• Journal of the Korean Society of Industry Convergence
• /
• v.25 no.4_2
• /
• pp.621-626
• /
• 2022

Tungsten is a high melting point metal unlike other steel materials, and it is difficult to manufacture because of its high melting temperature. In this study, pressure sintering process method was applied to manufacture the tungsten materials at low temperature. Therefore, it is necessary to densify the sintered material by using a sintering additive. Studies have been conducted on how the amount of titanium for sintering tungsten affects the mechanical properties of tungsten in this study. In order to secure the densification mechanism of tungsten powder during the sintering process, the characteristics of the sintered tungsten material according to the change of titanium content were evaluated. It was investigated the relationship between sintering parameters and mechanical properties for densification of microstructures. The sintered tungsten materials according to sintering additive content showed high sintered density (about 16.31g/cm³) and flexural strength (about 584 MPa) when the content of sintering additive was 3 wt%. However, as the content of the sintering additive increases, mechanical property of flexural strength is decreased, and the porosity is increased due to the heterogeneous sintering around titanium.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.11a
• /
• pp.214-216
• /
• 2006

In this study, in order to develop the composition ceramics for low loss and low temperature sintering multilayer piezoelectric actuator, PMN-PZN-PZT ceramics were fabricated using two stage calcination method and $Li_2CO_3$, $Bi_2O_3$ and CuO as sintering aids and their piezoelectric characteristics were investigated according to the 2nd calcination and sintering temperature. At the calcination temperature of $750^{\circ}C$ and sintering temperature of $930^{\circ}C$, density, electromechanical coupling factor ($k_p$), mechanical quality factor ($Q_m$), Dielectric constant (${\varepsilon}_r$) and piezoelectric constant ($d_{33}$) of specimen showed the optimum value of $7.94g/cm^2$ 0.581, 1554, 1555 and 356pC/N, respectively for multilayer piezoelectric actuator application.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.8
• /
• pp.608-613
• /
• 2013

In this paper, the low-temperature sintering of $TiO_2$ is approached to solve the problem of high temperature sintering which decreases the interconnection between particles or between substrate and particle. $TiO_2$ paste is prepared with Titanium (IV) isopropoxide as the precursor material and calcinate at different conditions (low temperature). In the results, since the changing of temperature and time of sintering, crystalline phase do not change and the intensities of anatase, rutile phase are higher. At $110^{\circ}C$, 7 h sintering condition, crystalline size of anatase and rutile phase are the smallest which are 13.07 and 17.47 nm, respectively. In addition, the highest zeta potential is about 32.77 mV and the repulsive force increases thus leading to the best of the dispersion characteristics between $TiO_2$ particles. Futhermore, DSSCs at that condition exhibits the highest efficiency with the values of $V_{oc}$, $J_{sc}$, FF and ${\eta}$ are 0.69 V, $8.60mA\;cm^{-2}$, 67.93% and 4.06%, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.321-322
• /
• 2007

In this thesis, the sintering properties and piezoelectric properties of $Pb[(Co_{0.5}W_{0.5})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.07}(Zr_{0.52}Ti_{0.48})_{0.9}]O_3+0.5[wt%]MnO_2$ ceramics has been systematically investigated as a function of the sintering temperature after manufacturing the specimens with a general method. The lattice constant from the analysis of crystal structure showed that the pychlore structure was decreased with the increase of the sintering temperature. Density was decreased by increasing $B_2O_3$. TCFr was showed its minimum variation rate of 0.35~-0.52[%] in the sintered temperature 950[$^{\circ}C$], $B_2O_3$ 3[wt%]. The electromechanical coupling coefficient (Kp) showed its maximum of 31.116[%] in the sintered temperature 1050[$^{\circ}C$], and its minimum of 20.220[%] in the sintered temperature 1150[$^{\circ}C$].

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.8 no.4
• /
• pp.514-519
• /
• 2020

In this study, cement clinkers were sintered at each temperature by replacing some of the clay components of cement clinkers with coal materials. The mineral phase change of sintered cement clinker was quantitatively analyzed by XRD-Rietveld method. As the sintering temperature of cement clinker increased, the amount of belite decreased, the amount of alite increased, and the amount of free-CaO decreased. The form of alite and belite could be distinguished at sintering temperature of 1450℃ or higher. The crystal size was greatly increased at 1500℃ sintering. It was confirmed that the excessive sintering was progressed. Free-CaO decreased with the increase of sintering temperature. At 1450 ℃ or higher, it was less than 0.5%. In 1450℃ or greater, it is determined that enough sintering is included. Therefore, the application of fly ash as a raw material of cement clinker was judged to be usable as a source of chemical components of alumina and iron raw materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.4
• /
• pp.350-356
• /
• 2006

In this study, piezoelectric transformer was manufactured at the sintering temperature of $950^{\circ}C$, and then the feasibility of application to low temperature sintering piezoelectric transformers was investigated by evaluating the electrical characteristics of it. The voltage ratio of piezoelectric transformer showed the maximum value at the resonant frequency of input part, and increased according to the increase of load resistance. The output power and efficiency of piezoelectric transformer showed the superior properties when the output impedance of it coincides with the load resistance. Piezoelectric transformer manufactured at the low temperature of $950^{\circ}C$ showed the heat generation less than $20^{\circ}C$ at the output power of 30 W, and stable driving characteristics.

