Effect of Temperature on the Course of Thiuram-Accelerated Sulfur Vulcanization

1976 ◽  
Vol 49 (5) ◽  
pp. 1193-1199 ◽  
Author(s):  
V. Ducháček
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Activation Energies ◽  
Effect Of Temperature ◽  
Crosslinking Reaction ◽  
Curing Process ◽  
Sulfur Vulcanization ◽  
Good Accordance

Abstract These results confirm the validity of our theory of thiuram-accelerated sulfur vulcanization supposing that ZnDMDC arising from TMTD and zinc oxide is the actual accelerator in this type of curing system. The formation of ZnDMDC from TMTD during the curing process affects particularly the slow crosslinking reaction. Therefore, the activation energy of slow crosslinking is in very good accordance with the activation energy of TMTD decrease, and its value differs significantly from the activation energies of fast crosslinking and degradation. Simultaneously, these facts answer the question why the shape of the cure curves depends strongly on the temperature of cure.

scholarly journals Photocatalytic Degradation of Textile Dyeing Wastewater Using Titanium Dioxide and Zinc Oxide

2008 ◽  
Vol 5 (2) ◽  
pp. 219-223 ◽  
Author(s):  
Abbas J. Attia ◽  
Salih H. Kadhim ◽  
Falah H. Hussein
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Titanium Dioxide ◽  
Photocatalytic Degradation ◽  
Irradiation Time ◽  
Effect Of Temperature ◽  
Dyeing Wastewater ◽  
Textile Dyeing ◽  
Textile Factory ◽  
Textile Dyeing Wastewater

Photodegradation of a real textile dyeing wastewater taken from Hilla textile factory in Babylon Governorate, Iraq have been investigated. Photocatalytic degradation was carried out over suspensions of titanium dioxide or zinc oxide under ultraviolet irradiation. Photodegradation percentage was followed spectrophometrically by the measurements of absorbance at λmax equal to 380 nm. The rate of photodegradation increased linearly with time of irradiation when titanium dioxide or zinc oxide was used. A maximum color removal of 96% was achieved after irradiation time of 2.5 hours when titanium dioxide used at 303K and 82% color reduction was observed when zinc oxide used for the same period and at the same temperature. The effect of temperature on the efficiency of photodegradation of dyestuff was also studied. The activation energy of photodegradation was calculated and found to be equal to 21 ± 1 kJ mol-1 on titanium dioxide and 24 ± 1 kJ mol-1 on zinc oxide.

INFLUENCE OF THE CROSSLINK STRUCTURE ON THE ACTIVATION ENERGY CALCULATED UNDER THERMO-OXIDATIVE CONDITIONS

2018 ◽  
Vol 91 (1) ◽  
pp. 205-224 ◽  
Author(s):  
Richard J. Pazur ◽  
T. Mengistu
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
High Temperature ◽  
Oxidation Process ◽  
Activation Energies ◽  
Structure Stability ◽  
Temperature Oxidation ◽  
Network Chain ◽  
Temperature Activation ◽  
Sulfur Donor

ABSTRACT A series of six carbon black reinforced brominated poly(isobutylene-co-isoprene) (BIIR) compounds has been developed varying only in cure system type: sulfur, sulfur donor, zinc oxide, peroxide, phenolic resin, and ionic. Compounds were aged from room temperature up to 115 °C, and hardness, mechanical properties, and network chain density were measured. Non-Arrhenius behavior was observed due to data curvature from 70 to 85 °C. The oxidation process was adequately described by assigning low (23–85 °C) and high (85–115 °C) temperature regimes. Heterogeneous aging due to diffusion limited oxygen (DLO) occurred for heat aging above 85 °C, and all measured responses except tensile strength were strongly affected, causing lower activation energies. The activation energy for the high temperature oxidation process is in the range of 107 to 133 kJ/mol in the following ascending order: zinc oxide, ionic, sulfur donor, sulfur, peroxide, and resin. The midpoint of the high temperature activation energies is of the same order as the BIIR and poly(isobutylene) elastomers. The low temperature activation energy is in the range of 55–60 kJ/mol and is likely due to a combination of oxidative chain scission (crosslink density loss) and crosslinking recombination (network building) reactions. Apart from the crosslink structure stability, the presence of unsaturation along the polymer chain after vulcanization affects the high temperature activation energy.

