“…According to the changes in activation energy, the thermal transformation process of mixed oil can be divided into three stages. This is consistent with published and our previous work reports . The changes in activation energy of the three samples with the increase in progress of the reaction are presented in Table .…”
In this work, the kinetic and thermodynamic parameters of mixed oil during the process of thermal conversion are analyzed using a kinetic model and thermodynamic calculations combined with thermogravimetric analysis. On the basis of the Flynn-Wall-Ozawa kinetic model, the calculated activation energies change in the reaction progress of mixed oil. Additionally, the thermal conversion process can be divided into three stages. The reaction mechanism is the exponential law mode in the first phase, and the latter two stages belong to the random nucleation and subsequent growth model, but they have completely different ways of nucleation and crystal growth. During the whole thermal conversion of mixed oil, △H ≠ > 0, and it does not show that the thermal conversion of mixed oil is a completely endothermic process; △G ≠ > 0 and represents a nonspontaneous reaction; and the change of the △S ≠ value is the most complicated.
“…According to the changes in activation energy, the thermal transformation process of mixed oil can be divided into three stages. This is consistent with published and our previous work reports . The changes in activation energy of the three samples with the increase in progress of the reaction are presented in Table .…”
In this work, the kinetic and thermodynamic parameters of mixed oil during the process of thermal conversion are analyzed using a kinetic model and thermodynamic calculations combined with thermogravimetric analysis. On the basis of the Flynn-Wall-Ozawa kinetic model, the calculated activation energies change in the reaction progress of mixed oil. Additionally, the thermal conversion process can be divided into three stages. The reaction mechanism is the exponential law mode in the first phase, and the latter two stages belong to the random nucleation and subsequent growth model, but they have completely different ways of nucleation and crystal growth. During the whole thermal conversion of mixed oil, △H ≠ > 0, and it does not show that the thermal conversion of mixed oil is a completely endothermic process; △G ≠ > 0 and represents a nonspontaneous reaction; and the change of the △S ≠ value is the most complicated.
“…In the first step, the PE- co -DPA copolymer(I) with a specific concentration of reactive diphenylacetylenyl (DPA) side groups (discussed later) is melt-mixed with an excess amount of petroleum pitch. It has been widely known that thermal polycondensation between pitch (PAH) molecules starts at about 350 °C, , which is considered an unwanted reaction at this stage. Therefore, by controlling the mixing temperature at 310 °C, the Diels–Alder [2 + 4] cycloaddition reaction between highly reactive acetylene moieties in DPA side groups and PAH molecules in the pitch selectively happens to generate the desirable PE- g -PAH graft copolymer(II) with some ungrafted (excess) pitch molecules.…”
Polyethylene (PE) has the potential to become a promising carbon fiber (CF) precursor in terms of excellent melt-processibility, high carbon content (>85 wt %), and low material cost. However, the PE polymer is completely degraded at temperatures >480 °C under an inert atmosphere. In this study, we have investigated CF precursors based on a PE-g-PAH graft copolymer with several grafted PAH (polyaromatic hydrocarbons from a petroleum pitch) side groups and some ungrafted (free) pitch molecules that serve as precursors and plasticizers to lower its melt viscosity during melt-spinning. The presence of grafted PAH groups in the PE chain not only enhances the compatibility between the PE-g-PAH copolymer and free pitch molecules in the precursor but also assists in the one-step thermotransformation process to achieve a high C-yield. Thermogravimetric (TGA) analysis, evolved gas analysis mass spectrometry, oscillating rheology, solid-state 13 C NMR, Raman spectroscopy, and X-ray diffraction were employed to monitor melt-processing and thermal transformation. Melt-spinning of this PE-g-PAH/Pitch blend precursor is suitable in the temperature range of 320−340 °C. Thermal transformation, including crosslinking, dehydrogenation of the PE chain, and carbonization, happens stepwise between 350 and 1000 °C under a noble gas atmosphere. Compared with the corresponding petroleum pitch, this PE-g-PAH/Pitch blend precursor exhibits a higher carbon yield (>70%) at 1000 °C. The resulting carbon derived from this precursor (without tension) at 1100 °C shows a similar d-spacing and stacking height but a higher lateral size compared to those typically observed in PAN-based carbon fibers. Overall, the discovery of this PE-g-PAH/Pitch precursor potentially provides an alternative strategy for preparing carbon fibers with a lower cost, less energy consumption, and easier handling throughout the entire production process.
“…Aromatic ring mode can also be seen around 1600 cm −1 . Finally, upon amine functionalization, -C = O (carbonyl) peaks appeared at 1720 cm −1 and N–H groups can be seen at 3400–3700 cm −1 (Cheng et al 2014 ; Çelik et al 2016 ; Lin et al 2005 ). Fig.…”
In this study, a highly sensitive, electrochemical, and label-free DNA impedimetric sensor was developed using carbonized glass fiber-coal tar pitch (GF-CTP) electrodes supported with gold nanoparticles (AuNPs) for the detection of HIV-1 gene. Thiol-modified GF-CTP electrodes were prepared using amine crosslinking chemistry and AuNPs were self-assembled obtaining highly conductive nanoelectrodes, GF-CTP-ATP-Au. All steps of electrode modifications were characterized using electrochemical, spectroscopic, and microscopic methods. GF-CTP-ATP-Au electrode was then modified with a capture DNA probe (C-ssDNA) and optimized with a target DNA probe in terms of hybridization time and temperature between 30 and 180 min and 20-50 °C, respectively. Finally, the analytic performance of the developed ssDNA biosensor was evaluated using electrochemical impedance spectroscopy. The calibration of the sensor was obtained between 0.1 pM and 10 nM analyte working range. The limit of detection was calculated using signal to noise ratio of 3 (S/N = 3) as 13 fM. Moreover, interference results for two noncomplementary DNA probes were also tested to demonstrate non-specific ssDNA interactions. An electrochemical label-free DNA impedimetric sensor was successfully developed using a novel GF-CTP-ATP-Au electrode. This study suggests that highly sensitive DNA-based biosensors can be developed using relatively lowcost carbonaceous materials.
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