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.

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.

Photocatalytically Active Cotton Fabrics Produced with Anatase Synthesized Using a Low-Temperature Sol-Gel Process

2018 ◽  
Vol 762 ◽  
pp. 408-412
Author(s):  
Raivis Eglītis ◽  
Gundars Mežinskis
Keyword(s):  
Photocatalytic Activity ◽  
Uv Light ◽  
Sol Gel ◽  
Average Particle Size ◽  
Synthesis Method ◽  
Average Particle ◽  
X Ray Diffraction ◽  
Sol Gel Process ◽  
Anatase Nanoparticles ◽  
Pre Treatment

In this work two different hydrosols were used to impregnate a commercially available cotton fabric with anatase nanoparticles to give it photocatalytic activity. To increase the activity, different pre-treatment methods were applied. The nanoparticle size was determined using dynamic light scattering and x-ray diffraction and the fabrics were examined using scanning electron microscopy. Photocatalytic activity was measured using the degradation of methyl-orange while irradiating the samples with UV light. The synthesis method allowed to produce anatase with an average particle size of 32 to 37 nm depending on the synthesis method used.

A Calcination Technology for Ultrafine La3NbO7 Powder Prepared by Sol-Gel Process

2011 ◽  
Vol 412 ◽  
pp. 271-274
Author(s):  
Ying Li ◽  
Qiang Xu ◽  
Ling Dai
Keyword(s):  
Single Phase ◽  
Sol Gel ◽  
Average Particle Size ◽  
Complex Method ◽  
Average Particle ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Acid Complex ◽  
Calcination Process ◽  
Sol Gel Process

In order to prepare ultrafine La3NbO7 powder, a potential material for thermal barrier coatings, the calcination process of La3NbO7 was studied in this paper.The precursor of La3NbO7 was synthesized by using a citric acid complex method. A calcination process had been systematically investigated. The reaction temperature was determined by differential scanning calorimetry (DSC). The phase composition of powders was characterized by X-ray diffraction (XRD), and the morphology was obtained by scanning electron microscope (SEM). The results revealed that the single-phase La3NbO7 powder could be successfully prepared while the calcination temperature exceeded 800°C and a better morphology could be maintained at 800°C for 4 hours. Considering all above, an optimum calcination scheme was adopted at 800°C for 4 hours. The as-prepared La3NbO7 powders had a grain size of about 50nm and an average particle size of about 300nm.

Preparation of Nano-TiO2 Using a Sol-Gel Process Mediated in Reverse Microemulsion Combined with a Solvent Thermal Technique

2011 ◽  
Vol 287-290 ◽  
pp. 1731-1734 ◽  
Author(s):  
Han Sheng Li ◽  
Hang Xu ◽  
Shi Ying Wang ◽  
Ya Lin Pan ◽  
Qin Wu ◽  
...  
Keyword(s):  
Sol Gel ◽  
Average Particle Size ◽  
High Photocatalytic Activity ◽  
Reverse Microemulsion ◽  
Molar Ratio ◽  
Average Particle ◽  
Anatase Structure ◽  
Sol Gel Process ◽  
Triton X ◽  
Thermal Technique

Anatase nano-titania (nano-TiO2) was prepared by using a sol-gel process mediated in reverse microemulsion combined with a solvent thermal technique. The results show that the anatase structure appears in the calcination temperature range of 400-510°C, while the transformation of anatase into rutile takes place above 510°C. The average particle size (dP) of the nano-TiO2 increases with the rise of water/Triton X-100 molar ratio (ω) but decreases with the rise of acetyl acetone/n-TBT molar ratio (p) and n-hexanol/Triton X-100 molar ratio (m). The obtained TiO2 particles with a small size have high photocatalytic activity.

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 Sol-gel synthesis of anatase nanopowders for efficient photocatalytic degradation of herbicide Clomazone in aqueous media

2017 ◽  
Vol 49 (3) ◽  
pp. 319-330
Author(s):  
Aleksandar Golubovic ◽  
Bojana Simovic ◽  
Slavica Gasic ◽  
Dusan Mijin ◽  
Aleksandar Matkovic ◽  
...  
Keyword(s):  
Photocatalytic Degradation ◽  
Surface Area ◽  
Active Substance ◽  
Anatase Phase ◽  
Sol Gel ◽  
Aqueous Media ◽  
Average Particle Size ◽  
Commercial Product ◽  
Average Particle ◽  
Developed Surface

