• 한국결정성장학회지
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• 제3권1호
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• pp.37-44
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• 1993

수열반응법으로 합성한 칼시아 안정화 지르코니아 분말을 $1200^{\circ}C~1400^{\circ}C$의 온도에서 소결시켜 Ca-TZP 세라믹스를 제조한 후 소결체의 물성과 $250^{\circ}C$에서의 등온 상전이 거동을 고찰하였다. 그 결과 소결밀도가 약 97%이고 평균 입자크기가 $0.1~0.25{\mu}m$인 미세한 구조의 정방정상 지르코니아 다결정체(Ca-TZP) 세라믹스를 제조할 수 있었다. 이러한 Ca-TZP 세라믹스는 종래의 Y-TZP 세라믹스에 비햐여 열안정성이 매우 우수하였다.

• 한국세라믹학회지
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• 제30권12호
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• pp.1015-1022
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• 1993

The formation process of polycrystalline YIG(Y3Fe5O12) prepared by conventional method in Fe2O3-Y2O3 system was investigated. Effect of the microstructure of sintered body on electromagnetic properties was also investigated. Orthoferrite (YFeO3) was formed between 900 and 110$0^{\circ}C$. Formation of YIG phase begin at 110$0^{\circ}C$ with sharp increased saturation magnetization simultaneously. YIG phase is identified as single phase above 120$0^{\circ}C$. The microstructures and electromagnetic properties of sintered bodies are varied due to calcination condition of starting materials. The sintered YIG of calcined sample at 110$0^{\circ}C$ has such magnetic properties as Bs=1580G, BHC=1.89Oe, Tc=570K, ΔH(9.3GHz)=78Oe.

• Metals and materials international
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• 제24권6호
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• pp.1303-1308
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• 2018

A new sintering technique for enhancing a densification and hardness of sintered titanium body by supplying hydrogen was developed (Hydrogen Sintering Process, HSP). The HSP was developed by only injecting hydrogen into an argon atmosphere during the core time. As a result, sound titanium sintered bodies with high density and hardness were obtained by the HSP. In addition, a pore size and number of the HSP specimens were smaller than those of the argon atmosphere specimen. It was found that the injecting hydrogen into the argon atmosphere by HSP can prevent the formation of oxide layers, resulting in enhanced densification and hardness.

• 한국분말재료학회지
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• 제13권5호
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• pp.313-320
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• 2006

The present study is to analyze the thermoelectric properties of $Bi_{0.4}Sb_{1.6}Te_3$ thermoelectric materials fabricated by the mechanical grinding process. The $Bi_{0.4}Sb_{1.6}Te_3$ powders were prepared by the combination of mechanical milling and reduction treating methods using simply crushed pre-alloyed $Bi_{0.4}Sb_{1.6}Te_3$ powder. The mechanical milling was carried out using the tumbler-ball mill and planetary ball mill. The tumbler-ball milling had an effect on the carrier mobility rather than the carrier concentration, whereas, the latter on the carrier concentration. The specific electric resistivity and Seebeck coefficient decreased with increasing the reduction-heat-treatment time. The thermal conductivity continuously increased with increasing the reduction-heat-treatment time. The figure of merit of the $Bi_{0.4}Sb_{1.6}Te_3$ sintered body prepared by the mechanical grinding process showed higher value than one of the sintered body of the simply crushed powder.

• 한국표면공학회지
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• 제28권4호
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• pp.207-218
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• 1995

Tungsten(W) metal has excellent properties in heat-resistance, corrison-resistance and impact-resistance but W-Metal is hard to sinter because higher than $2,000^{\circ}C$ is required to sinter W-powder. Con-sequently, a deposit technique of Nikel Phosphorus(NiP) on W-powber by the liquid reduction precipitation method was performed. Sintering temperature of the resulting W-NiP composite was lowered around to $1,000^{\circ}C$, and the mechanical properties of the sintered body was studied. The most suitable conditions for NiP thin film deposit on W-Powder by the liquid reduction precipitation method, which are composition, concentration, pH and temperature of the liquid reduction solution, were considered. The activated sintering was carried out in a reducing condition furnace. Components and properties of the sintered body were investigated by the density and the hardness measurements, X- ray diffraction analysis, and microscopic photographs of the surface. Quantity of NiP thin film on W-powder could be varied by the change of the liquid reduction solution composition. The sintering temperature of W-NiP composite powder is lowered to $950^{\circ}C$ from $2,000^{\circ}C$ and the hardness is increased (ca. 720 Hv). Large shrinkage could be observed since density was increased from 5.5 to 11.0 g/$cm^2$ which 86.2% of theoretical density. W metal and $Ni_3P$ crystal were detected through X-ray diffraction on the sintered body. Perfectly activated sintering was observed by microscopic photographs.

