• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.497-500
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• 2008

This research carries out experiments for hydration exothermic rate and adiabatic temperature rise of concrete to examine the characteristics of the hydration heat of high flowing self-compacting concrete with a normal strength. As a result of the hydration exothermic rate experiment, the high flowing self-compacting concrete that used Lime stone powder and fly ash as polymers shows that its hydration heat amount reduces due to the reduction of unit cement. The result measured the adiabatic temperature rise of concrete presents that high flowing self-compacting concrete having lots of binder contents has a good performance in temperature reduction due to the effect of polymer and that triple adding high flowing self-compacting concrete has a similar temperature rise speed with conventional concrete. As a result of the research, high flowing self-compacting concrete shows a better temperature reduction performance for the binder content per unit than conventional concrete. In addition, it is judged that triple adding high flowing self-compacting concrete with a specified concrete strength 30 MPa is more beneficial in temperature reduction and early hydration heat than double adding high flowing self-compacting concrete.

• Analytical Science and Technology
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• v.14 no.3
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• pp.197-202
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• 2001

The characteristics of the electrochemically Li intercalated synthetic graphite were determined from the studies with XRD method, DSC and solid $^7Li-NMR$ spectrophotometric analysis. From the results of X-ray diffraction method, it was found that the compounds in the stage 1 structure were predominantly formed. The enthalpy and entropy changes of the compounds can be obtained from the differential scanning calorimetric analysis results. From these results, it was found that exothermic and endothermic reactions of lithium intercalated into synthetic graphite are related to thermal stability of lithium ion between carbon graphene layers. From the $^7Li-NMR$ data, scientific observation found that bands are shift toward higher frequencies with increasing lithium concentration because non-occupied electron shells of Li increased in charge carrier density. Line widths of the Li intercalated synthetic graphite compounds decreased slowly because of non-homogeneous local magnetic order and the random electron spin direction for substituted Li.

• Analytical Science and Technology
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• v.11 no.3
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• pp.156-160
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• 1998

SiC is synthesized by sol-gel and carbothermal reaction method from various carbon sources and Si source and characterized through the results of DSC and XRD. More SiC has been formed in carbothermal reaction than sol-gel method. From the XRD results, the degree of formation of SiC increases in the order of petroleum cokes, activated carbon, artificial graphite all in two introduced methods. Based on the DSC data, the enthalpy values for the exothermic reaction decrease in the order of activated carbon, petroleum cokes, artificial graphite in carbothermal reaction methods, while those for the endothermic reactions increase in the reverse order. But, the enthalpy values for the exothermic reactions decrease in the order of petroleum cokes, activated carbon, artificial graphite in sol-gel methods.

• Bulletin of the Korean Chemical Society
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• v.11 no.4
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• pp.276-281
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• 1990

The equivalent conductance of univalent cation (potassium, silver, thallium and ammonium) perchlorates in methanol containing 18-membered crown ethers, 18-crown-6 (18C6) and 1,10-dithia-18-crown-6 (DT18C6) were measured at different temperatures. The equivalent conductances of ammonium perchlorate were increased by increasing content of DT18C6 exceptionally, due to more favorable solvations than complexations. From the equivalent conductance changes, the formation constants for 1:1 compmlexes have been determined, and the values of enthalpy and entropy changes have been calculated. The complexations of 18C6 and DT18C6 with the univalent cations under investigation are all exothermic and the ${\Delta}$S values are all negative and no considerable differences around 50 J/ (k mol). The selectivity order of 18C6 is $K^+ > Tl^+ > Ag^+ > NH_4^+$, while that of DT18C6 is $Ag^+ > Tl^+ > NH_4^+ > K^+$. By sulfur substitutions in 18C6 result in significant decrease in stability, but the stability of $Ag^+$-DT18C6 complex are $10^4$ times larger than those of $K^+$. This increase of stabilities for $Ag^+$-DT18C6 complex are primary due to the result of favorable exothermic heat of reaction between the polarizable soft cation and soft sulfur centers. In NMR experiment, the stepwise additions of cation perchlorates into crown ether solutions induced two major spectral changes. First, the resonance all shift down field and the cation induced shifts were linear up to 1:1 cation/crown ratio, above which no further changes were observed. On the basis of these results, it could be concluded that 1:1 complex is formed. Second, the magnitudes of cation induced shifts were different each other in same ligand. By addition of silver ion to the solution of DT18C6, the largest shift of proton peak near the sulfur atom was observed. These effects are also arisen from the results of covalent bonding between "soft-soft" interactions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.4
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• pp.398-404
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• 2007

In this paper, thermal characteristics of a nitrous oxide ($N_2O$) catalytic reactor with packed-bed geometry are theoretically and numerically investigated. Several researchers experimentally presented that catalytic decomposition of $N_2O$ in a packed bed generates about 82kJ/mole in the exothermic reaction. Based on the results they have studied the catalytic decomposition of $N_2O$ in a packed bed to use it not only as a mono-propellant thrust for small satellites but also as an igniter system for hybrid rockets. So we aim to identify important parameters existing in an $N_2O$ packed-bed geometry, and to clarify its critical effect on thermal characteristics of the catalytic igniter using a porous medium approach.

• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.59-63
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• 2012

The use of dry chemical powder has been increased as it can be stored for a long period and sustain in stable condition compared to gas or liquid phase extinguishing agents. A new type of dry chemical powder using Zeolite was produced in the research. Chemical powder was adsorbed into Zeolite 13X, a porous material appearing negative catalytic effect, to create extinguishing powder obtaining core shell structure and measured physical properties and run a small scale fire extinguishment. SEM, XRD, TA analysis was also executed, and extinguishing characteristics were measured by fire extinguishing experiment on oil pool fire. The experiment showed that the average particle size of Zeolite 13X was equivalent, indicating about $3{\pm}1{\mu}m$ and thermal analysis result illustrated that Zeolite 13X showed exothermic reaction peaks at $900^{\circ}C$ due to solid-state transformation. Extinguishing characteristics on oil fire of $NaHCO_3$/Zeolite 13X and $NH_4H_2PO_4$/Zeolite were improved, influenced by adsorbed extinguishing powders on Zeolite 13X and Zeolite 13X that contains high phase transition temperature.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.21 no.3
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• pp.107-113
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• 2015

This work focused on the study of thermal properties and kinetic behavior of LDPE-nanoclay composite films. The effect of nanoclay content (0.5, 1, 3, and 5 wt%) on thermal stability and crystallization characteristics of the nanocomposites were investigated by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The results from endothermic curve showed that the nanoclay played an important role in the crystallization of nanocomposites by acting as nucleating agent. From exothermic curve, there was a crystallization temperature shift which was attributed to crystallization process induced by nanoclay. The TGA results showed that the addition of nanoclay significantly increased the thermal stability of LDPE matrix, which was likely due to the characteristic of layered silicates/clays dispersed in LDPE matrix as well as the formation of multilayered carbonaceous-silicate char. A well-known Coats-Redfern method was used to evaluate the decomposition activation energy of nanocomposite. It was demonstrated that introducing of nanoclay to LDPE matrix escalated the activation energy of nanocomposite decomposition resulting in thermal stability improvement.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.5-8
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• 2007

In this paper, numerical investigation has been carried out to study performance of methane autothermal reformer and dynamic behavior for light-off under various operating conditions. In order to simulate the given problems, numerical methods are incorporated using finite-volume method. In addition, porous medium approach is accepted because the catalytic phenomena occur in porous media. Also, start-up issue is significant in autothermal reformer although the reaction is marginally exothermic. Thus, in this study transient behavior has been also investigated to find out optimal operating conditions for start-up.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.1009-1012
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• 2003

A novel powder processing technique for the preparation of copper activated zinc sulfide (ZnS:Cu,Al) phosphor by combustion process has been proposed. Exothermic reaction between dissolved copper nitrate and carbohydrazide give small-sized particles in presence of alkali metal halides at lower temperature than the traditional method of preparation. This new route takes less than five minutes and requires much less energy. The optical and luminescence characteristics of ZnS:Cu,Al phosphor thus prepared were found to be enhanced significantly. Carbohydrazide acted as fuel at $500^{\circ}C$ with rapid heating and then the phosphors obtained were heated at $900^{\circ}C$ in an inert atmosphere for 3hrs to get better luminescent properties.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1123-1130
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• 2006

This study discusses about research efforts of hydrogen generation from hydrocarbon(e.g., diesel, gasoline, natural gas, and LPG), especially, butane reforming by using Autothermal Reforming Reaction (ATR) technology. Several catalysts were selected for butane ATR. Thermodynamic reactor conditions (temperature, $O_2$/C, S/C) are varied and reforming characteristics of 2 catalysts (Pt and Rh on ceramic supports) and 1 commercial catalyst (FCR-HC35) have been examined. To understand reaction behaviors in an ATR reactor comprehensively, temperature profiles of reactor were observed. By mass transfer limitation, fuel conversion decreases when GHSV increases. Significant temperature variation along the reactor was observed and it was mainly due reaction kinetics difference between exothermic oxidation and endothermic reforming reaction.