• 한국표면공학회지
• /
• 제22권1호
• /
• pp.26-42
• /
• 1989

It has between investigated that the optimum spaying conditions, such as, spraying distance, fusing temperature and fusing time, ect, in a Ni-cr base self fluxing alloy sprayed on the mild steel substrate by oxygen-acetylenc flame spraying. Sprayed specimens on various conditions were fuused in a vacuum furnace and the results were as follows. The optimum spraying condition for excellent coating layer are obtained under spraying distances, fusing temperature and fusing and time ; 180~240mm,1050~110$0^{\circ}C$and 15~30min, respectively. The adhesive strength and surface hurface hardness of the as sprayed specimens were very low by mechanical bonding becaus of the diffusion layer during process. The carbides and borides and formed in the sprayed coating layer and densification of the layer was resulted from the elimination of pores and oxides. The hardness of sprayed coating layer, particularly in the high temperature, was superior to ordinary tool steels.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
• /
• pp.645-648
• /
• 1999

With the variation of the sintering temperature and the amounts of B$_2$O$_3$, Bi$_3$O$_3$ and V$_2$O$_{5}$ , the densification and the piezoelectric properties of the MnO$_2$-doped PMN-PZT were investigated. The additives decreased the sintering temperature of ceramics. In the case of 0.5wt% B$_2$O$_3$, the sintering density, the mechanical quality factor, the electromechanical coupling factor and the piezoelectric constant were 7.51 (g/㎤), 1397, 51.1% and 305 (X10$^{-12}$ C/N) respectivly at 105$0^{\circ}C$. And the addition of lwt% Bi$_2$O$_3$, they were 7.59 (g/㎤) ,833,49.8% and 308 (X10$^{-12}$ C/N) respectivly at 1000 $^{\circ}C$.

• 한국재료학회지
• /
• 제24권3호
• /
• pp.145-151
• /
• 2014

Solution-based Sb-doped $SnO_2$ (ATO) transparent conductive oxides using a low-temperature process were fabricated by an electrospray technique followed by spin coating. We demonstrated their structural, chemical, morphological, electrical, and optical properties by means of X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, atomic force microscopy, Hall effect measurement system, and UV-Vis spectrophotometry. In order to investigate optimum electrical and optical properties at low-temperature annealing, we systemically coated two layer, four layer, and six layers of ATO sol-solution using spin-coating on the electrosprayed ATO thin films. The resistivity and optical transmittance of the ATO thin films decreased as the thickness of ATO sol-layer increased. Then, the ATO thin films with two sol-layers exhibited superb figure of merit compared to the other samples. The performance improvement in a low temperature process ($300^{\circ}C$) can be explained by the effect of enhanced carrier concentration due to the improved densification of the ATO thin films causing the optimum sol-layer coating. Therefore, the solution-based ATO thin films prepared at $300^{\circ}C$C exhibited the superb electrical (${\sim}7.25{\times}10^{-3}{\Omega}{\cdot}cm$) and optical transmittance (~83.1 %) performances.

• 한국재료학회지
• /
• 제30권11호
• /
• pp.573-580
• /
• 2020

YAG (Yttrium Aluminum Garnet, Y₃Al₅O₁₂) has excellent plasma resistance and recently has been used as an alternative to Y₂O₃ as a chamber coating material in the semiconductor process. However, due to the presence of an impurity phase and difficulties in synthesis and densification, many studies on YAG are being conducted. In this study, YAG powder is synthesized by an organic-inorganic complex solution synthesis method using PVA polymer. The PVA solution is added to the sol in which the metal nitrate salts are dissolved, and the precursor is calcined into a porous and soft YAG powder. By controlling the molecular weight and the amount of PVA polymer, the effect on the particle size and particle shape of the synthesized YAG powder is evaluated. The sintering behavior of the YAG powder compact according to PVA type and grinding time is studied through an examination of its microstructure. Single phase YAG is synthesized at relatively low temperature of 1,000 ℃ and can be pulverized to sub-micron size by ball milling. In addition, sintered YAG with a relative density of about 98 % is obtained by sintering at 1,650 ℃.

• 한국세라믹학회지
• /
• 제52권5호
• /
• pp.374-379
• /
• 2015

Mullite-matrix and $Al_2O_3$-matrix composites were fabricated with 30 wt% hydroxyapatite (HA) and tricalcium phosphate (TCP), respectively, as additives to give bioactivity. A diphasic gel process was employed to lower the densification temperature of the mullite matrix to $1320^{\circ}C$. A polymer complexation process was used to synthesize a TCP powder that was fully densified at $1250^{\circ}C$, for application to the matrix. For the HA/mullite composite, HA decomposed during sintering by reactions with the matrix components of $Al_2O_3$ and $SiO_2$, resulting in a mixture of $Al_2O_3$, TCP, and other minor phases with a low densification of less than 88% of the theoretical density (TD). In contrast, the TCP/$Al_2O_3$ composite was highly densified by sintering at $1350^{\circ}C$ to 96%TD with no reaction between the components. Different from the TCP monolith, the TCP/$Al_2O_3$ composite also showed a fine microstructure and intergranular fracture, both of which characteristics are advantageous for strength and fracture toughness.

