• Journal of the Korean Wood Science and Technology
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• v.44 no.5
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• pp.776-784
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• 2016

In this study, green Larix kaempferi lumber was heat-treated by using superheated steam (SHS) at a pilot scale and then various physico-mechanical properties of the heat-treated wood were evaluated and compared with the properties of conventional hot air (HA) heat-treated wood. Decay resistance of brown rot fungi and compressive strength parallel to the grain of the SHS heat-treated wood without occurrence of drying check from green lumber were increased. On the other hand, density, equilibrium moisture content, shrinkage, and bending strength of the SHS heat-treated wood were lower than those of the conventional HA heat-treated wood. Because heat transfer and thermal hydrolysis of SHS heat treatment was accelerated by a large amount of water, the effect of SHS heat treatment on the physico-mechanical properties was higher than that of HA heat treatment at the similar conditions of temperature and time. From the results of this study, because green lumber can be heat-treated without occurrence of cracks or checks by using SHS and similar heat treatment effect on the physico-mechanical properties of wood can be produced despite a low temperature or short time of heat treatment, it is expected that heat time and energy consumption could be reduced by using SHS.

• Journal of the Korean Ceramic Society
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• v.41 no.4
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• pp.334-339
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• 2004

Microstructures and mechanical properties of SPSed monolithic HAp, HAp-Ag, and HAp-ZrO$_2$sintered bodies were investigated by the XRD, SEM, and TEM techniques. The nano-sized HAp powders were successfully synthesized by precipitation of Ca(NO$_3$)$_2$4$H_2O$ and (NH$_4$)HPO$_4$solution. In the HAp-Ag composite, the shrinkage cavities were observed at the interfaces between HAp and large sized Ag particles due to the mismatch of their thermal expansion coefficients. However, no found the defect at the interfaces between HAp and fine-sized Ag particles. In the HAp-ZrO$_2$composite. nano-sized ZrO$_2$particles were almost dispersed at the grain boundaries of HAp phase. The fracture toughness of HAp-Ag and HAp-ZrO$_2$ composites were increased due to the plastic deformation and phase transformation mechanisms of the dispersed fine Ag and ZrO$_2$phase in the HAp matrix, respectively.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.233-239
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• 2014

The slagging which generated from ash deposition on furnace wall and tube in boiler reduces the heat transfer efficiency and damages to safety of boiler. The slag flow behavior in boiler is affected by melting temperature which is related to ash compositions. In this study, the behavior of slag is researched by using ash fusibility test, called TMA (Thermo-Mechanical Analysis). The technique measures the percentage shrinkage as the function of temperature, T25%, T50%, T75%, T90%. These temperatures indicate different stages of melting. Then, the effect of ash chemical compositions measured from XRF (X-ray Fluorescence Spectrometer) to ash fusion temperatures is discussed. Among the chemical compositions, refractory and fluxing influence on ash fusibility is described. High levels of refractory component and limited amount of fluxing components ($Fe_2O_3$, $K_2O$, CaO) increase overall melting temperatures. High $SiO_2/Al_2O_3$ ratio decrease high melting temperatures (T75%, T90%). Meanwhile, the presence of reasonable levels of fluxing components reduces overall melting temperature. A presence of fluxing component such as $K_2O$ and CaO is found to decrease the T25% values significantly. From this research, it is possible to make a reasonable explanation and prediction of ash fusion characteristic from analysis of TMA results and ash chemical compositions.

• Membrane Journal
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• v.18 no.1
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• pp.84-93
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• 2008

Poly(vinylidene fluoride) has received much attention in the last several years for the lithium secondary batteries. In this study, to enhance the porosity, PVdF was prepared by phase inversion method using as an additive, PEG (poly(ethylene glycol)), with N,N-dimethylformamid as a solvent. The pores are generated during the solvent and non-solvent exchange process in the coagulation bath filled with non-solvent (distilled water). The surface and cross-section of the membranes were observed with a scanning electron microscopy (SEM). The mechanical property of the membrane was determined by using an universal testing machine (UTM) and thermal property was verified by heat shrinkage. Uniformed sponge structure of PVdF-PEG membrane for the lithium secondary batteries was prepared with 10 wt% of PEG concentration in the PVdF-PEG solution. Porosity, elongation and tensile strengh of the membrane were 87%, 75.45%, and 275. 27 MPa respectively.

