Synthesis of ZnO Nanostructures by Thermal Evaporation on Graphite

2007 ◽  
Vol 124-126 ◽  
pp. 575-578
Author(s):  
Kon Bae Lee ◽  
Ki Seop Cho ◽  
Won Hee Lee ◽  
Hoon Kwon
Keyword(s):  
Temperature Region ◽  
Thermal Evaporation ◽  
Metal Catalyst ◽  
Zno Nanostructures ◽  
Zno Nanowire ◽  
Zno Particles ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Zno Powder ◽  
Lower Temperature Region

ZnO nanostructures have been synthesized on graphite substrates by thermal evaporation of ZnO powder without a metal catalyst at a temperature of 1300. The colors of the as-synthesized products gradually change from white and brown to gray as the distance from the source material increases. ZnO particles were formed at higher temperature region. ZnO particles gradually changed into ZnO nanowire as the temperature decreased. Finally, ZnO nanowires disappeared completely and only Zn particles were observed at lower temperature region.

scholarly journals Electrical Conduction in Some Nickelates

2011 ◽  
Vol 8 (1) ◽  
pp. 83-90
Author(s):  
Kanchan Gaur ◽  
Shalini Shalini ◽  
Satyendra Singh
Keyword(s):  
Temperature Region ◽  
Conduction Mechanism ◽  
Charge Carriers ◽  
Band Model ◽  
Orthorhombic Unit Cell ◽  
Dominant Conduction Mechanism ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Lower Temperature Region ◽  
Band Type

This paper reports electrical conductivity (s) and Seebeck coefficient (s) study on rare-earth nickelates RNiO3 where R = Nd, Sm and Eu in the temperature range 400-1200 K. They have orthorhombic unit cell. The majority charge carriers are holes throughout the measurement. Both s and S variations show three regions. In higher temperature region (Above 1000K) dominant conduction mechanism is intrisic band type whereas below this temperature, hopping of holes from Ni3+ to Ni2+ centres takes place. In lower temperature region, the electrical conductions is taken over by acceptor type impurities. The conduction mechanism is explained on the basis of every band model. Break temperatures as well as mobility have also been evaluated.

Comparative study of in situ polymerized waterborne polyurethane/nano-silica composites and polyethersiloxanediol-modified polyurethane

2016 ◽  
Vol 30 (1) ◽  
pp. 107-120 ◽  
Author(s):  
Han Yan-ting ◽  
Cheng Zheng ◽  
Dong Wei ◽  
Zhang Fan ◽  
Xin Zhong-yin
Keyword(s):  
Temperature Region ◽  
Film Formation ◽  
Waterborne Polyurethane ◽  
Nano Silica ◽  
Elongation At Break ◽  
Lower Elongation ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Lower Temperature Region

The waterborne polyurethane/nano-silica composites (WPU/nano-silica, WPUS) and WPU composites modified by polyethersiloxanediol (WPUPES) were prepared, respectively. The properties of WPUS and WPUPES were investigated by various characterizations. The results showed both WPUS and WPUPES had better waterproof property and thermal stability than neat WPU. However, WPUPES has a lower elongation at break due to the higher micro-phase separation. This is ascribed to migration and aggregation of siloxane segments during the film formation. The tensile strength of WPUS was higher than that of neat WPU. This is attributed to the WPUS chain restriction caused by the network and physical cross-link points of nano-silica particles. Moreover, the glass transition temperature of WPUS shifted to higher temperature region while that of WPUPES shifted to lower temperature region.

Study of averaged collision strength of non-Maxwellian distribution in plasma

2017 ◽  
Vol 31 (23) ◽  
pp. 1750213
Author(s):  
Jian He ◽  
Qingguo Zhang
Keyword(s):  
Temperature Region ◽  
Electronic Energy ◽  
Atmospheric Plasma ◽  
Maxwellian Distribution ◽  
Kappa Distribution ◽  
Collision Strength ◽  
Higher Temperature ◽  
The Difference ◽  
Lower Temperature ◽  
Lower Temperature Region

In this paper, kappa distribution of electronic energy is discussed for non-Maxwellian distribution. Taking silicon III 189.2 nm line in solar atmospheric plasma as an example, we discuss the kappa distribution and the Maxwellian distribution when temperature varies from [Formula: see text] K to [Formula: see text] K, and we calculate the averaged collision strengths of the kappa distribution and the Maxwellian distribution. Results indicate that the kappa distribution is close to the Maxwellian distribution with the increase of parameter [Formula: see text], and the difference of the averaged collision strength between the kappa distribution and the Maxwellian distribution is not very large in the higher temperature region from [Formula: see text] K to [Formula: see text] K, while that is large in the lower temperature region from [Formula: see text] K to [Formula: see text] K. This discussion will be significant in study of plasma quantitatively.

