• Resources Recycling
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• v.18 no.5
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• pp.19-25
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• 2009

Molybdenite concentrate ($MoS_2$) is the major mineral for the molybdenum industry, of which the industrial processing is first converted to technical grade molybdenum trioxide ($MoO_3$) by its oxidative roasting and purification, used as a raw material for manufacturing several molybdenum compounds. In the present work, detailed experimental results for the oxidative roasting of low grade Mongolian molybdenite concentrate are presented. The experiments were carried out in the temperature range of 793 to 823 K under an oxygen partial pressure range of 0.08 atm to 0.21 atm by using a thermogravimetric analysis technique. The molybdenite concentrate was an average particle size of $67\;{\mu}m$. In the oxidative roasting of low grade Mongolian molybdenite concentrate, more than 95% of molybdenite was converted to molybdenum trioxide in 60 min. at 828 K. The lander equation was found to be useful in describing the rates of the oxidative roasting and the reaction order with respect to oxygen concentration in a gaseous mixture with nitrogen was 0.11 order.

• Elastomers and Composites
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• v.46 no.2
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• pp.164-170
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• 2011

In this study, silicone rubber filled with environmentally-friendly perlite was prepared by mechanical mixing in order to improve thermal properties, such as heat and fire resistances. We found that the properties of silicone rubber composites depended on perlite concentration by various characterization methods. Thermogravimetric analysis(TGA) indicated that the initial degradation temperature of silicone/perlite composite was higher than that of pristine silicone rubber. The gas torch test showed that the opposite side temperature of composite materials was remarkably low as compared to that of pristine silicone rubber. In addition, the composites containing 5 wt% and 10 wt% of perlite showed remarkable thermal stability at elevated temperatures according to the results of both fireproof furnace tests under the RABT condition and carbonization furnace tests. The images from a scanning electron microscope(SEM) showed the degree of dispersion of perlite in silicone rubber. Finally, it was confirmed that limited oxygen index(LOI) was increased with perlite concentration.

• Polymer(Korea)
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• v.31 no.6
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• pp.518-525
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• 2007

The thermomechanical properties and morphologies of nanocomposite fibers of poly(ethylene terephthalate)(PET) incorporating thermally stable organoclays are compared. Dodecyltriphenyl-phosphonium-mica($C_{12}PPh-Mica$) and 1-hexadecane benzimidazole-mica ($C_{16}BIMD-Mica$) were used as reinforcing fillers in the fabrication of PET hybrid fibers. Dispersions of organoclays with PET were studied by using the in-situ polymerization method at various organoclay contents to produce nano-scale composites. The thermo-mechanical properties and morphologies of the PET hybrid fibers were determined using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), wide angle X-ray diffraction (XRD), electron microscopy (SEM and TEM), and a universal tensile machine (UTM). Transmission electron microscopy (TEM) micrographs show that some of the clay layers are dispersed homogeneously within the polymer matrix on the nano-scale, although some clay particles are agglomerated. We also found that the addition of only a small amount of organoclay is enough to improve the thermal stabilities and mechanical properties of the PET nanocomposite fibers. Even polymers with low organoclay content (<5 wt%) were found to exhibit much higher thermo-mechanical values than pure PET fibers.

• Journal of the Korean Wood Science and Technology
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• v.43 no.3
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• pp.344-354
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• 2015

To investigate the effects of ionic liquid pretreatment on biomass, giant miscanthus was treated with 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) and 1-butyl-3-methylimidazolium acetate ([Bmim][OAc]) at three temperature conditions ($90^{\circ}C$, $110^{\circ}C$, and $130^{\circ}C$). As temperature condition increased, yield of the cellulose-rich product (CP) was reduced from 87.2% to 67.6%, while yield of the ionic liquid lignin (ILL) increased from 2.2% to 9.9%. Compared to the ILL, CP had lower carbon contents and higher oxygen contents. Enzymatic hydrolysis of CPs showed that conversion ratio of CP treated with [Emim][OAc] at $110^{\circ}C$ was 56.7%, the highest digestibility. Thermogravimetric analysis indicated that the maximum degradation rate decreased as temperature condition increased. In addition, maximum degradation temperature of ILL treated with [Emim][OAc] ranged from 274 to $279^{\circ}C$ which was lower than that of ILL treated with [Bmim][OAc]. Analytical date for ${\beta}$-O-4 linkage frequency in the ILL revealed that ${\beta}$-O-4 linkage frequency in the ILL decreased as the temperature rose. Furthermore, the highest S/G ratio of the ILL was determined to ca. 1.2 obtained from [Bmim][OAc] treatment at $110^{\circ}C$.

