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.

Preparation and Characterization of Phloroglucinol-Resorcinol-Formaldehyde Carbon Aerogels

2013 ◽  
Vol 423-426 ◽  
pp. 523-527
Author(s):  
Xuan Liu ◽  
Zhen Fa Liu ◽  
Hao Lin Fu ◽  
Rui He ◽  
Li Hui Zhang
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
High Specific Surface Area ◽  
Carbon Aerogels ◽  
Resorcinol Formaldehyde ◽  
Sol Gel Process ◽  
Solvent Replacement ◽  
Organic Aerogels

Phloroglucinol-resorcinol-formaldehyde organic aerogels (PRF) were prepared using phloroglucinol, resorcinol and formaldehyde in a sol-gel process, solvent replacement and drying at room temperature. The phloroglucinol-resorcinol-formaldehyde carbon aerogels (CPRF) were prepared by charring the PRF at high temperature under the aegis of helium flow. The microstructure of CPRF was characterized by infrared spectroscopy, specific surface area analyzer and scanning electron microscopy. The results showed that the CPRF had continuous network structure and high specific surface area.

A Comparison of Methods for Determining Surface Areas of Carbon Black

1973 ◽  
Vol 46 (1) ◽  
pp. 192-203 ◽  
Author(s):  
R. A. Klyne ◽  
B. D. Simpson ◽  
M. L. Studebaker
Keyword(s):  
Carbon Black ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Surface Areas ◽  
Furnace Black ◽  
Area Increase ◽  
Experimental Errors ◽  
Specific Surface Areas ◽  
Surface Area Increase

Abstract 1. The various tint tests correlate with each other—it does not make much difference which of the three procedures is used. The discrimination between similar blacks is comparable. Specific surface areas obtained by the three methods are comparable and differences appear to be due to experimental errors. (Compare Figures 5–7). 2. Surface areas larger than some 90 to 100 m2/g cannot be reliably determined from tint strength measurements alone. 3. Structure exerts a pronounced effect on tint strength of furnace blacks, especially above 90 to 100 m2/g. Porosity and/or composition are apparently also variables which affect tinting strength. 4. Densichron reflectance on the dry carbon black can be used to estimate specific surface areas up to about 140 m2/g; but, since theabsoluteerrorincreases as the specific surface area increases, this method loses some of its reliability at values above about 110 m2/g. The relative error in reflectance determinations does not vary greatly over the furnace-black range. Densichron reflectance is influenced by composition, evidently due to composition-related differences in optical properties of the carbons. 5. In CTAB adsorption measurements, titration errors and handling errors tend to be rather constant for blacks of different surface area. Hence, CTAB permits better discrimination among blacks of small particle size. 6. The errors in Densichron reflectance surface area increase with specific surface area. Hence, the deviations between CTAB and reflectance surface area which are due to experimental error increase with the surface area of the sample.

Preparation and Characterization of Ultralow Density Silica Aerogels by Acetonitrile Supercritical Drying

2012 ◽  
Vol 519 ◽  
pp. 83-86 ◽  
Author(s):  
Guang Wu Liu ◽  
Xing Yuan Ni ◽  
Bin Zhou ◽  
Qiu Jie Yu
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Silica Aerogel ◽  
Sol Gel ◽  
Supercritical Drying ◽  
Silica Aerogels ◽  
High Specific Surface Area ◽  
Molar Ratio ◽  
Sol Gel Process

This paper deals with the synthesis of ultralow density silica aerogels using tetramethyl orthosilicate (TMOS) as the precursor via sol-gel process followed by supercritical drying using acetonitrile solvent extraction. Ultralow density silica aerogels with 6 mg/cc of density was made for the molar ratio by this method. The microstructure and morphology of the ultralow density silica aerogels was characterized by the specific surface area, SBET, SEM, and the pore size distribution techniques. The results show that the ultralow density silica aerogel has the high specific surface area of 812m2/g. Thermal conductivities at desired temperatures were analyzed by the transient plane heat source method. Thermal conductivity coefficients of silica aerogel monoliths changed from 0.024 to 0.043W/ (m K) as temperature increased to 400°C, revealed an excellent heat insulation effect during thermal process.

