scholarly journals Features of obtaining the catalyst for the synthesis of carbon nanotubes

2019 ◽  
Vol 81 (2) ◽  
pp. 261-267 ◽  
Author(s):  
E. A. Burakova ◽  
G. S. Besperstova ◽  
M. A. Neverova ◽  
A. G. Tkachev ◽  
N. V. Orlova ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Thermal Decomposition ◽  
Metal Oxide ◽  
Specific Surface ◽  
Surface Area ◽  
Nanostructured Materials ◽  
Specific Surface Area ◽  
Oxide System ◽  
Decomposition Stage ◽  
Al2o3 Catalyst

In this paper, the features of obtaining a Co-Mo/Al2O3 catalyst to synthesize carbon nanotubes (CNTs) by thermal decomposition were studied. It was revealed that the duration of the pre-catalyst thermal decomposition stage in the process of developing a metal oxide system has a significant impact on its activity in the synthesis of carbon nanostructured materials by chemical vapor deposition (CVD). It was proved that an effective catalyst for CNTs synthesis can be obtained by through thermal decomposition of the pre – catalyst, without calcination of the metal oxide system. The use of the Co-Mo/Al2O3 catalyst, synthesized in such a way, in the CVD process makes it possible to reduce the cost of synthesized CNTs. Using scanning electron microscopy, it was shown that the size of the grains, and specific surface area of the formed Co-Mo/Al2O3 catalyst depend on the thermal treatment conditions of the pre-catalyst. Under the conditions for the implementation of the pre-catalyst thermal decomposition stage (temperature, volume, duration, etc.), it is possible to contro not only the characteristics of the resulting catalyst (specific surface area, efficiency), but also the characteristics of the CNTs (diameter, degree of defectiveness). In the course of experiments, the optimal modes of implementation of the method for obtaining the Co-Mo/Al2O3 catalyst allowed forming a system with a specific surface area of ~ 108 m2/g. The use of the resulting catalyst in the synthesis of nanostructured materials provides a high specific yield of multi-walled CNTs with a diameter of 8-20 nm and a degree of defectiveness of 0.97.

The Influence of Fe/Al Molar Ratio on Microreactor-Based Catalyst Preparation and Carbon Nanotube Preparation

2021 ◽  
Vol 1036 ◽  
pp. 130-136
Author(s):  
Ting Qun Tan ◽  
Lei Geng ◽  
Yan Lin ◽  
Yan He
Keyword(s):  
Carbon Nanotubes ◽  
Catalytic Activity ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Small Diameter ◽  
High Specific Surface Area ◽  
Detection Methods ◽  
Molar Ratio ◽  
High Catalytic Activity

In order to prepare carbon nanotubes with high specific surface area, small diameter, low resistivity, high purity and high catalytic activity, the Fe-Mo/Al2O3 catalyst was prepared based on the microreactor. The influence of different Fe/Al molar ratios on the catalyst and the carbon nanotubes prepared was studied through BET, SEM, TEM and other detection methods. Studies have shown that the pore structure of the catalyst is dominated by slit pores at a lower Fe/Al molar ratio. The catalytic activity is the highest when the Fe/Al molar ratio is 1:1, reaching 74.1%. When the Fe/Al molar ratio is 1:2, the catalyst has a higher specific surface area, the maximum pore size is 8.63 nm, and the four-probe resistivity and ash content of the corresponding carbon nanotubes are the lowest. The higher the proportion of aluminum, the higher the specific surface area of the catalyst and the carbon nanotubes, and the finer the diameter of the carbon nanotubes, which gradually tends to relax. The results show that when the Fe/Al molar ratio is 1:2, although the catalytic activity of the catalyst is not the highest, the carbon nanotubes prepared have the best performance.

