• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.93-97
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• 2003

Using alumina-glass infiltrated material which has been in the spotlight of biomaterials including dental material, appropriate composition of glass infiltrated material mainly depends on the thermal expansion coefficient. To obtain proper compositional glass of suitable thermal expansion coefficient effiiently. a Taguchi analysis was conducted. The influence of alkali oxide and alkali earths oxide, which affect mostly the thermal expansion coefficient of glass infiltrated material, was infiltrated material, the effect having influenced on the thermal expansion coefficient of glass was presented in this order (Na$_2$O≫K$_2$O ≫MgO≒CaO). The effect of Na$_2$O was about eight times as great as the effects of MgO, CaO and $K_2$O was about four times. Among the interaction affects of each variables the interaction affects of $K_2$O-CaO showed most significantly and thermal expansion property of specified composition was predicted by calculating contribution rate on each level of variables and interaction affects.

• Journal of the Korean Ceramic Society
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• v.37 no.2
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• pp.122-127
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• 2000

The thermal expansion, thermal stability, mechanical strength and infrared radiative property of Al2TiO5-clay composites, prepared from synthesized Al2TiO5 and clay, were investigated to develop a material for far infrared radiators. The emittance of composites containing 10~50 wt% clay, heated at 1,20$0^{\circ}C$ for 3 h, increased with increasing clay content and emittance was about 0.3 and 0.92 in the ranges of 3,400~2,500 cm-1 and 2,500~400cm-1, respectively. The bulk density and bending strength of the Al2TiO5-clay composites increased with increasing clay content. 50 wt% Al2TiO5-50 wt% clay composite, heat-treated at 1,20$0^{\circ}C$, had an adequate strength for infrared radiators; 80 MPa. The degree of thermal expansion hysteresis decreased with increasing clay content and the mean thermal expansion coefficient increased with increasing clay content. The thermal expansion coefficient of 50 wt% Al2TiO5-50 wt% clay composite heated at 1,20$0^{\circ}C$ was 5.78$\times$10-6/$^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.42 no.5 s.276
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• pp.346-351
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• 2005

The linear thermal expansions of $UO_2$ and $(U_{1-y}Ce_y)O_2$ pellet were measured from room temperature to $1400^{\circ}C$ as a function of Ce contents (0, 7.63, 14.84, and $21.68 mol\%$) by using the TMA(Thermo-Mechanical Analysis) method. From the measured data, the linear thermal expansion rate, the coefficient of linear thermal expansion and density variation with temperature were calculated, and the best-fitted temperature-dependent equations were recommended. It was shown that the rate and coefficient of $(U_{1-y}Ce_y)O_2$ thermal expansion increased and the density decreased with increasing Ce contents.

• Journal of Korea Foundry Society
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• v.2 no.4
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• pp.2-8
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• 1982

The behavior of sand and mold at high temperatures was generally agreed to importantly affect the quality of castings made. By changing water content through 2,4,6 and 8%, and bentonite content through 5,7,9 and 11%, specimens have been made according to the respective composition. Specimens have been subjected to hot compressive strength and thermal expansion at 400, 600, 800 and $1000^{\circ}C$ respectively. The results obtained were as follows ; 1. At each temperature, thermal expansion decreased and hot compressive strength increased with the increase in water content. 2. After thermal expansion was peaked at approximately $1000^{\circ}C$ the contraction and maximum hot compressive strength appeared. 3. At each temperature, maximum hot compressive strength appeared 2%, 4,6% and 8% water content for 7%, 9% and 11% bentonite content respectively. 4. When 2% $H_2O$ was added, though bentonite content was increased, hot compressive strength did not rarely change. 5. Until the thermal expansion was completed the required time was 15-18 minutes at $400^{\circ}C$ and $600^{\circ}C$, and 10-13 minutes at $800^{\circ}C$. At $1000^{\circ}C$, the required time was 7-9 minutes in order to gain the maximum expansion, after that, contraction proceeded during 3-4 minutes before expansion was completed.

• Journal of Korea Foundry Society
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• v.9 no.1
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• pp.80-88
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• 1989

SGCI(Spheroidal Graphite Cast Iron), CVGCI(CV Graphite Cast Iron) and FGCI(Flake Graphite Cast Iron) having different contents of Mn($0.25%{\sim}0.85%$) and Ni($0.3%{\sim}1.2%$) were produced, respectively. The thermal expansion and thermal conductivity of the cast iron were investigated in the temperature range of $50^{\circ}C{\sim}300^{\circ}C$. As the graphite nodularity of the cast iron increases, thermal expansion coefficient increases, thermal conductivity and electrical conductivity to thermal conductivity ratio decrease. The thermal expansion coefficient of the cast iron increases with increasing Mn content and decreases with increasing Ni content. The thermal conductivity of the cast iron decreases with increasing Mn and Ni contents.