• The Journal of Advanced Prosthodontics
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• 제15권5호
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• pp.248-258
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• 2023

PURPOSE. This study aims to evaluate the effects of exposure energy on the lateral resolution and mechanical strength of dental zirconia manufactured using digital light processing (DLP). MATERIALS AND METHODS. A zirconia suspension and a custom top-down DLP printer were used for in-office manufacturing. The viscosity of the suspension and uniformity of the exposed light intensity were controlled. Based on the exposure energy dose delivered to each layer, the specimens were classified into three groups: low-energy (LE), medium-energy (ME), and high-energy (HE). For each energy group, a simplified molar cube was used to measure the widths of the outline (X_o and Y_o) and isthmus (X_i and Y_i), and a bar-shaped specimen of the sintered body was tested. A Kruskal-Wallis test for the lateral resolution and one-way analysis of variance for the mechanical strength were performed (α = .05). RESULTS. The zirconia green bodies of the ME group showed better lateral resolution than those of the LE and HE groups (both P < .001). Regarding the flexural strength of the sintered bodies, the ME group had the highest mean value, whereas the LE group had the lowest mean value (both P < .05). The ME group exhibited fewer agglomerates than the LE group, with no distinctive interlayer pores or surface defects. CONCLUSION. Based on these findings, the lateral resolution of the green body and flexural strength of the sintered body of dental zirconia could be affected by the exposure energy dose during DLP. The exposure energy should be optimized when fabricating DLP-based dental zirconia.

• 한국세라믹학회지
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• 제21권4호
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• pp.366-372
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• 1984

Unstabilized Zirconia was added to basic composition under 44$mu extrm{m}$ of 57.80wt% Clay-22.20wt% Chamotte-20.00wt% Agalmatolite system. Here the amount and the particle size of Zirconia were 5-25wt% and -20${\mu}{\textrm}{m}$ respectively and the body of these composition was first at 135$0^{\circ}C$. The results obtained from examining the properties of sintered body were as follows. 1. Firing linear shrinkage apparent density and bulk density apparent porosity and water absorption of the samples had the tend to increase according as the particle size of zirconia became larger and the amount of zirconia increased. 2. Modulus of rupture was inversely proportional to the particle size and the additive amount of zirconia, . Especially in case that the particle size of zirconia over 5${\mu}{\textrm}{m}$ and the additive amount of zirconia was 25wt% the modulus of rupture had shrunk drastically. 3. The maximum value of KIC was obtained at 20wt% additive amount of zirconia according to the each particle size of zirconia. Especially the highest value of KIC is 2, 173 M. Pa. M1/2 when the particle size of zirconia is 5~10${\mu}{\textrm}{m}$ and the additive amount is 20wt%.

• 한국세라믹학회지
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• 제48권3호
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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.

• 한국재료학회지
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• 제11권6호
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• pp.465-471
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• 2001

수용성 매체에서 젤-케스팅 공정을 이용하여 용융실리카를 기본으로 하는 다성분계 세라믹 코어 (中子)를 제조하고, 소결조건에 따른 제반 기계적 물성과 알칼리 부식용액에 의한 용출특성을 고찰하였다. 1000cP (at $50sec^{-1}$ ) 이하의 낮은 점도를 갖는 50vol%의 고농도 다성분계 세라믹 슬림의 제조가 가능하였다. 성형체는 안정화시킨 슬림을 몰드에 부어 상온에서 겔화시킨 후 $25^{\circ}C$, 80% 상대습도 분위기 하에서 48시간동안 건조시켜 제조하였으며 건조된 성형체에는 균열이 발생하지 않았다. 세라믹 코어 성형체의 소결온도가 상승할 수록 상온강도, 겉보기 밀도, 수축률은 시편의 기공도와 역비례하여 증가하였다. 세라믹 코어 소결체의 용출속도는 동일한 온도에서 알칼리 부식용액의 농도에 의존하였으며, 소결체의 기공도가 클수록 증가하였다.

• 대한치과기공학회지
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• 제34권2호
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• pp.113-119
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• 2012

Purpose: Zirconia blocks for all ceramic dentures are divided into two groups. One is pre-heated block and the other is binder added block. In this study, the possibility of recycling the remained parts of binder added block after CAD/CAM machining with slip casting process was investigated. Methods: Owing to the binder added block contain large amount of organic matter, Binder burn-out was must be carried out before ball milling for preparing the casting slip. Binder burn-out was accomplished at $600^{\circ}C$ for 10 hours. Ball milling was performed with 5mm zirconia ball and 60mm polyethylene bottle. From 0% to 5% at 1% intervals of alumina was added to zirconia powder for preparing slip. Solid casting was achieved with plaster mold. Cast bodies were dried and sintered at $1,500^{\circ}C$ for 1 hour. Linear shrinkage, apparent porosity, water absorption, bulk density, and flexural strength were tested. Microstructures were observed by SEM, EDS and XRD analysis were executed. Results: Optimum slips for casting was prepared with 300g ball, 100g powder, and 180g distilled water. Cast body without alumina showed 26% of linear shrinkage, 6.07 of apparent density, and 470MPa of three point bend strength. On the other hand, as received zirconia block, which was sintered at the same conditions, showed 23% of linear shrinkage, 6.10 of apparent density, and 680MPa of three point bend strength. When 3% of alumina was added to zirconia, sintered body showed 23% of linear shrinkage, 6.10 of apparent density, and 780MPa of three point bend strength. SEM photomicrographs and EDS analysis showed alumina particles uniformly dispersed in zirconia matrix, and XRD analysis showed no phase transformation of tetragonal zirconia particles was occurred when alumina was added. Conclusion: According to the all of this experimental results, 3% of alumina added cast zirconia body showed excellent mechanical properties more than as received binder containing zirconia block.