• Journal of the Korean Ceramic Society
• /
• v.32 no.10
• /
• pp.1111-1116
• /
• 1995

To use dielectric material of high power multilayer capacitor, the composition of the commercial CaTiO3 was changed to decrease the sintering temperature, and the physical and electrical properties were investigated. Series of experiments showed that CaTiO3 with sintering additives had the highest density, the highest shrinkage, the lowest dielectric constant, the lowest loss factor, and the lowest temperature coefficient of capacitance (TCC). These properties had the constant values at sintering temperature of above 120$0^{\circ}C$.

• Journal of the Korean Ceramic Society
• /
• v.16 no.1
• /
• pp.3-12
• /
• 1979

The effects of sintering temperature and sintering atmosphere on magnetic properties and microstructuresof Mn-Zn ferrites have been studied. Mixture of 52.8mole% $Fe_2O_3$, 26.4mole% MnO, 15.1mole0% ZnO and 5.7mole% NiO was prepared, and 0.1mole% CaO, 0.02mole% $SiO_2$ were added as minor additives. After calcining and ball milling the powder was granulated for compacting. The specimens were sintered at $1, 250^{\circ}$, $1, 300^{\circ}$and 1, 35$0^{\circ}C$ in the various atmosphere of $N_2$, $N^_2\DIV0.6% O_2$, $N_2＋2.7% O_2$, $N_2＋4.1% O_2$, $N^2＋8.2% O_2$ and air for 3 hours and cooled in $N_2$ atmosphere. The grian growth rate and densities increase as sintering temperature and oxygen content of atmosphere increase. At the sintering temperature of $1, 250^{\circ}C$ the initial permeabilities increase as oxygen content of atmosphere increase. At the sintering temperature of$ 1, 300^{\circ}$and $1, 350^{\circ}$ the initial permeabilities show maximum values at $N_2＋4.1% O_2$ atmosphere. The secondary peaks of initial permeabilities are observed between 100$^{\circ}$and 20$0^{\circ}C$, and the positions of secondary peaks move to higher temperature as oxygen content of atmosphere increases. Q-factors decrease as sintering temperature increases and oxygen content of atmosphere decreases.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.5
• /
• pp.417-421
• /
• 2006

In this study, in order to develop low temperature sintering piezoelectric ceramics for LTCC (Low-Temperature Cofired Ceramic) multilayer piezoelectric actuator, PMW-PMN-PZT ceramics using $0.2wt%\; Li_2CO_3$ and $0.25wt%\;CaCO_3$ as sintering aids were investigated according to the varation of PMW substution. Composition ceramics could be sintered at $900^{\circ}C$ by adding sintering aids. As the amount of PMW substitution increased, the crystal structure of PMW-PMN-PZT ceramics moved from tetragonal phase to rhombohedral phase gradually, and MPB(Morphotrophic Phase Boundary) region appeared at 2 mol% PMW substitution. At the sintering temperature of $900^{\circ}C$, the density, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant(${\epsilon}r$), piezoelectric constant(d33) and Curie temperature(Tc) of 2 mol% PMW substituted PMW-PMN-PZT ceramics showed the optimal values of $7.88g/cm^3$, 0.58, 1002, 1264, 352 pC/N and $336^{\circ}C$, respectively, for LTCC multilayer piezoelectric actuator application.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.10 no.3
• /
• pp.211-218
• /
• 2022

Coal ash is being considered as a source of silica and alumina for cement clinker. The purpose of this study was to investigate the effect on cement clinker sintering by confirming the high-temperature microstructural change according to the firing temperature in the cement clinker sintering process of coal ash. In the coal ash used as a raw material for cement clinker, the shape change of the particle surface was confirmed from the sintering tem perature of 950 ℃. The shape of the coal ash disappeared from the sintering temperature higher than 1250 ℃. It was confirmed that the Al and Fe components of the coal ash were converted to the cement interstitial phase at a temperature higher than 1350 ℃. In addition, the clinker using a large amount of coal ash as a raw material showed a low content of Lime and a high content of Belite in the sintering tem perature range of 1150~1200 ℃. From this, it was confirmed that the formation of calcium silicate mineral proceeds more easily at the initial sintering temperature by the application of coal ash.