Frontiers of carbon materials as capacitive deionization electrodes

2020 ◽  
Vol 49 (16) ◽  
pp. 5006-5014 ◽  
Author(s):  
Yuanyuan Li ◽  
Nan Chen ◽  
Zengling Li ◽  
Huibo Shao ◽  
Liangti Qu
Keyword(s):  
Carbon Nanotubes ◽  
Activated Carbon ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Carbon Materials ◽  
High Specific Surface Area ◽  
Carbon Aerogels ◽  
Capacitive Deionization

Carbon materials are widely used as capacitive deionization (CDI) electrodes due to their high specific surface area (SSA), superior conductivity, and better stability, including activated carbon, carbon aerogels, carbon nanotubes and graphene.

scholarly journals Simultaneous deposition of Au nanoparticles during flame synthesis of TiO2 and SiO2

2003 ◽  
Vol 18 (1) ◽  
pp. 115-120 ◽  
Author(s):  
L. Mädler ◽  
W. J. Stark ◽  
S. E. Pratsinis
Keyword(s):  
Metal Oxide ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Au Nanoparticles ◽  
Visible Region ◽  
Gold Deposits ◽  
Absorption Bands ◽  
Oxide Support ◽  
Metal Oxide Support

Nanostructured gold/titania and gold/silica particles with up to 4 wt% Au were made by a single-step process in a spray flame reactor. Gold(III)-chloride hydrate and titania- or silica-based metalorganic precursors were mixed in a liquid fuel solution, keeping concentrations in the flame and overall combustion enthalpy constant. The powders were characterized by x-ray diffraction, transmission electron microscopy, Brunauer–Emmett–Teller, and ultraviolet–visible analysis. The titania or silica specific surface area and the crystalline structure of titania were not affected by the presence of gold in the flame. Furthermore the size of the gold deposits was independent of the metal oxide support (TiO2 or SiO2) and its specific surface area (100 and 320 m2/g, respectively). The gold nanoparticles were nonagglomerated, spherical, mostly single crystalline, and well dispersed on the metal oxide support. Depending on the Au weight fraction (1, 2, and 4 wt%) the Au nanoparticles' mass mean diameter was 3, 7, and 15 nm, respectively, on both titania and silica. The particles showed surface plasmon absorption bands in the ultraviolet–visible region, which is typical for nano-sized gold. This absorption band was red shifted in the case of the titania support, while no shift occurred with the silica support.

CVD Synthesis of Multi-Walled Carbon Nanotubes onto Different Catalysts at Low Temperature

NANO ◽  
2018 ◽  
Vol 13 (04) ◽  
pp. 1850036 ◽  
Author(s):  
Guiqiang Diao ◽  
Hao Li ◽  
Hao Liang ◽  
Iryna Ivanenko ◽  
Tetiana Dontsova ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Low Temperature ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Lithium Ion ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

Multi-walled carbon nanotubes (MWCNTs) were synthesized onto a series of individual and bimetallic catalysts by the chemical vapor deposition (CVD) of acetylene at low temperature (600[Formula: see text]C). The catalysts were prepared by two methods, i.e., precipitation and sol–gel, with two different carriers – MgO and Al2O3. The catalysts were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal gravimetric (TG) analysis, low-temperature adsorption of nitrogen. The yield of the MWCNTs was calculated in two ways, while the highest yield of 800% was achieved onto the two-component NiO/Co2O3/MgO catalyst, SEM and transmission electron microscopy (TEM) results confirm that uniform tube-like structure MWCNTs with the yield of 410% were obtained onto Co2O3/Al2O3 catalyst. These MWCNTs are smooth and pointing in the same direction. Their tube diameter is about 20[Formula: see text]nm, which is the smallest around all observed MWCNTs. Moreover, nonuniform curved bamboo-like MWCNTs with nozzles in the yield of 760% were obtained onto NiO/V2O3/MgO catalyst. Their diameter ranges from 25[Formula: see text]nm to 50[Formula: see text]nm. Results show that single-component catalyst promotes the growth of uniform and smaller nanotubes. Among the as-grown nanotubes, their specific surface area increases and average pores diameter reduces after the treatment with concentrated nitric acid at reflux and washing condition. The largest specific surface area (305[Formula: see text]m2/g) and average pores diameter (26[Formula: see text]m2/g) are processed to MWCNTs grown onto the NiO/Co2O3/MgO catalyst. MWCNTs with such large structural adsorption characteristics and purity of more than 99% obtained with yield 800% show potential use for preparation of nanocomposites as anode materials in lithium ion batteries.

