• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.3
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• pp.133-137
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• 2002

$ZnWO_4$ nano-powders were successfully synthesized at low temperature by polymerized complex method using zinc acetate and tungstic acid as starting materials. The polymeric precursors were heat-treated at temperatures from 300 to $600^{\circ}C$ for 3 h. The precursors and heat-treated powders were evaluated for crystallization process, thermal decomposition, surface morphology and crystallite size. Crystallization of the $ZnWO_4$ powders were detected at $400^{\circ}C$ and entirely completed at a temperature of $600^{\circ}C$. The particles heat-treated at $400^{\circ}C$ showed primarily co-mixed morphology with spherical and silk-worm-like forms, while the particles heat-treated at $500^{\circ}C$ showed more homogeneous morphology. The average crystalline sizes were 17.62~24.71 nm showing an ordinary tendency to increase with the temperatures from 400 to $600^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.33 no.10
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• pp.1079-1088
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• 1996

Discontinuous ${\gamma}$-LiAlO2 fibers for fiber-reinforcing MCFC matrixes have been produced by the sol-gel process using the centrifugal spinning apparatus of the Rotary type. Gel fibers could be obtained through spinning of stable LiAlO2 complex polymetric sols under the optimum spinning conditions (hollow-disc rotating velocity 9000 rpm sol feeding rate of 4ml/min flowing N2 temperature of 4$0^{\circ}C$ and flowing N2 pressure of 4 bar). It was found that defect free and densified ${\gamma}$-LiAlO2 fibers with the relative density of 98% and the mean diameter of 4.7${\mu}{\textrm}{m}$ were prepared when the spinned fibers were heat-treated to 100$0^{\circ}C$ on the specified heating schedule. in particular the mean diameter and length of fibers could be controlled by the pressure of flowing N2 and the chopping-sieving method respectively.

• Journal of the Korean Ceramic Society
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• v.41 no.6
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• pp.439-443
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• 2004

SrAl$_2$O$_4$ powder was prepared by polymerized complex method and its nucleation was observed at different temperatures and times. Problems of inhomogeneity and high synthesis temperature induced by solid state reaction could be solved by using polymeric precursors. The process of decomposition by heat treatment above 40$0^{\circ}C$ was observed by Scanning Electron Microscopy (SEM) and elemental analyzer. Crystallization of SrAl$_2$O$_4$ occured at about 90$0^{\circ}C$ and its crystalline size. which was determined by using Transmission Electron Microscopy (TEM) and X-Ray Diffractometer (XRD). was about 30∼50 nm.

• Journal of the Korean Society of Safety
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• v.7 no.2
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• pp.24-29
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• 1992

The exhausted gases were analyzed and the countermeasures were studied to solve the environmental pollution caused by waste gases in Chung-Ju Industral Complex. The eleven working places were selected to analysis the compositions and concentrations of the exhausted gases by gas chromatograph and membrane method. The five companies which have used organic solvents were shown lower content than TLV and the environmental limits. But the concentration of lead in a electric product company was revealed higher than TLV. The waste gases of the four companies which have used asbestos were shown lower values than TLV and the environmental limit. The exhausted gases, SO$_2$and NO$_2$of two companies which have used fossile fuels were also analyzed. The NO$_2$concentration of one company which haven't disposal system was shown higher than the environmental limit.

• Journal of Powder Materials
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• v.12 no.4 s.51
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• pp.249-254
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• 2005

Titanium dioxide was prepared by Polymer Complex Solution Method(PCSM) according to the mole ratio of Titanium (IV) isopropoxide(TTIP)/solvent and polymer(Poly Ethylene Glycol). Polymer electrolytes were usually made by dispersing preproduced ceramic nanoparticles in a polymer matrix. Using this method, pure and nano-sized $TiO_2$ powder was synthesized through a simple procedure and polymer entrapment route. At the optimum amount of the polymer, the titanium ions are dispersed in solution and a homogeneous polymeric network is formed. The maximum intensity of anatase phase of $TiO_2$ was achieved by calcining at $500^{\circ}C$ for 2h. The synthesized $TiO_2$ powders were nano-sized and the average size was about 50nm. Anatase/Rutile ratio of the synthesized $TiO_2$ was 70%/30%.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.132-135
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• 2006

Injection molding is a flexible production technique for the manufacturing of polymer products, but introduces residual stresses. Residual stresses in a structural material or component are those stresses which exist in the object without other external loads. The layer removal and hole drilling method are used for the measurement of residual stress in injection molded polystyrene part. The hole drilling method is potentially more flexible for determining residual stress in complex geometries and can be used as an adoptable technique for the measurement of residual stress in polymeric materials. Results obtained by experiments agree with each other.