• Journal of the Korean Wood Science and Technology
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• v.41 no.1
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• pp.1-11
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• 2013

In this study, we investigated chemical characteristics of solid residues obtained from inorganic acid hydrolysis of hybrid poplar (Populus alba ${\times}$ glandulosa). Different concentration (72, 36, 18%) of sulfuric acid and hydrochloric acid were used for first hydrolysis step and second hydrolysis step were carried out after equally dilution to 4%. Solid residues after consecutive two step hydrolysis were named to RS72 (Residue from Sulfuric acid 72%), RS36, RS18, as well as RC36 (Residue from hydroChloric acid 36%) and RC18, respectively. The yield of RS decreased from 71.2% to 21.4% with increasing sulfuric acid concentration in the first hydrolysis step, whereas that of RC showed little difference (67.0% to 65.0%), irrespective of hydrochloric acid concentration. The lignin content in solid residue was 23.6% for both of RS36 and RS18, 25.6% for RC36 and 27.3% for RC18, respectively. The results of pyrolyzer-GC/MS showed that 24 cellulose derivatives (Levoglucosan, Furfural) and 21 lignin derivatives (Guaiacol, Syringol) were detected. Thermogravimetric analysis indicated that the yield of char increased and maximum wieght loss rate decreased with increasing lignin portion of solid residue. Therefore, structure of lignin was condensed effectively by sulfuric acid and by high concentration of acid.

• Journal of the Korean Ceramic Society
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• v.41 no.5
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• pp.410-416
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• 2004

In this study, we fabricated magnetite coated on a cordierite honeycomb which has complex shape by ultrasound-enhanced ferrite plating. The effects of the plating condition on the formation of the magnetite and its microstructure were investigated. The magnetite coated on the honeycomb became an oxygen-deficient ferrite by H$_2$ gas reduction, then the effects of the molar concentrations of ammonium acetate for $CO_2$ gas decomposition have been studied. As the molar concentration of a pH buffer($CH_3$COONH$_4$, 0.1946∼0.3892 M) solution increased, the average particle size increased about 200∼250 nm. The magnetite coated on the honeycomb was reduced by H$_2$ gas for 2 h at 30$0^{\circ}C$. The inner pressure change in the cell began to occur at 315∼34$0^{\circ}C$. The H$_2$-Reduced magnetite coated on the honeycomb at 35$0^{\circ}C$ contained an oxygen deficient magnetite and $\alpha$-Fe phase. The thermogravimetric analysis with H$_2$ reduction and $CO_2$ decomposition were carried out with the magnetite coated on the honeycomb. A weight loss in process of H$_2$ reduction occurred between 32$0^{\circ}C$ and 34$0^{\circ}C$, while a weight gain was observed during the $CO_2$ decomposition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.56-56
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• 2010

Single-walled carbon nanotubes (SWCNTs) have attracted much attention as a promising material for transparent conducting films (TCFs), due to their superior electrical conductivity, high mechanical strength, and complete flexibility as well as their one-dimensional morphological features of extremely high length-to-diameter ratios. This study investigated three kinds of SWCNTs with different purities: as-produced SWCNTs (AP-SWCNTs), thermally purified SWCNTs (TH-SWCNTs), thermally and acid purified SWCNTs (TA-SWCNTs). The purity of each SWCNT sample was assessed by considering absorption peaks in the semiconducting ($S_{22}$) and metallic ($M_{11}$) tubes with UV-Vis NIR spectroscopy and a metal content with thermogravimetric analysis (TGA). The purity increased as proceeding the purification stages from the AP-SWCNTs through the thermal purification to the acid purification. The samples containing different contents of SWCNTs were dispersed in water using sodium dodecyl benzensulfate (SDBS). Aqueous suspensions of different purities of SWCNTs were prepared to have similar absorbances in UV-Vis absorption measurements so that one can make the TCFs possess similar optical transmittances irrespective of the SWCNT purity. Transparent conductive SWCNT networks were formed by spraying an SWCNT suspension onto a poly(ethyleneterephthalate) (PET) substrate. As expected, the TCFs fabricated with AP-SWCNTs showed very high sheet resistances. Interestingly, the TH-SWCNTs gave lower sheet resistances to the TFCs than the TA-SWCNTs although the latter was of higher purity in the SWCNT content than the former. The TA-SWCNTs would be shortened in length and be more bundled by the acid purification, relative to the TH-SWCNTs. For both purified (TH, TA) samples, the subsequent nitric acid ($HNO_3$) treatment greatly lowered the sheet resistances of the TCFs, but almost eliminated the difference of sheet resistances between them. This seems to be because the electrical conductivity increased not only due to further removal of surfactants but also due to p-type doping upon the acid treatment. The doping effect was likely to overwhelm the effect of surfactant removal. Although the nitric acid treatment resulted in the similar. electrical properties to the two samples, the TCFs of TH-SWCNTs showed much lower sheet resistances than those of the TA-SWCNTs prior to the acid treatment.

