The diffusion of aluminium and gallium in zinc oxide

1969 ◽  
Vol 22 (2) ◽  
pp. 325 ◽  
Author(s):  
VJ Norman
Keyword(s):  
Zinc Oxide ◽  
Diffusion Coefficient ◽  
Chemical Method ◽  
Surface Concentration ◽  
Activation Energies ◽  
Temperature Range ◽  
Polycrystalline Zinc ◽  
Substitutional Diffusion ◽  
Oxide Crystals ◽  
Limiting Value

Solubilities and rates of substitutional diffusion of aluminium and gallium in polycrystalline zinc oxide have been determined in the temperature range 750-1000� by a chemical method previously described. The solubility of aluminium in zinc oxide, expressed in ions cm-3, is given by the expression n = 1.0 x 1023exp(-1.08k-1T-1), and the solubility of gallium by n = 2.7 x 1021exp(-0.59k-1T-1), where the activation energies are expressed in eV. The rates of diffusion of both aluminium and gallium were found to be dependent on surface concentration up to a limiting value, at which the diffusion coefficient of aluminium is D = 5.3 x 10-2 exp(-2.74k-1T-1) cm2 sec-1, and that of gallium is D = 3.6 x 104 exp(-3.75k-1T-1) cm2 sac-1. ��� It is shown that supersaturation of both aluminium and gallium in the zinc oxide crystals occurs above 800�.

The effect of doping on the non-stoicheiometry of zinc oxide

1968 ◽  
Vol 21 (2) ◽  
pp. 299 ◽  
Author(s):  
VJ Norman
Keyword(s):  
Electrical Conductivity ◽  
Zinc Oxide ◽  
Diffusion Coefficient ◽  
Electron Concentration ◽  
Direct Measure ◽  
Chemical Methods ◽  
Polycrystalline Zinc ◽  
Substitutional Diffusion ◽  
Electron Deficiency ◽  
Effect Of Doping

Chemical methods previously described have been applied, with minor modifications, to the analysis of the non-stoicheiometry of polycrystalline zinc oxide which had been doped with gallium or lithium by heating in air. It is shown that, under these conditions, the methods provide a direct measure of electron concentration, and of the concentration of the impurifying element occupying substitutional positions in the zinc oxide lattice. Under the specified conditions of doping, electron concentrations ranged from 6.9 x 1018 electrons cm-3 for samples doped with gallium to an electron deficiency of 2.6 x 1018 holes cm-3 for lithium-doped samples. The effect of doping on the electrical conductivity is briefly shown. The methods provide a convenient and accurate means of determining rates of substitutional diffusion in zinc oxide. The diffusion coefficient of gallium at 950� was calculated to be 4.7 x 10-15 cm2 sec-1.

Diffusion of Nb in Nb-H Alloys

2005 ◽  
Vol 237-240 ◽  
pp. 346-351
Author(s):  
Yoshihiro Yamazaki ◽  
Takahiro Iida ◽  
Yoshiaki Iijima ◽  
Yuh Fukai
Keyword(s):  
Diffusion Coefficient ◽  
Activation Energies ◽  
The Self ◽  
Exponential Factor ◽  
Temperature Range ◽  
Self Diffusion ◽  
Diffusion Enhancement ◽  
The Difference ◽  
Self Diffusion Coefficient ◽  
Hydrogen Dissolution

Self-diffusion coefficient of 95Nb in NbHx alloys (x=0.05,0.25 and 0.3) has been determined in the temperature range from 823 to 1323 K by using a serial sputter-microsectioning technique. The self-diffusion coefficient of Nb in the NbHx alloys are larger than that in Nb, suggesting that vacancies are formed by hydrogen dissolution, that is, the formation of hydrogen-induced vacancies. The value of the pre-exponential factor for the Nb diffusion in the NbH0.05 alloy is five times larger than that in Nb, while the difference in the activation energies between the NbH0.05 alloy and pure Nb is small. The self-diffusion enhancement in the NbH0.05 alloy is mainly caused by lowering in vibrational frequencies of atoms in the immediate neighborhood of hydrogen-induced vacancies.

Self-diffusion in Molten Zinc Bromide

1963 ◽  
Vol 18 (12) ◽  
pp. 1247-1248 ◽  
Author(s):  
Carl-Axel Sjöblom
Keyword(s):  
Diffusion Coefficient ◽  
Experimental Error ◽  
Activation Energies ◽  
Zinc Bromide ◽  
Molten Zinc ◽  
Temperature Range ◽  
Self Diffusion ◽  
Bromide Ion

The diffusion coefficient of the bromide ion in molten zinc bromide has been measured in the temperature range 415—547°C. The results can be described by the following equation1:D = 0.114 exp [ — (17 050 ± 500) /R T].D is expressed in cm2s-1, R in cal · mole-1 · degree-1 and T in degrees KELVIN. A comparison with earlier measurements 2 shows that the activation energies of cation and anion are equal within the experimental error, and that D- is considerably greater than D+ in the whole temperature range.