• Elastomers and Composites
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• v.37 no.4
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• pp.234-243
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• 2002

A general scheme of a rubber structure is proposed. Using the thermomechanical method(TMA), some changes in the molecular and topological structures for uncured and cured, and unfilled and filled rubbers during processing are shown. In our investigations as region it is understood a complex structure, which is expressed at the thermomechanical curve(TMC) as a zone differed from others in thermal expansion properties. This zone is between the noticed temperatures of relaxation transitions, usually on the level like those determined by DMTA at 1Hz. These regions, which shares, are not stable, and differ in molecular-weight distribution(MWD) of chain fragments between the junctions. Differences in dynamics of the formation of the molecular and topological structures of a vulcanizate are dependent on the rubber formulation, mixing technology and curing time. Some of characteristics of these regions correlate with mechanical properties of vulcanizates what is shown for NR rubbers containing ENR or CPE as a polymeric additive. It is well known that the state of order influences diffusivity of low-molecular substances into the polymer matrix. Because of this, the two topological amorphous regions should influence the distribution of the ingredients and resulting in rubber compounds' heterogeneity, and related properties of cured rubber. Investigation of this problem is expected to be, in the future, one of the essential factors in determining further improvement of polymeric materials properties by compounding with additives and in reprocessing of rubber scrap.

• Journal of the Korean GEO-environmental Society
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• v.15 no.12
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• pp.35-42
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• 2014

The efforts to reduce carbon emission have been made in many aspects and in road, the study to develop the construction method which will replace asphalt and cement is also underway. But given the low cost and high performance offered by cement, among many solidification agents, it's difficult to seek the competent alternative. Polymeric material has been used in various ways for its advantages including lightweight and easy process for complex function and generates less carbon emission, and thus it would possibly be efficient if it replaces soil pavement using cement. This study, using three different types of organic polymeric solidification agents with different solidification principle, is intended to identify the difference in strength depending on curing method, natural dry or oven dry. Applicability of organic polymeric solidification agents to walkway and bike lane was investigated and as a result of unconfined strength test, all of them satisfied the minimum strength requirements of bike lane. Furthermore, strength characteristics of soil pavement depending on variation of water content was evaluated to identify the relationship, thereby appropriate curing method using organic polymeric solidification agent is proposed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.5
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• pp.197-201
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• 2010

$ZnWO_4$ nanocrystallines were prepared from polymeric complex method using microwave irradiation. The average nanocrystalline sizes were 18~25 nm showing an ordinary tendency to increase with the temperatures from 400 to $600^{\circ}C$. Bulk type single crystals of $ZnWO_4$ were grown successfully in the [100], [010] and [001] directions using the Czochralski method. The effect of the growth parameters, such as the rotation speed, pulling rate and diameter of the grown crystals, were examined. The hardness, thermal expansion coefficients and dielectric constants of the crystals were evaluated.

• Journal of the Korean Ceramic Society
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• v.39 no.3
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• pp.321-326
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• 2002

ZnWO$_4$ nano-powders were successfully prepared by polymerized complex method using zinc nitrate and tungstic acid as starting materials. In order to investigate the thermal decomposition and crystallization process, the polymeric precursors were heat-treated at temperatures from 300 to 600$^{\circ}$C for 3 h, and the heat-treated powders were characterized by XRD and FTIR. The surface morphology of the heat-treated powders were observed using SEM and TEM. The crystallite size was measured by X-ray analysis. Crystallization of the ZnWO$_4$ powders were detected at 400$^{\circ}$C and entirely completed at a temperature of 600$^{\circ}$C. The particles heat-treated 400 and 500$^{\circ}$C showed primarily co-mixed morphology with spherical and silkworm-like forms, while the particles heat-treated at 600$^{\circ}$C showed more homogeneous morphology. The average crystalline size were 19.9∼24.nm showing an ordinary tendency to increase with the temperatures from 400 to 600$^{\circ}$C.