• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 하계학술대회 논문집
• /
• pp.693-696
• /
• 2001

The (Ba$_{0.3}$Bi$_{0.3}$Sr$_{0.4}$)TiO$_3$[BBST] ceramics were prepared by conventional mixed oxide method. The structural properties of the BBST ceramics with sintering temperature were investigated by XRD, SEM, EDS. In the case of BBST ceramics sintered at 1150~135$0^{\circ}C$, the $Ba_{0.5}$Sr$_{0.5}$TiO$_3$and SrBi$_4$Ti$_4$O$_{15}$ phase were coexisted. The 2$\theta$ value of the BST (110) peaks were shifted to the lower degree at the sintering temperature of 130$0^{\circ}C$ and 135$0^{\circ}C$. The grains of the BBST ceramics sintered at 130$0^{\circ}C$ and 135$0^{\circ}C$ were not appeared. Increasing the sintering temperature, the densities of the BBST ceramics were increased. In the BBST ceramics sintered at 130$0^{\circ}C$ and 135$0^{\circ}C$, the mole ratio of Bi was decreased.d.ed.d.d.d.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1994년도 추계학술대회 논문집
• /
• pp.8-12
• /
• 1994

Solid solutions $Sr_2$($Ta_{1-x}$$Nb_{x}$)$_2$$O_{7}$ (x = 0.0 - 1.0) composed of strontium-tantalate (low Curie temperature) and strontium-niobate (high Curie temperature) were prepared by the conventional mixed oxide method and the molten salt synthesis method (flux method). Phase relation, sintering temperature, grain-orientation and dielectric properties were investigated for sintered ceramic samples 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. Single phase $Sr_2$$Nb_2$$O_{7}$ powder was synthesized by using flux method at lower temperatures, and sintering temperature was also reduced by using flux method derived powder than using mixed-oxide derived powder. Sintering characteristics and dielectric properties of specimens prepared by flux method were better than those derived through the conventional method.

• The Korean Journal of Ceramics
• /
• 제1권1호
• /
• pp.45-54
• /
• 1995

Four kinds of silicon nitride based ceramic materials have been hot pressed. Effect of the sintering additives on the phase transformation, microstructural development and mechanical properties was investigated. While sintering under the same condition a big difference among the microstructures of the specimens, they appeared alike if sintered to have a similiar $\alpha$-$\beta$ phase ratio. The specimen of the stoichiometric $\alpha$-$\beta$ sialon composition showed very limited amount of the intergranular glassy phase and a significant degree of the residual stress. It exhibited almost no strength degradation up to $1300^{\circ}C$, and the strength of the specimen degraded more as its composition deviated from the stoichiometry.

• 한국재료학회지
• /
• 제9권1호
• /
• pp.51-56
• /
• 1999

The $BaTiO_3$ powders were synthesized by GNP (Glycine-Nitrate process). The powders were prepared using carbonate and alkoxide as starting materials and nitric acid was used as a solvent for starting materials as well as an oxidant for combustion. the effects of aggregates in $BaTiO_3$ powders on green densities, sintering and dielectric characteristics were investigated. When the glycine/cation molar ratio was 1.2, reactivity of self-combustion was most intensive and the degree of aggregates after calcination was low. On sintering at $1400^{\circ}C$, maximum theoretical relative density(94.99%%0 was obtained in case of 1.2 molar ratio of glycine/cation. The dielectric constant of this sintered $BaTiO_3$ was 1919.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
• /
• pp.763-768
• /
• 2003

This study is to specify the properties of solidification/stabilization of heavy metals in connection with looking over the hydration features of non-sintering cement using industrial by-products. In this study, we added Cr and Pb to non-sintering cement(NSC), ordinary portland cement (OPC), and Blast-furnace slag cement(BSC) to specify the solidification process. Heavy metal leaching test was carried out to evaluate solidification degree of various cement. Follow result, marking no higher than 0.7% of un-solidified ratio of BSC was the most predominant result when we mixed the materials with Cr. 5.8% for NSCI and 6.2% for NSC2. On the contrary, in case of adding Pb, NSCl and NSC2 made better solidification results than those of OPC(below 0.2%) and BSC(below 0.05%), marking nearly 0%.

