• Korean Journal of Materials Research
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• v.34 no.1
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• pp.12-20
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• 2024

This study successfully prepared high-porosity aluminosilicate fibrous porous ceramics through vacuum suction filtration using aluminosilicate fiber as the primary raw material and glass powder as binder, with the appropriate incorporation of glass fiber. The effects of the composition of raw materials and sintering process on the structure and properties of the material were studied. The results show that when the content of glass powder reached 20 wt% and the samples were sintered at the temperature of 1,000 ℃, strong bonds were formed between the binder phase and fibers, resulting in a compressive strength of 0.63 MPa. When the sintering temperatures were increased from 1,000 ℃ to 1,200, the open porosity of the samples decreased from 89.08 % to 82.38 %, while the linear shrinkage increased from 1.13 % to 10.17 %. Meanwhile, during the sintering process, a large amount of cristobalite and mullite were precipitated from the aluminosilicate fibers, which reduced the performance of the aluminosilicate fibers and hindered the comprehensive improvement in sample performance. Based on these conditions, after adding 30 wt% glass fiber and being sintered at 1,000 ℃, the sample exhibited higher compressive strength (1.34 MPa), higher open porosity (89.13 %), and lower linear shrinkage (5.26 %). The aluminosilicate fibrous porous ceramic samples exhibited excellent permeability performance due to their high porosity and interconnected three-dimensional pore structures. When the samples were filtered at a flow rate of 150 mL/min, the measured pressure drop and permeability were 0.56 KPa and 0.77 × 10^-6 m² respectively.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.246-252
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• 2016

Complex designed silica-based ceramic cores were fabricated by ceramic injection molding. Slow heating rate (0.2K/min) for debinding restrained bloating on the surface of ceramic cores. To investigate effect of sintering conditions on mechanical properties of ceramic cores, green bodies were sintered at temperatures in a range from $1150^{\circ}C$ to $1400^{\circ}C$ for various dwelling times (6 h to 48 h). Sintering above $1300^{\circ}C$ for 12 h and dwelling time over 24 h at $1200^{\circ}C$ reduce the flexural strength and increase the linear shrinkage of ceramic cores. Cristobalite, formed by high sintering temperature or long dwelling time, induces reduction of mechanical properties due to its phase transformation, which is accompanied by volume contraction and microcracking. Ceramic core sintered at $1200^{\circ}C$ for 12 h endured wax patterning and shell molding, and was manufactured successfully.

• Journal of the Korean Ceramic Society
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• v.37 no.3
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• pp.211-218
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• 2000

The attrition-milled powder mixtures of Al and Al2O3 were oxidized below 140$0^{\circ}C$ for 1 hr and post-sintered at 150$0^{\circ}C$ and 1$600^{\circ}C$ for 2 hr. During attrition milling, ZrO2 was added to the system by grinding effect of ZrO2 balls. The average particle size of the powder mixtures was decreased by the attrition milling as the aluminum content decrease. Above 120$0^{\circ}C$, sintering behaviro was observed on the fine Al2O3 particles resulted from the oxidation of Al. The specimens heat-treated at 140$0^{\circ}C$ for 1 hr showed the bending strength of 166 MPa and hardness of 220 MPa. The specimens post-sintered at 1$600^{\circ}C$ for 2hr had a linear shrinkage of 9~12% and a relative density of about 95%. After the post-sintering, the specimens having 55 vol% Al content revealed the bending strength of 513 MPa and hardness of 718 MPa. The Weibull modulus to the bending strength was about 16.

• Journal of Korea Foundry Society
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• v.10 no.1
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• pp.64-70
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• 1990

In order to lower the cabon content of sintered products below the solubility of austenite, Fe-oxide was added to cast iron powder of which matrix was pearlite. And the effects of it on some sintering properties and mechanical properties were investigated. Roughly speaking, the linear shrinkage, density, and tensile strendth of sintered properties increased as the sintering temperature became higher, the size distribution of powder became finer, and the amount of Fe-oxide added became less. The maximum tensile strength of sintered products was $78㎏f/mm^2$ more or less, of which carbon content was 1.4% and sintering temperature was $1180^{\circ}C$.

• Journal of Powder Materials
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• v.5 no.4
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• pp.241-249
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• 1998

Sintering kinetics of ball-milled $MoSi_2$ was studied with the addition of Ni. $MoSi_2$ powder with the average particle size of 1 $\mu\textrm{m}$ was obtained from ball-milling of 10 $\mu\textrm{m}$ powder. Small amount of Ni was added to the ball-milled $MoSi_2$ powder by salt solution and reduction method. The powder was compacted into cylindrical shape at 200 MPa and isothermally sintered in a $H_2$ atmosphere at the temperature range of 1100~$1400^{\circ}C$ for 3~600 minutes. The changes of linear shrinkage and sintered density were monitored as a function of sintering time. The microstructure was observed by using optical microscopy and scanning electron microscopy. Phases were identified by X-ray diffratometer and electro-probe micro analysis. Sintering kinetics of Ni-added powder was compared to as-milled powder and the apparent activation energy was calculated from Arrhenius plot.

