Hong-Ryun Jung

Adsorption of toluene on carbon nanofibers prepared by electrospinning

This paper reports the novel results of activated carbon nanofibers (ACNF) used to improve the toluene adsorption capacity. The ACNF was prepared by stabilization, carbonization and activation after electrospinning the polymer solution of polyacrylonitrile (PAN) in N, N-dimethylformamide. The average diameter of the ACNF was approximately 300 nm, ranging from 200 to 500 nm. The toluene adsorption capacity of ACNF10 activated at 1000 degrees C increased to 65 g-toluene/100 g-ACNF. This was attributed to the high specific surface area (1403 m(2)/g), large micropore volume (0.505 cm(3)/g), and narrow average pore diameter (6.0 A). The oxygen to carbon ratio (O/C ratio) in ACNF10 was 1.8%. This O/C ratio appears to induce a higher toluene adsorption capacity, which originates from a non-polar interaction between the ACNF surface and toluene. In conclusion, the electrospun ACNF prepared in this study promotes the adsorption of toluene through the high specific surface area, large pore volume, narrow pore diameter and low O/C ratio.

A Hydrous Ruthenium Oxide-Carbon Nanofibers Composite Electrodes Prepared by Electrospinning

Ruthenium-embedded carbon nanofibers were prepared by the processes of stabilization, carbonation, and activation after electrospinning a composite solution of ruthenium(III) acetylacetonate and polyacrylonitrile in N,N-dimethylformamide. When Ru particles were embedded in the carbon nanofibers, the average pore diameter increased from 2.0 to 2.5 nm. The Ru particles were embedded randomly within the carbon fibers, and the size distribution of the Ru particles ranged from 2 to 15 nm. The specific capacitance of the carbon nanofiber without the Ru loading was 140 F/g, while that of 7.31 wt % Ru-carbon nanofibers increased to 280% as 391 F/g. This was attributed to the synergistic effect of electric double-layer capacitance as a result of the expansion of the average pore diameter as well as the pseudocapacitance by the well-dispersed Ru particles.

Preparation and Characterization of Ni-Sn/Carbon Nanofibers Composite Anode for Lithium Ion Battery

The Ni and Sn-embedded carbon nanofiber (Ni-Sn/CNF) nanocomposites as anode materials were prepared by using electrospinning technique and optimum thermal process. The fine structure of Ni-Sn/CNF was scrutinized by EXAFS. The nanocomposite prepared at 700°C had disordered Ni 3 Sn 2 , disordered NiO, amorphous SnO x and crystalline SnO 2 phases created as tiny particles in the carbon nanofibers (CNF). The 100th discharge capacity of Ni-Sn/CNFs were ranked as follows by their preparation temperature: 700°C (641 mAh g ―1 )>600°C (573 mAh g ―1 )>800°C (559 mAh g ―1 ), and their initial coulomb efficiencies were ranked by preparation temperature: 700°C (60%)>600°C (58%)>800°C (55%). The excellent specific discharge capacity and cycle retention of the sample prepared at 700°C were attributed to the formation of Ni 3 Sn 2 intermetallic compounds, the buffering role of the CNF, and the good distribution of active particles by electrospinning.

Electrospun Activated Carbon Nanofibers Electrodes Based on Polymer Blends

Activated carbon nanofibers (ACNFs) based on a polymer blend, which consists of polyacrilonitrile (PAN) and cellulose acetate (CA), were prepared by electrospinning and subsequent thermal treatment. The diameter of ACNF increased with increasing CA content. The electrical conductivity increased with the addition of CA due to a larger oxygen amount of CA molecules. The specific surface area and average pore diameter of CA-free ACNF (CP) were 742 m 2 /g and 2.0 nm, respectively, while those of 15 wt % CA-blended ACNF (15CP) increased to 1160 m 2 /g and 2.8 nm, respectively. The capacitance of CP was 141 F/g at 1 mA/cm 2 , whereas that of 15CP increased to 245 F/g. This is why the CP is predominated by small surface area with microporos- ity, whereas the 15CP is affected by higher surface area with better mesoporosity due to the combination of electrospinning based on polymer blends and thermal treatment.

Preparation and ionic conductivity of sulfonated-SEBS/SiO2/plasticizer composite polymer electrolyte for polymer battery

Abstract Sulfonated poly(styrene–ethylene–buthylene–styrene) (SSEBS) for a polymer electrolyte membrane was prepared according to the capacity of ion exchange. SSEBS was sufficient to utilize with the polymer electrolyte membrane from the viewpoint of appearance, tensile strength, and ionic conductivity. The SSEBS/SiO2/plasticizer composite polymer electrolyte for the polymer battery was fabricated with various silica contents. LiClO4 or LiCF3SO3 was used as a salt, EC/PC (1:1 vol.%) as solvents, SiO2 as a filler, and DBP as a plasticizer, respectively. The ionic conductivity was enhanced with increasing the degree of sulfonation. The ionic conductivity reached 2.6×10−3 S/cm when the content of silica was 12 wt.% at 1 M LiClO4 in EC/PC (1:1 vol.%) and 40 wt.% for plasticizers. However, if the content of silica was too excessive, the ionic conductivity was decreased due to restriction of ionic movement.

SYNTHESIS OF HIGHLY CRYSTALLINE OLIVINE-TYPE LiFePO4 NANOPARTICLES BY SOLUTION-BASED REACTIONS

LiFePO4 nanocrystals were synthesized in various polyol media without any further post-heat treatment. The LiFePO4 samples synthesized using three different polyol media namely, diethylene glycol (DEG), triethylene glycol (TEG), and tetraethylene glycol (TTEG), exhibited plate and rod-shaped structures with average sizes of 50–500 nm. The X-ray diffraction (XRD) patterns were indexed on the basis of an olivine structure (space group: Pnma). The samples prepared in DEG, TEG, and TTEG polyol media showed reversible capacities of 123, 155, and 166 mAh/g, respectively, at current density of 0.1 mA/cm2 with no capacity fading and exhibited excellent capacity retention up to the 50th cycle. In particular, the samples showed excellent performances at high rates of 30 and 60 C with high capacity retention. It is assumed that the nanometer size materials (~50 nm) possessing a highly crystalline nature may generate improved performance at high rate current densities.

Electrochemical Performance of Electrospun ACNF Electrodes Using Polymer Blend

The aim of this work is to fabricate the electrospun ACNF electrodes with highly electrochemical performance using polymer blend of polyacrilonitrile (PAN) – cellulose acetate (CA) for supercapacitors. The blended ACNFs have a lager specific surface area and an average pore diameter compared to non-blended ACNFs. That was occurred by formation of valley due to difference of pyrolysis between PAN and CA. The blended ACNFs also had higher electrical conductivity than to nonblended ACNFs. The specific capacitances of the prepared webs ranged from 141 to 221 F/g, depending on the CA blending ratio. The 30 wt.% CA blended ACNFs exhibited the highest capacitance as 221 F/g. This was attributed to the increase of specific surface area, pore diameter and electrical conductivity.