Low Temperature Synthesis of Mesoporous SiC in Dual-Confined Spaces via Magnesiothermic Reduction

NANO ◽  
2019 ◽  
Vol 14 (09) ◽  
pp. 1950115 ◽  
Author(s):  
Zeng-Rong Wang ◽  
Long Liu ◽  
Xue Zhang ◽  
Jia-Lin Xu ◽  
Qiang Sun
Keyword(s):  
Low Temperature ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Catalyst Support ◽  
Reduction Process ◽  
Carbon Matrix ◽  
Carbon Composite ◽  
Magnesiothermic Reduction ◽  
Confined Spaces

Silicon carbide (SiC), especially mesoporous SiC has been in immense vogue for more than a decade because of its intriguing properties and wide applications. However, it is still challenging to synthesize mesoporous SiC with good structural integrality, large specific surface area and desirable porosity at a low temperature. In this study, we reported a “dual-confined spaces”-assisted synthesis of mesoporous SiC using well-assembled SiO2/carbon composite as precursor via a magnesiothermic reduction process. The well-crystallinity mesoporous SiC presented a mesopore structure with high specific surface area of 267.3 m2 g[Formula: see text] and large mesopore size of ca. 10[Formula: see text]nm can be directly fabricated at a temperature of at least 550∘C and the optimum synthesis temperature is 650∘C. During the synthesis, mesoporous carbon matrix and a pressure-tight stainless steel reactor were served as “dual-confined spaces” to avoid the aggregation of silica and the silicon residue left in the final SiC sample. Furthermore, the as-prepared mesoporous SiC showed prominent performance as catalyst support for the reduction of 4-nitrophenol to 4-aminophenol.

scholarly journals Low-Temperature Synthesis of Monolithic Titanium Carbide/Carbon Composite Aerogel

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2527
Author(s):  
Tingting Niu ◽  
Bin Zhou ◽  
Zehui Zhang ◽  
Xiujie Ji ◽  
Jianming Yang ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Electron Microscope ◽  
Low Temperature ◽  
Titanium Carbide ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Carbon Composite ◽  
Composite Aerogel ◽  
X Ray

Resorcinol-formaldehyde/titanium dioxide composite (RF/TiO2) gel was prepared simultaneously by acid catalysis and then dried to aerogel with supercritical fluid CO2. The carbon/titanium dioxide aerogel was obtained by carbonization and then converted to nanoporous titanium carbide/carbon composite aerogel via 800 °C magnesiothermic catalysis. Meanwhile, the evolution of the samples in different stages was characterized by X-ray diffraction (XRD), an energy-dispersive X-ray (EDX) spectrometer, a scanning electron microscope (SEM), a transmission electron microscope (TEM) and specific surface area analysis (BET). The results showed that the final product was nanoporous TiC/C composite aerogel with a low apparent density of 339.5 mg/cm3 and a high specific surface area of 459.5 m2/g. Comparing to C aerogel, it could also be considered as one type of highly potential material with efficient photothermal conversion. The idea of converting oxide–carbon composite into titanium carbide via the confining template and low-temperature magnesiothermic catalysis may provide new sight to the synthesis of novel nanoscale carbide materials.

scholarly journals Using non-equilibrium state in the MoO3-H-C system for low temperature synthesis of ultradispersed molybdenum carbide powders

2008 ◽  
Vol 2 (2) ◽  
pp. 97-102 ◽  
Author(s):  
M.P. Savyak ◽  
I.V. Uvarova ◽  
T.M. Yarmola
Keyword(s):  
Low Temperature ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Molybdenum Carbide ◽  
Molybdenum Trioxide ◽  
Reduction Process ◽  
Carbide Formation ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis

Pd additives and atomic hydrogen can accelerate kinetic processes in molybdenum reduction from molybdenum trioxide with hydrogen at 350?C in the presence of carbon. Such a low temperature reduction process (starting temperature 300-350?C) promotes the formation of a thermodynamically unstable nanodispersed phase with the specific surface area of 280 m2/g, which may be related to the formation of the intermediate cubic molybdenum suboxide Mo1-xO, responsible for the preservation of the MoO3 faceting. The specific surface area of 280 m2/g corresponds to the particle size ~3 nm. The phase transformation leading to the formation of Mo2C in the MoO3-Pd-H2-C system at a relatively low temperature (650?C) is the result of relaxation of the high free energy in the thermodynamically unstable system. The carbide formation process at such a low temperature yields carbide with the specific surface area from 4 to 40 m2/g (depending on the carbide-forming component), which can be easy sintered. The morphology of this carbide inherits the faceting of the initial whiskerous trioxide molybdenum. The microhardness of the sintered samples is significantly higher than that of carbide produced traditionally at high temperature.

scholarly journals Development and Characterization of Composite Carbon Adsorbents with Photocatalytic Regeneration Ability: Application to Diclofenac Removal from Water

