• Journal of the Korean Ceramic Society
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• v.37 no.4
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• pp.302-307
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• 2000

The objective of this study was to investigate the sintering behavior, crystallization characteristic of glass-ceramic and optimal sintering condition on the glass/ceramic composite for fabricating substrate of LTCC. Glass/ceramic composite was made from alumina powder and glass frit, which was composed of SiO2-TiO2-RO-PbO/(R: Ba, Sr, Ca), and was sintered for 0, 30, 60minutes in the temperature range from 700$^{\circ}C$ to 1000$^{\circ}C$. Properties of frit and glass/ceramic compsoite were analyzed by DTA, XRD, SEM and Network Analyzer and so on. Main sintering mechanism was densification occurred above 730$^{\circ}C$ by viscous flow and crystallization starting about 780$^{\circ}C$ affected sintering also. So viscous flow was affected by sintering temperature, duration time, and creation of crystallization phase etc. From this study, it was possible to fabricate glass/ceramic composite by changing sintering temperature and duration time.

• Korean Journal of Materials Research
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• v.26 no.4
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• pp.216-221
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• 2016

A sintering process for copper based films using a rapid thermal process with infrared lamps is proposed to improve the electrical properties. Compared with films produced by conventional thermal sintering, the microstructure of the copper based films contained fewer internal and interfacial pores and larger grains after the rapid thermal process. This high-density microstructure is due to the high heating rate, which causes the abrupt decomposition of the organic shell at higher temperatures than is the case for the low heating rate; the high heating rate also induces densification of the copper based films. In order to confirm the effect of the rapid thermal process on copper nanoink, copper based films were prepared under varying of conditions such as the sintering temperature, time, and heating rate. As a result, the resistivity of the copper based films showed no significant changes at high temperature ($300^{\circ}C$) according to the sintering conditions. On the other hand, at low temperatures, the resistivity of the copper based films depended on the heating rate of the rapid thermal process.

• Journal of Powder Materials
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• v.21 no.2
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• pp.102-107
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• 2014

A high temperature dilatometer attached to a graphite furnace is built and used to study the sintering behavior of $B_4C$. Pristine and carbon doped $B_4C$ compacts are sintered at various soaking temperatures and their shrinkage profiles are detected simultaneously using the dilatometer. Carbon additions enhance the sinterability of $B_4C$ with sintering to more than 97% of the theoretical density, while pristine $B_4C$ compacts could not be sintered above 91% due to particle coarsening. The shrinkage profiles of $B_4C$ reveal that the effect of carbon on the sinterability of $B_4C$ can be seen mostly below $1950^{\circ}C$. The high temperature dilatometer delivers very useful information which is impossible to obtain with conventional furnaces.

• Electrical & Electronic Materials
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• v.8 no.2
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• pp.158-164
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• 1995

Solid solutions Sr$_{2}$(Ta$_{1-x}$ Nb$_{x}$)$_{2}$O$_{7}$, (x=0.0-1.0), composed of strontium tantalate(Tc=-107.deg. C) and strontium-niobate(Tc=1342.deg. C) were prepared by the conventional mixed oxide method and the flux method(molten salt synthesis method). Phase relation, sintering temperature, grain-orientation and dielectric properties for sintered ceramic samples were investigated with different compositions. Both Curie temperature and dielectric constant at Curie temperature were increased, and sintering behavior and the degree of grain-orientation were improved with the increase of Nb content. The single phase Sr$_{2}$(Ta/sib 1-x/Nb$_{x}$)$_{2}$O$_{7}$ powder was synthesized by using the flux method at lower temperatures, and sintering temperature was also reduced by using the flux method-derived powder than using the mixed oxide-derived powder. Sintering characteristics and dielectric properties of the specimens prepared by the flux method were better than those derived through the conventional mixed oxide method.thod.hod.

• Journal of Powder Materials
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• v.24 no.2
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• pp.108-114
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• 2017

We fabricate fine (<$20{\mu}m$) powders of $Bi_{0.5}Sb_{1.5}Te_3$ alloys using a large-scale production method and subsequently consolidate them at temperatures of 573, 623, and 673 K using a spark plasma sintering process. The microstructure, mechanical properties, and thermoelectric properties are investigated for each sintering temperature. The microstructural features of both the powders and bulks are characterized by scanning electron microscopy, and the crystal structures are analyzed by X-ray diffraction analysis. The grain size increases with increasing sintering temperature from 573 to 673 K. In addition, the mechanical properties increase significantly with decreasing sintering temperature owing to an increase in grain boundaries. The results indicate that the electrical conductivity and Seebeck coefficient ($217{\mu}V/K$) of the sample sintered at 673 K increase simultaneously owing to decreased carrier concentration and increased mobility. As a result, a high ZT value of 0.92 at 300 K is achieved. According to the results, a sintering temperature of 673 K is preferable for consolidation of fine (<$20{\mu}m$) powders.