• Journal of the Korean Ceramic Society
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• v.29 no.9
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• pp.711-718
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• 1992

Pb(Fe1/2Nb1/2)O3 was prepared by the molten salt synthesis method using an equimolar mixture of NaCl-KCl. Initial particle size could be controlled by varying the weight ratio of the NaCl-KCl to raw materials from 0.1 to 1.0, and the initial particle size effects on the sintering and dielectric properties of Pb(Fe1/2Nb1/2)O3 were investigated at the sintering temperature range from 90$0^{\circ}C$ to 105$0^{\circ}C$. As the weight ratio of salt increased, the average particle size decreased and the particle size distributions tended to narrow. As the initial particle size decreased, the linear shrinkage and density increased due to the promotion of densification. Dielectric constant increased with decreasing the initial particle size resulting from the increase of density and grain size.

• Journal of the Korean Ceramic Society
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• v.27 no.1
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• pp.55-61
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• 1990

Effect of Al2O3 addition on the mechanical properties and microstructure of Ce-TZP were studied. 12, 14, 16Ce-TZP containing 0-40wt% Al2O3 were prepared by sintering at 155$0^{\circ}C$ for 2h. in air. Density, linear shrinkage, bending strength, Vickers hardness, microstructuer and the amount of stress induced phase transformation were examined. Vickers hardness increased linearly with increasing amounts of Al2O3. The amount of transformation and fracture toughness decreased linearly with increasing amount of Al2O3. Linear shrinkage and relative density decreased with increasing Al2O3 content in all composition of Ce-TZP. Grain growth of Ce-TZP was inhibited by Al2O3 dispersion and fracture mode of Ce-TZP/Al2O3 composites transformed from intergranular to transgranular fracture as the amount of Al2O3 increased. TEM observation revealed that Al2O3 particles were located mainly at grain boundaries of ZrO2.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1548-1554
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• 2008

The market of silver precious metal clay (PMC) is promising as its application for agile metal craft. The property of suitable hardness and shrinkage as well as environment-safe is strictly required as people make the final product with bare hands. We propose a silver PMC with new organic binder made of palm oil, glycolic acid and water. Then we prepared disk specimen of our proposed PMC and well-known commercial PMC. We investigated the hardness, weight change, linear shrinkage, density and micro structure evolution with sintering temperature of $700{\sim}900^{\circ}C$ ($50^{\circ}C$ gap) for 15minutes. We confirm our proposed PMC has suitable property for craft product comparable for commercial PMC, and the optimum sintering condition is $850^{\circ}C$-15minutes for metal craft application.

• Journal of the Korean Ceramic Society
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• v.48 no.3
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• pp.228-235
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• 2011

Sintering behavior and lightweight characteristics of porcelain by addition of FAHM (Fly-Ash Hollow Microsphere) were evaluated. Green body of Backja composition (general porcelain) in which FAHM was added(15 and 20 wt%) was made by slip casting method. The green body was sintered at 1270 and $1290^{\circ}C$ and maintained for 1h. The bulk density and linear shrinkage of the sintered body with FAHM (20 wt%) decreased. As the contents of FAHM. increased, mullite and cristobalite phases increased. In the microstructure, FAHM shells remained after sintering, and the generation of mullite fibers around FAHM shells also were confirmed. the weight of porcelain with of 20% FAHM decreased by 40% and residual FAHM shells promoted the mullite of generation in the matrix.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.384-389
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• 2011

Gas pressure sintering (GPS) of reaction bonded silicon nitride (RBSN) was performed using $Lu_2O_3-SiO_2$ additive and the properties were compared with those of specimens prepared using high purity $Si_3N_4$ powder. The relative density of RBSN and compacted $Si_3N_4$ powder were 68.9 and 47.1%, and total linear shrinkage after sintering at $1900^{\circ}C$ were 14.8 and 42.9%, respectively. High nitrogen partial pressure (5MPa) was required during sintering at $1900^{\circ}C$ in order to prevent the decomposition of the nitride and to promote the formation of SiC. The relative density and 4-point bending strength of RBSN and $Si_3N_4$ powder compact were 97.7%, 954MPa and 98.2%, 792MPa, respectively, after sintering at $1900^{\circ}C$. The sintered RBSN also showed high fracture toughness of 9.2MPam$^{1/2}$.