The Vulcanization of Elastomers. VII. The Vulcanization of Natural Rubber with Thiuram Disulfides. Part IV

1957 ◽  
Vol 30 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Walter Scheele ◽  
Peter Stange
Keyword(s):  
Zinc Oxide ◽  
Natural Rubber ◽  
Constant Temperature ◽  
Rate Constants ◽  
Experimental Error ◽  
Oxide Content ◽  
Oxide Crystals ◽  
Kinetics Of ◽  
Limiting Value

Abstract The present paper deals with the kinetics of the thiuram vulcanization at varying thiuram disulfide concentrations as well as with the influence of the zinc oxide content upon vulcanization at constant temperature (120° C). It was found : 1. The limiting value of dithiocarbamate formation of 66 mole per cent relative to the amount of thiuram disulfide used is—within wide limits—independent of the initial thiuram disulfide concentration. 2. At constant thiuram disulfide concentration the limiting value of dithiocarbamate formation is unchanged when the zinc oxide content is successively increased. 3. Changing the zinc oxide content while the thiuram disulfide concentration is kept constant exerts an influence on the kinetics of the decrease of thiuram as well as on the increase of dithiocarbamate. The rate constants of both reactions increase. 4. It is concluded from these results that in all probability vulcanization is initiated on the surface of the zinc oxide crystals. 5. Even in stocks containing as much as 40 g. zinc oxide per hundred g. of compounds, the limiting value of dithiocarbamate formation remains unchanged. This was verified by the analysis of vulcanizates after extremely long cure times. The average limiting value of two experiments after 24 hours of cure was 65 mole per cent which corresponds to a two-thirds reaction within the experimental error.

scholarly journals Effect of Temperature on Electrical Conductivity of Zinc Oxide- Polyvinyl Alcohol Nanocomposites

2020 ◽  
Vol 9 (4) ◽  
pp. 1863-1865
Keyword(s):  
Zinc Oxide ◽  
Polyvinyl Alcohol ◽  
Zno Nanoparticles ◽  
Activation Energies ◽  
Dc Conductivity ◽  
Effect Of Temperature ◽  
Characterization Methods ◽  
Temperature Range ◽  
Different Temperatures ◽  
Lower Temperature

A set of zinc oxide (ZnO)/polyvinyl alcohol (PVA) nanocomposites were prepared by mixing presynthesized zinc oxide nanoparticles and polyvinyl alcohol (PVA) in different weight percentages with solution casting technique.Different characterization methods are carried out to determine the material properties. The effects of ZnO nanoparticles loading level on electrical properties of the nanocomposites were investigated in details. The intermolecular interactions within the polymer nanocomposites were explored by FTIR and XRD. The formation of nanocomposites and changes were investigated by SEM analysis.It showed that ZnO nanoparticles were homogeneously dispersed throughout the whole polymeric matrix. DC conductivity was measured in the temperature range 70-300K and it obeys Arrhenius relation. Activation energies were evaluated from Arrhenius plots for all compositions. The samples show a semiconductor-like behavior in regions I (300-130 K) and II (130-70K).The activation energies are smaller at lower temperature range as compared to higher temperature range. The change in conduction mechanism arises at different temperatures, which are feature of the samples. As the ratio of ZnO to polymer changes these switching positions are shifted to upper temperatures. All the composites obey the Arrhenius equation for the conductivity mechanism which confirms that the nanocomposites are thermally activated. The dc conductivity of all the samples follows a simple hoping type of charge conduction method. This is evident from Fourier Transform Infrared Spectroscopy (FTIR) studies.

scholarly journals High-Temperature Deformation of Naturally Aged 7010 Aluminum Alloy

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 581
Author(s):  
Abdulhakim A. Almajid
Keyword(s):  
Activation Energy ◽  
Aluminum Alloy ◽  
High Temperature ◽  
Threshold Stress ◽  
Activation Energies ◽  
Temperature Deformation ◽  
High Temperature Range ◽  
Temperature Range ◽  
True Activation Energy ◽  
Two Temperatures

This study is focused on the deformation mechanism and behavior of naturally aged 7010 aluminum alloy at elevated temperatures. The specimens were naturally aged for 60 days to reach a saturated hardness state. High-temperature tensile tests for the naturally aged sample were conducted at different temperatures of 573, 623, 673, and 723 K at various strain rates ranging from 5 × 10−5 to 10−2 s−1. The dependency of stress on the strain rate showed a stress exponent, n, of ~6.5 for the low two temperatures and ~4.5 for the high two temperatures. The apparent activation energies of 290 and 165 kJ/mol are observed at the low, and high-temperature range, respectively. These values of activation energies are greater than those of solute/solvent self-diffusion. The stress exponents, n, and activation energy observed are rather high and this indicates the presence of threshold stress. This behavior occurred as a result of the dislocation interaction with the second phase particles that are existed in the alloy at the testing temperatures. The threshold stress decreases in an exponential manner as temperature increases. The true activation energy was computed by incorporating the threshold stress in the power-law relation between the stress and the strain. The magnitude of the true activation energy, Qt dropped to 234 and 102 kJ/mol at the low and high-temperature range, respectively. These values are close to that of diffusion of Zinc in Aluminum and diffusion of Magnesium in Aluminum, respectively. The Zener–Hollomon parameter for the alloy was developed as a function of effective stress. The data in each region (low and high-temperature region) coalescence in a segment line in each region.

scholarly journals Luminescence of Zinc Oxide Crystals Controlled by Electrode Potential and Electrochemical Reactions

1972 ◽  
Vol 57 (3) ◽  
pp. 1026-1032 ◽  
Author(s):  
Günter Petermann ◽  
Helmut Tributsch ◽  
Roberto Bogomolni
Keyword(s):  
Zinc Oxide ◽  
Electrode Potential ◽  
Electrochemical Reactions ◽  
Oxide Crystals

Anomalous thermal desorption from polycrystalline zinc oxide films

1984 ◽  
Vol 121 (3) ◽  
pp. L85-L88 ◽  
Author(s):  
T.L. Tansley ◽  
C.P. Foley ◽  
D.F. Neely
Keyword(s):  
Zinc Oxide ◽  
Thermal Desorption ◽  
Oxide Films ◽  
Zinc Oxide Films ◽  
Polycrystalline Zinc
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