• 한국세라믹학회지
• /
• 제49권6호
• /
• pp.586-591
• /
• 2012

$Zr_2WP_2O_{12}$ powder, which has a negative thermal expansion coefficient, was synthesized by a solid-state reaction with $ZrO_2$, $WO_3$ and $NH_4H_2PO_4$ as the starting materials. The synthesis behavior was dependent on the solvent media used in the wet mixing process. The $Zr_2WP_2O_{12}$ powder prepared with a solvent consisting of D. I. water was fully crystallized at $1200^{\circ}C$, showing a sub-micron particle size. According to the results obtained from a thermal analysis, a $ZrP_2O_7$ was synthesized at a low temperature of $310^{\circ}C$, after which it was reacted with $WO_3$ at $1200^{\circ}C$. A new sintering additive, $Al(OH)_3$, was applied for the densification of the $Zr_2WP_2O_{12}$ powders. The cold isostatically pressed samples were densified with 1 wt% $Al(OH)_3$ additive or more at $1200^{\circ}C$ for 4 h. The main densification mechanism was liquid-phase sintering due to the liquid which resulted from the reaction with amorphous or unstable $Al_2O_3$ and $WO_3$. The densified $Zr_2WP_2O_{12}$ ceramics showed a relative density of 90% and a negative thermal expansion coefficient of $-3.4{\times}10^{-6}/^{\circ}C$. When using ${\alpha}-Al_2O_3$ as the sintering agent, densification was not observed at $1200^{\circ}C$.

• 한국세라믹학회지
• /
• 제36권6호
• /
• pp.583-589
• /
• 1999

In the fabrication of ceramic chip couples for high frequency application such as the mobile communication equipment the formation of electrode lines and Ag diffusion were investigated with heat treatment conditions for removing organic binders. The deformation and densification of the electrode line greatly depended on the binder burnout process due to the overlapped temperature zone near 400$^{\circ}C$ of the binder dissociation and the solid phase sintering of the silver electrode. Ag ions were diffused into the glass ceramic substrate. The Ag diffusion was led by the glassy phase containing Pb ions rather than by the crystalline phase containing Ca ions. The fact suggests that the Ag diffusion could be controlled by managing the composition of the glass ceramic substrate.

• 한국세라믹학회지
• /
• 제34권3호
• /
• pp.289-295
• /
• 1997

저손실 Mn-Zn 페라이트의 제조공정과 첨가제가 코아의 미세구조와 전기적 특성에 미치는 영향을 조사하였다. C\ulcorner와 SiO2를 원료분체혼합시에 첨가하는 경우보다 하소분체의 재분쇄시에 첨가할 때가 작고 균일한 소결체를 얻을 수 있었다. 산소분압(Po2)이 높아짐에 따라 미세구조가 불균일해졌고 DF(disaccomodation fac-색)가 증가하였다. 또한 하소온도가 높고 분쇄시간이 짧은 소결체의 경우 치밀한 속도가 감소하여, 130$0^{\circ}C$까지 정상입성장거동을 보였고, 따라서 높은 소결온도에서도 비교적 저손실 Mn-Zn 페라이트를 얻을 수 있었다. 장시간 분쇄하거나 하소온도가 낮은 시편의 경우는 치밀화속도의 증가에 기인하여 120$0^{\circ}C$이하의 저온 소결시 미립자의 저손실 Mn-Zn 페라이트를 얻을 수 있었으나 소결온도 125$0^{\circ}C$이상에서는 비정상 입성장을 유발시켰다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 추계학술대회 논문집
• /
• pp.281-281
• /
• 2007

Low Temperature Co-fired Ceramic (LTCC) technology has been used in electronic device for various functions. LTCC technology is to fire dielectric ceramic and a conductive electrode such as Ag or Cu thick film below the temperature of $900^{\circ}C$ simultaneously. The glass-ceramic has been widely used for LTCC materials due to its low sintering temperature, high mechanical properties and low dielectric constants. To obtain the high strength, addition of filler, the microstructure should have various crystals and low pores in a composite. In this study, two glass frits were mixed with different alumina size(0.5, 2, 3.7um) and sintered at the range of $850{\sim}950^{\circ}C$. The microstructure, crystal phases, thermal and mechanical properties of the composites were investigated using FE-SEM, XRD, TG-DTA, Dilatomer. When the particle size of $Al_2O_3$ filler increased, the starting temperatures for the densification of the sintered bodies, onset point of crystallization, peak crystallization temperature in the glass-ceramic composites decreased gradually. After sintered at $900^{\circ}C$, the glass frits were crystallized as $CaAl_2Si_2O_8\;and\;CaMgSi_2O_6$. The purpose of our study is to understand the relationship between the $Al_2O_3$ particle size and thermal properties in composites.

• 한국결정성장학회지
• /
• 제8권4호
• /
• pp.619-625
• /
• 1998

저온소성용 글라스/세라믹 복합체 제조시 사용되는 유리 프릿트의 연화점과 유리의 함량이 소결특성에 미치는 영향에 대해 고찰하였고, 이에 따라 고밀도의 저온소성용 글라스/세라믹 복합체를 제조하였다. 유리의 함량이 증가함에 따라 복합체의 소결밀도는 증가하였고, 이때 사용되는 유리의 연화점이 낮을 경우 유리의 함량이 적은 시현의 경우에도 변형이 일어남을 알수 있었다. 유리의 연화점이 높은 유리를 사용한 시편의 경우, 유리의 함량을 증가시켜도 시편의 변형은 일어나지 않았으며, 소결밀도는 계속적으로 증가하여 치밀화가 하고 있음을 알수 있었다. 이러한 유리함량과 유리의 연화점이 소결특성에 미치는 영향을 고찰함으로써 높은 밀도의 동시소성용 글라스/세라믹을 제조할 수 있는 유리의 연화점과 유리함량을 예측할 수 있었고, 이에따라 $790^{\circ}C$의 연화점을 갖는 유리를 유리 프릿트로 사용함으로써 $900^{\circ}C$의 소성온도에서 소결밀도 97%이상의 고밀도의 저온소성용 글라스/세라믹 복합체를 제조할 수 있었다.