An-Najah Staff

Thermogravimetry analyses have been employed to study the catalytic effect of different metal oxide nanoparticles on the thermo-oxidative decomposition of asphaltenes at isothermal conditions. Three metal oxide nanoparticles were considered in this study, namely: NiO, Co3O4 and Fe3O4. Results showed that the presence of nanoparticles decreased the activation energy of asphaltenes oxidation and enhanced the reaction rate. It appears that the thermo-oxidative reaction is metal oxide specific. The obtained kinetic data showed that NiO has the highest reaction rate followed by Co3O4 and then Fe3O4, which suggests a change in the reaction mechanism. Isothermal conversion for thermal oxidation of asphaltenes at 360 °C without nanoparticles and at 300 °C in the presence of nanoparticles. View high quality image (142K) ⺠Metal oxide nanoparticles enhanced the reaction rate of asphaltene thermo-oxidation. ⺠The thermo-oxidative reaction is metal oxide specific. ⺠NiO nanoparticles have the highest reaction rate. ⺠Differences in activation energy for different nanoparticles suggest different reaction mechanisms.

The effect of infrared laser of wavelength (λ=1064 nm), pulse energy of 40 mJ/pulse at a repetition rate of 10 Hz, on the activation energy of CR-39 polymer, solid state nuclear track detector, has been investigated. Fifteen detectors were divided into three sets of equal numbers. The first set (un-exposed to laser beam), used as a reference set, was irradiated in close contact with an alpha source (²⁴¹Am). The second set (post-exposed) was first exposed to alpha radiation in close contact to the same ²⁴¹Am source and then treated in air with laser at energy intensity 8 J/cm². For the third set (pre-exposed), the process was reversed (laser+alpha) under the same conditions. The activation energies of bulk etch (E_B) for unexposed, post-exposed and pre-exposed are found to be equal to 0.98, 0.91, and 1.0 eV, respectively. The respective activation energies of track etch (E_T) for unexposed, post-exposed and pre-exposed are found to be equal to 0.71, 0.75, and 0.97 eV. These results show that E_B for post-exposed and pre-exposed samples remain, to within the experimental uncertainty, comparable to that of un-exposed sample which indicates that laser irradiation has a small effect on E_B. Also, the results of E_T for post-exposed and un-exposed samples are in close proximity with a slight increase for the former. The increase in E_T of pre-exposed CR-39 polymer due to IR exposure is discussed on the basis of cross linking processes occurring during the exposure. This increase in E_T leads to the hardening of the detector material of the pre-exposed sample. The hardening of the detector material is crucial in applications of CR-39 polymer such as in cosmic ray and cold fusion research.

The effect of infrared laser of wavelength (λ=1064 nm), pulse energy of 40 mJ/pulse at a repetition rate of 10 Hz, on the activation energy of CR-39 polymer, solid state nuclear track detector, has been investigated. Fifteen detectors were divided into three sets of equal numbers. The first set (un-exposed to laser beam), used as a reference set, was irradiated in close contact with an alpha source (241Am). The second set (post-exposed) was first exposed to alpha radiation in close contact to the same 241Am source and then treated in air with laser at energy intensity 8 J/cm2. For the third set (pre-exposed), the process was reversed (laser+alpha) under the same conditions. The activation energies of bulk etch (EB) for unexposed, post-exposed and pre-exposed are found to be equal to 0.98, 0.91, and 1.0 eV, respectively. The respective activation energies of track etch (ET) for unexposed, post-exposed and pre-exposed are found to be equal to 0.71, 0.75, and 0.97 eV.These results show that EB for post-exposed and pre-exposed samples remain, to within the experimental uncertainty, comparable to that of un-exposed sample which indicates that laser irradiation has a small effect on EB. Also, the results of ET for post-exposed and un-exposed samples are in close proximity with a slight increase for the former. The increase in ET of pre-exposed CR-39 polymer due to IR exposure is discussed on the basis of cross linking processes occurring during the exposure. This increase in ET leads to the hardening of the detector material of the pre-exposed sample. The hardening of the detector material is crucial in applications of CR-39 polymer such as in cosmic ray and cold fusion research.