• Carbon letters
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• v.19
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• pp.57-65
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• 2016

Isroaniso matrix precursor synthesized from commercially available petroleum pitch was stabilized in air. The influence of oxygen mass gain during stabilization on the yield of matrix precursor was studied. Additionally, the influence of pressure on the yield of the stabilized matrix precursor in a real system was studied. The fourier transform infrared spectrometry (FTIR), thermogravimetric analysis (TGA), yield, yield rate, and yield impact were used to check the effect of stabilization and pressure on the yield of the matrix precursor and the end properties of the composite thereafter. The results showed that the yield increased with stabilization duration up to 20 h whereas it decreased for stabilization duration beyond 20 h. Further results showed that the stabilized matrix precursor for a duration of 5 h could withstand almost two-fold greater hot-pressing pressure without resulting in exudation as compared to that of a 1 h stabilized matrix precursor. The enhanced hot-pressing pressure significantly improved the yield of the matrix precursor. As a consequence, the densification and mechanical properties were increased significantly. Further, the matrix precursor stabilized for a duration of 20 h or more failed to provide proper and uniform binding of the reinforcement.

• Korean Journal of Materials Research
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• v.23 no.2
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• pp.143-148
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• 2013

Well-distributed $SnO_2$-Sn-$Ag_3Sn$ nanoparticles embedded in carbon nanofibers were fabricated using a co-electrospinning method, which is set up with two coaxial capillaries. Their formation mechanisms were successfully demonstrated. The structural, morphological, and chemical compositional properties were investigated by field-emission scanning electron spectroscopy (FESEM), bright-field transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In particular, to obtain well-distributed $SnO_2$ and Sn and $Ag_3Sn$ nanoparticles in carbon nanofibers, the relative molar ratios of the Ag precursor to the Sn precursor including 7 wt% polyacrylonitrile (PAN) were controlled at 0.1, 0.2, and 0.3. The FESEM, bright-field TEM, XRD, and XPS results show that the nanoparticles consisting of $SnO_2$-Sn-$Ag_3Sn$ phases were in the range of ~4 nm-6 nm for sample A, ~5 nm-15 nm for sample B, ~9 nm-22 nm for sample C. In particular, for sample A, the nanoparticles were uniformly grown in the carbon nanofibers. Furthermore, when the amount of the Ag precursor and the Sn precursor was increased, the inorganic nanofibers consisting of the $SnO_2$-Sn-$Ag_3Sn$ nanoparticles were formed due to the decreased amount of the carbon nanofibers. Thus, well-distributed nanoparticles embedded in the carbon nanofibers were successfully synthesized at the optimum molar ratio (0.1) of the Ag precursor to the Sn precursor after calcination of $800^{\circ}C$.

• Progress in Superconductivity
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• v.5 no.1
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• pp.65-69
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• 2003

Many researches on fabrication process for BSCCO precursor powders have been developed for high J$_{c}$ BSCCO-2223 tape. Spray pyrolysis method for fabrication of precursor powder has many advantages, such as high purity, fine particle size and low carbon content of BSCCO precursor powder. Fine, spherical powders were prepared by ultrasonic spray pyrolysis from the aqueous solution of metal nitrates. BSCCO precursor powders were synthesized with various solutes concentration and heat treatment conditions. Average particle size for spray pyrolysis powders was $1.5∼3\mu\textrm{m}$. Bi-2223/Ag tape was prepared by PIT method and followed by various sintering conditions. BSCCO precursor powders were characterized by XRD, SEM, EDS, Carbon content and particle size analysis.s.

• Journal of the Korean Ceramic Society
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• v.33 no.12
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• pp.1387-1393
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• 1996

A study on mesophase pitch as a matrix precursor of carbon fiber reinforced carbon (C/C) composite has been recently presented. This study is concerned with the production of mesophase pitch as matrix precursors for C/C composite from coal tar pitch. A commercial coal tar pitch was heat-treated at 25$0^{\circ}C$ for 2 hours to remove low molecular weight fraction from the pitch then increasing the temperature of the pitch to between 350~45$0^{\circ}C$ to produce mesophase pitch. The pitch was continuously stirred during this time and nitrogen gas was continuously bubbled through the pitch. Spherical and bulk mesophases were formed in the pitch after heat-treatment,. Parent and mesophae pitches were characterized by elemental analysis coke yield solubi-lity in tetrahydrofuran and hexane and an optical microscopy to measure the mesiophase content. It was neces-sary to produce C/C composite that a mesophase pitch with about 30-40 vol% mesophase spherulites can be infiltrated into a fiber preform without a filter effect as a matrix precursor conditions. This condition was satisfied with mesophase pitch heat treated at 40$0^{\circ}C$ for 2 hours. The other heat treatment conditions showed the nuclei of mesophase or bulk mesophae which were not satisfied with the matix precursor condition.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.283-283
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• 2006

Multigram-scale product exclusively containing magnetic carbon nanoparticles (MNCPs) with uniform size was successfully fabricated without a specific separation process. The iron-doped PPy nanoparticles were synthesized by micelle templating and used as the carbon precursor in order to generate MCNPs. The magnetic carbon nanoparticles possessed a microporous structure and exhibited ferromagnetic properties at room temperature. This approach may be an effective alternative to generate magnetic carbon nanoparticles against the conventional arc-discharge technique.

