• Environmental Engineering Research
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• v.24 no.4
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• pp.591-599
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• 2019

To convert sewage sludge to energy, drying-gasification characteristics during microwave heating were studied. During the gasification of carbon dioxide, the main products were gas, followed by char, and tar in terms of the amount. The main components of the producer gas were carbon monoxide and hydrogen including a small amount of methane and light hydrocarbons. They showed a sufficient heating value as a fuel. The generated tar is gravimetric tar, which is total tar. As light tars, benzene (light aromatic tar) was a major light tar. Naphthalene, anthracene, and pyrene (light polycyclic aromatic hydrocarbon tars) were also generated, but in relatively small amounts. Ammonia and hydrogen cyanide (precursor for NO_x) were generated from thermal decomposition of tar containing protein and nitrogen in sewage sludge. In the case of sludge char, its average pore diameter was small, but specific area, pore volume, and adsorption amounts were relatively large, resulting in superior adsorption characteristics.

• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.532-539
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• 1996

Diamond-like carbon (DLC) films were deposited on silicon substrates by the plasma decomposition of hydrocarbons under various conditions, and studied by the spectroscopic ellipsometry (SE). We used the effective medium approximation with the dispersion model developed by Forouhi and Bloomer to determine simultaneously both the structure and the optical constants of the DLC films from their ellipsometric spectra. Especially, we investigated the variation of the multilayer structure including the interface layer, of the refractive indices, and of the extinction coefficients as the deposition conditions were varied; substrate pretreatment procedure, hydrocarbon precursors, and the substrate bias voltage were varied.

• Journal of the Korean Chemical Society
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• v.30 no.2
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• pp.207-215
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• 1986

A new method was proposed to improve removal of nitrogen oxides $(NO_x)$ in exhaust gas by the reduction method using ammonia. At the relative humidity of 60%, 50 ppm of $NO_x$ was decomposed at the rate of 1% per hour in the reaction chamber. On the other hand, by adding $NH_3$ which was 5 times more concentrated than NOx, the decomposition rate increased to 6% per hour for 50 ppm $NO_x$ and 10% per hour for 20ppm $NO_x$. Within the actual exhausted gases, the decomposition rate of $NO_x$ reached the maximum 15% per hour because of coexisted reducing gases, such as hydrocarbon and carbon monoxide, and excess humidity containing trace metal ions. In the presence of acidic $SO_2$ gas, the decomposition rate of $NO_x$ decreased. The decomposition of $NO_x$ seems to be caused by the mist which is added to the system, and $NH_3$ in the mist which reduces $NO_x$.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.181.2-181.2
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• 2014

A single-layer graphene has been uniformly grown on a Cu surface at elevated temperatures by thermally processing a poly (methyl methacrylate) (PMMA) film in a rapid thermal annealing (RTA) system under vacuum. The detailed chemistry of the transition from solid-state carbon to graphene on the catalytic Cu surface was investigated by performing in-situ residual gas analysis while PMMA/Cu-foil samples being heated, in conjunction with interrupted growth studies to reconstruct ex-situ the heating process. We found that the gas species of mass/charge (m/e) ratio of 15 ($CH_3{^+}$) was mainly originated from the thermal decomposition of PMMA, indicating that the formation of graphene occurs with hydrocarbon molecules vaporized from PMMA, such as methane and/or methyl radicals, as precursors rather than by the direct graphitization of solid-state carbon. We also found that the temperature for dominantly vaporizing hydrocarbon molecules from PMMA and the length of time, the gaseous hydrocarbon atmosphere is maintained, are dependent on both the heating temperature profile and the amount of a solid carbon feedstock. From those results, we strongly suggest that the heating rate and the amount of solid carbon are the dominant factors to determine the crystalline quality of the resulting graphene film. Under optimal growth conditions, the PMMA-derived graphene was found to have a carrier (hole) mobility as high as ${\sim}2,700cm^2V^{-1}s^{-1}$ at room temperature, which is superior to common graphene converted from solid carbon.

• Membrane Journal
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• v.33 no.6
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• pp.325-343
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• 2023

Direct methanol fuel cells (DMFCs) have been attracting attention as energy conversion devices that can directly supply methanol liquid fuel without a fuel reforming process. The commercial polymer electrolyte membranes (PEMs) currently applied to DMFC are perfluorosulfonic acid ionomer-based PEMs, which exhibit high proton conductivity and physicochemical stability during the operation. However, problems such as high methanol permeability and environmental pollutants generated during decomposition require the development of PEMs for DMFCs using novel ionomers. Recently, studies have been reported to develop PEMs using hydrocarbon-based ionomers that exhibit low fuel permeability and high physicochemical stability. This review introduces the following studies on hydrocarbon-based PEMs for DMFC applications: 1) synthesis of grafting copolymers that exhibit distinct hydrophilic/hydrophobic phase-separated structure to improve both proton conductivity and methanol selectivity, 2) introduction of cross-linked structure during PEM fabrication to reduce the methanol permeability and improve dimensional stability, and 3) incorporation of organic/inorganic composites or reinforcing substrates to develop reinforced composite membranes showing improved PEM performances and durability.