Radiolysis of ortho- and meta-terphenyl

1968 ◽  
Vol 46 (20) ◽  
pp. 3129-3136 ◽  
Author(s):  
A. W. Boyd ◽  
M. Tomlinson
Keyword(s):  
Temperature Region ◽  
Pulse Frequency ◽  
Fast Neutrons ◽  
Reaction Sequence ◽  
Radiolytic Decomposition ◽  
Higher Temperature ◽  
A Chain ◽  
Lower Temperature ◽  
Lower Temperature Region ◽  
Intermittent Irradiation

A summary is presented of a series of investigations of the radiolytic decomposition of ortho- and meta-terphenyl by reactor radiation with varying proportions of fast neutrons and gamma rays and of meta-terphenyl by 1.3 MeV electrons in the temperature range 100 to 450 °C with radiation intensities from 0.01 to 2 Mrads/s. The observations indicate two regions of radiolytic decomposition with a transition zone at 350 to 400 °C. In the lower temperature region, G(decomposition) varied little with temperature, increased with linear energy transfer (l.e.t.), was independent of intensity, and yielded mainly high boiling products. Particular attention was given to the high temperature region, where G(decomposition) increased rapidly with temperature, was independent of l.e.t., was greater at low intensities than at high intensities, increased with increased pulse frequency for intermittent irradiation, and yielded a greater proportion of benzene and biphenyl. Thermally initiated reaction appeared unimportant except in the absence of radiation. A reaction sequence is given which accounts for these observations in terms of reactions of radical precursors and radicals of the cyclohexadienyl type. A chain reaction occurs in the higher temperature region.

Low-Temperature Growth of Flower-Shaped UV-Emitting ZnO Nanostructures on Steel Alloy by Thermal Evaporation

2007 ◽  
Vol 7 (12) ◽  
pp. 4421-4427 ◽  
Author(s):  
Ahmad Umar ◽  
S. H. Kim ◽  
J. H. Kim ◽  
Y. K. Park ◽  
Y. B. Hahn
Keyword(s):  
Thermal Evaporation ◽  
Hexagonal Phase ◽  
Zinc Powder ◽  
Hexagonal Structure ◽  
Structural Defects ◽  
Metal Catalyst ◽  
Steel Alloy ◽  
Zno Nanostructures ◽  
Uv Emission ◽  
Wurtzite Hexagonal Phase

Flower-shaped ZnO nanostructures, containing the triangular-shaped petals (sharpened tips and wider bases) have been achieved by simple thermal evaporation of high purity metallic zinc powder in the presence of oxygen at 440 °C on steel alloy substrate without the use of metal catalyst or additives. Detailed structural studies confirm that the obtained flower-shaped nanostructures are single crystalline and possesses a wurtzite hexagonal structure, grown along the c-axis in the [0001] direction. Raman and room temperature photoluminescence analysis substantiate a wurtzite hexagonal phase with a good crystal quality and a strong UV emission at 378 nm, respectively, indicating few or no structural defects. Additionally, a detailed possible growth mechanism has also been discussed.

Effects of Microstructure on the Electrical Conductivity of SrCo0.8Fe0. 2O3_δ

1999 ◽  
Vol 575 ◽  
Author(s):  
K. Zhang ◽  
M. Miranova ◽  
Y. L. Yang ◽  
A. J. Jacobson ◽  
K. Salama
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Size Effect ◽  
Temperature Region ◽  
Grain Size Effect ◽  
Average Grain Size ◽  
Lower Temperature ◽  
Lower Temperature Region ◽  
Test Temperature Range

ABSTRACTThe effect of microstructure on the electrical conductivity of SrCO0.8Fe0.2O3_δ (SCFO) was investigated in air using a four-point dc method. In the test temperature range of 200 to 900 °C, the electrical conductivity of this material was observed to increase with the increase of the average grain size in the lower temperature region where the conductivity increases with the increase of the temperature. The activation energy is decreased with the increase of the grain size in this region, 0.04 ± 0.004 ev for 4.1μm sample and 0.01 ± 0.001 ev for 14.8 μm sample. When temperature is further increased, the conductivity of this material decreases with the increase of the temperature, and the grain size effect becomes less noticeable.