TiO2 nanopowders were produced by sol-gel technique using TiCl4 as a starting material. For the preparation of crystalline anatase with developed surface area, this aqueous solution has been mixed with 0.05 M or 0.07 M (NH4)2SO4 solution in a temperature-controlled bath. The pH values of the suspension were 7, 8 or 9. According to the x-ray diffraction (XRD) analysis the anatase crystallite sizes were about 12 nm, which coincided with the average particle size revealed by scanning electron microscopy (SEM). The Raman scattering measurements have shown the presence of a small amount of highly disordered brookite phase in addition to dominant anatase phase with similar nanostructure in all synthesized powders. BET measurements revealed that all synthesized catalysts were fully mesoporous, except the sample synthesized with 0.07 M (NH4)2SO4 at pH=9, which had small amount of micropores. The photocatalytic degradation of herbicide Clomazone was carried out for both the pure active substance and as the commercial product (GAMIT 4-EC) under UV irradiation. The best photocatalytic efficiency was obtained for the catalyst with the largest specific surface area, confirming this parameter as crucial for enhanced photocatalytic degradation of the pure active substance and commercial product of herbicide Clomazone.

TEM measurement of surface area of automotive catalysts

1994 ◽  
Vol 52 ◽  
pp. 776-777
Author(s):  
M. H. Yao ◽  
D. R. Liu ◽  
R. J. Baird ◽  
R. K. Usmen ◽  
R. W. McCabe
Keyword(s):  
Electron Microscopy ◽  
Surface Area ◽  
Average Particle Size ◽  
Weighted Average ◽  
Average Particle ◽  
Automotive Catalysts ◽  
Surface Areas ◽  
Measuring Surface ◽  
Major Factors ◽  
Average Size

The specific surface area of supported noble metal particles in an automotive catalyst is defined as the exposed surface area per unit mass of these particles. It is of great importance to know this parameter, since this is one of the major factors that determine the effectiveness of the catalyst. Commonly used methods for characterizing catalysts, such as X-ray diffraction and TEM, do not directly provide a measure of surface area, but, instead, provide a measure of the “average size” of supported particles. Moreover, the “average sizes” obtained from different experimental techniques are often not comparable. Furthermore, many previous electron microscopy catalyst studies measured only simple average particle size, and no detailed procedure for measuring area-weighted average size or surface area appear to have been reported.In the current study, a procedure for measuring surface area of supported particles by transmission electron microscopy(TEM) was developed, and applied to measure surface areas of various production three-way automotive catalysts.

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 Synthesis and electrochemical properties of LaMnO3 orthosized nanomaterial for supercapacitor applications

2020 ◽  
Vol 21 (2) ◽  
pp. 219-226
Author(s):  
B. K. Ostafiychuk ◽  
H. M. Kolkovska ◽  
I. P. Yaremiy ◽  
B. I. Rachiy ◽  
P. I. Kolkovskyi ◽  
...  
Keyword(s):  
Sol Gel ◽  
Average Particle Size ◽  
Specific Capacity ◽  
Spherical Shape ◽  
Coherent Scattering ◽  
Coherent Scattering Region ◽  
Average Particle ◽  
Sol Gel Process ◽  
Average Size ◽  
Supercapacitor Applications

In this work, the perovskite LaMnO3 material has been prepared based on the sol-gel process of synthesis with the participation of combustion. According to the X-ray phase analysis, it was determined that the obtained material consists of LaMnO3 one phase (space group Pm-3m). Nevertheless, it has been determined that the average size of the coherent scattering region of the obtained material is about 24 nm. Moreover, the average particle size is 40-60 nm in case the approximation that the particles are spherical shape. Thus, it has been determined that the specific surface area of the material is 42.1 m2/g. The electrochemical investigations have been performed using nanosized LaMnO3 powder as a cathode material for electrochemical capacitors. The LaMnO3 material under research showed a specific capacity of 40 F/g at a discharge of up to 1V.

scholarly journals Fabrication and characterisation of Fe2O3/chitosan aerogel-like spheres

2021 ◽  
Vol 10 (1) ◽  
pp. 74-78
Author(s):  
Nhan Dang Thi Thanh ◽  
Don Truong Thi ◽  
Thang Le Quoc ◽  
Tien Tran Dong ◽  
Son Le Lam
Keyword(s):  
High Surface ◽  
Sol Gel ◽  
Average Particle Size ◽  
High Surface Area ◽  
Hollow Structure ◽  
Average Particle ◽  
X Ray Diffraction ◽  
Factors Affecting ◽  
Sol Gel Process ◽  
High Surface Area Materials

Presently, biopolymer materials have been given more attention for their outstanding properties, high efficiencies and promising applications in various fields. In this study, Fe2O3/chitosan aerogel-like spheres were successfully prepared from chitosan and FeCl3 by sol–gel process and freeze-drying to provide high-surface area materials. The factors affecting the material synthesis have been studied. The asprepared Fe2O3/chitosan material was characterized by Infrared Spectroscopy (IR), X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) methods. The results showed that the aerogel spheres have a hollow structure made of chitosan nanofibril networks. Fe2O3 nanoparticles get high crystallinity and have an average particle size of 33 nm.

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