Production of tungsten powders with highly developed surface

The process of producing tungsten powders with a highly developed surface by reducing its oxide compounds with magnesium vapor in the temperature range 600—750 °C under dynamic vacuum (0.01 kPa) and with a residual argon pressure in the reactor 0.5—10 kPa has been studied. During the reduction of magnesium and calcium tungstates, tungsten powders were obtained with a specific surface area of 40 m2·g–1, characterized by a mesoporous structure.

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Influence of the Calcination Temperature on the properties of The Alumina as Catalyst Support for Catalysis

Paliva ◽

10.35933/paliva.2020.04.03 ◽

2020 ◽

pp. 155-161

Author(s):

Tomáš Hlinčík ◽

Veronika Šnajdrová ◽

Veronika Kyselová

Keyword(s):

Specific Surface ◽

Surface Area ◽

Calcination Temperature ◽

Specific Surface Area ◽

Catalyst Support ◽

Chemical Properties ◽

Total Pore Volume ◽

Temperature Range ◽

Calcination Temperatures ◽

Physical And Chemical

Alumina is commonly used in industrial practice as a catalyst support and it is made from boehmite. Depending on the calcination temperature, this mineral is transformed into various crystalline modifications which have different physical and chemical properties. For this reason, the following parameters were determined at different calcination temperatures: length, width, material hardness, specific surface area and total pore volume. The results show that with increasing calcination temperature there have been significant changes which may be important when using the material as a catalyst support, e.g. in the preparation of catalysts or in the design of cat-alytic reactors. The specific surface area, which decreases in the temperature range 450–800 °C, is an important parameter for the preparation of catalysts, so it is appropriate to choose a temperature of 600 °C, when the specific surface area is above 200 m2·g-1. The effect of calcination temperature on the structural transitions of boehmite was also monitored. The results showed that γ-Al2O3 has the most suitable properties as a catalyst sup-port in the temperature range 450–800 °C.

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New Electrodes Prepared from Mineral and Plant Raw Materials of Kazakhstan

Eurasian Chemico-Technological Journal ◽

10.18321/ectj440 ◽

2016 ◽

Vol 18 (2) ◽

pp. 141 ◽

Cited By ~ 1

Author(s):

A.A. Atchabarova ◽

R.R. Tokpayev ◽

A.T. Kabulov ◽

S.V. Nechipurenko ◽

R.A. Nurmanova ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Electrode Materials ◽

Raw Materials ◽

Hydrothermal Carbonization ◽

Walnut Shell ◽

High Background ◽

Plant Raw Materials ◽

Developed Surface

Electrode materials were prepared from activated carbonizates of walnut shell, apricot pits and shungite rock from “Bakyrchik” deposit, East Kazakhstan. Physicochemical characteristics of the obtained samples were studied by the Brunauer-Emett-Taylor method, scanning electron microscopy, Raman spectroscopy and other methods. Electrochemical properties of the obtained materials were studied by the method of cyclic voltammetry. It was found that the samples have an amorphous structure. Samples based on plant raw materials after hydrothermal carbonization at 240 °С during 24 h, have more homogeneous and developed surface. Specific surface area of carbon containing materials based on apricot pits is 1300 m2/g, for those on the based on mineral raw material, it is 153 m2/g. It was shown that materials after hydrothermal carbonization can be used for catalytic purposes and electrodes after thermal carbonization for analytical and electrocatalytic purposes. Electrode obtained by HTC have electrocatalytic activity. CSC 240 has high background current (slope i/Е is 43 mА V–1 cm–2), low potential of the hydrogen electroreduction (more positive by ~ 0.5 V than samples based on plant raw materials). The reaction of DA determination is more pronounced on the electrodes obtained by HTC 240 °C, 24 h, due to the nature, carbon structure and high specific surface area of obtained samples.

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Preparation of Nitrogen-Deficient Graphitic Carbon Nitride with a Large Specific Surface Area by Melt Pretreatment and Its Photocatalytic Performance

NANO ◽

10.1142/s1793292020500794 ◽

2020 ◽

Vol 15 (06) ◽

pp. 2050079

Author(s):

Xuelei Li ◽

Jinfeng Bai ◽

Jiaqi Li ◽

Chao Li ◽

Junru Zhang ◽

...