scholarly journals Synthesis and sintering of nano-sized BaSnO3 powders containing BaGeO3

2018 ◽  
Author(s):  
Roberto Köferstein
Keyword(s):  
Thermal Decomposition ◽  
Specific Surface ◽  
Relative Density ◽  
Surface Area ◽  
Specific Surface Area ◽  
Solid Solutions ◽  
Sintering Temperature ◽  
Soaking Time ◽  
Fine Microstructure ◽  
Sintering Behaviour

The formation of solid solutions of the type[Ba(HOC2H4OH)4][Sn1−xGex(OC2H4O)3] as BaSn1-x/GexO3 precursor and the phase evolutionduring its thermal decomposition are described in this paper. The 1,2-ethanediolato complexescan be decomposed to nano-sized BaSn1−x/GexO3 preceramic powders. Samples with x = 0.05consist of only a Ba(Sn,Ge)O3 phase, whereas powders with x = 0.15 and 0.25 showdiffraction patterns of both the Ba(Sn,Ge)O3 and BaGeO3 phase. The sintering behaviour wasinvestigated on powders with a BaGeO3 content of 5 and 15 mol%. These powders show a specific surface area of 15.4−15.9 m2/g and were obtained from calcination above 800 °C.The addition of BaGeO3 reduced the sintering temperature of the ceramics drastically.BaSn0.95Ge0.05O3 ceramics with a relative density of at least 90 % can be obtained by sinteringat 1150 °C for 1 h. The ceramic bodies reveal a fine microstructure with cubical-shaped grainsbetween 0.25−0.6 μm. For dense ceramics the sintering temperature could be reduced down to1090 °C, when the soaking time was extended up to 10 h.

Nd-Doped Barium Cerate Nano-Sized Catalyst Converts CH4 into CO2 at Lower Temperature Compared to Noble Metal-Based Pd/Al2O3 Catalyst

2021 ◽  
Vol 10 (3) ◽  
pp. 01-08
Author(s):  
Khalid Ouzaouit ◽  
Abdelhay Aboulaich
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Catalytic Properties ◽  
Area Measurement ◽  
Barium Cerate ◽  
In Situ Ftir Spectroscopy ◽  
Lower Temperature ◽  
Doped Barium Cerate ◽  
Al2o3 Catalyst

The present paper describes the synthesis and first application of Nd-doped BaCeO3 nanoparticles as catalyst for the catalytic oxidation of methane (CH4) into CO2. Nd-doped barium cerate BaCeO3 nanoparticles, with the formula BaNdxCe(1-x)O3, have been prepared using a simple sol gel method starting from acetate precursors. The as-prepared nanoparticles have been fully characterized by XRD, TEM, HRTEM and specific surface area measurement. Results confirmed the formation of highly crystallized nano-sized particles with small crystallite size. In-situ FTIR spectroscopy was used to study the catalytic conversion of methane (CH4) into CO2 in the presence of the as-prepared Nd-doped BaCeO3 nanocatalyst. The catalytic properties of such nanocatalysts have been discussed and correlated to Nd-doping rate, crystallite diameter, and specific surface area of the materials. Excellent catalytic properties have been obtained with BaNd0.05Ce0.95O3, such as, superior conversion efficiency, longer catalysis lifetime and lower activation temperature compared to un-doped BaCeO3 catalyst. Interestingly, it was found that BaNd0.05Ce0.95O3 nanocatalyst successfully converts the totality of CH4 present in a mixture of CH4-Air into CO2 at much lower temperature compared to the conventional Pd/Al2O3 catalyst.

