• Journal of the Korean Ceramic Society
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• v.19 no.2
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• pp.101-108
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• 1982

As raw materials wollastonite, kaolin and pyrophyllite were used to synthesize mullite, anorthite and pseudowoll-astonite which were known as low thermal expansion substance. Increasing the amount of wollastonite in the composition resulted in a linear thermal expansion behavior. However, the increases of pyrophyllite indicated the relatively unstable themmal expansion behavior, because the phase transition occured in quartz of the pyrophyllite compositon. To lowering sintering temperature feldspar (Kebook and Anyang) were added in the composition that showed the linear thermal expantion behavior, and over 50'C were lowered.

• Transactions of Materials Processing
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• v.24 no.1
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• pp.44-51
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• 2015

The current study seeks to examine the effects of V and C additions on the mechanical and low thermal expansion properties of a high strength invar base alloy. The base alloy (Fe-36%Ni-0.9%Co-2.75%Mo-0.7Cr-0.23Mn-0.17Si-0.3%C, wt.%) contains $Mo_2C$ carbides, which form as the main precipitate. In contrast, alloys with additions of 0.4%V+0.3%C (alloy A) or 0.4%V+0.45%C (alloy B) contain $Mo_2C$+[V, Mo]C carbides. The average thermal expansion coefficients of these high strength invar based alloys were measured in the range of $5.16{\sim}5.43{\mu}m/m{\cdot}^{\circ}C$ for temperatures of $15{\sim}230^{\circ}C$. Moreover, alloy B showed lower thermal expansion coefficient than the other alloys in this temperature range. For the mechanical properties, the [V, Mo]C improved hardness and strengths(Y.S. and T.S.) of the high strength invar base alloy. T.S.(tensile strength) and Y.S.(yield strength) of hot forged alloy B specimen were measured at 844.6MPa and 518.0MPa, respectively. The tensile fractography of alloy B exhibited a ductile transgranular fracture mode and voids were initiated between the [V, Mo]C particles and the matrix. Superior properties of high strength and low thermal expansion coefficient can be obtained by [V, Mo]C precipitation in alloy B with the addition of 0.4%V and 0.45%C.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.6
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• pp.412-419
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• 2000

There has been a considerable attention on Invar alloys due to its low thermal expansion property. A low thermal expansion property of Invar alloys, lower than $10^{-6}$ near the room temperature, is attractive for electric transmission lines and precision machine tools. However, the expansion property of Invar alloys is limited below about 520K, and mechanical properties are relatively low to apply to electric transmission line. In order to improve mechanical properties in this alloy, Ti alloying element was added to the $Ni_{38}-Mo_2-Cr_1-Fe$ invar alloy. The microstructure Ti added alloy showed finer than that of the unalloyed one. It was found that the (Mo, Ti), Mo carbide formed by Ti addition obstacled grain growth by pinning effect and supplyed recrystallization sites during heat-treatment. Optimum heat-treatment conditions with Ti addition were also discussed in the modified Invar alloy.

• Transactions of Materials Processing
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• v.8 no.3
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• pp.247-247
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• 1999

The segregation (distribution) of nickel and the composition of its constituents influence the low thermal expansion characteristics (Invar effect) in Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy. The change of coefficient of the thermal expansion and magnetic properties were studied as an aspect of carbon addition causing the segregation of Ni in primary austenite of as-cast Fe-30 wt.% Ni-12.5 wt.% Co Invar alloy. The coefficient of thermal expansion of Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy showed its lowest value at 0.08 wt.% carbon, increased with increasing carbon content in the range of 0.08-1.0 wt.%C, kept constant at 1.0-2.0 wt.%C and decreased at carbon higher than 2.0 wt.%. The effective distribution of the coefficient of nickel in as-cast Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy increased with increasing carbon content. The volume fraction of they phase of Fe-30 wt.% Ni-12.5 wt.% Co-xC alloy increased with increasing carbon content. The microstructure of Fe-30 wt.% Ni-12.5 wt.% Co-xC alloy changed with the carbon content was independent of the coefficient of thermal expansion. The Curie temperature changed linearly with the carbon content and was similar to the change of the coefficient of thermal expansion. Moreover, the coefficient of thermal expansion decreased when the ratio of saturation magnetization to Curie temperature ($\sigma_s/T_c$) increased, decreasing the Curie temperature and showed a specific relationship with the magnetic properties of the Fe-30 wt.% Ni-12.5 wt.% Co-xCInvar alloy.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.6
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• pp.730-740
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• 1999