• Journal of the Korean Chemical Society
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• v.47 no.3
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• pp.250-256
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• 2003

In this work, the effect of cationic initiator content on the electron-beam (EB) curing process of diglycidylether of bisphenol-A (DGEBA) resin was studied using near-infrared spectroscopy (NIRS), thermogravimetric analysis (TGA), and critical stress intensity factor $(K_{IC})$. Benzylquinoxalinium hexafluoroantimonate (BQH) were used as an initiator and its content was varied from 0.5 to 3 phr. NIRS measurements showed that the hydroxyl group of EB-cured epoxy resin was increased with increasing the BQH content. Thermal stability and $K_{IC}$ value of EB-cured epoxy resin were increased with increasing the BQH content but were decreased above 2 phr content. These results could be attributed to the decrease of the conversion and degree of crosslinking. In another word, the conversion and degree of crosslinking were restricted by the incomplete network structure from high reactivity at the BQH content above 2 phr, resulting in decreasings of thermal stability and $K_{IC}$.

• Clean Technology
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• v.23 no.4
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• pp.378-387
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• 2017

To obtain epoxy resin with permanently attached flame-retardant groups, phosphorus compound containing di-hydroxyl group [10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phospha phenanthrene-10-oxide, DOPO-HQ] and silicone compound containing di-hydroxyl group (polydimethylsiloxane, hydroxyl terminated, PDMS) were reacted with uncured epoxy prepolymer (diglycidyl ether of bisphenol A, DGEBA) and then cured using 4,4-diaminodiphenylmethane (DDM) as a crosslinking agent. The properties of the resulting epoxy materials were characterized using Fourier transform infrared (FTIR) spectrometer, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limiting oxygen index (LOI) test/vertical burning test (UL 94-V test), tensile properties test and impact test. This study examined the effect of phosphorus/silicone compound contents on the thermal/mechanical properties and flame retardancy of cured epoxy resins containing phosphorus and silicone compounds. It was found that the thermal/mechanical properties of epoxy resins containing phosphorus and silicone components were higher than those of simple epoxy resin. The flame-retardancy (LOI: 29.9 ~ 31.8% and UL 94-V: V-0) of all samples containing phosphorus compound and phosphrous compound/silicone compound was found to be passed the flame-retardant requirements (LOI: > 30%, UL 94-V: V-0) of LOI and vertical burning tests. However, the flame-retardancy (LOI: 21.4% and UL 94-V: no rating) of simple epoxy resin was found to be failed the flame-retardant requirements.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.24-34
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• 1998

In this research, effects of the types and amounts of binders and additives on desulfurization and regeneration reactivities of zinc titanate were investigated. Bentonite and kaolinite were used as binders and Mo-based, Ni-based, and Cu-based compounds were used as additives. A thermogravimetric analyzer (TGA) was utilized to investigate reactivities of desulfurization and regeneration for each sorbent. Two-cycle reactions of desulfurization-regeneration were performed in the TGA reactor. Results of XRD analysis showed that all sorbents had the crystalline phases of $Zn_2TiO_2$ and $Zn_2Ti_3O_8$ irrespective of the type and amount of binder and additive. Kaolinite-bound sorbents gave higher surface areas than bentonite-bound ones and the surface areas and pore volumes of sorbents increased with amount of binder increased. It was found that the most suitable temperatures for desulfurization and regeneration were 680$^{\circ}$C and 730$^{\circ}$C, respectively, and the sorbent prepared by the addition of 3 mol% CuO showed the best performance in terms of desulfurization and regeneration. Nio-added sorbents had good regenerability whereas $MoO_3-based$ sorbents showed poor performance. In cycle experiments in a fixed bed reactor 3 mol% CuO-added sorbents showed high reactivity.