• KSBB Journal
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• v.28 no.6
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• pp.356-365
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• 2013

The novel Aloe gels were prepared with dewatering and impregnation by soaking (DIS) processing of Aloe vera leaf slice at four different temperatures (25, 35, 45 and $55^{\circ}C$), using dehydration solution of 40% (w/v) polyethylene glycol (PEG4000). The PEG-impregnation to Aloe vera leaf slice during DIS was observed depending on immersion temperature, and the PEG-impregnated Aloe vera gel (PEG-i-AVG) obtained was characterized using $^1H$ NMR, FT-IR, GPC, XRD and TGA. The PEG-i-AVG had the higher levels of Aloe bioactives (glucomannan and O-acetyl contents) and better quality indices by $^1H$ NMR and FT-IR spectroscopy than those of native Aloe gel. Also, the obtained Aloe gel maintained the bimodal patterns in higher molecular weight region by GPC indicating no degradation of polysaccharide from native Aloe gel. The result observed by SEM confirmed a surface modification by forming the porous structure, and TGA result exhibited better thermal stability than that of native Aloe gel. XRD result revealed that the crystalline structure in Aloe gel was led by incorporation of PEG. Significant decrease of %insolubility and high enhancement of water solubility index were observed, respectively, and highly ordered conformation such as a helix structure was also indicated by Congo red reaction. We concluded that the modification effect for enhancing function of native Aloe gel was successfully obtained by DIS process using PEG as a dehydrating agent. These results suggested that this DIS process had a high potential for developing a new minimally processed product from Aloe vera leaf.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.537-542
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• 2011

Magnesium hydroxide as a non-halogen flame retardant has increasing attention due to its non-toxicity, high decomposition temperature and smoke suppressant ability during combustion. For the application of magnesium hydroxide retardant to the textile by soaking and coating method, the prerequisite for the coating is a small particle size, stable dispersion, and adhesion to the textile. The dispersion of $Mg(OH)_2$ particles and stability of the coating was checked by monitoring the change of transmittance and backscattering by varying the types of dispersion agents, binder, solvent, and $Mg(OH)_2$ source, and their compositions in the coating. The $Mg(OH)_2$ dispersion coating was applied to PET(poly(ethylene terephthalate)) non-woven textile. The physical properties are characterized by surface morphology, amount of coating, particle dispersion, and adhesion test. The flame retardant $Mg(OH)_2$ coated textile has been compared by limited oxygen index(LOI) and thermal gravimetry and differential scanning calorimetry(TG-DSC). It was found that phosphorous additive may give synergistic effect on $Mg(OH)_2$ flame retardant coating to make the flame retardant PET non-woven textile.

• Korean Journal of Materials Research
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• v.21 no.1
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• pp.8-14
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• 2011

To improve the chemical stability of metal, the ceramic coatings on metallic materials have attracted interest from many researchers due to the chemical inertness of ceramic materials. To endure strong acids, SiOC coating on metal substrate was carried out by dip coating method using 20wt% polyphenylcarbosilane solution; SiC powder was added to the solution at 10wt% and 15wt% to improve the mechanical properties and to prevent cracks of the film. Thermal oxidation as a curing step was carried out at $200^{\circ}C$ for crosslinking of the polyphenylcarbosilane, and the coating samples were pyrolysized at $800^{\circ}C$ under argon to convert the polyphenylcarbosilane to SiOC film. The thicknesses of the SiOC coating films were $2.36{\mu}m$ and $3.16{\mu}m$. The quantities of each element were measured as $SiO_{1.07}C_{6.33}$ by EPMA, and it can be confirmed that the SiOC film from polyphenylcarbosilane was formed in a manner that was carbon rich. The hardness of the SiOC film was found to be 3.2Gpa through nanoindentor measurement. No defect including cracks appeared in the SiOC film. The weight loss of the SiOC coated stainless steel was within 2% after soaking in 10% HCl solution at $80^{\circ}C$ for one week. From these results, SiOC coating shows good potential for application to protect against severe chemical corrosion of stainless steel.

• Journal of the Korean Wood Science and Technology
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• v.39 no.3
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• pp.221-229
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• 2011

Due to the increase of oil price and the environmental issue such as the emission of volatile organic compounds, the necessity for developing alternative resins of petroleum-based adhesive resins, which have extensively been used for the manufacture of wood-based products, has been speculation since the early 1990. In our study, rapeseed flour (RSF), which is the by-product of bio-diesel produced from rapeseed, were hydrolyzed by enzymes. As a crosslinking agents of the RSF hydrolyzates, phenol-formaldehyde prepolymers (PF) were prepared. The RSF hydrolyzates and PF were mixed to complete the formulation of RSF-based adhesive resins, and the resins were applied to make the laminated veneer lumber (LVL). The physical and mechanical properties of the LVL were measured to examine whether RSF can be used as raw materials of adhesive resins for the fabrication of LVL or not. The average moisture content and soaking delamination rate of the LVL bonded with RSF-based adhesive resins exceeded the minimum requirement of KS standard. Moreover, thermal analysis of the RSF-based resins showed similar tendencies except for the RSF-based adhesive resins formulated with pectinase-hydrolyzed RSF. The bending strengths of the LVL were higher than that of the LVL made with commercial PF resins. These results showed the potential of RSF as a raw material of alternative adhesives for the production of LVL. Further works on the optimal conditions of RSF hydrolysis and spreading characteristics for RSF-based adhesive resins is required to improve the adhesive performance of RSF-based resins.

