• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1679-1684
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• 2011

Interfacial reactions kinetics often differ from kinetics of bulk reactions. Here, we describe how the density change of an immobilized reactant influences the kinetics of interfacial reactions. Self-assembled monolayers (SAMs) of alkanethiolates on gold were used as a model interface and the Diels-Alder reaction between immobilized quinones and soluble cyclopentadiene was used as a model reaction. The kinetic behavior was studied using varying concentrations of quinones. An unusual threshold density of quinones (${\Gamma}_c$ = 5.2-7.2%), at which the pseudo-first order rate constant started to vary as the reaction progressed, was observed. This unexpected kinetic behavior was attributed to the phase-separation phenomena of multi-component SAMs. Additional experiments using more phase-separated two-component SAMs supported this explanation by revealing a significant decrease in ${\Gamma}_c$ values. When the background hydroxyl group was replaced with carboxylic or phosphoric acid groups, ${\Gamma}_c$ was observed at below 1%. Also, more phase-separated thermodynamically controlled SAMs produced a lower critical density (3% < ${\Gamma}_c$ < 4.9%) than that of the less phaseseparated kinetically controlled SAMs (6.5% < ${\Gamma}_c$ < 8.9%).

• Korean Journal of Materials Research
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• v.12 no.12
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• pp.947-954
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• 2002

HCl concentration and reaction time are the decisive factors in determining the structure of precipitates in the process of synthesis of $TiO_2$ particles from aqueous $TiOCl_2$ solution by precipitation and the volumetric proportion of brookite phase in $TiO_2$ particles can be controlled by these two factors. As reaction rate increases with increase of reaction temperature, the reaction time, at which maximum volumetric proportion of brookite phase in $TiO_2$ particles was obtained, was reduced. The brookite was transformed directly to rutile phase with only increase of reaction time. And precipitation was delayed with increase of HCl concentration because the amount of $H_2$O, which is necessary source of oxygen for conversion of $Ti^{+4}$ to $TiO_2$, was relatively reduced with increase of that. Brookite in the mixture phase powder was finally transformed to rutile phase via anatase through heat-treatment.

• Korean Journal of Materials Research
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• v.16 no.1
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• pp.50-57
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• 2006

Phase mixtures of Titanium boride, nitride, and carbide powder were produced by the reduction of a mixture of titanium and boron oxides with carbon via a gas-solid phase reaction. Boron oxides produce a vapour phase or decompose to a metal sub-oxide gaseous species when reduced at elevated temperature. The mechanism of BO sub-oxide gas formation from $B_2O_3$ and its subsequent reduction to titanium diboride for the production of uniform size hexagonal platelets is explained. These gaseous phases are critical for the formation of boride, nitride and carbide ceramics. For the production of ceramic phase composite microstructures, the nitrogen partial pressure was the most critical factor. Some calculated equilibrium phase fields has been verified experimentally. The theoretical approach therefore identifies conditions for the formation of phase mixtures. The thermodynamic and kinetic factors that govern the phase constituents are also discussed.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.3
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• pp.1225-1233
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• 2015

This study aims to clarify the psychosocial reactions of female patients with gynecological cancer undergoing chemotherapy and in the process of suffering from alopecia and to examine their nursing support. The target group comprised female patients who had received two or more cycles of chemotherapy, were suffering from alopecia, and were aged 30-65. Data were collected from semi-structured interviews, conducted from the time the patients were informed by their doctors that they might experience alopecia due to chemotherapy to the time they actually experienced alopecia and until they were able to accept the change. Inductive qualitative analysis was employed to close in on the subjective experiences of the cancer patients. The results showed the existence of six phases in the psychosocial reactions in the process of alopecia: phase one was the reaction after the doctor's explanation; phase two was the reaction when the hair starts to fall out; phase three was the reaction when the hair starts to intensely fall out; phase four was the reaction when the hair has completely fallen out; phase five was the reaction to behavior for coping with alopecia; and phase six was the reaction to change in interpersonal human relationships. The results also made it clear that there are five types of reaction patterns as follows: 1) treatment priority interpersonal relationship maintenance type; 2) alopecia agitated interpersonal relationship maintenance type; 3) alopecia agitated interpersonal relationship reduction type; 4) alopecia denial interpersonal relationship reduction type; and 5) alopecia denial treatment interruption type. It is important to find out which of the five types the patients belong to early during treatment and provide support so that nursing intervention that suits each individual can be practiced. The purpose of this study is to make clear the process in which patients receiving chemotherapy come to accept alopecia and to examine evidence-based nursing care on patients with strong mental distress from alopecia.

• Bulletin of the Korean Chemical Society
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• v.18 no.9
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• pp.985-994
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• 1997

The reaction of gas-phase atomic hydrogen with hydrogen atoms chemisorbed on Fe(110) surface is studied by use of classical trajectory procedures. Flow of energy between the reaction zone and bulk solid phase has been treated in the generalized Langevin equation approach. A London-Eyring-Polanyi-Sato energy surface is used for the reaction zone interaction. Most reactive events are found to occur in strong single-impact collisions on a subpicosecond scale via the Eley-Rideal mechanism. The extent of reaction is large and a major fraction of the available energy goes into the vibrational excitation of H2, exhibiting a vibrational population inversion. Dissipation of reaction energy to the heat bath can be adequately described using a seven-atom chain with the chain end bound to the rest of solid. The extent of reaction is not sensitive to the variation of surface temperature in the range of Ts=0-300 K in the fixed gas temperature, but it shows a minimum near 1000 K over the Tg=300-2500 K.

