothermal sintering experiments showed that the sintering mechanism of non-doped and PEG+La(III)-doped Al2O3 aerogels is surface diffusion. The specific surface areas of alumina samples decrease rapidly during the initial period of sintering, and more slowly with prolonged sintering time. The change of the porous structure is correlated with the phase transformation of ?-Al2O3 during calcinations of Al2O3 aerogels. The surface area of non-doped Al2O3 aerogels came to about 20 m2g-1 with heat-treatment at 1100?C because of crystallization of ?-Al2O3 after densification. In the case of heattreatment at 1200?C, the largest surface area was observed for PEG+La(III) doped Al2O3 aerogels and the XRD pattern showed only low ordered ?-Al2O3. These indicate that the addition of PEG+La(III) to boehmite sol prevents Al2O3 aerogels from sintering and crystallizing to the ?-Al2O3 phase. Even after 20 h at 1000?C, PEG+La (III)-doped alumina samples maintain a rather good specific surface area (108 m2 g-1) in comparison to the non-doped, containing mainly ?-Al2O3 and minor amounts of ?-Al2O3. Aluminum-oxides with these structural and textural properties are widely used as a coatings and catalyst supports in the field of various catalysis.

Ultrahigh Surface Area Nanoporous Silica Particles via an Aero-Sol−Gel Process

Langmuir ◽  
2004 ◽  
Vol 20 (7) ◽  
pp. 2523-2526 ◽  
Author(s):  
S. H. Kim ◽  
B. Y. H. Liu ◽  
M. R. Zachariah
Keyword(s):  
Surface Area ◽  
Sol Gel ◽  
Silica Particles ◽  
Nanoporous Silica ◽  
Sol Gel Process

Texture Evaluation of Sol-Gel Derived Mesoporous Bioactive Glass

2013 ◽  
Vol 284-287 ◽  
pp. 230-234
Author(s):  
Yu Jen Chou ◽  
Chi Jen Shih ◽  
Shao Ju Shih
Keyword(s):  
Surface Area ◽  
Calcination Temperature ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Nitrogen Adsorption ◽  
Bioactive Glasses ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Adsorption Desorption

Recent years mesoporous bioactive glasses (MBGs) have become important biomaterials because of their high surface area and the superior bioactivity. Various studies have reported that when MBGs implanted in a human body, hydroxyl apatite layers, constituting the main inorganic components of human bones, will form on the MBG surfaces to increase the bioactivity. Therefore, MBGs have been widely applied in the fields of tissue regeneration and drug delivery. The sol-gel process has replaced the conventional glasses process for MBG synthesis because of the advantages of low contamination, chemical flexibility and lower calcination temperature. In the sol-gel process, several types of surfactants were mixed with MBG precursor solutions to generate micelle structures. Afterwards, these micelles decompose to form porous structures after calcination. Although calcination is significant for contamination, crystalline and surface area in MBG, to the best of the authors’ knowledge, only few systematic studies related to calcination were reported. This study correlated the calcination parameters and the microstructure of MBGs. Microstructure evaluation was characterized by transmission electron microscopy and nitrogen adsorption/desorption. The experimental results show that the surface area and the pore size of MBGs decreased with the increasing of the calcination temperature, and decreased dramatically at 800°C due to the formation of crystalline phases.

Preparation of Macroprous C12A7 Mayenite Monoliths via a Sol-Gel Process with Nitrates as Precursors

2018 ◽  
Vol 768 ◽  
pp. 211-217 ◽  
Author(s):  
Rui Wang ◽  
Yu Kun Sun ◽  
Bao Jia Qi Jiang ◽  
Hui Yang ◽  
Xing Zhong Guo
Keyword(s):  
Heat Treatment ◽  
Phase Separation ◽  
Binary System ◽  
Propylene Oxide ◽  
Crystalline Phase ◽  
Sol Gel ◽  
Single Crystalline ◽  
Sol Gel Process

Macroporous Ca12Al14O33(C12A7) mayenite monoliths have been successfully prepared via a sol-gel process in the presence of propylene oxide (PO) and poly (ethyleneoxide) (PEO). Gelation of CaO-Al2O3binary system with nitrates salts as additional precursors is accelerated by PO as an acid scavenger, while PEO works as a phase separation inducer to mediate the phase separation of the system. Appropriate PO and PEO amounts allow the formation of monolithic xerogel with interconnected macropores and co-continuous skeletons. The resultant dried gels are amorphous and the single crystalline phase Ca12Al14O33mayenite forms after heat-treatment at 1100 °C in air, while the macrostructure is preserved with a porosity as high as 78% and smoother and denser skeletons.

scholarly journals Anodizing of Aluminum Coated with Zirconium Oxide by a Sol-Gel Process I. Effect of Heat Treatment on the Formation of the Anodic Oxide Film

1999 ◽  
Vol 67 (12) ◽  
pp. 1243-1248 ◽  
Author(s):  
Keiji WATANABE ◽  
Masatoshi SAKAIRI ◽  
Hideaki TAKAHASHI ◽  
Katsumi TAKAHIRO ◽  
Shinji NAGATA ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Oxide Film ◽  
Zirconium Oxide ◽  
Sol Gel ◽  
Anodic Oxide ◽  
Anodic Oxide Film ◽  
Sol Gel Process

Low Temperature Preparation of Mullite Whisker via Non-Hydrolytic Sol-Gel Process Combined with Molten Salt Method

2014 ◽  
Vol 936 ◽  
pp. 975-980 ◽  
Author(s):  
Kai Lin Fu ◽  
Wei Hui Jiang ◽  
Guo Feng ◽  
Jian Min Liu ◽  
Qian Wu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Low Temperature ◽  
Molten Salt ◽  
Sol Gel ◽  
Growth Direction ◽  
Treatment Temperature ◽  
Molten Salt Method ◽  
Low Temperature Preparation ◽  
Sol Gel Process ◽  
Temperature Preparation

Mullite whisker was prepared at low temperature via non-hydrolytic sol-gel (NHSG) process combined with molten salt method. The influence of heat treatment temperature was studied on the morphology and the microstructure of whisker, and its growth mechanism was also described. The results show that the mullite whisker appears at the lowest temperature of 750 °C, and optimized mullite whisker can be prepared at 850 °C with the growth direction of [00, whose diameter is in the range of 170~300 nm with the aspect ratio of >30.

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