• The Korean Journal of Food And Nutrition
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• v.11 no.2
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• pp.237-242
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• 1998

This study was carried out to process canned ark shell with highly quality by management of proper processing conditions for prevention of oxidation and discoloration by heating. Ark shell has hemoglobin as blood pigment in red blood shell which same as other cockles. Hemoglobin is easy to come oxidation and browning reaction, and it has large contents of carotenoid as meat pigment. Proximate compositions in ark shell were 76.9% of moisture, 18.1% of crude protein, 1.8% of crude lipid, 1.3% of carbohydrate and 1.6% of crude ash. And contents of carotenoid and hemoglobin were 0.67~1.02mg% and 0.98~1.64g/dl, respectively. When the living ark shell was soaked in 2% NaCl solutions, about 89% of mud was removed after 10 hours soaking, and over 91% was removed when the pH was adjusted to 7.5. Carotenoid pigment were prepared that extracted from ark shell by using acetone. And determined visible spectrum were two peak at 452nm and 687nm, and λmax were 452nm. During thermal treatment at 95$^{\circ}C$, 111$^{\circ}C$, 116$^{\circ}C$ and 121$^{\circ}C$ for 60 minutes, retention ratio of carotenoid were 71.8%, 66.8%, 64.4% and 36.5%, and after 120 minutes retention ratio were 56.6%, 30.6%, 30.3% and 17.2%, respectively. When heated at 95$^{\circ}C$, 111$^{\circ}C$, 116$^{\circ}C$ and 121$^{\circ}C$, formation of browning material were increased at high temperature and long time treatment.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.6
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• pp.709-734
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• 2001

The aims of this experiment were to investigate the strain and temperature changes simultaneously within autopolymerzing acrylic resin specimens. A computerized data acquisition system with an electrical resistance strain gauge and a thermocouple was used over time periods up to 180 minutes. The overall strain kinetics, the effects of stress relaxation and additional heat supply during the polymerization were evaluated. Stone mold replicas with an inner butt-joint rectangular cavity ($40.0{\times}25.0mm$, 5.0mm in depth) were duplicated from a brass master mold. A strain gauge (AE-11-S50N-120-EC, CAS Inc., Korea) and a thermocouple were installed within the cavity, which had been connected to a personal computer and a precision signal conditioning amplifier (DA1600 Dynamic Strain Amplifier, CAS Inc., Korea) so that real-time recordings of both polymerization-induced strain and temperature changes were performed. After each of fresh resin mixture was poured into the mold replica, data recording was done up to 180 minutes with three-second interval. Each of two poly(methyl methacrylate) products (Duralay, Vertex) and a vinyl ethyl methacrylate product (Snap) was examined repeatedly ten times. Additionally, removal procedures were done after 15, 30 and 60 minutes from the start of mixing to evaluate the effect of stress relaxation after deflasking. Six specimens for each of nine conditions were examined. After removal from the mold, the specimen continued bench-curing up to 180 minutes. Using a waterbath (Hanau Junior Curing Unit, Model No.76-0, Teledyne Hanau, New York, U.S.A.) with its temperature control maintained at $50^{\circ}C$, heat-soaking procedures with two different durations (15 and 45 minutes) were done to evaluate the effect of additional heat supply on the strain and temperature changes within the specimen during the polymerization. Five specimens for each of six conditions were examined. Within the parameters of this study the following results were drawn: 1. The mean shrinkage strains reached $-3095{\mu}{\epsilon},\;-1796{\mu}{\epsilon}$ and $-2959{\mu}{\epsilon}$ for Duralay, Snap and Vertex, respectively. The mean maximum temperature rise reached $56.7^{\circ}C,\;41.3^{\circ}C$ and $56.1^{\circ}C$ for Duralay, Snap, and Vertex, respectively. A vinyl ethyl methacrylate product (Snap) showed significantly less polymerization shrinkage strain (p<0.01) and significantly lower maximum temperature rise (p<0.01) than the other two poly(methyl methacrylate) products (Duralay, Vertex). 2. Mean maximum shrinkage rate for each resin was calculated to $-31.8{\mu}{\epsilon}/sec,\;-15.9{\mu}{\epsilon}/sec$ and $-31.8{\mu}{\epsilon}/sec$ for Duralay, Snap and Vertex, respectively. Snap showed significantly lower maximum shrinkage rate than Duralay and Vertex (p<0.01). 3. From the second experiment, some expansion was observed immediately after removal of specimen from the mold, and the amount of expansion increased as the removal time was delayed. For each removal time, Snap showed significantly less strain changes than the other two poly(methyl methacrylate) products (p<0.05). 4. During the external heat supply for the resins, higher maximum temperature rises were found. Meanwhile, the maximum shrinkage rates were not different from those of room temperature polymerizations. 5. From the third experiment, the external heat supply for the resins during polymerization could temporarily decrease or even reverse shrinkage strains of each material. But, shrinkage re-occurred in the linear nature after completion of heat supply. 6. Linear thermal expansion coefficients obtained from the end of heat supply continuing for an additional 5 minutes, showed that Snap exhibited significantly lower values than the other two poly(methyl methacrylate) products (p<0.01). Moreover, little difference was found between the mean linear thermal expansion coefficients obtained from two different heating durations (p>0.05).