scholarly journals Arrhenius Plot Analysis of the Temperature Effect on the Biodegradation Rate of 2-chloro-4-nitrophenol

2020 ◽  
Vol 8 (2) ◽  
pp. 219
Author(s):  
Mohd Yunus Shukor
Keyword(s):  
Activation Energy ◽  
Growth Rate ◽  
Regression Analysis ◽  
Arrhenius Plot ◽  
Activation Energies ◽  
Effect Of Temperature ◽  
Biodegradation Rate ◽  
Arrhenius Model ◽  
Plot Analysis ◽  
First Time

Several models are available to determine the effect of temperature on the growth rate of microorganisms on substrates. An example is Arrhenius model, which is very popular because it has few parameters. For the first time, a discontinuous chevron-like graph of apparent activation energy based on the Arrhenius plot on the growth of 2-chloro-4-nitrophenol by Cupriavidus sp. is reported. The plot of ln mm against 1/T shows a discontinuous chevron-like graph for the entire investigated temperature range with an inflection at 27.75°C. This indicates that the existence of 2 activation energies for growth on 2-chloro-4-nitrophenol ranges from 20 to 40°C. Furthermore, a regression analysis from 20–25°C and 30–40°C results in activation energies of 88.71 kJmol-1 and 75.16kJ mol-1, respectively. This is probably the first time a Chevron-like graph was observed for the Arrhenius plot on the effect of temperature on the growth rate of 2-chloro-4-nitrophenol.

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.

Studying the Effect of Different Parameters on Photocatalytic Degradation of Commercial Safranin-T Dye by Using ZnO/V2O5 Nanocomposite

2021 ◽  
Vol 19 (8) ◽  
pp. 59-65
Author(s):  
Ameerah S. Jawad ◽  
Hazim Y. Al- gubury
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Light Intensity ◽  
Photocatalytic Degradation ◽  
Degradation Process ◽  
Effect Of Temperature ◽  
Hydrothermal Processes ◽  
Oxide Vanadium ◽  
Effect Of Light ◽  
Safranin T

Photocatalytic-degradation process of Safranin-T dye in this article has been investigated by using prepared nanocomposite and solar lamp. Zinc oxide/vanadium pentoxide nanocomposite was prepared using “hydrothermal processes”. The degradation of dye was performed by irradiated aqueous suspended solutions containing different concentrations of dye using 0.2g/100ml of nanocomposite. The effect of various factors on the photocatalytic-degradation process of Safranin-T dye was tested to reach an optimal state, where they involve the effect of the nanocomposite mass and the effect of Safranin-T dye concentration the effect of light intensity and effect of temperature. The activation energy has been calculated equal 28.84 kJ.mole-1 The irradiated solutions were studied using UV-Vis spectrophotometer.

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 Effect of CaO on catalytic combustion of semi-coke

2021 ◽  
Vol 10 (1) ◽  
pp. 011-020
Author(s):  
Luyao Kou ◽  
Junjing Tang ◽  
Tu Hu ◽  
Baocheng Zhou ◽  
Li Yang
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Combustion Rate ◽  
Activation Energies ◽  
Combustion Reaction ◽  
Tg Analysis ◽  
Conversion Rates ◽  
Apparent Activation Energies ◽  
Ozawa Integral Method ◽  
Addition Amount

Abstract Generally, adding a certain amount of an additive to pulverized coal can promote its combustion performance. In this paper, the effect of CaO on the combustion characteristics and kinetic behavior of semi-coke was studied by thermogravimetric (TG) analysis. The results show that adding proper amount of CaO can reduce the ignition temperature of semi-coke and increase the combustion rate of semi-coke; with the increase in CaO content, the combustion rate of semi-coke increases first and then decreases, and the results of TG analysis showed that optimal addition amount of CaO is 2 wt%. The apparent activation energy of CaO with different addition amounts of CaO was calculated by Coats–Redfern integration method. The apparent activation energy of semi-coke in the combustion reaction increases first and then decreases with the increase in CaO addition. The apparent activation energies of different samples at different conversion rates were calculated by Flynn–Wall–Ozawa integral method. It was found that the apparent activation energies of semi-coke during combustion reaction decreased with the increase in conversion.

