Nanosized Silicon Carbide Obtained from Rice Husks

2010 ◽  
Vol 159 ◽  
pp. 153-156 ◽  
Author(s):  
Dimitar D. Radev ◽  
Ivan Uzunov
Keyword(s):  
Thermal Decomposition ◽  
Silicon Carbide ◽  
Low Temperatures ◽  
Xrd Analysis ◽  
Rice Husks ◽  
Rice Hulls ◽  
High Temperature Materials ◽  
Thermal Regimes ◽  
Scale Properties ◽  
Pure Sio2

Two ways to obtain nanosized silicon carbide (SiC) powders from the products of thermal decomposition of rice hulls and posterior thermal and chemical treatment of SiO2-C precursors are shown in the present paper. The reagents and products were analyzed using BET, DTA, IR, XRD and SEM/TEM. Precursors obtained from rice husks containing pure SiO2 and a controlled SiO2-C ratio were used for the synthesis of SiC. The synthesis of SiC proceeded for 30-45 min in a graphite heater furnace under protective Ar atmosphere at relatively low temperatures (1450oC-1550oC). Nanosized dimensions of reagents obtained from rice husks and their high activity allow obtaining SiC in relatively milder thermal regimes. TEM and XRD analysis revealed synthesis of nanostructured mainly β-SiC with a mean crystallite size of 40-100 nm. Due to their purity and nano-scale properties, the products obtained are appropriate for production of bulk SiC or design of SiC–based ultra high-temperature materials using the methods of powder metallurgy.

Analysis of nitromethane thermal decomposition at low temperatures

2013 ◽  
Vol 54 (2) ◽  
pp. 131-138 ◽  
Author(s):  
N. M. Kuznetsov ◽  
Yu. P. Petrov ◽  
S. V. Turetskii
Keyword(s):  
Thermal Decomposition ◽  
Low Temperatures

scholarly journals Effect of TiO2 Nanoparticles on Physical and Mechanical Properties of Cement at Low Temperatures

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Li Wang ◽  
Hongliang Zhang ◽  
Yang Gao
Keyword(s):  
Mechanical Properties ◽  
Low Temperatures ◽  
Cement Hydration ◽  
Setting Time ◽  
Physical And Mechanical Properties ◽  
Xrd Analysis ◽  
Cementitious Materials ◽  
Strength Test ◽  
Hydration Degree ◽  
Time Test

Low temperature negatively affects the engineering performance of cementitious materials and hinders the construction productivity. Previous studies have already demonstrated that TiO2 nanoparticles can accelerate cement hydration and enhance the strength development of cementitious materials at room temperature. However, the performance of cementitious materials containing TiO2 nanoparticles at low temperatures is still unknown. In this study, specimens were prepared through the replacement of cement with 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, and 5 wt.% TiO2 nanoparticles and cured under temperatures of 0°C, 5°C, 10°C, and 20°C for specific ages. Physical and mechanical properties of the specimens were evaluated through the setting time test, compressive strength test, flexural strength test, hydration degree test, mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) analysis, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) in order to examine the performance of cementitious materials with and without TiO2 nanoparticles at various curing temperatures. It was found that low temperature delayed the process of cement hydration while TiO2 nanoparticles had a positive effect on accelerating the cement hydration and reducing the setting time in terms of the results of the setting time test, hydration degree test, and strength test, and the specimen with the addition of 2 wt.% TiO2 nanoparticles showed the superior performance. Refined pore structure in the MIP tests, more mass loss of CH in TGA, intense peak appearance associated with the hydration products in XRD analysis, and denser microstructure in SEM demonstrated that the specimen with 2 wt.% TiO2 nanoparticles exhibited preferable physical and mechanical properties compared with that without TiO2 nanoparticles under various curing temperatures.

scholarly journals Synthesis of Silicon Carbide from Coked Rice Hulls and Coked Bamboos.

1995 ◽  
Vol 111 (8) ◽  
pp. 559-563 ◽  
Author(s):  
Hironori HAMASAKI ◽  
Hiroshi TATEYAMA ◽  
Kunio KIMURA ◽  
Kazuhiko JINNAI
Keyword(s):  
Silicon Carbide ◽  
Rice Hulls

Structural refinement of Nd[Fe(CN)6]·4H2O and study of NdFeO3 obtained by its oxidative thermal decomposition at very low temperatures

2005 ◽  
Vol 178 (3) ◽  
pp. 847-854 ◽  
Author(s):  
M. Carolina Navarro ◽  
Elisa V. Pannunzio-Miner ◽  
Silvina Pagola ◽  
M. Inés Gómez ◽  
Raúl E. Carbonio
Keyword(s):  
Thermal Decomposition ◽  
Low Temperatures ◽  
Structural Refinement