• Journal of Technologic Dentistry
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• v.32 no.1
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• pp.9-16
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• 2010

This study sought to apply different MgO additions to Zirconia (20wt % Frit) and thereby determine its mechanical properties depending upon variation of temperature, as a part of elementary study. First, in terms of sintering density depending on sintering conditions, it was found that sintering density increased as temperature varied from $1100^{\circ}C$ to $1300^{\circ}C$. As the addition of MgO increased, it was found that sintering density tended to decrease at each temperature. For the maximum sintering density obtained from pellet, it was found that 3wt% MgO addition specimens sintered at $1300^{\circ}C$ had its maximum sintering density as high as 97.39%. This study measured mechanical properties of these specimens, and it was found that their bending strength tended to decrease as the content of MgO addition increased. And it was found that their bending strength reached up to 162 MPa when 3wt% MgO was added to them for sintering process at $1300^{\circ}\Delta C$. It was also found that those specimens had Vickers microhardness up to 4.6 GPa when 5wt% MgO was added to them for sintering process at $1300^{\circ}C$.

• Journal of Powder Materials
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• v.13 no.2 s.55
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• pp.129-137
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• 2006

In this study, high purity fine $BaTiO_3$ powders were prepared by SHS (Self-propagating High-temperature Synthesis). We would examinate the study of sintering properties and characteristics as a function of temperature with various additives (binder, sintering agent). In separately binder addition, the green and sintered density of specimen were increased as binder content increases. The increased porosity resulted in fine grain size due to the inhibition of grain boundary moving. The $Al_{2}O_{3},\;TiO_{2}$ and MgO playa role of increasing dielectric constants at room temperature. These values were decreased at curie temperature. In case of $SiO_2$, the Curie temperature was decreased. In this study, a high dielectric ceramic capacitor material with temperature stability was synthesized by using various additives.

• Journal of Sensor Science and Technology
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• v.26 no.3
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• pp.214-222
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• 2017

In this study, the effects of internal heat treatment associated sintering temperatures were simulated by the Finite Element Method (FEM). The sintering mechanism of pulsed current activated sintering process (PCAS) is still unclear because of some unexplainable heat transfer phenomena in coupled multi-physical fields, as well as the difficulty in measuring the interior temperatures of metal powder. We have carried out simulation study to find out thermal distributions between graphite mold and Ruthenium powder prior to PCAS process. For PCAS process, heating rate was maintained at $100^{\circ}C/min$ the simulation indicates that the sintering temperature range was between $1000^{\circ}C$ to $1300^{\circ}C$ under 60 MPa. The heat transfer inside the Ruthenium sintered-body sample was modelled through the whole process in order to predict the minimum interior temperature. Thermal simulation shows that the interior temperature gradient decreased by graphite punch length and calculation results well agreed with the PCAS field test results.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1997.10a
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• pp.7-7
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• 1997

During sintering of very porous green bodies, as obtained by compaction of hard powders - such as tungsten carbide or ceramics - or by injection moulding, important shrinkage occurs. Due to heterogeneous green density field, gravity effects, friction on the support, thermal gradients, etc., this shrinkage is often non-uniform, which' may induce significant shape changes. As the ratio of compact dimension to powder size is very high, the mechanics of continuum is relevant to model such phenomena. Thus numerical techniques, such as the finite element method can be used to simulate the sintering process and predict the final shape of the sintered part. Such type of simulation has much been developed in the last decade firstly for hot isostatic pressing and next for die compaction. Finite element modelling has been recently applied to free sintering. The simulation of sintering should be based on constitutive equations describing the thermo-mechanical behaviour of the material under any state of stress and any temperature which may arise within the sintering body. These equations can be drawn either from experimental data or from micromechanical models. The experiments usually consist in free sintering and sinter-forging tests. Indeed applying more complex loading conditions at high temperature under controlled atmosphere is delicate. Micromechanical models describe the constitutive behaviour of aggregates of spheres from the deformation of two-sphere contact either by viscous flow or grain boundary diffusion. Such models are not able to describe complex microstructure and mechanisms as observed in real materials but they can give some basic information on the formulation of constitutive equations. Practically both experimental and theoretical approaches can be coupled to identify the constitutive equations. Such procedure has been performed for modelling the sintering of compacts obtained by die pressing of a mixture of tungsten carbide and cobalt powders. The constitutive behaviour of this material during sintering has been described by a linear viscous constitutive model, whose functions have been fitted from results of free sintering and sinter-forging experiments. This model has next been introduced in ABAQUS finite element code to simulate the sintering of heterogeneous green compacts of various geometries at constant temperature. Examples of simulations are shown and compared with experiments.

• Transactions of Materials Processing
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• v.16 no.3 s.93
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• pp.210-214
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• 2007

Manufacturing bulk nanostructured materials with least grain growth from initial powders is challenging because of the bottle neck of bottom-up methods using the conventional powder metallurgy via compaction and sintering. In the study, densification behavior of nano Cu powders during pressureless sintering was investigated using an in-situ optical dilatometer technique. The initial heating and steady temperature stages during the sintering of nano Cu powder compacts were observed. At the initial heating stage, the powder compact has many porosities and full densification needs high temperature and/or high pressure sintering. In the experimental analysis, changes in geometry and density were measured and discussed for optimal consolidation and densification by the in-situ optical dilatometer.