• International Journal of Highway Engineering
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• v.17 no.3
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• pp.85-95
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• 2015

PURPOSES : Recently, bonded concrete overlay has been used as an alternative solution in concrete pavement rehabilitation since its material properties are similar to those of the existing concrete pavements. Deteriorated concrete pavements need rapid rehabilitation in order to prevent traffic jams on Korean expressways. Moreover, speedy and effective repair methods are required. Therefore, the use of bonded concrete overlay with ultra-rapid hardening cement has increased in an effort to reopen promptly the expressways in Korea. However, mobile mixer is required for ultra-rapid hardening cement concrete mixing in the construction site. The use of mobile mixer causes various disadvantages aforementioned such as limitation of the construction supply, open-air storage of mixing materials, increase in construction cost, and etc. In this study, therefore, hydration accelerator in-situ mixing on polymer modified concrete produced in concrete plant is attempted in order to avoid the disadvantages of existing bonded concrete overlay method using ultra-rapid hardening cement. METHODS : Bonded concrete overlay materials using ultra-rapid hardening cement should be meet all the requirements including structural characteristics, compatibility, durability for field application. Therefore, This study aimed to evaluate the application of hydration accelerator in-situ mixing on polymer modified concrete by evaluating structural characteristics, compatibility, durability and economic efficiency for bonded concrete overlay. RESULTS : Test results of structural characteristics showed that the compressive, flexural strength and bond strength were exceed 21MPa, 3.15MPa and 1.4MPa, respectively, which are the target strengths of four hours age for the purpose of prompt traffic reopening. In addition, tests of compatibility, such as drying shrinkage, coefficient of thermal expansion and modulus of elasticity, and durability (chloride ions penetration resistance, freezing-thawing resistance, scaling resistance, abrasion resistance and crack resistance), showed that the hydration accelerator in-situ mixing on polymer modified concrete were satisfied the required criteria. CONCLUSIONS : It was known that the hydration accelerator in-situ mixing on polymer modified concrete overlay method was applicable for bonded concrete overlay and was a good alternative method to substitute the existing bonded concrete overlay method since structural characteristics, compatibility, durability were satisfied the criteria and its economic efficiency was excellent compare to the existing bonded concrete overlay methods.

• Proceedings of the KACD Conference
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• 2001.05a
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• pp.235-237
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• 2001

;Dentistry has benefited from tremendous advances in technology with the introduction of new techniques and materials, and patients are aware that esthetic approaches in dentistry can change one's appearance. Increasingly. tooth-colored restorative materials have been used for restoration of posterior teeth. Tooth-colored restoration for posterior teeth can be divided into three categories: 1) the direct techniques that can be made in a single appointment and are an intraoral procedure utilizing composites: 2) the semidirect techniques that require both an intraoral and an extraoral procedure and are luted chairside utilizing composites: and 3) the indirect techniques that require several appointments and the expertise of a dental technician working with either composites or ceramics. But, resin restoration has inherent drawbacks of microleakage. polymerization shrinkage, thermal cycling problems. and wear in stress-bearing areas. On the other hand, Ceramic restorations have many advantages over resin restorations. Ceramic inlays are reported to have less leakage than resin restoration and to fit better. although marginal fidelity depends on technique and is laboratory dependent. Adhesion of luting resin is more reliable and durable to etched ceramic material than to treated resin composite. In view of color matching, periodontal health. resistance to abrasion, ceramic restoration is superior to resin restorationl. Materials which have been used for the fabrication of ceramic restorations are various. Conventional powder slurry ceramics are also available. Castable ceramics are produced by centrifugal casting of heat-treated glass ceramics. and machinable ceramics are feldspathic porcelains or cast glass ceramics which are milled using a CAD/CAM apparatus to produce inlays (for example, Cered. They may also be copy milled using the Celay apparatus. Pressable ceramics are produced from feldspathic porcelain which is supplied in ingot form and heated and moulded under pressure to produce a restoration. Infiltrated ceramics are another class of material which are available for use as ceramic inlays. An example is $In-Ceram^{\circledR}$(Vident. California, USA) which consists of a porous aluminum oxide or spinell core infiltrated with glass and subsequently veneered with feldspathic porcelain. In the 1980s. the development of compatible refractory materials made fabrication easier. and the development of adhesive resin cements greatly improved clinical success rates. This case report presents esthetic ceramic inlays for posterior teeth.teeth.