• Korean Chemical Engineering Research
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• v.48 no.4
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• pp.417-422
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• 2010

Nanosized $TiO_2$ particles were prepared by hydrothermal method from the aqueous peroxotitanate solution using the different carboxylic acids as an additives. The physical properties of prepared nanosized $TiO_2$ particles were investigated and we also examined the activity of $TiO_2$ particles as a photocatalyst on the decomposition of methylene blue. The major phase of all the prepared $TiO_2$ particles was an anatase structure regardless of carboxylic acids and a rutile peak was observed above $700^{\circ}C$. The photocatalytic activity increased with an increase of hydrocarbon number of carboxylic compounds and the highest activity was shown on the catalysts which was prepared using succinic acid as an additive and calcined at $500^{\circ}C$.

• Applied Chemistry for Engineering
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• v.34 no.6
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• pp.619-625
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• 2023

In order to solve problems caused by the heat load of hypersonic aircraft, this study examined the optimization of the Si/Al ratio of the catalyst and nickel ion exchange to improve the performance of the hydrocarbon decomposition reaction (endothermic reaction). It was confirmed that the catalysts prepared through Si/Al ratio optimization and nickel ion exchange showed about 10% improvement in heat absorption performance compared to thermal cracking at 4 MPa and 550 ℃. FT-IR and NH₃-TPD analyses were found to identify factors affecting activity changes, and it was observed that the Si/Al ratio of the HZSM-5 catalyst was closely correlated with acid site development and catalytic activity. In addition, TGA and O₂-TPO analyses were conducted to observe the carbon deposition inhibition properties of the nickel-added catalyst.

• Journal of Powder Materials
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• v.12 no.6 s.53
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• pp.413-421
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• 2005

Copper is able to work as a current collector under wide range of hydrocarbon fuels without coking in Solid oxide fuel cells (SOFCs). The application of copper in SOFC is limited due to its low melting point, which result in coarsening the copper particle. This work focuses on the sintering of copper powder with ceria coating layer. Ceria-coated powder was prepared by thermal decomposition of urea in $Ce(NO_3)_3\cdot6H_2O$ solution, which containing CuO core particles. The ceria-coated powder was characterized by XRD, ICP, and SEM. The thermal stability of the ceria-coated copper in fuel atmosphere $(H_2)$ was observed by SEM. It was found that the ceria coating layer could effectively hinder the grain growth of the copper particles.

• ETRI Journal
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• v.16 no.3
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• pp.1-10
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• 1994

Undoped GaAs has been successfully grown by chemical beam epitaxy (CBE) via surface decomposition process using arsine $(AsH_3)$ and trimethylgallium (TMG). Three distinct regions of temperature-dependent growth rates were identified in the range of temperatures from 570 to $690^{\circ}C$. The growth rates were found strongly dependent on the V/III ratio between 5 and 30. The growth rate at low V/III ratio seems to be determined by arsenic produced on the surface, whereas at high V/III ratio it shows dependence on the adsorption of TMG. Hall measurement and photoluminescence (PL) analysis show that the films are all p-type and that carbon impurities are primarily responsible for the background doping. Carbon concentrations have been found to be reduced by two orders of magnitude as compared to those of epilayers grown by CBE which employs TMG and arsenic obtained from precracked $AsH_3$ in a high temperature cell. It was also found that hydrogen atoms dissociated from unprecracked $AsH_3$ play an important role in removing hydrocarbon-containing species resulting in a significant reduction of car-bon impurities.

• Macromolecular Research
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• v.14 no.5
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• pp.491-498
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• 2006

The thermal degradation of poly(hexamethylene guanidine) phosphate (PHMG) was studied by dynamic thermogravimetric analysis (TGA) and pyrolysis-GC/MS (p-GC). Thermal degradation of PHMG occurs in three different processes, such as dephosphorylation, sublimation/vaporization of amine compounds and decomposition/ recombination of hydrocarbon residues. The kinetic parameters of each stage were calculated from the Kissinger, Friedman and Flynn-Wall-Ozawa methods. The Chang method was also used for comparison study. To investigate the degradation mechanisms of the three different stages, the Coats-Redfern and the Phadnis-Deshpande methods were employed. The probable degradation mechanism for the first stage was a nucleation and growth mechanism, $A_n$ type. However, a power law and a diffusion mechanism, $D_n$ type, were operated for the second degradation stage, whereas a nucleation and growth mechanism, $A_n$ type, were operated again for the third degradation stage of PHMG. The theoretical weight loss against temperature curves, calculated by the estimated kinetic parameters, well fit the experimental data, thereby confirming the validity of the analysis method used in this work. The life-time predicted from the kinetic equation is a valuable guide for the thermal processing of PHMG.