• Tribology and Lubricants
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• v.13 no.4
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• pp.60-65
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• 1997

The tungsten disulfide $(WS_2)$ solid lubricant was synthesized by two different reaction processes, i.e., the reaction between $CS_2$ gas phase and solid $WO_3$powder, and the vapour phase transport method of tungsten and sulfur in a high vacuum. The chemical and physical characteristics of synthesized $WS_2$powder were analyzed in terms of the average particle size, morphology, crystalline phase etc. in comparison with those of commercial $WS_2$powder. The solid $WO_3$ powder with the average size of 0.2 ${\mu}{\textrm}{m}$ was reacted with $CS_2$gas flowed with$N_2$or 96%$N_2{\times}4%H_2$forming gas for 36 h and 24 h at 90$0^{\circ}C$ respectively. $WS_2$ crystalline phase was then formed through the intermediate phase of .$W_{20}O_{58}$ In the case of vapour phase transport method, the 3.5 wt% iodine was added as a vapour transport reagent into the composition of tungsten and sulfur powders maintaining a constant molar ratio of W:S=1:2.2. The mixture was then heat treated at 85$0^{\circ}C$ for 2 weeks in vacuum. The reaction product obtained showed the average size of 12 ${\mu}{\textrm}{m}$ and the hexagonal plate shape of typical solid lubricant with 2H-$WS_2$crystalline phase.

• Journal of the Korean Ceramic Society
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• v.35 no.11
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• pp.1190-1196
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• 1998

Ultrafine ${\beta}$-SiC powders were synthesized by the vapor phase reaction of TMS[Si(CH3)4] in hydrogen The reaction temperature and TMS concentration were varied from 1000 to 1400$^{\circ}C$ and from 1 to 10% respectively. The average particle size and phase of the powders were analyzed by TEM and XRD. Ultrafine ${\beta}$-SiC powders were synthesized above 1000$^{\circ}C$ and the crystallinity of the powders increased with increasing reaction temperature. Shape of the particles were spherical and had average size of about 20 nm which showed no difference as the reaction temperature and TMS concentration increased. From the FT-IR analysis the absorption bands of Si-C of the powders shifted to higher wavenumber as the reaction temperature increased,. Under the condition of total gas flow above 1500cc/min ${\beta}$-SiC and poly-Si powders were obtained simultaneously. The Si-O bond intensity was increased under the condition of total gas flow rate above 1000cc/min which might be due to oxidation formed on poly-Si.

• Macromolecular Research
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• v.11 no.4
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• pp.267-272
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• 2003

The isothermal cure reactions of blends of epoxy (DGEBA, diglycidyl ether of bisphenol A)/anhydride resin with polyamide copolymer (poly(dimmer acid-co-alkyl polyamine)) or PEI were studied using differential scanning calorimetry (DSC). Rheological measurements have been made to investigate the viscosity and mechanical relaxation behavior of the blends. The reaction rate and the final cure conversion were decreased with increasing the amount of thermoplastics in the blends. Lower values of final cure conversions in the epoxy/thermoplastic blends indicate that thermoplastics hinder the cure reaction between the epoxy and the curing agent. Complete miscibility was observed in the uncured blends of epoxy/thermoplastics up to $120^{\circ}C$ but phase separations occurred in the early stages of the curing process at higher temperatures than $120^{\circ}C$. According to the rheological measurement results, a rise of G' and G" at the onset of phase separation is seen. A rise of G' and G" is not observed for neat epoxy system since no phase separation is seen during cure reaction. At the onset of phase separation the rheological behavior was influenced by the amount of thermoplastics in the epoxy/thermoplastic blends, and the onset of phase separation can be detected by rheological measurements.

• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.44-49
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• 2000

Silicon nitride powders, were synthesized by the vapor phase reaction using SiH4-NH3 gaseous mixture. The reaction temperature, ratio of NH3 to SiH4 gas and the overall gas quantity were varied. The synthesized powders were characterized using X-ray, TEM, FT-IR and EA. The synthesized silicon nitride powders were in amorphous state, and the average particle size was about 100nm. TEM analysis revealed that the particle size decreased with increasing reaction temperature and gas flow quantity. As-received amorphous powders were annealed in nitrogen atmosphere at 140$0^{\circ}C$ for 2h, then the powders were completely crystallized at 0.2 ratio of NH3 to SiH4.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.5
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• pp.386-393
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• 2008

The Sulfur-iodine(SI) thermochemical cycle is one of the most promising methods for massive hydrogen production. For the purpose of continuous operation of SI cycle, phase separation characteristics into two liquid phases ($H_2SO_4$-rich phase and $HI_x$-rich phase) were directly investigated via Bunsen reaction. The experiments for Bunsen reaction were carried out in the temperature range, from 298 to 333 K, and in the $I_2/H_2O$ molar ratio of $0.109{\sim}0.297$ under a continuous flow of $SO_2$ gas. As the results, solubility of $SO_2$, decreased with increasing the temperature, had considerable influence on the global composition in the Bunsen reaction system. The amounts of impurity in each phase(HI and $I_2$ in $H_2SO_4$-rich phase and $H_2SO_4$ in $HI_x$-rich phase) were decreased with increasing $H_2SO_4$ molar ratio and temperature. To control the amounts of impurity in $HI_x$-rich phase, temperature is a factor more important than $I_2/H2_O$ molar ratio. On the other hand, the affinity between $HI_x$ and $H_2O$ was increased with increasing $I_2/H2_O$molar ratio.