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 173
Author(s):  
Velma Beri Kimbi Yaah ◽  
Satu Ojala ◽  
Hamza Khallok ◽  
Tiina Laitinen ◽  
Marcin Selent ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Functional Groups ◽  
Specific Surface Area ◽  
Palm Kernel ◽  
Hydrothermal Carbonization ◽  
Carbon Composite ◽  
Carbon Adsorbents ◽  
Regeneration Ability ◽  
Activation Temperature

This paper presents results related to the development of a carbon composite intended for water purification. The aim was to develop an adsorbent that could be regenerated using light leading to complete degradation of pollutants and avoiding the secondary pollution caused by regeneration. The composites were prepared by hydrothermal carbonization of palm kernel shells, TiO2, and W followed by activation at 400 °C under N2 flow. To evaluate the regeneration using light, photocatalytic experiments were carried out under UV-A, UV-B, and visible lights. The materials were thoroughly characterized, and their performance was evaluated for diclofenac removal. A maximum of 74% removal was observed with the composite containing TiO2, carbon, and W (HCP25W) under UV-B irradiation and non-adjusted pH (~5). Almost similar results were observed for the material that did not contain tungsten. The best results using visible light were achieved with HCP25W providing 24% removal of diclofenac, demonstrating the effect of W in the composite. Both the composites had significant amounts of oxygen-containing functional groups. The specific surface area of HCP25W was about 3 m2g−1, while for HCP25, it was 160 m2g−1. Increasing the specific surface area using a higher activation temperature (600 °C) adversely affected diclofenac removal due to the loss of the surface functional groups. Regeneration of the composite under UV-B light led to a complete recovery of the adsorption capacity. These results show that TiO2- and W-containing carbon composites are interesting materials for water treatment and they could be regenerated using photocatalysis.

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

Paliva ◽  
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.

The Carbon Deposition during Iron Ore Reduction in Carbon Monoxide

2012 ◽  
Vol 625 ◽  
pp. 243-246
Author(s):  
Shu Hua Geng ◽  
Wei Zhong Ding ◽  
Shu Qiang Guo ◽  
Xiong Gang Lu
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Iron Ore ◽  
Iron Reduction ◽  
Carbon Deposition ◽  
Reduction Process ◽  
Ore Reduction ◽  
X Ray ◽  
Iron Ore Reduction

Iron ore reduction and carbon deposition in pure CO was investigated by using thermogravimetric (TG) method over the temperature range of 0-1200°C. The results of the work may be summarized as follows: in CO stream, carbon deposition occurred below 900°C, no carbon deposition was found above 1000°C. X-Ray analysis of the reacted sample indicated that the carbon deposition occurred with the iron was reduced. The iron reduction process and carbon deposition occurred simultaneously. The rate of carbon deposition changed with the transformation of iron oxides. The specific surface area and pore structure of reduced samples were analyzed. The specific surface area changed with the amount of carbon deposition.

Influence of Preparation Parameters on the New NSR Catalyst Support Material

2011 ◽  
Vol 412 ◽  
pp. 361-364
Author(s):  
Wei Jun Zhang ◽  
Yuan Feng Huang ◽  
Li Shen ◽  
Jun Liu ◽  
Xiao Qing Luo ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Calcination Temperature ◽  
Specific Surface Area ◽  
Catalyst Support ◽  
Atomic Ratio ◽  
High Specific Surface Area ◽  
Support Material ◽  
Co Precipitation

A series of Ba-Al-O/NSR supports were prepared by co-precipitation in this work. The effect of Al/Ba atomic ratio and calcination temperature on the structure and texture of the supports was investigated carefully. The XRD spectra show that Ba is mainly exist in the form of BaAl2O4, and Al exists in Al2O3. The results of SBET indicate that the supports possess relative high specific surface area (70~150 m2/g). The effect of different parameters on the process of supports synthesized was investigated carefully. The results show that the structure and specific surface area of support is significantly depended on calcination temperature.

scholarly journals The effect of aluminium oxide on the reduction of cobalt oxide and thermostabillity of cobalt and cobalt oxide

2011 ◽  
Vol 9 (5) ◽  
pp. 834-839 ◽  
Author(s):  
Zofia Lendzion-Bieluń ◽  
Roman Jędrzejewski ◽  
Walerian Arabczyk
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Cobalt Oxide ◽  
Specific Surface Area ◽  
Hydrogen Reduction ◽  
Aluminium Oxide ◽  
Reduction Process ◽  
Oxide Phase ◽  
Recrystallization Process ◽  
Average Size

AbstractDuring precipitation and calcination at 200°C nanocrystalline Co3O4 was obtained with average size crystallites of 13 nm and a well developed specific surface area of 44 m2 g−1. A small addition of a structural promoter, e.g. Al2O3, increases the specific surface area of the cobalt oxide (54 m2 g−1) and decreases the average size of crystallites (7 nm). Al2O3 inhibits the reduction process of Co3O4 by hydrogen. Reduction of cobalt oxide with aluminium oxide addition runs by equilibrium state at all the respective temperatures. The apparent activation energy of the recrystallization process of the nanocrystalline cobalt promoted by the aluminium oxide is 85 kJ mol−1. Aluminium oxide improves the thermostability of both cobalt oxide and the cobalt obtained as a result of oxide phase reduction.

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.

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