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.

Low temperature synthesis of monodisperse nanoscaled ZrO2with a large specific surface area

2013 ◽  
Vol 42 (2) ◽  
pp. 432-440 ◽  
Author(s):  
Nicole Zink ◽  
Franziska Emmerling ◽  
Tobias Häger ◽  
Martin Panthöfer ◽  
Muhammad Nawaz Tahir ◽  
...  
Keyword(s):  
Low Temperature ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Large Specific Surface Area ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis

scholarly journals LOW-TEMPERATURE SYNTHESIS OF BARIUM TITANITE IN AQUEOUS SOLUTION

2018 ◽  
Vol 61 (12) ◽  
pp. 56-62 ◽  
Author(s):  
Alexandr V. Agafonov ◽  
Konstantin V. Ivanov ◽  
Olga V. Alekseeva
Keyword(s):  
Heat Treatment ◽  
Barium Titanate ◽  
Thermal Treatment ◽  
Low Temperature ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Temperature Phase ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis

Barium titanate powder with average particle size near 300 nm was produced using the low-temperature synthesis. It was established using scanning electron microscopy that at the thermal treatment, the particles gradually decrease with the formation of polydisperse aggregates. Based on the thermogravimetric analysis of the synthesized powder held in air for 4 months, it was shown that along with the low-temperature phase, the sample contains a high-temperature phase of carbonates, which removes at ~ 900 °C. Sorption characteristics of barium titanate thermally treated at various temperatures were obtained from the results of adsorption-desorption of nitrogen vapors. The specific surface area of the BaTiO3 powder was 76 m2/g. It was found that further heat treatment leads to a decrease in the specific surface area. The X-ray diffraction analysis of barium hydroxotitanil annealed at temperatures from 120 °C to 800 °C showed that the thermal treatment of the sample leads to the formation of a completely formed phase of barium titanate. The DSC temperature was used to determine the Curie temperatures for a HTB powder thermally treated in the temperature range from 120 to 800 °C. Dielectric spectra of suspensions of the synthesized powder were obtained during the heat treatment. <span style="opacity: 0;"> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . </span>

A facile low-temperature synthesis of hierarchical porous Co3O4 micro/nano structures derived from ZIF-67 assisted by ammonium perchlorate

2019 ◽  
Vol 6 (3) ◽  
pp. 715-722 ◽  
Author(s):  
Kun Zhao ◽  
Haitao Li ◽  
Shouqin Tian ◽  
Wenjuan Yang ◽  
Xiaoxia Wang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Specific Surface ◽  
Surface Area ◽  
Ammonium Perchlorate ◽  
Specific Surface Area ◽  
Large Specific Surface Area ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Nano Structures ◽  
Hierarchical Porous

Sub-micro hierarchical porous Co3O4 dodecahedra with a large specific surface area (106.11 m2 g−1) were synthesized by the thermolysis of ZIF-67 at a low temperature of 268 °C assisted by ammonium perchlorate (AP).

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 zeolite from perlite waste — Part II: characteristics of the products

2014 ◽  
Vol 32 (4) ◽  
pp. 526-532 ◽  
Author(s):  
Magdalena Król ◽  
Justyna Morawska ◽  
Włodzimierz Mozgawa ◽  
Waldemar Pichór
Keyword(s):  
Phase Composition ◽  
Low Temperature ◽  
Specific Surface ◽  
Cation Exchange ◽  
Cation Exchange Capacity ◽  
Exchange Capacity ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Synthesis Parameters ◽  
Autogenous Pressure

AbstractThe paper investigates the properties of sodium zeolites synthesized using the hydrothermal method under autogenous pressure at low temperature with NaOH solutions of varying concentrations. During this modification, zeolites X, Na-P1 and hydroxysodalite were synthesized. The synthesis parameters, and thus, phase composition of resulting samples, significantly affected the specific surface area (SSA) and cation exchange capacity (CEC). SSA increased from 2.9 m2/g to a maximum of 501.2 m2/g, while CEC rose from 16 meq/100 g to a maximum of 500 meq/100 g. The best properties for use as a sorbent were obtained for perlite waste modified with 4.0 M NaOH at 70 °C or 80 °C.

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