• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.111-119
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• 2011

Recently, urban redevelopment programs and expansion of social infrastructure have caused massive amounts of construction waste in construction fields, and the mounds of it keep increasing every year. The disposal of construction waste is emerging as a national and social issue and the recycled powder generated by the treatment process of waste concrete is all being abolished or buried. Therefore, the purpose of this study is to utilize waste sludge generated by the wet-type treatment process of waste concrete as materials(binder, filler) for cement composite. This study evaluates physical and mechanical properties of mortar using recycled powder according to heating temperature, contents and applications. As a result of the chemical analysis, recycled powder is composed mainly of CaO and $SiO_2$, and that it is even lower in the content of CaO than OPC. The charateristics of mortar using recycled powder, according to drying and heating temperature, shows that as the heating temperature increases, flow decreases. Also, compressive strength and porosity of mortar using recycled powder was superior when heating temperature was $600^{\circ}C$. Thus, it is revealed that an effective development of recycled powder is possible since the binder by cement composite recovers a hydraulic property during heating at $600^{\circ}C$.

• Membrane Journal
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• v.16 no.4
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• pp.268-275
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• 2006

Novel SILEMs were prepared by multi-stage phase separation process combined by the low temperature phase separation (LTPS) and the high temperature phase separation (HTPS) using room temperature ionic liquids (RTILs) which have a high ionic conductivity. PVDF and imidazolium series ionic liquids were used as membrane material and electrolyte, respectively. To study the ion conducting properties, the SILEMs were tested using LCR meter at temperature controlled from 30 to $130^{\circ}C$. Under humid conditions, with increasing temperature from 30 to $100^{\circ}C$, the ion conductivity of the cast $Nafion^{(R)}$ membrane increased linearly, but then started to decrease after $100^{\circ}C$. However, in the case of the SILEMs, with increasing operating temperature, the ion conductivity increased. Also, the ion conductivity behaviors of the SILEMs were almost same, regardless of humidity. The ion conductivity of the SILEMs was $2.7{\times}10^{-3}S/cm$ and increased almost linearly up to $2.2{\times}10^{-2}S/cm$ with increasing temperature to $130^{\circ}C$. The effects of an inorganic filler on the physical properties of the SILEMs were studied using the $SiO_2$. The addition of $SiO_2$ could improve the mechanical strength of the SILEMs, though the ionic conductivity was decreased slightly.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.2 s.25
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• pp.107-113
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• 2006

Water treatment plant sludge occurred in sedimentation and inverse wash process is generally disposed by ocean dumping or reclamation after dehydration processing using mechanical or natural dry method. Recently, ocean dumping of sludge is limited actually by London Convention. Physical, chemical, and geotechnical characteristics of water treatment plant sludge were analyzed by experiments. The possibilities for recycling of the dehydration sludges as materials for covering sanitary landfill were examined. Experiments performed with sludges mixed with general soil to improved the sludge properties are the hydrometer analysis, the liquid and plastic limit test, the specific gravity test, the compaction test, and the unconfined compression test. The value of ${\gamma}_{dmax}$ is increased and OMC(Optimum Moisture Content) is lessened with mixed sludge. The value of maximum compressive strength and friction angle are increased and the cohesion is decreased with mixed sludge. The ratio between sludge and soil in mixed sludge was 3:7 and the strength of mixed sludge showed $3.6kg/cm^2$. These results satisfy the regulation of U.S. E.P.A regarding materials for covering sanitary landfill.

• Elastomers and Composites
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• v.38 no.1
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• pp.81-87
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• 2003

In this work, $Fe_3O_4$ (magnetite), conductive filler was prepared from $FeCl_2{\cdot}4H_2O,\;(CH_2)_6N_4$ (hexamethylene tetramine), and $NaNO_2$, followed by mixing with crystallizable chloroprene rubber(CR). The influence of conductive filler content on the properties of the conductive composite was studied and temperature dependence of the electrical conductivity (${\sigma}$) was also investigated. It is found that the percolation threshold concept holds true for the conductive particle-filled composite where ${\sigma}$ indicates a nearly sharp increase when the fraction of magnetite in the mixture exceeds 27%. The temperature dependence of ${\sigma}$ is thermally activated blelow or at the $P_c$. Magnetite acts as reinforcement and conductive filler for CR rubber. Moreover, it is shown that the composite with magnetite of 50 phr gives the most significant mechanical properties for tensile strength and elongation at break, which is due to the formation of optimum physical interlock and crosslinking. The results of 100%, 200%, and 300% moduli suggest that the moduli are related with reinforcement effect of magnetite and viscosity of the blend.

• Elastomers and Composites
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• v.49 no.1
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• pp.24-30
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• 2014

3-Amino-1,2,4-triazole (ATA) (2.5 and 5.0 phr) was incorporated into a immiscible maleated ethylene propylene diene rubber(mEPDM)/maleated high density polyethylene(mHDPE) (50 wt%/50 wt%) blend by melt mixing. Effects of the ATA on structure, mechanical and rheological properties of the blend was investigated. FT-IR and DMA results revealed that supramolecular hydrogen bonding interactions between the polymer chains occur by reaction of ATA with maleic anhydride grafted onto the component polymers in the blend, which induces the physical crosslinks in the blend. FE-SEM analysis showed that mEPDM forms a dispersed phase in continuous mHDPE matrix, and the blend with the ATA has finer phase morphology as compared to the blend without the ATA. By the addition of ATA in the blend, there were significant increases in tensile strength, modulus and elongation-at-break as well as elastic recoverability. Melt rheology studies revealed that ATA induced substantial increase in storage modulus and complex viscosity of the blend at the melt state.