Keyword(s):

Visible Light ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Carbon Nitride ◽

Mesoporous Structure ◽

Graphitic Carbon ◽

Graphitic Carbon Nitride ◽

Large Specific Surface Area ◽

X Ray

In this study, nitrogen-deficient graphitic carbon nitride (M-LS-g-C3N4) with a mesoporous structure and a large specific surface area was obtained by calcination after melt pretreatment using urea as a precursor. X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption, X-ray photoelectron spectroscopy (XPS), UV-Vis, ESR and photoluminescence (PL) were used to characterize the structure, morphology and optical performance of the samples. The TEM results showed the formation of a mesoporous structure on the 0.1[Formula: see text]M-LS-g-C3N4 surface. The porous structure led to an increase in the specific surface area from 41.5[Formula: see text]m2/g to 124.3[Formula: see text]m2/g. The UV-Vis results showed that nitrogen vacancies generated during the modification process reduced the band gap of g-C3N4 and improved the visible light absorption. The PL spectra showed that the nitrogen defects promoted the separation of photogenerated electron–hole pairs. In the visible light degradation of methyl orange (MO), the reaction rate constant of 0.1[Formula: see text]M-LS-g-C3N4 reached 0.0086[Formula: see text][Formula: see text], which was 5.05 times that of pure g-C3N4. Superoxide radicals and photogenerated holes were found to be the main active species in the reaction system. This study provides an efficient, green and convenient means of preparing graphitic carbon nitride with a large specific surface area.

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Synthesis and properties of composite material CoFe2O4/C

Proceedings of the Voronezh State University of Engineering Technologies ◽

10.20914/2310-1202-2019-4-184-189 ◽

2020 ◽

Vol 81 (4) ◽

pp. 184-189

Author(s):

N. P. Shabelskaya ◽

M. A. Egorova ◽

G. M. Chernysheva ◽

A. N. Saliev ◽

A. N. Yatsenko ◽

...

Keyword(s):

Composite Material ◽

Activated Carbon ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Average Crystallite Size ◽

Nitrogen Adsorption ◽

Lattice Parameter ◽

Transition Elements ◽

Developed Surface

Scientific interest in the processes of forming the structure of magnetic spinels and composites based on them is due to the possibility of synthesis of materials with multifunctional properties. The process of formation of cobalt (II) nanocrystalline ferrite and CoFe2O4/C composite material is studied. The mechanism of formation of structure of materials including a stage of formation of hydroxides of transition elements, precursors on the basis of complex connections of cations of iron and cobalt with citric acid and their subsequent destruction at heating is offered. The synthesized materials were characterized by x-ray phase analysis, electron microscopy, low-temperature nitrogen adsorption, Debye-Scherrer methods. It is shown that cobalt (II) ferrite has a developed surface, the value of the surface area according to the BET method is 16 m2/g, the average size of the crystallites determined by the Debye-Scherrer equation is 4.0 nm. Activated carbon with a specific surface area of 685 m2/g was used to prepare the composite material. The resulting composite material has a surface area of 222 m2/g, the average crystallite size of 1.1 nm. Cobalt (II) ferrite, included in the composition of the composite material CoFe2O4/C, has a slightly higher value of the lattice parameter, compared with pure cobalt (II) ferrite, which is associated with a decrease in the degree of spinel inversion. The synthesized composite material was tested in the process of adsorption of copper (II) cations from an aqueous solution. It is shown that CoFe2O4/C exhibits an increased adsorption capacity for copper (II) cations in comparison with pure activated carbon, despite a decrease in the specific surface area. The result is explained by the involvement of cobalt (II) ferrite in the adsorption process. The obtained materials may be of interest as catalysts, adsorbents.

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Enhancement in Graphitization of Ordered Mesoporous Carbon by Assistance of Soybean Oil Surfactant

VNU Journal of Science Natural Sciences and Technology ◽

10.25073/2588-1140/vnunst.4989 ◽

2020 ◽

Vol 36 (3) ◽

Author(s):

Le Thi Thu Hang ◽

Hoang Thi Bich Thuy

Keyword(s):

