• Composites Research
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• v.30 no.2
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• pp.116-125
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• 2017

The purpose of this study is to develop silicon carbide fiber showing an excellent mechanical properties under highly oxidative conditions at high temperature. Polycarbosilane(PCS) as a preceramic precursor was used for making the SiC fiber. PCS fiber was taken by melt spinning method followed by melting the PCS at $300{\sim}350^{\circ}C$ in N2 gas. The Curing of PCS fiber was carried out in air oxygen chamber, prior to high temperature pyrolysis. Degree of cure was calculated by characteristic peak's ratio of Si-H to $Si-CH_3$ in FT-IR spectra before and after curing of PCS fiber. The properties of SiC fiber was affected greatly by the degree of cure. The SiC fiber produced by controlling fiber tension during heat treatment showed good properties. The SiC fiber exposed to $1000^{\circ}C$ at air from 1 min. up to maximum 50 hrs showed around 60% reduction in tensile strength. We found that large amount of carbon content on the fiber surface after long-term exposure has resulted in lower tensile strength.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.93-100
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• 2019

In this study, the mechanical properties of early-age concrete were evaluated by mixing the electric arc furnace oxidizing slag fine aggregate with 30% and 50% replacement ratio. Slump test, air content test and unit volume weight test were performed for fresh concrete, and compressive strength test and chloride penetration experiments were carried out in hardened concrete. The compressive strength increased up to 7 days of curing age with increasing replacement ratio of the electric furnace oxidizing slag, but the strength decreased to 90% level of OPC concrete at 28 days of age. Regarding the result of chloride penetration test, no significant differences from OPC concrete were evaluated, which shows a feasibility of application to concrete aggregate.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.5
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• pp.620-632
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• 2017

A chemical vapor curing method(CVC) was developed to cure polycarbosilane(PCS) fibers by using cyclohexene vapour as a non-oxygen active reactant, instead of air in oder to prepare the silicon carbide(SiC) fiber with low oxygen content. A cross-linked PCS fibers by cyclohexene vapor showed a completely different variation in IR spectra in comparison to the air-cured PCS fiber. CVC method resulted in less than 3 wt% in oxygen content. In this experiment conditions, The average tensile strength and modulus of SiC fiber obtained by CVC had 1995 MPa and 183 GPa respectively, which is higher than that of SiC fiber prepared by air-curing process.

• Journal of the Korea Institute of Building Construction
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• v.18 no.1
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• pp.9-15
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• 2018

Radon gas, which is present on the earth, is a primary carcinogen released from rocks, soil, building materials, etc., and exists as a unique gas phase. In order to solve the risk of radon gas, we evaluated the basic performance which can be used as indoor finishing materials in addition to the radon gas reduction properties of the matrix using anthracite. An anthracite used as a conventional filter material was used to produce a matrix, and a test was conducted to replace the gypsum board, which is one of the building materials used in the existing room. As the anthracite replacement ratio increases, flexural failure load strength increases and thermal conductivity tends to decrease. Depending on the thickness of the board, the reduction performance of radon gas shows a slight difference.

• Composites Research
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• v.26 no.5
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• pp.322-327
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• 2013

Carbon fiber-reinforced SiC matrix composites have good oxidation resistance and thermal shock resistance. These properties have allowed the composites to be applied to high-temperature structures. In this study, $C_f/SiC$ composites were fabricated via precursor infiltration and pyrolysis (PIP) process, including liquid phase infiltration and chemical vapor curing using cyclohexene. The final $C_f/SiC$ composites, which have gone through the PIP process five times, showed a density of $1.79g/cm^3$, as compared to a density of $0.43g/cm^3$ for pre-densified bare carbon fiber preform. As for the oxidation resistance characteristics, the weight of $C_f/SiC$ composite was maintained at 81% at $1400^{\circ}C$ in air for 6 hours. Chemical vapor curing (CVC) using cyclohexene has shown to be an effective method to achieve high densification, leading to increased oxidation resistance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.97-103
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• 2017

As the shortage of concrete aggregates is intensifying, the development of alternative resources is urgent. As the amount of steel slag increases year by year, attempts are being made to recycle slag into high-value-added products in order to develop an efficient resource recycling industry based on slag and to obtain economic benefits. However, the use of electric arc furnace oxidizing slag (EOS) as building materials is practically limited because it contains unstable materials. In this paper, physical properties of concrete were evaluated by using electric arc furnace slag aggregate. It has been produced with two levels of general strength area W / C 45% and high strength area W / C 30%. Fresh concrete has been tested in air content, flow and slump, unit weight. The properties of the cured concrete were investigated by compressive strength, bending strength and unit volume weight. As a result of this study, strength of concrete increased with increasing EOS aggregate mixture.