• Fibers and Polymers
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• v.5 no.1
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• pp.31-38
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• 2004

In the present paper, a variety of fiber reinforcements, for instance, stabilized OXI-PAN fibers, quasi-carbon fibers, commercial carbon fibers, and their woven fabric forms, have been utilized to fabricate pseudo-unidirectional (pseudo-UD) and 2-directional (2D) phenolic matrix composites using a compression molding method. Prior to fabricating quasi-carbon fiber/phenolic (QC/P) composites, stabilized OXI-PAN fibers and fabrics were heat-treated under low temperature carbonization processes to prepare quasi-carbon fibers and fabrics. The thermal conductivity and thermal expansion/contraction behavior of QC/P composites have been investigated and compared with those of carbon fiber/phenolic (C/P) and stabilized fiber/phenolic composites. Also, the chemical compositions of the fibers used have been characterized. The results suggest that use of proper quasi-carbonization process may control effectively not only the chemical compositions of resulting quasi-carbon fibers but also the thermal conductivity and thermal expansion behavior of quasi-carbon fibers/phenolic composites in the intermediate range between stabilized PAN fiber- and carbon fiber-reinforced phenolic composites.

• Journal of Technologic Dentistry
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• v.43 no.3
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• pp.71-76
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• 2021

Purpose: In this study, thermal properties were observed by measuring the extent of thermal expansion and the amount of thermal residue that appears upon burnout on a workpiece made by using a dental digital light processing (DLP) three-dimensional (3D) printer. Methods: Thermal properties of workpieces manufactured by using two 3D printers were observed. The specimens were designed in cylindrical form with dimensions 10 mm in diameter and 10 mm in height. The control specimen was made of wax, and the experimental specimen was made of resin. The thermal expansion rate was measured by applying heat to three types of specimens, and burnout residue was measured. Results: The thermal expansion rate of the wax pattern (WP) specimen was 0.93%±0.05%, of the RP1 specimen was 1.30%±0.08%, and of the RP2 specimen was 1.20%±0.09%. Measuring the recovered residue yielded residual amounts of 0.2% for the WP specimen, 1.1% for the RP2 specimen, and 1.8% for the RP1 specimen. Conclusion: 1. From measurements of the workpieces manufactured by dental DLP 3D printing, the thermal expansion rate was found to be higher than that of wax. 2. As a result of measuring burnout residues on the workpieces manufactured by dental DLP 3D printing, the required summoning temperature to obtain suitable castings was determined to >750℃.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.3
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• pp.339-346
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• 2018

A geological repository system consists of a disposal canister with packed spent fuel, buffer material, backfill material, and intact rock. The buffer is indispensable to assure the disposal safety of high-level radioactive waste. Since the heat generated from spent nuclear fuel in a disposal canister is released to the surrounding buffer materials, the thermal properties of the buffer material are very important in determining the entire disposal safety. Especially, since thermal expansion can cause thermal stress to the intact rock mass in the near-field, it is very important to evaluate thermal expansion characteristics of bentonite buffer materials. Therefore, this paper presents a thermal expansion coefficient prediction model of the Gyeongju bentonite buffer materials which is a Ca-bentonite produced in South Korea. The linear thermal expansion coefficient was measured considering heating rate, dry density and temperature variation using dilatometer equipment. Thermal expansion coefficient values of the Gyeongju bentonite buffer materials were $4.0{\sim}6.0{\times}10^{-6}/^{\circ}C$. Based on the experimental results, a non-linear regression model to predict the thermal expansion coefficient was suggested and fitted according to the dry density.

• Journal of the Korean Ceramic Society
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• v.40 no.11
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• pp.1127-1131
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• 2003

Phosphate glasses known for low melting temperature glasses in electrical parts has been recently used in wide area with modification of thermal properties using alkali oxides. It is our purpose to find a correlation between thermal expansion coefficient, glass transition temperature and melting temperature through investigating thermal properties in P$_2$O$\sub$5/-SnO-ZnO-SiO$_2$/B$_2$O$_3$. As a result, the product of thermal expansion coefficient and the glass transition temperature in the glasses is found to be a constant value would be a unique value for knowing one of thermal properties.

• The Journal of Engineering Research
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• v.6 no.2
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• pp.141-151
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• 2004

The physical properties of gold investment materials are depending on it's thermal expansion coefficients, compressive strength, and particles size distributions. Normally the gold investment materials are consisted of cristobalite, quartz and plaster. Since the thermal expansion coefficient of cristobalite and quartz are $2.6\times10^{-6}/^\circC$, $2.32\times10^{-6}/^\circC$, respectively, the composition ratio of each components influence the thermal and clinical properties of gold investment materials. Recently are imported from overseas and the commercial market is expected to expand. Thus it is necessary to develop the optimum strength and compressive strength of gold investment materials which the an homogeneous size distribution and thermal expansion coefficients. Therefore two different experiments has been done. Firstly the homogeneous cristobalite and quartz are made by pulverizing milling. Secondly the compressive strength and thermal expansion coefficients are analysed by the composition ratio of cristobalite and quartz. As a results of experiments, homogeneous distribution of cristobalite and quartz are observed by pulverizing and milling. The optimum compressive strength was obtained at the ratio of 45:25 cristobalite, quartz respectively.