Young-Seak Lee

Improvement of Thermal Stability of Electrospun PAN Fibers by Various Additives

In order to improve the thermal stability of PAN-based electrospun fibers, AP-PER-MEL and TiO2 were added in to the fibers as additives. The polymer composite with uniformly mixed additional agents was obtained. In case of non-treated sample, the fibers were burn off completely with high rate within 620oC. But in case of treated samples (EF-M and EF-MT), it nis sure that the thermal stability was improved by studying TGA data and ISO flammability test about 20 and 30%, respectively. A synergy effect of adding two kinds of agents (AP-PER-MEL and TiO2) into PAN-based electrospun fibers was confirmed. Through SEM images, it is confirmed that the fiber shape can be kept even after addition of agents (AP-PER-MEL and TiO2). Finally the thermal stability of fibers was largely developed with keeping the nature of PAN-based fibers effectively. n nKeywords : Thermal stability, Fiber, Electrospinning

Na 3 PO 4 Flame Retardant Treatment on Lyocell Fiber for Thermal Stability and Anti-oxidation Properties

The improved thermal stability and anti-oxidation properties of lyocell fiber were studied based on flame retardant treatment by using Na PO solution. The optimized conditions of flame retardant treatment were studied on various concentrations of Na PO and the mechanism was proposed through experimental results of thermal stability and anti-oxidation. The integral procedural decomposition temperature (IPDT), limiting oxygen index (LOI) and activation energy (E ) increased 30, 160% respectively via flame retardant treatment. It is noted that thermal stability and anti-oxidation improved based on char and carbon layer formation by dehydrogenation and dissociation of C-C bond resulting the hindrance of oxygen and heat energy into polymer resin. The optimized conditions for efficient flame retardant property of lyocell fiber were provided using Na PO solution and the mechanism was also studied based on experimental results such as initial decomposition temperature (IDT), IPDT, LOI and E .

Applications of Carbon Materials for Ferroelectric and Related Materials

Ferroelectricity is spontaneous electric polarization of a material without an external electric field and the polarization can be reversed by applying an external electric field as shown in Fig.1 (Kanzig, 1957; Lines & Glass, 1979). Because the spontaneous polarization of the material is changed by an external stimulus, ferroelectric materials are also piezoelectric and pyroelectric, when the stimuli are force and heat, respectively. Ferroelectric materials have non-linear polarization; thus, they can be used as capacitors with tunable capacitance. Moreover, the hysteresis effect of the spontaneous polarization of ferroelectric materials enables the application of ferroelectric random-access memories (RAMS) for computers and radio-frequency identification (RFID) cards (Buck, 1952). In addition, piezoelectric materials are used for high voltage power source, sensors, and actuators. In these systems, it is evident that ferroelectric and related materials are not used alone. For complete systems, other materials are required to compensate for the poor properties, such as the low conductivity of piezoelectric concrete, or to enhance their performance (Shifeng, 2009; Ishiwara 2009).

NO Gas Sensing of ACFs Treated by E-beam Irradiation in H 2 O 2 Solution

>> In this study, we treated pitch-based activated carbon fibers (ACFs) in hydrogen peroxide using electron beam (E-beam) irradiation to improve nitrogen monoxide (NO) sensing ability as an electrode material of gas sensor. The specific surface area of ACFs treated by E-beam irradiation with 400 kGy increased from 885 m 2 /g (pristine) to 1160 m 2 /g without any changes in structural property and functional group. The increase in specific surface area of the E-beam irradiated ACFs enhanced NO gas sensing properties such as response time and sensitivity. When the ACFs irradiated with 400 kGy, response time was remarkably reduced from 360 s to 210 s and sensitivity was increased by 4.5%, compared to the pristine ACFs. These results demonstrate convincingly that surface modification of ACFs using E-beam in hydrogen peroxide solution can enhance textural properties of ACFs and NO gas sensing ability of gas sensor at room temperature.