• Carbon letters
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• v.10 no.3
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• pp.198-201
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• 2009

Among other filters such as light filter, wave filter, air filter, ultra filter and filter paper, a novel adsorption filter from thermostable polyester nonwoven fabrics immobilized with functional super activated carbon by means of quinoline soluble, activateable isotropic pitch binder were developed in this study. The activated carbon precursor is available in the market branded as coconut shell based activated carbon(CCS-AC) produced by Dongyang Carbon Co. Ltd. BET-surface area of this precursor was $1,355\;m^2/g$, after KOH-activation it increased over $2,970\;m^2/g$ and was named as super activated carbon. In the preliminary research, this precursor was impregnated with $PdCl_2$(0.188 wt%) $KMnO_4$(3 wt%) and redox-agent(CuCl2, 0.577 wt%) in order to promote TOF up to 100/h and Selectivity up 99% and patented as a functional AC for the ethylene adsorption. The enhancement of the isotropic pitch binder to the AC-immobilized adsorption filter was BET-surface area upgraded by $266\;m^2/g$ and promoted the Iodine- and MB-adsorption by 1.4 times, respectively and also micro pore wide ranges < $5{\AA}{\sim}30\;{\AA}$ >.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.3025-3032
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• 2012

Carbon microcapsules containing silicon nanoparticles (Si NPs)-carbon nanotubes (CNTs) nanocomposite (Si-CNT@C) have been fabricated by a two step polymerization method. Silicon nanoparticles-carbon nanotubes (Si-CNT) nanohybrids were prepared with a wet-type beadsmill method. A polymer, which is easily removable by a thermal treatment (intermediate polymer) was polymerized on the outer surfaces of Si-CNT nanocomposites. Subsequently, another polymer, which can be carbonized by thermal heating (carbon precursor polymer) was incorporated onto the surfaces of pre-existing polymer layer. In this way, polymer precursor spheres containing Si-CNT nanohybrids were produced using a two step polymerization. The intermediate polymer must disappear during carbonization resulting in the formation of an internal free space. The carbon precursor polymer should transform to carbon shell to encapsulate remaining Si-CNT nanocomposites. Therefore, hollow carbon microcapsules containing Si-CNT nanocomposites could be obtained (Si-CNT@C). The successful fabrication was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). These final materials were employed for anode performance improvement in lithium ion battery. The cyclic performances of these Si-CNT@C microcapsules were measured with a lithium battery half cell tests.

• Carbon letters
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• v.15 no.1
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• pp.25-31
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• 2014

A microstructure analysis is carried out to optimize the process parameters of a randomly oriented discrete length hybrid carbon fiber reinforced carbon matrix composite. The composite is fabricated by moulding of a slurry into a preform, followed by hot-pressing and carbonization. Heating rates of 0.1, 0.2, 0.3, 0.5, 1, and $3.3^{\circ}C/min$ and pressures of 5, 10, 15, and 20 MPa are applied during hot-pressing. Matrix precursor to reinforcement weight ratios of 70:30, 50:50, and 30:70 are also considered. A microstructure analysis of the carbon/carbon compacts is performed for each variant. Higher heating rates give bloated compacts whereas low heating rates give bloating-free, fine microstructure compacts. The compacts fabricated at higher pressure have displayed side oozing of molten pitch and discrete length carbon fibers. The microstructure of the compacts fabricated at low pressure shows a lack of densification. The compacts with low matrix precursor to reinforcement weight ratios have insufficient bonding agent to bind the reinforcement whereas the higher matrix precursor to reinforcement weight ratio results in a plaster-like structure. Based on the microstructure analysis, a heating rate of $0.2^{\circ}C/min$, pressure of 15 MPa, and a matrix precursor to reinforcement ratio of 50:50 are found to be optimum w.r.t attaining bloating-free densification and processing time.

• Carbon letters
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• v.15 no.4
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• pp.247-254
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• 2014

In this work, thermal treatment accompanied with different acid treatments was applied to a commercial coal tar pitch (CTP) to obtain a spinnable precursor pitch for carbon fiber. In the case of thermal treatment only, a relatively high reaction temperature of between $380^{\circ}C$ and $400^{\circ}C$ was required to obtain a softening point (SP) range of $220^{\circ}C-260^{\circ}C$ and many meso-phase particles were created during the application of high reaction temperature. When nitric acid or sulfuric acid treatment was conducted before the thermal treatment, the precursor pitch with a proper SP range could be obtained at reaction temperatures of $280^{\circ}C-300^{\circ}C$, which were about $100^{\circ}C$ lower than those for the case of thermal treatment only. With the acid treatments, the yield and SP of the precursor pitch increased dramatically and the formation of meso-phase was suppressed due to the lower reaction temperatures. Since the precursor pitches with acid and thermal treatment were not spinnable due to the inhomogeneity of properties such as molecular weight distribution and viscosity, the CTP was mixed with ethanol before the consecutive nitric acid and thermal treatments. The precursor pitches with ethanol, nitric acid, and thermal treatments were easily spinnable, and their spinning and carbon fiber properties were compared to those of air blowing and thermal treated CTP.

• Carbon letters
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• v.6 no.3
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• pp.173-180
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• 2005

In this study, AR (aromatic resin) pitch was employed as the matrix-precursor for carbon/carbon composite because it exhibits much higher coke yield than coal tar pitch. As a result, a fabrication process of carbon/carbon composites can be shortened. It has been known that the pitches may cause swolling problem during the carbonization process. In order to restrain the swelling occurrence, a small quantity of carbon black was added to the AR pitch. Due to addition of carbon black the swelling was decreased largely and the perform can be infiltrated with the AR pitch. The densification efficiency of the performs was compared with various matrix-precursors. The coke yield of matrixprecursors, the morphology and the degree of graphitization of carbon matrix were analyzed.