• Polymer(Korea)
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• v.25 no.6
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• pp.855-865
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• 2001

The optimization condition of injection molding for a commercial product of TV speaker grille of A Company was induced using a CAE software of Moldflow. The flow and packing phase analysis was performed by using flow balance, runner balance, and the intermediate one by using the above two balances, which were used for controlling the amount of packing resins into the cavity, Later, the analysis performed by using the measured viscosity (local database) at various shear rates and the results were compared with the computer simulation using the standard database. Flow balance induced minimized weld line resulted in a better appearance and physical properties of the were line, but exhibited a disadvantage of large deformation and gas formation due to over-packing of the molten resin in the center of the speaker grille. Runner balance improved the disadvantage of the flow balance by controlling the amount of molten resin injected from the gate, however resulted reduced mechanical properties and poor appearance of the weld line. However, the modified method induced from the flow and runner balance improved the disadvantages by changing the runner size. In addition, the analyses based on the local database and the standard database were compared. Although the measured viscosity was slightly higher and the temperature distribution was broader than the standard database, no distinct difference was obtained from the analysis using the two different databases.

• Journal of the Korean Wood Science and Technology
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• v.34 no.4
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• pp.15-21
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• 2006

Composite materials were prepared by impregnating water glass into the wood, followed by soaking in solutions of boric acid or phosphoric acid. The effects of these treatments on the physical and mechanical properties of the specimens and especially on its heat resistance were investigated. 1) Weight Percent Gain (WPG)s increased with increase of concentrations of water glass. However, there was little relationship between treatment temperatures and WPG. Generally, WPGs of double treated specimens were higher than single treated ones. 2) Percent shrinkages in each directions of the specimens treated with water glass had higher value than other specimens. Percent shrinkages of the specimens treated with boric acid or phosphoric acid were decreased as compared with untreated specimen. However, the specimens treated with water glass or phosphoric acid showed very high hygroscopicity. 3) The bending strengths of all specimens treated inorganic substances were slightly decreased. However, the values of compressive strength and hardness of most specimens treated with inorganic substances increased or similar to that of untreated specimen except for a phosphoric acid treated specimens. 4) The specimens had good heat resistance. Weight losses of all specimens treated inorganic substances were about 50~70%. In particular, the specimens treated at $300^{\circ}C$ and $400^{\circ}C$ almost kept their shapes.

• Journal of the Korean Wood Science and Technology
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• v.38 no.6
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• pp.587-601
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• 2010

This review attempted to overview characteristics of nanocellulose from various sources, its isolation methods, and properties of nanocellulose-based nanocomposites. Currently, nanocelluloses could be obtained from a variety of cellulose sources, including wood pulp, tunicate, bacterial cellulose etc., and are isolated by various ways such as chemical, physical, or biological methods. The length and width of nanocellulose is in the range of 100~300 nm long and 5~50 nm wide although characteristics of nanocellulose shows a wide variability, depending on sources and isolation method. Nanocellulose is also being used as a reinforcement in the nanocomposites via various methods. Many water soluble polymers were reinforced by the incorporation of nanocellulose, which significantly improves tensile and storage moduli of the nanocomposites. In order to be used for hydrophobic polymers, the surface of nanocellulose was modified. Even though there is a significant progress in the utilization of nanocellulose as a reinforcement of polymers, further research is required to find a niche market of nanocellulose-reinforced nanocomposites. In addition, isolation methods of producing the nanocellulose in a large quantity for commercial applications should be developed to extend the application of nanocellulose-based bio-nanocomposites in future.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.901-908
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• 2018

Graphite is used as a sample anode active material. However, since the maximum theoretical capacity is limited to $372mA\;h\;g^{-1}$, a new anode active material is required for the development of a high capacity lithium ion battery. The maximum theoretical capacity of Si is $4200mA\;h\;g^{-1}$, which is higher than that of graphite. However, it is not suitable for direct application to the anode active material because it has a volume expansion of 400%. In order to minimize the decrease of the discharge capacity due to the volume expansion, the Si was pulverized by the dry method to reduce the mechanical stress and the volume change of the reaction phase, and the change of the volume was suppressed by coating the carbon layers to the particle size controlled Si particles. And carbon fiber is grown like a thread on the particle surface to control secondary volume expansion and improve electrical conductivity. The physical and chemical properties of the materials were measured by XRD, SEM and TEM, and their electrochemical properties were evaluated. In this study, we have investigated the synthesis method that can be used as anode active material by improving cycle characteristics of Si.

• Journal of the Korean Wood Science and Technology
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• v.10 no.3
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• pp.52-67
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• 1982

We have relatively heavy stocks of hardwood which consist of inferior and nonproductive natural hardwood species in Korea. As conception above to develope these forest resources, the study was carried out to obtain the basical data for the reasonable and efficient utilization of hardwoods. The sample trees were selected 11 natural hardwood species grown in Kangwon-do region and Kwangnoong Experimental Forest. We have investigated anatomical, physical and mechanical properties of them. Especially, Quercus species which is a major species in the forests was investigated on qualities of trees, logs and lumbers, recevery of bucking and lumber yield, etc.