• Nuclear Engineering and Technology
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• v.32 no.6
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• pp.559-565
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• 2000

The sintering behavior of UO$_2$-Gd$_2$O$_3$fuel pellets under H$_2$gas has been investigated using dilatometry and XRD methods. The addition of TiO$_2$or Al(OH)$_3$increased the density and grain size. A density of 95% TD and a grain size larger than 6 ${\mu}{\textrm}{m}$ are achieved by the addition of 0.1 wt% TiO$_2$or Al(OH)$_3$. It was found that the densification of UO$_2$-Gd$_2$O$_3$pellets was suppressed in the temperature range of 1300 to 150$0^{\circ}C$, compared to UO$_2$pellets. The formation of a (U,Gd)O$_2$solid solution is the main reason for the suppression of densification. The role of TiO$_2$in densification and grain growth is discussed on the basis of the densification cuwe and ceramography.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.816-817
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• 2006

Hydrogen, in even small quantities, is extremely deleterious to the sintering of aluminium. Understanding the cause of this effect is complicated by the multiple interactions that occur in multi-component systems. In this work, we examine the sintering rsponse of Al-2Mg (a simplified system) in pure nitrogen and nitrogen-hydrogen using dilatometry, differential scanning calorimetery, thermogravimetry and metallography.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.407-408
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• 2006

Dimensional precision is a critical parameter in net shape processing of ferrous PM components. Sinter-hardening alloys undergo a transformation from austenite to martensite. Martensite formation expands the sintered compact, while tempering hardened steels results in shrinkage. In addition, martensitic regions with high Cu and C contents may contain large amounts of retained austenite. The presence of martensite and retained austenite, in addition to the tempering step, all play a role in the final dimensions of a component. This paper investigates the dimensional and microstructural changes to two sinter-hardening grades through different post-sintering thermal treatments.

• Journal of Electrochemical Science and Technology
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• v.2 no.1
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• pp.45-50
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• 2011

A series of expanded graphites is prepared from graphite oxide by changing the heat-treatment temperature, and their lithiation/de-lithiation mechanism and rate performance are examined. A featureless sloping profile is observed in their charge-discharge voltage and dilatometry profiles, which is contrasted by the stepwise plateau-like profiles observed with the pristine graphite. With an increase in the heat-treatment temperature from $250^{\circ}C$ to $850^{\circ}C$, the interlayer distance becomes smaller whereas the electric conductivity becomes larger, both of which are resulted from a removal of foreign atoms (mainly oxygen) from the interlayer gaps. The expanded graphite that is prepared by a heat-treatment at $450^{\circ}C$ delivers the best rate performance, which seems to be a trade-off between the $Li^+$ ion diffusivity that is affected by the interlayer distance and electrical conductivity.

• 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 Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.666-669
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• 2002

The differences of the effects of mechanical substance pre-activation in the mills with divers force effect schemes on the self-propagating high temperature synthesis (SHS) of the $SiO_2$ + 37.5% Al system were investigated. The power saturation of activated material state are estimated referring on the variations of dilatometry curve paths. The effects of activation time on the temperature of sample self-ignited in the furnace, combustion temperature and completeness of the quartz reaction with aluminium were determined. The enhancing effects of organic modifiers of quartz particle surfaces on the further SHS synthesis development were shown.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.51-53
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• 1999

The crystallization mechanism of an amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ phase were studied from the relations between crystallization and volume changes by dilatometry. Further, the effect of addition of CdO on the crystallization mechanism and superconductivity was discussed. The shrinkage of the amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ occurred with the crystallization of $Bi_{2}$$Sr_{2}$Cu$O_{6}$ phase decrease with increasing CdO content with a minimum at x=0.4. Better superconductivity was obtained in the specimens formation less amount of the$Bi_{2}$$Sr_{2}$Cu$O_{6}$ phase during the crystallization process.

• Korean Journal of Crystallography
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• v.14 no.1
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• pp.7-12
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• 2003

The compound SrA1₂(BO₃)₂O is a good host lattice for negative thermal expansion. We have measured thermal expansion over the limited temperature range by X-ray diffraction and ceramic dilatometry. In the aluminum borate compound, a thermal contraction is observed with a coefficient -1.64×10/sup -4/ Å/℃ on the c axis in the temperature range 23∼215℃ and with a maximum change -1.75㎛ in length of a ceramic bar of 20㎜ in the temperature range 110∼170℃, respectively.

• Korean Membrane Journal
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• v.1 no.1
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• pp.8-24
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• 1999

free volume in polymers is defined as the difference of the specific volume and the volume which is not available for the particular molecular motion which is responsible or the process that is considered . Relations between free volume and viscosity free volume and diffusion coefficient are pre-sented both in the case of simple low molecular weight liquids and in the case of polymers. Molecular models and free volume models are reminded starting from the equilibrium state equation of Simha and Somcynski. The non equilibrium situations of specific volume of glass polymers below Tg are shown introducing different relaxation volume equations which involve different material's parameters and con-cept of the fictitious temperature. The diffusivity equations of Vrentas and Duda are introduced both for the glassy and rubbery states. The possibility of introducing time relaxation functions is also suggested. The importance of finding experimental evidences of the free volume is stressed. highlights of the free volume measurement methods are given in particular as to dilatometry photocromy fluorescence electron spin resonance small angle X-ray scattering positron annihilation spectroscopy.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1126-1127
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• 2006

The kinetics of sintering of Co-Fe materials was studied. The main objective was to establish the effects of iron content and sintering parameters on the microstructure and phase composition of the as-sintered material. Specimens containing from 3 to 25 wt.% iron were sintered in a dilatometer for one hour at 900, 1000 and $1150^{\circ}C$ in either hydrogen or nitrogen atmosphere. The length of specimens during the heating, hold at temperature and cooling steps were monitored to establish the sample's shrinkage. Microstructural observations were carried out on polished and etched transverse sections which were also subjected to the X-ray phase analysis.