Sol-gel Synthesis of a Novel χSm2Ti2O7/HZSM-5 Composite Photocatalyst for the Promoted Activity on RBR X-3B Degradation

2017 ◽  
Vol 14 (1) ◽  
pp. 17-25
Author(s):  
Wenjie Zhang ◽  
Jiao Yang ◽  
Ling Du
Keyword(s):  
Photocatalytic Activity ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Pyrochlore Phase ◽  
Bandgap Energy ◽  
Powder Materials ◽  
Sol Gel Synthesis ◽  
Adsorption Desorption

Background: Pyrochloro structured Sm2Ti2O7 has photocatalytic activity on degradation of organic substances and on hydrogen evolution from water. Powder materials usually encounter the obstacle of separating from treated water. HZSM-5 zeolite is a kind of porous structured material with large surface area. Its role as a support for Sm2Ti2O7 is interesting. Methods: The supported Sm2Ti2O7 was synthesized using sol-gel method. The composite χSm2Ti2O7/HZSM-5 was characterized by XRD, SEM, TEM, FT-IR/FIR, UV-Vis DRS, N2 adsorption- desorption and XPS measurements. Photocatalytic degradation of Reactive Brilliant Red X-3B (RBR X-3B) was measured to evaluate the activity of the composite. Results: Sm2Ti2O7 is in the pyrochlore phase after loading on the surface of HZSM-5 zeolite. The crystal cell of pyrochlore Sm2Ti2O7 continuously expanses with decreasing Sm2Ti2O7 loading content in the composite. Bandgap energy of Sm2Ti2O7 is enlarged after supporting. The specific surface area of Sm2Ti2O7 was enlarged from 9.8 m2/g to 93 m2/g after loading. Both of the adsorption capacity and photocatalytic activity of the χSm2Ti2O7/HZSM-5 are greater than those of pure Sm2Ti2O7. After 120 min of irradiation, 73.1% of the initial RBR X-3B molecules are decomposed on 70%Sm2Ti2O7/HZSM-5, and only 27.7% of the dye is decomposed on the bare Sm2Ti2O7. Conclusion: Sm2Ti2O7 crystal growth is constrained after loading due to dispersion of Sm2Ti2O7 on the surface of HZSM-5. The specific surface area of Sm2Ti2O7 is significantly enlarged after loading. All the supported samples have greatly enhanced photocatalytic activity as compared to the bare Sm2Ti2O7.

scholarly journals Preparation and characterization of high specific surface area Mn3O4 from electrolytic manganese residue

2010 ◽  
Vol 8 (5) ◽  
pp. 1059-1068 ◽  
Author(s):  
Tiefeng Peng ◽  
Longjun Xu ◽  
Hongchong Chen
Keyword(s):  
Particle Size ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Magnetic Measurements ◽  
High Specific Surface Area ◽  
Surface Areas ◽  
Electrolytic Manganese ◽  
Electrolytic Manganese Residue ◽  
Specific Surface Areas

AbstractMn3O4 powders have been produced from Electrolytic Manganese Residue (EMR). After leaching of EMR in sulfuric acid, MnSO4 solution containing various ions was obtained. Purifying the solution obtained and then adding aqueous alkali to the purified MnSO4 solution, Mn(OH)2 was prepared. Two methods were employed to produce Mn3O4. One way was oxidation of Mn(OH)2 in aqueous phase under atmosphere pressure to obtain Mn3O4. The other way was roasting Mn(OH)2 precursors in the range of 500°C to 700°C. The prepared samples were investigated by using several techniques including X-ray powder diffraction (XRD), Fourier Transformation Infra-Red (FTIR) spectra, and Brunauer-Emmett-Teller (BET) specific surface area instrument. Particle distribution and magnetic measurements were carried out on laser particle size analyzer, vibrating sample magnetometer (VSM). Through XRD, FTIR and determination of total Mn content (TMC), the products prepared were confirmed to be a single phase Mn3O4. BET specific surface areas can reach to 32 m2 g−1. The results indicated that products synthesized by aqueous solution oxidation method had higher specific surface areas and smaller particle size than those prepared by means of roasting. However the products prepared using the above two methods showed no obvious differences in magnetic property.