The photochemical and thermal decompositions of hydrogen sulphide

1953 ◽  
Vol 216 (1126) ◽  
pp. 344-361 ◽  
Keyword(s):  
Thermal Decomposition ◽  
Quantum Yield ◽  
Hydrogen Sulphide ◽  
Low Temperatures ◽  
Room Temperature ◽  
Large Fraction ◽  
Kcal Mole ◽  
Hydrogen Atoms ◽  
Photochemical Decomposition ◽  
Bimolecular Mechanism

The photochemical decomposition of hydrogen sulphide has been investigated at pressures between 8 and 550 mm of mercury and at temperatures between 27 and 650° C, using the narrow cadmium line ( λ 2288) and the broad mercury band (about λ 2550). At room temperature the quantum yield increases with pressure from 1.09 at 30 mm to 1.26 at 200 mm. Above 200 mm pressure there was no further increase in the quantum yield. Temperature had little effect on the quantum yield at λ 2550, but there was a marked increase in the rate of hydrogen production between 500 and 650° C with 2288 Å radiation. This may have been caused by the decomposition of excited hydrosulphide radicals. The results are consistent with a mechanism involving hydrogen atoms and hydrosulphide radicals. The mercury-photosensitized reaction is less efficient than the photochemical decomposition, the quantum yield being only about 0.45. The efficiency increased with temperature and approached unity at high temperatures and pressures. This agrees with the suggestion that a large fraction of the quenching collisions lead to the formation of Hg ( 3 P 0 ) atoms. The thermal decomposition is heterogeneous at low temperatures and becomes homogeneous and of the second order at 650° C. The experimental evidence suggests the bimolecular mechanism 2H 2 S → 2H 2 + S 2 . The activation energies are 25 kcal/mole (heterogeneous) and 50 kcal/mole (homogeneous).

The Effect of the Pyrolysis Furnace Type on the Yield of Silicon Carbide Whiskers Produced from Rice Husks

2011 ◽  
Vol 312-315 ◽  
pp. 346-351 ◽  
Author(s):  
Reza Eslami Farsani ◽  
Farshad Akhlaghi ◽  
Arman Sedghi
Keyword(s):  
Silicon Carbide ◽  
Maximum Yield ◽  
Horizontal Tube ◽  
Vertical Tube ◽  
Tube Furnace ◽  
Rice Husks ◽  
Silicon Carbide Whiskers ◽  
Pyrolysis Furnace ◽  
Vertical Tube Furnace ◽  
Lower Production

The production of silicon carbide whiskers (SiCw) by using rice husks has attracted a considerable attention due to a lower production cost as compared to the other processing routs. In the present investigation, the effect of pyrolysis furnace type (vertical tube, horizontal tube, and graphite chamber) on the yield of the resultant SiCw was investigated. It was concluded that the maximum yield was achieved by using a horizontal tube furnace whereas the minimum yield was obtained in a vertical tube furnace. These results were rationalized in terms of the different conditions for the evacuation of the produced gases from the different pyrolysis furnaces.

THE THERMAL DECOMPOSITION OF HYDROGEN PEROXIDE VAPOUR. II.

1947 ◽  
Vol 25b (2) ◽  
pp. 135-150 ◽  
Author(s):  
Paul A. Giguère
Keyword(s):  
Activation Energy ◽  
Hydrogen Peroxide ◽  
Thermal Decomposition ◽  
Low Temperatures ◽  
Hydrocyanic Acid ◽  
Quartz Surface ◽  
First Order ◽  
Acid Washing ◽  
Reaction Vessels ◽  
Low Pressures

The decomposition of hydrogen peroxide vapour has been investigated at low pressures (5 to 6 mm.) in the temperature range 50° to 420 °C., for the purpose of determining the effect of the nature and treatment of the active surfaces. The reaction was followed in an all-glass apparatus and, except in one case, with one-litre round flasks as reaction vessels. Soft glass, Pyrex, quartz, and metallized surfaces variously treated were used. In most cases the decomposition was found to be mainly of the first order but the rates varied markedly from one vessel to another, even with vessels made of the same type of glass. On a quartz surface the decomposition was preceded by an induction period at low temperatures. Fusing the glass vessels slowed the reaction considerably and increased its apparent activation energy; this effect was destroyed by acid washing. Attempts to poison the surface with hydrocyanic acid gave no noticeable result. The marked importance of surface effects at all temperatures is considered as an indication that the reaction was predominantly heterogeneous under the prevailing conditions. Values ranging from 8 to 20 kcal. were found for the apparent energy of activation. It is concluded that the decomposition of hydrogen peroxide vapour is not very specific as far as the nature of the catalyst is concerned.

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