Pore structure of pyrolyzed scrap tires

2008 ◽  
Vol 62 (1) ◽  
Author(s):  
Zuzana Koreňová ◽  
Juma Haydary ◽  
Július Annus ◽  
Jozef Markoš ◽  
L’udovít Jelemenský
Keyword(s):  
Thermal Decomposition ◽  
Carbon Black ◽  
Specific Surface ◽  
Pore Structure ◽  
Surface Area ◽  
Specific Surface Area ◽  
Nitrogen Flow ◽  
Solid Matter ◽  
Scrap Tires ◽  
Different Temperatures

AbstractInternal structure of carbon black produced by pyrolysis (CBp) of rubber samples from the top and bottom parts of sidewall and tread of a passenger car tire was investigated in nitrogen flow at different temperatures. The pore structure (specific surface area, pore size distribution, and porosity) of CBp and commercial CB, was compared. The development of pore structure and the increase of the specific surface area were most intensive during the thermal decomposition at temperatures ranging from 300°C to 500°C. This is caused by the intensive release of volatiles during the pyrolysis. After the pyrolysis was finished, at temperatures above 500°C, further decomposition of solid matter was associated with a slight increase of the specific surface area.

scholarly journals Adsorptive and Electrochemical Properties of Carbon Nanotubes, Activated Carbon, and Graphene Oxide with Relatively Similar Specific Surface Area

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 496
Author(s):  
Krzysztof Kuśmierek ◽  
Andrzej Świątkowski ◽  
Katarzyna Skrzypczyńska ◽  
Lidia Dąbek
Keyword(s):  
Carbon Nanotubes ◽  
Graphene Oxide ◽  
Activated Carbon ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Carbon Materials ◽  
Organochlorine Compound ◽  
Carbon Surface ◽  
Negative Effect

Three carbon materials with a highly diversified structure and at the same time much less different porosity were selected for the study: single-walled carbon nanotubes, heat-treated activated carbon, and reduced graphene oxide. These materials were used for the adsorption of 2,4-D herbicide from aqueous solutions and in its electroanalytical determination. Both the detection of this type of contamination and its removal from the water are important environmental issues. It is important to identify which properties of carbon materials play a significant role. The specific surface area is the major factor. On the other hand, the presence of oxygen bound to the carbon surface in the case of contact with an organochlorine compound had a negative effect. The observed regularities concerned both adsorption and electroanalysis with the use of the carbon materials applied.

Influence of Carbon Nanotubes on the Performances of LiFePO4

2010 ◽  
Vol 148-149 ◽  
pp. 1133-1137
Author(s):  
Li Ming Feng ◽  
Teng Gai ◽  
Xue Wei
Keyword(s):  
Carbon Nanotubes ◽  
Particle Size ◽  
Electrical Resistivity ◽  
Carbon Source ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Specific Capacity ◽  
Doping Amount ◽  
Mechanical Mixing

To improve the performances of LiFePO4, a positive material in lithium battery, research on the influence of doping amount and doping form of carbon nanotubes (CNTS) on electrical resistivity, specific capacity, specific surface area and particle size distribution of LiFePO4 powder was conducted. The results indicated that, addition of CNTS significantly reduced the electrical resistivity no matter in pure LiFePO4 or LiFe0.98Mg0.02PO4; with same usage, coating of CNTS as carbon source performed better than mechanical grinding and mixing with LiFePO4. With the increase of CNTS content, a rising trend of both specific surface area (BET) and particle size (D50) in LiFePO4 powder was observed, but seeing a slight drop in discharge capacity under the rates of 0.2C and 0.5C. When the content of CNTS reached 3% (by mass) respectively through mechanical mixing and being added as carbon source, electrical resistivity of pure LiFePO4 dropped from over 105Ω•cm to 1868Ω•cm and 27Ω•cm accordingly, and that of LiFe0.98Mg0.02PO4 dropped from over 105Ω•cm to 4800Ω•cm.

Sign in / Sign up

Export Citation Format

Share Document