• 대한심미치과학회지
• /
• 제23권2호
• /
• pp.77-79
• /
• 2014

There are several factors affected fractures of full contour zirconia (FCZ) dental prosthesis in laboratory process. First, residual moisture can cause zirconia cracks. Complete dry is requisite before zirconia sintering to prevent zirconia cracks. Second, slow cooling rate is essential to prevent cracks during zirconia sintering process. Cracks in bridge pontic area, thick dental implant prosthesis can be prevented by slow cooling rate such as 3 degree Celsius per minute during zirconia sintering. Third, slow heating rate and slow cooling rate during staining and glazing procedure is necessary to inhibit thermal shock of sintered dental zirconia. Lower preheat temperature of porcelain furnace is recommended. Finally, using diamond disc to open embrasure can lead cracks.

• 한국분말재료학회지
• /
• 제10권3호
• /
• pp.168-171
• /
• 2003

Interpenetrating phase composites of $TiB_2$-Cu system were produced via Spark-Plasma Sintering (SPS) oi nanocomposite powders. Under simultaneous action of pressure, temperature and electric current titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a fine-grained skeleton. Increasing SPS-temperature and he]ding time promote densification due to local melting of copper matrix When copper melting is avoided the compacts contain 17-20% porosity but titanium diboride skeleton is still formed representing the feature of SPS . High degree of densification and formation of titanium diboride network result in increased hardness of high-temperature SPS-compacts.

• Journal of Magnetics
• /
• 제9권1호
• /
• pp.9-12
• /
• 2004

We have investigated sintering effects on Fe/Mo ordering and magnetoresistance (MR) in double perovskite-reflection lines due to $Sr_2FeMoO_6$ (SFMO). Polycrystalline samples have been prepared by the conventional solid-state reaction by sintering in a stream of 5% $H_2/Ar$ gas. All samples are single phase and exhibit a series of superstructurecation ordering at Fe and Mo sites. As sintering temperature increases from 900 to $1300^{\circ}C$, the degree of Fe/Mo ordering increases from 82 to 92%, magnetization (15 K, 7 kOe) increases from 1.6 to 2.7 ${\mu}_B/f.u.,$ and Curie temperature increases at a rate of 4.3 K/% with the increase of Fe/Mo ordering ratio. The magnitude of MR measured at 5 K is 19% for sample prepared at $1000^{\circ}C$ with magnetic fields of 7 kOe. The observed MR is proportional to the square of magnetization indicating that the MR feature in SFMO is explained by the spin-polarized tunneling at grain boundaries.

• 한국재료학회지
• /
• 제28권6호
• /
• pp.343-348
• /
• 2018

Recently, the properties of nanostructured materials as advanced engineering materials have received great attention. These properties include fracture toughness and a high degree of hardness. To hinder grain growth during sintering, it is necessary to fabricate nanostructured materials. In this respect, a high-frequency induction-heated sintering method has been presented as an effective technique for making nanostructured materials at a lower temperature in a very short heating period. Nanopowders of W and $Al_2O_3$ are synthesized from $WO_3$ and Al powders during high-energy ball milling. Highly dense nanostructured $W-Al_2O_3$ composites are made within three minutes by high-frequency induction-heated sintering method and materials are evaluated in terms of hardness, fracture toughness, and microstructure. The hardness and fracture toughness of the composite are $1364kg/mm^2$ and $7.1MPa{\cdot}m^{1/2}$, respectively. Fracture toughness of nanostructured $W-Al_2O_3$ is higher than that of monolithic $Al_2O_3$. The hardness of this composite is higher than that of monolithic W.

• 한국세라믹학회지
• /
• 제35권7호
• /
• pp.706-714
• /
• 1998

The MgO-{{{{ { {Al }_{2 }O }_{3 } }}-{{{{ { {SiO }_{2 } }_{ } }}system containing alumina powder was fabricated sintered at various temperature and analyzed in order to study the sintering mechanism and crystallization characteristics. The specimen composed of glass powder with average particle size of 8.27 $\mu\textrm{m}$ and 0-40 vol% alumina powder were sint-ered for 3 hrs at the temperature between 850$^{\circ}C$ and 1350$^{\circ}C$ The sintering mechanism consists of the redis-tribution of particles occuring at 750$^{\circ}C$ and the viscous flow at 850∼950$^{\circ}C$. The degree of crystallization and sintering temperatue were dependent upon the ratio of glass/alumina. The second phase from the reaction between glass and alumina was not observed which was confirmed by XRD and properties analysis. The density dielectric constant and specific resistivity of specimen were 2.30∼3.26g/cm2 5.8∼7.38 at 1 GHz density dielectric constant and specific resistivity of specimen were 2.30∼3.26g/cm3 5.8∼7.38 at 1GHz and 1.23∼4.70${\times}$107 $\Omega$$.$m respectively.