• Elastomers and Composites
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• v.47 no.4
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• pp.336-340
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• 2012

Residual stress in the injection molded part is originated from thermal shrinkage and shear stress during injection molding process. There are many measurement methods of residual stress in the plastic part. Residual stress in opaque products can be measured by chemical cracking test. This method enables the solvent and specimen to react and to cause cracks. Cracks developed according to the level of residual stress. Thus the stresses in plastic part can be quantitatively measured by counting the number of cracks or measuring the size of cracks. Relationship between stress and number of cracks in a plastic specimen has been investigated in this study. Bergen jig was used to give a strain in the specimens those were molded using PC/PBT and PC/ABS. Solvent for the chemical cracking test was prepared using tetrahydrofuran and methyl alcol with the ratio of 1 to 3. Stresses in the specimen can be calculated by strains those were imposed by Bergen jig. Cracks were developed for stress higher than certain level. The number of cracks increased by second order function for stress.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.5
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• pp.217-222
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• 2023

The purpose of this paper was to synthesize a polymer organic hard mask that simplifies the manufacturing process, reduces process time significantly, and thereby lowers manufacturing costs. The results of measuring residual metals through vapor refining showed that 9-Naphthalen-1-ylcarbazole(9-NC) measured 101.75ppb in the 4th zone, 2-Naphthol (2-NA) measured 306.98ppb in the 5th zone, and 9-Fluorenone(9-F) measured between 129.05ppb across the 4th and 5th zones. After passing through a filtration system, the synthesized organic hard mask measured residual metals in the range of 9 to 7ppb. Additionally, the thermal analysis indicated a decrease of 2.78%, a molecular weight of 942, carbon content of 89.74%, and a yield of 72.4%. The etching rate was measured at an average of 18.22Å/s, and the coating thickness deviation was averaged at 1.19. For particle sizes below 0.2㎛ in the organic hard mask, no particles were observed. By varying the coating speed at 1,000, 1,500, and 1,800rpm and measuring the resulting coating thickness, the shrinkage rate ranged from 17.9% to 20.8%. The coating results demonstrated excellent adhesion to SiON, and it was evident that the organic hard mask was uniformly applied.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.365-371
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• 2013

Purpose: In this study, we evaluated the physical and thermal properties of the compositions made by blending glass fiber (GF) of different contents into glass fiber polyamide-66, and investigated if the compositions applying to the glasses frame to replace the TR-90, which is polyamide-12 resin used as an injection-type spectacle frame material. Methods: To investigate the characteristics change of polyamide-66 (PA-66) compositions with the change of the content of glass fibers, we produced a composition of the content by using a twin-screw extruder. The mechanical strength of the composition production was measured and coating properties as well as cutting processability were evaluated. We evaluated the applicability of the glasses frame by comparison the results of new compositions with characterizations of traditional TR. Results: For the results of the characterization of Polyamide-66/GF composition, we found that the higher increase of content of the glass fiber, the less mold shrinkage rate, and the mechanical strength was increased. Tensile strength increased from $498kg/cm^2$ for 0 wt% of the content of the glass fibers to $849kg/cm^2$ for 30 wt% of the content of the glass fibers. As a result of a coating evaluation, the strength of coating was 4B in the GF 5wt% and 5B, which was extremely good coating characteristics, in the over than GF 5 wt%. Conclusions: In case that 30 wt% of the glass fiber was blended, the mechanical strength was greatly improved, the hardness was increased, injection temperature increased due to increase of the viscosity, and the flow mark of the product may occur. The paint coating of PA-66 blended with glass fiber was all excellent. With general evaluating physical properties and workability properties it was determined that around 10 wt% of the content of the glass fibers was possible to apply a spectacle frame.