scholarly journals Adsorption of water vapour and the specific surface area of arctic zone soils (Spitsbergen)

2018 ◽  
Vol 32 (1) ◽  
pp. 19-27 ◽  
Author(s):  
Jolanta Cieśla ◽  
Zofia Sokołowska ◽  
Barbara Witkowska-Walczak ◽  
Kamil Skic
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Water Vapour ◽  
Specific Surface Area ◽  
Nitrogen Adsorption ◽  
Total Carbon ◽  
Arctic Zone ◽  
Surface Areas ◽  
Arctic Soils ◽  
Specific Surface Areas

AbstractWater vapour/nitrogen adsorption were investigated and calculated the specific surface areas of arctic-zone soil samples (Turbic Cryosols) originating from different micro-relief forms (mud boils, cell forms and sorted circles) and from different depths. For the characterisation of the isotherms obtained for arctic soils, the Brunauer-Emmet-Teller model was then compared with the two other models (Aranovich-Donohue and Guggenheim-Anderson-de Boer) which were developed from Brunauer-Emmet-Teller. Specific surface area was calculated using the Brunauer-Emmet-Teller model at p p0−1range of 0.05-0.35 for the water vapour desorption and nitrogen adsorption isotherms. The values of total specific surface area were the highest in Cryosols on mud boils, lower on cell forms, and the lowest on sorted circles. Such tendency was observed for the results obtained by both the water vapour and nitrogen adsorption. The differences in the values of specific surface area at two investigated layers were small. High determination coefficients were obtained for relationships between the specific surface areas and contents of clay and silt fraction in Cryosols. No statistically significant correlation between the total carbon amount and the values of specific surface area in Cryosols has been found.

scholarly journals The Effects of Various Parameters of the Microwave-Assisted Solvothermal Synthesis on the Specific Surface Area and Catalytic Performance of MgF2 Nanoparticles

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3566
Author(s):  
Yawen Wang ◽  
Zahra Gohari Bajestani ◽  
Jérôme Lhoste ◽  
Sandy Auguste ◽  
Annie Hémon-Ribaud ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Solvothermal Synthesis ◽  
Catalytic Performance ◽  
High Specific Surface Area ◽  
Microwave Assisted ◽  
Surface Areas ◽  
Specific Surface Areas ◽  
Nanoparticle Sizes

High-specific-surface-area MgF2 was prepared by microwave-assisted solvothermal synthesis. The influences of the solvent and the magnesium precursors, and the calcination atmospheres, on the nanoparticle sizes and specific surface areas, estimated by X-Ray Powder Diffraction, N2 sorption and TEM analyses, were investigated. Nanocrystallized (~7 nm) magnesium partially hydroxylated fluorides (MgF2−x(OH)x) with significant specific surface areas between 290 and 330 m2∙g−1 were obtained. After activation under gaseous HF, MgF2−x(OH)x catalysts underwent a large decrease of both their surface area and their hydroxide, rates as shown by their 19F and 1H solid-state NMR spectra. Expect for MgF2 prepared from the acetate precursor, an activity of 30–32 mmol/h∙g was obtained which was about 40% higher compared with that of MgF2 prepared using Trifluoroacetate method (21.6 mmol/h∙g).

scholarly journals Inhibition of tetrachloroethene and trichloroethene on methanogenesis in anaerobic sludges from various origins

2020 ◽  
Vol 81 (3) ◽  
pp. 544-549
Author(s):  
A. M. Wang ◽  
C. S. Hwu ◽  
C. H. Wu
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Physical Factor ◽  
Anaerobic Treatment ◽  
Contaminated Groundwater ◽  
Biological Factors ◽  
Methanogenic Activity ◽  
Surface Areas ◽  
Specific Surface Areas