The purpose of this study was to investigate setting and thermal expansion of dental soldering investments. In order to compare expansion rates and to investigate the effect of water/powder ratio on expansion, setting and thermal expansion of low dental soldering investments were measured under three different water/powder ratio conditions. standard, 20% decreased and 20% increased. Setting expansion of investments was measured by use of dialgauge method. Each measurement was started two minutes later from the beginning of spatulation and recorded every one minute for one hour. Thermal expansion of cylindrical test specimens, 10mm diameter, 50mm length, was recorded in a thermodilatometer at heating rate of $10^{\circ}C$ per minute from $25^{\circ}C\;to\;700^{\circ}C$. The results of this study were obtained as follows: 1. Setting expansion rates under the standard water/powder ratio condition were 0.198% in Speed-E, 0.090% in Deguvest, 0.080% in CM and Hi-temp. Setting expansion of Speed-E was significantly different from those of CM, Deguvest and Hi-temp, and setting expansion of Deguvest was significantly different from those of CM and Hi-temp(p<.05). 2. Under the decreased water/powder ratio condition, there was significant increase in setting expansion of 4 dental soldering investments (p<.05). 3. There were no significant differences in setting expansions of investments except Hi-temp between standard and increased water/powder ratio condition(p<.05). 4. Thermal expansion rates under the standard water/powder ratio condition were 1.923% in Deguvest, 1.629% in Speed-E, 1.619% in Hi-temp and 1.580% in CM. No significant differences in thermal expansions under the standard water/powder ratio condition existed only between Speed-I and Hi-temp(p<.05) 5. Under the decreased water/powder ratio condition, there was significant increase in thermal expansion of CM and Deguvest but decrease in thermal expansion of Speed-E (p<.05). 6. Under the increased water/powder ratio condition, there was significant decrease in thermal expansion of CM, Deguvest and Speed-I but decrease in thermal expansion of Hi-temp(p<.05).

• The Korean Journal of Ceramics
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• v.2 no.4
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• pp.246-250
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• 1996

The thermomechanical properties of materials from the system Al2O3-SiO2-TiO2(Tialite-Mullite) were investigated by correlating the thermal expansion anisotroypy, flexural strength and Young's modulus with grain size and atructural microcracking during cooling. Microcracking temperatures were determined by measuring the hysteresis of the thermal expansion anisotropy with dilatometry. Single phase Aluminium Titanate is a low strength material, while composites with more than 10 vol% mullite as second phase enhance the Young's modulus, thermal expansion coefficient and room temperature strength.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1346-1348
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• 2001

Generally, Invar alloy shows very low thermal expansion characteristics, lower than $2{\times}10^{-6}$/K approximately. To apply Fe-Ni-Co-C Invar alloy as a core material for large ampacity transmission line we studied the effects of magnetic properties on coefficient of thermal expansion. The coefficient of thermal expansion(CTE) suddenly decreases with addition of a little carbon(0.08%), increases with the increasing carbon and has a constant value at the composition over than 1.0%C. The trend of Curie temperature change with carbon is similar with that of CTE. Therefore, the CTE has a linear relationship with Curie temperature. However, the CTE linearly decreases with the ratio of saturation magnetization and Curie temperature(${\sigma}_s/T_c$).

• Journal of the Korean Ceramic Society
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• v.29 no.8
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• pp.646-650
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• 1992

Effect of Li2O.4B2O3 frit addition on microstructural and thermal expansion behaviour of the $\beta$-spodumene ceramics made from kaolinite was investigated. With 2.0~4.0 wt% frit addition, the densification by liquid phase sintering caused low water absorption below 3% and enhancement of beding strength. As the amount of frit addition was increased, thermal expansion coefficient was increased to large scale, but in 2 wt% frit addition, its thermal expansion coefficient was constrained to 1.92$\times$10-6$^{\circ}C$-1.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.4
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• pp.41-47
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• 2019

The advent of highly integrated, high-power electronics requires low a coefficient of thermal expansion performance to prevent delamination between the heat dissipation material and substrate. This paper reports a preliminary study on the manufacturing technology of gas reaction control composite material, focusing on the prediction of the thermal expansion coefficients of Al-AlN composite materials. We obtained numerical equivalent property values by using finite element analysis and compared the values with theoretical formulas. Al-AlN should become the optimal composite material when the proportion of the reinforcing phase is approximately 0.45.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.6
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• pp.835-842
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• 2009

The present thesis carried out a research on a compression pressure's reduction phenomenon and its countermeasure according to the thermal efficiency improvement method by a Miller method in 4-cycle low speed diesel engine. In case of retardation of intake valve closing time in a engine, the theoretical heat efficiency shows a remarkably reducing trend when a compression ratio is not compensated. Accordingly, the thermal efficiency showed an increasing trend in case of compensating the compression ratio. Especially, it could be understood that the theoretical heat efficiency at near ABDC $100^{\circ}$ of intake valve closing time in case of compensation of the compression ratio was improved by around 25.1%, and the mean effective pressure was also increased by around 18.6%. Also, as the retardation of intake valve closing time increases, air quantity becomes insufficient due to a backflow phenomenon of intake air and thus thermal efficiency was decreased in a high load operation domain. The solving method of this problem is possible by supercharge. Therefore, in order to improve thermal efficiency by retardation of ntake valve closing time, the thermal efficiency improvement according to low compression is possible when there are a compensation device of a compression ratio and a supercharge device. This is a problem-solving method of low compression and high expansion cycle.