• Journal of the Korea Institute of Building Construction
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• v.14 no.4
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• pp.308-313
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• 2014

Recently, for longevity of resident building, the main trend is that the change of the inside space organization of resident building from wall construction to rhamen construction, which resulted in increase in use of lightweight composite panel. Thus, in this study, authors analyzed the engineering property of oxide of magnesium depending on the magnesium chloride addition ratio. The results of this research is expected to contribute on providing a fundamental material for the surface materials of lightweight composite panel. As the result of the experiment, as fluidity increased, air content decreased and initial set and final set as the magnesium chloride addition ratio increase. In the aspect of flexural strength and compressive strength, the test specimen showed the highest strength at 40% of the magnesium chloride addition ratio. At 20% of the magnesium chloride addition ratio, the test specimen showed the lowest water absorption rate. As the magnesium chloride addition ratio increases, the expansibility tends to increase as well in the aspect of shrinkage strain. After observing microstructure, we can see hydration products in the form of needle. It appeared high flexural strength because the hydration products have mineral fibrous tissue shape, which also contribute to the cause of the expansibility.

• 보존과학연구
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• s.32
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• pp.37-52
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• 2011

This study investigates the hardening characteristics of the mixture lacquer and glue at room temperature. Diverse samples were made from manufacturing of glue to the adding ratio in sap of the lacquer tree. After the examination of moisture content of samples, it has been seen that there is no relation with glue's kinds or adding ratio, but only with contain level of moisture. The samples made with film shape in order to examine the drying time. Samples with isinglass needed for over three days and had smooth surface. However, samples mixed with animal glue dried within a day and had ripples on the surface because of fast drying rate. In addition, the samples with isinglass had slow change of colour in early step of drying and no colour difference after completely drying although it had significant changes to black oxide as soon as contact with air. In structural analysis with FT-IR showed that the carbonyl bond increased in the samples of mixed with glue, compared to raw lacquer and treated lacquer.

• Tuberculosis and Respiratory Diseases
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• v.59 no.6
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• pp.690-695
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• 2005

Nitric acid is an oxidizing agent used in metal refining and cleaning, electroplating, and other industrial applications. Its accidental spillage generates oxides of nitrogen, including nitric oxide (NO) and nitrogen dioxide ($NO_2$), which cause chemical pneumonitis when inhaled. The clinical presentation of a nitric acid inhalation injury depends on the duration and intensity of exposure. In mild cases, there may be no symptoms during the first few hours after exposure, or the typical symptoms of pulmonary edema can appear within 3-24 hours. However, in cases of prolonged exposure, progressive pulmonary edema develops instantaneously and patients may not survive for more than 24 hours. We report a case of a 44-year-old male who was presented with acute respiratory distress syndrome after nitric acid inhalation. He complained of cough and dyspnea of a sudden onset after inhaling nitric acid fumes at his workplace over a four-hour period. He required endotracheal intubation and mechanical ventilation due to fulminant respiratory failure. He was managed successfully with mechanical ventilation using positive end expiratory pressure and systemic corticosteroids, and recovered fully without any deterioration in his pulmonary function.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.44 no.3
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• pp.211-218
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• 2018

Instant face lifting cosmetics contain various film forming agents for stretching the wrinkles on the skin surface. But, most of the film-forming polymers have sticky feels. And they are easily scrubbed out when skin is rubbed on. In this study, we focused on the influence of sodium silicate that has rapid film forming effect on skin surface and immediate wrinkle reducing effect. Sodium silicate, also known as water glass or soluble glass, is a compound containing sodium oxide and silica. Sodium silicate is a white powder that is readily soluble in water, producing an alkaline solution. Sodium silicate is stable in neutral and alkaline solutions. The sodium silicate solution hardens by drying in air and rapidly forms a thin film. When the solution is applied to the skin, the fine membrane coating is formed by water evaporation and ionic bond re-formation. It also makes the strong siloxane (Si-O) bonding on the skin surface. When these fixation properties are applied to cosmetics, they can give remarkable skin tightening effect. The sodium silicate solution can provide the lifting effect by forming a film on skin at a proper concentration. But, skin irritation may be caused with too high concentration of sodium silicate. We studied a desirable range of the sodium silicate concentration and combination with other fixatives for skin care formulation that has no sticky feels and no scrubbing out phenomenon. Immediate lifting gel was developed by using sodium silicate and various thickening systems. Among of the various thickeners, aluminum magnesium silicate showed the best compatibility with sodium silicate for rapid lifting effect. This instant physical lifting gel was confirmed as a low stimulating formula by skin clinical test.