Soybean Oil ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Pore Volume ◽

Mesoporous Carbon ◽

Mesoporous Structure ◽

Ordered Mesoporous Carbon ◽

Graphitization Degree ◽

Ordered Mesoporous

In this work, highly ordered mesoporous graphitic carbon (G-CMK3) has been prepared successfully by a nano-casting method using sucrose as carbon source, mesoporous silica as hard template, and soybean oil as surfactant. In the absence of soybean oil surfactant, the synthesized ordered mesoporous carbon material, CMK-3, revealed a low graphitization degree with a specific surface area of 1049.1 m2/g and a high pore volume of 1.172 cm3/g. However, with the assistance of soybean oil surfactant, the graphitization degree was improved significantly, which was confirmed by the decrease in the ID/IG intensity ratio of the D (disordered or amorphous structure) and G (graphitic structure) peaks from 0.98 to 0.83. After the synthesis in the presence of soybean oil, G-CMK3 carbon maintained the integrity of the mesoporous structure albeit with a slight decrease in its specific surface area (845.2 m2/g) as well as pore volume (0.858 cm3/g).

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Synthesis and Structural Characterization of SiO2-Al2O3 Xerogels

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.336-338.2286 ◽

2007 ◽

Vol 336-338 ◽

pp. 2286-2289

Author(s):

Fei He ◽

Xiao Dong He ◽

Yao Li

Keyword(s):

Structural Change ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Sol Gel ◽

Nitrogen Adsorption ◽

Mesoporous Structure ◽

Supercritical Drying ◽

High Specific Surface Area ◽

Molar Ratio

Low-density xSiO2-(1-x)Al2O3 xerogels with x=0.9, 0.8, 0.7, 0.6 (mole fractions) were prepared by sol-gel and non-supercritical drying. Silica alkogels, which were the framework of binary composite materials, formed from tetraethyl orthosilicate (TEOS) by hydrolytic condensation with a molar ratio of TEOS: H2O: alcohol: hydrochloric acid: ammonia =1: 4: 10: 7.5×10-4: 0.0375. Aluminum hydroxide derived from Al(NO3)3·9H2O and NH4OH acting in the alcohol solution under the condition of catalyst. After filtrating and washing, the precipitation was mixed into silica sols to form SiO2-Al2O3 mixed oxide gels with different silicon and aluminum molar ratio. The structural change and crystallization of the binary xerogels were investigated after heat treatment at 600 for 2 h by the means of X-ray diffraction. Nitrogen adsorption experiment was performed to estimate specific surface area, porous volume and pore size distribution. The structural change of xerogels was observed by FT-IR spectroscopy. The resulting mixed xerogels possess of mesoporous structure which is characteristic of cylindrical pores, high specific surface area of 596-863 m2/g and a relatively narrow pore distribution of 2.8-30 nm. Al2O3 is introduced into the SiO2 phase and some of Al-O-Si bonds form.

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Efficient Sunlight-Induced Methylene Blue Removal over One-Dimensional Mesoporous Monoclinic BiVO4Nanorods

Journal of Analytical Methods in Chemistry ◽

10.1155/2012/345247 ◽

2012 ◽

Vol 2012 ◽

pp. 1-9 ◽

Cited By ~ 10

Author(s):

Linrui Hou ◽

Long Yang ◽

Jiaoyang Li ◽

Jie Tan ◽

Changzhou Yuan

Keyword(s):

Methylene Blue ◽

Specific Surface ◽

Band Gap ◽

Surface Area ◽

Specific Surface Area ◽

Mesoporous Structure ◽

High Specific Surface Area ◽

One Dimensional ◽

Light Region ◽

Degussa P25

Sunlight-driven mesoporous BiVO4nanorods with monoclinic structure have been successfully synthesizedviaa simple hydrothermal method. The as-prepared one-dimensional BiVO4nanorods exhibited high specific surface area due to their unique mesoporous structure. The mesoporous BiVO4nanorods possessed strong photoabsorption properties in the visible light region as well as the ultravisible region, and the band gap was estimated to beca.2.18 eV. The photocatalytic activities were evaluated by decolorization of methylene blue under sunlight irradiation. Photocatalytic tests demonstrated that the decolorization rate of as-prepared mesoporous BiVO4nanorods was even up to 98.8% in 180 min, much better than that prepared by solid-state reaction (23.1%) and the commercial TiO2(Degussa P25) (14.2%) under the same conditions, due to their higher specific surface area and appropriate band gap. Moreover, the unique BiVO4nanorods exhibit high stability after five photocatalytic degradation recycles.