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.154-155
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• 2012

The promise of nano-crystalites (nc) as a technological material, for applications including display backplane, and solar cells, may ultimately depend on tailoring their behavior through doping and crystallinity. Impurities can strongly modify electronic and optical properties of bulk and nc semiconductors. Highly doped dopant also effect structural properties (both grain size, crystal fraction) of nc-Si thin film. As discussed in several literatures, P atoms or radicals have the tendency to reside on the surface of nc. The P-radical segregation on the nano-grain surfaces that called self-purification may reduce the possibility of new nucleation because of the five-coordination of P. In addition, the P doping levels of ${\sim}2{\times}10^{21}\;at/cm^3$ is the solubility limitation of P in Si; the solubility of nc thin film should be smaller. Therefore, the non-activated P tends to segregate on the grain boundaries and the surface of nc. These mechanisms could prevent new nucleation on the existing grain surface. Therefore, most researches shown that highly doped nc-thin film by using conventional PECVD deposition system tended to have low crystallinity, where the formation energy of nucleation should be higher than the nc surface in the intrinsic materials. If the deposition technology that can make highly doped and simultaneously highly crystallized nc at low temperature, it can lead processes of next generation flexible devices. Recently, we are developing a novel CVD technology with a neutral particle beam (NPB) source, named as neutral beam assisted CVD (NBaCVD), which controls the energy of incident neutral particles in the range of 1~300eV in order to enhance the atomic activation and crystalline of thin films at low temperatures. During the formation of the nc-/pm-Si thin films by the NBaCVD with various process conditions, NPB energy directly controlled by the reflector bias and effectively increased crystal fraction (~80%) by uniformly distributed nc grains with 3~10 nm size. In the case of phosphorous doped Si thin films, the doping efficiency also increased as increasing the reflector bias (i.e. increasing NPB energy). At 330V of reflector bias, activation energy of the doped nc-Si thin film reduced as low as 0.001 eV. This means dopants are fully occupied as substitutional site, even though the Si thin film has nano-sized grain structure. And activated dopant concentration is recorded as high as up to 1020 #/$cm^3$ at very low process temperature (＜ $80^{\circ}C$) process without any post annealing. Theoretical solubility for the higher dopant concentration in Si thin film for order of 1020 #/$cm^3$ can be done only high temperature process or post annealing over $650^{\circ}C$. In general, as decreasing the grain size, the dopant binding energy increases as ratio of 1 of diameter of grain and the dopant hardly be activated. The highly doped nc-Si thin film by low-temperature NBaCVD process had smaller average grain size under 10 nm (measured by GIWAXS, GISAXS and TEM analysis), but achieved very higher activation of phosphorous dopant; NB energy sufficiently transports its energy to doping and crystallization even though without supplying additional thermal energy. TEM image shows that incubation layer does not formed between nc-Si film and SiO2 under later and highly crystallized nc-Si film is constructed with uniformly distributed nano-grains in polymorphous tissues. The nucleation should be start at the first layer on the SiO2 later, but it hardly growth to be cone-shaped micro-size grains. The nc-grain evenly embedded pm-Si thin film can be formatted by competition of the nucleation and the crystal growing, which depend on the NPB energies. In the evaluation of the light soaking degradation of photoconductivity, while conventional intrinsic and n-type doped a-Si thin films appeared typical degradation of photoconductivity, all of the nc-Si thin films processed by the NBaCVD show only a few % of degradation of it. From FTIR and RAMAN spectra, the energetic hydrogen NB atoms passivate nano-grain boundaries during the NBaCVD process because of the high diffusivity and chemical potential of hydrogen atoms.