scholarly journals The Effect of α-Al(MnCr)Si Dispersoids on Activation Energy and Workability of Al-Mg-Si-Cu Alloys during Hot Deformation

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xiaoguo Wang ◽  
Jian Qin ◽  
Hiromi Nagaumi ◽  
Ruirui Wu ◽  
Qiushu Li
Keyword(s):  
Activation Energy ◽  
Aluminum Alloys ◽  
Constitutive Equation ◽  
Hot Deformation ◽  
Flow Instability ◽  
Void Formation ◽  
Activation Energies ◽  
Compression Tests ◽  
Softening Mechanism ◽  
Dynamic Softening

The hot deformation behaviors of homogenized direct-chill (DC) casting 6061 aluminum alloys and Mn/Cr-containing aluminum alloys denoted as WQ1 were studied systematically by uniaxial compression tests at various deformation temperatures and strain rates. Hot deformation behavior of WQ1 alloy was remarkably changed compared to that of 6061 alloy with the presence of α-Al(MnCr)Si dispersoids. The hyperbolic-sine constitutive equation was employed to determine the materials constants and activation energies of both studied alloys. The evolution of the activation energies of two alloys was investigated on a revised Sellars’ constitutive equation. The processing maps and activation energy maps of both alloys were also constructed to reveal deformation stable domains and optimize deformation parameters, respectively. Under the influence of α dispersoids, WQ1 alloy presented a higher activation energy, around 40 kJ/mol greater than 6061 alloy’s at the same deformation conditions. Dynamic recrystallization (DRX) is main dynamic softening mechanism in safe processing domain of 6061 alloy, while dynamic recovery (DRV) was main dynamic softening mechanism in WQ1 alloy due to pinning effect of α-Al(MnCr)Si dispersoids. α dispersoids can not only resist DRX but also increase power required for deformation of WQ1 alloy. The microstructure analysis revealed that the flow instability was attributed to the void formation and intermetallic cracking during hot deformation of both alloys.

New experiments on the relationship between light-induced defects and photoconductivity degradation

2001 ◽  
Vol 664 ◽  
Author(s):  
Stephan Heck ◽  
Howard M. Branz
Keyword(s):  
Activation Energy ◽  
Defect Density ◽  
Activation Energies ◽  
Dangling Bond ◽  
Fast Recovery ◽  
Slow Recovery ◽  
Degradation Model ◽  
Induced Defects ◽  
The Relationship ◽  
Hydrogenated Amorphous

ABSTRACTWe report experimental results that help settle apparent inconsistencies in earlier work on photoconductivity and light-induced defects in hydrogenated amorphous silicon (a-Si:H) and point toward a new understanding of this subject. After observing that light-induced photoconductivity degradation anneals out at much lower T than the light-induced increase in deep defect density, Han and Fritzsche[1] suggested that two kinds of defects are created during illumination of a-Si:H. In this view, one kind of defect degrades the photoconductivity and the other increases defect sub-bandgap optical absorption. However, the light-induced degradation model of Stutzmann et al.[2] assumes that photoconductivity is inversely proportional to the dangling-bond defect density. We observe two kinds of defects that are distinguished by their annealing activation energies, but because their densities remain in strict linear proportion during their creation, the two kinds of defects cannot be completely independent.In our measurements of photoconductivity and defect absorption (constant photocurrent method) during 25°C light soaking and during a series of isochronal anneals between 25 < T < 190°C, we find that the absorption measured with E ≤1.1 eV, first increases during annealing, then exhibits the usual absorption decrease found for deeper defects. The maximum in this absorption at E ≤1.1eV occurs simultaneously with a transition from fast to slow recovery of photoconductivity. The absorption for E ≤1.1eV shows two distinct annealing activation energies: the signal rises with about 0.87 eV and falls with about 1.15 eV. The 0.87 eV activation energy roughly equals the activation energy for the dominant, fast, recovery of photoconductivity. The 1.15 eV activation energy roughly equals the single activation energy for annealing of the light-induced dangling bond absorption.

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