Abstract Nine anaerobic sludges were screened to obtain the most effective methanogenic inoculum for the anaerobic treatment of groundwater that is contaminated with tetrachloroethene (PCE) or trichloroethene (TCE). The selection was based on the toxicity of PCE or TCE to acetoclastic methanogens in different sludges. The effects of two biological factors, sludge origin and specific acetoclastic methanogenic activity, and a physical factor, specific surface area of sludge, on the degree of inhibition were examined and compared. The fifty percent inhibition concentrations (IC50) of PCE and TCE that were obtained from 30 °C batch inhibition tests ranged from 0.18 to 0.41 and 1.71 to 3.31 mM, respectively, for the examined sludges. The toxicity of the contaminants to anaerobic sludges did not depend on the two biological factors but was closely correlated with the specific surface area of sludge. Suspended sludges, which have higher specific surface areas than granular sludges, suffered much greater inhibition. This paper suggests the use of anaerobic granular sludges as inocula in bioreactors for treating PCE- and TCE-contaminated groundwater to reduce the effect of their inhibition.

scholarly journals Ultradrawing and Ultimate Tenacity Properties of Ultrahigh Molecular Weight Polyethylene Composite Fibers Filled with Nanosilica Particles with Varying Specific Surface Areas

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Jen-taut Yeh ◽  
Chuen-Kai Wang ◽  
Lu-Kai Huang ◽  
Chih-Chen Tsai ◽  
Wei-Yu Lai
Keyword(s):  
Molecular Weight ◽  
Specific Surface ◽  
Tensile Properties ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Surface Areas ◽  
Ultrahigh Molecular Weight ◽  
Specific Surface Areas ◽  
Nanosilica Particles

Original and/or functionalized nanosilica particles with a quoted specific surface area of 100, 300, and 600 m2/g, respectively, were used to investigate the influence of specific surface areas of nanosilica particles on ultradrawing and ultimate tensile properties of ultrahigh molecular weight polyethylene (UHMWPE), UHMWPE/nanosilica, and UHMWPE/functionalized nanosilica fibers. The specific surface areas of well-dispersed functionalized nanosilica particles in UHMWPE/functionalized nanosilica fibers can positively affect their ultradrawing, orientation, ultimate tensile properties, and “micro-fibrils” morphologies. Excellent orientation and ultimate tensile properties of UHMWPE/nanofiller fibers can be prepared by ultradrawing the UHMWPE/functionalized nanosilica as-prepared fibers with optimal contents of the best prepared functionalized nanosilica particles well dispersing in the as-prepared fibers. The ultimate tensile strength value of the best prepared UHMWPE/functionalized nanosilica drawn fiber reaches 7.6 GPa, which is about 2.3 times of those of the best prepared UHMWPE drawn fiber without addition of any nanofiller. Specific surface area, morphological and Fourier transform infrared analyses of original and functionalized nanosilica particles, and/or investigations of thermal, orientation factor, and ultimate tensile properties of as-prepared and/or drawn UHMWPE/functionalized nanosilica fibers were performed to understand the above improved ultradrawing and ultimate tensile properties of the UHMWPE/functionalized nanosilica as-prepared and/or drawn fibers.

Determination of low specific surface areas of minerals and oxides by gas–solid chromatography

1982 ◽  
Vol 60 (22) ◽  
pp. 2859-2862 ◽  
Author(s):  
Peter R. Tremaine ◽  
Alfred G. Wikjord ◽  
Jacques C. Leblanc
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Retention Volume ◽  
Volume Data ◽  
Surface Areas ◽  
Specific Surface Areas ◽  
Bet Equation

Gas–solid chromatography is shown to provide a method for measuring the specific surface area of non-porous particulate mineral or oxide samples in the range 0.005 to 0.5 m2 g−1 with precision as high as ±10%. Mesitylene is a convenient sorbate and was found to occupy an area of 71 ± 5 Å2 per molecule on silicate surfaces, by calibration with glass particles having well defined surface geometries. The rather low values obtained for the C parameter, when fitting retention volume data to the BET equation, suggest that the area occupied by mesitylene may be affected by the surface on which it is adsorbed. Hydrocarbon contaminants are a major interference. No specialized instrumentation is required.

Sign in / Sign up

Export Citation Format

Share Document