Steady State Conduction Behaviour of Liquid Crystalline Polyurethane

2013 ◽  
Vol 856 ◽  
pp. 210-214
Author(s):  
Jitender Kumar Quamara ◽  
Satish Kumar Mahna ◽  
Sohan Lal ◽  
Pushkar Raj
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
Temperature Region ◽  
Liquid Crystalline ◽  
Ionic Conduction ◽  
Schottky Type ◽  
Order Of Magnitude ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Type Conduction

The steady state measurements in Liquid crystalline polyurethane (LCPU) have been investigated for different fields (4 - 45 kV/cm) and temperatures (50°-220°C). The nature of conduction processes has been determined by estimating ion jump distances (a) and Schottky coefficients. The order of magnitude of a in the temperature region 150°C and below does not seem to support an ionic conduction. However the magnitude of a at higher temperatures (180°C and above) indicates the possibility of ionic conduction. There is a definite possibility of a Schottky type conduction at lower temperature and a Poole Frankel type conduction at higher temperature (100°C). The activation energy associated with the high temperature region lies between 0.26 eV and 0.65 eV depending on the field whereas in the low temperature region the activation energy lies between 0.82 eV and 0.95 eV depending on the applied electric field. The dual slopes in the log I versus 1/T curves indicate the presence of more than one type of trapping levels.

scholarly journals Study on Gasification of Coal under Pressure Hydrogasification at Lower Temperature Region

1981 ◽  
Vol 60 (1) ◽  
pp. 31-38
Author(s):  
Mitsuo KOBAYASHI ◽  
Yuzo TODA ◽  
Tsutomu KATO ◽  
Hitohisa KATO ◽  
Mamoru KAIHO ◽  
...  
Keyword(s):  
Temperature Region ◽  
Lower Temperature ◽  
Lower Temperature Region

scholarly journals The highly efficient removal of HCN over Cu8Mn2/CeO2 catalytic material

RSC Advances ◽  
2021 ◽  
Vol 11 (15) ◽  
pp. 8886-8896
Author(s):  
Zhihao Yi ◽  
Jie Sun ◽  
Jigang Li ◽  
Yulin Yang ◽  
Tian Zhou ◽  
...  
Keyword(s):  
Temperature Region ◽  
Efficient Removal ◽  
Highly Efficient ◽  
Effective Removal ◽  
Catalytic Material ◽  
Lower Temperature ◽  
Lower Temperature Region

In this work, porous CeO2 flower-like spheres loaded with bimetal oxides were prepared to achieve effective removal of HCN in the lower temperature region of 30–150 °C.

The homogeneous thermal conversion of methane to higher hydrocarbons in the presence of ethylene

1990 ◽  
Vol 68 (8) ◽  
pp. 1401-1407 ◽  
Author(s):  
Alain R. Bossard ◽  
Margaret H. Back
Keyword(s):  
Temperature Region ◽  
Thermal Conversion ◽  
Methyl Radical ◽  
Chain Propagation Reaction ◽  
Volatile Products ◽  
Conversion Of Methane ◽  
Higher Hydrocarbons ◽  
Lower Temperature ◽  
Low Pressures ◽  
Lower Temperature Region

The pyrolysis of mixtures of methane and ethylene has been studied over the temperature range 774–853 K at total pressures below atmospheric to explore the effectiveness of ethylene as a catalyst for conversion of methane to higher hydrocarbons. Pyrolysis of ethylene alone at these temperatures yields ethane, propylene, butene-1, and butadiene as the major volatile products. In the lower temperature region the addition of methane increased the rate of production of ethane through the chain propagation reaction,[Formula: see text]thus effecting the conversion of methane to ethane. The rates of formation of butene-1 and butadiene were not appreciably altered and that of propylene was increased only at low pressures of ethylene. At higher temperatures methane caused a substantial increase in the rate of production of propylene, the result of the increasing importance of the methyl radical in the propagation reactions. Thus ethylene can efficiently convert methane to ethane or to propylene depending on the temperature of the reaction. Addition of small quantities of butene-1, which acted as a secondary initiator, to the mixtures increased considerably the overall rate of the conversion of methane. A mechanism is discussed which accounts for the main features of the reactions. Keywords: methane, ethylene, kinetics, pyrolysis, catalysis.

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