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Structural Characterization and Adsorption Capability of Carbonaceous Matters Extracted from Carbonaceous Gold Concentrate

Minerals ◽

10.3390/min11010023 ◽

2020 ◽

Vol 11 (1) ◽

pp. 23

Author(s):

Huiqun Niu ◽

Hongying Yang ◽

Linlin Tong

Keyword(s):

Particle Size ◽

Humic Acid ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Pore Diameter ◽

Mesoporous Structure ◽

Average Pore Diameter ◽

Average Pore ◽

Complex Organic Compound

In this paper, the structures of element carbon and humic acid extracted from carbonaceous gold concentrate were characterized employing a variety of analytical methods. The extracted amounts of ECE (elemental carbon extract) and HAE (humic acid extract) were 14.84–38.50 and 11.55–28.05 mg g−1, respectively. SEM and porosity analysis indicated that ECE occurred mostly as irregular blocky particles with a mesoporous surface with the average pore diameter being 31.42 nm. The particle size of ECE was mainly ranged from 5.5 to 42 μm and the specific surface area was 20.35 m2 g−1. The physicochemical features and structure of ECE were close to activated carbon, and the crystallinity was slightly lower than graphite. The particle size distribution of HAE varied from 40 to 400 nm with the specific surface area of 42.84 m2 g−1, whereas the average pore diameter of HAE was 2.97 nm. FTIR and UV–VIS analyses indicated that HAE was a complex organic compound containing the enrichment of oxygen-containing structure. The results showed that the adsorption amounts of ECE and HAE under the acidic conditions were 470.46 and 357.60 mg g−1, respectively. In an alkaline environment, the amount of ECE was 449.02 mg g−1 and the value of HAE was 294.72 mg g−1. ECE mainly utilized the outer surface and mesoporous structure to adsorb gold, while the functional groups’ complexation or surface site adsorption was the leading approach for HAE to adsorb gold.

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Selective Crystallization of Silicoalumophosphate Sapo-11 With A Micromesoporous Structure

Science Journal of University of Zakho ◽

10.25271/sjuoz.2021.9.2.827 ◽

2021 ◽

Vol 9 (2) ◽

pp. 109-111

Author(s):

Zulfiya Khayrullina ◽

Kanaan R. Ahmed ◽

Samara Kambarova ◽

Marat Agliullin

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Molecular Sieve ◽

Mesoporous Structure ◽

Selective Crystallization ◽

Scanning Electron

ABSTRACT:The authors have proposed a method for the selective crystallization of a SAPO-11 silicoaluminophosphate molecular sieve with a micro-mesoporous structure. It has been shown that crystallization of a silicoaluminophosphate gel, in the preparation of which its isopropoxide is used as a source of aluminum, makes it possible to obtain a SAPO-11 molecular sieve with a specific surface area of ~ 207 m2 / g, a volume of micro- and mesopores of ~ 0.08 and 0.09 cm3 / g. , respectively. Using scanning electron microscopy, it was demonstrated that the crystals of the material are pseudospherical particles ~ 8-10 microns in size, consisting of aggregates of nanocrystals ~ 100-200 nm in size.

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Preparation and Microstructure Analysis of TiC-Derived Carbons with Hierarchical Pore Structure

Journal of Nanomaterials ◽

10.1155/2015/163415 ◽

2015 ◽

Vol 2015 ◽

pp. 1-7

Author(s):

Jin Jia ◽

Aiguo Zhou ◽

Yuanyuan Zhu ◽

Jiang Liu ◽

Shihao Feng ◽

...

Keyword(s):

Specific Surface ◽

Pore Structure ◽

Surface Area ◽

Specific Surface Area ◽

Amorphous Carbon ◽

Microstructure Analysis ◽

Temperature Range ◽

Hierarchical Pore Structure ◽

Hierarchical Pore ◽

Small Parts

Carbide-derived carbons (CDCs) with hierarchical pore structure are prepared from commercial TiC powders by chlorination at temperature range of 600–1100°C. As-synthesized CDCs mainly consist of amorphous carbon and there exists a graphitization trend at chlorinating temperature above 800°C. If chlorinating temperature is below 1000°C, CDC particles maintain the shape of original TiC particles. Above 1000°C, obvious cracks appear in CDC particles and some particles are broken into small parts. The specific surface area (SSA) of CDCs is in the range from 672 m2/g to 1609 m2/g. The highest SSA is 1609 m2/g for CDC chlorinated at 1000°C. Most pores in these CDCs are micropores with the size of 0.7–2 nm. However, some mesopores and macropores also exist.

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